Vehicle steering apparatus

1. A vehicle steering apparatus comprising:

an actuator that generates a steering force;

a first speed reduction mechanism connected to the actuator;

a second speed reduction mechanism connected to the first speed reduction mechanism; and

a steering mechanism connected to the second speed reduction mechanism, wherein

a sub-assembly that includes the actuator and the first speed reduction mechanism is configured,

the actuator includes a plurality of electric motors each of which includes a rotary shaft,

the first speed reduction mechanism includes a plurality of drive members and a common driven member that follows the drive members, and

the drive members are connected to the rotary shafts of the corresponding electric motors, and joined to the driven member in a power transmittable manner.

2. The vehicle steering apparatus according to claim 1 , wherein

the rotary shaft of each of the electric motors and a pivot of the driven member are parallel to each other.

3. The vehicle steering apparatus according to claim 2 , wherein the drive members and the driven member of the first speed reduction mechanism include gears engaging with each other or pulleys joined to each other in a power transmittable manner via an endless belt.

4. The vehicle steering apparatus according to claim 2 , wherein

the driven member includes two helical gears joined to a same axis, and

tooth trace directions of the two helical gears are different from each other.

5. The vehicle steering apparatus according to claim 1 , wherein

the plurality of drive members and the driven member are joined to each other in a power transmittable manner via an endless belt,

the drive members are joined to the rotary shafts of the corresponding electric motors rotatably integrally, and

the plurality of drive members include a drive member inscribed about the endless belt and a drive member circumscribed about the endless belt.

6. The vehicle steering apparatus according to claim 1 , comprising: a rotation angle detection device that detects a rotation angle of the rotary shaft of any one of the plurality of electric motors, or any one of the drive members and the driven member.

7. The vehicle steering apparatus according to claim 1 , comprising: a rotation angle detection device that detects a rotation angle of the driven member.

8. The vehicle steering apparatus according to claim 1 , wherein

in a power transmission region between the drive members and the driven member, a plurality of resilient bodies are interposed in a compressed state between the drive members and the driven member, and

the plurality of resilient bodies apply resilient forces different from each other.

9. The vehicle steering apparatus according to claim 1 , further comprising: a connection member that electrically connects the actuator to external wiring, wherein

the sub-assembly includes a housing for housing the actuator and the first speed reduction mechanism,

the connection member includes first and second terminals connectable to each other according to an operation of joining the actuator and the housing to each other, and

the first and second terminals are disposed inside the housing.

10. The vehicle steering apparatus according to claim 9 , wherein

the housing includes a motor fixing member to which the plurality of electric motors are fixed,

the first terminal is provided on the plurality of electric motors, and

the second terminal is provided on internal coupler fixed to the motor fixing member.

11. The vehicle steering apparatus according to claim 9 , wherein

the housing includes a motor fixing member to which the plurality of electric motors are fixed, and a cover housing covering the plurality of electric motors and the motor fixing member, and

the plurality of electric motors are disposed between an inner surface of an end wall of the cover housing and the motor fixing member, and

the first terminal is provided on the plurality of electric motors, and

the second terminal is provided on internal coupler fixed to the inner surface of the end wall of the cover housing.

12. The vehicle steering apparatus according to claim 11 , wherein

the connection member includes an external coupler disposed on the outer surface of the cover housing,

the external coupler includes a third terminal, and

the second terminal and the third terminal are connected to each other via a flexible printed board installed along an inner surface of the cover housing.

13. The vehicle steering apparatus according to claim 1 , wherein

the driven member includes an annular driven member,

an inner periphery of the annular driven member is joined to the drive members in a power transmittable manner, and

a lubricant is filled in a power transmission region between the drive members and the annular driven member.

14. The vehicle steering apparatus according to claim 1 , wherein

the sub-assembly includes a housing for housing the actuator and the first speed reduction mechanism, and

a lubricant is filled in the housing.

15. The vehicle steering apparatus according to claim 1 , wherein the driven member includes an annular driven member having an inner periphery connected to the drive members in a power transmittable manner, and the first reduction mechanism includes a bearing supporting an outer periphery of the annular driven member.

16. The vehicle steering apparatus according to claim 1 , wherein

the plurality of electric motors further include:

a first electric motor that generates a leftward steering force that should be applied to the steering mechanism or a rightward steering reaction force that should be applied to the steering member to be operated by a driver;

a second electric motor that generates a rightward steering reaction force that should be applied to the steering mechanism or a leftward steering reaction force that should be applied to the steering member;

a turning-back detection device that detects a turning-back operation of the steering member; and

a drive control section that drives either one of the first and second electric motors to generate a steering force or a steering reaction force in a corresponding direction, and supplies a driving electric current that does not generate a steering force or a steering reaction force to the other one of the first and second electric motors when the turning-back operation is not detected by the turning-back detection device.

17. The vehicle steering apparatus according to claim 16 , wherein

the turning-back detection device includes a direction detection device that detects a direction of steering by the driver,

and when the direction detection device detects a leftward operation, the drive control section drives the first electric motor in a corresponding direction, and when the turning-back detection device detects the leftward operation as the leftward turning-back operation, the drive control section supplies an electric current that is for rotation in a direction opposite to the corresponding direction and compensates inertia caused when the rotation direction of the second electric motor mechanically joined to the first electric motor is reversed to the second electric motor, and

when the direction detection device detects a rightward operation, the drive control section drives the second electric motor in a corresponding direction, and when the turning-back detection device detects the rightward operation as the rightward turning-back operation, the drive control section supplies an electric current for compensating the inertia to the first electric motor.