In the field of hydraulic excavator, the purpose of energy-saving control is not only to improve fuel efficiency, but also to achieve a series of effects to reduce the cost of use. According to the data, nearly 40% of engineering machinery failures come from hydraulic systems and about 15% from engines. The energy saving technology, can improve the utilization ratio of engine power, reducing the loss of hydraulic power system, power system and load the required power to better match, reduce the work intensity of the engine and hydraulic components, improve the reliability of the equipment in use.

 

 

From the perspective of development at home and abroad, the energy-saving control of hydraulic excavator has the following development trend:

 

 

1) electro-hydraulic proportional control is intelligent

 

 

Electro-hydraulic ratio control has been applied to engineering machinery since the early 1980s, and has been widely used in hydraulic excavators. Electro-hydraulic proportional technology used in engineering machinery, could save complex, large hydraulic signal transmission line, the electricity signal transmission hydraulic parameters, not only can speed up system response, and make the whole excavator control of power system more convenient and flexible. After entering the 90 s, with the development of computer technology, electro-hydraulic proportional control further "intelligent", electro-hydraulic proportional pump and the application of proportional valve is increasing, thus appeared the "intelligent hydraulic excavator. This kind of intelligence is mainly reflected in the following aspects. First of all, computers can automatic monitoring of hydraulic system and the operation parameters of diesel engine, such as pressure, rotating speed of diesel engine, and can according to these parameters automatic control of the excavator power system running in high efficiency and energy saving. Secondly, the ability to complete some semi-automatic operations, such as leveling and slope repair, will reduce the proficiency of drivers, but the work quality will be greatly improved. Thirdly, fault diagnosis can be made according to the monitored operating parameters, which is convenient for excavator maintenance. These functions have greatly improved the performance of excavators.

 

 

2) electric injection control of diesel engine

 

 

In the traditional diesel engine with mechanical speed regulation, the circulating oil supply and advance Angle of fuel injection pump are all affected by the speed of rotating speed, which makes it difficult to further improve the performance of diesel engine. After application on diesel engine efi control, can make the pump cycle oil and fuel injection advance Angle is no longer affected by rotation speed, thus enables excavator has been working in the best state, and accelerates the speed of response. The development of electric injection controller of diesel engine is an important link to improve the energy saving of excavator.

 

 

3) load sensing control will continue to develop

 

 

Load sensing control began to rise in the 1970s, and various manufacturers of hydraulic parts of engineering machinery have launched a series of related products. The system is energy-efficient and maneuverable, and even unskilled drivers can adapt quickly. Proportional distributing valve is further promoted the load sensing technology in the application of excavator, excavator maneuverability to improve, solve the western countries due to the lack of skilled driver. Therefore, the demand of load sensing control excavators in developed countries will increase further.

 

 

4) six-way multi-way valve continues to exist

 

 

Although the four-way valve load sensing system can provide accurate operation, but not all situations requires accurate operation, load sensing system and skilled drivers can also use the excavator to complete accurate operation. More importantly, the high price of load sensing systems limits its use in developing countries. At present, many of the world famous excavator manufacturers, their products both use four-way valve load sensing control excavator, have used six valve hydraulic system such as flow of positive and negative flow control excavator. Sophisticated manufacturing techniques and low prices will allow the six-way valve to continue to function.

 

 

5) further improve the valve control energy-saving control

 

 

In the hydraulic system with six-way multi-way valves, there are still many improvements, such as maneuverability and energy saving, etc., which are still being studied by foreign excavator manufacturers.

 

 

6) multi-function combination

 

 

In order to improve the performance of excavators, the combination of various energy-saving measures will be more extensive. In the previous system, the hydraulic pump has been integrated with a variety of functions, but due to the restrictions of various conditions, generally no more than three. As shown in figure 14 of the hydraulic pump, integrated pressure cut off, is flow control and function of power limitation, relatively popular in the market at present all kinds of hydraulic pump principle diagram, also has a variety of functions are integrated. With the development of hydraulic technology, it is possible to integrate more functions on the pump.

 

 

7) variable parameter control

 

 

For excavator to better adapt to the working conditions of load requirements, the dynamic system of some internal control components will no longer be a fixed value set parameters, but can be changed by excavator specific working conditions. For example, in the production of the EX series Hitachi construction machine excavator, load sensing valve set pressure compensator differential pressure can change according to the working condition, enhanced the adaptability of excavator is working. It can be predicted that in the future excavator power system, there will be more control parameters that can be adjusted to make excavator work more efficiently and easier to operate.

 

 

8) pump - engine matching control will be further "intelligent".

 

 

With the help of computer control technology, the matching control between pump and engine will further realize "intelligence", and the combination between the two will be closer and realize integrated control. In this control, the controller can according to the change of working conditions, automatically adjust hydraulic pump and motor, the guaranteed output for the needs of work, make the lowest fuel consumption.

 

 

9) field bus technology and embedded system will be widely used

 

 

With the improvement of hydraulic excavator "intelligence" degree, all kinds of sensors, the controller will spread excavator, this will cause the excavator inside are full of all kinds of wire, the joint, and lower the control system is complicated, reliability. The method to solve this problem is a field bus, with a serial line all the sensors, controllers and actuators connected, in the guarantee system with powerful functions at the same time, has a simple structure and high reliability. At present, in the field of walking machinery, such a field bus, called CAN bus, has not been widely used in excavators. The development of electronic technology makes control chip the size of the smaller, more powerful, almost don't take any space on excavators, fully embedded into the various internal components, which is the development direction of excavator control system in the future.