WO2022049558A1

WO2022049558A1 - A method for manufacturing a suspension arm for an automotive suspension and suspension arm obtained by said method

Info

Publication number: WO2022049558A1
Application number: PCT/IB2021/058117
Authority: WO
Inventors: Salvatore SOTTILE; Andrea Santini; Marco GOIA
Original assignee: Marelli Suspension Systems Italy S.P.A.
Priority date: 2020-09-07
Filing date: 2021-09-07
Publication date: 2022-03-10
Also published as: CN116018253A; EP4210974A1; IT202000021133A1

Abstract

A method for manufacturing a suspension arm (9) for an automotive suspension comprises the steps of preparing composite pre-pregs; by means of compression molding in a closed mold press, shaping said composite pre-pregs so as to obtain two respective half-shells (10); assembling said two half-shells (10), so that said half-shells form a core (12) within which a cavity (14) is defined; preparing additional composite charges and positioning them inside the mold; by means of compression molding in a closed mold press, shaping said charges whereby each half-shell (10) is entirely covered with them, whereby said half-shell creates an external body (16) that entirely encloses the core (12).

Description

A METHOD FOR MANUFACTURING A SUSPENSION ARM FOR AN AUTOMOTIVE SUSPENSION AND SUSPENSION ARM OBTAINED BY SAID METHOD

Technical field

This invention relates, in general, to the automotive field; in particular, the invention relates to a method for manufacturing a structural component of a motor vehicle with a hollow section made of composite material, particularly a suspension arm of a motor vehicle, and a suspension arm obtained by said method.

Prior art

The suspension arm is an element of the kinematic system that is implemented by the front or rear suspension system of the vehicle.

Basically, the suspension arm has a function of being load-bearing and connecting between moving parts (wheel strut, shock absorber system) and fixed parts (body, chassis, crossmember) of the vehicle. The type of connected parts varies depending on the architecture.

In the field of structural suspension components and, more specifically, components of an automotive suspension arm, the materials commonly used are cast iron, aluminum, and steel, according to well-known technological processes such as sheet metal forming, forging, and die-casting in different configurations.

The technological evolution in the production of these components, as well as the increasingly stringent requirement to reduce the weight of structural suspension components, has led to an increasingly frequent shift to the product configuration with single- shell or double- shell formed sheet metal, depending on the final performance required at the vehicle level. In the case of metal components with hollow sections, it is therefore necessary to carry out successive technological processes such as, by way of example, continuous and spot welding, with the related design constraints (sizing of fins, accessibility of the torch, etc.).

In order to make the components lighter, composite materials, generally processed by pultrusion, have been widely used in the automotive industry.

However, in the case of hollow components with complex shapes, such as suspension arms, pultrusion is not suitable, thus the prior art does not contemplate solutions for making a structural component of a motor vehicle (such as, in particular, a suspension arm) that, while retaining the shape and functionality of a traditional metal component, has improved features in terms of weight and flexibility.

These limitations, understandably, undermine the possibility of having more high- performance components with respect to the known configurations.

Summary of invention

An object of this invention is to overcome the aforementioned problems.

To achieve this, a structural component of a vehicle, e.g., a suspension arm, a suspension strut, a chassis beam, etc., is made from composite fillers, shaped by compression molding in a closed mold press to form (at least) two half-shells that, once assembled, will delimit the internal cavity of the final component. The hollow core, formed by the two assembled half-shells, is then placed inside a mold, and the final geometry is made by overmolding in a closed mold press with the use of composite filler material that, once the mold is closed, will fill all the cavities thereof, thus creating a body having the final geometry of the component.

At the end of the process, the hollow core is then sealed within a monolithic block and shaped with the geometry of the final component. Due to such a configuration, the structural component made of composite material with a hollow section according to the invention is lighter with respect to a corresponding conventional steel, aluminum or cast iron component, while maintaining its performance.

The two (or more) internal shells, forming the hollow core of the component, are made using the well-known compression molding process in a closed mold press.

The material considered is a fiber-reinforced composite that may be continuous (unidirectional fibers or fabrics with different balances and/or different orientations), discontinuous, or mixed (hybrid structure comprising a continuous fiber laminate that is unidirectional or balanced according to a stacking sequence dependent on the mechanical features to be achieved, reinforced by co-molded ribs made of discontinuous fiber).

The resin may be either thermosetting or thermoplastic.

