Simple planetary reduction gear

A simple planetary reduction gear comprising:

• a motor;
• and
• a simple planetary mechanism including a sun gear which is connected to a motor shaft of the motor, a planetary gear which is supported by a carrier, and an internal gear with which the planetary gear internally meshes,
• wherein the simple planetary reduction gear is used in a vertically installed state,
• wherein the sun gear includes a shaft portion which protrudes to a load side coaxially with a shaft center of the sun gear,
• wherein the shaft portion is supported by a bearing which is disposed between an outer circumference of the shaft portion and an inner circumference of the carrier,
• wherein the internal gear is integrated with a casing of the simple planetary reduction mechanism,
• wherein an air vent port provided in the casing and an air vent passage which causes the air vent port and an upper space of the simple planetary reduction mechanism to communicate with each other are provided,
• wherein the casing is divided into at least a first member and a second member, and
• wherein the air vent passage is not directly opened to the upper space of the simple planetary reduction mechanism and communicates with the upper space of the simple planetary reduction mechanism via a gap between the first member and the second member.