Development Of Comprehensive Performance Detection System For Four-circuit Protection Valve

In the automotive air brake system, four-circuit protection valve is the critical component, which can guarantee the normal work of the other circuits, when a certain brake circuit failure happens. However the current testing equipments of four-circuit protection valve have many problem, such as low test precision, lack of test items, low test efficiency and so on. Aimed at these problems, a set of special on-line detection device for four-circuit protection valve is desgined, which contributes to quality control of four-circuit protection valve and road safety, the article’s main research contents include:Firstly, Based on the physical structure and working process of four-circuit protection valve, both mathematical model of valve core movement in the process of opening and closing, and mathematical model of body flow characteristic in detection system are stablished. The conclusion is present:the structure factors which affect the performance of four-circuit protection valve includes spring pre-tightening force and seal lip seal area; the factors in the detection system affect pressure characteristics test values include intake throttle aperture, sampling interval and exhaust diameter, etc.Secondly, in allusion to four-circuit protection valve problems such as leakage and pressure maladjustment, combined with the mathematical model and the national industry standard, a set of comprehensive performance testing system is designed, to realize the test of whole sealing, single-track sealing, opening pressure, cutoff pressure, static closing pressure and dynamic closing pressure, etc. The system hardware includes the automatic clamping control part, gas circuit on-off control part, data acquisition control part, failure simulation control part; system software based on LabVIEW development environment to realize the function of parameter configuration, data acquisition, performance test, data processing, data management, and so on.Thirdly, according to the physical structure of four-circuit protection valve, the simulation model of four protection valve circuit was built, as well as detection system. The simulation analysis is carried for four-circuit protection valve in opening and closing process, the test data of detection system shows that model is accurate and reliable. By using the simulation model to analysis the detection system factors of the four-circuit protection valve in the process of opening and closing, conclusions are proposed:reducing the intake pipe orifice improve test stability of opening pressure obviously, and the test data is stable and reliable when the effective flow area of intake pipe is 0.5mm2; the closing pressure increases with the enlargement of exhaust diameter, the effective flow area of pipe which is used to exhaust, and the effective flow area of pipe which is used to simulate pipe burst; reducing system sampling interval will omit pressure characteristic value uneasily, the test line is authentic and integrated when system sampling interval is 0.001s. At the same time, through the test verify an accurate adjustment method of opening pressure. Furthermore, in allusion to the working characteristics of four-circuit protection valve, simulation analysis was carried out for different structure types of four-circuit protection valve, in order to provides the theory basis for structure design of four-circuit protection valve and improve the precision and stability of the testing instrument.Fourthly, the test are taken for various performance of four-circuit protection valve by using the designed detection system, to accomplish the analysis of error sources, uncertainty evaluation of test result, and calculation of system’s performance index. The results indicate that the detection system of four-circuit protection valve satisfy acceptance requirements of the new equipment.