METHOD OF CONTROLLING AN ENGINE DURING TRANSIENT OPERATING
CONDITIONS
TECHNICAL FIELD
[0001] The subject invention generally relates to a method of controlling an
internal combustion engine, and more specifically to a method of minimizing soot
emissions from a diesel engine during operation of the diesel engine in a transient
operating condition.
BACKGROUND OF THE INVENTION
[0002] Internal combustion engines, and diesel engines in particular, are designed
to operate efficiently with low emissions during a steady state operating condition, and
tend to produce a large volume of soot emissions, i.e., smoke, during transient operating
conditions of the engine. Transient operating conditions occur when the engine operates
outside of the steady state operating condition, and may include, but are not limited too,
initial engine start-up, accelerating from a low engine speed, a load increase on the
engine while the engine maintains a constant engine speed, and an engine speed decrease
while the load on the engine remains constant.
[0003] The transient operating conditions are generally associated with a lack of
combustion air flowing into the engine for a given amount of fuel injected into the
engine, causing a rich combustion that produces a large volume of soot emissions in the
exhaust. In order to meet Federal emissions guidelines and requirements, the engine may
include a particulate filter that filters the soot emissions from the exhaust. However, the
particulate filters currently available must be regenerated on a regular basis to maintain
proper operation.
SUMMARY OF THE INVENTION
[0004] A method of controlling an internal combustion engine coupled to a
mechanically driven supercharger controlling a flow of air to the engine is disclosed. The
method includes defining a steady state operating condition of the engine; monitoring an
operating parameter of the engine to determine if the engine is operating outside of the
steady state operating condition in a transient operating condition; and adjusting the flow
of air from the supercharger during operation of the engine in the transient operating
condition. The flow of air supplied from the supercharger maintains a fuel/air mixture of
the engine to within a pre-determined ratio to minimize emissions from the engine during
operation of the engine in the transient operating condition.
[0005] A method of minimizing emissions from a diesel engine coupled to a
mechanically driven supercharger controlling a flow of air to the diesel engine is also
disclosed. The method includes defining a steady state operating condition of the engine;
defining a transient operating condition of the engine as operation of the engine outside
of the steady state operating condition; associating a range of values of an operating
parameter of the engine with the steady state operating condition; measuring a value of
the operating parameter during operation of the engine; comparing the measured value of
the operating parameter with the associated range of values of the operating parameter to
determine if the measured value of the operating parameter is in the transient operating
condition; and adjusting the flow of air from the supercharger during operation of the
diesel engine in the transient operating condition. The flow of air supplied from the
supercharger maintains a fuel/air mixture of the diesel engine to within a pre-determined
ratio to minimize emissions from the diesel engine during operation of the diesel engine
in the transient operating condition.
[0006] Accordingly, the method supplies a flow of combustion air to the engine
during transient operating conditions independently of a flow rate of the exhaust gas to
maintain a proper fuel/air ratio by increasing the flow rate of air supplied to the engine
from the supercharger prior to increasing the fuel injection rate to the engine.
Maintaining the proper fuel/air ratio minimizes soot emissions during operation of the
engine in the transient operating conditions. The reduced soot emissions allow the engine
to operate for extended periods of time without the need to regenerate a particulate filter.
[0007] The above features and advantages and other features and advantages of
the present invention are readily apparent from the following detailed description of the
best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 is a schematic cross sectional view of a first embodiment of an
internal combustion engine.
[0009] Figure 2 is a schematic cross sectional view of a second embodiment of an
internal combustion engine.
[0010] Figure 3 is a flow chart showing a method of controlling the internal
combustion engine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] Referring to the Figures, wherein like numerals indicate corresponding
parts throughout the several views, a first embodiment of an internal combustion engine
is shown generally at 20 in Figure 1. The engine 20 includes a conventional engine, such
as a diesel engine or a gasoline engine. As shown in Figure 1, the engine 20 is coupled to
a "superturbo" boosting system, which includes both a turbocharger 22 and a
supercharger 24 disposed in-line with each other to increase the boost, i.e., pressure, of
combustion air of the engine 20.
