U.S. patent application number 15/131356 was filed with the patent office on 2016-10-20 for harmonic gear drive.
The applicant listed for this patent is NABORS LUX FINANCE 2 SARL. Invention is credited to Andrew GORRARA, Siamak SHAHIPASSAND, Ola STENGEL.
Application Number | 20160305528 15/131356 |
Document ID | / |
Family ID | 56108451 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160305528 |
Kind Code |
A1 |
SHAHIPASSAND; Siamak ; et
al. |
October 20, 2016 |
Harmonic Gear Drive
Abstract
A harmonic gear drive includes an input shaft and an output
shaft. The input shaft is mechanically coupled to a wave generator
which has a varying diameter. The wave generator is positioned
within a flex spline which includes external teeth. The external
teeth of the flex spline engage with internal teeth of a fixed
spline and an output spline when the major diameter of the wave
generator is aligned therewith. The output spline has a different
number of teeth from the input spline such that, as the wave
generator is rotated and the flex spline rotates, the output spline
is rotated relative to the fixed spline.
Inventors: |
SHAHIPASSAND; Siamak;
(Stavanger, NO) ; GORRARA; Andrew; (ALGARD,
NO) ; STENGEL; Ola; (Sandnes, NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NABORS LUX FINANCE 2 SARL |
Luxembourg |
|
DE |
|
|
Family ID: |
56108451 |
Appl. No.: |
15/131356 |
Filed: |
April 18, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62150101 |
Apr 20, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16H 2049/003 20130101;
F16H 49/001 20130101; E21B 4/006 20130101 |
International
Class: |
F16H 49/00 20060101
F16H049/00 |
Claims
1. A harmonic gear drive comprising: an input shaft; a wave
generator mechanically coupled to the input shaft, the wave
generator having a varying diameter, the portion of the wave
generator having the largest diameter defining a major diameter of
the wave generator; a flex spline, the flex spline being generally
tubular and including external teeth, the flex spline positioned
about the wave generator; a fixed spline, the fixed spline being
including a first number of internal teeth that engages the
external teeth of the flex spline aligned with the major diameter
of the wave generator; and an output spline, the output spline
including a second number of internal teeth adapted to engage the
external teeth of the flex spline aligned with the major diameter
of the wave generator, the second number of internal teeth being
different from the first number of internal teeth.
2. The harmonic gear drive of claim 1, further comprising an output
sub mechanically coupled to the output spline.
3. The harmonic gear drive of claim 2, further comprising at least
one bearing between the output sub and the input shaft.
4. The harmonic gear drive of claim 1, wherein the input shaft is
mechanically coupled to an output shaft of a motor.
5. The harmonic gear drive of claim 4, wherein the motor is a mud
motor or electric motor.
6. The harmonic gear drive of claim 5, wherein the input shaft is
formed as part of a rotor of the motor.
7. The harmonic gear drive of claim 4, wherein the input shaft
further comprises a transmission coupling to mechanically couple
the input shaft to the output shaft of the motor.
8. The harmonic gear drive of claim 7, wherein the transmission
coupling comprises a castellation formed on the input shaft and a
corresponding castellation formed on the output shaft of the
motor.
9. The harmonic gear drive of claim 4, further comprising a fixed
sub, the fixed sub mechanically coupled to the fixed spline and the
motor.
10. The harmonic gear drive of claim 9, further comprising at least
one bearing between the fixed sub and the input shaft.
11. The harmonic gear drive of claim 1, wherein the wave generator
is generally elliptical in cross section.
12. The harmonic gear drive of claim 1, wherein the difference
between the first number of teeth and the second number of teeth is
between 1 and 10.
13. The harmonic gear drive of claim 1, wherein the external teeth
of the flex spline comprise a first set of teeth and a second set
of teeth, the first set of teeth engaging the internal teeth of the
fixed spline and the second set of teeth engaging the internal
teeth of the output spline.
14. The harmonic gear drive of claim 1, further comprising a needle
bearing positioned between the flex spline and the wave
generator.
15. The harmonic gear drive of claim 1, wherein the input shaft,
wave generator, flex spline, fixed spline, and output spline are
generally tubular having a central bore formed therethrough.
