U.S. patent application number 10/763473 was filed with the patent office on 2005-07-28 for actuation assembly for variable geometry turbochargers.
Invention is credited to Arnold, Steven Don, Haug, Peter M..
Application Number | 20050160731 10/763473 |
Document ID | / |
Family ID | 34795039 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050160731 |
Kind Code |
A1 |
Arnold, Steven Don ; et
al. |
July 28, 2005 |
ACTUATION ASSEMBLY FOR VARIABLE GEOMETRY TURBOCHARGERS
Abstract
Improved actuation assemblies are used with variable geometry
turbochargers comprising a plurality of movable aerodynamic vanes
attached to a movable unison ring that is coupled to an actuator.
The actuation assembly includes a crank arm that is attached at a
first end to the actuator, and at a second end to the unison ring.
A first gear member is attached to the crank arm second end and
includes teeth. The unison ring includes a second gear member
attached thereto that also comprises teeth. The teeth of the first
and second gear-members are cooperatively engaged with one another.
The second gear member is movably attached to the unison ring to
maintain predetermined distance between the first and second gear
members during operation of the turbocharger and related thermal
movement of the unison ring.
Inventors: |
Arnold, Steven Don; (Rancho
Palos Verdes, CA) ; Haug, Peter M.; (Redondo Beach,
CA) |
Correspondence
Address: |
Ephraim Starr, Division General Counsel
Honeywell International Inc.
23326 Hawthorne Boulevard, Suite #200
Torrance
CA
90505
US
|
Family ID: |
34795039 |
Appl. No.: |
10/763473 |
Filed: |
January 23, 2004 |
Current U.S.
Class: |
60/602 |
Current CPC
Class: |
F02B 37/24 20130101;
Y02T 10/144 20130101; Y02T 10/12 20130101; F05D 2230/232 20130101;
F05D 2250/411 20130101; F01D 17/165 20130101; F05D 2220/40
20130101; F05D 2260/4031 20130101; F05D 2250/281 20130101 |
Class at
Publication: |
060/602 |
International
Class: |
F02D 023/00 |
Claims
What is claimed is:
1. An actuation assembly for moving in unison a plurality of
aerodynamic vanes disposed within a variable geometry turbocharger
that includes an actuator coupled to a moving unison ring, the
unison ring being disposed within a turbocharger turbine housing
and attached to the plurality of aerodynamic vanes, the actuator
comprising a crank arm rotatably disposed within the turbine
housing and attached at a first end to the actuator and to a second
end to the unison ring, wherein the crank arm second end includes a
first gear member comprising teeth, and the unison ring includes a
second gear member comprising teeth, wherein the teeth of the first
and second gear members are cooperatively engaged with one another,
and wherein the second gear member is coupled to the unison ring by
cooperative surface features to permit unison ring thermal
expansion and contraction movement during turbocharger operation
while maintaining engagement between the first and second gear
members.
2. (canceled)
3. The actuation assembly as recited in claim 1 wherein the first
gear member is a pinion gear and the second gear member is a rack
gear.
4. (canceled)
5. The actuation assembly as recited in claim 1 wherein the
cooperative surface features comprise a tongue that cooperates
within an opening, and wherein the tongue and opening are sized to
permit thermal expansion and contraction movement between the
unison ring and rack gear.
6. The actuation assembly as recited in claim 5 wherein the tongue
projects outwardly from the unison ring, and the opening is
disposed within a surface of the rack gear.
7. A turbocharger assembly comprising: a turbine housing; a turbine
wheel carried within the turbine housing and attached to a shaft; a
plurality of vanes pivotably disposed within the turbine housing; a
moving unison ring attached to the plurality of vanes to move the
vanes in unison with one another, the unison ring including a first
gear member having teeth attached thereto; a crank arm disposed
within the turbine for moving the unison ring, the crank arm
including a second gear member at one of its ends and having teeth
that are engaged with the teeth of the first gear member; and means
for maintaining engagement between the first and second gear
members during operation of the turbocharger, the means being an
cooperative surface features between the unison ring and the first
gear member.
8. The turbocharger assembly as recited in claim 7 wherein the
first gear member is a rack gear and the second gear member is a
pinion gear.
