Selective Catalytic Reduction Catalyst Preheat and Exhaust Burner Air Control

Abstract

The present invention discloses an exhaust control system for a vehicle comprising: a fuel injector, which is configured to inject fuel into a combustion chamber of a burner of an exhaust system upstream of a selective catalytic reduction (SCR) catalyst; an air pump, which is configured to pump air into the combustion chamber of the burner; a spark plug, which is configured to ignite an air / fuel mixture in the combustion chamber of the burner; a fuel control module, which is configured to selectively actuate the fuel injector and start fuel injection when the engine is turned off and before the engine is started; a pump control module, which is configured to selectively turn on the air pump when the engine is turned off and before the engine is started; and a spark control module, which is configured to selectively apply power to the spark plug and start providing spark when the engine is turned off and before the engine is started.

Description

Technical Field

[0001] The present disclosure relates to exhaust control systems and methods, and more particularly to systems and methods for controlling selective reduction catalyst (SCR) temperature and air flow into an exhaust system. Background Art

[0002] The information provided in this section is for the purpose of generally presenting the context of the present disclosure. Work by the presently listed inventors within the scope described in this section and aspects of this specification that would not be considered prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art against the present disclosure.

[0003] Air is drawn into the engine through an intake manifold. The air mixes with fuel from one or more fuel injectors to form an air / fuel mixture. The air / fuel mixture is combusted within one or more cylinders of the engine. The combustion of the air / fuel mixture produces torque.

[0004] The combustion of the air / fuel mixture produces exhaust gas that is expelled from the cylinders to the exhaust system. Exhaust gas from an engine burning diesel fuel with excess air may contain particulate matter (PM) and gases. The exhaust gas contains nitrogen oxides (NOx), such as nitrogen monoxide (NO) and nitrogen dioxide (NO2). Exhaust treatment systems can be used to reduce the amount of NOx and PM in the exhaust gas.

[0005] The exhaust treatment system may include a diesel oxidation catalyst (DOC). The DOC removes hydrocarbons and / or carbon oxides from the exhaust. The exhaust treatment system may also include a diesel particulate filter (DPF), which removes particulate matter (PM) from the exhaust. The exhaust treatment system may also include a selective catalytic reduction (SCR) catalyst. A diesel exhaust fluid (DEF) injector injects DEF (e.g., an aqueous urea solution) into a decomposition tube or reactor located upstream of the SCR catalyst. When the DEF encounters hot exhaust in the decomposition tube, the water partially evaporates and the urea decomposes to form ammonia. The ammonia (NH3) provided by the DEF is absorbed by the SCR catalyst. When ammonia is present on the surface of the SCR catalyst and the catalyst is hot, the NOx in the exhaust will react with the ammonia to form nitrogen (N2). In this way, the amount of NOx emitted by the engine is reduced.

[0006] The SCR catalyst may only react effectively with NOx at elevated exhaust temperatures. Exhaust temperatures at engine start-up are typically so low that unacceptable levels of NOx may be emitted from the vehicle.

[0007] It is desirable to warm up the SCR catalyst before the engine is started. Warming up the SCR catalyst before the engine is started can allow the SCR catalyst to start reacting with NOx more quickly after the engine is started. It is also desirable to maximize the life of the burner that can be used to warm up the SCR catalyst. Summary of the invention

[0008] In a feature, an exhaust control system for a vehicle includes: a fuel injector configured to inject fuel into a combustion chamber of a burner of an exhaust system upstream of a selective catalytic reduction (SCR) catalyst; an air pump configured to pump air into the combustion chamber of the burner; a spark plug configured to ignite an air / fuel mixture in the combustion chamber of the burner; a fuel control module configured to selectively actuate the fuel injector and begin fuel injection when the engine is turned off and before the engine is started; a pump control module configured to selectively turn on the air pump when the engine is turned off and before the engine is started; and a spark control module configured to selectively apply power to the spark plug and begin providing a spark when the engine is turned off and before the engine is started.

[0009] In a further feature, the starting module is configured to selectively generate an engine start signal before the engine is started, wherein the fuel control module is configured to actuate the fuel injector and start fuel injection in response to the generation of the engine start signal when the engine is turned off and before the engine is started; the pump control module is configured to turn on the air pump in response to the generation of the engine start signal when the engine is turned off and before the engine is started; and the spark control module is configured to apply power to the spark plug and start providing spark in response to the generation of the engine start signal when the engine is turned off and before the engine is started.

[0010] In further features, the start module is configured to generate the engine start signal in response to determining that a distance between the mobile device and the vehicle transitions from (a) greater than a predetermined distance to (b) less than the predetermined distance.

[0011] In further features, the wireless transceiver module is configured to: wirelessly communicate with the mobile device; and determine a distance between the mobile device and the vehicle based on a signal received from the mobile device.

[0012] In further features, the start module is configured to generate the engine start signal in response to unlocking of one or more doors of the vehicle.

[0013] In further features, the mobile device is a key fob.

[0014] In further features, the start module is configured to selectively generate the engine start signal based on a current time.

[0015] In further features, the start module is configured to generate the engine start signal in response to determining that a predetermined period of time has elapsed after a user exits the vehicle.

[0016] In further features: a diesel exhaust fluid (DEF) injector is configured to inject DEF into the exhaust system upstream of the selective catalytic reduction (SCR) catalyst; and a DEF control module is configured to selectively actuate the DEF injector and initiate DEF injection when the engine is off and before the engine is started.

