Title of Invention	A METHOD FOR REDUCING NOX EMISSION FOR DIESEL ENGINES
Abstract	An emissions control method may include injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating temperature is greater than a first limit, terminating the injecting when a temperature of a catalyst in communication with exhaust gas exiting the DOC is greater than a second limit, and injecting a dosing agent into the exhaust gas after the terminating.

Title of Invention

A METHOD FOR REDUCING NOX EMISSION FOR DIESEL ENGINES

Abstract

An emissions control method may include injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating temperature is greater than a first limit, terminating the injecting when a temperature of a catalyst in communication with exhaust gas exiting the DOC is greater than a second limit, and injecting a dosing agent into the exhaust gas after the terminating.

Full Text	PERTURBATION CONTROL STRATEGY FOR LOW-TEMPERATURE UREA SCR NOX REDUCTION FIELD [0001] The present disclosure relates to exhaust treatment systems, and more particularly to NOx emissions reduction. BACKGROUND [0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. [0003] Selective catalytic reduction (SCR) catalysts and diesel oxidation catalysts (DOC) are commonly used with diesel engines for emissions reduction. In the SCR process, NOx reacts with a reductant which is injected by a dosing system into the flue or exhaust gas stream to be absorbed onto a SCR catalyst. The injected dosing agent (e.g. urea) breaks down to form ammonia (NH3), which is the reductant utilized to react with the NOx producing nitrogen (N2) and water (H20). [0004] However, the SCR process typically requires relatively high exhaust gas temperatures, such as temperatures greater than 220 °C. In conventional diesel applications, relatively low exhaust gas temperatures, such as temperatures less than 220 °C, can be experienced frequently. Therefore, external heating devices may be used to maintain SCR catalyst temperatures during periods of low exhaust gas temperature. SUMMARY [0005] An emissions control method may include injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating temperature is greater than a first limit, terminating the injecting when a temperature of a catalyst in communication with exhaust gas exiting the DOC is greater than a second limit, and injecting a dosing agent into the exhaust gas after the terminating. [0006] The catalyst may include a selective catalytic reduction (SCR) catalyst and the dosing agent injection may be terminated when the SCR catalyst temperature is less than a third limit. Injection of the fuel may begin again after termination of the dosing agent injection when the DOC operating temperature is greater than the first limit. [0007] A control module may include a diesel oxidation catalyst (DOC) control module, a selective catalytic reduction (SCR) catalyst control module, and a dosing agent control module. The DOC control module may control a temperature of a DOC in communication with an exhaust gas from an engine. The SCR catalyst control module may be in communication with the DOC control module and may control a temperature of a SCR catalyst by selectively injecting a fuel into the exhaust gas provided to the DOC when the DOC temperature is greater than a first limit. The SCR catalyst control module may terminate the injecting when the SCR catalyst temperature is greater than a second limit. The dosing agent control module may be in communication with the SCR catalyst control module and may control injection of the dosing agent into the exhaust gas after the terminating. [0008] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. DRAWINGS [0009] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. [0010] Figure 1 is a schematic illustration of a vehicle according to the present disclosure; [0011] Figure 2 is a control block diagram of the control module shown in Figure 1; and [0012] Figure 3 is a flow diagram illustrating steps for control of the vehicle of Figure 1. DETAILED DESCRIPTION [0013] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 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, or other suitable components that provide the described functionality. [0014] Referring now to Figure 1, an exemplary vehicle 10 is schematically illustrated. Vehicle 10 may include an engine assembly 12 and an exhaust after-treatment system 14. Engine assembly 12 may include an engine 16 having a cylinder 18, an intake manifold 20 and an exhaust manifold 22. Air flows into intake manifold 20 through a throttle 24. The air is mixed with fuel and the air and fuel mixture is combusted within cylinder 18 to drive a piston (not shown). Although a single cylinder 18 is illustrated, it is appreciated that engine 16 may include additional cylinders 18. For example, engines having 2, 3, 4, 5, 6, 8, 10, 12 and 16 cylinders are anticipated. The fuel is provided from a fuel source 26 and is injected into the air stream using an injector 28. [0015] Exhaust is produced through the combustion process and is exhausted from cylinder 18 into exhaust manifold 22. Exhaust after-treatment system 14 treats the exhaust flowing therethrough to reduce emissions before being released to the atmosphere. Exhaust after-treatment system 14 may include a dosing system 32, a diesel oxidation catalyst (DOC) 34, first and second NOx sensors 36, 37, a selective catalytic reduction (SCR) catalyst 38, and a diesel particulate filter (DPF) 40. First and second NOx sensors 36, 37 may be responsive to a NOx level of the exhaust and may generate respective signals based thereon. [0016] Temperature sensors TA, TB and Tc may be located along the exhaust path. Temperature sensor TA may located upstream of DOC 34 at an inlet thereof and temperature sensor TB may be located downstream of DOC 34 and upstream of SCR catalyst 38 at an inlet thereof. Temperature sensor Tc may be located downstream of SCR catalyst 38. DOC 34 reacts with the exhaust to reduce emission levels of the exhaust. DPF 40 may be located downstream from SCR catalyst 38 and may filter diesel particulates to further reduce emissions. [0017] Dosing