Abstract:
The present invention is a device for controlling torque output of wind turbine blades, which can effectively keep the torque output of the blades of a wind turbine in constant and maintain the output stability of the wind turbine further. The present invention does not need any external power input and measurement signal generated from other devices and is a fully passive device which keeps the output of a wind turbine in constant. When the wind speed varies in the rated range, the present invention would adjust the pitch angle of the blades correspondingly and keep the output of a wind turbine in constant. When the wind speed is not in the rated range, the present invention would stop the rotation of the blades, so the output stability of the wind turbine can be kept, and the durability of the wind turbine can also be maintained.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a device for controlling the torque output of the blades of a wind turbine, and particularly to such device, which could effectively control and maintain the torque output of the blades of a wind turbine to the generator without requiring any external power input and measurement signal generated from other devices. 
     DESCRIPTION OF THE RELATED ART 
     A wind turbine is mainly composed of blades, a transmission system, a generator, and a control system. To maintain a constant output of the generator, the blades or the transmission system has to be adjusted by the control system to maintain a constant torque input to the generator. When the torque inputted to the generator is not in the rated range, no matter it is too high or too low, the output of the generator will fail to meet what are required in the specification and would cause exceptions. Besides, an exceeding torque input would also shorten the service life of the associate components of a wind turbine. 
     Currently, the wind turbine mostly maintains the constant torque inputted to the generator by measuring the rotation speed or the torque exerted on the generator from the transmission system. Afterward the control system processes the measurement signals and then drives an oil hydraulic equipment to change the pitch angles of the blades of the wind turbine to adjust the power coefficient of the blades. 
     In addition, an anemometer is employed to measure the wind speed. When the wind speed is lower than or beyond the rated range, the control system manipulates the oil hydraulic equipment or other manners to drive the braking system to stop the rotation of the blades of the wind turbine. 
     Currently, most of the wind turbines in the market utilize an anemometer, a torsiometer, and a tachometer to measure the wind speed, the torque exerts on the generator, and the rotation speed of the spindle of the generator respectively. The control system would take these measurement signals as the control inputs to control the pitch angle of the blades and verify whether the braking system must be activated to stop the rotation of the blades. Thus, the pitch angle of the blades and the braking system could be controlled well, and the torque output of the blades can be maintained. 
     However, the measuring equipment and the drivers of the braking system and the pitch angle adjustment system, such as oil hydraulic equipment, all would consume energy. Besides, the utilization of the measuring equipment and the drivers not only increases the composition complexity of the wind turbine but also increases the set-up and operation cost. Besides, the reliability of this kind of wind turbine is also reduced because of the composition complexity. Therefore, the prior art may not meet with the requirement for the user&#39;s actual need. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a fully passive device for keeping the output of a wind turbine in constant. The present invention maintains the output stability of the wind turbine by controlling the torque which the blades generate without requiring any external power input or and any measurement signal generated from other equipment. Hence, the energy consumption, the composition complexity, the set-up and the operation cost of the wind turbine would be effectively reduced, while the reliability can be preserved or improved. 
     To achieve the above objects, the present invention comprises a coaxial planetary gearbox, a front high speed transmission axis, a torque control device, a rear high speed transmission axis, a braking system, and a pitch angle adjustment axis. A coaxial planetary gearbox is installed on a framework to convert a low rotation speed and high torque input generated by the blades into a high rotation speed and low torque output. A front high speed transmission axis connects to the planetary gearbox to transmit the high rotation speed and low torque output to a torque control device. A torque control device connects to the front high speed transmission axis to transmit the torque from the front high speed transmission axis to a rear high speed transmission axis. The torque control device comprises a transmission sliding bush, a thrust flange fixed on the transmission sliding bush, a torque maintaining spring connects the thrust flange and a thrust block fixed on the framework. The transmission sliding bush comprises a front ring, a front key, a connector, a rear key and a rear ring. A rear high speed transmission axis connects to the torque control device to transmit the torque from the torque control device to a generator. A braking system is installed on the framework and is between the coaxial planetary gearbox and the generator to stop the rotation of the blades when the wind speed is not in the rated range. A pitch angle adjustment axis connects a pitch angle adjustment device which adjusts the pitch angle of the blades and the torque control device to transmit the pitch angle adjustment output from the torque control device to the pitch angle adjustment device so the torque output of the blades can be kept in constant. 
