• Journal of the Korean Magnetics Society
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• v.24 no.5
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• pp.152-159
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• 2014

Magnetic gear can transmit torque without any mechanical contact among rotational parts in rotating mechanical systems. Especially, magnetic gear using rare-earth PMs can be used in variety of industry application because of their great power efficiency. Thus, recent trend shows that magnetic gear can be replaced with common mechanical gear. This paper deals with comparison and torque analysis for magnetic gears with parallel and Halbach magnetization according to various design parameters. Using a two dimensional (2D) finite element (FE) analysis, suitable gear ratio is selected. We performed analysis for magnetically connected inner and outer torque with respect to various design parameters including thickness of inner and outer PM, steel pole angle, segments of Halbach array and magnetization pattern of inner and outer PMs. Finally, we can obtain improved design model having parallel and Halbach magnetization with larger torque, compared with an initial design model.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1988.06a
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• pp.28-30
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• 1988

윤활시스템에서 마모는 상대적인 운동을 하는 두 물체사이에서 표면상태, 접촉조건 및 분위기등의 제요소들에 의해 발생되며, 형태학적으로 scuffing, scoring, pitting 및 fretting 등으로 분류된다. 윤활조건의 특성에 따라 미끄럼 접촉에서는 mild wear, severe wear로 구분되며, 이들의 마모 생성기구의 차이는 접촉상대속도, 하중 및 표면조도등의 정도에 기인된다. mild wear에서 severe wear 영역으로 전이될 때의 가혹한 조건에서 생성되는 마모현상을 scuffing wear라 하며, 이는 접촉면에서의 표면돌기의 직접접촉에 의한 cold welding 현상, 즉 local welds의 특성을 지닌 마멸형태로 정의한다. 이의 생성은 접점간의 하중 및 미끄럼 속도가 증가됨에 따라 온도상승에 기인되어 순간적으로 발생된 마찰열이 그 원인이 있으며, 기어, cam 및 tappet, 피스톤링 및 실린더 라이너 등의 마멸현상이 대표적인 예이다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1391-1394
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• 2007

In order for Hypoid gear development. Gears are required to sustain heavy loads or on applications where the gear box is made or a material with a different coefficient of thermal expansion form that or the gears and shafts, it is desirable to make a deflection and contact check under load. The deflection test is performed in the actual gear mounting using completely processed gear. This test should cover the full operating range of gear loads from no load to peak load. Under peak load the contact pattern should extend to the tooth boundaries without showing a concentration of the contact pattern at any point on the tooth surface.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.171-176
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• 2002

This paper is the study on stress analysis of spur gear using a finite element method. Gear drives constitute very important mechanisms in transmitting mechanical power processes compromising several cost effective and engineering advantages. The load transmission occurred by the contacting surfaces arises variable elastic deformations which are being evaluated through finite element analysis. The automatic gear design program is developed to model gear shape precisely. This gear design system developed was used by pre-processor of FEM packages. The distribution of stresses at contacting surfaces was examined when a pair of gear contact.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1347-1354
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• 1994

This paper deals with the experimental research, including measurement and analysis and field survey, on the causes of occurring noise defective gear boxes in hoist production plant in order to reduce the fraction of their occurrence. In this reserch following investigations are performed : measurement and gear-boxes, examination of each machining process of production, measurement and analysis of dimensional accuracy of each part, comparative vibration test with exchanging inaccurate parts. From these investigations, it is found that the machining accuracy of pinion gear tooth thickness is the most sensitive factor of noise problem. By maintaining the tooth thickness error within 0.05 mm tolerance in the gear cutting process, the fraction of noise defective gear-boxes are greatly reduced to less than 2%, where the usual rate of it has been 20-50%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.380-388
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• 2016

Using the magnet gear, it is possible to transmit power without mechanical contact. As the drive shaft in a magnet gear-based speed reducer system is isolated from the drive shaft, the system is a two-inertia resonance system that should cope with an external load with the limited air-gap stiffness. On the other hand, the drive shaft or low-speed side is controlled only by the torque of the drive shaft through an air-gap, and the excessive oscillation or the slip can then be generated because of an abrupt disturbance that is different from the general mechanical gear system. Therefore, the disturbance loaded at the low speed side should be measured or estimated, and considered in the control of the driving shaft. This paper proposes a novel full-state feedback controller with a reduced-order observer for the speed reducer system using a magnet gear with a unified harmonic modulator. The control method was verified by simulation and experiment. To estimate the load at the low speed side, a novel observer was designed, in which the new state variable is introduced and the new state equation is formulated. Using a full-state feedback controller including the observer, the test result against disturbance was compared with two D.O.F PI speed controllers. The pole slip was compensated within relatively a short time, and the simulation result about the estimated variable shows a similar tendency to the test result. The test results showed that the magnet gear-based reducer can be applied to an accurate servo system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.741-742
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.761-762
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• 2010

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.35-44
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• 2022

This study aims to evaluate the stress and life of cylindrical roller bearings used in aircraft gearboxes, and to select a roller profile that minimises the contact stress between bearing rollers and raceways. The mounting clearance of four points contact ball bearing was determined, so that cylindrical roller bearings support all radial loads, and the bearing mounting position was determined to maximise the bearing lives. In addition, the static safety factor and dynamic life of bearing were predicted according to ISO 76 & ISO/TS 16281 using the load spectrum determined based on the operating load cases of aircraft gearboxes. Furthermore, the optimal roller profile was selected by analysing the contact stress according to the roller profile shape, and the safety of each roller was evaluated. The results stated that the required safety factor and lifetime were satisfied, and Johns Gohar roller profile was optimal.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.870-875
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• 1986

In this study, full-rounded tip curve of rack and its mating fillet curve of pinion in Involute-circular arc composite tooth profile are derived. Mechanical characteristics are calculated analytically, i.e., Specific sliding, Nominal bending stress at working root circle and the Contact factor of the arc of contact in circular arc part to the arc of double contact. These characteristics compared with standard involute tooth profile are improved in circular arc part of composite tooth profile. To obtain more efficient composite tooth profile, we studied these characteristics with regard to the changes of unwound angle and radius of circualr arc. And a design method of composite tooth profile is suggested. Composite tooth profile are compared with standard involute tooth profile.