Rear lower control arm for a motor vehicle

Abstract

A rear lower control arm (5) for a motor vehicle includes a top member (5t) and a bottom member (5b) that together define a hollow volume (5h), the top member (5t) and the bottom member (5b) each including a top first aperture (17t) and a bottom first aperture (17b) and a top second aperture (19t) and a bottom second aperture (19b), wherein the top member (5t) and the bottom member (5b) are joined together by fastening at least a portion of the top horizontal surface outer periphery (5tho) and at least a portion of the bottom horizontal surface outer periphery (5bho), at least a portion of the top first aperture side wall outer periphery (17tso) and at least a portion of the bottom first aperture side wall outer periphery (17bso), at least a portion of the top second aperture side wall outer periphery (19tso) and at least a portion of the bottom second aperture side wall outer periphery (19bso) together.

Description

TECHNICAL FIELD

[0001] The present invention relates to a rear lower control arm for a motor vehicle. In particular, the present invention relates to a rear lower control arm for a vehicle having a rear wheel drive propulsion or a four wheel drive system or an electric or hybrid powertrain. BACKGROUND

[0002] Rear suspension assemblies of these types of vehicles are subjected to high forces associated with the moment applied by the rear propulsion device and carry, depending on the type of vehicle, important weights associated with one or more of the following elements: electric motor, battery, internal combustion engine, four wheel drive management devices, etc.

[0003] This combination of high torques and loads applied on the rear suspension creates challenging conditions for the structural elements that link the rear wheels to the rest of the vehicle, among which are generally the rear lower control arms, which can be said to be the most important structural components that link the rear wheels to the body of the vehicle.

[0004] In addition to the above structural requirements of the rear lower control arms, there is also an effort to reduce the weight of the rear lower control arms. Indeed, car manufacturers are constantly looking for weight reduction solutions, generally to address environmental issues associated with gas consumption for internal combustion engine vehicles and to provide greater driving autonomy in the case of electric or hybrid vehicles. In the specific case of the rear lower control arms, the mass of the component is particularly critical because it is included in the so-called unsprung mass of the vehicle. This unsprung mass corresponds to all the elements that are not supported by the suspension springs of the vehicle. This unsprung mass includes the wheels and the lower control arms. Reducing the unsprung mass of the vehicle is a key factor in improving the handling and overall passenger comfort of the vehicle.

[0005] Hollow rear lower control arm designs, also known as clamshell designs, have appeared on the market to address the weight reduction challenge and to enable the production of the rear lower control arms using sheet metal stamping instead of casting, which is generally more expensive and less productive. These designs, such as for example disclosed by KR20170079400, include a top part and a bottom part that are joined together around their edges and a hole that accommodates a spring perch. Although this concept is indeed successful in reducing the weight of the component, it is generally unsatisfactory in terms of vibration performance because the larger generally flat surfaces of the top part and the bottom part resonate in panel modes and exhibit poor performance. This concept is also unsatisfactory in terms of stiffness because the larger generally flat surfaces will tend to deform under bending or torsional loads. SUMMARY

[0006] The object of the present invention is to remedy the drawbacks of current flip design by providing a rear lower control arm with a flip design that maintains industrial manufacturability and has improved vibration and stiffness performance and also provides additional weight reduction.

[0007] To this end, the present invention relates to:

[0008] A rear lower control arm for a motor vehicle, the rear lower control arm comprising a top part and a bottom part together defining a hollow volume, the top part and the bottom part each comprising respectively:

[0009] - a top horizontal surface and a bottom horizontal surface, the top horizontal surface and the bottom horizontal surface being respectively delimited by a top horizontal surface outer periphery and a bottom horizontal surface outer periphery;

[0010] - a top side wall and a bottom side wall, the top side wall and the bottom side wall extending in a general direction of at least 45° compared to the horizontal plane along at least a portion of the top horizontal surface outer periphery and of the bottom horizontal surface outer periphery, the top side wall and the bottom side wall being delimited by a top side wall outer periphery and a bottom side wall outer periphery;

[0011] - a top first hole and a bottom first hole, the top first hole and the bottom first hole each comprising a top first hole side wall and a bottom first hole side wall extending in a general direction of at least 45° compared to the horizontal plane, the top first hole side wall and the bottom first hole side wall being delimited by a top first hole side wall outer periphery and a bottom first hole side wall outer periphery;

[0012] - a top second hole and a bottom second hole, the top second hole and the bottom second hole each comprising a top second hole side wall and a bottom second hole side wall extending in a general direction of at least 45° compared to the horizontal plane, the top second hole side wall and the bottom second hole side wall being delimited by a top second hole side wall outer periphery and a bottom second hole side wall outer periphery;

[0013] wherein the top part and the bottom part are joined together by:

[0014] - by fastening at least a portion of the top horizontal surface outer periphery and at least a portion of the bottom horizontal surface outer periphery together,

[0015] - by fastening at least a portion of the top first hole side wall outer periphery and at least a portion of the bottom first hole side wall outer periphery together,

[0016] - and by fastening at least a portion of the top second hole side wall outer periphery and at least a portion of the bottom second hole side wall outer periphery together.

