U.S. patent application number 14/820394 was filed with the patent office on 2015-12-03 for controllable mechanical transmission for downhole applications.
The applicant listed for this patent is Schlumberger Technology Corporation. Invention is credited to Keith R. Nelson, Todor Sheiretov.
Application Number | 20150345598 14/820394 |
Document ID | / |
Family ID | 51703057 |
Filed Date | 2015-12-03 |
United States Patent
Application |
20150345598 |
Kind Code |
A1 |
Nelson; Keith R. ; et
al. |
December 3, 2015 |
Controllable Mechanical Transmission For Downhole Applications
Abstract
A transmission for rotatably coupling an input shaft with an
output shaft about a longitudinal axis is disclosed, which may
include a continuous variable transmission and an output torque
sensing control mechanism. The continuous variable transmission may
be a toroidal disc continuous variable transmission. The output
torque sensing control mechanism may include a spring and an
intermediary output shaft rotatably connected with an output
rotating member of the continuous variable transmission, and the
output shaft may be externally threaded and matable with an
internally threaded portion of the intermediary output shaft.
Inventors: |
Nelson; Keith R.; (Sugar
Land, TX) ; Sheiretov; Todor; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schlumberger Technology Corporation |
Sugar Land |
TX |
US |
|
|
Family ID: |
51703057 |
Appl. No.: |
14/820394 |
Filed: |
August 6, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14054386 |
Oct 15, 2013 |
9115793 |
|
|
14820394 |
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Current U.S.
Class: |
476/1 ; 476/40;
74/640 |
Current CPC
Class: |
F16H 15/503 20130101;
E21B 23/001 20200501; Y10T 74/19 20150115; F16H 59/14 20130101;
B60W 10/04 20130101; E21B 4/006 20130101; Y10T 477/688 20150115;
F16H 61/6647 20130101; B60W 10/109 20130101; F16H 15/40 20130101;
E21B 3/02 20130101 |
International
Class: |
F16H 15/40 20060101
F16H015/40; F16H 61/664 20060101 F16H061/664; E21B 4/00 20060101
E21B004/00; F16H 59/14 20060101 F16H059/14 |
Claims
1. A transmission system for rotatably coupling an input shaft with
an output shaft about a longitudinal axis, the transmission
comprising: a continuous variable transmission; and an output
torque sensing control mechanism.
2. The transmission system of claim 1, wherein at least a portion
of the output shaft is externally threaded, and the output torque
sensing control mechanism comprises: a spring; and an intermediary
output shaft having an internally threaded portion matably
receivable with the externally threaded portion of the output
shaft, the intermediary output shaft movable in the longitudinal
direction as the intermediary output shaft is threaded with the
output shaft.
3. The transmission system of claim 1, wherein the continuous
variable transmission comprises: an input rotating member rotatably
connected to the input shaft; an output rotating member; a toroidal
disc provided between the input rotating member and the output
rotating member; and a toroidal disc arm connected to the toroidal
disc and operable to pivot the toroidal disc between multiple
positions between the input rotating member and the output rotating
member.
4. The transmission system of claim 3, wherein at least a portion
of the output shaft is externally threaded, and the output torque
sensing control mechanism comprises: a spring; and an intermediary
output shaft rotatably connected to the output rotating member, the
intermediary output shaft having an internally threaded portion
matably receivable with the externally threaded portion of the
output shaft, the intermediary output shaft movable in the
longitudinal direction as the intermediary output shaft is threaded
with the output shaft.
5. The transmission system of claim 4, wherein the spring is
positioned proximate to the input shaft, and the output torque
sensing control mechanism further comprises: a first longitudinal
member having ends and provided between the spring and the toroidal
disc arm; and a second longitudinal member having ends and provided
between the toroidal disc arm and the intermediary output
shaft.
6. The transmission system of claim 4, wherein the spring is
provided around at least a portion of the input shaft.
7. The transmission system of claim 4, further comprising a
transmission housing substantially enclosing the output torque
sensing control mechanism and the continuous variable
transmission.
8. The transmission system of claim 7, wherein the transmission
housing includes a window provided proximate to the toroidal disc
arm.
