Global Vehicles

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December 2002
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Demio/Mazda2 shares the new small B-segment platform with Ford of Europe, on which Mazda designed its own unique five-door body. This is the sports version.

Following quickly on the heels of the new Mazda6 sedan (see feature in November AEI), Mazda has developed a new Mazda2/Demio that shares the small B-segment platform with Ford's European Ford Fiesta and its derivatives. Mazda will consign the car's European production to Ford's Valencia, Spain, factory, including powertrains procured from Ford. The Japanese-market Demio, which is also exported to Australia and Asian countries, is built at Mazda's main assembly plant, and its new MZR series engines are also produced at the Hiroshima engine factory.

The new "Z" engine is an exclusive property of Mazda unlike the midsize MZR 1.8- to 2.3-L I4, which is a global engine for Ford Group.

It is interesting to note that the B-platform project was initiated in Dearborn, MI, where neither Ford nor Mazda sold B-cars. (At present, Toyota sells the only B-segment car in the U.S. with the Echo sedan, soon to be followed by the Scion bb-X). It was Ford of Brazil that urgently needed a new B-car, thus the location. Engineers from Ford of Europe and Mazda joined the Dearborn team in the program's early phase. The project then moved to Ford's European R&D; arm, and a thirty-strong team from Hiroshima led by Kiyoshi Fujiwara was assigned there to jointly design the platform. Fujiwara is Program Manager, 5th Platform (B-segment or "small" cars), otherwise known as Chief Engineer of the Demio/Mazda2.

The Z-series employs a high-pressure die-cast, horizontally split cylinder block, and variable induction.

The B-segment is one of the most hotly contested in Europe and now Japan, since the launches of such best-selling products as Toyota's Vitz/Yaris and their derivatives as well as Honda's Fit/Jazz. These competitors are quite roomy for their small outer sizes and are versatile in accommodation. The new Mazda2/Demio (hereinafter referred to by its export name, Mazda2) is therefore larger than the European Ford Fiesta, its outer size falling between the Fiesta and the small Ford Fusion MPV.

The Mazda2 measures 3925 mm (155 in) long, 1680 mm (66 in) wide, and 1545 mm (61 in) tall. Its width and an engine displacement under 2.0 L classify it as a "small car" in Japan, thus receiving minor annual tax concessions. The overall height allows the car to be taken in a typical mechanized public/private-parking pallet. The Mazda2 rides on a 2490-mm (98-in) wheelbase and 1475-mm (58-in) front and 1450-mm (57-in) rear tracks. Mass ranges between 1060 and 1110 kg (2340 and 2450 lb).

The Mazda2's chassis is based on the Ford global small platform with MacPherson strut front (top) and twist-beam rear suspension.

The chassis design is shared with the Ford Fiesta in that front MacPherson struts and rear twist-beam axle are employed. The front suspension arms are attached to a pressed-steel welded subframe, which is directly bolted onto the bodyshell. The elaborate (because it carries both Mazda and Ford powertrains with different shapes, thus different vibration frequencies) subframe also carries the engine mounts. An additional member placed within reinforces the subframe. Because of the layout, twin cables, versus the previous rod system, operate the five-speed manual transmission.

The type-MZR "Z" series is another all-new engine design. Unlike the bigger global MZR (1.8- to 2.3-L displacement), this engine is an exclusive for Mazda vehicles with an annual maximum production of 290,000 units. The aluminum cylinder block is high-pressure die-cast as in the Millenia V6. The cylinder block is split horizontally at the crankshaft center and the lower block carries bearing caps, again like the Millenia. Dual overhead camshafts are chain driven, and in turn act on four valves per cylinder via bucket tappets. No clearance-adjusting shim is used on or within the tappet. Tappets are automatically selected during assembly to ensure correct clearances. The Z-series covers the 1.3- to 1.6-L displacement range, with the possibility of adding a couple hundred more cm³. The engine is fitted with S-VT, sequential variable (valve) timing, as standard equipment.

