DE202017101725U1 - Rolling bearing with an electrically insulating layer - Google Patents

Abstract

Rolling bearing having a first raceway element and a second raceway element between which rolling elements are arranged rollable, and an electrically insulating layer on a surface of the first and / or second raceway element, wherein the electrically insulating layer is formed as a ceramic layer and of an alumina Al2O3 and titanium oxide containing mixture of metal oxides, characterized in that the insulating layer comprises titanium compounds containing or consisting of reduced titanium oxide TiOx and / or metallic titanium Ti, and wherein the insulating layer further comprises a sealer consisting of a cured synthetic resin.

Description

The invention relates to a rolling bearing with an electrically insulating layer on a surface of a raceway element of the rolling bearing. Furthermore, the invention relates to a machine arrangement with an electrically insulating layer on a surface of a housing element or a machine part.

There are already rolling bearings with a ceramic coating on a surface of an outer ring known to prevent passage of current through the bearing. The ceramic coating acts as an electrically insulating layer.

From the DE 10 2013 104 186 A1 are known bearing rings, which have on the surface of a ceramic coating wherein the coating has a proportion of pores of 10% to 50% which are filled with a plastic.

Furthermore, from the EP 1 528 274 B1 a rolling bearing unit having an electrically insulating layer on a surface of a raceway element, wherein the electrically insulating layer is a gray aluminum oxide having Al ₂ O ₃ mixed with TiO ₂ , wherein the amount of TiO _{2 is} less than 1% by weight. Although the coating containing TiO _{2 has} a lower electrical resistance than a pure aluminum oxide Al ₂ O ₃ coating, the chosen coating has the advantage that the proportion of titanium dioxide makes the coating adhere better to the metallic surface of the raceway.

Furthermore, from the JP 2008050669 A a rolling bearing of a rolling bearing is known which has a thermally sprayed ceramic layer on the surface having a porosity of 2% to 6%. The porosity is filled with an organic sealer.

From the JP 5850464 B is a race of a rolling bearing is known which has a spray-coated ceramic layer on the surface, which has a content of titanium dioxide TiO ₂ between 2% and 40%.

From the US 8,425,120 B2 a ceramic coating of alumina and titanium dioxide on a race is known, which has a content of titanium dioxide TiO ₂ of 0.01% to 0.02% by weight and the particle size of alumina from 10 .mu.m to 50 .mu.m, the average size between 15 .mu.m and 25μm.

The invention has for its object to further develop a rolling bearing with an electrically insulating coating such that the electrical resistance of the layer in operation at different operating conditions maintains a reliably high value at the same time thin cross-section of the layer.

The solution of this object by the invention is characterized in that the electrically insulating layer is formed as a ceramic layer and made of a alumina Al ₂ O ₃ and titanium oxide-containing mixture of metal oxides, wherein the insulating layer comprises titanium compounds, the reduced titanium oxide TiO _x and or titanium metallic Ti or consist thereof and wherein the insulating layer further comprises a sealer, which consists of a cured synthetic resin.

According to the invention, the ceramic layer is made of a powder which consists of metal oxides in powder form. The powder used for the preparation consists essentially of alumina Al ₂ O ₃ and titanium oxide. The titanium oxide is essentially present as titanium dioxide TiO ₂ , but may also contain a minor proportion of substoichiometric titanium oxide TiO _x , for example TiO _1.7 . The ceramic layer of the invention on the surface of the race member includes chemically reduced titanium oxide TiO _x and / or metal Ti substantially. In this case, the reduced titanium oxide TiO _x can be in various oxidation than titanium (II) oxide TiO titanium (III) oxide, Ti ₂ O ₃ and non-stoichiometric suboxides TiO _x , for example TiO _1.7 are present. Furthermore, the titanium oxide can also be present as unreduced titanium dioxide, titanium (IV) oxide TiO ₂ . However, it is essential here that the ratio of reduced titanium oxide including metallic titanium to unreduced titanium dioxide in the ceramic layer is at least 20%, preferably at least 50%, most preferably at least 80%.

Titanium oxide in both the powder form and the ceramic layer are generally compounds of titanium with oxygen, such as titanium (II) oxide TiO, titanium (III) oxide Ti ₂ O ₃ , titanium (IV) oxide TiO ₂ , and non-stoichiometric titanium suboxides with a composition of TiO to Ti ₂ O.

