A world first for Hyundai hybrid

  • 21-May-2009 02:19 EDT
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Hyundai's Elantra LPI Hybrid is based on a flywheel-mounted motor-generator-type parallel hybrid system. It has a lithium-ion polymer battery, a 1.6-L engine, and a 15-kW electric motor.

What Hyundai Motor says is the world’s first hybrid-electric with a liquefied petroleum injected (LPI) engine will go on sale in its initial target market of homeland Korea beginning in July. Called the Elantra LPI HEV, the vehicle uses lithium-ion polymer batteries.

Hyundai unveiled the car at the recent Seoul Motor Show in the South Korean capital.

Korea is heavily dependent on oil imports. The Elantra LPI HEV will help reduce national energy consumption by promoting diversified energy usage, the automaker said. Hyundai, which is to expand its hybrid vehicle lineup to include a full-hybrid version of the Sonata replacement due in 2010, did not specify the timetable for foreign sales of its hybrids.

Lee Hyun-Soon, Vice Chairman and Chief Technology Officer of the Hyundai-Kia Corporate Research and Development Division, said the Elantra LPI HEV has a Gamma engine of 1.6-L displacement and a 15-kW electric motor. It is a “prime example of Hyundai innovation” because the company has leveraged its world leadership in LPG-fueled vehicles to the development of a hybrid that will be economical to operate. All key components, including the motor, battery, and dc/dc converter, have been developed by Hyundai and its local partners, according to Lee.

The flywheel-mounted motor-generator parallel hybrid system was developed independently at Hyundai’s Hybrid Vehicle Development Center in Namyang, Korea. Using a continuously variable transmission (CVT), the Elantra LPI HEV is a mild hybrid boasting fuel economy of 17.2 km/L—a 41.4% improvement over a conventional Elantra with a 1.6-L engine and automatic transmission.

For improved thermal efficiency, the Atkinson cycle is employed and the compression ratio has been increased from 10.5 to 12.0. To increase mechanical efficiency, the valve spring load and piston ring tension were reduced. Further reductions in friction were achieved via tappets with a diamond-like carbon coating and piston skirt with a molybdenum disulfide coating.

Continuously variable valve timing is applied on the intake camshaft, and electronic throttle control was adopted.

The CVT is equipped with a new van Doorne-type metal transmission belt, and in the interest of better fuel economy a wet-type multidisc is fitted as a starting device instead of a torque converter. A chain-driven external gear type oil pump and torsional damper are installed on the front side of the CVT.  Also, special step-cut seals are applied to minimize leakage. On starting the clutch, a direct solenoid is used for precise control and a separate/variable cooling system is applied. As a result of these improvements, the transmission efficiency of the CVT is better than competitors', according to Hyundai.

A hydraulic limp-home mode is available in case of transmission control unit malfunction.

The electric motor in the hybrid powertrain is a pancake-type interior permanent magnet synchronous motor (IPMSM) installed between the engine and the CVT. The IPMSM includes a revolver-type position sensor which sends rotor position data to the MCU. Peak efficiency is over 95%. The magnet shape and arrangement of the motor (gull-wing) is optimized for performance. A split-type winding core has been applied on the stator. The MCU and battery system share an integrated forced-air cooling system. The electric motor is air-cooled.

LG Chem is the sole supplier of the Li-ion polymer rechargeable batteries. Li-ion polymer has significant advantages over conventional Li-ion, including greater energy density, lower manufacturing costs, more robustness regarding physical damage, and more charge-discharge cycles before storage capacity begins to degrade, Hyundai says. The battery pack for the Elantra LPI HEV has passed the company's 300,000-km (186,000-mi) durability test and has been thoroughly tested for overcharging and collision safety.

The battery operates at a nominal voltage of 180 V and has a capacity of 5.3 A·h. It is packaged together with the integrated power module, along with the battery-management system, motor control unit, dc/dc converter, and cooling fan. The role of the battery-management system is to monitor the status of the entire system and control the temperature accordingly.

Unlike a conventional vehicle, the Elantra LPI HEV does not have an alternator. In its place, there is a dc/dc converter, which in the interest of improved fuel economy replaces the conventional alternator to supply energy for auxiliary power needs.

The hybrid-electric control unit is a supervisory controller. Using information from the vehicle, driver, engine, power electronic components, and battery, it determines the operation of the engine, transmission, and motor and sends out control signals as a command/request to controllers.

In an HEV in which the traction motor is directly attached to the engine and transmission through a clutch instead of a torque converter, there is a problem of backward slip on slanted roads at the moment of engine restart after idle stop. To prevent slippage, a creep aid system has been devised into the brake system. The function of the antislip system is to briefly maintain brake oil pressure just after the driver has released the foot brake to make enough creep torque at engine restart.

The Elantra LPI HEV emits just 102 g/km of CO2 and 90% less emissions than an equivalent gasoline-powered Elantra, and as such qualifies as a super ultra low emission vehicle (SULEV). LPG, sometimes referred to as auto gas, is a low-carbon-emitting hydrocarbon fuel that burns more cleanly than gasoline or diesel and is free of the particulates associated with the latter.

Hyundai developed its first hybrid-electric vehicle in 1995 when it unveiled the Future Green Vehicle at the Seoul Motor Show. In 1999, it showed an Elantra HEV, and in 2000 it showed an Accent HEV, both of which featured hard-type parallel electric drive systems and integrated starter/generator technology. However, those vehicles did not go into mass production.

In 2004, the company delivered 50 Getz gas-electric hybrid vehicles (B-segment vehicles badged as the Hyundai Click in the Korean market) to Korean government agencies as part of a fleet demonstration project. These were mild-type hybrid systems using 12-kW motors and nickel metal-hydride batteries. The hybrid technology development program continued to expand, and in 2005 Hyundai and affiliate Kia Motors Corp. delivered 350 more units to the demonstration fleet. An additional 730 units were delivered in 2006 with 1682 more in 2007, including Accent HEVs.

The Elantra LPI HEV has a unique instrument cluster with improved visibility via a semi-supervision type panel and a negative LCD for the odometer/trip meter. The cluster also features a radiant-type LED backlight and uniform intensity of illumination.

Also at the Seoul Motor Show, Hyundai unveiled its first Plug-in HEV concept car, called Blue-Will. Promising an electric-only driving distance of up to 64 km (40 mi) on a single charge and a fuel economy rating of up to 2.2 L/100 km, Blue-Will, code-named HND-4, is Hyundai’s fourth concept vehicle.

Hyundai unveiled five commercial vehicles at the show: a new concept model, a hydrogen fuel cell bus, a Universe Limousine, a Universe CNG tourist bus, and a Trago three-rear-axle 24-ton (22-t) dump truck. A Trago Hi-Cab 6 x 2 tractor, along with the Powertec diesel engine that satisfies Euro 4 emissions standards, also was displayed.

Shown as well was the Q-CNG (compressed natural gas) engine, an environmentally friendly engine boasting a maximum output of 340 hp (254 kW).

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