system 32 may include a dosing agent injector 42 and a dosing agent storage tank 44. The dosing system 32 may selectively inject a dosing agent into the exhaust stream to further reduce emissions. For example, dosing agent storage tank 44 may include a supply of urea that is injected into the exhaust stream by dosing agent injector 42, as discussed below. The rate at which the dosing agent is injected into the exhaust stream may be determined based on the signals generated by one or more of the various sensors described herein. First and second NOx sensors 36, 37 may be used to determine NOx conversion efficiency and to determine proper urea dosing quantities as applied by the dosing agent injector 42. The exhaust and dosing agent mixture reacts within the SCR catalyst 38 to further reduce exhaust emissions. [0018] With additional reference to Figure 2, control module 50 may include a DOC temperature control module 52, a SCR catalyst temperature control module 54, and a dosing agent control module 56. DOC temperature control module 52 may be in communication with SCR catalyst temperature control module 54 and may control a temperature of exhaust gas provided by engine 16 to DOC 34 and may determine an operating temperature of DOC 34. Control of the temperature of exhaust gas provided to DOC 34 may include control of combustion parameters for engine 16. For example, DOC temperature control module 52 may adjust an opening of throttle 24 to control an air flow into engine 16. The operating temperature of DOC 34 may be determined by temperature sensor TB. [0019] DOC temperature control module 52 may also control an injection of fuel into cylinder 18. More specifically, DOC temperature control module 52 may control injector 28 to provide for pilot injection of fuel into cylinder 18. Pilot injection includes injection of a small amount of fuel into cylinder 18 prior to the main charge. The pilot charge generally starts to burn before the main charge of fuel is injected, providing for prompt ignition of the main charge without significant delay. A variety of other methods may additionally be employed to increase the exhaust gas temperature provided to DOC 34. [0020] SCR catalyst temperature control module 54 may be in communication with dosing agent control module 56 and may generally control a temperature of exhaust gas provided to SCR catalyst 38 and may determine an operating temperature of SCR catalyst 38. More specifically, SCR catalyst temperature control module 54 may generally control injection of fuel from fuel source 26 to an exhaust gas from cylinder 18. SCR catalyst temperature control module 54 may generally control the temperature of exhaust gas provided to SCR catalyst 38 through a post injection process. During post injection, fuel may be injected into cylinder 18 by injector 28 during an exhaust stroke or into the exhaust flow path from cylinder 18 to DOC 34 by a secondary injector (not shown). Post injection generally provides a quantity of fuel to the exhaust stream for combustion within DOC 34. Post injection may generally provide an increase in the temperature of exhaust gas exiting DOC 34 and being provided to SCR catalyst 38 through the combustion within DOC 34. The operating temperature of SCR catalyst 38 may be determined by temperature sensor Tc. [0021] Dosing agent control module 56 may be in communication with dosing agent storage tank 44 and dosing agent injector 42. As indicated above, dosing agent control module 56 may be in communication with SCR catalyst temperature control module 54. Dosing agent control module 56 may generally control injection of a dosing agent into the exhaust gas from engine 16 based on the temperatures controlled and determined by DOC temperature control module 52 and SCR catalyst temperature control module 54, as discussed below. [0022] Referring now to Figure 3, control logic 100 generally illustrates emissions control for vehicle 10, and more specifically a perturbation control strategy. Control logic 100 may begin at block 102 where DOC temperature (TDOC) is determined. TDOC may be determined by temperature sensor TB. Control logic 100 may then proceed to block 104 where TDOc is compared to a first predetermined limit (LIMIT). The first predetermined limit may generally correspond to a temperature greater than or equal to 230 °C. If TD0C is below the first predetermined limit, control logic 100 proceeds to block 106 where TD0C is increased. TD0C may be increased in a variety of ways by DOC temperature control module 52, including control of throttle 24 and pilot injection, as discussed above. Control logic 100 may then return to block 102 where TD0C is again evaluated. [0023] If block 104 determines that TD0C is greater than the first predetermined limit, control logic 100 may proceed to block 108 where SCR catalyst temperature control module 52 may apply post injection. As discussed above, post injection generally includes injection of fuel into the exhaust stream provided by engine 16 to DOC 34. Control logic 100 may then proceed to block 110 where SCR temperature (TSCR) is determined. [0024] TSCR may be determined by temperature sensor Tc. Once TSCR is determined at block 110, control logic 100 may proceed to block 112 where TSCR is compared to a second predetermined limit (LIMITH). The second predetermined limit may be greater than the first predetermined limit and may generally correspond to a temperature greater than or equal to 300 °C. If TSCR is less than the second predetermined limit, control logic 100 may return to block 108 where post injection continues. If TSCR is greater than the second predetermined limit, control logic 100 may proceed to block 114 where post injection is terminated. Once post injection is terminated, control logic 100 may proceed to block 116 where a dosing agent is applied to the exhaust gas. [0025] Application of the dosing agent may be controlled by dosing agent control module 56. The dosing agent may be applied at a location between DOC 34 and SCR catalyst 38. More specifically, the dosing agent may be applied at a location between an outlet of DOC 34 and an inlet of SCR