According to the invention, the ceramic layer further comprises a sealer, which consists of a cured synthetic resin. The advantage here is that the combination of a ceramic layer comprising reduced titanium oxide and / or metallic titanium with a synthetic resin leads to an electrically insulating layer, which has a significantly improved electrical insulation effect in permanently moist environment compared to previously known ceramic layers , The water resistance, referring to the electrical Properties, the ceramic layer is much better than in the previously known ceramic layers. It has been found that the electrical resistance, starting from a resistance value in an ideal dry environment to a resistance value in a maximum wet environment, is set to a resistance value compared to a comparable sealed ceramic layer which consists exclusively of pure white aluminum oxide Al ₂ O ₃ There is at least a factor of 10 higher resistance reserves.

According to a preferred embodiment, it is provided that the synthetic resin contains or consists of cured phenolic resin or a hardened anaerobic adhesive.

An anaerobic curing adhesive can be understood to mean dimethacrylic acid esters which are prepared, for example, by esterification of methacrylic acid with tetraethylene glycol to give tetraethylene glycol dimethacrylate and which then become a cured methacrylate resin by polymerization.

The advantage here is that a sealing of the reduced titanium oxide or titanium-containing ceramic layer with phenolic resin promotes curing of the phenolic resin and leads to a stabilization of the cured phenolic resin. Partly responsible for this are, for example, the strongly reducing properties of TiO. Furthermore, the reduced titanium oxide inclusions contained in the layer, which cause a metal-catalyzed curing of the alkene radicals of the phenolic resins, can also promote stabilization. Furthermore, the combination of the ceramic layer with phenolic resin according to the invention has the advantage that a color change of the sealed layer is prevented over time, since a uniform coloration of the sealed ceramic layer sets substantially immediately after curing. A phenolic resin which contains phenol, phenol-2-methyl and / or propylene has turned out to be particularly advantageous. Another advantage is that the phenolic resin can penetrate by capillary action into the finest interstices and pores of the ceramic layer or can be pressed into this, for example with Vakuumimprägnation, and cured there.

The further preferred sealing of the ceramic layer with the anaerobic adhesive such as methacrylate resin has the advantage that the combination of methacrylate resin with the reduced titanium oxide or titanium-containing ceramic layer supports the, preferably radical, polymerization of the methacrylate resin. The advantage here is that the methacrylate resin can penetrate by capillary action into the finest interstices and pores of the ceramic layer or can be pressed into this, for example with Vakuumimprägnation, and there anaerobically, ie cured under oxygen-free conditions. The titanium compounds present in the layer, metallic titanium and reduced titanium oxide, act as catalyst for the crosslinking, ie curing of the methacrylate resin. The preferred combination of metallic titanium and or reduced titanium oxide in the ceramic layer with methacrylate resin as organic sealer has surprisingly been found that the ceramic layer is ideally suited as an electrical insulation layer under moist ambient conditions although the layer of metallic titanium or TiO as electrical conductor and / or or reduced titanium oxide as a semiconductor. The advantage here is that due to the reduced titanium oxide and or the metallic titanium, the curing of the resin can proceed completely because reduced titanium oxide and or metallic titanium, which is adjacent to resin-filled pores and thus in direct contact with the resin as individual starting points for serve an anaerobic radical polymerization. If these starting points are evenly distributed in the ceramic layer, a complete polymerization of the resin takes place in the entire layer. Instead of methacrylate resin, it is also possible to use other anaerobic adhesives which catalytically cure analogously in cooperation with the reduced titanium oxide.

A preferred embodiment provides that the cured anaerobic methacrylate resin contains polymerized polyethylene glycol dimethacrylate. Triethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate have proved to be particularly advantageous as constituents of the methacrylate resin. Furthermore, cyclohexadiene or isobenzofurandione or maleic anhydride alone or in combination is advantageous as an additional component.

A preferred embodiment provides that the ceramic layer has a porosity of less than 40%, preferably less than 12%, and the pores have an average diameter between 0.5 .mu.m and 20 .mu.m, preferably between 0.5 .mu.m and 7 .mu.m, wherein the pores with the hardened synthetic resin are filled. An advantage of this combination of porosity and average pore size is that the synthetic resin used before penetrating reliably penetrates the entire ceramic layer, since the selected porosity and pore size evenly distributed in the layer resin reservoirs are formed which are interconnected largely by capillary. In this way, the liquid synthetic resin can be applied to the surface of the ceramic layer and passes through these reliably, for example by capillary action over the entire depth.

