Abstract:
A lubricating device for gear trains ( 10 ), especially for wind power stations, includes at least two gear stages ( 16,18 ) that are disposed next to each other and are effectively interconnected, and a lubricant circuit ( 20 ) into which at least one filter unit ( 26 ) is mounted. To prevent stagnant resting zones for the lubricant from being created within the gear train housing including the gear stages, while ensuring that the entire lubricant that circulates in the gear stages is fed to the filter unit to be drawn off and filtered within predefined periods of time, the lubricant circulating inside the lubricant circuit ( 20 ) is discharged at one gear stage ( 18 ), is drawn off through the filter unit, and can then be fed to the other gear stage ( 16 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a lubricating device for gear trains, especially for wind power stations, with at least two gear stages located next to one another, and dynamically connected to one another, and a lubricant circuit having at least one filter unit. 
     BACKGROUND OF THE INVENTION 
     Lubrication devices for gear trains in wind power stations are known and readily available on the market. In the manner of closed circulating lubrication, the lubricant, especially in the form of lubricating oil, is removed by gear oil pumps from the gear sump of the gear housing with the gear stages, supplied to filtering by the filter unit, for filtering, and discharged again to the interior of the gear housing to remove fouling, including in the form of metal shavings, from the lubricant. In spite of these measures, premature damage to the gears, which often occurs after six months, takes place in practical applications, both within the planet stage and on the spur wheel stage generally forming the two gear stages for the rotor of a wind power station. In particular, the planet stage often fails due to defective planet bearings, as do the gear oil pumps of wind power stations due to metal shavings which occur with increased frequency in the lubricant circuit. The reason for such failures is that within the spur wheel stage, due to the formation of resting zones with large areas for the lubricant (oil), it becomes possible for heavy metal particles to settle in those resting zones. Often lubricant or oil exchange takes place only in the area of the spur wheel stage so that lubricant exchange takes place only conditionally, and contaminated or dirty lubricant can remain on the sides of the planet stage and can cause damage there. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide improved lubrication devices that are reliable and economical in use, and ensure long-lasting gear train operation, thereby contributing to increasing the time between expensive maintenance intervals. 
     This object is basically achieved by a lubrication device where, on one gear stage, the lubricant circulating in the lubricant circuit is drawn off, cleaned by the filter unit and then delivered to the respective other gear stage. Stationary resting or stagnation zones for the lubricant within the gear housing with the gear stages are avoided. In definable time intervals, all the lubricant circulating in the gear stages is delivered to the filter unit to be cleaned and filtered by it. For an average person skilled in the art in the area of lubrication devices, especially in the area of wind power stations, it comes as a surprise that, with the measure of permanent circulation while avoiding stationary resting zones in the lubricant or gear oil bath, improved possibility for cleaning the lubricant flow by the filter unit is obtained. In particular, the heavy metal particles which otherwise settle can be continuously supplied to the circulation process. This ability leads to relief of the gear oil pumps and ultimately also of the gear stages, from which serious contaminants are removed. The pumps and gear stages can then perform their functions for a long time. The improved lubricant delivery at the respective gear stage also contributes to the extended performance. 
     In one preferred embodiment of the lubrication device of the present invention, provision is made such that in order to implement splash lubrication, the gear stages each individually and at least partially pass through a type of immersion bath with a lubricant reserve. The lubricant reserve has a subdivision such that each gear stage is assigned its own bath area. Preferably, the subdivision and the lubricant amount in the immersion bath are chosen such that overflowing lubricant from one gear stage with lubricant supply travels to the bath area of the following gear stage with lubricant removal. This configuration provides optimum lubrication of the gear stages within the immersion bath of the lubricant, while still ensuring that within the immersion bath lubricant displacement and the respective continuous drawing off take place. Removal of fouling from the lubricant or gear oil bath is then achieved continuously. 
