Method for regenerating an exhaust aftertreatment device

Abstract

Method (400) for regenerating an exhaust aftertreatment device (70), comprising the following: Performing combustion in a cylinder (30) of an engine (10) during a cylinder cycle (402), Injecting a quantity of fuel in a fuel injection pulse after a combustion event in the cylinder (30) and before closing an exhaust valve (54) during of the cylinder cycle, wherein the amount of fuel in the fuel injection pulse is adjusted for a density of a gas mixture in the cylinder (30) and in response to a volumetric efficiency of the engine (10) (404-414), wherein the amount of injected fuel is less than an amount of injected fuel that results in liquid fuel impacting a cylinder wall (32), wherein the amount of fuel in the fuel injection pulse is adjusted in response to an estimated temperature in the cylinder (30) at a time when the amount of fuel in the fuel injection is injected, and Regenerating the exhaust aftertreatment device (70) via the amount of fuel.

Description

BACKGROUND / SUMMARY

[0001] Diesel engines have a relatively high efficiency compared to other internal combustion engines. This higher engine efficiency is associated with lower exhaust gas temperatures. Lower exhaust gas temperatures can make the regeneration of aftertreatment systems more difficult, as these systems often begin to regenerate at higher temperatures. One way to generate higher temperatures in an exhaust system is to inject fuel late in a cylinder cycle (e.g., during an exhaust stroke) so that the fuel can oxidize in the exhaust system, thereby increasing the exhaust system temperature. However, if liquid fuel is injected during an exhaust stroke, some of the injected fuel may strike the cylinder walls in liquid form.Fuel that comes into contact with cylinder walls in liquid form can break down the oil film on the cylinder wall and increase cylinder wall wear. Furthermore, liquid fuel can penetrate the engine crankcase and dilute the engine oil. Therefore, it may be desirable to reduce the amount of injected liquid fuel that reaches the cylinder walls during injection.

[0002] Document DE 38 32 270 A1 describes a fuel supply control system for an internal combustion engine. Document US 2011 / 0041476 A1 describes a method for estimating the oxygen concentration downstream of a diesel oxidation catalyst.

[0003] European patent application EP 1 798 404 A1 and US patent application US 2007 / 0 137 179 A1 describe a method for regenerating an aftertreatment device via a post-injection control system. The method estimates a fuel mist decay length based on a differential pressure between the inside and outside of an injector nozzle. The method adjusts the fuel injection time so that the fuel mist decay length is less than a distance S to a cylinder wall. However, the fuel mist decay length determined via a pressure differential may not be as precise as desired. Consequently, under certain conditions, fuel mist may still impact the cylinder walls.

[0004] The inventor of the present invention has recognized the aforementioned disadvantages and has developed a method for regenerating an exhaust aftertreatment device, comprising: performing a combustion in a cylinder of an engine during a cylinder cycle, injecting a quantity of fuel in a fuel injection pulse after a combustion event in the cylinder and before the closing of the exhaust valve during the cylinder cycle, wherein the quantity of fuel in the fuel injection pulse is adjusted for a density of a gas mixture in the cylinder, and regenerating an aftertreatment device via the quantity of fuel.

[0005] By adjusting the post-injection fuel quantity in response to the cylinder mixture density, it is possible to better estimate the amount of injected fuel that impacts the cylinder wall in liquid form. This ensures that the fuel injected to regenerate the aftertreatment system is less than the amount that impacts the cylinder wall in liquid form during injection. Specifically, fuel mist penetration estimation can be improved by considering cylinder density and temperature. Cylinder mixture density and temperature provide a more accurate fuel mist penetration estimate than cylinder pressure or injection pressure differential because they account for both fuel vaporization and momentum transfer.

[0006] Furthermore, the inventor also determined that the volumetric cylinder efficiency is another parameter that can be considered to improve estimates of fuel mist penetration. The volumetric cylinder efficiency can influence both the temperature of gases within a cylinder and the proportions of air and residual exhaust gas that make up the cylinder mixture. In this way, the volumetric cylinder efficiency can affect the density and temperature within the cylinder at the time of injection. Consequently, by considering the cylinder mixture density, the volumetric cylinder efficiency, and the temperature, the timing of the post-injection fuel quantity can be improved, so that the fuel mist approaches the cylinder wall more closely but does not strike the cylinder wall in liquid form.As a result, larger quantities of fuel can be injected into a cylinder without the fuel in liquid form coming into contact with the cylinder walls.

[0007] The described approach can offer several advantages. Specifically, it can reduce engine degradation. Furthermore, by reducing engine oil dilution, it can reduce engine emissions.

