Siemens VDO Electronic Wedge Brake—Industry Is Skeptical
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Vol. 20, No. 4◆◆ www.hansenreport.com May 2007 Combustion Siemens VDO Electronic Wedge Pressure Sensors Brake—Industry Is Skeptical Find Production Compelling Reasons Needed to of a concept that has been around for a long time. EWB is an electromechanical The idea to use in-cylinder pressure Switch from Hydraulic brake that can be operated at 14 volts, sensors as part of a feedback control loop Ford and General Motors are seriously because it relies in part on the mechanical to manage the combustion event has been considering Siemens VDO’s Electronic advantage of the wedge. To actuate brak- talked about for decades. Now it appears Wedge Brake (EWB). General Motors has ing, an electric motor moves a wedge con- that they will finally be put into produc- a particular program in mind, a 2011 or nected to a brake pad located between the tion applications starting with 2012 fuel-cell hybrid. And Ford—once brake caliper and the brake disc. The rota- Volkswagen/Audi and General Motors Siemens can demonstrate production-in- tion of the wheel and the resulting fric- V6 diesel engines. Both new engines will tent actuator prototypes—will probably tion automatically reinforce the wedge go into production by the end of 2007. give Siemens a development contract, “so effect. Siemens began its efforts to indus- The end of 2007 is also when Beru we can do some rough testing and see trialize the wedge brake when it purchased (Ludwigsburg, Germany) will begin ship- what fails,” said Pim van der Jagt, Ford Bernd Gombert’s firm, eStop, in early ping its intelligent glow plugs with inte- manager of global vehicle dynamics. Dr. 2005. In late 2006 Siemens wrote in a grated strain gauge pressure sensors to GM van der Jagt would first consider the EWB press release, “The EWB is set for inclu- Europe and another European customer. for a low-volume hybrid vehicle, in order sion in every vehicle class, from economy According to Automotive Engineering Inter- to get field experience with it. “EWB is up to large trucks, in the medium term.” national, GM’s 2.9-liter engine “will debut interesting enough to put resources and Currently, 98 Siemens engineers are work- in the 2009 Cadillac CTS in Europe, and money toward developing it, but we’re not ing on the Electronic Wedge Brake. will also power Opel, Saab and Vauxhall 100% convinced it will work,” he noted. However, even high-tech pioneer models.” While the wedge brake is a well-publi- BMW isn’t jumping at the chance to In 2008 Volkswagen will begin ship- cized German invention, we could find no adopt the EWB. “We investigated electro- ping the new Touareg with its clean diesel German carmakers willing to champion mechanical brakes in the early 1990s. We engine, the BlueTDI, which meets even the technology as an alternative to hy- looked thoroughly at the pros and cons the most challenging U.S. exhaust emis- draulic brakes in conventional vehicles. and came to the conclusion that there is sion standards, the so-called Tier 2 Bin 5 That was somewhat surprising given the really no hard argument you can use to limits adopted by California, Massachu- propensity of the German auto industry to justify the electromechanical brake,” setts, New York, Vermont and Maine. The pioneer new technology. noted Heinz Leffler, in charge of brake engine will use an in-cylinder pressure Stephan Wolfsried is head of electrical/ and chassis development at BMW. “My sensor to optimize injection and combus- electronics and chassis development for personal view is, if I do not have a driver tion. the Mercedes car group. “The guy who that really requires power brakes it will be Stricter emission limits on nitrogen invented it [Bernd Gombert] came to Turn to Braking, page 3 oxides (NOx) and particulate matter Conti Teves, came to Bosch, to all the big (PM) in Europe have forced some diesel brake suppliers. All of them are very suspi- Convert Your Print Subscription engine-makers to consider using pressure cious about whether the wedge is a work- to an E-Subscription— sensors in anticipation of Euro 5 limits, ing principle. I have my doubts about which are scheduled to go into effect in whether Siemens will be successful, be- And enjoy the benefits of earlier deliv- 2009. Euro 6, which as proposed would cause after discussing it a couple of times ery of every issue of The Hansen Report. take effect in 2014, will place even stricter in this