Indian Patents. 269036:A HUMIDITY BASED CONTROL SYSTEM AND METHOD OF CALIBRATING THE SAME

Title of Invention	A HUMIDITY BASED CONTROL SYSTEM AND METHOD OF CALIBRATING THE SAME
Abstract	A humidity based control system for an internal combustion engine includes a calculation module and a calibration module. The calculation module determines a humidity of air used in a combustion process of the internal combustion engine. The control module selectively controls spark timing and exhaust dilution in the internal combustion engine based on the humidity.

Full Text	General Motors No. GP-306198 Attorney Docket No. 8540P-000306 A HUMIDITY BASED CONTROL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60/842,512, filed on September 5, 2006. The disclosure of the above application is incorporated herein by reference. FIELD [0002] The present disclosure relates to an internal combustion engine, and more particularly to method to control spark timing and exhaust dilution to improve fuel economy and drivability. BACKGROUND [0003] Efficiency of an internal combustion engine may be controlled by adjusting spark timing and an exhaust dilution that is combusted by the engine. Spark timing may be defined as generating a spark at a specific time relative to a position of a piston in a combustion chamber. A preferred spark timing occurs when the engine has a maximum output power. Output power is directly proportional to pressure within a combustion chamber of the engine. To obtain maximum pressure in the combustion chamber, the spark ignites the air/fuel mixture at a time before the piston is at top dead center permitting heated gases time to fully expand as the piston reaches top dead center. 1 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 [0004] The engine system may also dilute the air/fuel mixture to improve engine efficiency. Exhaust dilution may improve engine efficiency by reducing pumping losses. When exhaust gases are introduced during an intake stroke of a combustion event, the engine requires less air thereby reducing pumping power losses of the engine. An engine control system may use an exhaust gas recirculation (EGR) system to re-circulate exhaust gases back into the intake manifold. In addition, a set of cam phasers may be used to control valve timing in order to retain exhaust gases in the combustion chamber. [0005] Optimal spark timing and dilution values of the engine are typically determined experimentally in a single set of air conditions. However, engines may not always operate in the same set conditions due to geographic location, seasonal changes, and/or other circumstances. When engine performance is not optimized, the engine system may experience reduced fuel economy and sluggish engine output. SUMMARY [0006] A humidity based control system for an internal combustion engine according to the present disclosure includes a calculation module and a calibration module. The calculation module determines a humidity of air used in a combustion process of the internal combustion engine. The calibration module selectively controls spark timing of the internal combustion engine based on the humidity. 2 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 [0007] In other features, the calibration module selectively controls exhaust gas recirculation in the internal combustion engine based on the humidity. When the humidity is increasing, the calibration module increases the spark timing and decreases the exhaust gas recirculation. When the humidity is decreasing, the calibration module decreases the spark timing and increases the exhaust gas recirculation. The exhaust gas recirculation is controlled with an exhaust gas recirculation valve and/or a cam phaser. [0008] In still other features, the calculation module includes a water vapor pressure module, a partial pressure module, and a humidity module. The water vapor pressure module generates a water vapor pressure signal based on an air intake temperature signal and a barometric pressure signal. The partial pressure module generates a partial pressure signal based on a relative humidity signal and the water vapor pressure signal. The humidity module calculates the humidity based on the partial pressure signal and the barometric pressure signal. [0009] Further areas of applicability of the present disclosure 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 disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS [0010] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 3 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 [0011] FIG. 1 is a functional block diagram of an exemplary engine system using a humidity based control system according to the present disclosure; [0012] FIG. 2 is a functional block diagram of the humidity based control system according to the present disclosure; and [0013] FIG. 3 is a flow chart illustrating exemplary steps taken by the humidity based control system to adjust spark timing and exhaust dilution according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0014] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. As used herein, the term module or device refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. [0015] According to the present disclosure, a humidity based control system compensates for atmospheric conditions during engine operation. More specifically, the humidity based control system determines a humidity level based on various sensors and adjusts spark timing and dilution of an air/fuel mixture based on the humidity level. 