catalyst 38. As discussed above, the dosing agent may include urea. Once the dosing agent has been applied at block 116, control logic 100 may proceed to block 118 where TSCR is again determined. Once TSCR is determined, control logic 100 may proceed to block 120 where TSCR is compared to a third predetermined limit (LIMIT,.). The third predetermined limit may be less than or equal to the first predetermined limit and may generally correspond to a temperature less than or equal to 220 °C. [0026] If TSCR is greater than the third predetermined limit, control logic 100 returns to block 116 where application of the dosing agent continues. If the TSCR is less than the third predetermined limit, control logic 100 proceeds to block 122 where application of the dosing agent is terminated. Once application of the dosing is terminated at block 122, control logic 100 may terminate, completing one cycle of the perturbation control strategy. [0027] Control logic 100 may generally loop continuously during operation of engine 16. More specifically, a subsequent cycle of control logic 100 may once again begin at block 102. Therefore, the fuel injection at block 108 and the dosing at block 116 may be turned on and off opposite one another to provide the perturbation control strategy. The perturbation control strategy may generally eliminate interference of hydrocarbons (HC) with the NO to N02 conversion within DOC 34, enhancing NOx reduction within SCR catalyst 38 at temperatures between LIMITi.and LIMITH. [0028] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms Therefore, while this disclosure includes particular examples, 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, the specification, and the following claims. CLAIMS What is claimed is: 1. A method comprising: injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating temperature is greater than a first limit; terminating said injecting when a temperature of a catalyst in communication with exhaust gas exiting said DOC is greater than a second limit; and injecting a dosing agent into said exhaust gas after said terminating. 2. The method of claim 1, further comprising increasing said DOC operating temperature to said first limit before said injecting the fuel. 3. The method of claim 1, further comprising terminating said injecting the dosing agent when said catalyst temperature is below a third limit. 4. The method of claim 3, further comprising injecting said fuel into said engine exhaust gas after said terminating said injecting the dosing agent. 5. The method of claim 3, wherein said third limit is less than or equal to said first limit. 6. The method of claim 1, wherein said DOC operating temperature is determined by an exhaust gas temperature at a location between said DOC and said catalyst. 7. The method of claim 1, wherein said catalyst temperature is determined by an exhaust gas temperature at an outlet of said catalyst. 8. The method of claim 7, wherein said injecting the dosing agent includes injecting said dosing agent in said exhaust gas at a location between an outlet of said DOC and an inlet of said catalyst. 9. The method of claim 8, wherein said dosing agent includes urea. 10. The method of claim 1, wherein said second limit is greater than said first limit. 11. The method of claim 1, wherein said catalyst includes a selective catalytic reduction (SCR) catalyst. 12. A method comprising: injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating temperature is greater than a first limit to increase a temperature of a selective catalytic reduction (SCR) catalyst in communication with exhaust gas exiting said DOC; terminating said injecting when said SCR catalyst temperature is greater than a second limit; injecting a dosing agent into said exhaust gas at a location between said DOC and said SCR catalyst after said terminating; and terminating said injecting the dosing agent when said SCR catalyst temperature is less than a third limit. 13. The method of claim 12, wherein said second limit is greater than said first limit. 14. A control module comprising: a diesel oxidation catalyst (DOC) control module that controls a temperature of a DOC in communication with an exhaust gas from an engine; a selective catalytic reduction (SCR) catalyst control module in communication with said DOC control module that controls a temperature of a SCR catalyst by selectively injecting a fuel into said exhaust gas provided to said DOC when said DOC temperature is greater than a first limit, said SCR catalyst control module terminating said injecting when said SCR catalyst temperature is greater than a second limit; and a dosing agent control module in communication with said SCR catalyst control module that controls injection of a dosing agent into said exhaust gas after said terminating. 15. The control module of claim 14, wherein said dosing agent control module terminates said injection of said dosing agent when said SCR catalyst temperature is less than a third limit. 16. The control module of claim 15, wherein said third limit is less than or equal to said first limit. 17. The control module of claim 15, wherein said SCR catalyst control module selectively resumes injection said fuel into said exhaust gas provided to said DOC when said DOC temperature is greater than said first limit after said injection of said dosing agent is terminated. 18. The control module of claim 14, wherein said SCR catalyst temperature is determined by an exhaust gas temperature at a location at an outlet of said SCR catalyst. 19. The control module of claim 14, wherein said dosing agent is injected at a location between an outlet of said DOC and an inlet of said SCR catalyst. 20. The control module of claim 19, wherein said dosing agent includes urea. An emissions control method may include injecting a fuel into an engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating temperature is greater than a first limit, terminating the injecting when a temperature of a catalyst in communication with exhaust gas exiting the DOC is greater than a second limit, and injecting a dosing agent into the exhaust gas after the terminating.

