Structural component for a motorcycle, manufacturing method thereof and motorcycle provided with the component

Abstract

The finding relates to a structural component for a motorcycle, a method of manufacturing said component and a motorcycle provided with the component, according to which the component has a body (10) for connecting to the motorcycle frame, and at least a first end extension (5, 5 6), or arm, which protrudes from said connecting body (10) and is shaped to support a motorcycle wheel; and wherein the first end extension (5, 6) has a through-opening (11), or window, which is perimetrically surrounded by an internally empty, annular space (12).

Description

[0001] DESCRIPTION

[0002] STRUCTURAL COMPONENT FOR A MOTORCYCLE, MANUFACTURING METHOD THEREOF AND MOTORCYCLE PROVIDED WITH THE COMPONENT

[0003] Technical field

[0004] The present invention relates to a structural component for a motorcycle, a manufacturing method of said component and a motorcycle provided with the component.

[0005] The structural component according to the present invention is advantageously applied as a support element for a motorcycle wheel, interposed between the frame of the motorcycle and the wheel itself.

[0006] In particular, the present invention is advantageously applied to the construction of a so-called rear “swingarm" of a motorcycle, i.e., the component which in motorcycle jargon identifies the structural component which allows the rear wheel to be supported by transferring power to it from the engine through the drive axle.

[0007] In general, the characteristics of a rear swingarm derive from a compromise between road holding needs and rider comfort requirements. When high driving performance is required, in particular for motor races, the rear swingarm must be particularly light and, at the same time, characterized by a high stiffness.

[0008] To meet both the requirements of lightness and stiffness, materials such as aluminum alloys or carbon fiber have been known to be used to make box-like and / or profiled structures provided with a plurality of transverse ribs, the latter arranged and shaped to give the necessary bending and torsional stiffness to the swingarm.

[0009] Background art

[0010] Two rear swingarm configurations are known in the technical field: the so-called "single-sided" configuration; and the so-called "double-sided" configuration. The single-sided swingarm, which has the advantage of allowing faster maintenance, is provided with a single arm which starts from the motorcycle frame and ends on one side of the rear wheel, usually the left side.

[0011] The double-sided swingarm, on the other hand, which has the advantage of being lighter than a single-sided swingarm with the same stiffness, is provided with two arms that start from the motorcycle frame and end each one on a respective side of the rear wheel.

[0012] Without loss of generality, the following discussion will make explicit reference to rear double-sided swingarms, to which the present invention is particularly advantageously applied.

[0013] Therefore, as mentioned above, the present invention relates in general to a structural component for a motorcycle and a manufacturing method of the component, which, according to a generic preferred embodiment, is a support element of a motorcycle wheel, in particular of the rear wheel. In this context, according to an even more specific, but not exclusive, embodiment, the supporting element is a double-sided rear swingarm. Double-sided rear swingarms may have a symmetrical shape relative to a median plane of the motorcycle, interposed longitudinally between the arms, or they may be asymmetrical, generally distinguished by a conformation optimized to allow other components to have a more linear path. Generally, the chain passage is provided on the left side, while the exhaust system tailpipe is often provided on the right side.

[0014] Generally, a double-sided rear swingarm has at least one front extension, i.e., facing towards the front of the motorcycle, which is pivotably mounted onto the frame to allow the swingarm to swing in the median longitudinal plane of the motorcycle, a central body, on which the rear suspension of the motorcycle is mounted, which is interposed between the frame and the swingarm itself, and a pair of rear extensions, each defined by a respective arm terminating at its end with a fork end for supporting the rear wheel. Furthermore, one of the two arms has a chain hole.

[0015] For example, some of the rear double-sided swingarms are known from patent documents EP 1905683 A1 and WO 2004 / 024548 A1 .

[0016] Other types of swingarms are known, for example, in US2015130161 , EP1547913A1 , US1 1072387B2, US2022315159A1 , and

[0017] DE102019125202A1.

[0018] Specifically, document US2015130161 shows a motorcycle swingarm where the arms are internally hollow. However, the described swingarm is difficult to make precisely because of its hollowness, and the manufacturing process is demanding.

[0019] The rear swingarms known from the aforementioned documents do not fully meet the requirements of lightness and stiffness highlighted above, and furthermore, their construction is rather complex.