4 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 [0016] Referring now to FIG. 1, a functional block diagram of an engine system 100 includes an engine 102 that combusts an air/ fuel mixture to produce drive torque. Air is drawn into an intake manifold 104 through a throttle 106. The throttle 106 regulates air flow into the intake manifold 104. Air within the intake manifold 104 is distributed into a cylinder 110. Although four cylinders are illustrated, it can be appreciated that the engine 102 may include additional or fewer cylinders 110. For example, engines having 2, 3, 4, 5, 6, 8, 10 and 12 cylinders are contemplated. [0017] A fuel injector (not shown) injects fuel which is combined with air as it is drawn into the cylinder 110. A fuel injection system (not shown) provides a desired air-to-fuel ratio within each cylinder 110. An intake valve 114 selectively opens and closes to enable the air/fuel mixture to enter the cylinder 110. The intake valve position is regulated by an intake cam shaft 116. A piston (not shown) compresses the air/fuel mixture within the cylinder 110. A spark plug 118 initiates combustion of the air/fuel mixture driving the piston in the cylinder 110. The piston drives a crankshaft (not shown) to produce drive torque. The crankshaft rotatably drives camshafts 116,120 using a timing chain (not shown) to regulate the timing of intake and exhaust valves 114, 121. Although a single intake camshaft and a single exhaust camshaft are shown, it is appreciated that dual intake camshafts and dual exhaust camshafts may be used in a v-type cylinder configuration. Likewise, electro-hydrolic valve actuation, or other valve systems. 5 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 [0018] Exhaust gases within the cylinder 110 are forced out of an outlet (not shown) when the exhaust valve 121 is in an open position. The exhaust valve position is regulated by the exhaust cam shaft 120. The exhaust gases are released into the atmosphere through an exhaust 124. [0019] The engine 102 may include an intake cam phaser 128 and an exhaust cam phaser 130 that regulate rotational timing of the intake and exhaust cam shafts 116,120, respectively. More specifically, a phase angle of the intake and exhaust cam phasers 128, 130 may be retarded or advanced to control rotational timing of the input and output cam shafts 116, 120. By controlling rotational timing of the cam shafts 116,120 the amount of exhaust gases retained in the cylinder can be regulated. [0020] The engine system 100 may include an exhaust gas recirculation (EGR) valve 132. The EGR valve 132 selectively opens and closes to regulate a flow of exhaust gases back into the intake manifold 104. Introducing exhaust gases into an intake stroke of the combustion event tends to limit the amount of oxygen available for combustion. Limiting the oxygen available for combustion lowers combustion temperatures and reduces engine emissions. When the EGR valve 132 is optimized with spark timing, fuel economy and/or performance may be improved. [0021] An intake air temperature sensor 136 is responsive to intake air temperature and generates an intake air temperature signal 138 based thereon. A barometric pressure sensor 148 is responsive to atmospheric pressure and generates a barometric pressure signal 150 based thereon. A relative humidity 6 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 sensor 154 is responsive to an amount of water that air can hold based on temperature and generates a relative humidity signal 155 based thereon. A humidity based control system 134 controls engine 102 operation based on the intake air temperature signal 138, the barometric pressure signal 150, and the relative humidity signal. [0022] Referring now to FIG. 2, the humidity based control system 134 includes a calculation module 170 and a control module 172. The calculation module 170 determines a humidity based on the intake air temperature signal 138, the barometric pressure signal 150, and the relative humidity signal 155. The control module 172 determines whether the humidity has increased or decreased since a previous cycle and generates a control signal to adjust spark timing and/or dilution of the air/fuel mixture. [0023] The calculation module 170 may include a saturation water vapor pressure module 174, a partial pressure module 176, and a humidity module 178. The saturation water vapor pressure module 174 determines a saturation water vapor pressure value based on the intake air temperature signal 138 and the barometric pressure signal 150. More specifically, the saturation water vapor pressure value may be determined using the following formula: where es is the saturation water vapor pressure value, p is the barometric pressure, and T is intake air temperature. The saturation water vapor pressure module 174 generates a water vapor pressure signal 175 based on the saturation water vapor pressure value. 7 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 [0024] The partial pressure module 176 determines a partial pressure of water vapor value based on the relative humidity signal 155 and the water vapor pressure signal 175. More specifically, the partial pressure of water vapor value may be determined using the following formula: where e is the partial pressure of water vapor value,  is relative humidity, and es is the saturation water vapor pressure value. The partial pressure module 176 generates a partial pressure signal 177 based on the partial pressure of water vapor value. [0025] The humidity module 178 determines the humidity based on the partial pressure signal 177 and the barometric pressure signal 150. More specifically, the humidity may be determined using the following formula: where h is the humidity, p is the barometric pressure, and e is the partial pressure of water vapor value. The humidity module 178 generates a humidity signal 179 based on the humidity. The control module 172 generates the control signal to adjust spark timing and/or dilution of the air/fuel mixture based on the humidity