Effect of operating temperature of hydraulic fluid on the service life of automatic transmission

Abstract

According to the recommendations of the automatic transmission manufacturer, the average operating temperature of its hydraulic fluid should be 80-950C.
Exceeding the hydraulic temperature more than 1100C under heavy-duty conditions can reduce its service life by several times. The automatic transmission is the most heat-stressed unit of all vehicle transmission units.
High speeds of hydraulic fluid movement in the torque converter lead to its intensive aeration, increased foaming, accelerating oil oxidation and reducing its service life.
The article is devoted to the analysis of the influence of the working fluid temperature on the reliability of automatic transmissions. To ensure normal automatic transmission temperature, there are various layouts of heat exchangers, which have their own advantages and disadvantages. Among them are: a separately remote heat exchanger for the automatic transmission; built into the main cooling radiator, as well as separate radiators for cooling the transmission fluid.
The layout and design of heat exchangers of automatic transmissions of passenger cars are studied. The main advantages and disadvantages of the designs of the heat exchangers used are presented. Based on the experimental data, a third-degree polynomial equation was obtained to predict the service life of the working fluid.
Taking into account the technical features and design complexity of various types of automatic transmissions of cars, one of the most important issues of their technical operation is reliability.
The article presents the results of operational tests on the replacement of the hydraulic fluid of automatic transmissions of passenger cars under operating conditions in Tashkent. When using automatic transmissions, it is always necessary to monitor the temperature of the automatic transmission. In modern cars, there is no thermometer on the dashboard for the driver to constantly monitor the operating temperature of the hydraulic fluid. The ELM 327 scanner allows you to partially eliminate this drawback and makes it possible to determine the temperature parameters of the automatic transmission.
Our observations carried out at car service stations show that more than 50% of automatic transmission failures occur due to overheating of its hydraulic fluid. To obtain objective information on the operational reliability of the automatic transmission, the authors of the work conducted operational tests. Hydromechanical planetary automatic transmissions were subjected to the experiment.
Based on the analytical review and our operational studies, recommendations are given for the use of an additional radiator for cooling the automatic transmission hydraulic fluid of UzAvto Motors vehicles, such as Chevrolet Gentra, Cobalt, Nexia 3 and Tracker 2. Since, in hot climate conditions, normal cooling of the automatic transmission hydraulic fluid is not fully ensured.