The electrification of drive trains based on internal combustion engines, engine start stop (ESS), hybridization and automation are placing new requirements on manual transmissions. Whereas the first engine start-stop systems are still based on traditional components, advanced generations of these systems will increasingly be integrated in the flow of information of vehicles thereby creating significant potential for improvements in comfort and energy efficiency. An important component for modern drive train solutions in this regard is Schaeffler’s sensor detent, a sensor element for detecting neutral gear. It reliably detects the selected drive position and sends this information to the control units incorporated in the vehicle. The system is characterized by high component functional integration and it is the result of consistent further development of existing components to incorporate new functions.
Classic detents have always traditionally been part of Schaeffler’s product range. They provide automobile manufacturers all over the globe with a large number of solutions that can be used to customize the gearshift “feel” of vehicles with manual transmissions to match specific brands and vehicles.
Schaeffler’s new detent combines an existing detent with a sensor for measuring lift. The Schaeffler sensor detent functions as follows: The forced stroke of the detent that occurs during gearshift operations is recorded and processed in the gearshift unit using the sensor on the detent and the relevant signal is sent to the integrated connector. Depending on requirements, the sensor can handle PWM (pulse width modulation) or SENT (single edge nibble transmission) protocols and can also output analog signals.
The sensor detent positions the gearshift unit in neutral in all shift gates and simultaneously detects this position. This ensures high accuracy.
In conjunction with the second detent of the gearshift, the system means that customer-specific demands in terms of gearshift and selection forces are met and the required gearshift comfort is ensured. The sensors used mean neutral position is detected without contact and therefore without wear. The sensor detent also detects reverse gear position and outputs the relevant signal. This means the contact reverse light switch and all mechanical interfaces are omitted. The standardization of the layout of the electronics and the programmability of the sensor (end of line programming) provides ideal adaptability.
Whereas first-generation neutral gear detection systems mostly comprise an add-on sensor with a separate magnet and are fitted on three mounting locations, Schaeffler’s new sensor detent does not require add-on components and it is fitted in only one installation location. Furthermore, the new detent means the selector shaft and the housing do not need to be additionally machined for mounting.
“The new sensor detent offers a highly-integrated solution for detecting neutral and reverse gear for manual transmissions and it creates one of the prerequisites for engine start-stop systems”, explains Stanislav Massini, Director of Advance Development and Mechatronics at the Shift Systems Product Line at Schaeffler. “Its high level of integration means some components, various fixing elements and some steps of the manufacturing process are no longer required.”
The new sensor system makes an important contribution to reducing fuel consumption and cutting harmful emissions and also enables vehicle weight and costs to be optimized. The Schaeffler sensor detent is already in volume production and is available for start-stop applications.
Romain Nicolas opinion:
Reliability of neutral position detection is key for Stop & Start application as inhibition of the function often depends on availability of signals like neutral detection, vehicle speed or starter status. Thus, improving reliability of such a sensor will automatically improve fuel economy over life time of the vehicle as it will increase the availability of the Stop & Start function. However, if product cost is taken into account, is the business case favorable considering the savings in terms of warranty cost?