     In a preferred embodiment of the present invention, the front transmission axis has a front guide which connects to the front key and is disposed at the farther end away from the coaxial planetary gearbox. 
     In a preferred embodiment of the present invention, the shape of the front guide depends on the magnitude of the torque being transmitted and the properties of the torque maintaining spring. 
     In a preferred embodiment of the present invention, the configuration of the torque control device can be a cylinder type, a linkage type, or a combination of the previous two. 
     In a preferred embodiment of the present invention, the rear high speed transmission axis has a rear guide which connects to the rear key and is disposed at the farther end away from the generator. 
     In a preferred embodiment of the present invention, the shape of the rear guide depends on the magnitude of the torque being transmitted and the properties of the torque maintaining spring. 
     In a preferred embodiment of the present invention, the braking system comprises a front braking driving ring installed on the front high speed transmission axis, a rear braking driving ring installed on the rear high speed transmission axis, a disk braking calipers fixed on the framework, and a braking disk fixed on the rear high speed transmission axis and partially contained in the disk braking calipers. 
     In a preferred embodiment of the present invention, the configuration of the pitch angle adjustment axis can be a solid axis, a hollow axis, a bush, or a combination of the previous three. 
     In a preferred embodiment of the present invention, the pitch angle adjustment axis connects the pitch angle adjustment device and the torque control device. 
     In a preferred embodiment of the present invention, a low speed transmission axis is disposed between the blades and the coaxial planetary gearbox to transmit the torque from the blades to the coaxial planetary gearbox. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic isometric view of a wind turbine according to the present invention; 
         FIG. 2  is a schematic side view of the wind turbine according to the present invention; 
         FIG. 3  is a schematic side view of the present invention; 
         FIG. 4  is a schematic partial side view of the present invention; and 
         FIG. 5  is a schematic cross sectional view of the transmission sliding bush according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1  to  FIG. 5 , where  FIG. 1  is a schematic isometric view of the wind turbine according to the present invention,  FIG. 2  is a schematic side view of the wind turbine according to the present invention,  FIG. 3  is a schematic side view of the present invention,  FIG. 4  is a schematic partial side view of the present invention, and  FIG. 5  is a schematic cross sectional view of a transmission sliding bush according to the present invention. 
     As shown, the present invention is a fully passive device for fixing the torque output of the blades of a wind turbine  1 . The wind turbine  1  comprises a blade assembly  2 , the present invention  3 , a generator  4 , and a framework  5 . The blade assembly  2  comprises a pitch angle adjustment device  21  and blades  22 . As such, the present invention  3  can effectively maintain a constant torque generated by the blades  22  to the generator  3  without requiring any external power input and measurement signal generated from other devices. Therefore, the energy consumption, the composition complexity, and the set-up and operation cost could be effectively reduced, and the reliability of the wind turbine could be increased. 
     The present invention  3  comprises a coaxial planetary gearbox  31 , a front high speed transmission axis  32 , a torque control device  33 , a rear high speed transmission axis  34 , a braking system  35 , a low speed transmission axis  36 , and a pitch angle adjustment axis  37 . 
     The coaxial planetary gearbox  31  is fixed on the framework  5  to convert a low rotation speed and high torque input from the blade assembly  2  into a high rotation speed and low torque output to the front high speed transmission axis  32 . 
     The front high speed transmission axis  32  connects the coaxial planetary gearbox  31  and the torque control device  33 , and it transmits the torque from the coaxial planetary gearbox  31  to the torque control device  33 . The front high speed transmission axis  32  has a front guide  321  disposed at the farther end away from the coaxial planetary gearbox  31 . The shape of the front guide  321  depends on the magnitude of the torque being transmitted and the properties of the torque maintaining spring  333 . The front guide  321  is connected to the front key  3312  to transmit the torque of the front high speed transmission axis  32  to the torque control device  33 . In addition, when the front guide  321  connects to the front key  3312 , the transmitted torque will be in a form of a combination of a push force and a torque. 
