ball joint

Abstract

Ball joint, in particular for a motor vehicle, comprising a case (12), a ball stud (16) with a ball head (18), and a first and a second bearing shell (20, 22) for supporting the ball head (18), characterized in that In addition to the first and second bearing shells (20, 22), at least one further overload bearing surface (24) is provided.

Description

[0001] The present invention relates to a ball joint, in particular for a motor vehicle, comprising a housing, a ball stud with a ball head and a first and a second bearing shell for supporting the ball stud.

[0002] Ball joints of this type are commonly used in general mechanical engineering, particularly in vehicle manufacturing, and in a wide variety of applications. The bearing shells enclose the ball head of the ball stud without play. To achieve a defined preload and consistent frictional resistance of the ball joint, high demands are placed on the dimensional accuracy of the bearing shells during manufacturing and on their dimensional stability due to wear or settling during operation. To compensate for manufacturing-related and operational wear-related dimensional inaccuracies, it is known to use split bearing shells. A disadvantage of such ball joints is that, to transmit high loads, especially at high temperatures, either a different material must be used for the bearing shells or the diameter of the ball head must be increased to avoid exceeding the permissible surface pressure of the bearing shells.Exceeding the permissible surface pressure leads to excessive settling of the bearing shells and thus to an unacceptably large amount of free play in the ball joint. In the worst case, this can result in failure of the ball joint.

[0003] US 4 003 666 A shows a ball joint for a motor vehicle.

[0004] Based on this, the present invention aims to provide a ball joint that enables the transmission of high loads even at high temperatures, while maintaining a largely constant frictional resistance. Furthermore, the ball joint should be as simple in design as possible and largely pre-assemblable.

[0005] This problem is solved by a ball joint having the features of claim 1. Advantageous embodiments of the invention are defined in the dependent claims.

[0006] In the ball joint according to the invention, at least one overload bearing surface is provided in addition to the first and second bearing shells. The invention is based on the fundamental concept of dividing the bearing arrangement of the ball stud into a "normal bearing" and an "overload bearing." This allows the normal bearing, formed by the two bearing shells, to be designed for the loads that typically occur, thereby achieving particularly low friction coefficients. It is not necessary to design the bearing shells with a large diameter to accommodate high point loads, which is unnecessary for the normal loads and would lead to increased friction. Excessively high loads, on the other hand, are absorbed by an overload bearing in the form of the at least one additional bearing surface, thus protecting the normal bearing from excessively high loads.The design specifically ensures that the ball head only makes contact with the overload bearing surface above a selectable load. Under loads where the specified forces are not exceeded, only the first and second bearing races are subjected to stress. Exceeding the selected load causes the ball head to deflect from its normal position beyond a certain point, causing it to make contact with the overload bearing surface. Because the higher loads are then absorbed by an additional bearing surface, the increase in surface pressure on the first and second bearing races is reduced, thus largely preventing the maximum permissible surface pressure of these races from being exceeded. This reduces settling, allowing the preload of the ball joint to be maintained for a longer period. The probability of ball joint failure is reduced, and its service life is increased.Furthermore, the material can be specifically chosen so that the frictional resistance is as low as possible under any load.

[0007] Preferably, the overload bearing surface is designed as an annular surface surrounding the ball head. This design is based on the understanding that the loads that occur typically act in a radial direction, relative to the ball stud in its non-displaced position.

[0008] The inner diameter of the overload bearing surface can be larger than the diameter of the ball head, so that contact between the overload bearing surface and the ball head only occurs above a certain force level or corresponding deflection of the ball head. Alternatively, the inner diameter of the overload bearing surface can be essentially matched to the diameter of the ball head, so that contact between the ball head and the overload bearing surface occurs even under normal loads. In any case, the crucial point is that force transmission between the ball head and the housing via the overload bearing surface only occurs once a specific force level is reached.

[0009] Preferably, the overload bearing surface is formed on an overload bearing component separate from the bearing shells. This makes it possible to manufacture the bearing shells on the one hand and the overload bearing component on the other from materials that represent an optimal compromise between their properties and costs for the respective requirements.

