Using compressed air to detect the reliability of clutch sealing performance

The use of compressed air to detect the reliability of clutch sealing performance Beijing / Xue Qingwen In the past, the traditional maintenance of automotive assembly parts of the use of compressed air has been inseparable, and still is still used by everyone. Dust removal and drying after cleaning parts are indeed the result of compressed air. Of course, it is really convenient to use. However, it does not know how much it can really be used in the sealing performance detection of sealing components, but for experienced teachers, it is indeed possible to basically judge the sealing performance of components. Although the gas and the liquid belong to the same fluid, the hydraulic test effect on the hydraulic component sealing performance test is of course convincing due to the limitation of the gas incompressibility and the like, and it can be seen that the compressed air test has little effect. Therefore, in the repair industry, we can see that the maintenance technicians of the automatic transmission professional repair shop absolutely do not use compressed air to test the sealing performance of hydraulic components, and instead replace them with hydraulic testing equipment, commonly known as "pressing machine". By observing the amount of leakage to determine the sealing performance of the components; but the non-professional repair shop is not able to repair the automatic transmission every year, so some professional equipment is not available, so that the maintenance masters continue to use the "compressed air test." "The method to test the sealing performance of hydraulic components. The following is a case to illustrate the current detection of automatic transmissions should focus on the detection of the terminal components (clutch or brake).

Model: A 2009 FAW-Volkswagen Magotan sedan equipped with a 1.8T engine and equipped with a TF-60SN 6-speed automatic transmission manufactured by Aisin, and Volkswagen named 09G transmission. The mileage of the vehicle is approximately faulty: user The reflection is only that the transmission has a idling phenomenon during the shifting process and that the hotter the car is, the more obvious it is. The repairing party is a comprehensive auto repair factory in the field. The real phenomenon obtained by the main train through the road test is: the engine is idling when the 3rd gear is changed to 4th gear, that is, the 3-4 transmission is slipping, and 4-5 gears and 5 There is also a slip phenomenon in the -6 block. In the case of a large throttle test, the transmission cannot be changed to the 5th and 6th gears at all, and sometimes the transmission fault light will be illuminated, and the electronic control system will report the fault code for the "transmission gear ratio error". The small throttle test will reduce the slippage phenomenon. At the same time, if the vehicle is stopped for several hours and then the vehicle is re-commissioned, if the throttle is not accelerated, the transmission is basically normal, but the fault phenomenon appears after running for a while.

Fault diagnosis: Considering that the fault of the transmission is related to temperature and at the same time related to the throttle opening, the master of the repair shop is not eager to dismantle the transmission. Therefore, it is still starting from the basics. The user knows that the car has been maintained and repaired at the repair station, but the vehicle has traveled 90000km, but the transmission ATF oil has not been replaced. In this way, the master teacher is not eager to replace the ATF, but first verify the quality of the ATF, so as to avoid replacing the ATF after the transmission friction element is injured, it is meaningless, that is, it may be necessary to disassemble the automatic transmission for maintenance. Release the ATF inside the transmission and remove the transmission sump. The ATF color that was first released was really not very good. Normally it should be pink, but it was reddish brown and obviously deteriorated, but no impurities or other particles were found in the oil pan. Therefore, it should be basically explained that there should be no problem with the mechanical components inside the transmission. In order to be on the safe side, the more experienced masters used the "compressed air" to carry out the pressure test on all the terminal parts, and by pressing, they also heard the "beep" sound of the piston of each component during operation. Although it is not clear which oil channel hole is which component oil pressure is provided, after all, it is known from the maintenance information that the 09G transmission has only five terminal components, namely three clutches and two brakes, that is, at random. As long as 5 sounds are obtained during the compressed air test, these terminal components are good. In this way, the inspection further convinced the repair shop master that the transmission mechanical component body should be good, and the problem should be in other aspects.

