Abstract:
A lubricant heating mechanism is provided with a tank accumulating therein lubricant; a lubricant pump; a heater provided in the tank to heat the lubricant; and a baffle plate at least partially covering the heater. The tank is provided with a suction port drawing out the lubricant from the tank to the lubricant pump. The baffle plate is provided to convect the heated lubricant toward the suction port.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a lubricant heating mechanism, a gear mechanism, and a wind turbine generator using the same, and more particularly, to a heating mechanism for heating lubricant when an equipment is started in an extremely cold environment. 
       BACKGROUND ART 
       [0002]    There arises a necessity to heat lubricant, when a wind turbine generator or other equipment is used in an extremely cold environment. The viscosity of the lubricant increases in an extremely cold environment, and an excessively increase in the viscosity of the lubricant enhances the load of a lubricant circulation pump, and may cause malfunction of the circulation pump. To address this, the lubricant is heated by a heater, when the temperature of the lubricant is low. For example, US Patent Application Publication No. 2009/0191060 A1 (Patent Document 1) discloses a technique for providing a heater in an exhaust pipe which evacuates lubricant from a gearbox to a pump. 
         [0003]    One problem is that it takes a long time to reheat the lubricant in an equipment tank when the equipment stops operating in an extremely cold environment. In an equipment used in an extremely cold environment, a heater is provided in a lubricant tank to heat lubricant; however, the viscosity of the lubricant increases when the lubricant accumulated in the equipment tank is cooled after the machine stops operating in the extremely cold environment. Occurrence of convection is suppressed in the cooled lubricant, which has a high viscosity; convection occurs to the lubricant right on the heater and the lubricant right on the heater is promptly heated, while no convection occurs laterally and below the heater and the lubricant lateral of and below the heater is difficult to be heated. 
         [0004]    Particularly, this problem is serious when a suction port drawing out the lubricant from the equipment tank into a lubricant pump is positioned laterally of the heater because of the equipment layout. It takes long time to restart the lubricant pump, since the lubricant near the suction port is not heated. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Document 1: US Patent Application Publication No. US 2009/0191060 A1 
       
     
       SUMMARY OF INVENTION 
       [0006]    It is, therefore, an object of the present invention to provide a lubricant heating mechanism capable of reducing time necessary to restart a lubricant pump after the lubricant in an equipment tank is cooled, and a wind turbine generator using such lubricant heating mechanism. 
         [0007]    In an aspect of the present invention, a lubricant heating mechanism is provided with: a tank accumulating therein lubricant; a lubricant pump; a heater provided in the tank to heat the lubricant; and a baffle plate at least partially covering the heater. The tank is provided with a suction port drawing out the lubricant from the tank to the lubricant pump. The baffle plate is provided to convect the heated lubricant toward the suction port. 
         [0008]    When the lubricant heating mechanism further includes a gear, it is preferable that the baffle plate is provided to cover a lower portion of the gear and to function as an oil pan holding the lubricant near the gear. 
         [0009]    The baffle plate is preferably provided away from a sidewall of the tank, the sidewall having the suction port provided thereon. 
         [0010]    In another aspect of the present invention, a lubricant heating mechanism is provided with: a tank accumulating therein lubricant; a lubricant pump; and a heater provided in said tank to heat said lubricant. The tank is provided with a suction port drawing out the lubricant from the tank to the lubricant pump, the suction port being provided laterally of the heater. The lubricant located near the suction port is heated faster than the lubricant near a portion above the heater on a liquid surface of the lubricant. 
         [0011]    In still another aspect of the present invention, a gear mechanism is provided with a tank portion accumulating therein lubricant; a gear; an oil pan provided to cover a lower portion of the gear to hold the lubricant near the gear; and a heater provided in the tank portion to heat the lubricant. The tank is provided with a suction port drawing out the lubricant from the tank to a lubricant pump. The oil pan covers the heater at least partially and functions as a baffle plate convecting the heated lubricant toward the suction port. 
