U.S. patent application number 12/717033 was filed with the patent office on 2011-06-09 for vacuum supply system.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to Ross Dykstra Pursifull.
Application Number | 20110132331 12/717033 |
Document ID | / |
Family ID | 44080772 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110132331 |
Kind Code |
A1 |
Pursifull; Ross Dykstra |
June 9, 2011 |
VACUUM SUPPLY SYSTEM
Abstract
A method of operating a boosted engine system is described in
which an ejector coupled with a fuel vapor purging system can
generate vacuum during both purging and non-purging conditions, and
during both boosted and non-boosted conditions. The vacuum can
therefore be used to power vacuum actuated brakes, and/or other
vacuum actuators, irrespective of the purging conditions, and
irrespective of boost levels.
Inventors: |
Pursifull; Ross Dykstra;
(Dearborn, MI) |
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
Dearborn
MI
|
Family ID: |
44080772 |
Appl. No.: |
12/717033 |
Filed: |
March 3, 2010 |
Current U.S.
Class: |
123/478 ;
123/520; 123/564 |
Current CPC
Class: |
Y02T 10/144 20130101;
F02M 25/089 20130101; F02M 25/0836 20130101; Y02T 10/12 20130101;
F02B 37/186 20130101; F02B 37/162 20190501 |
Class at
Publication: |
123/478 ;
123/520; 123/564 |
International
Class: |
F02M 51/00 20060101
F02M051/00; F02M 33/02 20060101 F02M033/02; F02B 33/00 20060101
F02B033/00 |
Claims
1. A method of operating a boosted engine system including a fuel
vapor canister, a purge pump, and an ejector, comprising, pumping a
purge flow through the fuel vapor canister, through the ejector,
and into an engine intake; and applying the ejector to a vacuum
actuator.
2. The method of claim 1, wherein the vacuum actuator includes a
power brake or a wastegate actuator.
3. (canceled)
4. The method of claim 1, wherein the ejector is positioned
downstream of the purge pump.
5. The method of claim 1, wherein pumping a purge flow includes,
opening a canister vent valve, closing a vapor bypass valve, and
operating the pump.
6. The method of claim 1, wherein pumping a purge flow to an engine
intake includes pumping the purge flow to downstream of an intake
throttle and/or upstream of a compressor.
7. The method of claim 5, further comprising, pumping an air flow,
while bypassing the fuel vapor canister, through the ejector and
into to the engine intake; and applying vacuum from the ejector to
the vacuum actuator.
8. The method of claim 7, wherein pumping an air flow includes,
closing the canister vent valve, opening the vapor bypass valve,
and operating the pump, the method further comprising, in the
absence of engine boost, applying a vacuum from the engine intake
to the vacuum actuator and/or the fuel vapor canister.
9. (canceled)
10. The method of claim 1, wherein pumping a purge flow includes
pumping a purge flow through the fuel vapor canister, then through
the ejector, and then into an engine intake.
11. A method of operating a fuel vapor recovery system including a
fuel vapor canister, a purge pump, and one or more ejectors, the
fuel vapor recovery system coupled to a boosted engine intake,
comprising, during a purging condition, operating the purge pump to
pump a purge flow through the canister, through the one or more
ejectors, and into the engine intake, and applying vacuum from the
one or more ejectors to a vacuum actuator; and during a non-purging
condition, operating the purge pump to drive an air flow bypassing
the canister, through the one or more ejectors, and into the engine
intake, and applying vacuum from the one or more ejectors to the
vacuum actuator.
12. The method of claim 11, wherein the one or more ejectors are
positioned downstream of the purge pump.
13. The method of claim 11, wherein the one or more ejectors
includes a first ejector coupled to a first actuator, positioned
downstream of the purge pump, and a second ejector coupled to the
first actuator, positioned downstream of the purge pump and
upstream of a compressor.
14. The method of claim 11, wherein the vacuum actuator is a power
brake.
15. The method of claim 11, wherein the vacuum actuator is a
wastegate actuator.
16. The method of claim 11, wherein at least some of the purge flow
and/or air flow is delivered to the engine intake downstream of an
intake throttle, and at least some of the purge flow and/or air
flow is delivered to the engine intake upstream of a
compressor.
