Design Principles of a Four Bar Crank Continuously Variable Transmission

2008 ◽  
Author(s):  
W. Allan Yates
Keyword(s):  
Design Principles ◽  
Angular Speed ◽  
Continuously Variable Transmission ◽  
Drive Shaft ◽  
The Other ◽  
Energy Utilization ◽  
Link Length ◽  
Peak Efficiency ◽  
Vector Solution ◽  
Variable Transmission

Continuously Variable Transmissions (CVTs) can be used to optimize the energy utilization of systems by allowing the prime mover to operate at speeds of peak efficiency while allowing the driven components to move at desired speeds. A CVT saves energy by reducing the off-peak efficiency of a system. The basic design principles of a Continuously Variable Transmission composed of a sequence of 4-bar cranks are discussed. The vector solution for 4-bar cranks is iteratively solved for a crank sequence to illustrate how different output speeds can be obtained from the same input speed. This is accomplished by varying the length of the connecting link on each 4-bar crank in the sequence. Solutions are plotted. Each 4-bar crank is located on the same drive shaft and the same driven shaft. Each crank has the same drive link length and the same driven crank length. A one way clutch located on each driven link transmits motion to the driven shaft. The cranks are positioned so that they are out of phase with each other so that only the fastest crank transmits motion, over-running all the other cranks. For a given length of the connecting link, the motion of the driven shaft is not uniform. This is due to the 4-bar crank transmission of peak speed. As one 4-bar crank moves, at some point the angular speed of the driven link will overtake the speed of the driven link on the other crank sets. It will then peak and then slow to be overtaken by another crank-set. The more evenly distributed crank-sets used the more uniform the motion will be. In this sense, a given length of connecting link for the sequence of cranks will generate an average drive shaft speed. If the length of the connecting link in a 4-bar crank is changed, a change in motion of the driven shaft will occur. By changing the length of the connecting link on the 4-bar cranks, the average speed of the driven shaft can be changed. A CVT is made by infinitesimally changing the length of the connecting link. This infinitesimal change is easily accomplished via standard components such as pneumatic or hydraulic cylinders or various other means.

scholarly journals Design Principles and Traction Performance of a Novel Zero-spin Rolling Conical Traction Continuously Variable Transmission

2020 ◽  
Author(s):  
Chao Li ◽  
Xiuquan Cao ◽  
Qing-tao Li
Keyword(s):  
Numerical Model ◽  
Computational Models ◽  
Design Principles ◽  
Transmission Efficiency ◽  
Continuously Variable Transmission ◽  
Transmission Ratio ◽  
Variable Transmission ◽  
Contact Models ◽  
Spin Momentum

Abstract In the existing traction continuously variable transmission (CVT), half toroidal CVT (HT-CVT) is considered to have a better traction performance. However, the HT-CVT has the spin losses due to its structural limitations, which significantly influences the traction efficiency. In this paper, the kinematic qualities and contact models of a novel zero-spin rolling conical CVT (RC-CVT) are studied, and then the rollers and conical disks are compactly designed through the proposed design principles. Subsequently, the transmission efficiency is investigated by using a detailed numerical model and compared with HT-CVT. Based on these computational models and parameters, the practical spin ratio, spin momentum and traction efficiency of RC-CVT are calculated and compared with HT-CVT. The results show that the practical spin ratio and spin momentum of RC-CVT are much smaller than that of HT-CVT, and the efficiency on fixed transmission ratio is consequently higher than that of HT-CVT.

FRICTIONAL PROBLEMS IN CONTINUOUSLY VARIABLE TRANSMISSION BELT DRIVES

Tribologia ◽  
2017 ◽  
pp. 93-100 ◽  
Author(s):  
Wojciech SZCZYPIŃSKI-SALA ◽  
Krzysztof DOBAJ ◽  
Adam KOT
Keyword(s):  
High Performance ◽  
Angular Speed ◽  
Continuously Variable Transmission ◽  
Design Parameters ◽  
Belt Drive ◽  
Power Losses ◽  
Belt Drives ◽  
Variable Transmission ◽  
Drive Systems ◽  
The Impact

The article describes the results of the research carried out on the evaluation of the influence of friction pairs (rubber belt – belt pulley in belt drive) on the ability to transmit power. In order to determine the characteristics of the belt drive operation, measurements were made on a real belt drive from the drive train of a light two-wheeled vehicle. The measurement was carried out in conditions of changes in the dynamic load. The measurements of the belt slip on the belt pulley within the whole range of the changes of gear ratios and angular speed of the engine were made. During the tests, belts made from various rubber mixtures were compared. The values of the friction coefficients between the surface of belts and the belt pulley were measured. Model analyses of the impact of belt slip on the wheel related to the temperature of Belt drive elements were also made. Generally, one can ascertain that, in belt drive systems, power losses are a combination of speed losses and torque losses. The increase in the efficiency of belt drives is possible by decreasing power losses. It is possible to obtain the high performance of continuously variable transmission belt drives with a V- belt solely with the proper choice of the design parameters, which is possible only after the exact recognition of the operational characteristics unique to this class of belt drive systems.

scholarly journals Experiment and numerical modeling of asymmetrically initiated hexagonal prism warhead

2017 ◽  
Vol 9 (1) ◽  
pp. 168781401668796 ◽  
Author(s):  
Yuan Li ◽  
Yuquan Wen
Keyword(s):  
Numerical Modeling ◽  
The Other ◽  
Energy Utilization ◽  
Hexagonal Prism ◽  
Cylindrical Structure ◽  
Damage Probability ◽  
Other Hand ◽  
Density Enhancement ◽  
Fragment Distribution ◽  
Velocity Enhancement

Traditional fragmentation warheads are usually initiated on the axis, producing a uniform fragment distribution around the warhead, but only little portion of them can be imposed on the targets. The aimable warhead, on the other hand, using the off-axis initiations or the structure deforming, can improve the warhead energy utilization highly. Seeking methods to both enhance the fragment velocity and density has significant value for improving the target damage probability. In this article, a warhead shaped as hexagonal prism was studied using arena experiment and numerical modeling and compared with the traditional cylindrical structure. The fragment velocities and target hit patterns of the two types of warheads under axial initiation and asymmetrical initiation are obtained. It is revealed that for the hexagonal prism warhead, the asymmetrical initiation can enhance the fragment velocities by 27.71% and enhance fragment density by 34.09% compared to the axial initiation. The fragment velocity enhancement is close to that of the cylindrical warhead, but the fragment density enhancement is far above the cylindrical warhead. This indicates that the asymmetrically initiated hexagonal prism warhead is a very effective aimable warhead.

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