9. A downhole tractor comprising: a motor; an input shaft rotatably
driven by the motor; a transmission system connected to the input
shaft, the transmission system comprising: a continuous variable
transmission, and an output torque sensing control mechanism; and
an output shaft rotatably connected to the transmission system.
10. The downhole tractor of claim 9, wherein the motor is an
electrically driven motor.
11. The downhole tractor of claim 9, wherein the continuous
variable transmission of the transmission system comprises: an
input rotating member rotatably connected to the input shaft; an
output rotating member; a toroidal disc provided between the input
rotating member and the output rotating member; and a toroidal disc
arm connected to the toroidal disc and operable to pivot the
toroidal disc between multiple positions between the input rotating
member and the output rotating member.
12. The downhole tractor of claim 11, wherein the output torque
sensing control mechanism of the transmission system comprises: a
spring; and an intermediary output shaft rotatably connected to the
output rotating member, the intermediary output shaft having an
internally threaded portion matably receivable with the externally
threaded portion of the output shaft, the intermediary output shaft
movable in the longitudinal direction as the intermediary output
shaft is threaded with the output shaft.
13. The downhole tractor of claim 12, wherein the output torque
sensing control mechanism of the transmission system further
comprises: a first longitudinal member provided between the spring
and the toroidal disc arm; and a second longitudinal member
provided between the toroidal disc arm and the intermediary output
shaft, wherein the ends of the first and second longitudinal
members proximate the toroidal disc arm are rounded so as to permit
the toroidal disc arm to pivot while contacting the first and
second longitudinal members.
14. A method for downhole conveyance comprising: providing a
downhole tractor comprising: a motor, an input shaft rotatably
driven by the motor, a transmission system connected to the input
shaft, the transmission system comprising: a continuous variable
transmission, and an output torque sensing control mechanism, an
output shaft rotatably connected to the transmission system, and a
downhole tractor connected to the output shaft; inserting the
downhole tractor, the output shaft, and the transmission system
into a hole; and operating the motor thereby propelling the
downhole tractor.
15. The method of claim 14, further comprising orienting the
transmission system, the output shaft and the downhole tractor
horizontally with respect to earth in order to perform logging
operations with a logging tool operatively connected with the
downhole tractor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 14/054,386, filed Oct. 15, 2013, which is
herein incorporated by reference.
FIELD OF THE DISCLOSURE
[0002] This disclosure relates generally to downhole applications
and, more particularly, the design of transmission systems for use
in downhole applications.
BACKGROUND
[0003] Downhole technology, such as systems and methods for
drilling oil wells and other subterranean holes or shafts, has
historically relied on mechanical gearboxes for regulating output
shaft speed. These mechanical gearboxes typically have a fixed gear
ratio, which results in a fixed operating envelope whereby the
drilling system is designed to produce a maximum torque. Typical
gearboxes can thus deliver a maximum torque as needed, but this
conversely results in slower overall drive shaft angular speed due
to elevated gearbox ratios that may be required. With fixed gear
ratios, either angular speed or torque may need to be sacrificed.
This is particularly problematic in attempting to maintain peak
power of an electric driving motor. Ideally, the torque and angular
speed would respond such that the peak power and premium
performance of the motor is maintained. In a peak power phase, the
drive motor is operating at its highest possible efficiency.
[0004] Continuous Variable Transmissions (CVT) have been known for
a long time and refer to the general class of gearbox transmissions
that can automatically and continuously adjust between a minimum
and a maximum gear ratio. A variety of CVTs have been developed and
utilized in various industries, particularly the automobile
industry in order to optimize engine performance and improve fuel
economy. CVTs have the benefit of allowing the input shaft to
maintain a constant angular velocity over a range of output
velocities. Several types of CVTs include: hydrostatic, toroidal,
variable-diameter pulley, magnetic, infinitely variable,
ratcheting, nautical incremental, cone, radial roller, and
planetary transmission systems.
