Diesel engine particulate filter regeneration system and method

Abstract

The present application relates to a diesel engine particulate filter regeneration system and method. The present application describes a method and system for supplying post-injection fuel to a two-stroke diesel engine. In one example, in response to the amount of internal residual combustion products in the cylinder, the post-injection fuel timing is adjusted so that less post-injection fuel can be trapped in the cylinder in subsequent cycles of the cylinder. In response to the internal residual in the cylinder, the start of the post-injection fuel timing and the amount of post-injection fuel can be adjusted.

Description

Background Art

[0001] Diesel engines may include a particulate filter in their exhaust system to capture carbonaceous soot that may be produced as a byproduct of combustion. Over a period of time, the particulate filter may fill with soot such that it may provide a more significant restriction to the exhaust. The particulate filter may be regenerated by increasing the exhaust temperature and supplying an oxygen-rich exhaust mixture to the particulate filter so that the soot held within the particulate filter is burned, thereby regenerating the particulate filter.

[0002] One way to increase the exhaust temperature is to supply fuel that does not participate in the combustion in the engine cylinder to the oxidation catalyst. The fuel burns in the oxidation catalyst to increase the exhaust temperature, and then the exhaust temperature increases the particulate filter temperature so that the soot in the particulate filter can be burned, thereby regenerating the particulate filter. The fuel can be supplied to the oxidation catalyst by injecting a post-injection fuel pulse into the cylinder so that the fuel can be ejected from the cylinder during the exhaust stroke of the cylinder. That is, when the exhaust valve of the cylinder opens, the expanded combustion gas leaves the cylinder with the fuel that does not participate in the combustion. Because the intake and exhaust valves overlap very little, and because the exhaust and fuel flow back into the cylinder via the exhaust valve closure is reduced, most of the fuel that has been injected into the cylinder leaves the cylinder. However, a two-stroke diesel engine may not include an intake valve or an exhaust valve to prevent the exhaust and fuel from flowing back into the cylinder when providing a post-injection fuel pulse to promote the regeneration of the particulate filter. Further, the exhaust and intake ports of the cylinders of the two-stroke diesel engine may be opened simultaneously over a long crankshaft angle duration, so that the exhaust and post-injection fuel may be sucked back into the cylinder. Therefore, the post-injected fuel may participate in combustion within the cylinder during a subsequent cylinder cycle, which may be undesirable. It is therefore desirable to provide a method of regenerating a particulate filter of a two-stroke diesel engine such that a majority of the post-injected fuel leaves the engine cylinder and reaches an oxidation catalyst to facilitate particulate filter regeneration. Summary of the invention

[0003] The inventors herein have recognized the above challenges and have developed a particulate filter regeneration method that includes: receiving sensor data to a controller; and adjusting, via the controller, a postinjection fuel pulse width provided to a second fuel injector of the cylinder in response to an internal residual in the cylinder estimated based on the sensor data.

[0004] By adjusting the post-injection fuel pulse width in response to the internal residual amount, a particulate filter can be regenerated via injecting fuel into a cylinder of a two-stroke diesel engine. Further, the present method can reduce or help ensure that less fuel injected during one cylinder cycle remains in the cylinder until a subsequent cylinder cycle. Reducing the amount of fuel retained from one cylinder cycle to the next cylinder cycle can reduce the likelihood of fuel auto-ignition. Further, engine torque production can be made more consistent.

[0005] The present description may provide several advantages. Specifically, the method may improve particulate filter regeneration of a two-stroke diesel engine. Further, the method may improve engine torque control by improving control of the amount of fuel combusted in a cylinder cycle. Additionally, the method may provide improved control of the amount of post-injection fuel injected into the exhaust system for particulate filter regeneration.

[0006] The above advantages and other advantages and features of the present specification will become apparent in the following detailed description when considered alone or in conjunction with the accompanying drawings.

[0007] It should be understood that the above summary is provided to introduce a selection of concepts further described in the detailed description in a simplified form. It is not meant to establish key or essential features of the claimed subject matter, the scope of which is solely defined by the claims attached to the detailed description. Furthermore, the claimed subject matter is not limited to embodiments that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A schematic diagram showing an engine;

[0009] Figure 2 An example particulate filter regeneration sequence is shown;

[0010] Figure 3 showing post fuel injection timing relative to piston position; and

[0011] Figure 4 is an example method for regenerating a particulate filter. DETAILED DESCRIPTION

[0012] The present description relates to regenerating a particulate filter of a two-stroke diesel engine. Figure 1 An example of a supercharged two-stroke diesel engine is shown. Figure 1 The diesel engine in the embodiment is an opposed piston engine, but the method described herein may also be applied to a two-stroke engine comprising a single piston in each engine cylinder. Figure 2 An example particulate filter regeneration sequence is shown. Figure 3The fuel injection timing of a two-stroke diesel engine is shown in FIG. Figure 4 A method for regenerating a particulate filter is shown in FIG.

[0013] Reference Figure 1 Opposed-piston internal combustion engine 10 comprising a plurality of cylinders, one of which is activated at Figure 1 The controller 12 receives the Figure 1 The signals of various sensors are used Figure 1 Various actuators are controlled to adjust engine operation based on received signals and instructions stored in the controller's memory.

[0014] Engine 10 includes cylinder 30 and cylinder wall 32, wherein intake piston 36a and exhaust piston 36b are positioned in cylinder wall 32 and connected to crankshaft 40a and crankshaft 40b respectively. Crankshaft 40a and crankshaft 40b may be coupled together via a belt, chain or gears. Crankshaft 40a and crankshaft 40b may be rotated by motor 77 (e.g., a starter motor) to start rotating engine 10. Cylinder 30 is shown to be in communication with intake manifold 44 and exhaust manifold 48 via intake passages 44a and 44b and exhaust passages 48a and 48b.

