Since tyre pressure monitoring systems (TPMS) became mandatory equipment on North American light vehicles, volumes have soared while profit margins have taken a nose dive.  As manufacturers face pressure to innovate just to maintain those margins at barely acceptable levels, Matthew Beecham reviews some novel technical advances in the TPMS arena.

There are basically two main types of TPMS available on the market: indirect and direct.  Indirect systems are those which use algorithms to interpret signals in ABS brake system. It uses wheel speed sensors and can detect a deflated tyre because it rotates more slowly. Direct are those which use separate radio sensors mounted in each wheel which detect deflation and then transmit that information to the driver via a radio frequency signal. By installing tyre monitoring systems, additional benefits include increased fuel economy, longer tyre wear, fewer crashes due to tyre blowouts, immobilised vehicles or poor vehicle handling from pressure loss and hydroplaning.

Why the sudden interest?

Thanks to the Firestone recall of 6.5 million tyres in North America during summer 2000, TPMS have become a big business. In the wake of tyre safety concerns, the US Congress passed the TREAD Act (Transportation Recall Enhancement, Accountability and Documentation) in November 2000.  The TREAD Act, among other things, required that the US National Highway Traffic Safety Administration (NHTSA) develop some rules and regulations that require all light vehicles sold after 1 September 2007 must have TPMSs fitted as standard equipment.  The TREAD Act also requires that TPMSs must be capable of warning drivers if a tyre is significantly under-inflated.

In response to mandates of the TREAD Act, the NHTSA published a ruling in June 2002 that contained provisions for both direct and indirect tyre pressure monitoring. 

Legal battles dampen growth

Three consumer safety groups went to court to dispute NHTSA's fulfillment of the TREAD Act that allowed carmakers to install what they claimed to be ineffective (indirect) TPMS.  In 2003, a three-judge panel of the US Court of Appeal for the Second Circuit ordered the NHTSA to re-write the rules.

Still, NHTSA dragged its feet for nearly a year, and the safety groups returned to the court in July 2004, asking it to order the agency to act.  In April 2005, the NHTSA released their final rule, requiring manufacturers to install a four-tyre TPMS that is capable of detecting when a tyre is 'more than 25% under-inflated' and warn the driver.   Manufacturers of direct TPMS were delighted with this announcement, claiming that only direct measurement systems can meet the more stringent NHTSA requirements.

Indirect methods, however, should not be ruled out. Sweden's NIRA Dynamics AB has been developing in directing TPMS for some time and claims their systems can perform the job less money.  Over the past year or so, Dr Urban Forssell, president and CEO of NIRA Dynamics AB says the company has "increased our business with our lead customer and also started development projects with several new customers." 

Final ruling opens the floodgates--

Although NHTSA's final ruling on mandating direct TPMS in the US has certainly clarified the position for the automotive industry, the murky legal situation has led to postponed orders by the OEMs for TPMSs.  "Over the past three years, our TPMS business has been rather flat," said Dr Rainer Podeswa, member of the executive board, responsible for R&D with Sales OEM, Beru AG.  "But we expect a distinct rise in unit sales in 2006 and 2007 due to the mandatory introduction of direct-measuring systems for vehicles newly registered in the US and the ramp-up of existing orders from German carmakers for US export." Podeswa says the company has won a "major order" from a German carmaker that plans to fit all of its vehicles destined for export to the US with its TSS as standard equipment starting this year.  Podeswa added: "Other German producers also intend to incorporate Beru's TSS as standard equipment in their vehicles exported to the US as of this year."  Beru already supplies TPMSs to BMW, Audi, VW, Porsche, and DaimlerChrysler as an optional extra.   About three-quarters of the company's production is for these German-built vehicles destined for the US.  The rest is for the European and Asian markets.  "Although all of the premium car manufacturers offer direct TPMS as an option in Europe, the take-up rates are disappointing," said Podeswa. 

