WO2004055402A1

WO2004055402A1 - Antifriction bearing comprising integrated lubricating material

Info

Publication number: WO2004055402A1
Application number: PCT/DE2003/004125
Authority: WO
Inventors: Martin Engler; Edmund Föhr; Walter Schumacher-Ruf
Original assignee: Myonic Gmbh
Priority date: 2002-12-16
Filing date: 2003-12-12
Publication date: 2004-07-01
Also published as: DE10259003A1; AU2003294656A1; BR0317378A; EP1573215A1; JP2006509975A

Abstract

The invention relates to an antifriction bearing (5, 6) comprising integrated lubricant, the parts that are moved towards each other being in superficial contact. At least one portion of the area of at least one of said parts is coated with a lubricant.

Description

"Rolling bearings with integrated lubricating material"

The invention relates to a roller bearing according to the preamble of claim 1. So far for high-speed devices such as compressors, turbines, machining spindles, ball bearings, turbomolecular pumps or the like, high-precision ball bearings with n • Dm ^> million (n = speed [l / min], D _m = ball center circle [mm]) used. Such bearings are regularly provided with oil lubrication.

In many applications, the lubrication of rolling bearings with an oil is not a major problem. In special applications, however, the use of an oily lubricant is considerably disruptive if the lubricant can get into sensitive work areas in which such lubricants are undesirable.

High-speed rolling bearings are used in a wide range of applications, for example in dental hand instruments. Here it is immediately understandable that the lubricant used can get into the working area of the drill and thus into the cavity to be processed in the patient's mouth, among other things, via the storage and the accommodation of the drill. Even the smallest amounts of lubricant in a tooth cavity have the consequence that the filling of the cavity administered can no longer be guaranteed satisfactorily because, among other things, its adhesion in the cavity is restricted.

According to the state of the art, however, repeated oiling of the instruments is absolutely necessary. Experience shows that this usually happens irregularly, and then oil is often supplied in excess, which in turn has a negative effect on the operating behavior and the service life and also negatively influences the quality of work due to oil leakage during operation as drops or oil mist.

Methods are known from coating technology with the aid of which bodies can be coated. A base body coated in this way and a coated or uncoated counter body can then be moved relative to one another in dry running. As a result of this movement, material is transferred from the coated base body to the non-coated counterpart and both rolling surfaces are smoothed out by this movement, among other things.

The object of the invention is to provide a high-speed rolling bearing, in particular a miniature bearing, in which the moving components contained therein at usual high speeds while ensuring low waste heat, while ensuring high running smoothness and while maintaining the previous service life without the risk of leakage Oil can be operated and that avoids the disadvantages of the prior art described. Presentation of the invention

This object is achieved by claim 1. Advantageous refinements result from the subclaims.

With the aid of the features according to the invention from claim 1, in which at least one of the parts has an at least partial surface coating with a lubricant, a rolling bearing is created which does not require any lubricant supplied from the outside.

In the following, “lubricating material” means all materials that have a lubricating effect without being differentiated.

In the following, “lubricants” are also understood to mean in particular those lubricating materials that are not bound in the solid, such as oils or fats.

“Lubricant” in the following also means in particular lubricating materials that are bound in a solid and / or that can also release lubricants themselves.

The coating itself can also be understood as a lubricant which is firmly connected to the base material or also has at least one intermediate layer, for example as a carrier layer. In the case of a self-lubricating coating, the amount dispensed should preferably be so small that, even with partial atomization or pulverization, it only occurs locally in the area of the bearing and thus has no negative influence on the work result. This has the advantage that the lubricant is only present at the points at which friction processes take place.

In particular, the rolling elements, i.e. in the case of ball bearings, the bearing balls and / or the outer ring and / or the inner ring and / or a bearing cage can be considered. In the case of the outer and / or inner ring, the raceway is preferably designed according to the invention.

With the help of such solid lubrication, the oil can be replaced as a lubricant in order to implement an oil-free concept.

Lubricant is generally required wherever there is a need to reduce friction or wear and / or to adjust surface properties in a targeted manner. The operator no longer has to periodically lubricate the bearing according to the invention, which also prevents maintenance errors during maintenance. In addition, the internal and external contamination of the instruments or devices provided with the bearing with lubricant is prevented.

