Refrigeration device with improved DC motor
View Patent ↗A miniature cooling device includes numerous improvements capable of increasing the reliability and useful lifetime of the device, as well as improving electrical power to cooling power conversion efficiency. The improvements include a unitary DC motor shaft design that incorporates a unitary mass flywheel into the shaft element and provides a solid shaft cross-section for increasing magnetic flux density in the DC motor. Additional improvements include a bend resistant flexible vane in the DC motor to compression piston drive coupler, reduced dead space volume within the compression cylinder, improved heat dissipation by a cylinder head cover and an athermalized compressor design that provides uniformly efficient operation over a wide range of operating temperatures. Further improvements include fabrication and coating improvements that increase the life of compression piston and compression cylinder wear surfaces.
1. A method for forming a gas compressor comprising the steps of:
forming a thin walled cylinder sleeve with an inside and an outside diameter; said inside diameter comprising a cylinder bore diameter;
applying a wear resistant coating having a hardness of RC 60 or more to at least the cylinder bore surface;
forming a compression piston with an outside diameter for mating with the cylinder bore, the compression piston comprising a solid cup shaped element having a solid circular disk-shaped closed end for compressing a gas and an annular cylindrical wall portion for mating with the cylinder bore along most of a longitudinal length of the cylinder bore;
applying a first layer of malleable, vibration dampening material that includes a solid lubricating compound impregnated therein over the piston outside diameter, said first layer being applied in sufficient thickness that the piston diameter is oversized compared to said cylinder bore diameter;
installing the piston into the cylinder bore by a press fit and attaching the piston to a drive mechanism for reciprocating the piston within the cylinder bore until a sufficient amount the first layer of material applied to the piston outside diameter is removed, to provide a substantially zero clearance fit between the piston outside diameter and the cylinder bore;
installing the cylinder sleeve and mating piston into a crankcase formed with a bore for receiving the cylinder sleeve therein, and bonding the cylinder sleeve outside diameter to the crankcase bore;
continuing to remove the first layer of material applied to the piston outside diameter until a substantially uniform non-zero clearance fit is provided between the piston outside diameter and the cylinder bore;
cleaning loose material from the piston and the cylinder sleeve; and,
applying a second layer comprising a hard wear resistant material onto the piston outside diameter over said first layer, said second layer being applied to a thickness consistent with restoring a substantially zero clearance fit between the piston outside diameter and the cylinder bore.
2. The method of claim 1 wherein said first layer of material comprises a polymetric reinforced PTFE compound applied with a thickness in the range of 0.13-0.38 mm, (0.005-0.015 inches).
3. The method of claim 1 wherein said second layer of material comprises a hard ceramic compound applied to a thickness of approximately 0.25 microns, (10 micro inches) by an ion beam assisted deposition process.
4. The method of claim 3 wherein said ceramic compound comprises CrN.