Tech Briefs

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Tubular side airbags from Freightliner

Freightliner Trucks has introduced a Tubular Side Airbag System that is designed to reduce injuries to drivers of heavy-duty truck in rollover accidents. The system deploys a tubular-shaped airbag on the driver's side of the truck to cushion the driver's head during rollover. The system will be offered on the company's Century Class S/T and Argosy heavy-duty trucks.

"More than half of all heavy-duty truck driver fatalities occur during rollover accidents," said Gary Rossow, Director of Government Technical Affairs for Freightliner LLC. "The Tubular Side Airbag System addresses a leading potential cause of those deaths - head contact with the vehicle interior."

During a rollover accident, the driver's head and body often are propelled upwards and sideways as the truck proceeds through the rollover. Even a driver wearing a seatbelt is vulnerable to injury as his or her head strikes surfaces on the left-side interior of the truck. To alleviate these kinds of injuries, the system inflates a 0.7-m (2.3-ft) long, 0.01-m³ (0.42-ft³) airbag that extends from the A-post to the upper B-post. An integrated sensor monitors the truck's angular or roll acceleration and deploys the airbag as rollover begins to occur. The airbag is positioned at head-level so as the truck rolls over, the driver's head contacts the side airbag rather than the side window or surfaces above it.

According to Rossow, the airbag system differs in concept from the side airbags now available on some automobiles. "Most automobile side airbags are designed to protect the driver or passengers during a side-impact-type accident, where another vehicle impacts the side of the car causing head and body trauma to occupants," he said. "While the goal of Freightliner's Tubular Side Airbag is the same - injury reduction - our system specifically addresses the dynamics of a truck rollover accident, where a truck driver faces peril not so much from an exterior force but from the forces and motion generated by the rolling truck."

The system works in conjunction with Freightliner's Seat Pretensioner Activation for Crash Survival Enhancement (SPACE) system, an advanced occupant restraint system introduced in 1995. During a rollover or major frontal impact, SPACE pulls the driver away from the roof and steering wheel by automatically lowering the driver's air suspension seat and tensioning the seatbelt. Freightliner also offers a Driver Front Airbag that deploys from the steering wheel during a major frontal collision to cushion the driver's head and body from impact with the steering wheel, steering column, and other forward surfaces.

"The SPACE system pulls the driver away from potentially dangerous surfaces while the airbags cushion the driver's head from frontal or side impacts," said Rossow. He added that truck drivers must wear their seatbelts for these systems to be effective. "Wearing a seatbelt remains the fundamental way to prevent injury during any vehicle accident."

Accoridng to Freightliner, its Century Class S/T SleeperCab is the first North American Class 8 truck cab that meets or exceeds Swedish and European ECE R-29 and SAE crash test requirements. Cab integrity is retained even in a 48-km/h (30-mph) barrier impact. Other safety features include collapsible steering shafts, soft and rounded dash switches, and seatbelts that are easier to adjust and more comfortable to wear.

Production of trucks with Tubular Side Airbag Systems begins this year.

- Jean L. Broge

Ford research benefits senior drivers

Driver fatality rates increase past the age of about 50, according to research conducted by the National Highway Traffic Safety Administration (NHTSA). To improve safety for its older customers, Ford Motor Co. is researching and developing new methods of occupant safety including crash avoidance, crashworthiness, and post-crash assistance.

A need to better understand the special requirements of older customers led to Ford's development of the Third Age Suit in conjunction with the University of Loughborough.

Jeffrey Pike, Senior Technical Specialist at Ford, described crash avoidance as any feature or capability that will help avoid a crash directly or indirectly. Some concept technologies currently under development at Ford include a speed control that automatically slows the vehicle if it is getting too close to the vehicle in front or a speed control device that warns the driver that his vehicle is rapidly approaching another vehicle.

A night vision display is a technology that could warn the driver during nighttime, rain, or other poor visibility conditions by showing the road ahead, indicating if there is an obstacle and its approximate location. The display could be used as a navigational aid in other instances as well. "In concept, the display could also show outside vehicle signage, which prevents the driver from surveying and trying to read signs and, in doing so, not paying attention to the road," said Pike.

Crashworthiness refers to the safety performance of the vehicle if a crash occurs. One injury reduction concept is a seatbelt and airbag that adapt to characteristics of the driver and the crash. The concept considers seating, height, weight, age of the driver, and how fast the vehicle is going. During implementation, the seatbelt has limiting force, and the airbag inflates at different rates based on the above characteristics.