When used in a dental instrument, the treatment has the advantage that no lubricant escapes from the instrument and thus cannot get into the patient's cavity to be treated. This concept relates to hand instruments that are powered by air as well as to hand instruments that are powered by air With the help of a motor, in particular an electric motor.

Also in the other applications mentioned at the beginning, e.g. in vacuum technology, especially in

Ultra-high vacuum technology, etc. the disruptive effect of an oil or its vapor is avoided with a bearing according to the invention. In addition, a bearing according to the invention offers the advantage in all applications of being maintenance-free, at least with regard to the lubrication.

A particular hurdle when the invention came about was to gain knowledge regarding the behavior of the smallest components under the specific loads that prevail in the miniature bearing area. The experience regarding the behavior of coatings, as is currently the subject of research in classic mechanical engineering, particularly in materials science and coating technology, cannot be transferred linearly to ever smaller components due to physical and metallurgical effects. Rather, as the size decreases, the influence of the stress caused by e.g. static loads and the influence e.g. of tolerances, surface finish, crystal and structure structures, metallurgical diffusion processes etc.

In addition, there are the typical loads for miniature bearings in many applications, such as revolutions from 40,000 rpm to 400,000 l / min depending on the application, some of them over several gear stages, e.g. with a total gear ratio of the order of approx. 1 : 5, can be achieved, and furthermore the highest possible smoothness and low heat development is required, often high Temperature resistance must be guaranteed. These loads increasingly occur in bearings with n • D _m > _ 1 million (n = speed [l / min], D _m = ball center circle [mm]).

It is sufficient if only one component has a coating as long as lubrication takes place due to the lubricant provided in the coating, the lubricant also being able to remain on the coating and then not being transferred to the uncoated part.

If, according to a first further development, coating material is transferred from the coated component to the uncoated component and the lubricant bound therein is also transferred with the coating material, this has the advantage that components which have already been coated in production can be combined with uncoated components. After a running-in phase, the surfaces in contact show behavior as if the surfaces were already coated from the start.

If a plurality of parts moving relative to one another with the requirement of lubrication are present, it is advantageous to apply a lubricant-transferring coating to at least one of the parts, it also being possible to provide different coatings. It is not necessary to coat all of the components that are moving relative to one another, as long as it is ensured that at the points at which the relative movement takes place during the rolling process, either by coating only one component or by transferring material, for example by removal processes Lubrication is present. If the bound lubricant and the uncoated counter surface are designed such that the lubricant adheres to the counter surface, the material transfer from the part carrying the coating to the initially uncoated part enables both surfaces to be smoothed, as a result of which the operating temperature is reduced and smooth running is increased.

A further advantage results if the coating has a different composition from the side of the component to be coated towards the free surface. As a result, different functions can be set, such as the adhesion of the coating to the base body on the one hand and its abrasion resistance with respect to the part moved to it on the other hand. In addition, the coating is independent of the geometry of the object to be coated.

If the proportion of lubricant on the free surface of the coating is increased compared to the side of the component to be coated, this has the advantage that the engaging partner is better supplied with lubricant.

The development, in which the coating comprises at least one carrier layer connected to the surface of the coated part and at least one lubricant layer, brings with it the advantage of specifically adjusting the adhesion of the coating to the part carrying the coating.

If the lubricant from the coating is a solid lubricant, it can be ensured that No components that could cause contamination are released outside of operation.

If the components embedded in the coating can assume a liquid state during operation, it is advantageously ensured that the lubrication takes place only during operation and only locally.

If the coating includes a metal-doped, diamond-like carbon layer (DLC), excellent lubrication is ensured while ensuring abrasion resistance.

If a carrier layer is metallic, this has the advantage of being able to adjust the surface hardness in a targeted manner. The surface hardness of the coated part can be lower.

If the coating comprises a single or multi-layer polymer layer, this allows a wide range of applications, since the potential of usable organic compounds is extremely high. Of particular interest are polymers which have a low coefficient of friction, good pressure and flexibility properties and are abrasion-resistant and hard. Against this background, PTFE is an option. The surface of such a polymer layer is then the working surface of one of the rolling partners.

