Bosch: Clutch-by-wire prevents stalling, boosts mpg



BOXBERG, Germany -- Robert Bosch's eClutch system could help put manual transmissions back on car buyers' shopping lists.



The eClutch eliminates two things drivers dislike most about cars with stick shifts: stalling and frequent use of the clutch pedal in stop-and-go traffic.



The eClutch can also improve fuel economy between 5 and 10 percent, Bosch engineers say.



During a recent press event here, reporters test drove an Audi A3 hatchback that Bosch had fitted with an eClutch. The car uses a standard clutch pedal and shifter and looks like any other vehicle with a manual transmission. The drive was staged on the company's test track in a variety of driving conditions.



First, I tried to stall the car. With the engine idling, the clutch pedal pressed to the floor and the shifter in first gear, I removed my foot from the clutch pedal as fast as I could without accelerating. But instead of stalling, the A4 juddered slightly, then began moving smoothly. The tachometer needle barely wavered.



Bosch says its eClutch for manual transmissions

• Prevents stalling

• Eliminates frequent use of the clutch pedal in stop-and-go traffic

• Saves fuel



Later, while moving in first gear, I kept my foot off the clutch pedal and pressed the brake pedal. As the car slowed, the clutch disengaged and the engine idled patiently. When the car stopped, the engine continued idling smoothly.



Vehicles with manual transmissions have a clutch master cylinder and a clutch slave cylinder. The master cylinder is connected to the clutch pedal. It forces pressurized hydraulic fluid to the slave cylinder, which pushes a bearing against a spring-loaded plate that clamps the clutch disc to the engine's flywheel. Little has changed with this low-tech setup in the past 50 years.



With the eClutch, Bosch created an electric clutch master cylinder that is connected via sensors to the vehicle's engine computer, suspension and transmission.



By keeping tabs on vehicle speed and engine revolutions, the eClutch prevents stalling and smooths shifts. And that's where most of the fuel economy savings come from says, Kersten Wehmeir, a Bosch engineer who has worked on the eClutch since its inception.



"There is no system out there like it. It's clutch-by-wire. It's far less expensive than a dual-clutch automated manual transmission," he says.



If the system has a drawback, it's the clutch pedal's artificial feel. I could tell electronics were operating the clutch when I pressed the pedal. Though the pedal is easy to depress, it lacks feedback desired by drivers who prefer manual transmissions.



Wehmeir says Bosch is seeking its first customer for the eClutch.