Test method and equipment of the hottest power hyd

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Power hydraulic pump test method and test equipment Abstract: This paper analyzes the shortcomings of the power steering hydraulic pump test method, and puts forward a new test method. The production practice shows that the test method is easy to operate, and the test results can truly and accurately reflect the service performance of the steering hydraulic pump, and introduces the power steering hydraulic pump test equipment

key words: power steering; Hydraulic pump; Test method; Test equipment

1. Introduction

the automobile power steering hydraulic pump is the heart of the power steering system. Its performance has an important impact on the performance of the automobile power steering system, and will directly affect the steering and handling stability of the automobile. In addition, with the continuous application of new materials, new processes and new structures, as well as the introduction of a large number of high-speed steering hydraulic pumps for cars, the experimental research on the performance of steering hydraulic pumps is more urgent. Therefore, it is necessary to conduct in-depth discussion on the test methods of steering hydraulic pumps, put forward effective test methods, improve the test means, and conduct in-depth research on the characteristics of steering hydraulic pumps

during the test of the power steering hydraulic pump, the main parameters to be measured are not only the temperature, flow, pressure, speed, torque and other characteristic parameters of the general hydraulic pump, but also the special structure and use requirements of the power steering hydraulic pump determine its specific performance. Therefore, how to accurately and conveniently measure the performance parameters of the steering hydraulic pump when developing the power steering hydraulic pump test bench, Is the most critical issue

2. Test method for power steering hydraulic pump

test standard for steering hydraulic pump "zbt23002 bench test method for automotive power steering hydraulic pump" was formulated in 1984, promulgated and implemented in 1987, and has been used for more than ten years. At that time, the domestic automobile power steering hydraulic pump products were all gear pumps, and the automobile steering hydraulic pump was still blank

with the rapid development of the automobile industry in recent years, the power steering hydraulic pump industry has also made great progress. The steering vane pump has almost replaced the gear pump, and the steering hydraulic pump for cars has been widely used. Especially with the introduction of a large number of foreign technologies, the original test methods have been relatively backward, and the existing products can not be comprehensively and accurately tested. Especially in the first quarter of 1997, Chongqing Automobile Research Institute found that the original test method was far from meeting the inspection requirements of existing products, and it was difficult to operate in the test process, so it was difficult to make a comprehensive, fair and accurate evaluation of the quality of products

therefore, in order to meet the development needs of China's automotive industry products and effectively control product quality, it is necessary to conduct in-depth discussion and Research on the test methods

2.1, 0.85pmax pressure concept

the original test method requires that during performance tests such as running in and flow detection, the product is carried out under the maximum working pressure Pmax. At this time, the safety valve of the steering hydraulic pump has been fully opened and is in the cut-off state with flow of 0. The test is impossible at all, and the pump is easy to burn. In order to avoid opening the steering hydraulic pump safety valve during the test, the steering hydraulic pump safety valve must be locked before the test. This method is equivalent to the adjustment of the hydraulic pump, so this method is neither scientific nor in line with the loading conditions, nor can it detect the product performance comprehensively and accurately. Therefore, the concept of 0.85pmax pressure is put forward, that is, the product is tested for performance such as running in and flow detection under the condition of 0.85 times the maximum pressure. At this time, the safety valve of the steering hydraulic pump will not open, so the detected performance can accurately reflect the real situation of the steering hydraulic pump

2.2. Air tightness test

the original test method has no air tightness test requirements. A large number of tests show that the air tightness test can accurately and reliably reflect the sealing of the steering hydraulic pump seals and the assembly quality between the parts, and the test is simple, feasible, low-cost and easy to be popularized and applied

2.3. Oil temperature of reliability test

the working conditions of steering hydraulic pump are much more complex than those of general engineering pumps

when in use, the steering hydraulic pump is often under complex working conditions with variable speed and pressure, and the oil temperature changes violently and in a large range. In addition, a small orifice is installed at the oil outlet of the steering hydraulic pump, so that the excess flow overflows and directly returns to the oil inlet chamber, forming a small cycle in the steering hydraulic pump, which makes the heating phenomenon of the steering hydraulic pump much more serious than that of the general pump. At the same time, due to structural limitations, the steering hydraulic pump is generally installed next to the engine on the whole vehicle, and the ambient temperature is very high, so the steering hydraulic pump is more heated. Moreover, there is very little oil in the power steering system, generally 1 ~ 3l, and its heat is not easy to be dissipated

therefore, in order to accurately assess the service performance and service life of the steering hydraulic pump, it is appropriate to ensure that the extrusion quality inspection temperature is about 70 ℃

2.4. Cut off test

in the original test method, the cut-off test is proposed with reference to the test method of general pumps. As the power steering gear assembly generally has a travel unloading valve, when it is turned to the limit position, the travel unloading valve will be opened to make the steering hydraulic pump in the unloading state. Even if there is no stroke unloading valve, there will inevitably be a certain amount of internal leakage in the power steering gear assembly, so the steering hydraulic pump will not be in the cut-off state. In particular, the vane pump has almost no cut-off capacity. Therefore, the cut-off test item should be canceled

