Title of Invention

A MASS AIR FLOW SENSOR MEASUREMENT CORRECTION SYSTEM AND A METHOD OF CORRECTION FOR A TURBO CHARGED DIESEL ENGINE OPERATING UNDER TRANSIENT CONDITIONS

Abstract A mass airflow sensor measurement correction system for a turbocharged diesel engine operating under transient conditions includes a signal input device that generates an engine speed signal based on an engine speed of a turbocharged diesel engine. A control module receives the engine speed signal and calculates a correction value of mass airflow from a differential of the engine speed signal and a constant.
Full Text 1
GP-306156
METHOD FOR DYNAMIC MASS AIR FLOW
SENSOR MEASUREMENT CORRECTIONS
FIELD OF THE INVENTION
[0001] The present invention relates to a mass air flow system of an
internal combustion engine, and more particularly to systems and methods for
correcting a mass air flow sensor measurement of the system.
BACKGROUND OF THE INVENTION
[0002] Mass Air Flow (MAF) can be measured using hotwire or
hotfilm anemometer type sensors. These types of sensors are used in engine
control systems for gasoline engines and diesel engines. MAF
measurements are used to control the proportion of fuel to air in the engine.
MAF sensors convert air flowing past a heated sensing element into an
electronic signal. The strength of the signal is determined by the energy
needed to keep the element at a constant temperature above the incoming
ambient air temperature. As the volume and density (mass) of airflow across
the heated element changes, the temperature of the element is adjusted to
maintain the desired temperature of the heating element. The varying current
flow parallels the particular characteristics of the incoming air (hot, cold, dry,
humid, high/low pressure). A control module monitors the changes in current
to determine air mass and to calculate precise fuel requirements.
[0003] During transient engine operations, MAF sensor reading
delays, or phase shifts can adversely affect control of the air fuel ratio, engine
smoke control systems, and exhaust gas recirculation (EGR) systems. Many
attempts have been made to overcome the transient delay of MAF sensor
readings. One approach applies digital averaging software and filtering
functions to artificially shift MAF sensor signals. Another method applies a
manifold volume filling model.

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[0004] These methods were developed to correct MAF sensor over
predictions of fresh air mass per cylinder. The methods do not correct severe
under predictions of fresh air mass per cylinder. Under predictions can occur
during transient operations of the engine. An under prediction of air flow can
severely penalize the vehicles driveability. The methods also fail to take into
account engine speed change effects. The methods are not applicable to
initial vehicle launch conditions of a diesel engine with a turbocharger where
manifold pressure changes are small due to turbo lag, but rapid changes in
engine speed are present.
[0005] Speed-density calculations or multi-zoned Dyna-Air
algorithms are also used instead of MAF sensors. These methods can be
complicated and require the availability of large sets of test data
SUMMARY OF THE INVENTION
[0006] Accordingly, a mass airflow sensor measurement correction
system for a turbocharged diesel engine operating under transient conditions
includes a signal input device that generates an engine speed signal based
on an engine speed of a turbocharged diesel engine. A control module
receives the engine speed signal and calculates a correction value of mass
airflow from a differential of the engine speed signal and a constant
[0007] In other features, the constant is determined from at least
one of a displacement volume of the engine, a volumetric efficiency of the
engine, a temperature of an intake manifold, and a gas constant. The
constant can be adjusted based on delays of the signal input device and
delays of control module processing.

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[0008] In another feature, the control module determines a
differential of the engine speed signal and calculates a correction value from
the constant and the differential according to the following equation.

[0009] In another feature, the mass airflow sensor measurement
correction system includes a second signal input device that generates a
manifold absolute pressure signal based on a pressure of an intake manifold
coupled to the engine. The control module receives the manifold absolute
pressure signal and calculates a correction value of mass airflow from the
engine speed signal, the manifold absolute pressure signal, and the constant
according to the following equation:

[0010] In still other features, the control module determines a
differential of the engine speed signal, determines a differential of the
manifold absolute pressure signal, and calculates a correction value based on
the differential of the engine speed, the differential of the manifold absolute
pressure signal, the constant, and a second constant according to the
following equation:

[0011] In yet another feature, the control module determines a
differential of the manifold absolute pressure signal and calculates the
correction value based on the differential of the manifold absolute pressure
signal and the first constant according to the following equation:


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[0012] In yet another feature, the control module determines a mass
airflow per cylinder value from the correction value. The control module
controls a fuel injector of the engine based on the mass airflow per cylinder
value.
[0013] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter. It should
be understood that the detailed description and specific examples, while
indicating the preferred embodiment of the invention, are intended for
purposes of illustration only and are not intended to limit the scope of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will become more fully understood
from the detailed description and the accompanying drawings, wherein:
[0015] Figure 1 is a functional block diagram illustrating a
turbocharged diesel engine system;
[0016] Figure 2 is a cross sectional view of a cylinder of a diesel
engine;
[0017] Figure 3 is a flowchart illustrating the steps of a method
executed by a control module of the engine system that calculates a MAF
sensor correction value; and
[0018] Figure 4 is a graph illustrating the results of the MAF sensor
correction method.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the invention, its
application, or uses. For purposes of clarity, the same reference numbers will
be used in the drawings to identify the same elements. As used herein, the
term module and/or device refers to an application specific integrated circuit
(ASIC), an electronic circuit, a processor (shared, dedicated, or group) and
memory that execute one or more software or firmware programs, a
combinational logic circuit and/or other suitable components that provide the
described functionality.
[0020] Referring now to Figure 1, a turbocharged diesel engine
system 10 includes an engine 12 that combusts an air and fuel mixture to
produce drive torque. Air enters the system by passing through an air filter
14. After passing through the air filter, air is drawn into a compressor 16 The
compressor 16 compresses the air entering the system 10. The greater the
compression of the air generally, the greater the output of the engine 12
Compressed air then passes through an air cooler 18 before entering into an
intake manifold 20. Cooling the air makes the air denser. The air cooler 18
then releases the air into an intake manifold 20. Air within the intake manifold
20 is distributed into cylinders 22. Although a single cylinder 22 is illustrated,
it can be appreciated that the dynamic mass airflow measurement correction
system of the present invention can be implemented in engines having a
plurality of cylinders including, but not limited to, 2, 3, 4, 5, 6, 8, 10 and 12
cylinders.
[0021] Referring now to Figure 2, an intake valve 24 of the engine
selectively opens and closes to enable the air to enter the cylinder 22 The
intake valve position is regulated by an intake camshaft (not shown). A fuel
injector 26 simultaneously injects fuel into the cylinder 22. The fuel injector 26
is controlled to provide a desired air-to-fuel (A/F) ratio within the cylinder 22
A piston 28 compresses the A/F mixture within the cylinder 22. The
compression of the hot air ignites the fuel in the cylinder 22, which drives the

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piston 28. The piston 28, in turn, drives a crankshaft 30 to produce drive
torque. Combustion exhaust within the cylinder 22 is forced out an exhaust
port when an exhaust valve 32 is in an open position. The exhaust valve
position is regulated by an exhaust camshaft (not shown). Although single
intake and exhaust valves 24, 32 are illustrated, it can be appreciated that the
engine 12 can include multiple intake and exhaust valves 24, 32 per cylinder
22.
[0022] Referring back to Figure 1, combustion exhaust within the
cylinder is forced out of the exhaust port into an exhaust manifold 33.
Whereupon, exhaust can be returned to the intake manifold 20 and/or treated
in an exhaust system (not shown) and released to the atmosphere. In an
alternative embodiment, an exhaust gas recirculation (EGR) system (shown in
phantom) can also be included in the system. The EGR system includes an
EGR cooler 35 and an EGR valve 37 that regulates exhaust flow back into the
intake manifold 20. The mass of exhaust air that is recirculated back into the
intake manifold 20 also reduces the combustion temperature in the engine
cylinder, and affects engine torque output.
[0023] A mass airflow (MAF) sensor 40 senses the mass of the
intake airflow and generates a MAF signal 42. An intake manifold
temperature (IMT) sensor 44 senses a temperature of the intake manifold and
generates an intake manifold temperature signal 46. A manifold absolute
pressure (MAP) sensor 48 senses the pressure within the intake manifold 20
and generates a MAP signal 50. An engine speed sensor 52 senses a
rotational speed of the crankshaft 30 of the engine 12 and generates an
engine speed signal 54 in revolutions per minute (RPM).
[0024] A control module 60 receives the above mentioned signals
42, 46, 50, and 54. The control module 60 controls the engine system 10
based on an interpretation of the signals and the mass airflow sensor
correction method of the present invention. More specifically, the control
module 60 interprets the signals and calculates a mass airflow correction
value from the signals during transient engine operations using fundamental