16. The harmonic gear drive of claim 15, further comprising a drive
shaft extending through the central bore.
17. The harmonic gear drive of claim 1, wherein the output sub is
coupled to an RSS housing of an RSS.
18. The harmonic gear drive of claim 1, wherein the wave generator
is an eccentric cam.
19. The harmonic gear drive of claim 1, wherein the wave generator
is generally elliptical in cross section.
20. A method comprising: providing a harmonic gear drive including:
an input shaft; a wave generator mechanically coupled to the input
shaft, the wave generator having a varying diameter, the portion of
the wave generator having the largest diameter defining a major
diameter of the wave generator; a flex spline, the flex spline
being generally tubular and including external teeth, the flex
spline positioned about the wave generator; a fixed spline, the
fixed spline being including a first number of internal teeth that
engages the external teeth of the flex spline aligned with the
major diameter of the wave generator; and an output spline, the
output spline including a second number of internal teeth adapted
to engage the external teeth of the flex spline aligned with the
major diameter of the wave generator, the second number of internal
teeth being different from the first number of internal teeth;
engaging the teeth of the flex spline with the internal teeth of
the fixed spline and the output spline; elastically deforming the
flex spline with the wave generator such that at least one tooth of
the flex spline engages the internal teeth of the fixed spline and
the output spline; rotating the wave generator such that the flex
spline is elastically deformed while remaining engaged with the
internal teeth of the fixed spline and the output spline such that
the output spline rotates relative to the fixed spline.
21. The method of claim 20, wherein the input shaft is coupled to
an output shaft of a motor, and the method further comprises
rotating the input shaft with the motor.
22. The method of claim 21, wherein the input shaft is coupled to
the output shaft of the motor by a transmission coupling, the
transmission coupling comprising a castellation formed on the input
shaft and a corresponding castellation formed on the output shaft
of the motor, and the method further comprises interlocking the
castellations.
23. The method of claim 20, wherein the input shaft, wave
generator, flex spline, fixed spline, and output spline are
generally tubular having a central bore formed therethrough.
24. The method of claim 20, wherein the wave generator is generally
elliptical in cross section.
25. The method of claim 20, further comprising: providing a needle
bearing between the wave generator and the flex spline; and
reducing friction between the wave generator and the flex spline as
the wave generator is rotated.
26. The method of claim 20, wherein the output spline is rotated at
a speed different than the input shaft.
27. The method of claim 26, wherein the ratio between the speed at
which the output spline rotates and the speed at which the input
shaft rotates is determined by the ratio of the difference in
number of teeth between the output spline and the fixed spline and
the number of teeth on the flex spline.
28. A rotary steerable system comprising: a harmonic gear drive
comprising: an input shaft; a wave generator mechanically coupled
to the input shaft, the wave generator having a varying diameter,
the portion of the wave generator having the largest diameter
defining a major diameter of the wave generator; a flex spline, the
flex spline being generally tubular and including external teeth,
the flex spline positioned about the wave generator; a fixed
spline, the fixed spline being including a first number of internal
teeth that engages the external teeth of the flex spline aligned
with the major diameter of the wave generator; and an output
spline, the output spline including a second number of internal
teeth adapted to engage the external teeth of the flex spline
aligned with the major diameter of the wave generator, the second
number of internal teeth being different from the first number of
internal teeth; a motor having an output shaft mechanically coupled
to the input shaft; an RSS housing mechanically coupled to the
output spline; and a drive shaft extending through an interior of
the harmonic gear drive and the RSS housing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a nonprovisional application which
claims priority from U.S. provisional application No. 62/150,101,
filed Apr. 20, 2015, the entirety of which is hereby incorporated
by reference.
TECHNICAL FIELD/FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to power
transmission mechanisms and specifically to power transmission
mechanisms in downhole tools.
BACKGROUND OF THE DISCLOSURE
[0003] In a wellbore, rotation of components relative to the rest
of the drill string may be desired. Typically, rotation downhole is
generated by a motor such as an electric motor or mud motor.