9. (canceled)
10. (canceled)
11. The turbocharger assembly as recited in claim 9 wherein the
cooperative surface features comprise a tongue that projects from
one of the unison ring and rack gear, into an opening of the other
of the unison ring and rack gear.
12. A turbocharger assembly comprising: a turbine housing; a
turbine wheel carried within the turbine housing and attached to a
shaft; a plurality of vanes pivotably disposed within the turbine
housing; a moving unison ring attached to the plurality of vanes to
move the vanes in unison with one another, the unison ring
including a rack gear having teeth attached thereto; a crank arm
disposed within the turbine for affecting movement of the unison
ring, the crank arm including a pinion gear at one of its ends that
has teeth that are engaged with the teeth of the rack gear; wherein
the rack gear is attached to the unison ring by cooperative surface
features to permit unison ring thermal movement during turbocharger
operation while maintaining a tolerance between the pinion gear and
rack gear.
13. A method for actuating a plurality of movable aerodynamic vanes
within a variable geometry turbocharger, the method comprising the
step of rotating a crank arm that is disposed within a turbine
housing of the turbocharger, the crank arm having a first gear
member attached at one of its ends that is engaged with a second
gear member that is attached to a moving unison ring by cooperative
surface features, the unison ring being disposed within the
turbocharger, wherein the step of rotating the crank arm causes the
unison ring to be rotated by the engagement of the first and second
gear members, and wherein the unison ring is coupled to the
plurality of aerodynamic vanes to move the vanes in unison.
Description
FIELD OF INVENTION
[0001] This invention relates generally to the field of
turbochargers and, more particularly, to variable geometry
turbochargers having a plurality of movable aerodynamic vanes, and
an actuation assembly for more efficiently and dependably moving
the vanes within the turbocharger.
BACKGROUND OF THE INVENTION
[0002] Turbochargers for gasoline and diesel internal combustion
engines are devices known in the art that are used for pressurizing
or boosting the intake air stream, routed to a combustion chamber
of the engine, by using the heat and volumetric flow of exhaust gas
exiting the engine. Specifically, the exhaust gas exiting the
engine is routed into a turbine housing of a turbocharger in a
manner that causes an exhaust gas-driven turbine to spin within the
housing.
[0003] The exhaust gas-driven turbine is mounted onto one end of a
shaft that is common to a radial air compressor mounted onto an
opposite end of the shaft and housed in a compressor housing. Thus,
rotary action of the turbine causes the air compressor to spin
within the compressor housing. The spinning action of the air
compressor causes intake air to enter the compressor housing and be
pressurized or boosted a desired amount before it is mixed with
fuel and combusted within the engine combustion chamber.
[0004] In a turbocharger, it is often desirable to control the flow
of exhaust gas to the turbine to improve the efficiency or
operational range of the turbocharger. Variable geometry
turbochargers (VGTs) have been configured to address this need. A
type of such VGT is one having a variable or adjustable exhaust
nozzle, referred to as a variable nozzle turbocharger.
[0005] Different configurations of variable nozzles have been
employed in variable nozzle turbochargers to control the exhaust
gas flow. One approach taken to achieve exhaust gas flow control in
such VGTs involves the use of multiple vanes, which can be fixed,
pivoting and/or sliding, positioned annularly around the turbine
inlet.
[0006] The vanes are commonly controlled by a unison ring to alter
the throat area of the passages between the vanes, thereby
functioning to control the exhaust gas flow into the turbine. The
unison ring is disposed within the turbine housing and is rotated
by an actuator assembly to move the vanes in a manner to provide
the desired control of gas flow. VGTs known in the art make use of
a crank arm to translate an actuation movement provided by an
actuator to the unison ring. The crank arm is connected to the
unison ring by a pin and slot arrangement, wherein the crank arm
includes an offset pin that is engaged within a slot in the unison
ring. Configured in this manner, actuation of the crank arm causes
the offset pin to be moved in a clockwise or counter-clockwise
direction, thereby effecting rotational movement of the unison ring
in a respective direction.