Full Text

PERTURBATION CONTROL STRATEGY FOR LOW-TEMPERATURE UREA
SCR NOX REDUCTION
FIELD
[0001] The present disclosure relates to exhaust treatment systems,
and more particularly to NOx emissions reduction.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may not constitute prior art.
[0003] Selective catalytic reduction (SCR) catalysts and diesel
oxidation catalysts (DOC) are commonly used with diesel engines for emissions
reduction. In the SCR process, NOx reacts with a reductant which is injected by
a dosing system into the flue or exhaust gas stream to be absorbed onto a SCR
catalyst. The injected dosing agent (e.g. urea) breaks down to form ammonia
(NH3), which is the reductant utilized to react with the NOx producing nitrogen
(N2) and water (H20).
[0004] However, the SCR process typically requires relatively high
exhaust gas temperatures, such as temperatures greater than 220 °C. In
conventional diesel applications, relatively low exhaust gas temperatures, such
as temperatures less than 220 °C, can be experienced frequently. Therefore,
external heating devices may be used to maintain SCR catalyst temperatures
during periods of low exhaust gas temperature.

SUMMARY
[0005] An emissions control method may include injecting a fuel into an
engine exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC
operating temperature is greater than a first limit, terminating the injecting when a
temperature of a catalyst in communication with exhaust gas exiting the DOC is
greater than a second limit, and injecting a dosing agent into the exhaust gas
after the terminating.
[0006] The catalyst may include a selective catalytic reduction (SCR)
catalyst and the dosing agent injection may be terminated when the SCR catalyst
temperature is less than a third limit. Injection of the fuel may begin again after
termination of the dosing agent injection when the DOC operating temperature is
greater than the first limit.
[0007] A control module may include a diesel oxidation catalyst (DOC)
control module, a selective catalytic reduction (SCR) catalyst control module, and
a dosing agent control module. The DOC control module may control a
temperature of a DOC in communication with an exhaust gas from an engine.
The SCR catalyst control module may be in communication with the DOC control
module and may control a temperature of a SCR catalyst by selectively injecting
a fuel into the exhaust gas provided to the DOC when the DOC temperature is
greater than a first limit. The SCR catalyst control module may terminate the
injecting when the SCR catalyst temperature is greater than a second limit. The
dosing agent control module may be in communication with the SCR catalyst