[0020] Additionally, the many crosswise ribs that distinguish the arms of swingarms of the type described here are generally made by casting, which, unless the arms are subsequently boxed inside enclosing shells, causes the ribs themselves to be exposed to the elements, and thus a receptacle for the possible deposit of dirt and debris.

[0021] Moreover, a possible boxed enclosure of the arms by means of shells, in addition to making the manufacturing of the swingarm even more complex and expensive, inevitably leads to an increase in the weight of the swingarm itself.

[0022] Disclosure of the invention

[0023] The object of the present invention is to provide a structural component for a motorcycle, in particular which either is or can be shaped for use as a rear swingarm of a motorcycle, has an optimized stiffness-to-weight ratio at the same time, and is also relatively simple and inexpensive to manufacture.

[0024] A further object of the present invention is to provide a manufacturing method for a structural component for a motorcycle, in particular which is or can be shaped for use as a rear swingarm of a motorcycle and which allows the manufacturing of complex shapes, in particular with an optimized stiffness-to-weight ratio, in a relatively simple and cost-effective manner.

[0025] A further object of the present invention is to provide a manufacturing method of a structural component for a motorcycle, in particular which is or can be shaped for use as a rear swingarm of a motorcycle, which allows a relatively simple and inexpensive manufacturing of complex shapes, in particular optimized to promote an effective evacuation of possible debris or dirt and / or to reduce or cancel possible turbulence as the motorcycle advances.

[0026] Said objects are fully achieved by the present invention, which is characterized as illustrated in the claims provided below.

[0027] In particular, according to an aspect of the present invention, a structural component for a motorcycle is provided, comprising a body for connecting to the motorcycle frame, and at least a first end extension, or arm, which protrudes from said connecting body and is shaped to support a motorcycle wheel; in which said first end extension has a through-opening, or window, which is perimetrically surrounded by an internally empty, annular space.

[0028] According to a further aspect of the present invention, said annular space is at least partly open in communication with the outside. According to a further aspect of the present invention, said annular compartment is at least partially open in communication with the outside when the swingarm is in use, i.e., at the end of its manufacturing, i.e., when it is mounted on the vehicle.

[0029] Therefore, it is clarified that this opening is a permanent opening of the swingarm and not determined by progressive machining of the swingarm (e.g., openings due to semi-finished products that will compose the swingarm) as, for example, in document US2015130161 .

[0030] In one embodiment, the compartment is at least partially open to the outside to define an access which faces toward the through-opening. More in detail, the through-opening defines a perimeter edge, and the compartment access is arranged precisely at the perimeter edge.

[0031] The perimeter edge comprises a first surface, facing the inside of the swingarm i.e., the other arm, and a second surface, facing the side of the swingarm. Said first and second surfaces mutually converge at a junction point. Said first and second surfaces define a convex "V" perimeter edge shape.

[0032] The compartment access is obtained on the second surface of the perimeter edge. In particular, the access extends from the junction point toward the inside of the swingarm (toward the other arm).

[0033] In one embodiment, the compartment access extends about the perimeter edge on at least two sides, preferably at least three sides of the through- opening. In one embodiment, the compartment access extends around the perimeter edge surrounding the through-opening for at least 70% of the extent of the perimeter edge. The portion of the second surface remains to join the first surface to the respective arm. It is arranged on the opposite side of the through-opening relative to the seats which receive the fulcrum of the motorcycle frame.

[0034] It is worth noting that this configuration can be adopted on only one of the two arms, or on both arms.

[0035] According to a further aspect of the present invention, said annular compartment is at least partially closed to define at least one empty tubular duct.

[0036] According to a further embodiment of the present invention, said first end extension has, at the end opposite said connecting body, a fork end for the motorcycle wheel, and in which said through-opening is interposed between said connecting body and the fork end.

[0037] According to a further aspect of the present invention, the aforementioned structural component comprises two of said first end extensions, or arms, which protrude from the same side with respect to said connecting body. According to a further aspect of the present invention, said connecting body comprises a central body and two second end extensions both protruding from the side opposite to the first end extensions relative to said central body and shaped to be pivotably mounted on the motorcycle frame.

