Title of Invention

AN AIRFLOW DETERMINATION SYSTEM AND A METHOD FOR DETERMINING A MASS AIRFLOW INTO A CYLINDER OF AN ENGINE

Abstract An air flow state determining system that determines a mass air flow into a cylinder of an engine having a cam phaser includes a first module that determines whether an air flow state is one of steady-state and transient based on a cam phaser position. A second module determines the mass air flow using one of a mass air flow sensor signal and a speed density relationship based on whether the mass air flow state is one of steady-state and transient.
Full Text 1
GP-306843-PTE-CD
METHOD FOR DETECTING STEADY-STATE AND TRANSIENT AIR FLOW
CONDITIONS FOR CAM-PHASED ENGINES
FIELD OF THE INVENTION
[0001] The present invention relates to vehicle engine systems, and
more particularly to detecting a state of air flow delivered to a cylinder of an
engine.
BACKGROUND OF THE INVENTION
[0002] Engines combust a mixture of air and fuel (air/fuel) to drive a
piston in a cylinder. The downward force of the piston generates torque. A
throttle controls air flow delivered to the cylinders. By determining the amount of
air ingested by the cylinders, the fuel mass can be calculated and a proper
air/fuel mixture can be delivered to the cylinders to obtain the desired air-fuel
ratio and torque.
[0003] Air flow delivered to the cylinders can be measured using a
mass air flow (MAF) sensor. The MAF sensor measures the air flow across the
throttle. During steady-state air flow conditions, the air flow measured across the
throttle provides an accurate estimation of the fresh air flow delivered to the
cylinders. Because the MAF sensor measures air flow across the throttle and not
the air into the cylinders, it is most accurate during steady-state conditions, and is
less accurate during transient conditions (e.g., when additional air must flow

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across the throttle to increase the manifold absolute pressure (MAP), or when the
mass of airflow must be reduced to reduce the MAP).
[0004] Air flow can be estimated using a speed density calculation,
which is typically based on MAP, engine RPM, as well as intake air temperature
and pressure. The speed density calculation is only an approximation that is
valid as long none of the parameters that are not explicitly accounted for in the
calculation varies. However, because the not accounted for parameters do vary
over a period of time while driving the vehicle, the speed density calculations are
only accurate for a short period of time and need to be adjusted over time. In
order to maintain the accuracy of the speed density calculations during transient
conditions, the MAF sensor is used during stead state conditions to correct
speed density calculation.
[0005] In engines without variable cam phasing (VCP) or variable cam
timing (VCT), if the mass of fresh air entering the cylinder changes (i.e., is
transient) there is a corresponding increase or decrease in MAP. This indicates
that the mass of air is either being accumulated or depleted in the intake
manifold. During such transient conditions, the speed density calculation is used
to determine the mass air flow entering the cylinders. The determination of
whether the mass air flow is steady-state or transient can be made by means
such as that described in commonly assigned U.S. Patent No. 5,423,208, the
disclosure of which is incorporated herein by reference. The control module uses
the appropriate method of estimating the mass air flow into the cylinder based on

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the air flow state.
[0006] However in engines with VCP or VCT, changes in cam position
can occur without changing the MAP while causing the MAF sensor reading to
change by a large amount. This occurs because the VCP or VCT system allows
varying amounts of residual exhaust gas back into the intake manifold, which
replaces the fresh air mass in the manifold. As a result, more or less air flows
through the throttle and the air flow is transient. Traditional air flow
transient/steady-state detection methods, like that disclosed in U.S. Patent No.
5,423,208, will see no change in MAP ans incorrectly determine that the air flow
is steady-state.
SUMMARY OF THE INVENTION
[0007] Accordingly, the present invention provides an air flow state
determining system that determines a mass air flow into a cylinder of an engine
having a cam phaser. The system includes a first module that determines
whether an air flow state is one of steady-state and transient based on a cam
phaser position. A second module determines the mass air flow using one of a
mass air flow sensor signal and a speed density relationship based on whether
the mass air flow state is one of steady-state and transient.

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[0008] In other features, the system further includes a third module that
processes the cam phaser position using a first order linear model and calculates
an updated intermediate value based on a cam phaser position. The air flow
state corresponding to cam phaser motion is determined based on the updated
intermediate value. The air flow state is determined based on a difference
between the updated intermediate value and a previous intermediate value.
[0009] In another feature, the system further includes a filter module
that filters the cam phaser position.
[0010] In yet other features, the system further includes a dead-band
module that adjusts the cam phaser position based on a calibrated offset. The
system further includes a minimizing module that minimizes the cam phaser
position to zero if the adjustment results in the cam phaser position being less
than zero.
[0011] 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.