[0017] In further features, the DEF control module is configured to selectively activate the DEF injector and initiate DEF injection when the engine is shut down and before the engine is started in response to determining that a temperature of the SCR catalyst is greater than a predetermined temperature.

[0018] In further features, the DEF control module is configured to not activate the DEF injector and not perform DEF injection when the temperature of the SCR catalyst is below the predetermined temperature before the engine is started at the engine shutdown.

[0019] In further features, the air valve receives air from the air pump and is configured to output air to a second location different from a combustion chamber of the burner when opened.

[0020] In further features, the flame sheath includes an inner surface that defines the combustion chamber and an outer surface, wherein the second location is adjacent to the outer surface of the flame sheath.

[0021] In further features, the second location is downstream of the combustion chamber.

[0022] In a feature, an exhaust control method for a vehicle includes: selectively injecting fuel into a combustion chamber of a burner of an exhaust system upstream of a selective catalytic reduction (SCR) catalyst via a fuel injector; selectively pumping air into the combustion chamber of the burner via an air pump; selectively igniting an air / fuel mixture in the combustion chamber of the burner via a spark plug; when the engine is turned off and before the engine is started: actuating the fuel injector and starting fuel injection; turning on the air pump; and applying power to the spark plug and starting to provide spark.

[0023] In a further feature, the exhaust control method further includes selectively generating an engine start signal before the engine is started, wherein actuating the fuel injector and starting fuel injection includes actuating the fuel injector and starting fuel injection in response to the generation of the engine start signal; starting the air pump includes starting the air pump in response to the generation of the engine start signal; and applying power to the spark plug and starting to provide a spark includes applying power to the spark plug and starting to provide a spark in response to the generation of the engine start signal.

[0024] In further features, the selectively generating the engine start signal before the engine is started includes generating the engine start signal in response to determining that the distance between the mobile device and the vehicle transitions from (a) greater than a predetermined distance to (b) less than the predetermined distance.

[0025] In further features, the exhaust control method further includes: wirelessly communicating with the mobile device; and determining a distance between the mobile device and the vehicle based on a signal received from the mobile device.

[0026] In further features, the selectively generating the engine start signal before the engine is started includes generating the engine start signal in response to unlocking of one or more doors of the vehicle.

[0027] In further features, the selectively generating the engine start signal before the engine is started includes generating the engine start signal under at least one of the following circumstances: based on the current time; and in response to determining that a predetermined period of time has passed after the user leaves the vehicle.

[0028] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present disclosure will be more fully understood from the detailed description and the accompanying drawings, in which:

[0030] Figure 1 is a functional block diagram of an example engine system;

[0031] Figure 2 is a functional block diagram of an example exhaust control system;

[0032] Figure 3 , Figure 4A and Figure 4B is a functional block diagram of an example air valve connection; and

[0033] Figure 5is a flow chart depicting an example method for controlling DEF injection, heating, and air flow prior to engine start.

[0034] In the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0035] A control module controls injection of diesel exhaust fluid (DEF) into an exhaust system upstream of a selective catalytic reduction (SCR) catalyst. The SCR catalyst receives exhaust gas output by an engine of a vehicle. The exhaust gas contains nitrogen oxides (NOx). The DEF contains urea and water. Heat from the exhaust gas decomposes urea from the DEF into ammonia (NH3). The SCR catalyst stores the ammonia. The ammonia reacts with NOx in the exhaust gas, thereby reducing the amount of NOx output from the SCR catalyst.

[0036] The engine may generate high levels of NOx at start-up. However, the amount of ammonia stored on (by) the SCR at start-up may be low. The temperature of the exhaust gas at engine start-up may be too low to process the DEF injected into the decomposition tube into ammonia. Therefore, the NOx output of the vehicle may be relatively high after the engine is started.

[0037] The present application relates to using a burner to warm up an SCR catalyst before the engine is started, such as when a mobile wireless device (e.g., a key card, a cellular phone, etc.) enters a predetermined distance of a vehicle or when a time-based system is used. The mobile device entering the predetermined distance of the vehicle may indicate that the engine start will likely occur in the near future. An example of a time-based system includes, for example, starting a timer when the driver leaves the vehicle. If the driver typically leaves the vehicle for a predetermined period of time (e.g., rest, meal, etc.) before returning, the burner can be turned on for a predetermined preheating period of time before the predetermined period of time has passed. Another example of a time-based system includes tracking when the vehicle is typically started on different days (e.g., 7:30 a.m. Monday to Friday) and turning on the burner for a predetermined period of time before this time. The burner burns air and fuel to warm up the SCR catalyst. Combustion can be initiated by a spark plug or another type of ignition device. The spark plug can also be used to sense whether a flame is present. The heating power of the burner can depend on the fuel flow rate and the degree of completion of the combustion reaction. When a stoichiometric excess of air is provided relative to the fuel flow rate, the combustion reaction will proceed to completion. This may be referred to as lean burn.

[0038] Warming up the SCR catalyst can prepare the SCR catalyst to store ammonia to react with NOx faster than without warming, thereby reducing the vehicle's NOx output after engine start. In order to preheat the exhaust system, the exhaust burner can be operated under conditions that provide lean combustion to minimize emissions. Maximum NOx emissions can occur in combustion close to the stoichiometric ratio, while as the combustion becomes richer (providing a stoichiometric excess of fuel to the burner), emissions of CO and unburned hydrocarbons increase. When operating the burner under lean conditions, the excess air flow also provides more gas molecules to carry heat downstream to the emission control device.

