2012 Volume 53 Issue 616 Pages 439-444
A number of reduction gear units with small electric motors as power sources are used in automobiles. Smaller units with a low energy consumption are required for future electric vehicles. Although worm gears are widely used in units with a large gear ratio, their efficiency is too low. Therefore, only large motors can be applied in cases where a large torque is required. Even cylindrical gear pairs and/or face gears with a large gear ratio could enable reduction gear units to have a higher efficiency and a lower energy consumption. For this purpose, helical gears with a small number of teeth and a large helix angle are necessary. In the present paper, cold form rolling for forming such gears was proposed. The tooth form accuracy of form-rolled gears was compared with those cut using a hob. Furthermore, the efficiency and service life of the gears were examined. The results show that cold form rolling can be used to form helical gears with a small number of teeth and a large helix angle.