1. Field of the Invention
The present invention relates to the structure of a worm gear integrally attached to an output shaft of a motor.
2. Description of the Related Art
At present, when worm gears are attached to output shafts, either the output shafts have worm gears cut directly into them or worm gears separate from the output shafts are attached by pressure to the output shafts so as to be integral with the output shafts. Because of a strong demand in recent years for compact and lightweight worm gears, various attempts have been made to employ a type of worm gear integrally attached to the output shaft. The reason for this is that the diameter of this output shaft can be reduced. Such a worm gear is disclosed in, for example, Japanese Patent Laid-Open Publication No. 60-95257. The relationship between the length of the worm gear and the pitch of a worm tooth has not hitherto been examined. The length of the worm gear is arbitrarily set, and the worm gear is cut in accordance with this length, and used as it is. For this reason, the shape of one end of the worm gear where it is cut differs from the shape of the other end where it is cut. When the worm gear is directly attached to the output shaft, the output shaft is no longer balanced, thus causing the problem of unsmooth rotation of the output shaft.