No abstract

The oil film between the friction disks of the hydro-viscous clutch is taken as the research object. Considering the groove structure of the friction disks, the mathematical model of the oil film flow field is established. The finite difference algorithm is utilized to solve the velocity, the pressure, and the pressure coefficient of the oil film. The incipient position of oil film shear cavitation under different groove structure parameters is carried out. The numerical results indicate that the groove has a great influence on the oil film velocity and pressure. The oil film cavitation inception occurs first in the upstream position of the groove area. The area fraction of cavitation inception is directly proportional to the width and depth of the groove and inversely proportional to the section parameter and inclination angle of the groove. This research provides an efficient and accurate method for predicting the oil film shear cavitation inception.

The drag torque produced by the viscous shearing action of lubricating oil is an important component of the power loss of wet clutches. Studying the prediction model and its influencing factors will provide important theoretical support for reducing the drag torque. Taking a single friction pair wet clutch as the research object, this research obtained the oil film shrinkage under different working conditions based on the VOF model. On this basis, a drag torque calculation model considering the surface tension and shrinkage of oil film is established, in which the drag torque is composed of the torque transmitted by oil film in the oil film continuous zone and the torque transmitted by oil-liquid and gas-liquid in the oil film rupture area, respectively. Comparing the theoretical drag torque with the simulation and experimental results, the variation law of drag torque with the speed difference under different oil film thicknesses and different supply flow is obtained, and the validity of the theoretical model is also verified. Results show that increasing the oil film thickness and decreasing the supply flow will lead to a decrease in drag torque, which provides a useful reference for reducing the drag torque.

The torque to volume ratio and time response characteristics of the clutch during vehicle travel power generation are important issues that affect the quality and efficiency of power generation. In this work, a magnetorheological clutch was established based on the magnetorheological effect and analyzed its magnetic field strength, maximum output torque, time response characteristics, and temperature rise characteristics in driving power generation. The results indicate that the maximum torque of 77.05 N·m is only 3.68% less than the designed value. MR clutches have a better torque to volume ratio for the same volume. The MR clutch can realize millisecond regulation of power output characteristics, the response time of the torque loading section is about 345 ms, while the response time of the torque withdrawal section is about 680 ms. The MR clutch has good heat dissipation performance with an external water-cooling device. Using an MR clutch as a governor for traveling vehicle power generation, the time-varying engine speed is converted to a constant speed by continuously adjusting the excitation current, which can provide more efficient power generation.