Suspension element

Abstract

The invention relates to a suspension element (8) comprising a main body (9) made of an elastic material consisting of a plurality of coils (10) and having a tubular cross section defining a longitudinal passage (11), the suspension element (8) being characterized in that the thickness of the wall of the main body (9) varies along its length (x-x').

Description

Description Title of the invention: Suspension element Technical Field

[0001] The present exposition relates to a suspension element, such as a spring, a stabilizer assembly comprising such a suspension element, and a method for calculating the variable wall thickness of this suspension element. Previous technique

[0002] The automotive suspension (or stabilizer assembly) is a complex system that plays a crucial role in managing the interactions between the vehicle and the road surface. Its primary function is to maintain optimal contact between the wheels and the road, thereby ensuring stable handling, increased comfort, and enhanced safety. To achieve these objectives, the suspension must absorb and dissipate shocks and vibrations caused by road irregularities, while allowing the vehicle to remain maneuverable and maintain good traction.

[0003] By way of example, a stabilizer assembly 1 for a vehicle, according to the prior art, is illustrated in Figure 1. It comprises two suspension elements, springs 2 and 3, which work together with connecting rods 4 and 5. Each connecting rod 4 and 5 is attached to a mounting point on a wheel 6 and 7 respectively, generally at a suspension support. This connection allows the connecting rods 4 and 5 to transfer the forces and movements of the springs 2 and 3 directly to the wheels 6 and 7. The two wheels 6 and 7 are generally connected by a stabilizer bar, which is not visible in the figure. The stabilizer bar, also called an anti-roll bar, is a suspension element of the vehicle. This bar's function is to create a spring that connects the two wheels of the same axle.This allows for a reduction in body roll during cornering and a reduction in deformations suffered by the suspension, in order to maintain the tires of said wheels 6 and 7 in optimal contact with the ground and to ensure maximum grip.

[0004] In other words, each end of the stabilizer bar is thus fixed to the suspension triangle of each wheel 6 and 7, via the links 4 and 5, while its central part is fixed to the chassis of the vehicle using at least two bearings.

[0005] More specifically, suspension components, particularly springs and shock absorbers, in automotive suspension systems play a key role in supporting the vehicle's weight and absorbing shocks. Thus, such a spring compensates for road variations and maintains a constant ride height despite load changes. Springs act as elastic elements that compress and expand to manage dynamic forces.

[0006] Among the various spring configurations available on the market, tubular springs possess unique technical characteristics that can improve the overall performance of the suspension. Such a tubular spring is distinguished by its tubular cross-section. This configuration gives the spring a hollow structure with a longitudinal passage that extends along the entire length of the suspension element. The main body of the spring (or more generically, the "suspension element" throughout this application) is made from an elastic material chosen for its deformation and energy restitution properties, which are essential for suspension functions.

[0007] Thus, by this configuration, each tubular spring 2 and 3 is effectively integrated into the connecting rods. These springs are also generally inserted into specific bores of said connecting rods 4 and 5.

[0008] Unlike conventional coil or leaf springs, the tubular spring, by virtue of its tubular shape, allows for controlled deformation under load, thus absorbing road irregularities more effectively. Furthermore, the tubular spring is often lighter than its traditional counterparts while allowing for more compact integration into suspension systems.

[0009] However, although the tubular spring offers several advantages in the vehicle suspension system, it presents specific challenges related to its design objectives.

[0010] One of the main challenges is stress concentration. Indeed, tubular springs can have localized stress zones. In other words, stress concentration refers to the tendency of stresses, intended to act on the spring, to cluster in specific areas of the spring, thus creating points of weakness. Consequently, these areas can be subject to uneven wear, increasing the risk of breakage. Therefore, a uniform distribution of stresses is important to avoid weak points that could lead to premature failure.

[0011] The spring is subjected to various types of stress, each of which can contribute to stress concentration. Bending stresses develop when the spring absorbs loads, particularly during compression or relaxation. Torsional stresses, as well as compressive and tensile stresses, can also occur and cause stress concentrations.

