DE102012015445A1 - Rolling bearing-supported shaft comprises shaft body made of first material, comprising bearing points respectively having running surface for rolling bodies, which is applied as layer of thermally sprayed second material on shaft body - Google Patents

Abstract

Rolling bearing-supported shaft comprises at least one shaft body made of a first material, comprising bearing points respectively having a running surface for rolling bodies. The running surface is applied as a layer of a thermally sprayed second material on the shaft body at least in the region of the respective bearing point. An independent claim is also included for manufacturing the shaft, comprising (a) providing the shaft body, (b) providing the second material, (c) applying a layer of the second material on the shaft body at least in the region of the bearing points, by thermal spraying, to form the running surfaces, and (d) post-processing the shaft body at least in the region of the bearing points, for dimensioning the running surfaces.

Description

The invention relates to a roller bearing shaft and a manufacturing method for such a shaft.

Shafts, in particular crankshafts for reciprocating engines such as internal combustion engines, can be stored relatively free of play, wear and smooth running in comparison to a plain bearing in a rolling bearing.

Plain bearings are, however, since they usually consist of separable bearings, easier to assemble. If a rolling bearing with standard bearings, which consist of inner ring, rolling elements and outer ring, be used for the storage of an internal shaft section, there are two options for mounting: either the shaft or the bearing inner ring must be made divisible, both with increased costs and a dramatic loss of rigidity and reliability is associated with problems in operation especially at the joints of the two inner ring and / or shaft parts occur.

Due to the described disadvantages rolling bearings in internal combustion engine construction are not widely used, but they offer great potential in terms of downsizing and ever-increasing liter performance.

Rolling bearings, with suitable lubrication, have a significantly lower bearing friction than plain bearings, are wear-resistant and smooth-running even during cold starts and do not require such complex lubricating devices as slide bearings, as a result of which relatively small lubricant pumps can be used.

Roller bearings, in particular crankshafts, are known from the prior art, in which a bearing inner ring is manufactured directly on the shaft body.

The DE 10 2010 034 960 A1 describes a shaft made of a cast iron material and a method for its production. There, a bearing element made of steel is poured into the shaft body at a bearing for a rolling bearing. The shaft is made by a process in which the bearing element made of steel is inserted into a casting of the shaft and then the casting mold is poured out with cast iron. In the case of the shaft described there or the method described there, the occurring thermal distortion and the high manufacturing tolerances, which require a high degree of post-processing, are disadvantageous.

Further, the DE 10 2007 028 888 A1 a method for increasing the strength of a component, in particular a crankshaft. There, a nitriding layer is applied to the entire component and this layer partially removed in the next step with a machining process. In the areas with the nitriding layer removed, we then carry out a work hardening to increase the near-surface hardness. The method disadvantageously involves many steps, and only parts of the same base material are available for areas of the crankshaft (eg, crank webs and main bearing journals) that actually make different demands on a material.

Further, the DE 2010 012 100 A1 a crankshaft and a method for manufacturing, wherein the crankshaft there at least partially made of a steel. After forging a crankshaft blank, it is at least subjected to a BY treatment at the subsequent bearing points, this terming thermal methods for adjusting microstructural and / or surface properties from forging heat.

Based on this prior art, it is an object of the present invention to provide an improved roller bearing shaft, which is one-piece, wear-resistant, space-saving and inexpensive to produce.

This object is achieved by a roller bearing shaft with the features of claim 1.

In addition, the task results to provide a manufacturing method for a roller bearing shaft according to the invention, which allows the production of a shaft with high tolerances, low Zerspanaufwand and with a few steps.

This object is achieved by a manufacturing method for a roller bearing shaft with the features of claim 6.

Further developments of the shaft and the method are set forth in the subclaims.

A first embodiment of the roller bearing shaft according to the invention has a shaft body made of a first material with bearing points, each with a running surface for rolling elements. In this case, the running surface is applied to the shaft body as a layer of a thermally sprayed second material at least in the area of the respective bearing point.

The bearing point forms in the shaft according to the invention, the inner ring of a rolling bearing, whereby the space occupied by the rolling bearing space, compared with the use of standard bearings, is reduced. In addition, an integrated inner ring simplifies the assembly of such a shaft, since so only the outer ring of the bearing can be made split. Furthermore, the shaft body can be made in one piece because of this and is not divided axially as in known constructions. The inner ring integrated in the shaft also provides a secondary cost advantage, since the number of parts can be reduced and complex components, such as a split shaft body, can be avoided.

By thermal spraying very wear-resistant and by anchoring or clamping the layer with the substrate well adhering layers can be produced with a layer thickness up to 5 mm. The layer which forms the running surface in the shaft according to the invention can advantageously have a thickness of between 0.1 and 0.5 mm.