control module and may control injection of the dosing agent into the exhaust gas
after the terminating.
[0008] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the description and
specific examples are intended for purposes of illustration only and are not
intended to limit the scope of the present disclosure.
DRAWINGS
[0009] The drawings described herein are for illustration purposes only
and are not intended to limit the scope of the present disclosure in any way.
[0010] Figure 1 is a schematic illustration of a vehicle according to the
present disclosure;
[0011] Figure 2 is a control block diagram of the control module shown
in Figure 1; and
[0012] Figure 3 is a flow diagram illustrating steps for control of the
vehicle of Figure 1.
DETAILED DESCRIPTION
[0013] The following description is merely exemplary in nature and is
not intended to limit the present disclosure, application, or uses. It should be
understood that throughout the drawings, corresponding reference numerals
indicate like or corresponding parts and features. 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, or other
suitable components that provide the described functionality.
[0014] Referring now to Figure 1, an exemplary vehicle 10 is
schematically illustrated. Vehicle 10 may include an engine assembly 12 and an
exhaust after-treatment system 14. Engine assembly 12 may include an engine
16 having a cylinder 18, an intake manifold 20 and an exhaust manifold 22. Air
flows into intake manifold 20 through a throttle 24. The air is mixed with fuel and
the air and fuel mixture is combusted within cylinder 18 to drive a piston (not
shown). Although a single cylinder 18 is illustrated, it is appreciated that engine
16 may include additional cylinders 18. For example, engines having 2, 3, 4, 5,
6, 8, 10, 12 and 16 cylinders are anticipated. The fuel is provided from a fuel
source 26 and is injected into the air stream using an injector 28.
[0015] Exhaust is produced through the combustion process and is
exhausted from cylinder 18 into exhaust manifold 22. Exhaust after-treatment
system 14 treats the exhaust flowing therethrough to reduce emissions before
being released to the atmosphere. Exhaust after-treatment system 14 may
include a dosing system 32, a diesel oxidation catalyst (DOC) 34, first and
second NOx sensors 36, 37, a selective catalytic reduction (SCR) catalyst 38,
and a diesel particulate filter (DPF) 40. First and second NOx sensors 36, 37
may be responsive to a NOx level of the exhaust and may generate respective
signals based thereon.

[0016] Temperature sensors TA, TB and Tc may be located along the
exhaust path. Temperature sensor TA may located upstream of DOC 34 at an
inlet thereof and temperature sensor TB may be located downstream of DOC 34
and upstream of SCR catalyst 38 at an inlet thereof. Temperature sensor Tc
may be located downstream of SCR catalyst 38. DOC 34 reacts with the
exhaust to reduce emission levels of the exhaust. DPF 40 may be located
downstream from SCR catalyst 38 and may filter diesel particulates to further
reduce emissions.
[0017] Dosing system 32 may include a dosing agent injector 42 and a
dosing agent storage tank 44. The dosing system 32 may selectively inject a
dosing agent into the exhaust stream to further reduce emissions. For example,
dosing agent storage tank 44 may include a supply of urea that is injected into
the exhaust stream by dosing agent injector 42, as discussed below. The rate at
which the dosing agent is injected into the exhaust stream may be determined
based on the signals generated by one or more of the various sensors described
herein. First and second NOx sensors 36, 37 may be used to determine NOx
conversion efficiency and to determine proper urea dosing quantities as applied
by the dosing agent injector 42. The exhaust and dosing agent mixture reacts
within the SCR catalyst 38 to further reduce exhaust emissions.
[0018] With additional reference to Figure 2, control module 50 may
include a DOC temperature control module 52, a SCR catalyst temperature
control module 54, and a dosing agent control module 56. DOC temperature
control module 52 may be in communication with SCR catalyst temperature

