Causes of the idle jitter of a light truck's cab and its improvement
To find out the problem of cab idle jitter from the operation of a light truck air compressor,the vibration acceleration of the seat,engine and air compressor is measured.The excitation source of cab jitter under idle conditions,the vibration isolation of the powertrain suspension system,and the reciprocating inertial force of the air compressor are analyzed.An improvement scheme is designed via simulation and experimentation,and test verification is performed.The results indicate that the vibration of the air compressor serves as the driving source of cab jitter.The operating frequency of the air compressor approximates the natural frequencies of several rigid body modes of the powertrain,thus leading to a poor vibration isolation effect at this frequency.By decreasing the reciprocating inertia mass of the air compressor and optimizing the excess balance rate of the crankshaft,the vibration of the air compressor body can be reduced,and the optimal excess balance rate is determined to 0.25.By increasing the air compressor speed ratio from 0.68 to 1.0,the operating frequency of the air compressor has been increased from 8.5 Hz to 12.5 Hz.After the optimization,the vibration acceleration amplitude of the seat under idle condition has been decreased from 0.044g to 0.019g,fulfilling the subjective evaluation requirements of customers.
idle jitterair compressorrigid body modereciprocating inertial forceexcess balance methodair compressor speed ratio
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