The main objective of this chapter is dynamic structural and thermal analysis of multi speed transmission gearbox (medium duty truck) using Finite Element Analysis (FEA). To evaluate the dynamic strength of transmission gearbox assembly transient structural analysis was performed. Dynamic varying loads at different rotational speed were applied to perform the transient analysis. In gear meshing operation at high rotational speed and loading condition, frictional heat is generated inside gearbox assembly. To reduce the effect of frictional heat, gear oil is used. In this research study gear oil SAE 85W140 was used for cooling and performance enhancement. Steady state thermal analysis was performed to evaluate the thermal effect of frictional heat, rotational speed of shafts (pinion, gear) and load with gear oil lubrication. In thermal effect gearbox surface temperature was measured at different points. FEA simulation results have been validated using experimental results available in literature.
TopIntroduction
Multi speed transmission gearbox is assembly of gears. The gearbox assembly is used for varying torque and gearing condition. Shifting from lower to higher gearing reduces torque value but increases rotational speed. In this chapter the object is multi speed transmission gearbox. This transmission gearbox consists of 4 set of gears excluding reverse gear. This transmission assembly is used in heavy vehicle medium duty trucks. Gear oil is used as lubricant for moving parts, dissipates frictional heat from gearbox assembly, prevent overheating of gears and it also works as vehicle performance enhancer. The operating temperature of gear oil varies (-18 to 110)0C. In past two decades various research studies has been performed in field of transmission gearbox concern with gear oil physical properties, material mechanical properties variation for gearbox housing, looseness study of gearbox, dynamic vibration, power-flow in transmission etc.
Kumar (2015) have studied the heavy duty truck transmission casing for different material application. The main objective of this study was selecting best suited material for transmission housing based on vibration suitability. A series of four materials has been selected Al alloys, Mg alloys, Structural Steel and Grey cast iron FG 260. The best suited material is grey cast iron FG 260. Zimparov (2002) have studied the design problem of the heat exchangers for cooling purpose. Entropy generation and irreversible friction flow problem was considered here. The objective was to design a heat exchanger with minimum system losses. Bozca (2010) have optimized the vehicle gearbox geometry. The authors have studied the rattle noise problem in transmission assembly. It is caused by torsional vibration transmitted from engine to the shaft of transmission. Rattle noise were calculated by varying various parameters. The authors have performed the numerical, analytical and experimental work.
Salah (2007) have investigated the vehicle fuel economy problem. Fuel economy of vehicle is governed by gear oil and proper functioning of transmission assembly. The aim of study was to find a relation between transmission cooling and vehicle fuel economy. The results were in favor and show that proper and efficient gear oil cooling reduces the fuel consumption by 1.0-1.4%. Kumar (2014) have studied the looseness study of truck transmission system. The loose frequency varies from (1311-3110) Hz. Looseness condition of transmission reduces the frequency range and increases the chances of resonance. The simulation results were obtained for different looseness condition of transmission casing. Zero displacement constraint based boundary condition was applied by constraining all 37 bolt holes.
Karamavruc (2011) have studied the thermal properties of gear oil. Density, specific heat capacity, thermal conductivity and viscosity are the thermo-physical properties that highly depend on temperature. Viscosity changes in exponential manner but other thermo-physical properties changes in linear manner. Pennestri (2012) have studied the power flow mechanism in transmission gearbox assembly using graph theory method. They have also calculated the efficiency of epicyclic gearbox used in hybrid vehicles.
Quaiyum (2012) has studied the Automatic Transmission Fluid (ATF). He designed a Minichannel Heat Exchanger (MICHX) for cooling application. The wind tunnel based experimental setup was used for the micro channel analysis. ATF flow on a mini channel heat exchanger was studied for varying heat transfer coefficient and Reynold’s no. Researchers have also studied vehicle transmission lubrication, transient analysis of gear interaction, dynamic vibration analysis, thermal balance, gear interaction and gear oil lubrication of transmission Kouroussis (2015). Long, (2003) have studied the different parameters on single pair of meshing gear tooth. The varying parameters were load, rotational speed and convection heat transfer coefficient. The rotational speed varies (2000-10000) rpm. For combined loading condition the temperature variation of gear tooth is (70-135)0C. In study average heat transfer coefficient varies (100-350) w/m2k depends on radious of gear. The FEA results were compared with experimental results. Altinbalik (2015) has studied the gear profile for load optimization using theoretical and experimental approach. They have found the lowest load value for forming process of gear using lateral extrusion and forward extrusion.