FUEL INJECTION CONTROL METHOD

Abstract

Method for a power machine (10) comprising the following: in response to the fact that a predicted peak cylinder pressure for a planned main fuel injection into a cylinder (30) occurs later than at a threshold time, dividing the planned main fuel injection into at least a first and a second injection, wherein the first injection is advanced relative to the time of the planned main fuel injection; and setting a time and duration for both the first and second injections based on a peak pressure target of the cylinder (30), wherein the power engine (10) is a turbocharged power engine comprising an inlet compressor driven by an exhaust gas turbine, and wherein the duration of the second injection is further set based on an inlet temperature of the turbine and wherein the duration is shortened if the turbine inlet temperature increases above a threshold temperature.

Description

Technical field

[0001] The present application relates generally to an internal combustion engine having multiple injections per cylinder per combustion cycle. Background and brief description

[0002] During selected engine operating conditions, the combustion phase may be retarded to reduce peak cylinder pressures. Therefore, peak cylinder pressures can be reduced to keep cylinder pressures within a limit above which cylinder integrity may be compromised. Retarded combustion may involve retarded injection timing (to a suboptimal point) in spark-ignition engines or retarded fuel injection in compression-ignition engines. Retarded combustion may also be used during engine calibration when an exhaust aftertreatment device (e.g., an aftertreatment system coupled to a diesel engine) is not fully functional. In this case, retarded combustion is used to increase exhaust gas temperature and reduce NOx emissions.

[0003] US 2011 / 0172 897 A1 relates to a plant control device comprising a plant model and a device for determining the control input. The plant model estimates a controlled variable of the plant based on an input containing a control parameter in order to set a first controlled variable of the plant. DE 10 2013 223 489 A1 discloses a method for controlling an internal combustion engine, wherein an injection process is divided into a pre-injection, a main injection, and a post-injection. DE 10 2008 000 916 A1 relates to a combustion control device for a direct-injection compression-ignition engine, which is used in a power system with a compression-ignition engine and a direct-injection fuel injector. DE 101 59 017 A1 and DE 10 2007 013 119 A1 describe further methods for controlling an injection process of an internal combustion engine.

[0004] The inventors here have recognized that retarding the combustion timing to limit peak cylinder pressures can impair engine performance, particularly at full load. Retarding the combustion timing also results in higher fuel consumption and exhaust gas temperatures than would be possible with more advanced timing, thus limiting the engine's torque and power output. This problem can be exacerbated when the engine is running on low-energy-density fuels, such as biodiesel, or other oxygen-enriched fuels.

[0005] Similarly, if late-adjusted combustion is used to accelerate catalyst heating, there may be an increase in hydrocarbon (HC) emissions. Limiting the combustion delay to control HC emissions can result in limiting the level of exhaust gas temperature or enthalpy that can be provided by the combustion phase (in other words, less than the desired level of heating). Other calibration parameters, such as EGR flow, can be adjusted to provide a trade-off with exhaust gas temperature. However, calibration may not be as efficient in engine systems with multiple exhaust catalysts.For example, if an upstream oxidation catalyst becomes partially or fully active before a downstream reduction catalyst, the engine can be further calibrated for reduced HC emissions, although the exhaust gas temperature is limited at a higher NOx level. Overall, the engine's performance is degraded, and the engine may become non-compliant with emissions standards.

[0006] In some engine systems, instead of retarding the combustion phase, peak ignition pressures and exhaust gas temperatures can be increased by enlarging the fuel injector size. The larger nozzle size allows for a higher fuel flow through an injector, resulting in a greater quantity of fuel being delivered to a cylinder per injection. However, inventors have recognized that the additional hardware can increase engine costs. Furthermore, the larger nozzle size can also lead to reduced fuel economy and engine performance.

[0007] In one example, some of the above problems can be at least partially addressed by a method for a power engine according to claim 1, comprising: in response to a predicted peak cylinder pressure occurring later than a threshold time for a planned main fuel injection into a cylinder, splitting the planned main fuel injection into at least a first and a second injection, the first injection being advanced relative to the time of the planned main fuel injection. In this way, exhaust gas temperatures can be controlled while maintaining cylinder pressure within limits, thereby improving power engine efficiency.

[0008] Furthermore, the above problems can also be solved, at least partially, by a method for a power machine according to claim 9 or claim 14.

[0009] As an example, a main fuel injection can be split into two or more injections to provide a cylinder pressure profile in which the peak cylinder pressure is at a target pressure. Specifically, if the originally planned main fuel injection has a peak cylinder pressure higher than the target cylinder pressure (that is, a defined peak cylinder pressure target for the given engine operating conditions), the main injection timing can be retarded to limit the cylinder pressure.To compensate at least partially for the loss of efficiency and enthalpy resulting from retarding the combustion phase, the main fuel injection can be split into at least two injections. The first injection occurs earlier than the originally planned main fuel injection time, and the second injection occurs at a time equivalent to or later than the originally planned main fuel injection time. The timing of the split injections can be set based on engine parameters such as engine speed, load, boundary conditions, and engine architecture.During the advance of the first injection timing, a proportion of the total fuel supplied in the first injection is increased so that the peak cylinder pressure resulting from the first injection is at or just below the target peak cylinder pressure (or limit). At the same time, the amount of fuel supplied in the second injection is reduced accordingly to maintain the total fuel injection quantity of the originally planned injection (or with a set injection quantity to meet a user-directed engine torque). The timing of the second injection is retarded so that the peak cylinder pressure resulting from the second injection is as close as possible to the peak cylinder pressure of the first injection, while keeping the cylinder pressure within the cylinder pressure limit.In one example, split fuel injection can be used for a main fuel injection in each cylinder until the exhaust gas temperature is sufficiently high to heat one or more exhaust catalysts, such as an upstream oxidation catalyst and a downstream reduction catalyst. Additionally or alternatively, split fuel injection can be maintained until the exhaust gas temperature is high enough to keep the turbine inlet temperature above a target temperature.

[0010] By using split fuel injection when peak cylinder pressure limits are reached or exceeded, engine efficiency is improved, and maximum torque is achieved while keeping the exhaust gas temperature below the maximum exhaust gas temperature limit. In this case, splitting the main injection allows more fuel to be injected, producing more torque without increasing exhaust gas temperatures. By using split injection to accelerate catalyst start-up, the injection timing of the split injection can be shifted to increase exhaust gas temperatures when they are below the maximum exhaust gas temperature limit. In this case, split injection can also be used to provide a main injection-post-injection strategy.

[0011] In this way, a main fuel injection can be split into a first injection, which is advanced as much as possible, and a second injection, which is as close as possible to the end of the first injection. Using split injection reduces the amount of combustion phase retardation required to keep peak cylinder pressures within pressure limits. Therefore, this improves fuel economy and engine performance, especially under high loads. Additionally, the peak cylinder pressures of the first and second injections can be provided sufficiently close together to allow exhaust gas temperatures to rise rapidly, thereby improving emissions performance and reducing turbo lag. This enables increased engine power even when operating with low-energy-density fuels.Furthermore, the increased engine performance can be achieved without costly hardware modifications, such as when using low-flow injectors.

[0012] It is understood that the above summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the full description. It is not intended to highlight any key features or essential characteristics of the claimed invention, the scope of which is defined solely by the claims following the full description. Furthermore, the claimed invention is not limited to implementations that resolve the disadvantages mentioned above or in any other part of this disclosure. Brief description of the drawings Fig. Figure 1 shows a schematic representation of a power machine. Fig. Figure 2 presents a flowchart of an exemplary method for adjusting the profile of a main injection and a preceding pre-injection according to the present disclosure. Fig. Figure 3 presents a flowchart illustrating an exemplary procedure for determining whether to split the main fuel injection based on exhaust gas temperature and cylinder pressure limitations. Fig. Figure 4 presents a flowchart illustrating an exemplary procedure for calibrating each injection of a split main fuel injection system. Fig. Figure 5 represents an exemplary use of a split main fuel injection for cylinder pressure and / or exhaust gas temperature control. Fig. Figure 6 presents a flowchart illustrating an exemplary procedure for determining whether to split the main fuel injection based on exhaust catalyst conditions. Detailed description

[0013] The following description relates to a method for controlling and adjusting the profile (including timing, quantity and number of injections per cycle) of a main fuel injection and optionally a preceding fuel pre-injection in a power engine system, such as the power engine system from Fig. 1. A power machine control system can have a control routine, such as the example routines from Fig. 2-4 and 6, to perform at least one main fuel injection into a cylinder based on engine operating conditions, in order to increase engine torque and power while keeping cylinder peak pressures within predefined limits. In particular, the engine can be operated with multiple injections per combustion cycle, with the injections calibrated based on exhaust temperature and cylinder pressure constraints, as in Fig. 5 shown.