[0017] The inventors have found that the introduction of additional holes allows, unexpectedly, an enhanced vibration and stiffness performance compared to prior art designs. The inventors have also found that such a component can be manufactured using industrially viable methods.

[0018] Other optional features of the rear lower control arm according to the invention, considered individually or according to any possible combination of techniques:

[0019] - the top part and the bottom part are joined together by welding.

[0020] - the top first hole side wall outer periphery and the bottom first hole side wall outer periphery are joined together by the intermediate portion of the first intermediate part, wherein the top first hole side wall outer periphery is attached to the first intermediate part along a top first hole assembly outer periphery, the bottom first hole side wall outer periphery is attached to the first intermediate part along a bottom first hole assembly outer periphery, and wherein said top first hole assembly outer periphery is positioned higher in the elevation direction than said bottom first hole assembly outer periphery.

[0021] - the top second hole side wall outer periphery and the bottom second hole side wall outer periphery are joined together by the intermediate portion of the second intermediate part, wherein the top second hole side wall outer periphery is attached to the second intermediate part along a top second hole assembly outer periphery, the bottom second hole side wall outer periphery is attached to the second intermediate part along a bottom second hole assembly outer periphery, and wherein said top second hole assembly outer periphery is positioned higher in the elevation direction than said bottom second hole assembly outer periphery.

[0022] - the rear lower control arm comprises four attachment points for chassis elements of the vehicle, said four attachment points being equipped with bushings comprising a vibration damping material.

[0023] - the top side wall and the bottom side wall do not extend around the entire length of the top horizontal surface outer periphery and the entire length of the bottom horizontal surface outer periphery, respectively, the areas where the top side wall and the bottom side wall do not extend being referred to as top side wall openings and bottom side wall openings, respectively, and wherein the bushings are located between at least a portion of said top side wall openings and at least a portion of said bottom side wall openings.

[0024] - the top part and the bottom part are made of steel with an ultimate tensile strength higher than 780 MPa, measured according to ISO standard ISO 6892-1 published in October 2009.

[0025] The invention also relates to a method for producing a rear lower control arm as described above, said method comprising the following steps:

[0026] a / providing a first flat sheet, a second flat sheet;

[0027] b / shaping said first flat sheet and said second flat sheet to produce a top part and a bottom part, the top part and the bottom part comprising respectively a top horizontal surface and a bottom horizontal surface, a top side wall and a bottom side wall, a top horizontal surface outer periphery and a bottom horizontal surface outer periphery, a top side wall outer periphery and a bottom side wall outer periphery, the top part and the bottom part further comprising respectively a top first hole and a bottom first hole, said first hole comprising respectively a top first hole side wall and a bottom first hole side wall, and a top first hole side wall outer periphery and a bottom first hole side wall outer periphery, and the top part and the bottom part further comprising respectively a top second hole and a bottom second hole, said second hole comprising respectively a top second hole side wall and a bottom second hole side wall, and a top second hole side wall outer periphery and a bottom second hole side wall outer periphery;

[0028] c / coupling said top part and said bottom part together by fastening the top part and the bottom part together along at least a portion of the top side wall outer periphery and at least a portion of the bottom side wall outer periphery, by fastening the top part and the bottom part together along at least a portion of the top first hole side wall outer periphery and at least a portion of the bottom first hole side wall outer periphery, and by fastening the top part and the bottom part together along at least a portion of the top second hole side wall outer periphery and at least a portion of the bottom second hole side wall outer periphery.

[0029] According to other optional features of the rear lower control arm production method according to the invention, considered separately or in combination with any possible technical features, the method further comprises the following steps:

[0030] - providing a first intermediate part, and coupling the top first hole side wall outer periphery and the bottom first hole side wall outer periphery to said first intermediate part to form a top first hole assembly outer periphery and a bottom first hole assembly outer periphery,

[0031] - providing a second intermediate part, and coupling the top second hole side wall outer periphery and the bottom second hole side wall outer periphery to said second intermediate part to form a top second hole assembly outer periphery and a bottom second hole assembly outer periphery,

[0032] - providing a bushing comprising a vibration damping material, and positioning said bushing between the previously arranged top side wall opening and the bottom side wall opening. BRIEF DESCRIPTION OF DRAWINGS

[0033] Other aspects and advantages of the present invention will appear as the following description, given by way of example and with reference to the appended drawings, makes clear, in which:

[0034] Figure 1 is a general perspective view of a vehicle according to the invention.

