JP5459538B2 - Tapered roller bearing - Google Patents

Description

  The present invention relates to a tapered roller bearing having an outer ring, an inner ring and a tapered roller and lubricated with lubricating oil.

  Conventionally, as a tapered roller bearing lubricated with lubricating oil, there is one described in Japanese Patent Laid-Open No. 11-48805 (Patent Document 1) for the purpose of improving the lubrication state. This tapered roller bearing or tapered roller bearing device has an inner ring, an outer ring, and a tapered roller, and the inner peripheral surface of the inner ring is fixed to the pinion shaft of the differential gear device, while the outer peripheral surface of the outer ring Is fixed to an annular partition wall in the differential gear device.

  In the tapered roller bearing device, the lubricating oil flowing from the ring gear of the differential gear device through the lubricating oil passage is passed from the small diameter end surface side to the large diameter end surface side of the tapered roller in the axial direction of the tapered roller bearing. The tapered roller bearing is lubricated by passing it from one opening to the other.

  However, the tapered roller bearing device has a lubricating oil used in a differential gear device in addition to a type in which the lubricating oil flows between one inner ring and the other outer ring from the one axial direction to the other axial direction. Is a lubricating oil with high viscosity suitable for preventing seizure of meshing parts of various gears such as ring gears and side gears, so that a tapered roller as a rolling element, a raceway surface of an outer inner ring, and a large collar part of an inner ring The shearing / stirring resistance at the rolling or sliding contact part of the roller is originally high, and the amount of lubricating oil that accompanies the rotation of the tapered roller bearing cage increases, and the heat generation and rotational torque increase associated with these are compared. Big.

  In addition, in JP 2007-032806 A (Patent Document 2), in order to solve the above problem, in order to suppress the heat generation and the increase of the rotational torque caused by the lubricating oil accompanying the rotation of the cage, It has been disclosed to provide an anti-rotation portion made of an uneven surface or an oil repellent on the surface of the cage.

  However, it is not possible to sufficiently suppress the heat generation and the increase in the rotational torque related to the lubricating oil only by suppressing the lubricating oil accompanying the cage. Further, the lubricating oil used in the differential gear device is a so-called gear oil, which has a relatively high viscosity as described above and contains a relatively large amount of extreme pressure agent and the like. Therefore, it is physically and chemically active against the treatment layer with the oil repellent, and improvement is also demanded from this point.

JP 11-48805 A JP 2007-032806 A

  The present invention provides a tapered roller bearing having a configuration capable of suppressing an increase in heat generation and rotational torque related to lubricating oil without deteriorating lubricating performance by optimizing a portion subjected to oil repellent treatment. Is an issue. At the same time, in oil repellency treatment, we provide tapered roller bearings that have a structure that can further suppress heat generation and increase in rotational torque by improving durability and providing stable oil repellency. The task is to do.

  In order to solve the above-described problems, the tapered roller bearing according to the first invention is characterized by having the following configuration.

That is, a tapered roller having an outer ring, an inner ring, a plurality of rolling elements disposed between the outer ring and the inner ring, a cage that holds the rolling elements apart, and a portion that makes rolling contact with a lubricating oil and a portion that makes sliding contact is lubricated. In the bearing
The rolling element is a tapered roller,
Having a rolling surface and a large-diameter side end surface and a small-diameter side end surface;
The end face on the large diameter side is a roller head that is in sliding contact with the large collar of the inner ring,
It consists of a large-diameter side end surface that has a substantially flat bottom portion that is depressed toward the small-diameter side end surface portion from the roller head through a substantially conical transition portion,
The inner ring has a raceway surface on which the rolling elements roll on the outer peripheral surface,
A small diameter side end surface and a large diameter side end surface;
A large brim where the roller head of the rolling element comes into sliding contact,
It has a large collar part outer diameter surface that forms a large collar part,
The outer ring has a raceway surface on which the rolling elements roll on the inner peripheral surface,
It consists of a small diameter side end surface and a large diameter side end surface,
at least,
The outer surface of the rolling element, excluding the roller head and the transition portion of the substantially conical shape,
The outer surface of the outer ring excluding the outer peripheral surface and the large-diameter end surface,
The outer surface of the inner ring excluding the inner peripheral surface, the large-diameter side end surface, the large brim outer diameter surface and the large brim portion,
On the entire surface of the cage,
Oil-repellent treatment is given ,
In the oil repellent treatment, a metal oxide layer is formed on the surface of the base material forming the inner ring, outer ring, rolling element, and cage, and then an oil repellent layer is provided.
The metal oxide layer, the surface of the base material,
Water, an alkylalkoxy metal salt having a metal species of silicon, titanium, or aluminum and a lower alkyl having 1 to 6 carbon atoms in the alkyl portion, or a halogen alkoxy metal salt;
A lower alcohol having 1 to 6 carbon atoms;
Metal oxide fine particles having an average particle diameter of 1 nm to 200 nm as essential components,
after contacting the first solution having a pH of 6 or less,
Contains alkali metal salts,
by contacting a second solution having a pH of 11-13,
A metal oxide layer is formed on the surface of the base material, and then
The surface of the base material on which the metal oxide layer is formed,
Water and a fluorine-containing coupling agent containing silicon, titanium, or aluminum;
Containing a lower alcohol having 1 to 6 carbon atoms,
After contacting with a third solution having a pH of 6 or less,
Contains alkali metal salts,
by contacting with a fourth solution having a pH of 11-13,
It is an oil repellent layer provided on the metal oxide layer.

