Method for manufacturing an axle arm and axle arm thus produced

Abstract

The invention relates to a method for manufacturing an axle arm (2, 3) comprising the following steps: - providing a reinforcement (17); - inserting a rod (33) of a positioning guide (34) into a hole (20) in the reinforcement (17) and then positioning and holding the reinforcement (17) relative to a pre-formed sheet (22) by means of said positioning guide (34) and a locking member; - shaping the pre-formed sheet (22) to form an axle arm (2, 3) having a tubular structure around the reinforcement (17) while said reinforcement (17) is held in position relative to the pre-formed sheet (22) by the positioning guide (34); and - welding the reinforcement (17) inside said tubular structure. Figure to be published with the abbreviation: Fig. 6

Description

Title of the invention: Method for manufacturing an axle arm and axle arm thus produced

[0001] The invention relates to the field of motor vehicles.

[0002] The invention relates more specifically to an axle arm, in particular for a flexible rear axle of a motor vehicle and a method of manufacturing such an axle arm.

[0003] A flexible rear axle, also called a deformable axle or semi-rigid axle, is a component commonly used in motor vehicles. The flexible axle is generally associated with coil springs and shock absorbers that work together to absorb shocks and maintain vehicle stability.

[0004] The flexible axle comprises two axle arms, each connecting one of the rear wheels to the body, and a torsion beam connecting the two axle arms to each other. Each axle arm is equipped with an axle head, which is welded to said axle arm and serves as a mounting point for a wheel bearing.

[0005] To ensure their lightness, axle arms are generally made from sheet metal. To obtain the desired shape, the sheet metal is first bent to create a tubular structure. Then, the edges of the sheet metal are welded together to ensure the complete closure of the tubular structure section.

[0006] The axle head comprises a mounting flange having openings for receiving fasteners to secure the wheel bearing to the axle head and two mounting wings, folded perpendicularly to the mounting flange, which allow the axle head to be welded to the axle arm. Each of the mounting wings has a contact edge with a concavity that is complementary to the convexity of the axle arm and along which the axle head is fixed to the axle arm.

[0007] It was found that the loads applied to the axle heads caused punching deformations of the axle arms, particularly in the area where the axle head fixing wings are welded to the axle arm.

[0008] To prevent such deformations, it is known to reinforce this area of ​​the axle arm. One approach is to weld a reinforcement inside the longitudinal arm to remedy the punching problem. However, this is only possible if the tubular cross-section of the axle arm is sufficiently large, because otherwise there is not enough space to install a tool to hold the reinforcement in position during welding and to maneuver the welding torch. An alternative approach is to add reinforcements to the outside of the longitudinal arm by connecting them at the axle head. However, this solution is difficult to implement due to a very constrained environment, involving the passage of the wheel bearing fixing screws to the axle head, the clearance required for the passage of the fixing screw mounting tools, as well as the freedom of movement of the spring, the shock absorber, and the routing of the brake cables.

[0009] Also, a problem which arises and which the present invention aims to solve is to provide a method for manufacturing an axle arm which is simple to implement and which makes it possible to produce an axle arm which is more resistant to deformations.

[0010] In order to solve this problem, and according to a first object, a method for manufacturing an axle arm is proposed comprising the following steps: - provide a reinforcement comprising at least one locking member and a through hole; - insert a rod of a positioning guide into the hole of the reinforcement and then position and hold the reinforcement relative to a pre-formed sheet metal by means of said positioning guide and the locking member; - shaping the preformed sheet metal to form an axle arm having a tubular structure around the reinforcement while said reinforcement is held in position relative to the preformed sheet metal by the positioning guide and by the locking device; the locking device restricting or blocking a rotation of the reinforcement around the rod and / or a translation of the reinforcement along the rod; - weld the longitudinal edges of the formed sheet metal to close the tubular structure; - remove the positioning guide; and - weld the reinforcement inside said tubular structure.

[0011] Thus, the reinforcement is integrated into the tubular structure of the axle arm during its shaping, which simplifies the manufacture of said axle arm. The reinforcement is then welded to said tubular structure while the positioning guide is removed, which allows the passage of the welding torch even when the tubular structure has smaller dimensions.