A further preferred embodiment provides that the reduced titanium oxide and the metallic titanium contained in the ceramic layer are formed as inclusions, which in a direction parallel to the surface of the ceramic layer have a substantially greater average extent than in a direction perpendicular to the surface of the ceramic layer. Inclusions are preferably lamellar or scaly (in English splat) formed. In this case, inclusions preferably have a mean extent <15 μm, preferably less than 5 μm, in the direction perpendicular to the surface of the ceramic layer. Parallel to the surface of the ceramic layer, that is to say in the longitudinal extent of the scale-like inclusions, these have an average extent of 5 μm to 80 μm. The advantage of this scale-like embodiment of the reduced titanium oxide and / or titanium-containing inclusions is that they have a very large surface in relation to their volume, compared to spherical inclusions. At least larger inclusions have such a scale-like structure. The large surface area ensures that enough pores are directly adjacent to a surface of these inclusions. Thus they can enter into catalytic active contact with the resin. By aligning the flaky inclusions parallel to the surface, the likelihood that resin penetrating perpendicularly to the surface on its way into the depth of the ceramic layer inevitably encounters a flaky inclusion of reduced titanium oxide or titanium thus oriented transversely to the penetration direction. Overall, the ratio of surface area to volume of at least larger inclusions can keep the proportion of titanium compounds in the ceramic layer low without bringing the surface of the inclusions in contact with the resin below a value required for reliable catalytic polymerization. Since titanium compounds constitute an electrical semiconductor or even an electrical conductor, a small proportion of titanium compounds is desirable from this point of view. In other words, if the inclusions of the titanium compounds in the ceramic layer were spherical in shape at the same proportion across all sizes, a surface available for contact with the resin would be much smaller. In order to obtain the same surface area, one would have to increase the proportion of titanium compounds, which has a negative effect on the electrical resistance of the ceramic layer.

A preferred embodiment provides that the proportion of aluminum oxide Al ₂ O ₃ in the ceramic layer is 96% to 99.7% by weight and the proportion of titanium compounds is 0.3 to 4% by weight. Particularly preferred is a proportion of 1% -2% of the titanium compounds in the ceramic layer. In this case, any titanium compound in the ceramic layer, that is to say optionally titanium dioxide TiO ₂ , titanium (II) oxide TiO, titanium (III) oxide Ti ₂ O ₃ , substoichiometric titanium oxide TiO _x and metallic titanium Ti, is considered as titanium compound.

A preferred layer thickness is between 10 μm and 3000 μm, more preferably between 750 μm and 3000 μm

• – Bereitstellen eines Pulvers welches Aluminiumoxid Al₂O₃ und Titanoxid enthält
• – Thermisches Aufspritzen des Pulvers auf eine Oberfläche des Laufringelementes,
• – Aufbringen eines organischen Sieglers auf die aufgespritzte Schicht.

Nach der Erfindung wird beim Aufspritzen des Aluminiumoxid Al₂O₃ und Titanoxid enthaltenden Pulvers das im Pulver enthaltene Titanoxid zumindest teilweise chemisch zu TiOx und/oder TiO und/oder zu metallischem Titan Ti reduziert. Als weiterer bevorzugter Schritt härtet der Siegler nach dem Aufbringen im Zusammenwirken mit dem zumindest teilweise chemisch zu TiOx und/oder TiO und/oder zu metallischem Titan Ti reduziertem Titanoxid aus.A raceway element of the rolling bearing according to the invention with an electrically insulating layer on a surface of the raceway element is produced by a thermal spraying process, with the steps:

• - Providing a powder containing alumina Al ₂ O ₃ and titanium oxide
• Thermal spraying of the powder onto a surface of the raceway element,
• - Apply an organic sieve on the sprayed layer.

According to the invention, during the spraying of the aluminum oxide Al ₂ O ₃ and titanium oxide-containing powder, the titanium oxide contained in the powder is at least partially reduced chemically to TiOx and / or TiO and / or to metallic titanium Ti. As a further preferred step, the sealer hardens after application in cooperation with the at least partially chemically reduced to TiOx and / or TiO and / or to metallic titanium Ti titanium oxide.

