ball joint

Abstract

Ball joint with a bearing shell (2) made of polyoxymethylene and a ball stud (5) provided with a joint ball (3) made of metal, which is slidably mounted in the bearing shell (2) with its joint ball (3), wherein the bearing shell (2) consists of a polyoxymethylene copolymer whose melt flow index is less than or equal to 2.2 cubic centimeters per ten minutes.

Description

[0001] The invention relates to a ball joint with a bearing shell made of polyoxymethylene and a ball stud provided with a metal joint ball, the ball of which is slidably mounted in the bearing shell. The invention further relates in particular to the use of polyoxymethylene as the material of a bearing shell of a ball joint, which has the bearing shell and a ball stud provided with a metal joint ball, the ball of which is slidably mounted in the bearing shell.

[0002] Such a ball joint and the use of polyoxymethylene as the material of a bearing shell of a ball joint are known from DE 10 2010 037 586 A1.

[0003] Ball joints used in motor vehicle chassis typically comprise ball shells made of a polyoxymethylene homopolymer (POM-H) and steel joint balls. During driving, such ball joints are subjected to high-frequency, low-amplitude compressive loads, such as those exerted by the joint ball on the bearing shell. These loads can lead to depolymerization of the bearing shell in the area of ​​the contact surface between the joint ball and bearing shell, a process also known as "highway wear." To prevent this wear, the joint balls are provided with chemically hardened surfaces, usually by nitriding or oxidation.

[0004] However, the production of chemically hardened surfaces involves additional costs and transport effort, since the hardening is usually not carried out by the ball stud manufacturer, but externally.

[0005] Based on this, the invention is based in particular on the object of being able to prevent or at least reduce the aforementioned depolymerization of the bearing shell in a cost-effective manner.

[0006] This object is achieved according to the invention by a ball joint according to claim 1 and by a use according to claim 7. Preferred developments of the invention are given in the subclaims and in the following description.

[0007] A ball joint with a bearing shell made of polyoxymethylene and a ball stud provided with a metal joint ball, which is slidably mounted with its joint ball in the bearing shell, is further developed according to the invention in particular in that the bearing shell consists of a polyoxymethylene copolymer whose melt flow index is less than or equal to 2.2 cubic centimeters per ten minutes.

[0008] It has been found that a polyoxymethylene copolymer, also known as POM-C, can resist depolymerization better than a polyoxymethylene homopolymer (POM-H). However, since a polyoxymethylene copolymer tends to flow and / or creep, it is important to ensure that the melt flow index (MVR) is less than or equal to 2.2 cubic centimeters per ten minutes. This is particularly feasible because, in a polyoxymethylene copolymer, the material properties, such as the melt flow index, can be adjusted by adjusting the nature and / or arrangement of the comonomers.

[0009] The melt flow index is determined at a temperature of 190°C, which can also be referred to as the test temperature. Although this temperature is higher than the usual operating temperature of the bearing shell, which is less than or equal to 80°C, the above-mentioned specifications for the melt flow index have proven suitable. This is particularly true even at 100°C, which is or is approximately a critical temperature for the ball joint. The melt flow index of the polyoxymethylene copolymer is advantageously equal to or approximately equal to 1.40 cubic centimeters per ten minutes. In particular, the melt flow index is determined using a test weight of 2.16 kg.

[0010] The bearing shell is preferably an injection-molded part. The bearing shell is preferably manufactured by injection molding. In particular, the polyoxymethylene copolymer is injection-moldable.

[0011] The bearing shell preferably comprises a bearing shell pin opening. In particular, the ball pin extends out of the bearing shell through the bearing shell pin opening. The bearing shell is, for example, a spherical shell. Advantageously, the bearing shell has a bearing surface, in particular a hollow spherical one, against which the joint ball rests. A lubricant is preferably provided between the bearing shell or its bearing surface and the joint ball.

[0012] The joint ball, in particular, forms the head of the ball stud. For example, the joint ball is also referred to as the ball head of the ball stud. The joint ball is preferably made of an iron material. In particular, the joint ball is made of steel.

