The 644K Hybrid Wheel Loader utilizes two sources of energy, diesel and electric, capturing regenerated energy as it is being created and using it to power the machine. According to John Deere, the 644K Hybrid can reduce fuel consumption up to 25%.
The 644K Hybrid is equipped with a John Deere PowerTech 6.8-L interim Tier 4 engine that runs at an operator-selected constant speed from 900 to 1,800 rpm. The hybrid boasts a net 229 hp and is equipped with all the key features of the conventional John Deere K-Series Wheel Loader line.
The machine’s hybrid technology delivers performance that is equal to or better than the conventional 644K, depending on the application. The engine’s constant operating speed maintains continuous hydraulic flow at all times, which delivers crisp hydraulic responsiveness and reduces cycle times. The electric motor smoothly delivers torque, resulting in fluid operation and a smoother ride.
Another benefit of the hybrid design is noise reduction on the jobsite. Since the engine runs at a constant speed instead of increasing and decreasing speed as the machine is worked, the engine noise is continuous and therefore less noticeable to both the operator inside the cab and bystanders outside.
During operation, a simplified PowerShift, countershaft-style transmission maintains smooth shifting for added productivity whether the operator is stockpiling, truck loading, or ramp climbing. The 644K Hybrid has four operating speed ranges, but no reverse gear or clutches as direction changes are performed by the electric motor. An integrated, spring-applied, hydraulically released wet-disc park brake requires reduced maintenance and increased machine uptime.
Like conventional K-Series Loaders, a Sealed Switch Model (SSM) gives fingertip control of keyless start and 24 other machine functions. New to the SSM are engine speed adjust and coast control. The coast control feature allows the operator to enable dynamic braking through the SSM, reducing mechanical brake wear.
Technology
Four main components pace the 644K’s electric-drive technology – the generator, inverter, motor, and brake resistor.
The generator is brushless and converts the rotational energy from the engine into three-phase alternating current (AC) electrical energy. It can also be driven as a motor to use recycled energy to drive hydraulics and save fuel.
The inverter is a solid-state electronic system designed for reliability, durability, and long life. The water-cooled inverter delivers electrical energy to the motor as demanded by the operator.
The single electric motor is also brushless for added reliability and converts three-phase (AC) back to rotational energy and torque. The motor replaces the job of a torque convertor, but can also work as a generator to recycle energy back into the system.
The water-cooled brake resistor passively consumes energy whenever the power electronics actively control its circuit and is only needed to consume excess recycled energy.
