COVER 1776712 - Caterpillar

Small Displacement Change Operation
Illustration 1 g00846914
Travel motor (partial diagram) (1) Check valve (2) Check valve (3) Pilot port (4) Displacement change valve (5) Passage (6) Piston chamber (7) Port (supply oil or return oil) (8) Piston (9) Swashplate (10) Port (supply oil or return oil) (11) Drain port
Illustration 2 g00846924
Small displacement change operation (1) Check valve (2) Check valve (3) Pilot port (4) Displacement change valve (6) Piston chamber (7) Port (supply oil or return oil) (8) Piston (9) Swashplate (10) Port (supply oil or return oil) (12) Passage (13) Passage (return) (14) Hydraulic tank (15) Spool chamber (16) Spool (17) Spring (18) BodyWhen the travel speed control switch on the control panel is pushed and the rabbit appears on the display, the machine is in HIGH SPEED MODE. In this condition, an input signal from the travel speed control switch is sent to the engine and pump controller. The pressure sensor for the pump delivery also provides an input signal to the engine and pump controller. When the travel load is light and when the pump delivery pressure is below a certain level, the output signal from the pressure sensor for the pump delivery is below a certain level. When the pump delivery pressure is below a certain level, the engine and pump controller energizes the travel speed solenoid. When the travel speed solenoid is energized, pilot system oil flows into pilot port (3) of displacement change valve (4). Spool (16) moves to the left against the force of spring (17) until the spool contacts body (18). Main pump oil flows from port (10) of the travel motor through check valve (2). The main pump oil then flows through spool chamber (15) and passage (12) to piston chamber (6). The oil in piston chamber (6) moves piston (8) against swashplate (9). As a result, the angle of swashplate (9) is decreased and the motor displacement is decreased. The travel speed is maximum in this condition.Large Displacement Change Operation
Illustration 3 g00846939
Large displacement change operation (1) Check valve (2) Check valve (3) Pilot port (4) Displacement change valve (6) Piston chamber (7) Port (supply oil or return oil) (8) Piston (9) Swashplate (10) Port (supply oil or return oil) (12) Passage (13) Passage (return) (14) Hydraulic tank (15) Spool chamber (16) Spool (17) Spring (18) BodyWhen the angle of swashplate (9) in the travel motor increases, the displacement of the travel motor increases. The angle of swashplate (9) in the travel motor will increase and the travel speed will decrease during the following two conditions.
The angle of swashplate (9) in the travel motor will increase and the travel speed will decrease when an increase in pump pressure occurs.When the machine is in HIGH SPEED MODE and the pump delivery pressure increases above a certain level, the engine and pump controller de-energizes the travel speed solenoid. When the travel speed solenoid is de-energized, pilot system oil stops flowing into pilot port (3) of displacement change valve (4). Spool (16) moves to the right