Study On Hydraulic Actuator Of Electro-hydraulic Mix-drive Cooling System In Construction Machinery

At present, the fan of the construction machinery cooling system mainly uses the traditional crankshaft fixed transmission ratio driving, at the same time, it bears heat engine dissipation task and hydraulic oil dissipation task of transmission system, hydraulic lifting and steering system, so its heat dissipation strength is heavy. This driving method makes engine starting torque larger, preheating time longer, cooling deficient at low speed with heavy loading and cooling excessive at high speed with light loading. Therefore, it will cause the engine cooling unreasonable, the consumption of fan energy larger, decrease the dynamic output of engine, meanwhile, the installation position of the fan is limited and the working noises become larger.In order to solve this problem, we design a new electro-hydraulic mixed driving cooling control system, which divides the original cooling system into two independent parts, the engine cooling system and the hydraulic oil cooling system. They are controlled by the same SCM. In engine cooling system, the fan has been designed into hydraulic driving way and realized stepless regulation. According to control current of the proportion valve, the system can adjust the peripheral discharge of proportion valve to control speed of the fan, while hydraulic oil cooling system uses electromotor to drive hydraulic oil cooling fan. Both the engine cooling system and the hydraulic oil cooling system work independently based on their cooling requirements.The principles of this new cooling system are discussed in detail in the paper, and the thermodynamic parameters and the main hydraulic element parameters in hydraulic driving system of engine cooling system are reselected. Each element and pipe fitting in hydraulic system, each heat dissipation element and the Electromagnetic Proportion Overflow Valve are selected renewably by taking the R4105T-diesel engine whose rated power is 45kw for prototype, and the matching design between fan and radiator is also completed. In order to control water cycle, the electric pump is designed. The water is not cycled in previous experiments, but is controlled by the SCM which is based on the coolant temperature, and the loop of the electrohydraulic proportion voltage regulation- stepless voltage regulation has also been determined. At last, we complete the contrastive experiments in preheating time and fuel consumption at the CLG816- miniature loader.The cooling fan and radiator can be disposed separately and flexibly in this system. When the cooling fans and pumps are installed coaxially, they can reduce the radial clearance of the fan installation and improve the volumetric efficiency. The experiment shows that the new electro-hydraulic mixed driving intelligent cooling control system can solve the problem of engine overheating in the engineering machinery, and also has the advantage of preheating quickly, saving fuel land decreasing noise with small size and strong power. So the new system corresponds to the development trend of the modern engine cooling system. When it is popularized and applied in the engineering machinery, we will get well social and economic benefit.