[0008] Furthermore, this approach can be used without costly cylinder sensors. It can also extend engine oil change intervals and / or allow for a smaller oil sump containing less oil.

[0009] The above advantages and other advantages and features of the present invention will be readily apparent from the following detailed description, considered alone or in conjunction with the accompanying drawings.

[0010] It should be understood that the summary above is provided to introduce, in simplified form, a selection of concepts that are further described in the full description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the full description. Furthermore, the claimed subject matter is not limited to implementations that overcome any disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE FIGURES Fig. Figure 1 shows a schematic diagram of an engine, Fig. Figure 2 shows an example of fuel mist penetration length, Fig. Figures 3A to 3B show example diagrams of how cylinder mixture density and temperature can affect the fuel mist penetration length, and Fig. Figure 4 shows an exemplary method for regenerating a post-treatment device. DETAILED DESCRIPTION

[0011] The present invention relates to a method for regenerating an exhaust aftertreatment device. Fig. Figure 1 shows an example of a turbocharged diesel engine, where the process is described by Fig. 4 initiates the regeneration of the aftertreatment device by controlling the afterburn fuel injection. Fig. Figure 2 shows an exemplary fuel mist penetration length, which provides a basis for the amount of fuel that can be injected to initiate the regeneration of the aftertreatment device. Fig. Figures 3A to 3B illustrate how cylinder mixture density and pressure can influence the fuel mist penetration length. Finally, Fig. 4 an exemplary method for regenerating a particle filter.

[0012] With reference to Fig. 1 is an internal combustion engine 10, comprising several cylinders, one of which is in Fig. The engine 10, as shown in Figure 1, is controlled by an electronic engine control unit 12. The engine 10 includes a combustion chamber 30 and cylinder walls 32, with a piston 36 arranged therein and connected to a crankshaft 40. The combustion chamber 30 is shown with an intake valve 52 and an exhaust valve 54 respectively, in conjunction with an intake manifold 44 and an exhaust manifold 48. Each intake and exhaust valve can be actuated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57.

[0013] A fuel injection device 66 is shown arranged to inject fuel directly into the combustion chamber 30, a process known to those skilled in the art as direct injection. The fuel injection device 66 supplies fuel in proportion to the pulse width of a signal from the control unit 12. The fuel is supplied to the fuel injection device 66 by a fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distributor (not shown). The fuel pressure supplied by the fuel system can be adjusted by changing a position valve that regulates the flow to a fuel pump (not shown). Additionally, a metering valve can be arranged in or near the fuel distributor for fuel control.A pump metering valve can also regulate the fuel flow to the fuel pump, thereby reducing the amount of fuel pumped to a high-pressure fuel pump.

[0014] The intake manifold 44 is shown in conjunction with an optional electronic throttle 62, which sets the position of a throttle plate 64 to control airflow from an intake charging chamber 46. A compressor 162 draws air from an air inlet 42 to supply the charging chamber 46. Exhaust gases rotate a turbine 164, which is coupled to the compressor 162 via a shaft 161. In some examples, an intercooler may be provided. The compressor speed can be adjusted by setting the position of a variable vane control 72 or by a compressor bypass valve 158. In alternative examples, a boost pressure control valve 74 may replace or be used in addition to the variable vane control 72. The variable vane control 72 sets the position of turbine blades with variable geometry.The exhaust gases can pass through the turbine 164, supplying little energy to rotate it when the blades are in an open position. Conversely, when the blades are in a closed position, the exhaust gases can pass through the turbine 164 and exert increased force on it. Alternatively, the boost pressure control valve 74 allows the exhaust gases to bypass the turbine 164, thereby reducing the amount of energy supplied to the turbine. The compressor bypass valve 158 allows compressed air from the compressor 162 outlet to be recirculated to the compressor 162 inlet. This reduces the efficiency of the compressor 162, thereby influencing the compressor 162 flow rate and lowering the inlet manifold pressure.

[0015] Combustion is initiated in the combustion chamber 30 when the fuel ignites without an externally supplied spark as the piston 36 approaches top dead center during the compression stroke. In some examples, a UEGO sensor 126 can be coupled to the exhaust manifold 48 upstream of an exhaust aftertreatment device 70. In other examples, the UEGO sensor can be located downstream of one or more exhaust aftertreatment devices. Furthermore, in some examples, the UEGO sensor can be replaced by a NOx sensor that incorporates both NOx and oxygen measuring elements.

[0016] At lower engine temperatures, a glow plug 68 can convert electrical energy into heat energy to increase the temperature in the combustion chamber 30. By increasing the temperature of the combustion chamber 30, it can be easier to ignite a cylinder-fuel-air mixture via compression.

