Abstract
Double-flow hydrovolumetric mechanical transmissions is an advanced technical solution that aims to increase productivity, improve efficiency and convenience of control over wheeled and tracked tractors. Their arrangement renders considerable potential for their modernization and makes it possible to introduce recuperation systems that would enhance their performance efficiency coefficient to the level of mechanical transmissions. Innovativeness of these transmissions and the lack of a sufficient number of prototypes largely hinder their implementation in production. A large number of possible HT circuits necessitates the creation of an original bench-prototype for each of them. In order to solve this task, we proposed in this paper a kinematic circuit of the universal testing laboratory bench for HT of the tracked tractor. Its design makes it possible to study HT circuits of the type with a differential «at the output», the type with a differential «at the input» for both wheeled and tracked vehicles, and to simulate the process of work of a hydrovolumetric turning mechanism. Introduction of electric generators to the design makes it possible to estimate in practice the effectiveness of recuperation of kinetic energy at braking, as well as parasite power that circulates in the closed circuit of HT during acceleration and braking. We give quasi-static characteristics of basic HT circuits that are simulated at the laboratory bench. The results were obtained based on an improved mathematical model that makes it possible to determine the volumetric, mechanical, and full performance efficiency coefficient of separate hydraulic machines in the direct and reverse flows of power and special working regions of hydraulic gear. For the transmissions with a differential «at the output», maximal performance efficiency coefficient reaches 83 %, indicating the proper selection of gear ratios and standard size of hydraulic machines. The results obtained are of interest for industrial and design organizations, specializing in the development of transmissions for transportation vehicles. Employing the developed bench would significantly reduce the time between designing and industrial implementation. There is a possibility to confirm experimentally the efficiency and high technical-economic indicators of the proposed transmission. Such a bench will make it possible for scientific institutions to discover new phenomena and processes in HT, systematize the influence of gear ratios of reducers, planetary mechanisms, and their number, on the working processes in HT.
Highlights
It is impossible to fully utilize the potential of modern energy-intensive tractor without a highly efficient transmission, which would make it possible to perform tillage opera tions at the required agrotechnical speed and would at the same time allow the tractor to move along general-purpose motor roads
All these properties are demonstrated by doubleflow hydromechanical transmissions (HT)
A key requirement to them is a maximally possible performance efficiency coefficient, which can be achieved by aligning the ratios of toothed gears and planetary mechanisms that make up its structure, as well as the correct choice of standard size for volumetric hydraulic machines
Summary
It is impossible to fully utilize the potential of modern energy-intensive tractor without a highly efficient transmission, which would make it possible to perform tillage opera tions at the required agrotechnical speed and would at the same time allow the tractor to move along general-purpose motor roads. The main advantage of transmissions of HT type with a differential «at the input» [2] is the ability to implement the so-called fast-reverse – switching from forward to backward course with no participation of additional levers and pedals, but only by controlling a parameter e of the hydromechanical transmission (HT) Their performance efficiency coefficient is approximately 3–5 % lower than that in the schemes of the first type. A key requirement to them is a maximally possible performance efficiency coefficient, which can be achieved by aligning the ratios of toothed gears and planetary mechanisms that make up its structure, as well as the correct choice of standard size for volumetric hydraulic machines
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