U.S. patent application number 14/835947 was filed with the patent office on 2017-03-02 for cylinder cutout system and method.
This patent application is currently assigned to CATERPILLAR INC.. The applicant listed for this patent is Caterpillar Inc.. Invention is credited to Frank J. Lombardi, Derek E. Nieman, Jeffrey J. Ribordy, Derek Tanis, Ramamurthy Vaidyanathan.
Application Number | 20170058803 14/835947 |
Document ID | / |
Family ID | 57909106 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170058803 |
Kind Code |
A1 |
Nieman; Derek E. ; et
al. |
March 2, 2017 |
Cylinder Cutout System and Method
Abstract
The disclosure describes an internal combustion engine and a
method for operating an internal combustion engine, in which an
electronic controller is programmed to determine whether the
internal combustion engine is operating within a cylinder cutout
enabling region and, when the engine operates in the cylinder
cutout enabling region, to cutout one or more of the engine
cylinders by causing the cutout cylinder's fuel injector to cease
injecting fuel into cutout cylinder, and to also cause the
still-active engine cylinders to operate with an additional amount
of fuel such that a steady state engine torque output remains
unchanged before and after the second cylinder is cutout.
Inventors: |
Nieman; Derek E.; (Peoria,
IL) ; Vaidyanathan; Ramamurthy; (Peoria, IL) ;
Tanis; Derek; (Peoria, IL) ; Ribordy; Jeffrey J.;
(Chillicothe, IL) ; Lombardi; Frank J.; (Metamora,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Caterpillar Inc. |
Peoria |
IL |
US |
|
|
Assignee: |
CATERPILLAR INC.
Peoria
IL
|
Family ID: |
57909106 |
Appl. No.: |
14/835947 |
Filed: |
August 26, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 10/12 20130101;
F02D 41/10 20130101; F02D 41/0007 20130101; Y02T 10/144 20130101;
F02D 41/0097 20130101; F02D 41/08 20130101; F02D 41/0087
20130101 |
International
Class: |
F02D 41/00 20060101
F02D041/00 |
Claims
1. An internal combustion engine, comprising: a cylinder case
forming at least a first cylinder and a second cylinder, each of
the first cylinder and the second cylinder slidably containing a
respective piston; a turbocharger having a turbine associated with
a compressor, the turbine operating the compressor from exhaust gas
provided by at least the first cylinder during operation; a first
fuel injector disposed to inject fuel into the first cylinder
during operation, and a second fuel injector disposed to inject
fuel into the second cylinder during operation; a plurality of
sensors configured to provide signals indicative of engine
operating parameters during operation; and an electronic controller
configured to receive the signals from the plurality of sensors and
to provide commands to the first fuel injector and to the second
fuel injector, the commands causing the first fuel injector or the
second fuel injector to inject the fuel into, respectively, the
first cylinder or the second cylinder; wherein the electronic
controller is programmed to determine whether the internal
combustion engine is operating within a cylinder cutout enabling
region and, when the engine operates in the cylinder cutout
enabling region, to cutout the second cylinder by causing the
second fuel injector to cease injecting fuel into the second
cylinder and the first fuel injector to inject an additional amount
of fuel into the first cylinder, such that a steady state engine
torque output remains unchanged before and after the second
cylinder is cutout.
2. The internal combustion engine of claim 1, wherein the cylinder
cutout enabling region includes idle engine operation.
3. The internal combustion engine of claim 1, wherein the cylinder
cutout enabling region includes no load to low load engine output,
and low engine speed.
4. The internal combustion engine of claim 1, wherein the cylinder
case forms additional cylinders, and wherein the electronic
controller is programmed to cutout at least one of the additional
cylinders.
5. The internal combustion engine of claim 4, wherein the
electronic controller is further programmed to cause the first fuel
injector to incrementally increase an amount of fuel injected into
the first cylinder for every additional cylinder that is
cutout.
6. The internal combustion engine of claim 1, wherein the signals
indicative of engine operating parameters include signals
indicative of engine speed and engine load.
7. The internal combustion engine of claim 6, wherein the signals
further include a desired engine load output.
8. The internal combustion engine of claim 7, wherein the signals
further include a time since a change in engine operation
occurred.
9. The internal combustion engine of claim 1, wherein the
additional amount of fuel injected into the first cylinder when the
second cylinder has been cutout is arranged and configured to
increase a temperature and a pressure of exhaust gas provided to
the turbine after the second cylinder cutout as compared to a
corresponding temperature and pressure of exhaust gas provided to
the turbine before the second cylinder cutout with the engine
operating at a constant engine speed and a constant engine load
output.
10. The internal combustion engine of claim 1, wherein the internal
combustion engine includes more than two cylinders, and wherein the
electronic controller is further programmed to determine the number
of engine cylinders to cutout based on the signals.
11. The internal combustion engine of claim 10, wherein the
electronic controller is programmed to change which cylinder is
cutout during operation.