[0017] In one example, the exhaust aftertreatment device 70 can include a particulate filter and catalyst blocks. In another example, multiple emission control devices, each with multiple blocks, can be used. In one example, the exhaust aftertreatment device 70 can include an oxidation catalyst. In other examples, the emission control device can include a NOx storage catalyst or selective catalytic reduction (SCR) and / or a diesel particulate filter (DPF).

[0018] Exhaust gas recirculation (EGR) can be provided to the engine via an EGR valve 80. The EGR valve 80 is a three-way valve that closes or allows exhaust gas to flow from downstream of the exhaust aftertreatment device 70 to a position in the engine air intake system upstream of the compressor 162. In alternative examples, the EGR can flow from upstream of the turbine 164 to the intake manifold 44. The EGR can bypass an EGR cooler 85, or alternatively, the EGR can be cooled by passing through the EGR cooler 85. In other examples, a high-pressure and a low-pressure EGR system can be provided.

[0019] Control unit 12 is located in Fig. Figure 1 shows a conventional microcomputer, which includes: a microprocessor unit 102, input / output ports 104, a fixed memory 106, a random access memory 108, a battery-powered memory 110 and a conventional data bus.It is shown that, in addition to the signals discussed above, the control unit 12 receives various signals from sensors coupled to the engine 10, including: the engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114, a position sensor 134 coupled to an accelerator pedal 130 to sense an accelerator pedal position set by a foot 132, a measurement of the engine manifold pressure (MAP) from a pressure sensor 121 coupled to the intake manifold 44, a boost pressure from a pressure sensor 122, an exhaust oxygen concentration from an oxygen sensor 126, an engine position sensor from a Hall effect sensor 118 sensing the position of a crankshaft 40, a measurement of the mass of air entering the engine from a sensor 120 (e.g., a hot-wire air flow meter), and a measurement of the Throttle position from sensor 58.The barometric pressure and exhaust pressure can also be sensed (sensor not shown) or derived for processing by the control unit 12. In a preferred aspect of the present description, the engine position sensor 118 generates a predetermined number of pulses at equal intervals with each revolution of the crankshaft, from which the engine speed (rpm) can be determined.

[0020] During operation, each cylinder within the engine 10 typically goes through a four-stroke cycle: The cycle includes the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke. During the intake stroke, the exhaust valve 54 generally closes and the intake valve 52 opens. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder, thus increasing the volume within the combustion chamber 30. The position at which the piston 36 is near the bottom of the cylinder and at the end of its stroke (i.e., when the combustion chamber 30 has its maximum volume) is typically referred to by experts as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head, thus compressing the air within the combustion chamber 30.The point at which the piston 36 is closest to the cylinder head at the end of its stroke (i.e., when the combustion chamber 30 has its smallest volume) is typically referred to by experts as top dead center (TDC). In a process referred to below as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected into a cylinder several times during a single cylinder cycle. In a process referred to below as ignition, the injected fuel is ignited by compression ignition, resulting in combustion. During the expansion stroke, the expanding gases push the piston 36 back to bottom dead center (BDC). The crankshaft 40 converts the piston motion into torque of the rotating shaft.Finally, during the exhaust stroke, the exhaust valve 54 opens to release the burnt air-fuel mixture into the exhaust manifold 48, and the piston returns to top dead center (TDC). It should be noted that the above is shown only as an example, and that the opening and / or closing times of the intake and exhaust valves can vary, for example, to ensure positive or negative valve overlap, late intake valve closing, or various other effects. Furthermore, in some examples, a two-stroke cycle may be used instead of a four-stroke cycle.

[0021] Consequently, the system of Fig. 1 for an engine comprising a cylinder and an exhaust system, an aftertreatment device in an exhaust system, a fuel injection device supplying fuel to the cylinder, and a control unit comprising instructions stored in a non-volatile memory to regenerate an aftertreatment device, wherein the control unit includes additional instructions to adjust the quantity of fuel supplied to the cylinder via the fuel injection device in response to the volumetric efficiency of the cylinder and the temperature of the gas in the cylinder following a combustion event in the cylinder during a current cycle of the cylinder, and the quantity of fuel injected following the combustion event and prior to the closing of an exhaust valve of the cylinder during a cycle of the cylinder.

[0022] The system of Fig. 1 implies that the amount of injected fuel is less than the amount of injected fuel that would result in liquid fuel impacting the cylinder wall. The engine system further includes additional control unit instructions to provide multiple fuel injections after the combustion event and before the exhaust valve closes. The engine system further includes additional control unit instructions to inject fuel into a second cylinder after a combustion event in the second cylinder during a current cylinder cycle of the second cylinder and in response to the volumetric efficiency of the second cylinder.The engine system further includes the even distribution of a residue of a post-injection fuel quantity for a cylinder cycle between a maximum number of fuel injections that occur after combustion in the cylinder and from the closing of the exhaust valve in the cylinder.

