Performance of integrated retainer rings in silicon micro-turbines with thrust style micro-ball bearings

Abstract

This work explores the performance of different silicon retainer ring designs when integrated into silicon micro-turbines (SMTs) incorporating thrust style bearings supported on 500 μm diameter steel balls. Experimental performance curves are presented for SMTs with rotor diameters of 5 mm and 10 mm, each with five different retainer designs varying in mechanical rigidity, ball pocket shape and ball complement. It was found that the different retainer designs yielded different performance curves, with the closed pocket designs consistently requiring lower input power for a given rotation speed, and the most rigid retainers giving the best performance overall. Both 5 mm and 10 mm diameter devices have shown repeatable performance at rotation speeds up to and exceeding 20 000 RPM with input power levels below 2 W, and devices were tested for over 2.5 million revolutions without failure. Retainer rings are commonly used in macro-scale bearings to ensure uniform spacing between the rolling elements. The integration of retainers into micro-bearings could lower costs by reducing the number of balls required for stable operation, and also open up the possibility of 'smart' bearings with integrated sensors to monitor the bearing status.

Vibration-Based Diagnostics for Rotary MEMS

“…Due to the complexities of scaling down to the microscale, a ball bearing separator bracket is not used, so balls are free to re-distribute, rub against, or impact with other balls [27]. Additionally, the tolerances of the raceway dimensions allow for some radial ball movement in the direction of centripetal force.…”

“…For the RMD used in this diagnostic platform, a retainer ring is not used due to the lack of a microscale fabrication solution, allowing the micro-balls to freely adjust their spacing [27]. Two configurations of device were fabricated for demonstrating the relationship between rolling friction and dynamic performance.…”

Electromagnetic Linear Vibration Energy Harvester Using Sliding Permanent Magnet Array and Ferrofluid as a Lubricant

“…For conventional macro scale power generators, the electromagnetic power generation principle and rotary turbines supported by ball bearings dominated. For miniature and micro scale power generators, rotary turbines supported by miniature bearings, metal balls, and air-bearing have been proposed [ 9 , 10 , 11 ]. In contrast, spherically or cylindrically-shaped permanent magnets or metal structures have been utilized as springless proof mass in vibration energy harvesters to provide smooth motion with less friction and wear [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”

A novel sandwich differential capacitive accelerometer with symmetrical double-sided serpentine beam-mass structure

“…Several different masks can be buried in the silicon dioxide layer with a photolithography process before etching, and these buried masks can be opened at a preferred time by etching silicon dioxide instead of performing thermal oxidization photolithography again, making the fabrication process more convenient and efficient. The fabrication process described here is similar to the multistep etching process based on a stepped oxide mask for the fabrication of a silicon micro-turbine (SMT) described in [10]. Meanwhile, the beam thickness can be well controlled by controlling the etching time, making it possible to form accelerometers with different sensitivities without changing the masks or the silicon wafer.…”