Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF 'I'HE INVENTION
This invention relates to turbochargers and control
devices therefor. More specifically, this invention relates
to an improved pressure-responsive actuator for controlling
the operation of a turbocharger.
Turbochargers are well known in the prior art, and
typically comprise a turbine for driving a compressor to sup-
ply relatively high pressure charge air to a combustion
engine. The turbine is rotatably driven by exhaust gases from
the engine, and in turn rotatably drives a compressor for
compressing intake air supplied to the engine. One major
design problem with turbochargers, however, is that the rota-
tional speed of the turbine and the compressor increases as
the speed and/or load of the engine-increases. At relatively
high operating speeds or loads, it is possible for the turbine
and compressor to be driven at speeds above critical design
limits, or for the compressor to supply charge air to the
engine at boost pressures higher than the engine can with-
stand.
A wide variety of control devices for turbochargers
has been developed to limit the rotational speed of the turbo-
charger compressor, and thereby control the level of boost
supplied by the compressor~ Such devices may be mounted
either on the compressor or the turbine, and commonly include
blow-off or pop-off valves, turbine wastegate valves, compres-
sor inlet control valves, and the like. These valve devices
are generally similar to each other in principle in that each
comprises a valve responsive to a predetermined pressure level
or pressure differential to restrict the availability of gases
for driving the turbine, or for compression by the compressor.
For example, a turbine wastegate valve operates within a
passage bypassing the turbine, and when opened by a pressure
responsive valve actuator, allows a portion of the engine
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exhaust gases to bypass the turbine to atmosphere. In this
manner, the turbine is rotatably driven by a relativ ly re-
duced mass flow of exhaust gases to limit the rotational
speed of the turbine, and thereby also limit the rotational
speed and resultant boost pressure of the compressor.
Pressure responsive valve actuators typically com-
prise an actuator housing including a diaphragm dividing the
housing into a pair of separated chambers. Inlet ports are
provided for coupling the two chambers to different sources
of pressure to subject the diaphragm to a predetermined pres-
sure differential. Changes in the pressure differential, such
as may occur during increase or decrease in engine speed or
load, cause displacement of the diaphragm which in turn dis-
places an actuator rod connected to the diaphragm. The rod
projects out of the housin~, and is connected to an appro-
priate valve structure on the compressor or turbine for posi-
tioning the valve to control turbocharger operation~
In practice, one major consideration in the design
of pressure responsive valve actuators is to provide an ade-
quate seal allowing passage of the actuator rod through theactuator housing without significant gas leakage. This is
particularly important wherein the pressure sources coupled
to the actuator housing comprise gaseous air-fuel mixtures,
and wherein the actuator housing is mounted close to hot
engine components or the turbine of the turbocharger. In
this regard, prior art seals which satisfactorily prevent
gas leakage have restricted movement of the actuator rod to
axial movement only. This type of seal finds it~ primary
application whexein the actuator rod comprises a valve stem
connected directly to or formed integrally with a valve head,
and wherein axial rod movement is sufficient to properly
position the valve head. See, for example, U. S. Patent Nos.
3,035,408; 3,091,077; 3,104,520; 3,195,~05; 3,196,606;
3,270,495; 3,389,553; 4,005,578; 4,005,579 and 4,019,323; all
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of which relate to valve actuators with axially movable valve
stems or rods. However, it is sometimes desirable to use
other types of valve structures, such as a relatively inex-
pensive butterfly valve or the like positionally adjusted by
movement of a crank arm. With these valve structures, at
least some arcuate motion of the actuator rod is required
for adjusting the position of the valve. However, with prior
art devices wherein the actuator rod is constrained for axial
movement, relatively complex and multiple link mechanical
couplings have been required between the rod and the valve
structure for providing the desired arcuate movement. See,
for example, U. S. Patent Nos. 2,356,124; 2,374,708 and
3,096,614.
