• Journal of Drive and Control
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• v.15 no.4
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• pp.1-10
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• 2018

Spool displacement of a direction control valve is the standard signal to measure the bandwidth frequency of the direction control valve. When the spool displacement signal is not available, it is suggested in this study to use the metering hydraulic line as an alternative way to measure - 90 degree phase bandwidth frequency of the hydraulic direction control valve. Dynamics of the hydraulic line is composed of inertia, capacitance, and friction effects. The effect of oil inertia is dominant in common hydraulic line dynamics and the line dynamics is close to a derivative action in a range of high frequency; such as a range of bandwidth frequency of common directional control valves. Phase difference between spool displacement and line load pressure is nearly constant as a valve close to 90 degree. If phase difference is compensated from the phase between valve input and pressure, compensated phase may be almost same as the phase of spool displacement that is a standard signal to measure phase bandwidth frequency of the directional control valve. A series of experiments were conducted to examine the possibility of using line pressure in to measure phase bandwidth frequency of a directional control valve. Phase bandwidth frequency could be measured with relatively high precision based on metering hydraulic line technique and it reveals consistent results even when valve input, oil temperature, and supply pressure change.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.555-560
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• 2000

The modeling and the numerical analysis are done so as to develop the Computer Aided Design program for the design of flow control valve attached to the vane pump. The factors affecting the flow rate characteristics, are analyzed by the experiments and the numerical methods. It is shown that the main factor affecting to the first control flow is the diameter of small rod of the spool, the main factor affecting to the second control flow is the diameter of big rod of the spool, the main factors affecting to the cut off are the main spring constant, the initial displacement of main spring and small diameter of the spool, and the dropping slope characteristics of flow rate are decided by the chamfer of spool and the dynamic characteristics of the spool.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.230-231
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• 2005

As environmental problems are important, automotive industries are developing various techniques to prevent air pollution. One of these is Positive Crankcase Ventilation (PCV) system. It removes blowby gas which includes about 30% hydrocarbon of total generated quantity. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates differently according to various operating conditions of an automotive engine. As this valve is very important, designers are feeling to design it because of both small size and high velocity. For this reason, we numerically investigated to understand both spool dynamic motion and internal fluid flow characteristics. As the results, spool dynamic characteristics, i.e. displacement, velocity, acting force, increase in direct proportion to the magnitude of differential pressure and indicate periodic oscillating motions. And, the velocity at the orifice region decreases according to the increase of differential pressure because of energy loss which is caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in the front of spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement. We expect that PCV valve designers can easily understand fluid flow inside a PCV valve with our visual information for their help.

• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.15-20
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• 2012

PCV(Positive Crankcase Ventilation) system is designed to remove blowby gas. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates various operating conditions of an automotive engine. As this valve plays a crucial role, the demand in its design is high owing to the small size and high velocity. For this reason, a numerical investigation was carried out to understand both the spool dynamic motion and internal fluid flow characteristics. As a result, the spool dynamic characteristics(i.e. displacement, velocity, acting force), increase in direct proportion to the magnitude of the pressure difference and indicate periodic oscillating motions. Moreover, the velocity at the orifice region decreases according to the increase in differential pressure due to energy loss caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in front of the spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.721-724
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• 2002

This study deals with a dynamic behavior analysis of pump control regulator varied the swash plate tilting angle with the positive and negative direction. To accomplish it's purpose, modeling and displacement response analysis about principal parts (spool, servo piston, feedback lever, sleeve) of pump control regulator was performed. We have been able to verifying the propriety of servo mechanism and design parameters of pump control regulator by research results. So, it respect to utilized with useful research data at variable displacement control valve development of variable displacement piston pump.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.67-72
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• 2011

Solvent-free paint is sprayed from higher-pressure conditions, because the viscosity is large. The hydraulic actuator which can be operated under higher-pressure condition is required to spray solvent-free paints in painting process for the environmental protection. The purpose of this paper is to develop the hydraulic actuator under higher-pressure conditions for solvent-free paint spraying system. The hydraulic actuator consists of inner spool, outer spool and ball. The analysis of a structural stability was conducted by using ANSYS V11 under the design condition of upward and downward movement of spool. As a result, the maximum von-Mises stress applied on spool under 4mm displacement showed a value of 106MPa which was greater than the allowable stress of the spool with a value of 250MPa and a value of safety factor 3. This result suggested that the spool system be unstable under the design condition so that it was necessary for the spool system to be reinforced to secure the structural stability.

• Journal of Drive and Control
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• v.14 no.2
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• pp.1-8
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• 2017

The spool displacement of a directional control valve can be considered as the standard signal for the measurement of its bandwidth frequency. When the spool displacement is not available, the metering-orifice system is suggested in this study as an alternative way to measure the - 3 dB amplitude-ratio bandwidth frequency of the hydraulic directional-control valve. The amplitude ratio of the metering-orifice pressure can be adjusted to equal that of the spool displacement through the controlling of the metering-orifice opening area. A series of experiments were conducted to verify the effectiveness of the metering-orifice system. The metering orifice was confirmed as adequate for the measurement of the - 3 dB amplitude-ratio bandwidth frequency.

• Journal of Drive and Control
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• v.13 no.2
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• pp.42-50
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• 2016

The conventional technique to measure the hysteresis and the null of servo valves is defined in ISO 10770-1 and based on load flow signal of the servo valve. A new technique based on the transmission line pressures is suggested in this study. The new measuring method was verified through a series of experiments. No hysteresis was observed between the spool displacement and the transmission line pressures, load pressure or each chamber pressure. Some hysteresis was observed between valve input and pressures, which was found to be the same as those of load flow and spool displacement for the valve input. By using the chamber pressures, the hysteresis and the null are easier to measure than the load pressure or differential pressure between those two chamber pressures because the chamber pressures showed sharp edges.

• Journal of Drive and Control
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• v.18 no.2
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• pp.9-19
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• 2021

The spool displacement signal of a directional control valve, including the servo valve, can be considered as the standard signal to measure dynamic characteristics. When the spool displacement signal is not available, the velocity signal of a metering cylinder piston can be used. In this study, the frequency response characteristics of the metering cylinder are investigated for the spool displacement input. The transfer functions of the servo valve-metering system are derived taking into consideration the oil inertia effect in the transmission lines. The theoretical results of the transfer functions are verified through computer simulations and experiments. The oil inertia effect in the transmission lines was found to have a very significant effect on the bandwidth frequency of the servo valve-metering cylinder system. In order to more precisely measure the dynamic characteristics of a servo valve, the metering cylinder should be set up to minimize the oil inertia effect by increasing the inner diameters of the transmission lines or shortening their lengths.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.5
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• pp.87-95
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• 2000

The numerical analysis and the experiments are carried out to develop the design program for the flow control valve attached to the vane pump for power steering. The factors affecting the flow rate characteristics are analyzed by the experiments and the numerical analysis. The results are summarized as follows; (1) the main factors affecting to the first and second control flow rate are the diameter of big and small rod of the spool. (2) the cut off is mainly affected by the main spring constant, the initial displacement of main spring and the small diameter of the spool. (3) the dropping slope characteristics are decided by the chamfer of spool and the dynamic characteristics of the spool.