Abstract
During practical 30000km road driving and 500hour engine test rig test for vehicle and engine reliability, one minibus appears the phenomenon of generator-compressor bracket fracture and leads the generator-compressor-crankshaft belt rupture. It seriously affects the vehicles operation performance. Combining test research method and analytical analysis technology, this paper seeks the fracture occurrence mechanism of the generator-compressor bracket system and puts forward corresponding control measure.
Firstly, under different engine rotating, the article carries through engine test rig test and measures the generator-compressor bracket systems 4 specific spots vibration acceleration signal which direction is vertical to the bracket plane. Then it analysiss the acceleration signals spectrum characteristic and vibration intensity vs. engine rotate speed. The result indicates the vibration signals peak frequency has distinct correlation with generator rotate frequencys 1st and 3rd harmonious order. Namely along with the increasing of the generator rotate speed, the peak frequency is also increase lineally. Furthermore while the generator rotate speed is 8400rpm, accordingly the engine rotate speed is 4000rpm, the system has the most violent vibration intensity namely appears resonance.
Secondly, the article establishes the generator-compressor and its bracket systems FEA model, which can reflect each components connecting relationships and exterior, constrains. Based on this model, it calculates the systems constrain mode. The result shows the system has two resonance frequencies at 145.5Hz and 433.2Hz, which separately corresponding to 1 time and 3 times of generator rotate frequency while engine rotate speed is 4150rpm. Both the test rig analysis and FEA results are unanimous. Hence it can be concluded that the reason for the bracket fracture and belt rupture is unreasonable system dynamical characteristic.
Finally the article redesigns the systems structure.
Through separating the installation of generator and compressor, it cuts off vibration propagation path and then avoids the above phenomenon. The modified measure is also proved valid through practical road driving test.