[0014] Now referring to Fig. Figure 1 shows a schematic representation of a cylinder of a multi-cylinder engine 10, which may be included in a vehicle's drive system. The engine 10 may be controlled, at least partially, by a control system comprising a controller 12 and by input from a vehicle operator 132 via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. A combustion chamber 30 (also called a cylinder 30) of the engine 10 may comprise combustion chamber walls 32 with a piston 36 positioned therein. The piston 36 may be coupled to a crankshaft 40 such that a reciprocating motion of the piston is converted into a rotary motion of the crankshaft. The crankshaft 40 may be coupled to at least one drive wheel of a vehicle via an intermediate gear system (not shown).Furthermore, a starter motor can be coupled to the crankshaft 40 via a flywheel (not shown) to enable the start-up of the power machine 10.

[0015] The combustion chamber 30 can receive intake air from an intake manifold 44 via an intake pipe 42 and can discharge combustion gases via an exhaust manifold 48 to an exhaust pipe 68. The intake manifold 44 and the exhaust manifold 48 can be selectively connected to the combustion chamber 30 via an intake valve 52 and an exhaust valve 54, respectively. In some embodiments, the combustion chamber 30 can include two or more intake valves and / or two or more exhaust valves.

[0016] At the in Fig. In the example shown, the inlet valve 52 and the exhaust valve 54 can be controlled by cam actuation via respective cam actuation systems 51 and 53, respectively. The cam actuation systems 51 and 53 can each comprise one or more cams and utilize one or more cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) systems, which can be operated by the control unit 12 to vary the valve operation. The position of the inlet valve 52 and the exhaust valve 54 can be determined by the position sensors 55 and 57, respectively. In alternative embodiments, the inlet valve 52 and / or the exhaust valve 54 can be controlled by electric valve actuation.For example, cylinder 30 may alternatively include an inlet valve controlled by electric valve actuation and an exhaust valve controlled by cam actuation, including CPS and / or VCT systems.

[0017] In some embodiments, each cylinder of the engine 10 can be equipped with one or more fuel injectors to supply fuel. As a non-limiting example, cylinder 30 is shown with a fuel injector 66. The fuel injector 66 is shown coupled to cylinder 30 to inject fuel directly into it proportional to the pulse width of the FPW signal received by the controller 12 via the electronic driver 69. In this way, the fuel injector 66 provides what is known as direct injection of fuel into the combustion chamber 30. In other examples, the fuel injector 66 may be mounted, for example, on the side of the combustion chamber or on the top of the combustion chamber. In other examples, the fuel injector 66 may be coupled to an intake port to provide what is known as port fuel injection.Furthermore, cylinder 30 can be configured to receive fuel from any of the multiple direct fuel injectors, the multiple port fuel injectors, or from both a port and a direct fuel injector. Fuel can be supplied to the fuel injector 66 by a fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distributor.

[0018] Fuel can be supplied to cylinder 30 via the fuel injector 66 by means of multiple injections during a combustion cycle. These multiple injections can include multiple injections during the compression stroke, multiple injections during the intake stroke, or a combination of some direct injections during the compression stroke and some during the intake stroke. As referred to here Fig. As described in sections 2-4, exhaust gas temperatures can be increased under selected conditions by splitting a main fuel injection (i.e., an injection following a pre-injection and preceding a post-injection) into two or more injections. The two or more split injections can occur during a single compression stroke for a compression-ignition engine, with the timing and duration of the injections adjusted so that peak cylinder pressures resulting from each split injection are at a target pressure (e.g., at or just below a cylinder pressure limit, but not above it) and occur sequentially (e.g., within a threshold distance / time of each other). Additionally, based on NVH considerations, a pre-injection can also be split into one or more injections.

[0019] Similarly, if multiple fuel injectors are coupled to the cylinder, each injector can supply a portion of the total fuel injection that is burned in cylinder 30. Furthermore, the distribution and / or relative amount of fuel supplied by each fuel injector can vary with operating conditions, such as engine load, engine temperature, knocking, etc. It should be noted that these are merely examples of different injection and split ratios, and that other injection and split ratios may be used. It is also understood that port-injected fuel can be supplied during an intake valve-open event, an intake valve-closed event (for example, essentially before an intake stroke, such as during an exhaust stroke), and during both open and closed intake valve operation.

[0020] In one example, the engine 10 can be a diesel engine that combusts air and diesel fuel by compression ignition. In other, non-limiting embodiments, the engine 10 can combust a different fuel, including gasoline, biodiesel, or an alcoholic fuel mixture (e.g., gasoline and ethanol or gasoline and methanol), by compression ignition and / or spark ignition. Therefore, the embodiments described here can be used in any suitable engine, including, but not limited to, diesel and gasoline compression-ignition engines, spark-ignition engines, direct or port injection engines, etc. In examples where the engine is a compression-ignition engine, the timing of the combustion phases can be varied (e.g., retarded) by adjusting (e.g., retarding) the fuel injection timing.In examples where the engine is a spark-ignition engine, the timing of combustion phases can be varied (e.g., retarded) by adjusting (e.g., retarding) the ignition timing or fuel injection timing, or by varying the ignition energy.

[0021] The intake line 42 can include a throttle valve 62 with a throttle disc 64. In this particular example, the position of the throttle disc 64 can be varied by the control unit 12 by means of a signal provided to an electric motor or actuator contained within the throttle valve 62, a design generally referred to as electronic throttle control (ETC). In this way, the throttle valve 62 can be operated to vary the intake air supplied to the combustion chamber 30, along with other engine cylinders. The position of the throttle disc 64 can be provided to the control unit 12 by a throttle position signal TP. The intake line 42 can include a mass airflow sensor 120 and an intake manifold pressure sensor 122 to provide the control unit 12 with the corresponding MAF and MAP signals.

[0022] Furthermore, in the disclosed embodiments, an exhaust gas recirculation system (EGR system) can direct a desired portion of the exhaust gas from the exhaust port 68 via an EGR port 140 to the intake manifold 44. The amount of EGR supplied can be varied by the control unit 12 via the EGR valve 142. By introducing exhaust gas into the engine 10, the amount of oxygen available for combustion is reduced, thereby, for example, lowering combustion flame temperatures and reducing the formation of NOₓ. xThe exhaust gas emissions can be reduced. As shown, the EGR system further includes an EGR sensor 144, which can be located within the EGR channel 140 and can provide a reading of the exhaust gas pressure and / or temperature and / or concentration. Under certain conditions, the EGR system can be used to control the temperature of the air-fuel mixture within the combustion chamber, thus providing a method for controlling the ignition timing during some combustion modes. Furthermore, under certain conditions, a portion of the combustion gases can be retained or trapped in the combustion chamber by controlling the exhaust valve timing, such as by controlling an adjustable valve timing mechanism.

[0023] An exhaust system 128 comprises an exhaust gas sensor 126, which is coupled to the exhaust manifold 48 upstream of the exhaust gas purification system 70. The exhaust gas sensor 126 can be any suitable sensor for providing an indication of an exhaust air-fuel ratio, such as a linear oxygen sensor or UEGO sensor (universal or wideband exhaust oxygen sensor), a dual-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC or CO sensor.

[0024] The exhaust gas purification system 70 is shown arranged along the exhaust pipe 68 downstream of the exhaust gas sensor 126. The exhaust gas purification system 70 can be a selective catalytic reduction (SCR) system, a three-way catalyst (TWC), or a NOₓ system. x-trap, various other exhaust gas purification devices, or combinations thereof. For example, the exhaust gas purification system 70 may include an SCR catalyst 71 and a diesel particulate filter (DPF) 72. In some embodiments, the DPF 72 may be located downstream of the SCR catalyst 71 (as in Fig. 1) may be arranged, while in other embodiments the DPF 72 may be arranged upstream of the SCR catalyst 71 (not shown in Fig. (1 shown). The exhaust gas purification system 70 may further comprise an exhaust gas sensor 162. The sensor 162 may be any suitable sensor capable of indicating the concentration of the exhaust gas components, such as NO. x , NH3, and it can be, for example, an EGO or a particulate matter (PM) sensor. In some embodiments, the sensor 162 can be located downstream of DPF 72 (as in Fig. 1 shown), while in other embodiments the sensor 162 may be positioned upstream of DPF 72 (not shown in Fig. 1 shown). Furthermore, it is understood that more than one sensor 162 can be provided at any suitable position.

[0025] In some embodiments, the exhaust gas purification system 70 can be regularly reset during the operation of the engine 10 by operating at least one cylinder of the engine in a specific air-fuel ratio.

[0026] Control unit 12 is located in Fig. 1 shown as a microcomputer comprising a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 106, working memory 108, maintenance memory 110, and a data bus.The control unit 12 can communicate with sensors coupled to the engine 10 and therefore receive various signals and information from them, in addition to the signals discussed previously, including a measurement of the induced mass air flow (MAF) from the mass air flow sensor 120; engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling jacket 114; a profile ignition pickup signal (PIP) from a Hall sensor 118 (or another type) coupled to the crankshaft 40; a throttle position (TP) from a throttle position sensor; an absolute manifold pressure signal (MAP) from sensor 122; and the exhaust gas component concentration from exhaust gas sensors 126 and 162.From the PIP signal, the controller 12 can generate an engine speed signal in RPM (revolutions per minute). It should be noted that various combinations of the above sensors can be used, such as a MAF sensor without a MAP sensor, or vice versa. In stoichiometric operation, this sensor can provide an indication of engine torque. Furthermore, this sensor, together with the engine speed, can provide an estimate of the charge (including air) introduced into the cylinder. In one example, sensor 118, which is also used as an engine speed sensor, generates a predetermined number of evenly spaced pulses with each revolution of the crankshaft.