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BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will become more fully understood from
the detailed description and the accompanying drawings, wherein:
[0013] Figure 1 is a functional block diagram of an engine system
regulating using the air flow state detection control in accordance with the
present invention;
[0014] Figure 2 is a flowchart illustrating exemplary steps executed by
the air flow state detection control according to the present invention; and
[0015] Figure 3 is a functional block diagram of exemplary modules
that execute the air flow state detection control of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The following description of the preferred embodiment 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 similar elements. As used herein, the term
module 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.

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[0017] Referring now to Figure 1, an engine system 10 is schematically
illustrated. The engine system 10 includes an engine 12 that combusts an air
and fuel (air/fuel) mixture to produce drive torque. Air is drawn into an intake
manifold 14 through a throttle 15. The throttle 15 regulates mass air flow (MAF)
into the intake manifold 14. The position of the throttle 15 is adjusted based on a
signal from a pedal position sensor 16 indicative of a position of an accelerator
pedal 17. Air is drawn into a cylinder 20 of the engine through an intake valve
18. Although four cylinders 20 are illustrated, it can be appreciated that the
engine system 10 can include, but is not limited to, 2, 3, 4, 5, 6, 8, 10 and 12
cylinders.
[0018] The air is mixed with fuel and is combusted within the cylinder
20 to reciprocally drive a piston (not shown) within the cylinder, which rotatably
drives a crankshaft 24. Exhaust is exhausted from the cylinder through an
exhaust valve 19 and into an exhaust manifold 25. A fuel injector (not shown)
injects the fuel that is combined with the air. The fuel injector can be an injector
that is associated with an electronic or mechanical fueling system, or another
system for mixing fuel with intake air. The amount of fuel injected by the fuel
injector is regulated based on the mass air flow into the cylinder 20 to deliver a
desired air/fuel ratio.

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[0019] The opening and closing of the intake and exhaust valves 18,
19 are regulated by an intake camshaft 22 and an exhaust camshaft 23,
respectively. The crankshaft 24 rotatably drives intake and exhaust camshafts
22, 23 using a chain/belt and pulley system (not shown) to regulate the timing of
the opening and closing of the intake and exhaust valves 18, 19, with respect to
a piston position within the cylinder 20. Although a single intake camshaft 22 and
a single exhaust camshaft 23 are illustrated, it is anticipated that dual intake
camshafts and dual exhaust camshafts may be used.
[0020] An intake cam phaser 26 and an exhaust cam phaser 27 vary
an actuation time of the intake and exhaust camshafts 22, 23, respectively, which
mechanically actuate the intake and exhaust valves 18, 19. More specifically,
the rotational position of the intake and exhaust cam shafts 22, 23 can be
advanced and/or retarded relative to a position of the piston within the cylinder 20
to vary the actuation time of the opening and/or closing of the inlet and/or
exhaust valves 18, 19. In this manner, the timing and/or lift of the intake and the
exhaust valves 18, 19 can be varied with respect to one another and/or with
respect to a location of the piston within the cylinder 20.
[0021] Adjustment of the intake and exhaust camshafts 22, 23 using
the intake and/or exhaust cam phasers 26, 27 can affect the MAP. For example,
when the cam phasers 22, 23 are adjusted to increase air delivered to the
cylinders 18, less exhaust residual flows into the intake manifold 14 displacing
less fresh air mass. As a result, the mass of combustible air increases.

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Conversely, the intake and exhaust cam phasers 26, 27 can be adjusted to
reduce air delivered to the cylinders 20, while increasing the exhaust gas residual
entering the intake manifold 14. As a result, there is more air mass entering the
intake manifold 14 and hence the cylinder 14.
[0022] When the intake and/or exhaust cam phasers 26, 27 remain in a
constant position, the actuation timing of the intake and exhaust valves 18, 19
remains constant. As a result, steady-state air flow occurs and a constant
amount of air is delivered to the cylinders 20. However, when the intake and/or
exhaust cam phasers are adjusted, the actuation timing is correspondingly
adjusted and the amount of air delivered into the cylinder 20 either increases or
decreases. The resulting sudden change in air flow is typically referred to as an
air transient. An air transient that results from a change in the camshaft position
typically exists whenever the intake and/or exhaust cam phasers 26, 27 are
moved from a fixed position.
[0023] The engine system 10 further includes an air flow sensor 30, an
engine speed sensor 31, cam phaser position sensors 32, 33, an intake manifold
air temperature sensor 34 and a MAP sensor 35. A control module 36 receives
the signals generated by the various sensor and regulates operation of the
engine system 10 based on the air flow state detection system of the present
invention. The air flow sensor 30 measures an amount of air flowing through
throttle 15 and the engine speed sensor 31 is responsive to the rotational speed
of the engine 12. The intake manifold temperature sensor 34 measures an air