[0007] It is known that VGTs comprising such a crank arm-unison
ring arrangement can be prone to suffer from two types of issues. A
first issue involves sliding friction and the fact that the crank
arm pin that engages the unison ring is know to incur a severe
amount of sliding friction, which can cause the pin and/or unison
ring slot to wear in an aggressive manner. Such wear can impact the
desired interplay of the crank arm and unison ring by not providing
the full range of desired movement, or ultimately can cause the
crank arm pin to break, thereby prohibiting desired unison ring
movement.
[0008] A second issue involves the high and cyclic temperatures
that the VGT turbine housing and all parts disposed therein are
subjected to. In this aggressive temperature environment, the VGT
parts are exposed to constant thermal expansion and contraction
cycles. Depending on the location, size, and materials used to form
the parts that contact one another, i.e., the crank arm pin and
unison ring slot, these interconnecting parts may undergo different
degrees of thermal expansion and contraction. Such different
thermal expansion and contraction characteristics can cause the
crank arm pin to bind within the unison ring slot, thereby
impairing efficient and dependable unison ring actuation.
[0009] It is, therefore, desired that an improved actuation
assembly be constructed in a manner that minimizes or eliminates
potential impairments to proper vane actuation caused either by
unwanted sliding friction or thermal expansion/contraction binding
between coupled actuating members. It is desired that such an
improved actuation assembly be constructed in a manner capable of
providing reliable vane actuation movement after repeated cycles of
turbocharger operation. It is further desired that such an improved
actuation assembly be configured in a manner permitting retrofit
use in existing VGTs without significant modification.
SUMMARY OF THE INVENTION
[0010] Improved actuation assemblies, constructed in accordance
with the principles of this invention, are specifically designed
for use with variable geometry turbochargers comprising a plurality
of movable aerodynamic vanes that are disposed within a
turbocharger turbine housing. The turbocharger includes an actuator
that is coupled, by virtue of the actuation assembly, to a movable
unison ring also disposed within the turbine housing. The unison
ring is attached to the plurality of aerodynamic vanes.
[0011] The actuation assembly comprises a crank arm that is
rotatably disposed within the turbine housing. The crank arm is
attached at a first end to the actuator, and is attached at a
second end to the unison ring. A first gear member is attached to
the crank arm second end, and includes a number of teeth. The
unison ring includes a second gear member attached thereto that
also comprises a number of teeth. The teeth of the first and second
gear members are cooperatively engaged with one another.
[0012] The actuation assembly comprises means for maintaining a
predetermined distance between the first and second gear members
during operation of the turbocharger and related thermal movement
of the unison ring. In an example embodiment, such means is
provided in the form of cooperative coupling members between the
unison ring and second gear member, whereby such cooperative
coupling members are configured to both provide a dependable
attachment therebetween, as well as allow-for a predetermined
amount of movement of the second gear member on the unison ring so
as to maintain a desired distance or tolerance between the first
and second gear members during turbocharger operation and thermal
expansion of the unison ring relative to the crank arm.
[0013] Improved actuation assemblies of this invention operate to
minimize or eliminate potential impairments to proper vane
actuation caused either by unwanted sliding friction or thermal
expansion/contraction binding between coupled actuating
members.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention will be more clearly understood with reference
to the following drawings wherein:
[0015] FIG. 1 is a perspective view of a turbine side of a prior
art variable geometry turbocharger;
[0016] FIG. 2 is a side elevational view of the turbine housing
with a portion cut-away to show an improved actuation assembly
constructed according to the principles of this invention; and
[0017] FIG. 3 is a detailed side elevational view of the improved
actuation assembly of FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The invention, constructed in accordance with the principles
of this invention, comprises an improved actuation assembly for
causing rotational movement of a unison ring used in a
turbocharger, including but not limited to a variable geometry
turbocharger (VGT). For convenience, an exemplary embodiment using
a VGT will be described throughout this specification. However, it
will be readily understood by those skilled in the relevant
technical field that the improved crank arm assembly of the present
invention could be used in a variety of turbocharger
configurations.
[0019] FIG. 1 illustrates a known VGT 10 that includes a turbine
housing 12. An exhaust gas-driven turbine 17 is rotatably disposed
within the housing and is mounted onto one end of a shaft 18 that
is common to a radial air compressor (not shown) mounted onto an
opposite end of the shaft 18 and housed in a compressor housing.
