Ball joint

Abstract

The invention relates to a ball joint, in particular for wheel suspensions of motor vehicles, having an outer more or less cylindrical housing, an inner joint element having a ball pivot bearing a ball section, and a bearing ring enclosing the ball section, such bearing ring being retained in the cylindrical housing, and having annular seals on both sides of the ends of the ball pivots, annular gaps which are indirectly or directly filled with a damping fluid being formed around the ball pivots adjacent to the ball section in order to achieve a hydraulic damping function.

Description

[0001] The invention relates to a ball joint, in particular for wheel suspensions of motor vehicles, as specified in the preamble of claim 1.

[0002] A ball joint such as this is disclosed in DE 42 07 602 A1, for example. Such joints, which are rotatable about the central axis of the ball and pivotable through a limited pivoting angle, are often used as suspension joints in wheel suspensions of motor vehicles. In addition to their reliability and smoothness of operation, such ball joints are assigned a specific damping function for eliminating vibrations.

[0003] The object of the invention is to propose a generic ball joint which is advantageous from the viewpoint of structure and production technology and which performs a specific damping function.

[0004] It is claimed for the invention that this object is attained by the characteristics specified in claim 1. Advantageous developments of the invention are set forth in the other claims.

[0005] It is proposed in accordance with the invention that annular gaps filled directly or indirectly with a damping fluid be formed around the ball pivot adjacent to the ball section. The damping fluid, preferably one of high viscosity, both ensures smooth operation of the ball joint nearly free of wear and at the same time effectively damps vibrations around the center of the ball within a specific frequency range, in particular when the joint is used as journal bearing in wheel suspensions of motor vehicles. The damping fluid may possess electrorheologic or magnetorheologic properties.

[0006] In a structurally favorable embodiment the annular gaps may be bounded essentially by annular extensions on the bearing ring enclosing the ball section. By preference the length of the annular gap should be greater than its width by a factor of 3 in order to ensure adequate damping operation. In addition, the annular gaps preferably may be formed between tapering ball pivot sections and correspondingly configured extensions on the bearing ring; this results in rugged pivot structure and structurally more favorable sealing between the ball pivot ends and the outer cylindrical housing of the ball joint.

[0007] An indirect layout in which annular tubes filled with damping fluid are used in the annular gaps is proposed as an alternative to direct introduction of the damping fluid into the annular gaps. Specific damping properties of the ball joint may also be imparted by shaping of the annular tubes (e.g., by use of fabric reinforcements) and by functional separation of lubrication of the joint (e.g., with grease) and the damping medium.

[0008] The annular tubes may be seated in prismatic guide rings of the cylindrical housing and butt against annular collars of the ball pivot sections formed in the area of the tubes. When the ball joint is free of load this results in more or less linear contact between the ball pivot sections and the tubes, contact which does not impair smooth operation of the ball joint and also ensures a specified damping behavior.

[0009] Use of a damping fluid possessing electrorheologic or magnetorheologic properties makes it possible to create a continuously variable damping characteristic.

[0010] Such use permits configuration of a ball joint with controllable torsion damping (driving-dependent change in the damping property) which may be employed, for example, to reduce vibration problems in multiple-rod axles.

[0011] A damping fluid characterized by rheologic action presents the advantage of rapid response behavior (damping control almost in real time, so that damping in the area of the natural wheel frequency as well is possible). The damping characteristic of the rheologic fluid may be modified by means of a control device and the damping characteristic of a ball joint controlled accordingly.

[0012] Two exemplary embodiments of the invention are described in greater detail in what follows. The accompanying drawing, in the form of diagrams, shows in

[0013] FIG. 1, a longitudinal section through a ball joint for wheel suspensions of motor vehicles with specified annular gaps filled with damping fluid on both sides of the ball section; and

[0014] FIG. 2, another longitudinal section through a ball joint with hoses filled with a damping fluid mounted in annular gaps on both sides of the ball section.

[0015] FIG. 1 shows a ball joint designated as 10 which consists essentially of an outer cylindrical housing 12, an inner rotation-symmetric joint element 14 with a ball pivot 18, 20 bearing a ball section 16 and a bearing ring 22 enclosing the ball section 16.

[0016] The joint element 14 has a through opening 24 by means of which this element may be fastened by means of a screw to a wheel carrier of a wheel suspension of a motor vehicle. The cylindrical housing 12 may also be rigidly connected by a method not illustrated to a guide rod of the wheel suspension. The housing 12 and the joint element 14 are made conventionally of metal, while the bearing ring 22 is made of a suitable plastic such as polymethylene oxide.

[0017] The bearing ring 22 enclosing the ball section 16 is designed to be of two parts, with a plane of separation 22a extending vertically relative to the joint central axis 26, and is kept axial in the cylindrical axis 12 both on the circumference side and both on an annular collar 28 on one side and on a screwed-in clamping ring 30 on the other.

[0018] Annular seals 32 which seal the ball joint 10 from the exterior, but without impairing the required pivotability of the inner joint element 14 about the ball section center point 34, are mounted between the cylindrical sections of the ball pivot 18, 20 and the front ends of the cylindrical housing 10.

[0019] In addition, conical ball pivot sections 18a, 20a tapering toward the ends of the ball pivot are formed between the cylindrical sections of the ball pivot 18, 20 and the ball section 16. In conjunction with annular extensions 36,38 also tapering internally, these ball pivot sections form on the bearing ring 22 annular gaps 40,42 having a length l and a mean width b, to which the statement l≧3b applies.