[0039] If the temperature of the SCR catalyst becomes higher than a predetermined temperature at which the injected DEF can decompose into ammonia to be stored by the SCR catalyst before engine start, then DEF injection may be initiated. Initiating DEF injection before engine start may reduce vehicle NOx output after engine start.

[0040] During preheating with the burner, an air valve may be actuated to allow some of the air to not flow through the combustion zone, but to be directed elsewhere. This serves several purposes, the primary one being that more gas molecules will pass through the system so that more heat is carried downstream to the emissions control device. Additionally, the air-fuel ratio fed into the combustion zone of the burner may be optimized for stable combustion and low emissions. Additionally, the air bypassing the combustion zone may be directed into the annular space between the flame sheath and the housing of the burner components so as to maintain the temperature of the flame sheath (e.g., a thin-walled metal tube) to ensure its durability to high temperature oxidation. Finally, the air may simply enter the exhaust duct where it will be used to maintain the temperature of the gas mixture entering the DOC (or first temperature sensitive emissions control device) below the durability limit of this device.

[0041] Reference now Figure 1 , a functional block diagram of an example engine system 100 is presented. Engine 102 generates propulsion torque for a vehicle. The vehicle may have a 4-level rating, a 5-level rating, a 6-level rating, a 7-level rating, or an 8-level rating, such as a rating from the U.S. Department of Transportation (DOT). The rating of a vehicle is based on a gross vehicle weight rating (GVWR). In general, GVWR increases with increasing ratings, and vice versa. Although engine 102 is shown and will be discussed as a diesel engine, engine 102 may be another suitable type of engine. One or more electric motors (or motor-generators) may additionally generate propulsion torque.

[0042] Air is drawn into the engine 102 through an intake manifold 104. One or more fuel injectors (e.g., fuel injector 110) inject fuel, which mixes with the air to form an air / fuel mixture. The air / fuel mixture is combusted in a cylinder (e.g., cylinder 114) of the engine 102. The fuel injector 110 injects fuel directly into the cylinder 114. Heat from compression in the cylinder 114 may induce combustion in the cylinder 114. The ECM 108 controls the injection of fuel through the fuel injector 110. Although the engine 102 is depicted as including one cylinder, the engine 102 may include more than one cylinder. One fuel injector may be provided for each cylinder.

[0043] Exhaust gas is discharged from the engine 102 to an exhaust system 120. The exhaust gas may contain particulate matter (PM) and exhaust gas. The exhaust gas (gas) contains nitrogen oxides (NOx), such as nitrogen monoxide (NO) and nitrogen dioxide (NO2). The exhaust system 120 includes a treatment system that reduces the amount of NOx and PM in the exhaust gas.

[0044] The exhaust system 120 includes a diesel oxidation catalyst (DOC) 122, a diesel particulate filter 126, and one or more selective catalytic reduction (SCR) catalysts, such as SCR catalyst 124-1 and SCR catalyst 124-2 (collectively referred to as "SCR catalyst 124"). SCR catalyst 124-1 may, for example, include iron zeolite or another suitable type of SCR catalyst. SCR catalyst 124-2 may include copper zeolite or another suitable type of SCR catalyst. In various embodiments, SCR catalysts 124-1 and 124-2 may be implemented in the same housing.

[0045] Exhaust flows from the engine 102 to the DOC 122. Exhaust output from the DOC 122 flows to the DPF 126. The DPF 126 filters particulates in the exhaust. In various embodiments, the DPF 126 and the DOC 122 may be implemented in the same housing. Exhaust flows from the DPF 126 to the SCR catalyst 124.

[0046] The diesel exhaust fluid (DEF) injector 130 injects DEF into the exhaust system 120 upstream of the SCR catalyst 124. For example, the DEF injector 130 can inject DEF into a decomposition tube 131, where water in the injected DEF evaporates and urea decomposes and hydrolyzes into NH3. The decomposition tube 131 can also be referred to as a reactor. For example only, the decomposition tube 131 can be located between the DPF 126 and the SCR catalyst 124. DEF contains urea (e.g., CO(NH2)2) and water. Before injection, the DEF is stored in a DEF tank 132. The DEF pump 134 draws DEF from the DEF tank 132 and pumps the DEF to the DEF injector 130.

[0047] The exhaust control module 138 controls actuation (eg, opening and closing) of the DEF injector 130 and, therefore, injection of DEF into the exhaust system 120. The exhaust control module 138 may also control operation of the DEF pump 134, such as to maintain a predetermined pressure of the DEF input to the DEF injector 130.

[0048] When the engine is running, normal burner and DEF control can be used. When the engine is running, urea from DEF injected by DEF injector 130 reacts with hot exhaust gas to produce ammonia, and the ammonia is supplied to SCR catalyst 124. The heat evaporates water in DEF, and ammonia (NH3) is supplied to SCR catalyst 124.

[0049] The SCR catalyst 124 stores (ie, absorbs) ammonia supplied from the DEF. The SCR catalyst 124 catalyzes a reaction between the stored ammonia and NOx passing through the SCR catalyst 124.

[0050] The amount of ammonia stored by the SCR catalyst 124 may be referred to as a current storage amount. The current storage amount may be expressed as a mass of ammonia (eg, grams), moles of ammonia, or another suitable measure of the amount of ammonia stored by the SCR catalyst 124.

[0051] The percentage of NOx input to the SCR catalyst 124 that is removed from the exhaust gas via reaction with ammonia may be referred to as NOx conversion efficiency. The NOx conversion efficiency depends on the current storage capacity of the SCR catalyst 124. For example only, the NOx conversion efficiency may increase as the current storage capacity of the SCR catalyst 124 increases, and vice versa.