[0005] In the context of downhole applications, some
conceptualizations of CVT's have been disclosed, however. For
instance, U.S. Pat. No. 7,481,281 to Schuaf, the entirety of which
is incorporated herein by reference, generally discloses a hollow
disc toroidal CVT in FIG. 16 and a ball toroidal CVT in FIG. 17 of
Schuaf. These toroidal CVT's may be utilized in connection with a
hydraulic, or fluidic, turbine assembly, illustrated in FIG. 21 of
Schuaf. In view of Schuaf, a problem remains with downhole
applications in that designed CVTs are still too large for some
downhole applications, are limited in their ability to accommodate
extremely high or sudden rotation resistance differences between
the input and output shafts, as may be experienced from material
resistance in downhole applications, and are limited to usage with
hydraulic drive motors. As such, a more efficient and adaptable
transmission system is needed. Moreover, Schuaf does not allow for
automatic transmission ratio adjustment as a function of output
torque.
BRIEF SUMMARY OF THE DISCLOSURE
[0006] The following presents a simplified summary of the
disclosure in order to provide a basic understanding of some
aspects of the invention. This summary is not an extensive overview
of the invention. It is intended to neither identify key or
critical elements of the invention nor delineate the scope of the
invention. Its sole purpose is to present some concepts of the
invention, in accordance with the disclosure, in a simplified form
as a prelude to the more detailed description that is presented
later.
[0007] In one embodiment of the disclosure, a transmission system
is provided for rotatably coupling an input shaft with an output
shaft about a longitudinal axis. The transmission system may
include a continuous variable transmission and an output torque
sensing control mechanism.
[0008] In another embodiment of the disclosure, a downhole tractor
may include a motor, an input shaft rotatably driven by the motor,
a transmission system connected to the input shaft, with the
transmission system including a continuous variable transmission
and an output torque sensing control mechanism, and an output shaft
rotatably connected to the transmission system.
[0009] In an additional embodiment, a method for downhole
conveyance may include providing a downhole tractor, the downhole
tractor including a motor, an input shaft rotatably driven by the
motor, a transmission system connected to the input shaft, the
transmission system including a continuous variable transmission
and an output torque sensing control mechanism, an output shaft
rotatably connected to the transmission system, and a logging tool
connected to the output shaft; inserting the logging tool, the
output shaft, and the transmission system into a hole; and
operating the motor thereby propelling the downhole tractor.
[0010] The following description and the annexed drawings set forth
certain illustrative aspects of the invention. These aspects are
indicative, however, of but a few of the various ways in which the
principles of the invention may be employed and the present
invention is intended to include all such aspects and their
equivalents. Other advantages and novel features of the invention
will become apparent from the following description when considered
in conjunction with the drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1 illustrates a front perspective sectioned view of an
embodiment of a transmission system in accordance with the
disclosure, with the section taken along the longitudinal axis;
[0012] FIG. 2 illustrates a side sectioned view of the transmission
system of FIG. 1, with the section taken along the longitudinal
axis;
[0013] FIG. 3 illustrates an enlarged front perspective sectioned
view of the transmission system of FIG. 1, with the section taken
along the longitudinal axis;
[0014] FIG. 4 illustrates a rear sectioned view of the transmission
system of FIG. 1, with the section taken along the longitudinal
axis;
[0015] FIG. 5 illustrates a rear sectioned view of the transmission
system of FIG. 1, with the transmission housing removed and with
the section taken along the longitudinal axis;
[0016] FIG. 6 illustrates a top sectioned view of the transmission
system of FIG. 1, with the transmission housing removed and with
the section taken along the longitudinal axis;
[0017] FIG. 7 illustrates a schematic of a downhole tractor having
the transmission system of FIG. 1.;
[0018] FIGS. 8A-8E illustrate a conceptualization of the
functioning of output torque sensing control mechanism as may be
included in embodiments of a transmission system in accordance with
the disclosure;
[0019] FIG. 9A illustrates a tractor power curve diagram with
increased power from an embodiment of a transmission system in
accordance with the disclosure;
[0020] FIG. 9B illustrates an efficiency loading curve diagram
identifying maximum efficiency obtained by using an embodiment of a
transmission system in accordance with the disclosure; and
[0021] FIG. 10 illustrates a conceptualization of the functioning
of a continuous variable transmission system as may be included in
embodiments of a transmission system in accordance with the
disclosure.
