Fig. 3 Three-dimensional figure of radiant sound (3 hours)
Fig. 4 Three-dimensional figure of vibration (3 hours)
It is characterized in that the distribution of high level values is present at 2, 4, 6, 8, 10, 12 and 14kHz around Point a (70°), Point b (160°) and Point c (295°). The level change is characteristic, showing the bow-shaped pattern, which is symmetrical in the right-to-left direction around three crank angles. The bow-shaped pattern is considered to be generated by the sliding of the piston moving vertically with the cylinder liner wall. That is, because the source of generation of the vibration passes in the vicinity of the installation place of the sensor, the change in the vibration appears as the change in the frequency between in the approaching time and after the passing. From this finding, the position of three crank angles at the center of the pattern show the timing when the piston passes the measurement point, and from the figure of the valve timing, three points (a, b, and c) indicates the passing timing of the piston of No. 1 cylinder is moved from the top dead center to the bottom dead center, the passing timing of the piston of No. 2 cylinder is moved from B.D.C. to T.D.C. and the passing timing of the piston of No. 1 cylinder is moved from B.D.C. to T.D.C.. In the same figure, light and shade lines indicating the high level similar to that in Fig. 3 can be seen in the ranges of the crank angles A, B and C. These lines can be concluded to be the vibration attributable to the combustion of No. 1, No. 3 and No. 2 cylinders. When Fig. 3 is again compared with Fig. 4, the change in the frequency can also be seen at Points a, b and c similar to Fig. 4. This change does not show a bow-shaped pattern as clear as that in the vibration (Fig. 4), but shows that the sound by the piston slide is indicated in a bow-shaped pattern. Figs. 5 and 6 are the three-dimensional figures indicating the radiant sound and the vibration in ten hours after the shop trial run was started. In Fig. 5 of the radiant sound, the sound in the combustion appears in the ranges of A, B, and C similar to Figs. 3 and 4. However, any bow-shaped pattern attributable to the piston slide confirmed in Fig. 3 can hardly be confirmed. On the other hand, in Fig. 6 to indicate the vibration, the vibration caused by the combustion appears in the ranges of A, B and C, and the characteristic bow-shaped pattern attributable to the piston motion can be confirmed at 3 points of a, b and c. However, compared with Fig. 4, the vibration level is dropped by about 10dB.
These four three-dimensional figures show that the data on the radiant sound and the vibration in 3 hours and in 10 hours after the shop trial run was started, is respectively changed. In particular, in the three-dimensional figure of the radiant sound, the bow-shaped pattern is almost in-recognizable in only 10 hours after the engine was started. It can be concluded to be difficult from the above-mentioned the radiant sound results to detect the information by the slide.