17. The method of claim 11, further comprising, adjusting a fuel
injection to the engine during a transition between the purging and
non-purging conditions, wherein the adjustment includes, during the
purging condition, adjusting a fuel injection responsive to the
purge flow, and during the non-purging condition, adjusting a fuel
injection responsive to the air flow, wherein adjusting the fuel
injection responsive to the purge flow includes reducing fuel
injection based on an amount of fuel vapors in the purge flow.
18-19. (canceled)
20. The method of claim 11, wherein pumping a purge flow includes
pumping a purge flow through the fuel vapor canister, then through
the ejector, and then into an engine intake.
21. An engine system, comprising, an engine intake; a boosting
device including a compressor configured to boost intake air; a
fuel vapor canister configured to receive fuel vapors from a fuel
tank, the fuel vapor canister communicating with atmosphere via a
first canister vent valve and a second vapor bypass valve; a purge
pump; an ejector coupled downstream of the pump; a vacuum actuator;
and a controller configured to, operate the compressor to provide a
boost; and in the presence of boost, operate the purge pump to pump
a purge flow through the canister, through the ejector, into the
engine intake, during purging conditions; and operate the purge
pump to pump an air flow bypassing the canister, through the
ejector, into the engine intake, during non-purging conditions; and
during purging and non-purging conditions, apply vacuum from the
ejector to the vacuum actuator.
22. The system of claim 21, wherein driving pumping a purge flow
includes opening the opening the canister vent valve and closing
the vapor bypass valve, and wherein pumping an air flow includes
opening the vapor bypass valve and closing the canister vent
valve.
23. The system of claim 22, wherein the vacuum actuator is one of a
power brake and a wastegate actuator, and wherein the controller is
further configured to, in the absence of boost, apply vacuum from
the engine intake on the fuel vapor canister and/or ejector.
24. The system of claim 21, wherein pumping a purge flow to the
engine intake includes driving at least some purge flow to the
engine intake downstream of an intake throttle, and driving at
least some purge flow to the engine intake upstream of the
compressor.
25. (canceled)
Description
FIELD
[0001] The present description relates to methods and systems for
providing a vacuum for various actuators, including a power brake
and a fuel vapor recovery system, in a vehicle with a boosted
internal combustion engine.
BACKGROUND/SUMMARY
[0002] Vehicles may be fitted with emission control systems wherein
vaporized hydrocarbons (HCs) released from a fuel tank (for
example, during refueling) are captured and stored in a fuel vapor
canister packed with an adsorbent. At a later time, when the engine
is in operation, the evaporative emission control system may use a
vacuum (or pressure) to purge the vapors into the engine intake
manifold for use as fuel. The purge flow vacuum (or pressure) may
be generated by one or more pumps and/or ejectors.
[0003] One example approach for providing sufficient vacuum for a
fuel purge flow is illustrated by Kakimoto et al. in US
2006/0196482 A1. Herein, blow-by gas and purge gas are delivered to
the engine intake together. Specifically, blow-by gas is pumped to
the engine intake through an ejector in such a manner that a fuel
vapor purge flow is also sucked into the intake by using a negative
pressure (that is, vacuum) generated by the high-speed flow of the
blow-by gas through the ejector.
[0004] However, the inventors herein have recognized potential
issues with such an approach. In one example, pump operation is
necessitated for generating a vacuum at the ejector and for drawing
a purge flow, irrespective of whether the engine is boosted or not.
Thus, due to dependence on pump operation for purging, during
conditions where pump operation is limited or restricted, a purge
flow may not be possible. Additionally, the need for constant pump
operation during purging may add to fuel costs while decreasing
pump life. In another example, a flow of blow-by gases is
necessitated for generating the vacuum at the ejector and for
drawing the purge flow. Thus, during purging conditions when a flow
of blow-by gases to the intake is not desired, or not available, a
purging operation may not be performed. In still another example,
the vacuum generated at the ejector may only be used for drawing a
purge flow. Thus, an alternate vacuum actuator, such as a power
brake, may not be operated using the ejector vacuum during a
purging operation. Thus, an additional pump and/or ejector may be
required to generate the vacuum required for the power brake. As
such, this may increase component cost.
