CVT Efficiency Research Articles

The analysis of an influence of rubber V-belt physical properties on CVT efficiency

This work deals with the analysis of the CVT efficiency for three different rubber V-belts. The bench tests have been conducted on the complete light two-wheeled vehicle drive system so the experiments refer to real exploitation conditions. The research has been performed for fixed gear ratios. The overall efficiency and belt slip have been specified. The longitudinal belt velocity has been measured by the contactless measurement head. The basic belts physical properties have been estimated and significant dissimilarities of their construction details, used materials and stiffness parameters have been revealed. The explicit differences of overall efficiency and belt slip have been observed between tested belts. The V-belt features limiting specified type of losses contributes to increasing other losses at the same time. Furthermore the gear ratio essential influence on the belt slip has been noticeable. The amount of slip value indicates that this is significant part of the total power losses as it has been described by Bertini. However it clashes with the Chen research, where the slip corresponds with the marginal part of the overall losses.

Optimization of CVT Efficiency Based on Clamping Force Control

In order to improve the transmission efficiency of CVT under various driving conditions, this paper proposes an integrated control strategy for optimization of clamping force in pulley. The strategy is based on driving conditions identification and slip trend observer. A Simulink-AMESim co-simulation model is established. Simulation conditions include the acceleration conditions, uphill road conditions, and urban + suburban circle conditions, simulation results show that the new strategy can optimize the transmission efficiency of CVT and therefore increase the fuel efficiency of the vehicle.

Reverse Optimization Algorithm of CVT‘s Energy Economy

Taking CVT plug-in hybrid electric vehicle as the study subject, the objective function of the energy economy is created. In view of engine, motor efficiency and CVT efficiency coupled relationship; proposed reverse optimization algorithm to solve function. The target speed ratio of optimal energy economy is obtained in different SOC (State Of Charge), velocity, acceleration and slope.

Research on the Regenerative Braking Control Strategy Considering Battery/Motor/CVT Joint High Efficiency for CVT Hybrid Electric Vehicle

The traditional regenerative braking control strategies for hybrid electric vehicle just only considers to ensure motor to work along with the battery/motor joint optimal efficiency curve, but not consider CVT efficiency, yet in fact that the CVT efficiency varies with the operating condition between 70% and 95% variation and can not be neglected. Based on the analysis of the relationship among the synthesis efficiency and the efficiency of the NiMH battery, ISG motor and CVT, the battery/motor/CVT joint high efficiency are calculated, then the joint high efficiency optimum working curve is drawn, finally the regenerative braking control strategy adopted with the joint high efficiency optimum working curve is proposed. Compared to the offline simulation and HIL test results adopted with the battery/motor joint high efficiency optimum working curve, the motor average generating efficiency increases by 2.23%, braking energy recovery rate increases by 4.09% through offline simulation, and the average generating efficiency increases by 1.13% through HILS test. Both results show that the proposed regenerative braking control strategy can realize the battery, motor and CVT to work with joint high efficiency which fatherly enhances braking energy recovery rate under guaranteeing entire vehicle braking security condition.

Optimization Study of CVT Speed Ratio to Plug-In Hybrid Electric Vehicle

Taking CVT plug-in hybrid electric vehicle as the study subject, the objective function of the energy economy is created. In view of engine, motor efficiency and CVT efficiency coupled relationship; proposed reverse optimization algorithm to solve function. The target speed ratio of optimal energy economy is obtained in different SOC (State Of Charge), velocity, acceleration and slope. On the Matlab/Simulink platform, the system simulation model is built and simulated. The results shows that the target speed ration optimized control law in the case of no additional hardware cost , energy economy save about respectively 3.6% ,4.6%,6.7% in driving cycles of the NEDC,UDDS,HWFET before optimization.

Experimental investigation on the efficiency of the pulley-drive CVT

Because of their outstanding advantages over other transmissions, rubber V-belt pulley drive CVTs have been extensively used in low-power vehicles, such as scooters and snowmobiles. A rubber V-belt CVT installed on a snowmobile is used here to research transmission efficiency. The power loss of CVTs, including torque loss and speed loss, is studied based on an analysis of the transmission mechanism of CVTs. Experiments on CVT efficiency are conducted on a specific CVT test bench, on which the values of torque, speed, and displacement, etc., are measured. Results show that the variation trend of the efficiency is close to the operating conditions of CVTs and optimal structural parameters are given that can serve as a beneficial references for designing and tuning CVTs.