However, the rotation rate of electric motors and mud motors may be
too rapid for the desired rotation. When a relatively slow rotation
relative to the rest of the drill string is desired, one or more
transmission devices may be required.
SUMMARY
[0004] The present disclosure provides for a harmonic gear drive.
The harmonic gear drive may include an input shaft. The input shaft
may be generally tubular. The harmonic gear drive may include a
wave generator mechanically coupled to the input shaft. The wave
generator may have a varying diameter. The portion of the wave
generator having the largest diameter may define a major diameter
of the wave generator. The harmonic gear drive may include a flex
spline. The flex spline may be generally tubular and may include
external teeth. The flex spline may be adapted to be positioned
about the wave generator and to be elastically flexed thereby as
the wave generator is rotated. The harmonic gear drive may include
a fixed spline. The fixed spline being annular in shape and
including a first number of internal teeth adapted to engage the
external teeth of the flex spline aligned with the major diameter
of the wave generator. The harmonic gear drive may include an
output spline, the output spline being annular in shape and
including a second number of internal teeth adapted to engage the
external teeth of the flex spline aligned with the major diameter
of the wave generator. The second number of internal teeth may be
different from the first number of internal teeth.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The present disclosure is best understood from the following
detailed description when read with the accompanying figures. It is
emphasized that, in accordance with the standard practice in the
industry, various features are not drawn to scale. In fact, the
dimensions of the various features may be arbitrarily increased or
reduced for clarity of discussion.
[0006] FIG. 1 depicts a cross section view of a harmonic gear drive
consistent with at least one embodiment of the present
disclosure.
[0007] FIG. 2 depicts an exploded partial cross section view of the
harmonic gear drive of FIG. 1.
[0008] FIG. 3 depicts a partially disassembled end view of the
harmonic gear drive of FIG. 1.
[0009] FIG. 4 depicts a cross section view of a harmonic gear drive
consistent with at least one embodiment of the present
disclosure.
DETAILED DESCRIPTION
[0010] It is to be understood that the following disclosure
provides many different embodiments, or examples, for implementing
different features of various embodiments. Specific examples of
components and arrangements are described below to simplify the
present disclosure. These are, of course, merely examples and are
not intended to be limiting. In addition, the present disclosure
may repeat reference numerals and/or letters in the various
examples. This repetition is for the purpose of simplicity and
clarity and does not in itself dictate a relationship between the
various embodiments and/or configurations discussed.
[0011] As depicted in FIGS. 1, 2, harmonic gear drive 100 may
mechanically couple between input shaft 101 and output sub 103.
Input shaft 101 may be mechanically coupled to the output shaft of
a motor (not shown). The motor may, for example and without
limitation, be a mud motor, electric motor, or any other motor
suitable for use in a wellbore. In some embodiments, input shaft
101 may be mechanically coupled directly to an output shaft of the
motor. In some embodiments, input shaft 101 may include one or more
power transmission couplings that mechanically couple input shaft
101 to the output shaft of the motor. For example and without
limitation, in some embodiments, the transmission coupling may
include castellations 105 as depicted in FIGS. 1, 2. Castellations
105 may be formed in input shaft 101 and may link with
castellations formed in the output shaft of the motor to allow
rotational forces to be transmitted into input shaft 101 by
interlocking the castellations 105.
[0012] Input shaft 101 may be mechanically coupled to wave
generator 107. In some embodiments, input shaft 101 and wave
generator 107 may be generally tubular, allowing a central bore to
be formed therethrough. In some embodiments in which harmonic gear
drive 100 is used as part of a downhole tool, the central bore may
allow, for example and without limitation, the circulation of
drilling fluid therethrough. Wave generator 107 may be formed as an
integral part of input shaft 101. In some embodiments, wave
generator 107 may constitute an eccentric cam having a varying
diameter. For example, as depicted in FIG. 3, wave generator 107
may be generally elliptical in cross section. As used herein,
"major diameter" of wave generator 107 describes the portion or
portions of wave generator 107 having the largest diameter,
depicted in FIG. 3 as D.sub.M. One having ordinary skill in the art
with the benefit of this disclosure will understand that depending
on the cross-sectional shape of wave generator 107, one or more
major diameters D.sub.M may be formed. "Diameter" as used with
respect to a point along the outer perimeter of wave generator 107
means a line measured from the point through the center to a point
on the perimeter of wave generator 107 opposite the point.