[0012] According to embodiments, such an axle arm may include one or more of the following characteristics.

[0013] According to one embodiment, the reinforcement is made of metal.

[0014] According to one embodiment, the preformed sheet metal has a U-shaped cross-section with two branches, the reinforcement being positioned in a plane of said section between the branches of the U.

[0015] According to one embodiment, the process further includes a shaping step, in particular by stamping, of a flat sheet in order to form the preformed sheet having the U-shaped cross-section.

[0016] According to one embodiment, the reinforcement is fixed to the tubular structure by one or more weld points before removing the positioning guide and then welding The reinforcement is attached inside the tubular structure by means of one or more weld lines, each formed along an edge of the reinforcement. This prevents any movement of the reinforcement within the tubular structure before and during its attachment to the tubular structure by welding.

[0017] According to one embodiment, the locking member is a tab that protrudes from a body of the reinforcement and the preformed sheet metal has a slot and the tab is fitted into the slot when positioning the reinforcement relative to the preformed sheet metal.

[0018] According to another embodiment, the locking member comprises at least one edge of said reinforcement and the preformed sheet metal comprises a groove and said edge is embedded in the groove when positioning the reinforcement relative to the preformed sheet metal.

[0019] According to yet another embodiment, the locking member comprises a first folded tab formed along a first edge of said reinforcement.

[0020] According to an advantageous variant of said embodiment, the reinforcement comprises a second locking member, the second locking member comprising a second folded tab formed along a second edge of the reinforcement which is opposite the first edge.

[0021] According to one embodiment, the first folded leg and the second folded leg are oriented in the same direction.

[0022] According to another embodiment, the first folded leg and the second folded leg are respectively oriented in two opposite directions.

[0023] According to one embodiment, the reinforcement has a body that conforms to an internal profile of the tubular structure. This ensures better resistance to stress.

[0024] According to one embodiment, the positioning guide rod has a shoulder and the positioning guide rod is inserted into the hole in the reinforcement until the reinforcement butts up against the shoulder.

[0025] According to a second aspect, the invention relates to an axle arm obtained by the aforementioned process.

[0026] Such an axle arm comprises a tubular structure and a reinforcement welded inside the reinforcement structure; said reinforcement comprising a through hole and at least one locking member, said locking member being capable of restricting or blocking a rotation of the reinforcement around an axis of the hole and a translation along the axis of the hole before the reinforcement has been welded to the reinforcement structure.

[0027] According to one embodiment, the axle arm further comprises an axle head having a mounting flange, a rear mounting wing, and a front mounting wing; the mounting flange having openings, each intended to receive a fastener for attaching a wheel support member to the axle head; the front mounting wing and the rear mounting wing being folded relative to to the mounting flange and having a berthing edge having a concavity in which the tubular structure of the axle arm is at least partially inserted and along which said berthing edge is welded to said tubular structure; the reinforcement being positioned at the rear fixing wing of the axle head.

[0028] Thus, the reinforcement ensures a strengthening of the axle arm in the area where the stresses are, in operation, the greatest.

[0029] Other features and advantages of the invention will become apparent from the following description of particular embodiments of the invention, given by way of example but not limitation, with reference to the accompanying drawings in which:

[0030] [Fig-1] is a top view of a rear flexible axle of a motor vehicle;

[0031] [Fig.2] is a side perspective view of an axle arm equipped with a head axle.

[0032] [Fig.3] is a rear view of an axle arm equipped with an axle head according to the prior art, i.e. without reinforcement in the area in which the rear fixing wing is welded to the tubular structure of the axle arm.

[0033] [Fig.4] is a schematic perspective view of an axle arm equipped with a reinforcement.

[0034] [Fig.5] illustrates a reinforcement equipped with a locking device according to a first embodiment.

[0035] [Fig.6] is a diagram illustrating the different stages of the manufacturing process of the axle arm.

[0036] [Fig.7] is a schematic view illustrating a positioning guide whose rod is inserted into a hole in a reinforcement.

[0037] [Fig.8] illustrates a reinforcement equipped with a locking device according to a second embodiment.

