TERMINAL-BLADE 9R9806 - Caterpillar

Illustration 3 g06051197
Propel Hydraulic System Reverse Travel
(1) Left motor
(2) Servo piston
(3) Shift spool
(4) Manual brake release
(5) Brake pressure switch
(6) Load sensing signal
(7) Hydraulic services pump
(8) Steering manifold
(9) Motor shift valve
(10) Pressure-reducing valve
(11) Clutch valve (FWA option)
(12) Shift spool
(13) Servo piston
(14) Right motor
(15) Left parking brake
(16) To FWA manifold (FWA option)
(17) Parking brake valve
(18) Direction control valve
(19) Left propel pump
(20) Servo piston
(21) Combination valve
(22) Combination valve
(23) Charge relief valve
(24) From FWA manifold (FWA option)
(25) POR valve
(26) Charge pump
(27) Flush spool
(28) Flush relief valve
(29) Balance orifice
(30) Servo piston
(31) Combination valve
(32) Charge relief valve
(33) From hydraulic filter
(34) From FWA manifold (FWA option)
(35) Flush spool
(36) Flush relief valve
(37) Charge pump
(38) Right propel pump
(39) POR valve
(40) Combination valve
(41) Direction control valve
(42) Balance orifice
(43) To FWA manifold (FWA option)
(44) Right parking brakeWhen the machine is traveling in reverse, the reverse pump control solenoids in direction control valves (18) and (41) are energized. The electronic control system analyzes input signals to determine the magnitude of the output signal which is sent to the reverse pump control solenoids.Charge oil flows across direction control valves (18) and (41) and acts against servo pistons (20) and (30). This pressure causes the servo pistons to shift. When the servo pistons shift, this action changes the angle of the swashplates in the corresponding pump. Under these conditions, propel pumps (19) and (38) generate flow in the corresponding reverse hydraulic circuits.Reverse circuit oil flows to reverse combination valves (22) and (31). Inside the combination valve, the oil closes the makeup valves and acts against the relief valves. If the pressure in the reverse circuit reaches 43 000 1500 kPa (6240 200 psi), the relief valve opens. Under these conditions, the valve directs oil from the reverse circuit into the charge circuit.Reverse circuit oil acts against flushing spools (27) and (35) and causes the valve spools to shift. This shift allows oil from the forward circuit to act against flushing relief valves (28) and (36). The flushing relief valve opens and directs a controlled amount of oil to the motor case drain line. As the flushing valves remove oil from the forward circuits, the pressure in the forward circuits decreases. When the forward circuit pressure decreases below charge pressure, the makeup valve in the forward circuit opens. This action allows cool, filtered oil from the charge circuits to flush the propel circuits.Reverse circuit oil flows to the front-wheel assist manifold. The front-wheel assist system is disabled when the machine is operating in reverse. In this case, the reverse circuit oil flows through the front-wheel assist manifold and to the propel motors.Oil in the reverse circuit causes propel motors (1) and (14) to turn. After the motor turns, the pressure of the forward circuit oil is reduced. Reduced-pressure oil returns to the forward circuit and completes the drive circuit.Inside the propel pumps, return oil is directed to the following locations:
Flushing spools (27) and (35)
Forward combination valves (21) and (40)
The reverse side of propel pumps (19) and (38)When the shift switch is in the