[0012] Another equally important challenge is reducing the weight of the spring to improve the vehicle's energy efficiency. More specifically, by decreasing the vehicle's overall mass, the energy required to move it is reduced, which can lead to lower fuel consumption. This challenge is now even more crucial in the context of increasingly stringent environmental standards and efforts to develop more environmentally friendly vehicles. Furthermore, it is known that a lighter spring improves the suspension's response to road irregularities. This results in better tire grip, more stable handling, and an overall improvement in vehicle maneuverability.

[0013] However, it is necessary to ensure that the weight reduction does not affect the spring's performance, as this could compromise its strength. To this end, it is important to find a balance between lightness and robustness. If the spring is too light, it may not be able to withstand the dynamic and static loads to which it is subjected, which can lead to deformation, breakage, or premature failure.

[0014] It should be noted that the use of lightweight materials, such as aluminum alloys, can help to reduce weight, but these materials can be more expensive and require specialized treatments to maintain their mechanical properties.

[0015] Finally, corrosion resistance is critical for the durability of springs, particularly when exposed to road pollution, including dust and water spray, which can seep in and cause localized corrosion of the tubular spring. These substances can have corrosive properties that react with the spring material, initiating the degradation process. For example, dust particles can adhere to the spring, acting as abrasives and altering its surface, making it more susceptible to attack by corrosive agents.

[0016] Thus, the challenges associated with tubular springs, in terms of stress level, weight, and corrosion resistance, require meticulous attention at both the design and manufacturing stages. There is therefore a need to develop a tubular spring capable of meeting these objectives while avoiding the creation of new problems. Description of the invention

[0017] The present description relates to a suspension element comprising a main body made of elastic material consisting of a plurality of turns and having a tubular cross-section defining a longitudinal passage, the suspension element being characterized in that the main body has a wall thickness that varies along its length.

[0018] The suspension element of the invention is designed with a key feature: a wall thickness that varies along its length. This innovative design makes it possible to overcome several technical challenges associated with the use of such suspension elements, for example springs, particularly in suspension systems.

[0019] In the application as a whole, it should be noted that each suspension element can be considered as a spring and that each spring can be generalized to a suspension element.

[0020] As explained above, one of the major challenges in the design of tubular springs is stress concentration, which can lead to weak points and uneven wear, thus increasing the risk of breakage. Thanks to the variable wall thickness, the stress distribution is adjusted (smoothed) along the spring. Thus, in areas where stresses are higher, a thicker wall of the main body will strengthen the structure and reduce stress concentration, while in less stressed areas, a thinner wall will maintain flexibility.

[0021] Weight reduction is another important objective in the design of suspension systems. By incorporating variable wall thickness, the amount of material is minimized where it is not needed, while maintaining a robust structure where it is crucial. This optimization reduces the overall weight of the suspension component, thereby improving the vehicle's fuel efficiency and handling without compromising its overall performance.

[0022] The variable wall thickness allows the spring stiffness to be modulated at different sections along its length. In sections where the wall is thicker, the spring exhibits higher stiffness. This means it offers greater resistance to compression or stretching, which is useful in areas where higher forces are expected or desired to limit deformation. Conversely, sections with a thinner wall have lower stiffness, allowing the spring to deform more easily under lighter loads. This promotes smoother shock absorption and better adaptation to minor road irregularities.

[0023] According to embodiments of the invention, the distribution of the wall thickness along the main body is determined as a function of the value of the stresses likely to be exerted on the main body, so as to present a variable stiffness defined over its length and to balance the distribution of said stresses.

[0024] The wall thickness distribution is determined according to the stress values ​​to which the spring will be (or is likely to be) subjected. This stress analysis is based on the principles of materials mechanics and elasticity theory, which are well known to those skilled in the art. For example, critical areas that may be subjected to higher stresses can be identified using finite element analysis (FEA).

[0025] According to embodiments of the invention, the stresses that may be exerted on the main body include torsional stresses, and / or shear stresses, and / or hydrostatic pressure stresses, and / or bending stresses.