--for a commodity market

SmarTire has also been in the TPMS business for some time, serving the OE and aftermarket.    In explaining the impact of the NHTSA final ruling on its TPMS business over the past year or so in the US, Richard Whitehead, marketing manager for SmarTire Systems Inc said:  "The legislation has been interesting for us in that it has changed tyre pressure monitoring from a value proposition business to that of a commodity. When we were preparing for the NHTSA ruling it seemed that tyre pressure monitoring was really the place to be for regular passenger cars because it was a guaranteed industry.  But as soon as that took place, the product became a commodity and automakers were no longer looking for the best system but the cheapest.  Yet SmarTire has always been positioned in the market place as the premier TPMS supplier.  We have the best system in the market but the Big Three weren't interested. Consequently, we decided to target the high-end automotive market.  We are now on Aston Martin, Morgan and Bentley vehicles.  So the NHTSA legislation changed our target from mass market to more nice markets.  It also supported the expansion of our product line into different market verticals."

As far as the Japanese market for TPMS is concerned, growth rates have been slow, as Ryozou Okumura, deputy general manager of Denso's body electronics components business, said:  "We see that the growth rate in Japan has been low for the past several years.  The increase of run-flat tires in the market is driving the demand for tyre pressure monitoring in Japan."  He added that the Japanese car makers adopt both direct and indirect systems for Japanese market, and direct systems for the North American market to meet the legislation.  In commenting when we could see legislation for TPMS in Japan, Okumura added:  "We assume that such legislation will be introduced in Japan in about ten years."

Rich Wolfe, CEO, EnTire Solutions LLC also predicts "slow growth" for TPMS in the Korean and Japanese markets over the next five years  EnTire Solutions LLC is a 50/50 joint venture between TRW Automotive and Michelin, founded in September 2003. Headquartered in Farmington Hills, Michigan, Entire Solutions develops and sells a direct TPMS for passenger cars and light trucks serving the worldwide market.

As far as the Chinese market for TPMS is concerned, manufacturers expect a growth market but have yet to see it take off.   Pierre Menendes, corporate and technical communications manager for Michelin told us:  "Everything that can improve fuel efficiency and lower emissions is of prime importance in China. Having a correct pressure does improve fuel consumption efficiency and at the same time improves safety. Tire pressure monitoring systems are therefore a good device and with vehicles in China having more and more the latest technology, you can assume the systems will develop.  But it will take time."

Tomorrow's technology

Last summer, Beru introduced its third generation TPMS (which Beru refers to as its TSS, Tyre Safety System).  The new system consists of a control unit with integrated aerial, plus four electronic wheel-mounted devices. The sensor, transmitter and battery are combined into one unit. The technical advantage is that position allocation takes place by evaluating the rotation direction signals that comes from the individual electronic wheel units and are transmitted by radio.  Furthermore, the movement of the vehicle is evaluated in combination with the axle-specific separation of the wheel electronics.   Beru's Podeswa added: "Although we have bi-directional solution in series production it is an expensive system to produce.  The next generation, however, will be able to automatically detect the position of the tyre thereby eliminating the need for bi-directional technology.  For instance, if you change the tyre then the sensor will be able to automatically detect that change."

Siemens VDO and Goodyear have collaborated on the development of a second generation of tyre pressure control systems which warn drivers when low tyre pressure is increasing fuel consumption and tyre wear, dubbed Tire IQ. While Siemens VDO offers the electronics expertise, its strategic partner has the tyre-related know-how.  What makes this system different?  A spokesman for Siemens VDO Automotive told us:  "Tire IQ is more than just TPMS. It is the first validated intelligent tyre system architecture. Bringing intelligence into the tyre itself opens the door to new functionalities for improved vehicle safety and driving comfort. After proving the feasibility of electronics integration in passenger car tyres, Siemens VDO and Goodyear are now actively working on function development and commercialisation of the intelligent tyre."  How does it work?  "Tyre mounted IQ rings include a tyre electronics and a 360° antenna that ensures a bi-directional communication in the 130 kHz band.