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engine airflow physics. The correction value is then applied to an air per
cylinder calculation. An air per cylinder value is then used to control the fuel
injector 26 of the cylinder 22. The air per cylinder value can also be used to
control the EGR system and/or a smoke control system (not shown)
[0025] A description of the mass airflow sensor correction method
follows. Real engine airflow verses theoretical airflow for a four stroke engine
can be related with the volumetric efficiency ηv of the engine by the following
equation:
simplified as
Where, MAF is the mass air flow of the system in grams per second The
control module 60 determines this value from the MAF signal 42. Vdisp is the
engine displacement volume in liters. Vdisp can vary according to the size and
number of cylinders 22 of the engine 12. Dividing Vdisp by two calculates the
actual displacement of a cylinder 22 for a four stroke engine operating with
two revolutions per cycle. RPM is the engine speed in revolutions per
minute. The control module 60 determines this value from the engine speed
signal 52. Dividing by sixty converts the equation to seconds.
[0026] ρcharge is the charge density of the air in kilograms per meters
cubed. The control module 60 calculates ρcharge from the following equation

Where, MAP is the intake manifold absolute pressure in kilopascals
determined from the MAP signal 48. Rcharge is a gas constant and IMT is the
intake manifold temperature in Kelvin determined from the IMT signal 44

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[0027] To clarify mass airflow dependency on the inputs, the
equation can be arranged into an explicit form:

[0028] In the above relation, engine displacement volume Vdisp and
gas Rcharge are nearly constant. ηv is the volumetric efficiency that measures
how well a cylinder 22 is breathing. The variation of ηv can be moderate,
ranging from ten to twenty percent. The variation of IMT can also be
moderate, averaging near twenty percent in some cases. The parameters
with large variations in value are RPM and MAP. RPM and MAP can
experience percentage changes as large as two hundred to three hundred
percent. For example, an RPM range can be from 600 RPM at idle to a high
of 3200. A MAP range can be from nearly 100 kPa at idle for operation at sea
level to a high of 275 kPa. While exemplary ranges are disclosed, other
values may be used.
[0029] By grouping small variation parameters into a constant K, the
major changes in MAF can be predicted from changes in RPM and MAP by
the following equation:

The constant K can be selectable based on the displacement volume,
manifold temperature, gas constant and volumetric efficiency of the system
The constant can also take into account system delays from sensor readings
or controller processing and/or time differences due to varying lengths and
volumes of the components of the engine system 10.

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[0030] Referring now to Figure 2, steps executed by the control
module according to the MAF sensor correction method is shown. Control
interprets signals from sensors of the system in step 100. The interpreted
signals are used in a calculation of a differential of MAF. In step 110, control
may choose to neglect interactions between RPM and MAP and calculate a
MAF differential in step 120 from a constant K1, an RPM, a constant K2, a
MAP differential, and an RPM differential. The constants K1 and K2 can be
selectable. The relation can be illustrated by the following equation:

[0031] Otherwise, in step 130, control may choose to neglect the
MAP signal and calculate a MAF differential in step 140 from a constant K3
and an RPM differential. The constant K3 can be selectable. The following
equation shows the relationship:

[0032] Alternatively, in step 150, control may choose to neglect
RPM and calculate a MAF differential in step 160 from a constant K4 and a
MAP change. The constant K4 can be selectable. The following equation
shows the relationship:


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[0033] Otherwise, control calculates a MAF differential by taking into
account interactions between MAP and RPM, an RPM differential, a MAP
differential, and a constant K0 in step 170. The constant K0 can be selectable.
The following equation shows the relationship:

[0034] Based on the MAF differential, an air per cylinder value can
be calculated. In step 180, control adds the MAF differential to a calculated
MAF per cylinder (MAFPC) value. The MAFPC is calculated from the MAF,
the RPM and a constant value. The constant value is determined from the
number of revolutions per cycle and the number of cylinders per engine. For
a four stroke, two revolutions per cycle, eight cylinder engine, the constant
value is 15. Where 60 minutes per second is multiplied by 2 revolutions per
cycle and divided by 8 cylinders per engine The equation for MAFPC with the
constant value 15 is shown as:

[0035] Referring now to Figure 4, a graph plotting example results
of the correction method applied to a four stroke eight cylinder engine is
shown. Time of execution in seconds is displayed along the x-axis at 200.
MAF per cylinder per RPM is displayed along the left side y-axis at 210.
Throttle position in percent is displayed along the right side y-axis at 220.
Throttle position values plotted in percent illustrate a transient condition of the
engine at 230. Speed density values calculated from traditional regressive
test data is shown at 240. MAF per cylinder values without the inclusion of
the correction method is shown at 250. The effectiveness of the new MAF per
cylinder correction calculation is shown at 260 where the plotted calculated
MAF per cylinder value including the correction term nearly matches the
values for the traditional speed density calculation.