[0005] Thus, in one example, some of the above issues may be
addressed by a method of operating a boosted engine system
including a fuel vapor canister, a purge pump, and an ejector. In
one embodiment, the method may comprise pumping a purge flow
through the fuel vapor canister, then through the ejector, and then
to an engine intake, and applying vacuum from the ejector to a
vacuum actuator.
[0006] For example, a purge pump and at least one ejector may be
configured in series and may be coupled between an engine intake
manifold and a fuel vapor recovery system such that, during a
boosted engine operation, a flow of air and/or fuel vapors may be
pumped to the engine intake through the ejector, thereby creating a
vacuum at the ejector. In one example, during purging conditions, a
canister vent valve may be opened and the purge pump may be
operated to pump a fuel vapor purge flow through the fuel vapor
canister, then through the ejector, and then to the engine intake.
By pumping a purge flow through the ejector before delivery of the
purge flow to the engine intake, a vacuum may be advantageously
generated at the ejector during boosted engine operation. This
vacuum may be applied from the ejector to a vacuum actuator, such
as a power brake and/or a wastegate actuator. As such, additional
secondary ejectors may be coupled to the primary ejector to further
deepen the generated vacuum. In this way, during purging
conditions, a purge pump may be operated to provide a vacuum for
drawing fuel vapors and also for actuating a vacuum actuator.
[0007] In another example, during a non-purging condition, the
canister vent valve may be closed, a vapor bypass valve may be
opened, and the purge pump may be operated to bypass the fuel vapor
canister and pump air (e.g., fresh air not mixed with fuel vapors)
through the ejector to the engine intake. The vacuum generated by
the pumping of air through the ejector, may be applied from the
ejector to the vacuum actuator. In this way, during non-purging
conditions, the purge pump may be operated to provide a vacuum for
various vacuum actuators. In comparison, when the engine is not
boosted, the intake manifold vacuum may be applied to draw a purge
flow from the fuel vapor recovery system during purging conditions,
without operating the purge pump. Similarly, during purging and
non-purging conditions, intake manifold vacuum may be applied for
vacuum actuator actuation.
[0008] In alternate examples, the pump may be located upstream or
downstream of the fuel vapor storage canister. In either pump
configuration, the ejector may be located with its exit flowing
towards a low pressure.
[0009] In this way, a purge flow may be drawn to an engine intake,
in the presence or absence of engine boost, without requiring
constant purge pump operation. Further, the purging operation may
be performed independent of a blow-by gas flow. Specifically, in
the absence of boost, an engine intake manifold negative pressure
may be used to draw a purge flow, while a purge pump may be used to
draw a purge flow in the presence of boost. Additionally, a vacuum
may be drawn at the ejector coupled downstream of the pump during
every purging operation. Specifically, by pumping the purge flow
through an ejector before delivering purged fuel vapors to the
engine intake, a vacuum may be generated at the ejector during
boosted conditions, which may be advantageously used for actuating
additional vacuum actuators. Consequently, the need for dedicated
vacuum pumps for the vacuum actuators may be reduced.
Alternatively, the purge flow driven vacuum may be used in addition
to a dedicated vacuum pump, enabling the use of a smaller vacuum
pump for the vacuum actuator and/or a shorter duration of vacuum
pump operation. By enabling purging and vacuum actuation under most
engine operating conditions, vehicle fuel economy and emissions may
be improved.
[0010] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows a schematic depiction of an engine and an
associated fuel vapor recovery system.
[0012] FIGS. 2-3 show example embodiments of the fuel vapor
recovery system of FIG. 1.
[0013] FIG. 4 shows a high level flow chart illustrating a routine
that may be implemented for purging a fuel vapor canister, and for
generating a vacuum at the ejector of FIG. 1, during purging and
non-purging conditions, in the presence or absence of engine
boost.
