ENGINE AR-COMPLETE 2240497 - Caterpillar

Illustration 1 g01377351
Hydraulic Schematic (Neutral) (1) Interlock solenoid (optional) (2) Neutral brake solenoid (3) Propulsion pump assembly (4) From oil cooler (5) Charge filter (6) Control group (7) Charge relief valve (8) Blocked filter bypass valve (9) Charge pump (10) Propulsion pump (11) Forward relief valve (12) Servo piston (13) Reverse relief valve (14) Rear propulsion motor (15) Forward makeup valve (16) Front propulsion motor (17) Bypass valve (18) Reverse makeup valveReturn oil from the auxiliary hydraulic system flows through the charge filter. This oil supplies the suction side of the charge pump. The charge pump produces flow when the engine is operating. Charge oil is directed to the cartridges of the main relief valves, to the charge relief valve, and to an orifice that is upstream from the neutral brake solenoid. When the parking brake switch is in the ON position, the neutral brake solenoid is de-energized. When de-energized, the neutral brake solenoid prevents charge oil from reaching the control group and from reaching the parking brake piston cavities. Under these conditions, both sides of the servo piston in the pump are open to the hydraulic tank, and all the brake piston cavities are open to the tank. The centering springs in the servo piston cause the piston to hold the swashplate at zero angle. The springs that are acting against the brake pistons engage the disks of the parking brakes.As long as the parking brake switch remains in the ON position, the neutral brake solenoid prevents the pump servo from moving the swashplate out of the zero angle position. This is true regardless of the position of the propulsion lever.Charge pressure acts on the charge relief valve. When charge pressure reaches 2400 150 kPa (348 22 psi), the oil pressure overcomes the spring force and the charge relief valve opens. This action directs charge pump flow into the case drain.Charge pressure acts against the makeup valves in the relief valve cartridges. If the pressure in either the forward loop or the reverse loop falls below charge pressure, the makeup valves open and charge oil flows into the loop. Machines can be equipped with an interlock solenoid. On these machines, the interlock solenoid is de-energized when the operator is not in the seat. When this solenoid is de-energized, a passage is opened between the two sides of the servo piston.
Illustration 2 g01377352
Hydraulic Schematic (Forward) (1) Interlock solenoid (optional) (2) Neutral brake solenoid (3) Propulsion pump assembly (4) From oil cooler (5) Charge filter (6) Control group (7) Charge relief valve (8) Blocked filter bypass valve (9) Charge pump (10) Propulsion pump (11) Forward relief valve (12) Servo piston (13) Reverse relief valve (14) Rear propulsion motor (15) Forward makeup valve (16) Front propulsion motor (17) Bypass valve (18) Reverse makeup valveWith the parking brake switch in the OFF position, the neutral brake solenoid directs charge oil into the control group and into the piston cavities of the parking brakes. The charge pressure in the parking brake piston