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[0036] Those skilled in the art can now appreciate from the
foregoing description that the broad teachings of the present invention can be
implemented in a variety of forms. Therefore, while this invention has been
described in connection with particular examples thereof, the true scope of the
invention should not be so limited since other modifications will become
apparent to the skilled practitioner upon a study of the drawings, the
specification and the following claims.

12
CLAIMS
What is claimed is:
1. A mass airflow sensor measurement correction system for a
turbocharged diesel engine operating under transient conditions, comprising:
a engine speed signal input device that receives an engine
speed signal based on an engine speed of a turbocharged diesel engine; and
a control module that receives said engine speed signal and that
calculates a correction value of mass airflow from a differential of said engine
speed signal and a first constant and that applies said correction value to a
measured mass airflow value.
2. The system of claim 1 wherein said first constant is determined
from at least one of a displacement volume of said engine, a volumetric
efficiency of said engine, a temperature of an intake manifold, and a gas
constant.
3. The system of claim 2 wherein said first constant is adjusted
based on delays of said signal input device and delays of said control module
processing.
4. The system of claim 1 wherein said control module determines
said differential of said engine speed signal and calculates said correction
value from said first constant and said differential according to the following
equation:

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5. The system of claim 1 further comprising a manifold absolute
pressure signal input device that receives a manifold absolute pressure signal
based on a pressure of an intake manifold coupled to said engine, and
wherein said control module is receptive of said manifold absolute pressure
signal and is operable to calculate a correction value of mass airflow from said
engine speed signal, said manifold absolute pressure signal, and said first
constant.
6. The system of claim 5 wherein said control module determines a
differential of said engine speed signal, determines a differential of said
manifold absolute pressure signal and calculates said correction value based
on said engine speed signal, said manifold absolute pressure signal, said
differential of said engine speed signal, said differential of said manifold
absolute pressure signal, and said first constant according to the following
equation:
7. The system of claim 5 wherein said control module determines a
differential of said engine speed signal, determines a differential of said
manifold absolute pressure signal, and calculates said correction value based
on said differential of said engine speed, said differential of said manifold
absolute pressure signal, said first constant, and a second constant according
to the following equation:


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8. The system of claim 7 wherein said second constant is determined
from at least one of a displacement volume of said engine, a volumetric
efficiency of said engine, a temperature of an intake manifold, and a gas
constant.
9. The system of claim 8 wherein said second constant is adjusted
based on delays of said signal input device and delays of control module
processing.
10. The system of claim 1 further comprising a manifold absolute
pressure signal input device that receives a manifold absolute pressure signal
based on an air pressure of an intake manifold, and wherein said control
module is receptive of said manifold absolute pressure signal and is operable
to calculate said correction value of mass airflow from said manifold absolute
pressure signal and said first constant.
11. The system of claim 10 wherein said control module determines
a differential of said manifold absolute pressure signal and calculates said
correction value based on said differential of said manifold absolute pressure
signal and said first constant according to the following equation

12. The system of claim 1 wherein said control module determines a
mass airflow per cylinder value from said correction value.
13. The system of claim 12 wherein said control module controls a fuel
injector of said engine based on said mass airflow per cylinder value.
14. A method of correcting a mass airflow sensor measurement of
an engine operating under transient conditions, comprising:
detecting a speed of an engine;

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determining a first differential of said speed of said engine; and
calculating a value for a mass airflow sensor measurement
based on said first differential of said speed and a first constant
15. The method of claim 14 further comprising selecting a first
constant based on at least one of a displacement volume of said engine, a
volumetric efficiency of said engine, a temperature of an intake manifold, and
a gas constant.
16. The method of claim 14 wherein said step of calculating is
based on the following equation:

17. The method of claim 14 further comprising:
detecting an air pressure form an intake manifold of said engine,
determining a second differential of said air pressure of said
manifold; and
wherein said step of calculating is further described as
calculating a correction value based on said first differential of said speed,
said first constant, said second differential of said air pressure, and a second
constant.
18. The method of claim 17 wherein said step of calculating is
based on the following equation:

19. The method of claim 17 further comprising selecting a second
constant based on at least one of a displacement volume of said engine, a
volumetric efficiency of said engine, a temperature of an intake manifold, and
a gas constant.

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20. The method of claim 17 wherein said step of calculating is further
described as calculating a correction value based on said speed of said
engine, said first differential of said speed, said first constant, said air
pressure, and said second differential of said air pressure.
21. The method of claim 20 wherein said step of calculating is
based on the following equation:

22. The method of claim 14 further comprising calculating a mass
airflow per cylinder value based on said correction value.
23. The method of claim 22 further comprising controlling fuel of
said engine based on said mass airflow per cylinder value
24. The method of claim 22 further comprising controlling an
exhaust gas recirculation system of said engine based on said mass airflow
per cylinder value.
25. The method of claim 22 further comprising controlling a smoke
control system based on said mass airflow per cylinder value.