[0035] Figure 2is a perspective view of the overall rear suspension train according to the application.

[0036] Figure 3 is a perspective view of the rear carrier and the rear lower control arm assembly according to the application.

[0037] Figure 4 is a perspective view of the rear lower control arm assembly and the wheel according to the application.

[0038] Figure 5 is a perspective view of the rear lower control arm according to the application.

[0039] Figure 6 is an exploded view of the rear lower control arm according to the application.

[0040] Figure 7 is a cross-sectional view of the rear lower control arm according to the application along the I-I cross-sectional plane defined in Figure 5 .

[0041] Figure 8 is a cross-sectional view of the rear lower control arm according to the application along the II-II cross-sectional plane defined in Figure 5 . DETAILED DESCRIPTION

[0042] In the following description, the terms "upper", "lower", "front", "rear", "lateral" and "longitudinal" are defined according to the usual orientation of the vehicle on which they are installed. More specifically, the terms "upper" and "lower" are defined according to the elevation direction of the vehicle, the terms "front", "rear" and "longitudinal" are defined according to the front / rear direction of the vehicle, and the term "lateral" is defined according to the width of the vehicle. The term "height" refers to the distance between two points, lines, surfaces or bodies measured in the horizontal direction.

[0043] The yield strength, the ultimate tensile strength, as well as the uniform elongation and the total elongation are measured according to the ISO standard ISO 6892-1 published in October 2009.

[0044] By average thickness of a component or of a portion of a component, it is meant the overall average thickness of the material constituting the component after the material has been formed from an initially flat sheet into a three-dimensional component.

[0045] With reference to Figure 1 , Figure 2 and Figure 3 , the rear suspension 3 of the motor vehicle 1 comprises, for example, a rear carrier 4, two rear lower control arms 5, two vibration dampers 7, two wheels 9, and elements linking the wheels 9 to the rear lower control arms 5, for example steering knuckles 11 and one-piece links 13.

[0046] The rear bracket 4 houses a rear internal combustion engine or a rear electric motor or a rear four-wheel drive management system (these elements are not depicted in the figures). The rear bracket 4 is attached to the body of the vehicle 1, for example by fastening the rear suspension corner 6 to a rear member (not depicted in the figures).

[0047] The rear bracket 4 is also attached to a rear lower control arm 5, which is present on the right and on the left of the vehicle. Said rear lower control arm 5 is a structural link between the body of the vehicle, to which the rear bracket 4 is attached, and the wheel 9.

[0048] A vibration damper 7 is attached to the rear lower control arm 5. For example, as depicted in Figure 2 , the vibration damper is a helical spring. A gas spring cylinder or a hydraulic spring cylinder can also be used as vibration damper 7. Thanks to the presence of the vibration damper 7, the wheel can move up and down independently of the body of the vehicle, thus allowing a comfortable ride even on bumpy roads. Moreover, thanks to this suspension system, all four wheels of the vehicle stay on the road during driving, which is an essential element for good vehicle handling and overall safety. The suspension system is adjusted to provide the best compromise between vehicle comfort and vehicle handling.

[0049] The rear lower control arm 5 is equipped with a bushing 15, which serves to house the attachment point of the elements to which the rear lower control arm 5 is attached. For example, the bushing 15 is made of a steel cylindrical shell that houses a vibration-damping material, for example a rubber-like material, to absorb the vibrations coming from the interaction between the wheel, the tyre and the road.

[0050] With reference to Figure 4 , Figure 4 An example is shown in which the rear lower control arm 5 is fixed to the wheel 9, to which it is attached to a steering knuckle 11, which is itself connected to a wheel hub 10, and to an integral link 13, which is itself connected to the steering knuckle 11.

[0051] With reference to Figure 3 , the other two bushings in the particular embodiment depicted are attached to fixing points on the rear bracket 4.

[0052] With reference to Figure 5 and Figure 6 , the rear lower control arm 5 is made up of a top part 5t and a bottom part 5b, which define a hollow volume 5h therebetween.