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temperature within the intake manifold 14 and the MAP sensor 35 measures the
MAP within the intake manifold 14.
[0024] The cam phaser position sensors 32, 33 are coupled to the
intake cam phaser 26 and the exhaust cam phaser 27, respectively, and are
responsive their respective rotational positions. When the rotational position of
the intake and the exhaust cam phasers 26, 27 is adjusted, the cam phaser
rotational sensors 32, 33 output a position signal to the control module 36. The
position signals can be filtered prior to being received by or within the control
module 36 using a first order lag filter to remove any high frequency noise that
may exist.
[0025] Airflow transients can occur due to changes that a traditional air
flow transient/steady state detector can detect as well as changes in the cam
phaser 26,27 position, which the traditional transient/steady state detector does
not detect. Accordingly, the air flow state detection control of the present
invention detects whether the mass air flow is in a steady-state or a transient
state based on a signal from a traditional transient/steady state detection control
and further based on the rotational velocity of the cam phasers 26, 27.
Furthermore, the control module 36 determines the mass air flow into the
cylinders 20 based on whether the mass air flow is deemed steady-state or
transient.

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[0026] Although the air flow state detection control detects steady-state
air flow and/or transient air flow based on the intake cam phaser 26 and/or the
exhaust cam phaser 27 rotational velocities, the air flow state detection control
will be based on the rotational velocity of the intake cam phaser 26 alone being
used to detect a steady-state air flow and/or transient air flow.
[0027] At each intake reference pulse, which is based on the engine
RPM sensor signal, the air flow state detection control determines the intake cam
position (GICAM) based on the intake cam position sensor signal. 6ICAM can be
filtered using a first order lag filter (e.g., y = ay + (1-a)x). Proper selection of the
filter coefficient (a) enables successful sampling as slow as every other intake
reference pulse. The air flow state detection control subtracts a calibrated offset
(GTHR) from the filtered GICAM to remove a dead-band associated with GICAM (i.e., a
cam phaser adjustment value that does not affect MAF). If the difference is less
than 0, GICAM is set it to 0).
[0028] The air flow state detection control inputs GICAM into a first order
model, which is provided by the following equation:

where X is an intermediate variable, k is the current event and is incremented
each intake reference event, and a and |3 are pre-determined model or filter
coefficients, a and (3 are determined using various optimization techniques, such
that the following relationship is minimized:
|[X(k) - X(k - 1)] - MAP(k) - MAP(k - 1)]

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where MAP(k) - MAP(k - 1) is the change in intake manifold pressure due to
only a change in intake cam position. If the following relationship is true:

the mass air flow is transient and a transient flag is set. Otherwise, the mass air
flow is steady-state and a steady-state flag is set.
[0029] If the steady-state flag is set, the control module 36 operates in
a steady-state mode and estimates cylinder mass air flow based on the air flow
sensor 30. If the transient flag is set, the control module 36 estimates air flow
based on the speed density approach according to the following equation:

where ma is mass air into the cylinder, R is the universal gas constant, Vd is the
displacement volume of the engine 12, nV is the volumetric efficiency of the
engine 12, Tl is the temperature of the air delivered into the intake manifold 14
and Pm is the intake manifold pressure. Since R and Vd are constants for a given
engine, the volume of the engine 12 can be defined according to the following
equation:


12
Substituting Ve into equation (1), mass of air into the cylinder 20 can be defined
according to the following equation:

