Search results for "continuously variable transmission"

Direct analysis of power-split CVTs: A unified method

2018

Abstract This paper provides a fast kinematic analysis method for compound power-split CVTs, which consents to identify their functional parameters. Such parameters permit the assessment of power flows, torques and efficiency, and the design of equivalent transmissions by the use of a recently published mathematical model. The same method can easily address either simpler or more complex transmissions by mean of kinematic equivalent parameters, without the need to arrange separate systems of equations. As a case study, we performed the kinematic analysis of the “Voltec” multi-mode GM transmission.

Analysis of the maximization of wind turbine energy yield using a continuously variable transmission system

2017

Abstract In this paper, an analytic study of the subject of mechanical power transmission in HAWT wind turbine has been carried out. For the most part, the study analyzes the use of continuously variable transmission (CVT) in order to allow the turbine and the electric generator to couple, allowing in turn, an unremitting transmission ratio adjustment. In low-wind sites, the design criteria suggest an oversizing of the wind turbine in order to generate adequate electrical power even at low wind speed. The proposed solution enhances the space of operating points since it allows the electric generator to release the rotational speed from the turbine one (limited due to structural integrity). …

A new approach to the design of a speed-torque-controlled rubber V-belt variator

2005

This paper presents a new model for a torque-speed-sensing rubber V-belt variator. The actuators are of the centrifugal roller kind on the driver side and a helical torque cam plus a compression-torsion spring on the driven side. The equations permit designing the actuator geometry in order to keep the transmissible torque as close as possible to the torque request in the whole operative field. Moreover, a procedure is suggested for the most proper design of an automatic variator of this kind. It permits choosing the required variogram of the transmission, i.e. the matching between the engine and the transmission, and designing the actuators: roller mass, housing shape, contact plate angle…

Efficiency of Split-Way CVT's. A simplified model

2007

ABSTRACT In this paper, a general formula is obtained for the efficiency of all types of Split-Way CVT, consisting of one or two epicyclic trains, a number of fixed ratio gears and one variable speed unit (CVU). It is based on the application of the principle of virtual works and on the simplifying hypothesis that all the dissipation is lumped inside the CVU. The comparison with some experimental results from the literature shows a surprisingly good fit, also in the neighbourhoods of zero speed ratio. INTRODUCTION The possibility of changing the speed ratio continuously between the primary and the secondary shaft of a mechanical transmission is a very interesting topic, mainly in the automo…

V-Belt Winding along Archimedean Spirals During the Variator Speed Ratio Shift

2010

Starting from a previous model for the shift mechanics of rubber belt variators, this lecture elaborates practical design formulas for the torque and the axial thrust making use of the very close resemblance of the belt path to a linear spiral of Archimedes along a large part of the arc of contact. In addition, as an alternative to the modern calculus tools, it is shown how the drive variables can be equally calculated applying some propositions of Archimedes’ classical treatise πeρί ‘eλίκων (On Spirals).

Split-Way CVTs: Parametric Analysis and Design

The thesis provides a parametric analytical method for the analysis and design of power-split continuously variable transmissions, which represent the state of the art for heavy-duty vehicles and hybrid electric cars. The functioning of any driveline is described by mean of a simple set of kinematic parameters, regardless of the constructive scheme. The calculation of the control torques remains straightforward even when both inertial effects and mechanical losses are taken into account. A simple design procedure is described and generalized in order to address any order of driveline, including multimode transmissions. The final layout is generated additively, without the need to analyze hu…

Functional design of power-split CVTs: An uncoupled hierarchical optimized model

2017

Abstract This paper provides a new model for the preliminary design of compound power-split CVTs. Unlike the existing models, the presented method allows the engineers to prioritize functionality and efficiency of the transmission, while delaying the choice of the involved gear sets’ layout as long as possible. The design approach follows a specific priority order, and each step deals with one particular issue, without mutual interference. A smart design-chart eases the assessment and the comparison of the only eligible alternatives, and eventually leads to a final feasible constructive scheme, which can be an excellent concept for further optimization and implementation. Moreover, the mode…

Implicit regulation for automotive variators

2001

A well-known practice uses mechanical variators to realize the so-called continuously variable transmissions (CVTs) for automotive application. A remarkable problem for one of the most used CVTs is given by the hydraulic control of the axial thrust on the half-pulleys that is necessary for torque transmission. It involves a heavy decrease in transmission efficiency. In the present paper, the possible production of the required axial thrust by a simple spring to eliminate hydraulic losses is analysed. It is shown that the power capacity of such a regulated variator is near to the maximum possible, and the belt torque loss is always considerably lower than the sum of the belt and pump losses…