[0053] The top member 5t includes a top horizontal surface 5th and a top sidewall 5ts. The top horizontal surface 5th is bounded by a top horizontal surface outer periphery 5tho. The top sidewall 5ts is bounded by a top sidewall outer periphery 5tso. The top horizontal surface 5th extends in a generally horizontal plane and forms a major surface of the top member 5t. The top sidewall 5ts extends along at least a portion of the top horizontal surface outer periphery 5tho. The top sidewall 5ts extends in a generally direction that is inclined at least 45 degrees relative to the horizontal direction. In certain embodiments, as Figure 6 As depicted in FIG, the top sidewall 5ts does not extend along the entire length of the top horizontal surface outer periphery 5tho. The discontinuous areas of the top sidewall 5ts are referred to as top sidewall openings 5tsa. Advantageously, the presence of these openings 5tsa allows for the accommodation of bushings 15 in the corners of the rear lower control arm 5. These bushings 15 are used to connect the rear lower control arm 5 to other components, such as the rear bracket 4 and the components that link the rear lower control arm 5 to the wheel 9. Furthermore, the presence of the top sidewall openings 5tsa in the corners of the top component 5t makes it easier to manufacture the top component 5t from stamping a flat sheet of material. In fact, if the top sidewall 5ts extended along the entire top horizontal surface outer periphery 5tho, including the corners of the top component 5t, the top component 5t would have regions where deformation would extend in three different directions: vertically and in two orthogonal horizontal directions. This type of deformation is difficult to achieve with high-strength materials, such as high-strength steel. Therefore, the presence of the top sidewall openings 5tsa advantageously increases the feasibility of stamping the top component 5t.

[0054] Similar to the top member 5t, the bottom member 5b includes a bottom horizontal surface 5bh and a bottom side wall 5bs. The bottom horizontal surface 5bh is bounded by a bottom horizontal surface outer periphery 5bho. The bottom side wall 5bs is bounded by a bottom side wall outer periphery 5bso. The bottom horizontal surface 5bh extends in a generally horizontal plane and forms a major surface of the bottom member 5b. The bottom side wall 5bs extends along at least a portion of the bottom horizontal surface outer periphery 5bho. The bottom side wall 5bs extends in a generally direction that is inclined at least 45 degrees compared to the horizontal direction. In certain embodiments, as Figure 6As depicted in FIG. 1 1, the bottom side wall 5bs does not extend around the entire length of the bottom horizontal surface outer periphery 5bho. The discontinuous areas of the bottom side wall 5bs are referred to as bottom side wall apertures 5bsa. Advantageously, the presence of these apertures 5bsa allows the accommodation of bushings 15 in the corner portions of the rear lower control arm 5. Said bushings 15 serve to connect the rear lower control arm 5 to other elements, such as the rear bracket 4, and elements linking the rear lower control arm 5 to the wheel 9. Furthermore, the presence of bottom side wall apertures 5bsa in the corner portions of the bottom part 5b makes it easier to manufacture the bottom part 5b by stamping a flat sheet. Indeed, if the bottom side wall 5bs extended along the entire bottom horizontal surface outer periphery 5bho including the corner portions of the bottom part 5b, the bottom part 5b would have areas that would be deformed to extend in three different directions (a vertical direction and two orthogonal horizontal directions). This type of deformation is difficult to achieve with high-strength materials, such as high-strength steel. Thus, the presence of bottom side wall apertures 5bsa advantageously increases the stamping feasibility of the bottom part 5b.

[0055] In a particular embodiment, as depicted in FIG. 1 1, Figure 6 As depicted in FIG. 1 1, the bottom side wall 5bs does not extend around the entire length of the bottom horizontal surface outer periphery 5bho. The discontinuous areas of the bottom side wall 5bs are referred to as bottom side wall apertures 5bsa. Advantageously, the presence of these apertures 5bsa allows the accommodation of bushings 15 in the corner portions of the rear lower control arm 5. Said bushings 15 serve to connect the rear lower control arm 5 to other elements, such as the rear bracket 4, and elements linking the rear lower control arm 5 to the wheel 9. Furthermore, the presence of bottom side wall apertures 5bsa in the corner portions of the bottom part 5b makes it easier to manufacture the bottom part 5b by stamping a flat sheet. Indeed, if the bottom side wall 5bs extended along the entire bottom horizontal surface outer periphery 5bho including the corner portions of the bottom part 5b, the bottom part 5b would have areas that would be deformed to extend in three different directions (a vertical direction and two orthogonal horizontal directions). This type of deformation is difficult to achieve with high-strength materials, such as high-strength steel. Thus, the presence of bottom side wall apertures 5bsa advantageously increases the stamping feasibility of the bottom part 5b. Figure 5 As depicted in FIG. 1 1, the bottom side wall 5bs does not extend around the entire length of the bottom horizontal surface outer periphery 5bho. The discontinuous areas of the bottom side wall 5bs are referred to as bottom side wall apertures 5bsa. Advantageously, the presence of these apertures 5bsa allows the accommodation of bushings 15 in the corner portions of the rear lower control arm 5. Said bushings 15 serve to connect the rear lower control arm 5 to other elements, such as the rear bracket 4, and elements linking the rear lower control arm 5 to the wheel 9. Furthermore, the presence of bottom side wall apertures 5bsa in the corner portions of the bottom part 5b makes it easier to manufacture the bottom part 5b by stamping a flat sheet. Indeed, if the bottom side wall 5bs extended along the entire bottom horizontal surface outer periphery 5bho including the corner portions of the bottom part 5b, the bottom part 5b would have areas that would be deformed to extend in three different directions (a vertical direction and two orthogonal horizontal directions). This type of deformation is difficult to achieve with high-strength materials, such as high-strength steel. Thus, the presence of bottom side wall apertures 5bsa advantageously increases the stamping feasibility of the bottom part 5b.

