John Deere says its new 644K hybrid wheel loader was borne of the desire to integrate the best technology available to the industry and provide customers improved uptime and productivity, while lowering daily operating cost.
The 644K uses two sources of energy: diesel and electric. The hybrid loader captures regenerated energy as it's being created and uses it to power the machine. Four main components comprise its 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 ac electrical energy. It can also be driven as a motor to use recycled energy to drive hydraulics and save fuel.
A solid-state electronic system defines the inverter, which was designed for reliability, durability, and long life. The water-cooled inverter delivers electrical energy to the motor as demanded by the operator.
Its 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.
Equipped with a John Deere Power Systems PowerTech 6.8-L Tier 4 Interim/Stage IIIB engine that runs at an operator-selected constant speed from 900 to 1800 rpm, the hybrid offers 229 hp (170 kW) net.
According to Deere, while the 644K hybird is equipped with all the key features of the conventional K-series wheel loader line, its 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 offers crisp hydraulic responsiveness and reduces cycle times. The electric motor smoothly delivers torque resulting in fluid operation and a smoother ride. As a result, the 644K hybrid, with an operating weight of 40,436 lb (18,341 kg), is manageable for novice and experienced operators alike.
Deere says the 644K hybrid can reduce fuel consumption up to 25%, helping contractors lower their daily operating costs. Another advantage is its controllability, "virtually becoming an extension of the operator."
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.
As with 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.