Fig. 14 Journal tilting movements by measurement
Fig. 15 Statistic results of journal tilting angle
As a result of the comparison, the theoretical calculation model is high validity to simulate the journal movement behavior even if under uneven alignment condition.
4.3 Confirmation of Actual Adjustment for Misalignment
The performance of bearing load capacity increases with a decrease of journal tilting. A viewpoint of decreasing the tilting angle, simulation on changing the thickness of the No.1 bearing has been carried out by this calculation model.
Figure 15 shows the statistic results of tilting angle of No.1, No.2 and No.3 journal. The statistic values are the average of journal tilting angle and the maximum of absolute journal tilting angle.
As shown in figure 15 (a), the averages of the journal tilting angle both in No.1 and in No.2 bearing decrease by exchanging a thinner thickness metal. But the average of No.3 journal remains constant. Therefore exchanging No.1 metal has no effect on No.3 journal.
As shown in figure 15 (b), the maximum of the absolute journal tilting angle in No.1 bearing decreases with a thinning of No.1 metal thickness. However the maximum of No.2 journal increases in the range of less than +0.1 mm thickness. The maximum of No.3 journal also remains constant.
On the actual procedure for misalignment for No.1 bearing, the exchanging value of thickness is between 0.0 mm and -0.2 mm for standard thickness. As shown in figure 15, the average and the maximum of No. 1 journal decrease. The increasing quantity of No.2 journal tilting angle is less than the value of No.1 journal. Therefore the exchanging range for actual procedure is judged by the efficiency for No.1 bearing by this calculation model.
5. CONCLUSIONS
The objective of this study is to disclose journal movement behavior under uneven alignment between journal and main bearing. Journal center locus and journal tilting angle were measured in actual engines. A simplified theoretical calculation model has also been developed to simulate the journal movement behavior. Theoretical results were compared with measured results. The summary is as follows:
(1) The features of journal center locus and journal tilting angle have been clarified in four representative main bearings in actual engines.
(2) Although the theoretical calculation model only consists of simplified crankshaft, bearings and beating supports, the calculation model can simulate the journal center locus and journal tilting angle with high validity.
(3) The calculation model can successfully predict the journal movement behavior under uneven alignment.
(4) The efficiency of adjustment of bearing height on the actual procedure is also confirmed by using this model. It is necessary to grasp the actual alignment condition with high accuracy when using the theoretical calculation model for actual engine. For improving the reliability of engine, we would like to develop the efficient theoretical calculation system for actual engine.
REFERENCE
[1] Booker, J. F., Trans. ASME, J. Lub. Tech., Vol. 93, No. 1 (1971), p168.
