Patent Application
20130126274
The present invention pertains to an aerosol lubricating device, an arrangement with such a lubricating device, as well as a corresponding lubricating method.
The lubrication of machine elements with lubricants such as different types of grease, oil or solid lubricant fulfills different functions. On the one hand, it serves for preventing or reducing wear phenomena at contact points between so-called friction partners, for diminishing stress concentrations, for example, in rolling bearings and for reducing additional frictional shearing stresses on surfaces. Lubricants are furthermore used for corrosion protection and also for cooling machine elements if a sufficient lubricant exchange and therefore a corresponding dissipation of heat can be ensured.
The objective of lubrication consists of separating contacting surfaces of the friction partners by means of a hydrodynamic liquid film or a protective reaction layer. In the hydrodynamic formation of lubricating films, an elastic deformation frequently also plays an important role such that one refers to so-called elastohydrodynamic lubrication in this case. The main objective of lubrication is a complete separation of the friction partners. This can be achieved with a suitable combination of the lubricant viscosity, the moving speed of the friction partners and the contact pressure, as well as corresponding constructive adaptations.
As mentioned above, different types of lubricating oil, lubricating grease and solid lubricant are used as lubricants. This application mainly focuses on liquid lubricants such as, e.g., lubricating oils. Important parameters of lubricating oils that can be influenced are the density, the viscosity index, the shear stability, the so-called Cloud-and-Pour point, the neutralization capacity, the neutralization value, the total base number and the flash point. Furthermore, the thermal capacity, the air absorption capacity and the content of water and foreign matter influence the properties of lubricating oil.
Various types of lubricant additives are known for modifying tribologically relevant lubricating oil properties, for example, the viscosity/temperature behavior and/or the frictional and wear behavior, as well as for improving the oxidation resistance or the prevention of foaming.
Additives may be added to lubricating oil in the form of commercially available so-called additive packets. In modern motor oils, 10 to 20% of the overall volume consists of additives. Polymeric additives typically form another 3% of the overall volume.
The service life of lubricating oils is limited. Due to interactions with the system to be lubricated and the surrounding atmosphere, the service life of the lubricating oil and of the entire tribological system can be significantly reduced. In this context, oxidation processes that lead to an increase of the neutralization value and therefore an increased corrosiveness of the lubricating oil are considered particularly critical. An increase of the viscosity causes the tribological properties of the system to change over time. Deposits formed due to corrosion by separating lubricating oil components can cause blockages. A loss of additives can result in certain components of the lubricating oil no longer being sufficiently protected such that its quality deteriorates. Consequently, frequent oil changes or maintenance intervals are required.
It would therefore be desirable to increase the service life of a lubricating oil or, more generally, a liquid lubricant, particularly a lubricating oil that is based on minimal oil.
Based on these circumstances, the present invention proposes an aerosol lubricating device for a device to be lubricated with at least two friction partners, an arrangement with such a lubricating device, as well as a corresponding lubricating method.
The invention proposes a lubricating device that can be coupled with a device to be lubricated and comprises means for producing an oxygen-free aerosol of a liquid lubricant (e.g., a lubricating oil) in a carrier fluid, as well as means for supplying the correspondingly produced aerosol to the device to be lubricated. The preferred carrier fluid used is gaseous and contains no oxygen. The carrier fluid preferably is also free of other corrosive components, particularly water and abradant particles.
The FIGURE shows a lubricating arrangement according to an embodiment of the invention.
Although the present invention refers to an “oxygen-free” aerosol or an “oxygen-free” carrier fluid, these terms also include an aerosol or carrier fluid that still has slight (residual) contents of dissolved oxygen or is able to produce slight amounts of oxygen. Although it is desirable that the lubricant protection gas is completely oxygen-free, this is usually associated with significant additional costs.
Methods for removing oxygen, for example, from corresponding gases are sufficiently known. For example, oxygen can be condensed out of air in a cooling trap or catalytically separated. Inert gases such as argon, nitrogen or carbon dioxide may also be provided in liquid, oxygen-free form and transferred into the gaseous phase prior to the utilization in a lubricant protection gas.
The inventive measures make it possible to create an oxygen-free lubricant/gas system in a device to be lubricated that is permanently available in said device and significantly prolongs the service life of frictional components. Consequently, the maintenance intervals of corresponding systems can be significantly extended such that higher availability and/or lower maintenance costs are achieved. Due to a corresponding oxygen-free lubricant atmosphere, it is also possible to utilize oxygen-sensitive lubricant additives without having to carry out a frequent lubricant change.
The lubricating device may include means for producing an oxygen-free aerosol in the form of a lubricant reservoir and a feed device that is arranged in the lubricant reservoir and serves for introducing the carrier fluid into the lubricant. The feed device may consist, for example, of a gas bubbling device that makes it possible to produce gas bubbles that flow through the lubricant and during this process produce an aerosol and/or a lubricant mist. The gas bubbles may be produced, for example, by a filter (membrane or frit), wherein the gas bubble size is influenced with the respective pore size. The introduction of the carrier fluid and therefore the production of the aerosol may take place continuously or intermittently, e.g., in lubricating intervals.
Typical gas throughputs lie, for example, in the range between 1 liter and 20 standard cubic meters per second.
In the context of the present invention, an “aerosol” refers to any system, in which a liquid lubricant is present in a gaseous carrier fluid, e.g., in the form of droplets. The respective droplet size may significantly vary in this case and lie in the range between 0.5 nm and several 10 μm.