[0026] According to embodiments of the invention, the variable wall thickness is designed to be thicker in longitudinal areas of the main body that are likely to be subjected to high stresses, and thinner in longitudinal areas of the main body that are likely to be subjected to lower stresses.

[0027] According to embodiments of the invention, the main body comprises along its length, a first portion constituting a first end of the main body, a second portion constituting a second end of the main body, and a third portion constituting a central zone located between the first portion and the second portion, the first portion and / or the second portion being thinner than the third portion.

[0028] The main body is thus divided here into three distinct portions covering three specific wall thickness alternatives, the first alternative being in which the first end is thinner than the central zone. This means that the first end is more flexible and less rigid compared to the central zone, which is advantageous for allowing some controlled deformation at this end, while maintaining increased robustness in the central zone to withstand greater loads.

[0029] In the second alternative, the second end is thinner than the central area. This alternative is useful when the design requires increased flexibility at the other end of the spring.

[0030] Finally, in the third alternative, both ends are thinner than the central zone. In other words, both ends (first and second portions) are designed with a wall thickness less than that of the central zone. In this case, the central zone of the spring, being the thickest, provides the greatest rigidity and strength, while the thinner ends provide increased flexibility at both ends of the spring.

[0031] According to embodiments of the invention, the longitudinal passage is a tube pre-treated by implementing a heat treatment, or a non-pre-treated tube.

[0032] Heat treatment consists of heating a pre-treated tube to a controlled temperature, followed by cooling, and then tempering. Heat treatment reduces internal residual tensile or tensile stresses that may be present in the material. By eliminating these internal stresses, the spring becomes less likely to crack or fail prematurely under prolonged stress conditions.

[0033] The use of an untreated tube is another option that may be preferred to heat treatment for various reasons, including the applied stress. In particular, using such a tube can simplify the manufacturing process because there is no need for heat treatment, thus reducing the production steps and, consequently, the time and costs associated with manufacturing.

[0034] According to embodiments of the invention, the ends of the main body are sealed.

[0035] Sealing the ends of the main body is advantageous because it provides greater protection for the spring against external elements that could compromise its performance and durability. One of the main threats to this type of spring is corrosion, especially when the spring is exposed to harsh environmental conditions, such as road pollution.

[0036] By sealing the ends of the main body, these infiltrations are prevented, which considerably reduces the risk of corrosion. This protection then helps to extend the service life of the spring.

[0037] Several sealing methods are possible and known to those skilled in the art. These methods include forging or adding a polymer plug. It is also advantageous to introduce corrosion protection into the internal wall of the main body.

[0038] According to embodiments of the invention, the elastic material is made of composite, or steel, or a steel-based alloy, the elastic material having a hardness greater than 200 HV, preferably greater than 450 HV.

[0039] Of course, the term <HV> (for "Hardens Vickers" in English) is known to those skilled in the art in the field of metallurgy and materials science more generally. This term refers to the Vickers hardness scale. This measurement is used to evaluate a material's resistance to permanent deformation under load.

[0040] According to embodiments of the invention, the winding of the plurality of turns is carried out cold, or hot, in particular by additive manufacturing.

[0041] Cold winding consists of forming the coils of the spring at room temperature, without heating the base material.

[0042] Unlike cold winding, hot winding involves heating the material before winding it to form the coils. Heating makes the material more malleable, facilitating the shaping of the coils.

[0043] Among the processes implemented at heat, we can mention additive manufacturing such as the process called Wire Arc Additive Manufacturing (WAAM) known to those skilled in the art, which involves the use of a metal wire which will be melted by an electric arc.

[0044] When the spring has a conical profile, that is, a shape where the diameter of the spring varies along its length, typically decreasing from one end to the other, the spring can be made from bars (profiles, in the technical jargon of the invention) which are segments of material. In this process, the bars are not wound around a mandrel to form a spiral. Instead, the bar is mechanically deformed to create the conical profile, without prior heating.

[0045] For the sake of completeness, all the means of implementation described in this application for manufacturing the different parts of the suspension element can be transposed to process steps of the manufacturing of the suspension element.