12. The internal combustion engine of claim 1, wherein the cylinder
case further forms a third cylinder, a fourth cylinder, a fifth
cylinder and a sixth cylinder, for a total of six cylinders, and
further includes a third fuel injector configured to inject fuel
into the third cylinder, a fourth fuel injector configured to
inject fuel into the fourth cylinder, a fifth fuel injector
configured to inject fuel into the fifth cylinder, and a sixth fuel
injector configured to inject fuel into the sixth cylinder, and
wherein the electronic controller is further programmed to
selectively cutout one, two, three or four of the six
cylinders.
13. A method for operating an internal combustion engine having a
cylinder case forming at least a first cylinder and a second
cylinder, each of the first cylinder and the second cylinder
slidably containing a respective piston, a turbocharger having a
turbine associated with a compressor, the turbine operating the
compressor from exhaust gas provided by at least the first cylinder
during operation, a first fuel injector disposed to inject fuel
into the first cylinder during operation, a second fuel injector
disposed to inject fuel into the second cylinder during operation,
a plurality of sensors configured to provide signals indicative of
engine operating parameters during operation, and an electronic
controller configured to receive the signals from the plurality of
sensors and to provide commands to the first fuel injector and to
the second fuel injector, the commands causing the first fuel
injector or the second fuel injector to inject the fuel into,
respectively, the first cylinder or the second cylinder, the method
comprising: determining in the electronic controller when the
internal combustion engine is operating within a cylinder cutout
enabling region; and when the engine operates in the cylinder
cutout enabling region, using the electronic controller to cutout
the second cylinder by causing the second fuel injector to cease
injecting fuel into the second cylinder and the first fuel injector
to inject an additional amount of fuel into the first cylinder,
such that a steady state engine torque output remains unchanged
before and after the second cylinder is cutout.
14. The method of claim 13, wherein the cylinder cutout enabling
region includes idle engine operation.
15. The method of claim 13, wherein the cylinder cutout enabling
region includes no load to low load engine output, and low engine
speed.
16. The method of claim 13, wherein the cylinder case forms
additional cylinders, and wherein the method further comprises
cutting out at least one of the additional cylinders in the
electronic controller.
17. The method of claim 16, wherein the method further comprises
causing the first fuel injector to incrementally increase an amount
of fuel injected into the first cylinder for every additional
cylinder that is cutout.
18. The method of claim 13, wherein the signals indicative of
engine operating parameters include signals indicative of engine
speed and engine load.
19. The method of claim 18, wherein the signals further include a
desired engine load output.
20. The method of claim 19, wherein the signals further include a
time since a change in engine operation occurred.
Description
TECHNICAL FIELD
[0001] This patent disclosure relates generally to internal
combustion engines and, more particularly, to reciprocating piston
engines.
BACKGROUND
[0002] Typical internal combustion engines include a reciprocating
piston disposed within a cylinder having a closed end. A variable
volume created between the piston, the cylinder, and the closed end
encloses and compresses a fluid, which can include air, a mixture
of air and exhaust gas, a combustible mixture, and other fluids.
During operation, combustion of the fuel/air mixture creates hot
and expanding exhaust gases, which push the piston along the
cylinder. The piston is connected to a crankshaft, which includes
an offset lobe connected to the piston via a connecting rod such
that power generated during combustion pushes the piston, which in
turn causes the crankshaft to rotate and produce useable power.
[0003] In turbocharged engines a performance tradeoff exists
between turbo performance at rated power and boost available at no
or low load conditions. For example, engine operation at rated
power requires a large frame size turbine and compressor, which can
effectively draw power from the engine's exhaust gas and use a
portion of that power to compress air provided to the engine for
combustion. At rated power, the engine will burn a large amount of
fuel, which requires a large amount of air to maintain a desired
air to fuel ratio. The relatively large turbocharger frame size can
provide the appropriate air amount at a relatively low engine
pumping loss, which increases engine efficiency. However, while
engine operation at the rated power tends to require a large
turbocharger frame size, as discussed above, low or no load engine
performance, and also engine transient performance when the engine
is accelerating, tends to require a smaller frame size. This is
because the rotational inertia of the turbine and compressor wheel,
and also the pressure that can be built up in the turbine and
compressor, and also the rate at which pressure can be built up,
will be improved from a smaller frame size turbocharger, which will
also include smaller turbine and compressor wheels having a smaller
rotational inertia permitting them to accelerate faster. The effect
of a delay in engine power output increase because of the
turbocharger is sometimes referred to as turbocharger or turbine
lag or delay.
[0004] Thus, a tradeoff exists when sizing a turbocharger for an
internal combustion engine. Typically, engines use a relatively
larger frame size turbocharger to achieve desired operational
characteristics at high engine loads, which compromises low end
engine performance and can increase turbocharger lag. In an engine
having a larger frame size turbocharger, at low or no engine load
conditions such as idle, accelerating engine performance, snap
torque increases and the like will be affected and limited by the
amount of air that the turbocharger can provide if the engine is to
maintain a desired air/fuel ratio.