[0023] With reference to Fig. Figure 2 now shows an exemplary fuel mist penetration length. A fuel injector 216 supplies fuel to the combustion chamber 30 in the form of a mist that has an upper mist cone boundary 210, a mist cone centerline 211, and a lower mist cone boundary 214. The distance between the nozzle 216 and a cylinder wall 230 across the mist cone centerline 211 is given by L1. The distance L1 is the distance of the greatest fuel mist penetration into the cylinder. Consequently, the distance L1 is a distance that determines how far the fuel mist penetration is allowed to travel before the fuel strikes the cylinder wall. Therefore, the fuel penetration length is adjusted over time by controlling the fuel injection device to a distance less than L1.

[0024] With reference to Fig. Figure 3A shows a graph of the relationship between liquid fuel penetration and cylinder temperature for a constant-density injection environment. The x-axis represents the cylinder mixture temperature, and the y-axis represents the liquid fuel penetration length or distance. It can be observed that the liquid fuel penetration decreases with increasing injection environment temperature (i.e., increasing cylinder temperature).

[0025] Fig. Figure 3B shows a graph of fuel mist penetration versus fuel density at constant temperature. The x-axis represents the cylinder mixture density, and the y-axis represents fuel mist penetration. The graph shows that fuel mist penetration increases with decreasing cylinder density. Therefore, under constant temperature conditions, if the cylinder mixture density is higher, the fuel mist cannot penetrate as far into the cylinder as if the cylinder density were lower. Consequently, at higher cylinder densities, the fuel injection rate can be increased over time, allowing more fuel to be injected without impacting the cylinder walls. Fig. 3A to 3B, that the cylinder density and temperature can be used to determine the fuel mist penetration distance.

[0026] With reference to Fig. Figure 4 now shows an exemplary method for regenerating an aftertreatment device while reducing the possibility of fuel in the oil. The method of Fig. Method 4 is described in relation to a single cylinder, but it can be applied to all engine cylinders. The method of Fig. 4 can be executed as instructions in a non-volatile memory of the in Fig. The data may be stored in control unit 12 as shown in point 1. Furthermore, the procedure can be carried out by Fig. 4 the in Fig. Provide the 3 shown operating sequence.

[0027] In step 401, procedure 400 assesses whether regeneration of an aftertreatment device is desired. In one example, the aftertreatment device is a diesel particulate filter (DPF). In another example, the aftertreatment device is an LNT (Low Nutrient Replacement). In the example where the aftertreatment device is a DPF, procedure 400 may judge that DPF regeneration is desirable if a pressure drop across the DPF is greater than a threshold. If procedure 400 judges that it is desirable to regenerate the DPF, the answer is yes, and procedure 400 proceeds to 402. Otherwise, the answer is no, and procedure 400 proceeds to exit.

[0028] In process 402, process 400 injects and combusts a main fuel injection pulse. The main fuel injection pulse can be injected into the cylinder during a compression stroke or during both the compression and expansion strokes. Furthermore, in some examples, pilot injections precede the main injection. The main injection can occur during the compression stroke, the expansion stroke, or both. Additionally, in some examples, one or more injections that participate in combustion in the cylinder during a cylinder cycle can be injected after the main fuel injection. These injections can be described as post-combustion injections.

[0029] In procedure 400, method 404 determines a post-injection fuel quantity. The post-injection fuel quantity is a quantity of fuel defined in mg / stroke or similar units. A post-injection fuel quantity is the amount of fuel injected into a single cylinder, and the fuel supplied to the aftertreatment device may be injected into one or more cylinders. The fuel may be injected into any cylinder of a group of cylinders during a period after combustion in the cylinder and before the cylinder's exhaust valve closes.

[0030] In one example, the post-injection fuel quantity is the amount of fuel injected into a cylinder after a combustion event in that cylinder and before the cylinder's intake valves open. The post-injection fuel quantity is determined from a table of empirically determined values, which are indexed based on engine speed and load. Additionally, the post-combustion fuel injection can be performed in response to the temperature of the aftertreatment device, such that the fuel injection quantity is adjusted to increase or decrease the temperature of the aftertreatment device. Method 400 proceeds to 406 after the desired post-injection fuel quantity has been determined.

