Actuator

1. An actuator comprising:

a motor;

an output shaft; and

a speed reduction mechanism for transmitting rotation of the motor to the output shaft by reducing a rotation speed,

wherein the speed reduction mechanism includes:

at least one gear having a shaft hole;

a support shaft inserted into the shaft hole and holding the gear rotatably;

wall portions provided at both ends of the support shaft in a manner sandwiching the gear; and

a wear powder holding portion provided radially outside an outer periphery of the support shaft and in at least one of two end portions of the shaft hole and the wall portions in a manner to hold wear powder or foreign substance without scattering.

2. The actuator according to claim 1 , wherein:

an opening area of the shaft hole in the wear powder holding portion of the gear is larger than an opening area of the shaft hole which is other than the wear powder holding portion.

3. The actuator according to claim 1 , wherein:

a cross-sectional area of the support shaft perpendicular to an axis of the support shaft at the wear powder holding portion is smaller than a cross-sectional area of the support shaft perpendicular to the axis of the support shaft at a position other than the wear powder holding portion.

4. The actuator according to claim 1 , wherein:

the wear powder holding portion is formed as a recess portion formed in the wall portion.

5. The actuator according to claim 4 , wherein:

the gear includes a protruding portion protruding in a direction along the support shaft and entering the wear powder holding portion.

6. The actuator according to claim 4 , wherein:

the recess portion includes a protruding portion protruding in a direction along the support shaft and entering the wear powder holding portion provided in the gear.

7. The actuator according to claim 1 , wherein:

a radial distance of the wear powder holding portion in the gear is larger than a distance between the support shaft and the gear at a position other than the wear powder holding portion.

8. The actuator according to claim 1 , wherein:

a distance in a direction along the shaft at the wear powder holding portion is larger than a distance between the gear and the wall portion.

9. The actuator according to claim 1 , wherein:

a radial distance of the wear powder holding portion in the gear is larger than a distance between the support shaft and the wall portion.

10. The actuator according to claim 1 , wherein:

one of the wall portions fixes the support shaft; and

the other of the wall portions includes a positioning portion for positioning the support shaft without fixing.

11. The actuator according to claim 1 , further comprising:

a housing portion for accommodating the speed reduction mechanism therein; and

a case portion for covering the housing portion,

wherein the wall portions are provided in the housing portion and the case portion.

12. The actuator according to claim 1 , further comprising:

a rolling bearing provided at a fitting portion between the gear and the support shaft,

wherein the rolling bearing has at least one of a configuration in which an outer ring is fixed to the gear and a configuration in which an inner ring is fixed to the support shaft.

13. The actuator according to claim 12 , wherein:

the outer ring of the rolling bearing is fixed to the gear and the inner ring is fixed to the support shaft.

14. The actuator according to claim 1 , further comprising:

a magnetic circuit portion for generating a magnetic flux for detecting a rotational position of the gear; and

a magnetic flux detection portion for detecting the magnetic flux generated by the magnetic circuit portion.

15. The actuator according to claim 1 , wherein:

at least one of the shaft hole of at least one of the gears of the speed reduction mechanism and the support shaft is made of metal.

16. The actuator according to claim 1 , wherein:

the output shaft is connected to drive a turbocharging pressure control valve of a turbocharger.