| A heavy-duty automobiles transmission has the features of compact structure,bearing a large load, and encountering complex working conditions. A quantity of heatmost of which is transferred into lubricant oil will be generated during operation due tothe friction losses of gearing mesh, bearing friction, churning oil. If the lubricationsystem has no enough ability to dissipate the generated heat from friction losses, thetemperature of lubricant oil will go up. Excessive high temperature of lubricant oil willlead to a drop of lubricant oil viscosity, reduction of the oil membrane thickness, eventhe agglutination damage of gear surfaces and bearings. On the country, theperformances of the transmission will be weakened due to the excessive lowtemperature of lubricant oil if the lubrication system has a strong cooling ability.Therefore, it is necessary to analyze the flow and heat conduction of the transmissionlubrication system to ensure the temperature of the lube to be kept in a suitable rangeand enough flow and pressure at each node in the lubrication system, which ensures thetransmission to operate normally under various working conditions. The main contentsof this dissertation include the following points.①The elementary theory will be presented, which comes down to the calculation ofthe flow and heat transfer of the lubrication system of the transmission, including theequation of flow calculation and the calculation method of pipe flow resistance, and thebasic theory of computation of heat conduction and convection heat transfer.②The component of lubrication system and the theory of lubrication of thetransmission in a heavy-duty automobile will be introduced. According to thecharacteristics of lubrication system structure, the software AMESIM will be analyzedon the basis of fluid mechanics. Moreover, the flow calculation and analysis module ofrelated components, including lube, oil pump and the passage of lube, will beestablished. The flow calculation model of transmission lubrication system can also becompleted.③The calculating method of the convection heat transfer coefficient of someelements, such as the inside and outside of the box of transmission, axles, bearings,gears, will be ascertained. The estimating method of heat quantity, generating from thefriction loss of gearing mesh, friction loss of all kinds of bearing, friction loss of gear’schurning oil in the internal transmission, will be discussed. The quantity of the exchanging heat will be calculated from the temperature field and the surface of the boxin the typical oil temperature by using the finite element to analyze software ANSYS,which will be acted as the input parameters of gridding model of the transmission.④Based on the AMESET second exploration platform of AMESIM software, theheat production and heat transfer calculation module in the internal components oftransmission has been exploited, analyzing the passage of heat flow of the maincomponents in transmission. The simulation model of heat transfer of transmissionlubrication system is established by thermal gridding method. The temperature of thelube, with the changing of time, is discussed under various working conditions,measuring the temperature of lube under the directly working condition on the specialtest table for transmission to verify the correctness of the simulation model.According to the simulation calculation results, installing the heat exchanger canstrengthen the ability of cooling lubrication system under the condition in which thebalanced temperature of lube is higher than the designed requirements to ensure thetemperature of the lube reaches the criterion.⑤With the combination of the heat transfer calculation lubrication system andflowing calculation model, the changing circumstance of each node’s flux oftransmission will be analyzed in the typical working conditions, evaluating whether thelubrication flux of main nodes meets the requirements of the heat dissipation. |
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