Post-crash assistance could include an automatic system that signals for help. "Because older drivers are more susceptible to being disoriented after a crash, a vehicle could feature a 'Where am I?' button," said Pike. "This button could tell the driver where he is and send out an automatic notification for assistance to an outside party."

The Focus was the first Ford product to benefit from extensive use of the Third Age Suit during the development stage.

Immediate notice of an accident to emergency workers can theoretically include information such as the number of vehicle occupants, their seating position, seatbelt usage, and airbag deployment. Such information would better prepare rescue workers when they arrive on the scene.

Additional post-crash concepts could include automatically activating emergency flashers and/or unlocking the doors when a crash occurs. Airbag deployment could also be used as a threshold for the vehicle's cell phone to automatically send an "SOS."

Ford's Third Age Suit - which looks like a cross between a beekeeper's protective gear and an astronaut suit - is a tool currently in use to help engineers and designers understand the physical limitations that sometimes accompany old age. The suit ages Ford engineers 30 years by restricting their agility and thus enables the engineers to better simulate and anticipate the driving capabilities and demands of aging baby boomers. The suit adds bulk and restricts movement in key areas of the body such as the knees, elbows, stomach, and back. Gloves that lessen the sense of touch and goggles that simulate cataracts also reduce capabilities. Developed in 1994, the Third Age Suit continues to be used in the ergonomics training of program teams.

"Ford's Third Age Suit and all of the extensive research combine to result in cars with features that are beneficial for everyone, not just older drivers," said Pike.

- Jean L. Broge

Toyota diesel catalytic converter

The word "diesel" is likely to conjure up the image of a necessary evil in Japan, with more emphasis on the noun than the adjective.

The island country offers no truck routes. Commercial vehicles, from small delivery vans to behemoth semis, travel on the country's trunk, suburban, and urban expressway networks, similiar to America's freeway system but slower and with hefty tolls. Heavy vehicles traverse on surface thoroughfares and peripheral roads in built-up commercial and residential areas, mixed with other wheeled and pedestrian traffic.

A Diesel Particulate-NOx Reduction (DPNR) 2-L catalytic converter for small displacement 2-L engines.

Commercial vehicles are invariably powered by the diesel engine because of its superior thermal efficiency and 30% lower fuel cost than the gasoline engine because of preferential taxation. However, the diesel is disliked and blamed for causing hazardous air pollution because of two toxic substances - oxides of nitrogen (NOx) and particulate matter (PM). The Governor of Tokyo plans to impose stricter emissions standards than the national ones, and he may openly discourage the citizenry from buying diesel-powered cars. Diesel passenger cars are sparse in Japan anyway because of their high initial purchase prices, noise, odor, and, more significantly, shorter average driving distances, which may not justify the initial cost.

Reduction of carbon dioxides has become increasingly important since it is a suspected contributor to the global warming effect. Toyota's approach toward the "ultimate eco (-logy and-nomy) automobile" is multi-pronged and includes the diesel for its high fuel efficiency and reduced CO₂ emissions.

If the two offending exhaust components, NOx and PM, could be greatly reduced, the diesel engine would be able to cast off its villainous image and emerge as a shining knight. Toyota's weapon is its Diesel Particulate-NOx Reduction (DPNR) system, and the company believes it will be able to kill the two noxious birds with one stone (AEI, October 2000).

DPNR is the development of Toyota's NOx-storage-and-reducing catalytic converter technology that has already been applied to some of the company's production lean-burn gasoline- engine cars. Metal platinum is used as the catalytically active substance that reduces NOx emissions. The DPNR converter substrate is not unlike a diesel PM burn-off filter, which is again similar to the spark-ignition engine's three-way catalyst. The Cordierite ceramic monolith substrate has the ends of honeycombs sealed off alternately. Exhaust gas, therefore, flows through the porous ceramic walls to adjacent channels, then to the rear exhaust pipe. As the exhaust gas flows through the monolith walls, it bounces through the complex pores, promoting reaction with the active substance.

The DPNR converter reduces NOx and PM simultaneously and efficiently, according to Toyota. During the lean operation, NO and excess oxygen (O₂) in the exhaust gas reacts with the platinum catalyst and changes to NO₂, which is absorbed into the storage layer. At the same time, very active oxygen (O*) is also stored. When the converter system is momentarily switched to rich operation, hydrocarbon (HC) and carbon monoxide (CO) react with the platinum substance. The stored NO comes out, reacting with CO and turning to N₂ and CO₂. O* also comes out of storage, adding to NOx reduction.