The turbine housing 12 is configured having an exhaust gas inlet 14
that is configured to direct exhaust gas radially to the turbine
wheel, and an exhaust gas outlet (not shown) that is configured to
direct exhaust gas axially away from the turbine wheel 17 and the
turbine housing 12. A volute (not shown) is connected to the
exhaust inlet 14, and an outer nozzle wall is incorporated in the
turbine housing adjacent the volute. Exhaust gas, or other high
energy gas supplying the turbocharger 10, enters the turbine
housing through the inlet 14 and is distributed through the volute
in the turbine housing 12 for substantially radial delivery to the
turbine wheel 17 through a circumferential nozzle entry.
[0020] Multiple vanes 22, which can be fixed, pivoting and/or
sliding, are positioned annularly around an inlet portion 20 of the
turbine housing. The vanes 22 are commonly controlled to alter the
throat area of the passages between the vanes, thereby functioning
to control the exhaust gas flow into the turbine. An arm or post 26
is interposed between an axial surface of the vanes and a nozzle
ring, and is used to connect the vanes within the turbine
housing.
[0021] A unison ring 34 is positioned adjacent the vanes, over an
axial surface opposite from that connected to the arms or ports,
and is movably disposed within +he turbine housing 12, radially
around the turbine wheel 17. Generally speaking, the nozzle and
unison ring assembly operate to control the flow of exhaust gas
entering the turbine housing 12 to the turbine wheel 17 by virtue
of moving the vanes, thereby regulating turbocharger operation. The
assembly includes the nozzle ring 24 that is attached to, for
example, a nozzle wall of the turbine housing 12, and that is
positioned concentrically around the turbine wheel 17. The unison
ring 34 is configured to move the plurality of vanes in unison.
[0022] The vanes 22 are positioned concentrically around and
upstream of the turbine wheel 17. The vanes are moved in unison by
the unison ring to control the amount of exhaust gas flow directed
to the turbine. The vanes each comprise a member or feature that is
configured to cooperate with a complementary member or feature in
the unison ring. In en example embodiment, the vane includes an
actuation tab 30 that projects outwardly from an axial vane surface
opposite from the nozzle ring. The actuation tabs 30 are sized,
shaped, and positioned to be engaged within respective actuation
slots 32 in the unison ring. Configured in this manner, in
conjunction with the pivoting mounting of the vanes with the nozzle
ring, rotational clockwise or counter-clockwise movement of the
unison ring 34 within the turbine housing effects respective
opening and closing movement of the vanes.
[0023] The unison ring 34 is rotated within the turbine housing 12
by cooperation with a crank arm 36. The crank arm 36 is coupled at
one of its ends to an actuator (not shown) that is configured to
rotate the crank arm in a clockwise or counter-clockwise direction
to effect desired unison ring movement. The crank arm 36 includes
an offset pin 38 projecting from its opposite end that is sized,
shaped and positioned to engage an elliptical slot 40 in the unison
ring 34. Configured in this manner, rotation of the crank arm
causes the offset pin 38 to effect rotational movement of the
unison ring, via its engagement within the slot 40. In an example
embodiment, crank arm 36 rotation of approximately 120 degrees can
cause the unison ring 34 to rotate approximately 20 degrees.
[0024] FIGS. 2 and 3 illustrate an example embodiment of an
improved actuation assembly 42 constructed in accordance with this
invention. The assembly comprises a crank arm 44 having a pinion
gear 46 (crank arm pinion) at an axial end of the arm that is
coupled to or that connects with the unison ring 48. The pinion
gear 46 comprises a number of gear teeth 47 and can be attached to
the crank arm by conventional method, e.g., by threaded attachment,
welding or the like.
[0025] A rack gear (gear segment) 50 is attached to the unison ring
48. The rack gear 50 may be connected to the unison ring 48 by
conventional attachment method such as welding or the like.
However, in a preferred embodiment, the rack gear 50 is coupled to
the unison ring 48 by engagement between cooperative rack gear and
unison ring surface features or coupling members. More
specifically, the unison ring and rack gear can be joined together
by cooperative coupling members that are designed to both provide a
secure point of attachment, and to allow for a desired degree of
thermal expansion/contraction movement between the rack gear and
unison ring to thereby minimize or eliminate altogether unwanted
thermally induced binding between the pinion gear 46 and rack gear
50.
