Structure optimization design approach of friction pairs for low-temperature rise wet brake in hydraulic motor

Cam-lobe radial-piston hydraulic motors are widely used in large heavy-duty machinery as direct-drive components of hydraulic systems. Due to their extremely high output torque and power density, the wet brake equipped with the hydraulic motors are necessary to achieve ultra-high braking torque in a compact space. However, due to a large number of internal friction pairs and small fit clearance between multiple friction pairs in wet brake, the rotation of the friction pairs in non-braking state will cause large friction torque loss and obvious temperature rise, thereby leading to the thermal failure of wet brake. How to optimize the structure of friction pairs to reduce the temperature rise of wet brake in non-braking state is a persistent challenge. Existing structure optimization design approaches of friction pairs in brakes mainly focus on the structure of each friction pair, which ignore the effect of fit clearance between the friction pairs on the temperature rise of brakes. Nevertheless, the fit clearance between friction pairs is an important factor that affect the temperature rise. For that, this study proposes a two-step structure optimization design approach of friction pairs for low-temperature rise wet brake in hydraculic motor, which simultaneously considers the fit clearance between the friction pairs and the structure of each friction pair. In this approach, the design process could be divided into two steps: firstly, the influence of fit clearance between multiple friction pairs on the temperature rise of wet brake in non-braking state is analyzed and optimized by the temperature rise theoretical model; secondly, in order to further reduce the temperature rise of wet brake, the oil groove structure of each friction plate are introduced and optimized by fluid-solid-thermal coupling simulation method. By this approach, the low-temperature rise structure of friction pairs with the optimized fit clearance between multiple friction pairs and oil grooves of each friction plate. Finally, a series of experiments are conducted to verify the effectiveness of the design approach. The result show that the temperature rise of wet brake could be effectively reduced 12 % by optimizing the structure of wet brake, demonstrating that the structure optimization design approach could provide a theoretical guidance to design low-temperature rise wet brake for large torque hydraulic motors.