SCREWDRIVER GP 1U7230 - Caterpillar

Forward Travel at Overspeed
Illustration 2 g03878501
Hydraulic schematic of the travel motor (forward and destroked position)
(1) Pilot line from travel motor control solenoid (creeper)
(2) Shift piston
(3) Cutoff valve
(4) Travel motor
(5) Crossover relief valve
(6) Line from travel main control valve
(7) Shuttle valve
(8) Makeup valve
(9) Actuator piston
(10) Counterbalance spool
(11) Travel brake valve
(12) Travel control valve
(13) Pilot line from travel pilot control valve
(14) Pressure compensator valve
(15) Travel pilot solenoid
(16) Travel pilot valve (Forward)
(17) Travel pilot valve (Reverse)
(18) Hydraulic line from implement pump to travel control valve
(19) Pilot line from travel pilot valve to reverse side travel control valve
(20) Implement pump
(21) Unloading valve
(22) Travel motor control solenoid (creeper)
(23) Travel activation solenoid
(24) Pilot manifold
(25) Pilot pump Travel brake valve (11) blocks the return oil from the motor to the tank in the condition of overspeeding. By measuring the RPM in the transmission, the travel motor control solenoid (creeper) (22) will reduce the pressure that is supplied to shift piston (2). The reduced pressure allows shift piston (2) to shift upward. A decrease of the oil pressure in the forward side of the travel motor will cause cutoff valve (3) to shift upward. The shift opens the head end of actuator piston (9) to the hydraulic tank. Oil is allowed to flow into the rod end of actuator piston (9). Oil flows to the rod end of actuator piston (9). Actuator piston (9) moves downward in order to upstroke the motor toward the maximum angle. Machine speed is reduced.The pressure in the return passage opens crossover relief valves (5). Makeup oil flows to the supply passage for lower pressure.Once overspeeding is reduced, the travel motor control solenoid (creeper) (22) will increase the pressure that is supplied to shift piston (2). The increased pressure will allow oil to flow to the head end of actuator piston (9). Actuator piston (9) moves upward in order to destroke the motor toward the minimum angle. Machine speed is increased. The process mentioned is a continuous electronic process.Forward Travel at Creeper Speed
Illustration 3 g03878505
Hydraulic schematic of the travel motor (forward and destroked position)
(1) Pilot line from travel motor control solenoid (creeper)
(2) Shift piston
(3) Cutoff valve
(4) Travel motor
(5) Crossover relief valve
(6) Line from travel main control valve
(7) Shuttle valve
(8) Makeup valve
(9) Actuator piston
(10) Counterbalance spool
(11) Travel brake valve
(12) Travel control valve
(13) Pilot line from travel pilot control valve
(14) Pressure compensator valve
(15) Travel pilot solenoid
(16) Travel pilot valve (Forward)
(17) Travel pilot valve (Reverse)
(18) Hydraulic line from implement pump to travel control valve
(19) Pilot line from travel pilot valve to reverse side travel control valve
(20) Implement pump
(21) Unloading valve
(22) Travel motor control solenoid (creeper)
(23) Travel activation solenoid
(24) Pilot manifold
(25) Pilot pump In Illustration 3, the pilot oil pressure (1) from the travel motor control solenoid (creeper) (22) is cut off. Shift piston (2) shifts upward in order to upstroke the motor. The pressure in the travel system is directed by shift piston (2) to the rod end of actuator piston (9). Actuator piston (9) moves fully downward to the maximum angle. Machine speed is reduced.Travel