The Development of ECU-Integrated Electric Oil Pump for Powertrain 2017-01-1229
Electric oil pumps (EOP) for automobiles are used to lubricate and cool moving parts and supply oil pressure to components. Conventional EOPs consist of two separate units including a motor driver and a pump system comprised of a motor and a pump, which impedes layout flexibility for vehicles. To overcome this shortcoming, we have developed an ECU (electronic control unit)-integrated oil pump in which a driver, a motor and a pump are incorporated as a single unit. In the course of the project, we focused on improving vibration resistance and developing a compact design.
The first challenge was to improve vibration resistance because of the driver located in close proximity to the powertrain. Since the driver is installed on the motor unit via electrically welded bus bars, the joints of the driver and the bus bar become susceptible to vibration. As a solution, the newly developed spring plate is inserted in the limited space between the bearing holder and the bus bar ring, which significantly reduces resonance of the bus bar ring.
The next focus was to develop a compact design by shortening the shaft length and developing a highly efficient internal gear pump. The shaft length is significantly reduced by fewer bearing parts and the single motor/pump shaft design. The total shaft length is 27 % shorter and the developed EOP is 10 % lighter, compared to conventional EOPs. To improve the efficiency, we obtained the optimized gear pump side clearance applicable to a wide range of oil temperatures ranging from -30 °C to 130 °C. These design improvements have led to the total efficiency of the motor and the pump exceeding 50 %, which is double the efficiency of conventional EOPs.
With these technologies, we have successfully developed a compact and highly-efficient ECU-integrated oil pump that offers greater layout flexibility.