DETAILED DESCRIPTION
[0022] The following detailed description and the appended drawings
describe and illustrate some embodiments of the invention for the
purpose of enabling one of ordinary skill in the relevant art to
make and use the invention. As such, the detailed description and
illustration of these embodiments are purely illustrative in nature
and are in no way intended to limit the scope of the invention, or
its protection, in any manner. It should also be understood that
the drawings are not to scale and in certain instances details have
been omitted, which are not necessary for an understanding of the
present invention, such as details of fabrication and assembly. In
the accompanying drawings, like numerals represent like
components.
[0023] In one embodiment of the disclosure, a transmission system
for rotatably coupling an input shaft with an output shaft about a
longitudinal axis may include a continuous variable transmission
and an output torque sensing control mechanism. The transmission
system allows for automatic transmission ratio adjustment as a
function of output torque. As such, the transmission system enables
torque sharing and speed control between multiple prime movers. An
example of where use of the transmission system can be used is in
downhole tractor applications where multiple continuous variable
transmissions may have to work together to provide torque sharing
and speed control with multiple prime movers.
[0024] The transmission system may have at least a portion of the
output shaft externally threaded, and the output torque sensing
control mechanism may include a spring and an intermediary output
shaft having an internally threaded portion matably receiveable
with the externally threaded portion of the output shaft, and the
intermediary output shaft may be movable in the longitudinal
direction as the intermediary output shaft is threaded with the
output shaft. The continuous variable transmission may include an
input rotating member rotatably connected to the input shaft, an
output rotating member, a toroidal disc provided between the input
rotating member and the output rotating member, and a toroidal disc
arm connected to the toroidal disc and operable to pivot the
toroidal disc between multiple positions between the input rotating
member and the output rotating member. A portion of the output
shaft may be externally threaded, and the output torque sensing
control mechanism may include a spring and an intermediary output
shaft rotatably connected to the output rotating member, the
intermediary output shaft having an internally threaded portion
matably receivable with the externally threaded portion of the
output shaft, the intermediary output shaft movable in the
longitudinal direction as the intermediary output shaft is threaded
with the output shaft. The spring may be positioned proximate to
the input shaft, and the output torque sensing control mechanism
may further include a first longitudinal member having ends and
provided between the spring and the toroidal disc arm, and a second
longitudinal member having ends and provided between the toroidal
disc arm and the intermediary output shaft, with the ends of the
first and second longitudinal members proximate the toroidal disc
arm rounded so as to permit the toroidal disc arm to pivot while
contacting the first and second longitudinal members. The spring
may be provided around at least a portion of the input shaft. The
spring moves the continuous variable transmission to a default
known position, which is the lowest gear ratio. The transmission
system may include a transmission housing substantially enclosing
the output torque sensing control mechanism and the continuous
variable transmission. The transmission housing may include a
window provided proximate to the toroidal disc arm.
[0025] In another embodiment of the disclosure, a downhole tractor
may include a motor, an input shaft rotatably driven by the motor,
a transmission system connected to the input shaft, the
transmission system including a continuous variable transmission
and an output torque sensing control mechanism, and an output shaft
rotatably connected to the transmission system. The motor may be an
electrically driven motor. The continuous variable transmission of
the transmission system may include an input rotating member
rotating member rotatably connected to the input shaft, an output
rotating member, a toroidal disc provided between the input
rotating member and the output rotating member, and a toroidal disc
arm connected to the toroidal disc and operable to pivot the
toroidal disc between multiple positions between the input rotating
member and the output rotating member. The output torque sensing
control mechanism of the transmission system may include a spring
and an intermediary output shaft rotatably connected to the output
rotating member, the intermediary output shaft having an internally
threaded portion matably receivable with the externally threaded
portion of the output shaft, the intermediary output shaft movable
in the longitudinal direction as the intermediary output shaft is
threaded with the output shaft. The output torque sensing control
mechanism may further include a first longitudinal member provided
between the spring and the toroidal disc arm, and a second
longitudinal member provided between the toroidal disc arm and the
intermediary output shaft, with the ends of the first and second
longitudinal members proximate the toroidal disc arm rounded so as
to permit the toroidal disc arm to pivot while contacting the first
and second longitudinal members.
