• Journal of Biosystems Engineering
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• v.40 no.2
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• pp.95-101
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• 2015

Purpose: During the start-up period, the response time of a hydraulic system increases in the winter because of the increased oil viscosity caused by the cold weather. The problems of delayed tractor starting and excessive wear of the clutch disk occur for these reasons. Therefore, this study develops an analysis model using the commercial hydraulic analysis program AMESim to examine the characteristics of delays in power shuttle starting at different oil temperatures. Methods: In the experiment, a tractor was stationary on a flat surface with the engine running at a constant speed of 1,080 rpm. The forward lever was then pressed to activate the power shuttle at three different oil temperatures, and the pressure changes were measured. The pressure on the forward clutch control valve was measured by a pressure gauge installed on the hydraulic line supplied to the transmission from the main valve. An analysis model was also developed and verified with actual tests. Results: The trend of the simulated pressures of the power shuttle is similar to that of the measured pressures, and a constant modulation period was observed in both the simulation and test results. However, the difference found between the simulation and test results was the initial pressure required to overcome the initial force of the clutch spring. Conclusions: This study also examines the characteristics of the delayed startup of the power shuttle at different oil temperatures through simulations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.521-528
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• 2009

One of reliability measurements of vehicle is estimated by driving mileage but the reliability of component, such as an hydraulic clutch system, is defined from the number of successful operational cycle. Relationship between these reliability measurement variables(mileage and cycle) should be examined first of all in the reliability estimation of components. Relationship between mileage and cycles is commonly known as linear function. However, the gradient depends on the operational environmental condition. Therefore, estimation of mission profile variable should be done with correlation analysis at the same time. In this paper, we derive mission profile variable of an hydraulic clutch system by field vehicle test and suggest the determination process of durability test parameters of CMC(Clutch Master Cylinder) with mission profile variable.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.75-82
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• 2007

The AMT(Automated Manual Transmission) has been developed by utilizing the auto clutch system and the automatic shift mechanism, to automate the clutch operation and shift operation of the existing MT(Manual Transmission). The use of hydraulic actuator for each actuator of the clutch and gear has realized a reduction of fuel consumption and exhaust emission. In this paper, we develop a simulator for the transmission control system of the AMT using AMESim. The developed simulator can be applied to design the hydraulic select actuator system of an AMT.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1572-1577
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• 2003

The powershift transmission have the advantage of easier operation and higher efficiency by using the hydraulic clutch and mechanical power transfer system. It is important to control the engaging pressure and time. The hydraulic control system is used for these controls of the modulator valve, the accumulator, the sump valve and etc. This study have made a simulator for verifying the pressure characteristic of the shuttle powershift transmission and developed the computer simulation model of the hydraulic components and system by using 'AMESim'. As a result, the design parameters which have an effect on the pressure modulation are verified to the spring stiffness of the modulator valve and the volume of the accumulator.

• Journal of the Korean Society of Industry Convergence
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• v.13 no.1
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• pp.15-22
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• 2010

This paper was originated to set up a test equipment and to obtain the proper installation condition of the plastic damper for the hydraulic clutch control system. Performance tests with different specifications have been applied to the damper to investigate the workability and the vibration characteristics of each case, and the result was utilized into the system simulation for the optimal condition for the damper. The procedure has been developed to set up a damper test system to analyze the dynamic properties and the operation of the system, and further to setup a simulation program for the realistic situations. The result can also be applied to the dampers and the clutch systems to be developed in the future for the property tests and the optimization of the installation conditions.

• Journal of Biosystems Engineering
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• v.28 no.3
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• pp.187-198
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• 2003

This study was conducted to investigate the effect of design parameters of modulating valve and hydraulic clutch on the shift quality of a power shuttle transmission using a computer simulation. Computer simulation models of a hydraulic control system and a power shuttle drive train were developed and verified by an experimental power train in a laboratory. The software EASY5 was used for the modeling and simulation of the power shuttle transmission. Results of the study were summarized as follows: For a good shift quality. it is required to reduce the transient torque transmitted to the output shaft of the transmission as much as possible. This may be achieved by reducing the modulating time and clutch pressure. It was found that the design parameters most significantly affecting the modulating time and clutch pressure were the spring constant and displacement of a load piston of the modulating valve, and the spring constant and damping of the clutch piston. The modulating time decreased as the spring constant increased and increased as the displacement of the load piston decreased. The transient torque decreased as the modulating time increased. However their relationships were not always linear. As the damping decreased, both the modulating pressure and time decreased, which also resulted in a decrease in the transient torque. The spring constant of the clutch piston affected the modulating time and the peak transient torque. As the spring constant of the clutch increased, the peak transient torque decreased.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.68-84
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• 2000

A study to reduce the transient torque in shifting in automatic transmission has been very important issue. Recently it is really dominant to decrease the torque by using independent-acting hydraulic circuit because we can control the clutch pressure actively and elaborately. So we design the new hydraulic circuit to control the clutches in automatic transmission and make the module library of computer simulations, We apply the results to GM model automatic transmission and carry out 1longrightarrow4 shifting simulations. By this work we recognize the capability of active and elaborate clutch pressure control using new hydraulic circuit. In addition We develop the tool to simulate the powertrain system. It is easier to update and exchange the subsystem model or parameters than conventional simulation tools.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.10-21
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• 1996

In this study, as a strategy to improve shift characteristics, the authors developed a new style pressure modulator which can reduce shock torque during power shift by modulating the pattern of pressure increase in the cylinder for actuating the clutch. The remarkable merits of this new pressure modulator lie in its structural simplicity and durability, because the modulator is only composed of a poppet type valve and a few orifices. The usefulness of the new pressure modulator is confirmed by experiments and numerical analyses on a clutch control hydraulic system simplified for easy test. Also, the excellency of the transmission with the new pressure modulator is verified by experiments on a test bench for simulating the running power train of an excavator.

• Tribology and Lubricants
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• v.29 no.1
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• pp.1-6
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• 2013

Hydraulic transmission is the main component delivering power to the drive wheels of an excavator during forward and backward movement, and it has low speed, high torque and high speed, low torque gear change ratios as a forward/backward two-speed main function. It also has additional function of ensuring that the excavator is stably fixed on the ground with the built-in parking brake during excavation operations. In this study, optimal design specifications are determined by modeling and simulating about the multi-disc-type friction clutch, which is the main component improving the reliability of the hydraulic transmission for a 14-ton wheel excavator, and the friction properties of the transmission clutch are analyzed by performing sample tests.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.284-294
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• 1996

In this paper, dynamic characteristics of an AT clutch system were investigated considering the dynamics of check ball and hydraulic control valves. Dynamic model of a pressure control solenoid valve (PCSV) was obtained by Bondgraph and permeance method. Also, the clutch piston and check ball dynamics were modeled by considering the effect of centrifugal force of the oil entrapped in the clutch chamber. In order to validate the dynamic models obtained, plunger displacement of PCSV and pressure response of the clutch supply lines were compared with the available experimental data, which were in good accordance with the numerical results. Using the dynamic model of the clutch system, simulations were performed to investigate the effect of the rotational speed on the response of clutch cylinder pressure, clutch piston and check ball displacement, and oil flow rate into the cylinder and flow rate out of the check valve.