Sealed bearing assembly

The present invention relates to a sealed bearing arrangement comprising at least bearing with an outer ring and an inner ring between which a rolling chamber is defined, wherein a set of rolling elements is arranged. The bearing may be arranged in a housing. The housing and/or that the rolling chamber may be provided with lubricant.

During operation the temperature in the bearing increases which results in an expansion of the air which is present in the rolling chamber and/or housing of the bearing. A part of it will therefore leave the bearing. Cooling down will cause an inverse process. This in turn, resides in a certain air exchange in the bearing assembly during which fresh oxygen is transported from the outside to the inside. Under transient running conditions, i.e., condi tions where the speed or load will vary, the heat development and therefore bearing tem perature will vary over time, leading to a continuous supply of oxygen. The constant sup ply of fresh oxygen leads to a constant oxidation of the lubricant, which ends in a degrada tion of the lubricant and a decreased service life. Consequently, the lubricant has to be ex changed frequently, which requires frequent service intervals, downtimes of the bearing and increases the costs.

Consequently, it is an object of the present invention to provide a bearing assembly with improved lubrication properties.

The object is solved by a sealed bearing arrangement as claimed in the independent claims. In the following a sealed bearing arrangement is disclosed, wherein the bearing arrange ment comprises at least a bearing with an outer ring and an inner ring between which of rolling chamber is defined. In the rolling chamber at least one set of rolling elements is ar ranged. The bearing may be accommodated in a housing which is adapted to seal off the bearing from an outside environment. Alternatively or additionally, the rolling chamber is sealed off from an environment by at least one sealing element. Further, a lubricant, such as grease, is included in the rolling chamber and/or in the inner space of the housing.

For improving the lubrication properties and reduce lubrication degradation due to oxida tion, the inner ring, the outer ring, the sealing element and/or the housing further comprises at least one opening for providing a fluid passage through the inner ring and/or the outer ring and/or the sealing element and/or into the inner space of the housing, wherein the opening is fluid tightly connected to an oxygen removing element and/or to a gas tank, which provides an oxygen poor to free fluid to the rolling chamber and/or the inner space of the housing.

Due to the oxygen removing element and/or the gas tank providing an oxygen poor to free fluid, the exposure of the lubricant to oxygen is largely reduced, which in turn increases the service life of the lubricant and thereby of the bearing assembly.

According to a further preferred embodiment, the oxygen removing element comprises a material which is adapted to absorb oxygen and release absorbed oxygen based on a change of at least one physical parameter which impacts on the oxygen removing element. This allows for removing oxygen from the rolling chamber and/or the inside of the housing as will be described in detail below.

Thereby, the physical parameter may be temperature and/or pressure.

It is further preferred, if the oxygen removing element comprises a honeycomb structure or similar structure or structure, which generates a large surface area. This allows for a maxi mum active area for absorbing/desorbing oxygen in an element which requires a minimum of space. According to a further preferred embodiment, the oxygen removing element comprises ze olite and/or activated carbon and/or activated graphite. These materials are known to ab sorb oxygen based on temperature and also provide a structure with a maximized active surface compared to the overall size.

According to a further preferred embodiment, the gas tank comprises nitrogen. Nitrogen is known to be inert to react with any lubricant used in bearing applications.

According to a further preferred embodiment the lubricant is grease.

The oxygen removal in such a sealed bearing works as follows:

During operation of the bearing the bearing elements are heated. Thus, also the air inside the rolling chamber or the housing is heated. Due to this heating the air expands and in creases the air pressure in the housing/rolling chamber. Due to this pressure increase, the “warm” air streams through the venting holes/openings and thereby also through the oxy gen removing element. In case that oxygen removal of the material of the oxygen remov ing element is triggered by e.g. temperature, the increased temperature in the element hin ders the absorption of oxygen and/or may allow for a desorption of oxygen in the oxygen removing element, so that oxygen is transported out of the bearing/housing and also out of the oxygen removing element.

When the operation is terminated or when the speed and/or load on the bearing is reduced and the bearing arrangement is cooling down, the bearing is sucking up air through the venting holes/openings. Thanks to the oxygen removing element arranged in the opening, oxygen will be absorbed to the oxygen removing element and the oxygen cannot enter the rolling chamber/housing. This is particularly possible, if in the“hot” phase, the oxygen is desorbed from the surface of the oxygen removing element and transported to the outside environment, which leaves the oxygen removing element free for absorbing fresh oxygen. The result should ultimately be an oxygen free gas environment inside of the bear ing/housing so that oxidation of the lubricant may be reduced and lubricant service life may be increased.

The same concept applies for the gas tank where oxygen which is initially present in the air inside of the bearing is replaced by the gas which is provided by the gas tank. This also reduces oxidation of the lubricant inside the housing/rolling chamber, as the supply of fresh oxygen is terminated.

Further preferred embodiments are defined in the dependent claims as well as in the de scription and the figures. Thereby, elements described or shown in combination with other elements may be present alone or in combination with other elements without departing from the scope of protection.

In the following, preferred embodiments of the invention are described in relation to the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

The figures show:

Fig. 1 : a schematic sectional view of a bearing assembly according to a first embodiment of the present invention;

Fig. 2: a schematic sectional view of an oxygen removing; and

Fig. 3 : a schematic sectional view of a bearing assembly according to a second embodi ment of the present invention.