  According to the present invention, not only the lubricating oil, which is the gear oil, is prevented from being entangled with the cage, but also a more suitable portion is subjected to an oil repellent treatment, so that the lubrication of the tapered roller bearing is impaired. In addition, it is possible to make the flow of the lubricating oil inside the tapered roller bearing more suitable. Therefore, it is possible to effectively suppress an increase in heat generation and rotational torque related to the lubricating oil.

  Here, the cause of heat generation and increase in rotational torque related to lubricating oil is the case where heat generation and rotational torque increase due to agitation / shearing of lubricating oil in a portion not necessarily required for the lubrication of tapered roller bearings There are many.

  In the case of this first invention, in the tapered roller bearing, there is no oil repellency on the contact surface between the roller head of the rolling element and the large collar portion of the inner ring, which is a part that is prone to problems such as seizure due to insufficient lubrication. It has not been processed. For this reason, a large amount of lubricating oil is distributed over this portion that has not been subjected to the oil repellent treatment.

  Furthermore, a normal tapered roller has a large-diameter end face that is recessed from the roller head to a small-diameter end face through a transition portion having a substantially conical shape on the large-diameter end face and having a substantially flat bottom. . In addition, the large collar portion usually has a large collar outer diameter surface for forming the large collar portion. These substantially conical transition portions and outer diameter surfaces of the large collar portions are formed continuously on the roller heads of the rolling elements and the large collar portions of the inner rings, respectively.

  Therefore, in the case of this first invention, the oil repellent treatment is not performed on the portion adjacent to the portion where the lubrication is insufficient and a defect such as seizure is likely to occur. For this reason, the lubricating oil suitably adheres to this portion, and from here on the contact surface between the roller head of the rolling element and the large collar portion of the inner ring, where the lubrication is insufficient and defects such as seizure are likely to occur. Lubricating oil is more easily distributed.

  Although the detailed mechanism is unclear, it is possible to suitably suppress the heat generation and the increase in rotational torque of the tapered roller bearing by the above-described action.

Furthermore, preferably, as the second invention, in the first invention,
The first solution contains, as the metal oxide fine particles, fine particles made of silica, titania, or alumina having an average particle diameter of 1 nm or more and 200 nm or less in a proportion of 0.1 wt% or more and 5.0 wt% or less. It is characterized by this.

Hereinafter, the first and second inventions will be described more specifically.