[0027] In addition to the sensors mentioned above, a combustion sensor (not shown) can be coupled to a single cylinder on a cylinder-by-cylinder basis. The combustion sensor can be a suitable sensor known in the field, such as a knock sensor, a vibration sensor, a temperature sensor, a pressure sensor, etc., or any combination thereof. The combustion sensor can detect combustion-related parameters, such as, for example, peak pressure value, the location of a peak pressure, the time of a peak pressure, or any combination thereof. For example, each cylinder can include an internal cylinder pressure sensor to estimate cylinder pressure changes during a combustion event in the cylinder. A peak cylinder pressure (e.g., peak pressure value and time) can be determined based on the output of the internal cylinder pressure sensor.

[0028] The controller 12 receives signals from the various sensors. Fig. 1 and suspends the various actuators Fig. 1. to adjust the operation of the power engine based on the received signals and instructions stored in a memory of the controller. For example, based on an input from the cylinder pressure sensor, the controller can set the time and duration for opening a cylinder fuel direct injection valve. As another example, based on an input from the cylinder pressure sensor, the controller can set the spark ignition timing. The read-only memory 106 can be programmed with non-volatile, computer-readable data representing instructions that can be executed by the processor 102 to perform the routines described below, as well as other variations that are anticipated but not specifically listed. Exemplary routines are given here with reference to Fig. 2-5 and 6 described.

[0029] As described above, shows Fig. 1 only one cylinder of a multi-cylinder engine, and each cylinder can likewise include its own set of inlet / exhaust valves, fuel injectors, etc.

[0030] Now referring to Fig. Figure 2 shows an exemplary method 200 for combustion phase control. In particular, combustion phases can be adjusted by setting the profile of a pre-fuel injection and a main fuel injection to provide a desired enthalpy while enabling a target cylinder peak pressure to be achieved. Method 200 can thus constitute a primary control loop for combustion phase control. Instructions for executing Method 200 and the remaining methods contained herein can be executed by a control device based on instructions stored in a memory of the control device and in conjunction with signals received from sensors of the engine system, such as those mentioned above with reference to Fig. The sensors described in section 1 will receive data. The controller can use the power machine actuators of the power machine system to adjust the power machine operation according to the procedures described below.

[0031] In the case of 202, the procedure involves estimating and / or measuring engine operating conditions. These include, for example, engine speed, indicated torque demand, indicated mean effective pressure (IMEP), manifold pressure (MAP), manifold air flow (MAF), ambient conditions (e.g., ambient temperature, pressure, and humidity), engine fuel consumption (relative to a target fuel consumption rate), etc. Other parameters that may be considered include engine geometry (bore size, engine displacement, effective compression ratio, etc.) and intake boundary conditions (pressure, temperature, mass flow, etc.). Furthermore, the type of fuel injected into the engine (or available in the fuel tank) may be determined.In one example, this includes determining the octane rating of the available fuel and / or the energy density of the available fuel.

[0032] At 204, a pre-fuel injection profile can be determined based on estimated engine operating conditions. Therefore, pre-injection can include an injection used as a source of ignition (rather than spark plugs) for a subsequent main combustion. It is understood that here, all fuel injections supplied prior to a main injection are referred to as pre-injections. As an example, the pre-injection quantity can be 1–20% of the total injected fuel, depending on the total fuel quantity requested and the minimum delivery quantity of an injector at a given distributor pressure.

[0033] Determining the pre-fuel injection profile involves determining the injection timing, the total amount of fuel to be injected, and the injection duration. For example, pre-injection might be initiated at 40° BTDC and continue until 32° BTDC. For instance, in a 6.7-liter engine operating at idle, the total amount of fuel supplied might be 10 mg / stroke. Here, idle pre-injection amounts could range from 7% (or 0.7 mg / stroke as a minimum) to 20% (or 2 mg / stroke). In an example of a 3.2-liter engine operating at approximately 7 mg / stroke, the pre-injection amount could be approximately 2 mg / stroke or higher.

[0034] At 206, a main fuel injection profile can be determined based on estimated engine operating conditions. Therefore, the main injection can encompass the injection used for the main combustion event in the cylinder. It is understood that here, all fuel injections supplied after a pre-injection and before a post-injection are referred to as main injections. As an example, the main injection can provide 55-98% of the total fuel, depending on the total fuel quantity requested and the minimum delivery quantity of an injector at a given distributor pressure.

[0035] Determining the main fuel injection profile involves determining the injection time, the total amount of fuel to be injected, and the injection duration. Additionally, as referenced in Fig. As described in section 3, determining the main fuel injection profile also includes determining whether the main fuel injection should be administered as a single injection or divided into several smaller injections. Therefore, during engine operation at full load, the timing of a planned main fuel injection can be retarded (also referred to here as a retarded combustion phase) to reduce peak cylinder pressures below a cylinder pressure limit. The peak pressure is limited to mitigate cylinder degradation. However, the retarded combustion phase results in a suboptimal combustion timing, leading to a higher than desired engine fuel consumption rate. Additionally, exhaust gas temperatures may be higher than desired.This not only affects engine fuel economy but also engine performance due to limitations in engine torque and power. In some examples, it can also lead to non-uniform heating and activation of exhaust catalysts (for instance, because an upstream catalyst is activated while a downstream one remains inactive). As explained here, in response to the predicted peak cylinder boost pressure for a planned main fuel injection into a cylinder occurring later than a threshold time, where the threshold time is an optimal time based on maximum engine output torque (i.e., during late-adjusted combustion phase conditions), an engine control unit can split the planned main fuel injection into at least a first and a second injection.Furthermore, the first injection can be advanced relative to the planned main fuel injection time, while the second injection is delayed relative to the planned main fuel injection time. The technical benefit of splitting the main injection into several smaller injections is that, by using a smaller delay in the combustion phase, a greater amount of enthalpy can be extracted from the combustion event, while keeping the cylinder pressures closer to the target pressure (and within the cylinder's pressure limit). This allows for improved fuel economy and engine performance.

[0036] Therefore, the main injection profile can be adjusted to influence the primary fuel injection(s), which significantly affects the engine's power output. Typically, pre-injections do not directly and significantly increase the engine's power output or torque delivery. Therefore, the main injection profile can leave the pre-injection profile unchanged. However, a split main injection strategy can utilize a pre-injection (that is, an injection designated as a "pre-injection" by the engine control unit), but the injected quantity would be very large (>10%) and timed to produce substantial positive work from the engine. In this case, the pre-injection can be used as an additional main injection event, and not for a longer duration than originally intended (or designated) as a conventional pre-injection.In other words, and as explained below, the "pre-injection" can become a main injection regardless of its designation.

[0037] At 208, it can be confirmed whether a split main injection has been activated. As subsequently referred to in the procedure from Fig. As described in section 3, in one example, split main injection can be activated in response to a scheduled main fuel injection being delayed by more than a threshold time. Alternatively, split main injection can be activated in response to a peak cylinder pressure for the scheduled main fuel injection occurring later than a threshold time. When split main injection is activated, the procedure at 209 includes determining an initial profile for the split fuel injection. For example, a number of split injections can be determined. Therefore, the main injection can be split into at least a first and a second injection.In addition to the number of split injections, the initial split injection profile may include an initial timing control of each injection (such as a start of injection time, an end of injection time and an average injection time), a duration of each injection and an amount of fuel at each injection.

[0038] The absolute maximum number of injections can be limited by the engine control unit based on engine conditions and, furthermore, on injector capabilities. The number of injections can be determined by the fuel injector based on operating conditions and the minimum residence time between injections. For example, the number of fuel injections can be set to a level sufficient to produce a constant / flat cylinder pressure at maximum cylinder pressure level as early as possible in the compression stroke, while simultaneously advancing the end of the combustion period as much as possible. A greater number of fuel injections allows for greater control over the rate of heat release from combustion while minimizing peaks in the cylinder pressure curve.It also adds additional dwell times between injections, which delays the end of the final fuel injection and thus delays the end of the combustion time.

[0039] At 210, the procedure further includes calibrating the split injection. As referenced in Fig. As described in section 4, calibrating the main fuel injection involves adjusting the quantity, timing, and duration of each split fuel injection based on a cylinder's peak pressure to optimize the main injection advance and provide two or more peaks at a target cylinder pressure (such as maximum cylinder pressure). The injections can be calibrated to improve the engine's fuel economy (such as by reducing brake-specific fuel consumption, BSFC) and to extract the maximum enthalpy / heat from the combustion event.During the split injection calibration, the procedure proceeds to 218, updating the engine calibration settings, and at 220 the engine is operated, supplying fuel according to the specified fuel injection profiles and calibrated settings.

