Causes of Microslip in a Continuously Variable Transmission

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Songho Kim ◽  
Carl Moore ◽  
Michael Peshkin ◽  
J. Edward Colgate
Keyword(s):  
Contact Area ◽  
Gear Ratio ◽  
Continuously Variable Transmission ◽  
Rolling Contact ◽  
Rolling Contacts ◽  
Variable Transmission ◽  
Toothed Gears

The continuously variable transmission (CVT) is a type of transmission that can adopt any arbitrary gear ratio. Whereas typical transmissions utilize toothed gears, the CVT employs a sphere in rolling contact with a set of rollers; loads applied to the CVT are supported across these rolling contacts, resulting in microslips of varying amounts at each contact area. In this paper, we describe the causes of microslips in the CVT and ways to lessen them through an alternative CVT design.

Optimization of Hydraulic Pressure for Continuously Variable Transmission

2011 ◽  
Vol 317-319 ◽  
pp. 529-532
Author(s):  
Kei Lin Kuo
Keyword(s):  
Torque Converter ◽  
Transmission Efficiency ◽  
Gear Ratio ◽  
Continuously Variable Transmission ◽  
Hydraulic Pressure ◽  
Primary Input ◽  
Input Shaft ◽  
Variable Transmission ◽  
Labview Program ◽  
Set Up

Compared to conventional transmission layouts, Active continuously variable transmission (CVT) provides smoother gear shifting and gear ratio in smaller increments, and is, therefore, more accommodating the needs of both the driver and passengers. A few notable improvements are enhanced passenger comfort, higher transmission efficiency, and improved acceleration. Incorporating all of the above qualities has become a major developmental focus for the automotive industry, and the potential for improvement warrants further investigation. A CVT controls the gear ratio by changing the diameters of the primary (input) and the secondary (output) pulleys by adjusting the hydraulic pressure applied to each using valves. Hydraulic pressure in the channel is developed using a basic pump connected to the input shaft. Excess pressure produced at higher speed is wasted. This study aims to minimize this hydraulic pressure without affecting the transmission’s performance, in order to conserve energy. A user interface was set up and the CVT’s torque converter was modified such that the inner and outer shafts could be operated independently, allowing for full control of hydraulic pressure .This experiment successfully achieved, via a custom LabVIEW program, its goal of controlling the gear ratio between the primary and secondary pulleys whilst operating at lower pressures to those specified by the manufacturer. This proves that it is possible to fully control the CVT whilst operating at a reduced hydraulic pressure.

Methods for Controlling a Wind Turbine System With a Continuously Variable Transmission in Region 2

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Andrew H. Rex ◽  
Kathryn E. Johnson
Keyword(s):  
Wind Turbine ◽  
Gear Ratio ◽  
Continuously Variable Transmission ◽  
Variable Speed ◽  
Wind Turbine System ◽  
Variable Speed Wind Turbine ◽  
Fast Wind ◽  
Variable Transmission ◽  
Integral Controller ◽  
Proportional Integral Controller

Variable speed operation enables wind turbine systems to increase their aerodynamic efficiency and reduce fatigue loads. An alternative to the current electrically based variable speed technologies is the continuously variable transmission (CVT). A CVT is a transmission whose gear ratio can be adjusted to take on an infinite number of settings within the range between its upper and lower limits. CVT research in wind turbine applications predicts an improvement in output power and torque loads compared with fixed-speed machines. Also, a reduction in the harmonic content of the currents is anticipated by eliminating the power electronics. This paper develops a model that combines a CVT model with the FAST wind turbine simulator for simulating the system’s performance in MATLAB/SIMULINK. This model is useful for control development for a variable-speed wind turbine using a CVT. The wind turbine with CVT is simulated using two controllers: a proportional-integral controller and a nonlinear torque controller of the type commonly used in the wind industry.

scholarly journals On a Simplified Model for Numerical Simulation of Wear During Dry Rolling Contacts