[0010] In particular, the overload bearing component is designed to have a higher stiffness and / or higher temperature resistance than the material of the first and second bearing shells. If the selected load on the ball joint is exceeded, the overload bearing component, due to its higher stiffness, absorbs the majority of the resulting forces, thus reducing the load on the first and second bearing shells. The stiffness of the overload bearing component material can be specifically adapted to the forces and surface pressures acting upon it, while the materials of the first and second bearing shells can be designed for normal loads. Advantageously, the first and second bearing shells are designed to absorb a large proportion of the loads occurring during operation of the ball joint.Furthermore, if particularly high temperatures occur, this can also be taken into account by selecting suitable materials.

[0011] By dividing the load conditions according to the invention into a normal load range and a peak load range, it is not necessary to design all bearing shells for the peak load, but only the overload bearing component. The ball joints can be made smaller, since the inventive solution reduces the need to increase the diameter of the ball head to reduce the surface pressure under peak loads. Since materials with high stiffness and temperature resistance are usually more expensive than materials whose stiffness and temperature resistance are within the normal range, the cost of a ball joint according to the invention can be reduced while simultaneously achieving a high load-bearing capacity.

[0012] For the purposes of the invention, the attribute "overload" is to be understood as meaning that an overload only occurs when the level of normal, i.e., small, loads acting on the ball joint is exceeded. In other words, an overload involves a comparatively high force level, which leads to a force flow between the ball head and the housing via the overload bearing surface. Whereas previously a gap existed between the ball head and the overload bearing surface under normal loads, the ball head now comes into contact with the overload bearing surface under overload. It is understood that all components of the ball joint according to the invention are designed to withstand the force level under overload. Thus, it is ensured that damage to the ball joint or even failure under overload is prevented.

[0013] According to a preferred embodiment, at least one of the bearing shells is provided with a receptacle for the overload bearing component. This allows the relative positions of the bearing shells and the ball stud to be determined, at least provisionally, even before they are installed in the ball joint housing. This simplifies and speeds up the assembly of the ball joint. Furthermore, the positioning of the overload bearing component relative to the bearing shells is improved during operation.

[0014] According to a preferred embodiment, the overload bearing component is provided for in the receptacle by means of a positive and / or frictional fit. This makes it possible to pre-assemble the ball joint outside the housing and then insert it into the housing as a unit.

[0015] Preferably, the overload bearing component is a sheet metal ring. This allows the overload bearing component to be manufactured at very low cost.

[0016] An advantageous embodiment consists in the sheet metal ring being provided with elastically and / or plastically deformable spring elements formed by punched-out sections. This allows the overload bearing component to be reliably positioned inside the ball joint with minimal effort.

[0017] According to an alternative design, the overload bearing component can also be a ring made of a plastic material, for example PEEK. In this way, the overload bearing component can be manufactured as a section of a ring profile.

[0018] According to a preferred embodiment, the two bearing shells and the overload bearing component form a pre-assemblable unit. This allows the bearing shells and the overload bearing component to be pre-assembled outside the housing in such a way that the components remain connected to each other without further measures. They are then inserted into the housing, which is then closed, for example by a lid or by plastically deforming the housing edge.

[0019] According to a preferred embodiment, the housing has at least one first recess into which a corresponding first projection engages, the projection being provided on at least one of the bearing shells or the overload bearing component. This design allows for easy assembly of the ball joint. The first recesses can be closed or open in one direction. The projections provided on the bearing shells or the overload bearing component can be elastically deformable, so that when the bearing shells are inserted into the housing, they deform elastically until they engage in the first recesses. They then return to their original position and determine the position of the bearing shells.If the first recesses are open on one side, they prevent the bearing shells from rotating and position them towards the closed side of the first recesses as soon as the projections contact the closed side. In this case, the projections do not deform elastically when the bearing shells are inserted into the housing. Axial displacement of the bearing shells is particularly advantageous when using a preload element.

