FR3092078A3 - Method of producing an axle arm by overmolding on a metal part of different material - Google Patents

Abstract

The invention relates to a method of assembling a longitudinal arm (12) of an axle (10) for a motor vehicle on a metal part (32) comprising a step of molding the arm (12) in an incompatible material for welding. with the material constituting the metallic part (32), characterized in that during the molding step (E3), the arm (12) is overmolded on a first section (34) of the transverse end of the part (32) metallic, said inserted section (34), a second end section (36) of the metal part (32), called free section (36), projecting transversely from the arm (12). The invention also relates to an axle (10) comprising such arms (12). Figure for the abstract: Figure 2

Description

Method for producing an axle arm by overmolding on a metal part of different material

Technical field of the invention

The invention relates to a method for assembling a longitudinal arm of an axle for a motor vehicle on a metal part comprising a step of molding the arm in an incompatible material for welding with the material constituting the metal part.

Technical background

It is known to equip the rear axles of motor vehicles with an axle of the "semi-rigid" type. Such an axle mainly comprises two longitudinal arms between which extends a crosspiece which is elastic in torsion and rigid in bending. Each arm is linked to the crosspiece by an embedding-type link.

Each arm has a front end which is pivotally mounted on the vehicle frame while a rear end carries a rear wheel of the vehicle.

The crosspiece extends transversely between the two arms, offset longitudinally towards the rear with respect to the front ends of the arms. The elastic properties of the crosspiece allow it in particular to fulfill an anti-roll function which limits the roll of the bodywork. For example, it is known to produce tubular steel crosspieces.

Furthermore, it is also known to make the longitudinal arms out of an aluminum-based material, in particular an aluminum alloy. Such arms thus have satisfactory mechanical characteristics while making it possible to lighten the weight of the vehicle.

However, it is very complex to attach the steel crosspiece by welding to the aluminum alloy arms. This requires welding techniques which are much more complex and expensive than the conventional welding techniques by simple deposition of a weld bead. Furthermore, such a fixing by welding does not have the resistance and endurance characteristics necessary to withstand the forces applied to the axle.

To circumvent this problem, two solutions are currently known.

The first solution consists in welding flanges, for example of steel, at the end of the crosspiece. The free edges of each end of the crosspiece are shaped so as to be contiguous over their entire length with one face of the sole. A weld bead is placed over the entire length of the joint between the crosspiece and the sole. Each sole is then fixed against the associated arm by means of screws.

This first solution makes it possible to obtain a solid and resistant attachment of the arms to the crosspiece.

However, the gain in mass is not optimal due to the presence of soles and screws. The weight of these added elements significantly increases the axle, for example of the order of 3 kg. However, the use of aluminum alloy arms aims on the contrary to lighten the axle. This first solution is therefore not optimal.

A second solution has also been proposed which consists in gluing the ends of the crosspiece to the arms. This solution advantageously makes it possible to keep a light axle because no massive part is used for fixing the arms.

However, the bonding operation remains very delicate. In some cases, the adhesion of the glue may prove to be insufficient, causing premature damage to the axle.

The invention proposes a method for assembling a longitudinal arm of an axle for a motor vehicle on a metal part comprising a step of molding the arm in an incompatible material for welding with the material constituting the metal part,

characterized in that during the molding step, the arm is molded over a first transverse end section of the metal part, said inserted section, a second end section of the metal part, said free section, projecting transversely of the arm.

According to other characteristics of the process carried out according to the teachings of the invention:

- The inserted section of the metal part has a wall shaped as a section with a transverse axis;

- at least one of the faces of the wall of the inserted section is equipped with reliefs prior to the molding step, to allow the mechanical connection with the material of the molded arm on said reliefs;

- the wall of the inserted section of the metal part comprises at least one through hole;

- the inserted section of the metal part comprises several orifices distributed along the profile;

- the arm is made of a metallic material based on aluminium;

- the metal part is made of a metal material based on iron, such as steel.