     In another, especially preferred embodiment of the lubrication device of the present invention, lubricant removal includes of a suction device, and the lubricant supply includes an injection device. In the gear housing for the respective gear stage, the indicated devices are mounted diagonally opposite one another, extending through the upper and lower area of the housing. Due to this diagonal configuration, optimum lubricant distribution within the gear stages takes place. The transit time for the lubricant between the gear stages from the injection side to the suction side is likewise optimized. 
     Preferably, the gear stage comprises a planet gear and a spur gear. By the planet gear, it is possible to bring the rotor of the wind power station with its low rpm to higher rpm as required, to drive a generator for generating current or the like by the spur gear, in the known manner. For long-lasting and good lubricant operation, it has proven favorable to provide injection of a cleaned lubricant for the planet gear and to implement suction for contaminated lubricant on the spur gear stage. 
     The filter unit used preferably in the lubrication device in the direction of lubricant delivery has a fine filter which is safeguarded with a bypass, followed by a coarse filter connected downstream in series. Cleaning results are especially good when the filter fineness of the coarse filter is chosen to be approximately 5 to 10 times coarser than the filter fineness of the fine filter. Such a preferably suitable filter unit is described in DE 101 05 612 A1 of Hydac Filtertechnik GmbH. 
     The lubrication device of the present invention need not be limited to gear stages in wind power stations. It can also be used for other gear stages and gear configurations, with and without planet gears. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings which form a part of this disclosure: 
         FIG. 1  is a schematic, block diagram, not to scale, of a lubrication device according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The lubrication device is used for a gear train  10 . The gear train  10  shown in  FIG. 1  is used in so-called wind power stations, in which a rotor (not shown), driven by the force of the wind, delivers its output power to an input shaft  12 . After passing through the gear train  10  the respective output power is delivered to an output shaft  14  which, for example, can be connected to a generator (not shown) for generating electrical current. Since the rotor generally has very low rpm and the generator operation requires correspondingly higher input rpm, the gear train provides a step-up ratio from low to high rpm by a factor i of for example 1:80. The pertinent gear train assemblies for wind power stations are conventional, and need not be described in further detail. 
     Such gear trains generally have two gear stages  16 ,  18 , with each gear stage having several stage parts. In particular, the first gear stage  16  includes planet gear and the second gear stage  18  includes a spur gear, with those stages also being referred to as the planet stage and the spur stage, respectively. The lubrication device of the present invention, in the manner of a closed circle or loop, has a lubricant circuit  20 . To propel the lubricant, a conventional motor pump unit  22  is used, and is subsequently safeguarded in the lubricant delivery or downstream direction by a check valve  24  of conventional design. A filter unit  26  is connected subsequently or downstream between the motor pump unit  22  and the two gear stages  16 ,  18 . 
     As illustrated in the block diagram, on the second gear stage  18 , the lubricant circulating in the lubricant circuit  20  is removed and then is supplied via the motor pump unit  22  to the filter unit  26  before the lubricant cleaned in this way is then supplied to the first gear stage  16 . The lubricant circulation can be carried out independently of whether the rotor and accordingly the gear train  10  are in operation or not. In this manner, by a control which is not detailed, the lubricant can be cleaned even if the system itself is shut down, for example because, with respect to the prevailing wind, operation of the system would not be profitable. 
     To implement splash lubrication for gear stages  16 ,  18  an immersion bath  28  is provided having a definable lubricant reserve and into which the gear stages  16 ,  18  with their gear wheels are at least partially immersed. A subdivision  30  is placed in the immersion bath  28 , with each gear stage  16 ,  18  thus being assigned its own bath area  32 ,  34  in the process. In particular, the subdivision  30  and the lubricant amount in the immersion bath  28  are chosen such that the overflowing lubricant  36  (see arrow representation) travels from first gear stage  16  with lubricant supply  38  to the second bath area  34  with the following gear stage  18  with lubricant removal or outlet  40  of the immersion bath  28 . 