[0026] In an additional embodiment of the disclosure, a method for
downhole conveyance may include providing a downhole tractor
including a motor, an input shaft rotatably driven by the motor, a
transmission system connected to the input shaft, the transmission
system comprising a continuous variable transmission and an output
torque sensing control mechanism, an output shaft rotatably
connected to the transmission system, and a logging tool connected
to the output shaft; inserting the logging tool, the output shaft,
and the transmission system into a hole; and operating the motor
thereby propelling the downhole tractor. The method for downhole
conveyance may also include orienting the transmission system, the
output shaft and the logging tool horizontally with respect to the
earth in order to perform logging operation in the hole.
[0027] With reference to FIGS. 1-6, an input shaft 102 and an
output shaft 104 in a downhole application may be rotatably
connected to each other by a transmission system 100. A CVT system
110 may be rotatably connected to input shaft 102 at a first or
input end, and CVT system 110 may be rotatably connected to an
intermediary output shaft 120 at a second or output end opposed to
the first end of CVT 110. Intermediary output shaft 120 may thereby
be rotatably connected to output shaft 104 in order to transitively
connect input shaft 102 with output shaft 104 through transmission
system 100. The input shaft 102, output shaft 104, CVT system 110,
and intermediary output shaft 120 may be individually rotatable
about a central axis 200 extending longitudinally through
transmission system 100.
[0028] Transmission system 100 may include a transmission housing
106 for covering or protecting the internal components of
transmission system 100. In some embodiments, transmission housing
106 is rotationally stable or secure while many of the internal or
partially internal components, including input shaft 102, output
shaft 104, CVT system 110, and intermediary output shaft 120 are
freely rotatable. In order to secure input shaft 102 to housing
106, a housing end 108A may be provided on a first or input end of
housing 106. A housing end 108B may also be provided on a second or
output end of housing 106 for securing output shaft 102 with
transmission system 100. Each housing end 108A, 108B may include
any number of bearings 122 in order to permit the free rotation of
input shaft 102 and output shaft 104 about central axis 200. In
downhole applications, transmission system 100 may have small
dimensions. Some downhole applications, such as wireline tractors,
may have small dimensions due to the narrowness of the hole and
operating space. Embodiments of the transmission system 100 may be
manufactured to accommodate small operating dimensions. For
instance, one embodiment of transmission system 100 features a
housing 106 with a diameter of approximately 1.8 inches. In some
embodiments the diameter of the housing 106 can be less than 3
inches in order to accommodate small downhole applications.
Additionally, the longitudinal length of transmission system 100,
measured from housing end 108A to housing end 108B, may be
approximately 6 inches in one embodiment. In some embodiments, the
length of transmission system 100 may be between 4 and 10
inches.
[0029] CVT system 110 may be a toroidal disc CVT system, as shown
for instance in the illustrated embodiment, however other known or
to be developed CVT systems for rotatably connecting input shaft
102 with intermediary output shaft 104 are contemplated within the
disclosure. Illustrative CVT systems can include those that use
balls, discs, and the like. Toroidal CVT system 110 may include a
first or input rotating member 112, a second or output rotating
member 114, and any number of toroidal discs 116 provided between
first and second rotating members 112, 114. The toroidal discs 116
may be held between first and second rotating members 112, 114 by a
disc arm 118. In the illustrated embodiment, two toroidal discs 116
are provided. It should be appreciated by those of ordinary skill
in the art that CVT system 110 may operate to provide an infinite
number of gear ratios between first and second rotating members
112, 114 depending on the position of the toroidal discs 116. By
virtue of their direct or transitive connection with members 112,
114, there may be an infinite number of gear ratios between input
shaft 102 and output shaft 104. The rolling or moving between gear
positions of toroidal discs 116 may be accomplished in part by the
swinging of disc arm 118. Each disc arm may be pivotally secured to
a portion of system 110. In order to accommodate the swinging of
disc arm 118, a space or window 124 may be provided in housing 106
so that disc arm 118 will not contact or be interfered with by
housing 106 as disc arm 118 swings between gears ratios.
[0030] Fasteners 130 may be provided for securing input shaft 102
with first rotating member 112. The fasteners 130 may also be
provided for securing intermediary output shaft 120 with second
rotating member 114. Fasteners 130 may be bolts, screws or any
other known or to be developed fastening devices.
