For the research of tooth surface friction, more attention is paid to the heating and energy consumption caused by friction, and the vibration caused by friction has not been paid enough attention. In the earlier research of gear dynamics, the periodic friction excitation of tooth surface is often ignored or equivalent to viscous damping. Tooth surface friction is one of the excitation sources that can not be ignored in the study of gear dynamics; Due to the influence of nonlinear time-varying characteristics such as time-varying meshing stiffness, change of lubrication conditions between teeth and micro characteristics of tooth surface on tooth surface friction, its dynamic excitation mechanism becomes complex.
Through experimental research, Houser et al found that friction has an important impact on load transmission when it deviates from the direction of meshing line, and becomes more obvious under the condition of high torque and low speed. They analyzed the gear noise with friction excitation and bending moment as excitation. Through experimental research, velex et al. Found that the tooth surface friction is a non negligible excitation source for spur and helical gear systems without error, especially for the translational vibration in helical gears with large coincidence. Kim et al. Analyzed the air noise caused by tooth surface roughness by experimental method, pointed out the important influence of tooth surface micro morphology on gear noise, and related tooth surface micro morphology, tooth surface friction excitation and gear vibration noise for the first time. Lundvall et al. Established the dynamic model of multi degree of freedom spur gear, solved the influence of tooth surface friction on the dynamic response characteristics of the system by numerical method, and studied the influence of tooth profile modification on transmission error considering tooth surface friction. Considering the tooth deviation and time-varying meshing stiffness, velex et al. Analyzed the influence of tooth surface friction on the dynamic response characteristics of helical gear system by using recursive program, and found that the friction between teeth induces oscillation force at low speed. Valentin et al. Carried out the gear friction experiment through the dynamic detection device. The research shows that the tooth surface friction is also one of the sources of vibration and noise. When the friction excitation is transmitted between the bearing and the gearbox, it has an important impact on the deviation of the meshing line. Rebbechi et al. Successfully calculated the tooth surface friction by using the variation law of tooth root stress. Lida et al. Ignored the influence of dynamic meshing force fluctuation caused by time-varying meshing stiffness on the gear meshing action line, and used a simple single degree of freedom gear torsional vibration model to study the influence of spur gear friction on the dynamic response characteristics of gear system. The research results show that the time-varying friction on gear tooth surface will increase the system damping and vibration. He et al. Established more accurate dynamic models of single degree of freedom and multi degree of freedom spur and helical gear systems, considered the actual time-varying stiffness, and studied their dynamic response with constant friction coefficient; Noise prediction and experimental test considering sliding friction based on source path – receiver model. Considering the interaction between gear wear and dynamics, DIN et al studied the influence of tooth profile wear on the dynamics and vibration characteristics of gear system.
Wang Yi et al. Took a pair of helical gear system pairs as the research object. Assuming that the friction coefficient is constant and the load on the contact line is evenly distributed, they analyzed the dynamic response of helical gear system with and without friction. The results show that under the action of friction, the vibration in the direction perpendicular to the gear meshing line intensifies, which has an adverse impact on the stability of gear transmission system. Wang Sanmin et al. Considered the factors such as friction, clearance and timely variable stiffness, studied the influence of friction on the periodic response and chaotic response of gear system by using the nonlinear dynamic model of spur gear pair, and found that friction increased the components of superharmonic and subharmonic response of the system, making the system enter the chaotic state in advance. Chen Siyu used a single degree of freedom nonlinear model considering friction excitation, time-varying stiffness and tooth side clearance to study the effects of damping ratio, excitation frequency, friction coefficient and initial error on the steady-state response of gear nonlinear vibration system. Zang Lei used ADAMS software to analyze the friction dynamics of spur gear system, and studied the variation laws of tooth surface meshing force, friction force and friction coefficient between spur gear teeth. Sun Yuehai et al. Considered the gear mass eccentricity and tooth meshing friction, established the dynamic model of the vibration of the involute gear transmission system, and analyzed the dynamic response results of the gear system under specific transmission conditions. Considering the overall gear error and tooth surface friction, Li Wenliang constructed the dynamic model of single degree of freedom helical gear system, and analyzed the effects of helical gear resonance, load and damping on dynamic transmission error. Considering the coupling relationship between the tribological characteristics and dynamic behavior of the meshing pair under mixed elastohydrodynamic lubrication, Dong Huili established a single degree of freedom friction dynamic model of the helical gear system, and studied the effects of tooth profile modification, tooth surface morphology, tooth end modification and helix angle on the dynamic characteristics and lubrication characteristics of the helical gear system.
To sum up, the current research on gear friction excitation mainly focuses on spur gears. The meshing contact line of helical gears is inclined, and the time-varying of the contact line and the opposite direction of friction on the contact lines on both sides of the pitch line make the helical gear friction excitation complex.