Metal working – Method of mechanical manufacture – Gear making
Reexamination Certificate
2000-06-29
2002-04-30
Echols, P. W. (Department: 3726)
Metal working
Method of mechanical manufacture
Gear making
C029S090600, C418S061300
Reexamination Certificate
active
06378206
ABSTRACT:
TECHNICAL FIELD
The invention relates to a method of fabricating an internal-gear pin retaining ring for retaining pins (conceptually including rollers of great diameter) in an internal meshing gear mechanism having an internal gear, whose teeth are constituted by the pins, and an external gear put into internal mesh with the internal gear.
The invention also relates to internal meshing planetary gearing or a hydraulic motor pump fabricated through the use of this fabrication method.
BACKGROUND ART
Those internal meshing gear structures heretofore known widely include a double row type internal meshing planetary gear structure comprising: a first shaft; eccentric bodies which are rotated by the rotation of the first shaft; a plurality of external gears attached to the eccentric bodies via bearings so as to be capable of eccentric rotations; an internal gear which comes into internal mesh with the external gears via its inward teeth constituted by outer pins; and a second shaft coupled to the external gears via inner pins which extract only the rotational components of the external gears.
FIGS. 17 and 18
show a conventional example of this structure. In this conventional example, the above-described structure is applied to “reduction gears” by making the first shaft an input shaft, making the second shaft an output shaft, and fixing the internal gear.
On the input shaft
1
are fitted eccentric bodies
3
a
and
3
b
with a predetermined phase difference therebetween (180°, in this example). Each of the eccentric bodies
3
a
and
3
b
is off the center of the input shaft
1
(center O
1
) by an eccentricity e (center O
2
). Two external gears
5
a
and
5
b
are attached in double rows to the respective eccentric bodies
3
a
and
3
b
via bearings
4
a
and
4
b
. These external gears
5
a
and
5
b
have a plurality of inner roller holes
6
a
and
6
b
through which inner pins
7
and inner rollers
8
are inserted.
The external gears are provided in two (in double 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
5
a
and
5
b
mentioned above are provided outward teeth
9
of trochoidal tooth profile or circular arc tooth profile. The outward teeth
9
are put into internal mesh with the internal gear which is fixed to a casing
12
. The internal gear
20
consists of a pin retaining ring
10
and outer pins
11
. The pin retaining ring
10
has a plurality of axially-extending pin retaining holes
13
of half-round shape in its inner periphery. The outer pins
11
are rotatably fitted to the pin retaining holes
13
with some play, and form circular arc teeth with the portions exposed from the pin retaining holes
13
.
The inner pins
7
penetrating through the external gears
5
a
and
5
b
mentioned above are firmly fixed or fitted to a flange portion around the output shaft
2
.
One rotation of the input shaft
1
makes one rotation of the eccentric bodies
3
a
and
3
b
. This one rotation of the eccentric bodies
3
a
and
3
b
urges the external gears
5
a
and
5
b
to oscillate and rotate about the input shaft
1
. However, since their rotations on the axis are restricted by the internal gear
20
, the external gears
5
a
and
5
b
almost exclusively make oscillations while internally meshing with this internal gear
20
.
Now, given that the number of teeth on the external gears
5
a
and
5
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. Accordingly, each rotation of the input shaft
1
shifts (rotates) the external gears
5
a
and
5
b
with respect to the internal gear
20
fixed to the casing
12
, by the amount corresponding to one tooth. This means that one rotation of the input shaft
1
is reduced to −1/N rotations of the external gears
5
a
and
5
b.
The oscillating components in the rotations of the external gears
5
a
,
5
b
are absorbed by the clearances between the inner roller holes
6
a
,
6
b
and the inner pins
7
(inner rollers
8
). Thus, only the rotational components thereof are transmitted via the inner pins
7
to the output shaft
2
.
This consequently achieves speed reduction of −1/N in reduction ratio (the negative sign represents a reverse rotation).
Incidentally, this internal meshing planetary gear structure is now being applied to various kinds of reduction gears or step-up gears. For example, while the first shaft and the second shaft make the input shaft and the output shaft and the internal gear is fixed in the structure described above, reduction gears can also be constructed by making the first shaft the input shaft, making the internal gear the output shaft, and fixing the second shaft. Moreover, “step-up gears” can be constructed by reversing the input and output shafts in these structures.
By the way, in order to miniaturize the internal meshing planetary gear mechanism of this type and enhance its load capacity, the internal gear
20
, among those parts having meshing portions or sliding portions, must be made to have high strength properties. In addition, the external gears
5
a
,
5
b
, the outer pins
11
, the inner rollers
8
, the inner pins
7
, the bearings
4
a
,
4
b
, and the eccentric bodies
3
a
,
3
b
must be made to have both high strength properties and high hardness properties. Therefore, the parts mentioned above are usually fabricated of metal materials having such properties.
The metal materials having high strength properties and high hardness properties, however, commonly have relatively greater coefficients of friction. Therefore, the sliding contact surfaces using these metal materials require oil or grease lubrication. Since the lubrications are achieved by forming an oil film on the contact surfaces, clearances therefor must be formed between the mutual contact surfaces in the transmission mechanism. These clearances are also necessary to absorb elastic deformations produced in power transmission and machining errors of the component parts.
Such clearances can cause play and backlash of the entire mechanism, thereby precluding rotations on one side from taking the form of rotations on the other side immediately. Such a delay in response will hereinafter be referred to as angle backlash. The angle backlash like this can cause a drop in control accuracy when the transmission mechanism is used as a control mechanism. Elimination of such angle backlash requires that the clearances be reduced, which unfavorably lowers the lubrication performance in terms of lubricating-oil maintenance. Consequently, the reduction of angle backlash and the improvement of lubrication remain contradictory to each other. In particular, control mechanisms prefer smaller friction on their contact surfaces since they repeat starts and stops frequently, while lubrication is an inevitable technical matter in reducing friction. Eventually, the reduction of angle backlash would be a technical matter of great difficulty.
In the meantime, it is also publicly known to form chemical conversion coating, such as phosphatic coating, on the sliding portions to lower the coefficient of friction on the sliding portions. This chemical conversion coating itself does not posses a low coefficient of friction, but retains a large amount of lubricating oil in its minute asperities to achieve the low coefficient of friction.
In this view, the chemical conversion coating mentioned above may be applied to the meshing portions and the sliding contact surfaces in a transmission mechanism. The chemical conversion coating itself, however, is easy to wear, and a problem exists because the coating comes off in a short time.
With the objective of providing a structure and a fabrication method of a contact surface for reducing the clearances between the contact surfaces in a transmission unit and allowing long-term maintenance of lubricating oil, the present applicants have proposed, in Japanese Patent Application No. Sho 60-271649 (Japanese Pa
Ishikawa Tetsuzo
Minegishi Kiyoji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Echols P. W.
Sumitomo Heavy Industrie's, Ltd.
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