DETAILED DESCRIPTION
[0014] The following description relates to systems and methods for
generating an ejector generated vacuum using purge pump flow during
fuel vapor canister purging and non-purging conditions. As shown in
FIGS. 1-3, a purge pump may be coupled to a fuel vapor canister of
a fuel vapor recovery system to pump a purge flow through a fuel
vapor canister into a boosted engine intake manifold. One or more
ejectors may be coupled to the pump and the purge flow may be
pumped through the canister, through the ejector(s), and to the
engine intake. As such, the pumping of the purge flow through the
ejector may provide a negative pressure at the ejector which may be
applied from the ejector to a vacuum actuator (such as, a power
brake and/or a wastegate actuator). A controller may be configured
to perform routines, such as depicted in FIG. 4, to operate a purge
pump in the presence of engine boost to generate a vacuum at the
ejector. By pumping a purge flow through the ejector during purging
conditions, vacuum actuation may be enabled during purging
conditions. By pumping an air flow through the ejector, while
bypassing the fuel vapor canister during non-purging conditions,
vacuum actuation may be enabled during non-purging conditions. In
the absence of engine boost, the negative pressure of the intake
manifold may be advantageously used to draw a purge flow and for
vacuum actuation. In this way, vacuum actuation may be enabled
during purging and non-purging conditions without operating a
dedicated vacuum pump. Furthermore, purging may be performed
without constantly operating a purge pump. By using a common pump
for both a purge flow and vacuum actuation, component reduction
benefits may be achieved.
[0015] FIG. 1 shows a schematic depiction of a vehicle system 6.
The vehicle system 6 includes an engine system 8 coupled to a fuel
vapor recovery system 22 and a fuel system 18. The engine system 8
may include an engine 10 having a plurality of cylinders 30. The
engine 10 includes an engine intake 23 and an engine exhaust 25.
The engine intake 23 includes a throttle 62 fluidly coupled to the
engine intake manifold 44 via an intake passage 42. The engine
exhaust 25 includes an exhaust manifold 48 leading to an exhaust
passage 35 that routes exhaust gas to the atmosphere. The engine
exhaust 25 may include one or more emission control devices 70,
which may be mounted in a close-coupled position in the exhaust.
One or more emission control devices may include a three-way
catalyst, lean NOx trap, diesel particulate filter, oxidation
catalyst, etc. It will be appreciated that other components may be
included in the vehicle system, such as a variety of valves and
sensors, as further elaborated in the example embodiments of FIGS.
2-3.
[0016] Throttle 62 may be located in intake passage 42 downstream
of a boosting device, such as turbocharger 50, or a supercharger.
Turbocharger 50 may include a compressor 52, arranged between
intake passage 42 and intake manifold 44. Compressor 52 may be at
least partially powered by exhaust turbine 54, arranged between
exhaust manifold 48 and exhaust passage 35. Compressor 52 may be
coupled to exhaust turbine 54 via shaft 56. Compressor 52 may be
configured to draw in intake air at atmospheric air pressure and
boost it to a higher pressure. Using the boosted intake air, a
boosted engine operation may be performed.
[0017] An amount of boost may be controlled, at least in part, by
controlling an amount of exhaust gas directed through exhaust
turbine 54. In one example, when a larger amount of boost is
requested, a larger amount of exhaust gases may be directed through
the turbine. Alternatively, for example when a smaller amount of
boost is requested, some or all of the exhaust gas may bypass
turbine 54 via turbine bypass passage 64, as controlled by
wastegate 60. The position of wastegate 60 may be controlled by a
wastegate actuator (not shown) as directed by controller 12. In one
example, the wastegate actuator may be a vacuum-driven solenoid
valve. As further elaborated in FIGS. 2-4, the wastegate actuator
may be actuated by vacuum applied from an ejector coupled to fuel
vapor recovery system 22. The vacuum may be generated at the
ejector in response to a purge flow pumped through the ejector
during purging conditions, and/or an air flow pumped through the
ejector during non-purging conditions.
[0018] An amount of boost may additionally or optionally be
controlled by controlling an amount of intake air directed through
compressor 52. Controller 12 may adjust an amount of intake air
that is drawn through compressor 52 by adjusting the position of
compressor bypass valve 58 in compressor bypass passage 68. In one
example, when a larger amount of boost is requested, a smaller
amount of intake air may be directed through the compressor bypass
passage.
