Electric drive device and electric power steering device

1. An electric drive device comprising:

a motor housing accommodating therein an electric motor that drives a mechanical control element;

a pair of supporting stems arranged so as to face to each other on an end surface, which is an opposite side to an output shaft portion of a rotation shaft of the electric motor, of the motor housing and extending in a direction of the rotation shaft which is an opposite direction to the output shaft portion;

a heat radiation base body arranged between the pair of supporting stems and extending in the same direction as those of the supporting stems;

fixing bolts screwed into the heat radiation base body from a radially outer side to a radially inner side through the supporting stems and connecting the supporting stems and the heat radiation base body;

one electronic control unit of a redundant system, the one electronic control unit arranged along a direction in which the heat radiation base body extends and having a board that is also arranged along the direction in which the heat radiation base body extends and that is fixed to the heat radiation base body with thermal conduction to the heat radiation base body allowed; and

the other electronic control unit of the redundant system, the other electronic control unit arranged along a direction in which the heat radiation base body extends and having a board that is also arranged along the direction in which the heat radiation base body extends and that is fixed to the heat radiation base body with thermal conduction to the heat radiation base body allowed.

2. The electric drive device as claimed in claim 1 , wherein:

the supporting stem is formed integrally with the end surface of the motor housing, and the motor housing and the heat radiation base body are made of the same metal.

3. The electric drive device as claimed in claim 2 , wherein:

the heat radiation base body is fixed to the end surface of the motor housing at a position close to an area where the rotation shaft is disposed, and

the one electronic control unit and the other electronic control unit are arranged at opposite sides of the heat radiation base body.

4. The electric drive device as claimed in claim 3 , wherein:

the heat radiation base body has fixing surfaces of the boards of the one electronic control unit and the other electronic control unit, accommodation recessed portions formed on the respective fixing surfaces, and fixing flat surface portions enclosing the respective accommodation recessed portions,

power conversion circuit boards that form the one and the other electronic control units are fixed to the accommodation recessed portions, and

control circuit boards that form the one and the other electronic control units are fixed to the fixing flat surface portions so as to cover the respective power conversion circuit boards.

5. The electric drive device as claimed in claim 4 , wherein:

a power conversion circuit and a power supply circuit except an electrolytic capacitor are mounted on the power conversion circuit boards forming the one and the other electronic control units, and

a microcomputer that controls the power conversion circuit, a peripheral device and the electrolytic capacitor of the power supply circuit are mounted on the control circuit boards forming the one and the other electronic control units.

6. An electric power steering device comprising:

an electric motor providing a steering assistive force to a steering shaft on the basis of an output from a torque sensor that detects a turning direction and a turning torque of the steering shaft;

a motor housing accommodating therein an electric motor that drives a mechanical control element;

a pair of supporting stems arranged so as to face to each other on an end surface, which is an opposite side to an output shaft portion of a rotation shaft of the electric motor, of the motor housing and extending in a direction of the rotation shaft which is an opposite direction to the output shaft portion;

a heat radiation base body arranged between the pair of supporting stems and extending in the same direction as those of the supporting stems;

fixing bolts screwed into the heat radiation base body from a radially outer side to a radially inner side through the supporting stems and connecting the supporting stems and the heat radiation base body;

one electronic control unit of a redundant system, the one electronic control unit arranged along a direction in which the heat radiation base body extends and having a board that is also arranged along the direction in which the heat radiation base body extends that is fixed to the heat radiation base body with thermal conduction to the heat radiation base body allowed; and

the other electronic control unit of the redundant system, the other electronic control unit arranged along a direction in which the heat radiation base body extends and having a board that is also arranged along the direction in which the heat radiation base body extends and that is fixed to the heat radiation base body with thermal conduction to the heat radiation base body allowed.

7. The electric power steering device as claimed in claim 6 , wherein:

the supporting stem is formed integrally with the end surface of the motor housing, and the motor housing and the heat radiation base body are made of the same metal.

8. The electric power steering device as claimed in claim 7 , wherein:

the heat radiation base body is fixed to the end surface of the motor housing at a position close to an area where the rotation shaft is disposed, and

the one electronic control unit and the other electronic control unit are arranged at opposite sides of the heat radiation base body.

9. The electric power steering device as claimed in claim 8 , wherein:

the heat radiation base body has fixing surfaces of the boards of the one electronic control unit and the other electronic control unit, accommodation recessed portions formed on the respective fixing surfaces, and fixing flat surface portions enclosing the respective accommodation recessed portions,

power conversion circuit boards that form the one and the other electronic control units are fixed to the accommodation recessed portions, and

control circuit boards that form the one and the other electronic control units are fixed to the fixing flat surface portions so as to cover the respective power conversion circuit boards.

10. The electric power steering device as claimed in claim 9 , wherein:

a power conversion circuit and a power supply circuit except an electrolytic capacitor are mounted on the power conversion circuit boards forming the one and the other electronic control units, and

a microcomputer that controls the power conversion circuit, a peripheral device and the electrolytic capacitor of the power supply circuit are mounted on the control circuit boards forming the one and the other electronic control units.