The present invention overcomes the problems and
disadvantages of the prior art by providing an improvecl actu-
ator for controlling the operation of a turbocharger having
an outwardly projecting actuator rod, ahd means for sealing
the housing to allow for axial and angular movement of the
actuator rod with respect to the housing.
SUMMARY OF THE INVENTION
In accordance with the invention, a turbocharger
control actuator comprises an actuator housing with an inter
nal diaphragm dividing the housing into a pair of separate
chambers~ The diaphragm is connected to an actuator rod
projecting through one of the chambers and outwardly from the
housing for connection to a turbocharger control valve, such
as a turbine wastegate valve. The diaphragm and the rod
displace in response to a predetermined pressure differential
applied to the diaphragm via ports opening into the chambers
for connecting said chambers to a selected pair of pressure
sources~ Where one of the pressure sources comprises a vacuum
such as the inlet pressure of a turbocharger compressor, the
vacuum port is sized larger than the other port whereby
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excessive pressure build-up in the actuator housing is avoided
in the event oE diaphragm breakage.
In one embodiment of the invention, a sealing washer
has an inner diameter for closing slidable reception over the
actuator rod outside the actuator housing. The washer is
movably retained in abutting relation with the exterior sur-
face of the housing by an actuator mounting bracket secured
to the housing, and allowing sliding movement of the washer
adjacent the housing outer face. Accordingly, the rod is
axially movable with respect to the washer, and the washer
slidably shifts with respect to the housing to allow angular
rod movement.
- In another embodiment of the invention, a generally
elongated, annular elastomeric seal is received over the
actuator rod and has one end secured to the rod within the
housing as by a snap ring. The elastomeric seal extends along
the rod, and terminates in a radially outwardly extending
enlarged bead sealingly trapped between the exterior surface
of the housing and an actuator mounting bracket. Accordingly 7
the elastomeric seal pr~vents gas leakage between the rod and
the housing and resiliently allows axial and angular rod
movement with respect to the housing.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the invention.
In such drawings:
Figure 1 is a schematic illustration of a control
actuator of this invention mounted on a turbocharged combus-
tlon engine;
Fiyure 2 is an enlarged fragmented elevation view
of the actuator;
Figure 3 is a fragmented horiæontal section taken
on the line 3-3 of Figure 2;
Figure 4 is a fragmented elevation view similar to
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Figure 2 showing an a~ter~a-te e~odiment of the invention; and
Figure 5 is a frag~nented horizontal section taken on
the line 5-5 of Figure 4.
DETAILED l)E C I TI_OF THE PREFERRED EMBODIrlENT
An actllator 10 of this invention is shown in Figure
1 mounted on a turbocharged combustion engine 12. The engine
12 is generally conventional in form, and may comprise any of
a wide variety of internal combustion engines such as a reci-
procating engine of the type used for automotive vehicles
having a driven crank shaft 14 for power output. Intake charge
air for the engine is supplied through an intake manifold 16
from a compressor 18 of a turbocharger 20. The compressor 18
draws ambient air through an inlet 22, and compresses ~he air
for supply to the engine. Exhaust gases expelled by the en-
gine are coupled to a turbine 24 of the turbocharger via an
exhaust manifold 26 before discharge through exhaust conduits
28. In operation, the exhaust gases rotatably drive the tur
bine 24 which, in turn, drives the compressor 18 via a shaft
(not shown) in a central housing 30.