µ-Club, the community of all the E-subscribers have already read the May limitations on NOx and PM. By then brake guys in Europe, we don’t see a real issue of The Hansen Report online. pressure sensors will be used more widely. benefit in cost, weight or functionality. So You don’t need to wait until your current What’s special about the Beru imple- why would we bring an actuator into a print subscription expires to upgrade to mentation is the way the pressure sensor rough environment, with vibration, shock electronic delivery. We’ll credit the remain- and signal-conditioning circuitry is inte- and temperature?” der of your print subscription term toward grated into the glow plug, which at its tip Electronic Wedge Brake is the Siemens the cost of a new E-subscription. Visit Turn to Sensors, page 2 VDO brand name for an implementation www.hansenreport.com for details. Sensors... Continued from page 1 reaches 1,000 degrees Celsius. “The first Beru Pressure Sensor Glow Plug challenge was how to integrate a pressure sensor with a diameter of 20 mm into a plug glow plug with a diameter of 10 mm,” said Technical features of the PSG: ◆ Sensor principle: piezoresistive Ron de Groot, global powertrain strategy high current connection ◆ Flexible heating rod for pressure manager for Sensata, whose micro-fused transmission printed circuit board with electronics silicon strain gauge (MSG) pressure sen- ◆ Robust sealing element between body sor is built into the Beru glow plug. and heating rod “Normally, the glow plug has a heat ◆ Miniaturized electronics integrated in the seal rod, or pin, that’s press fit into the body,” upper part of the glow plug measuring diaphragm ◆ explained Hans Houben, vice president in Calibrated and customer-specific glow plug body charge of engineering at Beru. “To trans- programmed ◆ Integrated concentric automotive plug mit the pressure from the plug’s tip to the glow plug heating rod pressure sensor at the other end we made the pin moveable by means of a metal bel- lows, similar to the part used in piezoelec- Honda has developed a prototype of a either one sensor per engine for cetane tric fuel injectors. “We chose Sensata’s super-clean diesel engine slated for intro- detection, or one sensor per cylinder for pressure sensor because it is proven tech- duction in the U.S. market in 2008. The combustion control, as in premixed nology already used by the millions,” said prototype includes a cylinder pressure sen- charge compression ignition (PCCI) en- Mr. Houben. Sensata’s MSG sensor de- sor to detect the cetane number, a mea- gines. Cetane level detection may be nec- rives from the piezoresistive effect of sili- sure of diesel fuel’s ability to quickly essary in the United States, where the con, which changes in resistance as a ignite. However, Honda hasn’t yet de- quality of diesel fuel varies more than it function of mechanical stress. It is widely cided, or isn’t saying, if the production does in Europe. ◆ used to measure brake and fuel pressure. version will also include pressure sensing, Ludwigsburg Automotive Electronics Conference Worth the Trip As automotive electronics conferences The conference and exhibition is inti- go, this one, programmed by VIPs of the mate and very friendly with ample oppor- German car industry, is among the best. tunities to network and learn about what’s The Eleventh International Congress on next in automotive electronics. About Advances in Automotive Electronics, to 400 management-level attendees are ex- be held July 17 and 18, 2007, in pected, almost all of whom are multi- © 2007 Paul Hansen Associates, 150 Ludwigsburg, Germany, features two days lingual Germans. Pinehurst Rd., Portsmouth, NH 03801, of presentations by some of the leading Exhibit space for about 35 suppliers is USA. Telephone: 603-431-5859. Fax: 603- lights of the German auto electronics in- sold out. 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Back issues are available Audi; Uwe Michael, director electrical/ Mercedes-Benz. for $50 each. Index and multi-user electronic electronics systems, Porsche; and Walter It is produced by the German publica- subscription information is available at Kuffner, director electronics driving tion Automobil Elektronik and the Manage- www.hansenreport.com. Paul Hansen Asso- dynamics, BMW. ment Information Center. The conference ciates is a strategy and market research Each presentation is followed by a manager, Marcus Dworak, can be reached firm consulting to the electronics industry.