[0020] The annular gaps 40, 42 are filled with a high-viscosity incompressible damping fluid or oil which is tightly enclosed between the seals 32 inside the ball joint 10 and which simultaneously acts as a lubricant.

[0021] When vibration of the ball joint 10 is excited around the ball section center point 34, the annular gaps 40,42 narrow and widen on both sides of the ball section 16 respectively and in the process displace the damping fluid in the circumferential direction, this resulting in performance of a specified damping function. The damping properties may be determined by the configuration of the annular gaps 40, 42 and the structure of the annular seals 32 respectively.

[0022] In order to avoid repetition, the ball joint 50 shown in FIG. 2 is described only to the extent that it differs from the ball joint 10 shown in FIG. 1. Functionally identical parts are provided with the same reference numbers.

[0023] The ball joint 50 in turn has a cylindrical outer housing 52, an internal joint element 54 with a ball section 56 and adjoining ball pivot 58, 60.

[0024] The bearing ring 62 enclosing the ball section 56 is retained axially one on side by an annular collar 64 of the housing 52 and by a screwed-in clamping ring 66 on the other.

[0025] Adjoining the foregoing a guide ring 68, 70 prismatic in cross-section is fastened in the housing 52 (is pressed in or screwed in).

[0026] Spherical annular collars 72, 74 are formed on the ball pivots 58, 60 radially opposite the guide rings 68, 70.

[0027] Fabric-reinforced elastic rubber tubes 80, 82 filled with a high-viscosity damping fluid are formed in the annular gaps 76, 78 between the guide rings 68,70 and the ball pivots 58, 60.

[0028] The tubes 80,82 are seated to approximately half their circumference in the prismatic guide rings 68, 70 and on the other side rest against the spherical annular collars 72, 74 of the ball pivots 58, 60.

[0029] The annular gaps 76, 80, in turn, are sealed from the exterior by the annular seals 32.

[0030] The damping properties of the ball joint 50 are determined chiefly on the basis of the configuration of the tubes 80, 82, the guide rings 68, 70, the ball pivots 58, 60 with or without the annular collars 72, 74, and, lastly, the seals 32. Lubricant and damping medium may be specified and employed separately.

[0031] If a damping fluid possessing an electrorheologic property is used, it is necessary to use an electric insulating layer in the through opening (24) of the joint element (14, 54). Similarly, the cylindrical housing (12, 52) must be enclosed in an electrically insulating layer. The insulating layer may be, for example, in the form of an electrically insulating material (such as a plastic). This is necessary in order to prevent a short circuit when electric control voltage is applied to the electrorheologic fluid. The electric control voltage is provided by a control device.

[0032] The electric insulating layer may be dispensed with when a magnetorheologic fluid is used. A magnetic field which permits control of the damping characteristic of the ball joint is generated in the cavities through which damping fluid flows, by way of an external power supply applied to an electric coil in the joint element (14, 54) or in the cylindrical housing (12,52).

Claims

1. A ball joint, in particular for wheel suspensions of motor vehicles, having an outer more or less cylindrical housing, an inner joint element having a ball pivot bearing a ball section and a bearing ring enclosing the ball section which is retained in the cylindrical housing, and annular seals on both ends of the ball pivot, characterized in that there are formed around the ball pivot (18, 20), adjacent to the ball section (16), annular gaps (40, 42) which are directly or indirectly filled with a damping fluid.

2. The ball joint as claimed in claim 1, wherein the annular gaps (40, 42) are bounded essentially by annular extensions (36, 38) on the bearing ring (22).

3. The ball joint as claimed in claim 1 or 2, wherein the annular gaps (40, 42) as seen in cross-section have a length (l) at least threefold the mean width (b) of such annular gaps (l≦3 b).

4. The ball joint as claimed in claims 1 to 3, wherein the ball pivot sections (18a, 20a) delimiting the annular gaps (40, 42) and the extensions (36, 38) are conical in form, with diameters decreasing in the direction of the ends of the ball pivot.

5. The ball joint as claimed in one or more of the preceding claims, wherein annular tubes (80, 82) filled with damping fluid are mounted in the annular gaps (76, 78).

6. The ball joint as claimed in claim 5, wherein the annular tubes (80, 82) are retained in guide rings (68, 70) prismatic in cross-section of the cylindrical housing (52).

7. The ball joint as claimed in claim 5 or 6, wherein annular collars (72, 74) spherical in shape are formed on the ball pivots (58,60) in the area of the tubes (80, 82).

8. The ball joint as claimed in one or more of the preceding claims, wherein the damping fluid possesses electrorheologic properties.

9. The ball joint as claimed in claim 8, wherein an electric field is formed, on the joint element (15, 54) and the cylindrical housing (12, 52), in the cavities through which the damping fluid flows, by way of a control device having an external power supply, which electric field permits control of the damping characteristic of the ball joint.

10. The ball joint as claimed in claims 8 and 9, wherein an insulating ring of an electrically insulating material (such as a plastic) is introduced into the through opening (24) of the joint element (14, 54) and wherein the cylindrical housing (12, 52) is enclosed in an electrically insulating ring in order to prevent voltage equalizing by way of an electric short circuit.

11. The ball joint as claimed in one or more of the preceding claims 1 to 7, wherein the damping fluid possesses magnetorheologic properties.

12. The ball joint as claimed in claim 11, wherein a magnetic field is formed by way of an external power supply on an electric coil in the joint element (15, 54) or in the cylindrical housing (12, 52), in the cavities through which the damping fluid flows, which magnetic field permits control of the damping characteristic of the ball joint.