  The metal oxide layer and the water / oil repellent layer are alkylalkoxy metal salts in which the surface of the cage is water and the metal species is silicon, titanium, or aluminum, and the alkyl portion is a lower alkyl having 1 to 6 carbon atoms. Or metal oxide fine particles (silica, titania, alumina, magnesia, calcium oxide, zinc oxide, etc.) having an average particle size of 1 nm to 200 nm and a halogen alkoxy metal salt, a lower alcohol having 1 to 6 carbon atoms, ) And an essential component, and after contact with a first solution having a pH of 6 or less, the cage is brought into contact with a second solution containing an alkali metal salt and having a pH of 11 to 13. After the metal oxide layer forming step of forming a metal oxide layer on the surface of the metal and the metal oxide layer forming step, the surface of the cage is made of silicon, titanium, or A fluorine-containing coupling agent containing aluminum, water, a lower alcohol having 1 to 6 carbon atoms, and after contacting with a third solution having a pH of 6 or less, containing an alkali metal salt And a water / oil repellent layer forming step of forming a water / oil repellent layer on the metal oxide layer by contacting with a fourth solution having a pH of 11-13. Is preferred.

  The first solution contains, as the metal oxide fine particles, fine particles composed of silica, titania, or alumina having an average particle diameter of 1 nm to 200 nm in a proportion of 0.1 wt% to 5.0 wt%. It is preferable to do.

  In the case of a cage made of synthetic resin, it is preferable to perform the metal oxide layer forming step after performing a hydrophilic treatment step on the surface of the cage. Examples of the hydrophilic treatment step include a method of forming a hydroxyl group on the surface of the cage by plasma treatment, glow discharge, corona discharge, ultraviolet irradiation or the like.

  By setting the pH of the first solution used in the metal oxide layer forming step to 6 or less, the hydrolysis reaction of the alkyl alkoxy metal salt or the halogen alkoxy metal salt is promoted. Further, by adjusting the pH of the second solution to 11 or more and 13 or less, the dehydration condensation reaction between the hydroxyl group (—OH) of the hydrolysis reaction product and the hydroxyl group (—OH) of the cage surface is promoted. As a result, the metal oxide layer is formed on the surface of the cage in a state where it is chemically bonded.

  Moreover, the hydrolysis reaction of the said fluorine-type coupling agent is accelerated | stimulated by making pH of the 3rd solution used at a water / oil repellent layer formation process into 6 or less. Further, by setting the pH of the fourth solution to 11 or more and 13 or less, the dehydration condensation reaction between the hydroxyl group (—OH) of the hydrolysis reaction product and the hydroxyl group (—OH) of the surface of the metal oxide layer is promoted. The As a result, a water / oil repellent layer is formed on the surface of the metal oxide layer in a state of being strongly chemically bonded.

Further, in the metal oxide layer forming step, a metal oxide layer (a layer made of an oxide of a metal constituting an alkoxy metal salt) is included in the first solution when it is formed on the film formation surface of the cage. The metal oxide fine particles are bonded to the deposition surface, so that the metal oxide layer is densely formed. Further, irregularities due to the fine particles are formed on the surface of the formed metal oxide layer, and the surface area ratio (the ratio of the actual surface area to the area assumed to be a smooth surface) increases. When the surface area ratio of the metal oxide layer increases, the surface area ratio of the water and oil repellent layer, which is the upper layer, also increases and a dense water and oil repellent layer is formed. The oil repellency is improved and the water / oil repellency film is firmly bonded to the film formation surface. The surface area ratio of the metal oxide layer and the water / oil repellent layer is preferably 1.1 or more.

  Specific examples of the alkoxy metal salt (the alkyl alkoxy metal salt and the halogen alkoxy metal salt) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrachlorosilane, and metal species, where the metal species is silicon. Examples include titanium, tetramethoxy titanate, tetraethoxy titanate, tetrapropoxy titanate, tetrabutoxy titanate, and trimethoxy aluminate, triethoxy aluminate, tripropoxy aluminate whose metal species is alumina.

  It is particularly preferable that the metal species of the metal oxide forming the metal oxide fine particles and the metal species of the alkoxy metal salt contained in the first solution are the same.

  The average primary particle size of the metal oxide fine particles is preferably 2 nm to 100 nm, more preferably 2 nm to 80 nm, and still more preferably 10 nm to 50 nm. Moreover, it is also possible to mix and use metal oxide fine particles having different average primary particle sizes. When the average primary particle size is less than 1 nm, the effect of increasing the surface area ratio is small, and when it exceeds 200 nm, the film tends to fall off from the film formation surface.

  The content of the metal oxide fine particles in the solution is preferably 0.1 to 3% by mass, and more preferably 0.2% to 2.5% by mass. If the content of the metal oxide fine particles in the solution is less than 0.1% by mass, the effect of densifying the metal oxide layer is small. As a result, the fine particles fall off and the water and oil repellent film is likely to be defective.