Such, d. h., From two different materials existing wave can be advantageously designed so that different wave ranges, eg. B. the crank webs, main journal and connecting rod journal in a crankshaft, each of which may be made of a material adapted to the specific requirements. Thus, the journals should have a high hardness and abrasion resistance, while the crank webs and the shaft body should have about a high strength and a correspondingly high density. This wide range of material requirements can be realized only to a limited extent with only one base material, even if it is present in different heat or surface treatment states. Although a shaft could consist entirely of a "bearing steel", but that would be unnecessarily expensive. By contrast, the shaft according to the invention can be made of a conventional material, as already used for the production of shafts, while only the bearing points are provided with a layer of a material adapted to the requirements, whereby considerable cost reductions can be implemented.

Moreover, the second material used to make the tread may be a steel having a hardness in the range of 45 to 75 HRC and preferably 55 to 65 HRC.

For the highest possible wear resistance, a high hardness is desirable, and the hardness of the second material used for the tread should also be matched to the hardness of the rolling elements. Furthermore, the hardness should not be too high, so that the tread and shock loads, as they can occur during operation of a reciprocating engine, without damage, ie brittle fracture, can cope. The necessary hardness of the steel can be achieved, for example, by a martensite or bainite hardening.

Further, the steel may have a chemical composition of 0.5 to 2.0 wt.%, Preferably 1.0 to 1.5 wt.%, C (carbon) and / or 0.25 to 1.25 wt. %, preferably 0.5 to 1.0 wt .-%, Cr (chromium) and / or Ni (nickel) and / or Mn (manganese). The composition contains a residual amount of Fe which compensates for the 100% by weight.

In addition, the steel may also contain the alloying elements vanadium and / or molybdenum. Suitable steels are for example high-chromium stainless steels, such as the X65Cr14 or the X105CrMo17, high-temperature steels, such as the 80MoCrV42-16, or the 100Cr6 or its derivatives.

Alternatively, the second tread material may also be a ceramic, with silicon carbide ceramics or silicon nitride ceramics being advantageous due to strength and hardness.

Ceramics can also be applied by thermal spraying with sufficient layer thicknesses. In addition, it can thus achieve a significantly higher hardness and abrasion resistance, and this can contribute to a low-wear operation even under unfavorable lubrication conditions.

Furthermore, the shaft according to the invention may be a crankshaft and / or a camshaft and / or a balance shaft, wherein the bearing points may be arranged on shell and / or on end faces of the shaft body.

A bearing point on a lateral surface of the shaft is suitable for a radial bearing and a bearing point on an end face for axial bearing. Are in a reciprocating engine, in particular an internal combustion engine, for example, all balancing, crankshaft and cam shafts according to the invention with entirely ceramic bearings, even oil-free operation is conceivable, whereby an oil pump would become obsolete. It is only necessary to ensure that the requirements for the tribological stability of the cylinder liner (s) are met.

• a) Bereitstellen des Wellenkörpers,
• b) Bereitstellen des zweiten Werkstoffs,
• c) Aufbringen einer Schicht des zweiten Werkstoffs auf den Wellenkörper zumindest im Bereich der Lagerstellen mittels thermischem Spritzen, dadurch Ausbilden der Laufflächen,
• d) Nachbearbeiten des Wellenkörpers zumindest im Bereich der Lagerstellen, dadurch auf Maß bringen der Laufflächen.

A first embodiment of the production method according to the invention for a roller bearing shaft according to the invention comprises the steps:

• a) providing the shaft body,
• b) providing the second material,
• c) applying a layer of the second material to the shaft body at least in the region of the bearing points by means of thermal spraying, thereby forming the running surfaces,
• d) reworking of the shaft body at least in the region of the bearing points, thereby bring to measure the treads.

The second material can be supplied in powder or wire form depending on the thermal spraying process used. With thermal spraying processes, it is possible to produce any desired layer thicknesses of a few up to a few mm. By reworking the shaft as a final step, the surface roughness of the treads is also adjusted.

The shaft body is fed to the process as a forged or cast blank, the dimensions of which already correspond to the nominal dimensions in essential dimensions. Only the treads or bearings have yet to be processed, d. h., The method is suitable for "near-net-shape production". In addition, the method advantageously has a small number of steps and is easy to automate, whereby the thermal spraying can be automated. In addition, only small amounts of heat are introduced into near-surface layers, which contributes to the fact that the roller bearing shaft can be manufactured with high tolerances and lowest thermal distortion. In known manufacturing methods, which include about classic curing or BY treatment, the occurring thermal distortion is greater due to the large heat input.

Additionally, before step c), step
c ') activating the surface of the shaft body in the region of the bearing points, preferably by means of sandblasting and / or mechanical milling and / or abrasive roughening,
be executed.

This step serves to improve the adhesion of the layer to the substrate. Since, during thermal coating, as a rule no cohesive connection between the layer and substrate is established, but the layer adheres to the surface of the substrate due to mechanical clamping or non-positive anchoring, a predefined roughened surface is necessary for good adhesion. Abrasive roughening is a process in which the surface is treated, for example, with a high-pressure water jet with addition of garnet. Alternatively or additionally, the activation of the surface can be done by chemical treatment of the surface and / or the application of adhesion-promoting agents.