[0056] The top part 5t and the bottom part 5b are assembled by fastening them together along an assembly outer rim 5w to form the rear lower control arm 5. The assembly outer rim 5w extends along at least a portion of the top side wall outer periphery 5tso and at least a portion of the bottom side wall outer periphery 5bso. The assembly outer rim 5w is formed by, for example, welding, more particularly, for example, by Metal Active Gas welding (MAG welding) or by laser welding. Because the top part 5t and the bottom part 5b comprise side walls 5ts, 5bs that are substantially inclined by at least 45° compared to the horizontal direction, the top horizontal surface 5th and the bottom horizontal surface 5bh are spaced apart from each other by a distance h measured in the vertical direction. The top horizontal surface 5th and the bottom horizontal surface 5bh thus define a hollow volume 5h therebetween. The presence of this hollow volume 5h gives the rear lower control arm 5 rigidity.

[0057] The rear lower control arm 5 further comprises a first hole 17 designed to accommodate a bottom end of the vibration damper 7. The first hole 17 is formed by assembling a top first hole 17t and a bottom first hole 17b formed respectively in the top part 5t and the bottom part 5b. Said top first hole 17t and bottom first hole 17b comprise respectively a top first hole side wall 17ts and a bottom first hole side wall 17bs, which are respectively delimited by a top first hole side wall outer periphery 17tso and a bottom first hole side wall outer periphery 17bso. Said top first hole side wall outer periphery 17tso and bottom first hole side wall outer periphery 17bso are joined together, for example by welding, more particularly, for example, by MAG welding or laser welding. In a particular embodiment, as depicted in Figure 7 Said top first hole side wall outer periphery 17tso and bottom first hole side wall outer periphery 17bso are not joined together directly but by an intermediate portion of a first intermediate part 17m. Optionally, said first intermediate part 17m, commonly referred to as a spring bracket, is provided with a substantially horizontal lower portion 17mh on which a first end of the vibration damper 7 can rest. The top first hole side wall outer periphery 17tso is fastened to the first intermediate part 17m along a top first hole assembly outer rim 17tw and the bottom first hole side wall outer periphery 17bso is fastened to the first intermediate part 17m along a bottom first hole assembly outer rim 17bw, which is positioned lower than the top first hole assembly outer rim 17tw in the elevation direction.

[0058] The presence of the first intermediate part 17m allows to form more easily the top part 5t and the bottom part 5b by stamping from a flat sheet. Indeed, to form the top first hole side wall 17ts and the bottom first hole side wall 17bs, it is necessary to perform a flanging operation whereby the sides of the hole previously formed in the flat sheet are progressively deformed in a direction substantially perpendicular to the plane of the sheet. The greater the deformation of the sides of the hole when performing the flanging operation, the more the sides of the hole are susceptible to crack formation. This phenomenon is well known and the tendency of the material to resist to the flanging deformation is called hole expansion rate, which is defined by the standardized test ISO 16630. This is particularly critical in the case of high strength materials, for example in the case of high strength steel, for example in the case of an ultimate tensile strength higher than 590 MPa. Thanks to the presence of the first intermediate part 17m, the sum of the height of the top first hole side wall 17ts and the height of the bottom first hole side wall 17bs can be lower than the total height h separating the top horizontal surface 5th and the bottom horizontal surface 5bh. Thus, by limiting the height of the top first hole side wall 17ts and the height of the bottom first hole side wall 17bs, the presence of the first intermediate part 17m allows to limit the risk of crack formation associated with the flanging operation on the top first hole side wall outer periphery 17tso and on the bottom first hole side wall outer periphery 17bso.