17
26. A method of correcting a mass air flow sensor measurement of
an engine system with an intake manifold, comprising:
detecting an air pressure of a manifold;
determining a first differential of said air pressure; and
calculating a correction value for a mass airflow sensor
measurement based on said first differential of said air pressure and a first
constant.
27. The method of claim 26 further comprising selecting a first
constant based on at least one of a displacement volume of said engine, a
volumetric efficiency of said engine, a temperature of an intake manifold, and
a gas constant.
28. The method of claim 26 wherein said step of calculating is
based on the following equation:

29. The method of claim 26 further comprising calculating a mass
airflow per cylinder value based on said correction value.
30. The method of claim 29 further comprising controlling fuel of
said engine based on said mass airflow per cylinder value
31. The method of claim 29 further comprising controlling an
exhaust gas recirculation system based on said mass airflow per cylinder
value.
32. The method of claim 29 further comprising controlling a smoke
control system based on said mass airflow per cylinder value.

A mass airflow sensor measurement correction system for a
turbocharged diesel engine operating under transient conditions includes a
signal input device that generates an engine speed signal based on an engine
speed of a turbocharged diesel engine. A control module receives the engine
speed signal and calculates a correction value of mass airflow from a
differential of the engine speed signal and a constant.

Documents:

01477-kol-2007-abstract.pdf

01477-kol-2007-assignment.pdf

01477-kol-2007-claims.pdf

01477-kol-2007-correspondence others 1.1.pdf

01477-kol-2007-correspondence others 1.2.pdf

01477-kol-2007-correspondence others.pdf

01477-kol-2007-description complete.pdf

01477-kol-2007-drawings.pdf

01477-kol-2007-form 1.pdf

01477-kol-2007-form 2.pdf

01477-kol-2007-form 3.pdf

01477-kol-2007-form 5.pdf

01477-kol-2007-priority document.pdf

1477-KOL-2007-ABSTRACT.pdf

1477-KOL-2007-AMANDED CLAIMS.pdf

1477-KOL-2007-ASSIGNMENT 1.1.pdf

1477-KOL-2007-ASSIGNMENT.pdf

1477-KOL-2007-CORRESPONDENCE 1.1.pdf

1477-KOL-2007-CORRESPONDENCE 1.2.pdf

1477-KOL-2007-CORRESPONDENCE OTHERS 1.3.pdf

1477-KOL-2007-CORRESPONDENCE OTHERS 1.4.pdf

1477-KOL-2007-CORRESPONDENCE OTHERS 1.5.pdf

1477-KOL-2007-DESCRIPTION (COMPLETE).pdf

1477-KOL-2007-DRAWINGS.pdf

1477-KOL-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

1477-KOL-2007-EXAMINATION REPORT.pdf

1477-KOL-2007-FORM 1.pdf

1477-KOL-2007-FORM 18.pdf

1477-KOL-2007-FORM 2.pdf

1477-KOL-2007-FORM 26.pdf

1477-KOL-2007-FORM 3 1.1.pdf

1477-KOL-2007-FORM 3.pdf

1477-KOL-2007-FORM 5.pdf

1477-KOL-2007-GRANTED-ABSTRACT.pdf

1477-KOL-2007-GRANTED-CLAIMS.pdf

1477-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1477-KOL-2007-GRANTED-DRAWINGS.pdf

1477-KOL-2007-GRANTED-FORM 1.pdf

1477-KOL-2007-GRANTED-FORM 2.pdf

1477-KOL-2007-GRANTED-LETTER PATENT.pdf

1477-KOL-2007-GRANTED-SPECIFICATION.pdf

1477-KOL-2007-OTHERS 1.1.pdf

1477-KOL-2007-OTHERS.pdf

1477-KOL-2007-PETITION UNDER RULR 137.pdf

1477-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-01477-kol-2007.jpg


Patent Number 250016
Indian Patent Application Number 1477/KOL/2007
PG Journal Number 48/2011
Publication Date 02-Dec-2011
Grant Date 29-Nov-2011
Date of Filing 29-Oct-2007
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS, INC.
Applicant Address 300 GM RENAISSANCE CENTER, DETROIT, MICHIGAN
Inventors:
# Inventor's Name Inventor's Address
1 YUN XIAO 2372 HICKORY POINT DRIVE ANN ARBOR, MICHIGAN 48105
PCT International Classification Number F02D41/18; G01F25/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/466862 2006-11-03 U.S.A.