Abstract
The vibration caused by the friction characteristic of the clutch during the vehicle start-up process has an impact on driveline torsional oscillation. This results in the occurrence of the stick-slip phenomenon which in turn aggravates the torsional oscillation. In this study, the dynamic model of the wet clutch was built and the self-excited vibration and stick-slip phenomenon during clutch engagement were theoretically analyzed and numerically simulated. The vehicle start-up driveline model was then built with consideration of the stiffness of the shafts, the time-varying mesh stiffness of the gear set, and system damping. The start-up process of the vehicle was simulated through the adoption of a constant engine speed control strategy, and the influence of the control and structure parameters on the stick-slip phenomenon during the vehicle start-up process was investigated. The results showed that increasing the relative speed threshold value of the constant engine speed control decreases the likelihood of the occurrence of the clutch stick-slip action, and the shaft stiffness, system damping, and inertia of each component also affect the stick-slip phenomenon during vehicle start-up.
Highlights
It is essential to ensure smoothness during the process of vehicle shifting and start-up to obtain driving comfort and prolong the service life of the driveline system
The FIV causes two kinds of vibration: the self-excited vibration, which is caused by the variation of the friction coefficient with the relative speed, known as the friction coefficient negative gradient, and the clutch stick-slip action, a phenomenon involving the intermittent stick and slip of clutch contact faces, which is caused by the friction characteristic of the clutch and system dynamics
This study focuses on the effect of the control and structure parameters of the stick-slip phenomenon during the vehicle start-up process
Summary
It is essential to ensure smoothness during the process of vehicle shifting and start-up to obtain driving comfort and prolong the service life of the driveline system. When the rotation speed fluctuation amplitudes of the clutch drum and clutch hub are large enough, the value of the relative speed between the clutch drum and clutch hub may become zero at a certain point in time, causing the clutch to engage in what is referred to as stick on, whereas, when the torque transmitted by the clutch exceeds the static friction capacity of the clutch owing to the torsional oscillation, the clutch disengages and begins to slip in a bid to protect the clutch. During the clutch engagement process, the intermittent lock and slip phenomenon, known as the stick-slip phenomenon, occurs This action is related to two functions: the fluctuation of the rotation speed of clutch drum and hub, and the fluctuation of the torque transmitted by the clutch. In this research study, the establishment of the driveline model considers the friction characteristic of the clutch contact faces, the stiffness and damping of the shafts, and the mesh stiffness of the gear set.
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