signal 179. [0026] Referring now to FIG. 3, exemplary steps of the humidity based control system 134 are generally identified at 300. The process begins in step 305 when the engine 102 is turned on. In step 310, the calculation module 170 8 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 determines the humidity. In step 320, the calibration module 172 determines whether the humidity is increasing or decreasing. More specifically, the calibration module compares the humidity to a previous humidity calculated during the previous cycle. If the humidity is increasing, the spark timing is advanced in step 330. In step 340, the humidity based control system 134 decreases dilution of the air/fuel mixture using the EGR valve 132 and/or the cam phasers 128,130. In step 350, the humidity based control system 134 determines whether the engine 102 is running. If the engine is running, the process returns to step 310. If the engine 102 is not running, the process ends in step 360. [0027] If the calibration module 170 determines that the humidity is decreasing in step 320, spark timing is retarded in step 370 to allow correct combustion phasing. In step 380, the humidity based control system 134 increases dilution of the air/fuel mixture using the EGR valve 132 and/or the cam phasers 128,130 and proceeds to step 350. Thus, when less moisture is in the air, more exhaust gases are introduced to dilute the air/fuel mixture. [0028] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and the following claims. 9 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 CLAIMS What is claimed is: 1. A humidity based control system for an internal combustion engine, comprising: a calculation module that determines a humidity of air used in a combustion process of the internal combustion engine; and a calibration module that selectively controls spark timing of the internal combustion engine based on said humidity. 2. The humidity based control system of claim 1 wherein said calibration module selectively controls exhaust gas recirculation in the internal combustion engine based on said humidity. 3. The humidity based control system of claim 2 wherein said calibration module increases said spark timing when said humidity is increasing. 4. The humidity based control system of claim 3 wherein said calibration module decreases said exhaust gas recirculation when said humidity is increasing. 10 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 5. The humidity based control system of claim 2 wherein said calibration module decreases said spark timing when said humidity is decreasing. 6. The humidity based control system of claim 5 wherein said calibration module increases said exhaust gas recirculation when said humidity is decreasing. 7. The humidity based control system of claim 2 wherein said exhaust gas recirculation is controlled with an exhaust gas recirculation valve. 8. The humidity based control system of claim 2 wherein said exhaust gas recirculation is controlled with a cam phaser. 9. The humidity based control system of claim 1 wherein said humidity is based on an air intake temperature signal, a barometric pressure signal, and a relative humidity signal. 11 General Motors No, GP-306198 Attorney Docket No. 8540P-000306 10. The humidity based control system of claim 9 wherein said calculation module comprises: a water vapor pressure module that generates a water vapor pressure signal based on said air intake temperature signal and said barometric pressure signal; a partial pressure module that generates a partial pressure signal based on said relative humidity signal and said water vapor pressure signal; and a humidity module that calculates said humidity based on said partial pressure signal and said barometric pressure signal. 12 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 11. A method to calibrate an internal combustion engine, comprising: determining a humidity of air used in a combustion process of the internal combustion engine; and selectively controlling spark timing of said internal combustion engine based on said humidity. 12. The method of claim 11 further comprising selectively controlling exhaust gas recirculation in the internal combustion engine based on said humidity. 13. The method of claim 12 further comprising increasing said spark timing when said humidity is increasing. 14. The method of claim 13 further comprising decreasing said exhaust gas recirculation when said humidity is increasing. 15. The method of claim 12 further comprising decreasing said spark timing when said humidity is decreasing. 16. The method of claim 15 further comprising increasing said exhaust gas recirculation when said humidity is decreasing. 13 General Motors No. GP-306198 Attorney Docket No. 8540P-000306 17. The method of claim 12 wherein said exhaust gas recirculation is controlled with an exhaust gas recirculation valve. 18. The method of claim 12 wherein said exhaust gas recirculation is controlled with a cam phaser. 19. The method of claim 11 wherein said humidity is based on an air intake pressure, a barometric pressure, and a relative humidity. 20. The method of claim 19 wherein: a water vapor pressure is based on said air intake temperature; a partial pressure is based on said relative humidity and said water vapor pressure; and said humidity is based on said partial pressure and said barometric pressure. Dated this 31st day of AUGUST 2007 14 A humidity based control system for an internal combustion engine includes a calculation module and a calibration module. The calculation module determines a humidity of air used in a combustion process of the internal combustion engine. The control module selectively controls spark timing and exhaust dilution in the internal combustion engine based on the humidity.