[0052] However, the current storage amount of the SCR catalyst 124 is limited to a maximum amount of ammonia. This maximum amount of ammonia is referred to as the maximum storage capacity of the SCR catalyst 124. Maintaining the current storage amount of the SCR catalyst 124 near the maximum storage capacity ensures that the maximum possible amount of NOx is removed from the exhaust gas. In other words, maintaining the current storage amount close to the maximum storage capacity ensures that the maximum possible NOx conversion efficiency is achieved.

[0053] However, there is an inverse relationship between the maximum storage capacity and the temperature of the SCR catalyst 124. More specifically, during engine operation, the maximum storage capacity decreases as the SCR temperature increases, and vice versa.

[0054] The reaction of ammonia with NOx produces nitrogen and water. Other components of the exhaust gas, such as oxygen (O2), may also participate in the reaction of ammonia with NOx.

[0055] One or more sensors may be implemented in the exhaust system 120, such as one or more NOx sensors, one or more temperature sensors, one or more oxygen sensors, and / or one or more other types of sensors. For example, a temperature sensor may measure the temperature of the SCR catalyst 124. In various embodiments, the temperature of the SCR catalyst 124 may be estimated based on one or more exhaust temperatures. Other example types of sensors include a mass air flow rate (MAF) sensor, a recirculated exhaust gas flow rate (EFR) sensor, an intake air temperature (IAT) sensor, a coolant temperature sensor, a manifold absolute pressure (MAP) sensor, an engine speed (RPM) sensor, an exhaust pressure sensor, and / or one or more other suitable sensors. The sensors in the Figure 1 In the unified display of 150.

[0056] The burner 154 may also be coupled to the exhaust system 120, such as upstream of the DOC 122 and the DPF 126. The burner 154 may include a fuel injector 158, a spark plug 162, and an air pump 166. Although an example of a burner 154 including a spark plug is provided, the present application is also applicable to other types of igniters and ignition devices.

[0057] When turned on, the air pump 166 pumps air into the combustion chamber (within the flame sheath 156) and to the exhaust system 120. The fuel injector 158 injects fuel (e.g., diesel fuel) into the combustion chamber. The fuel mixes with the air from the air pump 166. The spark plug 162 generates a spark in the combustion chamber. The spark ignites the air and fuel from the fuel injector 158 and the air pump 166. The flame sheath 156 is configured to protect the flame in the combustion chamber from being blown out, for example, by exhaust gas from the engine 102 when the engine 102 is running.

[0058] The combustion of the air and fuel produces hot gases, which can be used to heat one or more components of the exhaust system 120 and / or for one or more other reasons. The exhaust control module 138 controls the injection of fuel through the fuel injector 158, the spark generation through the spark plug 162, and the operation of the air pump 166. In various embodiments, the exhaust control module 138 can control the speed of the air pump 166 regardless of whether the burner 154 is receiving fuel for combustion. When receiving fuel, the exhaust control module 138 can control the speed of the air pump 166 to achieve a desired air-fuel ratio. If the burner 154 is operated while the engine is running, the exhaust control module 138 can operate the burner 154 over the entire air-fuel ratio range that can achieve stable combustion.

[0059] The air pump 166 also pumps air to an air valve (V) 170. The air valve 170 adjusts the air flow to a second location, such as around the flame sheath 156. The air flowing around the flame sheath 156 can cool the flame sheath 156 and extend the life of the flame sheath 156. In various embodiments, the second location can be between the flame sheath 156 and an exhaust pipe 174 connected to the burner 154, such as Figure 3 Alternatively, the air valve 170 can output air from the air pump 166 directly to the exhaust pipe 174, such as Figure 4A Alternatively, the air valve 170 may output air from the air pump 166 to the exhaust pipe 174 upstream of the burner 156, such as Figure 4B The exhaust control module 138 also controls actuation of the air valve 170 .

[0060] When the engine 102 is running, an engine control module (ECM) 108 controls the torque output of the engine 102. The ECM 108 also controls starting and shutting down the engine 102. The ECM 108 can start the engine 102, for example, in response to user actuation of a combination of one or more user input devices (e.g., an ignition button or switch of the vehicle) and / or one or more user input devices of a key fob. The ECM 108 can shut down the engine 102, for example, in response to user actuation of one or more user input devices (e.g., an ignition button or switch of the vehicle) and / or one or more user input devices of a key fob.

[0061] As discussed above, the exhaust control module 138 can control the injection of DEF through the DEF injector 130. For example only, the exhaust control module 138 can control the timing and rate of DEF injection. By controlling the DEF injection, the exhaust control module 138 controls the supply of ammonia to the SCR catalyst 124 and the current storage amount of the SCR catalyst 124.

[0062] The rate at which DEF is injected may be referred to as a DEF injection rate (e.g., g / sec). The rate at which ammonia is supplied to the SCR catalyst 124 may be referred to as an ammonia supply rate (e.g., g / sec). The exhaust control module 138 may determine a target supply rate for supplying ammonia to the SCR catalyst 124, determine a target DEF injection rate to achieve the target supply rate, and control injection of DEF at the target DEF injection rate.

