CARBONITRIDING OF UNIVERSAL JOINT BUSHES

Abstract

Universal joint bushes for universal joints are disclosed, as well as methods of making or treating the universal joint bushes. The universal joint bush may include an outer ring, which has a peripheral layer (R) formed by at least one measure for diffusing an element into regions of the universal joint bush near the surface. The peripheral layer (R) of the outer ring may include nitrogen. A method for producing a universal joint bush having a nitrogen-containing peripheral layer (R) may include preparing a universal joint bush made from a case-hardened steel and diffusing, via a thermochemical treatment, nitrogen into regions of the universal joint bush that are close to the surface in order to form the nitrogen-containing peripheral layer (R). The thermochemical treatment may be carried out in a temperature range of at least 800 C.

Claims

1. A universal joint bush for universal joints, comprising: an outer ring, which has a peripheral layer (R) formed by at least one measure for diffusing an element into regions of the universal joint bush near the surface, wherein the peripheral layer (R) of the outer ring comprises nitrogen.

2. The universal joint bush as claimed in claim 1, wherein the nitrogen-containing peripheral layer (R) has a predetermined layer thickness (d) in the range of from 1 to 50 m.

3. The universal joint bush as claimed in claim 1, wherein the universal joint bush has a core (K), which is surrounded by the peripheral layer (R), wherein the peripheral layer has a nitrogen content of at least 0.04% and the nitrogen content is higher than that of the core (K).

4. The universal joint bush as claimed in claim 1, wherein the universal joint bush comprises a case-hardened steel, wherein the case-hardened steel is selected from the group consisting of DC04, C15, 16MnCr5, 25CrMo4 and SCM415.

5. The universal joint bush as claimed in claim 1, wherein the universal joint bush comprises a wall thickness in a range between 0.5 mm and 6 mm.

6. A method for producing a universal joint bush and/or for increasing the wear resistance of a universal joint bush having a nitrogen-containing peripheral layer (R), comprising the following steps: preparing a universal joint bush made from a case-hardened steel, diffusing, via a thermochemical treatment, nitrogen into regions of the universal joint bush that are close to the surface in order to form the nitrogen-containing peripheral layer (R), and wherein the thermochemical treatment is carried out in a temperature range of at least 800 C.

7. The method as claimed in claim 6, wherein the diffusion is carried out in such a way that a nitrogen-containing peripheral layer (R) having a predetermined layer thickness (d), preferably from 1 to 50 m, is formed.

8. The method as claimed in claim 6, wherein preparation comprises deep drawing or machining of a preform.

9. The method as claimed in claim 6, wherein the diffusing includes case hardening using a carbonitriding method and/or plasma nitriding and/or gas nitriding and/or gas carbonitriding.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The disclosure is explained in greater detail below by illustrative embodiments in conjunction with associated drawings. In these schematic drawings:

[0056] FIG. 1 shows a section through a first illustrative embodiment of a universal joint bush;

[0057] FIG. 2 shows a section through a second illustrative embodiment of a universal joint bush; and

[0058] FIG. 3 shows a section through a third illustrative embodiment of a universal joint bush.

DETAILED DESCRIPTION

[0059] FIG. 1 shows a first illustrative embodiment of a universal joint bush 1 for universal joints for use in drive shafts and steering shafts of a vehicle, wherein the universal joint bush 1 comprises an outer ring 2.

[0060] In the example under consideration, the universal joint bush 1 essentially has two vertical components and one horizontal component, which are connected to one another, in particular being formed integrally. Said components together form a cup-shaped universal joint bush 1, wherein the horizontal component illustrated forms the outer ring 2.

[0061] Arranged in the region between the three components is a rolling element of a needle bearing or a roller 3 of a needle bearing. As a result, the horizontal component or outer ring 2 thus forms a rolling element race, at least on the inside of the cup-shaped universal joint bush 1, on which race the roller 3 can roll.

[0062] For the sake of completeness, it should be mentioned that the said three components of the universal joint bush 1 have different wall thicknesses W0 (wall thickness of the end of the cup-shaped universal joint bush 1), W1 (wall thickness of the outer ring 2 of the universal joint bush 1), W2 (wall thickness of a flanged edge on the open side of the cup-shaped universal joint bush 1)as illustrated in FIG. 1. Said wall thicknesses W0, W1, W2 or a wall thickness W of the universal joint bush 1 are/is preferably in a range between 0.5 mm and 6 mm.

[0063] The outer ring 2 has a peripheral layer R formed by at least one measure for diffusing an element into regions of the universal joint bush 1 that are near the surface. This peripheral layer R of the outer ring 2 comprises nitrogen or is advantageously enriched with an increased proportion of nitrogen.