     In the selected embodiment, the lubricant removal  40  is formed with a suction device, while the lubricant supply  38  is formed with an injection device. The suction and injection actions are adjustable by the working capacity of the motor pump unit  22 . In particular, the indicated injection device is configured such that, for the purposes of a spraying-on process, parts of the first gear stage  16  are covered or fogged with the lubricant over a large area. 
     As also illustrated in  FIG. 1 , in the gear housing  10  for the respective gear stages  16 ,  18 , the devices  38 ,  40  are mounted diagonally opposite one another. The lubricant supply  38  extends through the upper part of the housing  10 . The lubricant removal  40 , in the form of a suction device, penetrates the housing area from the housing bottom. With respect to the diagonal configuration, it basically is also possible in one embodiment, which is not detailed, to supply the injection amount to the top of the spur wheel stage and to implement suction on the bottom of the planet stage. Since the planet stage in terms of its support is highly susceptible to fouling, it has proven advantageous to implement the diagonal arrangement. As already described, diagonal fluid guidance is promoted and improved in that the overflowing lubricant  36  is relayed from one bath area  32  into the other bath area  34  and then is available to a filtration process by the filter unit  26 . Sedimentation or settling, especially of heavy fouling components such as metal shavings or the like, in the bath area  32  is thus effectively controlled. 
     The filter unit  26  can be provided with a filter element. It has proven advantageous to provide a fine filter  44  safeguarded with a bypass  42  (spring-loaded check valve) in the lubricant delivery direction, followed by a coarse filter  46  connected downstream in series. In normal operation, the fine filter  44  performs removal of fouling in the lubricant circuit  20 . If the fine filter fail  44  fails, especially should it be clogged with dirt, the bypass valve  42  opens and to then supply the fluid flow to the coarse filter  46 . Coarser dirt is then retained by the coarse filter  46  and cannot penetrate into the gear train  10  with its gear stages  16 ,  18  to cause damage. It has been found to be especially favorable for this application if the coarse filter is designed to be 10 times more coarse than the filter stage of the fine filter  44 . Thus, the fine filter  44  can have a filter fineness of 5 μm and the coarser protective filter can have a filter fineness of 50 μm particle size. The pertinent, series-connected filter stages are prior art and it has proven especially effective to use filter units  26  according to DE 101 05 612 A1 (corresponding to U.S. Pat. No. 7,279,091). 
     By a combination of suction from the oil sump on the spur wheel area and injection of lubricant into the planet stage after cleaning by the filter unit  26 , lubricant supply for the gear train parts of wind power stations is achieved which ensures reliable and long-lasting, trouble-free operation even under harsh ambient conditions and with hard use. 
     The lubricant device of the present invention can be used by itself as a modular unit. It can also be installed as an additional system to standard circulation lubrication or to immersion bath lubrication. Furthermore, the possibility also exists of integrating an additional intake filter or intake screen (not shown) in the intake line to the motor pump unit  22  to protect the hydraulic pump against damage caused by dirt. Analysis of the contents of an intake screen yields conclusions regarding wear processes in the gear train. The subdivision of the bath areas within the gear housing can also be formed by ribs or stiffeners of the gear housing. The planet stage  16  shown in  FIG. 1  has so-called planet wheels which revolve around the sun wheel shown lowermost in the FIGURE. As viewed in the FIGURE, the internal geared wheel is shown uppermost. The structure of the planet gearing is conventional so that it will not be described in further detail. 
     As shown in  FIG. 1 , a gear stage or planet stage  16  forms the planet gearing or the so-called planet part of the gear train. Conversely, two gear stage or spur wheel stages  18  form the actual spur gear which is also called the spur part of the gear train. The diagonal lubrication concept of the present invention for the lubrication device can also be used for gear trains with a different number of gear stages. The check valve  24  inserted downstream from the pump  22  is optional, and not absolutely necessary. In particular the pertinent check valve  24  would be suited for pressure limitation. The oil flow from the check valve could then be routed to the intake side of the pump (not shown).