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Hydraulic fluid (HF) specifications for mobile construction equipment called JCMAS HK and HKB have been established by the Fuels and Lubricants Committee of Japan Construction Mechanization Association (JCMA). The specifications are designated by two viscosity categories of single grade and multigrade. Each category has ISO viscosity grade (VG) 32 and 46. The JCMAS HK oils are recommended for use in hydraulic systems designed at pressure up to 34.3MPa(5000psi) and to heat hydraulic fluid up to 100 °C. These oils also provide wear control, friction performance, oxidation and rust protection, seal swell control and filterability performance. Two piston pump test procedures were developed to evaluate lubricating performance of these oils under high pressure conditions. The JACMAS HKB oils are classified as environmentally friendly oils due to the additional requirement for biodegradability.

We have found that most commercially available biodegradable hydraulic oils show low static friction coefficients not depending on the kinds of wet friction materials. Since hydraulic motors of a hydraulic excavator contain wet parking brakes, the most commercially available biodegradable hydraulic oils can not provide enough brake torque capacity to park safely. Furthermore, all kinds of commercially available biodegradable hydraulic oils do not have adequate oil performance for a hydraulic system of construction eq ipment. Thus we have developed a n high performance biodegradable hydraulic oil. To obtain a high static friction coefficient and compatibility with elastomers, a new synthetic ester base fluid has been developed. To improve oxidation stability and to attain compatibility with mineral oil based hydraulic oils,. an additive formulation has also been developed.

Torqflow transmission, which is composed of planetary gear mechanism, multiple disk clutches and a hydraulic control unit, has been adapted for Construction Machine because it allows an easy selection of speeds (forward or reverse). Recently a rubber facing material with high coefficient friction has been used disk clutch's facing parts for compact design. Meanwhile, it's heat conduction is inferior to metalic disk to be usually used, so at engage time temperature of rubber facing disk is higher than metalic and it's ablasive wear ratio, which is verified to have influence on facing temperature by experiments, is increased far more than before. Therefore prediction of facing temperature has been more important than before. Now, in this report, study on transient thermal analysis is introduced because it's accuracy has come to practical level.

The four models of the new PC-Series hydraulic excavators, the PC200-3, PC220-3, PC300-3, and PC400-3, ranging from 18-ton to 40-ton capacity, were brought to the market in 1984, and they have been highly appreciated by the customers for their stability and performance. During the developing stage of these new models, we thoroughly researched and analyzed how hydraulic excavators had been used under various working conditions in order to grasp the qualities which the customer's demand. To realize those qualities, we effectively used mechatronic technology in addition to our unique technologies. The results of the above are the electronic OLSS equipped with a mode changeover mechanism, an automatic decelerating system, a new hydraulic system, etc., which lower fuel consumption, increase workability, lower noise, and improve driveability. In addition, the appearance of each model is improved, and many features including the new monitoring system have been installed.