Heat Balance Analysis And Simulation Of A Mechanical Gearbox

Gearbox as a very important component of the vehicle transmission, has a significant impact on the performance of vehicle transmission. The performance of the gearbox is not only depends on the structure of its own, but also depends on its heat intensity of the structural elements. Therefore, the state of thermal balance of the gearbox has a significant impact on transmission performance. The study on heat balance of gearbox is of great significance.In this paper, heat production, thermal resistance between the components of gearbox, and its influencing factors have been studied under different stalls, different engine torque and rotational speed. Established a heat transfer network model of gearbox heat transfer system, use MATLAB programming, solve the temperature of the gearbox components when the system reached steady state by iterative method.And based on the steady-state solution, make use of MATLAB toolbox--Simulink,the dynamic simulation of heat balance of the gearbox heat transfer system has been carried out, in order to be able to more realistically reflect the thermal balance state of the gearbox in the actual use of condition.1) Taking account of the structure and movement of the gearbox, analysis of the four types of heat source of the heat transfer system: power loss of a pair of gear meshing, bearing friction power loss, power loss of oil film shearing and churning oil power loss. Deduced the calculation formulas of the heat capacity of these four heat source, and focused on analysis of influencing factors of the heat production of the various heat source. The conclusion to be drawn from them, although each heat source has its own influencing factors, they have a common trend: the greater the transmission speed and the torque, the greater the heat production is. In addition to gear mesh power loss, the other three heat sources increases with component size. Lubricant viscosity and density also affect the production of these four sources of heat energy, power loss of the meshing gear decreased with lubricants viscosity and density, the other three sources of heat production increases with viscosity and density of lubricants.2) Thermal resistance is another factor that impact on thermal transfer system of gearbox. In this paper, in accordance with the transfer line of the heat generated by the heat source in the gearbox, find out the thermal resistance on the heat transfer line, and thermal resistance is conducted in accordance with the classification of heat transfer, and the formula for calculating the various types of resistance have been derived.3) The Biot of every components of the gearbox has been checked, and heat balance system model of the gearbox has been simplified according to the results. The thermal network model and the thermal balance equation have been established in accordance with the heat transfer line.4) The components temperature of gearbox has been calculated under different stalls, different engine torque and rotational speed when the system reached steady state, and the impact on the temperature by Lubricants viscosity has been studied. Obviously, with the increase of the stalls, the equilibrium temperature of the components in the gearbox increase significantly; components near heat source has a relatively high temperature, lubricants is a major driving force for cooling.5) Established simulation models in Simulink which to simulate torque, rotation speed of first axis of the gearbox and gearbox temperature. And simulate a long time, high speed and idling operating conditions to simulate the actual driving circumstances. Found that the change rate of gearbox temperature is much slower than the vehicles driving condition changes.