In the following same or similar functioning elements are indicated with the same refer ence signs.

Figure 1 shows a schematic sectional view of a bearing assembly 1. The bearing assembly 1 comprises a bearing 2 which is housed in a housing 4. The bearing 2 supports a shaft 6. As can be further seen in Fig. 1, the housing 4 seals off the bearing 2 from an outside envi ronment 8. The in the space 10 of the housing 4, in which also the bearing 2 is accompa nied, a lubricant, such as the grease, is provided.

For allowing a pressure equalization with the outside environment 8, the housing 4 is fur ther equipped with openings 12, which allow an air flow from the inside of the housing to the outside and vice versa. Since such an airflow also provides fresh oxygen to the inner space 10, which in turn might oxidized the lubricant, at least one oxygen removing element 14 is arranged in the/at the opening 12. The oxygen removing element 14 is illustrated in figure 2 and preferably has a honeycomb structure. Such are oxygen removing element may be made from zeolite, activated carbon, activated graphite or any other oxygen ab sorbing/desorbing material with a surface increasing structure.

The oxygen removing feature of such bearing assembly 1 works as follows:

During operation the bearing 2 heats up, which in turn increases also the temperature in side of the housing 4. Consequently, also the air and/or the lubricant present inner space 10 of the housing 4 heats up which results in an expansion and a pressure increase. Due to the pressure increase air is pressed through the opening 12 and thereby through the oxygen removing element 14. Preferably, the oxygen removing element has an oxygen desorbing property with increased temperature so that oxygen is transported from the inner space 10 of the housing 10 as well as from the oxygen removing element 14 to the outside environ ment 8.

As soon the operation of the bearing 2 is terminated, the temperature decreases and the bearing assembly 1 cools down. This in turn results in a pressure decrease in the inner space 10 of the housing 4 which reverses the gas flow through the opening 12 and the oxy gen removing element 14. In case the oxygen removing element is made e.g. from a mate rial with oxygen removing properties at lower temperatures, then the oxygen is removed from the air streaming through the gas removing element 14 and the opening 12. Conse quently, the oxygen amount in the inner space 10 of the housing 4 is reduced, which in turn reduces the oxidation of the lubricant inside the housing and increases the service life of the lubricant and/or of the bearing.

Fig. 3 shows a sectional view of a further embodiment of a bearing assembly of the present invention. A bearing assembly 1 is illustrated having an outer ring 16 and an inner ring 18 which define a rolling chamber 20 between each other. In the rolling chamber 20 rolling elements 22 are arranged. As can be further seen from Fig. 3, the rolling elements 22 are maintained by a cage 24 in a regularly spaced apart condition and the rolling chamber 20 is sealed off from the environment 8 by a sealing element 26. In the illustrated embodiment, the sealing element 26 is fixed to the outer ring 16 and in gliding contact to the inner ring 18 with lip 28.

During operation of the bearing 1, the temperature in the rolling chamber 20 increases which results in a pressure increase inside of the rolling chamber 20. In known bearings such a pressure increase triggers a lifting off of the lip 28 of the sealing element 26 from the gliding surface of the inner ring 18 for balancing the pressure difference and releasing air from the rolling chamber 20. After the operation of the bearing has been stopped the bearing cools down, which results in low pressure in the rolling chamber 20, which is also balanced by air being transported over the sealing lip 28.

For avoiding the lifting motion of the sealing lip 28 triggered by the pressure differences, it is proposed to provide an opening in the sealing element 26 in which at oxygen removing element 14 is arranged and/or with which a gas tank 30 is connected. This allows for an air exchange over the oxygen removing element, which reduces the overall oxygen the amount in the rolling chamber, as explained above. Instead of providing the opening in the sealing element, it is also possible to provide the opening in the inner and/or altering.

In case a gas tank is fluid tightly connected to the opening of the sealing element, the air is not equipped with fresh oxygen from the outside environment 8, but with an oxygen free gas, such as nitrogen, which also reduces the oxidation of the lubricant in the rolling chamber. The size of the gas tank may be adapted to the expected pressure differences and the expected air exchange through the sealing element. Of course, such a gas tank may also be provided to the housing illustrated in Fig. 1 and in addition to any oxygen removing el ement.

This embodiment has a further benefit as the extensive wear due to the lifting off motion of the sealing lip is avoided. This in turn allows for an increase service life of the sealing ele ment and therefore of the bearing.

As can be further seen in the Fig. 1 and Fig. 3, the bearing is not restricted to a certain em bodiment of the bearing so that any bearing, e.g. a roller bearing, such as a tapered roller bearing or any kind of ball bearing, may be used with this invention.

In summary the oxygen removing element as well as the gas tank allows for an air ex change in the bearing without adding fresh oxygen to the inside of the bearing or the hous ing. This in turn, allows for the reduced oxidation of the lubricant and thereby for an in creased service life of the grease/the bearing. Reference signs

1 bearing assembly

2 bearing

4 housing

6 shaft

8 outside environment

10 inner space

12 openings

14 oxygen removing element 16 outer ring

18 inner ring

20 rolling chamber

22 rolling element

24 cage

26 sealing element

28 sealing lip

30 gas tank