[0019] Fuel system 18 may include a fuel tank 20 coupled to a fuel
pump system 21. The fuel pump system 21 may include one or more
pumps for pressurizing fuel delivered to fuel injectors 66 of
engine 10. While only a single fuel injector 66 is shown,
additional injectors are provided for each cylinder. It will be
appreciated that fuel system 18 may be a return-less fuel system, a
return fuel system, or various other types of fuel system. A fuel
pump may be configured to draw the tank's liquid from the tank
bottom. Vapors generated in fuel system 18 may be routed to a fuel
vapor recovery system 22, described further below, via conduit 31,
before being purged to the engine intake 23. As further elaborated
in FIG. 2, during a purging condition, air may be drawn in through
the fuel vapor recovery system through vent 27 and canister vent
valve 204. Fuel tank vapors may be vented through the tank top. The
fuel tank 20 may hold a plurality of fuels, including fuel
blends.
[0020] Fuel vapors stored in fuel vapor recovery system may be
purged to engine intake 23 during purging conditions. Specifically,
a purge flow may be driven by purge pump 71, and may be directed to
the engine intake post-throttle, along first conduit 26, and/or
into the pre-compressor engine air inlet, along second conduit 28.
As such, second conduit 28 is atypical of production designs. By
driving a purge flow to the engine intake through an ejector (shown
in FIGS. 2-3) coupled, in series, downstream of the purge pump, a
vacuum may be created at the ejector. The ejector may be
operationally coupled to one or more vacuum actuators, such as a
power brake and/or a wastegate actuator. By creating a vacuum at
the ejector by driving the purge flow through the ejector, vacuum
necessary for operating the vacuum actuators may be generated while
reducing the need for a dedicated vacuum pump.
[0021] Vehicle system 6 may further include control system 14.
Control system 14 is shown receiving information from a plurality
of sensors 16 (various examples of which are described herein) and
sending control signals to a plurality of actuators 81 (various
examples of which are described herein). As one example, sensors 16
may include exhaust gas sensor 126 (located in exhaust manifold
48), temperature sensor 128 and pressure sensor 129 (located
downstream of emission control device 70). Other sensors such as
additional pressure, temperature, air/fuel ratio, and composition
sensors may be coupled to various locations in the vehicle system
6. As another example, actuators 81 may include fuel injectors 66,
throttle 62, compressor 52, purge pump 71, a fuel pump of pump
system 21, wastegate 60, wastegate actuators, compressor bypass
valve 58, etc. The control system 14 may include an electronic
controller 12. The controller may receive input data from the
various sensors, process the input data, and trigger the actuators
in response to the processed input data based on instruction or
code programmed therein corresponding to one or more routines. An
example control routine is described herein with reference to FIG.
4.
[0022] FIGS. 2-3 depict example embodiments of the fuel vapor
recovery system of FIG. 1. As elaborated herein, during purging
conditions, a controller may operate a purge pump of the fuel vapor
recovery system to drive a purge flow through a fuel vapor
canister, and through an ejector, and then purge the stored fuel
vapors in a boosted engine intake. By driving the purge flow to the
engine intake through the ejector, a vacuum may be created at the
ejector, which may be applied to a vacuum actuator, thereby
reducing the need for a dedicated vacuum pump for the actuator.
[0023] As depicted in FIG. 2, embodiment 200 of fuel vapor recovery
system 22 includes a fuel vapor retaining device, depicted herein
as fuel vapor canister 202. Canister 202 may be filled with an
adsorbent capable of binding large quantities of vaporized HCs. In
one example, the adsorbent used is activated charcoal. Canister 202
may receive fuel vapors from fuel tank 20 through conduit 31. While
the depicted example shows a single canister, it will be
appreciated that in alternate embodiments, a plurality of such
canisters may be connected together. Canister 202 may communicate
with the atmosphere through vent 27. Canister vent valve 204 may be
located along vent 27, coupled between the fuel vapor canister and
the atmosphere, and may adjust a flow of air and vapors between
canister 202 and the atmosphere. In one example, operation of
canister vent valve 204 may be regulated by a canister vent
solenoid (not shown). For example, based on whether the canister is
to be purged or not, the canister vent valve may be opened or
closed.
