The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. However, it has been well known that the corresponding gear pairs are relatively weak under the situation of imp...The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. However, it has been well known that the corresponding gear pairs are relatively weak under the situation of impact loadings. To improve this phenomenon, a new pretensioning gear system with cycloid teeth rather than the involute ones was proposed, and dual cycloidal gear mechanisms were designed for satisfying geometric constraints and dynamic loading conditions. The simulations of the prototypes were conducted by LS-DYNA program and the experiments for a prototype were performed for a dynamic model with impact loading devices. The results show that the better operation and the smoother motion are confirmed in the proposed cycloidal gear system rather than the conventional one without interferences between gear teeth under the impact of a crash.展开更多
A dynamic model of a helical gear rotor system is proposed.Firstly,a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed.The gear mesh is represented by a pair of cylinder...A dynamic model of a helical gear rotor system is proposed.Firstly,a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed.The gear mesh is represented by a pair of cylinders connected by a series of springs and the stiffness of each spring is equal to the effective mesh stiffness.Combining the gear dynamic model with the rotor-bearing system model,the gear-rotor-bearing dynamic model is developed.Then three cases are presented to analyze the dynamic responses of gear systems.The results reveal that the gear dynamic model is effective and advanced for general gear systems,narrow-faced gear,wide-faced gear and gear with tooth profile errors.Finally,the responses of an example helical gear system are also studied to demonstrate the influence of the lead crown reliefs and misalignments.The results show that both of the lead crown relief and misalignment soften the gear mesh stiffness and the responses of the gear system increase with the increasing lead crown reliefs and misalignments.展开更多
A calculation method for the friction coefficient and meshing efficiency of plastic line gear(LG)pair under dry friction conditions was studied theoretically and experimentally,taking a polyoxymethylene parallel line ...A calculation method for the friction coefficient and meshing efficiency of plastic line gear(LG)pair under dry friction conditions was studied theoretically and experimentally,taking a polyoxymethylene parallel line gear pair(POM PLGP)as an example.Firstly,the geometric and mechanical models of PLGP were built by considering the effects of misalignment and loaded deformation under the actual operating condition.Then,the friction coefficient of POM specimens was obtained via the ball-on-disk experiment,of which the value varies between 0.35 and 0.45 under the experimental conditions.The calculation formula for the friction coefficient of POM LG pair was obtained by fitting the friction coefficient of the POM specimens,and the meshing efficiency of POM LG pair was calculated based on the calculation formula for friction coefficient and the meshing efficiency calculation approach.Finally,the meshing efficiency of POM PLGP specimens was measured using a homemade gear meshing efficiency test rig.The experimental results validated the feasibility of the proposed calculation method for the friction coefficient and meshing efficiency of the plastic LG pair.This study provides a method for the calculation of the friction coefficient and meshing efficiency of plastic gear pairs under dry friction conditions.It also provides the basis for the wear calculation of plastic LG pair under dry friction conditions.展开更多
The meshing surfaces of a gear pair are rough from a microscopic perspective and the surface topography will affect the dynamic response.To study the influence of real surface topography on the gear system dynamic per...The meshing surfaces of a gear pair are rough from a microscopic perspective and the surface topography will affect the dynamic response.To study the influence of real surface topography on the gear system dynamic performance,this paper es-tablishes a 3-degree of freedom transverse-torsional dynamic model with regard to the morphology of the interface.By fractal theory,the expression of backlash be-tween gears is modified based on the height of asperities.The time-varying sifness is calculated according to the fractal method rather than assuming a constant,which is more realistic.The dimensionless dynamic differ ential equations are established and solved with surface topography affected backlash function and time-varying sifess.The dynamic response of the gear system with respec to fractal dimension and fractal roughness is analyzed.展开更多
基金supported by the Changwon National University in 2011-2012,Korea
文摘The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. However, it has been well known that the corresponding gear pairs are relatively weak under the situation of impact loadings. To improve this phenomenon, a new pretensioning gear system with cycloid teeth rather than the involute ones was proposed, and dual cycloidal gear mechanisms were designed for satisfying geometric constraints and dynamic loading conditions. The simulations of the prototypes were conducted by LS-DYNA program and the experiments for a prototype were performed for a dynamic model with impact loading devices. The results show that the better operation and the smoother motion are confirmed in the proposed cycloidal gear system rather than the conventional one without interferences between gear teeth under the impact of a crash.
基金Projects(51605361,51505357) supported by the National Natural Science Foundation of ChinaProjects(XJS16041,JB160411) supported by the Fundamental Research Funds for the Central Universities,China
文摘A dynamic model of a helical gear rotor system is proposed.Firstly,a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed.The gear mesh is represented by a pair of cylinders connected by a series of springs and the stiffness of each spring is equal to the effective mesh stiffness.Combining the gear dynamic model with the rotor-bearing system model,the gear-rotor-bearing dynamic model is developed.Then three cases are presented to analyze the dynamic responses of gear systems.The results reveal that the gear dynamic model is effective and advanced for general gear systems,narrow-faced gear,wide-faced gear and gear with tooth profile errors.Finally,the responses of an example helical gear system are also studied to demonstrate the influence of the lead crown reliefs and misalignments.The results show that both of the lead crown relief and misalignment soften the gear mesh stiffness and the responses of the gear system increase with the increasing lead crown reliefs and misalignments.
基金The authors gratefully acknowledge the support from the National Natural Science Foundation of China(No.51575191)2019 Guangzhou Technology Project(No.201904010368).
文摘A calculation method for the friction coefficient and meshing efficiency of plastic line gear(LG)pair under dry friction conditions was studied theoretically and experimentally,taking a polyoxymethylene parallel line gear pair(POM PLGP)as an example.Firstly,the geometric and mechanical models of PLGP were built by considering the effects of misalignment and loaded deformation under the actual operating condition.Then,the friction coefficient of POM specimens was obtained via the ball-on-disk experiment,of which the value varies between 0.35 and 0.45 under the experimental conditions.The calculation formula for the friction coefficient of POM LG pair was obtained by fitting the friction coefficient of the POM specimens,and the meshing efficiency of POM LG pair was calculated based on the calculation formula for friction coefficient and the meshing efficiency calculation approach.Finally,the meshing efficiency of POM PLGP specimens was measured using a homemade gear meshing efficiency test rig.The experimental results validated the feasibility of the proposed calculation method for the friction coefficient and meshing efficiency of the plastic LG pair.This study provides a method for the calculation of the friction coefficient and meshing efficiency of plastic gear pairs under dry friction conditions.It also provides the basis for the wear calculation of plastic LG pair under dry friction conditions.
基金This study is supported by the National Natural Science Foundation of China(Grant No.52075392)Fundamental Research Funds for the Central Universities(Grant No.2042021kf0024).
文摘The meshing surfaces of a gear pair are rough from a microscopic perspective and the surface topography will affect the dynamic response.To study the influence of real surface topography on the gear system dynamic performance,this paper es-tablishes a 3-degree of freedom transverse-torsional dynamic model with regard to the morphology of the interface.By fractal theory,the expression of backlash be-tween gears is modified based on the height of asperities.The time-varying sifness is calculated according to the fractal method rather than assuming a constant,which is more realistic.The dimensionless dynamic differ ential equations are established and solved with surface topography affected backlash function and time-varying sifess.The dynamic response of the gear system with respec to fractal dimension and fractal roughness is analyzed.