[0005] Various solutions have been proposed in the past to address
issues with turbocharger lag. For example, certain engines may use
more than one turbocharger that operate in sequence or in parallel.
In such engines, a large turbocharger may be used primarily for
high load conditions while a second, smaller turbocharger may be
used at low or no load conditions. These differently sized
turbochargers, however, may still not address quick power increases
of the engine output when the engine is operating at a mid-range
condition. Other engines use two turbochargers in parallel, each of
which is sized for a mid-engine range. These engines too, however,
may not effectively and efficiently operate at rated power and no
or low load conditions, and they may also increase engine pumping
losses by the additional exhaust and fresh air conduits that are
required to connect them to the engine.
[0006] An additional solution proposed in the past to in an attempt
to decrease the effects of turbocharger lag in engine performance
is to use a turbine having a variable frame. While a turbine of
this type can simulate a smaller frame turbine, which can help in
the low end of engine performance, the compressor is typically a
fixed-frame compressor that is sized for the high end of engine
performance, so the solution is only partly suited to address
transient engine performance.
SUMMARY
[0007] In one aspect, the disclosure describes an internal
combustion engine that includes a cylinder case forming at least a
first cylinder and a second cylinder, each of the first cylinder
and the second cylinder slidably containing a respective piston, a
turbocharger having a turbine associated with a compressor, the
turbine operating the compressor from exhaust gas provided by at
least the a first cylinder during operation, a first fuel injector
disposed to inject fuel into the first cylinder during operation,
and a second fuel injector disposed to inject fuel into the second
cylinder during operation, a plurality of sensors configured to
provide signals indicative of engine operating parameters during
operation, and an electronic controller configured to receive the
signals from the plurality of sensors and to provide commands to
the first injector and to the second injector, the commands causing
the first injector or the second injector to inject the fuel into
the respective first cylinder or second cylinder. The electronic
controller is programmed to determine whether the internal
combustion engine is operating within a cylinder cutout enabling
region and, when the engine operates in the cylinder cutout
enabling region, to cutout the second cylinder by causing the
second fuel injector to cease injecting fuel into the second
cylinder and the first fuel injector to inject an additional amount
of fuel into the first cylinder, such that a steady state engine
torque output remains unchanged before and after the second
cylinder is cutout.
[0008] In another aspect, the disclosure describes a method for
operating an internal combustion engine having a cylinder case
forming at least a first cylinder and a second cylinder, each of
the first cylinder and the second cylinder slidably containing a
respective piston, a turbocharger having a turbine associated with
a compressor, the turbine operating the compressor from exhaust gas
provided by at least the a first cylinder during operation, a first
fuel injector disposed to inject fuel into the first cylinder
during operation, a second fuel injector disposed to inject fuel
into the second cylinder during operation, a plurality of sensors
configured to provide signals indicative of engine operating
parameters during operation, and an electronic controller
configured to receive the signals from the plurality of sensors and
to provide commands to the first injector and to the second
injector, the commands causing the first injector or the second
injector to inject the fuel into the respective first cylinder or
second cylinder. The method includes determining in the electronic
controller when the internal combustion engine is operating within
a cylinder cutout enabling region, and, when the engine operates in
the cylinder cutout enabling region, using the electronic
controller to cutout the second cylinder by causing the second fuel
injector to cease injecting fuel into the second cylinder and the
first fuel injector to inject an additional amount of fuel into the
first cylinder, such that a steady state engine torque output
remains unchanged before and after the second cylinder is
cutout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a block diagram of an engine in accordance with
the disclosure.
[0010] FIG. 2 is a fragmented view of an engine cylinder in
accordance with the disclosure.
[0011] FIG. 3 is a block diagram for a cylinder cutout controller
in accordance with the disclosure.
[0012] FIG. 4 is a qualitative chart of a change in fueling when
one or more cylinders are cutout, in accordance with the
disclosure.
[0013] FIG. 5 is a qualitative chart comparing boost and torque
output for a baseline engine condition and a cylinder cutout
condition in accordance with the disclosure.
[0014] FIGS. 6 and 7 are pressure charts or turbine inlet pressure
and compressor outlet pressure for various engine operating
conditions in accordance with the disclosure.
[0015] FIG. 8 is a chart of various engine operating parameters in
accordance with the disclosure.
[0016] FIG. 9 is a flowchart for a method of operating an engine in
accordance with the disclosure.
DETAILED DESCRIPTION
[0017] This disclosure relates to internal combustion engines
having reciprocating pistons operating within cylinders formed in a
cylinder block. In the embodiments illustrated herein, one or more
cylinders of the engine are cutout when the engine is operating at
low load, or an no load, which has the unexpected and surprising
effect of increasing engine boost pressure, and which allows the
engine to accelerate and increase its torque output faster than an
engine that has all cylinders firing from the same starting
point.