2.5. Variable speed impact test

as we all know, due to the special working conditions of steering, it is impossible for the steering hydraulic pump to be in a continuous overload state during driving. On the contrary, during the driving process, the driving speed of the car is constantly changing, and the steering system is always ensuring that the car runs according to a certain track. Due to the road surface, the steering wheels are also constantly impacted by the road surface, so the steering hydraulic pump is constantly subjected to the impact load during the driving process

in order to make the test conditions consistent with the actual service conditions and make the test data truly and accurately reflect the service life of the steering hydraulic pump, it is proposed to change the continuous overload test in the original test method into the variable speed impact test

3. Introduction to the structure of the test bench

the drive device adopts AC variable frequency speed regulation, and the AC motor directly drives the tested pump through the connecting sleeve and sliding block. For test pieces with different installation forms, it is only necessary to replace the connecting flange and sliding block

the oil tank is installed on the workbench with a volume of about 150L. A 3kW heater is installed in the oil tank. The bottom of the oil tank is about 200mm high from the center of the drive shaft. The diameter of the oil suction port is 30mm, which can ensure that the tested liquid pressure pump can absorb oil well. The oil tank panel is equipped with a vacuum gauge and a pressure gauge to monitor the vacuum at the oil suction port and the loading pressure at the oil outlet

quick change connectors are used at the oil suction and return ports to make the installation simple and rapid and prevent the oil from flowing out of the oil tank

4. Hydraulic system of the test-bed

the test-bed is loaded by the proportional relief valve, which is controlled by the computer through the electrical signal, and fine tuned by the pressure sensor feedback signal compared with the relief valve. The loading is accurate, and the automation of the loading process is realized

as the test piece is constantly replaced, it will bring a lot of pollutants to the whole system, and the proportional overflow valve has high requirements for the cleanliness of the oil. Therefore, in order to ensure the normal operation of the whole system. Two stage high pressure filtration is adopted in the design. Make the filtering precision reach 5 μ m. And adopt totally enclosed oil tank

the viscosity of the oil is greatly affected by the oil temperature. In order to ensure the accuracy of the flow test, the system uses a water cooler to strictly control the oil temperature within ± 2 ℃

5. Test system of the test-bed

the test parameters of the test-bed include four parameters: speed, flow, pressure and temperature

the speed sensor is an inductive sensor. Its output is a sine wave signal. After being amplified by a triode, it is shaped by a Schmidt circuit (4093 chip) and input to the input end of the inverter (4011) through resistance voltage division. Then the output end of the inverter is connected to the G2 end of the computer 7210 board. Since the reliable trigger level of the 4093 chip is above 6V, the voltage applied to the triode and 4093 is 12V. In this way, the high level output after 4093 shaping is 12V and the low level is 0V, while the computer input voltage should not be higher than 5V. Therefore, the 5V voltage pulse signal is sent to the computer after resistance voltage division and reverse circuit

the output of the flow sensor itself is a 12V pulse signal, and each pulse represents 0.1L. When counting the flow pulses, if the number of pulses is counted at a fixed time, the maximum number of pulses can be approximately lost. Moreover, due to the short test time, the number of lost pulses will be amplified, which will inevitably lead to large measurement error. Therefore, when counting the number of flow pulses, the method of measuring time with fixed pulse is more accurate

in order to reduce interference, 4 ~ 20mA analog quantity is used for pressure and temperature signals, and the signals are directly sent to the 5411 board through the hk16 core plug for a/d conversion

the correct grounding of the test bench can prevent external interference signals. Due to the serious interference in use, after a lot of exploration on the grounding problem of the test system, the interference problem was finally satisfactorily solved. No matter whether the protection mode is grounding protection or zero protection, the route of the line must be as follows: the zero (ground) line first enters the grounding terminal of the frequency converter, then leads to the test bench, and then connects with the control cabinet (pay attention not to use single core wire). Since the frequency converter is hung on the control cabinet, the shell of the frequency converter must be insulated from the cabinet when installing the inverter

6. The test-bed computer system

control software is an advanced multi task industrial control configuration software based on MS-DOS operating system. The software has the advantages of full Chinese Graphical prompt, simple and reliable operation, good interface, etc. It has been proved to be an excellent industrial control configuration software

6.1. The host of the hardware system

is ipc486dx4/100

epson300k printer

6 the state has issued the opinions on the development of innovative new materials 2. The software system

industrial control configuration software can graphically display working conditions, print reports, and provide manual and automatic operation images. There are graphs in manual operation, which leads to the prompt function of operating stress range

this industrial control configuration software consists of the following files:

e executable software

t configuration data file

cqhi16j 116 dot matrix font

t model data file

7 conclusion

through a large number of experiments, a practical and feasible test method for steering hydraulic pump is put forward. It has been proved that the test method is easy to operate and the test results can truly and accurately reflect the service performance of the steering hydraulic pump. It has been proved that the zybt- Ⅱ steering hydraulic pump test-bed of "very strange" car has safe and reliable operation, stable performance, full automation of the test process, simple operation, strong adaptability, accurate and reliable test results, and greatly improves the test efficiency, which is worth popularizing and using widely. (end)

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