  The shape of the metal oxide fine particle is not particularly limited, and a spherical shape, a rectangular shape, a flat shape, a fiber shape, a whisker shape, or the like can be used. For example, if it is a fibrous thing, the length of a fiber can be 1 nm or more and 200 nm or less. Moreover, you may mix and use the thing of a different shape. Moreover, if an average primary particle diameter is 1 nm or more and 200 nm or less, a porous thing etc. can also be used.

  Specifically describing an example of the composition of the first solution, the alkoxy metal salt is 1% by mass to 10% by mass, the water is 1% by mass to 20% by mass, the alcohol is 30% by mass to 95% by mass, The metal oxide fine particles are 0.1 mass% or more and 5 mass% or less, and the pH is adjusted to 6 or less with hydrochloric acid. In this case, it is preferable to mix components other than hydrochloric acid in advance, stir for several tens of minutes to several hours so that the metal oxide fine particles become uniform, and finally adjust the pH using hydrochloric acid.

  The second solution and the fourth solution are particularly preferably sodium hydroxide aqueous solutions. Further, alkali metal carbonates such as sodium carbonate, potassium carbonate and sodium hydrogen carbonate can also be used. Various pH buffering agents may be used in combination.

  In addition, when the first solution and the third solution contain a lower alcohol having 1 to 6 carbon atoms, the solubility of the alkoxy metal salt and the fluorine-based coupling agent is increased and a stable solution is obtained. As the lower alcohol having 1 to 6 carbon atoms, methanol, ethanol, 1-propanol, 2-propanol, butanol, hexanol, cyclohexanol and the like can be preferably used. More preferably, ethanol is used.

The fluorine-based coupling agent containing silicon, titanium, or aluminum contained in the third solution is contained in the metal species of the metal oxide fine particles contained in the first solution, or contained in the first solution. It is preferable to have the same metal species as the metal species of the alkoxy metal salt. Further, it is preferable to use a fluorine-based coupling agent (fluorine-based silane coupling agent) whose metal species is silicon.

  Specifically, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane, 1H, 1H, 2H, 2H-perfluorodecyltrimethoxysilane, 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane-3 -Heptafluoroisopropoxypropyltrichlorosilane, 1H, 1H, 2H, 2H-perfluorododecyltriethoxysilane, 3-trifluoroacetoxypropyltrimethoxysilane and the like can be used.

As described above, by making the oil repellency treatment according to the first and second inventions, it is possible to obtain an oil repellency treatment having sufficient durability even when the oil repellent treatment is applied to the rolling surface. In addition, the effects of the first invention can be imparted more stably over a longer period.

In addition, the oil repellent treatment according to the first and second inventions is chemically and physically stable, and the conventional oil repellent treatment, for example, Knox Guard manufactured by Nippon Mektron Co., Ltd., which is a commercially available oil repellent. It can be made stronger than processing by 420ST or the like.

Further, according to this onset bright, because that will effectively supplied to the site in need of lubricating oil may be, for example, those lubricating oil amount filled into the gear box or the like minimum. In addition to reducing energy loss by reducing rotational torque, the amount of original lubricating oil used can be reduced, and the environmental load can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the tapered roller bearing which suppressed the heat_generation | fever and the increase in rotational torque which concern about lubricating oil can be obtained.

The cross section of the tapered roller bearing which concerns on embodiment of this invention is shown.

Hereinafter, embodiments of the present invention will be described in more detail.
FIG. 1 shows a cross section of a tapered roller bearing according to the present invention. The tapered roller bearing is basically formed from an inner ring 1, an outer ring 2, a plurality of rolling elements 3 that are tapered rollers disposed between the inner ring 1 and the outer ring 2, and a cage 4 that holds the rolling elements. The outer ring 2 is rotatably supported by the rolling element 3.

  The rolling element 3 has a small diameter side end surface which is a left end surface in FIG. 1 and a large diameter side end surface which is a right end surface in FIG. 1. The large-diameter side end surface is recessed substantially through the transition portion 8 from the large-diameter side end surface toward the small-diameter side end surface in a generally conical shape from the roller head 5 in sliding contact with the inner ring large collar portion 21. A flat bottom 7 is provided. In the example of FIG. 1, the rolling surface 19 is in rolling contact with the raceway surface 16 of the outer ring 2 and the raceway surface 17 of the inner ring 1.