The Mazda2's modular instrument panel is built up in a subassembly section one floor below the main vehicle assembly area.

The 1.5-L ZY-VE unit is rated at 83 kW (111 hp) at 6000 rpm and 140 N•m (103 lb•ft) at 4000 rpm, and the smaller 1.3-L ZJ-VE produces 67 kW (90 hp) at 6000 rpm and 124 N•m (91 lb•ft) at 3500 rpm. The Z-series adopts a modular induction system, including the plastic equal-length four-branch manifold, fuel injectors, and engine-management computer built and supplied by Denso, greatly reducing assembly steps and number of components. Transmission choices are Mazda's own five-speed manual and four-speed automatic, driving the front wheels.

A "white canvas top" allows some light to penetrate the Mazda2 cabin, while completely shutting out UV rays and shielding as much heat as a conventional steel roof.

Mazda has adopted a modular instrument panel approach with the Mazda2, which is built up in a subassembly section one floor below the main vehicle assembly area. Few Japanese OEMs have gone the route of supplier-built IP modules.

The interior is full of useful storage space and bins. The rear seat with split seatbacks may be double-folded flat by the pull of a lever. A unique feature is a large, power-operated, semi-transparent canvas top. The multi-layer top lets in 40% of the light, while completely shutting out ultraviolet rays. Heat transmission is no greater than with a light-color metal roof, and less than a dark one, according to Mazda. The top layer is Teflon-coated for durability.

- Jack Yamaguchi

Commercial hybrid vehicles from Japan

Pre-production models of Mitsubishi's urban transit IC/electric hybrid bus project were put in service at one of the recent World Cup football matches held in Japan. The roof hump accomodates the lithium-ion battery pack.

The Japanese medium- and heavy-duty commercial vehicle manufacturers are rushing to the IC/hybrid arena to prepare for diesel exhaust emissions regulations with a heavy emphasis on the two "enemy" pollutants in uniquely congested and mixed Japanese traffic: oxides of nitrogen (NOx) and particulate matter (PM) emissions. The regulations will be implemented in steps; the 2003 short-term regulations mandate the reduction of NOx to 3.38 g/kW and PM to 0.18 g/kW, followed by a 2005 long-term level that further reduces NOx to 2.0 g/kW and PM to 0.027 g/kW. It is unlikely that the government and public will relent at those levels, and further tightening may follow after 2010. The Japanese truck OEMs' livelihood and very survival still depend on the diesel, and they are striving to solve the toughest development challenges.

Senior Vice President Akio Hanawa, in charge of truck and bus R&D; at Mitsubishi Fuso Truck and Bus Co., "a company within a company" in the recently reorganized Mitsubishi Motor Corp., lists among the company's solutions: intercooled turbocharging of all diesel engines, common-rail injection employing 160-MPa (23.2-ksi) pressure, multiple (up to four) injections, electronically controlled water-cooled EGR, and the diesel particulate filter (DPF). For the 2005 long-term regulations, a variable-geometry turbocharger, a common-rail injection-pressure boost to 180 MPa (26.1 ksi), massive and precisely controlled cooled-EGR, and an NOx catalytic converter may be required, according to Hanawa.

A diesel/electric hybrid power source is a doable, effective, and attractive—if still very expensive in initial price—solution. Mitsubishi cites that, for urban route application, its prototype series hybrid bus will reduce fuel consumption by 30%, NOx emissions by 60%, and PM by 70%—measured on the Japanese 10/15 urban driving cycle.

Mitsubishi displayed a large hybrid bus for urban route uses at the 2000 Tokyo Commercial Vehicle Show, and has been developing the concept and vehicle. The Aerostar HEV (hybrid-electric vehicle) bus was put in service in June 2002, transporting spectators at one of the recent World Cup football matches held in Japan between the Japanese Railroad station and stadium. After the event, the bus was assigned to a private rail/bus company for regular route services.

