1 Introduction
Fig. Q Assembly drawing of main shaft and oil seal end cover
1 - Gland; 2 - Oil seal; 3 - Spindle; 4 - Oil seal end cover
On DF4 locomotives, the hydrostatic motor is used to drive the cooling fan to cool the cooling water system to maintain the normal oil and water temperature, thus ensuring the normal operation of the diesel engine. In the actual operation process, oil leakage of hydrostatic motor oil seal often occurs, which not only wastes oil and pollutes the environment, but also may make the cooling fan work abnormally when the oil leakage is serious, resulting in machine damage and temporary repair, and seriously affecting the railway transportation safety.
The main shaft of the hydrostatic motor adopts a skeleton oil-sealed axial sealing structure, and the oil seal model is SG65 × ninety × 12. Its assembly with the main shaft and oil seal end cover is shown in Fig. Q.
2 Fault analysis
An investigation was carried out on 51 DF4 locomotives in a locomotive depot. The main task of the locomotive is passenger and freight traction. Due to the large gradient of the line, many tunnels, and the long working time of the hydrostatic motor at full speed, there are also many oil leakage faults of the hydrostatic motor oil seal. A total of 22 oil leakage failures occurred in the hydrostatic motor oil seal within two years. The fault parts are mainly as follows:; 12 worn spindles; 9 oil seals are cracked; Others. The most dangerous one is oil seal crack, because there is a large amount of oil leakage after the failure, and the possibility of mechanical damage is the greatest; Secondly, the main shaft is worn.
3 Fault cause analysis
(1) The oil seal is damaged due to non-standard assembly.
In order to ensure a good sealing effect between the oil seal and the oil seal cap, the installation interference between the oil seal and the oil seal cap is 0.1~0.2mm, so the oil seal needs to have a large force during the installation of the oil seal cap. During the actual assembly, due to the lack of proper special press-fitting tools, workers often knock the oil seal with the wooden handle of a screwdriver or other objects, or simply press the oil seal with a sharp object to make it enter the oil end cover, which may cause the deformation of the iron skeleton of the oil seal and slight cracks in the oil seal rubber after the assembly, and may cause oil leakage or even oil seal rupture after the loading and use.
(2) The hydrostatic motor spindle is worn.
The working oil pressure of the hydrostatic motor is up to more than 14MPa. In order to make the oil seal work well, the inner diameter of the oil seal belt is about 3mm smaller than the outer diameter of the main shaft, and it is clamped on the main shaft with a spring. There is certain friction when the main shaft rotates and works. In addition, for the cooling fan installed on the main shaft of the hydraulic motor, there is no dynamic balance test device in each locomotive depot. When the fan works at full speed, the main shaft of the hydraulic motor will generate a certain deflection force, thus increasing the above friction. Therefore, after long-term use, the main shaft generally has a circumferential groove at the sealing belt, which affects the sealing effect of the oil seal. When the groove reaches a certain depth, the oil seal may leak.
4 Countermeasures
(1) Use thickened oil seal end cap. For the oil seal oil leakage caused by the wear of the main shaft, the traditional treatment method is generally to lift the leaking hydrostatic motor from the vehicle, repair the hydrostatic motor main shaft by coating or chrome plating, and put it into use after restoring its original size. This method has many inconveniences in the field practice. First, the hydrostatic motor on the vehicle only leaks oil from the oil seal. If the hydrostatic motor is lifted down and completely disassembled, it will inevitably cause a waste of human and material resources; Second, the chrome plating repair for the circumferential wear of the main journal of the hydrostatic motor is heavy and costly.
Figure R Thickened oil seal end cover
Through observation and analysis, we made a thickened oil seal end cover, and replaced it with the original oil seal end cover, which can adjust the position of the skeleton oil seal on the hydrostatic motor spindle, move the installation position of the oil seal up, avoid the wear part of the hydrostatic motor spindle, and make the spindle secondary use. The thickened oil seal end cover is shown in Figure R, and only need to increase the size of A and B in the oil seal end cover with the drawing number DLT220-00-O1-1 by 3mm.
(2) Use the special press tool for oil seal. For the failure of oil seal rupture, a special tool can be made, as shown in Figure S. When assembling the oil seal, increase the bearing area when the oil seal is pressed down to prevent damage to the oil seal rubber and the built-in framework.
Fig. S Oil seal mounting tool
By taking the above measures, the oil leakage failure of the static hydraulic motor oil seal in the locomotive depot has been significantly reduced, the machine damage and temporary repair caused by it have been effectively controlled, and the maintenance cost of the locomotive has been reduced, and the driving safety has been guaranteed.
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2023-02-28