When Komatsu engineers designed their new WA320-6 wheel loader, they specified hydraulics only where it would be most beneficial. Not surprisingly, then, hydraulics is used for propulsion, braking, steering, lifting, and all other implement controls, and even engine cooling. Not much left, is there?
It starts with hydrostatics
Of course, the primary function of any loader is to move material from one place to another. Therefore, the WA320-6 starts with a 167-hp (125 -kW) Tier-3 engine driving an elect ronical ly cont rol led hydrostatic transmission (HST) with variable shift control. The HST consists of a single variable- displacement axialpiston pump driving two variable-displacement piston motors, one for low-speed travel and one for high.
Engine power is transmitted through the HST to a transfer case, then mechanically out to differential gearing to the vehicle’s four drive wheels. The transfer case provides the gearing to allow the motors to operate at their most efficient speed range and generate enough torque to drive the machine.
When high drive torque is needed for digging, climbing, or initiating movement, the pump feeds both the high-speed and low-speed motor. The transfer case also contains a hydraulically actuated clutch that disengages the low-speed motor when the loader travels in high-speed mode. This prevents the low-speed motor from being an energy drag with the HST in the high-speed mode.
The variable-displacement system automatically adjusts to the tractive effort demand to provide maximum power and efficiency. Full auto-shifting eliminates any gear shifting and kickdown operation to allow the operator to concentrate on digging and loading. When decelerating, the HST acts as a dynamic brake on the mechanical drive system and can hold the loader in position on most workable slopes.
An inching pedal gives the operator excellent simultaneous control of travel and equipment hydraulic speeds. Pressing the inching pedal decreases pump flow to the motors, reducing ground speed and allowing the operator to use the accelerator to increase flow to the equipment hydraulics.
The WA320-6 also features a reversible hydraulic fan drive. The fan drive operates at the appropriate speed to keep the engine running within a narrow range of temperatures, which maximizes fuel economy and minimizes emissions. The fan drive has a reverse air-flow feature that prevents radiator clogs by pushing any accumulated debris out of the radiator.
For more information on Komatsu's WA320-6, click here.
