Challenges to apply to ATV the high performance automatic transmission that withstands sever working condition

The ATV (all terrain vehicle) is used under vary adverse conditions such as in extremely cold areas below -30?, extremely hot desert, or even in swamps, and its transmission requires very high durability and reliability. Furthermore, to allow operation by persons of various skill levels, simplification of operation such as use of an automatic system was called for. Honda challenged development of a compact HMT reliable enough to withstand the adverse environment while permitting use of engine brake for operations on various types of a terrain.
ATV used in a wide variety of environment
The conditions under which the ATV is used are harder than one can imagine. For example, the reliability of ATV sometimes makes a live-or-die difference in the extreme coldness of Alaska. Sometimes, the ATV has to be sturdy for towing a heavy object. Operations in sizzling desert or in water such as in a swamp have to be considered “normal” for an ATV. Effective engine braking is essential when coasting down a steep slope. Not only for utility purposes, Honda was trying to develop an ATV suitable for recreational uses such as hunting, touring, etc. Thus developed is the electronically controlled HMT system that fills such requirements for a high performance automatic transmission as the mount-ability in the engine, in addition to durability and reliability.

ATV (all terrain vehicle)
The ATV is a vehicle exclusively for off-road use, and standardized by ANSI, which is a federal standard of USA. [Vehicle width: 1,270mm or less, one-person seating, handlebar-type steering, 4 low pressure tires, sit-astride type seat, off highway]
Honda Four Trax Foreman Rubicon
[Water-cooled, 4-stroke, displacement: 499cc, horsepower: 19.9KW/6500rmp, torque: 37.8Nm/5000rmp, Hondamatic working pressure: 35.6MPa (max 60MPa)]
The HMT (hydraulic mechanical transmission) that ATV requires
In the development of HMT for an ATV, Honda aimed to attain a level of reliability and performance unattainable from a belt-pulley-type automatic transmission. Firstly, the transmission has to be as durable and reliable as the engine unit. Secondly, the same level of engine brake as a gear transmission has to be maintained. Additionally, the system has to allow smooth running while providing the rider with a directly-linked feeling, and the noises and vibrations that reduce comfort have to be minimized. The noises and vibrations from the hydraulic system and the transmission efficiency are the influential factors of the aforementioned requirements. Lastly, the unit has to be of a weight and size that permits mounting on an ATV. The key to realization of such a system was how much higher the working pressure could be increased.


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