Laser printers, which feature quiet, fast, high-quality printing, are evolving towards digital copiers with even faster and higher quality printing performance. This trend requires faster and more precise rotation of the polygon mirror motor of the laser beam scanning mechanism. Thus, bearings are becoming a key technology for the advancement of laser printers. This report proposes an integrated bearing unit that employs ferro-fluid for the bearing lubrication and seals in a new concept of leakage-free high-speed bearings. The intention is to take advantage of hydrodynamic oil-film bearings with high stiffness and damping characteristics to solve the oil leakage problem, and use them in place of ball-bearings or air bearings to get highly precise rotation. Leakage is completely prevented by using a compound seal of a ferro-magnetic seal and a viscous seal. The structural features of these bearings and experimental results concerning their lubrication and sealing performance and rotation accuracy when applied to a polygon mirror motor operating from 10000 to 30000 r/min are presented. The ferro-fluid bearings provide satisfactory friction torque and stiffness characteristics and the proposed bearing unit can be utilized with the polygon mirror motor.
In order to analyze turbine blades vibration caused by flutter, it is necessary to understand both aerodynamic damping and structural damping of high vibration stress. Flutter Vibration mode occurring in rated speed is non-synchronous mode. For measuring non-synchronous mode damping ratio of turbine blades, AC-type electromagnet which can generate high frequency excitation force was developed. Damping ratio characteristics of non-synchronous mode of nodal diameter 12,4 was measured in rotational test. For comparison, synchronous mode of nodal diameter 4 was measured, too. It was concluded as follows. (1) It is possible to excite non-synchronous mode by high frequency excitation electromagnet and calculate damping ratio from measurement resonance curve. (2) Damping ratio of non-synchronous mode ND12,4 was increased by increasing the excitation force. Synchronous mode ND4 is also a similar trend. (3) Nodal diameter 4 damping ratio of non-synchronous mode (Resonant speed=100%) was lower than synchronous mode (Resonant speed=75%).
This papcr presents a cemputational method of such randoln vibra し ion of the 加 rbinc bladcs using tbe multi ・ dc 呂 ree of 丘eedom spectmm analysis . This computational methed applied the cyclic synlme 町 method to thc spcctral a11農重 ys 童 s and enabled a large ・ scale calcu [ atien ofd }c steam 耄 urbine b ] ades . Also , thc random vibration examination by a simple b 【 ade model was d〔〕nc . and the probiems orthe ca 夏 cu 藍 ation conditioll were c [ ari [ ied. Both moda 】d臼mping and random excitation PSD are most impor 〔 ant factors of the calculat 三 〇 n . Thc calculation rcsu 【 ts were correspond { ng to the measurelnenLs weH , and the validity of tlle computational mcthod was confinned .
In order to analyze the blade vibration caused by flutter, it is necessary to understand both the aerodynamic damping and structural damping of the high vibration stress. Flutter Vibration mode occurring in the rated speed is non-synchronous mode. To measure non-synchronous mode damping, high frequency excitation magnet was developed. Damping characteristics of the non-synchronous mode of nodal diameter 12 and 4 were measured in the rotation test. For comparison, synchronous mode of nodal diameter 4 was measured. From these results, it was concluded as follows. (1) It is possible to excite non-synchronous mode by high frequency excitation magnet and measure the damping ratio. (2) According to the measurement results of non-synchronous mode of nodal diameter 12 and 4, damping ratio is increased if the excitation force become large. Synchronous mode of nodal diameter 4 is also a similar trend. (3) Nodal diameter 4 damping ratio of non-synchronous mode(Resonance speed:100%) was lower than synchronous mode(Resonance speed:75%). (4) When evaluating flutter which occurs at rated speed, it is necessary to measure structural damping ratio at rated speed.
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