Research And Development On Fatigue Testing System Of Gears In Drive-axle Assembly Of Heavy-duty Trucks

1. IntroductionThe over-loading and high-speed need of automobile has already become thetend of development of transportation. So it needs more advanced technology onheavy-duty trucks. The drive-axle, especially the inner main reducer composed ofhyperbolic gears, which is working at the foulest place is the most important part ofthe transmitting system of heavy-duty trucks. The gears transmit the power andchange the orientation of rotating, at the same time, their interface endures gratestress of tangency and friction when they are working . The load on th interface canget to 1 .7GPa and the strike olse can get to 2 .8GPa. Because of the the highspeed of slide and rigorous addition of lubrication, acute friction makes thetemperature of the part of the gear interface becomes higher sharply. It tends to besintered or agglutinate and invalidate in the end. So we can say, it is signality to paymore attention to the friction invalidation of the hyperbolic gears in drive-axle ofheavy-duty trucks and adopt the reasonable lubricating method to avoid frictioninvalidation.The purpose of research and developing this fatigue testing system of gears indrive-axle of heavy-duty trucks is based on these reasons above. It controls thetemperature of the lubricating oil by applying the theory of modern controllingmethod with computer and the PID(proportion,integral and differential) controllingstrategy which the integral part is apart when the difference between the inputvalue and the feedback value goes over the bounds which you gived, in order tosimulate the real vehicle working situation. Therefore, we can test and evaluate thelife-span of our trial-produced product—the heavy-duty trucks and the quality ofthe lubricating oil synthetically, then direct the development and the application ofthe new product experimentally.2. System Structure and Working PrinciplesThis fatigue testing system of gears in drive-axle of heavy-duty trucks, whosetorsion is loaded by mechanical facility is a computer controlling system which isused to control the temperature of lubricating oil real-timely with computer in orderto simulate the the real vehicle working situation and evaluate the life-span of thedrive-axle of heavy-duty trucks, especially the conic gears in the main reducer ofthe vehicle and the quality of the lubricating oil exactly. The whole system iscomposed of three parts:The test-bed whose torsion loaded is closed;The system oflubricating oil circulated out of the shell of the drive-axle;The computer systemwhich is used to detect the useful signal and control the oil temperature. Thesystem is used to test the life-span of the drive-axle assembly of heavy-duty truckswhich is produced by FAW.⑴the structure figure of the test-bed of the system.(as shown in figure 1)Because the test-bed which is composed of the main test drive-axle sampleand the assistant test drive-axle sample has close power in it, its primarycharacteristic is low power consumption, economical, easy to control and so on.Figure1:The structure of the drive-axle test-bed whose torsion loaded is closed1.Electrical motor 2.Transmitter 3.Main gear case 4.Chuck 5.Rev andtorsion sensor 6.Big gear to load torsion 7. Gimbal and transmission shaft8.Master sample of drive-axle 9,11.Side gear case 10.Assistant sample ofdrive-axle 12.Small electrical motor to load torsion 13.Small gear case to loadtorsion 14.Small gear to load torsion which can be moved along on the shaft.(The arrowhead in this figure is the orientation of the power)⑵The system figure of lubricating oil circulated out of the shell of thedrive-axle.(as shown in figure 2)Figure2:The figure of lubricating oil circulating pipeline of the drive-axle oiltemperature controlled systemCompared with the indirect method which change the temperature ofsurroundings out of the shell of the tested drive-axle in order to change thetemperature of the oil in it, the predominance of this kind of controlling methodwhich controls the oil temperature directly is easy to control,high precision ,economical and so on. Besides that, because of applying this higher ability ofexchanging-heat heat exchanger which the metallic pipe's shape is like a wave andhigh-power heater with a churn-up motor to mix-up the oil to be homogenized,improved the speediness of response observably.⑶The structure figure of the computer controlling system which is used todetect the signal and control the oil temperature.(as shown in Figure 3)Figure 3:The structure figure of the computer examining controlling systemThe computer examining and controlling system is the core part of the wholesystem. By using the temperature sensor at the bottom of the shell of the drive-axleto detect the inner oil temperature timely, and then transforming the signal intovoltage signal for A/D transformation. After that, the digital singal from the A/Dtransformer is gained by the computer and compared with the target temperaturevalue by the computer. Then the computer'software makes the difference betweenthe two temperature value become the input of the PID programme which theintegral part is apart when the difference goes over the bounds which you gived andoutput rectangular wave as the PWM control signal to drive the high-speedelectromagnetic on-off valve to work. Consequently, it achieves adjusting the fluxof the cooling water timely, meets the demands of control precision,the demandsof technics and the demands of safety by detecting the correlative signal,accomplishes the task that help the computer communicate with the tranducer andthe rev and torsion measure apparatus based on RS232 serial communicationprotocol.3. Application Programme of SystemFor system test software, we use C++ Builder software tool to exploit. TheC++ Builder provides the method how to modularized program. The driver of theData acquired card is programmed by the special driver developmentsoftware—Windriver. The integral apart digital PID control programme whosefeedback signal is temperature and executed part is high-speed electromagneticon-off valve is the principal part of the test software. The program is consisted ofabout six modules: parameter setting module,main software interface module,carddetecting module,sensor demarcating module and database query module. Aintegrated test course should be according to the process shown in the figure 4. Atthe beginning of the test, you should demarcate the sensors,examine the setting ofcommunication and set the parameters of the test, then detect the data acquired cardselectively. After that, you should go back the main interface of the software, in themain interface, you can record the characteristic parameters of the sampledrive-axle,set the bounds of the signals to alarm when they are beyond them,setthe working situation of the sample for testing,choose the method of data processand the frequence of the data refreshing and saving,make sure the path to save thedata,display the various signal value timely,draw the curve of the data dynamiclyand so on.Figure 4:The sketch of the control system modulesThe method of realizeing the sampling frequency: The primary basicrequirement of data acquiring is timing accurately, that is to say, sampling intervalhas better coherence. There we use multimedia timer to time accurately so as toimprove the veracity of the data greatly.Anti-interference of the system: Since the awful surroundings and theinterference fountainhead everywhere in the workshop, On hardware, we choosemanostat lowpass DC power,isolated transformer,UPS power,lowpass circuit,photoelectric coupling chip,twisted-pair and so on to isolate the interference fromelectric net supplying the power and process channels omnidirectionally. Onsoftware, we use the method that slippage average filter to pre-process.Furthermore, we send out communication orders repetitious in order to avoid theerror code.4. The results of the TestNow, this test system has been used to test the fatigue of the gears and thelife-span of the sample of heavy-duty trucks' drive-axle which is produced by FAW.Because of applying the data saving function,curve drawing function and dataanalysis function, we accomplish the test and evaluation on the life-span of JIEFANG trucks' drive-axle successfully. Furthermore, these results of the test directthe design,improvement,evaluation task on homemade heave-duty trucks'drive-axle and selection,development,improvement task on the gear lubricating oil,theoretically.The practice can prove this system's advantages, such as better performance,steady and reliable and data exact. This test system meet the demand of design anduse entirely, achieve well effect of testing, acquire good praise. So we can say, theachievement of researching and developing this project, not only meets therequirement of production in practice, but also contributes to the development ofexamining technicis of heavy-duty trucks for our country.