[0038] According to a further aspect of the present invention, said central body and at least one of said second end extensions have respective internal cavities in communication with each other, and in which at least one of said cavities is open and in communication with the outside.

[0039] According to a further aspect of the present invention, the aforementioned structural component is made by low-pressure shell casting using cores or binders consisting of foundry sand, e.g., silica sand or synthetic sand.

[0040] According to a further aspect of the present invention, the structural component could be made by injection molding of metal powders with at least one binder, and subsequent sintering.

[0041] According to a further aspect of the present invention, the aforementioned structural component is made as a single body, specifically as a monolithic metal body.

[0042] According to a further aspect of the present invention, the aforementioned structural component is made of aluminum alloy.

[0043] According to a further aspect of the present invention, a manufacturing method of a structural component for a motorcycle using low-pressure shell casting technology is provided.

[0044] The molten metal is pushed with compressed air into the shell; in this manner, the mold is filled in a controlled and uniform manner.

[0045] The low-pressure value makes it possible to use sand cores and thus make components with complex shapes, e.g., with cavities and openings, even small ones.

[0046] The use of "low" pressure also allows for particularly thin wall thicknesses. Pressure is kept constant during the solidification time to ensure that the casting component acquires a uniform density. Once solidification is complete, the component is cooled and the cores (binders) are removed by breaking them by vibration.

[0047] According to a design variation, a further molding methodology may also be used, again using low pressure, which may comprise the steps of mixing one or more metal powders, in particular containing aluminum particles, with a binder to make the cores or binders; melting and injection molding of the slurry into a mold; removing the binder which forms the cores (debinding) from the component taken out of the mold; sintering the component, performed subsequent to the step of binder removal (debinding) or integrated with the step of binder removal (debinding).

[0048] Brief description of drawings

[0049] Features and advantages will be clearer from the following description of a preferred embodiment shown by way of non-limiting example in the accompanying drawings, in which:

[0050] - Figure 1 is a plan view of a structural component for a motorcycle, in particular a rear swingarm, made according to the present invention;

[0051] - Figure 2 is a plan view of the inverted swingarm in Figure 1 ;

[0052] - Figure 3 is a first rear perspective view of the swingarm in Figure 1 , in particular from the side of the right side of the swingarm in Figure 1 ;

[0053] - Figures 4 and 5 are perspective section views corresponding to the view in Figure 3;

[0054] - Figure 6 is a second rear perspective view of the swingarm in Figure 1 , in particular from the left side of the swingarm in Figure 1 ;

[0055] - Figure 7 is a longitudinal perspective section view corresponding to the view in Figure 6; and

[0056] - Figures 8 and 9 are two rear perspective views of the swingarm in Figure 1 , respectively from the left and right side of the swingarm in Figure 1 , respectively.

[0057] As shown in the accompanying figures, a structural component for a motorcycle (not shown), made according to the present invention, is shown as a whole by reference number 1 .

[0058] Detailed description of preferred embodiments of the invention

[0059] The present invention relates to both the structural component 1 and the motorcycle which comprises this structural component as an innovative element.

[0060] In particular, the structural component 1 is a support element of a wheel (not shown) of the motorcycle, interposed between the frame (not shown) of the motorcycle and the wheel itself.

[0061] As shown and described below in the example given, the structural component 1 is shaped to support the rear wheel of the motorcycle.

[0062] In the following description, the structural component 1 is referred to as a "swingarm”.

[0063] The swingarm 1 , in particular, is of the so-called "double-sided" type and has:

[0064] - a pair 2 of front extensions, i.e., facing toward the front F of the motorcycle after assembly, which are shaped to be pivotably mounted onto the frame so as to allow the swingarm 1 to swing in the median longitudinal plane A of the motorcycle;

[0065] - a central body 3, on which the rear suspension (not shown) of the motorcycle is to be assembled; and

[0066] - a pair 4 of rear extensions, each defined by a respective arm 5, 6 terminating in a fork end 5a, 6a for supporting the rear wheel and facing toward the rear R of the motorcycle after assembly.

[0067] The front extensions are each defined by a respective lever arm 7, 8, which protrudes from the central body 3 and terminating, on the opposite side of the body 3, with a seat 7a, 8a for connecting to the fulcrum (not shown) of the motorcycle frame.