[0046] According to embodiments of the invention, when the winding of the plurality of turns is implemented, the suspension element is further subjected to internal shot peening by projection of abrasive particles, in particular steel or ceramic balls.

[0047] According to embodiments of the invention, the external tubular cross-section of the main body is circular, oval, conical, or polygonal in shape, the internal tubular cross-section of the main body being circular, oval, conical, or polygonal in shape.

[0048] It should be noted that the longitudinal passage may or may not be centered. When it is centered, this means that the passage has axial symmetry around its center.

[0049] According to embodiments of the invention, the longitudinal passage is adapted to accommodate a guide element or a central shaft intended to stabilize the suspension element in operation.

[0050] The present description further relates to a vehicle stabilizer assembly, comprising at least two suspension elements as defined above, and comprising a stabilizer bar or a transverse leaf, connecting said at least two suspension elements.

[0051] The present description also relates to a vehicle comprising a stabilizer assembly as defined above.

[0052] The present exposition also relates to a method for calculating the variable wall thickness of a suspension element as defined above, comprising the following steps: a) a step of acquiring a predetermined data set defining the suspension element, the predetermined data set including the number of turns, the diameter of the main body and the diameter of the turns of the suspension element, the diameter of the turns being constant over the entire length of the main body; b) a first estimation step, by implementing a first finite element analysis, of the behavior of the suspension element under different constraints; c) a step of adjusting the stiffness of the suspension element, the stiffness being variable over the length of the main body of the suspension element so as to balance the distribution of said stresses; d) a second estimation step, by implementing a second finite element analysis, of the behavior of the suspension element with its stiffness adjusted; and if the behavior of the suspension element conforms to a predetermined objective, the variable wall thickness is determined along the main body as a function of the adjusted stiffness; if the behavior of the suspension element does not conform to the predetermined objective, the process includes a repetition of its steps from step b) in which the predetermined data defining the suspension element are adjusted according to the deviation calculated by comparing said predetermined data and data defining the suspension element following the adjustment of its stiffness.

[0053] The first acquisition step a) does not preclude the predetermined data set defining the suspension element from being acquired in such a way as to design a suspension element having a solid wire. Such data, when representing a suspension element with a solid wire, are then adapted to correspond to the specifications of a tubular suspension element, i.e., having a hollow longitudinal passage.

[0054] Predetermined data, which are selected according to parameters defined in a specification (e.g., line of action, desired stiffness, dimensions, etc.), allows the suspension element model to be divided into a series of small, interconnected, discrete elements. Each element is subjected to specific stresses and forces, and the analysis allows the mechanical responses of the model as a whole to be calculated. The objective of this initial analysis is to understand how the suspension element reacts to different loads and stresses, identifying areas of high stress and potential weaknesses in the initial design. This preliminary estimation provides valuable information for the subsequent adjustment of the suspension element's stiffness.

[0055] Once the behavior of the suspension element has been estimated, the stiffness of the suspension element is adjusted (and therefore the thickness necessarily) to balance the distribution of stresses along its main body.

[0056] After adjusting the stiffness, a second finite element analysis is performed to evaluate the behavior of the suspension element with its adjusted stiffness. This analysis verifies whether the modifications have achieved the predetermined performance objectives. It allows measurement of whether the stress distribution is now balanced and whether the suspension element functions as expected under the applied loads.

[0057] If this second analysis reveals that the behavior of the suspension element meets the established criteria, the design parameters (predetermined data) are considered validated. Otherwise, the process requires a further iteration. Thus, if the behavior of the suspension element conforms to the predetermined objectives, the next step consists of determining the variable wall thickness along the main body as a function of the adjusted stiffness.

[0058] If the results of the second analysis do not meet the criteria, the process returns to the stiffness adjustment step (step b). The predetermined data are then modified according to the discrepancies observed between the initial data and the results after adjustment. This process is repeated until the suspension element meets the desired specifications.

