BOLT AS 1358578 - Caterpillar

Illustration 3 g03874324
Propel Pump Cross Section
(1) Right propel pump
(2) Left propel pump
(7) Charge relief valve
(8) Pump control solenoid for port "A"
(9) Pump control solenoid for port "B"
(12) Multifunction valve for port "B"
(16) Multifunction valve for port "A"
(21) Electric displacement control
(22) Displacement control spool
(23) Plunger
(24) Line to pump case
(25) Servo cylinder
(26) Servo piston
(27) Swashplate feedback linkage
(28) Line to pump case
(29) Line to case drain
(30) Rotating group
(31) Input shaft
(32) Swashplate
(33) Servo relief valves
(34) High-pressure side of loop
(35) Charge pump
(36) Return pressure line
(37) Combined suction and return filter Note: The above illustration shows the propel pump while the engine is operating, and the machine is traveling forward.Pump input shaft (31) turns rotating group (30) and charge pump (35) when the engine is running. The rotating group contains the piston assemblies and cylinder barrel. The charge pump receives supply oil from combined suction and return filter (37). Charge oil flows through internal passages to the following locations:
Charge relief valve (7)
Multifunction valve for port "B" (12)
Multifunction valve for port "A" (16)
EDC (21)Pump control solenoids (8) and (9) are proportional solenoids. The transmission ECM uses a pulse-width modulated signal to energize the EDC solenoids. Pump control solenoid for port "A" (8) is energized during forward travel. Pump control solenoid for port "B" (9) is energized during reverse travel. When the EDC solenoid is energized, plunger (23) moves. The distance that the EDC plunger moves is proportional to the signal from the transmission ECM. Metered charge oil from displacement control spool (22) acts against one side of servo piston (26). The opposite side of the servo piston is vented to case drain (29). The pressure of the metered charge oil against the servo piston causes the piston to move. This movement tilts swashplate (32) and causes piston displacement in rotating group (30). As the swashplate tilts, the rotation of the pump generates oil flow. Pump supply oil flows through the propel motor. The oil which flows through the motor causes the output shaft to rotate. As the load on the propel system increases, increased pressure in the system tends to move swashplate (32) toward the neutral position. This movement causes feedback linkage (27) to reposition displacement control spool (22) in order to send additional charge oil to servo piston (26). The increased pressure in the servo piston prevents the swashplate from moving back toward the neutral position. The feedback linkage prevents the servo from tilting the swashplate too far. Pump supply oil acts against the multifunction valve for port "A" (16). In the high-pressure side of loop (34), the multifunction valve acts as a pressure limiter and a pressure relief valve. When the pump supply oil pressure reaches the pressure-limiter setting, the pressure limiter opens. At this time, pump supply oil is metered to end of servo piston (26) that is open to the case drain. This action causes the pump to destroke in order to relieve the excessive load on the propel system. Note: The pressure-limiter function is used because no heat is generated, as