     The torque control device  33  can be a cylinder type, a linkage type, or a combination of the previous two. The torque control device  33  transmits the torque from the front high speed transmission axis  32  to the rear high speed transmission axis  34  and drives the pitch angle adjustment axis  37  to vary the pitch angle of the blades  22 . The torque control device  33  comprises a transmission sliding bush  331 , a thrust flange  332  disposed on the transmission sliding bush  331 , a torque maintaining spring  333  connects the thrust flange  33  and a thrust block  334  fixed on the framework  5 . The transmission sliding bush  331  is the component which could transmit the torque from the front high speed transmission axis  32  to the rear high speed transmission axis  34 . The thrust flange  332  is the interface of the forces from the transmission sliding bush  331  and the torque maintaining spring  333  and would drive the transmission sliding bush  331  to move toward the direction of the blade assembly  2  or the generator  4 . The torque maintaining spring  333  is used to counterbalance the force derived from the torque transmission process among the front high speed transmission axis  32 , the rear high speed transmission axis  34  and the transmission sliding bush  331 . The thrust block  334  is connected to an end of the torque maintaining spring  333  and counterbalances the force from the torque maintaining spring  333 . The transmission sliding bush  331  comprises a front ring  3311 , a front key  3312 , a connector  3313 , a rear key  3314 , and a rear ring  3315 . The front ring  3311  is used to keep the transmission sliding bush  331  moving along the surface of the front high speed transmission axis  32  smoothly. The front key  3312  connects to the front guide  321  to transmit the torque from the high speed transmission axis  32  to the transmission sliding bush  331 , and the transmitted torque will be in a form of a combination of a push force and a torque. The connector  3313  is used to transmit the driving force of adjusting the pitch angle of the blades from the torque control device  33  to the pitch angle adjustment axis  37 . The rear key  3314  connects to a rear guide  341  so as to transmit the torque from the transmission sliding bush  331  to the rear high speed transmission axis  34 , and the transmitted torque will be in a form of a combination of a push force and a torque. The rear ring  3315  is used to keep the transmission sliding bush  331  moving along the surface of the rear high speed transmission axis  34  smoothly. 
     The rear high speed transmission axis  34  is connected to the torque control device  33  to transmit the torque from the torque control device  33  to the generator  4 . The rear high speed transmission axis  34  has a rear guide  341  disposed at the farther end away from the generator  4 . The shape of the rear guide  341  depends on the magnitude of the torque being transmitted and the properties of the torque maintaining spring  333 . The rear guide  341  is connected to the rear key  3314  and transmits the torque from the torque control device  33  to the generator  4 . Besides, the transmitted torque will be in a form of a combination of a push force and a torque. 
     The braking system  35  is disposed between the coaxial planetary gearbox  31  and the generator  4  to stop the rotation of the blades  22  when the wind speed is not in the rated range. The braking system  35  comprises a front braking driving ring  351  installed on the front high speed transmission axis  32 , a rear braking driving ring  352  installed on the rear high speed transmission axis  34 , a disk braking calipers  353  fixed on the framework  5 , and a braking disk  354  fixed on the rear high speed transmission axis  34  and partially contained in the disk braking calipers  353 . When the wind speed is too slow, the front braking driving ring  351  will be pushed by the transmission sliding bush  331  and drives the disk braking calipers  353  to clamp the braking disk  354  to stop the rotation of the blade assembly  2 . 
     When the wind speed exceeds the rated range, the rear braking driving ring  352  will be pushed by the transmission sliding bush  331  and drives the disk braking calipers  353  to clamp the braking disk  354  to stop the rotation of the blade assembly  2 . The low speed transmission axis  36  is disposed between the blade assembly  2  and the coaxial planetary gearbox  31  to transmit the torque from the blade assembly  2  to the coaxial planetary gearbox  31 . 
