Ball toroidal CVT: a feasibility study based on topology, kinematics, statics and lubrication

Belfiore, Nicola Pio; Stefani, Giulia

doi:10.1504/ijvd.2003.003558

Cited by 14 publications

(9 citation statements)

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“…• the origin O c is the geometrical center of the socket, • the x-axis is parallel to the resultant force F applied to the ball, • the y-axis is parallel to the ball angular velocity, • the z-axis is parallel to the straight line which passes through the contact points (ball-toroidal cone and ball-central sphere), • ϕ and ϑ are the reference angles with respect to x-and z-axes, respectively, as depicted in Figure 5 Under the above listed assumptions and in the hypothesis of laminar flow, the Reynolds equation can be written in spherical coordinates as (1) where µ is the constant viscosity, p is the pressure, and U -= {0, U ϑ , U ϕ } is the local relative velocity vector (see also Figure 5). The relative velocity components along ϑ and ϕ are given by (2) (3) and the film thickness by (4) Substituting (2), (3), and (4) into (1), the equation (5) can be obtained, since, under the assumed hypotheses, δh/δt = 0 and ω x = ν z = 0.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…T he project of building a test bench dedicated to a lubricated spherical bearing began with a feasibility study on a novel friction-driven continuous variable transmission (CVT). 1 This system, called the ball toroidal CVT (BTCVT), is composed of two toroidal cones, one for the input and one for the output motions, together with a certain number of rollers, as depicted in Figures 1 and 2. Each roller is composed of two balls and one central sphere, arranged in such a way that power can flow from the input toroidal cone, all the way through the ball-sphere-ball systems, to the output cone, provided that there is enough friction to make spheres adhere during pure rolling.…”

Section: Introductionmentioning

confidence: 99%

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On a test bench for studying lubrication in a spherical bearing: simulations and experimental validation

et al. 2006

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In this paper a test bench dedicated to the analysis of a lubricated spherical pair is presented. The experimental set-up has been used to validate a numerical code that has been developed by the authors in order to simulate a complex lubricated spherical pair that affects the reliability of a novel continuous variable transmission (CVT). The test bench is modular and can be adapted to other lubricated pairs, either cylindrical or spherical. The stand is equipped with an I/O control card and allows the on-line acquisition of some important parameters. As for the numerical code, the finite-difference method has been used to solve the indirect problem in the lubricated spherical pad, under the condition of hydrodynamic regime, with externally pressurized inlets. Two simulators are needed since the physical properties of the test bench and the real system are different. The one that simulates the behavior of the spherical pair in the test stand has been used to ascertain the numeric approach prediction capability. Indeed, the experimental tests gave results which are in very good correspondence with the numerical predictions. Hence, the second simulator, which has been tailored on the particular spherical pair the CVT is equipped with, gained reliability in predicting the behavior of the real system under different load and speed conditions. These predictions have been useful in achieving new insights into the novel CVT, which, under this new light, has been criticized by making the point that its range of application in automotive is, at the actual state of the art, rather limited, in spite of a high intrinsic complexity.1 2 3 4 5 6 7 8 8 5 6 7 9 911. This makes the BTCVT very appealing for automotive applications, since the engine could work within optimized regions of the state variables, with great benefit for the efficiency.Unfortunately, the torques required in automotive applications are quite high and, therefore, a great normal force between rolling elements is expected to avoid sliding. On the other hand, the whole system must work in an oil bath, which makes it difficult to achieve a good traction effect between rolling elements. This problem is crucial for the effectiveness of the whole class of traction-driven CVTs and it has been partially solved only after the introduction of the so-called traction oils, which allow, under certain conditions, traction coefficients of up to 0.16 to be achieved. 2 By imposing the force balance on each ball, qualitatively represented in Figure 3, it can be shown 1 that each spherical socket must exert a great force on the corresponding ball, otherwise direct contacts will occur between balls and sockets. Hence, the whole functionality of the BTCVT relies on the effectiveness of these spherical pairs.On the other hand, the relative motion of the ball with respect to the socket has a spherical nature, which makes the adoption of rolling bearings very impractical. As a consequence, the only reasonable solution is a lubricated spherical pair and the real problem is so represe...

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Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On a test bench for studying lubrication in a spherical bearing: simulations and experimental validation

et al. 2006

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“…Both experimental and theoretical works have been dedicated to a huge amount of applications. In order to name a few of them, and only those which the authors have been involved into, it is worth noticing how the variety of the applications has been extended to very different fields, such as special transmissions (Belfiore and De Stefani, 2003; Belfiore et al, 2006a), gears (Belfiore, 2004; Belfiore et al, 2006b), metal forming (Belfiore et al, 2007), cold rolling (Bolt et al, 2010), and microsystems (Belfiore et al, 2014). However, more recently, the applications where an electric current is induced to flow through a pair of tribo-elements have received a certain attention in literature.…”

Section: Introductionmentioning

confidence: 99%

An accelerated test stand to assess wear in offshore wind turbines rolling bearings

et al. 2018

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Rolling bearings are universally adopted to serve as revolute joints in almost all mechanisms or machines, because they offer a convenient solution to the problem of minimizing friction and, simultaneously, providing a large load-carrying capacity at any kinematic regime, including slow or alternate rotations. However, in offshore wind turbines not only they reach large dimensions but also they move within strong electromagnetic fields created by the turbine generators. For example, considering the last amplification stadium epicyclic gearbox, they may serve to sustain elements rotating around floating shafts (planetary) which also move around a fixed principal shaft (solar). This article illustrates an original experimental test bench that simulates sliding and rolling contacts through which a test current is flowing. Unexpected and interesting results disclose how this particular field is challenging and how more investigations are still required to achieve an adequate and complete interpretation. The understanding of this phenomenon could give rise to modification to the composition and the microstructure of rollers and rings employed in offshore wind turbines.

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“…Authors in [13] propose a new mechanical press concept that equipped with a CVT to obtain more speed variability than the classical ones. There are different types of CVT systems: Toroidal [14][15], belt/chain [16,17] as shown in Figure 1, ball [18] and spherical [19]. In this paper, we focus on Gear Chain Industrial (GCI) chain CVT, which has become more common because of its low manufacturing costs and the possibility to be applied for extremely high torque applications.…”

Section: Introductionmentioning

confidence: 99%

An experimental study on the shifting dynamics of the chain CVT

Yıldız¹,

Bottiglione²,

Carbone³

2015

Third International Conference on Advances in Mechanical and Robotics Engineering- AMRE 2015

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This paper is concerned with an experimental analysis of the shifting dynamic behavior of a chain continuously variable transmission (CVT) system. Firstly, the steady-state experiments are carried out for different speed ratio. After that, the transient responses of the CVT, the main interest of this paper, are analyzed in different conditions. The tests are performed for different step changes of the ratio of the drive and driven clamping forces and for different angular velocities of drive side. The results demonstrate that the speed ratio reaches high value for high steps; however this relation is nonlinear. Moreover, it is realized that the characteristic shifting response time of speed ratio decreases as the angular velocity of drive pulley increases until a limiting value is reached.

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Ball toroidal CVT: a feasibility study based on topology, kinematics, statics and lubrication

Cited by 14 publications

References 0 publications

On a test bench for studying lubrication in a spherical bearing: simulations and experimental validation

On a test bench for studying lubrication in a spherical bearing: simulations and experimental validation

An accelerated test stand to assess wear in offshore wind turbines rolling bearings

An experimental study on the shifting dynamics of the chain CVT

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