Reserch On Friction Properties Of Gear Oil Used On Overloaded Transimission Synchronizer

Synchronizer devises which is one of the important part of the mechanical transmissions. Its performance is closely related with the gear oil. The poor quality of gear oil will reduce the friction of synchronizers and cause abrasion, which finally will lead to the failure of synchronizers and affect the vehicle shifting performance. Researching on the friction performance of gear oil on the override transmission synchronizer testing device can test the suitability between gear oil and transmission synchronizers, which will improve the efficiency of override transmission and extend its service life. All in all, it will produce great economic and social effects.This paper carries out the testing design of gear oil synchronizer, operation optimization, gear oil friction test, judgment standard and the failure reason of synchronizer. The main research results are as follows:(1) With the working principle of synchronizer, analyze the parameters of override transmission synchronizer (The transmission stress on engagement sleeve ranges from560～1277N and rotating speed ranges from563～2100r·min-1). It will turn the real condition to the condition in the test range (Transmission stress will be560～1277N, and the speed of main rotator will change from790～1399r·min-1). The design of research scheme will be carried out according to the factors above.(2) According to the test solution on the overloading transmission synchronizer test bench to carry out the working condition of optimization test. The results show: when the speed difference between the main shaft and the input shaft increases, the shift life will decrease; when the shift stress increases, the shift life will decrease at the very beginning, then rise up and at last decrease again. The range of real condition will be chosen according to result of test. Transmission stress will be900～1050N, and the speed of main shaft will range from950～1100r·min-1(3) The best condition will be chosen from the optimized condition to test the properties of gear oil (A, B, C and D). Analysis on failure of transmission by means of the real-time shifting characteristics curve, found that:with the number of shift increases, the frictional torque and the cone’s acceleration will decreases, which lead to the synchronous ring and cone can’t become synchronization; under the shift force, combining sets are forced to mesh with the cone, which causes a greater impact torque to make the synchronizer failure. The test results show that, the smooth of the friction pairs’ surface and the increase of bearing area, the contact stress and the local temperature will decrease. The oil deterioration and sludge formation during the test make the oil film between the friction pair surface hard to rupture, which leads to the decrease of friction coefficient and friction torque. The friction torque decline is the fundamental reason for the failure of the synchronizer. Based on the results of the test, shifting life, the friction coefficient and wear rate parameters are defined as the judge standard of gear oil’s friction properties. Four gear oil friction characteristics of the evaluation order is:B>C>A>D.