[0013] As depicted in FIGS. 1, 2, wave generator 107 may be
positioned within flex spline 109. Flex spline 109 may be a
generally tubular member having external teeth 111. In some
embodiments, flex spline 109 may engage with fixed spline 113 and
output spline 115. Fixed spline 113 and output spline 115 may be
annular bodies. Fixed spline 113 may be mechanically coupled to
fixed sub 117 such that it does not rotate relative to fixed sub
117. Fixed spline 113 may include internal teeth 114 adapted to
engage external teeth 111 of flex spline 109. Output spline 115 may
be rigidly mechanically coupled to output sub 103. Output spline
115 may include internal teeth 116 adapted to engage external teeth
111 of flex spline 109.
[0014] In some embodiments, flex spline 109 may elastically deform
in response to the rotation of wave generator 107. In some
embodiments, external teeth 111 of flex spline 109 may engage
internal teeth 114 of fixed spline 113 and internal teeth 116
output spline 115 where flex spline 109 is aligned with major
diameter D.sub.M of wave generator 107. As depicted in FIG. 3,
external teeth 111' are engaged with internal teeth 114 of fixed
spline 113, whereas external teeth 111'' are not. Wave generator
107 may slide within flex spline 109 as wave generator 107 is
rotated. In some embodiments, needle bearing 110 may be positioned
between wave generator 107 and flex spline 109. Needle bearing 110
may include a plurality of rollers or needles positioned between
the surfaces of flex spline 109 and wave generator 107 and to
rotate between flex spline 109 and wave generator 107. Needle
bearing 110 may, for example and without limitation, reduce
friction between wave generator 107 and flex spline 109 as flex
spline rotates around wave generator 107. As understood in the art,
needle bearing 110 may, in some embodiments, include additional
components such as races (not shown) without deviating from the
scope of this disclosure. As understood in the art, the teeth of
fixed spline 113 engaged with external teeth 111 of flex spline 109
may thus precess about internal teeth 114 of fixed spline 113 as
wave generator 107 is rotated.
[0015] As the engaged external teeth 111' precess, flex spline 109
rotates relative to fixed spline 113 based on the difference in
number of teeth between flex spline 109 and fixed spline 113.
[0016] As described above with respect to fixed spline 113,
external teeth 111' (aligned with major diameter D.sub.M of wave
generator 107) are likewise engaged with internal teeth 116 of
output spline 115. In some embodiments, output spline 115 may have
a different number of teeth than fixed spline 113. In some
embodiments, output spline 115 may have between 1 and 10 fewer
teeth than fixed spline 113. Because output spline 115 has a
different number of teeth than fixed spline 113, as flex spline 109
rotates within output spline 115 and the engaged external teeth
111' precess about the teeth of output spline 115, output spline
115 is rotated relative to fixed spline 113. The ratio between the
speed at which output spline 115 rotates relative to fixed spline
113 and the speed at which input shaft 101 rotates may be
determined by the ratio of the difference in number of teeth
between output spline 115 and fixed spline 113 and the number of
teeth in fixed spline 113. For example, in an embodiment in which
fixed spline 113 includes 160 teeth and output spline 115 includes
159, output spline 115 may rotate one tooth, or 1/160.sup.th of a
rotation for each rotation of wave generator 107. Thus, such a
harmonic gear drive 100 may have a gear-reduction ration of 160:1
between input shaft 101 and output sub 103. One having ordinary
skill in the art with the benefit of this disclosure will
understand that output spline 115 and fixed spline 113 may include
any suitable number of teeth and may have any tooth differential
without deviating from the scope of this disclosure.
[0017] In some embodiments, as depicted in FIGS. 1, 2, output sub
103 may be a generally tubular member that mechanically couples to
additional equipment (not shown), allowing the additional equipment
such as components of a bottom hole assembly to rotate relative to
fixed sub 117. In some embodiments, output sub 103 and fixed sub
117 may be adapted to support the rotation of input shaft 101. In
some embodiments, one or more bearings 119 may be positioned
between input shaft 101 and output sub 103 and/or fixed sub
117.