[0018] In one general aspect, the present disclosure describes a
method of operating a direct injection engine, in which an
injection signal is cutout, removed or temporarily suspended from
one or more cylinders when the engine is operating at a no-load or
a low-load condition such as idle. The cutting of the injection
signal may be implemented on the same cylinders or to different
cylinders as the engine operates. The non-fueling of a cylinder,
which is generally described herein as the cutting-out or a cutout
cylinder, causes the remaining cylinders, which are still firing,
to increase fueling to maintain overall engine power output.
However, because fewer than all cylinders are firing, the
non-firing or cutout cylinders are still consuming power, for
example, due to friction and to compress the air found therein,
which decreases overall engine efficiency. This decreased
efficiency is reflected in an overall higher fueling amount for the
same engine power output, which higher fueling translates directly
into increased energy supplied to the turbine, in the form of
pressure and temperature (or, in other words, enthalpy) in the
exhaust gas. The increased pressure and temperature of the exhaust
gas causes a higher energy conversion at the turbine of the engine,
which results in increased compressor work and, thus, higher engine
boost, which as used here describes the pressure of air provided to
an engine intake manifold, which may also include exhaust gas mixed
with the air. With more boost, the fuel system can inject more fuel
for the same air/fuel ratio, which in turn provides greater
instantaneous power capability for the same starting load of the
engine.
[0019] In one exemplary implementation, fueling thresholds can be
established in an electronic controller that operates the fuel
injectors of the engine such that a cylinder cutout strategy can be
activated and deactivated, depending on engine operating
conditions. In one example, when the desired engine fueling is
below a threshold for given time period, the controller may cause
the fueling to be cut from one or more engine cylinders. When the
desired fueling is above a threshold for a given time period, the
fueling may be restored to all engine cylinders by the controller.
The controller may further determine how many cylinders to cut
based on, for example, engine speed, engine load, engine fueling,
altitude, temperature and/or additional or different engine
operating parameters to maximize engine performance.
[0020] For the sake of illustration, an internal combustion engine
100 is shown in the block diagram of FIG. 1, and a fragmented view
of an engine cylinder 104 is shown in FIG. 2. The engine 100
includes cylinder block 102 that forms a plurality of engine
cylinders 104. In the illustrated embodiment, the engine 100
includes six cylinders 104 arranged in an inline configuration but
any other number of cylinders, including a single cylinder, can be
used, as well as any other cylinder configuration, such as a
V-configuration. As shown in FIG. 2, each cylinder 104 includes a
bore 106 slidably accepting therewithin a piston 108. As is known
from typical engine applications, pistons can be connected to an
engine crankshaft (not shown), which operates to provide a force
tending to move each piston within the cylinder bore, for example,
during a compression stroke, as well as can be moved by a force
applied by the piston to rotate the crankshaft, for example, during
a combustion or power stroke.
[0021] The cylinder 104 defines a variable volume 110 that, in the
illustrated orientation, is laterally bound by the walls of the
bore 106 and is closed at its ends by a top portion or crown of the
piston 108 and by a flame deck 112 of the cylinder head 113, which
is typically referred to as the lowermost surface of the cylinder
head that is open to the cylinder. As shown, the bore 106 is formed
within a hollow cylindrical sleeve 107 disposed within a bore 109
formed in the cylinder block 102, but other configurations may be
used. The variable volume 110 changes between maximum and minimum
capacity as the piston 108 reciprocates within the bore 106. In
this respect, the piston 108 continuously reciprocates between a
bottom dead center (BDC) position, in which the piston 108 is
retracted by a maximum distance within the bore 106, and a top dead
center (TDC) position, in which the piston 108 is inserted at a
maximum extent within the bore 106.
[0022] In reference to FIG. 1, each cylinder 104 includes at least
one intake valve 114 (two shown) and at least one exhaust valve 116
(two shown). The intake and exhaust valves 114 and 116 are
selectively activated to fluidly connect the variable volume 110
with sinks and sources of fluids during operation of the engine
100. Specifically, the intake valve 114 selectively blocks an
intake passage 120 that fluidly interconnects the variable volume
110 with an intake manifold 122. Similarly, the exhaust valve 116
selectively blocks an exhaust passage 124 that fluidly
interconnects the variable volume 110 with an exhaust manifold 126.
A fuel injector 132 is disposed to inject fuel within variable
volume 110 (FIG. 2) at appropriate times during operation.
[0023] In the exemplary embodiment of the engine 100 shown in FIG.
1, the engine 100 includes a turbocharger 134 having a turbine 136
connected to a compressor 138, but other configurations, such as
multi-staged, series or parallel turbocharger configurations may be
used. During operation of the engine 100, exhaust gas collected in
the exhaust manifold 126 is provided to drive the turbine 136
through an exhaust conduit 140. Exhaust conduit and after-treatment
components disposed downstream of the turbine 136 are not shown in
FIG. 1 for simplicity, but any appropriate configuration may be
used.