For better layer adhesion, the surface of the raceway element to be coated is preferably cleaned prior to thermal spraying and then dried and / or additionally sandblasted

The advantage here is that in the finished ceramic layer, the proportion of reduced titanium oxide can be significantly increased compared to the starting powder. Preferably, the powder essentially does not need to contain any reduced titanium oxide, but may contain exclusively titanium (IV) oxide TiO ₂ as the titanium oxide. In this case, the titanium dioxide TiO _{2 can be} chemically reduced to titanium (II) oxide TiO titanium (III) oxide Ti ₂ O ₃ and non-stoichiometric suboxides TiO _x , for example TiO _1.7 , by the thermal spraying method. Furthermore, the titanium dioxide TiO ₂ can be reduced to metallic titanium Ti. However, a powder can also be used as the starting powder, which in addition to titanium dioxide TiO ₂ already has a proportion of reduced titanium oxide. By the thermal spraying method, the proportion of reduced titanium oxide and / or metallic titanium can then be increased according to the invention.

A preferred embodiment of the method provides that the thermal spraying method Plasma spraying is. Alternatively, the thermal spray process may also be high velocity flame spraying. Furthermore, alternatively, the thermal spraying process may also be a thermal suspension spraying process.

It is advantageous that a chemical reduction of titanium compounds can be selectively controlled by plasma spraying or high-speed flame spraying, so that reduced titanium oxide and / or metallic titanium is contained in the sprayed-on layer.

A preferred embodiment of the method provides that the thermal spraying process with argon and / or hydrogen is carried out as part of the process gas. In this case, the gas mixture which is used to melt the supplied coating powder is referred to as the process gas. The process gas is so hot that it can be plasma-shaped.

In this case, the hydrogen contained in the plasma causes a chemical reduction of the titanium compounds. The quantity of the chemical reduction can be controlled particularly advantageously by the plasma spraying. Thus, for example, the ratio of argon to hydrogen in the plasma, the reduction components and their proportion in the sprayed layer can be adjusted specifically. An increase in the hydrogen content in the plasma, for example, increases the proportion of metallic titanium, which represents the end product of the chemical reduction. Alternatively, the spraying process can also be carried out with nitrogen or helium as the plasma process gas. Different process gases can also be used to set the reduction components and their proportions in the sprayed layer.

Furthermore, by a residence time of the powder in the plasma, which in turn can be adjusted via the gas flow and / or gas pressure in the plasma and the flight distance, the reduction ratio can be controlled. The temperature of the plasma can also be used to control the reducing components and their proportions in the sprayed layer. Preferably, the plasma spraying is carried out at a plasma temperature above 10,000 Kelvin.

By suitable parameters in plasma spraying, the pore size in the sprayed layer and the size and shape of the titanium compounds containing inclusions in the sprayed layer can be further adjusted. A preferred embodiment of the method in this case provides to carry out the method such that the porosity, the average pore size and the average size of the inclusions in different directions to the surface of the sprayed layer as stated above, formed in the sprayed layer.

A preferred embodiment of the method provides for organic sealer to be applied with a sealer containing methacrylate resin which anaerobically polymerizes in pores of the sprayed-on layer by mediating the reduced titanium oxide. It is advantageous that thereby the electrically insulating layer has a particularly good moisture resistance. As already described, the reduced titanium oxide acts as a metallic catalyst for the anaerobic polymerization of the resin.

A further preferred embodiment of the method provides that the step of providing a powder containing aluminum oxide Al ₂ O ₃ and titanium dioxide with a powder having a mean particle size depending on the thermal spraying of the powder from 0.01 .mu.m to 63 .mu.m, preferably in the plasma spraying between 5 .mu.m up to 63μm, most preferably between 10μm to 30μm. A preferred embodiment of the powder in this case provides that before being prepared from a powder comprising aluminum oxide Al ₂ O ₃ and a powder containing titanium dioxide in a desired mixing ratio, the powder is mixed to form a first powder, the desired mixing ratio being equal to the ratio of aluminum oxide Al ₂ O ₃ and all titanium compounds in the sprayed layer corresponds. It is preferably provided that the correspondingly mixed first powder is melted and homogenized. Subsequently, the cooled solid metal oxide block is ground again to a second powder. The advantage here is that the proportion of titanium compounds in the first and in the second powder remains the same overall, the proportion of grains in the powder containing titanium compounds in the second powder, however, is substantially greater than in the first powder, since in the first powder, the grains either of alumina Al ₂ O. ₃ or consist of titanium dioxide. In the second powder, the individual grains already consist of a mixture of aluminum oxide Al ₂ O ₃ and titanium compounds. It is advantageous here that the mean size of the inclusions containing titanium compounds can be reduced by a second powder produced in this way in comparison to a first powder with the same proportion of titanium compounds. Another advantage is the increased homogeneity and more uniform distribution of inclusions with titanium compounds in the sprayed layer. Alternatively, the powder may be prepared prior to providing from a powder containing aluminum oxide Al 2 O 3 which is melted and a powder containing titanium dioxide, which is added in a desired mixing ratio in the molten aluminum oxide Al 2 O 3 and is homogenized to a melt. Concentration shifts due to melt losses are present in both Production method considered in the mixing ratio of the melt. Subsequently, the cooled solid metal oxide block is ground to a second powder. The advantages described above apply to both production processes of the powder.