[0020] Preferably, a preload element is provided that elastically compresses at least one of the bearing shells against the ball head. Suitable springs or preloaded housing covers can be used as preload elements. The use of preload elements has the advantage that the preload of the ball joint can be precisely adjusted. Furthermore, it is easy to change the preload by replacing the preload elements, for example, if the ball joint is to be used in a different application. Preload elements also ensure that manufacturing inaccuracies or settling of the bearing shells during operation are compensated for and that impermissible free play of the ball joint is prevented. The frictional resistance of the ball joint remains largely constant, since the preload element exerts a consistently uniform force on the ball head.

[0021] According to a preferred embodiment, the housing is a bent sheet metal part. This results in low manufacturing costs.

[0022] According to one embodiment, the bearing shells are preloaded by means of the housing. This eliminates the need for separate preloading elements.

[0023] In principle, in addition to the overload component, further overload bearing surfaces can be provided, which become effective in special load situations. For example, it could be provided that ring-shaped overload components are effective under high axial loads on the ball joint and prevent overloading of the corresponding bearing shell in these cases.

[0024] The invention is explained in more detail with reference to preferred embodiments and the figures. These show... - Fig. 1 a sectional view of a first embodiment of a ball joint according to the invention, - Fig. 2 a sectional view of a second embodiment of a ball joint according to the invention with two different variants left and right, - Fig. 3 a sectional view of a third embodiment of a ball joint according to the invention, - Fig. 4 a partial section of a fourth embodiment of a ball joint according to the invention, - Fig. 5 a sectional view of a fifth embodiment of a ball joint according to the invention, - Fig. 6 a sectional view of a sixth embodiment of a ball joint according to the invention, - Fig. 7 a front view of an overload bearing component according to the invention in its initial state ( Fig. 7a) or in the maximally compressed state ( Fig. 7b); and - Fig. 8 a schematic sectional view of two variants of an eighth embodiment of a ball joint according to the invention, and - Fig. 9 a sectional view of a ninth embodiment of a ball joint according to the invention.

[0025] The in Fig. Figure 1 shows a first embodiment of the ball joint 10 according to the invention with a longitudinal axis L, comprising a housing 12 which is connected to an arbitrary component 14. The ball joint 10 further comprises a ball stud 16 with a ball head 18, wherein the ball head 18 has a diameter D and a center point M. The ball head 18 is supported in a first bearing shell 20 and a second bearing shell 22, which are annular in shape. An overload bearing surface 24 is provided between the two bearing shells, which is designed as the inner surface of an annular overload bearing component 25. An axial gap S is provided between the overload bearing component 25 and the first and / or the second bearing shell 20, 22, which ensures that the two bearing shells 20, 22 bear against the ball head 18 with a preload determined by the housing 12 and independent of tolerances of the overload bearing component 25.However, the gap S is dimensioned such that in every position of the overload bearing component 25 the overload bearing surface 24 is opposite the ball head 18.

[0026] In the initial state, there is also a gap between the overload bearing surface 24 and the ball head 18, since the inner diameter di of the overload bearing component 25 is slightly larger than the outer diameter D of the ball head 18.

[0027] Furthermore, the ball joint 10 has a sealing sleeve 26, which is attached to the housing 12 of the ball joint 10 by a metal ring 28. The sealing sleeve 26 prevents moisture and dirt from entering the ball joint 10.

[0028] In the example shown, the housing 12 is a sheet metal bent part. For assembly, the sheet metal can first be deep-drawn into a hollow cylinder, open at one end. The first bearing shell 20 and the overload bearing component 25 are then inserted into the housing 12 through this open end. Next, the ball stud 16 and the second bearing shell 22 are mounted. The open end of the housing 12 is then deformed, thus closing the housing 12, so that the bearing shells 20 and 22 are pressed against the ball head 18 with the desired preload. The sealing sleeve 26 is then fitted and secured to the housing 12 with a metal ring 28. Finally, the housing 12 can be attached to the component 14.

[0029] To explain the concept according to the invention, it shall now be assumed that the ball stud 16 is rigidly mounted and that the component 14 connected to the ball joint 10 is articulated both through the center point M and perpendicular to the section plane of Fig. The ball joint 10 can pivot about the longitudinal axis (arrow P1) as well as about the longitudinal axis L (arrow P2) (or vice versa, i.e., a rigidly mounted housing and a ball stud movable about two axes). Component 14 can, for example, be a tie rod of a vehicle steering system, and the ball stud 16 can be attached to a tie rod of a wheel carrier of a steerable vehicle wheel. The use of this ball joint 10 is not limited to this example; it can, for example, be provided between a wheel carrier and a suspension component.