The two half-shells constituting the cavity may then be made of continuous fiber (e.g., glass fiber, carbon, basalt, aramid), discontinuous fiber, discontinuous fiber with continuous fiber reinforcements or vice versa, according to the aforementioned compression molding techniques in a closed mold press (known per se).

The internal surface of the two half-shells forming the hollow core may be equipped with a system of ribs adapted to increase the resistance of the hollow core to deformation.

The hollow core is made by assembling the two half-shells. The assembly may be achieved by known techniques of geometric joining, continuous joining (e.g., bonding or friction welding), or discontinuous joining (e.g., nailing or riveting) by interposing metal inserts. The seats of the inserts may be co-molded directly into the surfaces of the two (or more) halfshells, forming the cavity. Adhesion at the polymer/metal interface may be improved chemically, according to known surface activation techniques, or mechanically, by making appropriate geometries or practicing appropriate treatments or processing according to the prior art. The final geometry is achieved by subsequent overmolding of the hollow core and of the reinforced composite material, according to known compression molding technologies in a closed mold press. The adhesion between the outer surfaces of the cavity and the filler material, expediently cured after firing in a hot mold or solidified in a cold mold (depending on the type of material matrix, and thus on the type of compression molding in a closed mold press), may be improved mechanically (e.g., by special geometries and/or surface processing, such as sandblasting), chemically (e.g., laser surface activation techniques), or by the interposition of a third medium (e.g., a known type of bonding agent).

During overmolding of the external body on the hollow core, the co-molding of metal inserts may be provided, which may form respective seats for bushings, ball joints, etc., to allow the subsequent connection of the component to the various components of the vehicle.

The aforesaid and other objects and advantages are achieved, according to one aspect of the invention, by a method for manufacturing a structural component of a motor vehicle with a hollow section made of composite material, particularly an automotive suspension arm, and by a suspension arm obtained by said method, having the features defined in the appended claims.

Brief description of the drawings

Functional and structural features of some preferred embodiments and implementation of a manufacturing method and a suspension arm according to the invention will now be described. Reference is made to the appended drawings, wherein:

- Fig. 1 is a schematic perspective view of a structural component of a motor vehicle, in particular an automotive suspension arm, according to one embodiment of this invention;

- Fig. 2 and 3 are, respectively, a schematic perspective and exploded view of a hollow core embedded within the suspension arm of Fig. 1, according to an embodiment of this invention;

- Fig. 4 and 5 are two perspective schematic views of a portion of an external body encompassing a half-shell of the internal core, in the absence and presence of a reinforcing rib associated with the half-shell, respectively, according to one embodiment of this invention; and

- Fig. 6 through 8 are respectively a perspective view of a suspension arm in an assembled condition of the external body and hollow core, a partial section of the arm of Fig. 6 wherein the internal body is visible, and a partial section of the arm of Fig. 6 wherein the internal body fitted with a reinforcing rib is visible, according to two respective embodiments of this invention.

Detailed description

Before describing a plurality of embodiments of the invention in detail, it should be clarified that the invention is not limited in its application to the construction details and configuration of the components presented in the following description or illustrated in the drawings. The invention may assume other embodiments and be implemented or constructed in practice in different ways. It should also be understood that the phraseology and terminology have a descriptive purpose and should not be construed as limiting.

Moreover, the following description will mainly refer to the manufacture of an arm for an automotive suspension. However, it is understood that the method according to the invention is generally applicable to any structural component of a motor vehicle which, due to its geometric, mechanical, and/or functional features, lends itself to being made by means of the claimed process (e.g., the strut of an automotive suspension, a beam of a chassis, etc.).

A method for manufacturing a structural component of a motor vehicle with a hollow section made of composite material comprises the step of preparing pre-impregnated fibers made of composite material. These materials belong to the type traditionally known as “pre-pregs,” and may initially be in the form of plates, sheets, or generally as fillers of semi-solid or pasty consistency.

Subsequently, said composite pre-pregs are shaped by compression molding in a closed mold press whereby two respective half-shells 10 are obtained. Basically, the material is loaded into the mold and, under the pressure imparted by the press (according to the well-known technique of compression molding in a closed mold press), it will flow inside the mold until it is imprinted with the desired shape, in this case, a half-shell.

Then, the two half-shells 10 are assembled whereby these mutually facing half-shells 10 form a core 12 within which a cavity 14 is defined.

Additional composite fillers are then prepared and placed inside the mold.

By compression molding in a closed mold press, said coating charges are shaped whereby each half-shell 10 is entirely covered with them, whereby said coating charges create an external shell 16 that entirely surrounds the core 12.

