The Research And Development Of The Automobile Engine Cooling System Test Bench

The function of engine cooling system is to make the engine work within an appropriate temperature range under all working condition. Engine cooling system must prevent the engine from being both overheated and supercooled. Water pump and cooling fan of traditional cars are usually driven by the engine through V belt, which is intertwined between crankshaft pulley and water pump pulley. Therefore, the rotational speed of water pump is in proportional relationship with the engine speed. This kind of driving means, namely, the rotational speed of water pump shaft and fan shaft change with the engine speed, causes various problems indeed. When the engine starts to run, the temperature remains quite low, resulting in the engine supercooled, while the engine is idle working, it may cause the engine overheated.A good control of the operating temperature of the engine can not only prolong the longevity of the engine but also improve starting performance, fuel-economic performance and emission performance of the engine. The key factor of the control of engine temperature lies in the control of the coolant temperature and rotational speed of water pump. Therefore, it is of significant importance to build a set of test-bed to explore the connection among the coolant temperature, rotational speed of water pump and operating condition of the engine.Based upon the above reasons, in this thesis, it builds a set of engine cooling system test-bed through PLC (Programmable Logic Controller). It applies high-powered servo motor to independently drive the water pump and uses the PLC of Siemens and necessary digital quantity input module and analog input module to automatically process various control signals including pressure signals, temperature signals as well as torque signals. In addition, it uses the in-built PID function of PLC and corresponding analog input module to precisely control the coolant temperature. In this thesis, it applies WinCC software as the upper computer control software and realizes the controllability, visibility and automation of the whole experiment process.In this thesis, with the controlling core of the system, namely, PLC, it proposes an overall project design and relevant electric schematic diagram and briefly introduces the design of the mechanical plan and relevant mechanical equipment selection. It attaches great importance to expound the implementation procedure of control programs of the test-bed, including main program, automatic test program and PID heating control program. At the end of this thesis, it also sheds lights on the implementation procedure of the upper computer control software. Through the seamless integration of upper computer control software and PLC program, it realizes the function of automatic acquisition, tabulation and filing of experiment data.Through repeated debugging, it concludes that the engine cooling system is accurate in temperature measurement, responsively sensitive and precise in control. It fully meets the expected experiment effect. It can be accurate to±1round of the control of rotational speed of water pump. Through the concise and visual WinCC upper computer control software, it makes the experiment easy and the results clear and explicit.