TANK & MTG GP-HYDRAULIC 1637934 - Caterpillar

Illustration 1 g02751689
(1) Charge pump (2) Hydraulic steering pumpTransmission two-section charge pump (1) is attached to the hydraulic steering pump (2).
Illustration 2 g02756789
Transmission charge pump (1) is a variable displacement piston type pump (3) combined with a fixed displacement gerotor type pump (4). The front section is the piston pump (3) which supplies oil to the transmission control valves and charge flow to the variator. The rear section is the gerotor pump (4) which supplies pressurized oil to the charge pump and lubrication oil to the transmission. Gerotor relief valve (9) prevents the fixed displacement gerotor from exceeding pressure limits of the system during startup with cold oil.
Illustration 3 g02752122
(5) Pressure cutoff compensator (6) Piston pump inlet (7) Gerotor discharge
Illustration 4 g02752123
(8) Piston pump discharge (9) Gerotor relief valve (10) Gerotor suction
Illustration 5 g02752157
Illustration 5 shows a section view of variable displacement piston pump and control valve. Internal oil passages connect the control valve as shown. When discharge pressure (11) reaches 25.5 bar (370 psi), the control spool moves to compress the spring and direct oil to the control piston passage (12) to destroke the pump. When discharge pressure is lower than 25.5 bar (370 psi), the spring forces the spool to the position shown. With the spool in the position shown oil will be directed from control passage (12) to case (13) allowing the pump to upstroke. The bias spring (14) forces the pump to maximum displacement when the machine is shut down.