  The inner ring 1 has an inner ring raceway surface 17 on which the rolling element 3 rolls, an inner ring small-diameter side end face 15, an inner ring large-diameter side end face 14, an inner ring large collar part 21, and an inner ring large collar part 21 on the outer circumferential surface thereof. The inner ring large collar part outer diameter surface 6 and the inner ring inner peripheral surface 11 fitted to the normal shaft are provided. Further, the inner ring large collar part chamfer 9 is often applied to the joint part between the inner ring large collar part outer diameter surface 6 and the inner ring large collar part.

  The outer ring 2 includes an outer ring raceway surface 16 on which the rolling element 3 rolls, an outer ring small-diameter side end surface 12, an outer ring large-diameter side end surface 13, and an outer ring outer peripheral surface 10 fitted to a normal housing.

  The cage is for holding the plurality of rolling elements 3 apart from each other, and is usually made of metal or synthetic resin.

  According to the first aspect of the present invention, at least in the rolling element 3, the outer surface excluding the transition portion 8 formed on the substantially conical shape and the roller head 5 is subjected to oil repellency treatment. Is an oil repellent treatment on the outer surface excluding the outer ring outer peripheral surface 10 and the outer ring large-diameter side end surface 13. In the inner ring 1, the inner ring inner peripheral surface 11, the inner ring large-diameter side end surface 14, and the inner ring large brim outer diameter surface. 6. The outer surface excluding the inner ring large collar portion 21 is subjected to an oil repellent treatment.

  Here, the inner ring inner peripheral surface 11 of the inner ring 1 and the chamfered portion between the inner ring inner peripheral surface 11 and the inner ring small-diameter side end surface 15, the outer ring outer peripheral surface 10 of the outer ring 2 and the joint between the outer ring outer peripheral surface 10 and the small-diameter side end surface 12. The chamfered portion may be subjected to an oil repellent treatment. On the contrary, the inner ring large collar portion chamfer 9 is preferably not subjected to an oil repellent treatment because if the oil adheres to the inner ring large collar portion chamfer 9, the lubricating oil is easily drawn into the sliding portion of the inner ring large collar portion 21 or the head 5.

  In the cage 4, an oil repellent treatment is performed on the entire surface.

  In the case of a differential device or the like that is normally used, lubricating oil is supplied from a gap formed between the inner ring small-diameter side end surface 15 of the inner ring 1 and the outer ring small-diameter side end surface 12 of the outer ring 2, and lubricates the inside of the bearing while passing through the bearing. The inner ring 1 is designed such that the lubricating oil is discharged from a gap formed by the outer ring surface 6 of the inner ring large collar portion of the inner ring 1 and the outer ring large diameter end surface 13 of the outer ring 2.

  At this time, the oil repellent treatment is applied to each predetermined portion as described above, so that, for example, the rolling surface 19 of the rolling element 3 or the sliding surface where the cage 4 and the rolling element 3 are in sliding contact with each other While supplying the minimum necessary amount of lubricating oil, the amount of lubricating oil accompanying these sliding, rolling and rotating can be suppressed by the effect of the oil repellent treatment. Therefore, unnecessary stirring and shearing of the lubricating oil can be suppressed, and an increase in heat generation and rotational torque can be suppressed or reduced.

  Further, in the tapered roller bearing, the inner ring large collar portion 21 where the sliding condition is severe and troubles such as seizure easily occur, and the head portion 5 is not oil-repellent, and is discharged from the oil-repellent portion. Lubricating oil is preferably gathered in this part. That is, the lubricating oil that should have adhered to the oil-repellent treated portion gathers in this portion, and lubrication of this portion is improved. Therefore, the tapered roller bearing according to the present invention can exhibit stable performance over a longer period.

In addition, since the bearings according to the first and second inventions suppress the increase in heat generation and rotational torque as described above, for example, other parts that share the tapered roller bearing and the lubricating oil in the differential device. For example, when it is desired to use a lubricating oil having a higher viscosity in order to prevent seizure on the gear surface or the like, heat generation and torque increase of the rolling bearing portion can be suitably suppressed. In other words, a higher viscosity lubricating oil can be used with the same heat generation and the same rotational torque.

