14-Dec-2010 18:26 GMT

The HR12DDR version of Nissan’s 1.2-L inline triple features direct fuel injection with two injectors per cylinder and an Eaton-supplied Roots supercharger. The engine operates on the Miller combustion cycle to achieve sub-100 g/km efficiency.

The electric car dawn may be fast approaching at Nissan, but the recently introduced 2011 Leaf EV represents only one of the company’s two-pronged vehicle strategy. The other part of the plan is “Pure Drive,” aimed at developing vehicles with high-efficiency internal-combustion engines (ICEs), transmissions, and hybrid systems.

The new March, known internally as K13, is the first of the Pure Drive efforts. According to Chief Vehicle Specialist Tsuyoshi Kobayashi, the car surpasses what he calls the “Magic 20” mark, a measure of the car’s efficiency. The “20” part refers to 20 kilometres per litre of fuel consumed, as measured on Japan’s rather optimistic 10/15-mode urban cycle. The new March achieves a claimed 26 km/L (about 61.5 mpg)—best in its class in the Japanese market.

In terms of fuel efficiency, the new March exceeds that of many Ka-class (660-cm³) mini vehicles. The achievement was “fervently wished for by our customers, dealers, and more so by us,” said Kobayashi, who is responsible for the car’s new V platform (the V stands for versatile).

CVTC, dual injectors are enablers

The car’s CO₂ emissions are 114 g/km, as measured by the UN ECE 101 standards. Yet Nissan wanted to challenge two-digit CO₂ numbers of the latest European diesel small cars with a gasoline engine model. It does so with the new European Micra, made in India and powered by a special HR12DDR version of the HR12 engine family. The car achieves a remarkable 95 g/km.

The new Micra’s 1.2-L three-cylinder engine is armed to the hilt with technology. It features direct fuel injection, an Eaton Roots-type supercharger, dual continuously variable cam phasers for valve timing control (CVTC), sodium-cooled exhaust valves, hydrogen-free DLC (diamond-like coating) piston rings, and oil jets for cooling the undersides of the piston crowns.

A Nissan engineer confided that the new gasoline engine is still less expensive than a comparable small-displacement diesel equipped with high-pressure common-rail injection, variable-geometry turbocharger, and a complex exhaust after-treatment.

The HR12DDR operates in the Miller (Atkinson) cycle. The enabler is the dual CVTC allowing late intake valve closing, thereby greatly reducing pumping loss. A high-compression ratio of 13:1 is quoted; however, it is really the Miller cycle’s expansion ratio that is comparable to a +9:1 compression ratio in a conventional engine.

The supercharger, equipped with an on/off clutch, is employed under heavier load and high rpm, staying dormant otherwise.

The supercharged HR12DDR produces power and torque equivalent to a naturally aspirated 1.5-L engine, according to Nissan. In its initial high-performance and super-frugal application in the Micra, a manual transmission and the Xtronic CVT with sub-geartrain will be offered.

Another new Pure Drive development is found in the Japan-market Juke, which is powered by an updated version of the HR15DE DOHC 1.5-L four-cylinder that was first introduced in 2004 in the Japanese Tiida (Versa). While inheriting the same designation, the new engine features significant changes.

First, it employs dual injectors per cylinder. The original HR has a single injector with 12 holes—six each injecting into one of the two intake ports. In the new engine, each of the intake ports has its own injector with 18 miniscule holes. As in the HR12DE triple, the straight port design that promotes charge tumble has replaced the double-deck version fitted with tumble-generating flap valve. Reduced air resistance brings a gain of about 4 kW (5.4 hp), according to Nissan.

The dual-injector HR15DE is equipped with dual CVTC, vs. the original engine’s intake-only version. The addition of phasers on both camshafts enables later exhaust closing and earlier intake opening, increasing overlap during steady-state operations, thereby reducing induction resistance. The dual CVTC also allows a late intake valve closing during idling, in a semi-Miller-cycle manner. This reduces pumping losses.

Using a high 10.5:1 compression ratio (and still content with regular grade gasoline), the dual-injector HR15DE produces 84 kW (113 hp) at 6000 rpm and 150 N·m (111 lb·ft) at 4000 rpm. The Japanese Juke is equipped with the Xtronic CVT with a sub-geartrain, providing a wide ratio span of 7.3.

A high-performance, all-wheel-drive model in the Juke range is powered by the new MR16DDT direct-injection, turbocharged engine. The MR is Renault-Nissan’s midsize inline four-cylinder engine family covering 1.6 to 2.0-L displacements. The 1.6-L MR16DDT produces 142 kW (190 hp) and 240 N·m (177 lb·ft).

Nissan is pursuing a vigorous downsizing path via direct injection and supercharging, the foremost and most determined effort among the Japanese OEMs.

The MR16DDT-powered Juke will be equipped with an advanced all-wheel-drive system with rear torque-vectoring facility.

