Driving force transmission device, and image forming apparatus

1. A driving force transmission device comprising:

a sun gear that rotates by receiving a driving force from a driving source;

an internal gear that is arranged coaxially with the sun gear;

a planetary gear that engages with the sun gear and the internal gear;

a rotary member that is provided coaxially with the sun gear and the internal gear and installed with the planetary gear so as to rotate corresponding to revolution of the planetary gear; and

an urging member that urges the planetary gear toward the rotary member, wherein

the planetary gear and the internal gear are configured of helical gears, and

the planetary gear is urged toward the rotary member by an axial force generated by the engagement between the planetary gear and the internal gear.

2. The driving force transmission device according to claim 1 ,

wherein the driving source is disposed on an opposite side to the rotary member interposing the sun gear therebetween and configured of a motor;

wherein the sun gear and the planetary gear are configured of helical gears; and

wherein the sun gear is urged in a direction away from the motor by an axial force generated by the engagement between the sun gear and the planetary gear.

3. The driving force transmission device according to claim 1 ,

wherein the sun gear, the planetary gear and the internal gear are configured of helical gears,

wherein the driving source is disposed on an opposite side to the rotary member interposing the sun gear therebetween and configured of a motor,

wherein a first axial force that urges the planetary gear toward the rotary member by the engagement between the planetary gear and the internal gear acts on the planetary gear,

wherein a second axial force that urges the planetary gear in a direction away from the rotary member by the engagement between the sun gear and the planetary gear acts on the planetary gear, and

wherein the first axial force is set to be greater than the second axial force, and an axial force that urges the sun gear in a direction away from the motor acts on the sun gear as a counteraction of the second axial force.

4. An image forming apparatus comprising:

an image holding member that holds a formed image;

a driving source that is used for rotationally driving the image holding member; and

a driving force transmission device that transmits a driving force from the driving source to the image holding member,

wherein the driving force transmission device according to claim 1 is used as the driving force transmission device.