A Study On The Calculation Method For Transverse Vibration Of The Belt In The Engine Front End Accessory Drive System

The front end accessory drive(FEAD)system is an important part of engine,which is composed of drive pulley,accessory pulley,belt,tensioner and other components.As a common transmission belt structure of FEAD system,the serpentine belt is excited by the torsional vibration of engine crankshaft in the process of system operation,which shows the coupling forms of transverse vibration,longitudinal vibration,lateral vibration and other vibration.The transverse vibration of the belt increases the noise of the front end of the engine,reduces the life of the belt,and affects the reliability of the FEAD system significance.For the FEAD system,the following researches are carried out in this paper:(1)Identify the parameters of the FEAD system.The dynamic and static performance tests of the serpentine belt and the tensioner are completed on MTS elastomer tester,the rotational inertia test of the FEAD accessory pulley rotor is completed on the moment of inertia test bench,the sliding friction coefficient test between the serpentine belt and the pulley is completed on the sliding friction coefficient test bench.The influence factors of the input parameters of FEAD system are studied by sorting out the test data.(2)Taking a six pulley-belt drive system as the research object,the mathematical model of belt-pulley coupling vibration of the FEAD system is established,in which the serpentine belt is simplified as a Bernoulli-Euler beam with longitudinal motion,the pulleys are simplified as homogeneous rigid disk,and the tensioner is simplified as a spring-damping element.Considering the coupling effect between the transverse vibration of the belt and the rotating vibration of the tensioner arm,the hysteretic characteristic of the tensioner arm is transformed into equivalent viscous damping,and the equations of the FEAD system in the reference state and stable state are established.The actual motion state of the FEAD system is excited by the fluctuation of the speed of the crankshaft.The motion state equations of the FEAD system are obtained by linearization based on the steady state.(3)The dynamic response of the six pulley-belt drive system is solved.The steady-state solution of the system is obtained by using the boundary value problem method.For the convenience of calculation,the transverse vibration displacement of the span is discretized into the product of time function and space function by using the Galerkin method.The dynamic response of the system under the crankshaft speed fluctuation is expressed as the sum of the steady-state response and the fluctuation response outside the steady-state solution by using the harmonic increment method.The transverse vibration displacement of the span and the swing angle fluctuation of the tensioner arm are solved by using the complex mode theory.The transverse vibration displacement of the adjacent belt segments of the tensioner and the swing angle fluctuation of the tensioner arm in the six pulley-belt drive system were tested.The accuracy of the mathematical model of the FEAD system and the solution method of the system dynamic response under the crankshaft speed fluctuation were verified by comparing the calculation results with the test results.The influence of input parameters such as elastic modulus,bending stiffness on the dynamic response of the system is studied,which provides a theoretical basis for the reliability of the layout of the FEAD system.The research of this paper provides a basis for further research on the layout and reliability determination of the FEAD system.In this paper,the modeling method of the FEAD system and the solution method of dynamic response of the system have a certain reference value for solving complex mechanical dynamics problems.