control module 54 and may control a temperature of exhaust gas provided by
engine 16 to DOC 34 and may determine an operating temperature of DOC 34.
Control of the temperature of exhaust gas provided to DOC 34 may include
control of combustion parameters for engine 16. For example, DOC temperature
control module 52 may adjust an opening of throttle 24 to control an air flow into
engine 16. The operating temperature of DOC 34 may be determined by
temperature sensor TB.
[0019] DOC temperature control module 52 may also control an
injection of fuel into cylinder 18. More specifically, DOC temperature control
module 52 may control injector 28 to provide for pilot injection of fuel into cylinder
18. Pilot injection includes injection of a small amount of fuel into cylinder 18
prior to the main charge. The pilot charge generally starts to burn before the
main charge of fuel is injected, providing for prompt ignition of the main charge
without significant delay. A variety of other methods may additionally be
employed to increase the exhaust gas temperature provided to DOC 34.
[0020] SCR catalyst temperature control module 54 may be in
communication with dosing agent control module 56 and may generally control a
temperature of exhaust gas provided to SCR catalyst 38 and may determine an
operating temperature of SCR catalyst 38. More specifically, SCR catalyst
temperature control module 54 may generally control injection of fuel from fuel
source 26 to an exhaust gas from cylinder 18. SCR catalyst temperature control
module 54 may generally control the temperature of exhaust gas provided to
SCR catalyst 38 through a post injection process. During post injection, fuel may

be injected into cylinder 18 by injector 28 during an exhaust stroke or into the
exhaust flow path from cylinder 18 to DOC 34 by a secondary injector (not
shown). Post injection generally provides a quantity of fuel to the exhaust stream
for combustion within DOC 34. Post injection may generally provide an increase
in the temperature of exhaust gas exiting DOC 34 and being provided to SCR
catalyst 38 through the combustion within DOC 34. The operating temperature
of SCR catalyst 38 may be determined by temperature sensor Tc.
[0021] Dosing agent control module 56 may be in communication with
dosing agent storage tank 44 and dosing agent injector 42. As indicated above,
dosing agent control module 56 may be in communication with SCR catalyst
temperature control module 54. Dosing agent control module 56 may generally
control injection of a dosing agent into the exhaust gas from engine 16 based on
the temperatures controlled and determined by DOC temperature control module
52 and SCR catalyst temperature control module 54, as discussed below.
[0022] Referring now to Figure 3, control logic 100 generally illustrates
emissions control for vehicle 10, and more specifically a perturbation control
strategy. Control logic 100 may begin at block 102 where DOC temperature
(TDOC) is determined. TDOC may be determined by temperature sensor TB.
Control logic 100 may then proceed to block 104 where TDOc is compared to a
first predetermined limit (LIMIT). The first predetermined limit may generally
correspond to a temperature greater than or equal to 230 °C. If TD0C is below the
first predetermined limit, control logic 100 proceeds to block 106 where TD0C is
increased. TD0C may be increased in a variety of ways by DOC temperature

control module 52, including control of throttle 24 and pilot injection, as discussed
above. Control logic 100 may then return to block 102 where TD0C is again
evaluated.
[0023] If block 104 determines that TD0C is greater than the first
predetermined limit, control logic 100 may proceed to block 108 where SCR
catalyst temperature control module 52 may apply post injection. As discussed
above, post injection generally includes injection of fuel into the exhaust stream
provided by engine 16 to DOC 34. Control logic 100 may then proceed to block
110 where SCR temperature (TSCR) is determined.
[0024] TSCR may be determined by temperature sensor Tc. Once TSCR
is determined at block 110, control logic 100 may proceed to block 112 where
TSCR is compared to a second predetermined limit (LIMITH). The second
predetermined limit may be greater than the first predetermined limit and may
generally correspond to a temperature greater than or equal to 300 °C. If TSCR is
less than the second predetermined limit, control logic 100 may return to block
108 where post injection continues. If TSCR is greater than the second
predetermined limit, control logic 100 may proceed to block 114 where post
injection is terminated. Once post injection is terminated, control logic 100 may
proceed to block 116 where a dosing agent is applied to the exhaust gas.
[0025] Application of the dosing agent may be controlled by dosing
agent control module 56. The dosing agent may be applied at a location
between DOC 34 and SCR catalyst 38. More specifically, the dosing agent may
be applied at a location between an outlet of DOC 34 and an inlet of SCR