[0064] As illustrated in the enlarged view in FIG. 1, the nitrogen-containing peripheral layer R has a predetermined layer thickness d, said thickness being, in particular, in a range of from 1 m to 0.3 mm, preferably in a range of from 1 to 50 m.

[0065] The universal joint bush 1 furthermore has a core K, which is surrounded by the peripheral layer R, wherein the peripheral layer ideally has a higher nitrogen content than the core K, in particular an increased nitrogen content of at least 0.04%.

[0066] The universal joint bush 1 shown in FIG. 1 can be deep drawn and/or produced by a machining method, for example.

[0067] In this case, the universal joint bush 1 comprises a case-hardened steel or consists of a case-hardened steel, wherein DC04, C15, 16MnCr5, 25CrMo4 and/or SCM415 is preferably used as the case-hardened steel. Other grades of steel can, of course, also be used for case-hardened steels.

[0068] According to the disclosure, the universal joint bush 1, illustrated in FIG. 1, is produced by a method for producing a universal joint bush 1 and/or for increasing the wear resistance of a universal joint bush 1 having a nitrogen-containing peripheral layer R.

[0069] In a specific illustrative embodiment, this method advantageously comprises the following steps.

[0070] The first preferred step comprises preparing a universal joint bush 1 made from a case-hardened steel, in particular from DC04, C15, 16MnCr5, 25CrMo4 and/or SCM415. Here, preparation furthermore advantageously comprises deep drawing or machining, in particular turning or milling, of a preform or a blank, preferably of a formed part.

[0071] The machined or deep-drawn preform or universal joint bush 1 has a cup-shaped configuration, as illustrated in FIGS. 1-3, for example.

[0072] A subsequent or further step comprises carrying out at least one measure to diffuse nitrogen into regions of the universal joint bush 1 that are close to the surface in order to form the nitrogen-containing peripheral layer R.

[0073] It is advantageous here if a thermochemical treatment of the universal joint bush 1 is carried out as at least one measure for the formation of the nitrogen-containing peripheral layer R, wherein the thermochemical treatment is preferably carried out in a temperature range of at least 800 C.

[0074] It is advantageous if the at least one measure for the formation of the nitrogen-containing peripheral layer R is carried out in such a way that a nitrogen-containing peripheral layer R having a predetermined layer thickness d, preferably from 1 m to 0.3 mm, preferably from 1 to 50 m, is formed.

[0075] It is advantageous here if case hardening, preferably with the additional supply of nitrogen, in particular a carbonitriding method and/or plasma nitriding and/or gas nitriding and/or gas carbonitriding, is carried out as the at least one measure for the formation of the nitrogen-containing peripheral layer R. With the aid of said methods, nitrogen can be introduced into regions of the universal joint bush 1 that are close to the surface.

[0076] The above observations relating to the illustrative embodiment shown in FIG. 1 are likewise applicable to the other illustrative embodiments illustrated in FIGS. 2 and 3.

[0077] In contrast to the illustrative embodiment shown in FIG. 1, the universal joint bushes 1 in FIGS. 2 and 3 essentially have a different shape. In particular, these illustrative embodiments in FIGS. 2, 3 dispense with a second vertical component on the open side of the cup-shaped universal joint bush 1.

[0078] Common to all the abovementioned illustrative embodiments shown in FIGS. 1 to 3 is the fact that these illustrate universal joint bushes 1 for the steering and drive train of a vehicle.

[0079] The above embodiments are summarized once again briefly and in different words below.

[0080] It is conventional for traditional universal joint bushes 1 known from the prior art to be case hardened, wherein wear occurs on the rolling element race at small pivoting angles and simultaneously high pivoting frequencies. This result is bearing damage, which necessitates replacement of the universal joint bush.

[0081] The present disclosure therefore advantageously starts by addressing the problem of optimizing the bush body or the universal joint bush 1 or the outer ring 2 thereof in respect of wear protection.

[0082] In order to achieve optimization and to enhance the performance of universal joint bushes, these may be carbonitrided.

[0083] In this case, in contrast with conventional case hardening, nitrogen is additionally supplied to the atmosphere. This brings about better retention of hardness and thus additional wear protection for the race and hence a longer service life.

LIST OF REFERENCE SIGNS

[0084] 1 universal joint bush [0085] 2 outer ring [0086] 3 rolling element/roller of a needle bearing [0087] d layer thickness [0088] K core [0089] R peripheral layer [0090] W0 wall thickness [0091] W1 wall thickness [0092] W2 wall thickness