[0059] The rear lower control arm 5 also comprises a second hole 19 designed to increase the vibration and stiffness properties of the part and also to reduce the weight of the part. Said second hole 19 is formed by assembling a top second hole 19t and a bottom second hole 19b. Said top second hole 19t and bottom second hole 19b comprise respectively a top second hole side wall 19ts and a bottom second hole side wall 19bs, respectively delimited by a top second hole side wall outer periphery 19tso and a bottom second hole side wall outer periphery 19bso. Said top second hole side wall outer periphery 19tso and bottom second hole side wall outer periphery 19bso are joined together, for example by welding, more particularly for example by MAG welding or laser welding. In a particular embodiment, as illustrated in Figure 8As depicted in the figures, the top second aperture side wall outer periphery 19tso and the bottom second aperture side wall outer periphery 19bso are not directly joined together but are joined together by the intermediary of the second intermediate part 19m. The top second aperture side wall outer periphery 19tso is fastened to the second intermediate part 19m along the top second aperture assembly outer periphery 19tw, and the bottom second aperture side wall outer periphery 19bso is fastened to the second intermediate part 19m along the bottom second aperture assembly outer periphery 19bw, the bottom second aperture assembly outer periphery 19bw being positioned lower than the top second aperture assembly outer periphery 19tw in the elevation direction. As in the case of the first aperture 17, the use of a second intermediate part improves the formability of the second aperture formed by stamping by reducing the height of the top second aperture side wall 19ts and the height of the bottom second aperture side wall 19bs, and thus reduces the risk of crack formation associated with the flanging operation around the top second aperture side wall outer periphery 19tso and the bottom second aperture side wall outer periphery 19bso.

[0060] The inventors have surprisingly found that the introduction of the second aperture 19 greatly increases the vibrational and stiffness performance of the rear lower control arm 5, despite the fact that the second aperture 19 also reduces the overall weight of the part. It is a general common sense that the vibrational and stiffness performance of a part increases with the weight of the part. For example, increasing the average thickness of a part while keeping the same overall design will necessarily result in better vibrational and stiffness performance. However, in the current case, an improvement in vibrational and stiffness performance can be achieved while reducing the weight of the part.

[0061] For example, for a lower control arm 5 made of a top part 5t and a bottom part 5b, the top part 5t and the bottom part 5b being stamped parts produced by stamping a steel sheet having an average thickness of 18 mm and an ultimate tensile strength higher than 780 MPa, the inventors have found that the first vibrational mode of the part can be shifted from 295 Hz to 481 Hz by introducing only the second aperture 19 described above. In other words, the first mode is increased by 39%. These results were obtained using numerical calculations to simulate a free-free modal analysis. These results can also be obtained by physically manufacturing the same part having the same overall design, one part having only the first aperture 17 and a second part having the first aperture 17 and the second aperture 19 as previously described, and by measuring the response to vibrations using for example a laser Doppler vibrometer to assess the vibrations.

[0062] Modal analysis is performed to prevent problems in the field of NVH (Noise, vibration, and harshness). The goal is to have a first vibration mode that is sufficiently high, the exact value to be reached depending on the specific case, so that the rear lower control arm 5 is stiff enough for the transmission rate of the forces exerted on the wheel 9 to the rest of the body to be low. By ensuring a sufficiently high first vibration mode, the rear lower control arm 5 will not be the weak link in the chain that links the wheel to the rest of the body and passenger compartment.

[0063] This is achieved by forming a second hole 19 that ensures a further connection between the top horizontal surface 5th and the bottom horizontal surface 5bh outside the first hole 17. Thanks to the presence of this additional link, it is possible to overcome the limitation of flip-top designs that naturally have large flat panels in the top horizontal surface 5th and in the bottom horizontal surface 5bh, which are ideal candidates for vibration propagation.

[0064] The first hole 17 and the second hole 19 can be, for example, circular or elliptical in shape. In order to minimize stress concentrations that would have a negative impact on the fatigue performance of the component, it is preferable to design the holes with smooth profiles and to avoid any rough angles in the shape of the holes.

[0065] Thanks to the addition of the second hole 19, the vibration performance of the lower control arm 5 can be significantly improved. Because the second hole 19 also involves removing a portion of the constituent top horizontal surface 5th and bottom horizontal surface 5bh of the material, the presence of said second hole 19 also allows to reduce the weight of the component. The inventors found that the above-mentioned improvement of 39% in vibration performance is associated with a weight reduction of the component of about 5%.

[0066] The following process can be applied to manufacture the rear lower control arm 5 according to the invention:

[0067] a / providing a first flat sheet, a second flat sheet;

[0068] b / shaping the first and second flat sheets, for example by stamping, to produce a top part 5t and a bottom part 5b, the top part 5t and the bottom part 5b comprising respectively a top horizontal surface 5th and a bottom horizontal surface 5bh, a top side wall 5ts and a bottom side wall 5bs, a top horizontal surface outer periphery 5tho and a bottom horizontal surface outer periphery 5bho, a top side wall outer periphery 5tso and a bottom side wall outer periphery 5bso, the top part 5t and the bottom part 5b further comprising respectively a top first hole 17t and a bottom first hole 17b, the top first hole 17t and the bottom first hole 17b comprising respectively a top first hole side wall 17ts and a bottom first hole side wall 17bs, and a top first hole side wall outer periphery 17tso and a bottom first hole side wall outer periphery 17bso, and the top part 5t and the bottom part 5b further comprising respectively a top second hole 19t and a bottom second hole 19b, the top second hole 19t and the bottom second hole 19b comprising respectively a top second hole side wall 19ts and a bottom second hole side wall 19bs, and a top second hole side wall outer periphery 19tso and a bottom second hole side wall outer periphery 19bso;