[0013] The ball stud preferably extends in a longitudinal direction of the ball stud. In particular, the ball stud is assigned a central axis, which preferably runs centrally through the ball stud. The ball stud is preferably rotationally symmetrical or substantially rotationally symmetrical with respect to the or a central axis. The central axis preferably runs through the center of the joint ball. Advantageously, the central axis runs in the longitudinal direction of the ball stud.

[0014] The ball stud preferably comprises a stud region that extends in particular away from the joint ball, preferably in the longitudinal direction of the ball stud. Preferably, the stud region is rigidly connected to the joint ball. For example, the stud region is formed integrally with the joint ball. In particular, the ball stud forms a monolithic component. Preferably, the stud region is made of metal. Preferably, the stud region is made of a ferrous material. In particular, the stud region is made of steel.

[0015] The ball stud is preferably made of metal. The ball stud is preferably made of a ferrous material. In particular, the ball stud is made of steel.

[0016] Preferably, the breaking stress of the polyoxymethylene copolymer is as high as possible to withstand high loads. Preferably, the breaking stress, particularly in tension, of the polyoxymethylene copolymer is greater than or equal to 60 or 65 MPa. Advantageously, the breaking stress, particularly in tension, of the polyoxymethylene copolymer is equal to or approximately equal to 66 MPa.

[0017] Preferably, the elongation at break of the polyoxymethylene copolymer is as high as possible to withstand high loads. Preferably, the elongation at break, particularly in tension, of the polyoxymethylene copolymer is greater than or equal to 35% or 38%. Advantageously, the elongation at break, particularly in tension, of the polyoxymethylene copolymer is equal to or approximately equal to 40%.

[0018] Preferably, the elastic extensibility of the polyoxymethylene copolymer is as high as possible. This way, plastic deformation of the bearing shell, for example, can be avoided or at least reduced under higher loads.

[0019] Preferably, the tensile modulus of the polyoxymethylene copolymer is as high as possible to withstand high loads. Preferably, the tensile modulus of the polyoxymethylene copolymer is greater than or equal to 2465 MPa. Advantageously, the tensile modulus of the polyoxymethylene copolymer is equal to or approximately equal to 2700 MPa.

[0020] Compressive loads with high frequencies and small amplitudes exerted by the joint ball on the bearing shell lead in particular to a local increase in the temperature of the bearing shell. The heat deflection temperature of the polyoxymethylene copolymer is preferably as high as possible in order to be able to withstand high loads even at higher temperatures. The heat deflection temperature (HDT) of the polyoxymethylene copolymer is advantageously greater than or equal to 81 °C. The preferably maximum bending load is in particular 1.80 MPa, with a heat deflection temperature at this bending load being designated, for example, by HDT / A. In particular, the heat deflection temperature HDT / A is greater than or equal to 81 °C. The heat deflection temperature HDT / A of the polyoxymethylene copolymer is advantageously equal to or approximately equal to 92 °C, in particular at a preferably maximum bending load of 1.80 MPa.

[0021] According to an advantageous embodiment, fibers are or will be embedded in the polyoxymethylene copolymer of the bearing shell and / or in the bearing shell. These fibers are, for example, carbon fibers and / or aramid fibers and / or natural fibers and / or other fibers. The natural fibers are or include, for example, flax fibers.

[0022] According to an advantageous development, the joint ball is free of a chemically hardened surface. In particular, the surface of the joint ball is not subjected to any chemical hardening. Preferably, the material on the surface of the joint ball is or will be compacted, preferably relative to the bulk material of the joint ball, in particular by a physical process, for example by applying pressure, such as by rolling.

[0023] The ball joint preferably comprises a joint housing. The bearing shell is preferably arranged in the joint housing. Advantageously, the joint housing comprises a joint housing pin opening. In particular, the ball pin extends out of the joint housing through the joint housing pin opening.

[0024] The ball joint is or will preferably be provided for or in a vehicle, which is in particular a motor vehicle. For example, the vehicle is a passenger car or a truck.

