DESIGN OF A ROTARY FLEXURAL MICRO-BEARING

摘要

Micro-machines (μ-machines) and μ-devices are characterized by their small size, light weight, high energy-conversion efficiency and low energy consumption, quick response, high reliability, low cost, high integration, and high intelligence level, etc. Typical examples are μ-machine tools, μ-robotics, μ-aircrafts, μ-submarines, μ-devices and μ-instruments for medical applications, μ-satellites, μ-gears, μ-pumps, μ-valves, μ-sensors, and μ-actuators. A common feature to most of the μ-machines and μ-devices is that their structures are getting more and more complex and are often three-dimensional (3-D) while their sizes are becoming smaller and smaller, which imposes a critical challenge to their manufacturing issues. The existing MEMS and LIGA technologies have been widely used for 2-D and 2.5-D micro-manufacturing applications, however, they do not provide a capability for 3-D micro-manufacturing. Therefore, an important and challenging research topic has been to design μ-machines or μ-devices that are capable of 3-D μ-manufacturing at the nanometer accuracy level. This study proposes a novel rotary flexural μ-bearing that is capable of achieving rotational/oscillational motions at the nanometer level accuracy and a design methodology for such a bearing. The design of the μ-bearing is based on the principle of flexural mechanisms that realizes rotational/oscillational motions of one complete revolution through the elastic deformation of the elastic flexures. In the proposed design, the μ-bearing consists of four elements: an outer cage and an inner cage, a μ-shaft and a μ-elastic coupling. Both the inner and outer cages may contain one or more bearing sections, depending on the amount of angular displacement to be realized by the μ-bearing. The bearing sections allow the μ-bearing to rotate/oscillate in the circumferential direction when the μ-bearing is loaded by an external power source (e.g., a μ-servomotor). The inner and outer cages are nested and joined at one end. By axis-symmetrically arranging the elastic flexures in the inner and outer cages, the μ-bearing is extremely flexible in the circumferential direction, but highly stiff in all other directions.