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| Illustration 1 | g06314492 |
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(1) Near zero speed control valve
(2) Orifice (3) Fan motor (4) Fan speed sensor (5) Piston pump (6) Oil filter (7) Oil cooler (8) Cooler bypass valve (9) Temperature sensor | |
The ECM receives in put from fan speed sensor (4) and temperature sensor (9). The ECM uses the inputs to control the output piston pump (5) by stroking and destroking the pump.
Piston pump (5) pumps oil to fan motor (3). Near zero speed control valve (1) actuates when machine software determines from all the machine temperature sensors to slow fan down. Machine is in near zero when de-energized. Demand fan is allowed to operate normally (controlled fan) when near zero fan speed valve (1) is energized. The spool of the cooler bypass valve (8) is moved by a temperature valve. Bypass valve (8) prevent the hydraulic oil from over cooling and high temperature. Oil flows from bypass valve to either oil cooler (7), oil filter (6), or to both cooler (7) and filter (6) simultaneously.