Low carbon lower suspension arm

Abstract

The invention relates to a front lower suspension arm (16) of a motor vehicle, comprising a rear arm (20) having a rear end (26) adapted to be connected to a cradle of said motor vehicle and a forearm (22) substantially bent relative to said rear arm (20) by forming an elbow (24), said forearm (22) having a front end (28) adapted to be connected to a wheel support of said motor vehicle, while said elbow (24) is adapted to be connected to said cradle. The arm (16) comprises two first steel bar sections (32, 30) connected together to form said rear arm (20) and two second steel bar sections (34, 36) connected together to form said forearm (22). Figure to be published with the abstract: Fig. 2A

Description

Title of the invention: Low carbon lower suspension arm

[0001] The present invention relates to a low carbon front lower suspension arm for a motor vehicle.

[0002] The front lower suspension arms are among the essential elements of pseudo-McPherson type suspensions, commonly used on motor vehicles.

[0003] They are mounted articulated on the front cradle of the vehicle, on the right and on the left, and they receive at their end a wheel support or spindle.

[0004] Each of the arms comprises a rear arm having a rear end and a forearm bent relative to the rear arm and ending in a front end. Thus, the arm is connected to the cradle via the rear arm at its rear end and the elbow, while the front end of the forearm is equipped with a wheel support.

[0005] The arms are usually made from a main shell stamped from a steel plate and an additional reinforcement piece welded inside the shell. In addition, a socket is advantageously welded at the elbow to enable it to be pivotally mounted on the cradle.

[0006] Reference may be made to document EP 794 075, which describes such a lower suspension arm.

[0007] The steels used are then hot-rolled steels. And the hot-rolling process for steels requires the use of materials with recycled content rates of less than 30%. However, the more recycled material is used in steels, the fewer greenhouse gases are produced.

[0008] Consequently, manufacturing front suspension arms while reducing the emission of greenhouse gases equivalent to CO2> comes up against the rate of recycled material usable in steel.

[0009] Also, a problem which arises and which the present invention aims to solve is precisely to provide front suspension arms for which the emission of CO2 equivalent greenhouse gas has been reduced.

[0010] In order to solve this problem, a front lower suspension arm of a motor vehicle is proposed, comprising a rear arm having a rear end adapted to be connected to a cradle of said motor vehicle and a forearm substantially bent relative to said rear arm forming an elbow, said forearm having a front end adapted to be connected to a wheel support of said motor vehicle, while said elbow is adapted to be connected to said cradle.

[0011] And the suspension arm comprises two first sections of steel bar connected together to form said forearm and two second sections of steel bar connected together to form said forearm.

[0012] Thus, a characteristic of the invention lies in the use of steel bar sections. In other words, steel wire is used in bars, originating from the steel industry of "long products", and not from the steel industry of "flat products" where steel strips are obtained by rolling. The steel industry of "flat products" emits overall much more CO2 equivalent greenhouse gases than that of "long products", because it tolerates much less recycled materials.

[0013] Advantageously, the first and second sections of steel bar are forged so as to give them a particular shape.

[0014] According to the invention, the suspension arm comprises a plurality of third sections respectively connecting together said first and second sections. Thus, the first two sections of steel bar and the two second sections of steel bar are connected together by means of third sections which are welded. And these third sections are welded between the first and second sections, in predefined zones to be able to take up the mechanical stresses which are exerted on the suspension arms.

[0015] Furthermore, according to the invention, said first two sections and said second two sections are preferably substantially identical. In this way, the suspension arms are produced with standard elements. Consequently, the manufacturing costs of these arms are reduced.

[0016] Furthermore, according to a particularly advantageous characteristic of the invention, said first two sections and said second two sections are bent. They are for example bent during forging. The advantages of such bending will be explained in more detail in the following description.

[0017] In addition, the third sections of said plurality of third sections are advantageously curved. However, the third sections are shorter than the first and second sections. And they are advantageously all identical, so as to minimize the number of types of parts necessary for producing the suspension arms.

[0018] According to a particularly advantageous embodiment of the invention, one of said two first sections of steel bar extends in the extension of one of said two second sections of steel bar, while the other of said two first sections extends in the extension of the other of said two second sections. Preferably, said one of said two first sections and said one of said two second sections are connected together by weld beads. Also, said other of said two first sections and said other of said two second sections are also connected together by weld beads.

