5-10t Internal Combustion Counterbalance Forklift Truck Operation & Maintenance Manual
3.6 Oil Circuit System for Torque Converter
Refer to Fig 3-7.
After engine is started, the oil feed pump will work along with, and the oil of torque converter
will pass through the oil feed pump and be forced out to the control valve from oil sump
(namely the bottom of transmission) through oil filter.
The torque converter oil from oil feed pump is divided into two ways inside the case of torque
converter, one used for torque converter, and the other used for transmission.
The oil pressure used for clutch inside the transmission is adjusted to 1.2～1.5MPa through
pressure regulating valve, while the oil pressure used for torque converter is adjusted to 0.5～
0.7MPa through adjusting valve of torque converter. The pressure oil will afterwards reach the
blade lattice of torque converter, to lubricate the clutch unit after being cooled down through
oil cooler, and then return to the oil sump through oil filter, recycled in such a way.
When gear-shift valve stem is at the middle position (neutral gear), the oil circuit from
gear-shift slide valve to clutch is closed, and at this point, all the liquid will flow into the
torque converter.
When gear-shift valve stem is at forward or backward position, for the action of pressure
regulating valve, the oil enters into pressure accumulator, and therefore, oil pressure is
gradually increased during the period when clutch begins its action to full compression.
When pressure oil is filled up inside the pressure accumulator, the oil pressure is sharply
increased, for the hydraulic clutch to achieve a full engagement. When forward-gear or
backward-gear clutch is working, another kind of clutch (backward or forward) is under the
disengaged status, the oil from oil cooler lubricates it, to prevent adhesion between respective
plates, and to play a cooling function.
When inching pedal is pushed down, the inching valve takes action. Most oil inside the clutch
will be extracted through inching valve and return to the bottom of transmission (oil sump),
and the oil circuit is the same as the status at neutral gear.
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