Electric power steering apparatus

An electric power steering apparatus comprising:

• an electric motor having an output shaft;
• a speed-reduction mechanism for reducing rotational speed of said output shaft of said motor;
• a discrete power circuit board having power circuit parts mounted thereon, said power circuit parts including semiconductor switching elements for supplying electric power to said electric motor;
• a discrete control circuit board having general circuit parts generating little heat, said general circuit parts including a microcomputer for controlling said semiconductor switching elements according to an output signal from a torque sensor for measuring steering torque and according to an output signal from a vehicle speed sensor for measuring vehicle speed;
• a circuit case body made of an insulating material including an insert-molded wiring conductors and having a first connector adapted to connect with said torque sensor, a second connector adapted to connect said vehicle speed sensor and a third connector adapted to receive an electric power supplied from outside, said first, second and third connectors are integrally molded with said circuit case body;
• a heat sink for dissipating heat from said power circuit parts on said discrete power circuit board, said heat sink being mounted to said speed-reduction mechanism;
• and
• a controller formed by said discrete power circuit board, said discrete control circuit board and said circuit case body;
• wherein said discrete power circuit board and said discrete control circuit board are located opposite to each other along the axis of said output shaft of said electric motor within said circuit case body of said controller;
• and
• said electric motor and said heat sink are combined in such a way that said controller is sandwiched between said electric motor and said heat sink.