[0024] The turbine 136 drives the compressor 138, which compresses
filtered, ambient air from an intake duct 142 to provide
compressed, charge air to an air conduit 144. The air conduit 144
includes an optional charge air cooler (CAC) cooler 146, which
cools the charge air before it is provided to the intake manifold
122. The illustrated engine 100 further includes a high pressure
loop (HPL) exhaust gas recirculation (EGR) system, but other types
of EGR systems such as low or intermediate pressure systems may be
used. Depending the requirements of the specific engine
application, the EGR system may be omitted entirely. In the
illustrated embodiment, the EGR system includes an EGR cooler 148
that fluidly interconnects the exhaust manifold 126 with the intake
manifold 122 such that cooled exhaust gas can be provided to the
intake of the engine. An EGR valve 150 is disposed to meter the
amount of exhaust gas recirculated in this fashion.
[0025] The engine 100 further includes an electronic controller
152. The electronic controller 152 may be a single controller or
may include more than one controller disposed to control various
functions and/or features of the engine 100 and/or features of a
vehicle or machine in which the engine 100 is installed. For
example, a master controller, used to control the overall operation
and function of a machine, may be cooperatively implemented with a
motor or engine controller used to control the engine 100. In this
embodiment, the term "controller" is meant to include one, two, or
more controllers that may be associated with the engine 100 and
that may cooperate in controlling various functions and operations
of the engine 100 (FIG. 1), or any other embodiments for engines
described hereinafter. The functionality of the controller, while
described conceptually in the present disclosure to include various
discrete functions for illustrative purposes only, may be
implemented in hardware and/or software without regard to the
discrete functionality shown. Accordingly, various interfaces of
the controller are described relative to components of the engine
100 shown in FIG. 1, but such interfaces are not intended to limit
the type and number of components that are connected, nor the
number of controllers that are described.
[0026] Accordingly, the controller 152 is associated with each of
the fuel injectors 132 and the EGR valve 150 and configured to
selectively control their operation. The controller 152 is further
associated with sensors and actuators of the engine such as
crankshaft and/or camshaft position sensors (not shown), engine
speed and/or torque sensors (not shown), and other known sensors
and actuators that participate in providing functions and
information to the controller 152 to control and monitor engine
operation. Relative to the present disclosure, the controller 152
is programmed and configured to provide appropriate injection
commands to the fuel injectors 132 and to determine, during
operation, the number and timing of cylinder cutouts.
[0027] In the embodiment illustrated in FIG. 2, valve activation is
accomplished by a traditional cam-follower arrangement or any other
suitable fixed or variable valve activation arrangement. As shown,
each of the intake and exhaust valves 114, 116 has a respective
valve stem 154 that pushes the valve to open against a respective
closing spring 156. Each valve stem 154 is pushed by a valve bridge
158 that follows a respective lobe 160 of a rotating camshaft 162
in the known fashion. The rate of rotation of the camshaft may
depend on the particular mode of engine operation such as 4-stroke
operation, 6-stroke operation, and others.
[0028] Most engine operating cycles will include an intake stroke,
in which air or a mixture of air with exhaust gas will be admitted
into the variable volume 110, and a compression stroke, in which
the piston moves from the BDC position towards the TDC position. At
an intermediate position of the piston during the compression
stroke, during an expansion stroke, and/or during a fuel injection
carried out while the cylinder is undergoing an expansion stroke,
the injector may inject fuel within the variable volume to create a
combustible mixture that ignites and/or burns to create expanding
gases that push the piston during the power stroke. For those
cylinders that may be cutout, the step of fuel injection may be
omitted. In a hybrid implementation, to reduce the power
consumption of cutout cylinders, a small amount of fuel may be
added to the cutout cylinders to make up for the power consumed to
compress the air mixture during the compression stroke.
[0029] The methodology for implementing a cylinder cutout strategy,
and its effects in improving transient engine performance will now
be described in further detail. FIG. 3 is a block diagram of an
engine controller 200 in accordance with the disclosure. The
controller 200 may be an algorithm implemented and operating within
the controller 152 (shown in FIG. 1) that is suited for activating
or deactivating cylinders by sending or, respectively, not sending,
fueling commands to the various fuel injectors 132 (also shown in
FIG. 1) of the engine. The controller 200 receives various signals
indicative of an engine operating condition and various engine
operating parameters. In the illustrated embodiment, the controller
200 receives an engine speed signal 202 and an engine load signal
204, which may be indicative of an actual engine power or torque
output. The engine speed and load signals 202 and 204 are provided
to an engine map 206, which includes information about the engine
operating range in terms of speed and load. The controller further
receives a time signal 208 that is provided to a timer function
210. A desired engine load 212 is provided to a determinator
function 214. Additional and/or different signals may alternatively
be provided to the controller 200 than those shown, which are
presented in a simplified fashion for purpose of discussion.
