T-46
There will be an involute interference between the internal gear and the pinion cutter if the
number of teeth of the pinion cutter ranges from 15 to 22 (zc = 15 to 22). Table 5-3b shows the limit
for a profile shifted pinion cutter to prevent trimming interference while cutting a standard internal
gear. The correction (xc) is the magnitude of shift which was assumed to be: xc = 0.0075 zc + 0.05.
Table 5-3b The Limit to Prevent an Internal Gear from Trimming Interference
(a = 20°, x2 = 0)
There will be an involute interference between the internal gear and the pinion cutter
if the number of teeth of the pinion cutter ranges from 15 to 19 (zc = 15 to 19).
5.3 Internal Gear With Small Differences In Numbers Of Teeth
In the meshing of an internal gear and an external gear, if the difference in numbers of
teeth of two gears is quite small, a profile shifted gear could prevent the interference. Table 5-4
is an example of how to prevent interference under the conditions of z2 = 50 and the difference
of numbers of teeth of two gears ranges from 1 to 8.
All combinations above will not cause involute interference or trochoid interference,
but trimming interference is still there. In order to assemble successfully, the external
gear should be assembled by inserting in the axial direction.
A profile shifted internal gear and external gear, in which the difference of numbers of
teeth is small, belong to the field of hypocyclic mechanism, which can produce a large
z1
x1
z2
x2
aw
a
e
49
1.00
61.0605°
0.971
1.105
48
0.60
46.0324°
1.354
1.512
47
0.40
37.4155°
1.775
1.726
46
0.30
32.4521°
2.227
1.835
45
0.20
28.2019°
2.666
1.933
44
0.11
24.5356°
3.099
2.014
43
0.06
22.3755°
3.557
2.053
42
0.01
20.3854°
4.010
2.088
0
50
zc
xc
z2
zc
xc
z2
zc
xc
z2
15
0.1625
36
28
0.26
52
44
0.38
71
16
0.17
38
30
0.275
54
48
0.41
76
17
0.1775
39
31
0.2825
55
50
0.425
78
18
0.185
40
32
0.29
56
56
0.47
86
19
0.1925
41
33
0.2975
58
60
0.5
90
20
0.2
42
34
0.305
59
64
0.53
95
21
0.2075
43
35
0.3125
60
66
0.545
98
22
0.215
45
38
0.335
64
80
0.65
115
24
0.23
47
40
0.35
66
96
0.77
136
25
0.2375
48
42
0.365
68
100
0.8
141
27
0.2525
50
Table 5-4
The Meshing of Internal and External Gears
of Small Difference of Numbers of Teeth
(m = 1, a = 20°)