[0031] In addition to CVT system 110, an output torque sensing
control mechanism 150 may be integrated into transmission system
100. Output torque sensing control mechanism 150 may include a
spring or other biasing member 152, arms or longitudinal members
154, and an intermediary output shaft housing 156. Intermediary
output shaft housing 156 may be provided to secure intermediary
output shaft 120 as well as to engage with the longitudinal members
154. Intermediary output shaft housing 156 may include a first
portion 156A and a second portion 156B, each clampable together and
including an aligned aperture for receiving a portion of
intermediary output shaft 120 as well as output shaft 104. Bearings
122 may be provided between intermediary output shaft housing
portions 156A, 156B and intermediary output shaft 120 in order to
permit free rotation of intermediary output shaft 120. Intermediary
output shaft 120 may also include wings 162 which extend away
radially away from the intermediary output shaft 120, and at least
a distal portion of wings 162 may be clamped by a pair of bearings
122 provided within intermediary output shaft housing 156.
[0032] Intermediary output shaft 120 may be coupled to rotating
member 114 at a first end, and connected with output shaft 104 at a
second end. Intermediary output shaft 120 may include a bore 158
for receiving an end of output shaft 104. Bore 158 may be
internally threaded while the end of output shaft 104 may be
externally threaded and matable with the internal threading of bore
158. Additionally, intermediary output shaft housing 156 and
intermediary output shaft 120 may be operable to move or translate
longitudinally along axis 200 as intermediary output shaft 120 is
threaded onto output shaft 104. This threading operation enables
output torque sensing control mechanism 150 to function as
described herein, in accordance with the disclosure. Furthermore,
spring 152, which may be coiled or wrapped about a portion of input
shaft 102, may operate to provide a longitudinal translation force
against intermediary output shaft housing 156 through arms 154.
[0033] In some embodiments, arms 154 are composed of a first arm
154A and a second arm 154B. First arm 154A may be provided between
spring 152 and pivotable disc arm 118, and second arm 154B may be
provided between the opposed side of pivotable disc arm 118 and
intermediary output shaft housing 156, and connected to first
intermediary output shaft housing portion 156A. The ends of first
and second arms 154A, 154B, which contact pivotable disc arm 118
may be rounded so as to as to permit disc arm 118 to pivot or swing
between gear ratios. First and second arms 154A, 154B may be
provided between each disc arm 118 included in any particular
embodiment. In some embodiments, an intermediary disc 158 may be
provided between spring 152 and arm 154. The pivotable disc arm may
have a unique shape to mitigate or create a linear relationship to
the gear ratio; for example, the pivotable disc arm 118 can have a
shape to allow the disc arm 118 to maintain contact with the arm
154.
[0034] A longitudinal rod 160 may be insertable through first and
second rotating members 112, 114 along longitudinal axis 200.
Bearings 122 may be provided on either end of rod 160 in order to
permit the rod to freely rotate with respect to the CVT
transmission 110. An output end 162 of rod 160 may be matable with
intermediary output shaft 120 in order to permit mutual rotation of
rod 160 and intermediary output shaft 120 when they are mated. The
rod 160 can ensure that the first and second rotating members 112,
114 are in full compression, binding the toroidal disc 116.
[0035] FIG. 7 illustrates a schematic of a downhole tractor having
the transmission system of FIG. 1. In the illustrated embodiment, a
downhole tractor 700 includes a drive motor 300, input drive shaft
102, transmission system 100, and an output shaft 104 for driving
wheels, grippers, or tracks (not shown) of the downhole
tractor.
[0036] The drive motor 300 may be connected to input drive shaft
102. The drive motor 300 can be a direct current motor or an
alternating current motor. The drive motor 300 can be a three-phase
motor.
[0037] The input drive shaft 102 is connected to transmission
system 100, comprising CVT 110 and output torque sensing control
mechanism 150, which is connected to output shaft 104. Transmission
system 100 may thus operate using the output torque sensing control
mechanism 150 as a mechanism that determines how much torque is
desired and mechanically adjusts the CVT 110 to provide the optimum
results of the gear ratio. The CVT 110 may then operate as the
mechanism that enables the gear ratio between the input shaft 102
and the output shaft 104 to be altered, for instance between 0.5:1
and 2.0:1 in accordance with one embodiment.
