New Bell Plate Multi-inertia Channel Mount Vibration Isolation Study And Engine Mount System Decoupling

The engine mounts are vibration isolating elements installed between the vehicle frame and the engine,which play an important role in improving the Noise,Vibration,Harshness(NVH)of the vehicle.The desired properties of mounts require large stiffness and damping property under low frequency large amplitude excitation and small stiffness and damping under high frequency small amplitude excitation.Therefore,to meet the above complex vibration isolating requirements of the engine mounts under the wide frequency working conditions is a difficult area of research at present.In this paper,to solve the engine wide frequency vibration isolation problem,based on the analysis the dynamic characteristics of multi-inertia channel hydraulic mounts and the influence of the number of bell plate on the hydraulic mounts’ characteristics,a new bell plate controllable multi-inertia channel MRF(magnetorheological fluid)mount is proposed.The results shows that the novel MRF mount can achieve adjustable mount stiffness and damping in the frequency 0～50Hz,while minimum stiffness frequency 50Hz～200Hz.Besides,to acquire the real working condition of engine mount in the whole vehicle,the decoupling model of 12 degree of freedom mounts system considering the vehicle frame displacement response is proposed theoretically.Therefore,the research works and results of this paper are concluded as following:(1)The frequency and time domain analytic model of the multi-inertia channel hydraulic mounts are analytically investigated based on the lumped parameter and volume integration methods.Firstly,six hydraulic mount models with different combinations of inertial channels and flow channels are proposed,and then the analytical formulas of the frequency domain characteristics and time domain response of the hydraulic mounts are obtained by using the lumped parameter model and the convolution method,respectively.Secondly,the parametric analysis of hydraulic mounts is analyzed in the frequency and time domains and focus on the effect to transmitted forces and dynamic characteristics of hydraulic mounts.The parameters include inertia coefficients and damping coefficients of inertia channels,damping coefficients of orifice flow channels,decoupling membranes with different combinations of inertia channels and orifice flow channels.Finally,the results show that the orifice flow channel affects both high and low frequency dynamic characteristics of hydraulic mounts,and increasing the number of inertia channels broadens the low frequency dynamic characteristics of mounts.(2)A new type of bell plate hydraulic mount integrating multi-inertia channels is proposed to solve the high frequency hardening problem of the hydraulic mount.The high and low frequency dynamic characteristics of the decoupling membrane,the bell plate and the new bell plate(2 bell plates)hydraulic mounts are analyzed by inductive comparison,firstly.After that,a new type of bell plate multi-inertia channel hydraulic mount is proposed in conjunction with the multi-inertia channel hydraulic mount.And then the effect of different numbers inertia channels and bell plate to the high and low frequency dynamic characteristics of the mount is investigated.The results show that new bell plate hydraulic mount decreases the peak dynamic stiffness by69.88% compared with the conventional mount,so the decoupling membrane is the efficient method to involve the high-frequency hardening problem of the mounts.(3)A new type of bell plate controllable multi-inertia channel MRF mount is proposed to solve the engine wide frequency vibration isolation problem.A new bell plate controllable multi-inertia channel MRF mount that can achieve wide frequency isolation is designed.The channel switching ability of multi-fluid channel structure is verified through experiment firstly.Following,the magnetic circuit design,damping force analysis,Rate-dip flow channel optimization,and the effect of different inertia channel switching on the change of the dynamic characteristics of the mount are analyzed.Finally,a hierarchical controller with multi-island genetic algorithm for real-time optimization is proposed for vibration isolation control research of a mount system with a 1/4 vehicle model considering both pavement and engine excitation.The results show that the designed MRF mount has adjustable dynamic stiffness and damping under 0～50Hz frequency excitation,and has a small dynamic stiffness value under frequency range of 50Hz～200Hz,which can provide reasonable wide frequency vibration isolation property.(4)To obtain the vehicle frame displacement response through the coupling matrix,the decoupling matrix of the 12-degree-of-freedom mount system is derived and a multi-objective genetic algorithm optimization is proposed considering the decoupling of the mount system and the vehicle frame displacement response.Firstly,the coupling matrix of the 12-degree-of-freedom mount system is solved and the convergence of the coupling matrix is proved by the spectral radius.Then,the engine excitation vehicle frame(12 degrees of freedom)displacement response is obtained through the coupling matrix.Finally,based on the multi-objective genetic algorithm,the position and stiffness optimization design of multiple mount elements are carried out with the objectives of minimum vehicle frame displacement and maximum decoupling rate.The results show that the optimization based on the decoupling matrix can effectively improve the decoupling rate of the mount system and suppress the vehicle frame displacement vibration.