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1 Introduction
Automotive power steering hydraulic pump is the heart of the power steering system, and its performance is good or bad on the performance of automotive power steering system has an important impact, and will directly affect the steering and steering stability of the car. In addition, with the continuous introduction of new materials, new processes and structures, as well as the introduction of large numbers of high-speed steering hydraulic pumps for passenger cars, more and more research is needed on the performance of steering hydraulic pumps. Therefore, the test methods of steering hydraulic pumps must be further studied Explore, put forward effective test methods, improve the test means, in-depth study of steering hydraulic pump characteristics.
Power steering hydraulic pump in the test process, the main parameters to be measured in addition to the general hydraulic pump with the temperature, flow, pressure, speed, torque and other parameters, the power steering hydraulic pump due to the special structure and the use of requirements it has Therefore, how to accurately and conveniently measure the performance parameters of the steering hydraulic pump when developing a power steering hydraulic pump test stand is the most crucial issue.
2, power steering pump test method
Steering hydraulic pump test standard "ZBT 23002 vehicle power steering hydraulic pump bench test method" is formulated in 1984, promulgated in 1987, has been used for more than 10 years. At that time, the domestic automobile power steering hydraulic pump products are gear pumps, sedans steering hydraulic pump or blank.
With the rapid development of automobile industry in recent years, the power steering pump industry has made great strides. The steering vane pump has almost replaced the gear pump. The sedan steering hydraulic pump has been widely used, especially the introduction of a large number of foreign technologies. The original test method Has been more backward, can not fully and accurately detect existing products. In particular, in the first quarter of 1997, Chongqing Automobile Research Institute found that the original test method far failed to meet the testing requirements of existing products and was difficult to test during the task of undertaking the task of spot checking the quality of hydraulic steering pump delivered by the State Bureau of Technical Supervision. Operation, the quality of the product is difficult to make a comprehensive, fair and accurate evaluation. Therefore, in order to meet the needs of the development of China's automobile industry products, effectively control the quality of products, 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 doing performance tests such as run-in, flow test, the product is carried out under the maximum working pressure pmax, then turn to the hydraulic pump safety valve has been fully open, at a flow of 0 of the cut-off state, simply can not Test, and easy to pump. Test to avoid steering hydraulic pump safety valve open, before the test, you must lock the steering pump safety valve. This approach is equivalent to the hydraulic pump has been adjusted, so the method is neither scientific nor loading conditions, but also can not be more comprehensive and accurate detection of product performance. Therefore put forward the concept of 0.85 pmax pressure, that is, the product under the conditions of 0.85 times the maximum pressure to run and flow detection and other performance testing, then steering hydraulic pump safety valve will not open, so the detected performance accurately reflects the steering hydraulic Pump the real situation.
2.2, air tightness test
The original test method does not require air tightness test, through a large number of tests show that the air tightness test can accurately and reliably reflect the seal of the steering hydraulic pump and the assembly quality between the parts, and the test is simple, feasible, cost Low, easy to promote the application.
2.3, reliability test oil temperature
Steering hydraulic pump usage conditions than the general engineering use of pump conditions are much more complex. When used, the steering hydraulic pump is often in the complex conditions of speed and pressure change, the oil temperature changes drastically and the range is large. In addition to the steering pump port are installed at the orifice of a small aperture, the excess flow overflow overflow, and return directly into the oil chamber, the steering pump to form a small cycle, which makes the steering pump heat Phenomenon than the average pump is much more serious. At the same time, due to the structural constraints, the steering hydraulic pump is generally installed on the vehicle next to the engine, the ambient temperature is high, so steering hydraulic pump heating more serious. And little power steering fluid system, usually 1 ~ 3L, the heat is not easy to distribute.
Therefore, in order to accurately assess the steering performance and service life of hydraulic pump, the test oil temperature is appropriate at about 70 ℃.
2.4, cut-off test
The original test method in reference to the general test method of the pump, put forward a cut-off test. Because the power steering assembly generally have trip unloading valve, when it reaches the limit position, the trip unloading valve opens, so that the steering pump is unloaded. Even without a trip unloader valve, the steering hydraulic pump will not be in a cut-off state due to inevitable internal leakage within the power steering assembly. In particular, vane pump almost no current capacity. Therefore, the pilot project should be canceled.
2.5, variable speed impact test
As we all know, due to the special use of steering conditions, the car in the process of moving to the hydraulic pump is not likely to be in continuous overload state. On the contrary, the driving speed of the car is constantly changing, and the steering system is at any time to ensure that the car travels at a certain track. Due to the road, the steering wheel is constantly subjected to the reverse impact of the road surface, so the car driving process Steering hydraulic pump to withstand the impact load.
In order to make the test condition consistent with the actual working condition, the test data can reflect the service life of steering hydraulic pump accurately and accurately. Therefore, it is proposed to change the continuous overload test to the variable speed impact test in the original test method.