[0030] Referring now to Figure 2, a flowchart illustrates exemplary
steps executed by the air flow state detection control. In step 200, control
determines Θ|CAM- In step 202, control filters ΘICAM to provide a filtered 9ICAM- In
step 204, control subtracts 0THR from 8ICAM to remove the dead-band around the
parked position. Control determines whether ΘICAM is less than zero in step 206.
If ΘICAM is less than zero, control continues in step 208. If ΘICAM is not less than
zero, control continues in step 210. In step 208, control sets θIcAM to zero.
[0031] Control updates the intermediate variable X(k+1) in step 210. In
step 212, control determines whether the absolute value of the difference
between X(k+1) and X(k) is greater than ATHR- If the absolute value of the
difference between X(k+1) and X(k) is greater than ATHR, control continues in
step 214. If the absolute value of the difference between X(k + 1) and X(k) is not
greater than ATHR, control continues in step 216. In step 214, control sets the
transient flag and estimates the cylinder mass air flow using the speed density
approach in step 218. In step 216, sets the steady-state flag. In step 219,
control determines whether the traditional or standard transient/steady state
detection control has indicated that the air flow is steady state (SS) by setting a
SS flag. If the SS flag is set, control estimates the cylinder mass air flow using

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the MAF sensor 30 in step 220. If the SS flag is not set, control continues in step
218. In step 222, control sets X(k) equal to X(k+1) and control ends.
[0032] Referring now to Figure 3, exemplary modules that execute the
air flow state detection control will be described in detail. The exemplary
modules include a filter module 300, a dead-band module 302, a ΘICAM minimizing
module 304, an X updating module 306, a summer 308, an absolute value
module 310, a comparator module 312 a flag module 314 and a cylinder MAF
estimating module 316. The filter module 300 and the dead-band module 302
respectively filter and remove the dead-band value from Θ|CAM-
[0033] The ΘICAM minimizing module 304 caps the minimum value of
ΘICAM to zero, if Θ|CAM is less than zero after the dead-band removal operation.
The X updating module 306 determines X(k+1) based on X(k), 9ICAM and the first
order linear model described in detail above. The summer 308 determines the
difference between X(k+1) and X(k) and the absolute value module 310
generates the absolute value of the difference.
[0034] The comparator module 312 compares the absolute value of the
difference to ∆THR and outputs a first signal (e.g., 1) if the difference is greater
than ∆THR, and outputs a second signal (e.g., 0) if the difference is less than ∆THR-
The flag module 314 sets the steady-state or transient flag based on the output
of the comparator module 312. The cylinder MAF module 316 determines the
cylinder MAF based on either the MAF sensor signal or the speed density
calculation depending on the output of the comparator module 312 and the

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condition of the standard SS flag.
[0035] Those skilled in the art can now appreciate from the foregoing
description that the broad teachings 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.

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CLAIMS
What is claimed is:
1. An air flow state determining system that determines a mass air flow into a
cylinder of an engine having a cam phaser, comprising:
a first module that determines whether an air flow state is one of steady-
state and transient based on a cam phaser position; and
a second module that determines said mass air flow using one of a mass
air flow sensor signal and a speed density relationship based on whether said
mass air flow state is one of steady-state and transient.
2. The air flow determining system of claim 1 further comprising a third
module that processes said cam phaser position using a first order linear model
and calculates an updated intermediate value based on said cam phaser
position, wherein said air flow state is determined based on said updated
intermediate value.
3. The air flow determining system of claim 2 wherein said air flow state is
determined based on a difference between said updated intermediate value and
a previous intermediate value.

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4. The air flow state determining system of claim 1 further comprising a filter
module that filters said cam phaser position.
5. The air flow state determining system of claim 1 further comprising a
dead-band module that adjusts said cam phaser position based on a calibrated
offset.
6. The air flow state determining system of claim 5 further comprising a
minimizing module that minimizes said cam phaser position to zero if said
adjustment results in said cam phaser position being less than zero.
7. A method of determining a mass air flow into a cylinder of an engine
having a cam phaser, comprising:
monitoring a cam phaser position;
determining whether an air flow state is one of steady-state and transient
based on a cam phaser position; and
determining said mass air flow using one of a mass air flow sensor signal
and a speed density relationship based on whether said mass air flow state is
one of steady-state and transient.

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8. The method of claim 7 further comprising:
processing said cam phaser position using a first order linear model; and
calculating an updated intermediate value based on said cam phaser
position, wherein said air flow state is determined based on said updated
intermediate value.
9. The method of claim 8 wherein said air flow state is determined based on
a difference between said updated intermediate value and a previous
intermediate value.
10. The method of claim 7 further comprising filtering said cam phaser
position.
11. The method of claim 7 further comprising adjusting said cam phaser
position based on a calibrated offset.
12. The method of claim 11 further comprising minimizing said cam phaser
position to zero if said adjustment results in said cam phaser position being less
than zero.