[0038] [Fig.9] illustrates a reinforcement equipped with a locking device according to a third embodiment.

[0039] [Fig. 10] illustrates a reinforcement equipped with a locking device according to a fourth embodiment.

[0040] The orientations expressed in the description are given with reference to an orthonormal XYZ frame, shown in the figures, in which X represents the longitudinal direction, oriented from the front to the rear of the vehicle, Y the transverse direction oriented towards the right of the vehicle, and Z the vertical direction oriented towards the top of the vehicle in usual position, resting on its wheels.

[0041] Fig. 1 represents a flexible axle 1 of a rear axle of a motor vehicle. It has an H-shaped structure.

[0042] The axle 1 has two axle arms 2, 3. One end of each axle arm 2, 3, namely its front end 4, is articulated to the vehicle body via An elastic joint 5. Such an elastic joint 5 comprises, for example, an elastomer ring mounted radially between two metal rings. It thus allows limited rotation of the axle arms 2, 3 relative to the body while filtering vibrations and shocks.

[0043] The axle arms 2 and 3 are connected to each other by a cross member 6. The cross member 6 is designed to deform in torsion, particularly when the vehicle encounters irregularities in the road, which allows for limited relative movement of the rear wheels with respect to each other. This improves ride comfort by reducing the impact of bumps and potholes.

[0044] Each axle arm 2, 3 is equipped with a suspension cup 7 which is welded to said axle arm 2, 3 and which supports one end of one of the suspension springs 8. Each axle arm 2, 3 is also equipped with a mounting bracket, not shown, to which is attached one end of a suspension damper, also not shown.

[0045] Each of the axle arms 2, 3 is also equipped with an axle head 9, shown in figures 2 and 3, which is intended to secure a wheel bearing to said axle arm 2, 3.

[0046] The axle head 9 is made of metal, preferably steel, and is attached and welded to the axle arm 2, at a rear end of said axle arm 2. The axle head 9 has a mounting flange 10 which serves as a fixing point for the wheel bearing and has, for this purpose, holes 15 intended to receive fixing elements, not shown.

[0047] The mounting flange 10 extends in a longitudinal plane, perpendicular to the geometric axis of rotation of the wheel. The axle head 9 further comprises, on either side of the mounting flange 10, two fixing wings 11, 12, which allow the axle head 9 to be welded to the axle arm 2. The two fixing wings 11, 12 extend in planes substantially perpendicular to the plane of the mounting flange 10. The fixing wings 11, 12 each have a contact edge 13 which has a concavity complementary to the convexity of the axle arm 2. This concavity allows a part of the cross-section of the axle arm 2 to fit into the fixing wings 11, 12. The fixing wings 11, 12 are welded to the axle arm 2 along said concavity of the contact edge 13, for example by arc welding.

[0048] In the illustrated embodiment, the axle head 9 also includes a tab 14 which is folded under the axle arm 2, thus providing an additional support point and reinforcing the structure of the assembly. The tab 14 is advantageously welded to the lower portion of the axle arm 2.

[0049] Furthermore, as illustrated in Figures 2 and 3, the axle head 9 can be equipped with a reinforcing plate 16, made of metal, which notably increases the rigidity and strength of the axle head 9.

[0050] To reinforce it and prevent deformations in the area where the axle head 9 is welded, the axle arm 2, 3 is equipped with a reinforcement 17, as shown in [Fig.4],

[0051] The reinforcement 17 is preferably made of metal and, for example, of steel. It is placed inside the tubular section of the axle arm 2, 3, more precisely in the area where the axle head 9 is fixed, and optimally at the rear fixing flange 12, i.e. in the area where the forces exerted are greatest.

[0052] This reinforcement 17 extends vertically from one edge to the other of the tubular section. In other words, it is in contact with both the upper and lower parts of the tubular section of the axle arm 2, 3. The reinforcement 17 thus increases the resistance of the axle arm 2, 3 to compression, and more particularly to punching shear, against the localized forces exerted vertically by the axle head 9 on the axle arm 2, 3.

[0053] According to an advantageous embodiment, the body of the reinforcement 17, i.e., its effective compression portion, adopts a shape complementary to that of the tubular section. Thus, this configuration allows for optimal force distribution, ensuring better resistance to applied stresses and optimal integration within the axle arm 2, 3.