Full Text

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
A HUMIDITY BASED CONTROL SYSTEM FOR
AN INTERNAL COMBUSTION ENGINE
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/842,512, filed on September 5, 2006. The disclosure of the
above application is incorporated herein by reference.
FIELD
[0002] The present disclosure relates to an internal combustion engine,
and more particularly to method to control spark timing and exhaust dilution to
improve fuel economy and drivability.
BACKGROUND
[0003] Efficiency of an internal combustion engine may be controlled
by adjusting spark timing and an exhaust dilution that is combusted by the
engine. Spark timing may be defined as generating a spark at a specific time
relative to a position of a piston in a combustion chamber. A preferred spark
timing occurs when the engine has a maximum output power. Output power is
directly proportional to pressure within a combustion chamber of the engine. To
obtain maximum pressure in the combustion chamber, the spark ignites the
air/fuel mixture at a time before the piston is at top dead center permitting heated
gases time to fully expand as the piston reaches top dead center.
1

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
[0004] The engine system may also dilute the air/fuel mixture to
improve engine efficiency. Exhaust dilution may improve engine efficiency by
reducing pumping losses. When exhaust gases are introduced during an intake
stroke of a combustion event, the engine requires less air thereby reducing
pumping power losses of the engine. An engine control system may use an
exhaust gas recirculation (EGR) system to re-circulate exhaust gases back into
the intake manifold. In addition, a set of cam phasers may be used to control
valve timing in order to retain exhaust gases in the combustion chamber.
[0005] Optimal spark timing and dilution values of the engine are
typically determined experimentally in a single set of air conditions. However,
engines may not always operate in the same set conditions due to geographic
location, seasonal changes, and/or other circumstances. When engine
performance is not optimized, the engine system may experience reduced fuel
economy and sluggish engine output.
SUMMARY
[0006] A humidity based control system for an internal combustion
engine according to the present disclosure includes a calculation module and a
calibration module. The calculation module determines a humidity of air used in
a combustion process of the internal combustion engine. The calibration module
selectively controls spark timing of the internal combustion engine based on the
humidity.
2

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
[0007] In other features, the calibration module selectively controls
exhaust gas recirculation in the internal combustion engine based on the
humidity. When the humidity is increasing, the calibration module increases the
spark timing and decreases the exhaust gas recirculation. When the humidity is
decreasing, the calibration module decreases the spark timing and increases the
exhaust gas recirculation. The exhaust gas recirculation is controlled with an
exhaust gas recirculation valve and/or a cam phaser.
[0008] In still other features, the calculation module includes a water
vapor pressure module, a partial pressure module, and a humidity module. The
water vapor pressure module generates a water vapor pressure signal based on
an air intake temperature signal and a barometric pressure signal. The partial
pressure module generates a partial pressure signal based on a relative humidity
signal and the water vapor pressure signal. The humidity module calculates the
humidity based on the partial pressure signal and the barometric pressure signal.
[0009] Further areas of applicability of the present disclosure 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 disclosure, are intended for purposes of
illustration only and are not intended to limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present disclosure will become more fully understood from
the detailed description and the accompanying drawings, wherein:
3