Mitsubishi's bus is powered by a six-cylinder 8.2-L diesel engine that drives a 100-kW generator, its propulsion system by Siemens, which is similar to the one used in Mercedes-Benz's European transit bus project. Twin motors, each rated at maximum output of 150 kW, drive the rear wheels.

The low-floor Aerostar is a series hybrid with Mitsubishi's type 6M6 inline six-cylinder 8.2-L diesel. The engine drives a 100-kW generator, which charges the lithium-ion storage battery pack consisting of six modules, each module comprising 30 cells of 3.6 V. Total battery-pack voltage is 648 V. The battery design is based on a Mitsubishi system from an experimental coupe that challenged the world's EV distance record in late 1999, covering 2142 km (1330 mi) on a single charge. The battery system has since been further improved with cooperation from NEC. According to Mitsubishi, its charge density is on par with a capacitor, and is superior in output density.

The electric drive system is by Siemens, similar to the Mercedes-Benz bus application, employing twin electric motors, each with maximum power of 150 kW and driving the rear wheels via a reduction geartrain but no stepped gear transmission.

The bus starts off with the diesel shut down, enabling quieter operation for built-up residential areas or at night. For rapid acceleration or when negotiating hilly terrain, the engine/generator is employed, adding to the output of the battery pack. It also recharges the storage battery on the go. During deceleration and braking, the generator regenerates energy for storing in the battery and taking care of deceleration down to almost zero vehicle velocity. A dedicated motor drives the accessories including the power-steering pump and air compressor for the brake system.

Nissan Diesel prides itself in being the world's first manufacturer to launch a medium-size (4.0-ton load category) parallel diesel/electric hybrid truck employing a "Super Capacitor" for electric energy storage. A typical capacitor's drawback is its inferior energy density—or capacity—versus new chemical batteries such as the nickel/metal hydride and lithium-ion varieties, while it has good power (energy discharge), durability and longevity, and safety characteristics.

Nissan Diesel claims it has produced the world's first diesel/electric hybrid truck employing a Super Capacitor for electric energy storage. The system is a parallel-hybrid type combining a 7.0-L six-cylinder diesel and a 55-kW ac synchronous motor.

Nissan Diesel has been conducting research on the new high-energy-density capacitor in cooperation with Okamura Laboratory under the auspices of the semi-governmental entity NEDO (New Energy and Industrial Technology Development Organization) in the latter's ACE energy project. The Super Capacitor was first adopted in an experimental hybrid bus announced in June 2000. The bus is a series hybrid with a small-displacement (4.6-L) four-cylinder engine operating in the Miller-cycle principle with purely hydraulic valve actuation. The engine produces 55 kW (74 hp) at 1600-1800 rpm and drives an SPM synchronous generator of 51-kW output produced between 3870 and 4320 rpm. Twin SPM synchronous motors, each rated at maximum 75 kW, propel the vehicle. The capacitor unit has capacity of 1310 W•h and a mass of 194 kg (428 lb). The Super Capacitor installed in the production Condor capacitor-hybrid truck is an improved version of this unit. The capacitor module has 384 cells, operates at a maximum voltage of 346 V, has maximum capacity of 583 W•h, has a rated input/output of 60 kW, and measures 1105 x 505 x 470 mm (44 x 20 x 19 in). The Super Capacitor's energy density is 6.3 W•h/kg and possesses a high charge/discharge efficiency of 500 W•h/kg—which are both higher than the capacitor norm.

The capacitor's longevity in repeated and frequent regenerative decelerations is particularly suitable to commercial vehicles. Typically in Japan, the midsize truck covers over 600,000 km (370,000 mi) in its life, and in regenerative hybrid operation would go through as many as 2.4 million cycles of braking, versus median passenger car numbers of 150,000- 200,000 km (93,000-124,000 mi) and 600,000-800,000 braking cycles.

