Page 226 - Gear Technology Solutions

Ground gears show a very high gear quality which is why the amplitude inten-
sity of the tooth mesh frequency is particularly high. The attempt to break the
high intensity down by adding spacing errors failed for several reasons. The
random tooth spacing errors reduce the gear quality rating which makes it diffi-
cult to monitor how sound a grinding production is running. Furthermore, tooth
spacing variations reduce the effective contact ratio under load which affects
the load carrying capacity of a gearset [8].

However, the original goal, to reduce the vibration and noise emission of
gearsets has failed. In the example in Figure 5 the rack is shifted with a con-
stant speed. The gear rotates with a constant RPM while the teeth with a spac-
ing of P are in mesh. When the first tooth with a lower spacing P-D 1 contacts
the rack, an increased meshing impact and an additional deceleration occur.
The following tooth with a larger spacing P+D 2 causes a lower mesh impact
and an acceleration of the pinion rotation. Figure 6 shows on top the fast Fou-
rier transformation (FFT) of a single flank test working variation in case of a
meshing pinion and gear with high spacing quality. Analysis results of trial
gears, manufactured with spacing errors D of 5 micro-radiant showed in-
creased first harmonic amplitudes and additional low frequency amplitudes in
the range of the pinion and gear rotational frequency (bottom graphic in Figure
6). The additional bars in the entire frequency range reduce their amplitude
with increasing frequency (impulse effect). In summary, all tests done with
randomly applied spacing errors failed to reduce the tonality of these gearsets.

Figure 6: FFT of gear with perfect spacing (top),
and random spacing errors (bottom)

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