• Tribology and Lubricants
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• v.23 no.4
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• pp.149-155
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• 2007

The CAD model of a elliptical gear for wire cutting has been developed. The rolling contact of pitch ellipses whose rotation axes coincide with their focus has been analyzed, and the perimeter of the pitch ellipse has been divided into equal-length segments by the number of teeth. A master tooth profile, which is a composite curve of circular arcs that represents involute, has been introduced. The elliptical gear has been designed by imposing the master tooth on the divided points of the pitch ellipse, and a full fillet has been achieved between neighbour teeth. Thus, the whole profile of an elliptical gear is a composite curve of arcs only, and consequently NC codes for wire cutting can be easily generated. Furthermore, a computer simulation program is developed to verify the mesh of the elliptical gear.

• Tribology and Lubricants
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• v.24 no.5
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• pp.221-227
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• 2008

This paper presents a step-by-step design of noncircular gears. From the diagram of angular velocity ratio of a noncircular gear pair, the pitch curves of the two mating gears are determined, and the perimeter of the pitch curve has been divided into equal-length segments by the number of teeth. A master tooth profile, which is a composite curve of circular arcs that represents involute, has been introduced. A noncircular gear pair has been designed by imposing the master tooth on the divided points of the pitch curve, and a full fillet has been achieved between neighbour teeth. Thus, the whole profile of the noncircular gear is a composite curve of arcs only, and consequently NC codes for wire EDM can be easily generated.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.251-257
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• 2000

A numerical simulation of the temperature rise for sliding surface in dry contact is based on Jaeger's formula combined with a calculated heat input. A gear tooth temperature analysis was performed. The pressure distribution has the Hertzian pressure distribution on the heat source. The heat partition factor is calculated along line of action. A Temperature distribution of tooth surface is calculated about before and after profile modification. A Temperature of addendum and deddendum in modified gear have reduced.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.111-117
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• 2005

The vibration problems associated with gear coupled rotors have been the focus of much engineering work. These systems are complex and difficult to analyze in that they have the problems associated with conventional rotors plus those additional problems associated with the gear couplings. This paper examines the problems peculiar to the gear mesh. Because of the meshing action of gears, the elasticity of the gear teeth introduces time-varying stiffness coefficients into the governing equations of motion. This means that system response must be thought of in terms of Mathieu-type equations, where multiple-frequency response occur due to the periodic coefficients. The meshing action of the gears also couples the lateral and torsional gear motions. Gear errors, such as tooth profile and spacing errors, produce forces and torque that excite the system at multiple frequencies, some of which are much higher than shaft rotational speed. To investigate how to the time-varying stiffness in the gear teeth and the gear errors act one the dynamic response of the gear coupled rotors, a three-dimensional dynamic model with lateral-tortional oscillation is developed. The harmonic balance technique is employed to solve this mathieu-type problem.

• Tribology and Lubricants
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• v.34 no.6
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• pp.325-331
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• 2018

Automobiles and systems requiring high gear ratios and high power densities generally use worm gears. In particular, as worm gears have a small volume and self-locking function, home appliances such as refrigerators and washers consist of worm gears. We can classify worm gears into cylindrical worms and rectangular worms. According to the AGMA standard, there are four types of cylindrical worms, ZA, ZN, ZK and ZI, depending on the machining of the worm shaft. It is preferable to use a ZI-type worm shaft, which is a combination of a worm wheel having an involute helical tooth surface and a conjugate tooth surface. However, in many cases, industries mostly use ZK, ZN, and ZA worm shafts because of the ease of processing. This paper presents numerical approaches to produce ZI and ZA worm surfaces and worm wheel. For the analysis of the transmission error of a worm gear system, this study (1) generates surface profile functions of ZI profile worm gear and worm shaft based on the common rack theory, (2) adopts the Newton-Raphson method for the analysis of the gear surface contact condition, and (3) presents and compares the corresponding transmission errors of ZI and ZA worm gears.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.3
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• pp.13-18
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• 2011