[0063] The vehicle may include a wireless transceiver module 180 configured to wirelessly communicate with a mobile device (e.g., a key fob, a cellular phone, etc.) such as a mobile device 182 using a communication protocol. The communication protocol may be a Bluetooth (BT) (defined in part by IEEE 802.15) communication protocol, a WiFi (defined in part by IEEE 802.11) communication protocol, or another suitable communication protocol. The wireless transceiver module 180 communicates wirelessly via one or more antennas (e.g., antenna 184).

[0064] In response to the engine start, the NOx emissions of the vehicle may be relatively high. The present application relates to heating the SCR catalyst 124 when the engine 102 is turned off before the engine is started, such as when the mobile device communicating with the wireless transceiver module 180 changes from a predetermined distance greater than the vehicle to a predetermined distance less than the vehicle. Another indication of the upcoming engine start can be, for example, the unlocking of one or more door locks of the vehicle. In various embodiments, the wireless transceiver module 180 can unlock one, more than one, or all door locks of the door locks of the vehicle in response to receiving a user input to the mobile device. Another indication of the upcoming engine start can be, for example, a predetermined time period after the driver leaves the vehicle (e.g., rest, dining, etc.). For example, if the driver typically leaves the vehicle for 45 minutes, then the engine start can be considered to be about to occur 30 minutes after the driver leaves the vehicle. Another example of the indication of the upcoming engine start is included when the current date and time is at one or more predetermined dates and times. For example, if the engine typically starts at 7:30 am Monday to Friday, then the engine start can be considered to be about to occur at 7:15 am Monday to Friday. Before starting the engine 102 , the burner combusts air and fuel to warm the SCR catalyst.

[0065] The wireless transceiver module 180 can determine the distance between the mobile device and the vehicle, for example, using triangulation and multiple antennas of the vehicle. For example, the wireless transceiver module 180 can determine the distance of the mobile device to one antenna based on a relative signal strength indicator (RSSI) of a signal between the mobile device and the antenna. The RSSI can increase as the distance decreases, and vice versa. Although an example of RSSI is provided, another suitable signal strength indicator can also be used. The wireless transceiver module 180 can determine the distance between the mobile device and the vehicle based on the location of the antenna and the distance between the mobile device and the antenna (e.g., using an equation or a lookup table).

[0066] The pre-engine warm-up is performed by operating the burner 154 before the engine is started. The exhaust control module 138 can control the burner 154 (via the fuel supply of the fuel injector 158 and / or the air from the air pump 166). During the heating period, the air valve 170 can be partially or completely opened so that air flows to the second position through the air valve 170. This provides more gas to drive the heat further downstream. When the engine 102 is running after starting, the exhaust control module 138 can close the air valve 170 so that no air flows from the air pump 166 to the second position. Once the engine 102 is running, the exhaust gas from the engine 102 will have a greater flow rate than the flow rate of the air pump for the burner 156, so the air valve 170 will be closed, and the air flow rate of the burner 154 will also be reduced, so that the air-fuel ratio entering the combustion zone of the burner 154 will be within the target range for stable combustion, lean or rich, depending on the application.

[0067] The SCR catalyst 124 is cold at the start of warming. The burner 154 is first operated to heat the substrate of the exhaust system. Once the substrate is hot and the heat has also reached the decomposition tube, dosing can be initiated and performed. However, if the warm-up period is relatively long and the burner 154 continues to operate (in order to warm up the entire exhaust system), then DEF dosing can be stopped because the NH3 capacity of the SCR decreases as the temperature increases.

[0068] Figure 2 is a functional block diagram of an example exhaust control system. The target module 204 determines a target DEF dosing rate, for example, based on a target (ammonia) supply rate to the SCR catalyst 124. The target module 204 may determine the target DEF injection rate using one of a lookup table and an equation that relates the target supply rate to a target DEF injection rate. The target DEF injection rate corresponds to an injection rate of DEF to achieve a target supply rate of ammonia to the SCR catalyst 124. The target supply rate corresponds to a target rate at which ammonia is supplied to the SCR catalyst 124.

[0069] The DEF control module 208 controls the opening and closing of the DEF injector 130 to control injection and achieve a target DEF injection rate. The DEF control module 208 may open the DEF injector 130 by applying power (e.g., from a battery) to the DEF injector 130. The DEF control module 208 may close the DEF injector 130 by disconnecting the DEF injector 130 from power. The DEF control module 208 may control the DEF injector 130 using pulse width modulation (PWM) control or another suitable type of control.

[0070] The target module 204 may determine the target supply rate based on, for example, the target current storage level of the SCR catalyst 124, the current storage level of the SCR catalyst 124, and / or one or more other parameters. The target module 204 may determine the target supply rate using, for example, one of an equation and a lookup table that relates the target current storage level, the current storage level, and the other parameter(s) to the target supply rate.

[0071] When the engine is running, the target module 204 may determine the target current storage amount based on, for example, a predetermined percentage of the current maximum storage capacity of the SCR catalyst 124. The predetermined percentage may be, for example, 90%, 95%, or another suitable value that is less than or equal to 100% and greater than or equal to 50%. The predetermined percentage of 100% may, for example, increase the likelihood of ammonia slip in response to an increase in temperature, which results in a decrease in the maximum storage capacity and may cause ammonia to desorb from the SCR catalyst 124.

[0072] The storage capacity module 212 may determine the current maximum storage capacity based on the current temperature of the SCR catalyst 124. For example, the storage capacity module 212 may increase the current maximum storage capacity as the temperature decreases, and vice versa. The storage capacity module 212 may determine the current maximum storage capacity using one of a lookup table and an equation that relates the temperature of the SCR catalyst 124 to the maximum storage capacity.