[0059] The aforementioned features and advantages, as well as others, will become apparent upon reading the following detailed description, examples of embodiments of the vehicle stabilizer bar bearing, and the proposed stabilizer assembly. This detailed description refers to the accompanying drawings.

[0060] The accompanying drawings are schematic and are intended primarily to illustrate the principles of the exposition. On these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference symbols. [Fig. 1] Figure 1 is a perspective view of a stabilizing assembly comprising two suspension elements according to the state of the art; [Fig. 2A], [Fig. 2B] and [Fig. 2C] Figures 2A, 2B and 2C each schematically illustrate an alternative configuration of a suspension element according to an embodiment of the invention; [Fig. 3] Figure 3 schematically illustrates a first example of implementation of the invention when the prior art suspension element is subjected to torsional or shear stresses; [Fig. 4] Figure 4 schematically illustrates a second example of implementation of the invention when the prior art suspension element is subjected to hydrostatic pressure stresses or bending stresses; [Fig. 5] Figure 5 illustrates a flowchart showing the different steps of a method for calculating the variable wall thickness of the suspension element of the invention; and [Fig. 6] Figure 6 shows the force-compression relationship of the suspension element according to the state of the art and that of the suspension element according to the invention. Description of the methods of implementation and execution

[0061] It is recalled that a suspension element 8, according to the invention and as illustrated in Figures 2A, 2B and 2C, comprises a main body 9 made of an elastic material consisting of a plurality of turns 10 and having a tubular cross-section defining a longitudinal passage 11 along the x-x' axis. By way of example, the elastic material may be a composite, or steel, or a steel-based alloy. More generally, the elastic material has a hardness greater than 200 HV, preferably greater than 450 HV.

[0062] It should be noted that the external tubular cross-section of the main body 9 can be circular, oval, conical, or polygonal, and that the internal tubular cross-section of the main body 9 can be circular, oval, conical, or polygonal. The term "external" here refers to the shape of the outer contour of the main body 9, while the term "internal" refers to the shape of the inner contour.

[0063] The suspension element 8 is, for example, a spring and performs the same functions as the suspension element 2 or 3, according to the prior art. The longitudinal passage 11 can be a tube pre-treated by heat treatment, or an unpre-treated tube as explained above. Such a longitudinal passage is adapted to accommodate a guide element or a central shaft intended to stabilize the suspension element during operation.

[0064] The suspension element 8 according to the invention differs from that of the prior art in that it is designed so that the main body 9 has a variable wall thickness along its length (along the x-x' axis). In other words, there is a variation in the wall thickness of the main body 9 along its length. It is therefore not constant along its entire length. For example, some parts of the main body 9 may have a thicker wall to offer greater resistance to higher loads, while other parts may be thinner to reduce weight or offer greater flexibility.

[0065] Figure 2A schematically illustrates a first alternative configuration of the suspension element 9. Figure 2B schematically illustrates a second alternative configuration of said suspension element 9, and Figure 2C schematically illustrates a third alternative configuration of said suspension element 9. The three alternatives represent embodiments of the invention.

[0066] Furthermore, for the sake of completeness, the term "configuration" refers to a series of specific thicknesses of the wall of the main body 9. Thus, whatever the configuration, the main body 9 comprises along its length, a first portion P1 constituting a first end of the main body 9, a second portion P2 constituting a second end of the main body 9, and a third portion P3 constituting a central zone located between the first portion P1 and the second portion P2.

[0067] As illustrated in Figure 2A, in the first alternative, the two ends P1, P2 are thinner than the central zone P3. In other words, both ends (first and second portions P1, P2) are designed with a wall thickness less than that of the central zone P3.

[0068] As illustrated in Figure 2B, in the second alternative, the second end P2 is less thick than the central area P3 and the first end P1.

[0069] As illustrated in Figure 2C, in the third alternative, the first end P1 is thinner than the central zone P3 and the second portion P2. This means that the first end P1 is more flexible and less rigid compared to the central zone P3 and the second portion P2, which is advantageous for allowing some controlled deformation at this end, while maintaining increased robustness in the central zone to withstand larger loads.