The invention also relates to an axle for a motor vehicle comprising:

- A tubular crosspiece with a transverse axis which is elastically deformable in torsion, the crosspiece being made of steel;

- two longitudinal parallel arms, each of which is intended to be fixed to a body of the motor vehicle and each of which is rigidly fixed to a transverse end of the crosspiece,

characterized in that the arms are fixed to a metal part in accordance with the method carried out according to the teachings of the invention, the arms being fixed to the crosspiece by means of the metal part.

According to other characteristics of the axle produced according to the teachings of the invention:

- Each arm is fixed to the associated end of the crosspiece by welding the free section of the metal part with the crosspiece;

- The free section of the metal part is embedded in an end opening of the crossbeam before being fixed by welding.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

FIG. 1 is a perspective view showing a motor vehicle rear axle produced according to the teachings of the invention.

Figure 2 is a perspective view which shows an arm of the axle of Figure 1 assembled with a metal part in accordance with the teachings of the invention.

Figure 3 is a perspective view showing the metal part ready to be assembled with the arm of Figure 2.

Figure 4 is a sectional view along section plane '4-4 of Figure 2 which shows the material bridges for securely connecting the metal part with the arm.

Figure 5 is a schematic exploded perspective view which shows the arm just before its embedding in the crosspiece.

FIG. 6 is a block diagram which schematically represents the method of producing the axle according to the teachings of the invention.

Detailed description of the invention

In the remainder of the description, elements having an identical structure or analogous functions will be designated by the same references.

In the rest of the description, the longitudinal, vertical and transverse orientations indicated by the trihedron "L, V, T" of the figures will be adopted without limitation. The longitudinal direction "L" is oriented from rear to front according to the normal direction of movement of the vehicle. The vertical direction "V" is oriented from bottom to top from the ground on which the vehicle is resting towards the roof of the vehicle.

There is shown in Figure 1 a rear axle 10 of a motor vehicle. It is an axle 10 of the "semi-rigid" type. It comprises two parallel arms 12, referred to as longitudinal arms 12, each of which has an overall longitudinal main axis "A". The two longitudinal arms 12 are interconnected by a crosspiece 14 with main transverse axis "B".

Each longitudinal arm 12 extends from a first end 16 before to a second end 18 behind. Each longitudinal arm 12 is formed by a solid piece of aluminum-based material, such as an aluminum alloy. It has an inner side face 17 which faces the other arm 12.

The first front end 16 is intended to be pivotally mounted around a transverse axis on a chassis (not shown) of the vehicle.

A rear end section of each longitudinal arm 12 is provided with a bracket 20 which is intended to rotatably support an associated rear wheel (not shown) of the vehicle as well as a brake disc or drum 22 associated with the wheel. .

In the embodiment shown in Figure 1, the longitudinal arm 12 also includes a yoke 24 to support a shock absorber element 26, and a cup 28 to support a member 29 for the suspension of the vehicle. The clevis 24 and the cup 28 are here made in one piece with the arm 12.

The crosspiece 14 extends from a first section 30 of the transverse end to a second section 30 of the transverse end.

The crosspiece 14 is here in the form of a steel tube. At least the transverse end sections 30 of the crosspiece 14 have, in section along a longitudinal vertical plane, a closed profile. In the example shown in Figure 1, the crosspiece 14 has a closed profile over its entire length. The crosspiece 14 thus comprises a metal wall shaped in a tubular manner according to a closed profile.

The crosspiece 14 is made so as to be rigid in bending in the vertical plane and in the longitudinal plane and so as to be flexible in torsion about its main transverse axis "B". The wall of the crosspiece 14 has a first determined thickness which allows the crosspiece 14 to have sufficient flexibility in torsion to perform its anti-roll function.

Each end section 30 of the crosspiece 14 is rigidly fixed to the associated longitudinal arm 12 according to the same arrangement and according to the same method. The fixing of a single end section 30 of the crosspiece 14 on the associated longitudinal arm 12 will be described below with reference to FIG. 2, this description being applicable to the fixing of the other end section 30 on the other arm 12 longitudinal.

During its manufacture, the arm 12 is produced by molding an aluminum-based material during a molding step "E4", as will be explained in detail below.