A corresponding lubricating arrangement includes a device to be lubricated with at least two friction partners and a lubricating device of the above-described type. The lubricating device is provided with means for supplying the aerosol to the device to be lubricated in this case. The device to be lubricated and the lubricating device are connected to one another by a gas-tight channel. Due to the coupling of the lubricating device to the device to be lubricated, a closed system is created such that the admission of oxygen into the lubricating arrangement can be prevented.
A corresponding lubricating arrangement includes a device to be lubricated that is designed for the flow-through of the oxygen-free aerosol. In this way, a lubricant atmosphere or an oxygen-free aerosol can be continuously or intermittently regenerated in the device to be lubricated such that a particularly effective protection is achieved.
For this purpose, the device to be lubricated features outlet openings for liquid lubricant, aerosol and/or gas. A separating device for liquid lubricant and corresponding outlet openings may be provided for removing lubricant separated from the aerosol, e.g. due to condensation, from the device to be lubricated. The removed liquid lubricant can then be subjected, for example, to a cleaning process (e.g. by means of filtration or chemical processing) and/or once again supplied to a lubricating device. Gas that no longer contains any lubricant components can be removed from the system in the same fashion. It would also be possible for the aerosol to continuously flow through the device to be lubricated and to further treat the aerosol in a separating device. For example, liquid lubricant can be separated in a separating device and once again supplied to an inventive lubricating device as described above.
A lubricating arrangement may also be provided that includes a heating device for the carrier fluid, the lubricant and/or the aerosol. It is generally known that certain heated gases such as, for example, acetylene or carbon monoxide positively influence the tribological properties of a system to be lubricated. It would therefore be possible to provide a correspondingly heated gas flow by means of a gas heater. Corresponding heating devices ensure that parameters of the lubricant and/or the aerosol such as, for example, its density, its viscosity and/or its compressibility can be controlled particularly well.
At an elevated temperature in the lubricating device, it would be possible, if applicable, to make available a larger quantity of lubricant in the aerosol. If heated aerosol is introduced into a (cool) gearing, liquid aerosol particles are deposited on the respective components due to condensation such that a very good and purposeful lubrication can be achieved.
In this case, the heating may take place in the lubricating device, as well as in the device to be lubricated, wherein a gas flow, a lubricant and/or the obtained aerosol can be selectively heated.
An inventive lubricating method includes the production of an oxygen-free aerosol by utilizing the above-described lubricating device.
In a corresponding method, inert gases such as argon or nitrogen, as well as gases such as carbon dioxide, carbon monoxide and/or acetylene that are known to positively influence the tribological properties of a system to be lubricated may be used as carrier fluid. Corresponding gas mixtures may also be utilized.
The lubricant used consists of a lubricant that is based on mineral oil, particularly a mineral oil with polymeric additives and/or additives. As already mentioned above, the improved protection of the lubricant achieved with the inventive measures also makes it possible to utilize polymeric additives that could not be used in conventional lubricating systems so far because they would have been subjected to the damaging oxidation effect of oxygen. However, the utilization of the invention also makes it possible, in particular, to eliminate certain additives such as, e.g., antioxidants such that significant cost advantages can be realized.
As mentioned above, a certain viscosity, density and/or compressibility of the lubricant and/or the aerosol can be adjusted in a corresponding method. This can be realized, for example, with a suitable gas composition and gas temperature and/or a suitable flow speed or with correspondingly adjusted pressures.
The inventive method can be utilized in the number of devices to be lubricated such as, for example, turbines of wind power plants, engine parts, bearings, valves and valve drives, as well as cutting tools.
Other advantages and embodiments of the invention result from the description and the attached drawing Figure.
The characteristics described above and below can be used in the respectively described combination, and also in other combinations or individually without deviating from the scope of the present invention.
An exemplary embodiment of the invention is schematically illustrated and described in greater detail below with reference to the drawing Figure.
A lubricating arrangement or system according to an embodiment of the invention is illustrated in the Figure and altogether identified by the reference symbol 100. The lubricating arrangement 100 comprises a lubricating device 10 and a device 20 to be lubricated. The lubricating device 10 features means 11 for producing an oxygen-free lubricant aerosol with a reservoir 13 for liquid lubricant and a feed device 14 that is arranged in the reservoir 13 and serves for introducing a carrier fluid into the lubricant. The feed device 14 includes a supply line 15 for the carrier fluid (gas) and on its other end preferably a membrane and/or a frit, by means of which gas bubbles can be produced in the lubricant.
Means 12 are provided for transferring the aerosol produced by means of bubbling in the lubricating device into the device 20 to be lubricated.
The device 20 to be lubricated includes at least two friction partners 21, 22 or members that are symbolized in the form of toothed wheels and driven by motors M1 and M2. The friction partners 21, 22 are accommodated in a housing 23 that is at least partially gas-tight and realized such that an inflowing aerosol is present in the housing 23 in a controlled quantity and/or this aerosol can flow through the housing with a controlled speed. On its bottom side, the housing 23 may be provided with outlet openings 24 for liquid lubricant in order to ensure the removal of lubricant 26 condensed out of the aerosol. Outlet openings 25 for aerosol and/or gas may be provided at a different location, e.g., on the cover side of the housing 23.
The device 20 to be lubricated may also be selectively realized for oil bath lubrication, wherein a lubricant sump may be at least partially formed or supplied by the lubricant 26 condensed out of the aerosol.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 102 539.5 | May 2011 | DE | national |
