Abstract:
A roller bearing device ( 1 ) and to a method for operation thereof, including a roller bearing ( 2 ) having roller contacts ( 6, 7 ) in contact with a medium and lubricated by the liquid medium ( 10 ). In order to improve the lubrication and load capacity of such a medium-lubricated roller bearing ( 2 ) while simultaneously improving the biologically compatible behavior, a biologically neutral additive material ( 13 ) that thickens the medium is held available in a holding device ( 14 ) and metered to the roller contacts ( 6, 7 ) on demand.

Description:
FIELD OF THE INVENTION 
     The invention relates to a roller bearing device and a method for its operation with a roller bearing with roller contacts in contact with a medium and lubricated by the liquid medium. 
     BACKGROUND 
     Roller bearings that are in contact with a medium and are used, for example, in underwater applications, are exposed to continuous loads with the medium—here water—so that conventional roller contacts treated with synthetic or mineral lubricants are quickly washed away. Washing away such lubricants causes environmental problems, such as, environmental contamination due to eutrophication and the lack of biodegradability, especially for frequent or long-term use. To counteract the rapid loss of lubricant, dynamic seals of the intermediate space that is between the outer ring and inner ring and contains the roller contacts have been proposed in which a sealing unit is locked in rotation to the outer ring and inner ring on each side of the roller bearing and is sealed dynamically by means of a seal, for example, a lip seal. Here, moments of friction occur that adversely affect the efficiency of the roller bearing and thus of the application using the roller bearing. 
     Alternatively it is proposed to design roller bearings such that water acts as a lubricating medium. Here, very corrosion-resistant materials are required, especially in seawater environments. The load capacity of roller contacts lubricated only with water is comparatively low. Furthermore, so-called fouling must be taken into account, in which the roller contacts are obstructed with calcium-depositing microorganisms, wherein the roller contacts are permanently damaged. 
     SUMMARY 
     The object of the invention is thus to refine a roller bearing for improving medium-supported lubrication by the medium, in particular, water. 
     The objective is met by a method for operating a roller bearing device with a roller bearing with roller contacts that are in contact with a medium and are lubricated by the liquid medium, in particular, water, wherein a biologically neutral additive that thickens the medium is stored in a supply device and dosed as needed to the roller contacts. 
     Through the use of a biologically neutral additive that thickens the medium, such as water, the thickening of the medium improves the tribological effect of the medium that is made functional in this way, so that the load capacity of the roller contacts can be increased for the same rolling surface area. Furthermore, a medium that is made functional and rinsed out due to high medium pressure and/or medium flow can be replaced by the controlled dosing of additive. For the biologically neutral additive, this is an individual component, such as a gel or the like, or a mixture made from a thickener and corresponding additives. The additive is, in particular, biocompatible, preferably 100% biodegradable, and non-eutrophic. For example, thickeners can be degradable and non-eutrophic. For example, thickeners such as modified cellulose, amino acids, and the like could be used. This produces advantageous uses for water turbines, for example, current power generators, paper machines, food processing machines, agricultural devices, devices in the chemical and pharmaceutical industries, applications in ships, for example, on stern tubes, in military engineering, and the like. 
     Through the use of additives in connection with the medium, only a small quantity of additive, such as a thickener, is needed to achieve a desired lubricating effect for a specified tribological effect and load capacity, so that materials and costs are saved. Additives having a wear and/or corrosion reducing effect can be provided, so that, for example, long-term use in especially pure to heavily polluted fresh water and also, in particular, sea water, is possible. 
     According to one advantageous construction of the method, a dosing of the additive is controlled by a control parameter detected by means of a detection device mounted in the area of the roller contacts for detecting the viscosity of the medium. For example, a quartz viscometer can be arranged in the area of the rolling surfaces on a roller body cage or a stationary raceway, depending on the application on the outer or inner ring. This viscometer determines the viscosity of the composition of the medium and additive active on the roller contacts, such as the rolling surfaces, and doses additive by means of one or more dosing openings to the roller contacts, for example, by controlling a valve, such as an electrical proportional valve or the like, as a function of the viscosity converted into a control parameter, for example, an electrical signal. Here, the additive stored in the supply device, for example, a storage container arranged within or preferably outside of the medium, can be pressurized by the force of gravity or by means of preloading by a feed pump. 