[0069] c / joining together the top part 5t and the bottom part 5b by:

[0070] by fastening the top part 5t and the bottom part 5b together along at least a portion of the top side wall outer periphery 5tso and of the bottom side wall outer periphery 5bso to form an assembly outer periphery 5w, and by fastening the top part 5t and the bottom part 5b together along at least a portion of the top first hole side wall outer periphery 17tso and of the bottom first hole side wall outer periphery 17bso, and by fastening the top part 5t and the bottom part 5b together along at least a portion of the top second hole side wall outer periphery 19tso and of the bottom second hole side wall outer periphery 19bso.

[0071] For example, the joining operation is performed by MAG welding or laser welding.

[0072] In a particular embodiment, the assembly process further comprises the steps of:

[0073] - providing a first intermediate part 17m;

[0074] - joining the top first hole side wall outer periphery 17tso and the bottom first hole side wall outer periphery 17bso to the first intermediate part 17m to form a top first hole assembly outer periphery 17tw and a bottom first hole assembly outer periphery 17bw.

[0075] In a particular embodiment, the assembly process further comprises the steps of:

[0076] - providing a second intermediate part 19m;

[0077] - joining the top second hole side wall outer periphery 19tso and the bottom second hole side wall outer periphery 19bso to the second intermediate part 19m to form a top second hole assembly outer periphery 19tw and a bottom second hole assembly outer periphery 19bw.

[0078] In a particular embodiment, the assembly process can further comprise the following step between step b and step c:

[0079] - providing a bushing 15 comprising a vibration damping material;

[0080] - positioning the bushing between the previously arranged top side wall opening 5tsa and the bottom side wall opening 5bsa.

[0081] Advantageously, by positioning the bushing 15 between the top side wall opening 5tsa and the bottom side wall opening 5bsa, the bushing will naturally remain in place between the top horizontal surface 5th and the bottom horizontal surface 5bh.

[0082] In a particular embodiment, the top side wall opening 5tsa and the bottom side wall opening 5bsa are located in the corner portions of the top horizontal surface 5th and of the bottom horizontal surface 5bh.

Claims

1. A rear lower control arm (5) for a motor vehicle, the rear lower control arm (5) comprising a top part (5t) and a bottom part (5b) together defining a hollow volume (5h), the top part (5t) and the bottom part (5b) each comprising respectively: - a top horizontal surface (5th) and a bottom horizontal surface (5bh), the top horizontal surface (5th) and the bottom horizontal surface (5bh) being respectively delimited by a top horizontal surface outer periphery (5tho) and a bottom horizontal surface outer periphery (5bho); - a top side wall (5ts) and a bottom side wall (5bs), the top side wall (5ts) and the bottom side wall (5bs) extending in a direction of at least 45° compared to a horizontal plane along at least one portion of the top horizontal surface outer periphery (5tho) and at least one portion of the bottom horizontal surface outer periphery (5bho), the top side wall (5ts) and the bottom side wall (5bs) being delimited by a top side wall outer periphery (5tso) and a bottom side wall outer periphery (5bso); - a top first hole (17t) and a bottom first hole (17b), the top first hole (17t) and the bottom first hole (17b) comprising respectively a top first hole side wall (17ts) and a bottom first hole side wall (17bs) extending in a direction of at least 45° compared to a horizontal plane, the top first hole side wall (17ts) and the bottom first hole side wall (17bs) being delimited by a top first hole side wall outer periphery (17tso) and a bottom first hole side wall outer periphery (17bso); - a top second hole (19t) and a bottom second hole (19b), the top second hole (19t) and the bottom second hole (19b) comprising respectively a top second hole side wall (19ts) and a bottom second hole side wall (19bs) extending in a direction of at least 45° compared to a horizontal plane, the top second hole side wall (19ts) and the bottom second hole side wall (19bs) being delimited by a top second hole side wall outer periphery (19tso) and a bottom second hole side wall outer periphery (19bso); wherein the top part (5t) and the bottom part (5b) are joined together by: - fastening at least one portion of the top horizontal surface outer periphery (5tho) and at least one portion of the bottom horizontal surface outer periphery (5bho) together, - fastening at least one portion of the top first hole side wall outer periphery (17tso) and at least one portion of the bottom first hole side wall outer periphery (17bso) together, - and fastening at least one portion of the top second hole side wall outer periphery (19tso) and at least one portion of the bottom second hole side wall outer periphery (19bso) together.

2. The rear lower control arm (5) according to claim 1, wherein The top part (5t) and the bottom part (5b) are joined together by welding.