[0012] The turbocharger 22 is powered by exhaust gas provided by the engine 20
as is well known. The supercharger 24 is mechanically linked to the engine 20 and is
powered by the engine 20. The supercharger 24 may include a clutch 26, as shown in
Figure 1, interconnecting the engine 20 and the supercharger 24. Alternatively, as shown
in Figure 2, the supercharger 124 may be directly coupled to the engine 120 for
continuous operation of the supercharger 124 with the engine 120. The clutch 26 is
configured for selectively engaging and disengaging the supercharger 24. It should be
understood by those skilled in the art that the clutch 26 may, within the scope of the
present invention, comprise any type of clutch 26 (e.g., engageable friction discs,
electromagnetic, etc.) which is effective in transmitting mechanical drive from the
vehicle engine 20 (typically, but not necessarily, from the crankshaft) to the input shaft of
the supercharger 24. Also, as is also now well known to those skilled in the art, there
may be some sort of "step-up gear" speed increasing arrangement between the clutch 26
and the input shaft, with a typical ratio for such a speed increasing arrangement being in
the range of about 2:1 to about 4:1.
[0013] The boosting system includes a plurality of air ducts configured for
communicating the combustion air to the engine 20. The air ducts communicate the
combustion air to and from the engine 20. The air ducts include an intake 28, through
which the combustion air enters the boosting system in a direction indicated by arrow 30.
A first air duct 32 includes a filter 34, and is in fluid communication with an inlet of the
supercharger 24. The combustion air enters the boosting system through the intake 28,
and flows through the filter 34 toward the supercharger 24.
[0014] A second air duct 38 connects an outlet of the supercharger 24 with a
pumping portion, i.e., a compressor 42, of the turbocharger 22. A third air duct 44
interconnects an outlet of the compressor 42 with an inlet of an intercooler 46. The
function of the intercooler 46 is well known, and outside the scope of this invention.
Accordingly, the function of the intercooler 46 is not described in detail herein. A fourth
air duct 48 interconnects an outlet of the intercooler 46 with a combustion chamber 50 of
the engine 20.
[0015] Disposed within the fourth air duct 48 is an engine throttle 52, which is
shown in FIG. 1 in a fully open position. It should be appreciated that the engine throttle
52 may be controlled to be in any position between the fully open position shown in FIG.
1, and a fully closed position, which substantially blocks all air flow through the fourth
air duct 48, thereby limiting air flow into the combustion chamber 50 of the engine 20.
[0016] The turbocharger 22 also includes a turbine portion 54, which is
mechanically coupled to and configured to drive the compressor 42. A fifth air duct 56
interconnects the combustion chamber 50 of the engine 20 with an inlet of the turbine
portion 54 of the turbocharger 22 to provide the turbine portion 54 with the exhaust gas.
A sixth air duct 58 interconnects an outlet of the turbine portion 54 of the turbocharger 22
with exhaust exit 60. The exhaust gas flows out of the boosting system through the
exhaust exit 60 in a direction indicated by arrow 62.
[0017] A combustion air bypass duct 64 is disposed between the first air duct 32
and the outlet of the supercharger 24. A combustion air bypass valve 66 is disposed
within the combustion air bypass duct. The combustion air bypass valve 66 is normally
in a closed position when the supercharger 24 is operating to direct the combustion air
through the first air duct 32 to the supercharger 24. However, when reduced levels of
boost are sufficient, the combustion air bypass valve 66 may be moved from the closed
position of the combustion air bypass valve 66 toward an open position of the combustion
air bypass valve 66 to decrease the flow of combustion air through the supercharger 24,
and allow a portion of the combustion air to flow through the combustion air bypass duct
64, into the second air duct 38.
[0018] One result of moving the combustion air bypass valve 66 toward a more
open position is that the boost pressure of the combustion air in the second air duct 38
lower than the normal boost pressure present when the combustion air bypass valve 66 is
fully closed. As the vehicle engine 20 reaches relatively higher engine 20 speeds, the
clutch 26 may be disengaged, so that the supercharger 24 is not being driven. At the
same time, the turbocharger 22 is being driven by the flow of exhaust gas through the
fifth air duct 56. During this mode of operation, the combustion air bypass valve 66 is in
the fully opened position and should be large enough not to present any undesirable flow
restriction to the combustion air, which flows from the intake 28, through the first air
duct 32, through the combustion air bypass valve 66, through the combustion air bypass
duct 64, through the second air duct 38 and into the compressor 42 of the turbocharger
22.