         [0012]    In still another aspect of the present invention, a wind turbine generator is provided with: a main shaft supporting a wind turbine rotor and provided rotatably; a gear box having an input shaft connected to the main shaft; and a generator connected to an output shaft of the gear box. The gear box includes: a housing including a tank portion accumulating therein lubricant; a gear provided inside the housing; an oil pan provided to cover a lower portion of the gear, and holding the lubricant near the gear; and a heater provided in the tank portion. The housing is provided with a suction port drawing out the lubricant from the tank portion to a lubricant pump. The oil pan covers the heater at least partially and functions as a baffle plate convecting the lubricant toward the suction port. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a conceptual diagram showing a configuration of a lubricant circulation system provided with a lubricant heating mechanism in one embodiment of the present invention; 
           [0014]      FIG. 2A  is a diagram showing the behavior of heated lubricant in an equipment tank with a baffle plate; 
           [0015]      FIG. 2B  is a diagram showing the behavior of heated lubricant in an equipment tank without a baffle plate; 
           [0016]      FIG. 3  is a side view of a wind turbine generator in one embodiment of the present invention; 
           [0017]      FIG. 4  is a top view showing an internal structure of a nacelle of the wind turbine generator in one embodiment; 
           [0018]      FIG. 5  is a cross-sectional view showing a structure of a gear box in one embodiment; 
           [0019]      FIG. 6  is a perspective view showing a structure of a tank portion of the gear box shown in  FIG. 5 ; and 
           [0020]      FIG. 7  is a cross-sectional view showing the structure of the tank portion of the gear box shown in  FIG. 5 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0021]      FIG. 1  is a conceptual diagram showing the configuration of a lubricant circulation system  10  provided with a lubricant heating mechanism in one embodiment of the present invention. In this embodiment, the lubricant circulation system  10  includes an equipment tank  1 , a lubricant pump  2 , and an accessory  3 . The equipment tank  1  is a tank provided in equipment (such as a gearbox) or the like to accumulate lubricant therein. The lubricant pump  2  draws out the lubricant in the equipment tank  1  from a suction port  6  and feeds the lubricant to the accessory  3 . The accessory  3 , which includes a lubricant filter, a lubricant cooler and the like, performs necessary treatment on the lubricant and feeds the lubricant to the equipment. The lubricant used in various parts of the equipment is collected in the equipment tank  1 . It is preferable that heaters (not shown) are provided for respective pipes connecting the equipment tank  1 , the lubricant pump  2 , and the accessory  3 , so as to prevent cooling of the lubricant in the equipment tank  1 , the lubricant pump  2 , and the accessory  3 . 
         [0022]    A heater  4  for heating the lubricant is provided inside the equipment tank  1 . The heater  4  is used to heat the lubricant when the temperature of the lubricant inside the equipment tank  1  is low. The viscosity of the lubricant increases, when the equipment stops operating in an extremely cold state and the temperature of the lubricant falls. The lubricant pump  2  cannot operate when the viscosity of the lubricant is excessively increased. To address this, the lubricant pump  2  is started after the heater  4  sufficiently heats the lubricant, at the time of restarting the equipment. 
         [0023]    In this embodiment, a baffle plate  5  for controlling the convection of the lubricant is provided above the heater  4 . The baffle plate  5  is shaped and located to convect the lubricant toward the suction port  6 . This baffle plate  5  contributes to efficiently heat the lubricant in the region necessary for starting and to promptly restart the lubricant pump  2 . There is no need to heat the lubricant entirely in starting the lubricant pump  2 ; it is actually the lubricant near the suction port  6  that is necessary to be heated. Therefore, in this embodiment, the baffle plate  5  is provided to thereby promptly heat the lubricant near the suction port  6 ; this allows promptly starting the lubricant pump  2 . The function of the baffle plate  5  will be described below in detail. 
         [0024]      FIGS. 2A and 2B  are diagrams for showing the function of the baffle plate  5 .  FIG. 2A  shows the behavior of the heated lubricant for the case when the baffle plate  5  is provided.  FIG. 2B  is a diagram showing the behavior of the heated lubricant for the case when the baffle plate  5  is not provided. In  FIGS. 2A and 2B , a deep hatched portion indicates a portion in which the lubricant is heated to reduce the viscosity thereof. A light hatched portion indicates a portion in which the lubricant has a low temperature and low viscosity. 
