Motor-driven steering assist apparatus

1. A motor-driven steering assist apparatus interposed between a steering wheel and a wheel side steering member for assisting steering force which a driver applies to the steering wheel on the basis of a generating torque of an electric motor, the motor-drive steering assist apparatus comprising:

a single unit body covered by a housing has an input shaft to which the steering wheel is connected, an output shaft to which the wheel side steering member is connected, a torque sensor provided between the input shaft and the output shaft, the electric motor driven in correspondence to a detected torque of the torque sensor, and a gear train which transmits a rotation of the electric motor to the output shaft built-in,

an annular attaching portion surrounding the output shaft provided in a protruding manner in an attaching seat formed in the lower surface of the housing as seen from an axial direction of the output shaft,

wherein the annular attaching portion of the housing is inserted in an attaching hole provided in a vehicle body side attaching stay, the attaching seat of the housing is seated on a peripheral portion of the attaching hole of the vehicle body side attaching stay, and the vehicle body side attaching stay is pinched between a nut screwed from a leading end side of the annular attaching portion of the housing and the attaching seat.

2. A motor-driven steering assist apparatus as claimed in claim 1 , wherein an opening portion leaving the attaching hole open to the outer side is formed in the vehicle body side attaching stay, and an opening width of the opening portion is larger than an outer diameter of the output shaft, and smaller than a diameter of the attaching hole.

3. A motor-driven steering assist apparatus as claimed in claim 1 , the housing comprising first to third housings,

the first housing supports an upper end portion of the input shaft and the torque sensor,

the second housing supports an upper end portion of the output shaft,

the electric motor and the gear train,

the third housing supports a lower end portion of the output shaft, and

the attaching seat and the annular attaching portion are provided in a lower surface of the third housing.

4. A motor-driven steering assist apparatus as claimed in claim 3 , wherein an opening portion leaving the attaching hole open to the outer side is formed in the vehicle body side attaching stay, and an opening width of the opening portion is larger than an outer diameter of the output shaft, and smaller than a diameter of the attaching hole.

5. A motor-driven steering assist apparatus as claimed in claim 3 , wherein the locking portion of the vehicle body side attaching stay is formed by cutting up a part of the peripheral portion of the attaching hole, and

the locked portion comprises a concave locked portion provided in a part along a peripheral direction of the annular attaching portion in the attaching seat of the third housing.

6. A motor-driven steering assist apparatus as claimed in claim 3 , wherein the attaching seat and the annular attaching portion are received within a profile of the second housing as seen from an axial direction of the output shaft.

7. A motor-driven steering assist apparatus as claimed in claim 6 , wherein an opening portion leaving the attaching hole open to the outer side is formed in the vehicle body side attaching stay, and an opening width of the opening portion is larger than an outer diameter of the output shaft, and smaller than a diameter of the attaching hole.

8. A motor-driven steering assist apparatus as claimed in claim 1 , wherein in a state in which a locking portion is provided in the vehicle body side attaching stay, a locked portion is provided in the housing, the attaching seat of the housing is seated on the peripheral portion of the attaching hole of the vehicle body side attaching stay, and the locking portion and the locked portion are engagable so as to prevent the housing from rotating.

9. A motor-driven steering assist apparatus as claimed in claim 8 , wherein an opening portion leaving the attaching hole open to the outer side is formed in the vehicle body side attaching stay, and an opening width of the opening portion is larger than an outer diameter of the output shaft, and smaller than a diameter of the attaching hole.

10. A motor-driven steering assist apparatus as claimed in claim 8 , the housing comprising first to third housings,

the first housing supports an upper end portion of the input shaft and the torque sensor, the second housing supports an upper end portion of the output shaft, the electric motor and the gear train,

the third housing supports a lower end portion of the output shaft, and

the attaching seat and the annular attaching portion are provided in a lower surface of the third housing.

11. A motor-driven steering assist apparatus as claimed in claim 10 , wherein an opening portion leaving the attaching hole open to the outer side is formed in the vehicle body side attaching stay, and an opening width of the opening portion is larger than an outer diameter of the output shaft, and smaller than a diameter of the attaching hole.

12. A motor-driven steering assist apparatus as claimed in claim 10 , wherein the locking portion of the vehicle body side attaching stay is formed by cutting up a part of the peripheral portion of the attaching hole, and

the locked portion comprises a concave locked portion provided in a part along a peripheral direction of the annular attaching portion in the attaching seat of the third housing.

13. A motor-driven steering assist apparatus as claimed in claim 10 , wherein the attaching seat and the annular attaching portion are received within a profile of the second housing as seen from an axial direction of the output shaft.

14. A motor-driven steering assist apparatus as claimed in claim 13 , wherein an opening portion leaving the attaching hole open to the outer side is formed in the vehicle body side attaching stay, and an opening width of the opening portion is larger than an outer diameter of the output shaft, and smaller than a diameter of the attaching hole.