     The pitch angle adjustment axis  37  is connected to the blade assembly  2  and the torque control device  33  to transmit the pitch angle adjustment output from the torque control device  33  to the pitch angle adjustment device  21  of the blade assembly  2 , so as to change the pitch angle of the blades  22  and to maintain the torque output of the blades  22 . 
     The pitch angle adjustment axis  37  may be a solid axis, a hollow axis, a bush, or a combination of the previous three. The pitch angle adjustment axis  37  connects the blade assembly  2  and the torque control device  33  to transmit the pitch angle adjustment output of the torque control device  33  to the pitch angle adjustment device  21  so as to adjust the pitch angle of the blades  22  and to fix the torque output of the blades  22 . 
     Thus a novel device for controlling torque output of wind turbine blades is obtained. 
     When the present invention is implemented, the wind drives the blade assembly  2  to rotate and generates a torque output which will be transmitted to the coaxial planetary gearbox  31  through the low speed transmission axis  36 . The coaxial planetary gearbox  31  converts the low rotation speed and high torque input from the blade assembly  2  to a high rotation speed and low torque output to the front high speed transmission axis  32 . 
     The front guide  321  of the high speed transmission axis  32  is connected to the front key  3312  of the transmission sliding bush  331  of the torque control device to transmit the torque from the front high speed transmission axis  32  to the transmission sliding bush  331 . In this torque transmission process, a push force along the axial direction of the transmission sliding bush  331  will be derived. The rear high speed transmission axis  34  receives the torque from the transmission sliding bush  331  through the rear guide  341  and the rear key  3314  in the similar manner. The rear high speed transmission axis  34  transmits the torque it receives from the torque control device  33  to the generator  4 . 
     The derived force from the torque transmission process between the torque control device  33  and the front high speed transmission axis  32  or the rear high speed transmission axis  34  will be transmitted to the thrust flange  332 . When the derived force is smaller than the force which the torque maintaining spring  333  exerts on the thrust flange  332 , the transmission sliding bush  331  moves toward the direction of the blade assembly  2  and drives the pitch angle adjustment axis  37  to move in the same direction. This will drive the pitch angle adjustment device  21  to increase the power coefficient of the blades  22 , thereby the torque output of the blade assembly  2  will be increased. When the derived force is larger than the force which the torque maintaining spring  333  exerts on the thrust flange  332 , the transmission sliding bush  331  moves toward the direction of the generator  4  and drives the pitch angle adjustment axis  37  to move in the same direction. This will drive the pitch angle adjustment device  21  to decrease the power coefficient of the blades  22 , thereby the torque output of the blade assembly  2  will be reduced. 
     When the wind speed is too slow and is not in the rated range, the torque maintaining spring  333  pushes the transmission sliding bush  331  to contact the front braking driving ring  351  and makes the front braking driving ring  351  to move along the same direction and further drives the disk braking calipers  353  to clamp the braking disk  354 . Thus, the rotation of the blade assembly  2  can be stopped when the wind speed is too slow and is not in the rated range. 
     Similarly, when the wind speed exceeds the rated range, the transmission sliding bush  331  will contact the rear braking driving ring  352  and push the rear braking driving ring  352  to move in the same direction and further drive the disk braking calipers  353  to clamp the braking disk  354 . Thus, the rotation of the blade assembly  2  can be stopped when the wind speed exceeds the rated range. 
     Thus, the present invention utilizes the front high speed transmission axis, the rear high speed transmission axis, and the torque control device to control the torque output of the blades of a wind turbine in constant. When the wind speed is not in the rated range, the braking system will be activated through the interaction among the front braking driving ring, the rear braking driving ring, the front guide, the rear guide, the transmission sliding bush, and the torque maintaining spring to stop the rotation of the blades of a wind turbine. 
     To sum up, the present invention is a device for controlling torque output of wind turbine blades which effectively improves the demerits encountered in the prior arts, including higher energy consumption, set-up cost, and operation spending with lower reliability. From all these views, the present invention can be deemed as being more effective, practical, and useful for the consumer&#39;s demand, and thus meets with the patent requirements. 
     The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.