[0019] Furthermore, and as will be explained in more detail in the remainder of the description, said one of said two first sections and said one of said two second sections of steel bar define an extrados of the suspension arm, while said other of said two first sections and said other of said two second sections define a intrados.

[0020] According to a particularly advantageous embodiment of the invention, said one of said two first sections and said one of said two second sections are respectively coupled to two fourth sections of steel bar. The sections are advantageously coupled by means of weld beads. In this way, the suspension arm is substantially reinforced on its extrados side.

[0021] According to another variant, said other of said two first sections and said other of said two second sections are respectively coupled to two fifth sections of steel bar. The sections are preferably coupled by means of weld beads. In this way, the suspension arm is reinforced on the intrados side.

[0022] Furthermore, said rear end of said rear arm comprises an annular attachment having a first axis of symmetry substantially perpendicular to said rear arm, while said elbow comprises a tubular attachment having a second axis of symmetry substantially perpendicular to said first axis of symmetry. In this way, the rear end of the rear arm is mounted on the cradle in a vertical tenon. And the elbow is itself secured to the cradle in a horizontal tenon. It will be observed that the tenons advantageously take the form of a silentbloc.

[0023] As regards the steel of the steel bar sections, a bainitic type steel containing up to 0.30% carbon will be chosen, for example. Such a steel is then easily forged, and in addition, given its low carbon content, it is easily weldable. In this way, the sections can be forged and then more easily welded.

[0024] In addition, the steel for the sections comes from a long steel supply chain that allows the use of 50% to more than 80% recycled material. As a result, the "carbon footprint" of such steel is much lower compared to that of flat steel.

[0025] Other features and advantages of the invention will emerge from reading the description given below of particular embodiments of the invention, given for informational but non-limiting purposes, with reference to the appended drawings in which:

[0026] [Fig.l] is a partial schematic top view of a motor vehicle equipped with the subject of the invention;

[0027] [Fig.2A] is a schematic top view of the object of the invention according to a first embodiment;

[0028] [Fig.2B] is a schematic sectional view of the object of [Fig.2A] according to plane IIB - IIB;

[0029] [Fig.3A] is a schematic top view of the object of the invention according to a second embodiment;

[0030] [Fig.3B] is a schematic sectional view of the object of [Fig.3A] along plane IIIB - IIIB;

[0031] [Fig.4A] is a schematic top view of the object of the invention according to a third embodiment; and,

[0032] [Fig.4B] is a schematic sectional view of the object of [Fig.4A] along the plane IVB - IVB.

[0033] [Fig.l] partially shows the left front top of a motor vehicle 10, and it is inscribed in an orthogonal reference frame X, Y, Z, in which the X axis extends in a front-rear longitudinal direction of the motor vehicle, oriented towards the rear; the Y axis extends in a transverse direction of the vehicle, oriented from left to right when in a rolling situation; and the Z axis extends in a vertical direction, oriented away from the ground.

[0034] [Fig.l] schematically shows a chassis element 12 and a bodywork element 14 of the motor vehicle. Also, the chassis element 12 receives a left front lower suspension arm 16, making it possible to connect a left front wheel 18 and the chassis element 12.

[0035] The left front suspension arm 16 will be described in detail with reference to [Fig.2A] and [Fig.2B].

[0036] It comprises a rear arm 20 extended by a forearm 22. The rear arm 20 and the forearm 22 extend in directions substantially inclined relative to each other and thus define an elbow 24.

[0037] Also, the rear arm 20 has a rear end 26, while the forearm 22 has a front end 28.

[0038] And according to the invention, the rear arm 20 is formed from two first sections of steel bar 30, 32, and the forearm 22 is formed from two second sections 34, 36 of steel bar.

[0039] Steel bars come from the steel industry of "long products", and consequently, can incorporate a high percentage of recycled steel products, commonly called: "scrap". This percentage of recycled steel products can be greater than 50%, and go up to 80%. Consequently, the greenhouse gas emissions to implement these steel products are much lower than the steel products directly derived from iron ore and with which "flat products" are produced.

[0040] As regards the steel bar intended to produce the first and second sections, a bainitic type steel will be chosen, for example. In the range of steels of this type type, we will choose for example a bainitic type steel. From the range of steels of this type, we will choose one including for example: up to 0.30% carbon, 0.25% silicon, 1.00% manganese, 0.50% nickel, 1.00% molybdenum and 0.10% niobium. Such a steel is then easily forged, and moreover, given its low carbon content, it is easily weldable. In this way, the sections can be forged and then more easily welded.

