Planetary gear transmission systems or components – Planet periphery surrounds axis of interacting gear – Circumferentially spaced connector pins
Reexamination Certificate
2000-03-15
2002-08-27
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
Planet periphery surrounds axis of interacting gear
Circumferentially spaced connector pins
C475S183000, C475S337000
Reexamination Certificate
active
06440030
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention particularly relates to a driving apparatus having an oscillating internal meshing planetary gear structure as its speed change mechanism, such as a geared motor.
2. Description of the Related Art
Conventionally, oscillating internal meshing planetary gearing is widely known which has an internal gear and an external gear internal meshing with the internal gear, the center axis of the internal gear lying inside the periphery of the external gear [the gearing corresponding to International Patents Classification (IPC) F16H 1/32].
FIG. 22
shows an example of a geared motor that has conventional oscillating internal meshing planetary gearing of this type as its reduction gear unit, which is described in Japanese Patent Laid-Open Publication No.Hei 5-231482. This geared motor
1
includes the above-mentioned reduction gear unit (oscillating internal meshing planetary gear unit)
2
and a motor unit
3
connected and integrated with each other.
The reduction gear unit
2
has a casing
51
which is composed of a central casing
52
disposed at the axial center, a joint casing
53
on the side closer to the motor unit
3
, and a front casing
54
on the side opposite from the motor unit
3
. The motor unit
3
has a casing
55
which is composed of a cylindrical casing
56
having a stator and the like arranged inside, the joint casing
53
on the side closer to the reduction gear unit
2
, and a rear cover
57
on the side opposite from the reduction gear unit
2
. Here, the above-mentioned joint casing
53
comprises both parts of the casings
51
and
55
for the units
2
and
3
. Accordingly, the units
2
and
3
are integrally connected with each other through the joint casing
53
.
The reduction gear unit
2
has first and second shafts
11
and
12
serving as input and output shafts, respectively. Both the shafts are aligned on the center axis L of the unit. The first shaft
11
is disposed on one axial end of the reduction gear unit
2
. The second shaft
12
is on the other axial end of the reduction gear unit
2
.
Two eccentric bodies
13
a
and
13
b
are fitted on the outer periphery of the first shaft
11
so as to axially adjoin each other with a given phase difference therebetween (180°, in this example). These eccentric bodies
13
a
and
13
b
make rotations together with the first shaft
11
. The respective centers of the eccentric bodies
13
a
and
13
b
are a given eccentricity off the axis of the first shaft
11
. External gears
15
a
and
15
b
are fitted onto the outer peripheries of the eccentric bodies
13
a
and
13
b
via bearings
14
a
and
14
b,
respectively.
The plural rows of external gears
15
a
and
15
b
fitted on the eccentric bodies
13
a
and
13
b
are provided with a plurality of inner pin holes
16
a
and
16
b,
respectively. Inner pins
17
are fitted to the inner pin holes
16
a
and
16
b
with some play.
The external gears are provided in two (in plural rows) mainly for the sake of enhancing the transmission capacity, maintaining the strength, and keeping the rotational balance.
On the outer peripheries of the external gears
15
a
and
15
b
are provided outward teeth each having a trochoidal tooth profile or a circular arc tooth profile. These outward teeth come into internal mesh with an internal gear
20
that is provided concentrically with the first shaft
11
. The internal gear
20
is integrally formed on the inner periphery of the central casing
52
. Each inward tooth of the internal gear
20
is formed with an outer pin
21
held on the inner periphery of the central casing
52
.
The result is that the reduction gear unit
2
is characterized by having the internal gear
20
and the external gears
15
a,
15
b
internally meshing with the internal gear
20
, the center of the internal gear
20
lying inside the peripheries of the external gears
15
a,
15
b
(the characteristic prescribed in IPC F16H 1/32).
The two external gears
15
a
and
15
b
are interposed between a pair of support carriers
23
and
24
. These carriers
23
and
24
are rotatably supported by bearings
31
and
32
fitted to the inner peripheries of the joint and front casings
53
and
54
, respectively. The carriers
23
and
24
are also integrally connected with each other by a plurality of carrier pins (coupling pins)
25
and spacers
26
piercing through the external gears
15
a
and
15
b.
The inner pins
17
, fitted to the inner pin holes
16
a
and
16
b
in the above-mentioned external gears
15
a
and
15
b
with some play, are connected at both ends with the carriers
23
and
24
on both sides so as to be capable of sliding rotations. This allows only the rotational components of the external gears
15
a
and
15
b
to be transmitted through the inner pins
17
to the carriers
23
and
24
on both the sides.
The carrier
23
closer to the motor unit
3
is of annular shape having a center hole
23
a.
One end of the first shaft
11
lies inside the center hole
23
a
so that the end can be coupled to a motor shaft
61
.
The other carrier
24
is integrally formed on the base of the second shaft
12
, and has a recess
24
a
into which the other end of the first shaft
11
is inserted. A bearing
33
is fitted to the inner periphery of the central hole
23
a
in the carrier
23
, and a bearing
34
is fitted to the inner periphery of the other carrier
24
. The first shaft
11
is rotatably supported by the bearings
33
and
34
.
The motor shaft
61
of the motor unit
3
is supported at its rear end by a bearing
62
and at its front end by a bearing
63
. The bearings
62
and
63
are fitted to the rear cover
57
and the joint casing
53
, respectively. Here, the motor shaft
61
is aligned to be coaxial with the center axis L of the reduction gear unit
2
.
The extremity of the motor shaft
61
, projected outward from the front-side bearing
63
, is inserted into the reduction gear unit
2
. Within the center hole
23
a
in the carrier
23
of the reduction gear unit
2
, the extremity is coupled to the end of the first shaft
11
mentioned above via a coupling
70
.
In this case, splines are formed in the inner periphery of the coupling
70
and the outer peripheries of both shafts
11
and
61
so that the shafts
11
and
61
come into spline connection with each other through the coupling
70
. Here, the splines establish the floating connection between the first shaft
11
and the motor shaft
61
while allowing relative radial play therebetween.
Now, description will be given of the operation of this geared motor.
In the geared motor
1
of such constitution, one rotation of the first shaft
11
coupled to the motor shaft
61
makes one rotation of the eccentric bodies
13
a
and
13
b.
This one rotation of the eccentric bodies
13
a
and
13
b
urges the external gears
15
a
and
15
b
to oscillate and rotate about the first shaft
11
. However, since their free rotations on the axis are restricted by the internal gear
20
, the external gears
15
a
and
15
b
almost exclusively make oscillations while internal meshing with this internal gear
20
(this is a characteristic of speed reduction structures of this type).
Now, assuming that the number of teeth on the respective external gears
15
a,
15
b
is N and the number of teeth on the internal gear
20
is N+1, the difference between the numbers of teeth is “1.” On that account, each rotation of the input shaft
1
shifts (rotates) the external gears
15
a
and
15
b
by the amount corresponding to one tooth with respect to the fixed internal gear
20
. This means that one rotation of the first shaft
11
is reduced to −1/N rotations of the external gears
15
a
and
15
b.
The oscillating components in the rotations of the external gears
15
a
and
15
b
are absorbed by the clearances between the inner pin holes
16
a,
16
b
and the inner pins
17
. Thus, only the rotational components are transmitted via the inner pins
17
to the carriers
23
and
24
, and then
Minegishi Kiyoji
Tamenaga Jun
Yamamoto Akira
Arent Fox Kintner & Plotkin & Kahn, PLLC
Marmor Charles A
Parekh Ankur
Sumitomo Heavy Industrie's, Ltd.
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