2 C3873 Fluid enters the housing through the inlet port and is directed to the balance plate. The balance ring contains an inner and outer seal to separate the high and low pressure fluid passages. Fluid passes through the stationary bal- ance plate to the rotating disc valve. The rotating disc valve ports the fluid to the stationary valve plate and the proper side of the geroter pockets causing the rotor star to turn.
As the rotor star rotates, and each fluid pocket reaches its full open position, the return porting in the rotating disc valve opens to allow the fluid in the pocket area to pass back through the valve plate, disc valve, balance plate and out through the housing return port, as the pocket closes. The disc valve is timed to the gerotor rotor star to govern the the inlet fluid flow to the output shaft rotation. If the timing of the disc valve to the geroter star is off one tooth, the relationship of input fluid flow to output motor shaft rotation will be reversed.
2-27 DRIVE MOTOR 2.11 For smooth and continuous motor output rotation, the torque motor utilizes a disc valve which operates in syn- chronization with the geroler star. The disc valve arrange- ment consist of a stationary balance plate, rotating disc valve and a stationary valve plate. The disc valve contains an inlet fluid passage port for each star valley and a return fluid passage point. A separate crowned driveshaft is used to synchronize the disc valve and the geroler star so that they turn as one. To accept fluid from the disc valve, the valve plate also con- tains internal porting passages to each outer ring pocket area. C3488