[0041] Also, the bar from which the first 30, 32 and second 34, 36 sections are made has a diameter of between 15 mm and 25 mm, for example 20 mm. And furthermore, the first 30, 32 and second 34, 36 sections are all identical. They are curved, and their average radius of curvature is for example between 60 cm and 80 cm.

[0042] Thus, the first two 30, 32 sections are spaced apart from each other and are arranged substantially in the same plane Pm, as illustrated in [Fig.2B]. Also, they are oriented in such a way that their curvatures are in the same direction. In other words, their center of curvature is located on the same side of the rear arm 20.

[0043] Furthermore, the first two sections 30, 32 converge substantially towards each other from the elbow 24 towards the rear end 26.

[0044] The second sections 34, 36 extend respectively in the extension of the first sections 30, 32, converging themselves, from the elbow 24 towards the front end 28. They extend in the same plane as that defined by the first sections 30, 32.

[0045] Furthermore, the first 30, 32 and second 34, 36 sections are connected together by means of four third steel bar sections 40, 42, 44, 46.

[0046] The steel of the steel bar intended to produce the third sections is, for example, the same steel as that of the bar intended to produce the first 30, 32 and second 34, 36 sections. On the other hand, the diameter of the steel bar is smaller and it extends, for example, between 8 mm and 15 mm. In addition, the third sections 40, 42, 44, 46, all substantially identical, are shorter than the first 30, 32 and second 34, 36 sections. For example, their length is substantially equal to a quarter of the length of the first 30, 32 and second 34, 36 sections. In addition, they are also curved. Their radius of curvature is, for example, between 20 cm and 50 cm.

[0047] Among the four third steel bar sections 40, 42, 44, 46, a first 40 is connected by welding to the first two sections 30, 32. It substantially connects their middle parts together. Also, the concavity of the first third section 40 is oriented towards the rear end 26.

[0048] A second third section 42, oriented in the same way as the first third section 40, is connected by welding, both to the first 30, 32 and second 34, 36 sections at the elbow 24. In other words, the second third section 42 is connected to the two ends of the first 30, 32 and second 34, 36 sections.

[0049] The third third section 44 connects together one 32 of the first sections and one 36 of the second sections, which form an extrados 48 of the suspension arm 16. It is welded to the two ends of these first 32 and second 36 sections and extends projecting from the extrados 48.

[0050] Also, the convex part of the third third section 44 extends towards the inside of the arm 16.

[0051] The fourth third section 46 extends between the two second sections 36, 34 to which it is connected by welding. It is oriented so that one of its ends is connected to one 36 of the second sections while its convex part is connected to the other 34 of the second sections and its other end is connected to the second third section 42.

[0052] The first 30, 32 and second 34, 36 sections as well as the third sections 40, 42, 44, 46 extend substantially in the same plane and they form the same rigid part.

[0053] Furthermore, the rear end 26 of the rear arm 20 is provided with an annular attachment 50 to which the first two sections 30, 32 are welded. The annular attachment 50 has a first axis of circular symmetry A, substantially perpendicular to the mean plane defined by the first 30, 32, the second 34, 36 and the third 40, 42, 44, 46 sections. This mean plane corresponds to the plane of the figure.

[0054] In addition, a tubular attachment 52 is connected by welding to the third third section 44, outside the first 30, 32 and second 34, 36 sections, at the elbow 24. The tubular attachment 52 has a second axis of circular symmetry B, which is substantially perpendicular to the first axis of circular symmetry A. In addition, this second axis of circular symmetry B extends substantially in the mean plane defined by the first 30, 32, the second 34, 36 and the third 40, 42, 44, 46 sections.

[0055] Furthermore, the front end 28 of the forearm 22 is provided with a fixing plate 54, welded to the two ends of the two second sections 34, 36. The fixing plate 54 extends substantially in the aforementioned mean plane.

[0056] Thus, the tubular attachment 52 is pivotally mounted, towards the front of the chassis 12 as illustrated in [Fig.l] and along an axis substantially parallel to the longitudinal axis of the vehicle 10. The annular attachment 50 is mounted on the chassis 12, towards the rear, so that its axis of symmetry A is oriented substantially vertically. And the fixing plate 54 is connected to the wheel support 18.