The Condor hybrid system is a parallel variety propelled by the powertrain comprising a six-cylinder 7.0-L diesel rated at 152 kW (204 hp) at 3000 rpm and 500 N•m (369 lb•ft) at 1400 rpm. An ac permanent-magnet synchronous motor, producing 55 kW at 4060-9000 rpm and 130 N•m (96 lb•ft) at 1400 rpm, drives the vehicle via an automatically shifting mechanical transmission. The propulsion and regenerative motor is placed adjacent to the engine and transmission unit, and driving torque is transmitted via a primary reduction gearset, clutch, and secondary geartrain to the main drivetrain.

The vehicle moves off on electric power with the transmission in automatic mode. The driver can choose to start off with the engine by operating the clutch pedal. Initial acceleration is accomplished with both the engine and motor propelling the vehicle. At cruising speed and when the capacitor's voltage level drops below the set level, the engine takes over, which operates in its optimum efficiency range. The automatically shifted mechanical transmission has two operating modes: automatic and manual gear selection by the lever. Braking energy by the mechanical brakes and exhaust pressure retardation (the latter lever-operated) is converted to electricity by the propulsion motor/generator and inverter and stored in the capacitor. The hybrid system incorporates an engine stop/restart function when the vehicle is at standstill.

Nissan Diesel's 384-cell Super Capacitor rack is rated at 60kW with a maximum capacity of 583 W•h and maximum voltage of 346 V.

Nissan Diesel claims a 50% improvement in fuel consumption, and reduction in CO2 by 33% with the Condor capacitor-hybrid versus a comparable load-capacity truck. The forward-control, flatbed truck is 7970 mm (314 in) long, 2310 mm (91 in) wide, and 3320 mm (131 in) tall on a 4380-mm (172-in) wheelbase; has a maximum certified load capacity of 3300 kg (7300 lb); and a vehicle mass of 4580 kg (10,100 lb).

The Condor capacitor-hybrid is priced at 14.5 million yen (or about $123,000, at a $1-to-118-yen exchange rate)—two and a half times as expensive as a conventional diesel-powered version. However, its owner could receive up to 5.3 million yen in incentives and assistance from the government and industrial organizations for its ultralow-emissions capability.

If Nissan Diesel's sales plan for the Condor capacitor-hybrid truck is modest, it has a more ambitious plan for the Super Capacitor, which is produced at the company's Ageo factory in Japan. It is hopeful in marketing this superior electric energy storage unit to other manufacturers.

Hino Motor, the medium- and heavy-duty commercial vehicle specialist in the Toyota Group of companies, has announced a new switchable parallel/series hybrid system that can operate in either mode. As in the Nissan Diesel Super Capacitor project, the research and development was undertaken under the NEDO ACE project objectives for high-efficiency, clean urban public transport.

Nissan Diesel produces Super Capacitors at its Ageo factory in Japan.

The system consists of a diesel engine, permanent-magnet synchronous motor/generator, and a conventional transmission with two mechanical clutches—all placed in line and longitudinally. The first clutch is positioned between the engine and motor/generator, and the second between the motor/generator and transmission. Electricity is supplied to the motor via an inverter for propulsion, and braking energy is converted to electricity and stored in an ultracapacitor.

The operating principle is not unlike that of the Toyota Prius hybrid car. The motor moves the vehicle off and drives it during light load conditions. Both the engine and motor join to accelerate the vehicle and provide power for high-load operation. The engine is employed for constant cruising, with the motor/generator recharging the capacitor as required. Braking energy is transformed into electricity, recharging the capacitor as well as assisting retardation.

About 300 urban route buses employing Hino's HIMR parallel diesel/electric hybrid system are in operation. The new series/parallel system is a further step in improving fuel efficiency and reducing emissions. Hino claims an improvement of about 80% over a conventional diesel bus.

- Jack Yamaguchi

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