• International Journal of Automotive Technology
• /
• 제6권1호
• /
• pp.65-70
• /
• 2005

Pressure ripples, which are inevitably generated by a fluctuation of flow rate caused by a pump mechanism, include noises and vibrations in hydraulic pipeline. These noises and vibration deteriorate the stability and accuracy of hydraulic systems. The accumulator and hydraulic attenuator are normally used to reduce the pressure ripples. In this study, a parallel line is introduced to the hydraulic pipeline for the hydraulic system with a bent-axis piston pump as a method to reduce the pressure ripples. The dynamic characteristics of the hydraulic pipeline with a parallel line are analyzed by a transfer matrix in the frequency domain. The usefulness of the hydraulic pipeline with a parallel line was ascertained by experiment and simulation. The results from the experiment and simulation show that the hydraulic pipeline with a parallel line were effective in reducing the pressure ripples.

• 드라이브 ㆍ 컨트롤
• /
• 제15권4호
• /
• pp.1-10
• /
• 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.

• 자동차안전학회지
• /
• 제12권2호
• /
• pp.47-55
• /
• 2020

In this case study, the brake line failure of air over hydraulic(AOH) brake system is described. AOH brake system is applied to commercial vehicles between 5 to 8 tons. It consists of a hydraulic system using compressed air and operates the air master to form hydraulic pressure to transfer braking power to the wheels. When the brake lines of the system applied to vehicles with high load capacity are damaged, the braking force of one shaft is lost, and the braking distance increases rapidly, leading to a big accident. Failure of the brake line occurs due to various causes such as road surface fragmentation, corrosion of the line, and aged deterioration of air brake hose. The braking force could be decreased even when a very small break in the form of a pin-hole occurs. However, it is difficult to find a part where the thickness of the line is thin due to stone pecking or corrosion generated in the pin-hole formed on the brake line located under the lower part of the vehicle by the sensory evaluation or the conventional braking force test. Accordingly, it is necessary to analyze the condition and cause of the failure of the brake line more precisely when the accident investigation of the heavy vehicles, and also to examine the necessity of the advanced test for the aged brake line.

• 드라이브 ㆍ 컨트롤
• /
• 제11권4호
• /
• pp.32-38
• /
• 2014

The hydraulic fuse, which responds to the suddenly increased flow on rupture of a line and shuts off the fluid flow, would prevent large spillage of liquid. The quick-acting hydraulic fuse, which is mainly composed of a poppet, a seat, and a spring, must be designed to minimize the leaked flow and to prevent high collision speed between the poppet and seat during fuse operation on a line rupture. The optimal design parameters of a quick-acting hydraulic fuse were searched using the genetic algorithm and the complex method that are kinds of constrained direct search methods. The dynamic behavior of a quick-acting hydraulic fuse was researched using computer simulations that applied the obtained optimal design parameters.

• 한국정밀공학회지
• /
• 제20권9호
• /
• pp.70-76
• /
• 2003

In this study, the hydraulic breaker system was analyzed and simulated using. The simulation result was certified comparing with the experimental result. From the parametric analysis, the effects of each factor were revealed. Through the simulation with varying parameters, the method to reduce the return line pressure fluctuation was presented.

• 한국자동차공학회논문집
• /
• 제9권5호
• /
• pp.140-147
• /
• 2001

The solenoid valve in ABS hydraulics, modulator is a two directional on-off valve and is controlled by around 100Hz high speed pulse width modulation. When the inlet valve is switched from open state to closed state, there are braking force degration, noise and vibration due to pressure surge phenomena in the hydraulic line and wheel cylinder. In this study, identifies pressure surge phenomenon in the braking process of a ABS, and investigates the way to reduce the phenomenon. For the purpose theoretical analysis on the pressure surge in the closed state hydraulic line, characteristic curve method based on wave equation was utilized. During this analysis, we could find pressure surge characteristics change due to hydraulic line change and PWM control conditions. In conclusion, by using the results of this study for the pressure surge prediction and reduction method, we could expect braking performance enhancement in Anti-Lock Braking System.