[0070] It is important to note that other (alternative) wall thickness configurations are possible, in addition to those illustrated in Figures 2A, 2B, and 2C. Indeed, the thickness of the different portions of the suspension element can be adjusted according to the specific constraints applied to the suspension element 8 in a given application. For example, if an application requires increased flexibility at one end to absorb shocks, a configuration with a thinner wall at that point can be chosen. Conversely, if high strength is required at the center to support significant loads, the central portion P3 can be designed with an increased thickness.

[0071] Thus, the illustrated configurations should not be considered limiting or exclusive. They serve as examples to illustrate how the thickness of the different parts of the suspension element 8 can be modulated. It is therefore possible to consider a multitude of other configurations adapted to specific situations, while respecting the same basic principle: adapting the wall thickness based on the stresses likely to be applied, in order to optimize the performance of the suspension element 8.

[0072] Furthermore, the number of possible portions is not limited to three P1, P2, and P3. The wall of the main body 9 can be divided into more than three distinct sections or portions, each with a potentially different wall thickness. In other words, the main body 9 can be designed with any number of portions along its length, depending on the specific requirements of the application. For example, instead of being limited to a central portion P3 and two end portions P1 and P2, configurations are possible where the wall is subdivided into several intermediate portions, each with a wall thickness adapted to the local constraints.

[0073] Furthermore, whatever the configuration chosen by the person skilled in the art, it is advantageous to seal the ends of the main body 9 to avoid generating or propagating corrosion, and thus further optimize the performance of the suspension element 8.

[0074] To illustrate the invention more concretely, Figure 3 shows a configuration of the wall of the main body 9 that the invention proposes to produce following an analysis of the stresses likely to be applied to a suspension element, here torsional or shear stresses. When a force is applied tangentially to the surface of the element, it causes shear deformation. This stress is critical because it can lead to significant deformation of the coils. As for torsion, this occurs when the suspension element is subjected to a moment that tends to twist the coils around their longitudinal axis.

[0075] The prior art suspension element 2 is illustrated in this figure. To facilitate the analysis of the stresses experienced by the suspension element 2, a visual representation using shades of gray can be used on the coils. This type of visualization makes it possible to identify the areas of greatest stress and risk in the design.

[0076] In this diagram, the darker shades of gray indicate the parts (portions) of the element where the stresses, whether shear or torsional, are highest. These parts are critical because they are most likely to deform or fail under excessive load. Conversely, the lighter parts (portions) represent the areas of the suspension element where the stresses are less intense. These areas are subjected to less stress and play a less critical role in the overall strength of the element.

[0077] In addition to this visual analysis, a graph GR1 is generated showing how the load evolves along the winding of the turns. In this graph GR1, the x-axis represents the turn number, that is, the specific position of each turn along the winding of the suspension element 2. The y-axis represents the load expressed in megapascals (MPa), that is, the stress experienced by each turn as a function of its position. This graph GR1 thus allows visualization of the stress distribution along the wall of the suspension element 2.

[0078] A second graph GR2 is illustrated in addition, in which the ordinates Y represent the wall thickness of the suspension element 2 in millimeters (mm) and the abscissas X the stress in megapascals (MPa) which is applied to this suspension element 2.

[0079] In this second graph GR2, the resulting curve slopes downward from left to right. This indicates an inverse relationship between the thickness and the applied stress. In other words, as the stress increases, the thickness decreases.

[0080] Thus, the curve shows that the areas where the stress exerted on the wall is highest have a lower thickness. Conversely, the areas where the stress exerted on the wall is lowest have the highest thickness.

[0081] As explained above, the invention implements a variable wall thickness design that optimizes the management of stresses applied to the suspension element. According to the invention, the longitudinal areas of the main body of the suspension element that are likely to be subjected to high stresses are designed with an increased wall thickness. By increasing the thickness in the areas subjected to high stresses, the suspension element 2, according to the prior art, is strengthened (and thus becomes the suspension element of the invention) to handle these loads with a lower risk of failure. Conversely, the longitudinal areas where the stresses are lower are designed with a thinner wall thickness. This strategy makes it possible, on the one hand, to optimize the use of materials by reducing their quantity where they are not needed, and on the other hand, to make the suspension element lighter while maintaining its performance.