[0040] If a split main injection is not activated, the procedure at 212 includes determining whether the exhaust gas temperature is lower than a threshold temperature. In one example, the threshold temperature is based on the start-up or activation temperature of an exhaust catalyst, such as an upstream oxidation catalyst and / or a downstream reduction catalyst. If the exhaust gas temperature is not lower than the threshold, that is, if the exhaust gas is sufficiently hot, the procedure at 214 includes reducing the amount of fuel in the (single) main injection to reduce the exhaust gas temperature. The amount of fuel in the main injection can be reduced by decreasing the pulse width of the injection or by advancing the end of the injection (EOI) time.The procedure then proceeds to step 218, updating the engine calibration settings and operating the engine, supplying fuel according to the specified fuel injection profile.

[0041] If the exhaust gas temperature is lower than the threshold, that is, if the exhaust gas is not sufficiently hot, the procedure at 216 involves increasing the amount of fuel in the (single) main injection to meet the torque requirement while simultaneously raising the exhaust gas temperature. The amount of fuel in the main injection can be increased by increasing the pulse width of the injection or by retarding the end of the injection (EOI) point. The procedure then proceeds to 218, where the engine calibration settings are updated, and at 220 the engine is operated, with fuel being supplied according to the specified fuel injection profile and calibrated settings.

[0042] Now referring to Fig. Figure 3 provides an exemplary procedure 300 for determining a main injection profile. Specifically, procedure 300 enables a controller to decide whether the planned main injection should be split into several smaller injections. In other words, procedure 300 can represent a decision subroutine of the primary control loop of procedure 200 for activating split injection. In one example, procedure 300 can be implemented as part of procedure 200, as in Figure 206.

[0043] In the case of 301, the procedure involves retrieving data relating to the estimated power engine operating conditions (such as those specified in Fig. 2 at 202 were estimated and / or measured). Additionally, details of a planned main fuel injection can be retrieved. For example, the control unit can determine an originally planned main fuel injection profile based on the estimated operating conditions and then further determine, based on the specific considerations discussed below, whether the main fuel injection should be split.

[0044] In document 302, the procedure involves determining whether a peak cylinder pressure (peak_dr) and / or exhaust gas temperature (T_abg) and / or operator torque request (Dm_anf) and / or planned main fuel injection quantity (HptEinsp_menge) is higher than a corresponding limit. For example, a peak cylinder pressure target may be defined for the given engine operating conditions, and it may be determined whether the cylinder pressure is at or above the peak cylinder pressure target. The peak cylinder pressure may be above the target pressure if a planned main fuel injection into a cylinder occurs later than at a threshold time, such as later than an optimal time based on maximum engine output torque.If the relevant limits / targets have not been exceeded, the procedure at 304 includes determining whether the current engine speed and indicated torque justify split main injection. For example, the control may refer to a predefined calibration table that indicates injection profiles (e.g., single or split injection) as a function of engine speed and load. If the engine speed and torque do not justify split main injection, the procedure at 314 includes maintaining the main fuel injection as a single injection and not allowing split main injection. Here, the procedure may proceed to supply the engine with fuel for a single main fuel injection, with the timing and quantity as planned (according to the planned main injection fuel profile).

[0045] In some examples, it can additionally be determined, or optionally determined, whether a vehicle operator wanted to enable split fuel injection. If no user input regarding a request for split fuel injection is received, the procedure can maintain single main fuel injection.

[0046] If any of the parameters assessed at 302 has exceeded its corresponding targets / limits, the procedure proceeds at 306 to estimate or measure a maximum operating cylinder pressure. As used here, the maximum operating cylinder pressure is the maximum cylinder pressure produced by mechanical compression of the engine when the engine is rotating without any fuel injection or combustion. The maximum operating cylinder pressure can be calculated or estimated using cylinder internal pressure and / or temperature measurements, and / or calibration tables, and / or engine sensors that monitor engine boundary conditions. The estimates can be based, for example, on a calibration map stored in the controller's memory as a function of engine speed / load conditions.As another example, the estimates can be based on a correlation function that takes into account the engine's displacement, cylinder geometry, effective compression ratio, intake pressure, exhaust pressure, intake temperature, and airflow, among other factors. The estimate can also be based on the energy density of the available fuel in the fuel tank.

[0047] In document 308, the procedure involves determining a maximum cylinder pressure (or cylinder peak pressure limit) for the cylinder based on the current engine operating conditions. For example, a cylinder peak pressure limit for the cylinder can be determined based at least on engine speed and torque demand, and further based on temperatures, including turbine inlet temperature. The engine control can determine the maximum cylinder pressure based on, for example, a calibration table mapped as a function of engine speed to requested indicated torque, as well as turbine inlet temperature (with the limit being reduced when the turbine inlet temperature reaches a maximum threshold temperature). As another example, the maximum cylinder pressure can be based on a correlation function between engine speed and requested indicated torque.

[0048] In the case of 310, the procedure involves comparing the maximum pressure of the operating cylinder with the maximum cylinder pressure and estimating a peak pressure clearance based on the difference between the maximum pressure of the operating cylinder and the maximum cylinder pressure. Specifically, the control can subtract the maximum cylinder pressure (or cylinder pressure limit) from the estimated maximum pressure of the operating cylinder to produce an estimated peak pressure clearance.

[0049] In 312, the procedure involves determining whether the peak pressure margin is higher than a minimum threshold for split main injection (threshold_min). In other words, it determines whether the cylinder is operating at or outside the cylinder peak pressure target for the single main fuel injection. Therefore, if the cylinder is operating at or outside the cylinder peak pressure target for the single main fuel injection, the combustion phase may need to be retarded, resulting in losses of fuel and enthalpy. During such conditions, split main injection can advantageously be used to advance the combustion phase (or reduce the required amount of combustion phase retard) while maintaining the cylinder pressure within the limits.

[0050] In particular, when the peak pressure margin is higher than the threshold, the method described in 316 includes enabling split main fuel injection. For example, an instruction to enable split fuel injection can be sent from the control unit to the fuel injector. The method described in 318 further includes determining an initial split fuel injection profile. This can be a split fuel injection profile determined based on the operating conditions and the originally planned main fuel injection prior to further calibration. For example, a number of split injections can be determined. Therefore, the main injection can be split into at least a first and a second injection.In addition to the number of split injections, the initial split injection profile may include an initial timing control for each injection (such as a start of injection time, an end of injection time, and an average injection time), a duration for each injection, and an amount of fuel at each injection.

[0051] Therefore, the goal when setting the fuel injection profile is to maximize brake-specific fuel consumption (BSFC) and advance the end of combustion as much as possible while still meeting the user-defined load. The profile is set to produce a flat, or as flat as possible, pressure curve at maximum cylinder pressure while combustion is taking place in the cylinder. This ensures that the maximum amount of thermodynamic work (i.e., pressure multiplied by the change in volume) is generated.

[0052] As an example, the planned main injection can be divided into two or more smaller injections. The start of the injection time for the first of the smaller injections can be advanced (relative to the start time of the planned main injection), and the amount of fuel supplied in the first injection can be increased until a first peak pressure is reached at a target pressure. Specifically, one phase of the first injection is advanced while the quantity is adjusted to achieve the target pressure until maximum efficiency (as estimated by thermal efficiency, mean working pressure, combustion stability, etc.) is achieved. For example, the timing of the first injection can be advanced relative to the timing of the planned main fuel injection to maintain a peak cylinder pressure of the first injection at or below a peak pressure limit.The first injection cycle can be terminated when the peak cylinder pressure of the first injection reaches the peak pressure limit.

[0053] In another example, the timing, duration, and quantity of fuel delivered during the initial injection can be determined based on operator torque demand (or engine load). While adjusting the quantity of the initial injection, the quantity of a second (and one or more subsequent) injection(s) is reduced accordingly to achieve the total fuel quantity (as the planned main injection). The phase of the second (and one or more subsequent) injection(s) is then shifted as close as possible to the end of the preceding injection without exceeding the cylinder pressure target. The injection quantity is then maximized until the peak pressure is reached, assuming the cylinder pressure responds to the fuel quantity.For example, an engine control unit can retard the timing of the second injection relative to the scheduled main fuel injection time to maintain a peak cylinder pressure of the second injection at or below the peak pressure limit. The margin between the peak cylinder pressure of the second injection and the peak cylinder pressure of the first injection is limited by the injector, with the margin determined based on a minimum physical hardware delay between the end of the first injection and the start of the second injection.

[0054] Additionally or alternatively, if cylinder pressure does not respond to fuel quantity, the injection quantity can be maximized until a turbine inlet temperature reaches a target temperature. For example, if the turbine inlet temperature is not raised sufficiently, the duration of the second (or subsequent) injection(s) can be extended, or the end of the injection time can be retarded. For instance, the engine may be a turbocharged engine comprising an exhaust turbine-driven intake compressor, with the duration of the second injection set based on the turbine inlet temperature and shortened as the turbine inlet temperature rises above a threshold temperature. Optimizing based on cylinder pressure improves engine performance. Optimizing based on turbine inlet temperature can reduce turbo lag.It is understood that the timing and duration of both the first and second injections can be further adjusted based on an estimated BSFC of the engine to improve engine fuel economy while providing the late-adjusted combustion phase. Therefore, the timing and duration of the pre-fuel injection can be maintained during the splitting of the planned main fuel injection.