In many turbocharged engines, it is possible for the
turbocharger 20 to operate at rotational speeds higher than
the turbocharger mechanical components can withstand, or to
supply compressed charge air to the engine at boost pressures
higher than the engine can withstand. Specifically, at rela-
tively high operating speeds or loads, the mass flow rate of
exhaust gases is sufficient to drive the turbine 24 at a
rotational speed exceeding turbocharger or engine critical
design limits. To prevent damage to the system, limiting means
are provided for preventing the rotational speed of the turbine
and the compressor from exceeding a predetermined level, and
thereby limit the compressor boost pressure. As shown in
Figure 1, one such limiting ~eans comprises a wastegate valve
assembly 32 mounted on the turbine 24, and including a pivot
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pin 34 ~xtending outwardly from the turbine 24 and connected
to a crank arm 36. Movement of the crank arm 36 through an
arcuate path illustrated by the arrow 35 with respect to the
axis of the pivot pin 34 serves to move an internally mounted
valve (not shown), such as a butkerfly or flap valve, to open
and close a turbine bypass passage ~also not shown). More
specifically, the valve is disposed along an internal passage
communicating between the exhaust manifolcl 26 and the exhaust
conduits 28 so that a portion of the exhaust gases bypass the
turbine when the valve is open consequently to limit turbo-
charger rotational speed and boost. Importantly, the specific
construction of the turbine 24 including the valve assembly 32
and the bypass passage are generally well known in the art,
and thereby are not shown or described in substantial cletail.
However, for a specific example of a representative turbo-
charger including the turbine, valve assembly, and bypass
passage, see applicant's U. S. Patent No. 4,120,156.
The control actuator 10 of this invention is shown
in Figures ~ and 3. As shown, the actuator 10 comprises a
generally cylindrical metal housing 38 formed from complemerl-
tary upper and lower halves 40 and 42, respectively. The
housing halves 40 and 42 are each generally circular in cross
section, and include radially outwardly extending flanges 44
and 46, respectively. A circular diaphragm 48 formed from a
suitable flexible elastomeric material such as a fabric-based
fluorosilicone extends across the housing 38 to divide the
housing into two chambers 50 and 52. The periphery of the
diaphragm 48 is received between the flanges 44 and 46, and
is secured in place by means of the lower flange 46 rolled
over the outer edge of the upper flange 44.
The central portion of the diaphragm 48 is stiffened
by a pair of opposed retainer plates 54 and 56. An actuator
rod 58 extends through the diametric centers of the plates 54
and 56 and the diaphragm 48, and is secured thereto as by a
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pair of w~shers 60 and 62 secured to the rod 58. In practice,
the washer 60 may be formed integrally with the rod 58, and
the washer 62 may be interposed between the upper retainer
plate 54 and a staked end 63 at the upper end of the rod.
From the diaphragm 48l the rod 58 extends downwardly
through the chamber 52, and outwardly from the housing 38
through an opening 39. As shown in Figures l and 2, the lower
end of the rod 58 extends further through an opening 41 in a
bracket 64 provided for connection of the actuator lO to the
turbocharger 20 by bolts 66, and is threadably received in a
rod extension 68. The rod extension 68 in turn is pivotally
connected to the end of valve assembly crank arm 36 by a pin
70. Accord~gly, movement of the diaphragm 48 within the
housing 38 displaces the rod 58 to swing the crank arm 36
about the axis of the pin 34, and thereby open or close the
valve within the tur~ine 24. Importantly, the crank arm 36
swings through an arcuate path whereby the actuator rod 58
must be free to move axially and slightly angularly with
respect to the housing 38.
As shown in Figs. 2 and 3, sealing means are provi-
ded for sealing the passage of the rod 58 through the housing
38, as well as allowing axial and angular movement of the rod
with respect to the housing~ As sho~n, the lower exte:rior
face 71 of the housing 38 is recessed upwardly adjacent the
opening 39 to form a generally circular shaped seat 73 for
receiving a sealing washer 74~ The washer 74 preferably is
formed from a suitable low frict.ion synthetic resin such as
a fluorocarbon resin sold under the trademark Teflon, and has
an inner diameter for close but axially sliding reception and
sealing engagement over the actuator rod 58. Specifically,
in one embodiment of the invention, the washer 74 was formed
from about 75% Teflon, about 20% glass fibres, and about 5%
molybdenite. Importantly, the recessed seat 73 is sizPd to
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allow sliding movement of the washer 74 with respect to the
housing lower face 71 whereby the rod 58 is allowed to move
angularly through an arc of say about 10-20 degrees, illu-
strated by the arrow 77 in Figure 2, as well as axially with
respect to the housing, as illustrated by -the arrow 81. The
washer 74 is seated between the housing seat 73 and the
bracket 64 which is fixed to the housing lower face 71 as
by spot welding.
