114 VISUALIZATION OF OIL FILM BEHAVIOR ON FRICTION PLATE IN WET CLUTCH ENGAGEMENT

The working principle and motion process of an aviation wet clutch are analyzed. The initial velocity before the friction pair engaged is solved. The transient Reynolds equation is modified, and an oil film bearing capacity model and a micro-convex bearing capacity model are derived. The film thickness equation between N friction pairs and a pressure-plate is derived. A dynamic engaged model of springs, pistons, friction pairs, and pressure plates are established. The torque balance equation is established of two pairs of friction pairs. The friction torque, rate of change in the oil film, and law of relative change in speed are obtained. The results demonstrate that the spring preload and the viscosity of the lubricating oil have a significant influence on the engagement characteristics. Increasing the quality of the friction plate will reduce the time of engagement, whereas the quality of the friction plate has slight effect on the friction torque characteristics and oil film thickness. The initial speed generated by the collision process will reduce the output speed, sharply increase the torque peak at the lock, and increase the shift shock.

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Response Characteristics of Dynamic Torque for Wet Clutch Engagement: A Numerical and Experimental Study

Shock and Vibration ◽

10.1155/2021/5522998 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Zhigang Zhang ◽

Ling Zou ◽

Hang Liu ◽

Jin Feng ◽

Zhige Chen

Keyword(s):

Elastic Modulus ◽

Applied Pressure ◽

Asperity Contact ◽

Oil Film ◽

Response Characteristics ◽

Clutch Engagement ◽

Torque Response ◽

Wet Clutch ◽

Friction Lining ◽

Lubricant Viscosity

To determine the factors affecting the dynamic transmitted torque response characteristics of the wet clutch, the oil film pressure, the asperity contact pressure, the applied pressure, and the dynamic transmitted torque model were established, using the fourth-order Runge–Kutta numerical method to couple the oil film thickness and the speed difference to obtain the change curve of the joint pressure and the transmitted torque. The established model was used to study the influence of the pressure hysteresis time, lubricant viscosity, friction lining permeability, friction pair equivalent elastic modulus, and surface combined roughness RMS on the dynamic transmitted torque response during the wet clutch engagement. The results indicate that the longer the pressure hysteresis time, the smaller the permeability of the friction lining, the smaller the equivalent elastic modulus, the greater surface combined roughness RMS, the more delayed the response of the transmitted torque, and the smaller the level of jerk of the wet clutch engagement. Also, the lower the lubricant viscosity, the greater the permeability of the friction lining, and the smaller the equivalent elastic modulus is and the greater surface combined roughness RMS is, the more sensitive the transmitted torque response is to pressure response changes.

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Influence of operating conditions on friction and temperature characteristics of a wet clutch engagement

Tribotest ◽

10.1002/tt.3020070202 ◽

2000 ◽

Vol 7 (2) ◽

pp. 99-114 ◽

Cited By ~ 6

Author(s):

Mikael Holgerson

Keyword(s):

Operating Conditions ◽

Temperature Characteristics ◽

Clutch Engagement ◽

Wet Clutch

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Modeling and experimental research on engaging characteristics of wet clutch

Industrial Lubrication and Tribology ◽

10.1108/ilt-12-2017-0383 ◽

2019 ◽

Vol 71 (1) ◽

pp. 94-101 ◽

Cited By ~ 1

Author(s):

Yanzhong Wang ◽

Yuan Li ◽

Yang Liu ◽

Wei Zhang

Keyword(s):