To allow a solid and resistant fixing of the arm 12 on the crosspiece on the crosspiece 14, it is planned to overmold the arm 12 on a piece 32 of metal.

In the embodiment shown in Figure 2, the metal part 32 is an intermediate fixing part which is intended to be fixed later on the crosspiece 14, as will be explained in more detail later. The arm 12 is thus intended to be fixed on the crosspiece 14 via the metal part 32.

In a variant of the invention, not shown, the metal part is formed directly by the crosspiece of the axle.

In general, the metal part 32 is made of a different material from that which constitutes the arm 12.

The terms "different material" means that the arm 12 is made of a material which does not allow easy obtaining of strong and enduring fixing by welding with the material constituting the crosspiece 14. In other words, the material constituting the arm 12 is incompatible for conventional welding with the material constituting the crosspiece 14 because their physico-chemical properties, for example their melting temperature and/or their coefficient of expansion and/or their electrochemical potential, are too different to make it possible to obtain strong welding.

Being a metal part 32 intended to be fixed on the crosspiece 14 by welding, the metal part 32 consists of a material compatible for welding with the material constituting the crosspiece 14. The metal part 32 is for example made made of an iron-based material such as steel.

As shown in Figure 3, the metal part 32 has a first section 34 of transverse end which is intended to be taken in the material constituting the arm 12 during its molding. This section will be referred to below as section 34 inserted.

The metal part 32 also comprises a second transverse end section 36 opposite the inserted section 34 which is intended to protrude transversely from the inner side face 17 of the arm 12 in the axis of the crosspiece 14. This section will be described below. section 36 free.

In FIG. 3, the delimitation between the two sections 34, 36 has been represented by a broken line.

The inserted section 34 of the metal part 32 has a geometry which allows a connection to create an embedding type connection which is resistant and durable between the metal part 32 and the arm 12.

In the example shown in Figure 3, the metal part 32 generally has the shape of a profile extending along a main transverse axis "C". The profile is however likely to have dimensions that gradually reduce from the inserted section 34 towards the free end of the free section 36 to facilitate its embedding in the crosspiece 14, as will be explained later.

The metal part 32 thus has a wall 38 which, in vertical longitudinal section, has an open profile, for example in the shape of a "U" open longitudinally towards the front. Thus, the inserted section 34 has a flat vertical strip from the ends of which extend longitudinally forwards two flat wings. The wall 38 of the inserted section 34 thus has an external face 38A, facing in a direction opposite to the axis "C", and an internal face 38B, facing towards the axis "C".

The wall 38 of the metal part 32 advantageously has a greater thickness than that of the wall of the crosspiece 14. This makes it possible to give the metal part 32 rigidity and sufficient resistance to transmit the forces between the arm 12 and the crosspiece 14 .

To allow a solid and resistant connection between the arm 12 and the metal part 32 at the end of step "E4" of molding, at least one of the faces 38A, 38B of the wall 38 is equipped with reliefs, in projecting or recessed, allowing the mechanical connection with the material of the arm 12 molded on said reliefs.

More particularly, at least one orifice 40 passing right through the wall 38 of the inserted section 34 is made on the metal part 32 prior to step "E4" of molding. Advantageously, the wall 38 of the inserted section 34 of the metal part 32 comprises several orifices 40 which are distributed along the profile.

The orifices 40 are arranged at a distance from an edge 42 of the free transverse end of the section 34 inserted. Thus, each orifice 40 is delimited by a closed contour.

The orifices 40 here have a rectangular contour. As a variant, the orifices can also have other shapes, for example a circular shape.

The orifices 40 are made during a step "E1" of openwork by a machining operation such as drilling, cutting or punching.

During a forming step "E2", the metal part 32, first of all in the form of a flat plate, undergoes a forming operation, by bending or by stamping, to be shaped into a metal part 32 profiled. The openwork step "E1" is advantageously carried out before the forming step "E2". This makes it possible to simplify step "E1" of openwork.

Then, during step "E3" of molding, the inserted section 34 is received in a molding cavity of the arm 12, while the free section 36 remains outside the molding cavity.