During the lean operation, O* and O₂ continuously oxidize particulates. In the rich operation environment, O* released from the storage catalyst layer continuously oxidizes PM. The DPNR thus requires no reduction agent, such as ammonia, in the additional hydrolysis converter in the selective catalyst reduction system.

A typical application of the DPNR is to combine it with a turbocharged, common-rail, direct-injection engine with EGR, placing the converter downstream of the turbocharger. A prototype 4.2-L powerplant equipped with the DPNR was shown at the Tokyo Commercial Vehicle Show. The DPNR for this system was a switching type, alternating exhaust gas flow directions within the converter casing. While not yet theoretically verified, the switch-over DPNR's PM-cleansing ability is greatly enhanced, likely because of enlarged wall areas and retention of heat within. The switch-over DPNR is particularly suitable to larger displacement commercial vehicles, while the single-direction variety is suitable for passenger-car diesels. The DPNR catalyst's volume is about the same as the engine displacement; an experimental 2-L unit is intended for a passenger-car engine with that displacement, and a switch-over unit for a 4.2-L engine.

There are certain provisos for the DPNR application. It has to be combined with an electronically controlled, common-rail direct-injection engine, which is within the technological grasp of the world's leading diesel engine proponents and is the direction taken by the latest compression-ignition engine technology. More urgent and difficult yet is a greatly reduced sulfur content, less than 50 ppm in the fuel. No such fuel is currently available commercially; however, the oil industry as well as the automotive industry are moving toward reducing sulfur content since sulfates coming out of the tail pipe is another environmental concern.

Toyota claims the DPNR technology is capable of reducing the two pollutants down to 20% of the current regulation levels measured by the current Japanese 1997/98 standards for both diesel passenger cars and trucks. A senior engineer hoped that the DPNR would take Toyota diesel-powered car models through the forthcoming Euro IV standards, the most stringent in the world.

Toyota hopes to put a DPNR-equipped vehicle in production in 2003, most likely a Dyna-size forward-control midsize truck powered by a 4.2-L common-rail DI engine, subject to the availability of low sulfur-content fuel. According to a senior engineer at Toyota, a Europe-destined passenger-car model is a possibility. The engineer conceded, however, that his company's diesel expertise had been limited to commercial vehicle engines under 4.2-L displacement, and the company would have to explore the adaptability of the DPNR technology to heavier commercial vehicles in cooperation with Hino, the bus and truck specialist in the Toyota group. The engineer was candid enough to admit that the DPNR-equipped diesel might have to be operated in a slightly richer air/fuel environment to make up for the reduced sulfur content, which would incur a small increase in fuel consumption.

- Jack Yamaguchi

Diesel sulfur removal from Phillips

Phillips Petroleum Co. is developing an advanced sulfur removal technology (SRT) for diesel fuels. Like Phillips' S Zorb SRT for gasoline, S Zorb SRT for diesel is a proprietary refining process that significantly lowers the sulfur content in diesel blending streams while maintaining other important characteristics. Although the diesel technology is not yet available for licensing, laboratory tests have shown that very low sulfur levels are achievable at significantly lower pressures than conventional hydrotreating processes.

"Test results indicate that this advanced process will help refiners meet current and future sulfur regulations in North America and Europe," said John Mihm, Senior Vice President of Technology and Project Development at Phillips. "One of the most exciting attributes of the process is its nearly zero net hydrogen consumption." Sulfur content levels are reduced during the process with a minimal loss in octane and low volume loss while operating at cycle lengths commensurate with fluid catalytic cracker units.

The Phillips' technology uses a regenerable sorbent that chemically attracts sulfur and removes it from hydrocarbon streams. Conventional hydrotreating technologies require high-pressure reactors to produce low sulfur diesel, which results in higher capital requirements and excessive operating costs. The S Zorb SRT for diesel, which operates at moderate pressures, shows an ability to reach ultralow sulfur levels without significant hyrdogen consumption. This low net hydrogen consumption is a critical issue for hydrogen-scarce refineries and those refiners wishing to minimize hydrogen dependency. As an additional advantage, the sorbent material can be regenerated while the unit is operating, allowing for prolonged run times between shutdowns.

The technology is expected to help minimize capital costs and everyday operating expenses while achieving targeted product quality. Pilot plant testing of S Zorb SRT for diesel is currently underway at Phillips' research and development facilities.

- Jean L. Broge

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