• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.39-48
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• 2014

Variable valve actuation system is one of the widely used techniques to improve the fuel efficiency and power of automotive engines. 2-step variable valve actuation systems are also paid attention for the application to direct acting type valve train systems. Besides its advantages in size, weight, relatively simple structure, ets, however, 2-step variable valve actuation system has inherent disadvantages in dynamic instability of switching system to alter discontinuous lift modes. In this study, both experimental and analytical studies are performed to understand the dynamic behavior of a switching mechanism of a 2-step variable valve actuation system, and present a design method to improve its dynamic instability.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.137-142
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• 2006

The muffler which reduce the exhaust noise and vibration from engine influence on the engine performance. Recently, exhaust variable valve has set up in the muffler controls the backpressure in the exhaust system. And the backpressure variation according to the exhaust variable valve opening has developed the engine performance. First, the preceding of structural analysis is needed and simulation experiment is requested for the study on the design factor to influence on the operation of the exhaust variable valve. In this study, setting up the various variables according to each composition element needed for the structural analysis of the exhaust variable valve, it is experimented the analysis on the influence of each design factor with the calculation of stress distribution and the displacement to cause about the backpressure for the valve through parameter study.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.7-15
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• 2009

This paper introduces a new variable valve actuation mechanism with movable second cam center. Valve lift and open duration can be continuously varied according to engine speed and load conditions. A new method to analyze the kinematic relations between the first and second cam profiles and valve motion are also introduced. Because of rocker motion of the second cam, conventional motion conversion program could not be used in this problem. An example shows continuous variations of valve motion and adequate ramp incorporation throughout all valve lift modes. Valve acceleration profile at the high lift mode is similar to that of conventional valvetrains. Contact geometry analysis of the mechanism gives basic information on the load conditions between the components.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.28-35
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• 2015

Thin film electronic devices which brought the current mobile environment could be fabricated only under the high quality vacuum conditions provided by high vacuum systems. Especially for the development of advanced thin film devices, constant high quality vacuum as the deposition pressure is definitely needed. For this purpose, the variable conductance throttle valves were employed to the high vacuum system. In this study, the effects of throttle valve applications on vacuum characteristics were simulated to obtain the optimum design modelling of variable conductance of high vacuum system. Commercial simulator of vacuum system, $VacSim^{(multi)}$, was used on this investigation. Reliability of employed simulator was verified by the simulation of the commercially available models of high vacuum system. Simulated vacuum characteristics of the proposed modelling were agreed with the observed experimental behaviour of real systems. Pressure limit valve and normally on-off control valve were schematized as the modelling of throttle valve for the constant process-pressure of below $10^{-3}torr$. Simulation results were plotted as pump down curve of chamber, variable valve conductance and conductance logic of throttle valve. Simulated behaviors showed the applications of throttle valve sustained the process-pressure constantly, stably, and reliably.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.690-691
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• 2006

Variable valve timing unit, which is able to decrease environmental load and improve fuel economy is loaded onto many automobiles recently. This unit consists mainly of sprocket, housing and rotor. These parts are requested different properties according to environment. We produce sintered parts for variable valve timing unit by selecting compact, sinter process and special treatment according to demanded properties. In this paper, demanded properties of sintered parts for variable valve timing unit and adopted technique to satisfy them are presented.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.79-87
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• 1999

In this study, a new type of flow control valve which is SMA actuated flow control valve is presented. The flow control valve is actuated by a small motion of shape memory alloy. The performance of this valve as a position control component is analyzed by computer simulation. A variable structure control technique is applied for the position control by the flow control valve. The position control performance of the valve is evaluated on the step responses of a PID control by a electrohydraulic servo valve. For the simulation study, first, the mathematical model of a hydraulic system, which is consisted of the flow control valve and a hydraulic cylinder, is formulated. This mathematical model and the designed variable structure control algorithm are then combined by the MATLAB software. The same sequence of work is carried out for the PID position control system with a electrohydraulic servo valve. The simulation results show the validity of the new type of flow control valve as a variable position control component.

• Journal of ILASS-Korea
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• v.25 no.2
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• pp.45-50
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• 2020

Recently, global warming and environmental pollution are becoming more important, and fuel economy is becoming important. Each automobile company is actively developing various new technologies to increase fuel efficiency. CVVD(Continuously Variable Valve Duration) system means a device that continuously changes the rotational speed of the camshaft to change the valve duration according to the state of the engine. In this paper, VVT(Variable Valve Timing) and CVVD were applied to a single-cylinder diesel engine, and the characteristics of intake and exhaust flow rate and in-cylinder pressure characteristics were analyzed by numerical analysis. In order to analyze the effect of CVVD on the actual engine operation, the study was performed by setting the valve control and injection pressure as variables in two sections of the engine operating region. As a result, In the case of applying CVVD, the positive overlap with the exhaust valve is maintained, thus it is possible to secure the flow smoothness of air and increase the volumetric efficiency by improving the flow rate. The section 2 condition showed the highest peak pressure, but the pressure rise rate was similar to that of the VVT 20 and CVCD 20 conditions up to 40 bar due to the occurrence of ignition delay.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.80-85
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• 2003

In the present paper, dynamics analyses of pressure control characteristics have been performed in a variable pressure solenoid valve. A number of solenoid valves have been used in the electronic control system, especially automatic transmission of an automobile. Variable pressure solenoid valve is intended to produce spatial movement by the electrical signal. Dynamics analyses of pressure control characteristics have been practiced by the Finite Difference Method, which show the pressure distribution in the solenoid valve. The results of numerical analyses show the dependence of pressure distribution on the displacement of the spool in the solenoid valve, and then, are compared with the experimental results.

• Journal of Drive and Control
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• v.17 no.4
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• pp.87-96
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• 2020

In this study, a variable elasticity spring was applied to improve the pressure control precision of conventional relief valves. The equilibrium equation of the forces acting on the valve poppet was derived; it is demonstrated that matching the elastic rate of the pressure-adjusting coil spring to the equivalent elastic rate of the flow force improved the pressure override. The procedures that were used to design the variable elasticity spring are presented, and some applications of the variable elasticity spring are also introduced. Computer simulations were used to analyze three cases: a poppet-closed flow force structure, a poppet-open flow force structure with a constant elasticity spring, and a structure containing a variable elasticity spring. It is confirmed that the pressure control precision of the relief valve can be significantly improved upon by applying a variable elasticity spring to the poppet-open flow force structure.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.190-196
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• 2014

Exhaust system by reinforcement of environment regulation came to the foe study necessity. And Exhaust system has necessary to increase the engine performance and silence. From this cause, Automobile has significantly considered production expense. this study makes process for checking the characteristics about Exhaust variable valve within muffler. Variable valve might reduce the baffle within muffler, It was possible to remove the front muffler. Therefor, To miniaturize a size of muffler might be increased by performance through cost-cutting effect and controling of back pressure. Because the Study on Variable valve installed within muffler, to measure the real data was hardly resulted one of the assignments. From manufactured conduct device, might measure data one of piece which was up-graded of problem. Considering to these point, stressed pressure distribution has analyzed on cross section, floating characteristics about velocity distribution around variable valve using analysis as computational fluid dynamics of Ansys with completed measurement data.