[0038] FIGS. 8A-8E illustrate the functional concept of output
torque sensing control mechanism 150 in accordance with one
embodiment. FIGS. 8A-8D are sequentially ordered to illustrate the
longitudinal translation, which occurs as rolling resistances are
changed between a first end 400A of a shaft and a second end 400B
of a shaft. In FIG. 8A, second end 400B experiences an increase in
rolling resistance from a previous equilibrium state. In order to
equalize the rolling resistances, translation of the nut occurs due
to its threadable engagement with the shaft. At FIG. 8B, the nut
stops once the rolling resistances 400A, 400B have reached an
equilibrium. In FIG. 8C, the rolling resistance of 400B has
decreased and, by operation of spring 152, the nut is translated
back to equilibrium in FIG. 8D.
[0039] In the embodiment illustrated in FIG. 8E, input drive shaft
is threaded on the end and screwed into an adjoining tubular output
drive shaft, however it should be appreciated that in other
embodiments, such as the embodiment illustrated in FIGS. 1-6, the
output shaft 104 may threaded on the end and screwed into an
adjoining tubular shaft 158. In either embodiment, the threading
causes the threaded tubular shaft 158 to move with linear motion
towards the threaded shaft 104. This linear motion can be
mechanically linked to the CVT 110, for instance by contact between
arms 154A, 154B and disc shafts 118. This matable threading of the
shafts of output torque sensing control mechanism 150 can be
variably designed to establish a relationship between the motor
peak power setting and the output torque. For instance, a fine
thread pitch may be utilized to offer greater mechanical leverage,
while a coarser thread may be utilized to offer greater linear
motion (which in embodiment where arms 154A, 154B are linked with
disc shaft 118, may in turn offer greater maximum gear ratios for
CVT 110 by increasing the maximum pitch angle of disc shaft 118).
The shifting spring 152 may operate to move the tubular shaft back
to a known position when no torque is applied by the output shaft.
The known position would return the mechanically connected CVT 110
to a position where the gear ratio is less than 1; for example, the
gear ratio can be about 0.5. This would happen, for instance, if
the motor was turned off or experiencing minimal loading.
[0040] One downhole application of transmission system 100 may be
implemented with a wireline tractor. A motor spins a drive shaft
that is connected to a series of gearboxes, which mechanically
drive a wheel that is in contact with a downhole casing or
borehole. Based on the amount of tractor force to be applied to
convey or push payload services in horizontal environments, the
desired torque may be outputted. Where gear ratios are fixed, and
not variable, the tractors may be limited on downhole tractor speed
by the amount of maximum expected applied torque or tractor force.
By its inclusion in transmission system 100, CVT 110 allows the
motor 300 under light torque loading to increase the overall drive
shaft RPM, which thereby increases the forward tractor linear
speed. Moreover, the CVT 110 can be designed to ensure that as the
torque loading increases the gear ratio is increased to reduce
tractor speed and maintain the drive motor operating in the peak
power position for highest efficiency. The highest efficiency
position is factor to be considered as the demands on surface power
supplies, limitations on electrical transmission through collectors
and cables, and motor equipment safety may be considered.
[0041] Other downhole applications, may involve a bit cutting
downhole into an obstruction, casing, or borehole wall. As the bit
drills in, fluctuations in the drill torque are experienced by the
drive motor assembly. In worst case situations, the drill bit can
stall the motor by biting too hard or binding with the obstruction
casing or borehole. By utilizing a variable gear ratio mechanism,
the gear ratio would change such that the torque demands of the
motor would be within the capability of the drive motor. The
mechanism would continue to increase the gear ratio, which slows
the drill bit, but increases the amount of torque applied to the
drilling area.