[0025] The ball stud is preferably connected, preferably firmly and / or rigidly, to a machine part. The machine part is preferably a vehicle component, in particular of or a vehicle. Advantageously, the machine part is a chassis component, in particular of or a vehicle. The machine part is, for example, a wheel carrier, axle body, chassis control arm, chassis, or subframe of or a vehicle.

[0026] Preferably, the bearing shell and / or the joint housing are connected, preferably firmly and / or rigidly, to another machine part. The other machine part is preferably one or another vehicle component, in particular of the vehicle. Advantageously, the other machine part is one or another chassis component, in particular of the vehicle. The other machine part is, for example, a wheel carrier, axle body, chassis control arm, chassis, or subframe of the vehicle.

[0027] In particular, an axial direction is assigned to the ball joint and / or the bearing shell and / or the joint housing. The ball stud preferably extends in the axial direction or an axial direction through the bearing shell pin opening out of the bearing shell. The ball stud preferably extends in the axial direction or an axial direction through the joint housing pin opening out of the joint housing.

[0028] In particular, a longitudinal joint axis is assigned to the ball joint and / or the bearing shell and / or the joint housing. Preferably, the bearing shell is rotationally symmetrical or substantially rotationally symmetrical with respect to the or a longitudinal joint axis. In particular, the longitudinal joint axis runs in the axial direction. Preferably, the longitudinal joint axis runs through the center of the joint ball. Advantageously, the longitudinal joint axis runs centrally through the bearing shell pin opening. Preferably, the longitudinal joint axis runs centrally through the joint housing pin opening.

[0029] One or any direction running transversely to the axial direction and / or transversely to the longitudinal axis of the joint is referred to in particular as a radial direction. A direction running around the longitudinal axis of the joint, for example, is referred to as the circumferential direction. The term "at least one" also includes, in particular, the meaning of "one" or "exactly one."

[0030] The polyoxymethylene copolymer is or is formed, in particular, with ethylene oxide as a comonomer. For example, the polyoxymethylene copolymer is or is formed from formaldehyde and ethylene oxide and / or from trioxane and ethylene oxide. Trioxane is, in particular, a trimer of formaldehyde. For example, trioxane is or is formed by trimerization of formaldehyde. The polyoxymethylene copolymer is or is formed, in particular, with formaldehyde and / or trioxane as the main monomer.

[0031] The invention further relates in particular to the use of polyoxymethylene as a material for a bearing shell of a ball joint, which comprises the bearing shell and a ball stud provided with a metal joint ball, which is slidably mounted in the bearing shell with its joint ball. In particular, a polyoxymethylene copolymer is used as the material for the bearing shell, the melt flow index of which is less than or equal to 2.2 cubic centimeters per ten minutes.

[0032] The ball joint according to the use according to the invention is preferably the ball joint according to the invention. In particular, the use according to the invention and / or the ball joint described in connection therewith can be further developed according to all embodiments explained in connection with the ball joint according to the invention.

[0033] The invention is described below using a preferred embodiment with reference to the drawing. In the drawing: Fig. 1 a partially sectioned view of a ball joint according to an embodiment.

[0034] Out of Fig. Figure 1 shows a partially sectioned view of a ball joint 1 according to one embodiment, which comprises a bearing shell 2 in the form of a spherical shell and a ball stud 5 having a joint ball 3 and a stud region 4 extending away from the latter, which is slidably mounted in the bearing shell 2 with its joint ball 3. The bearing shell 2 is provided with a bearing shell stud opening 6 through which the ball stud 5 extends out of the bearing shell 2 in an axial direction x.

[0035] The ball joint 1 further comprises a joint housing 7 in which the bearing shell 2 is arranged. The joint housing 7 is provided with a joint housing pin opening 8 through which the ball pin 5 extends out of the joint housing 7 in the axial direction x. A sealing bellows 9 is attached to the joint housing 7, enclosing the ball pin 5, extending from the joint housing 7 to the pin area 4 and sealingly abutting it. The sealing bellows 9, which is preferably made of an elastomer, prevents, in particular, the penetration of dirt and moisture through the pin openings 6 and 8 into the bearing shell 2.