[0073] When the engine 102 is shut down before the engine is started, the target module 204 can set the target storage amount as a percentage of the maximum storage capacity of the SCR catalyst 124 at a specified temperature. For example, the target module 204 can set the target current storage amount to 100% of the maximum storage capacity of the SCR catalyst 124 at 150 degrees Celsius. Although these examples are provided, other percentages, temperatures, and target current storage values ​​can be used. The copper-zeolite SCR catalyst can have a storage level of about 3 grams per liter of substrate volume.

[0074] The storage module 216 may determine the current (ammonia) storage level of the SCR catalyst 124. When the engine 102 is turned off in response to an engine shutdown, the engine 102 does not output NOx. However, the current storage level of the SCR catalyst 124 when the engine is turned off will be known because the storage module 216 tracks the current storage level when the engine 102 is turned on. When DEF injection is performed while the engine 102 is turned off, the current storage level increases.

[0075] The storage module 216 may receive a current ammonia supply rate (e.g., grams per second). For example, the storage module 216 may receive a target supply rate from the target module 204. The storage module 216 may (mathematically) integrate the ammonia supply rate for each predetermined period of time to determine the mass of ammonia supplied to the SCR catalyst 124. When DEF injection is performed, the storage module 216 may add each mass of ammonia to the current storage amount (at that time) to update the current storage amount over time.

[0076] The temperature control module 220 controls operation of the air pump 166, the air valve 170, the fuel injector 158, and the spark plug 162. More specifically, a pump control module 224 controls operation of the air pump 166, and a fuel control module 228 controls operation of the fuel injector 158. A spark control module 232 controls the spark plug 162, and a valve control module 236 controls actuation of the air valve 170.

[0077] As described above, the ECM 108 controls engine starting. Before the ECM 108 starts the engine 102, the start module 240 can selectively generate a start signal indicating an upcoming engine start. For example, the start module 240 can generate the start signal when the mobile device is within a predetermined distance (e.g., 20 feet) of the vehicle. As discussed above, the wireless transceiver module 180 can determine the distance between the mobile device and the vehicle. Additionally or alternatively, the start module 240 can generate the start signal in response to unlocking one or more doors of the vehicle. Additionally or alternatively, the start module 240 can generate the start signal based on the current time, such as when the current time reaches a predetermined time at which the engine start typically occurs (e.g., every day, such as on weekdays).

[0078] When the start signal is generated, the pump control module 224 turns on the air pump 166. Additionally, the fuel control module 228 starts fuel injection via the fuel injector 158, and the spark control module 232 starts to provide a spark to ignite the air and fuel. Additionally, the valve control module 236 opens the air valve 170 to a predetermined open position so that some air from the air pump 166 flows to a second position, such as around the flame sheath 156. The predetermined open position may be partially or fully open. In order to provide a predetermined fuel-lean air / fuel mixture relative to a stoichiometric air / fuel mixture when the start signal is generated, at least one of the following occurs: (a) the fuel control module 228 may control (e.g., reduce) the fuel supply and (b) the valve control module 236 may open the air valve 170. Providing a fuel-lean air / fuel mixture may, for example, maximize the warming of the SCR catalyst 124 before the engine is started.

[0079] The engine status signal indicates whether the engine 102 is running (on), started (activated), or shut down (off). The ECM 108 may set the engine status signal and output the engine status signal to other modules.

[0080] Before the engine is started (when the start signal is generated but before the engine start has been initiated by the ECM 108), the DEF control module 208 may initiate DEF injection when the temperature of the SCR catalyst 124 is greater than a predetermined temperature. As described above, when the temperature is greater than the predetermined temperature, the injected DEF may decompose into ammonia to be stored by the SCR catalyst 124. For example, the target module 204 may set the target supply rate as described above to adjust the current storage amount of the SCR catalyst 124 toward or to a maximum storage capacity or a predetermined percentage of the maximum storage capacity before the engine is started.

[0081] When the engine status indicates that the engine 102 is running, such as after engine startup, the valve control module 236 may close the air valve 170 to a fully closed position so that all air output from the air pump 166 flows into the flame sheath 156. Normal control of the burner 154 and DEF injection may be performed.

[0082] With respect to setting a target DEF injection rate, the target module 204 may first determine the amount of NH3 to be input to achieve the target current storage amount based on the difference between the current storage amount and the target current storage amount. Second, based on the amount of NH3 to be input, the target module 204 may determine the amount of DEF to be injected into the decomposition tube 131 to provide the amount of NH3. The target module 204 may set the target injection rate based on various factors (e.g., over time), such as the SCR temperature or the temperature of the air leaving the DOC and DPF after the air pump 166 is turned on. For example, if the SCR temperature is too high or the temperature of the gas leaving the DPF 126 is too low, then DEF injection may be disabled. The SCR temperature may be determined, for example, based on an average of the exhaust gas temperatures entering and exiting the SCR catalyst 124. The exhaust temperature sensor operates based on the flowing gas, so the air pump 166 may be operated and DEF injection may be disabled for a period of time when the exhaust temperature sensor is ready.

[0083] When the temperature of the SCR catalyst 124 is below a predetermined temperature, the target module 204 may determine the enthalpy rate of the (hot) air from the DPF 126 and into the decomposition tube 131. The enthalpy rate may need to be X times the enthalpy consumption rate corresponding to the maximum allowed DEF dosing rate. The processing of DEF in the decomposition tube 131 is endothermic because each step in the process is endothermic, such as raising the temperature of the water from 25 degrees Celsius to 100 degrees Celsius, evaporating the water, sublimating the solid urea into gaseous urea, and decomposing the urea into NH3 and HNCO, etc. Therefore, the DEF dosing rate may have an associated DEF enthalpy consumption rate.

