The invention relates to a spindle motor for memory devices such as hard disk drives.
Conventional spindle motors for hard disk drives include a base plate or a base flange, a shaft, and a bearing system for rotationally supporting a motor's rotor driven by an electromagnetic force. The bearing system may be structured as a rolling bearing system or a hydrodynamic sliding bearing system.
In a conventional spindle motor having a stationary shaft, the shaft is firmly connected to the base plate or the base flange by means of a press-fit connection. To accomplish the connection, the base plate or the base flange features a drilled hole of a predetermined diameter and a predetermined length. One end of the shaft is pressed into and secured within the drilled hole. The outside diameter of the shaft is typically slightly larger than the inside diameter of the drilled hole of the base plate. This surplus is selected so as to ensure a minimal adhesive dimension, i.e., a certain adhesive strength, along the entire length of the joint. On the other hand, the surplus is selected to ensure that a maximum adhesive dimension is not exceeded. An excessive surplus would lead to an unacceptable strain on the components.
The greater the surplus and joint length, the higher is the press-in force required to join together the base plate and shaft. If the surplus or the joint length is reduced, adhesive strength may become too small. Increasing the surplus or joint length may result in damage to the components during the press-in procedure.