Automotive engineers are weight-conscious and always hunting for ways to trim it from a car or truck.
With that regard, Siemens/VDO, the automotive unit of Munich-based Siemens AG, thinks it’s on to something. It has developed a method to make brakes systems lighter and more potent.
It’s the electronic wedge brake. Unveiled at the 2005 Frankfurt Motor Show, it has attracted a good deal of interest from carmakers, said Brad Warner, spokesman for the Siemens/VDO research center in Auburn Hills, Mich.
Warner said Siemens/VDO cannot name names but says the electronic wedge could change the shape of automobiles when the first system shows up, expected in 2009, he said.
Bernd Gombert, the German engineer who holds the patent, says it’s the next step to brake-by-wire systems, that operate without mechanical or hydraulic linkages, in cars equipped only with 12-volt vehicle electrical system. Replacing the linkages with sensors and actuators creates more interior room in cars or allows them to be downsized.
Automakers have kicked around brake-by-wire technology in passenger cars for the more than a decade. In conjunction with that, they also have experimented with 42-volt electrical systems to accommodate such added electrical features.
David Cole, director of the Center For Automotive Research, says the 42-volt systems are expensive, relative to 12-volt systems, and will require cars to be rewired. Cost-cutting has stalled the 42-volt’s development, says Cole.
Gombert, however, says his system doesn’t need the juice from a 42-volt battery, making it considerably less expensive.
“It used to be the mechanical parts accounted for 70 percent of the cost of brake systems and electronics about 30 percent,” said Gombert, adding that wedge brakes will require “about 30 percent hardware and 70 percent electronics.” Siemens/VDO tests also demonstrate that vehicles with the wedge can stop in a shorter distance without brake fade, Gombert said. The system even keeps tabs on the brakes’ condition for the driver, he said.
Gombert points out that the idea is not all that new. Wedges were on wagons and carriages in the 18th and 19th Centuries. The are also widely used on tractor-trailers and heavy-duty trucks, according to Mike Pennington, a spokesman for ArvinMeritor, which make brakes for big rigs.
Siemen officials added that the technology behind the electronic wedge brake eliminates the need for components such as hydraulic pipes, brake cylinders, brake boosters or anti-lock braking control units.
This reduces weight and improves brake reliability, he said. Monitors will tell the driver when maintenance is necessary. The electronic wedge brake also can be converted into a parking brake with the flip of a switch, doing away with the need for a separate one of those, too. Gombert says the mechanical decoupling of the brake and pedal can eliminate the the often vexing pulsing of the ABS. Because the shift to such radical technologies can disquiet longtime drivers, a brake pedal will remain.
Carmakers may even build some resistance and travel into it to give the driver a feeling of control similar to that he has now, Gombert says, though but all the heavy lifting will be handled by the electronic actuator.
Warner notes that Siemens/VDO has two decades of experience with the electronic accelerator pedal, which is standard on millions of vehicles. That’s how electronic fuel injection works: Pressure on the accelerator electronically transmits the driver’s demands to the electronic engine control unit, Warner said.
In the future, driver assistance systems will monitor traffic and actively aid the driver in emergencies by operating the brakes and throttle, Siemens researchers say.
Gombert’s technology is one of the foundations those driver assistance systems, Warner said.
In fact, Siemens was so impressed with the wedge brakes that it bought Gombert’s company, eStop. He’s now executive vice president and chief technical officer of Siemens/VCO’s Body & Chassis electronics division.
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The wedge
Bernd Gombert, the German engineer who holds the patent for the electronic wedge brake, says cars with the system will have an intelligent braking module on each wheel.
The module consists of the brake pad, the wedge and wedge-bearing mechanism, the mechanical power transmission between ? two electric motors and sensors to monitor movement and force.
1. The sensors precisely measure wheel speed several hundred times per second and braking forces and wedge position.
2. When the driver presses the brake pedal, the system electronically tells the brake modules to go to work. When the signal is received, electric motors move the wedge into the optimum position to stop the car, according Siemens/VDO.
3. As the vehicle brakes, the pad attached to the wedge is pressed between the brake caliper and disk. As the wheel turns, the wedge effect intensifies, permitting the necessary braking power with the least complexity, said Gombert.
— Joseph Szczesny