[0055] At 320, the procedure then includes calibrating the split fuel injection, as referenced in Fig. 4. In 322, the method comprises maintaining the use of a split injection event over one or more cylinder combustion events until both the cylinder pressure and the turbine inlet temperature are at their target values. That is, the main injection for several successive cylinder combustion events can be split into several smaller injections until the target exhaust pressure and / or temperature profile is achieved.

[0056] If the peak pressure margin is lower than the threshold, the procedure at 314 involves maintaining the single main fuel injection and not allowing split main fuel injection. For example, an instruction to disable split fuel injection can be sent from the control unit to the fuel injector.

[0057] Now referring to Fig. Figure 4 shows an exemplary procedure 400 for calibrating split main fuel injection after a decision has been made to enable splitting. The calibration involves setting the timing and duration of each split fuel injection based on a cylinder peak pressure target or limit, as well as considerations of engine fuel consumption. For example, the setting may be based on an output from a cylinder internal pressure sensor relative to the defined cylinder peak pressure target. Procedure 400 can be a decision subroutine of the primary control loop of procedure 200 for split injection optimization. In an example, procedure 400 may be executed as part of procedure 200, as in figure 210, and / or as part of procedure 300, as in figure 320.

[0058] Procedure 400, at 402, includes confirming that split injection is possible. That is, it can be confirmed that a decision to split the main injection has been confirmed and that a signal to split the main fuel injection has been instructed by the engine control unit. Therefore, the split injection can include at least a first injection and a second injection. The main fuel injection can be split into even more injections. If the split injection is not confirmed, Procedure 404 includes maintaining a single main fuel injection.

[0059] In procedure 406, upon confirmation that split injection is enabled, the procedure involves estimating a peak cylinder pressure for each of the split fuel injections. For example, a peak cylinder pressure can be estimated for the first split main injection (main_inj_1) and for the second split main injection (main_inj_2). The peak cylinder pressure for each injection can be calculated or estimated using cylinder pressure and / or temperature measurements, and / or calibration tables, and / or engine sensors that monitor engine boundary conditions. The estimates can be based, for example, on a calibration map that is mapped as a function of engine speed / load conditions and stored in the control unit's memory.As another example, the estimates can be based on a correlation function that takes into account the engine displacement, cylinder geometry, effective compression ratio, intake pressure, exhaust pressure, intake temperature and airflow, among other factors.

[0060] The control system then proceeds to calibrate the first and second injections. In this example, the first and second injections are shown as being calibrated sequentially. However, it should be understood that in alternative examples, the first and second injections can be calibrated simultaneously.

[0061] In particular, at 408 it can be determined whether the estimated peak cylinder pressure for the first injection (peak_cylinder_pressure_1) is higher than a threshold. The threshold can be a maximum cylinder pressure (or a cylinder peak pressure limit) for the cylinder, which can be determined based on the engine operating conditions, such as engine speed and torque demand, as previously done at Fig. 3 discussed. If the peak cylinder pressure for the first injection is higher than the threshold, the procedure at 410 involves decreasing the amount of fuel in the first injection. The amount of fuel in the first injection of split injection can, as one example, be decreased using a closed-loop feedback control based on peak cylinder pressure (as measured by an internal cylinder pressure sensor). In another example, the amount of fuel in the first injection can be decreased using a forward-feed correlation between the amount of fuel, the start of the injection time, and a peak cylinder pressure for the first injection. Conversely, if the peak cylinder pressure for the first injection is lower than the threshold, the procedure at 412 involves increasing the amount of fuel in the first injection.The amount of fuel injected during the first injection of a split injection system can, for example, be increased using a closed-loop feedback control system based on the peak cylinder pressure (as measured by an internal cylinder pressure sensor). In another example, the amount of fuel injected during the first injection can be increased using a forward-feed correlation between the fuel quantity, the start of the injection time, and the peak cylinder pressure for the first injection.

[0062] Starting from both 410 and 412, the procedure continues at 414, where it is determined whether the engine's fuel consumption is at a minimum target rate. For example, it can be determined whether the engine's fuel consumption rate is at a lower BSFC limit. If so, the procedure at 416 involves maintaining the timing of the first injection. If, on the other hand, the engine's fuel consumption rate is not at the minimum target rate (that is, if the fuel consumption is higher than desired), the procedure at 418 involves adjusting the timing of the first injection. Here, the timing of the first injection can be advanced or retarded relative to the timing of the planned single main fuel injection.In one example, the timing can be set using a forward coupling correlation between fuel consumption, the start of the injection time, and the amount of fuel supplied at the first injection.

[0063] After calibrating the first injection, the procedure continues to calibrate the second injection. Specifically, from both 416 and 418, the procedure continues at 420, where it can be determined whether the estimated peak cylinder pressure for the second injection (peak_cylinder_pressure_2) is higher than a threshold. The threshold can be the maximum cylinder pressure (or a cylinder peak pressure limit) for the cylinder, which can be determined based on the engine operating conditions, such as engine speed and torque demand, as previously described in Fig. 3 discussed. In the present example, the peak pressure of the first and second injections is compared to a common threshold. However, it is understood that in alternative examples, the peak pressure of the second injection may be compared to a threshold that differs from (i.e., is higher or lower than) the threshold against which the peak pressure of the first injection is compared.

[0064] If the peak cylinder pressure for the second injection is higher than the threshold, the procedure at 422 involves retarding the timing of the second injection. Here, the timing of the second injection is retarded relative to the timing of the planned single main fuel injection. As one example, the timing of the second injection can be retarded using a closed-loop feedback control based on peak cylinder pressure (as measured by an internal cylinder pressure sensor). In another example, the timing of the second injection can be retarded using a forward-feed correlation between the start of the injection time and a peak cylinder pressure for the second injection.

[0065] If the peak cylinder pressure for the second injection is lower than the threshold, the procedure at 424 involves advancing the timing of the second injection. Here, the timing of the second injection is advanced relative to the timing of the planned single main fuel injection. As one example, the timing of the second injection can be advanced using a closed-loop feedback control based on peak cylinder pressure (as measured by an intra-cylinder pressure sensor). In another example, the timing of the second injection can be advanced using a forward-feed correlation between the start of the injection time and a peak cylinder pressure for the second injection.

[0066] Starting from both 422 and 424, the procedure continues at 426, where it is determined whether the exhaust gas temperature (T_abg) is higher than a threshold temperature. For example, it can be determined whether the exhaust gas temperature is higher than a temperature limit above which engine component deterioration may occur. Alternatively, it can be determined whether the exhaust gas temperature is higher than a catalyst start-up / activation temperature.

[0067] If the exhaust gas temperature is higher than the threshold temperature, the procedure at 428 involves reducing the amount of fuel in the second injection. In one example, the amount of fuel in the second injection of split injection can be reduced using a closed-loop feedback control loop based on exhaust gas temperature (as measured by an exhaust manifold temperature sensor). In another example, the amount of fuel in the second injection can be reduced using a forward-feed correlation between the end of the combustion time (or the end of the injection time for the second injection) and the exhaust gas temperature. Therefore, the timing of the second injection can be set so that the second injection is retarded relative to the first injection.

[0068] Conversely, if the exhaust gas temperature is lower than the threshold temperature, the procedure at 430 involves increasing the amount of fuel in the second injection. The amount of fuel in the second injection of the split injection system can, for example, be increased using a closed-loop feedback control system based on indicated torque. In another example, the amount of fuel in the second injection can be increased using a forward-feed correlation between fuel quantity and indicated torque for the second injection.

[0069] In some examples, the adjustment of the first and second injections is performed simultaneously. For instance, the fuel injection quantity of the first injection is adjusted to meet the user torque request, with the initial fuel injection quantity determined using a correlation or calibration map based on experimental data relating the main injection quantity to the indicated torque. This is done because the actual indicated or braking torque is not physically measured at the engine. The final injection of the split injections can then be used to meet the user torque request with the increased amount until the user-requested torque is reached and the exhaust gas temperature is below the maximum permissible exhaust gas temperature.Otherwise, the engine may reduce its own power output and stop increasing the amount of fuel for the final split main injection.

[0070] In examples where split injection includes additional injections, the engine control unit can calibrate the additional injections in the same manner as discussed above. After calibrating each of the first and second (and additional) injections, the calibrated settings can be updated in the engine control unit's memory, and the routine can end. The engine can then resume fuel delivery with the calibrated fuel injection settings.

[0071] In one example, the calibration procedure discussed above can be implemented as a fixed calibration strategy within the engine control unit. Alternatively, the calibration procedure can be coupled with a combustion feedback sensor, such as an internal cylinder pressure sensor, and the calibration can be activated as needed.