In addition, the respective specific properties when applying several materials, such as passivation, abrasion resistance, pressure stability, high sliding effect, layer thickness, number of layers, etc. can be set individually and specifically. By touching one Polymer coating with an uncoated surface transfers the specific properties of the respective polymer with the transfer of parts of the polymer to the previously uncoated side of the engagement partner. In addition, the shape of the object to be coated plays no role in the coating and a further advantage is that such polymer layers form a flat, homogeneous surface which is suitable as a rolling surface.

If additional functional layers are present in the coating, the specific properties of various functional layers can be combined with one another. If a layer of it e.g. has a pressure-stabilizing effect by distributing the pressure peaks acting on the coating in the layers, this improves the stability and service life of the component concerned and thus of the entire instrument.

The coating advantageously has an internal damping which reduces the running noise.

If the coating has an electrical resistance that changes due to wear, the reduction in the layer thickness, e.g. by abrasion, the qualitative and quantitative state of wear of the coating can be determined based on a change in resistance.

If the coating is electrically insulating, a measurement of the resistance can be used to determine whether the assemblies are electrically isolated as long as there is sufficient insulating coating. If the coating differs optically from the base material, this has the advantage that the state of wear can be recognized by an optically perceptible change in the coating.

If the optical properties such as color, degree of gloss (mirror effect) or color intensity of the coating change due to wear, this in turn has the advantage that the intensity of the wear depends on the location of wear due to a visually perceptible change in the coating, e.g. Entry marks, is recognizable.

If the coating reduces the surface hardness through the use of a polymer layer, it has a dampening effect, which has an advantageous effect on smooth running. However, if the coating leaves the surface hardness unchanged due to the use of a polymer layer, the friction resistance is reduced by the polymer layer. However, if the surface hardness is increased, the removal rate of the coating can be reduced. A common advantage remains that the running properties and abrasion properties can be adjusted with the help of the coatings.

Advantageously, at least one component of the rolling bearing is provided with a corresponding coating, so that lubrication is ensured in this way. In a ball bearing, for example, the inner ring and / or outer ring and / or the ball cage and / or the balls can be coated. If only one of the parts moving relative to one another is coated, this can reduce the manufacturing costs and enables an overall particularly thin functional layer, seen overall, via the material transfer to the uncoated part. If an additional first unbound lubricant, which corresponds to a second lubricating material, such as grease or oil, or additives with a comparable effect, is only provided on the surfaces of the parts in contact, an additional lubricating effect with the resulting further advantages, such as e.g. Improved smoothness can be achieved. In the case of such a combination of lubricating materials, the behavior of the overall system can be adjusted to a wide variety of user needs.

If the additional unbound lubricant has high adhesive and cohesive forces, it can be prevented from moving away from the additionally lubricated surfaces and in the vicinity of the place of use, e.g. vagabonded in the hand instrument or in the working area of the tool, whereby the adhesive forces serve primarily for the bond between two materials and the cohesive forces for the internal cohesion of the material. If both have a high value, it is guaranteed that the lubricant can develop its effect with pinpoint accuracy. This can in particular ensure that such a lubricant is applied once during production and that it no longer has to be applied during the life of the product.

If, in addition to the additional first lubricant already added, another unbound second lubricant, corresponding to a third lubricant, is introduced, such as oil in addition to lubricating grease in the bearing, the operating behavior can be adjusted with further parameters. For example, friction and so that the operating temperature can be reduced even further and the smoothness can be further increased.

If the bound lubricant is designed as a carrier for the further unbound lubricant, an interaction of the complementary properties of the respective substances can be ensured.

It is particularly advantageous if the coating can be sterilized and / or if the additional lubrication material (s) can be sterilized. This enables the sterility required in the field of medicine, among other things, to be achieved by sterilization. A high temperature and / or moisture resistance can also be advantageous in other areas of application.

If the lubricant of the coating and the further lubricant are selected so that they are compatible with a lubricant according to the prior art, the conventional care and lubrication with oil do not lead to a loss of the properties of the coating.

If the lubricant consists of several layers, a sliding and lubricating effect is also ensured between the layers of the lubricant, so that the lubricity is increased.

