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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The investigation and modelling of the steel compression V-belt continuously variable transmission

Micklem, J. D. January 1994 (has links)
No description available.
2

A Kinematic Analysis and Design of a Continuously Variable Transmission

Willis, Christopher Ryan 15 May 2006 (has links)
This thesis describes a method for analyzing and designing a continuously variable transmission (CVT). The analysis process is implemented in a software package that can be used to tune a CVT for a given application. The analysis is accomplished through the use of kinematic principles as well as equations developed from basic energy balances. Although the theory developed can be applied to any CVT, this thesis focuses on a case study using the Team Industries brand CVT applied to the Virginia Tech Mini Baja Team. The work was motivated by the team's need to have a reliable and inexpensive method for CVT tuning. Previous approaches to CVT tuning were strictly empirical and involved mechanical component replacement in a slow and expensive trialand- error optimization loop. The tuning software is intended to be a first step in the process of properly tuning a CVT for a specific application and not a complete replacement for the empirical methods employed previously. / Master of Science
3

An Investigation of a Positive Engagement, Continuously Variable Transmission

Andersen, Brian S. 15 June 2007 (has links) (PDF)
A continuously variable transmission (CVT) is a type of transmission that allows an infinitely variable ratio change within a finite range, allowing the engine to continuously operate in an efficient or high performance range. A brief history of CVTs is presented, including the families under which they can be categorized. A new family of CVTs, with the classification of positive engagement, is presented. Three different published embodiments of CVTs of the positive engagement type are presented describing a meshing problem that exists apparently regardless of the embodiment in this family. The problem is called the non-integer tooth problem and its occurrences are detailed in each of the three embodiments. Specific solutions to the problem, as embodied in each case, are presented. The proposed embodiment of a new, positive engagement, continuously variable transmission is described in detail with the derived general kinematic equations of its motion. The kinematic equations for two variant embodiments are also derived. The results of the meshing analysis for this new embodiment are given and the non-integer tooth problem is exposed in three different operating conditions of the CVT. Characteristics of a solution to the non-integer tooth problem are then described, which are applicable to the positive engagement family in general.
4

Modélisation dynamique d'une transmission à variation continue (CVT) à courroie de caoutchouc

Julió, Guifré January 2010 (has links)
Le développement d'outils prédictifs est nécessaire pour la conception des nouvelles générations de transmission à variation continue (CVT) à courroie de caoutchouc. Ce mémoire présente un modèle de CVT à courroie de caoutchouc, capable de prédire la réponse temporelle du rapport de transmission pour des variations de la force de serrage de la poulie motrice, du couple et du régime moteur. Pour ce faire, la courroie est discrétisée en noeuds sur lesquels s'exercent les forces internes de la courroie ainsi que les forces de contact imposées par les poulies. Les relations permettant de déterminer ces dernières sont développées, considérant la physique du contact entre les poulies et la courroie. La réponse temporelle du rapport de transmission est obtenue par la solution des équations différentielles découlant de l'application des lois de la mécanique classique sur les noeuds. Les résultats du modèle concordent avec les mesures expérimentales prises dans des conditions d'opération représentatives de l'exploitation normale des CVT. La similarité des prédictions du modèle et des résultats de tests est présentée à la fois pour le régime transitoire et les conditions stabilisées, validant que l'approche utilisée est valable et qu'elle permet l'obtention de résultats inatteignables jusqu'à présent. L'utilisation du modèle présenté dans ce mémoire aidera les concepteurs des futures générations de CVT en leur permettant d'anticiper le comportement de la transmission, sans avoir recours au prototypage.
5

Dynamic Simulation And Performance Optimization Of A Car With Continuously Variable Transmission

Guvey, Serkan 01 January 2003 (has links) (PDF)
The continuously variable transmission (CVT), which has been in use in some of the vehicles in the market today, presents the possibility of decoupling the engine speed and the vehicle speed. By this way, it is now possible to operate the engine at its maximum efficient or performance point and fix it at that operating point without losing from the vehicle speed. Instead of using gears, which are the main transmission elements of conventional transmission, CVT uses two pulleys and a belt. By changing the pulley diameters, a continuously variable transmission ratio is obtained. Besides all its advantages, it has some big drawbacks like low efficiency, torque transmission ability and limited speed range. With developing technology, however, new solutions are developed to eliminate these drawbacks. In this study simulation models for the performance and fuel consumption of different types and arrangements of continuously variable transmission (CVT) systems are developed. Vehicles, which are equipped with two different arrangements of CVT and an automatic transmission, are modelled by using Matlab&amp / #8217 / s simulation toolbox Simulink. By defining the required operating points for better acceleration performance and fuel consumption, and operating the engine at these points, performance optimization is satisfied. These transmissions are compared with each other according to their &amp / #8216 / 0-100 kph&amp / #8217 / acceleration performances, maximum speeds, required time to travel 1000 m. and fuel consumptions for European driving cycles ECE and EUDC. These comparisons show that CVT systems are superior to automatic transmission, according to their acceleration and fuel consumption performances. CVTs also provide smoother driving, while they can eliminate jerks at gear shifting points.
6