Another new Nissan engine, the MR9R, is a diesel member of the MR family. It is an original Renault design that Nissan worked on to meet Japan’s Draconian exhaust-emissions requirements. Thus powered, the X-Trail compact CUV is the only Japanese market entry to satisfy the regulations and be commercially offered in the country. (The only other “qualified” diesel passenger car at this time is the Mercedes-Benz E350 BlueTEC.)

The X-Trail exhaust after treatment system employs a new lean-NOx trap (LNT) catalyst, which Nissan claims is a world first in terms of its practical use. A long-awaited six-speed automatic transmission is now available in the diesel X-Trail.

7-speed hybrid transmission

The production version of a Pure Drive hybrid made a fall debut in the Nissan Fuga/Infiniti M luxury sedan. The system, previously detailed in AEI, is a parallel hybrid featuring a single motor and lithium-ion battery pack. The propulsion system comprises (as viewed from the front of the car) the VQ35 3.5-L V6, a single dry-plate clutch, an electric motor, and a JATCO seven-speed planetary gear automatic transmission.

The forward single dry-plate clutch (clutch No. 1) and the automatic’s rear clutch (clutch No. 2) are used to alternate between electric, ICE, and electric/ICE combined and regenerative modes.

The single-plate dry clutch (not unlike that in a manual gearbox car) and motor occupy the space previously occupied by the torque converter, thus fitting within the same transmission length. In fact, the hybrid transmission is based on Nissan-JATCO seven-speed automatic.

As sampled by AEI at Nissan’s Japan proving grounds, the car moves off the line and shifts through gears electrically, and at up to 70 to 100 km/h (43 to 62 mph), with the ICE cut off. Clutch No. 1 engages on the fly and starts the engine, determining engagement based on appropriate speed, load, and SoC (state of charge) in the process.

Nissan’s fleet-test program in the Los Angeles area, with each session lasting a week and including frequent freeway trips, showed that the car ran 59% of the time with the engine off—i.e., either running electrically or coasting/regenerating.

Nissan reports that fuel consumption was on par with a compact 1.8-L car while providing better than 3.5-L V6 on-road performance.

Jack Yamaguchi

Powertrains – Automotive Engineering International Online

SMA560 MEMS acceleration sensor for airbag control units
· Two sensing axes with separate measuring-range selection

· Measurement values output in Bosch-SPI or Open-SPI format

· SOIC8 package replaces SOIC14n package

The dual-axis SMA560 model for airbag control units marks Bosch’s entry into the fifth generation of micro-mechanical acceleration sensors. As opposed to sensors of the previous generation, this new model, in its SOIC8 housing, combines space savings of more than 40 percent with an unprecedented variety of functions. This means that circuit designers can assign one of four measuring ranges to each sensing axis independently. Via the serial peripheral interface, the sensor outputs the measuring values in either Bosch-SPI or Open-SPI format. The SMA560 can currently be ordered as a sample. The SMA550 sensor is available with the same parameters but with only one sensing axis – both are RoHs-compliant.

Flexible application
With two sensing axes, the SMA560 is ideal as a central sensor for the detection of frontal and side impacts. To record the different deceleration forces with even greater accuracy, application engineers can set the sensor’s measuring ranges for the two axes as required – to ±35 g, ±48 g, ±70 g, or ±96 g. The sensor can be operated with an operating voltage of 3.3 or 5 volts and consumes significantly less power than its predecessor. The wide operating temperature range of –40 °C to +105 °C and a self-test integrated into the sensor’s electronics ensure that the high standards of operating reliability required for airbag components are met. The bi-directional 16-bit SPI interface provides the measuring signal in 10-bit resolution.

In the fifth generation as well, Bosch’s sensor developers have elected to keep the tried and tested dual-chip solution within the sensor. Micro-machined microscopic springs and weights form the capacitive readings recorder; just one millimeter from this, an ASIC integrated into the sensor housing takes care of the signal conditioning and other electronic functions. Depending on the measurement values of the acceleration sensor, a control unit decides whether to activate the restraint systems, such as airbags and seat belt tensioners.

Expertise of the leading MEMS sensor manufacturer
From the very beginning, Bosch has played a key role in the development of MEMS technology (Micro-Electro-Mechanical Systems). The company has produced well over one billion MEMS sensors since production began in 1995. Some 220 million sensors left its Reutlingen plant in 2009, making Bosch the leading provider in the global MEMS sensor market. The company’s product portfolio includes pressure, acceleration, and yaw-rate sensors for numerous applications in the automotive industry and consumer electronics. The first MEMS acceleration sensors for airbag systems were launched in 1996, at that stage still in the PLCC28 package. The package size has been reduced step by step as a result of continuous further development. The SOIC16 package premiered in 2002; the SOIC14 package followed in 2006, and now gives way to the even smaller SOIC8 variant. For more information on Bosch’s sensor program, go to www.bosch-sensors.com.

Additional information can be accessed at www.bosch.com