Then, the arm 12 is produced by injecting the aluminum-based material in the liquid state into the molding cavity. The wall 38 of the inserted section 34 is kept at a distance from the internal surface of the cavity so that the wall 38 is entirely taken in the aluminum-based material during its solidification. Thus, the two faces 38A, 38B of the wall are each in contact with a layer 42A, 42B of aluminum-based material.

During this injection operation, the aluminum-based material fills the orifices 40 to join the two layers of aluminum-based material on either side of the wall 38. When the aluminum-based material solidifies, the material contained in the orifices 40 forms bridges 42C which connect the two layers 42A, 42B of material. The bridges 42C act as rivets which firmly hold the metal part 32 in position relative to the arm 12.

Each arm 12 thus equipped with the associated metal part 32 is then fixed to an associated end section 30 of the crosspiece 14 during an assembly step “E4”.

More particularly, the tubular crosspiece 14 opens transversely in both directions through an opening 44 located at each of its two end sections 30 .

Step "E4" of assembly on the crosspiece 14 is the same for both arms 12. It will be described for one of the arms 12, the description being applicable to the other arm 12 by symmetry.

The metal part 32 has a profile which is complementary to that of the opening 44 so that the free section 36 can be embedded transversely in the opening 44 until the edges of the opening 44 are in contact with the outer face 38A of the wall 38 of the section 36 free.

The metal part 32 is then fixed to the crosspiece 14 by welding. More particularly, a weld bead is formed along the line of contact between the edge of the opening 44 of the crosspiece 14 and the outer face 38A of the wall 38 of the free section 36 .

The fixing method thus makes it possible to obtain an axle 10 fitted with arms 12 made of an aluminum-based material which are easy to fix to the crosspiece 14 made of steel.

The connection between the arms 12 and the crosspiece 14 advantageously has great strength and great endurance.

In addition, the assembled axle 10 remains extremely light.

Claims (10)

Method for assembling a longitudinal arm (12) of an axle (10) for a motor vehicle on a metal part (32) comprising a step of molding the arm (12) in an incompatible material for welding with the material constituting the metal part (32),
characterized in that during the step (E3) of molding, the arm (12) is molded over a first section (34) of the transverse end of the metal part (32), said section (34) inserted, a second end section (36) of the metal part (32), said free section (36), projecting transversely from the arm (12). Method according to the preceding claim, characterized in that the inserted section (34) of the metal part (32) has a wall (38) shaped as a profile with a transverse axis (C). Method according to the preceding claim, characterized in that at least one of the faces (38A, 38B) of the wall (38) of the inserted section (34) is equipped with reliefs prior to the molding step, to allow the mechanical connection with the material of the arm (12) molded on said reliefs. Method according to Claim 3, characterized in that the wall (38) of the inserted section (34) of the metal part (32) comprises at least one through orifice (40). Method according to the preceding claim, characterized in that the inserted section (34) of the metal part (32) comprises several orifices (40) distributed along the profile. Method according to any one of the preceding claims, characterized in that the arm (12) is made of a metallic material based on aluminium. Method according to any one of the preceding claims, characterized in that the metallic part (32) is made of a metallic material based on iron, such as steel. Axle (10) for a motor vehicle comprising:
- A tubular crosspiece (14) with transverse axis (B) which is elastically deformable in torsion, the crosspiece (14) being made of steel;
- two longitudinal parallel arms (12), each of which is intended to be fixed to a body of the motor vehicle and each of which is rigidly fixed to a transverse end of the crosspiece (14),
characterized in that the arms (12) are fixed to a metal part (32) by overmolding according to any one of the preceding claims, the arms (12) being fixed to the crosspiece (14) via the part ( 32) metallic. Axle (10) according to the preceding claim, characterized in that each arm (12) is fixed to the associated end of the crosspiece (14) by welding the free section (36) of the metal part (32) with the crosspiece ( 14). Axle (10) according to the preceding claim, characterized in that the free section (36) of the metal part (32) is embedded in an opening (44) at the end of the crosspiece (14) before being fixed by welding. .