[0068] The suspension of the motorcycle is interposed between the frame and the swingarm 1 , to which it is constrained, by means of a fulcrum, at a seat 9 made in the central body 3. The central body 3 and lever arms 7 and 8 together define a body 10 connecting to the motorcycle frame, from which the arms 5 and 6 protrude to support the rear wheel of the motorcycle.

[0069] The rear extensions, i.e., the arms 5 and 6, protrude from the central body 3 on the same side from the central body 3 itself. In particular, the rear extensions protrude in a cantilevered manner from the central body 3 keeping substantially parallel to each other and giving the portion of the swingarm 1 which comprises a substantially U-shaped plan conformation. Instead, the front extensions, i.e., lever arms 7 and 8, both protrude on the opposite side of the rear extensions from the central body 3. In particular, the front extensions protrude in a cantilevered manner from the central body 3 diverging asymmetrically from each other and giving to the portion of the swingarm 1 comprising them a substantially U-shaped plan conformation.

[0070] As a whole, the front extensions, the central body 3 and the rear extensions give the swingarm 1 a substantially H-shaped plan conformation (Fig. 1 ; Fig. 2).

[0071] Hereinafter, the right side of the motorcycle means the side which is to the rider’s right when seated on the motorcycle, and the left side means the side which is to the rider’s left, again when in the seated position.

[0072] In the embodiment taken as an example here and shown in the accompanying figures, the arms 5 and 7 are the ones arranged on the left side of the motorcycle when the swingarm 1 is mounted onto the motorcycle. While the arms 6 and 8 are the ones arranged on the right side of the motorcycle when the swingarm 1 is mounted on the motorcycle. In the scope of both the V-shaped conformation described above and the U-shaped and H-shaped conformations described above, the swingarm 1 has an asymmetrical conformation relative to the longitudinal median longitudinal plane A of the motorcycle, which is interposed longitudinally, during assembly, between the arms 5 and 6 and between the arms 7 and 8 and coincides with the longitudinal symmetry plane of the rear wheel. This asymmetrical conformation is optimized to allow other components, in particular the chain (not shown) to have a more linear path. In particular, the chain must have a straight path, and for this purpose, the swingarm 1 is provided with a chain tunnel 13 made at the left arm 5.

[0073] Each of the two rear extensions, i.e., each of the two arms 5,6 has a through-opening 11 , or window, which is perimetrically surrounded by an internally empty, annular space 12.

[0074] The function of the opening 11 is prevalently to lighten the swingarm 1 .

[0075] The annular compartment 12 is at least partially open in communication with the outside. This conformation is particularly advantageous to allow the manufacturing process of the swingarm 1 according to the present invention, and in particular the step of removing the cores after the step of low-pressure molding has been performed and the metal has cooled (step of debinding) described below.

[0076] The hollow conformation of the annular compartment 12 is also advantageous for promoting effective evacuation of possible debris or dirt, as the motorcycle advances.

[0077] In other words, the opening 11 is surrounded by a wall 11a, which faces the motorcycle wheel after assembly. The wall 11 a extends crosswise from the opening 11. Furthermore, the wall 11 a is closed as a loop to guide a frame.

[0078] Structurally, the wall 11 a defines an annular rib. This conformation is particularly advantageous for optimizing the stiffness-to-weight ratio of the swingarml .

[0079] In particular, the wall 11 a has a thickness comprised between 3 mm and 5 mm thick. More in detail, the wall 11 a has a thickness of 3.5 mm.

[0080] More in detail, said annular compartment 12 is at least partially open in communication with the outside when the swingarm is in use, i.e., at the end of its manufacturing, i.e., when it is mounted on the vehicle.

[0081] In one embodiment, the compartment 12 is at least partially open to the outside to define an access 12c which faces towards the through-opening 11. More in detail, the through-opening 11 defines a perimeter edge BD (or frame), and such access 12c to the compartment 12 is arranged precisely at the perimeter edge BD.

[0082] The perimeter edge BD comprises a first surface SS1 , facing towards the inside of the swingarm i.e., the other arm, and a second surface SS2, facing towards the outer side of the swingarm. Said first and second surfaces SS1 , SS2 mutually converge at a junction point PC. Said first and second surfaces SS1 , SS2 define a convex "V"-shaped perimeter edge.