This study deals with the effect of the honing in SCM420H planetary gears. The hardness, tooth profile, lead and roughness of the gear surface can be improved by honing. Therein, the honing techniques are welcomed especially as one of the physical surface improvement methods. As a result, gear honing reduces vibration and noise, and will increase the life of gear. And gear honing also changes the surface of gear tooth in a short time and price, so it is a very important method in manufacturing industry. But nowadays, it is hard to find the detail information of gear honing. The test gear is a planetary gear which is used in the automotive industry. It is manufactured by the hobbing, shaving, carburizing and honing. This study investigates the effect of honing in surface shape of SCM420H planetary gears, including fatigue strength test and characteristics of honing of SCM420H planetary gears.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.2
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• pp.27-33
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• 1981

In the paper, it was attempted to verify how the strength around fillet area of shifted gear would be affected by variables such as number of teeth, shifted value, and diametral pitch. Thereafter, the Lewis' tooth factor of the shifted gear was computed in terms of previously mentioned variables in order to observe the characteristics of stress change related from tooth factor and tooth number with the parameter of shifted values and diametral pitches. From the results of quasi-theoretical values by Finite Element Method(F.E.M.)and experimental values through the photo-elastic tests, the followings were identified. The more the number of gear teeth increased, the more the profile of the tooth became close to that of rack, and accordingly the stresses in the fillet area decreased significantly in certain range. Furthermore, as the shifted value and pressure angle increase the stresses tend decrease. Moreover, the stresses analyzed by F.E.M. in the filled area became around 1.22 times larger than the stresses computed by Lewis' form factor, and this is supposed as on influence of the stress concentration in fillet area.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.422-427
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• 2000

Gear design carried in former type determined a few variables like module, pressure angle, helix angle. After investigating repeatedly results obtained through stress analysis and making a determination an optimal shape, but its design process was not only complex but also difficult to get a precise profile curve from operating by hand. In this study, rotating shape of gear profile curves were generated automatically with standard spur gear, equivalent helical gear, shifted gear & pinion by using developed program which is Auto_LISP language supported in Auto-CAD. Output tooth profile by using CAE program is applied as Preprocessor for stress analysis in each contact points. This program which can be determined rapidly an optimal shape of gear will be successfully supported for Small & Medium companies designing and manufacturing gears by using Auto-CAD.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.54-59
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• 2012

This study dealt with effect of the grinding in SCM420H planetary gears. The hardness, tooth profile, lead and roughness of the gear surface can be improved by grinding process. Therein, the grinding techniques are widely used especially as one of the physical surface improvement methods. As the results, the gear grinding process reduced vibration and noise, and increased the life of the gear. And the gear grinding improved the surface of gear tooth in a short time and low cost, thus, it is a very important process in manufacturing industry. But nowadays, it is hard to find the detail information of gear grinding process. The test piece is a planetary gear which is used in the industrial machine. The manufacture process of the test piece contains hobbing, shaving, carburizing and grinding. This study investigated the effect of the grinding process to the physiognomy and the fatigue strength of test piece which was made by SCM420H.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.5
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• pp.85-92
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• 1998

This present paper describes a mathematical model of profile shifted elliptical gears, and this model is based on the concepts of envelope theory and conjugate geometry between the blank and the straight-sided rack cutter. The geometric model of the rack cutter includes working regions generating involute curves and fillets for trocoidal curves, and furthermore the addendum modified coeff. is considered for avoiding undercutting. The addendum modified coeff. is changed linearly along with pitch curves and must be the same absolute value at both major semi-axis and minor semi-axis. If undercutting is at all pronounced, the undercut tooth not only are weakened in strength, but lose a small portion of the involute adjacent to the base circle, then this loss of involute may cause a serious reduction in the length of contact. A very effective method of avoiding undercutting is to use the so-called profile shifted gearing. Non-undercutting condition is examined with the change of eccentricity and addendum modified coeff. in elliptical gears and then the minimum number of tooth is proposed not to gernerate undercutting phenomenon.