     Alternatively or additionally, the dosing of additive can be controlled by a control parameter detected by means of a detection device mounted in the area of the roller contacts for detecting a fill level of a reservoir connected to the roller contacts. Here, the fill level of the reservoir, for example, of a channel or cavity connected directly to a roller contact and bounded by this roller contact can be detected visually or by detecting the pressure, an electrical resistance, by in some other way. 
     To reduce the contact of the medium on the contact surfaces, a free blowing device operated with compressed air can be provided on the side of the roller contacts opposite the dosing of the additive. This free blowing device places a gaseous cushion preferably from compressed air in front of the roller contacts, so that contact with the medium is reduced and therefore the discharge of medium made functional with the additive is at least reduced. This can further reduce the consumption of additive. 
     The problem is further solved by a roller bearing device for performing the proposed method. Here, a roller bearing is provided with an inner ring, an outer ring, and roller bodies that are distributed over the circumference between these rings and roll on the roller contacts of these rings, wherein for thickening the medium, in particular, water, present on the roller bodies, a supply device with the additive that thickens the medium and a dosing device that doses the additive to the roller contacts as a function of a control parameter detected by a detection device are provided. 
     According to one advantageous embodiment, the roller bearing device contains a dosing device with a feed pump preloading the additive in the supply device, a valve that can be switched as a function of the control parameter, and at least one dosing opening in the area of the roller contacts. 
     The detection device can be, for example, a viscometer, a fill level sensor detecting a fill level of a reservoir for the additive arranged on the roller contacts, or the like. 
     A free blowing device can be provided on the side of the roller bearing opposite the dosing device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in more detail with reference to embodiments shown in  FIGS. 1 to 3 . Shown are: 
         FIG. 1  a schematic diagram showing the function of a roller bearing device, 
         FIG. 2  a schematic diagram of a roller bearing device, and 
         FIG. 3  a schematic diagram of a roller bearing device modified relative to the roller bearing device of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows, as a block diagram, the schematic function of a roller bearing device  1  in an environment with a medium—here, water. Through the entry of water into the roller bearing, lubricant is discharged. To balance the loss of lubricant with the smallest possible input of material and to maintain it at least neutral ecologically for the environment, the water that is present is made functional by adding small quantities of additive—here, thickener—that forms the lubricant with the water by increasing the viscosity of the water. In this way, the dosing of the thickener can be kept at low quantities. For an appropriate composition of the thickener from a single component or a mixture of several individual components, the water that is made functional by means of the thickener can assume lubricating properties, for example, at the quality of ISO VG 220. Here the thickener can contribute 5 vol. % to the total volume of the lubricant and the water provides the remaining 95 vol. %. Here, both the thickener itself and also the lubricant that is optionally converted with a chemical reaction and/or formed using a physically associative method are preferably 100% biodegradable, non-eutrophic, and environmentally compatible. Chemical compounds or their mixtures, such as modified cellulose, amino acids, and the like, which form a lubricant of higher viscosity, for example, with hydrophilic media, can be used as the thickener. If necessary, additives, such as anti-corrosion components that are preferably also biologically neutral can be added to the thickener. 
     It can be used, in particular, in temperatures from −20° C. to 100° C., under pressure, or appropriate media loading up to 120° C. and is suitable, in particular, for current power generators, such as ocean current power generators, tidal energy power generators, and the like, due to their high tolerance to salt water. 