Research of CVT efficiency:-Comparison of a Toroidal CVT and a Belt CVT-

Research of CVT efficiency:-Comparison of a Toroidal CVT and a Belt CVT-

CVT dynamics: Theory and experiments

Abstract We present a detailed experimental study of the pushing V-belt CVT dynamics and compare the experimental data with the theoretical predictions of the Carbone, Mangialardi, Mantriota (CMM) model [G. Carbone, L. Mangialardi, G. Mantriota, The influence of pulley deformations on the shifting mechanisms of MVB-CVT, ASME Journal of Mechanical Design 127 (2005) 103–113]. A very good agreement between theory and experiments is found. In particular it is shown that, during creep-mode (slow) shifting, the rate of change of the speed ratio is a linear function of the logarithm of the ratio between the axial clamping forces acting on the two movable pulleys. The shifting speed is also shown to be proportional to the angular velocity of the primary pulley, and to increase as the clamping force on the secondary pulley is increased. Indeed, a growth of the clamping force increases the pulley bending and, therefore, in agreement with the CMM model, increases the shifting speed. The authors also propose a relatively simple differential equation to describe the creep-mode evolution of the variator. Few parameters appear in the formula, which may be calculated either experimentally or theoretically. The results of this study are of utmost importance for the design of advanced CVT control systems and the improvement of the CVT efficiency, cars’ drivability and fuel economy.

Study On Power Transmitting Efficiency Of CVT Using A Dry Hybrid V-belt

This paper presents the net power transmitting efficiency of CVT using a newly developed dry hybrid V-belt. The efficiency was measured by using a devised testing machine, which eliminates other power losses due to periphemls such as shafl flanges. Torques on both pulkys were measured with high accuracy by using strain gauges which were glued on the cantilever shafts. The CVT efficiency is divided into three regions with respeet to applied torque. At a low range of applied torque: region I, the efficien~ of CVT increases shmply with respeet to the applied torque, beeause the bending loss is almost constant for applied torque but the torque increases the total transmitting power. At region II (a middle range of applied torque), the efficiency is also constant with respect to transmitting torque since the relative energy loss due to belt bending decreases while the energy loss due to elastic slip increases with increasing the transmitting torque. They are equivalent with each other at this region, The efficiency sharply decreases at region III due to the remarkably increasing of the slip. The tmnsmitting efficiency increases with the low contraction force. The CVT shows the high transmitig ellkieney at the speed ratio 1.0. The transmitting efficiency decreases when the CVT system has the misalignrnenq because the sharing deformation of the belt strand influences the transmitting efficiency as well as the bending deformation. The appropriate initial setting misalignment exists to reduce the influence of the misalignment. It is found that the relationship between the traction coefficient and the transmitting efficiency is independent on the contraction force, speed ratio and the misalignment. The tmction coefficient could be a nondimensional applied torque for characterizing the efficiency of the dry hybrid V-belt type CVT.

Evaluation of split-path extended range continuously-variable transmissions for automotive applications

One potentially important application of continuously-variable transmissions (CVT's) is the improvement in fuel economy of internal combustion engine vehicles. However, many otherwise attractive CVT designs have a ratio coverage less than ideal for such applications. Split-path configurations can be used to extend the ratio coverage, providing even a geared neutral and reverse capability with some combinations of parameters. The increased coverage is in general achieved, however, only at the expense of lower overall CVT efficiency and a larger required variable unit capacity. All possible single-regime designs which use a single differential to extend the ratio coverage of the basic variable unit are considered, as well as two 2- regime designs. Data for the CVT efficiency characteristics are developed for both otherwise conventional vehicles and those utilizing an energy-storage flywheel, with steady speeds and three driving cycles used for the evaluation. It is found that the efficiency penalty for extending the ratio coverage can be quite severe for some combinations of system parameters and operating conditions, so that a complete analysis of this aspect is important when considering the concept for any specific application.