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
L. Chevalier ◽  
A. Eddhahak-Ouni ◽  
S. Cloupet
Keyword(s):  
Contact Area ◽  
Power Distribution ◽  
Contact Problems ◽  
Rolling Contact ◽  
Normal Loading ◽  
Fast Determination ◽  
Wear Process ◽  
Simplified Approach ◽  
Rolling Contacts

We deal with rolling contact between quasi-identical bodies. As normal and tangential problems are uncoupled in that case, the simplified approach to determine contact area and normal loading distribution for rolling contact problems is presented in Sec. 2. In Sec. 3, the solution of the tangential problem is used to update the rolling profiles and enables to follow the wear evolution versus time. The method used to solve the normal problem is called semi-Hertzian approach with diffusion. It allows fast determination of the contact area for non-Hertzian cases. The method is based on the geometrical indentation of bodies in contact: The contact area is found with correct dimensions but affected by some irregularities coming from the curvature’s discontinuity that may arise during a wear process. Diffusion between independent stripes smoothes the contact area and the pressure distribution. The tangential problem is also solved on each stripe of the contact area using an extension of the simplified approach developed by Kalker and called FASTSIM. At the end, this approach gives the dissipated power distribution in the contact during rolling and this power is related to wear by Archard’s law. This enables the profiles of the bodies to be updated and the evolution of the geometry to be followed.

Study on Optimal Load for Hydraulic Control System of Continuously Variable Transmission

2012 ◽  
Vol 516-517 ◽  
pp. 665-668
Author(s):  
Kei Lin Kuo
Keyword(s):  
Monitoring Program ◽  
Transmission Efficiency ◽  
Gear Ratio ◽  
Visual Programming ◽  
Continuously Variable Transmission ◽  
Operating Conditions ◽  
Hydraulic Pressure ◽  
Hydraulic Control ◽  
Main Research ◽  
Variable Transmission

In recent years, the main research focus for vehicle transmission systems has been the development of the Continuously Variable Transmission (CVT). CVTs can provide passengers with greater comfort, reduce energy consumption, and offer better transmission efficiency. CVT systems achieve the desired gear ratio by adjusting the hydraulic pressure on the rear and front pulleys using a solenoid valve. Our study aims to increase the efficiency of an existing CVT system, without reducing its performance. In this study have modified the CVT so that we can independently control the external and internal axes electronically. The speed of the hydraulic pump in the gearbox is not affected by the engine speed. In this way, In this study can achieve the lowest possible hydraulic pressure. In our study, In this study use the visual programming language LabVIEW as the human-machine interface for the monitoring program. In addition, a data acquisition system is used to collect experimental parameters, record data in real time, and perform data consolidation. Our system uses varying loads in order to evaluate the improvement in transmission efficiency over many operating conditions. Through the use of solenoids valves acting together, the pipeline hydraulic pressure can be varied. The widths of the front and rear pulleys are thus changed to achieve the goal of continuous variation. Under different loads, the relationships between the measured efficiency and the hydraulic pressure on the rear and front pulleys are used to verify and confirm the increase in efficiency achieved by controlling the hydraulic pressure.

Dynamics Analysis and Control of a Holonomic Vehicle With a Continuously Variable Transmission

2000 ◽  
Vol 124 (1) ◽  
pp. 118-126 ◽  
Author(s):  
Karim A. Tahboub ◽  
Harry H. Asada
Keyword(s):  
Dynamic Characteristics ◽  
Impedance Matching ◽  
Gear Ratio ◽  
Continuously Variable Transmission ◽  
Friction Compensation ◽  
Vehicle Stability ◽  
Dynamics Analysis ◽  
Dc Motors ◽  
Variable Transmission ◽  
And Control

