Patent Publication Number: US-8534990-B2

Title: Inlet guide vane drive system with spring preload on mechanical linkage

Description:
BACKGROUND OF THE INVENTION 
     This application relates to a mechanical linkage for driving a compressor inlet guide vane system for gas turbine engines, wherein a spring preload is included into the mechanical linkage. 
     Gas turbine engines include a compressor which compresses air and delivers it into a combustion section where it is mixed with fuel and burned. Products of this combustion pass downstream over a turbine section, driving turbine rotors to provide power to the gas turbine engine. 
     Inlet guide vanes typically control the flow of air to the compressor section. Variable vane systems are known. In such systems, an angle of incidence provided by the vanes, for guiding the air to the compressor, is varied depending upon the amount of air that is to be delivered to the compressor. 
     In one such system, a ring gear is driven to rotate through a mechanical linkage including a plurality of rods, and a hydraulic motor for driving the rods. The ring gear drives a plurality of sector gears to cause a plurality of vanes to rotate as the ring gear is driven to rotate between a full open and full closed position. 
     One challenge with these systems is that variables in the flow of air to the guide vanes, and the compressor, can cause vibration on the variable vanes, ring and sector gears, and across the mechanical linkage. 
     SUMMARY OF THE INVENTION 
     A variable vane system includes a plurality of vanes each being pivotal about an axis. A mechanical linkage drives the plurality of vanes to rotate about the axis. The mechanical linkage includes a ring gear meshing with a plurality of sector gears, which in turn drives the plurality of vanes. There is at least one rod to drive the ring gear to rotate. The rod is driven by a hydraulic motor. A spring bias force is provided in the mechanical linkage to resist oscillation. 
     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a turbine engine. 
         FIG. 2  shows a variable vane. 
         FIG. 3  shows a view of a drive system for a variable vane system. 
         FIG. 4  shows a portion of the  FIG. 3  embodiment. 
         FIG. 5  shows another portion of the variable vane system. 
         FIG. 6  shows a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A turbine engine  120  is illustrated in  FIG. 1 . A power section  122  includes a combustion section and a turbine section, as known. A compressor section delivers compressed air to the combustion section. As shown, the compressor section includes an inlet plenum  124  delivering air from a source of air past a plurality of inlet guide vanes  132  toward a low pressure impeller  126 . The low pressure impeller  126  delivers air to an outlet scroll  128 . A high pressure compressor  130  delivers air to the combustion section. An actuator  134  actuates the inlet guide vanes  132  to pivot. The positioning of the inlet guide vanes, and the reason for changing their positions is known, and relates to delivering a supply of air to the low pressure compressor impeller  126  in desired quantities. 
     As shown schematically in  FIG. 2 , the inlet guide vanes  132  include pivot pins  35  and  301  which allow the orientation of the inlet guide vanes  132  to pivot, to change the angle of incidence of air approaching the low pressure impeller  126 . In this manner, the amount of air delivered to the scroll  128 , can be controlled. As shown, the plenum  124  also delivers air to the impeller  130 . The scroll housing  128  may deliver the compressed air to downstream uses, such as the passenger cabin on an aircraft. 
     An actuation system  134  for driving the variable vanes is illustrated in  FIG. 3 . The general structure may be as known. As shown, a device  31  drives a ring gear  32  to rotate. The ring gear interacts through a sector gear  34 , to in turn rotate a plurality of vanes. The vane&#39;s pivot pins  35  are shown in this Figure. Actuation of the device  31  to turn the ring gear  32  is from a hydraulic servo motor  44 , driving a rod  42  which is pivotally connected at  41  into a hinge knuckle  38 . The hinge  38  in turn drives a second rod  36  to move the device  31 , and hence the ring gear. All of these components together can be seen as a mechanical linkage for pivoting the vane. 
       FIG. 4  shows a detail of a housing incorporating the hydraulic motor  44 . As shown, the rod  40  is connected to a piston head  60  movable within a fluid chamber  62 . Fluid supplies  56  and  58  drive the piston  60 , and hence the rod  40  to actuate the device  31 , and the ring gear  32 . In known systems, fuel is utilized as a hydraulic fluid to move the piston  60 . In this embodiment, a progressive helical spring  52  is connected between an end  50  of the rod  40  and an end wall  54  of the housing. The progressive helical spring has an increasing spring force which increases as the rod  40  moves to compress the spring. Thus, the spring resists translational oscillation or vibration on the rod if such is transmitted to the rod through the ring gear and from the vanes. Thus, the spring will hold the entire mechanical linkage more static and resist the tendency to oscillate due to such variable applied forces. 
       FIG. 5  shows a second embodiment  234 . Second embodiment  234  includes the rod  40  pinned at  41 , and the rod  36  driving the device  31  as in the prior embodiment. However, the spring is not included in the hydraulic motor  60  in this embodiment. Instead, a spring  66  is included into the hinge knuckle  400  as shown in  FIG. 6 . As shown, the rod  36  is driven by a pivot housing  160  carrying an arm  74  that in turn drives the rod  36 . A pin  65  mounts the pivot housing  160  for pivotal movement relative to a fixed housing  300  (see  FIG. 3 ) as driven by the rod  40 . 
     As can be appreciated from these Figures, as the rod  40  is driven to move inwardly and outwardly of the housing of the hydraulic motor  60 , it causes pivot housing  160  to pivot on the pin  65 . This causes the rod  36  to also move toward and away from the device  31 , and in turn cause the device, and hence the ring gear, to rotate. 
     Spring  66  is shown schematically in  FIG. 5 , and in more detail in  FIG. 6 . As can be appreciated, one end  72  of the spring sits against the fixed housing  300 . The other end  70  of the spring  66  sits against the pivot housing  160 . Thus, the spring  66 , which again may be a progressive spring, resists torsional oscillation delivered into the mechanical linkage, and from the rod  36  back toward the hydraulic motor  60 . Attachment points for each of the first and second rods to the pivot housing are provided, both being on the same side of the pivot pin  65 . 
     With either of the disclosed embodiments, the spring will resist any oscillation in the mechanical linkage that might be imposed by variable flow characteristics such as vortices, etc. 
     Although embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention, such as using torsional spring at sector gear locations. For that reason, the following claims should be studied to determine the true scope and content of this invention.