CYLINDER AS 2131240 - Caterpillar

Upstroking
Upstroking increases the pump displacement. Upstroking occurs when one or more of the temperature sensors sense a higher temperature. When a higher temperature is sensed, a signal is sent to the engine electronic control module (ECM). The engine ECM interprets the data. The ECM determines the proper amount of current that should be sent to solenoid valve (6). Solenoid valve (6) increases the signal pressure that is sent to pump control valve (10) through the load sensing line.The load sensing signal pressure enters through port (26) which fills the pressure cavity (27). The signal pressure and the force of spring (28) shifts compensator spool (24) to the left. The oil behind actuator piston (21) flows through passage (31) to the passage (case drain) (32). The force of spring (15) overrides the force of the oil pressure behind actuator piston (21). Then, the angle of swashplate (18) proportionally increases. When the angle of swashplate (18) increases, the pump upstrokes and the displacement of the pump increases.As the speed of fan motor (3) increases, the pressure that is needed to keep the fan motor rotating at that speed will increase. When the pump supply pressure reaches the spring setting of the pressure cutoff spool (29), the oil pressure behind the pressure cutoff spool will override cutoff spring (28). Pressure cutoff spool (29) shifts to the right. When pressure cutoff spool (29) moves to the right, the land on the cutoff spool will block the oil flow from actuator piston (21) to hydraulic tank (8). At the same time, pump supply oil is metered around the cutoff spool (29) by the land on the spool. The metered oil supply flows behind actuator piston (21). The oil pressure behind the actuator piston and spring (15) are equalized. The swashplate is at the angle for the adjusted maximum pressure. The pump will provide the fan system with the maximum flow in order to maintain the maximum fan speed. The maximum fan speed can be changed by adjusting force on spring (35) for cutoff spool (29) .Destroking
If the temperature of the sensors is dropping toward the key target temperatures, the engine ECM sends an increase in current to solenoid valve (6). Solenoid valve (6) shifts. The solenoid valve opens a path for oil that is above spool (24) in order to be metered out to the hydraulic tank. Solenoid valve (6) decreases the signal pressure to pump control valve (10) through the load sensing line. The force that is behind the left end of spool (24) works against spring (28) and control pressure in cavity (27). As signal oil from cavity (27) is released, the spool will move further to the right. As the spool begins to move to the right, pump supply oil will flow around the land on spool (24). The oil flows through pump control valve (10), through passage (31) and to actuator piston (21). The oil pressure increases at the actuator. The actuator moves to the left against the swashplate.