[0054] The reinforcement 17 is integrated into the axle arm 2, 3 during its forming process. In order to allow such integration into the axle arm 2, 3 during its forming, the reinforcement 17 is equipped, on the one hand, with a through hole 20, and on the other hand with one or more locking members which are configured to prevent or limit the movement of the reinforcement during the forming of the axle arm 2 as well as subsequently when it is welded to said axle arm 2, 3.

[0055] A reinforcement 17 according to a first embodiment is shown in [Fig.5]. In this embodiment, the locking member has a tab 18 which projects from the body of the reinforcement 17 and which is intended to fit into a slot 19 provided in the axle arm 2, 3.

[0056] Furthermore, the reinforcement 17 also has a through hole 20. As schematically shown in [Fig. 7], this hole 20 is for the passage of a rod 33 of a positioning guide 34. This positioning guide 34, as will be explained in more detail later, is used during the forming of the axle arm 2. The rod 33 is a shouldered rod, that is to say, it has a shoulder that bears against one of the faces of the reinforcement 17.

[0057] Thus, the positioning guide 34 allows the reinforcement 17 to be positioned relative to the positioning guide 34 by offering two degrees of translational constraint along axes perpendicular to that of the rod 33 and a restriction of the degree of freedom in translation along the X-axis. However, the positioning guide 34 does not modify the rotational degree of freedom of the reinforcement 17 around the rod 33 and does not completely block its translation along the rod 33. Thanks to the locking member, i.e. in the embodiment of [Fig. 5], the tab 18 which fits into the slot 19, these degrees of freedom are eliminated, thus immobilizing the reinforcement 17 relative to the axle arm 2 during forming.

[0058] A method for manufacturing an axle arm 2, 3 incorporating such a reinforcement 17 will now be described with reference to [Fig. 6]. A flat sheet 21, previously provided with the slot 19 intended to receive the tab 18 of the reinforcement 17, is first supplied and undergoes a first forming step to acquire a semi-tubular cross-section, i.e., a U-shaped cross-section. This operation is carried out by stamping the sheet 21 between a punch and a die whose U-shaped cross-sections are complementary.

[0059] Next, the reinforcement 17 is mounted on the rod 33 of the positioning guide 34, not shown in [Fig.6], so that one of its faces is in contact with the shoulder of the rod 33 and the locking member of the reinforcement 17 is positioned relative to the preformed sheet 22, which implies, in the embodiment of [Fig.5], the insertion of the tab 18 of the reinforcement 17 into the slot 19.

[0060] The pre-formed sheet metal 22 is then subjected to one or more forming steps until the final shape 23 of the axle arm is obtained. The sheet metal is thus wrapped around the reinforcement 17.

[0061] Welding operations are then carried out. The longitudinal edges 24, 25 of the sheet metal are fixed together by a weld 26 to ensure complete closure of the tubular section of the axle arm 2, 3, as illustrated in dotted lines on [Fig.6].

[0062] The reinforcement 17 is also welded inside the tubular structure of the axle arm 2, 3 by one or more weld lines 27.

[0063] In a preferred embodiment, the reinforcement 17 is first attached to the axle arm 2 by one or more spot welds, while the positioning guide 34 is still in place. Subsequently, the positioning guide 34 is removed to provide sufficient space for one or more weld lines 27 that securely join the reinforcement 17 to the axle arm 2.

[0064] A reinforcement 17 according to a second embodiment is shown in [Fig.8]. This reinforcement 17 differs from that described previously in connection with [Fig.5] in that it lacks a tongue 18. However, at least one of the edges 35 of the reinforcement 17 is embedded in a groove 28 formed in the sheet metal intended to form the tubular structure of the axle arm 2, 3.

