There are various power losses in the working process of excavator, among which the power matching loss is the dominant one. The power matching loss is due to the complex working conditions of the excavator and the drastic change of the load, which causes the diesel engine to deviate seriously from the economic working area, resulting in the low fuel utilization rate, especially in the case of high speed and small load. There are two main aspects of power matching: energy saving measures of hydraulic system based on engine-hydraulic pump matching and energy saving measures of hydraulic system based on hydraulic pump-load matching.
1.Engine-hydraulic pump matching energy saving control system
The energy saving measures of engine-hydraulic pump matching hydraulic system refer to the control of hydraulic pump and engine by adjusting and controlling, so that the engine works in the high efficiency area, so that the hydraulic pump can absorb the power of the engine more fully. By matching the engine and hydraulic pump reasonably, the fuel utilization ratio can be improved effectively and the purpose of energy saving can be realized. Its energy saving measures mainly include constant power control, automatic idle speed control, sub-working condition control and speed induction control. The application of constant power control is more cross power control, which can make full use of engine power and adjust the output flow according to the load condition of each hydraulic pump as the sub-power system. However, there are still shortcomings, the working point of hydraulic pump is limited to several counties, which can not match well with the load working point, and there is inevitably power loss. When the hydraulic system exceeds the set time, it realizes automatic idle speed, saves fuel consumption and reduces noise.
The engine and hydraulic pump are optimized according to the working conditions and requirements, and the throttle opening and the displacement of the hydraulic pump are controlled, which are generally divided into heavy load, general operation, light load and low idle speed. The distinction of working conditions can avoid engine working in high fuel consumption state as far as possible.
2.Hydraulic pump-load matching energy saving control system
The energy saving measure of hydraulic pump-load matching hydraulic system means that the hydraulic pump can provide energy according to the load and reduce the excess energy output of the hydraulic pump as far as possible. At present, there are mainly negative flow control, positive flow control and load sensitive control and other magic. The negative flow system is helpful to eliminate the air flow loss and throttling loss in the multi-way valve, but the deficiency is that the speed regulation range of the multi-way valve is limited and greatly affected by the load. The positive flow system only outputs the flow rate suitable for the pilot control pressure, so it can reduce the bypass throttling loss, but it can not be completely eliminated. Moreover, the existence of shuttle valve group has always been a deficiency in the positive flow control system, which increases the complexity of the system and affects the response speed of the system. Although the function of load sensitive system is superior, there are still many shortcomings. Because of the use of multi-sensors and signalling devices, when the pipeline in the system is longer, the pressure transfer lag will be caused, and it is difficult to realize rapid and stable control and cause energy loss.