[0031] In procedure 400, method 406 determines the mass in a cylinder receiving a post-injection fuel quantity at the time the fuel is injected into the cylinder. In one example, the mass in the cylinder is determined as a function of the mass airflow into the cylinder, the cylinder EGR quantity, the engine speed, the exhaust pressure, the volumetric efficiency, and the quantity of fuel injected into the cylinder prior to combustion during a cylinder cycle (e.g., the pre-injection fuel). Specifically, the mass of air in the cylinder is determined by an air mass flow sensor, and the cylinder EGR mass is determined by the intake air oxygen concentration, the exhaust air oxygen concentration, the intake manifold pressure, the intake manifold temperature, the engine speed, and the mass airflow into the engine.In one example, the EGR mass is determined according to the following equation: EGR=1−O2,int20.951−O2,exh20.95, where O 2,int the inlet oxygen concentration is O 2,exh The exhaust oxygen concentration is given, and 20.95 is an approximation of the oxygen percentage in air. In another example, the EGR mass can be determined using the following equation: EGR=1−mair⋅R⋅Tman⋅2⋅1000Pman⋅N⋅60⋅Vdisp⋅ηvol, where m air the mass of the air entering the engine, R is a gas constant, T man the intake manifold temperature is, P man The exhaust manifold pressure is N, the engine speed is V. displ the engine displacement is and η vol The volumetric efficiency is...

[0032] The mass fraction in the cylinder attributable to injected fuel is based on the mass of fuel injected before the post-injection fuel. The amount of fuel injected before the post-injection fuel can be determined from the desired fuel injection quantity for combustion.

[0033] The mass in the cylinder is further adjusted in response to the volumetric engine efficiency. In one example, the volumetric engine efficiency is estimated based on empirical data stored in tables or functions in the control unit memory. The volumetric efficiency data can be indexed based on engine speed, engine load, and engine valve timing. Alternatively, the volumetric efficiency can be set based on a sampled or derived exhaust pressure. The cylinder density is adjusted based on the determined volumetric engine efficiency. For example, if it is found that the volumetric engine efficiency is decreasing, it may be determined that the additional residue is located in the cylinders, thereby increasing the cylinder temperature and / or reducing the cylinder mixture density.The volumetric efficiency determines the mass of residues (e.g., internal EGR) in the cylinder, and then the fuel mass, air mass, and external EGR mass are summed to determine the mass of the cylinder mixture. After determining the mass in the cylinder, procedure 400 proceeds to 408.

[0034] The above procedure for determining the cylinder mass applies if fuel injection occurs before the exhaust valve opens. However, if fuel injection occurs after the exhaust valve opens, the above estimate of the cylinder mixture mass can be reduced in response to the time since the exhaust valve opened, the engine speed, and the change in the crankshaft angle since the exhaust valve opened. In one example, the change in the mixture mass in the cylinder is set based on an empirically determined multiplier, which is stored in memory and indexed according to the engine speed, the time since the exhaust valve opened, and the change in the crankshaft angle since the exhaust valve opened. In an alternative example, the mixture density in the cylinder can be estimated from exhaust pressure and temperature according to the thermal equation of state for ideal gases if fuel injection occurs after the exhaust valve opens.Specifically, the cylinder pressure and the exhaust pressure can be assumed to be equal if the cylinder mixture density is determined.

[0035] In procedure 400, method 408 estimates the cylinder temperature at the time fuel is injected for post-injection during a cylinder cycle. In an example, the temperature in a cylinder is determined using the following equations: PVn=C, where P is the cylinder pressure, V is the cylinder volume at a specific crankshaft angle, n is a constant between 1.3 and 1.4, and C is a constant. The constant C can be equated to a cylinder pressure at a cylinder volume such that the following equation can be formed: P1V1n=P2V2n.

[0036] When resolved according to the ratio of the pressures: P1P2=(V2V1)n.

[0037] According to the thermal equation of state for ideal gases: P1V1=mRT1⇒P1V1T1=mR P2V2=mRT2⇒P2V2T2=mR, where m is the number of moles of a gas, R is the gas constant, and T1 and T2 are the temperatures of the gas at P1V1 and P2V2, respectively. Specifically, T1 is the temperature at exhaust valve opening, V1 is the cylinder volume at exhaust valve opening, V2 is a cylinder volume at a time during the exhaust stroke, and T2 is a cylinder temperature during the exhaust stroke. Substituting these values ​​yields the following: P1V1T1=P2V2T2⇒P1P2=V2T1V1T2 and (V2V1)n=V2T1V1T2⇒(V2V1)n−1=T1T2, where the given T1 can be solved for T2. T1 can be estimated using lookup tables indexed based on engine speed and load. Procedure 400 proceeds to 410 after the cylinder temperature has been determined.