In a further embodiment of the method, after step c), step
c '') recompression of the shaft body at least in the region of the bearing points for generating compressive residual stresses, preferably by means of shot peening, tapping or rolling,
be executed.

The re-compaction serves to introduce compressive residual stresses into the material in the area of the bearing point. In such work-hardening methods, the plastic deformation locally increases the dislocation density, whereby hardness and strength increase, and thus the abrasion resistance can be further increased.

A thermal spraying process may be preferably arc spraying and / or flame spraying and / or plasma spraying. The post-processing may preferably include the use of separation methods with geometrically determined or unspecified cutting edge, preferably turning and / or grinding and / or lapping and / or polishing.

The appropriate thermal spraying method is to be selected depending on the second material used. If the tread is to be applied as a ceramic layer, the use of plasma spraying is particularly advantageous. These and other advantages will be set forth by the following description with reference to the accompanying figure.

The reference to the figure in the description is to aid in the description and understanding of the subject matter. The figure is merely a schematic representation of an embodiment of the invention.

The figure shows a side view of a roller bearing crankshaft.

In 1 is a roller bearing crankshaft 1 shown, the crank webs 4 , Connecting rod bearings 3 and main camps 2 having. Both the connecting rod bearings can be used 3 as well as the main camp sites 2 be fitted with rolling bearings. The shaft body may consist of a steel or cast iron material and on the bearings 2 . 3 According to the invention, a layer of a wear-resistant second material is applied by means of thermal spraying. Since the inner ring of the bearing through the bearings 2 . 3 itself is formed, is the assembly of such a crankshaft 1 simple, because no split inner ring is needed as part of a rolling bearing. In addition, such a crankshaft saves 1 Space, since the radial space requirement is lower due to the integrated inner ring, and weight.

The second material may in this case be a steel which advantageously has a hardness of at least 55 HRC or a ceramic, for example silicon carbide ceramic or silicon nitride ceramic, wherein the ceramic can not be applied by any thermal spray method but only by plasma spraying.

An alternative to thermal spraying is the use of electroplating or chemical coating processes, wherein, above all, a nickel-based coating is hard and wear-resistant.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010034960 A1 [0007]
• DE 102007028888 A1 [0008]
• DE 2010012100 A1 [0009]

Claims (10)

Rolling shaft ( 1 ) comprising at least one shaft body made of a first material with bearing points ( 2 . 3 ), each having a running surface for rolling elements, characterized in that the running surface as a layer of a thermally sprayed second material at least in the region of the respective bearing point ( 2 . 3 ) is applied to the shaft body. Wave ( 1 ) according to claim 1, characterized in that the second material is a steel having a hardness in a range of 45 to 75 HRC, preferably 55 to 65 HRC. Wave ( 1 ) according to claim 2, characterized in that the steel, the alloying constituents - 0.5 to 2.0 wt .-%, preferably 1.0 to 1.5 wt .-% C and / or - 0.25 to 1.25 Wt .-%, preferably 0.5 to 1.0 wt .-% Cr and / or - Ni and / or - Mn, wherein the composition contains a residual amount of Fe, which compensates the 100 wt .-%. Wave ( 1 ) according to claim 1, characterized in that the second material is a ceramic, preferably silicon carbide ceramic or silicon nitride ceramic. Wave ( 1 ) according to at least one of claims 1 to 4, characterized in that - the shaft ( 1 ) is a crankshaft and / or a camshaft and / or a balance shaft, and / or - the bearing points on shell and / or on end faces of the shaft body is arranged. Manufacturing method for a shaft ( 1 ) according to at least one of claims 1 to 5, comprising the steps: a) providing the shaft body, b) providing the second material, c) applying a layer of the second material to the shaft body at least in the region of the bearing points ( 2 . 3 ) by means of thermal spraying, thereby forming the running surfaces, d) reworking of the shaft body at least in the region of the bearing points ( 2 . 3 ), thereby tailoring the tread. Manufacturing method according to claim 6, wherein prior to step c) the step c ') activating the surface of the shaft body in the region of the bearing points ( 2 . 3 ), preferably by means of sandblasting and / or mechanical levitation and / or abrasive roughening. Manufacturing method according to claim 6 or 7, wherein after step c) step c '') recompression of the shaft body at least in the region of the bearing points ( 2 . 3 ) for generating residual compressive stresses, preferably by means of shot peening, tapping or rolling. Manufacturing method according to at least one of claims 6 to 8, wherein after step d) the step d ') partial hardening of the shaft body at least in the region of the bearing points ( 2 . 3 ), preferably by means of induction hardening or laser beam hardening. Manufacturing method according to at least one of claims 6 to 9, in which Thermal spraying is preferably arc spraying and / or flame spraying and / or plasma spraying Post-processing preferably involves the use of separation methods with geometrically determined or unspecified cutting edge, preferably turning and / or grinding and / or lapping and / or polishing.

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