[0082] Thus, the invention, using the analyses produced and illustrated by graphs GR1 and GR2, makes it possible to conceptualize a wall with variable thickness in order to balance the loads (smooth them out) and therefore lead to better management of localized stresses as a function of the turns. In other words, these analyses make it possible to design sections with specific thicknesses adapted to local loads, ensuring that each turn can manage the stresses imposed on it while maintaining the overall performance of the element. By adjusting the thickness according to the specific load of each turn, the suspension element can be optimized for maximum performance, offering a balance between strength, flexibility, and lightness.

[0083] Thus, the resulting suspension element 8 here comprises portions P+ and P- at its wall. The P+ portions represent the areas where the wall thickness has been increased and the P- portions represent the areas where the wall thickness has been decreased.

[0084] The P+ portions, therefore with increased wall thickness, are located in the sections where the stresses are expected to be highest. These areas are thus more robust in order to support greater loads. Conversely, the P- portions, therefore with reduced wall thickness, are located in the sections where the stresses are expected to be lowest. These areas are therefore designed to be thinner because they are subjected to lower loads.

[0085] Of course, this is an ideal embodiment which consists of adjusting the wall thickness of each turn according to the specific stresses it is subjected to. However, a person skilled in the art may choose not to adjust the thickness for each turn. This decision may be influenced by various factors, such as production costs, performance requirements, or technical constraints.

[0086] Figure 4 schematically illustrates a second example of an implementation of the invention when the prior art suspension element 2 is subjected to hydrostatic pressure stresses or bending stresses. Figure 4 reproduces the entire approach described in Figure 3 as well as all the reference numerals used therein.

[0087] Here, the stresses exerted are hydrostatic pressure stresses or bending stresses. Hydrostatic pressure stresses are forces exerted on a material due to the pressure of a fluid, such as water. Bending stresses, on the other hand, occur when a material is subjected to a load that causes deformation into curvature.

[0088] As in Figure 3, the resulting suspension element 8 here has P+ and P- portions in its wall. The P+ portions represent areas where the wall thickness has been increased, and the P- portions represent areas where the wall thickness has been decreased. The P+ portions, therefore with increased wall thickness, are located in the sections where the stresses are expected to be highest. These areas are thus more robust in order to support greater loads. Conversely, the P- portions, therefore with reduced wall thickness, are located in the sections where the stresses are expected to be lowest. These areas are therefore designed to be thinner because they are subjected to lower loads.

[0089] To perform the variable wall calculation of the suspension element, it is proposed, in a non-limiting manner, to implement the steps of a process 20 whose sequence is illustrated in figure 5 in the form of a flowchart.

[0090] More particularly, such a method 20 for calculating the variable wall thickness of the suspension element 8, includes a first step 21 of acquiring a set of predetermined data defining the desired suspension element.

[0091] These predetermined data include, for example, the number of turns and their diameter, the diameter of the main body, etc. In this example, such data were chosen according to a set of specifications that may include requirements such as the desired stiffness, the lifespan of the suspension element, and its dimensions. Based on these elements, the desired suspension element is conceptualized to meet these specifications.

[0092] However, it should be noted that these predetermined data may initially concern a suspension element with a solid (i.e., non-tubular) wire and a constant thickness. This simplifies the analysis and calculations, as well as the prediction of behavior under different loads.

[0093] More specifically, the aim is to be able to estimate the behavior of the tubular suspension element (i.e., with the main body having a longitudinal hollow passage). Thus, when the predetermined data relates to a suspension element with solid (non-hollow) wire, the process includes an additional step called conversion, which creates a model of a tubular suspension element equivalent to that with solid wire and initially exhibiting a constant thickness along the entire length of the main body wall. In other words, it involves transforming or transposing the characteristics of a suspension element with solid wire into a tubular version in order to meet the specifications. The predetermined data are then updated (number of turns, diameter of the main body, for example).