[0024] Purge pump 71 may be configured to pump a purge flow through
fuel vapor canister 202 on to engine intake 23. In one example,
purge pump 71 may be an electric pump driven by an electric motor.
In alternate embodiments, purge pump 71 may be engine-driven or may
share a shaft with a fuel pump. Purge pump 71 may be, for example,
a positive displacement pump, or a centrifugal (axial, mixed, or
radial) pump. In an alternate embodiment, purge pump 71 may be
located along vent 27. However, in this embodiment, the
functionality of valve 208 may be lost.
[0025] One or more ejectors may be positioned downstream of the
purge pump. For example, a first ejector 214 may be coupled
downstream of, and in series with, purge pump 71. During purging
conditions, purge pump 71 may pump the purge flow through fuel
vapor canister 202, then through ejector 214, and then to engine
intake 23. An engine controller may be configured to open canister
vent valve 204 to enable purge pump 71 to draw air mixed with fuel
vapors through the canister and then through first ejector 214. As
such, the pump-driven purge flow through the ejector may generate a
vacuum therein. First ejector 214 may be coupled to vacuum actuator
210 along vacuum line 226 and conduit 224. In one example, the
vacuum actuator may include a power brake. In another example, the
vacuum actuator may include a wastegate actuator. The generated
vacuum may be applied from first ejector 214 to vacuum actuator 210
during actuator operation (such as during power brake application,
or during wastegate actuation), thereby reducing the need for
operating a dedicated vacuum pump.
[0026] During non-purging conditions, purge pump 71 may be
configured to pump an air flow (that is, air not mixed with fuel
vapors), while bypassing fuel vapor canister 202, through ejector
214. Specifically, an engine controller may close canister vent
valve 204, and open vapor bypass valve 208 to enable purge pump 71
to draw fresh air through conduit 29, through first ejector 214,
and then pump the air flow to the engine intake. The pump-driven
flow of air through the ejector during non-purging conditions may
generate a vacuum in the ejector that may be applied from the
ejector to the vacuum actuator 210 during actuator operation. In
this way, by operating a purge pump, a vacuum may be generated at
ejector during purging and non-purging conditions.
[0027] The purge flow driven by purge pump 71 during purging
conditions, and/or the air flow driven by the purge pump during
non-purging conditions, may be directed to engine intake 23 through
at least one of a first conduit 26 and a second conduit 28.
Specifically, air and/or fuel vapors may be directed to engine
intake 23 downstream of intake throttle 62 along first conduit 26,
and/or to an engine air inlet upstream of compressor 52 along
second conduit 28. One or more check valves 228 may be included in
the fuel vapor recovery system to regulate the flow of vapors and
prevent the intake manifold pressure from flowing gases in the
opposite direction of the purge flow. For example, check valves 228
may be included in first conduit 26, second conduit 28, vacuum line
226, and conduit 224. Check valves 228 also passively insure that
the ejector exhausts to the lowest pressure node.
[0028] FIG. 3 shows an alternate embodiment 300 of the fuel vapor
recovery system. Herein, the one or more ejectors include a first
ejector 214 coupled to (first) vacuum actuator 210, positioned
downstream of purge pump 71, and a second ejector 314, coupled to
first ejector 214, and further coupled to the (first) vacuum
actuator 210, positioned downstream of purge pump 71 and upstream
of compressor 52, along second conduit 28. In one example, second
conduit 28 may be controlled with a solenoid valve or other valve
type to improve turbocharger spin-up. In this way, second ejector
314 may be included to further deepen engine vacuum. In an
alternate embodiment, first ejector 214 may be coupled to a first
vacuum actuator while second ejector 314 may be coupled to a second
actuator.
[0029] It will be appreciated that while the embodiments of FIGS.
2-3 illustrate a dual path system (into the engine intake manifold
and the engine air inlet), in alternate embodiments, a purge flow
may be directed to the engine intake along a single path system,
into either the engine intake manifold or the engine air inlet. It
will also be appreciated that while the depicted embodiments
illustrate purge pump 71 positioned to enable a drawing of air and
fuel vapors through the canister, purge pump 71 may alternatively
be positioned to push air through the canister (for example, to
clean the canister). Similarly, while the depicted embodiments show
ejectors 214, 314 positioned downstream of purge pump 71, in
alternate embodiments, one or more of the ejectors may be
positioned upstream of purge pump 71, or anywhere in the flow
created by purge pump 71. However, the ejector may have peak vacuum
generation when exhausting to the lowest pressure node.
