Nauka i Obrazovanie (Jan 2015)
Analyzing the Wheeled Vehicle Gearbox Structures for Running in Harsh Conditions
Abstract
In domestic automotive industry the need for transition from transmission with manual control to automatic gearboxes (GB) emerged long ago. Regarding the leading foreign manufacturers (Allison, ZF, Eaton, etc.), an experience in design of automatic transmissions and the level of technological development is incomparably small. Thus, to have an informed choice of the gearbox structure types and control system is a relevant problem. Application efficiency of this or other gearbox depends both on its adaptability to the actual operating conditions and on the quality of transition refinement. This paper analyzes the special features of the gear change process in the most common types of automatic gearboxes. Constructive feasibilities of an "ideal" gear change (without power loss) and strategies for gear shifting are compared. The paper offers an overview of common problems when achieving these goals and the ways to solve them. An automatic transmission of the particular type used in the wheeled vehicles under off-road conditions determines the probability of maintaining their mobility. This is due to the phenomenon of wheel`s breakdown to slipping caused by sharp increase of torque on the wheel. Planetary hydromechanical transmissions (AT) provide continuous input torque to the wheels, but they are expensive and difficult to manufacture and use. Besides, to provide a high number of density ratios in them is more complicated than in the automated and manual transmissions (AMT). This is important when moving long in the lower gears under difficult conditions. Compared with AT dual clutch transmissions due to design features require even more precise and fast control system of actuators and engine. Automation of constant-mesh or synchromesh transmissions provides a significant reduction in the duration of interruption in torque delivery. If it is not enough to increase mobility in the harsh conditions, a rational choice is to use a transmission type of TCCT (torque converter – clutch – (constant-mesh or synchromesh) transmission). Adding the torque converter to AMT increases the durability of clutch and synchronizers. It reduces the amount of gear changes and duration of interruption in torque delivery. Thus, the cost and repair complexity of such a transmission is much lower than those of AT. For almost 15 years there were no domestic scientific publications about economically perspective TCCT transmission. The fully automatic TCCT has been never investigated in domestic science.
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