When required by the ECU, a transceiver located in each wheel-well requests the needed information from the tyre electronics. These transponder-based tyre electronics then answers by sending the data back to the transceiver. The information is then processed in the integrated or stand alone ECU and then displayed on the Tire IQ information screen. The IQ rings are compatible with any tyres from any tyre manufacturer." Siemens VDO anticipate the market introduction for its intelligent tyre systems in 2012.

Meanwhile, Denso has developed and started the mass-production of a receiver and an electronic control unit (ECU) for the tyre pressure monitoring system, which meets the TREAD Act.   Ryozou Okumura, deputy general manager of Denso's body electronics components business, said:  "We are developing products for the next generation tyre pressure monitoring system that will be able to indicate the tire pressure for each tire position. Our most important new products in the next few years will be the components for a system that can indicate the tire pressure for each tire position. We are investigating additional functions for future tire pressure monitoring systems, along with working to improve product performances.  We cannot comment on the details."

In terms of its next generation TPMS, EnTire Solutions' Wolfe said:  "Over the next few years, EnTire Solution products will deliver smaller, lighter and less costly components that provide the same features and functions as today's enhanced and basic systems. In essence, EnTire Solution products will do more with less. For example, a 'basic plus' system which is a step up from a 'basic' system and is able to auto-locate tire position within minutes."

In the commercial vehicle market, Bridgestone has developed Aircept (a compression of Assistant Inner Ring interCEPTor), a tyre deflation safety device for large truck tyres. The Aircept system uses a rubber tube that fits between the wheel rim and the tyre. In the event of sudden tyre deflation, the new product will deploy to maintain sufficient tyre air pressure, enabling the driver to stop the vehicle safely. Neil Purves, manager, truck and bus OE engineering, Bridgestone Europe, told us:  "[Aircept] has been on Actros vehicles in serial production since November 2003 and a smaller number of vehicles on the road in Europe.  The Aircept has already proved itself in the field along with a couple of puncture cases where the vehicle has not only safely come to a standstill but has also been able to move off the road to get a tyre change." 

Continental Automotive Systems also offers both direct and indirect measuring systems for detecting air loss from tyres.   James Remfrey, head of technology benchmarking and placement, advanced development department, Continental Automotive Systems, said: "About six years ago, we introduced our DDS [Deflation Detection System], an indirect measuring system providing a warning signal when there is a decrease in tyre pressure within certain thresholds.  It used the ABS to monitor the speed of the wheels.  BMW was the first to use our system which proved to be a big success.  Today, we are also supplying our direct TPMS in-house technology in-house, combining it with other systems in the vehicle which we have considerable technical expertise.  For example, we are exploring ways in which to combine the use of vehicle antennas for remote keyless entry with tyre pressure monitoring.  We are also aiming to network our TPMS, DDS and ESP to contribute towards active accident avoidance, such as ESP control dependent of tyre pressure and load-dependent tyre pressure recommendation.  A battery-less sensor is under development.  The tyre will supply pressure and temperature data as well as useful ID information about the tyre itself."

Based in Northern Ireland, Schrader Electronics knows more about tyre pressure than most.  Its roots are in tyre accessory and component supplies.  Its founder invented the world's first tyre valve.  It has also been in the tyre pressure monitoring business longer than anyone else.  In summing-up tomorrow's TPMS technology, Carl Wacker, vice president of sales and marketing, Schrader Electronics, said: "The one thing that we shall see over time is more features being added using the data to enhance performance.  So we are actually going to see a proliferation of different products to match and align more with the market segmentation of the vehicle itself.  For instance, while low segment cars will have simpler TPMSs, high-end cars will come equipped with more complex systems, involving tyre pressure monitoring in other performance enhancement features like traction control."

Matthew Beecham