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Keeping watch on car emissions
Control of automobile exhaust emissions relies increasingly on On-Board Diagnostic systems.
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In many fields, innovation is driven as much by regulatory change as by ‘technology-push' or ‘market-pull'. In the automotive sector, manufacturers and component suppliers have, since the days of Ralph Nader's campaigns for improved car safety in the US during the 1960s and 1970s, responded to ever stricter environmental and safety legislation with an astonishing series of innovations. Competitiveness has been determined to a large extent by the ability to respond rapidly and cost-effectively to new laws, and patents have been a key tool.
In particular, automotive emissions have been and still are of great concern for environmental policies, because they are a major source of air pollution. For instance, in the US, they account for approximately 77% of carbon monoxide and 45% of ozone-causing nitrogen oxides. Methods employed to cut emissions are a combination of ever more sophisticated engine management systems, which reduce the amount of pollutants being formed, and devices in the exhaust system which neutralise any pollutants that leave the engine.
The most familiar device is the three-way catalytic converter installed on petrol cars, which converts carbon monoxide, NOx and hydrocarbons to the atmospheric gases carbon dioxide, nitrogen and water vapour. Diesel cars are equipped with even more complicated catalysts to take care of the treatment of soot particulate.
Catalysts are reliable but are not immune to failure. They can be damaged by overheating or ‘poisoned' by fuel contaminants such as lead and sulphur. Mechanical damage can also cause them to fail. So how can a car driver be sure that the catalyst is working correctly and that the exhaust emissions are within legal limits?
The answer is an On-Board Diagnostic (OBD) system which - among many other things - continually monitors the performance of the engine and exhaust.
Stringent standards for vehicle emissions
From 1970 on, the Environmental Protection Agency (EPA) of the US introduced a series of emission standards and requirements for the maintenance of vehicles. The development of OBD systems is to some extent the result of these standard-setting activities.
Indeed, a forerunner in the development and implementation of both OBD legislation and OBD systems is the United States, in particular the State of California, which introduced the first generation of OBD systems (OBD-I) in the 1980s. At federal level, the amendment of the Clean Air Act in 1990 mandated the compulsory installation of the sophisticated second generation standard (OBD-II) for all light-duty vehicles and trucks built since 1 January 1996. Although Japan formally mandated the implementation of OBD-II systems since October 2000, Japanese automobile manufacturers installed this type of system also since 1996.
In the European Union, the most stringent standards for vehicle emissions - as embedded in Euro III, IV and V standards for the years 2001, 2006 and 2009 respectively - are included in Directive 1999/96/EC. From 1 October 2005, new types of vehicles, and from 1 October 2006, all types of vehicles, should be equipped with an OBD system or an on-board measurement system (OBM).
"It comes as no surprise that the years directly following the crucial years, 1990 (in the US) and 1999 (in the EU) show a substantive increase in the volume of patent applications for OBD technologies", says Cees Withagen, Professor of Environmental Economics at the Free University of Amsterdam, who - together with Dr. Frans de Vries, Assistant Professor of Law and Economics at the University of Groningen - has made an extensive study of the relationship between patent applications in various fields and the preceding policy measures taken, including measures for OBD systems.
The Euro V standards place tighter limits on the emissions of hydrocarbons, oxides of nitrogen (NOx) and particulates, and will force car makers to clean up their emissions to the limits of available technologies.
Monitoring and Diagnosing the Efficiency of Catalytic Converters
Three principal technologies are used to monitor the conditions in the exhaust. An early one was patented by Bosch
(1)
and relies on two sensors that measure either the air/fuel ratio (lambda sensors) or the amount of oxygen (oxygen sensors) in the exhaust gases upstream and downstream of the catalyst. The catalyst promotes a reaction in which oxygen is consumed, so - if it is working correctly - oxygen will be removed from the exhaust gas and the sensors will reveal the difference. Lambda and oxygen sensors are expensive, so subsequent developments have relied on a single sensor downstream or upstream of the catalyst with the OBD comparing actual air/fuel ratio or oxygen level with that predicted by a model.
A second method, first patented by Nissan
(2)
, is to measure the temperature of the exhaust gas. The same reaction that consumes oxygen also generates heat, and the OBD system looks for evidence that the downstream gas is hotter than it would be if the catalyst were not working. Temperature sensors are cheaper than lambda sensors and can be used over a wider range of operating conditions. A recent patent by Degussa
(3)
shows a more sophisticated application of this principle. It is also possible to use sensors that respond directly to concentrations of the pollutant gases e.g. NOx. While these are common in test benches and workshops, they are too expensive to be fitted routinely to cars.