Furthermore, if the oil repellency treatment according to the first and second inventions is performed, the oil repellency treatment can be made more physically and chemically stable. It is also possible to use strong extreme pressure agents.

  The tapered roller bearing of the present invention can be suitably used for various mechanical devices because heat generation and rotational torque are suppressed to a lower level when lubricated with lubricating oil. In addition, as a mechanical device that can suitably use the tapered roller bearing of the present invention, a differential gear device, a transaxle device, or a pinion shaft support device for a vehicle having a pinion shaft such as a transfer device, or an axle device for an automobile or a railway vehicle Etc.

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 3 Rolling element 4 Cage 5 Roller head 6 Large collar outer diameter surface 7 Bottom 8 Transition part 9 Inner ring large collar chamfer 10 Outer ring outer peripheral surface 11 Inner ring inner peripheral surface 12 Outer ring small diameter side end surface 13 Outer ring large diameter Side end surface 14 Inner ring large diameter side end surface 15 Inner ring small diameter side end surface 16 Outer ring raceway surface 17 Inner ring raceway surface 19 Roller rolling surface 20 Inner ring small brim portion outer diameter surface 21 Inner ring large brim portion

Claims (2)

In a tapered roller bearing having an outer ring, an inner ring, a plurality of rolling elements disposed between the outer ring and the inner ring, a cage that holds the rolling elements apart, and a portion that makes rolling contact with a lubricating oil and a portion that makes sliding contact is lubricated. ,
The rolling element is a tapered roller,
Having a rolling surface and a large-diameter side end surface and a small-diameter side end surface;
The end face on the large diameter side is a roller head that is in sliding contact with the large collar of the inner ring,
It consists of a large-diameter side end surface that has a substantially flat bottom portion that is depressed toward the small-diameter side end surface portion from the roller head through a substantially conical transition portion,
The inner ring has a raceway surface on which the rolling elements roll on the outer peripheral surface,
A small diameter side end surface and a large diameter side end surface;
A large brim where the roller head of the rolling element comes into sliding contact,
It has a large collar part outer diameter surface that forms a large collar part,
The outer ring has a raceway surface on which the rolling elements roll on the inner peripheral surface,
It consists of a small diameter side end surface and a large diameter side end surface,
at least,
The outer surface of the rolling element, excluding the roller head and the transition portion of the substantially conical shape,
The outer surface of the outer ring excluding the outer peripheral surface and the large-diameter end surface,
The outer surface of the inner ring excluding the inner peripheral surface, the large-diameter side end surface, the large brim outer diameter surface and the large brim portion,
On the entire surface of the cage,
Oil-repellent treatment is given ,
In the oil repellent treatment, a metal oxide layer is formed on the surface of the base material forming the inner ring, outer ring, rolling element, and cage, and then an oil repellent layer is provided.
The metal oxide layer, the surface of the base material,
Water, an alkylalkoxy metal salt having a metal species of silicon, titanium, or aluminum and a lower alkyl having 1 to 6 carbon atoms in the alkyl portion, or a halogen alkoxy metal salt;
A lower alcohol having 1 to 6 carbon atoms;
Metal oxide fine particles having an average particle diameter of 1 nm to 200 nm as essential components,
after contacting the first solution having a pH of 6 or less,
Contains alkali metal salts,
by contacting a second solution having a pH of 11-13,
A metal oxide layer is formed on the surface of the base material, and then
The surface of the base material on which the metal oxide layer is formed,
Water and a fluorine-containing coupling agent containing silicon, titanium, or aluminum;
Containing a lower alcohol having 1 to 6 carbon atoms,
After contacting with a third solution having a pH of 6 or less,
Contains alkali metal salts,
by contacting with a fourth solution having a pH of 11-13,
A tapered roller bearing which is an oil repellent layer provided on the metal oxide layer . The first solution contains, as the metal oxide fine particles, fine particles composed of silica, titania, or alumina having an average particle diameter of 1 nm to 200 nm in a proportion of 0.1 wt% to 5.0 wt%. The tapered roller bearing according to claim 1 .

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