Brief description of the drawings

Exemplary embodiments of the invention are shown in the drawings. It shows the Fig. 1 is a Kop housing of a dental turbine in longitudinal section, the

Fig. 2 is a rolling bearing with shaft and gear, partially in longitudinal section, the

Fig. 3 shows the structure of a multifunctional hybrid layer and the

Fig. 4 shows a section through storage means designed according to the invention.

embodiment

In Fig. 1 the front part of a dental hand instrument is shown. The figure shows a sectional view of the front part of a dental turbine handpiece with a head housing 1, in which a rotor shaft 2 with a rotor 4 for a tool 3 to be driven is mounted in a known manner by means of roller bearings 5, 6. The rolling elements, here balls, are kept at a distance by a ball cage 10, 11.

In this turbine handpiece, the bearings 5, 6 and / or the cages 10, 11 are particularly suitable for a coating.

2 shows a section of a dental handpiece, in which two drive shaft sections 16, 17 are mounted inside a grip sleeve 15. A plurality of at least partially coated roller bearings 18, here embodied as ball bearings 18 and slide bearings 19, are provided for storage. The toothing of a transmission consists of two gear wheels 20, 21. The at least partially coated roller bearings 18 can be lubricated with a further lubricant. The roller bearings can also be replaced entirely by plain bearings, in which case a corresponding coating can be provided.

The structure of a multifunctional hybrid polymer layer as the first variant of the structure of a coating is shown in FIG. 3.

A passivation layer 42 is applied to the surface of the base body 41. Above this is a pressure-stabilizing layer 43, on which in turn a polymer layer 44 is applied as a functional layer. The layers are shown exaggerated and the total layer thickness is 1 -10 μm.

The advantages of a hybrid polymer layer are that each layer can perform a certain function, e.g. Passivation, abrasion resistance, pressure stability, high sliding effect, etc. The coating is also independent of the shape of the object to be coated in this case, and the layer thickness and number of layers are individually adjustable. The polymers form flat, homogeneous surfaces.

The inner layer of the polymer layer can consist of various layers of the same material. Ideally, these layers can support lubrication by sliding between these layers. In addition, bound lubricant can be embedded in the polymer and, in addition, unbound lubricant can also be applied, for example during assembly. The lubricity can be precisely adjusted through the interaction of the individual layers. 4a shows a base body 51, which is provided with a transition layer 52a and a support layer 52b, on which in turn a functional layer 53 containing or forming the lubricant is applied. The transition layer 52a establishes the connection to the base body 51, the support layer 52b enables pressure equalization. Alternatively, only one or more than two layers 52a, 52b can be used. Neither a carrier nor a functional layer is attached to the body 54 lying opposite the functional layer 53.

The rolling process and the processes that occur here result in changes in the coating distribution, as shown in FIG. 4b. The rolling process transfers material from the functional layer 53 to the opposite body 58, where it is deposited as the functional layer 53b. Rolling surfaces 55, 56 smoothed on both sides also occur on the functional layer 53a of the base body 51 or on the functional layer 53b.

The functional layer 53 can be a metal-doped DLC layer. These e.g. The layers that protect against wear prevent contact between the immediate rolling partners, namely the base bodies 51, 54. The properties of the entire functional layer are particularly about their layers, e.g. the individual layers 52a and 52b, individually adjustable. In the case of a first variant of such a layer examined, the functional layer 53 has a coefficient of friction of 0.03.

In addition, the functional layer 53 as a lubricant, here as a dry lubrication layer, has the features that it consists of modified tungsten disulfide in lamellar form, that it has a molecular bond and thereby at the same time a physical connection with the carrier material is established. As a result, there is ultimately a protective layer that is pronounced over the entire rolling path, which moreover does not have a toxic or corrosive effect and, above all, is compatible with oils, greases, solvents, petrol and the like. Alcohol is.

In a second embodiment of this type of surface coating with a metal-doped DLC layer, also referred to as WC / C, it is a hard material layer with dry lubrication properties, the hardness of which is approximately 1000 HV. The layer structure comprises an intermediate chrome layer and several lamellar WC / C layers. Overall, the layers have good cohesive properties. With a total layer thickness of 1 - 4 μm, there is also a very good adhesion property. Such a layer has a temperature resistance of 300 ° C and a theoretical coefficient of friction of 0.2 with a uniformly smooth surface structure.