3. The rear lower control arm (5) according to claim 1 or 2, wherein The top first hole side wall outer periphery (17tso) and the bottom first hole side wall outer periphery (17bso) are joined together by an intermediate portion of a first intermediate part (17m), wherein the top first hole side wall outer periphery (17tso) is attached to the first intermediate part (17m) along a top first hole assembly outer periphery (17tw), the bottom first hole side wall outer periphery (17bso) is attached to the first intermediate part (17m) along a bottom first hole assembly outer periphery (17bw), and wherein the top first hole assembly outer periphery (17tw) is positioned higher in the elevation direction than the bottom first hole assembly outer periphery (17bw).

4. The rear lower control arm (5) according to claim 1 or 2, wherein The top second hole side wall outer periphery (19tso) and the bottom second hole side wall outer periphery (19bso) are joined together by an intermediate portion of a second intermediate part (19m), wherein the top second hole side wall outer periphery (19tso) is attached to the second intermediate part (19m) along a top second hole assembly outer periphery (19tw), the bottom second hole side wall outer periphery (19bso) is attached to the second intermediate part (19m) along a bottom second hole assembly outer periphery (19bw), and wherein the top second hole assembly outer periphery (19tw) is positioned higher in the elevation direction than the bottom second hole assembly outer periphery (19bw).

5. The rear lower control arm (5) according to claim 1 or 2, comprising four attachment points for chassis elements of a vehicle, said four attachment points being equipped with bushings (15) comprising a vibration damping material.

6. The rear lower control arm (5) according to claim 5, wherein The top side wall (5ts) and the bottom side wall (5bs) do not extend around the entire length of the top horizontal surface outer periphery (5tho) and the entire length of the bottom horizontal surface outer periphery (5bho) respectively, the areas where the top side wall (5ts) and the bottom side wall (5bs) do not extend being referred to as a top side wall aperture (5tsa) and a bottom side wall aperture (5bsa) respectively, and wherein the bushings (15) are located between at least a portion of the top side wall aperture (5tsa) and at least a portion of the bottom side wall aperture (5bsa).

7. The rear lower control arm (5) according to claim 1 or 2, wherein The top part (5t) and the bottom part (5b) are made of steel having an ultimate tensile strength higher than 780 MPa, measured according to ISO standard ISO 6892-1 published in October 2009.

8. A method for manufacturing a rear lower control arm according to any one of claims 1 to 7, the method comprising the steps of: a / providing a first flat sheet, a second flat sheet; b / shaping said first and second flat sheets to produce a top part (5t) and a bottom part (5b) comprising respectively a top and bottom horizontal surface (5th, 5bh), a top and bottom side wall (5ts, 5bs), a top and bottom horizontal surface outer periphery (5tho, 5bho), a top and bottom side wall outer periphery (5tso, 5bso), said top and bottom parts (5t, 5b) further comprising respectively a top and bottom first hole (17t, 17b) comprising respectively a top and bottom first hole side wall (17ts, 17bs) and a top and bottom first hole side wall outer periphery (17tso, 17bso), and said top and bottom parts (5t, 5b) further comprising respectively a top and bottom second hole (19t, 19b) comprising respectively a top and bottom second hole side wall (19ts, 19bs) and a top and bottom second hole side wall outer periphery (19tso, 19bso); a top and bottom second hole side wall outer periphery (19tso, 19bso); c / joining said top part (5t) and said bottom part (5b) together by fastening said top part (5t) and said bottom part (5b) together along at least a portion of said top side wall outer periphery (5tso) and said bottom side wall outer periphery (5bso), by fastening said top part (5t) and said bottom part (5b) together along at least a portion of said top first hole side wall outer periphery (17tso) and said bottom first hole side wall outer periphery (17bso), and by fastening said top part (5t) and said bottom part (5b) together along at least a portion of said top second hole side wall outer periphery (19tso) and said bottom second hole side wall outer periphery (19bso).

9. The method according to claim 8, further comprising the steps of: - providing a first intermediate part (17m); - joining said top first hole side wall outer periphery (17tso) and said bottom first hole side wall outer periphery (17bso) to said first intermediate part (17m) to form a top first hole assembly outer periphery (17tw) and a bottom first hole assembly outer periphery (17bw).

10. The method according to claim 9, further comprising the steps of: - providing a second intermediate part (19m); - joining said top second hole side wall outer periphery (19tso) and said bottom second hole side wall outer periphery (19bso) to said second intermediate part (19m) to form a top second hole assembly outer periphery (19tw) and a bottom second hole assembly outer periphery (19bw).

11. The method according to claim 9 or 10, further comprising the steps of: - providing a bushing (15) comprising a vibration damping material - positioning the bushing (15) between the previously arranged top side wall aperture (5tsa) and the bottom side wall aperture (5bsa).

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