Abstract:
A clutch member for use in a generator clutch has actuation structure including a face with a ramp. The ramp has a ramp angle of between 6.2° and 6.4°. The clutch member may be a sliding decoupler shaft. In addition, a rotor and a generator including the clutch members are also disclosed and claimed.

Description:
BACKGROUND OF THE INVENTION 
     This application relates to a decoupler shaft and actuation yoke for use in selectively connecting an input shaft to a generator rotor shaft. 
     Generators as are typically utilized to generate electricity, include an input shaft that receives a source of rotation. As an example, gas turbine engines have a shaft, which drive the input shaft through a gear train. At times, it is undesirable for the generator to be driven to rotate. Thus, a clutch is provided to selectively connect the generator rotor shaft to the input shaft. The clutch typically includes a sliding toothed clutch member which is slid along an axis of rotation between engaged and disengaged positions. 
     In one known type of generator, the sliding clutch member includes a ramped face that interfaces with a ramp face on a yoke. The two faces are brought into contact with each other, and the yoke cams the sliding clutch member away from the input shaft such that teeth which are in engagement are moved out of engagement, and the sliding clutch member, and hence the generator rotor shaft is no longer driven. 
     In the existing clutch members, the angle of this ramp is undesirably large for applications that require decoupling capability at high-speeds. As an example, the lead or ramp angle has typically been 7°. The lead angle determines the rate at which the shaft can move axially. This relatively large lead angle results in high forces reacting at the engaging ramp and yoke faces when the decoupling event occurs at high shaft speeds. 
     SUMMARY OF THE INVENTION 
     A clutch member for use in a generator clutch has actuation structure including a face with a ramp. The ramp has a ramp angle of between 6.2° and 6.4°. The actuation yoke that engages the ramp has a complementary angled face. The clutch member may be a sliding decoupler shaft. 
     A rotor assembly for a generator includes a rotor shaft receiving a winding section. The rotor shaft receives a sliding clutch member in an internal bore. The clutch member and the rotor shaft each have splines for sliding movement of the clutch shaft within the rotor shaft. The clutch member has a first end provided with the splines, and a second end having actuation structure including teeth to mesh with teeth on an opposed jaw clutch. The spring that biases the jaw clutch into engagement is nested within the interior of the spline of sliding clutch member. The actuation structure further including a face with a ramp to receive an actuation yoke. The ramp has a ramp angle of between 6.2 and 6.4°. 
     A generator includes a stator surrounding a rotor shaft, said rotor shaft receiving a winding section. The rotor shaft further receives a sliding clutch member in an internal bore. The clutch member and the rotor shaft each have splines for sliding movement of the clutch member within the rotor shaft. The clutch shaft has a first end provided with the splines, and a second end having actuation structure including teeth to mesh with teeth on an opposed jaw clutch. The spring that biases the jaw clutch into engagement is nested within the interior of the spline of sliding clutch member. The actuation structure further includes a face with a ramp to receive an actuation yoke. The ramp has a ramp angle of between 6.2 and 6.4°. 
     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  is a drawing showing a generator. 
         FIG. 2  is a cross-sectional view of the generator. 
         FIG. 3  is a detailed view of a portion of a clutch incorporated into the generator. 
         FIG. 4  is a cross-sectional view through a sliding clutch member. 
         FIG. 5  is a detailed view of an actuation portion of the  FIG. 4  sliding clutch member. 
         FIG. 6  shows a helical ramp angle through a circumferential distance of the  FIG. 4  sliding clutch member. 
         FIG. 7  is an end view of the  FIG. 4  sliding clutch member. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a generator  20  including a stator  21 , shown schematically. A clutch member  22  has teeth that will selectively engage teeth on an input shaft  300 . The clutch member  22  may also be moved to engage or disengage from the input shaft  300 . 
     A main winding portion  24  rotates near the stator  21 . An exciter rotor  26  and a permanent magnet rotor  28  provide control and safety functions, and also are associated with their own stators (not shown). Bearings  30  and  32  are placed on opposed axial ends of the main winding section  24 . 
     Drive input  300  is shown in phantom in  FIG. 1  and a yoke  301  is shown schematically. The yoke  301  engages the cam surfaces on the clutch member  22  and is axially translated away from the input shaft  300  such that drive can be selectively decoupled. 
     Aspects of the teeth in the clutch members are found in co-pending patent application Ser. No. 12/436,168, filed on even date herewith, and entitled “High Speed Clutch Design with Jaw Tooth Profile to Reduce Separating Load.” 
     As shown in  FIG. 2 , generator  20  includes the bearings  30  and  32  mounted at each end of the main winding section  24 . Windings  37  and laminations  38  are received within this main winding section  24 . 
