Development Trend of Energy Saving Control of Hydraulic Excavator

In the field of hydraulic excavators, 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 the failures of construction machinery come from the hydraulic system, and about 15% of the failures come from the engine. After adopting energy-saving technology, it can improve the utilization rate of engine power, reduce the power loss of the hydraulic system, better match the power system with the power required by the load, reduce the working intensity of the engine and hydraulic components, and improve the reliability of the equipment in use.

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

1) Intelligent electro-hydraulic proportional control

Electro-hydraulic proportional control began to be applied to construction machinery in the early 1980 s, and has been widely used in hydraulic excavators. Electro-hydraulic proportional technology used in construction machinery, can save the complex, huge hydraulic signal transmission pipeline, electric signal transmission of hydraulic parameters, not only can speed up the system response, but also make the entire excavator power system control more convenient and flexible. After entering the 1990 s, with the development of computer technology, electro-hydraulic proportional control is further "intelligent", and the application of electro-hydraulic proportional pumps and proportional valves is increasing, resulting in "intelligent hydraulic excavators". This intelligence is mainly reflected in the following aspects. First of all, the computer can automatically monitor the operating parameters of the hydraulic system and diesel engine, such as pressure, diesel engine speed, etc., and can automatically control the entire excavator power system to run in a state of high efficiency and energy saving according to these parameters. Secondly, the ability to complete some semi-automatic operations, such as flat ground, slope trimming, etc., reduces the driver's proficiency requirements, but the quality of work can be greatly improved. Third, fault diagnosis can be carried out according to the monitored operating parameters, which is convenient for the maintenance of the excavator. The emergence of these functions, so that the performance of the excavator can be greatly improved.

2) Diesel engine EFI control

In the traditional mechanical speed-regulating diesel engine, the circulating fuel supply and fuel injection advance angle of the fuel injection pump are affected by the speed, which makes it difficult to further improve the performance of the diesel engine. After the application of electronic injection control on the diesel engine, the circulating fuel supply and fuel injection advance angle of the pump can no longer be affected by the speed, so that the excavator can always work in the best condition and speed up the response speed. The development of diesel engine electronic injection controller is an important link to improve the energy saving of excavator.

3) Load sensing control will continue to develop

Load sensing control from the 1970 s began to rise, the construction machinery hydraulic parts manufacturers have launched a series of related products. This system has good energy saving and maneuverability, and even unskilled drivers can adapt quickly. The emergence of proportional flow distribution valve further promotes the application of load sensing technology in excavators, further improves the maneuverability of excavators, and solves the problems caused by the lack of skilled drivers in western countries. Therefore, the demand for load sensing control excavators in developed countries will further rise.

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

Although the load sensing system using the four-way valve can provide accurate operation, not all situations require accurate operation, and skilled drivers can also use non-load sensing system excavator to complete accurate operation. More importantly, the high price of load sensing systems limits their use in developing countries. At present, many well-known excavator manufacturers in the world, both the use of four-way valve load sensing control excavator, but also the use of six-way valve hydraulic system such as positive flow, negative flow control excavator. Mature manufacturing technology and low prices will make the six-way multi-way valve continue to play a role.

5) Further improve valve-controlled energy-saving control

In the use of six-way multi-way valve hydraulic system, there are still many areas that can be improved, such as maneuverability, energy saving, etc., so far foreign excavator manufacturers are still studying.

6) Multi-functional combination

In order to improve the performance of the excavator, 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 limitations of various conditions, generally no more than three. In the hydraulic pump shown in Figure 14, the functions of pressure cut-off, positive flow control and power limitation are integrated, and various hydraulic pump schematics that are popular on the market at present are also integrated with multiple functions. With the development of hydraulic technology, it is possible to integrate more functions on the pump.

7) Variable parameter control

In order to make the excavator better adapt to the load requirements under various working conditions, the set parameters of some control elements in the power system will no longer be fixed values, but can change with the specific working conditions of the excavator. For example, on the EX series excavator produced by Hitachi Construction Machinery, the pressure compensator on the load sensing valve sets the pressure difference to change with the working conditions, enhancing the adaptability of the excavator. It can be predicted that in the future excavator power system, there will be more control parameters can be adjusted, so that the excavator work efficiency is higher and the operation is easier.

8) Pump-engine matching control will be further "intelligent"

With the help of computer control technology, the matching control of the pump and the engine will be further "intelligent", and the combination between the two will be closer to achieve integrated control. In this kind of control, the controller can automatically adjust the hydraulic pump and engine according to changes in working conditions to ensure that the output power meets the work needs while minimizing fuel consumption.

9) Fieldbus technology and embedded systems will be widely used

With the improvement of the degree of "intelligence" of hydraulic excavators, various sensors and controllers will be spread all over the excavator, which will lead to various wires and connectors inside the excavator, which will make the control system complex and reduce the reliability. The way to solve this problem is to use the field bus, with a serial line to connect all the sensors, controllers and actuators, to ensure that the system has a powerful function at the same time, with a simple structure and high reliability. At present, in the field of walking machinery, there is already such a field bus, called CAN bus, but it has not been widely used in excavators. The development of electronic technology makes the control chip smaller, more powerful, almost no space on the excavator, can be completely embedded in various components, which is the future direction of the development of the excavator control system.