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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.

KOMATSU has successfully developed and marketed the HYPER GX series computer-controlled, intelligent hydraulic excavators. The development concepts of the HYPER GX series are as follows: 1. To improve safety at construction sites by use of measuring functions which reduce the number of ancillary workers. 2. To improve working environment and the quality of work by use of automatic functions which reduce operator fatigue and time required to complete a job. 3. To solve the problem of shortage of experienced workers by the use of operator support functions which allow easy operation even for inexperienced or older operators. Representative of these is the fully automatic grading function, with which the movement of boom, arm and bucket is computer-controlled to enable automatic excavation at a predetermined gradient.

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.

Operations involving excavation of bedrock in large-scale civil engineering projects, or quarrying works for limestone or crushed rock can be broadly divided into two methods: blasting, and excavation using mechanical power. Ripping operation using bulldozers is typical example of the second method, and this method is superior because it is safe and does not cause pollutions. For this reason, its applicable range is being expanded including areas where the blasting method was being used. However, ripping operation using bulldozers demands a high level of training from the operator, and in addition to this, shoe slippage causes premature wear of the undercarriage and low fuel economy. The shoe slip control system that we have developed carries out sensing of the acceleration of the machine in forward and reverse directions, and sensing of the input / output speed of the torque converter, and in this way it always knows the traction and the slip ratio of the machine.

The paper provides mechanical and performance specifications for a giant 650 PS bulldozer and cites the outstanding features of this machine. The new bulldozer offers improvements in dozing, ripping, and pushing. It has an electropneumatic system employing solenoid valves and air cylinders, and it can be controlled by radio for unmanned operation in dangerous sites.

Closed-Center-type Load Sensing Systems for fluid power controls in hydraulic excavators, which had been considered as far back as 1955, were proposed in the U.S.A. in 1975, but were not feasible. In the late of 1980's European-made hydraulic excavators were equipped with load sensing systems, including flow dividing control. In the early 1990's, further improvement of CLSS's were made in Japan. CLSS's are capable of controlling complex motions of multiple actuators with high accuracy against varying loads under varying engine speed conditions, with expectations for improved controllability and compatibility of hydraulic excavators to many kinds of works in which attachments are used. Conversely, operators have made the best use of the characteristics of conventional fluid power systems, in which each actuator speed is varied by inertia or engine speed change.

After new transmission lubricants are developed there is an extensive validation program where friction durability testing is performed on multiple clutch materials. Each durability test can run for long terms and the entire validation program can take much longer terms. A well designed lubricant and friction material will deliver the necessary friction control for construction equipment to operate at optimum level. A mechanistic construct has been evaluated to calculate friction durability in clutch systems based on fluid and surface tribological properties. Fluid properties include both boundary frictional and rheological effects. Surface properties include elastic modulus, surface roughness, asperity density and asperity tip radius. Using this mechanistic construct friction durability has been predicted.