[0065] A reinforcement 17 according to a third embodiment is shown in [Fig.9]. In this embodiment, the reinforcement 17 has two folded tabs 29, 30 which are formed respectively along two opposite edges of said reinforcement 17. The folded tabs 29, 30 are oriented in the same direction. The folded tabs 29, 30 are advantageously positioned respectively against one and the other of the two arms of the U of the semi-tubular section of the pre-formed sheet 22. They then generate frictional forces against the axle arm 2, 3, thus limiting the rotational movements of the reinforcement 17 around the rod 33 of the positioning guide 34 or translational movements along the rod 33 during the forming of the axle arm 2, 3.

[0066] A reinforcement 17 according to a fourth embodiment is shown in [Fig. 10]. It differs from the third embodiment of [Fig.8] only in that the folded legs 31, 32 are oriented in opposite directions whereas they are oriented in the same direction on [Fig.8].

[0067] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0068] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0069] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Method of manufacturing an axle arm (2, 3) comprising the following steps: - providing a reinforcement (17) comprising at least one locking member (18, 35, 29, 30, 31, 32) and a through hole (20); - inserting a rod (33) of a positioning guide (34) into the hole (20) of the reinforcement (17) and then positioning and holding the reinforcement (17) relative to a preformed sheet (22) by means of said positioning guide (34) and the locking member (18, 35, 29, 30, 31, 32); - shaping the preformed sheet metal (22) to form an axle arm (2, 3) having a tubular structure around the reinforcement (17) while said reinforcement (17) is held in position, relative to the preformed sheet metal (22), by the positioning guide (34) and by the locking member (18, 35, 29, 30, 31, 32); the locking member (18, 35, 29, 30, 31, 32) restricting or blocking a rotation of the reinforcement (17) around the rod (33) and / or a translation of the reinforcement (17) along the rod (33);- weld the longitudinal edges (24, 25) of the tubular structure to close it; - remove the positioning guide (34); and - weld the reinforcement (17) inside said tubular structure.

2. A manufacturing method according to claim 1, wherein the preformed sheet (22) has a U-shaped cross-section with two arms and wherein the reinforcement (17) is positioned in a plane of said cross-section between the arms of the U.

3. A manufacturing method according to claim 1 or 2, wherein the reinforcement (17) is fixed to the tubular structure by one or more weld points before removing the positioning guide (34) and then the reinforcement (17) is welded inside the tubular structure by means of one or more weld lines (27) each formed along an edge of said reinforcement (17).

4. A manufacturing method according to any one of claims 1 to 3, wherein the locking member is a tab (18) projecting from a body of the reinforcement (17) and the preformed sheet (22) has a slot (19), and wherein the tab (18) is embedded in the slot (19) during the positioning of the reinforcement (17) relative to the preformed sheet (22).

5. A manufacturing method according to any one of claims 1 to 3, wherein the locking member comprises at least one edge (35) of said reinforcement (17) and the preformed sheet (22) comprises a groove (28) and wherein said edge (35) is embedded in the groove (28) when positioning the reinforcement (17) relative to the preformed sheet (22).

6. A manufacturing method according to any one of claims 1 to 3, wherein the locking member comprises a first folded tab (29, 31) formed along a first edge of said reinforcement (17).

7. A manufacturing method according to claim 6, wherein the reinforcement (17) comprises a second locking member, the second locking member comprising a second folded tab (30, 32) formed along a second edge of the reinforcement (17) which is opposite the first edge.

8. A manufacturing method according to any one of claims 1 to 7, wherein the rod (33) of the positioning guide (34) has a shoulder and wherein the rod (33) of the positioning guide (34) is inserted into the hole (20) of the reinforcement (17) until said reinforcement (17) comes to rest against the shoulder.

9. Axle arm (2, 3) obtained by a method according to any one of claims 1 to 8.

10. Axle arm (2, 3) according to claim 9, further comprising an axle head (9) having a mounting flange (10), a rear fixing wing (12) and a front fixing wing (11); the mounting flange (10) having openings (15) which are each intended to receive a fixing member for fixing a wheel support member to the axle head (9); the front fixing wing (11) and the rear fixing wing (12) being folded back from the mounting flange (10) and having a landing edge (13) having a concavity in which the tubular structure of the axle arm (2, 3) is at least partially inserted and along which said landing edge (13) is welded to said tubular structure; and in which the reinforcement (17) is positioned opposite the rear fixing wing (12) of the axle head (9).

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