Analyze the cause of the failure. According to the actual fault phenomenon and the control characteristics of the transmission, the possible causes of fault formation are as follows: 1 The first effect of the ATF's own performance is the friction coefficient of the friction element, which may cause the transmission to form a slip on the individual gear; 2 The problem is that the working oil pressure provided for the terminal component is low (the valve wears and the performance of the solenoid valve is degraded), and the friction process of the component cannot be satisfied. The insufficient torque generated by the friction causes the component to form a slip; 3 the terminal component itself causes the problem, and the friction component The friction coefficient of itself is too low, and the other is that the seal of the component itself is deteriorated, causing slippage; 4 there is oil pressure leakage in the middle link of the pressure source (pressure supply end) to the terminal component (execution end), which is provided by itself. The pressure is sufficient, and a part of the terminal is missing, which eventually leads to the terminal device failing to meet the real working requirements. 5 The problem of the electronic control system is caused by the temperature control and the oil pressure regulation function related to the throttle opening information. The gear shift caused by insufficient shifting oil pressure is instantaneously slipped.

According to the previous basic inspection and comprehensive analysis, everyone can reduce the number of faults that can be formed by 1_æ™·1, and through the investigation, the master thinks that the possibility of the electronic control system and the mechanical components itself is extremely small, and ATF And the possibility of hydraulic modules is greater. This determines the maintenance plan. With the consent of the user, it is decided to replace the automatic transmission ATF with the hydraulic module assembly (Note: the valve body failure probability of the transmission is indeed high). The valve body is brand new, ATF is also a large company to provide lubricants that meet the standards for the use of the transmission, but after the operation is completed, the automatic transmission specialist station technicians test the car, the original ancient swelling still exists, compared to the actual It has been alleviated, but the problem is that there is no cure. In this way, the author participated in the repair work of the transmission.

According to the description of the actual phenomenon, the author believes that the failure of the transmission is not like a difficult fault, and there should be a loophole in the inspection.

Therefore, as long as you follow the several possible reasons for the failure analysis and the careful investigation, it is easy to find out the problem. In this way, the field maintenance factory will send the entire transmission directly to our company through logistics.

Before the disassembly, we made a simple analysis of the failure of the transmission. Since the transmission failure is reflected in the 4th, 5th, and 6th gears, the K2 clutch of the transmission is the most suspected. In this way, we can carry out relevant detections in a targeted manner during disassembly. After removing the valve body, we directly find the oil supply hole of the K2 clutch (as shown), and also use the compressed air to apply pressure (Note: the pressure can not be too high, provide 400kPa right), pass), obviously, K2 clutch The leakage is large and the holding time is short. This fully demonstrates that the cause of the fault can be basically positioned: one is that the K2 clutch itself has poor piston tightness, and the other is that there may be leakage of the K2 oil supply passage (for example, at the seal ring). Further disassembling the transmission, observing the K2 oil supply support and the sealing ring above, there is no problem, decomposing the K2 clutch, only to find that the friction plate has extremely slight ablation. When the piston is taken out, everyone can see the problem at a glance, the original rubber piston There is damage at the outer edge (as shown). The point of failure was finally found, in a very inconspicuous place, but it caused such problems in the transmission. The reason for the damage of the piston is very simple: the first is that the ATF lubricating fluid is not replaced in time. In fact, the most critical K2 clutch piston damage is related to the transmission design. The clutch is a high-speed rotating component, and the clutch piston is just a linear motion process when working. If there is another rotation in the linear motion, it is naturally easy to damage the rubber seal on the outer edge.

Therefore, if the piston is not allowed to rotate in the clutch drum during the design process, only the linear motion will increase the service life of the clutch piston.

Troubleshooting: Replace the K2 clutch piston, all seal components and friction components, and completely eliminate the fault.

Fault summary: The solution of this case tells us that the fault of the transmission is very common, and it is very easy to solve. The fault is not solved once due to the shortage of equipment and the detection means in the maintenance. At the same time, the reliability of the traditional "compressed air test method" is obviously insufficient. In the actual maintenance, the pressure of the air pump is often adjusted very high when the worker master performs the hydraulic component sealing test, and the component piston can be heard during the pressurization. After the sound of the action, everyone thought that the sealing of this component is good. Everyone should remember that "compressed air" is also good, "hydraulic test" is also good, in fact, during this operation, I P is the transmission of the transmission in the static state is not a dynamic test in the work, so that these two types of æ³–fi-style means can not explain 100% of the quality of a t-component. Of course, hydraulic testing is standard, therefore, the degree of reliability It is much higher than the test of "compressed air". Therefore, it is very important for everyone to carry out the maintenance inspection of the automatic transmission science.

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