Electro-hydraulic control in the automatic transmission of automobiles requires the permanent application of a constant oil pressure to supply the actuators. An arrangement in which the pumps used for this purpose are driven by the combustion engine has its disadvantages: They either have to be re-started after every stoppage or run constantly in stand-by mode with a bypass valve. So there is a need for new solutions, particularly in conjunction with modern energy-saving concepts such as automatic start/stop, hybrid drives and gearbox "sailing mode". This is where compact, powerful electric motors supplying the necessary oil pressure really come into their own.
As automatic transmissions require the constant application of hydraulic control pressure, the inevitable leakage oil has to be replaced. Electrically driven oil pumps only operate when oil is actually required. Which is why the drive specialists from ebm-papst St. Georgen (see box) have developed an alternative concept to the mechanically operated control pressure pump: Electronically commutated DC motors (ECI) in the oil sump only drive an oil pump when necessary and independently of any mechanical connection. This paves the way for optimum electronic transmission management.
Customized electrical contacts and design versions are possible - for instance, integration of a pump flange into the motor end shield to reduce the number of interfaces. Combining motor manufacturing with coordinated process control and an analytical laboratory for constant production monitoring guarantees high quality assurance.