[0019] An exhaust gas bypass duct 68 interconnects the fifth air duct 56 with the
sixth air duct 58. An exhaust gas bypass valve, i.e., a wastegate 70, is disposed within
the exhaust gas bypass duct 68. The wastegate 70 may be made and function as is well
known in the turbocharger 22 art.
[0020] While a "superturbo" system is shown in Figure 1 and described above, in
which the supercharger 24 is disposed within the boosting system before the turbocharger
22, it should be appreciated that the relative positions of the supercharger 24 and the
turbocharger 22 may be reversed to define a "turbosuper" boosting system, in which the
turbocharger 22 is disposed in the boosting system prior to the supercharger 24.
[0021] Referring to Figure 2, a second embodiment of the engine is shown
generally at 120. Features of the second embodiment of the engine 120 that are identical
to the first embodiment of the engine 20 include the same reference numeral increased by
one hundred. For example, the filter, which is identified in the first embodiment of the
engine 20 by the reference numeral 34, is identified in the second embodiment of the
engine 120 by reference numeral 134.
[0022] The second embodiment of the engine 120 is similar to the first
embodiment of the engine 20 without the turbocharger 22 and associated air ducts. In
other words, the boosting system of the second embodiment of the engine 120 only
includes the supercharger 124, and does not include the turbocharger 22. As such, only
the differences between the first embodiment of the engine 20 and the second
embodiment of the engine 120 are described below. Accordingly, the features of the
second embodiment of the engine 120 shown in Figure 2, including the intake 128, the
arrow 130 indicating air flow into the intake 128, the fourth air duct 148, the throttle 152,
the arrow 162 indicating air flow from the exhaust exit 160, and the combustion air
bypass valve 166, each operate in the same manner as the corresponding features of the
first embodiment of the engine 20, and are not described in detail below.
[0023] Additionally, the second embodiment of the engine 120 does not include
the clutch 26 interconnecting the supercharger 124 and the engine 120. Accordingly, the
supercharger 124 is directly coupled to the engine 120 for continuous operation with the
engine 120.
[0024] Within the second embodiment of the engine 120, a seventh air duct 172
interconnects the outlet of the supercharger 124 and the inlet of the intercooler 146 with
the combustion air bypass duct 164 interconnecting the first air duct 132 and the seventh
air duct 172, and an eighth air duct 174 interconnects the engine 120 and the exhaust
exit 160 to convey the exhaust gas from the combustion chamber 150 of the engine 120
directly to the exhaust exit 160.
[0025] Referring to Figure 3, a method of controlling the internal combustion
engine 20, 120 is shown. Preferably, the engine 20, 120 includes a diesel engine. The
method includes defining a steady state operating condition of the engine 20, 120 (block
76). Defining the steady state operating condition of the engine 20, 120 may further
include defining an operating range within which the engine 20, 120 operates without
change over time. In other words, the steady state operating condition includes a range of
operating conditions that the engine 20, 120 normally operates within at a high efficiency
over time.
[0026] Defining the operating range may further include defining an engine
operating speed range, such as between 500 and 7000 rpm's. However, it should be
appreciated that the specific operating speed range varies with each specific engine 20,
120, and with different applications of the engine 20, 120.
[0027] The method further includes defining a transient operating condition of the
engine 20, 120 (block 78. The transient operating condition of the engine 20, 120 may be
defined as operation of the engine 20, 120 outside of the steady state operating condition.
The transient operating condition of the engine 20, 120 corresponds to a change of one or
more operating parameters of the engine 20, 120 over time. The operating parameters of
the engine 20, 120 remain substantially constant while the engine 20, 120 is operating in
the steady state operating condition. However, once outside of the steady state operating
condition, the operating parameters of the engine 20, 120 vary over time.