[0030] Normally, the loads are transmitted from the ball head 18 via the first and second bearing shells 20, 22 to the housing 12, and vice versa. The overload bearing surface 24 does not participate in the load transmission, as there is always a small gap between it and the ball head. Should the forces transmitted from component 14 to the housing 12 suddenly increase, for example due to an impact load while the vehicle is in motion, the ball stud 16 is deflected from its original position due to the elasticity of the first and second bearing shells 20, 22. If the degree of deflection is so large that it exceeds the gap between the ball head 18 and the overload bearing surface 24, the ball head 18 then comes into contact with the overload bearing surface 24, so that the forces then acting are no longer absorbed solely by the first and second bearing shells 20, 22, but also by the overload bearing component 25.

[0031] The material for the first and second bearing shells 20, 22 can be specifically adapted to the normal loads, with the use of POM (polyoxymethylene) being a suitable option, which allows the first and second bearing shells 22 to be manufactured as injection-molded parts. For the overload bearing component 25, which is only subjected to peak loads, the use of PEEK (polyetheretherketone) is recommended, allowing it to be manufactured as a pipe section of a profile part produced by continuous casting.

[0032] In Fig. Figure 2 shows a second embodiment of the ball joint 10 according to the invention, which operates according to the same principle as described for the first embodiment. In the variant shown in the left half, a preload element 30 in the form of a spring is provided, which preloads the first and second bearing shells 20, 22 against the ball head 18. Settling or wear of these bearing shells 20, 24 during operation is compensated for by compression, so that on the one hand no free play occurs, and on the other hand the joint preload is kept largely constant. Although no play S between the two bearing shells 20, 22 and the overload bearing component 25 is shown here, it is apparent to a person skilled in the art that in practice at least sufficient play exists to allow adjustment of the bearing shell 20 under the action of the preload element 30.

[0033] In the event of an overload, the ball head 18 can rest against the overload bearing component 25 after the bearing shells 20, 22 have been elastically deformed to a corresponding extent, or after it has pushed the bearing shells 20, 22 apart against the action of the preload element 30 so far that it can support itself on or rest against the overload bearing surface 24.

[0034] In the variant shown in the right half, the preload is not generated by the spring, but by a suitably designed, resilient bulge 30' on the base of the housing. The advantage of this variant is that fewer components are required, resulting in a more economical and robust construction.

[0035] In Fig. Figure 3 shows a third embodiment. In contrast to the two preceding embodiments, the housing 12 in the third embodiment is not designed as a bent sheet metal part, but as a solid part, for example, as a metal casting or a milled metal part. A separate cover 32 is provided, which can be attached to the housing 12 with fasteners, such as screws. Another difference from the first two embodiments is that the two bearing shells 20, 22 are received in the overload bearing component 25, which for this purpose is cylindrical, i.e., with a greater axial length. To facilitate assembly, the two bearing shells 20, 22 can be dimensioned relative to the overload bearing component 25 so that they are frictionally engaged within it.This allows the bearing shells 20, 22 to be largely pre-positioned around the ball head 18 before they are inserted into the housing 12 together with the overload bearing component 25. In the assembled state, a gap S remains between the cover 32 and the overload bearing component 25 or the housing 12 to ensure that the preload of the bearing shells 20, 22 is not affected by any tolerances of the overload bearing component 25.

[0036] In the fourth embodiment, which is in Fig. As shown in Figure 4, the housing 12 has first recesses 34 into which corresponding first projections 36 of the first and second bearing shells 20, 22 can be inserted or snapped into place. The first projections 36 can be elastically deformable, so that when the bearing shells 20, 22 are inserted into the housing 12, they deform elastically until they can engage in the first recesses 34. They then return to their original position and fix the position of the bearing shells 20, 22. If the first recesses 34 are open on one side (34a), they prevent the bearing shells from rotating and position them towards the closed side of the first recesses as soon as the first projections 36 abut the closed side. In this case, there is no elastic deformation of the first projections 36 when the bearing shells are inserted into the housing 12.