[0030] The engine map 206 interpolates an engine operating point or
condition based on the engine speed signal 202 and the engine load
signal 204 to determine whether the engine is operating within a
desired range for cylinder cutoff. For example, the desired range
for cylinder cutoff may include a range of low engine speeds, i.e.,
within an engine idle speed range, and relatively low or no engine
loads, for example, loads that are applied to an idling engine to
power auxiliary systems and the like. When the engine is operating
in the desired range for cylinder cutoff, the engine map 206 may
provide an enabling flag 216 to an AND comparator 218. The engine
map 206 may further provide an indication 217 of a change in engine
operating conditions each time the engine speed and/or the engine
load signals 202 and 204 change by more than a threshold or
predefined amount.
[0031] The timer function 210 may monitor the time signal 208, and
also the indication 217, and signal a steady engine operation
period 220 when engine operating conditions have not changed more
than a predefined amount for a predefined period. For example, the
timer function 210 may signal the steady engine operation period
220 when the engine has been idling for at least 5 minutes. The
steady engine operation period 220 is also provided to the AND
comparator 218.
[0032] The desired engine load 212, which may also be correlated to
a desired engine fueling rate, is provided to the determinator
function 214, which operates to determine whether the present
fueling rate of the engine and whether an increase in engine load
has been requested, for example, by the user or another function of
a machine controller, and provides an engine load indication 222 to
the AND comparator 218. The determinator function 214 further
provides a change magnitude indication 224 that may indicate the
magnitude of the change in engine load that has been requested by
the operator and/or the system in general.
[0033] When the engine is operating within a region of the engine
map that is not suited for quick load increases in engine output,
for example, such as idle, the engine map 206 may activate the
enabling flag 216, which indicates that a cylinder cutout strategy
can be activated to improve the transient response of the engine.
The cutout may then be implemented when the requested engine load,
a sudden load application is made to the engine, or the engine is
required to increase its speed and/or load quickly in a transient
change. The various engine regions may be predefined for static
conditions, such as an expected low boost condition at around idle,
and even for dynamic conditions, such as low boost that may limit
the engine's ability to increase fuelling, and thus, power, quickly
during operation. When the enabling flag 216 is present for a
predefined period, as indicated by activation of the steady engine
operation period 220, and a load increase has been requested, as
indicated by the indication 222, all signals provided to the AND
comparator 218 will be active, causing a cylinder cutout request
226 to activate at the output of the AND comparator 218.
[0034] Activation of the cylinder cutout request 226 is provided to
a cylinder cutout controller 228, which determines which engine
cylinders remain active, i.e., receive fuel commands to product
power, and which cylinders will be cutout, i.e., will receive a
minimal or no fuel injection command, during engine operation. The
cylinder cutout controller 228 includes a plurality of cylinder
command lines 230, one for each engine cylinder, which convey the
controller's commands to the injection module of the engine (not
shown here) and dictate which cylinders will continue receiving
fueling commands, and which cylinders will be cutout. Depending on
the magnitude of the power increase commanded by the user, as
provided by the engine magnitude indication 224, the controller 228
may command the cutout of one, two, three or more cylinders of the
engine, with an increasing number of cylinders being cut to
correspond to larger increases in requested engine power.
[0035] The more cylinders of the engine that are cutout, the larger
the amount of fuel injected into the operating or firing cylinders
is to ensure that engine power is maintained. A qualitative graph
showing an incremental fueling increase in firing cylinders in an
engine when cylinders are cutout is shown in FIG. 4. As shown in
the graph, where the horizontal axis 302 represents time, the left
vertical axis 304 represents the number of cylinders that are
cutout, and the right vertical axis 305 represents fueling per
still-firing engine cylinder, at a trigger time 303 when two
cylinders are cutout, as indicated by line 306, the fueling 308
increases from a low value 310 to a high value 312. The magnitude
of the fueling rate increase for the firing cylinders will depend
on the number of engine cylinders in the engine and also on the
number of cylinders that will be cutout. For purpose of
illustration, in an engine having two cylinders, when one of the
two cylinders is cutout, the remaining, still-firing cylinder, will
continue operating at a fueling rate that is at least double as
compared to the fueling rate for that cylinder when both cylinders
were firing and the engine operates at the same operating condition
in terms of engine speed and load.
[0036] Engine performance at no or low load conditions, such as
idle, during a cylinder cutout surprisingly and unexpectedly
improves the transient ability of the engine to increase the rate
load output increases. A qualitative graph showing a comparison
between a baseline engine transient ability, and the transient
ability for the same engine but with cylinder cutout being
implemented, is shown in FIG. 5. In this figure, a baseline curve
314 representing engine boost (defined as fluid pressure within the
engine's intake manifold, or an equivalent parameter) is at a
certain level 316 as indicated on a vertical axis 318.