[0083] The compartment access 12 is obtained on the second surface SS2 of the perimeter edge BD. In particular, the access 12c extends from the junction point PC toward the inside of the swingarm (toward the other arm).

[0084] In an embodiment, the compartment access 12 extends about the perimeter edge on at least two sides, preferably at least three sides of the through-opening 11. In one embodiment, the access 12c to the compartment 12 extends about the perimeter edge surrounding the through-opening 11 for at least 70% of the extent of the perimeter edge BD. The portion of the second surface SS2 which remains joining the first surface SS1 to the respective arm is arranged on the opposite side of the through-opening 11 from the seats 7a, 8a which receive the fulcrum of the motorcycle frame.

[0085] It is worth noting that this configuration can be adopted on only one of the two arms or on both arms.

[0086] The annular compartment 12 can also be at least partially closed to define at least one empty tubular pipe 12a. This conformation is particularly advantageous for further increasing the bending and torsional stiffness of the swingarm 1 .

[0087] In that case, the wall 11 a is partly closed back to form the aforementioned empty tubular duct 12a.

[0088] In the embodiment taken as an example here and illustrated in the accompanying figures, the annular compartment 12 of the arm 5, corresponding to the left side of the motorcycle after assembly, is fully open in communication with the outside (i.e., toward the motorcycle wheel), as a channel.

[0089] Instead, the annular compartment 12 of the arm 6, corresponding to the right side of the motorcycle after assembly, is partly open in communication with the outside (i.e., towards the motorcycle wheel), as a duct, and partly closed to define the aforementioned empty tubular duct 12a.

[0090] In both arm 5 and arm 6, the through-opening 11 is interposed between the connecting body 10 and the fork end 5a, 6a, the latter being arranged at the opposite end of the arm 5, 6 from which it extends in a cantilevered manner from the connecting body 10, and in particular from the central body 3.

[0091] What was said above in relation to each of the two rear extensions, i.e., each of the two arms 5, 6, may refer to a single arm of an embodiment not shown here in which the swingarm is of the single-sided type.

[0092] As shown in Figures 4, 5 and 7, the central body 3 and at least one of the front-end extensions, i.e., lever arms 7, 8, have respective internal cavities communicating with each other.

[0093] In particular, the terminal extension 7, which as mentioned is arranged on the left in the assembly, has an inner cavity 7b, which is open in communication with the outside and is in communication with the inner cavity 3a of the central body 3, which is also in communication with the outside.

[0094] This conformation is particularly advantageous to allow the manufacturing process of the swingarm 1 according to the present invention, and in particular the step of eliminating the cores, or debinding, described below.

[0095] The structural component according to the present invention, and in particular the swingarm 1 described above, are made according to a method, or manufacturing process, called low-pressure shell casting technology. The molten metal is pushed with compressed air into the shell; in this manner, the mold is filled in a controlled and uniform manner.

[0096] The low-pressure value makes it possible to use sand cores and thus make components with complex shapes, e.g., with cavities and openings, even small ones.

[0097] The use of "low" pressure also allows for particularly thin wall thicknesses. Pressure is kept constant during the solidification time to ensure that the casting component acquires a uniform density.

[0098] Once solidification is complete, the component is cooled, and the cores (binders) are removed by breaking them by vibration.

[0099] In more detail, a method for making a swingarm using the low-pressure die casting (LPDC) technique is best described below. Low-pressure casting involves a step of pressing the metal into a mold through the application of a pressure ramp. The method comprises a step of pressure holding during the solidification of the casing to ensure the feeding of volumetric shrinkage. Defining the correct ramp is crucial to achieve turbulence-free filling and properly managed solidification.

[0100] The method comprises one or more of the following steps:

[0101] - a step of mold preparation, comprising the following sub-steps:

[0102] - preheating the mold (usually, of steel) to avoid thermal shock and improve part quality.

[0103] - painting the mold with preferably aqueous suspension ceramicbased paints. This step helps to prevent the molten material from sticking to the molding surfaces of the mold. Correct paint management is also crucial to ensure the correct solidification of the casting.