[0038] In the cylinder temperature estimation of 408, T1 is the temperature at or before the exhaust valve opening, and T1 decreases as a function of the time since the exhaust valve opening, the crankshaft angle after the exhaust valve opening, and the engine coolant temperature if fuel injection occurs after the exhaust valve opening. The extent to which T1 decreases after the exhaust valve opening can be empirically determined and stored in memory for later use. The temperature setting T1 can be indexed via the time since the exhaust valve opening, the crankshaft angle since the exhaust valve opening, and the engine coolant temperature.

[0039] In procedure 400, method 410 determines the timing of the start of fuel injection for the post-injection fuel quantity. In one example, the start of fuel injection is determined empirically and stored in tables or functions in the control unit memory. The tables or functions can be indexed by engine speed, engine load, injection time during the intake and compression strokes, engine temperature, and intake air temperature. For example, the start of post-injection fuel injection can be based on a time measure or the crankshaft degrees since the end of combustion. The time of the end of combustion can be estimated based on empirically determined cylinder temperatures and pressures.If multiple post-injections are provided to a cylinder during a single cylinder cycle, the injection start time for each post-injection, following the first post-injection, is determined to be the injection end time for the cylinder's last injection event, plus the time required to reopen the fuel injection device. The injection start time for each post-injection is determined, and Procedure 400 proceeds to 412. Again, it should be noted that the post-injections occur after combustion in the cylinder and before exhaust valve closure.

[0040] In procedure 400, method 412 determines the amount of post-injection fuel that can be injected in a single injection without liquid fuel impacting the cylinder wall as fuel mist. As mentioned above, the desired post-injection fuel quantity determined in procedure 404 can be injected into one or more engine cylinders over multiple fuel injections. For example, each cylinder in a cylinder bank can provide two post-injections for four cylinder cycles until the entire desired post-injection fuel quantity has been injected to regenerate a DPF.

[0041] In one example, the quantity limit for a fuel injection provided to a cylinder is determined by looking up calculated or empirically determined fuel injection quantities stored in functions or tables indexed by cylinder mixture temperature, cylinder density, and biofuel content in the injected fuel. In one example, the post-injection fuel quantity is expressed as: Qpost,max=f(ρ(CA),T(CA)), where Q post,maxLet be the maximum post-injection fuel quantity for a single injection event after combustion and before the exhaust valve closes, ρ the cylinder mixture density as a function of the crankshaft angle, and T the cylinder gas mixture temperature as a function of the crankshaft angle. The cylinder density is based on the mass in the cylinder and the cylinder volume. In some examples, the crankshaft angle at the end of the post-injection fuel quantity can be estimated and iteratively adjusted, so that the post-injection quantity can be determined based on the cylinder density and temperature at the end of the injection time. Consequently, in one example, the post-injection fuel quantity is based on the end of the post-injection fuel time.

[0042] At 414, the procedure 400 injects as many maximum post-injection quantities, as specified at 410, as possible during a cylinder cycle, limited by the post-injection fuel quantity at 404. If the post-injection fuel quantity cannot be injected during as many fuel injections as can be provided in a cylinder cycle, the remaining fuel is divided among all post-injections during the current cylinder cycle. Consequently, for a given cylinder during a given cycle, there is a target or desired post-injection fuel quantity specified in mg. The target or desired post-injection fuel quantity is divided into several pulses after combustion in the cylinder and before the exhaust valve closes.Any remaining fuel is determined by equations that subtract the maximum post-injection fuel quantity for a given pulse from the total target or desired post-injection fuel quantity for a cylinder and cycle. This operation is performed iteratively until no further fuel or pulses are available. Because the desired post-injection fuel quantity must be met, the remaining fuel is divided between pulses. For example, any remaining fuel that does not fit within the timeframe between the end of combustion in the cylinder and the closing of the exhaust valve can be added to the fuel quantity of each post-combustion pulse in the cylinder and before the exhaust valve closes. Such an operation can minimize the possibility of cylinder wall wetting.For example, in one instance, the desired amount of post-injection fuel can be updated using the following equations: Qpost−Qinj=Qre m Qpost=Qrem where Q post the desired post-injection fuel quantity, as determined in 404, is where Q inj the amount of fuel injected during a most recent single post-injection of fuel, and where O rem This residue is the result of subtracting the most recent fuel injection quantity from the desired post-injection quantity. Procedure 400 proceeds to the initial stage after the post-injections for a cylinder cycle have been scheduled and / or injected.

