Constant pressure magnetically preloaded fdb motor

Abstract

The shaft may be supported for rotation by a conical bearing rotating within a sleeve. To prevent misalignment of the rotor and stator as the motor heats up and fluid viscosity changes, a magnetic preload is established; in a preferred embodiment, the magnetic preload is achieved using a magnetic back iron aligned with the stator magnet, the magnetic back iron being supported from the base. The shaft may further include a lower journal bearing for maintaining radial alignment and/or stiffness. A shaft may be supported for rotation relative to a sleeve by a combination of journal bearing and thrust bearing whose gaps are connected and grooved to cooperate. The bearing system includes a magnetic preload at the end of the shaft distal from the journal bearing/thrust bearing combination, the magnetic force balancing the spiral groove thrust bearing to maintain the bearing support for the shaft and the load (including hub and disc) that it supports. Further, the journal bearing balances against the thrust bearing so that as fluid is drawn further into the thrust bearing, it is withdrawn from the journal bearing to reduce the working area of the journal bearing. A reservoir terminating in a capillary seal also provided on the far side of the thrust bearing from the journal bearing. This design allows the journal bearing to drain itself as the thrust bearing spins up and its pressure increases so that the pressure of the journal bearing matches the thrust bearing.