         [0025]    As shown in  FIG. 2B , the heated lubricant convects only upward of the heater  4  for the case when the baffle plate  5  is not provided. This results in that the lubricant lateral of the heater  4  is heated only slowly, while the lubricant upward of the heater  4  is promptly heated. In an arrangement in which the suction port  6  is provided laterally of the heater  4 , it takes long time to heat the lubricant near the suction port  6 , resulting in that it takes long time to be ready to start the lubricant pump  2 . 
         [0026]    In this embodiment, as shown in  FIG. 2B , the baffle plate  5  directs the convection of the heated lubricant oil toward the suction port  6 , and this allows promptly heating the lubricant near the suction port  6 . More specifically, the lubricant near the suction port  6  is heated faster than the lubricant near a portion above the heater  4  on the liquid surface of the lubricant. Since the lubricant near the suction port  6  is promptly heated, it is possible to promptly start the lubricant pump  2 . 
         [0027]    The shape and position of the baffle plate  5  may be variously changed. For example, although the baffle plate  5  is shaped and located to completely cover up the upper portion of the heater  4  in  FIG. 2A , the baffle plate  5  does not necessarily cover the heater  4  completely. It should be noted, however, that it is preferable that the baffle plate  5  covers the heater  4  so as to accelerate the heating of the lubricant near the suction port  6 . 
         [0028]    As shown in  FIG. 2A , the baffle plate  5  is preferably disposed slightly away from the sidewall on which the suction port  6  of the equipment tank  1  is provided. This aims to suppress the degree of preventing circulation of the lubricant after starting the lubricant pump  2 . If the baffle plate  5  is attached directly to the sidewall of the equipment tank  1 , the lubricant returning from upward of the equipment tank  1  is prevented from returning to the suction port  6 . As shown in  FIG. 2A , the degree of preventing circulation of the lubricant is suppressed by providing the baffle plate  5  slightly away from the sidewall of the equipment tank  1 . 
         [0029]    The structure of the lubricant heating mechanism stated above is suited to be applied to various mechanisms in a wind turbine generator used in a cold region, particularly suited to be applied to a gear box. The structure of the gear box to which the lubricant heating mechanism according to the present invention is applied will be described below. 
         [0030]      FIG. 3  is a side view showing the configuration of a wind turbine generator  11  in one embodiment of the present invention. The wind turbine generator  11  includes a tower  12  built on a base  12   a , a nacelle  13  disposed on the top of the tower  12 , a rotor head  14  rotatably attached to the nacelle  13 , and wind turbine blades  15  attached to the rotor head  14 . The rotor head  14  and the wind turbine blades  15  constitute a wind turbine rotor. 
         [0031]    As shown in  FIG. 4 , one end of a main shaft  16  is connected to the rotor head  14  and the main shaft  16  is rotatably supported by a main shaft bearing  16   a . The other end of the main shaft  16  is connected to the input shaft of a gear box  17 . The output shaft of the gear box  17  is connected to a rotor of a generator  18 . When the rotor head  14  is rotated by wind power, the gear box  17  accelerates the rotation of the rotor head  14  and the accelerated rotation is transmitted to the rotor of the generator  18  to drive the generator  18 . As a result, electric power is obtained from the generator  18 . 
