• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.103-109
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• 2008

Semi-spherical CVT(SS-CVT) is one of friction drives, which transmits power via the friction force between a spherical shaped variator and output disks. The variator varies the speed ratio of SS-CVT continuously as well as transmits input power into the output shaft. Therefore two friction forces are normally applied on the variator; one is the longitudinal friction force for power transmission and the other is the lateral for shifting. In order to investigate the dynamic behavior of SS-CVT, we introduced a numerical model of 2-dimensional friction force using a function of slip ratio and slip angle. And a dynamic model, which describes the shifting mechanism of SS-CVT, is developed through 3-dimensional vector analysis. Finally we presented numerical results of the shift characteristics focused on the transient behavior of the variator's slip ratio and slip angle. The numerical results also show the typical CVT shifting characteristics of SS-CVT and stable shifting behaviors of the variator.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.81-91
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• 2000

Dynamic models of line regulator valve(LRV) and ratio control valve (RCV) are obtained for an electronic controlled CVT. LRV and RCV are operated by variable force solenoid(VFS). Considering the CVT shift dynamics, oil pump's efficiency and saturation characteristics of VFS, simulations are performed and compared with test results. Simulation results are in good agreement with the experiments, which shows the validity of the dynamic models of LRV and RCV obtained. In addition, the effects of the orifice size in the exhaust port of RCV are investigated. Simulation results show that as the orifice size decreases, the residual pressure in the primary actuator increases which insures the large torque transmission capacity, meanwhile the duration time for the downshift increases.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.59-64
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• 2024

In this study, we conducted research on a miniaturized transmission system suitable for ultra-compact electric vehicles, such as electric arts or small electric cars. While conventional electric vehicles eliminate multi-gear transmissions and control motor output or secure initial driving force through reducers, in vehicles like electric karts or compact electric cars, which have relatively small battery capacities, the driving range can be reduced or the motor can be stressed epending on the loading state. Therefore, in this study, we developed a low stage ratio 0.625 and high stage ratio 1.6 a two-stage transmission system that can change gears as needed, considering factors such as slope conditions and loading status, by applying the continuously variable transmission (CVT) mechanism. Based on the selected gear ratios, we designed the transmission and created a test rig to verify the power transmission efficiency of the developed transmission. Using the test rig, we varied the rotational speed and load of the transmission to confirm its power transmission characteristics and also examined the heat generation characteristics during shifting and operation. As a result, developed a two-stage transmission with a CVT structure.

• Journal of the Optical Society of Korea
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• v.10 no.2
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• pp.63-66
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• 2006

In microband-induced fiber gratings, polarization properties and birefringence are investigated as a function of an applied line force. With the transmission curves associated with the maximum and minimum resonant wavelengths, the polarization-dependent behaviors are analyzed. By increasing the transverse line force, the resonance wavelength for an incident light polarized to the same direction of the force is blue-shifted as much as 0.69 nm/(N/cm) while that for the other polarization is insensitive. Using the resonant wavelength separation corresponding to the force variation, the transverse effective index change or modal birefringence variation is obtained. The ratio of modal birefringence versus applied line force is ${\Delta}B/{\Delta}f_x={\sim}8.38{\times}10^{-7}$.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.75-81
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• 1999

In this paper, the details of electronically controlled CVT is described , which Kia Motor company recently developed in prototype form for hybrid passenger car. This transmission has two input shafts, one for engine and the other for traction motor. The shaft for traction motor is located at rear side which is extended from primary pulley shaft and connected to traction motor through adapter gear box. Adopting two input system, various driving mode is available such as motor alone driving in hybrid vehicle application. As far as electrohydraulic system concerned , this transmission uses two bleed type variable force solenoids for line pressure and ratio control, and one on-off solenoid for clutch control. Another feature for this transmission is that oil pump for transmission is separate from CVT for supplying oil pressure even at vehicle standstill.

• Journal of Power System Engineering
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• v.6 no.2
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• pp.73-81
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• 2002

In this study, electronically controlled automatic transmission adopted on a subcompact model in the market was modelled, and the driving performances of the transmission were simulated with the models. Kinetic and dynamic models of working components are established. The driving simulation program is developed with those models, and the various driving conditions are analyzed. With the results, the dynamic behaviour of the engine and the automatic transmission is easily understood. Especially, the transient performances of torque converter and clutches are deeply analyzed. Skipping the vehicle road test by using this analyzing tool, we can expect the cost down and the reduction of the development period of automatic transmission.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.199-205
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• 2000

The vibration and noise of gears is due to the vibration exciting force caused by the tooth stiffness which changes periodically as the mesh of teeth proceeds and by the transmission error, that is, the rotation delay between driving gear and driven gear caused by manufacturing error and alignment error in assembly and so on. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification, end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the mesh analysis of gears. The constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth fillet stress, surface durability and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. And, since the aspect ratio is an important parameter of tooth modification, we investigate the relation between it and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is to be utilized to resolve the problem of vibration of helical gears.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.557-566
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• 1991

The metal V-belt behavior of a continuously variable transmission was investigated analytically and experimentally. Numerical results showed that nondimensional belt radial displacement increased in the radial inward direction for the driven pulley, while that of the driver pulley increased for the first 90 degrees of the active are and decreased with the increasing torque load. Experimental results for the belt radial displacement were in good agreement with the theoretical results. However, the absolute magnitude of the belt radial displacement was so small that the change in the belt displacement could not be measured in the experimental range except for the inlet region of the driven pulley, where the radial inward displacement was observed due to the effect of bending moment. The speed ratio-axial force relationship derived from the belt behavior analysis also showed god agreement with the experiment.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.213-223
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• 1999

In this paper, input-output transmission characteristics of the Eclipse, which is a parallel machine tool capable of 5 face rapid machining, are investigated. By splitting the weighted Jacobian matrix into two parts, the force and moment transmission characteristics together with the velocity and angular velocity transmission characteristics are analyzed. A new manipulability measure, which combines the volume of the manipulability ellipsoid and the condition number of the splitted Jcobian matrix, is proposed. Two link parameters, the ratio of upper and lower platforms' radii and the length of a supporting link of the Eclipse, are designed by applying the new manipulability measure derived. Computer simulations are provided.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.2
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• pp.99-109
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• 1992

The response characteristics of a CVT vehicle is investigated numerically by using a Bondgraph model. Simulation result show the continuous behavior of the engine and the speed ratio for the CVT vehicle compared to the discrete behavior of the automatic transmission. Also, the optimal operation of the CVT which is derived from the speed ratio-torque-axial force equation from the previous works. It is found that the speed ratio of CVT has to be controlled corresponding to the optimal CVT ratio that makes the engine run on the optimal operating line.