[0037] At a trigger time 320, which is denoted along the horizontal
axis 322, a snap load increase is requested by the engine. In
response, an engine controller may begin increasing cylinder
fueling while maintaining a constant or at least a predefined air
to fuel ratio. The turbocharger lag discussed previously may limit
the engine's ability to increase its fueling, and thus the enthalpy
of the exhaust gas driving the turbine, which shapes an increasing
segment 324 of the baseline curve 314 representing engine boost up
to a target boost value 326. The rate of boost increase of the
engine also determines the rate at which fuel can be added to the
cylinders, and thus engine power output, which is represented by
the dashed-line curve 328. Accordingly, the engine torque increases
from an initial value 330 to a final value 332 along the curve 328,
as shown in the graph. The time for engine boost to reach the
target boost value 326 and the torque to reach the final value 332
is denoted as a baseline time 334.
[0038] Also shown in FIG. 5, for purpose of comparison, are curves
representing engine boost and engine torque for the same engine
that is operating with certain engine cylinders having been cutout.
Specifically, a cutout curve 336 representing engine boost is at a
certain, increased level 338 as indicated on the vertical axis 318.
When certain cylinders are cutout, the staring boost of the engine
is increased due to the increased power provided to the
turbocharger as compared to an engine operating at the same speed
and load with all cylinders firing. At the trigger time 320, the
same snap load increase is applied to the engine as the baseline
case described above, where all engine cylinders are firing.
[0039] In the case of the engine operating with cutout cylinders,
the engine controller may increase cylinder fueling to the firing
cylinders while maintaining a constant or at least a predefined air
to fuel ratio, which in this case, given the increased boost,
causes the engine to develop power faster. The turbocharger lag
discussed previously still limits the engine's ability to increase
its fueling, and thus the enthalpy of the exhaust gas driving the
turbine, but has a lesser effect. As a result, the cutout curve 336
forms an increasing segment 340 up to the target boost value 326
that is sharper than the corresponding increasing segment 324 of
the baseline curve 314. The sharper rate of boost increase of the
engine having cutout cylinders is also reflected in the sharper
increase in engine torque 342 from the initial value 330 to the
final value 332, as shown in the graph.
[0040] Advantageously, the time for engine boost when cylinders are
cutout, as indicated by the cutout curve 336, to reach the target
boost value 326, is considerably shorter than the baseline time. As
an illustration, the cutout curve 336 reaches the target boost
value 326 at a time 344, which as is shown in FIG. 5 is more than
50% faster than the time it takes the baseline curve 314 to reach
the same value. Similarly, the engine torque 342 reaches the final
value 332 faster than its baseline counterpart represented by the
dashed-line curve 328. In short, a time 346 representing the
shortening of the time required for the engine to reach desired or
target boost and torque represents a 55% reduction in the time
required for the engine to reach these parameters when certain
cylinders have been cutout. As shown, the engine has six cylinders
from which three have been cutout. Part of the reason for the
shorter time is an offset 348 in the boost and torque output of the
engine, which is a surprising, unexpected and direct result of
cylinder cutout low or no load engine performance.
[0041] Exemplary data of various engine operating parameters will
now be presented. FIGS. 6 and 7 are graphs showing the effect on
turbine inlet pressure, turbine inlet temperature, and compressor
outlet pressure for an engine, for example, the engine 100 shown in
FIG. 1 and having six cylinders, when one, two, three or four
cylinders have been cutout, which respectively leaves five, four,
three or two cylinders still firing. A data point is plotted for
each operating condition of the engine having the corresponding
number of cylinders firing. Accordingly, in reference to the graphs
of FIGS. 6 and 8, a first point 402 represents a collection of
baseline points at which all six engine cylinders are firing. At
the first points 402, as denoted in both FIGS. 6 and 7, a turbine
inlet temperature, which is represented by squares in FIG. 6, is at
about 200 deg. C., and the turbine inlet pressure, which is
represented by diamonds in FIG. 6, is at about 120 kPa-a. The
compressor outlet pressure, which is essentially an indication of
engine boost pressure and which is represented by diamonds in FIG.
7, is at about 115 kPa-a.
[0042] The graphs in FIGS. 6 and 7 show the effect on these
parameters when one, two, three and four cylinders are cutout. In
this way, a second set of points 404 represent a single cylinder
cutout (with five cylinders firing), a third set of points 406
represent two cylinders cutout (with four cylinders firing), a
fourth set of points 408 represent three cylinders cutout (with
three cylinders firing), and a fifth set of points 410 represent
four cylinders cutout (with two cylinders firing). As can be seen
from FIGS. 6 and 7, the trends for turbine inlet temperature,
turbine inlet pressure and the resulting boost produced by the
turbocharger are increasing for an increasing number of cutout
cylinders. For example, turbine inlet temperature increases by
almost 150% from the baseline when four cylinders are cutout.