In operation, the diaphragm 48 i5 subjected to a
predetermined pressure differential by means of hose fittings
67 and 69 suitably mounted on the housing 38 in alignment
with a pair of ports 78 and 80 opening into the chambers 50
and 52, respectively. In this manner, pressure from one
source is applied to the chamber 50, and pressure from a
second source is applied to the chamber 52, whereby the dia-
phragm 48 movably responds to the pressure differential. A
spring 82 is interposed between the lower retainer plate 56
and the lower face 71 of the lower housing half 42 to bias
the diaphragm 48 upwardly, and thereby provide a threshold
pressure differential at which diaphragm movement occurs.
In a typical application of the actuator 10, dis-
charge pressure from the compressor 18 is applied to the
upper chambex 50 via the port 78, and compressor inlet pres-
sure is applied to the lower chamber 52 via the lower port
80. In this manner, during engine operation, substantial
positive pressure is applied to the chamber 50, whereas a
sub-atmospheric or negative pressure is applied to the
chamber 52 to draw the washer 74 tightly against the seat
73 to seal against gas leakage~ When the differential be-
tween the pressures reaches a level governed by the charac-
teristics of the spring 82, the diaphragm 48 movably responds
to shift the actuator rod 58 in an axial direction to alter
the position of the wastegate valve in the turbine.
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Importantly, as shown, the siæe of the port 78 is substanti-
ally smaller than the size of the port 80 whereby pressure
build-up in the actuator is prevented in the event of dia-
phragm breakage or failure. That is, in the event of
diaphragm breakage, the port 80 is sized sufficiently to
evacuate the housing interior, including any gas under pres-
sure supplied via the port 80 whereby excessive pressure
build-up is prevented. This is particularly important when
the actuator is used in a conventional gasoline engine
automotive set-up wherein pressurized gases supplied -to the
actuator comprise volatile air-fuel mixtures which could
otherwise force past the sealing washer 74 toward hot engine
components for ignition.
An alternate embodiment of the invention is shown
in Figures 4 and 5. As shown, an elongated, annular resili-
ent seal 84 is received over the rod 58 within the lower
chamber 52. The seal 84 preferably is formed from an elasto-
meric material with a generally bellows shape, or with any
of a wide variety of shapes which may include one or more
convolutions along the length of the seal. The seal has its
upper end closely received about the rod 58 and sealingly
fixed in position thereon as by a snap ring 86. As shown,
the seal extends downwardly from the snap ring 86 in an
accordion-like fashion, and terminates in a radially outwardly
projecting enlarged bead 88 interposed between the lower face
71 of the housing and the mounting bracket 64. The bracket
64 serves to maintain the bead 88 of the seal 84 in position
in the same manner as the sliding washer 74 of the previous
embodiment. Accordingly, the seal 84 serves to allow sliding
axial movement of the rod 58 with respect to the housing 38
as well as a degree of angular movement for arcuately shif-
ting the position of the crank arm 36 on the turbocharger 20
(Figure 1).
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rrhe control actuator of -I:his invention may include
a wide variety of modifications and improvements within the
scope of this invention. For example, the valve assembly 32
may comprise any of a ~ide variety of valve assemblies such
as wastegate valves, pop-off valves, compressor inlet valves,
etc. Moreover, the actua-tor housing may be adapted to res-
pond to any chosen préssure or pressure differential wherein
an axially and angularly movable actuator rod projects out-
wardly from a sealed housing chamber. These and other
variations are believed to be within the skill of the art
when taken in conjunction with the invention as defined in
the appended claims.
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