[0043] Consequently, the procedure of Fig. 4 for a method for regenerating an exhaust aftertreatment device comprising the following: The method involves performing combustion in a cylinder of an engine during a cylinder cycle, injecting a quantity of fuel in a fuel injection pulse after a combustion event in the cylinder and before the exhaust valve closes during the cylinder cycle, wherein the quantity of fuel in the fuel injection pulse is adjusted for a specific density of a gas mixture in the cylinder, and regenerating an aftertreatment device via the quantity of fuel. The method includes adjusting the density for a quantity of exhaust gas in the cylinder before combustion occurs in the cylinder of the engine during the cylinder cycle. The method also includes adjusting the density for a quantity of fuel injected into the cylinder that participates in combustion during the cylinder cycle.

[0044] In some examples, the method further includes providing additional fuel injections to the cylinder during the cylinder cycle after the combustion event and before the exhaust valve closes, and adjusting the fuel quantity in the fuel injection pulse in response to the temperature of the gas mixture in the cylinder. The method includes the fuel injection pulse being one of several fuel pulses that sum to a desired post-injection quantity to regenerate an aftertreatment device, and further includes adjusting the fuel quantity in the fuel injection pulse in response to the amount of cylinder air introduced into the cylinder. The method further includes adjusting the amount of fuel in the fuel injection pulse in response to the volumetric efficiency of the engine.The method involves injecting less fuel than the amount of injected fuel that would result in liquid fuel impacting the cylinder wall. The method further includes adjusting the fuel quantity in the fuel injection pulse in response to an estimated temperature in the cylinder at the time the fuel is injected.

[0045] The procedure of Fig. Section 4 also provides for the regeneration of an exhaust aftertreatment device, which includes: performing combustion in a cylinder of an engine during a cylinder cycle, injecting a quantity of fuel in a fuel injection pulse after combustion in the cylinder and before the exhaust valve closes during the cylinder cycle, the quantity of fuel in the fuel injection pulse being adjusted for a volumetric cylinder efficiency, and regenerating an aftertreatment device via the quantity of fuel. In this way, the quantity of post-injected fuel takes into account a change in the volumetric engine efficiency, which can alter the liquid fuel penetration in the cylinder.

[0046] In one example, the method further includes providing additional fuel injections to the cylinder during the cylinder cycle after combustion and before the exhaust valve closes, and adjusting the amount of fuel injected in the fuel injection pulse in response to the temperature of a gas mixture in the cylinder. The method also includes the fuel injection pulse being one of several fuel pulses that sum to a desired post-injection quantity to regenerate an aftertreatment device.The method further comprises setting a subsequent fuel injection pulse, which is injected into the cylinder after combustion and before the exhaust valve closes during a subsequent cylinder cycle, wherein the subsequent fuel injection pulse is based on a remaining fuel quantity available for injection which, when added to a fuel quantity already injected, is equal to the desired post-injection quantity. The method includes estimating the volumetric efficiency of the cylinder based on engine speed and load. The method further includes basing the volumetric efficiency on the camshaft control.The method further includes reducing a desired post-injection fuel quantity based on the amount of fuel in the fuel injection pulse and iteratively reducing the desired post-injection fuel quantity based on the fuel injected into the cylinder after the fuel quantity in the fuel injection pulse has been injected.

[0047] As an average expert will be able to see, this can be in Fig.The procedures described in section 4 embody one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various illustrated steps or functions in the illustrated sequence may be executed in parallel or, in some cases, omitted. Likewise, the order of processing is not necessarily required to achieve the tasks, features, and benefits described herein but is provided for ease of illustration and description. Although not explicitly illustrated, a person skilled in the art will recognize that one or more of the illustrated steps, procedures, or functions may be executed repeatedly, depending on the particular strategy employed.

[0048] This concludes the description. A review by experts would reveal many changes and modifications without deviating from the spirit and scope of the description. For example, single-cylinder, inline-2, inline-3, inline-4, inline-5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations could utilize the present description to their advantage.