Similarly, turbine inlet pressure increases by 12.5% as compared to
the baseline when four of the six cylinders are cutout. Such
increases in pressure and temperature at the inlet of the turbine,
allow the turbine to extract more energy from the exhaust gas,
which means more energy is provided to the compressor, thus
increasing its work output. Accordingly, the compressor outlet
pressure increases by almost 20% as compared to the baseline when
four of the six cylinders are cutout.
[0043] Additional data points for the first through fifth sets of
points 402-410, as discussed above relative to FIGS. 6 and 7, are
shown in FIG. 8, where diamonds represent engine torque output,
squares represent fuel rate (per still-firing engine cylinder), and
triangles represent max. intake mean effective pressure (IMEP),
which is a parameter directly related to engine boost pressure. As
can be seen from the chart, for an engine torque that remains
relatively unchanged as more engine cylinders are cutout, the fuel
rate for the still-firing cylinders increases by about 30% as
compared to the baseline when four cylinders have been cutout. For
that same condition, the IMEP increases by more than 300% as the
fuel increases. This may mean that the still-firing cylinders work
harder to make up the loss of power generation from the cutout or
non-firing cylinders, which increases the temperature and pressure
of the exhaust gas provided to the turbocharger.
INDUSTRIAL APPLICABILITY
[0044] The present disclosure is applicable to internal combustion
engines and, specifically, engines having two or more reciprocating
pistons. In the disclosed embodiments, an engine having a fuel
injector configured to inject fuel directly into a respective
engine cylinder is described, but such embodiment is exemplary and
should not be understood as limiting to the scope of the invention.
In general, the present disclosure is applicable to any engine
type, including spark ignition or compression ignition engines.
Further, the present disclosure applies to engines operating with
any one or more fuel types such as gasoline, diesel, natural or
liquid petroleum gas, and other fuels and/or mixtures of fuels. The
fuel delivery into the engine cylinders may be accomplished by
direct injection, or may be provided upstream of the cylinders, for
example, in an intake manifold of the engine, an intake runner of
the cylinder, and other delivery modes. Lastly, although a four
stroke engine operating cycle is commonly used, more or fewer than
four strokes may be used.
[0045] A flowchart for a method of operating an engine in
accordance with the disclosure is shown in FIG. 9. In accordance
with the method, an engine controller monitors engine operating
parameters at 502 to determine, at 504, whether engine operation
has stabilized around a no-load or low-load engine operating
condition for a predefined period. The stabilized engine operation
in an enabling range for cylinder cutout may include comparing
engine speed and load, and also a timer value, with threshold or
enabling ranges. When the engine has been operating at an enabling
condition for at least a desired time, the controller enables
cylinder cutout at 506, which may include the optional operation of
dynamically determining how many cylinders to cutout based on the
then present engine speed and load. One or more cylinders are
cutout at 508, and the engine operates at the cylinder cutout
condition 510. Optionally, the controller may cutout different
cylinders at different times, with the total number of cutout
cylinders at any time being equal to a desired number of cutout
cylinders for the then-present engine operating condition. It is
noted that, in one embodiment, the engine may operate with all
cylinders firing, even if the engine operating point, for example,
the then-present engine speed and load, are within a cylinder
cutout enabling range of engine speeds and loads. A cutout of one
or more engine cylinders may be prompted by an increase in a
command for engine power such as an acceleration or an increase in
engine load. For example, an engine operating at low load, which
experiences a load increase, may implement a cutout of certain
engine cylinders when additional boost pressure is required to
quickly deliver the engine power requested. Other conditions may
include engine load acceptance, increasing engine speed and power
transient operation, and the like.
[0046] The cylinders remain cutout while no change in engine
operation has been detected in the controller at 512. When an
engine operating condition changes, e.g., when engine speed and
load have increased beyond a cutout enabling range or engine
operating points, the controller may reactivate all engine
cylinders at 514, and the process repeats while the engine
operates.
[0047] It will be appreciated that the foregoing description
provides examples of the disclosed system and technique. However,
it is contemplated that other implementations of the disclosure may
differ in detail from the foregoing examples. All references to the
disclosure or examples thereof are intended to reference the
particular example being discussed at that point and are not
intended to imply any limitation as to the scope of the disclosure
more generally. All language of distinction and disparagement with
respect to certain features is intended to indicate a lack of
preference for those features, but not to exclude such from the
scope of the disclosure entirely unless otherwise indicated.
[0048] Recitation of ranges of values herein are merely intended to
serve as a shorthand method of referring individually to each
separate value falling within the range, unless otherwise indicated
herein, and each separate value is incorporated into the
specification as if it were individually recited herein. All
methods described herein can be performed in any suitable order
unless otherwise indicated herein or otherwise clearly contradicted
by context.
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