       FIG. 2  shows the roller bearing device  1  of  FIG. 1  schematically in detail. The roller bearing  2  arranged around the shaft  3  with the inner ring  4 , the outer ring  5 , and the roller bodies  8  mounted in the bearing cage  9  distributed over the circumference between these rings and rolling on the roller contacts  6 ,  7  has an open design relative to the medium  10 , such as water. In this way, lubricant—symbolized by the arrow  12 —is discharged to the roller bearing  2  as a function of the prevailing flow of the medium  10  shown by means of the arrows  11 . 
     The lubricant not shown in detail here is formed on site from the medium  10  fed into the roller bearing  2  and the additive  13 , such as a thickener that is stored in the supply device  14  and dosed into the area of the roller contacts  6 ,  7  by means of the dosing opening  16  via the pressurized line  15 . Due to the flow of medium and the turbulence symbolized by the arrows  17  due to the rotating roller bearing  2 , the additive  13  and medium  10  are mixed together and a lubricant is produced that forms a lubricating film on the roller contacts  6 ,  7 . 
     To compensate the discharged lubricant, dosing of the additive  13  is provided. For this purpose, the additive  13  is dosed by means of the feed pump  18 , the preloading spring  19  that preloads the piston  20  of the supply device  14  and/or the like, and by means of the dosing valve  21 . The dosing valve  21  is included in the control loop  22  and opens when the detection device  23  detects a viscosity of the lubricant less than a specified threshold. The detection device can be, for example, a quartz viscometer that outputs, as a function of the viscosity, an electrical control parameter that is evaluated in a control unit containing the control loop  22 , wherein this controls the dosing valve  21 . 
       FIG. 3  shows a modification of the roller bearing device  1  of  FIG. 2  in the form of the roller bearing device la in a schematic diagram. In contrast to the detection device  23  of  FIG. 2 , the detection device  23   a  detects a fill level of a reservoir  24 , for example, in the form of a channel or a cavity in the bearing cage  9   a  that is in contact with the roller contact  6   a . Due to the presence of the medium  10 , the lubricant is produced continuously with the additive  13  discharged from the reservoir  24  and the medium  10 . If the fill level of the additive  13  in the reservoir falls below a specified threshold, the dosing valve  21   a  is opened and additive  13  is added. 
     Another difference is the free blowing device  25  that can also be used in the roller bearing device  1  of  FIG. 2 . The free blowing device  25  contains the pressurized volume  28  that is preloaded, for example, by means of the pressure pump  26  and stabilized by the preloading spring  27  and filled with gas, such as pressurized air and blows, continuously or intermittently, the preloaded gas via the pressurized line  29  onto the end side facing away from the end side that has the dosing device for the additive, so that the intermediate space  30  between the inner ring  4   a  and outer ring  5   a  of the roller bearing  2   a  is freely blown with the medium  10  symbolically in the direction of the arrows  31 . Due to the only reduced medium  10  in the intermediate space  30 , the flushing of lubricant is reduced, so that the consumption of additive  13  can be further restricted. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Roller bearing device 
           1   a  Roller bearing device 
           2  Roller bearing 
           2   a  Roller bearing 
           3  Shaft 
           4  Inner ring 
           4   a  Inner ring 
           5  Outer ring 
           5   a  Outer ring 
           6  Roller contact 
           6   a  Roller contact 
           7  Roller contact 
           8  Roller body 
           9  Bearing cage 
           9   a  Bearing cage 
           10  Medium 
           11  Arrow 
           12  Arrow 
           13  Additive 
           14  Supply device 
           15  Pressurized line 
           16  Dosing opening 
           17  Arrow 
           18  Feed pump 
           19  Preloading spring 
           20  Piston 
           21  Dosing valve 
           21   a  Dosing valve 
           22  Control loop 
           23  Detection device 
           23   a  Detection device 
           24  Reservoir 
           25  Free blowing device 
           26  Pressure pump 
           27  Preloading spring 
           28  Pressure volume 
           29  Pressurized line 
           30  Intermediate space 
           31  Arrow