[0026] In an example embodiment, the cooperative coupling members
are configured to provide a tongue and groove attachment
arrangement. Specifically, the unison ring 48 is configured having
a tongue 52 that projects a distance outwardly therefrom, and that
is sized and shaped to be accommodated by a groove or opening 54
disposed within a axially-facing surface of the rack gear 50.
Alternatively, if desired, the rack gear could comprise the tongue
coupling member, and the unison ring could comprise the groove or
opening coupling member. The rack gear 50 is preferably attached to
an axially-facing surface of the unison ring 48 that is opposite
from the vanes, i.e., a surface that is directed away from the
turbine wheel.
[0027] In a preferred embodiment, the groove or opening 54 is sized
having an additional degree of clearance for the tongue 52 to
permit a desire degree of unison ring thermal movement, e.g., to
permit the unison ring to grow or shrink radially relative to the
rack gear 50 in response to cyclic thermal expansion and
contraction during turbocharger operation. Configured in this
manner, the actuation assembly of this invention operates to
minimize or eliminate altogether unwanted thermally induced binding
between the pinion gear 46 and rack gear 50.
[0028] both greatly reduce the amount of crank arm 44 rotation
needed to effect a desired unison ring movement, and minimize the
presence of sliding friction and thermally induced binding inherent
in the conventional design.
[0029] When rotated, the crank arm pinion 46 operates to drive the
rack gear segment 50 in a circular arc around a centerline of the
turbocharger 10. The rack gear 50 drives the unison ring 48
circumferentially with a purely tangential force and zero relative
motion except when the unison ring 48 expands or contracts radially
due to transient thermal changes. Thereby, operating to greatly
reduce the amount of friction inherent in unison ring
actuation.
[0030] The rack gear 50 is piloted on a diameter 56 similar to that
of the unison ring 48. Thus, the theoretical center of the gear
segment 50 is the center of the pilot diameter 56. During
turbocharger operation, the thermal expansion growth of the rack
gear 50 (when taken independent of the unison ring) is relatively
small, as the dimension along the height of the rack gear from the
pilot diameter 56 to the tooth profile is small. Thus, the thermal
growth impaction the theoretical centerlines of the rack gear 50
and the pinion gear 46 is dramatically reduced.
[0031] The unison ring, however, being a large diameter hoop
undergoes a relatively large amount of thermal growth, thereby
operating to otherwise urge the rack gear towards the pinion gear.
This is why the rack gear and unison ring coupling members have
been specifically designed to accommodate a desired degree of
unison ring thermal expansion/contraction movement while at the
same time maintaining a desired distance between the rack gear and
pinion gear centerlines, i.e., while maintaining a desired
tolerance between the engaging gear teeth of the gear rack and
pinion gear to avoid unwanted binding.
[0032] It is desired that the pinion gear and rack gear each be
configured having a number of teeth that will provide a desired
degree of unison ring movement relative to crank arm rotation. In
an example embodiment, it is desired that the gear ratio between
the engaging gear members be such as to provide a complete range of
unison ring movement, and thus vane opening and closing movement,
by rotating the crank arm in the range of from about 30 to 180
degrees. The amount of crank arm rotation needed to provide a
complete range of unison ring movement is dependent on a number of
design factors that can vary depending on the particular
turbocharger design and application.
[0033] In an example embodiment, complete unison ring movement is
achieved by rotating the crank arm a total of 120 degrees, i.e.,
from -60 degrees to +60 degrees. Ideally, it is desired that the
amount of crank rotation to effect complete unison ring movement be
as low as possible to minimize the sliding friction component
between the two members. However, the low end of crank arm rotation
can also be influenced by the degree of control that is desired
over the unison ring movement. For example, if the gear ratio
between the gear members are such that complete unison ring
movement is achieved with only a slight crank arm rotation, the
ability to precisely control the degree of unison ring movement may
be reduced. Accordingly, the degree of control over unison ring
movement is one of the design factors to be considered.
[0034] Having now described the invention in detail as required by
the patent statutes, those skilled in the art will recognize
modifications and substitutions to the specific embodiments
disclosed herein. Such modifications are within the scope and
intent of the present invention.
* * * * *