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
[0011] FIG. 1 is a functional block diagram of an exemplary engine
system using a humidity based control system according to the present
disclosure;
[0012] FIG. 2 is a functional block diagram of the humidity based
control system according to the present disclosure; and
[0013] FIG. 3 is a flow chart illustrating exemplary steps taken by the
humidity based control system to adjust spark timing and exhaust dilution
according to the present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the disclosure, its
application, or uses. As used herein, the term module or device refers to an
application specific integrated circuit (ASIC), an electronic circuit, a processor
(shared, dedicated, or group) and memory that executes one or more software or
firmware programs, a combinational logic circuit, and/or other suitable
components that provide the described functionality.
[0015] According to the present disclosure, a humidity based control
system compensates for atmospheric conditions during engine operation. More
specifically, the humidity based control system determines a humidity level based
on various sensors and adjusts spark timing and dilution of an air/fuel mixture
based on the humidity level.
4

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
[0016] Referring now to FIG. 1, a functional block diagram of an engine
system 100 includes an engine 102 that combusts an air/ fuel mixture to produce
drive torque. Air is drawn into an intake manifold 104 through a throttle 106. The
throttle 106 regulates air flow into the intake manifold 104. Air within the intake
manifold 104 is distributed into a cylinder 110. Although four cylinders are
illustrated, it can be appreciated that the engine 102 may include additional or
fewer cylinders 110. For example, engines having 2, 3, 4, 5, 6, 8, 10 and 12
cylinders are contemplated.
[0017] A fuel injector (not shown) injects fuel which is combined with air
as it is drawn into the cylinder 110. A fuel injection system (not shown) provides
a desired air-to-fuel ratio within each cylinder 110. An intake valve 114
selectively opens and closes to enable the air/fuel mixture to enter the cylinder
110. The intake valve position is regulated by an intake cam shaft 116. A piston
(not shown) compresses the air/fuel mixture within the cylinder 110. A spark plug
118 initiates combustion of the air/fuel mixture driving the piston in the cylinder
110. The piston drives a crankshaft (not shown) to produce drive torque. The
crankshaft rotatably drives camshafts 116,120 using a timing chain (not shown)
to regulate the timing of intake and exhaust valves 114, 121. Although a single
intake camshaft and a single exhaust camshaft are shown, it is appreciated that
dual intake camshafts and dual exhaust camshafts may be used in a v-type
cylinder configuration. Likewise, electro-hydrolic valve actuation, or other valve
systems.
5

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
[0018] Exhaust gases within the cylinder 110 are forced out of an
outlet (not shown) when the exhaust valve 121 is in an open position. The
exhaust valve position is regulated by the exhaust cam shaft 120. The exhaust
gases are released into the atmosphere through an exhaust 124.
[0019] The engine 102 may include an intake cam phaser 128 and an
exhaust cam phaser 130 that regulate rotational timing of the intake and exhaust
cam shafts 116,120, respectively. More specifically, a phase angle of the intake
and exhaust cam phasers 128, 130 may be retarded or advanced to control
rotational timing of the input and output cam shafts 116, 120. By controlling
rotational timing of the cam shafts 116,120 the amount of exhaust gases retained
in the cylinder can be regulated.
[0020] The engine system 100 may include an exhaust gas
recirculation (EGR) valve 132. The EGR valve 132 selectively opens and closes
to regulate a flow of exhaust gases back into the intake manifold 104.
Introducing exhaust gases into an intake stroke of the combustion event tends to
limit the amount of oxygen available for combustion. Limiting the oxygen
available for combustion lowers combustion temperatures and reduces engine
emissions. When the EGR valve 132 is optimized with spark timing, fuel
economy and/or performance may be improved.
[0021] An intake air temperature sensor 136 is responsive to intake air
temperature and generates an intake air temperature signal 138 based thereon.
A barometric pressure sensor 148 is responsive to atmospheric pressure and
generates a barometric pressure signal 150 based thereon. A relative humidity
6