This paper presents kinematic and dynamic analysis of a holonomic vehicle with continuously-variable transmission. Four ball wheels, independently actuated by DC motors, enable for moving the vehicle in any direction within the plane and rotating it around its center. The angle between the two beams holding the balls can be changed to alter the gear ratio and other dynamic characteristics of the vehicle. This feature is exploited in augmenting the vehicle stability, optimizing output power, selecting an appropriate gear ratio, and in impedance matching. A simple adaptive friction-compensation-based controller is proposed to handle the complex friction properties.

scholarly journals Experimental Characteristics of Mechanical Continuously Variable Transmission with Internal Force Functions

2021 ◽  
Vol 20 (4) ◽  
pp. 310-319
Author(s):  
A. V. Yurkevich ◽  
A. V. Tereshin ◽  
V. A. Soldatkin
Keyword(s):  
Power Transmission ◽  
Rotation Frequency ◽  
Internal Force ◽  
Gear Ratio ◽  
Continuously Variable Transmission ◽  
Recording Equipment ◽  
Internal Link ◽  
Variable Transmission ◽  
New Type ◽  
Transformer Ratio

The paper proposes a new type of a mechanical continuously variable transmission with internal force functions  to upgrade the energy efficiency of a vehicle equipped with a conventional engine. The prototype of the transmission is a well-known V. F. Maltsev concurrent pulse variator in which freewheel mechanism driven members are supplemented with elastic torsions shafts. It is shown that the variator turns into a continuous transformer – a mechanical continuously variable transmission with internal force functions. There is an internal automaticity and continuity in the entire range of gear ratio changes. The configuration engineering solution is implemented in the engineering prototype. The aim of the research is experimental study of the properties and characteristics of such a mechanical continuously variable transmission. The kinematic configuration and the main structural dimensions of the engineering prototype are given. Special testing facility and measuring-and-recording equipment have been developed. A set of parameters to be recorded has been specified. The accuracy of their measurement is statistically estimated. The results of the experiments are presented in terms of output and input torque dependencies on the speed of the driven shaft. It is shown that the transmission characteristics in their dimensionless form (transformer ratio and efficiency) in the function of internal gear ratio are universal. The possibility of obtaining an infinite kinematic and significant power transmission ranges by independently changing the internal link oscillation range (level of the force function) and the rotation frequency of the drive shaft has been experimentally shown. The transmission  has high transforming and energy properties, which are higher than those of hydrodynamic gears.

scholarly journals Energy Consumption and Lifecycle Cost Analysis of Electric City Buses with Multispeed Gearboxes

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2117
Author(s):  
Antti Ritari ◽  
Jari Vepsäläinen ◽  
Klaus Kivekäs ◽  
Kari Tammi ◽  
Heikki Laitinen
Keyword(s):  
Energy Consumption ◽  
Programming Model ◽  
Search Algorithm ◽  
Cost Effective ◽  
Gear Ratio ◽  
Continuously Variable Transmission ◽  
Driving Cycle ◽  
Daily Schedule ◽  
Variable Transmission ◽  
Vehicle Dynamic Model

This study investigates the potential of improving the energy efficiency and reducing the lifecycle costs of electric city buses with multispeed gearboxes. A two-speed dual clutch gearbox and a continuously variable transmission were studied and compared to a reference fixed gear ratio powertrain. A novel two-level optimization model was introduced. The top level involves an exhaustive search algorithm and quasi-static vehicle dynamic model for optimizing the two-speed gearbox gear ratios, utilizing efficiency maps for the electric motor and the inverter. The second level is an integer programming model, which finds an optimal gear shifting policy subject to constraints on hysteresis and gear shifting induced losses. The model was applied with a standard driving cycle and additionally with three measured cycles acquired from a prototype battery electric city bus operating on a daily schedule on a suburban route in Espoo, Finland. The results showed that a two-speed gearbox reduced energy consumption by 2–3.2%, depending on the driving cycle characteristics. On the other hand, the continuously variable transmission was found to increase consumption by 1.9–4.0% due to large losses of the belt mechanism. It was concluded that the two-speed gearbox is a cost-effective investment for electric city buses characterized by operation profiles with frequent acceleration and braking events.

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