A third technology is used in diesel particulate filters. One consequence of the proposed Euro V standards is that all new diesel cars will need to be fitted with filters to remove the smoke from the exhaust gas. Accumulated soot is periodically burned off to ‘regenerate' the filter. As the soot builds up, so does the exhaust back pressure and this can be detected by pressure sensors on either side of the filter. A method of doing this has been patented by Renault
(4)
.The OBD system uses the pressure difference to indicate when it is time to regenerate the filter, usually by introducing a small amount of fuel into it to burn off the soot. Temperature sensors can be used to monitor the regeneration process and ensure that it proceeds properly.
This trend towards modelling the expected behaviour of the devices will continue, says Boye. "My impression is that car manufacturers want to rely more and more on the use of models for predicting the exhaust gas content, based on vehicle conditions and engine operating conditions. In this way the number of sensors is reduced to a minimum."
The OBD system will also need to monitor the new NOx storage catalysts required for lean-burn engines, but here again the trend is towards the use of models. "Two years ago, manufacturers wanted to make use of NOx sensors. But now they are trying to estimate the regeneration cycle of the NOx storage catalyst as they do for particulate filters," Boye says. "They want to avoid having a lean NOx sensor, and they want to avoid having a pressure sensor for the particulate filter."
From 2010, heavy goods vehicles in the US will also have to be fitted with OBD-II, and that introduces new demands for robustness and resistance to tampering. Further ahead are proposals for a third generation system, OBD-III, which will allow roadside testing of vehicle emission control systems by police officers or other authorised persons. At present motorists can ignore the dashboard indicator warning of catalyst malfunction, but in future they may risk prosecution if they drive with a defective catalyst - in much the same way as they already risk a fine if they drive with worn tyres or defective lights.
"Modern OBD systems will have to cope with all these developments and make sure that no manipulation is possible," says Boye. "So they will become even more complex."
From the perspective of patenting
As all examiners, Boye takes decisions about many patents a year. He is witness to the patent practices in the world of automotive patents. "Companies often hand in patent applications which appear to protect tiny details, and the examiners make sure these applications meet the standards of novelty and non-obviousness, if and when they are granted."
This occasional hurry to protect apparently minor inventions is a consequence of the highly competitive structure of the modern automotive industry, which has seen a small number of manufacturers outsourcing most of their engineering to a large number of suppliers.
Some specialist car makers, such as BMW and DaimlerChrysler, are still involved in the global engineering of their vehicles and many of their components, while others are now mainly concerned with design and branding, and buy in components from outside. First tier suppliers such as Bosch and Delphi have world markets in their own right, too, while second tier suppliers may only supply local markets and may even have just one customer.
The component supply and car manufacturing sectors both devote about 4% of their revenues to R&D, but suppliers have a much higher propensity to patent their inventions, as they have many more competitors trying to grab a share of their market. Of course, they protect them with regard to other suppliers rather than car makers themselves, which are their own customers. Car manufacturers, on the other hand, do not use patents to attempt to obtain a monopoly, but just to neutralise their competitors' patents.
But when is a claimed invention too trivial to be patented? "We have the concept of inventive step," Boye explains. "This is an important requirement to maintain high quality standards in the European Patent System. Often it involves a borderline decision, and we do find our way through it."
Patenting investments related to On-Board Diagnostic technology grew strongly in 1999 and 2000. (Click to enlarge )
February 2006, Bruxelles
- Journalist: Tony Jones, European Service Network
- Expert Opinion: Cees Withagen at the Free University of Amsterdam, and Frans de Vries at the University of Groningen; Michael Boye, Marcus Döring, Marios Sideris, and Philippe Vessière at the EPO.
- Chart and Data Research: Silvio Endrizzi, EPO.
- Photo Portrait: Erika Valencia, EPO.
- Research and Co-ordination: Leo Giannotti, EPO.
(1) DE2328459
(2) GB1373826
(3) EP1136671
(4) EP1316693
References:
F.De Vries and C.Withangen (2006) : Overview of OBD Legislation in the United States, Japan and Europe
M.Sideris (Elsevier bv.,1998) : Methods of Monitoring and Diagnosing the Efficiency of Catalytic Converters