3, test bed structure introduction
The drive adopts AC frequency conversion speed regulation. The AC motor directly drives the tested pump through the connecting sleeve and the slider. For the test specimens with different installation forms, only the connecting flange and the slider can be replaced.
The fuel tank is installed on the countertop with a capacity of about 150 L and a 3 kW heater is installed in the fuel tank. The bottom of the fuel tank is about 200 mm high from the center of the drive shaft. The diameter of the oil suction port is 30 mm. The fuel tank panel is equipped with vacuum gauges and pressure gauges to monitor the vacuum level in the suction port and the pressure at the port.
Suction and return ports are used quick change connector, making it easy to install, fast, while preventing tank oil outflow.
4, test bench hydraulic system
ZYBT-â…¡ type hydraulic steering pump hydraulic test bed as shown.
Hydraulic schematic diagram
The test bench is loaded with a proportional relief valve, which is controlled by a computer through a proportional solenoid valve for electrical signal control. The pressure relief valve is used to fine-tune the proportional relief valve through a pressure sensor feedback signal. The loading is accurate and the loading process is automated.
As the specimen is constantly changing, it is bound to bring a lot of pollutants throughout the system, while the proportional relief valve on the oil cleanliness requirements. Therefore, in order to ensure the normal operation of the entire system. Designed with two high-pressure filtration. The filter accuracy of 5 μm, and the use of fully enclosed fuel tank.
Oil viscosity is greatly affected by the oil temperature, in order to ensure accurate flow test, the system uses a water cooler to strictly control the oil temperature, the range of variation within ± 2 ℃.
5, test bench test system
The test bench test parameters are speed, flow, pressure, temperature and other four parameters.
The speed sensor is an inductive sensor whose output is a sine wave signal. After being amplified by a triode, the speed sensor is shaped by a Schmidt circuit (4093 chip), and is divided by a resistor to input to an input terminal of an inverter (4011) The output of the inverter is connected to the G2 terminal of the board of the computer 7210. Since the reliable trigger level of the 4093 chip is above 6 V, the voltage applied to the transistor and the 4093 is 12 V, so that the output high level of 4093 is 12 V and the low level is 0 V, while the computer The input voltage is not higher than 5 V is appropriate, so the resistor divider, and then by the reverse circuit, the 5 V voltage pulse signal into the computer.
The output of the flow sensor itself is a 12 V pulse signal, representing 0.1 L per pulse. When counting the flow pulse, if the pulse number is counted in time, the maximum can be approximated by dropping a pulse number, and because the test time is short, the lost pulse number will also be amplified, which will inevitably produce a larger measurement error. Therefore, when counting the number of flow pulses, it is more accurate to measure the time with pulse.
In order to reduce interference, the pressure and temperature signals are used 4 ~ 20 mA analog, the signal through the HK16 core plug directly to the 5411 board for A / D conversion.
Correct grounding of the test bench prevents external interference signals. Due to the use of the inverter, if the grounding method is wrong, the computer system will have serious interference. After a great deal of exploration on the grounding problem of the test system, the problem of interference finally solved satisfactorily. Regardless of whether the protection method is grounded protection or zero protection, the direction of the line must be as follows: zero (ground) line first into the inverter ground, and then lead to the test bench, and then connected with the control cabinet (be careful not to use a single Core wire). Since the inverter is hung on the control cabinet, when installing the variator, the shell of the inverter must be insulated from the cabinet.
6, test bed computer system
The control software is an advanced multi-tasking industrial control configuration software based on the MS-DOS operating system. The software has the advantages of full Chinese graphic prompt, easy operation and good interface. Proved by practice is a relatively good industrial control configuration software.
6.1, hardware system
The host is IPC486DX4 / 100
NA5411 and ACL7120 control templates
EPSON 300K printer
6.2, software system
Industrial control configuration software graphical display conditions, online printing statements, providing manual and automatic operation of the screen. In the manual operation with graphical tips.
The industrial control configuration software consists of the following documents:
CHZHI.EXE executable software
SYS.DAT configuration data file
CQHI16J.1 16 dot matrix font
CBTYPE.DAT model data file
7, conclusion
Through a large number of trials and groping, put forward a practical steering hydraulic pump test method. After more than a year of actual production proved that the test method is easy to operate, the test results can truly and accurately reflect the steering performance of the hydraulic pump. Proved by the use, ZYBT-â…¡ car steering hydraulic pump test bench safe and reliable, stable performance, the test process is fully automated, easy to operate, adaptable, accurate and credible test results, and greatly improve the test efficiency, with extensive promotion Use value.
Power steering hydraulic pump
The deficiency of the test method of the power steering hydraulic pump is analyzed. A new test method is put forward, which is proved by the production practice. The test method is easy to operate. The test results can truly and accurately reflect the service performance of the steering hydraulic pump. The power steering Hydraulic pump test equipment.