Electric drive device and electric power steering device

An electric power steering device comprising:

• an electric motor structured to apply a steering assist force to a steering shaft, depending on an output from a torque sensor, wherein the torque sensor is structured to sense a direction of rotation of the steering shaft and a rotating torque applied to the steering shaft;
• a motor housing structured to house the electric motor, wherein the motor housing includes an end face part opposite to an output part of a rotating shaft of the electric motor;
• and
• an electronic control part arranged at the end face part of the motor housing, and configured to drive the electric motor, wherein the electronic control part includes a control circuit part, a power supply circuit part, and a power conversion circuit part;
• wherein
• the end face part of the motor housing includes a power conversion heat dissipation region and a power supply heat dissipation region, wherein the power conversion circuit part is mounted to the power conversion heat dissipation region, and wherein the power supply circuit part is mounted to the power supply heat dissipation region;
• the control circuit part is contained on a first circuit board, wherein the first circuit board is disposed along a first plane perpendicular to the rotating shaft of the electric motor;
• the power supply circuit part is contained on a second circuit board, wherein the second circuit board is disposed along a second plane perpendicular to the rotating shaft of the electric motor;
• the first circuit board and the second circuit board are layered with each other in an axial direction of the rotating shaft of the electric motor;
• the control circuit part, the power supply circuit part, and the power conversion circuit part are covered by a metal cover, wherein the metal cover is fixed water-tightly to the end face part of the motor housing;
• and
• the end face part of the motor housing includes a step between the power supply heat dissipation region and the power conversion heat dissipation region such that the power supply heat dissipation region projects away from the electric motor in the axial direction of the electric motor with respect to the power conversion heat dissipation region.