[0036] The ball stud 5 extends in a ball stud longitudinal direction, which is Fig. 1 particularly coincides with the axial direction x. Furthermore, the ball stud 5 is rotationally symmetrical with respect to a central axis 10 running in the longitudinal direction of the ball stud 5, which in Fig. 1 is indicated by dash-dotted lines and runs through the center point 11 of the joint ball 3.

[0037] The ball stud 5 is firmly connected by its stud portion 4 to a chassis component 12 of a motor vehicle (shown only schematically). Furthermore, the joint housing 7 is firmly connected to another chassis component 13 of the motor vehicle. The chassis component 12 is, for example, a wheel carrier, and the other chassis component 13 is, for example, a chassis link.

[0038] The ball stud 5 is made entirely of steel, so the joint ball 3 is also made of steel. Furthermore, the bearing shell is made of a polyoxymethylene copolymer with a melt flow index of less than or equal to 2.2 cubic centimeters per ten minutes.

[0039] In particular, the melt flow index of the polyoxymethylene copolymer is equal to or approximately equal to 1.40 cubic centimeters per ten minutes. Preferably, the stress at break, in particular tensile, of the polyoxymethylene copolymer is equal to or approximately equal to 66 MPa. Preferably, the elongation at break, in particular tensile, of the polyoxymethylene copolymer is equal to or approximately equal to 40%. Advantageously, the tensile modulus of the polyoxymethylene copolymer is equal to or approximately equal to 2700 mPa. The heat distortion temperature HDT / A of the polyoxymethylene copolymer is equal to or approximately equal to 92 °C. Reference symbol 1 ball joint 2 bearing shell 3 Ball joint of the ball stud 4 Pin area of ​​the ball stud 5 ball studs 6 bearing shell pin opening 7 Joint housing 8 Joint housing pin opening 9 Sealing bellows 10 Center axis of the ball stud 11 Center of the joint ball 12 13 Chassis component Chassis component x axial direction

Claims

[1] Ball joint with a bearing shell (2) made of polyoxymethylene and a ball stud (5) provided with a ball joint (3) made of metal, which is slidably mounted with its ball joint (3) in the bearing shell (2), characterized by , that the bearing shell (2) consists of a polyoxymethylene copolymer whose melt flow index is less than or equal to 2.2 cubic centimeters per ten minutes. [2] Ball joint according to claim 1, characterized by that the tensile strength or breaking stress of the polyoxymethylene copolymer is greater than 60 MPa. [3] Ball joint according to claim 1 or 2, characterized by that the elongation at break of the polyoxymethylene copolymer is greater than 38%. [4] Ball joint according to one of the preceding claims, characterized by that the tensile modulus of the polyoxymethylene copolymer is greater than 2465 MPa. [5] Ball joint according to any one of the preceding claims, characterized bythat the heat deflection temperature HDT / A of the polyoxymethylene copolymer is greater than 81 °C. [6] Ball joint according to any of the preceding claims, characterized by , that the ball joint (3) is free from a chemically hardened surface. [7] Use of polyoxymethylene as a material for a bearing shell of a ball joint, which has the bearing shell (2) and a ball stud (5) provided with a ball joint (3) made of metal, which is slidably mounted with its ball joint (3) in the bearing shell (2), characterized by , that the material of the bearing shell (2) is a polyoxymethylene copolymer whose melt flow index is less than or equal to 2.2 cubic centimeters per ten minutes. [8] Use according to claim 7, characterized by that the tensile strength or breaking stress of the polyoxymethylene copolymer is greater than 60 MPa. [9] Use according to claim 7 or 8, characterized bythat the elongation at break of the polyoxymethylene copolymer is greater than 38%. [10] Use according to any one of claims 7 to 9, characterized by that the tensile modulus of the polyoxymethylene copolymer is greater than 2465 MPa. [11] Use according to any one of claims 7 to 10, characterized by that the heat deflection temperature HDT / A of the polyoxymethylene copolymer is greater than 81 °C. [12] Use according to any one of claims 7 to 11, characterized by , that fibers are embedded in the polyoxymethylene copolymer of the bearing shell. [13] Use according to any one of claims 7 to 12, characterized by , that the ball joint (3) is free from a chemically hardened surface.

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