[0030] Additionally, in some embodiments, a canister purge valve
may be included in-line with the outlet of canister 202, for
example, between canister 202 and purge pump 71. Alternatively, a
canister purge valve may be located in vacuum line 226. As such,
the canister purge valve may be a continuous device that meters
purge flow to the engine. Additionally, the canister purge valve
may enable a purge flow into the engine intake to be sufficiently
lowered. However, in embodiments where purge pump 71 is a variable
speed (or flow or displacement) positive displacement pump, the
canister purge valve may not be required as the metering function
of the purge valve may be taken over by the purge pump. In
embodiments where a purge pump technology is used that allows flow
through the pump when the pump is off, a canister purge valve may
be required to meter fuel vapor into the engine.
[0031] Now turning to FIG. 4, an example routine 400 is described
for generating a vacuum at the ejector(s) of FIGS. 2-3 during
purging and non-purging conditions, in the presence or absence of
engine boost. Specifically, the routine enables intake manifold
vacuum to be applied for drawing a purge flow and/or vacuum
actuator actuation, in the absence of boost, and enables a purge
pump to be operated in the presence of engine boost for drawing a
purge flow and generating a vacuum at the ejector(s) for vacuum
actuator actuation.
[0032] At 402, purging conditions may be confirmed. Purging
conditions may be confirmed based on various engine and vehicle
operating parameters, including an amount of hydrocarbons stored in
canister 202 being greater than a threshold, the temperature of
emission control device 70 being greater than a threshold, a
temperature of canister 202, fuel temperature, the number of engine
starts since the last purge operation (such as the number of starts
being greater than a threshold), a duration elapsed since the last
purge operation, fuel properties, and various others. If purging
conditions are confirmed, then at 404, a controller may open
canister vent valve 204 (for example, by energizing a canister vent
solenoid) while closing vapor bypass valve 208.
[0033] If purging conditions are confirmed, then at 403, it may be
determined whether a boost is present or not. As such, a boost
condition may be confirmed when a manifold intake pressure is
higher than an atmospheric pressure. If an engine boost is not
present, then at 406, an engine controller may open the canister
vent valve and close the vapor bypass valve. At 408, the engine
intake manifold vacuum may be used to draw a purge flow through the
fuel vapor canister into the engine intake. In this way, stored
fuel vapors may be purged to the engine intake in the absence of
engine boost without operating a purge pump. At 410, the engine
intake manifold vacuum may be applied to one or more vacuum
actuators, such as a power brake. In this way, vacuum actuation may
be enabled during purging conditions, in the absence of engine
boost, without operating a dedicated vacuum pump. Thus, in the
absence of boost, an engine controller may apply vacuum from the
engine intake to the fuel vapor canister and/or the vacuum
actuator.
[0034] If an engine boost is present at 403, then at 412, an engine
controller may open the canister vent valve and close the vapor
bypass valve. At 414, in the presence of boost, the purge pump may
be operated to pump a purge flow through the fuel vapor canister,
through the one or more ejectors, on to the engine intake. At least
some of the pumped purge flow may be delivered to the engine intake
downstream of an intake throttle and/or at least some of the pumped
purge flow may be delivered to the engine intake upstream of a
compressor. In this way, stored fuel vapors may be purged to the
engine intake in the presence of engine boost. Furthermore, the
pumping of purge flow through the ejector may be advantageously
used to generate a vacuum at the ejector. At 415, the controller
may apply the resultant vacuum from the one or more ejectors to one
or more vacuum actuators, such as a wastegate actuator. In this
way, vacuum actuation may be enabled while purging, in the presence
of engine boost, without operating a dedicated vacuum pump.