[0072] Furthermore, the calibration can be updated based on information regarding the type of fuel available for injection. For example, by using IMEP measurements or based on an output from an exhaust gas oxygen sensor, a control unit can determine whether the fuel has a higher or lower energy density and adjust the main injection calibration (including the number of split injections, the timing and duration of the split injections, etc.) accordingly, compensating for fuel variations. For example, if the fuel's energy density is lower (e.g., if the fuel is biodiesel or an oxygen-enriched fuel), the calibration might include a greater number of injections in the split injection. Conversely, if the fuel's energy density is higher (e.g., if the fuel is high-energy diesel or an oxygen-enriched fuel), the calibration might include fewer injections.(If the fuel is diesel), the calibration can involve a smaller number of injections in the split injection. Therefore, energy density directly influences injection durations. Higher energy density requires shorter injections, and in many cases, fewer injections are needed to achieve the same load and engine efficiencies. Furthermore, the control unit can make adjustments to the split injection in each individual cylinder based on information from a cylinder-specific combustion feedback system (such as an internal cylinder pressure sensor), thereby compensating for potential cylinder-to-cylinder differences in compression ratio or airflow.

[0073] Furthermore, the duration of the second injection can be adjusted based on turbine inlet temperature and / or NOx content in the exhaust gas and / or hydrocarbon levels in the exhaust and / or CO emissions in the exhaust gas. These values ​​can be modeled and measured. Additionally, the control system can switch between calibrations specifically tailored to individually warm up each aftertreatment catalyst.

[0074] As an example, a planned main injection profile might include a single late injection starting at 2 CAD before top dead center (TDC) and ending at 10 CAD after TDC, with peak cylinder pressure occurring at approximately 16 CAD after TDC. In response to the late combustion phase, the main injection might be split into two injections, including a first injection initiated at 10 CAD before TDC and lasting until 6 CAD before TDC, and a second injection initiated at 6 CAD before TDC and lasting until 12 CAD after TDC.

[0075] In another example, a first injection (including timing, duration, and fuel quantity) of the split injection system can be set based on a user torque request. Then, the second injection (including timing, duration, and fuel quantity) can be calibrated to generate exhaust gas temperature and enthalpy. This is because the second injection produces less torque than the first injection, as it occurs further from top dead center (TDC).

[0076] It is understood that, while the methods disclosed above discuss splitting a main injection and calibrating each of the split injections to increase cylinder pressure and exhaust gas temperature to target temperatures within predefined limits, in alternative examples the split injection can be calibrated to decrease cylinder pressures and exhaust gas temperatures to target temperatures. For example, calibration can be used to reduce peak cylinder pressure at a target torque and power level, thereby improving engine durability.

[0077] An embodiment of an exemplary split main fuel injection profile according to the present disclosure is shown in Fig. from Fig. 5 shown. Fig. This represents an engine position along the x-axis in degrees of crank angle (CAD - Crank Angle Degree). Now, referring to the upper plots in each figure, the curve represents 502 piston positions (along the y-axis) in relation to their position from top dead center (TDC) and / or bottom dead center (BDC), and further in relation to their position within the four strokes (intake, compression, power, and exhaust) of an engine cycle. Fig. This specifically represents the compression and power strokes to demonstrate fuel injections that occur at or approximately at top dead center (TDC) of the piston position between the compression and power strokes. As indicated by the sinusoidal curve 502, at the end of a compression stroke, a piston moves stepwise from bottom dead center (BDC) (after completion of an intake stroke) to TDC. The piston then returns to BDC at the end of the power stroke.

[0078] The middle plot of Fig. Figure 508 represents a cylinder pressure profile for a cylinder in which combustion is taking place. A cylinder pressure profile for a planned single main fuel injection in the cylinder, shown by the dashed curve 508, is compared with the cylinder pressure profile for a split main fuel injection in the cylinder, shown by the solid curve 506.

[0079] The lower plot 510 presents an exemplary fuel injection profile for the cylinder in which combustion is taking place. A fuel pressure profile (including timing, duration, etc.) for the planned single main fuel injection in the cylinder, shown by dashed lines (M1), is compared with the fuel injection profile for the split main fuel injection in the cylinder, shown by solid lines (M1' and M2'). In this example, the profile of a pre-injection (P1) preceding the main fuel injection is obtained.

[0080] In this example, the engine can be a compression ignition engine in which, as a non-restrictive example, a fuel such as diesel or biodiesel can be burned.

[0081] An engine control unit can determine an initial fuel injection profile to deliver a total amount of fuel. In the initial profile, the engine control unit can deliver the total amount of fuel to the cylinder as two injections, comprising an initial single pre-injection P1 (also referred to as a "rich" pre-injection) and a second single main injection M1. The first pre-injection P1 can be scheduled to be delivered earlier during the compression stroke at CAD1 for a duration d1, while the second main injection can be scheduled to be delivered later during the power stroke at CAD2 for a duration d2. For example, the first pre-injection P1, comprising 1-20% of the total injected fuel, can be scheduled to be delivered at 32CAD before top dead center (TDC). The remainder of the total fuel can then be delivered at 2CAD after TDC.As a result of this fuel injection profile, a peak cylinder pressure can occur at approximately 16 CAD before top dead center (TDC), as indicated by the dashed curve 508. Here, in order to ensure that the peak cylinder pressure does not exceed the peak cylinder pressure limit 504 (e.g., at approximately 150 bar), the combustion phase is retarded so that the peak cylinder pressure occurs later in the power stroke.

[0082] To increase combustion efficiency and improve exhaust gas temperature and cylinder pressure control, the planned single main fuel injection M1 can be divided into several smaller injections. In the present example, the single main injection is divided into a first main injection M1' and a second main injection M2'. The first main injection M1' is provided at CAD3 for a duration d3, while the second main injection M2' is provided at CAD4 for a duration d4. Specifically, the first main injection is advanced relative to the single main injection (CAD3 is advanced relative to CAD2), while the second main injection is retarded relative to the single main injection (CAD3 is retarded relative to CAD2). As an example, the first main injection can be provided at CAD10 after top dead center (TDC), while the second main injection is provided at CAD6 after TDC.

[0083] In addition to advancing the first injection, the duration of the first injection (and thus the amount of fuel in the first injection) is increased until a peak cylinder pressure resulting from the first injection (represented by a first bump 507a of plot 506) occurs at the target pressure, that is, at or just below pressure limit 504. Afterward, the remainder of the fuel is supplied in the second injection. For example, if the amount of fuel in the first injection is increased, the amount of fuel in the second injection is reduced accordingly to maintain the same total fuel quantity supplied in the split injection (that is, fuel_M1' + fuel_M2' = fuel_M1) as in the single main injection (M1).In the present example, a smaller portion of the total main fuel is provided at the first injection, while a remaining, larger portion is provided at the second injection.

[0084] The timing of the second injection is set based on the first injection such that the peak cylinder pressure resulting from the second injection (represented by a second bump 507b in Plot 506) also occurs at the target pressure and, furthermore, as close as possible to the end of the peak pressure of the first injection. That is, the second injection is advanced as much as possible to be as close as possible to the end of the injection time of the first injection, while keeping the peak cylinder pressure within limits. Additionally, the duration of the second injection can be set based on the turbine inlet temperature to provide sufficient exhaust heat.In other words, the timing of the first and second injections is set so that the peak pressures of the two injections (i.e., the bumps 507a and 507b) occur as close together as possible, for example, immediately one after the other, while remaining at or below pressure limit 504.

[0085] This allows cylinder pressure and turbine inlet temperature to be raised to their target values ​​by means of a smaller late adjustment of the combustion phase (in an example without late adjustment of the combustion phase).

[0086] Several benefits can be achieved by calibrating the main injection based on the cylinder peak pressure. For example, fuel economy and exhaust emissions are improved. Furthermore, the improvement in fuel economy and exhaust emissions can be increased when used with an engine system with low-flow injectors.

[0087] Now referring to Fig. Figure 6 presents an exemplary method 600 for adjusting the combustion phase and injection calibration in response to exhaust catalyst conditions. This method enables improved start-up of an upstream oxidation catalyst (such as a DOC) and a downstream reduction catalyst (such as an SCR) without compromising exhaust emissions or fuel economy.

[0088] In the case of 602, the method involves estimating and / or measuring exhaust gas conditions. These include, for example, exhaust gas temperature, exhaust gas pressure, and the temperature and activation state of one or more exhaust gas catalysts. The one or more exhaust gas catalysts of an exhaust gas purification device may include, for example, an upstream oxidation catalyst (such as a DOC) and a downstream reduction catalyst (such as an SCR). In addition to exhaust gas conditions, ambient conditions may also be evaluated.

[0089] At 604, it can be determined whether both the upstream and downstream exhaust catalysts are inactive. For example, if the exhaust gas temperature is below a threshold temperature, both catalysts can be determined to be inactive. In another example, both catalysts can be determined to be inactive during cold ambient conditions.

