Patent ID: 7181959

Claim:
A fatigue failure diagnostic method of a turbocharger for diagnosing the fatigue failure of a turbocharger, comprising the steps of: finding in advance the relationship between a maximum peak revolution speed at the time the revolution speed of the turbocharger is periodically and cyclically changed till the turbocharger is fatigue fractured, a revolution speed amplitude at this time, and a revolution speed variation cycle number at this time; measuring the revolution speed of the turbocharger; computing an accumulated fatigue value based on the measured revolution speed, the computation of the accumulated fatigue value including a step of reading the revolution speed in the peak point that was judged and substituting this revolution speed into the peak point revolution speed, a step of computing the revolution speed fluctuation width from the previous peak point by using this peak point revolution speed and the peak point revolution speed in the previous peak point, a step of substituting the peak point revolution speed into the maximum peak revolution speed, substituting the computed revolution speed fluctuation width into the revolution speed amplitude, and retrieving the revolution speed variation cycle number corresponding to those maximum peak revolution speed and revolution speed amplitude from the relationship, a step of calculating a fatigue value by using the retrieved revolution speed variation cycle number and conducting the prescribed computations, and a step of computing the accumulated fatigue value by using the calculated fatigue value and the accumulated fatigue value computed in the previous peak point; and executing the fatigue failure judgment of the turbocharger by comparing the computed accumulated fatigue value and the prescribed fatigue limit value; wherein the fatigue failure judgement is conducted each time a peak point of revolution fluctuation is judged based on the measured revolution speed.