Claims

[1] Method (400) for regenerating an exhaust aftertreatment device (70) comprising the following: Performing combustion in a cylinder (30) of an engine (10) during a cylinder cycle (402), Injecting a quantity of fuel in a fuel injection pulse after a combustion event in the cylinder (30) and before closing an exhaust valve (54) during of the cylinder cycle, wherein the amount of fuel in the fuel injection pulse is adjusted for a density of a gas mixture in the cylinder (30) and in response to a volumetric efficiency of the engine (10) (404-414), wherein the amount of injected fuel is less than an amount of injected fuel that results in liquid fuel impacting a cylinder wall (32), wherein the amount of fuel in the fuel injection pulse is adjusted in response to an estimated temperature in the cylinder (30) at a time when the amount of fuel in the fuel injection is injected, and Regenerating the exhaust aftertreatment device (70) via the amount of fuel. [2] Method (400) according to claim 1, wherein the density for a quantity of exhaust gas in the cylinder (30) is adjusted before the combustion is carried out in the cylinder (30) of the engine (10) during the cylinder cycle. [3] Method (400) according to claim 1, wherein the density is adjusted for an amount of fuel injected into the cylinder (30) which participates in combustion during the cylinder cycle. [4] Method (400) according to claim 1, further comprising providing additional fuel injections for the cylinder (30) during the cylinder cycle after the combustion event and before closing the exhaust valve (54) during the cylinder cycle and adjusting the amount of fuel in the fuel injection pulse in response to a temperature of the gas mixture in the cylinder (30). [5] Method (400) according to claim 1, wherein the fuel injection pulse is one of several fuel pulses which sum to a desired post-injection fuel quantity to regenerate the exhaust aftertreatment device (70), and which further comprises adjusting the fuel quantity in the fuel injection pulse in response to a cylinder air quantity introduced into the cylinder (30). [6] Method (400) for regenerating an exhaust aftertreatment device (70) comprising the following: Performing combustion in a cylinder (30) of an engine (10) during a cylinder cycle (402), injection a quantity of fuel in a fuel injection pulse after a combustion event in the cylinder (30) and before the closing of an exhaust valve (54) during the cylinder cycle, wherein the quantity of fuel in the fuel injection pulse is adjusted for a volumetric cylinder efficiency, wherein the quantity of injected fuel is less than a quantity of injected fuel that results in liquid fuel impacting a cylinder wall (32), wherein the fuel quantity in the fuel injection pulse is adjusted in response to an estimated temperature in the cylinder (30) at a time when the fuel quantity in the fuel injection is injected, and Regenerating the exhaust aftertreatment device (70) via the amount of fuel. [7] Method (400) according to claim 6, further comprising providing additional fuel injections for the cylinder (30) during the cylinder cycle after combustion and before closing the exhaust valve (54) during the cylinder cycle and adjusting the amount of fuel injected in the fuel injection pulse in response to a temperature of a gas mixture in the cylinder (30). [8] Method (400) according to claim 6, wherein the fuel injection pulse is one of several fuel pulses which sum to a desired amount of fuel post-injection to regenerate the exhaust aftertreatment device (70). [9] Method (400) according to claim 8, further comprising setting a subsequent fuel injection pulse which is injected into the cylinder (30) after combustion and before closing the exhaust valve (54) in the cylinder (30) during a subsequent cylinder cycle, wherein the subsequent fuel injection pulse is based on a fuel quantity remaining for injection which, when added to a fuel quantity already injected, is equal to the desired post-injection fuel quantity. [10] Method (400) according to claim 6, wherein the volumetric efficiency of the cylinder (30) is estimated on the basis of engine speed and load. [11] Method (400) according to claim 10, wherein the volumetric efficiency is further based on a cam timing. [12] Method (400) according to claim 6, further comprising reducing the desired post-injection quantity based on the amount of fuel in the fuel injection pulse and iteratively further reducing the desired post-injection quantity based on the fuel injected into the cylinder (30) after the fuel quantity in the fuel injection pulse has been injected. [13] Engine system comprising the following: an engine (10) which includes a cylinder (30) and an exhaust system, an exhaust aftertreatment device (70) in the exhaust system, a fuel injection device (66) that supplies fuel to the cylinder (30), and a control unit (12) which includes instructions stored in a non-volatile memory to regenerate an exhaust aftertreatment device (70), wherein the control unit (12) includes additional instructions to adjust an amount of fuel supplied to the cylinder (30) via the fuel injection device (66) in response to a volumetric efficiency of the cylinder (30) and a temperature of gases in the cylinder (30) after a combustion event in the cylinder (30) during a current cycle of the cylinder (30) at a time when the amount of fuel injected in the fuel injection is the amount of fuel injected after the combustion event and before the closing of an exhaust valve (54) of the cylinder (30) during a cycle of the cylinder (30), wherein the amount of injected fuel is less than an amount of injected fuel,which leads to liquid fuel hitting a cylinder wall (32). [14] Engine system according to claim 13, further comprising additional control unit instructions to provide multiple fuel injections after the combustion event and before the closing of the exhaust valve (54). [15] Engine system according to claim 13, further comprising the uniform distribution of a residue of a post-injection fuel quantity for a cylinder cycle between a maximum number of fuel injections following combustion in the cylinder (30) and the closing of the exhaust valve (54) in the cylinder (30).

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