[0090] When both catalysts are inactive, procedure 606 involves operating the engine at a lower EGR rate. Additionally, procedure 610 allows for maintaining a combustion timing at a target point (such as in MBT). By reducing the EGR rate in response to the inactive catalyst conditions, hydrocarbon emissions that occur when the catalysts are activated are reduced. Furthermore, the exhaust gas mass flow rates are increased.

[0091] Returning to step 604, if both catalysts are not inactive, step 610 can determine whether only the upstream exhaust catalyst is active. For example, if the exhaust gas temperature is higher than the activation temperature of the first catalyst but lower than the activation temperature of the second catalyst, only the first catalyst can be determined to be active. In another example, only the first, upstream catalyst can be determined to be active if the exhaust gas temperature was higher than the threshold temperature for a shorter duration.

[0092] If only the first, upstream catalyst is active, the procedure at 612 involves operating the engine with a higher EGR rate. Additionally, at 614, the combustion timing can be retarded to increase the peak cylinder pressure and further increase the exhaust gas temperature. The combustion timing can be retarded by dividing the main injection into two or more smaller injections and retarding the average start of the injection time. If necessary, a pre-injection preceding the main injection can also be divided into two or more smaller injections. Furthermore, the amount of fuel supplied to the cylinder via port injection can be increased.As a result of increasing EGR and retarding the combustion phase, exhaust gas temperatures may be increased and NOx levels reduced, at the expense of hydrocarbon emissions, which would further increase the exhaust gas temperature if oxidized above the first oxidation catalyst.

[0093] Here, both the higher and the lower EGR rate can be based on the age of the upstream and downstream catalyst as well as the exhaust gas temperature.

[0094] A level of combustion phase retardation and an increase in the applied EGR rate can be set based on one or more parameters related to the first oxidation catalyst, including catalyst core temperature, catalyst outlet temperature, total hydrocarbon (THC) emissions, and conversion efficiency. Additionally, the phase retardation and EGR rate can be increased based on catalyst age and engine temperature. Furthermore, split injection and EGR utilization can be calibrated in response to exhaust mass flow and / or exhaust temperature and / or catalyst temperature and / or estimated exhaust heat transfer coefficient and / or estimated exhaust Reynolds number and / or exhaust system heat transfer.These parameters can be calculated based on data estimated by a sensor, based on modeled data, or based on expected values ​​for one or more alternative calibrations.

[0095] Returning to 610, if the upstream catalyst is not the only active catalyst, it can be confirmed in 616 that both the upstream and downstream catalysts are active. For example, if the exhaust gas temperature is higher than the activation temperature of both the first and second catalysts, both catalysts can be determined to be active. In another example, both catalysts can be determined to be active if the exhaust gas temperature has been higher than the threshold temperature for an extended period.

[0096] When both the upstream and downstream catalysts are active, the procedure at 618 involves operating the engine at the higher EGR rate. Additionally, at 620, a combustion timing can be maintained at a target time (as with MBT). By increasing the EGR rate once both catalysts are active, fuel economy is improved and NOx emissions are reduced.

[0097] For example, the injection and EGR calibration applied when both catalysts are inactive might be a high-enthalpy calibration with a moderate exhaust gas temperature (e.g., low EGR rate, low internal EGR rate, cooled EGR, low-pressure EGR, high boost pressure), while the calibration applied when only the upstream catalyst is active might be a high-temperature calibration with a lower exhaust gas enthalpy (e.g., uncooled high-pressure EGR and / or internal EGR, low boost pressure). An engine control unit can select the calibration to apply based on the expected heat transfer to the catalyst(s). The difference between minimum THC and minimum NOx calibrations, as well as between low- and high-enthalpy calibrations, can be defined as simply by adjusting a single calibration parameter, such as the EGR rate.Alternatively, the change can include multiple calibration actuators, such as engine speed and / or load and / or EGR cooler bypass and / or internal EGR quantity and / or boost pressure, etc.

[0098] In yet another example, the control unit can divide the main fuel injection into at least a first injection and a second injection. The first injection can be advanced or retarded relative to the combustion timing of the planned main fuel injection, with the timing, duration, and amount of fuel in the first injection being set based on engine load or user torque demand. The second injection can then be set based on the catalyst temperature.For example, the timing of the second injection can be retarded relative to the first, and the amount of fuel in the second injection can be limited (below the desired amount) if the first, upstream catalyst has not yet reached startup. Conversely, the amount of fuel in the second injection is increased after the first catalyst has reached startup to enable the second catalyst to reach startup. Therefore, the amount of fuel in the second injection, rather than the first, can directly influence the catalyst temperature. However, the amount of fuel in the second injection is limited by hydrocarbon (HC) emissions. As a result, the amount of fuel in the second injection is limited until the upstream catalyst (e.g., the DOC, which is responsible for THC emissions in the exhaust) is active and has reached startup.Once the upstream catalyst is active, the amount of fuel in the second injection can be increased to raise the exhaust temperature and accelerate the activation of the second downstream catalyst. This is because the first upstream catalyst, once active, reduces hydrocarbon emissions, allowing more fuel to be added to the second injection without significantly increasing exhaust emissions. In an alternative example, the duration of the first injection is based on the temperature of the first, upstream catalyst, while the duration of the second injection is set based on the temperature of the second, downstream catalyst.

[0099] In this way, the engine calibration can be shifted along a NOx-THC trade-off curve. Furthermore, the calibration can continuously optimize exhaust conditions based on the functional state of the aftertreatment catalysts. Overall, the start-up time can be reduced while maintaining controlled exhaust emissions, thereby improving compliance with emissions regulations.

[0100] An exemplary method for a power engine comprises the following: in response to a predicted peak cylinder pressure occurring later than a threshold time for a planned main fuel injection into a cylinder, splitting the planned main fuel injection into at least a first and a second injection, the first injection being advanced relative to the time of the planned main fuel injection. In the preceding example, the method may additionally or optionally further comprise setting a time and duration of both the first and second injections based on a cylinder peak pressure target. In one or all of the preceding examples, setting based on a cylinder peak pressure threshold additionally or optionally comprises setting based on an output from a cylinder pressure sensor relative to the peak pressure target.In one or all of the preceding examples, the adjustment additionally or optionally comprises advancing the timing of the first injection relative to the time of the planned main fuel injection in order to maintain a peak cylinder pressure of the first injection at or below the peak pressure target. In one or all of the preceding examples, the method additionally or optionally comprises terminating a duration of the first injection when the peak cylinder pressure of the first injection reaches the peak pressure target. In one or all of the preceding examples, the adjustment additionally or optionally comprises retarding the timing of the second injection relative to a time of the first injection in order to maintain a peak cylinder pressure of the second injection at or below the peak pressure target.In one or all of the preceding examples, the engine is additionally or optionally a turbocharged engine comprising an inlet compressor driven by an exhaust gas turbine, wherein the duration of the second injection is further set based on an inlet temperature of the turbine and wherein the duration is shortened if the turbine inlet temperature increases above a threshold temperature. In one or all of the preceding examples, additionally or optionally, the timing and duration of both the first and second injections are further set based on an estimated BSFC of the engine.In one or all of the preceding examples, the planned main fuel injection is a main injection following a pre-fuel injection, and wherein the cylinder pressure has only two peaks, each of the two peaks corresponding to one of the two injections, and wherein the two peaks are within a threshold of each other, including within 10% of each other, but both below a maximum allowable cylinder pressure determined based on engine operating conditions. In one or all of the preceding examples, additionally or optionally, the planned main fuel injection is a main injection following a pre-fuel injection. In one or all of the preceding examples, additionally or optionally, a timing and duration of the pre-fuel injection are obtained during the splitting of the planned main fuel injection.

[0101] Another exemplary method for a power engine comprises: operating a power engine with a combustion timing at a target time and a lower EGR rate until a first, upstream exhaust catalyst is at a temperature higher than a threshold temperature; and then operating the power engine with a combustion timing that is retarded relative to the target time and a higher EGR rate to accelerate the heating of a second, downstream exhaust catalyst, the retarded combustion time comprising split fuel injection.In the preceding example, operating the engine with a combustion timing retarded relative to the target timing additionally or optionally involves splitting a planned main fuel injection into at least a first and second injection, wherein the timing of the first injection is calibrated based on a user torque request, and wherein the timing of the second injection is retarded relative to the timing of the first injection, and wherein the injection quantity of the second injection is based on exhaust gas temperature. In one or all of the preceding examples, additionally or optionally, both the lower and higher EGR rates are set based on the age of the first and second catalysts, an engine temperature, and an exhaust gas temperature.In one or all of the preceding examples, additionally or optionally, a duration between the end of the first injection and the start of the second injection is set based on the temperature of the second catalyst. In one or all of the preceding examples, additionally or optionally, the engine is a turbocharged engine, and the duration of the second injection is set based on the turbine inlet temperature and / or the NOx level in the exhaust gas and / or the hydrocarbon level in the exhaust gas and / or the CO level in the exhaust gas.