[0084] The difference between the enthalpy rate of the hot air flow produced by the air pump and the factor X may define the maximum enthalpy consumption rate, and thus the corresponding maximum DEF dosing rate. The target module 204 may then set the target DEF injection rate to result in dosing at the maximum enthalpy consumption rate.

[0085] The factor (value) X can be calibrated based on one or more characteristics of the decomposition tube 131. When DEF is injected into the decomposition tube 131, the droplets can impact the surfaces. These surfaces are heated by the hot air flow and cooled by the impacting droplets. If a wall film forms on the surface of the decomposition tube 131, the temperature will decrease, for example, due to evaporation of water in the DEF droplets. The target module 204 can limit the target DEF injection rate so that the enthalpy rate of the air is sufficient to keep the surface of the decomposition tube 131 hot and prevent wall film formation.

[0086] If the current storage level reaches the target storage level before the engine is started, the DEF injection and air pump 166 may be deactivated. If the burner 154 is already operating (providing heat), it is also deactivated.

[0087] Figure 5 is a flow chart depicting an example method for controlling DEF injection, heating, and air flow before engine start. Control begins at 504, where the target module 204 and the temperature control module 220 determine whether the engine 102 is off, e.g., whether the engine status signal indicates that the engine 102 is off. If 504 is true, control continues to 508. If 504 is false, control may remain at 504.

[0088] At 508, the start module 240 determines whether an engine start is about to occur, as described above. If 508 is true, control continues to 516. If 508 is false, control can return to 504 or remain at 508. Example indications of an imminent engine start include, for example, when the wireless transceiver module 180 determines that a mobile device associated with the vehicle is within a predetermined distance of the vehicle. In addition to or as an alternative to the mobile device being within a predetermined distance of the vehicle, the present application is also applicable to other predictive indicators of engine start, such as unlocking of vehicle door locks, the current time being within a predetermined time period when the vehicle is typically started, the current date and time being one of one or more predetermined dates and times, etc.

[0089] At 516, the temperature control module 220 turns on or maintains the burner 154 on. More specifically, the pump control module 224 turns on or maintains the air pump 166 on. The fuel control module 228 turns on or maintains the fuel supply via the fuel injector 158 on. The spark control module 232 turns on or maintains the spark from the spark plug 162 on. At 516, the valve control module 236 also opens the valve 170 to allow air to flow to the second position. In order to provide a fuel-lean air / fuel mixture to the burner 154, at least one of the fuel control module 228 and the valve control module 236 adjusts the fuel supply and / or the opening of the air valve, respectively.

[0090] At 520, the temperature control module 220 and the target module 204 determine whether the engine state is set to the engine start state. When the engine state is set to the engine start state, the ECM 108 starts (cranks) the engine 102. If 520 is true, control may end. If 520 is false, control may continue with 524.

[0091] At 524, the target module 204 may determine whether the temperature of the SCR catalyst 124 is greater than a predetermined temperature. If 524 is true, control may continue with 532. If 524 is false, the target module 204 may set the target DEF injection rate to zero, and at 528, DEF injection may be disabled, and control may return to 504.

[0092] At 532, the target module 204 determines a target storage amount (e.g., sets the target storage amount to a predetermined storage amount for engine starting), and the storage module 216 updates the current storage amount of the SCR catalyst 124. The storage module 216 may update the current storage amount by integrating the (current) target supply rate to determine the mass of ammonia supplied to the SCR catalyst, and adding the determined mass to the current storage amount. As discussed above, the target module 204 determines the target supply rate and the target DEF injection rate. At 536, the DEF control module 208 controls the DEF injector 130 to inject DEF based on or at the target DEF injection rate.

[0093] At 540 , the temperature control module 220 and the target module 204 determine whether the current storage amount has reached (eg, is greater than or equal to) the target storage amount. If 540 is true, the DEF injection and the burner 154 may be disabled, and control may end. If 540 is false, control may return to 504 .

[0094] The foregoing description is merely illustrative in nature and is by no means intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because other modifications will become apparent after studying the drawings, the specification and the following claims. It should be understood that one or more steps in the method can be performed in a different order (or simultaneously) without changing the principles of the present disclosure. In addition, although each of the above-mentioned embodiments is described as having certain features, any one or more of these features described in any embodiment of the present disclosure can be implemented in the features of any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the permutation of one or more embodiments with each other is still within the scope of the present disclosure.

[0095] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "near," "on top of," "above," "below," and "disposed." Unless explicitly described as "direct," when a relationship between a first element and a second element is described in the above disclosure, the relationship may be a direct relationship between the first element and the second element with no other intervening elements, but may also be an indirect relationship between the first element and the second element with one or more intervening elements (spatially or functionally) between the first element and the second element. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or, and should not be construed to mean "at least one of A, at least one of B, and at least one of C."

[0096] In the diagram, the direction of the arrow, as indicated by the arrow, generally represents the flow of information (such as data or instructions) that the diagram is concerned with. For example, when element A and element B exchange various information, but the information transmitted from element A to element B is relevant to the diagram, the arrow can be directed from element A to element B. This one-way arrow does not mean that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B can send a request for the information to element A or receive a confirmation of the information.

[0097] In this application, including the following definitions, the term "module" or the term "controller" may be replaced with the term "circuit". The term "module" may refer to, be a part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system on a chip.