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
sensor 154 is responsive to an amount of water that air can hold based on
temperature and generates a relative humidity signal 155 based thereon. A
humidity based control system 134 controls engine 102 operation based on the
intake air temperature signal 138, the barometric pressure signal 150, and the
relative humidity signal.
[0022] Referring now to FIG. 2, the humidity based control system 134
includes a calculation module 170 and a control module 172. The calculation
module 170 determines a humidity based on the intake air temperature signal
138, the barometric pressure signal 150, and the relative humidity signal 155.
The control module 172 determines whether the humidity has increased or
decreased since a previous cycle and generates a control signal to adjust spark
timing and/or dilution of the air/fuel mixture.
[0023] The calculation module 170 may include a saturation water
vapor pressure module 174, a partial pressure module 176, and a humidity
module 178. The saturation water vapor pressure module 174 determines a
saturation water vapor pressure value based on the intake air temperature signal
138 and the barometric pressure signal 150. More specifically, the saturation
water vapor pressure value may be determined using the following formula:

where es is the saturation water vapor pressure value, p is the barometric
pressure, and T is intake air temperature. The saturation water vapor pressure
module 174 generates a water vapor pressure signal 175 based on the
saturation water vapor pressure value.
7

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
[0024] The partial pressure module 176 determines a partial pressure
of water vapor value based on the relative humidity signal 155 and the water
vapor pressure signal 175. More specifically, the partial pressure of water vapor
value may be determined using the following formula:

where e is the partial pressure of water vapor value,  is relative humidity, and
es is the saturation water vapor pressure value. The partial pressure module 176
generates a partial pressure signal 177 based on the partial pressure of water
vapor value.
[0025] The humidity module 178 determines the humidity based on the
partial pressure signal 177 and the barometric pressure signal 150. More
specifically, the humidity may be determined using the following formula:

where h is the humidity, p is the barometric pressure, and e is the partial
pressure of water vapor value. The humidity module 178 generates a humidity
signal 179 based on the humidity. The control module 172 generates the control
signal to adjust spark timing and/or dilution of the air/fuel mixture based on the
humidity signal 179.
[0026] Referring now to FIG. 3, exemplary steps of the humidity based
control system 134 are generally identified at 300. The process begins in step
305 when the engine 102 is turned on. In step 310, the calculation module 170
8

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
determines the humidity. In step 320, the calibration module 172 determines
whether the humidity is increasing or decreasing. More specifically, the
calibration module compares the humidity to a previous humidity calculated
during the previous cycle. If the humidity is increasing, the spark timing is
advanced in step 330. In step 340, the humidity based control system 134
decreases dilution of the air/fuel mixture using the EGR valve 132 and/or the cam
phasers 128,130. In step 350, the humidity based control system 134
determines whether the engine 102 is running. If the engine is running, the
process returns to step 310. If the engine 102 is not running, the process ends in
step 360.
[0027] If the calibration module 170 determines that the humidity is
decreasing in step 320, spark timing is retarded in step 370 to allow correct
combustion phasing. In step 380, the humidity based control system 134
increases dilution of the air/fuel mixture using the EGR valve 132 and/or the cam
phasers 128,130 and proceeds to step 350. Thus, when less moisture is in the
air, more exhaust gases are introduced to dilute the air/fuel mixture.
[0028] Those skilled in the art can now appreciate from the foregoing
description that the broad teachings of the present disclosure can be
implemented in a variety of forms. Therefore, while this disclosure has been
described in connection with particular examples thereof, the true scope of the
disclosure should not be so limited since other modifications will become
apparent to the skilled practitioner upon a study of the drawings, specification,
and the following claims.
9

