Theoretical Model and Experimental Research on Friction and Torque Characteristics of Hydro-viscous Drive in Mixed Friction Stage

Abstract

The hydro-viscous drive (HVD) has been widely used in fan transmission in vehicles, fans, and scraper conveyors for step-less speed regulation or soft starting. In the mixed friction stage, the contact, friction, and torque characteristics of friction pairs are very complex and change at any time. The characteristics of the frictional and hydrodynamic lubrication states were studied in order to calculate and predict the friction and torque characteristics of the friction pairs in the mixed friction stage. The fluid torque was calculated by applying the average shear stress model and the load-carrying capacity of asperity was determined on the basis of the fractal contact theory. In addition, the contact friction coefficient of the friction pairs was taken into consideration and measured by using the MM1000-III friction and wear testing machine. The asperity friction torque and total torque in the mixed friction stage were obtained and finally, the test rig for the torque characteristics was set up. The results show that the contribution to the total torque is shared by the oil film and the asperity friction. The friction coefficient decreases sharply at first and then increases with a change in the relative rotational speed, following the Stribeck curve closely, and the contact frictional coefficient slowly decreases with increase in the pressure between the friction pairs. The torque between the friction pairs is provided by the asperity friction, and the torque due to the oil film reduces to zero. When the thickness of the oil film is small, a major contribution to the total torque is due to the asperity friction. The total torque also increases with the decrease in the film thickness ratio. Therefore, by theoretical analysis and experimental verification, the torque of the friction pairs in the mixed friction stage can be accurately calculated using the average shear stress model and asperity friction torque model.

AMT Starting Control as a Soft Starter for Belt Conveyors Using a Data-Driven Method

“…where is a penalty factor which is more than zero to limit the changes of . Taking the derivative of Equation ( 14) with respect to and letting its value be equal to zero, which means to minimize the estimation criterion function expressed by Equation ( 14), then the estimation algorithm of is obtained in Equation (15).…”

“…( ) sampling time. Therefore, the system can be transformed into a dynamic linear model based on Equation (15).…”

“…The principle of variable frequency drives is to adjust their frequency with change in motor speed [11]. Hydro-viscous drives mainly use a wet clutch to change the speed difference between the active and driven plates [12][13][14][15]. The variable frequency drives are used in dry locations with sufficient ventilation for the use requirements of the electrical equipment.…”

Influence of manufacturing surface topography on torque and load bearing capacity of hydro-viscous drive clutch under mixed lubrication stage

“…According to the fractal model of the clutch established above and the experimental analysis (Cui et al , 2019), the contact load under each film thickness ratio and the contact friction coefficient under each contact load are obtained. Therefore, the friction torque generated by the coarse peak contact can be written as: where f a denotes the contact friction coefficient.…”

“…The maximum transmission torque and load bearing capacity are two important parameters for HVD clutch, which have important implications for HVD capabilities (Cui et al , 2018b). Therefore, many studies have been carried out to investigate the influence of factors on these two parameters, such as oil groove structure (Cui et al , 2018b; Xie et al , 2017), oil characteristics (Xie and Hou, 2011) and surface topography (Cui et al , 2019). Among these factors, surface manufacturing topography is one of the most important (Berger et al , 1997).…”