21 September 2015

Compact ECI motors provide hydraulic pressure

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 automat

Robust oil pump system with excellent dynamic operation even at high oil temperatures.
Robust oil pump system with excellent dynamic operation even at high oil temperatures.

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.

The experts from the Black Forest make use of dynamic internal rotor motors (photo) which operate in the oil sump. The drives must function reliably with cold oil at low speed with high torque and with hot oil at high speed with low torque. The space available in the oil sump of an automatic transmission varies greatly and often requires extreme solutions: A short motor with a large diameter or exactly the opposite, in other words a long, slim motor. This makes the NAG3, IEP and DL382 motors with stack diameters of between 40 and 76 mm and differing lengths the ideal basic components to enable power, torque and design to be adapted to user requirements. The wet rotor motors provide full coverage of the range from 100 mNm to 2000 mNm or 40 to 500 W output power. Thermally stable high-performance magnets permit applications at operating temperatures from well below 0°C to above 100°C. Specially selected materials and varnishes are able to withstand even corrosive additives in the oil. 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. Motor manufacturing with coordinated process control in combination with an analytical laboratory for constant production monitoring guarantees one hundred per cent quality assurance.

Anja Niessner
Phone: +49 7724 81-1311

ebm-papst St. Georgen GmbH & Co. KG
Hermann-Papst-Straße 1
78112 St. Georgen