[0037] In the fifth embodiment, which is described in Fig. As shown in Figure 5, the preload element 30 is designed in the form of a spring-loaded cover 46. The bearing shell shown in the image above rests against a surface of the housing that is rounded with respect to the longitudinal axis L. Alternatively, the upper bearing shell could also rest against an inclined surface that is angled with respect to the longitudinal axis L. This rounded or inclined surface allows a (desired) settling effect to occur as a result of the preload exerted by the cover 46.

[0038] In Fig. Figure 6 shows a sixth embodiment, in a state under an overload in the direction of arrow F, in which the ball head is supported on the overload bearing surface 24. The longitudinal axis L1 is that of the ball joint which, in the case of normal loads, coincides with or deviates only insignificantly from the longitudinal axis L2 of the ball stud. In the Fig. In the state shown in Figure 6, the ball stud 16 is deflected from its normal position to such an extent that the ball head 18 rests against the overload bearing component 25. Furthermore, the first and second bearing shells 20, 22 have second recesses 38 into which the overload bearing component 25, designed as a hollow cylinder, can engage in a form-fit and / or friction-fit manner. The second recess 38a of the first bearing shell 20 is open radially outwards, viewed from the longitudinal axis L of the ball joint 10, while the second recess 38b of the second bearing shell 22 is closed radially outwards. In this way, the overload bearing component 25 can yield slightly elastically.

[0039] In Fig. Figure 7 is a front view of an overload bearing component 25 according to the invention in its initial state ( Fig. 7a) and in the maximally compressed state ( Fig. Figure 7b) shows variants for spring elements 40 above and below the dotted line, which are formed by bent material tabs beyond the cutouts 42. Advantageously, the overload bearing component 25 is made from a sheet metal part.

[0040] The spring elements 40 are arranged such that they come into contact with the respective adjacent bearing shells 20, 22 during assembly of the ball joint 10. When the housing 12 is closed, the spring elements 40 are compressed, causing them to deform elastically and thereby positioning the overload bearing component 25 between the two bearing shells. The spring elements 40 can be compressed to a maximum extent that the edges of the overload bearing component 25 are straight (see Fig. 7b).

[0041] Above the dotted line in Fig. In the variant shown in 7, the cutout 42 is essentially oval-shaped, in the unloaded state ( Fig. 7a). If the overload bearing component 25 is installed in the ball joint ( Fig. 7b), the upper edge of the spring element is pressed downwards or inwards until it is essentially flush with the upper edge of the overload bearing component 25 (in Fig. 7b then shown as a straight line). The deformation of the spring element 40 is possible because the cutout 42 deforms or shrinks into a crescent shape.

[0042] The variant of the punching 42 shown below the dotted line is designed in the form of a cap ( Fig. 7a, there upside down), which in the installed state of the overload bearing component 25 form a slot ( Fig. 7b) is narrowed. In this variant, it is also ensured that the spring element 40 has sufficient space to deform inwards when the overload bearing component 25 is installed.

[0043] For both variants of the spring elements 40, in Fig. 7b the force represented by arrows F which, in the event of deformation of the spring elements 40, is exerted on the components arranged adjacent to the overload bearing component 25 (in Fig. 7b bearing shells (not shown) act to place them under suitable preload.

[0044] In Fig. Figure 8 shows a simplified embodiment of the ball joint in which contact already exists between the ball head 18 and the overload bearing surface 24 under normal load. However, it is important that a force flow between the ball head and the housing via the overload bearing surface only occurs once a certain force level has been reached. Fig. 8a The overload bearing component can move into a recess in the housing until force transmission occurs. In Fig. 8b includes springs that serve to transmit power.