[0028] The operating parameters may include one or more operating parameters
of the engine 20, 120 chosen from a group of operating parameters including a fuel/air
ratio, a speed of the engine 20, 120, an exhaust gas emission level of the engine 20, 120,
a fuel flow injection timing of the engine 20, 120, and a flow rate of the combustion air.
It should be appreciated that the operating parameters of the engine 20, 120 may include
other parameters not described herein.
[0029] The method may further include associating a range of values of one or
more of the operating parameters with the steady state operating condition (block 80).
Accordingly, operation of the engine 20, 120 within the range of values for the operating
parameter corresponds to operation of the engine 20, 120 within the steady state
operating condition, whereas operation of the engine 20, 120 outside of the range of
values for the operating parameter corresponds to operation of the engine 20, 120 outside
of the steady state operating condition, i.e., operation in the transient operating condition.
[0030] The method may further include monitoring one or more of the operating
parameters of the engine 20, 120 to determine if the engine 20, 120 is operating within
the steady state operating condition, or outside of the steady state operating condition in
the transient operating condition (block 82). Monitoring the operating parameter may
further be defined as measuring a value of the operating parameter. Accordingly, the
vehicle may include one or more sensors for sensing the value of the operating parameter.
[0031] The method may further include comparing the measured value of the
operating parameter with the associated range of values of the operating parameter to
determine if the measured value of the operating parameter is outside of the range of
values of the operating parameter (block 84). If the measured value of the operating
parameter is within the range of values associated with the steady state operating
condition, then the engine 20, 120 is operating within the steady state operating
condition. However, if the measured value of the operating parameter is outside the
range of values associated with the steady state operating condition, then the engine 20,
120 is operating within the transient operating condition.
[0032] The method further includes adjusting the flow of air from the
supercharger 24, 124 during operation of the engine 20, 120 in the transient operating
condition (block 86). Adjusting the supercharger 24, 124 provides a continuous flow of
air to the combustion chamber 50, 150 of the engine 20, 120 at a sufficient flow rate to
maintain a proper fuel/air mixture to substantially within a pre-determined ratio. The pre-
determined ratio corresponds to the efficient operation of the engine 20, 120, in which the
engine 20, 120 is not operating too richly, i.e., too much fuel to the available amount of
combustion air. Maintaining the fuel/air mixture to within the pre-determined ratio
minimizes soot emissions from the engine 20, 120 during operation of the engine 20, 120
in the transient operating condition. Minimization of soot emissions from the engine 20,
120 increases the time between regeneration of a particulate filter (not shown) used to
filter the soot from the exhaust gas, i.e., the particulate filter lasts longer when the engine
20, 120 produces less soot in the exhaust.
[0033] Adjusting the flow of air from the supercharger 24, 124 may further
include adjusting the supercharger 24, 124 while the engine 20, 120 is operating in the
transient operating condition to ensure proper combustion air flow to the engine 20, 120
during operation of the engine 20, 120 in the transient condition. As described above,
maintaining the proper air flow to the combustion chamber 50, 150 of the engine 20, 120
ensures that the proper fuel/air ratio is maintained, which minimizes the soot emissions
from the engine 20, 120, particularly in a diesel engine.
[0034] The method may further include adjusting an input to the engine 20, 120
while maintaining the flow of combustion air from the supercharger 24, 124 when the
engine 20, 120 is operating in the transient operating condition, indicated at 88.
Adjusting the input to the engine 20, 120 assists in maintaining the fuel/air mixture to
within the pre-determined ratio. Adjusting the input to the engine 20, 120 may further be
defined as adjusting a fuel flow injection timing of the engine 20, 120. Adjusting the fuel
flow injection timing may be further defined as adjusting a fuel flow injection rate, i.e.
the flow rate of the fuel injected into the engine. It should be appreciated that the input to
the engine may include some other input not described herein.
[0035] The method may further include defining a plurality of intermediate
operating conditions within each transient operating condition. In other words, each
transient operating condition may be broken up into or include multiple intermediate
operating conditions. If the transient operating condition is broken up to define multiple
intermediate operating conditions, then adjusting the flow of air from the supercharger
24, 124 during operation of the engine 20, 120 in the transient operating condition may
further be defined as adjusting the flow of air from the supercharger 24, 124 to achieve
one of the plurality of intermediate operating conditions defined within the transient
operating condition. Additionally, the method may further include adjusting a fuel flow
injection timing, i.e., fuel flow rate, of the engine 20, 120 to achieve one of the plurality
of intermediate operating conditions defined within the transient operating condition.
