Working Process And Performance Research Of Engine Retarder

Engine is widely used as an auxiliary brake system in automobile deceleration process, at this time it is working as a retarder, it can provide a steady braking power and it's working temperature will keep constant for a very long time. Engine retarder makes the engine temperature not too lower than the engine's working temperature, and the braking power of engine retarder is distributed by differential, so the safety performance is enhanced. In china, the research level of engine retarder is still on the engine brake and the exhaust brake, the braking power is small and it can not fit the most of brake requirement. Recently, there is another engine retarder technology abroad, it changes the valve timing of the engine dragging process, which makes the braking power of engine retarder closely to the rated output, or even bigger than it. Furthermore, it can give the different braking power at the same engine speed. As there is lack of mature theory about the development of the engine's retard ability, this paper investigates the working process and the braking power development of engine retarder, gives a support in both theory and technology to develop high performance engine retarder.Firstly, the existing engine retarder technology is introduced; the relationship between the braking power and the working process in different engine retarder type is briefly analyzed. Based on above analysis, by the working process research when engine working as a retarder, the method to increase the braking power in every engine stroke and the effect of this method to the whole working process are analyzed, some methods to increase the engine braking power are concluded. Combined with the latest results of the variable valve actuation, a brand new ideal working process of engine retarder to get the largest braking power of the engine is put forward. A new concept of "engine braking power utilizing coefficient" to evaluate the utilizing level of the different engine retarder types to the largest braking power of the engine is put forward.Secondly, the mathematical model of the engine brake, engine exhaust brake, compression release engine retarder, engine bleed retarder, engine bleed retarder compound with the engine exhaust brake are set up. Through the mathematical calculation methods the performances of every kind engine retarder with the different structure parameters and different running parameters are simulated. The computer simulation results are fit with the experiments results. The computation methods and the results can be used to design the structure and analyze the performance of the engine retarder.The cam profile of the compression release engine retarder is designed by high-order polynomial functions. The calculation results show that, by properly choosing the parameters, the high-order polynomial is fit for the decompression cam profile, even the angles of basic segment are small. The performance of the decompression cam meets the requirement of the valve train and the compression release engine retarder.Finally, the vehicle braking stability is analyzed when engine retarder is working, a method that by adding the braking forces distribution ratio between the front and rear brake to improve the braking stability of vehicle is put forward when the engine retarder is co-working with the main brake system. The ability of vehicle going downhill is analyzed when engine retarder can offer a classification and big braking power. It shows that with the compression release engine retarder, vehicles can run at a steady economical speed on all slopes. An auto control of compression release engine retarder is designed by fuzzy control. The simulation shows that the designed control system can make the automobile run at a relatively steady speed, and during the process, the acceleration varies slightly, the designed control system is suitable for engineering practice.