Another aspect of the invention relates to a machine assembly having a rotatably mounted in a housing member machine part, wherein the machine part is mounted by means of a rolling bearing in the housing element, wherein a first surface of the rolling bearing is in contact with a surface of the housing member and a second surface of the rolling bearing with a Surface of the machine part is in contact, wherein the surface of the housing member and / or the surface of the machine part comprises an electrically insulating ceramic layer which is made of a alumina Al ₂ O ₃ and titanium oxide-containing mixture of metal oxides wherein the insulating layer comprises titanium compounds, the reduced Titanium oxide TiO _x and / or TiO and or metallic titanium Ti or consist of these and wherein the insulating layer further comprises a sealer which consists of a cured synthetic resin.

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 102013104186 A1 [0003]
• EP 1528274 B1 [0004]
• JP 2008050669 A [0005]
• JP 5850464 B [0006]
• US 8425120 B2 [0007]

Claims (10)

Rolling bearing with a first raceway element and a second raceway element, between which rolling elements are arranged rollable, and an electrically insulating layer on a surface of the first and / or second raceway element, wherein the electrically insulating layer is formed as a ceramic layer and of an alumina Al ₂ O. ₃ and titanium oxide containing mixture of metal oxides, characterized in that the insulating layer comprises titanium compounds containing or consisting of reduced titanium oxide TiO _x and / or metallic titanium Ti and wherein the insulating layer further comprises a sealer, which consists of a hardened synthetic resin. Rolling bearing according to claim 1, characterized in that the synthetic resin contains or consists of cured phenolic resin or a cured anaerobic adhesive, preferably methacrylate resin. Rolling bearing according to claim 2, characterized in that the cured methacrylate resin polymerized polyethylene glycol dimethacrylate, preferably triethylene glycol dimethacrylate and / or Tetraethylenglycoldimethacrylat contains. Rolling bearing according to claim 2, characterized in that the cured phenolic resin, phenol, phenol-2-methyl and / or propylene. Rolling bearing according to claim 1, characterized in that the ceramic layer has a porosity of less than 40%, preferably less than 12%, and the pores have a mean diameter between 0.5 .mu.m and 20 .mu.m, preferably between 0.5 .mu.m and 7 .mu.m, wherein the pores the cured synthetic resin are filled. Rolling bearing according to claim 1, characterized in that the proportion of aluminum oxide Al ₂ O ₃ in the ceramic layer is 96% to 99.7% by weight and the proportion of titanium compounds is 0.3 to 4% by weight. Rolling bearing according to claim 1, characterized in that in the ceramic layer, the reduced titanium oxide and / or the metallic titanium are formed as inclusions, which have a greater average extent in a direction parallel to the surface of the ceramic layer than in a direction perpendicular to the surface of the ceramic layer, wherein the inclusions perpendicular to the surface have an average extent of <15 microns, preferably less than 5 microns and in a direction parallel to the surface have an average extension of 5 .mu.m to 80 .mu.m. Rolling bearing according to claim 1, characterized in that the ceramic layer is applied by means of a thermal spraying process. Rolling bearing according to claim 8, characterized in that the ceramic layer is applied by means of a plasma scribing method with a hydrogen-argon plasma. Machine arrangement having a machine part rotatably arranged in a housing element, wherein the machine part is mounted in the housing element by means of a rolling bearing, wherein a first surface of the rolling bearing is in contact with a surface of the housing element and a second surface of the rolling bearing is in contact with a surface of the machine part, wherein the surface of the housing element and / or the surface of the machine part comprises an electrically insulating ceramic layer which is made of a mixture of metal oxides containing alumina Al ₂ O ₃ and titanium oxide, characterized in that the insulating layer comprises titanium compounds containing reduced titanium oxide TiO _x and / or TiO and or metallic titanium Ti or consist thereof and wherein the insulating layer further comprises a sealer, which consists of a cured synthetic resin.