[0035] If purging conditions are not confirmed at 402, then at 404,
it may be determined whether a boost is present or not. If an
engine boost is not present at 404, then at 416, an engine
controller may close the canister vent valve and open the vapor
bypass valve. At 418, the engine intake manifold vacuum may be
applied on one or more vacuum actuators, such as a power brake. In
this way, vacuum actuation may be enabled during non-purging
conditions, in the absence of engine boost, without operating a
dedicated vacuum pump. If an engine boost is present at 404, then
at 420, an engine controller may close the canister vent valve and
open the vapor bypass valve. At 422, the purge pump may be operated
to pump an air flow (that is, fresh air not mixed with fuel vapors)
through the one or more ejectors, and then into the engine intake,
while bypassing the fuel vapor canister. At least some of the
pumped air flow may be delivered to the engine intake downstream of
an intake throttle and/or at least some of the pumped air flow may
be delivered to the engine intake upstream of a compressor. In this
way, the flow of air through the ejector may be used to generate a
vacuum at the ejector. At 424 the generated vacuum may be applied
from the ejector to one or more vacuum actuators, such as a
wastegate actuator. In this way, vacuum actuation may be enabled
when not purging, in the presence of engine boost, without
operating a dedicated vacuum pump.
[0036] Additionally, a fuel injection to the engine may be adjusted
during a transition between purging and non-purging conditions. The
adjustment may include, for example, adjusting fuel injection
responsive to the purge flow during purging conditions, and
adjusting fuel injection responsive to the air flow during
non-purging conditions. In one example, during a boosted purging
condition, as the purge pump is operated to drive a purge flow
through the canister and the ejector to the engine intake manifold,
a fuel injection may be adjusted to a first, lower amount based on
an amount of fuel vapors being recycled to the engine intake in
purge flow. The amount of fuel vapors may be estimated based on,
for example, an air-fuel ratio sensor, a pressure difference in the
fuel canister before and after purging, input received during a
preceding fuel vapor canister storing operation, etc. In another
example, during a boosted non-purging condition, as the purge pump
is operated to drive an air flow through the ejector, and bypassing
the canister, to the engine intake manifold, a fuel injection may
be adjusted to a second, higher amount responsive to the air flow,
and taking into consideration that no fuel vapors are being
recycled to the engine intake. The air flow may be estimated based
on, for example, pump speed, pump efficiency, etc. In this way,
during a transition between purging and non-purging conditions, the
fuel injection may be adjusted to compensate for the presence or
absence of fuel vapors in the flow directed to the engine intake.
By reducing an amount of fuel injection based on an amount of fuel
vapors in the purge flow, engine efficiency during the transition
can be improved.
[0037] In this way, fuel vapors stored in a fuel vapor retaining
device may be purged in the presence or absence of engine boost. By
enabling purging during a wider range of engine operating
conditions, fuel vapor recovery may be improved. By pumping a purge
flow through an ejector, a vacuum may be generated that may be used
for the actuation of one or more vacuum actuators. By using a purge
pump for purging operations and for generating vacuum for vacuum
actuation, the need for additional vacuum pumps may be reduced,
thereby providing reduced component benefits.
[0038] Note that the example control and estimation routines
included herein can be used with various engine and/or vehicle
system configurations. The specific routines described herein may
represent one or more of any number of processing strategies such
as event-driven, interrupt-driven, multi-tasking, multi-threading,
and the like. As such, various acts, operations, or functions
illustrated may be performed in the sequence illustrated, in
parallel, or in some cases omitted. Likewise, the order of
processing is not necessarily required to achieve the features and
advantages of the example embodiments described herein, but is
provided for ease of illustration and description. One or more of
the illustrated acts or functions may be repeatedly performed
depending on the particular strategy being used. Further, the
described acts may graphically represent code to be programmed into
the computer readable storage medium in the engine control
system.
[0039] It will be appreciated that the configurations and routines
disclosed herein are exemplary in nature, and that these specific
embodiments are not to be considered in a limiting sense, because
numerous variations are possible. For example, the above technology
can be applied to V-6, 1-4, 1-6, V-12, opposed 4, and other engine
types. Further, one or more of the various system configurations
may be used in combination with one or more of the described
diagnostic routines. The subject matter of the present disclosure
includes all novel and nonobvious combinations and subcombinations
of the various systems and configurations, and other features,
functions, and/or properties disclosed herein.
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