Toyota Industries Corp. (TICO) is taking its knowledge of hybrid systems in the automotive market and applying it to lift trucks. The TICO Environmental Action Plan specifies four areas for action between now and 2011: curbing emissions and global warming, using resources more efficiently, reducing environmental risk factors, and consolidating environmental management. At the 2009 Promat Show, Toyota Material Handling unveiled a hybrid lift truck, which appears destined for production as such a product would help to reach these goals.
Two main differences between a standard internal-combustion (IC) model and the hybrid are the incorporation of hydraulic systems with the two power sources, all in a limited space envelope. The resultant vehicle should be of the same size and capacity of the IC version that it would replace. The engine is a smaller unit than currently used in other lines, and if produced the hybrid line would be sold alongside existing IC and all-electric versions currently available.
The hybrid system was developed in Japan, where there are devoted engineering resources for the project. Advances in battery technology and experiences on the automotive side could lower costs. Communication is ongoing as to the needs of a U.S.-market version, which would need to be propane-fueled; whereas Japan and Europe rely more on diesels, 97% of the IC market in the U.S. is LP-fueled.
The hybrid would have to match the turning radius, right-angle stacking dimensions, and overall width of the IC versions to be a viable choice, as those areas are critical to U.S .applications, especially for indoor trucks where as little as a 1.0- to 1.5-in (25- to 38-mm) difference could be detrimental to sales. The concept truck has a 5500-lb (2495-kg) capacity, 130-in (3300-mm) lift height, 50-in (1270-mm) width, and an unloaded top speed of 13 mph (21 km/h).
The hybrid system is much like that in Toyota hybrid cars and SUVs, with an IC engine coupled to a generator and a nickel metal-hydride battery. The battery is responsible for 100% of driving, while the hydraulics are connected via a driveshaft from the IC engine to the hydraulic pump. As a smaller engine is used that could struggle with heavy loads, the controller can sense a heavy load and reverse the generator, effectively turning it into an electric motor powered by the battery. Loads at close to capacity will call upon the battery and generator for assistance. This power is sent through a clutch when needed.
Electric drive motors, powered by the battery, are about twice as big as seen on current all-electric forklifts to obtain performance matching that of traditional IC lifts. Whenever the battery charge falls below 60 to 80%, the engine runs continuously; once above that region, the controller shuts off the engine, as in some hybrid automobiles. Overall target benefits are a 50% fuel efficiency gain and 50% reduction in emissions.
Added mass is a negative in the automotive world, although with lift trucks it can improve stability. The concept is slightly heavier than an equivalent IC version, although not much; mass distribution is key as well, and so the hybrid components are carefully placed.
An additional benefit is that the hybrid can be run, for a short period, entirely on electric power. The limited time would boil down to the small battery pack, which is not as robust as the lead-acid batteries in the all-electric versions. Hydraulics would receive power via the clutch from the reversed generator.
Target customers include primarily indoor, high-usage, and high-shuttle-run applications, which tend to spend the most on fuel.