Contact Surface ◽

Hydrodynamic Lubrication ◽

Load Capacity ◽

Lubricating Oil ◽

Centrifugal Effect ◽

Element Analysis ◽

Content Type ◽

Clutch Engagement ◽

Wet Clutch ◽

Engagement Process

PurposeTo gain in-depth understandings of engaging characteristics, the purpose of this paper is to improve the model of wet clutches to predict the transmitted torque during the engagement process.Design/methodology/approachThe model of wet clutch during the engagement process took main factors into account, such as the centrifugal effect of lubricant, permeability of friction material, slippage factor of lubricant on contact surface and roughness of contact surface. Reynolds’ equation was derived to describe the hydrodynamic lubrication characteristics of lubricant film between the friction plate and the separated plate, and an elastic-plastic model of the rough surfaces contact based on the finite element analysis was used to indicate the loading force and friction torque of the contact surface.FindingsThe dynamic characteristics of wet clutch engagement time, relative speed, hydrodynamic lubrication of lubricating oil, rough surface contact load capacity and transfer torque can be obtained by the wet clutch engagement model. And the influence of the groove shape and depth on the engaging characteristics is also analyzed.Originality/valueThe mathematical model of the wet clutch during the engagement process can be used to predict the engaging characteristics of the wet clutch which could be useful to the design of the wet clutch.

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The influence of repeated high-energy engagements on the permeability of a paper-based wet clutch friction material

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650117700807 ◽

2017 ◽

Vol 231 (12) ◽

pp. 1574-1582

Author(s):

Niklas Lingesten ◽

Pär Marklund ◽

Erik Höglund

Keyword(s):

High Energy ◽

Friction Material ◽

Sliding Surface ◽

Steel Core ◽

Interface Surface ◽

Clutch Engagement ◽

Wet Clutch ◽

Oil Flow ◽

Contradictory Behavior ◽

Test Cells

The behavior of a wet clutch during engagement is of great importance to the durability of the clutch and the drivability of a vehicle. While many different factors influence the engagement behavior, the focus of this paper is to investigate only one factor, the permeability of the wet clutch friction material. Two test cells for measuring the permeability of friction material mounted on clutch discs have been developed. The test cells were then used to examine the effect of clutch material ageing through clutch engagement on the permeability of the material. The tests were performed on full size friction discs including the steel core prior and subsequent to testing in a wet clutch engagement test rig. The ability of the friction material to allow for oil flow both through the sliding surface layer and the bulk of the material was measured. The results indicate that repeated clutch engagements will increase the bulk permeability. However, the repeated engagements will decrease the ability to pass fluid through the friction material sliding surface. This contradictory behavior could be explained by a combination of an increase in pore size through repeated compression and the surface glaze clogging of the friction interface surface pores.

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Research on the Wet Clutch Engagement Torque

Volume 7: 2nd Biennial International Conference on Dynamics for Design; 26th International Conference on Design Theory and Methodology ◽

10.1115/detc2014-34179 ◽

2014 ◽

Author(s):

Yingying Zhang ◽

Changle Xiang

Keyword(s):

Rough Surface ◽

Automatic Transmission ◽

Squeeze Film ◽

Real Contact Area ◽

Asperity Contact ◽

Time Flow ◽

Clutch Engagement ◽

Wet Clutch ◽

Lubrication Oil ◽

Engagement Process

The driving performance of the vehicle with automatic transmission is influenced by the performance of the wet clutch directly. But at present it is still a challenge to build a reliable predictable model for the torque of the engagement process of the wet clutch. Focusing on the wet clutch of vehicle, this paper starts from mechanism analysis, and a modified Reynolds equation with the consideration of the centrifugal force of the squeeze-film is established. In the model, we can consider the speeds of the friction and separator plates independently. At the same time, flow factors have been used to research the impacts of rough surface on the flow of the lubrication oil. In the three-dimensional solution domain, the circumferential pressure gradient of lubrication oil is considered. The model is solved with the finite volume method. The simulation of the torque of the asperity contact calculates the real contact area changed with the engagement process, and the microscopic texture direction of rough surface is considered. Subsequently, the squeeze-film flow model is combined with the asperity contact model to create an integrated clutch engagement model. Finally, the influence of applied force, viscosity of lubrication oil, friction material, the depth of grooves and the width of the grooves are investigated. Based on the comparison with the experimental data, the performance of the proposed model is found satisfactory. Because in this model more detail properties of material and geometric features of the friction plate are include, the wet clutch model developed in this research can become a baseline model for the prediction of the engagement behavior of a real wet clutch. The present model may become an efficient alternative to laboratory testing and lead to designs that can not be envisioned by other approaches.

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