     An enlarged portion  54  of the clutch member  22  is a close fit within an inner diameter of a rotor shaft  42 . The opposite end of the sliding clutch member  22  is supported at its spline  36  by the interior spline  52  of the rotor shaft  42 . Rectifier assembly  48  is shown schematically, and is positioned within a bore in the rotor shaft  42 . 
     Splines  52  are formed at an axially intermediate portion of the inner bore of the shaft  42 , and mate with splines  36  on the clutch member  22 . A spring  50  biases the clutch member  22  outwardly, and against the input shaft  300 . Spring  50  is contained within the inner diameter of end  102  of clutch member  22 , nested within the interior of its spline  36  offering significant packaging advantages. Further details of the operation of the generator  20  may be better understood from co-pending patent application Ser. No. 12/436,161, filed on even date herewith, and entitled “Generator Rotor with Improved Hollow Shaft,” and owned by the Assignee of this application. 
       FIG. 3  shows the sliding clutch member  22  having a ramp  108  with an open area  310  into which the yoke  301  will initially move. Teeth  110  on the clutch member  22 , and teeth  104  on mating input shaft  300  interfit to drive rotation from the input shaft  300  through the sliding clutch member  22 . When it is desired that there not be rotation of the clutch member  22 , or operation of the generator  20 , then the yoke  301  is moved into the position illustrated in  FIG. 3 , and is driven along the ramped surface  108 , with its mating ramp surface  122 . It should be understood the ramp surfaces  108  and  122  are formed to have complementary ramp angles. 
     As shown in  FIG. 4 , the clutch member  22  incorporates a central shaft  104  extending between an enlarged end  102  with splines  36 , a forward portion  54  which is received within an inner peripheral surface of the rotor shaft  42  (see  FIG. 2 ), the ramp  108 , and the jaw clutch teeth  110 . As shown in  FIG. 5 , the ramp  108  includes an enlarged area  310  into which the yoke will move. The teeth  110  are also shown. 
     As further shown in  FIG. 4 , an inner diameter within the teeth is d2. An inner diameter of the central portion  104  is d1 and the outer diameter of the central portion  104  is d4. An outer diameter of the portion  54  is d3. An inner diameter of end  102  is d5. In one embodiment, d1 was 0.545″ (13.8 mm), d2 was 0.567″ (14.4 mm), d3 was 1.919″ (48.74 mm), d4 was 0.745″ (18.9 mm), and d5 was 1.290″ (32.8 mm). A ratio of d1 to d2 is between 0.92 and 1.00, a ratio of d2 to d3 is between 0.29 and 0.30, a ratio of d1 to d4 is between 0.70 and 0.76, and a ratio of d1 to d5 is between 0.40 and 0.44. 
     Further, as is clear from  FIG. 4 , an oil dam/labyrinth seal  400  is mounted within a radially outwardly extending ledge  401 , extending radially outwardly from central shaft  104 , and connecting into the end  102  that receives the spline  36 . As shown, an axially leftmost end  410  of oil dam/labyrinth seal  400  extends axially beyond the ledge  401 . Returning to  FIG. 2 , an oil tube  40  is shown extending into the oil dam/labyrinth seal  400 . This oil tube will supply oil to the interior of the clutch member  22 . 
       FIG. 6  shows the ramp angle is an angle θ in this application, and shows the circumferential rollout view of in this ramp across a number of degrees. It also shows the open area  310  into which the yoke will move during engagement. In one embodiment, the angle θ was 6.3°. In preferred embodiments of this invention, θ can be between 6.2 and 6.4°. The yoke has a mating ramp angle that will correspond with θ. 
       FIG. 7  is an end view of a portion of the sliding clutch member  22  and shows an enlarged portion  54  and a truncated surface  112 . The truncated surface is at a tangent relative to a centerline of clutch member  22 , and extends over approximately 67°. Stated another way, the truncated surface  112  is formed at a secant relative to the enlarged portion. A radius to the truncated surface was 0.800″ (20.3 mm) in one embodiment providing an effective 1.600″ (40.6 mm) diameter, compared to an overall diameter of 1.919″ (48.74 mm) for the enlarged portion  54 . Preferably the ratio of the diameter to the truncated portion to the overall diameter of the enlarged portion is between 0.80 and 0.85. The relative location of the truncated surface  112  to the ramp  108  serves as a lightweight angular zone to account for the geometry of ramp  108  of sliding clutch member  22  for rotating balance purposes. The cut-out for the truncated surface  112  also serves as an oil flow orifice which prevents hydraulic lock (trapped volume) between the sliding clutch member  22  and the rotor shaft  42  during the decoupling event. 
     With the inventive face between the yoke and the sliding decoupler shaft, lower forces are required to accelerate the shaft. Thus, higher rotational speed capability is provided to the overall clutch, and hence the generator. 
     Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.