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13. A method of determining a mass air flow into a cylinder of an engine
having a cam phaser, comprising:
monitoring a cam phaser position;
filtering said cam phaser position;
processing said cam phaser position using a linear model to determine an
updated intermediate variable;
determining whether an air flow state is one of steady-state and transient
based on said updated intermediate variable and a previous intermediate
variable; and
determining said mass air flow using one of a mass air flow sensor signal
and a speed density relationship based on whether said mass air flow state is
one of steady-state and transient.
14. The method of claim 13 wherein said air flow state is determined based on
a difference between said updated intermediate value and said previous
intermediate value.

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15. The method of claim 13 further comprising adjusting said cam phaser
position based on a calibrated offset.
16. The method of claim 15 further comprising minimizing said cam phaser
position to zero if said adjustment results in said cam phaser position being less
than zero.

An air flow state determining system that determines a mass air flow into a
cylinder of an engine having a cam phaser includes a first module that
determines whether an air flow state is one of steady-state and transient based
on a cam phaser position. A second module determines the mass air flow using
one of a mass air flow sensor signal and a speed density relationship based on
whether the mass air flow state is one of steady-state and transient.

Documents:

00931-kol-2007-abstract.pdf

00931-kol-2007-assignment.pdf

00931-kol-2007-claims.pdf

00931-kol-2007-correspondence others 1.1.pdf

00931-kol-2007-correspondence others 1.2.pdf

00931-kol-2007-correspondence others.pdf

00931-kol-2007-description complete.pdf

00931-kol-2007-drawings.pdf

00931-kol-2007-form 1.pdf

00931-kol-2007-form 18.pdf

00931-kol-2007-form 2.pdf

00931-kol-2007-form 3.pdf

00931-kol-2007-form 5.pdf

00931-kol-2007-priority document.pdf

931-KOL-2007-(08-11-2011)-ABSTRACT.pdf

931-KOL-2007-(08-11-2011)-AMANDED CLAIMS.pdf

931-KOL-2007-(08-11-2011)-DESCRIPTION (COMPLETE).pdf

931-KOL-2007-(08-11-2011)-DRAWINGS.pdf

931-KOL-2007-(08-11-2011)-EXAMINATION REPORT REPLY RECEIVED.pdf

931-KOL-2007-(08-11-2011)-FORM 1.pdf

931-KOL-2007-(08-11-2011)-FORM 2.pdf

931-KOL-2007-(08-11-2011)-FORM 3.pdf

931-KOL-2007-(08-11-2011)-OTHERS.pdf

931-KOL-2007-(08-11-2011)-PETITION UNDER RULR 137.pdf

931-KOL-2007-ASSIGNMENT.pdf

931-KOL-2007-CORRESPONDENCE 1.5.pdf

931-KOL-2007-CORRESPONDENCE OTHERS 1.3.pdf

931-KOL-2007-CORRESPONDENCE-1.4.pdf

931-KOL-2007-EXAMINATION REPORT.pdf

931-KOL-2007-FORM 18.pdf

931-KOL-2007-FORM 26.pdf

931-KOL-2007-FORM 3.pdf

931-KOL-2007-FORM 5.pdf

931-KOL-2007-GRANTED-ABSTRACT.pdf

931-KOL-2007-GRANTED-CLAIMS.pdf

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

931-KOL-2007-GRANTED-DRAWINGS.pdf

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

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

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

931-KOL-2007-GRANTED-SPECIFICATION.pdf

931-KOL-2007-OTHERS.pdf

931-KOL-2007-PA.pdf

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


Patent Number 251672
Indian Patent Application Number 931/KOL/2007
PG Journal Number 13/2012
Publication Date 30-Mar-2012
Grant Date 27-Mar-2012
Date of Filing 28-Jun-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 RONALD A. DAVIS 1341 VAN STONE DRIVE COMMERCE TOWNSHIP, MICHIGAN 48382
2 GREGORY P. MATTHEWS 6021, BEACHWOOD DRIVE WEST BLOOMFIELD, MICHIGAN 48324
PCT International Classification Number F02D41/18; F02B3/00; F02D41/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/466,880 2006-08-24 U.S.A.