[0018] In some embodiments, fixed sub 117 may be mechanically
coupled to fixed spline 113 by, for example and without limitation,
one or more fasteners including linking pin 121 as depicted in FIG.
1. In some embodiments, output spline 115 may likewise be
mechanically coupled to output sub 103 by one or more fasteners
such as linking pin 123.
[0019] As understood by one having ordinary skill in the art with
the benefit of this disclosure, the difference in number of teeth
between fixed spline 113 and output spline 115 may be limited by
the need for the teeth to properly mesh with external teeth 111 of
flex spline 109. In some embodiments, flex spline 109 may include
two sets of external teeth 111, each adapted to mesh with one of
the teeth of fixed spline 113 or output spline 115. As understood
in the art, external teeth 111 in such an embodiment may, for
example and without limitation, include different tooth geometry,
spacing, or numbers. In some embodiments in which different sets of
external teeth 111 are used with fixed spline 113 and output spline
115, fixed spline 113 and output spline 115 may have the same
number of teeth, while each set of external teeth 111 of flex
spline 109 includes a different number of external teeth.
[0020] In some embodiments, as depicted in FIG. 4, input shaft 101'
may be formed as part of rotor 201 of electric motor 200. Electric
motor 200 may include outer housing 203 mechanically coupled to
fixed sub 117. Electric motor 200 may include stator 205. Stator
205, as understood in the art, may include windings 207 positioned
to induce rotating electromagnetic fields into the interior of
stator 205. In some embodiments, electric motor 200 may be an
induction motor. In such an embodiment, rotor 201 may include a
plurality of windings adapted to cause rotation of rotor 201 in
response to the rotating electromagnetic field induced by windings
207. In some embodiments, electric motor 200 may be a permanent
magnet motor. In such an embodiment, rotor 201 may include a
plurality of permanent magnets positioned to cause rotation of
rotor 201 in response to the rotating electromagnetic field induced
by windings 207.
[0021] In some embodiments, by forming input shaft 101' as a part
of rotor 201, backlash may be reduced or eliminated. In some
embodiments, bearings 119 may be sufficient to support and/or
stabilize the entire length of rotor 201, allowing electric motor
200 to operate without additional bearings. Additionally, the
overall length of harmonic gear drive 100 may be reduced.
[0022] In some embodiments, input shaft 101 and wave generator 107
may be formed as an integral unit. In some embodiments, input shaft
101 may have a wall thickness of between 3 mm and 20 mm at its
narrowest point and between 5 mm and 50 mm at its widest,
corresponding with the major diameter D.sub.M of wave generator
107.
[0023] In some embodiments, harmonic gear drive 100 may be used in
rotary steerable system (RSS) 300, depicted schematically in FIG.
4. RSS 300 may include RSS housing 301 and other components as
understood in the art. RSS housing 301 may be mechanically coupled
to output sub 103 and may be rotated relative to the rest of drill
string 305. In some embodiments, driveshaft 303 may be passed
through the interior of input shaft 101. In such an embodiment, the
diameter of driveshaft 303 able to be used with harmonic gear drive
100 may depend on the interior diameter of input shaft 101. In some
embodiments, by forming input shaft 101 as a generally thin-walled
member, the diameter of driveshaft 303 may be maximized for a given
outer diameter of harmonic gear drive 100.
[0024] The foregoing outlines features of several embodiments so
that a person of ordinary skill in the art may better understand
the aspects of the present disclosure. Such features may be
replaced by any one of numerous equivalent alternatives, only some
of which are disclosed herein. One of ordinary skill in the art
should appreciate that they may readily use the present disclosure
as a basis for designing or modifying other processes and
structures for carrying out the same purposes and/or achieving the
same advantages of the embodiments introduced herein. One of
ordinary skill in the art should also realize that such equivalent
constructions do not depart from the spirit and scope of the
present disclosure and that they may make various changes,
substitutions, and alterations herein without departing from the
spirit and scope of the present disclosure.
* * * * *