[0102] Another exemplary procedure for a supercharged engine comprises the following: during a first condition, splitting a fuel injection and advancing an average combustion timing of the split fuel injection based on peak cylinder pressure and turbine inlet temperature; and during a second condition, splitting the fuel injection and retarding the average combustion timing of the split fuel injection based on catalyst temperature.In one or all of the preceding examples, the splitting of the fuel injection additionally or as appropriate includes splitting a planned main fuel injection following a pre-injection of a combustion cycle, wherein during the first condition the average combustion time of the split fuel injection is advanced relative to a combustion time of the planned main fuel injection, and wherein during the second condition the average combustion time of the split fuel injection is retarded relative to the combustion time of the planned main fuel injection.In one or all of the preceding examples, the splitting additionally or optionally during the first condition comprises splitting the fuel injection into at least one first injection which is advanced relative to the combustion timing of the planned main fuel injection, and at least one second injection which is retarded relative to the combustion timing of the planned main fuel injection, wherein a duration of the first injection and a duration between the first injection and the second injection are set based on an estimated peak cylinder pressure relative to a cylinder pressure limit, and wherein a duration of the second injection is set based on the turbine inlet temperature.In one or all of the preceding examples, the splitting additionally or optionally during the second condition comprises splitting the fuel injection into at least one first injection that is advanced or retarded relative to the combustion timing of the planned main fuel injection, and at least one second injection that is retarded relative to the combustion timing of the first injection, wherein the first injection is based on engine load and the second injection is based on catalyst temperature.In one or all of the preceding examples, the engine additionally or as appropriate comprises both a first upstream exhaust catalyst and a second downstream exhaust catalyst coupled to an engine exhaust manifold, wherein during the first condition both the first and the second exhaust catalyst have reached startup, and wherein during the second condition the amount of fuel at the second injection is limited if the first exhaust catalyst has not reached startup, and wherein the amount of fuel at the second injection is increased after the first exhaust catalyst has reached startup, with the amount being increased to cause the second exhaust catalyst to start up.

[0103] The technical benefit of splitting a main injection into multiple smaller injections is that the engine's power, torque, and fuel consumption can be improved, even under conditions where injection timing is retarded to maintain cylinder pressures within peak pressure limits. By calibrating the injections, power output and torque delivery from the fuel injection can be increased without requiring costly and complex modifications to the engine hardware, such as those otherwise necessary to increase peak ignition pressure or exhaust gas temperature. Additionally, power output and torque delivery can be increased without increasing the size of the injector nozzle, which could otherwise worsen exhaust emissions and fuel economy. Furthermore, the approach is compatible with the use of low-flow nozzles.By enabling the use of low-flow nozzles, injector limitations that restrict the amount of fuel injected per injection can be overcome. Furthermore, target engine power and torque can be achieved even when using low-energy-density fuels. Finally, the catalyst start-up time can be reduced while still controlling exhaust emissions, thus improving compliance with engine emission regulations.

[0104] It should be noted that the exemplary control and estimation routines contained herein are applicable to various power machine and / or vehicle system designs. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and can be executed by the control system, including the controller, along with the various sensors, actuators, and other power machine hardware. The specific routines described herein may incorporate one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, various actions, operations, and / or functions shown may be performed in the presented sequence or in parallel, or in some cases, omitted.Accordingly, the processing sequence is not strictly necessary to achieve the features and advantages of the embodiments described here, but merely serves to facilitate presentation and description. One or more of the actions, operations, and / or functions shown can be performed repeatedly, depending on the strategy used. Furthermore, the described actions, operations, and / or functions can graphically represent code to be programmed in the non-volatile memory of the computer-readable storage medium in the power machine control system, with the described actions being implemented by executing the instructions in a system that includes the various power machine hardware components together with the electronic control system.

[0105] It is understood that the interpretations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. The above technology is applicable, for example, to V6, I4, I6, V12, 4-cylinder boxer, and other types of power engines. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and interpretations, and other features, functions, and / or properties disclosed herein.

[0106] The following claims specifically highlight certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element or "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more of these elements, without requiring or excluding two or more of them.

Claims

[1] Method for a power machine (10) comprising the following: in response to the fact that a predicted peak cylinder pressure for a planned main fuel injection into a cylinder (30) occurs later than at a threshold time, dividing the planned main fuel injection into at least a first and a second injection, wherein the first injection is advanced relative to the time of the planned main fuel injection; and setting a time and duration for both the first and second injections based on a peak pressure target of the cylinder (30), wherein the power engine (10) is a turbocharged power engine comprising an inlet compressor driven by an exhaust gas turbine, and wherein the duration of the second injection is further set based on an inlet temperature of the turbine and wherein the duration is shortened if the turbine inlet temperature increases above a threshold temperature. [2] Method according to claim 1, wherein the adjustment based on a peak pressure limit of the cylinder (30) comprises the adjustment based on an output of a cylinder internal pressure sensor relative to the peak pressure target. [3] Method according to claim 1, wherein the adjustment comprises advancing the timing of the first injection relative to a time of the planned main fuel injection in order to maintain a peak cylinder pressure of the first injection at or below the peak pressure target. [4] Method according to claim 3, wherein the duration of the first injection is terminated when the peak cylinder pressure of the first injection reaches the peak pressure target. [5] Method according to claim 3, wherein the adjustment further comprises delaying the timing of the second injection relative to a timing of the first injection in order to maintain a peak cylinder pressure of the second injection at or below the peak pressure target. [6] Method according to claim 1, wherein the timing and duration of both the first and second injections are further adjusted based on an estimated brake-specific fuel consumption (BSFC) of the engine (10). [7] Method according to claim 1, wherein the planned main fuel injection is a main injection following a pre-fuel injection, and wherein the cylinder pressure has only two peaks, each peak corresponding to one of the two main injections, and wherein the two peaks are within a threshold of each other, including within 10% of each other, but both below a maximum allowable cylinder pressure determined on the basis of engine operating conditions. [8] Method according to claim 7, wherein a time and duration of the pre-fuel injection are obtained during the splitting of the planned main fuel injection. [9] Method for a power machine (10) comprising the following: Operating a power engine (10) with a combustion timing at a target time and a lower EGR rate until the temperature of a first, upstream exhaust catalyst is higher than a threshold temperature; and then, operating the engine with a combustion timing retarded relative to the target timing and a higher EGR rate to accelerate the warm-up of a second, downstream exhaust catalyst, wherein the retarded combustion timing includes split fuel injection. [10] Method according to claim 9, wherein operating the engine (10) with a combustion timing delayed relative to the target timing comprises dividing a planned main fuel injection into at least a first and second injection, wherein a timing of the first injection is calibrated based on a user torque request and wherein a timing of the second injection is delayed relative to the timing of the first injection and wherein an injection quantity of the second injection is based on an exhaust gas temperature. [11] Method according to claim 10, wherein both the lower EGR rate and the higher EGR rate are set based on an age of the first and second catalyst, an engine temperature and an exhaust gas temperature. [12] Method according to claim 10, wherein a duration between an end of the first injection and a start of the second injection is set based on a temperature of the second catalyst. [13] Method according to claim 10, wherein the engine (10) is a turbocharged engine, and wherein the duration of the second injection is set based on a turbine inlet temperature and / or NOx level in the exhaust gas and / or hydrocarbon level in the exhaust and / or CO level in the exhaust gas. [14] Method for a supercharged power engine (10) comprising the following: during a first condition, splitting a fuel injection and advancing an average combustion timing of the split fuel injection based on a peak cylinder pressure and turbine inlet temperature; and during a second condition, splitting the fuel injection and retarding the average combustion timing of the split fuel injection based on a catalyst temperature. [15] Method according to claim 14, wherein the splitting of the fuel injection comprises splitting a planned main fuel injection following a pre-injection of a combustion cycle, wherein during the first condition the average combustion time of the split fuel injection is advanced relative to a combustion time of the planned main fuel injection, and wherein during the second condition the average combustion time of the split fuel injection is retarded relative to the combustion time of the planned main fuel injection. [16] Method according to claim 15, wherein the splitting during the first condition comprises splitting the fuel injection into at least a first injection which is advanced relative to the combustion timing of the planned main fuel injection, and at least a second injection which is retarded relative to the combustion timing of the planned main fuel injection, wherein a duration of the first injection and a duration between the first injection and the second injection are set based on an estimated peak cylinder pressure relative to a cylinder pressure limit, and wherein a duration of the second injection is set based on the turbine inlet temperature. [17] Method according to claim 15, wherein the splitting during the second condition comprises splitting the fuel injection into at least a first injection which is advanced or retarded relative to the combustion timing of the planned main fuel injection, and at least a second injection which is retarded relative to the combustion timing of the first injection, wherein the first injection is based on an engine load and the second injection is based on a catalyst temperature. [18] Method according to claim 17, wherein the engine comprises both a first upstream exhaust catalyst and a second downstream exhaust catalyst coupled to an engine exhaust manifold, and wherein during the first condition both the first and the second exhaust catalyst have reached startup, and wherein during the second condition the amount of fuel at the second injection is limited if the first exhaust catalyst has not reached startup, and wherein the amount of fuel at the second injection is increased after the first exhaust catalyst has reached startup, the amount being increased to cause the second exhaust catalyst to start up.

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