| Front end accessory drive (FEAD) and timing driving system are widely used inautomobile engines. For adjusting the tension force and reducing the vibration of thebelt, auto-tensioner with damping structure is widely used in the belt-driven system ofthe automobile engine. Compared with frictional tensioner, hydraulic tensioner hasbigger damping and can reduce pre-tension force of belt. Hydraulic tensioner is usedmore and more widely, because it can prolong the life of belt and bearing.There are very few researches about the damping characteristics of hydraulictensioner both at home and abroad. The theoretical study of damping characteristics hascertain significance both in academic and practical. The main contents and conclusionsof this dissertation are summarized as follows:①B y analyzing the structure and work process ofwidely used hydraulic tensioners,the structure and work principle in common is summarized. The provenance of thedamping is founded. The maximum of damping force and damping energy are used astwo main evaluating indicators of the damping characteristics of hydraulic tensioner.②Fluid-structure interaction finite element model of key part of hydraulictensioner is established in ADINA. Using the simulation result of the FEA model, theflow state of the oil in the annular gap and the main resource of damping force areanalyzed.③A ccording the knowledge of fluid mechanics, Pressure differential equation ofthe chamber with considering the compressibility of oil is obtained, the motiondifferential equation of the one way valve is also obtained. The hysteresis curve ofdamping force is plotted and damping energy and maximum damping force are obtainedwith numerical methods. This analytical model is validated with the result of FEAmodel.④By adopting the single factor method, the relationship between parameters anddamping characteristics of hydraulic tensioner is analyzed. Several conclusions areobtained. Aeration of oil reduces the damping. Compared with the situation that aerationis0.01%, damping energy reduces30%when the aeration is3%(when the excitingfrequency is100Hz). Proper viscosity (the dynamic viscosity should between1×10-9and4×10-9MPa*s) and lower viscosity-temperature coefficient (at least lower than0.031/℃)should be chosen. In order to ensure high level of damping energy both in lower and higher exciting frequency, size of the annular gap should between0.02and0.04mm,length of the annular gap should between10and40mm. Enlarging diameter of pistonand reducing the length of the high-pressure chamber can both enlarge the damping. Aslong as the increasing of the exciting amplitude, the damping energy increaseintensively. The increased multiple is about the square number of the increasedmultiple of exciting amplitude. The eccentricity will reduce the damping energy whenthe exciting frequency is high, but has little effect when the exciting frequency is low.Increasing the pressure of low-pressure chamber can enlarge the damping effectively. |
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