Base plate, motor, and disk drive device

1 . A base plate which is a portion of a housing of a disk drive device and is defined by a die-cast member comprising metal, the base plate comprising:

a bottom wall extending perpendicularly to a rotation axis of a disk extending in an up-down direction; and

a peripheral wall extending from a peripheral edge of the bottom wall to an axially upper side and surrounding a periphery of the bottom wall, wherein

the bottom wall comprises a screw hole recessed from a peripheral edge of a lower end surface to the axially upper side,

the screw hole comprises:

an inclined part defined to have an inner diameter that decreases from a lower end toward the axially upper side; and

a column body extending from an upper end of the inclined part to the axially upper side and defined with a threaded part to be screwed with a screw, and

in a cross section comprising a center line that passes through a center of the column body and extends in an axial direction, the inclined part is inclined at an inclination angle of 25° or more and 35° or less with respect to the center line.

2 . The base plate according to claim 1 , wherein

a diameter at the lower end of the inclined part is 4.0 mm or more and 4.6 mm or less.

3 . The base plate according to claim 1 , wherein

a lower end of a burr defined protruding from the inclined part is located on the axially upper side compared to a lower end of the bottom wall.

4 . The base plate according to claim 1 , wherein

a burr defined at the inclined part protrudes in a radial direction.

5 . The base plate according to claim 1 , wherein

the inclined part is defined by a plurality of inclined surfaces that have different inclination angles with respect to the center line and are arranged in the axial direction.

6 . The base plate according to claim 1 , wherein

the peripheral wall comprises:

a first recess defined by recessing an inner peripheral edge of an upper end surface to an axially lower side; and

a second recess defined by further recessing an inner peripheral edge of a bottom surface of the first recess to the axially lower side,

a ramp holding a head that reads or writes information from and to the disk is placed at a bottom of the second recess, and

an entire bottom of the first recess is located on the axially upper side compared to the bottom of the second recess.

7 . The base plate according to claim 6 , wherein

a radially inner surface of the second recess comprises:

a planar surface parallel to a radially outer surface of the peripheral wall; and

a curved surface that is curved and recessed to a radially outer side compared to the planar surface, and

a radially outer end of the curved surface is located on the radially outer side compared to a radially outer end of the planar surface.

8 . The base plate according to claim 7 , wherein

the first recess comprises a curved surface recess defined by recessing a bottom surface, which is continuous with the curved surface, to the axially lower side.

9 . The base plate according to claim 6 , wherein

on the axially lower side of the first recess, the bottom wall comprises a bottom wall recess recessed from the lower end surface to the axially upper side.

10 . A motor comprising:

the base plate according to claim 1 .

11 . A disk drive device comprising:

the motor according to claim 10 ;

a disk rotated around the rotation axis by the motor; and

a head that reads or writes information from and to the disk.