The fuel flow injection rate is adjusted after the flow of air from the supercharger 24, 124
is adjusted to achieve one of the plurality of intermediate operating conditions defined
within the transient operating condition. As such, if multiple intermediate operating
conditions are defined, the flow of air is adjusted to achieve a first of the intermediate
operating conditions, after which the fuel flow rate is adjusted to achieve the first of the
plurality of intermediate operating conditions. After the first of the intermediate
operating conditions is achieved, the flow of air from the supercharger is adjusted to meet
a second of the intermediate operating conditions, after which the fuel flow rate is
adjusted to achieve the second of the plurality of intermediate operating conditions. In
this manner, the operation of the engine progresses through each of the intermediate
operating conditions until the engine 20, 120 is operating within the steady state
operating condition.
[0036] While the best modes for carrying out the invention have been described
in detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of the
appended claims.
WE CLAIM
1. A method of controlling an internal combustion engine 20 coupled
to a mechanically driven supercharger 24 controlling a flow of air to the engine 20, the
method comprising:
defining a steady state operating condition of the engine 20;
monitoring an operating parameter of the engine 20 to determine if the
engine 20 is operating outside of the steady state operating condition in a transient
operating condition; and
adjusting the flow of air from the supercharger 24 during operation of the
engine 20 in the transient operating condition to maintain a fuel/air mixture to within a
pre-determined ratio to minimize emissions from the engine 20 during operation of the
engine 20 in the transient operating condition.
2. A method as set forth in claim 1 further comprising adjusting an
input to the engine 20 after adjusting the flow of combustion air from the supercharger 24
when the engine 20 is operating in the transient operating condition to maintain the
fuel/air mixture to within the pre-determined ratio.
3. A method as set forth in claim 2 wherein adjusting an input to the
engine 20 is further defined as adjusting a fuel flow injection timing of the engine 20.
4. A method as set forth in claim 1 further comprising associating a
range of values of the operating parameter with the steady state operating condition.
5. A method as set forth in claim 4 wherein monitoring an operating
parameter is further defined as measuring a value of the operating parameter.
6. A method as set forth in claim 5 further comprising comparing the
measured value of the operating parameter with the associated range of values of the
operating parameter to determine if the measured value of the operating parameter is
outside of the range of values of the operating parameter associated with the steady state
operating condition.
7. A method as set forth in claim 6 wherein the operating parameter
includes an operating parameter of the engine 20 chosen from a group of operating
parameters including a fuel/air ratio within the engine 20, a speed of the engine 20, an
exhaust gas emission level of the engine 20, a fuel flow injection timing of the engine 20,
and a flow rate of the combustion air.
8. A method as set forth in claim 1 wherein defining a steady state
operating condition is further defined as defining a operating range within which the
engine 20 operates without change over time.
9. A method as set forth in claim 8 wherein defining an operating
range is further defined as defining an engine 20 operating speed range.
10. A method as set forth in claim 8 further comprising defining a
transient operating condition of the engine 20 as operation of the engine 20 outside of the
steady state operating condition.
11. A method as set forth in claim 1 wherein the engine 20 includes a
diesel engine 20.

ABSTRACT
A method of controlling an engine 20 having a mechanically driven
supercharger 24 supplying a flow of air to the engine 20 includes defining a steady state
operating condition in which the engine 20 normally operates within efficiently. An
engine 20 parameter is monitored to determine if the engine 20 is operating within the
steady state operating condition, or outside the steady state operating condition in a
transient operating condition. If the engine 20 is operating outside the steady state
operating condition in the transient operating condition, the flow of air from the
supercharger 24 is adjusted to maintain a fuel/air mixture to within a pre-determined ratio
prior to increasing a fuel injection rate to the engine 20 to minimize soot emissions from
the engine 20 during operation of the engine 20 in the transient operating condition.