BRACKET AS 4479566 - Caterpillar

Illustration 5 g03014399
(29) Feedback link (30) Servo piston (31) Piston (32) Rotating group (33) Input shaft (34) Slipper pad (38) SwashplateEngine rotation turns pump input shaft (33), which then rotates rotating group (32). The rotating group (32) contains a piston (31) and barrel assembly. The pistons in the group rotate with the barrel assembly. The piston slipper pads (34) allow the pistons to follow the angle of swashplate (38). The rotating group only generates flow when the swashplate (38) is not at zero angle.When XA2 (FF) module in the cab sends an output signal to one of the solenoids, the solenoid moves a spool. Spool movement directs oil into the chamber at one end of servo piston (30) (the high side) and opens the chamber at the other end of servo piston (30) (the low side) to the case drain. Under these conditions, servo piston (30) moves.As servo piston (30) moves, the action of the control linkage causes the angle of swashplate (38) to change. As swashplate (38) moves, feedback link (29) tends to move the spool of the active solenoid back to neutral through an internal feedback spring. This action prevents servo piston (30) from tilting swashplate (38) too far by blocking the charge oil supply, once the tilt angle is equal to the input signal from XA2 module (FF) in the cab.The slipper pads (34) in each rotating group (32) follow the angle of swashplate (38). This action causes the pistons to move in and out of the barrel assembly as input shaft (33) rotates. As a piston moves out of the barrel assembly, oil in the low-pressure circuit is drawn into the piston chamber. As a piston moves into the barrel assembly, oil is forced out of the piston chamber and into the high-pressure circuit.
Illustration 6 g03015696
Propulsion pump pressure limiter valve (closed) (39) Spring (40) Poppet
Illustration 7 g03015817
Propulsion pump pressure limiter valve (open)High-pressure oil acts against one side of poppet (40) in the pressure limiter valve. A spring acts against the other side of the poppet. When the pressure in the high-pressure circuit reaches 37345 345 kPa (5420 50 psi), the force from the pressure moves the poppet against the force of spring (39). As the poppet moves, a passage opens. This opening purges high-pressure oil into the low side of the servo piston.The low side of servo piston (30) is open to the pump case drain across the spool in the EDC. However, the passage across the spool in the EDC cannot purge all the oil entering the servo piston through the pressure limiter. Therefore, the pressure in the low side of the servo piston increases. Eventually the pressure in the low side of the servo piston becomes greater than the pressure in the high side of the servo piston. In this case, the servo piston moves swashplate (38) to a lesser angle, and the flow from the pump decreases.Decreased pump flow results in reduced pressure in the high-pressure circuit. When the pressure is less