Depending on the setting, the lubrication sliding plane can be defined by the bound lubricant or by the unbound lubricant.

Claims

Expectations

1. Rolling bearing with integrated lubricating material for lubricating parts that are moved relative to one another, in particular with an inner ring each having a raceway and an outer ring, between which rolling elements, in particular bearing balls, are arranged, characterized in that at least one of the parts has an at least partial surface coating (52, 53) with a lubricant.

Rolling bearing according to claim 1, characterized in that n • D _m > 1 million (n = speed [l / min], D _m = ball center circle [mm]).

Rolling bearing according to claim 1 or 2, characterized in that the lubricant is designed such that it is transferred from the part carrying the coating to the uncoated part during the movement of the parts.

4. Rolling bearing according to one of claims 1 or 3, characterized in that the lubricant and the counter surface (57) of the uncoated part (54) are designed such that the lubricant adheres to the counter surface of the uncoated part (54).

Rolling bearing according to one of claims 1 to 4, characterized in that the coating has a different composition (52a, 52b, 53, 42, 43, 44) from the side of the component to be coated towards the free surface.

Rolling bearing according to one of the preceding claims, characterized in that the proportion of lubricant on the free surface of the coating (55) is increased compared to the side of the component to be coated.

7. Rolling bearing according to one of claims 1 to 6, characterized in that the coating comprises at least one carrier layer (52a, 42) connected to the surface of the coated part and at least one lubricant layer (53, 43, 44).

Rolling bearing according to one of claims 1 to 7, characterized in that the lubricant from the coating (53, 44) is a solid lubricant.

9. Rolling bearing according to one of claims 1 to 8, characterized in that the lubricant in the coating (53, 44) has embedded components which assume a liquid state during operation.

10. Rolling bearing according to one of claims 1 to 9, characterized in that the coating (53, 44) comprises a metal-doped, diamond-like carbon layer DLC.

11. Rolling bearing according to one of claims 1 to 10, characterized in that the coating comprises a single or multi-layer polymer layer (42, 43, 44).

12. Rolling bearing according to one of claims 1 to 11, characterized in that the carrier layer (42, 52a) is metallic.

13. Rolling bearing according to one of claims 1 to 12, characterized in that further functional layers (52a, 52b, 42, 43) are present in the entire coating, one of which is pressure-stabilizing.

14. Rolling bearing according to one of claims 1 to 13, characterized in that one or more layers of the coating have an internal damping.

15. Rolling bearing according to one of claims 1 to 14, characterized in that the electrical resistance of the coating changes due to wear.

16. Rolling bearing according to one of claims 1 to 15, characterized in that one of the several layers have an electrically insulating effect.

17. Rolling bearing according to one of claims 1 to 16, characterized in that the visually differs optically from the base material (51, 41).

18. Rolling bearing according to claim 17, characterized in that the optical properties of the coating change due to wear.

19. Rolling bearing according to one of claims 1 to 18, characterized in that the coating reduces the surface hardness or leaves it unchanged.

20. Rolling bearing according to one of claims 1 to 19, characterized in that at least one component of a rolling bearing is provided with a corresponding coating.

21. Rolling bearing according to one of claims 1 to 20, characterized in that at least one component of a plain bearing is provided with a coating.

22. Rolling bearing according to one of claims 1 to 21, characterized in that an additional lubricant is provided only on the surfaces of the parts in contact.

23. Rolling bearing according to one of claims 1 to 22, characterized in that the additional lubricant has high adhesive and cohesive forces.

24. Rolling bearing according to one of claims 1 to 23, characterized in that a further, second unbound lubricant is present.

25. Rolling bearing according to one of claims 1 to 24, characterized in that the lubricant is designed as a carrier for the lubricant or lubricants.

26. Rolling bearing according to one of claims 1 to 25, characterized in that the coating and / or the further lubricants can be sterilized.

27. Rolling bearing according to one of claims 1 to 26, characterized in that the lubricant of the coating (53, 44) and / or the further lubricant are selected such that they are compatible with a lubricant according to the prior art.

28. Rolling bearing according to one of claims 1 to 27, characterized in that the lubricant consist of several layers.