[0057] We will refer to [Fig.3A] and [Fig.3B] illustrating, according to another mode of implementation, all the elements of the object of [Fig.2A], which will present the same re references affected by a prime sign: "'", with in addition a doubling, of one 32' of the first sections, of one 36' of the second sections and of the third third section 44'.

[0058] Thus, said one 32' of the first sections, on the extrados 48', is doubled by a second first section 56. This second first section 56 extends parallel and above said one 32' of the first sections, as illustrated in [Fig.3B]. It is connected there for example by welding.

[0059] In the same way, said one 36' of the second sections is doubled by a second parallel second section 58 and also extending above.

[0060] And furthermore, the third third section 44', connecting together said one 32 of the first sections and said one 36 of the second sections, is itself doubled by another third third section 60 connecting the second second 58 and second first sections 56.

[0061] In this way, the 16' suspension arm is reinforced, essentially on its 48' extrados.

[0062] We will now refer to [Fig.4A] and [Fig.4B] showing, according to yet another mode of implementation, an additional reinforcement opposite the extrados 48”, on the intrados side.

[0063] Also, all the elements of the object of [Fig.3A], appear on [Fig.4A] and they will present the same references affected by a double prime sign: ““”. And in addition, the other 30” of the first sections, the other 34” of the second sections and all the other third sections 40”, 42” and 46” are doubled.

[0064] Thus, said other 30” of the first sections, opposite the extrados 48', i.e. the intrados, is doubled by a third first section 62 extending parallel and above, as illustrated in [Fig.4B].

[0065] In the same way, said other 34” of the second sections is doubled by a third second section 64 also extending parallel above.

[0066] And furthermore, the first third section 40'', the second third section 42'' and the fourth third section 46”, are themselves doubled by three other third third sections 66, 68, 70.

[0067] In this way, the 16” suspension arm is reinforced not only in the 48” extrados, but also on the opposite side in the intrados.

Claims

Claims

1. Front lower suspension arm (16) of a motor vehicle, comprising a rear arm (20) having a rear end (26) adapted to be connected to a cradle of said motor vehicle and a forearm (22) substantially bent relative to said rear arm (20) by forming an elbow (24), said forearm (22) having a front end (28) adapted to be connected to a wheel support of said motor vehicle, while said elbow (24) is adapted to be connected to said cradle; characterized in that it comprises two first sections of steel bar (32, 30) connected together to form said rear arm (20) and two second sections of steel bar (34, 36) connected together to form said forearm (22).

2. Front lower suspension arm according to claim 1, characterized in that it comprises a plurality of third sections (40, 42, 44, 46) respectively connecting together said first (30, 32) and second (34, 36) sections.

3. Front lower suspension arm according to claim 1 or 2, characterized in that said two first sections (30, 32) and said two second sections (34, 36) are substantially identical.

4. Front lower suspension arm according to any one of claims 1 to 3, characterized in that said two first sections (30, 32) and said two second sections (34, 36) are curved.

5. Front lower suspension arm according to any one of claims 1 to 4, characterized in that the third sections (40, 42, 44, 46) of said plurality of third sections are curved.

6. Front lower suspension arm according to any one of claims 1 to 5, characterized in that one (32) of said two first steel bar sections (30, 32) extends in the extension of one (36) of said two second steel bar sections (34, 36), while the other (30) of said two first sections extends in the extension of the other (34) of said two second sections.

7. A front lower suspension arm according to claim 6, characterized in that said one (32') of said two first sections and said one (36') of said two second sections are respectively coupled to two fourth steel bar sections (56, 58).

8. A front lower suspension arm according to claim 6 or 7, ca- characterized in that said other (30”) of said two first sections and said other (34”) of said two second sections are respectively coupled to two fifth sections of steel bar (62, 64).

9. Front lower suspension arm according to any one of claims 1 to 8, characterized in that said rear end (26) of said rear arm (20) comprises an annular attachment (50) having a first axis of symmetry A substantially perpendicular to said rear arm, while said elbow (24) comprises a tubular attachment (52) having a second axis of symmetry B substantially perpendicular to said first axis of symmetry A.

10. A front lower suspension arm according to any one of claims 1 to 9, characterized in that the steel of the steel bar sections comprises up to 0.3% carbon.

11. Front lower suspension arm according to any one of claims 1 to 10, characterized in that the steel of the sections comes from a long steel supply chain allowing the use of 50% to more than 80% recycled material.

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