Vocational Education Center Vocational Technology (CVT) In Community Umarizeiras, Maranguape-CE / EducaÃÃo profissionalizante do centro vocacional tecnolÃgico (CVT) na comunidade de Umarizeiras/Maranguape/CE

Paulo Henrique Freitas Maciel 08 November 2013 (has links)
nÃo hà / Historically, we can verify the educational duality in which we have a formation oriented to the ruling Ãlite and another one oriented to the workers who act in the capitalist production process. However, the expansion of the capitalism in the last four decades, we identify, as Karl Marx had already previewed, the intensification of the substitution of the living work (the human being) for the dead work (machines), causing crisis, because the market doesnât absorb so many workers in the production process. Therefore, the unemployment, is a reality that scares even the international organizations, like the United Nations (UN). In this context, the employability, in a world without jobs and the human capital theory emerge as new forms of social domination, internalizing in the individual the idea that he is the responsible for his precarious economic situation. In this regard, in this research we analyzed the formation of workers released by Centro Vocacional TecnolÃgico (CVT) â Technologic Vocational Center â through means of initial formation courses or professional qualification in the community of Umarizeiras, in Maranguape, town in the Metropolitan Region of Fortaleza, pointing contradictions imposed by the contemporary capitalism which limit that performance. The investigation took place with oral sources, through interviews with thirteen dwellers; and documents: booklets of the courses available by CVT and Estatuto da AssociaÃÃo de Moradores de Umazeira, which let us highlight the contradictions between the official speech and the reality lived by the subjects involved in that formation. The available courses by CVT to that community were fruit pulp process, chicken raising, E.V.A., computing, fruit sweets. All the interviewed subjects had already participated in one or more courses, motivated by the immediate objective of getting a job, fact that doesnÂt really happen; about the knowledge acquired in the courses, itâs rare to find someone who uses it in the daily life. We conclude, therefore, that the offer of the courses achieves rather an ideological objective, targeting to blame the individuals for their economic situation than a whole formation of the human being, having work as the educational principle. / Historicamente, verificamos a dualidade educacional em que temos uma formaÃÃo voltada para as elites dirigentes e outra para os trabalhadores que atuam no processo de produÃÃo capitalista. No entanto, na expansÃo do capitalismo nas Ãltimas quatro dÃcadas, identificamos, assim como jà tinha antecipado Karl Marx, a intensificaÃÃo da substituiÃÃo do trabalho vivo (o ser humano) pelo trabalho morto (as mÃquinas), ocasionando uma crise, pois o mercado jà nÃo absorve tantos trabalhadores no processo produtivo. O desemprego, portanto, à uma realidade que assusta atà mesmo os organismos internacionais, como a OrganizaÃÃo das NaÃÃes Unidas (ONU). Neste contexto, a empregabilidade, em um mundo sem emprego, e a teoria do capital humano surgem como novas formas de dominaÃÃo social, internalizando no indivÃduo a ideia de que à ele o responsÃvel por sua situaÃÃo econÃmica precÃria. Neste sentido, analisamos nesta pesquisa a formaÃÃo de trabalhadores desencadeada pelo Centro Vocacional TecnolÃgico (CVT), por meio de cursos de formaÃÃo inicial ou qualificaÃÃo profissional na comunidade de Umarizeiras, distrito de Maranguape, municÃpio da RegiÃo Metropolitana de Fortaleza (RMF), apontando as contradiÃÃes impostas pelo capitalismo contemporÃneo, que limitam aquela atuaÃÃo. A investigaÃÃo foi realizada a partir da articulaÃÃo de fontes orais, atravÃs de entrevistas com 13 (treze) moradores; e documentais: apostilas dos cursos disponibilizadas pelo CVT e o Estatuto da AssociaÃÃo de Moradores de Umarizeiras, o que nos permitiu colocar em evidÃncia as contradiÃÃes entre o discurso oficial e a realidade vivenciada pelos sujeitos envolvidos naquela formaÃÃo. Os cursos ofertados pelo CVT Ãquela comunidade foram: processamento de polpas, criaÃÃo de galinha caipira, E.V.A., informÃtica, doces de frutas e associativismo. A maioria dos entrevistados jà havia participado de um ou mais cursos, motivados pelo objetivo imediato da conquista de um emprego, fato que constatamos nÃo se realizar; sobre os conhecimentos adquiridos nos cursos, raros sÃo os que afirmam utilizarem em seu cotidiano. Conclui-se, portanto, que a oferta dos cursos cumpre mais um objetivo ideolÃgico com a funÃÃo de culpar o indivÃduo pela sua situaÃÃo econÃmica do que uma formaÃÃo integral de ser humano, tendo o trabalho como princÃpio educativo.
7

Analysis and Experimental Comparison of Models of a New Form of Continuously Variable Transmission

