All-electric forklift gets rid of hydraulics
SKF has replaced the engine and hydraulics in a forklift truck with batteries and electric actuators, to produce an all-electric forklift that it claims has many advantages. The prototype six-tonne vehicle, called the E-truck, is propelled by in-hub DC motors, is steered mechatronically, and uses electric actuators to lift and tilt the mast, and to shift it sideways.
According to Susan Langer, SKF`s global program manager for industrial vehicle systems, the actuators are more efficient than hydraulic systems. They can recover energy and feed it to the on-board battery as the load is lowered. She predicts that the quiet, precise, maintenance-free actuators will be more reliable than hydraulics and will save money over the life of the vehicle.
The mast height control system incorporates a bearing with sensor electronics to detect the height, speed and acceleration of the mast. As the mast is raised or lowered carrying a load of up to 3.5 tonnes it sends out a continuous signal to a dual-redundant controller which displays the values on a digital readout. On-board communications are via a CANbus system.
Other claimed advantages for the electrical lifting system are that it: avoids the risk of oil leakages; does not need complex peripherals; is insensitive to temperature; and gives the operator a clearer view. When the actuators are at a standstill, they stay in position, unlike many hydraulic systems which need additional brakes.
The E-truck uses a "steer-by-wire" system with no direct mechanical linkages to the wheels. This will allow truck manufacturers to program the "feel" and the number of lock-to-lock turns for their vehicles. The steering sensitivity could also vary with speed.
The 7.5kW direct drive wheel motors, developed for the role by a Dutch company, avoid the need for a gearbox and can also recover energy when braking.
At present, there are no plans to put the E-truck into production, but SKF is demonstrating the technology to the forklift industry. Initially, at least, the all-electric system would probably be more costly to produce than a traditional system.