[0045] In Fig. Figure 9 shows an embodiment in which the preload by which the upper bearing shell 22 is pressed against the ball head 18 is achieved by means of a spring element that is arranged within the overload bearing component or can be part of it. It is understood that the upper and lower edges of the overload bearing component are movable relative to each other so that the spring element can exert its effect. Alternatively, it can be an overload bearing component according to Fig. 7, in which the spring elements are integrated. In the same way as with Fig.5 (see the explanation above) it is important that at least one of the two bearing shells (here the upper bearing shell in the picture) is supported against the housing via a rounded (or alternatively: inclined) surface, so that the spring preload allows for the desired settling effect of the bearing shell!

Claims

[1] Ball joint, in particular for a motor vehicle, comprising a case (12), a ball stud (16) with a ball head (18), and a first and a second bearing shell (20, 22) for supporting the ball head (18), characterized by , that In addition to the first and second bearing shells (20, 22), at least one further overload bearing surface (24) is provided. [2] Ball joint according to claim 1, characterized by , that the overload bearing surface (24) is designed as a ring surface that surrounds the ball head (18). [3] Ball joint according to any one of the preceding claims, characterized by , that the overload bearing surface (24) is formed on an overload bearing component (25) that is separate from the bearing shells (20, 22). [4] Ball joint according to claim 3, characterized by, that the material of the overload bearing component (25) has a higher stiffness and / or a higher temperature resistance than the material of the first and second bearing shells (20, 24). [5] Ball joint according to one of claims 3 and 4, characterized by , that at least one of the bearing shells (20, 22) has a receptacle (38) for the overload bearing component (25). [6] Ball joint according to claim 5, characterized by , that the overload bearing component (25) is positively and / or frictionally engaged in the receptacle (38). [7] Ball joint according to any one of claims 3 to 6, characterized by , that the overload bearing component (25) is a sheet metal ring. [8] Ball joint according to claim 7, characterized by , that the sheet metal ring is provided with elastically and / or plastically deformable spring elements (40) formed by punched-out sections (42). [9] Ball joint according to any one of claims 3 to 6, characterized by, that the overload bearing component (25) is a ring made of PEEK. [10] Ball joint according to any one of claims 3 to 9, characterized by , that the two bearing shells (20, 22) and the overload bearing component (25) form a pre-assemblable unit. [11] Ball joint according to any one of the preceding claims, characterized by , that the housing (12) has at least one first recess (34) into which a corresponding first projection (36) engages, which is provided on at least one of the bearing shells (20, 22) or the overload bearing component (25). [12] Ball joint according to any one of the preceding claims, characterized by , that at least one of the bearing shells (20, 22) is elastically preloaded against the ball head (18). [13] Ball joint according to claim 12, characterized by a preloading element (30) that preloads at least one bearing shell (20, 22). [14] Ball joint according to claim 13, characterized by, that the preload element is a separate spring element (30) that is arranged between the housing (12) and the bearing shell (20, 22). [15] Spherical element according to claim 13, characterized by , that the preloading element is designed in the form of a cover (46) which closes the housing (12) to the outside. [16] Ball joint according to claim 13, insofar as it relates back to any one of claims 3 to 12, characterized by that the preload element is located within or is part of the overload bearing component (25). [17] Ball joint according to claim 12, characterized by , that the preload is exerted on at least one bearing shell (20, 22) by a suitable curvature of the housing. [18] Ball joint according to any one of claims 12 to 17, characterized by , that at least one of the two bearing shells (20, 22) is supported against the housing (12) on a surface which is inclined or rounded in relation to a longitudinal axis (L) of the ball joint. [19] Ball joint according to any one of the preceding claims, characterized by , that the housing (12) is a sheet metal bent part. [20] Ball joint according to one of claims 13 and 14, characterized by , that a sealing sleeve (26) is provided for sealing the ball joint (10), which is attached to a collar of the housing (12). [21] Ball joint according to any one of the preceding claims, characterized by , that from a certain force level a force flow exists between ball head (18) and housing (12) via the overload bearing surface (24). [22] Ball joint according to claim 21, characterized by , that the ball head (18) only comes into contact with the overload bearing surface (24) from the certain force level. [23] Ball joint according to any one of the preceding claims, characterized by , that the overload bearing surface (24) has an inner diameter (di) that is larger than the diameter (D) of the ball head (18).

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