INFLUENCE OF A NON-STANDARD GEOMETRY ... - Dunarea de Jos

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THE ANNALS OF UNIVERSITY “DUNĂREA DE JOS “ OF GALAŢI
FASCICLE VIII, 2004, ISSN 1221-4590
TRIBOLOGY
means that the tooth deflection has a reduced
influence on gear sliding velocity.
Table 3 presents the curved face width gear
geometry, at the gear face width end, defined by R g =
28 mm and several tool axis inclinations. Figure 9
shows the variations of the ideal and real sliding
velocity along half of the gear face width. It can be
seen that the ideal velocity varies, along the gear face
width, by 4.2% (β = 2°) to 10.7% (β = 8°). The real
sliding velocity variation is about 3.8% (β = 2°) and
9.8% (β = 8°).
The data show that the plastic non-standard gear
sliding velocity is affected by the independent
parameters that control gear geometry as follows:
- an increase in generating circle radius reduces both
the ideal and the real sliding velocity variation;
- an increase in tool axis inclination increases the
sliding velocity variation.
The variable tooth stiffness reduces the variation
of the real sliding velocity compared to the ideal
velocity, due to the decrease in tooth deflection from
the gear centre to its end sections.
6. CONCLUSIONS
An analysis on sliding velocity is developed
for the case of a plastic curved face width gear train,
with modified geometry, as the sliding velocity has a
direct influence on the gear flash temperature
generated. Experimental investigations on the thermal
behaviour of non-standard curved face width gears
showed that high temperatures were induced.
There are two peculiarities of these gears,
which required investigation as they influence the
variation in sliding velocity:
1. the gear geometry that is dependent on the gear
generating process, by the radius of the tool
“generating point”, that is provided with rotational
motion, as well as by the tool inclination axis;
2. the lower material stiffness that affects gear
meshing conditions;
The ideal sliding velocity is calculated using the
traditional practice for metal gears and considers the
influence of the gear geometry on its variation. As a
consequence of the base circle radius and pressure
angle variations, along the gear face width, the line of
action has an increased length and the maximum
sliding velocity is higher towards the gear face width
end sections.
The real sliding velocity considers the influence
of both the gear geometry and tooth deflection. It was
found out that the sliding velocity is mainly
influenced by the gear geometry. The gear tooth
deflections do not have a significant influence on the
sliding velocity - they reduced its variation compared
to the ideal calculation.
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