Direct-current motor and actuator

1. A direct-current motor comprising:

a rotor including: a rotor core which is provided with electromagnetic coils formed around the rotor core by distributed winding, and a cylindrical rotor shaft combined with the rotor core;

a thread provided on an inner periphery of a cylindrical member which is formed by a resin material inside the rotor shaft, and to convert torque of the rotor into thrust of an output shaft in a linear motion direction of the output shaft and

at least one annular collar provided on an outer periphery of the rotor shaft, the collar being integrated with the cylindrical member through an aperture penetrating an outer wall of the rotor shaft, wherein the collar is provided for part of the rotor shaft on an output side of the rotor core.

2. An actuator comprising:

the direct-current motor according to claim 1 ; and

the output shaft.

3. A direct-current motor comprising:

a rotor including: a rotor core which is provided with electromagnetic coils formed around the rotor core by distributed winding, and a cylindrical rotor shaft combined with the rotor core;

a thread provided on an inner periphery of a cylindrical member which is formed by a resin material inside the rotor shaft, and to convert torque of the rotor into thrust of an output shaft in a linear motion direction of the output shaft and

at least one annular collar provided on an outer periphery of the rotor shaft, the collar being integrated with the cylindrical member through an aperture penetrating an outer wall of the rotor shaft, wherein the at least one collar includes:

a collar provided for part of the rotor shaft on an opposite side to an output side of the rotor core; and

a collar provided for part of the rotor shaft on the output side of the rotor core.

4. An actuator comprising:

the direct-current motor according to claim 3 ; and

the output shaft.