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
CLAIMS
What is claimed is:
1. A humidity based control system for an internal combustion engine,
comprising:
a calculation module that determines a humidity of air used in a
combustion process of the internal combustion engine; and
a calibration module that selectively controls spark timing of the
internal combustion engine based on said humidity.
2. The humidity based control system of claim 1 wherein said
calibration module selectively controls exhaust gas recirculation in the internal
combustion engine based on said humidity.
3. The humidity based control system of claim 2 wherein said
calibration module increases said spark timing when said humidity is increasing.
4. The humidity based control system of claim 3 wherein said
calibration module decreases said exhaust gas recirculation when said humidity
is increasing.
10

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
5. The humidity based control system of claim 2 wherein said
calibration module decreases said spark timing when said humidity is
decreasing.
6. The humidity based control system of claim 5 wherein said
calibration module increases said exhaust gas recirculation when said humidity is
decreasing.
7. The humidity based control system of claim 2 wherein said exhaust
gas recirculation is controlled with an exhaust gas recirculation valve.
8. The humidity based control system of claim 2 wherein said exhaust
gas recirculation is controlled with a cam phaser.
9. The humidity based control system of claim 1 wherein said humidity
is based on an air intake temperature signal, a barometric pressure signal, and a
relative humidity signal.
11

General Motors No, GP-306198
Attorney Docket No. 8540P-000306
10. The humidity based control system of claim 9 wherein said
calculation module comprises:
a water vapor pressure module that generates a water vapor
pressure signal based on said air intake temperature signal and said barometric
pressure signal;
a partial pressure module that generates a partial pressure signal
based on said relative humidity signal and said water vapor pressure signal; and
a humidity module that calculates said humidity based on said
partial pressure signal and said barometric pressure signal.
12

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
11. A method to calibrate an internal combustion engine, comprising:
determining a humidity of air used in a combustion process of the
internal combustion engine; and
selectively controlling spark timing of said internal combustion
engine based on said humidity.
12. The method of claim 11 further comprising selectively controlling
exhaust gas recirculation in the internal combustion engine based on said
humidity.
13. The method of claim 12 further comprising increasing said spark
timing when said humidity is increasing.
14. The method of claim 13 further comprising decreasing said exhaust
gas recirculation when said humidity is increasing.
15. The method of claim 12 further comprising decreasing said spark
timing when said humidity is decreasing.
16. The method of claim 15 further comprising increasing said exhaust
gas recirculation when said humidity is decreasing.
13

General Motors No. GP-306198
Attorney Docket No. 8540P-000306
17. The method of claim 12 wherein said exhaust gas recirculation is
controlled with an exhaust gas recirculation valve.
18. The method of claim 12 wherein said exhaust gas recirculation is
controlled with a cam phaser.
19. The method of claim 11 wherein said humidity is based on an air
intake pressure, a barometric pressure, and a relative humidity.
20. The method of claim 19 wherein:
a water vapor pressure is based on said air intake temperature;
a partial pressure is based on said relative humidity and said water
vapor pressure; and
said humidity is based on said partial pressure and said barometric
pressure.

Dated this 31st day of AUGUST 2007
14

A humidity based control system for an internal combustion engine
includes a calculation module and a calibration module. The calculation module
determines a humidity of air used in a combustion process of the internal
combustion engine. The control module selectively controls spark timing and
exhaust dilution in the internal combustion engine based on the humidity.

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Patent Number

269036

Indian Patent Application Number

1221/KOL/2007

PG Journal Number

40/2015

Publication Date

02-Oct-2015

Grant Date

29-Sep-2015

Date of Filing

31-Aug-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	MICHAEL WAYNE LEIFERMAN	3684 ABERDEEN COURT, BRIGHTON MICHIGAN 48114-9062
2	LYNN A. TOTTEN	9500 WARNER RD. HASLETT, MICHIGAN 48840
3	PAUL R. HOZAK	3540 TRACY DRIVE STERLING HEIGHTS, MICHIGAN 48310
4	JEFFREY A. SELL	4348 MC NAY COURT SOUTH, WEST BLOOMFIELD, MICHIGAN 48323

PCT International Classification Number

F02P5/00; F02D23/00; F02D41/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/842512	2006-09-05	U.S.A.