[0098] The module may include one or more interface circuits. In some examples, these interface circuits may include wired or wireless interfaces, which are connected to a local area network (LAN), the Internet, a wide area network (WAN), or a combination thereof. The function of any given module of the present disclosure may be distributed between multiple modules connected via interface circuits. For example, multiple modules may allow load balancing. In another example, a server (also referred to as a remote or cloud) module may implement some functions on behalf of a client module.

[0099] The term code as used above may include software, firmware, and / or microcode, and may refer to a program, a routine, a function, a class, a data structure, and / or an object. The term shared processor circuit covers a single processor circuit that executes some or all of the code from multiple modules. The term group processor circuit covers a processor circuit that is combined with additional processor circuits to execute some or all of the code from one or more modules. References to multiple processor circuits cover multiple processor circuits on discrete chips, multiple processor circuits on a single chip, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit covers a single memory circuit that stores some or all of the code from multiple modules. The term group memory circuit covers a memory circuit that is combined with additional memory to store some or all of the code from one or more modules.

[0100] The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium as used herein does not encompass transient electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transient. Non-limiting examples of non-transient, tangible computer-readable media are: non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital tapes or hard drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0101] The devices and methods described in this application may be implemented in part or in full by a special purpose computer created by configuring a general purpose computer to perform one or more specific functions implemented in a computer program. The above-mentioned functional blocks, flow chart components and other elements may be transferred to a computer program by the routine work of an experienced technician or programmer.

[0102] The computer programs include processor executable instructions stored on at least one non-volatile tangible computer readable medium. The computer programs may also include or rely on stored data. The computer programs may include a basic input / output system (BIOS) that interacts with the hardware of the special-purpose computer, device drivers that interact with specific devices of the special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0103] A computer program may include: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated by a compiler from source code; (iv) source code executed by an interpreter; (v) source code compiled and executed by a real-time compiler, etc. By way of example only, the source code may be written using syntax from a language including: C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Fortran, Perl, Pascal, Curl, OCaml, HTML5 (Hypertext Markup Language 5th Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Visual Lua, MATLAB, SIMULINK, and

Claims

1. An exhaust control system for a vehicle, comprising: a fuel injector configured to inject fuel into a combustion chamber of a burner of the exhaust system upstream of a selective catalytic reduction (SCR) catalyst; an air pump configured to pump air into a combustion chamber of the burner through an air supply line; a spark plug configured to ignite an air / fuel mixture within a combustion chamber of the burner; a fuel control module configured to selectively actuate the fuel injector and initiate fuel injection when the engine is shut down and before the engine is started; a pump control module configured to selectively turn on the air pump when the engine is off and before the engine is started; as well as a spark control module configured to selectively apply power to the spark plug and begin providing a spark when the engine is shut down and before the engine is started; as well as an air valve that receives air from the air pump through the air supply line; wherein the valve control module is configured to control the air valve to output air to a second location different from the combustion chamber of the burner when the engine is shut down and before the engine is started; wherein the air supply line includes a branch located upstream of the air valve.

2. The exhaust control system of claim 1, further comprising a start module configured to selectively generate an engine start signal before the engine is started, in, The fuel control module is configured to actuate the fuel injector and initiate fuel injection in response to generation of the engine start signal when the engine is shut down and before the engine is started; The pump control module is configured to turn on the air pump in response to generation of the engine start signal before the engine is started when the engine is off; and The spark control module is configured to apply power to the spark plug and begin providing spark in response to generation of the engine start signal when the engine is shut down and before the engine is started.

3. The exhaust control system according to claim 2, wherein: The start module is configured to generate the engine start signal in response to determining that a distance between the mobile device and the vehicle transitions from (a) greater than a predetermined distance to (b) less than the predetermined distance.

4. The exhaust control system of claim 3, further comprising a wireless transceiver module configured to: wirelessly communicate with the mobile device; and A distance between the mobile device and the vehicle is determined based on the signal received from the mobile device.

5. The exhaust control system according to claim 2, wherein: The start module is configured to generate the engine start signal in response to unlocking of one or more doors of the vehicle.

6. The exhaust control system according to claim 3, wherein: The mobile device is a key fob.

7. The exhaust control system according to claim 2, wherein: The start module is configured to selectively generate the engine start signal based on a current time.

8. The exhaust control system according to claim 2, wherein: The start module is configured to generate the engine start signal in response to determining that a predetermined period of time has elapsed after a user exits the vehicle.

9. The exhaust control system of claim 1 further comprising: a diesel exhaust fluid (DEF) injector configured to inject DEF into the exhaust system upstream of the selective catalytic reduction (SCR) catalyst; as well as A DEF control module is configured to selectively actuate the DEF injector and initiate DEF injection when the engine is shut down and before the engine is started.

10. The exhaust control system of claim 9, wherein: The DEF control module is configured to selectively actuate the DEF injector and initiate DEF injection in response to determining that a temperature of the SCR catalyst is greater than a predetermined temperature when the engine is shut down and before the engine is started.

11. The exhaust control system according to claim 10, wherein: The DEF control module is configured to not activate the DEF injector and not perform DEF injection when the temperature of the SCR catalyst is lower than the predetermined temperature before the engine is started at the time of the engine shutdown.

12. The exhaust control system of claim 1 further comprising a flame sheath comprising: an inner surface defining the combustion chamber; and External surface, in, The second location is adjacent to the outer surface of the flame sheath.

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