[0094] The process 20 then includes a second step 22 which consists of implementing a first estimation step, by implementing a first finite element analysis of the behavior of the conceptualized (resulting) suspension element under different constraints.

[0095] Indeed, once the predetermined data has been acquired or updated, it is then possible to divide the model corresponding to the resulting suspension element into a series of small, interconnected, discrete elements as explained above. Each element is subjected to specific stresses and forces, and the analysis allows the mechanical responses of the model as a whole to be calculated. The objective of this initial analysis is to understand how the suspension element reacts to different loads and stresses, identifying areas of high stress and any potential weaknesses in the initial design. This preliminary estimation provides valuable information for the subsequent adjustment of the suspension element's stiffness.

[0096] The method 20 includes a third step 23 which consists of adjusting the stiffness of the suspension element, the stiffness being variable along the length of the main body of the suspension element so as to balance the distribution of said stresses. In other words, once the behavior of the suspension element has been estimated, the stiffness of the suspension element is adjusted (and therefore necessarily its thickness) to balance the stress distribution along its main body.

[0097] The process 20 continues with a fourth step 24, which consists of performing a second finite element analysis to evaluate the behavior of the suspension element with its adjusted stiffness. This analysis verifies whether the modifications have achieved the predetermined performance objectives. It allows us to measure whether the stress distribution is now balanced and whether the suspension element functions as expected under the applied loads.

[0098] Thus, if this second analysis reveals that the behavior of the suspension element meets the established criteria, the design parameters (predetermined data) are considered validated. Otherwise, the process requires a further iteration. In other words, if the behavior of the suspension element conforms to the predetermined objectives (see condition 25 in the figure), the process 20 continues with a fifth step 26, which consists of determining the variable wall thickness along the main body as a function of the adjusted stiffness.

[0099] However, if the results of the second analysis do not meet the criteria, the process 20 reverts to the third step 23 of stiffness adjustment. The predetermined data are then modified according to the discrepancies observed between the initial predetermined data and the results after adjustment. This process is repeated until the suspension element meets the desired specifications.

[0100] Figure 6 schematically illustrates a GR3 graph comparing the efficiency of a suspension element 2 or 3 according to the prior art and that of the suspension element 8 according to the invention. Whether the calculation of the variable wall thickness is carried out by method 20 or by any other method, so as to obtain the suspension element as defined by the invention, the results remain relevant and significant. Thus, regardless of the method used to determine the variable wall thickness, the results presented remain valid and relevant for demonstrating the efficiency and advantages of the invention.

[0101] Graph GR3 in Figure 6 shows the force-compression relationship of a suspension element. It illustrates the distance over which the spring is shortened when a force is applied. This relationship allows us to understand the mechanical behavior of the suspension element under load, and more specifically, largely reflects how the loads are distributed within the suspension element.

[0102] More specifically, on graph GR3, the ordinate Y axis represents the force, measured in newtons (N), and the abscissa X axis represents the compression, measured in millimeters (mm). Compression here refers to the reduction in the length of the suspension element under the effect of the applied force.

[0103] Graph GR3 presents two curves: a first curve C1 showing this evolution in the context of the use of the suspension element 2 or 3 according to the state of the art, and a second curve C2 showing this evolution in the context of the use of the suspension element 8 according to the invention.

[0104] More specifically, as illustrated, the relationship between force and compression is linear with respect to the prior art suspension element 2 or 3. This linearity is due to the fact that, when the suspension element has a wall of the same thickness, the spring stiffness remains constant throughout the compression. The force required to compress the spring then increases proportionally to the deformation.

[0105] As for the evolution of the second curve C2, it exhibits a different behavior from the first curve C1. As illustrated, the applied force remains low even when the compression increases. This indicates that the suspension element 8 of the invention is designed to distribute loads more uniformly. Thus, the variable wall thickness modifies the way in which forces are absorbed and redistributed, which is visible on the second curve C2.

[0106] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

[0107] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

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