[0104] - step of crucible filling in which the molten metal, preferably subjected to preventive alloy sanitization operations, is kept in a pressurized crucible, which is placed under the mold.

[0105] - step of pressurization and subsequent metal rising, including the following steps: - during the step of crucible filling, applying a controlled and repeatable pressure ramp up to maximum values between 0.3 bar and 0.7 bar, preferably between 0.45 bar and 0.55 bar.

[0106] - pressing the molten metal into a riser tube from where, by means of sprues, it flows into the mold cavity, filling figures and any feeder risers.

[0107] - step of controlled solidifying, in which the part cools and solidifies inside the mold. Preferably, this step is performed by means of thermal conditioning systems (electric water cooling and / or heating circuits).

[0108] - during the step of solidifying, pressure holding up to maximum pressure values of 0.8 bar to feed volumetric shrinkage of the casing.

[0109] - step of pressure release;

[0110] - step of casting extraction;

[0111] - step of sprue removal, any feeder risers and burrs.

[0112] In addition to the above, the following specifications are given with respect to the manufacturing method.

[0113] The pressure ramp gradually increases to a maximum of 0.5 bar during filling, and 0.8 bar max during solidification. Pressure is applied gradually to avoid turbulence and gas inclusions.

[0114] The filling speed in the swingarm manufacturing process may vary according to the diameter of the riser tube and the applied pressure, but, in any case, to ensure a proper compromise the speed is between 0.3-0.5 m / s to ensure smooth filling without turbulence.

[0115] The desired filling temperature is held between 650°C and 800°C, preferably about 720°C. This is the best compromise between fluidity and risk of oxidation or gas porosity.

[0116] The mold temperature is a controlled temperature that is kept between 350°C and 450°C to control and drive the solidification process. This avoids internal stresses in the part and deformation of the mold. The mold temperature control is carefully managed by the thermal conditioning systems.

[0117] The solidification time is generally kept between 120-300 seconds. According to a further molding method, there may be a step of mixing one or more metal powders with a binder to make a slurry; a step of melting and injection molding the slurry into a mold; a step of removing the binder (debinding) from the component extracted from the mold; and a step of sintering the component, in particular in an oven. The step of sintering can be followed by further steps of finishing. The metal powders preferably contain aluminum particles. Therefore, the resulting structural component is made of aluminum alloy. In this case, the metal powders preferably have a size between 0.1 and 25 pm to allow an optimal step of sintering.

[0118] The binder can be chosen from thermoplastic polymer-based binders, wax-based binders, gypsum- or ceramic-based binders, and metallurgical powder-based binders.

[0119] The binders based on thermoplastic polymers can be composed of thermoplastic resins, such as polyethylene or polypropylene. The amount of binder must be sufficient to allow all the voids between the particles (metal powders) to be filled and to lubricate the sliding of the particles during molding. At the same time, excess binder is undesirable because the shape of the component would be lost during debinding.

[0120] The step of binder removal can be accomplished by thermal process or by solvent or catalytic erosion.

[0121] The use of at least two binding components of which one is not reactive to the step of debinding is preferred so as to keep the component in shape between the step of debinding and the step of sintering which stabilizes the final shape, if these two steps are distinct.

[0122] During the step of debinding, the binder is removed from the component. In case of thermal process, the component is heated slowly to decompose the binder.

[0123] If a solvent is used, the component is immersed in a solvent which dissolves part of the binder, leaving a residue to hold the particles in place for the next step of sintering. The remaining binder is thermally extracted as part of the sintering cycle.

[0124] In the case of catalytic binder erosion, most of the binder is attacked by a catalytic vapor, while the remaining binder is removed during heating to the sintering temperature.

[0125] In any case, the openings described above with reference to compartments 12 and cavities 3a and 7b advantageously facilitate the removal of the binder, even in case of breakage and removal of cores by vibration.

[0126] The step of mixing can be followed by extruding the mixture into pellets, which are easier to transport for the successive step of injection molding. In this case, the step of casting and injection molding is performed from the pellets introduced into the mold.

[0127] The step of sintering can be incorporated directly into the thermal debinding cycle.

[0128] The sintering binds the particles together, leading to a densification of the material. Optimal results can be obtained, as mentioned above, with metal powders which have sizes between 0.1 and 25 pm.