• Nuclear Engineering and Technology
• /
• 제53권1호
• /
• pp.322-336
• /
• 2021

This paper presents a numerical prediction of the transient hydraulic loads acting on the tubes and external supports of a pressurized water reactor (PWR) steam generator (SG) during blowdown following a sudden feedwater line break (FWLB). A simplified SG model was used to easily demonstrate the prediction. The blowdown discharge flow was treated as a flashing flow to realistically simulate the transient flow fields inside the SG and the connected broken feedwater pipe. The effects of the SG initial pressure or the broken feedwater pipe length on the intensities or magnitudes of transient hydraulic loads were investigated. Then predictions of the decompression pressure wave-induced impulsive pressure differential loads on SG tubes and the transient blowdown loads on SG external supports were demonstrated and the general aspects of transient responses of such transient hydraulic loads to the FWLB were discussed.

• 산업기술연구
• /
• 제27권A호
• /
• pp.61-67
• /
• 2007

The construction machine is the composite machine assembled by about 30,000 parts. Excavator, one kind of a construction machine, plays the leading role for export of construction equipment. It is generally impossible to produce all of the items within one company. Especially the supply of hydraulic control valves, one of the core part of the construction equipment, depends on the import heavily. So it is important to make an efficient production plan of hydraulic control valves in the company. The most important thing for the production scheduling of a hydraulic control valve is to make production schedule keeping the start date for assembly line for an excavator and to make minimization of the stock level. The production plan of hydraulic control valve includes the decision of the quantity supplied by subcontractor. This paper presents a scheme for a scheduling system of the hydraulic control valve considering the schedule of the assembly line for excavator production. This paper provides a methodology, which can make a plan of supply and production and generate a detailed schedule for daily production.

• 한국자동차공학회논문집
• /
• 제12권2호
• /
• pp.109-116
• /
• 2004

Bent-axis piston pump have been commonly used in hydraulic systems because of high pressure level, best efficiency, low shear force on pistons and low operating costs. The other side, they have a few demerits like that they have the relatively high number of moving parts and more discharge pressure ripples. Especially, the discharge pressure ripples bring about vibrations and noises in hydraulic system components such as connecting pipes and control valves, so that these deteriorate the stability and accuracy of the systems. Therefore, the hydraulic systems having the bent-axis piston pump require the methods to reduce the discharge pressure ripples. So, the purpose of this paper is to reduce the discharge pressure ripples by the phase interference of pressure wave and to develope the analysis model of the pumps to predict the discharge pressure ripples. In this paper, the analysis model of the bent-axis piston pump was developed using the AMESim software, and the reliability of that was verified by the comparison with the experimental results. The hydraulic pipeline with a parallel line was used as the method to generate the phase interference of pressure wave. the dynamics characteristics of the hydraulic pipeline with a parallel line were analyzed by a transfer matrix method. the usefulness of the phase interference of pressure wave was investigated through the experiment and simulation. The results from the experiment and simulation said that the phase interference of pressure wave by the hydraulic pipeline with a parallel line could reduce the discharge pressure wave of the pump well. The analysis model of the bent-axis piston pump developed in this paper and the method of the phase interference by the hydraulic pipeline with a parallel line are expected to be helpful to achieve the design of the pump and to reduce the discharge pressure wave of the pump effectively.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.2024-2030
• /
• 2003

Design for a quite operation of fluid power system requires the understanding of noise and vibration characteristics of the system. This paper presents a dynamic response for design of hydraulic circuit. Experimental investigations on the attenuation characteristics of pressure ripple in automotive power steering hydraulic pipe with dynamic response of hydraulic pipe line is examined. Also, a mathematical model of hydraulic pipe is proposed to support design of the hydraulic circuit and analyze the attenuation characteristics of pressure ripples in a hydraulic pipe line. And analyze the impedance characteristics to determine the postion to construct accumulator for attenuation the pressure pulsation. The experimental results show that the pulsation attenuation characteristics of hydraulic hoses is remarkably affected by the flexible metal tube inserted coaxially inside a hydraulic hose with a finite length as well as viscoelastic properties of hose wall. It is also shown that the predicted results by the model proposed here agree well with the measured results over a wied range of frequency;