[0042] Referring now to FIGS. 9A and 9B, graphic illustrations are
provided to show attainable improved performance utilizing the
disclosed transmission system in downhole applications. In FIG. 9A,
a tractor power curve downhole illustrates the relationship between
tractor force (or load) and speed. As a drive motor speed
increases, the tractor load capability decreases. The tractor power
curve represents the fixed operating environment for known
embodiments where it was previously impossible to go faster than
3500 fph or slower than 500 fph. By utilizing transmission system
100, the speed may be further increased as shown by the
extrapolated line, while maintaining the same or nearly the same
motor power level. As the load is reduced to a minimal amount, the
gear ratio decreases more and more to allow the output shaft to
spin fast while the motor rotations per minute stay at its maximum
physical capability. Conversely, as the output shaft becomes more
loaded, the gear ratio is increased which thereby slows the shaft,
but increases the loading capacity. Essentially, the power curve
becomes dynamic, which allows it to expand into operating envelopes
that have been otherwise inaccessible due to downhole hardware
limitations of fixed gear ratio systems.
[0043] Another advantage is that the transmission system 100 can be
utilized to drive the loading to stay within a drive motor's peak
power position. That is, the gear ratio can change in order to
maintain maximum efficiency of a downhole motor for peak
performance. The efficiency loading curve of FIG. 9B illustrates a
peak efficiency, for one embodiment of a downhole application, at
approximately 5-lb-in. If the motor outputs any more or less
loading, the loss of operating efficiency results in wasted energy.
By utilizing the transmission system 100, the variable gear ratio
can be used to reduce or increase the motor torque to be the
highest efficiency. An example of this in practice would be a
downhole tractor conveying a tool in an openhole well. The load on
the downhole tractor will change when washouts, obstructions, or
other abnormalities are encountered, by utilizing transmission
system 100, the gear ratio can continuously change to increase or
decrease the amount of torque in order to maintain peak power
efficiency through the various naturally occurring torque
fluctuations of downhole conveyance.
[0044] FIG. 10 illustrates a conceptualization of a toroidal disc
CVT, which may be CVT 110 in embodiments of the disclosure. The
toroidal disc illustrated on the left side is the input shaft while
the toroidal disc on the right side is the output shaft. These
discs are connected by a roller disc, labeled as D.sub.R. As the
D.sub.R disc spins about point (X.sub.C, Y.sub.C) it simultaneously
contacts both toroidal discs. As illustrated, the D.sub.R disc
touches the input shaft at point (X.sub.MN, Y.sub.MN) and the
output shaft at point (X.sub.MX, Y.sub.MX). A change in angular
velocity and torque generated by roller disc D.sub.R touching the
toroidal discs at these two distinct points. The gear ratio is
created by the diameter D.sub.MX divided by D.sub.MN. By pivoting
roller disc D.sub.R about point (X.sub.C, Y.sub.C), the diameters
D.sub.MX and D.sub.MN change, which results in a variable gear
ratio. The output torque sensing control mechanism 150 may be
mechanically linked to the roller disc D.sub.R and creates the
pivot motion. As illustrated in FIGS. 1-6, this mechanical linkage
may occur at arms 154A, 154B. By configuring the ends of arms 154A,
154B to be rounded, the disc D.sub.R is may freely pivot as arms
154 are longitudinally displaced. As output torque sensing control
mechanism 150 demands more or less torque, a corresponding pivoting
motion of the D.sub.R about (X.sub.C, Y.sub.C) is created.
[0045] The descriptions set forth above are meant to be
illustrative and not limiting. Various modifications of the
invention, in addition to those described herein, will be apparent
to those skilled in the art from the foregoing description. Such
modifications are also intended to fall within the scope of the
concepts described herein. The disclosures of each patent, patent
application and publication cited or described in this document are
hereby incorporated herein by reference, in their entireties.
[0046] The foregoing description of possible implementations
consistent with the present disclosure does not represent a
comprehensive list of all such implementations or all variations of
the implementations described. The description of some
implementation should not be construed as an intent to exclude
other implementations. For example, artisans will understand how to
implement the invention in many other ways, using equivalents and
alternatives that do not depart from the scope of the invention.
Moreover, unless indicated to the contrary in the preceding
description, none of the components described in the
implementations are essential to the invention. It is thus intended
that the embodiments disclosed in the specification be considered
as illustrative, with a true scope and spirit of the invention
being indicated by the following claims.
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