[0129] Sintering shrinkage is uniform and isotropic. Sintering is preferably performed in a protective atmosphere or vacuum at a maximum temperature which causes rapid elimination of pores previously filled with binder.

[0130] Therefore, the structural component made according to the manufacturing process described above is a single body of high overall density, in particular a monolithic metal body that can be made with a complex shape, optimized to have a high stiffness-to-weight ratio, in particular.

Claims

CLAIMS1. A structural motorcycle component, comprising a body (10) for connecting to the motorcycle frame, and at least a first end extension (5, 6), or arm, which protrudes from said connecting body (10) and is shaped to support a motorcycle wheel; characterized in that said first end extension (5, 6) has a through-opening (11 ), or window, which is perimetrically surrounded by an internally empty, annular space (12).

2. The component according to claim 1 , characterized in that said annular space (12) is at least partly open and in communication with the outside.

3. The component according to claim 2, characterized in that the through- opening (11 ) defines a perimeter edge (BD) comprising an access (12c) to the compartment (12) to put the compartment (12) into communication with the outside.

4. The component according to claim 3, characterized in that the access (12c) surrounds the opening (11 ) for at least half of the perimeter edge (BD).

5. The component according to claim 3 or claim 4, characterized in that the thickness of the access along a direction perpendicular to the through- opening (11 ) is less than the thickness of the circumferential edge along the direction perpendicular to the through-opening (11 ).

6. The component according to any one of claims from 2 to 5, characterized in that said annular space (12) is at least partly closed to define at least one empty, tubular duct (12a).

7. The component according to any one of the preceding claims from 1 to6, characterized in that said first end extension (5, 6) has, at the end opposite said connecting body (10), a fork end (5a, 6a) for the motorcycle wheel, and wherein said through-opening (11) is interposed between said connecting body (10) and the fork end (5a, 6a).

8. The component according to any one of claims 1 to 7, characterized in that it comprises two of said first end extensions (5a, 6a), or arms, protruding from the same side of said connecting body (10).

9. The component according to claim 8, characterized in that said connecting body (10) comprises a central body (3) and two second end extensions (7, 8) both protruding from the side opposite to the first end extensions (5, 6) relative to said central body (3) and shaped to be pivotably mounted onto the motorcycle frame.

10. The component according to claim 9, characterized in that said central body (3) and at least one of said second end extensions (7, 8) have respective internal cavities (3a, 7b) in communication with each other, and wherein at least one of said cavities (3a, 7b) is open and in communication with the outside.

11. The component according to any one of claims 1 to 10, characterized in that it is made by injection molding of metallic powders with at least one binder, followed by sintering.

12. The component according to any of the preceding claims 1 to 11 , characterized in it is made as a single body, in particular as a monolithic metal body.

13. The component according to claim 11 or 12, characterized in that it is made from aluminum alloy.

14. A method for manufacturing a structural motorcycle component (1 ), in particular a component according to any one of the preceding claims from 1 to 13, comprising the steps of pressing the molten metal into a shell with compressed air; filling the mold in a controlled and uniform manner; using sand cores or binders; keeping the pressure constant during the solidification time to ensure that the molten component acquires a uniform density; removing the cores or binders.

15. The method according to claim 14, wherein in the step of pressing the molten metal is applied at a pressure of less than 0.8 bar.

16. The method according to claim 15, wherein in the step of pressing the molten metal is applied at a pressure of less than 0.6 bar.

17. The method according to claim 14, 15 or 16, wherein in the step of solidifying, the pressure is kept below 1 .5 bar.

18. The method according to claim 17, wherein in the step of solidifying, the pressure is kept below 0.9 bar.

19. The method according to any of the preceding claims, wherein the step of pressing the molten metal is applied at a pressure between 0.45 bar and 0.5 bar and wherein in the step of solidifying, the pressure is kept between 0.75 bar and 0.85 bar.

20. The method according to any of the preceding claims, wherein the molten metal is pressed at a speed comprised between 0.3-0.5 m / s.

21. A motorcycle comprising a structural component (1 ) according to any one of the preceding claims from 1 to 13.

22. A motorcycle comprising a structural component (1 ) made according to the method of claim 14.

Images