Continuously Variable Transmission Efficiency Research Articles

A Development of Tractor's Continuously Variable Transmission Based on Combined Planetary Gear Train (2nd Report, Design and Manufacture of Prototype Transmission and Experiments)

A new type of a tractor's continuously variable transmission (CVT), which consists of a 2 K-H type differential gear and a hydrostatic power transmission (HST) is devised. The hydrostatic power transmission (HST) consisted of a hydraulic pump and motor, which is a kind of CVT, has been applied to the smaller horsepower range of the tractor recently. One of concerns of the current HST system is lower efficiency on the power transmission. Then, further improvement for efficiency of the transmission is required more recently. The purpose of this development is to devise an adequate CVT providing with higher efficiency of the transmission in comparison with the current HST systems. Theoretical velocity ratio and efficiency of the CVT are investigated. And a prototype CVT is manufactured and incorporated into the tractor. The experimental results show that the efficiency of prototype CVT is several percent lower than theoretical value, but very nearly value. Then, the high efficient transmission for the tractor is offered. And the design method for the tractor's CVT that has high efficiency is built up.

Fatigue Life and Traction Modeling of Continuously Variable Transmissions

A model was developed to study the elastohydrodynamics and contact mechanics of toroidal Continuously Variable Transmission (CVT) type contacts. The aim is to predict the fatigue life, traction and efficiency of such contacts with the intention of making optimizations based on design criteria and constraints. A generalized Reynolds equation was developed for isothermal, transient lubrication of elliptical rough contacts with mixed rolling, two-dimensional sliding, and spinning conditions, incorporating any non-Newtonian model, roughness asperity isothermal elastoplastic interactions, and a three-dimensional subsurface stress analysis. The output is in the form of film thickness and traction maps, including contact efficiency, three-dimensional stress fields, and, finally, the predicted fatigue lives of CVT contacts, based on the Ioannides-Harris life model. A parametric study reveals the effect of surface roughness, lubricant bulk temperature, contact ellipticity ratio, slide-roll ratio, and contact load on the fatigue life, traction and contact efficiency of CVTs, and allows for design optimizations based on a compromise between life, traction and efficiency.

An experimental study on transmission efficiency of a rubber V-belt CVT

This paper presents an experimental investigation on the speed and torque loss components of the power loss of a rubber V-belt continuously variable transmission (CVT) as operating conditions (parameters) change. These conditions include the speed ratio, belt tension, rotational speed, external load, diameters of the pulley, etc. A dynamometer is constructed to measure the speeds and torques of the driving and driven pulleys so as to identify the losses and efficiency of the experimental CVT. The power loss of the CVT is investigated not only at constant running speeds but during acceleration when the speed ratio changed continuously. An uncertainty analysis is then performed for the estimation of the accuracy of experimental data. In addition, the repeatability of the experiment was studied to guarantee that reliable results were obtained. Experimental results demonstrated that the power loss as well as transmission efficiency of the CVT differed from those of the V-belt drives.

Development of Transmission by 3K-Type CVT. 2nd Report. Effect of Loading Cam on Efficiency.

A 3K-type planetary gears CVT (Continuously Variable Transmission) can be manufactured, which provides from zero to a high-speed ratio and output shaft characteristics with constant power. However, it is said that this type of mechanism is not as efficient as other types of transmissions. This report proposes that the mounting position of the loading cam affects the efficiency of this CVT. Three examples of position; of loading cams were supposed, and their efficiencies were numerically and experimentally obtained. The results of both experiments and equations were compared. From this comparison, it was found that the most appropriate position of the loading cam is between the track disk and the casing.