According to a preferred embodiment, the above method is configured to obtain a structural component in the form of an automotive suspension arm.

Expediently, the composite material used for making the half-shells 10 and/or for making the external body 16 comprises a thermoplastic or thermosetting resin matrix.

Preferably, the composite material used for making the half-shells 10 and/or for making the external body 16 is a material selected from the group consisting of Sheet Molding Compounds (“SMCs”), Advanced Sheet Molding Compounds (“A-SMCs”), Glass Fiber Sheet Molding Compounds (“GFSMCs”), Carbon Fiber Sheet Molding Compounds (“CFSMCs”), and Bulk Molding Compounds (“BMCs”). These composite materials are well known to the person skilled in the art.

According to one embodiment, the step of coupling the half- shells 10 to each other is performed by bonding or friction welding the edges of one half-shell 10 to the other halfshell 10.

According to an alternative embodiment, the step of coupling the half-shells 10 to each other in step (c) is performed by nailing or riveting the edges of the half-shells 10 to each other. There may further be provided the step of arranging a plurality of metal inserts 18, adapted to accommodate bushings and/or portions of ball joints, and the step of molding the external body 16 and said metal inserts 18.

According to one embodiment, the method comprises the step of applying ribs 20 to one or both of the half-shells 10, said ribs 20 being adapted to give the half-shells 10 greater resistance to deformation (e.g., greater flexural and/or torsional stiffness, and/or acting as a support to the inner core 12 during the step of overmolding the external body 16 to prevent the core 12 from deforming or collapsing). The ribs 20 extend within the cavity 14 and may be configured as a lattice of sheets extended between the inner walls of the hollow core 12.

According to an aspect of the invention, a suspension arm 9 for an automotive suspension is obtained by a method according to any of the embodiments of the above method, said suspension arm 9 comprising the core 12, made of composite material and hollow within, said core 12 being incorporated into the external body 16, made of composite material and comprising a plurality of seats 17 adapted to accommodate means for connecting said suspension arm 9 to a vehicle.

Various aspects and embodiments of a method for manufacturing an automotive component and a suspension arm obtained by such a method according to the invention have been described. It is understood that each embodiment may be combined with any other embodiment. Furthermore, the invention is not limited to the described embodiments, but may be varied within the scope defined by the appended claims.

Claims

8 CLAIMS

1. A method for manufacturing a suspension arm (9) for an automotive suspension, comprising the steps of: a) providing pre-pregs of composite material; b) by means of compression molding in a closed mold press, shaping said pre-pregs of composite material in such a way as to obtain two respective half-shells (10); c) assembling the two half-shells (10), so that the two half-shells (10) facing each other form a core (12) inside of which a cavity (14) is defined; d) providing additional coating charges of composite material, and placing them inside the die; e) by means of compression molding in a closed mold press, shaping said coating charges in such a way that each half-shell (10) is entirely covered by said coating charges, whereby said coating charges create an external body (16) which entirely encompasses the core (12).

2. The method according to claim 1, wherein the composite material of steps (a) and/or (d) comprises a thermoplastic or thermosetting resin matrix.

3. The method according to claim 1 or 2, wherein the composite material of steps (a) and/or (d) is a material selected from the group comprising Sheet Molding Compounds (SMCs), Advanced Sheet Molding Compounds (A-SMC), Glass Fiber Sheet Molding Compounds (GFSMC), Carbon Fiber Sheet Molding Compounds (CFSMC), and Bulk Molding Compounds (BMC).

4. The method according to any of the preceding claims, wherein step (c) is carried out by gluing or friction welding the edges of one half-shell (10) to the other half-shell (10).

5. The method according to any of claims 1 to 3, wherein step (c) is carried out by reciprocally nailing or riveting the edges of the half-shells (10).

6. The method according to any of the preceding claims, comprising the step of providing a plurality of metal inserts (18), adapted to receive bushings and/or portions of 9 ball joints, and the step of co-molding the external body (16) and said metal inserts (18).

7. The method according to any of the preceding claims, further comprising the step of applying ribs (20) to one or both of the half-shells (10), adapted to confer on the half-shells (10) a greater resistance to deformation, said ribs (20) extending into the cavity (14).

8. A suspension arm (9) for an automotive suspension, obtained by a method according to any of the preceding claims, said suspension arm (9) comprising a core (12), made of composite material and hollow inside, said core (12) being incorporated in an external body (16), made of composite material and comprising a plurality of seats (17) adapted to accommodate means for connecting said suspension arm (9) to a vehicle.