• Journal of the Korean Society for Precision Engineering
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• v.33 no.11
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• pp.927-935
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• 2016

A gerotor is suitable for miniature manufacturing because it has a high discharge per cycle and a simple structure, while also being widely used as lubrication oil of engines and the hydraulic source of automatic transmission. In the automobile industry, it has been necessary to continuously improve the flow rate and noise of internal gear pumps for better fuel efficiency through optimal gerotor design. In this study, to obtain an optimal gerotor with an ellipse-elliptical involute-ellipse combined lobe shape, an automatic program was developed for calculating performance parameters and drawing a gerotor profile. An oil pump was assembled with the optimal gerotor together with the port used at the actual field and CFD analysis was performed on this assembly using Ansys-CFX. A performance test for the oil pump was carried out and showed good agreement with the results obtained from the theoretical analysis and the CFD analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.594-602
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• 1990

A computer-aided design system of involute cylindrical gears(spur and helical gears) for power transmission is developed, in which the volume of a gear unit is minimized with satisfying various design constraints. As the design constraints, bending strength and pitting resistance of AGMA 218.01, scoring of Dudley's flash temperature, contact ratio, and involute interference of pinion are considered and effective factors for strength calculation(life, reliability, hardness ratio, load distribution, velocity, etc.) are also included. This complicated nonlinear optimization problem is solved by using ALM(Augmented-Lagrange-Multiplier) method with self scaling BFGS(Broydon-Fletcher-Goldfarb-Shanno) method employed for unconstrained optimization programming. This design method can be easily applied to designing power transmission gear unit in the machines of various kinds. It is expected for the proposed method to be a contribution for an automated design of gear unit towards weight minimization, miniaturization and high strength of gear unit.

• Transactions of Materials Processing
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• v.10 no.4
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• pp.302-310
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• 2001

The twisting and extrusion process of the product with involute helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted inclined die surface connecting the die enterance section and the die exit section linearly. In the analysis, the internal shear surface is defined as the curved twisted plane from the twisting of die surface and the shear work is calculated by the consumption of shear energy. The increase rate of angular velocity is determined by the minimization of plastic work. The angular velocity of die exit can be controlled by the land length and the length of inclined die. The alular velocity assums to be increased linearly by the axial distance from the die enterance to the die exit. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction constant.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.111-115
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• 2001

The die design for hot forging was investigated for manufacturing precisely of scroll rotor made with Al-Si alloy. A scroll rotor is a non-symmetric 3-D shape part, having involute wraps. Disk-shaped billet of Al-Si alloy was extruded to wraps and boss simultaneously. Because the involute wraps is not axi-symmetric, the flow velocity and the stress of die is very much different at each portion. Moreover, the die in wraps portion is a cantilever beam and fractured. In this paper, the analysis of forming and die stress is investigated using the FEM tool, DEFORM-3D. The tensile strength of tool material is $250kg/mm^{2}$. From the analysis results, we can find the maximum principal stress of die is over the fracture strength and redesign the die. The prototype forged part is superior in net shaping and microstructure.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.259-266
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• 2002

The basic concept of 'tooth profile modification' is to change a part of the involute profile to reduce the load in that area and appropriate profile modifications can help gears to run quietly and resist scoring, pitting and tooth breakage. In this study, the modification of tooth profile to make a smooth transmission of the normal loads in spur gears has been developed. The modified tooth profile has been determined by the total deflection at contact points. We use the AGMA Standard to design basic gear profile, We also developed a gear design Program using tooth profile modification

• 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.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.77-84
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• 2014

The worm gear is used in the motor drive system of automotive CVVL because of its compactness and self-locking ability. A ZK worm and an involute helical gear can be meshed in order to reduce production cost. However, the gearing is not suitable for the reliability and the NVH problem. To improve the dynamic performances, an optimal design process is considered. The transmission error is calculated theoretically and minimized with the several gear design parameters. An inequality condition such as the teeth interference elimination is added.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.7-14
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• 1998

Noncircular gears have been used for obtaining the modified anglualr velocity ratio between parallel axes. The elliptical gear, which is a kind of noncircular gears, makes use of ellipse as a pitch curve, and is applied for the measurement of the discharge of liquid. The applications of an elliptical gear are more advantageous than any other mechanism as like a crank-slider linkage or a cam mechanism in view of the accuracy and the reliability to transmit the prescribed motion. In this paper, acceding to the theoretical involute tooth profile, two pairs of the elliptical gears were manufactured by using CNC wire electronic discharge machine. The proper ranges of the operating pressure angle and of module not to generate under cutting are studied on the change of the eccentricity, because it is the eccentricity of the pitch curve that determines most of the characteristics of the elliptical gear and then the vibration analysis is executed for the verification of harmonious rotating.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.6
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• pp.142-148
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• 1997

In this paper, forging of internal triangular and involute serrations are analyzed by upper bound method. Kinematically admissible velocity fields for half pitch of the serration were proposed. It was assumed that the shape flow surface during forging is a straight line perpendicular to plane of symmetry. Using the suggested velocity fields, forging loads and relative pressures were calculated by numerical method. Experiments were carride out with commercial AI 2024 aluminium alloy. As a result, the calculated solutions are good agreement with experimental results, so it is useful to predict the loads for forging of internal serrations.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.202-211
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• 2002

The basic concept of 'tooth profile modification' to change a part of the involute profile to reduce the load in that area and appropriate profile modifications can help gears to run quietly and resist scoring, pitting and tooth breakage. In this study, the modification of tooth profile to make a smooth transmission of the normal loads in spur gears has been developed. The modified tooth profile has been determined by the total deflection at contact points. We use the AGMA Standard to design basic gear profile. We also developed a gear design program using tooth profile modification.