catalyst 38. As discussed above, the dosing agent may include urea. Once the
dosing agent has been applied at block 116, control logic 100 may proceed to
block 118 where TSCR is again determined. Once TSCR is determined, control
logic 100 may proceed to block 120 where TSCR is compared to a third
predetermined limit (LIMIT,.). The third predetermined limit may be less than or
equal to the first predetermined limit and may generally correspond to a
temperature less than or equal to 220 °C.
[0026] If TSCR is greater than the third predetermined limit, control logic
100 returns to block 116 where application of the dosing agent continues. If the
TSCR is less than the third predetermined limit, control logic 100 proceeds to block
122 where application of the dosing agent is terminated. Once application of the
dosing is terminated at block 122, control logic 100 may terminate, completing
one cycle of the perturbation control strategy.
[0027] Control logic 100 may generally loop continuously during
operation of engine 16. More specifically, a subsequent cycle of control logic 100
may once again begin at block 102. Therefore, the fuel injection at block 108
and the dosing at block 116 may be turned on and off opposite one another to
provide the perturbation control strategy. The perturbation control strategy may
generally eliminate interference of hydrocarbons (HC) with the NO to N02
conversion within DOC 34, enhancing NOx reduction within SCR catalyst 38 at
temperatures between LIMITi.and LIMITH.
[0028] Those skilled in the art can now appreciate from the foregoing
description that the broad teachings of the disclosure can be implemented in a

variety of forms Therefore, while this disclosure includes particular examples,
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, the
specification, and the following claims.

CLAIMS
What is claimed is:
1. A method comprising:
injecting a fuel into an engine exhaust gas provided to a diesel
oxidation catalyst (DOC) when a DOC operating temperature is greater than a
first limit;
terminating said injecting when a temperature of a catalyst in
communication with exhaust gas exiting said DOC is greater than a second limit;
and
injecting a dosing agent into said exhaust gas after said
terminating.
2. The method of claim 1, further comprising increasing said DOC
operating temperature to said first limit before said injecting the fuel.
3. The method of claim 1, further comprising terminating said injecting
the dosing agent when said catalyst temperature is below a third limit.
4. The method of claim 3, further comprising injecting said fuel into
said engine exhaust gas after said terminating said injecting the dosing agent.

5. The method of claim 3, wherein said third limit is less than or equal
to said first limit.
6. The method of claim 1, wherein said DOC operating temperature is
determined by an exhaust gas temperature at a location between said DOC and
said catalyst.
7. The method of claim 1, wherein said catalyst temperature is
determined by an exhaust gas temperature at an outlet of said catalyst.
8. The method of claim 7, wherein said injecting the dosing agent
includes injecting said dosing agent in said exhaust gas at a location between an
outlet of said DOC and an inlet of said catalyst.
9. The method of claim 8, wherein said dosing agent includes urea.
10. The method of claim 1, wherein said second limit is greater than
said first limit.
11. The method of claim 1, wherein said catalyst includes a selective
catalytic reduction (SCR) catalyst.

12. A method comprising:
injecting a fuel into an engine exhaust gas provided to a diesel
oxidation catalyst (DOC) when a DOC operating temperature is greater than a
first limit to increase a temperature of a selective catalytic reduction (SCR)
catalyst in communication with exhaust gas exiting said DOC;
terminating said injecting when said SCR catalyst temperature is
greater than a second limit;
injecting a dosing agent into said exhaust gas at a location between
said DOC and said SCR catalyst after said terminating; and
terminating said injecting the dosing agent when said SCR catalyst
temperature is less than a third limit.
13. The method of claim 12, wherein said second limit is greater than
said first limit.

14. A control module comprising:
a diesel oxidation catalyst (DOC) control module that controls a
temperature of a DOC in communication with an exhaust gas from an engine;
a selective catalytic reduction (SCR) catalyst control module in
communication with said DOC control module that controls a temperature of a
SCR catalyst by selectively injecting a fuel into said exhaust gas provided to said
DOC when said DOC temperature is greater than a first limit, said SCR catalyst
control module terminating said injecting when said SCR catalyst temperature is
greater than a second limit; and
a dosing agent control module in communication with said SCR
catalyst control module that controls injection of a dosing agent into said exhaust
gas after said terminating.
15. The control module of claim 14, wherein said dosing agent control
module terminates said injection of said dosing agent when said SCR catalyst
temperature is less than a third limit.
16. The control module of claim 15, wherein said third limit is less than
or equal to said first limit.

