B. The input shaft acts as a screw in a threaded hole, and input rotation causes the input shaft to move away from the input spline shaft, separating the driving dogs on the two shafts. When the driving dogs have been separated, the input spline shaft, which is still being driven by the aircraft engine, spins freely in the transmission without causing transmission rotation. Reset may be accomplished, only on the ground following engine shutdown, by pulling out on the reset handle until the solenoid nose pin snaps into position.
9. Generator Drive Cooling
A. Heat generated within the drive causes the drive oil temperature to rise. The scavenge pump forces the heated oil through the scavenge or line oil filter then through the external oil cooler and into the al1-attitude reservoir. Fan air from the engine passes over the inside portion of the cooler unit thereby cooling the oil. The cooler is located on the left side of the engine aft of the drive. (See figure 1.) The engine fan supplies the cooling air at all times in flight and on the ground. A line oil filter, which filters scavenge oil, is located in the oil out line between the drive unit and the CSD oil cooler. The filter functions as a protective device to prevent contamination of the oil cooler in the event of drive failure.
10. Operation
A. The drive unit of the constant speed drive system accepts torque from the engine at various speeds and delivers torque to the generator at a constant speed through the output shaft. The output shaft drives the governor, the scavenge pump and the charge pump. (See figure 2.) The charge pump maintains oil pressure at the stationary port plate for the fixed and variable displacement hydraulic units, and for speed control purposes by the governor and control cylinder. The piston of the control cylinder positions the movable portion of "wobbler," of the variable displacement hydraulic unit, in response to the oil pressure differences caused by the valve action of the governor. The governor ports oil to or from the control cylinder in response to small output speed changes. The hydraulic unit transmits only a portion of the input torque to the output shaft. The major portion of the torque is transmitted by the planetary differential gear train.
B. The planetary differential output speed is regulated by the combined action of the variable and fixed hydraulic units. The route the torque takes through the combined differential and hydraulic units is as follows:
(1) The input gear drives the carrier shafts through the center of the differential to the variable end of the hydraulic unit. (See figure 3.)
500
24-11-0 Page 12 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 15/70
H20796 H20854
500 Generator Drive Disconnect Mechanism
May 15/70 Figure 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 24-11-0 Page 13
Generator Constant Speed Drive Electrical Circuit 501
24-11-0 Figure 5 Nov 1/74
Page 14
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(2)
The variable hydraulic unit causes the required direction of rotation and speed of the fixed hydraulic unit.
(3)
The fixed unit drives the input ring gear in either direction and at various speeds, delivering torque through the planet gears to the output ring gear.
(4)
The output ring gear drives the output gear at the required 6000 rpm.
(5)
The overdrive and underdrive schematics of figure 3 indicate the constraining or assisting action furnished by the hydraulic unit to the differential. It will be noticed that in overdrive the variable unit is pumping and in underdrive the variable unit is motoring.
C. Heat generated by the drive unit is absorbed by the oil which collects in the sump. The scavenge pump forces this hot oil through the line filter, the external oil cooler, and into the swirl chamber of the al1-altitude reservoir. (See figure 2.) The temperature is sensed at two points by identical sensors connected to dual scale indicators on the overhead panel (P5-5). Oil temperature and temperature rise may be read on the indicators by means of the pushbutton switch also on the P5 panel.
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