Cyders, Timothy J. January 2012 (has links)
No description available.
8

Design of a High Speed Clutch with Mechanical Pulse-Width Control

Cusack, Jessy L 06 March 2013 (has links)
Kinetic energy storage via flywheels is an emerging avenue for hybrid vehicle research, offering both high energy and power density compared to more established electric and hydraulic alternatives. However, connecting the high speed flywheel to the relatively low speed drivetrain of the vehicle is a persistent challenge, requiring a transmission with high variability and efficiency. A proposed solution drawing inspiration from the electrical domain is the Switch-Mode Continuously Variable Transmission (SM CVT), which uses a high speed clutch to transfer energy to a torsion spring in discrete pulses with a variable duty cycle. The greatest limitation to the performance of this system is the speed and efficiency of commercial clutch technology. It is the goal of this thesis to develop a novel clutch which meets the actuation speed, controllability, and efficiency requirements of the SM CVT, with potential for reapplication in other rotary mechanical systems with switching functionality. The performance demands of the clutch were derived via a theoretical design case based on the performance requirements of a typical passenger vehicle, indicating the need for a sub-millisecond engagement and disengagement cycle. This is not met by any conventional clutch. Several concepts were considered across the fluid, electromagnetic and mechanical energy domains. A final concept was chosen which employs a friction disk style architecture, with normal force produced by compressing springs via an axial cam mounted to the flywheel. To control duty cycle, the cam was designed with a radially varying profile such that increasing radial position results in proportionally increasing ratio of high dwell to low dwell. Three synchronized followers are then translated radially on the cam by a control linkage. Analysis of the follower train dynamics and system stiffness were carried out to inform the design of a scaled benchtop prototype. Experimental testing was carried out to characterize the performance of the prototype. It was found that the intended functionality of the design was achieved, with discrete energy transfer accomplished via pulsing of the clutch. However, maximum efficiency was only 33% and torque capacity was only 65% of the intended 70Nm. Significant opportunity exists for improvement of the clutch performance in future research.
9

Derivation of solution for elliptical elastohydrodynamic contact patches with side-slip and its application to a continuously variable transmission

Schneider, Christopher William 27 February 2012 (has links)
Elastohydrodynamic lubrication (EHL) allows transfer of power and forces in gears and rolling bearings without surface-to-surface contact and is the basis for a continuously variable transmission studied in this report. Previous research constructed models and derived solution methods, but often lacked full explanations of the approach and was usually applied to limited and specific cases. This report precisely develops the numerical solution of EHL contact and includes the more general cases of elliptical contacts and side-slip. The model and numerical method are validated on known benchmark cases and test results. Side-slip is investigated and the results shown in this report. Finally, the model is used to determine the film thickness and pressure of a contact patch under identical conditions to that in a physical drive developed by Fallbrook Technologies in Austin, TX. A minimum film thickness of 0.8978 [mu]m is found, setting a benchmark for the maximum allowable surface roughness values to prevent surface-to-surface contact. Additionally, under normal drive conditions the film thickness to surface roughness ratio is in the range of ideal values for maximum life. / text
10

Development of a Novel Cam-based Infinitely Variable Transmission

Lahr, Derek Frei 28 December 2009 (has links)
An infinitely variable transmission (IVT) is a transmission that can smoothly and continuously vary the speed ratio between an input and output from zero to some other positive or negative ratio; they are a subset of continuously variable transmissions (CVTs), which themselves do not have the ability to produce a zero gear ratio. In this thesis, the operation, analysis, and development of a novel, highly configurable, Cam-based Infinitely Variable Transmission of the ratcheting drive type is presented. There are several categories of CVTs in existence today, including traction, belt, and ratcheting types. Drives of these types, their attributes, and associated design challenges are discussed to frame the development of the Cam-based IVT. The operation of this transmission is kinematically similar to a planetary gearset, and therefore, its operation is described with that in mind including a description of the six major components of the transmission, those being the cam, followers, carriers, planet gears, sun gears, and one way clutches. The kinematic equation describing its motion is derived based on the similarities it shares with a planetary gearset. Additionally, the equations for the cam design are developed here as the operation of the CVT is highly dependent on the shape of the cam. There are six simple inversions of this device and each inversion has special characteristics and limitations, for example, the available gear range. A method was developed to select the most suitable inversion, gearing, and follower velocity for a given application. The contact stress between the rollers and cam is the limiting stress within the transmission. A parametric study is used to quantify the relationship between this stress and the transmission parameters. Based off those results, two optimization strategies and their results are discussed. The first is an iterative brute force type numerical search and the second is a genetic algorithm. The optimization results are shown to be similar and successfully reduced the contact stress by 40%. To further improve the transmission performance, several mechanisms were developed for this unique transmission. These include a compact and lightweight differential mechanism based on a cord and pulley system to reduce the contact force on the rollers. In addition, a unique external/inverted cam topology was developed to improve the contact geometry between the rollers and said cam. A prototype was built based on both the optimization strategies and these mechanisms and is described within. Finally, a Prony brake dynamometer with cradled motor was constructed to test the transmission; the results of those tests show the Cam-based IVT to be 93% efficient at low input torque levels. / Master of Science

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