17. The control module of claim 15, wherein said SCR catalyst control
module selectively resumes injection said fuel into said exhaust gas provided to
said DOC when said DOC temperature is greater than said first limit after said
injection of said dosing agent is terminated.
18. The control module of claim 14, wherein said SCR catalyst
temperature is determined by an exhaust gas temperature at a location at an
outlet of said SCR catalyst.
19. The control module of claim 14, wherein said dosing agent is
injected at a location between an outlet of said DOC and an inlet of said SCR
catalyst.
20. The control module of claim 19, wherein said dosing agent includes
urea.

An emissions control method may include injecting a fuel into an engine
exhaust gas provided to a diesel oxidation catalyst (DOC) when a DOC operating
temperature is greater than a first limit, terminating the injecting when a
temperature of a catalyst in communication with exhaust gas exiting the DOC is
greater than a second limit, and injecting a dosing agent into the exhaust gas
after the terminating.

Documents:

209-KOL-2009-(03-04-2012)-ABSTRACT.pdf

209-KOL-2009-(03-04-2012)-CLAIMS.pdf

209-KOL-2009-(03-04-2012)-DESCRIPTION (COMPLETE).pdf

209-KOL-2009-(03-04-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

209-KOL-2009-(03-04-2012)-FORM-1.pdf

209-KOL-2009-(03-04-2012)-FORM-2.pdf

209-KOL-2009-(03-04-2012)-FORM-3.pdf

209-KOL-2009-(03-04-2012)-OTHERS.pdf

209-KOL-2009-(03-04-2012)-PETITION UNDER RULE 137-1.pdf

209-kol-2009-abstract.pdf

209-kol-2009-ASSIGNMENT-1.1.pdf

209-KOL-2009-ASSIGNMENT.pdf

209-kol-2009-CANCELLED PAGES.pdf

209-kol-2009-claims.pdf

209-KOL-2009-CORRESPONDENCE-1.1.pdf

209-KOL-2009-CORRESPONDENCE-1.2.pdf

209-kol-2009-CORRESPONDENCE-1.3.pdf

209-kol-2009-correspondence.pdf

209-kol-2009-description (complete).pdf

209-kol-2009-drawings.pdf

209-kol-2009-EXAMINATION REPORT.pdf

209-kol-2009-form 1.pdf

209-kol-2009-FORM 18-1.1.pdf

209-kol-2009-form 18.pdf

209-kol-2009-form 2.pdf

209-kol-2009-form 3.pdf

209-kol-2009-form 5.pdf

209-kol-2009-GPA-1.1.pdf

209-kol-2009-gpa.pdf

209-kol-2009-GRANTED-ABSTRACT.pdf

209-kol-2009-GRANTED-CLAIMS.pdf

209-kol-2009-GRANTED-DESCRIPTION (COMPLETE).pdf

209-kol-2009-GRANTED-DRAWINGS.pdf

209-kol-2009-GRANTED-FORM 1.pdf

209-kol-2009-GRANTED-FORM 2.pdf

209-kol-2009-GRANTED-FORM 3.pdf

209-kol-2009-GRANTED-FORM 5.pdf

209-kol-2009-GRANTED-LETTER PATENT.pdf

209-kol-2009-GRANTED-SPECIFICATION-COMPLETE.pdf

209-kol-2009-OTHERS.pdf

209-kol-2009-PETITION UNDER RULE 137.pdf

209-kol-2009-REPLY TO EXAMINATION REPORT.pdf

209-kol-2009-specification.pdf

209-kol-2009-TRANSLATED COPY OF PRIORITY DOCUMENT-1.1.pdf

209-KOL-2009-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

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Patent Number

262619

Indian Patent Application Number

209/KOL/2009

PG Journal Number

36/2014

Publication Date

05-Sep-2014

Grant Date

29-Aug-2014

Date of Filing

06-Feb-2009

Name of Patentee

GM GLOBAL TECHNOLOGY OPERATIONS, INC.

Applicant Address

300 GM RENAISSANCE CENTER DETROIT, MICHIGAN 48265-3000

Inventors:

#	Inventor's Name	Inventor's Address
1	SHOUXIAN REN	133 EDENWOOD DR. APT #203 ANN ARBOR, MI 48103

PCT International Classification Number

F27B15/00, C10M163/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	12/043,241	2008-03-06	U.S.A.