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Drive cuts fuel consumption 20%, emissions even more

Cargotec, Helsinki, Finland, provides cargo and load handling solutions around the world, with emphasis on environmental sensitivity. Cargotec recently introduced a hydraulic hybrid drive terminal tractor offering high performance, significant savings in fuel costs, and even greater reductions in NOx and particulate emissions. Integrated into Cargotec’s Kalmar Ottawa brand 4×2 off-highway terminal tractor, the hydraulic hybrid system is initially available to operators in North America.

The new Kalmar hybrid drive terminal tractor operates with a parallel hybrid hydraulic drive system to simultaneously transmit power from two distinct sources: the primary diesel engine, the secondary hydraulic motor, or both.

The new machine is the result of Cargotec’s partnership with Singapore Technologies Kinetics Ltd. (ST Kinetics) and its subsidiary Kinetics Drive Solutions (KDS). The Kalmar hydraulic hybrid drive terminal tractor is equipped with a parallel system that transmits power from two distinct sources: the primary diesel engine, the secondary hydraulic motor, or both. Kalmar has also participated in the EPA-led development of a hydraulic series hybrid terminal tractor.

Having an impact

“The normal application of a terminal tractor involves many stops and starts, where frequent idling and reverse motion are common,” explains Mikko Vuojolainen, Vice President, Terminal Tractors at Cargotec. “This inconsistent use of power makes it difficult to consistently capture regenerative energy using electric drives. After carrying out extensive testing on a variety of alternatives, it was clear that ST Kinetics’ Hy-Power hydraulic hybrid drive system combined with clean diesel engine technology offered the most benefits to the user and environment. In this application, energy is only transferred twice as opposed to four times with an electric hybrid.”

Although fuel consumption with the hydraulic hybrid system can vary depending on the application and driving style of the operator, in the typical port environment, fuel savings of 20% and an even greater reduction of NOX and particulate matter emissions can be achieved, according to Cargotec officials. Cargotec has given the new Kalmar hydraulic hybrid drive terminal tractor its Pro Future rating, adding to the company’s expanding portfolio of environmentally friendly solutions.

Vuojolainen continues, “The pressure to reduce emissions at ports and in urban areas is strongest in the United States. We have engineered the Kalmar hydraulic hybrid drive terminal tractor to help users meet ever-stricter regulations in this part of the world and to combat expensive exhaust after-treatment solutions. In addition to financial constraints, companies operating large fleets of equipment in confined spaces, often near urban developments, can come under significant pressure to reduce their environmental footprint.”

Other benefits

The Hy-Power hydraulic hybrid drive system also exhibits smooth acceleration, which helps reduce driver fatigue and driveline wear. The vehicle also has an inching function that allows it to advance without engine power, further saving fuel and eliminating emissions altogether.

Cargotec’s Kalmar terminal tractor features a parallel hybrid drive that can operate as a mechanical transmission, hydraulic, or combination of the two. Major hydraulic components (shown in green) include (left to right) motorpump, reservoir, and accumulators.

The configuration of the hydraulic hybrid components allows them to be easily accessed, and they have been built to outlast the normal life cycle of a terminal tractor. Scheduled maintenance intervals of the hybrid components are twice as long as those required to properly maintain a terminal tractor. The hybrid system does not require expensive replacement parts, further helping to drive down the machine’s lifetime operating costs.

Involved in multiple hybrid terminal tractor projects, Cargotec previously delivered a hybrid hydraulic drive machine to PSA Singapore Terminals together with ST Kinetics. Cargotec’s drive to reduce fuel consumption and emissions using hybrid technology goes back to 2008, when it became the industry’s first to offer straddle carriers and, later, shuttle carriers with hybrid drive systems.

KDS has developed a range of Hydro-Mechanical Infinitely Variable Transmission (HMIVT) systems that combine a hydrostatic transmission with a planetary gearset in a hybrid configuration. Existing HMIVT designs span a torque range from 800 to more than 2600 N-m. The HMIVT systems provide a parallel dual power path through the transmission, permitting it to transfer power in any of three modes: purely hydraulic, combined hydraulic and mechanical, or purely mechanical.

At low output speeds, most power is transmitted hydraulically, and a small amount mechanically. At high output speeds, all power is transmitted mechanically as the transmission locks up in an overdrive ratio allowing cruising speeds at low engine speed. Between these two extremes, power is transmitted as a mixture of hydraulic and mechanical, with the ratio continually favoring mechanical power as it progresses upward through the speed range.

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