Propeller-shaped impeller and railway carriage air-conditioning apparatus

A propeller-shaped impeller, comprising:

• a boss rotatable with a rotation shaft of a motor having a bearing surface from which the rotation shaft protrudes, the boss being configured to be placed on the bearing surface as being fitted to the rotation shaft of the motor;
• and
• an airflow producing unit including a plurality of blades protruding from the boss outwardly in a radial direction of the rotation shaft and rotatable together with the boss to produce an airflow,
• wherein the boss includes a first end surface configured to come in contact with the bearing surface when the boss is fitted to the rotation shaft with one end of the boss in a thickness direction parallel to the rotation shaft facing the bearing surface, and a second end surface configured to come in contact with the bearing surface when the boss is fitted to the rotation shaft with another end of the boss in the thickness direction facing the bearing surface, and
• a degree of symmetry defined by A/B falls within a range of 1.0 to 1.3 inclusive, where A is a height of the airflow producing unit from one end surface of the first end surface and the second end surface, B is a height of the airflow producing unit from another end surface of the first end surface and the second end surface, and A B.