         [0032]      FIG. 5  is a cross-sectional view showing the structure of the gear box  17  in this embodiment. The gear box  17  includes a planet gear mechanism  17   a , a gear speed-up mechanism  17   b , and a housing  19  accommodating therein the planet gear mechanism  17   a  and the gear speed-up mechanism  17   b . The planet gear mechanism  17   a  includes an input shaft  21 , a sun gear  22 , a plurality of planet gears  23  (one shown in  FIG. 5 ), an internal gear  24 , a plurality of planet pins  25  (one shown in  FIG. 5 ), and a sun gear shaft  26 . The input shaft  21  has an insertion hole  21   a  into which the main shaft  16  is inserted. The main shaft  16  is coupled to the input shaft  21  by fastening a shrink fit  21   b  with main shaft  16  inserted into the insertion hole  21   a . The shrink fit  21   b  is an annular mechanical element configured so that the inside diameter can be reduced by an external driving force. The shrink fit  21   b  is configured to be fastened by, for example, a bolt provided on the shrink fit  21   b  or hydraulic pressure. The input shaft  21 A is rotatably supported by a bearing  27  provided on the housing  19 . The input shaft  21  also functions as a carrier which supports the planet gears  23  in the planet gear mechanism  17   a . The planet gears  23  are located between the sun gear  22  and the internal gear  24 , and connected to the input shaft  21  by the plant pins  25  inserted into the planet gears  23 , respectively. The sun gear shaft  26  is connected to the sun gear  22  and used as an output shaft of the planet gear mechanism  17   a . When the input shaft  21  is rotated, the rotation of the input shaft  26  is transmitted to the sun gear  22  via the planet gears  23 , and the sun gear shaft  26  connected to the sun gear  22  is acceleratedly rotated. 
         [0033]    The gear speed-up mechanism  17   b  includes a first rotational shaft  31  connected to the sun gear shaft  26 , a first spur gear  32  connected to the first rotational shaft  31 , a second spur gear  33 , a second rotational shaft  34  connected to the second spur gear  33 , a third spur gear  35  connected to the second rotational shaft  34 , a fourth spur gear  36 , and an output shaft  37  connected to the fourth spur gear  35 . The first rotational shaft  31 , the second rotational shaft  34 , and the output shaft  37  are rotatably supported by bearings  38 ,  39 , and  40  provided in the housing  19 , respectively. Further, the first spur gear  32  is engaged with the second spur gear  33 , and the third spur gear  35  is engaged with the fourth spur gear  36 . In the gear speed-up mechanism  17   b  thus structured, when the sun gear shaft  26  is rotated, the rotation of the sun gear shaft  26  is transmitted to the first spur gear  32 , the second spur gear  33 , the third spur gear  35 , and the fourth spur gear  36 , and the output shaft  37  connected to the fourth spur gear  36  are acceleratedly rotated. That is, as a whole of the gear box  17 , when the input shaft  21  is rotated, the rotation of the input shaft  21  is accelerated by the planet gear mechanism  17   a  and the gear speed-up mechanism  17   b  and the accelerated rotation is outputted from the output shaft  37 . 
         [0034]    An oil pan  41  is provided to cover the lower portion of the second spur gear  33 . This oil pan  41  functions to hold the lubricant of an appropriate amount below the second spur gear  33  and to thereby reduce the agitation loss of the lubricant in the rotation of the second spur gear  33 . 
         [0035]    A space is provided inside the housing  19  below the oil pan  41 , and this space functions as a tank portion  19   a  that accumulates therein the lubricant (also see  FIGS. 6 and 7 ). Heaters  42  heating the lubricant are provided in the tank portion  19 . Suction ports  43  are also provided on the tank portion  19   a  at positions lateral of the heater  42 , respectively. The lubricant accumulated in the tank portion  19   a  is drawn out from the suction ports  43  by the lubricant pump, passes through the lubricant pump and the accessory, and returns into the housing  19 . The configuration shown in  FIG. 1  is applied to the configuration of the lubricant circulation system circulating the lubricant. 
         [0036]    In the structure of the gear box  17  shown in  FIGS. 5 to 7 , the oil pan  41  also functions as a baffle plate for the convection of the heated lubricant. That is, the presence of the oil pan  41  directs the convection of the heated lubricant toward the suction ports  43 , so that the lubricant near the suction ports  43  is promptly heated. This allows promptly starting the lubricant pump connected to the suction ports  43 . 
         [0037]    Although the configuration is shown in which the oil pan  41  provided below the second spur gear  33  of the gear box  17  also functions as the baffle plate controlling the convection of the lubricant, the configuration of using the oil pan provided below the gear as the baffle plate is applicable to other gear mechanisms. Alternatively, the baffle plate controlling the convection of the lubricant may be provided separately from the oil pan  41 .