BLDC motor manufacturing assembly line technology
This motor manufacturing assembly line technology relates generally to a brushless direct current (BLDC) motor assembly, and more particularly toward an improved method and structure for attaching permanent magnet segments on a rotor of the BLDC motor assembly.
With the advent of brushless direct current (BLDC) motor technology, the introduction of electronic motor control systems in various fields, the industry objectives of long life, high efficiency, reliability and low EM interference have become achievable. BLDC motor assemblies include a rotor assembly which is disposed for powered rotation within a station response to an electro-magnetic field generated by the stator. The rotor of a BLDC motor includes a plurality of magnetic segments arrayed in equal arcuate increments about its exterior Surface. Typically, the magnet segments are coated with a thin layer of protective material and then affixed to an underlying hub section of the rotor using a bonding adhesive.
In circumstances where the coating material is not securely adhered to the magnet segment, delamination can occur during operation. This catastrophic failure of magnet separation from the underlying hub surface can lead to motor damage. The prior art has suggested techniques other than adhesive for retaining magnet segments to the rotor in a BLDC motor assembly. It is an improved method and design for attaching permanent magnet segments into an operative array on a rotor for a brushless direct current electric motor assembly which is strong, light weight, and efficiently accomplished in high-volume production settings.
The method contemplates a method for attaching permanent magnet segments into an operative array on a rotor for a brushless direct current (BLDC) electric motor assembly of the type used in liquid fuel pumps and the like. The method comprises the steps of providing a rotary shaft having a hub section with an outer Surface, providing a plurality of permanent magnet segments, each magnet segment having opposing ends, and supporting the magnet segments in an operative position on the outer surface of the hub section. The step of supporting the magnet segments includes arranging the magnet segments side-by-side in equal arcuate increments around the outer surface of the hub.
The method further includes fabricating an annular ring from an electrically conductive material and loosely encircling at least one end of the Supported magnet segments with the ring.
The method is characterized by the step of rapidly shrinking the ring by inducing therein a powerful current flow using a high energy pulsed magnetic field to Squeeze each of the magnet segments into tight pressing engagement against the outer Surface of the hub and thereby collectively hold the magnet segments in the operative position upon the rotary shaft.
The method also contemplates a BLDC electric motor assembly of the type used in liquid fuel pumps and the like. The motor assembly comprises a stator for producing a controlled electro-magnetic field. The stator defines a central longitudinal axis of the motor assembly. A shaft is supported for rotation about the longitudinal axis, and includes a hub section having an outer Surface. A plurality of permanent magnet segments are supported on the outer Surface of the hub for rotation with the shaft. Each magnet segment has opposite, longitudinally spaced ends. The magnet segments are arranged side-by-side in equal arcuate increments around the hub. The motor assembly is characterized by an annular ring encircling at least one of the ends of the arrayed plurality of magnet segments, the ring having been deformed in an electro-magnetic forming operation so as to exert a generally uniform compression on each of the magnet segments to hold the magnet segments in an operative position around the hub. The ring thus formed operates to retain the magnet segments on the hub in a reliable, inexpensive manner which is efficiently carried out in high production environments.
Furthermore, the method contemplates a permanent magnet segment of the type used in an array of magnet segments Supported on a rotor in a BLDC electric motor assembly. The magnet segment comprises an inner Surface, a convex, semi-cylindrical outer Surface, an upper end, a lower end, and opposing, general parallel side edges respectively extending between the upper and lower ends. The magnet segment of this method is characterized by a first tongue adjacent one end of the upper and lower ends for receiving an annular ring to be subsequently deformed in an electro-magnetic forming operation so as to exert a generally uniform compression on the magnet segment to hold the magnet segment in its operative position upon the rotor.