[0015] The first fuel injector 69 and the second fuel injector 68 are shown as being positioned in the cylinder wall 32, and they can inject fuel directly into the cylinder 30, which is known to those skilled in the art as direct injection. The fuel is delivered to the first fuel injector 69 and the second fuel injector 68 by a fuel system including a fuel tank 95, a fuel pump 91, a fuel pump control valve 93, and a fuel rail (not shown). The fuel pressure delivered by the fuel system can be adjusted by changing the position valve that regulates the flow to the fuel pump (not shown). In addition, the metering valve can be located in or near the fuel rail for closed-loop fuel control. The pump metering valve can also regulate the fuel flow to the fuel pump, thereby reducing the fuel pumped to the high-pressure fuel pump. The first fuel injector is positioned so that its longitudinal axis 69d and the fuel spray cone 69c are at an obtuse angle 69b to the portion of the cylinder wall 32 located between the fuel injector 69 and the exhaust piston 36b. Therefore, the fuel spray cone 69c points in the direction of the intake piston 36a and away from the exhaust piston 36b. The second fuel injector 68 can be positioned so that its nozzle 68a is directed toward the exhaust passage 48a. When injecting fuel via the second fuel injector 68, the second fuel injector 68 can deliver the fuel in the fuel spray cone 68c to directly impinge on the exhaust passage 48a. Alternatively, the second fuel injector can be positioned so that its longitudinal axis 69b and the fuel spray cone 68c are at an acute angle 68d to the portion of the cylinder wall 32 between the fuel injector 68 and the exhaust piston 36b. Therefore, the fuel spray cone 68c points in the direction of the exhaust piston 36b and away from the intake piston 36a. In this way, the nozzle 69a can direct the fuel spray toward the intake piston 36a, and the nozzle 68a can direct the fuel spray toward the exhaust piston 36b.

[0016] Intake manifold 44 is shown communicating with optional electronic throttle 62, which adjusts the position of throttle plate 64 to control air flow from intake boost chamber 46. Supercharger compressor 162 is mechanically driven and draws air from downstream of turbocharger compressor 135. Turbocharger compressor 135 draws air from intake passage 42. Supercharger compressor 162 supplies air to boost chamber 46. Exhaust gas rotates turbocharger variable geometry turbine 137, which is coupled to turbocharger compressor 135 via shaft 136. Supercharger compressor 162 is mechanically driven via crankshaft 40b via shaft 161 and gearbox 163, which may be coupled to crankshaft 40b via mechanism 164 (e.g., gears, chain, or belt). The supercharger gearbox 163 includes a plurality of gear ratios for varying the speed of the supercharger compressor 162 relative to the speed of the crankshaft 40b. The supercharger compressor speed can be adjusted by selecting and engaging a gear 163a of the gearbox 163. In one example, a given engine crankshaft speed can rotate the supercharger compressor 162 at a first speed and a second speed by switching between a first gear ratio and a second gear ratio in the gearbox 163.

[0017] The supercharger compressor bypass valve 158 may be selectively opened to reduce the air pressure in the boost chamber 46 and return air and exhaust gas recirculation (EGR) to the upstream of the supercharger compressor 162. In some examples, the charge air cooler 156 may be disposed downstream of the supercharger compressor 162 to cool the air charge entering the cylinder 30. The charge air cooler bypass valve 157 may be selectively opened to bypass the charge air cooler 156. The position of the vane actuator 137a may be adjusted via the controller 12 to increase or decrease the rotation speed of the turbine 137. In an alternative example, the wastegate 137b may replace the vane actuator 137a, or the wastegate 137b may be used in addition to the vane actuator 137a. The vane actuator 137a adjusts the position of the variable geometry turbine vanes. When the vanes are in the open position, exhaust gas may pass through the turbine 137, supplying little energy to rotate the turbine 137. When the vanes are in the closed position, exhaust gas may pass through turbine 137 and exert increased force on turbine 137. Alternatively, a wastegate 137b or bypass valve allows exhaust gas to flow around turbine 137 in order to reduce the energy supplied to the turbine.

[0018] In an alternate example, supercharger compressor 162 may be positioned upstream of turbocharger compressor 135. Further, an air charge cooler (not shown) may be positioned downstream of where EGR passage 82 joins intake 43 between supercharger compressor 162 and turbocharger compressor 135. The air charge cooler would eliminate the need for an EGR cooler.

[0019] Exhaust gas may be recirculated to cylinder 30 via EGR system 81. The EGR system includes an optional EGR cooler 85, an EGR valve 80, an EGR passage 82, an EGR cooler bypass passage 84, and a cooled EGR passage 83. Exhaust gas may flow from exhaust manifold 48 to engine intake 43 between supercharger compressor 162 and turbocharger compressor 135. When the pressure in exhaust manifold 48 is greater than the pressure between turbocharger compressor 135 and supercharger compressor 162, EGR may flow to the engine intake. EGR may flow through EGR cooler 85 to reduce engine exhaust temperature. When the engine exhaust temperature is low, EGR may bypass EGR cooler 85.

[0020] After intake piston 36a covers intake passages 44a and 44b and exhaust piston 36b covers exhaust passages 48a and 48b, fuel may be injected into cylinder 30 as piston 36a and piston 36b approach each other. The fuel may then combust with the air in cylinder 30 as piston 36 approaches top dead center in a compression stroke. The fuel and air ignite via compression ignition. In some examples, a universal exhaust gas oxygen (UEGO) sensor 126 may be coupled to exhaust manifold 48 upstream of emissions device 70. In other examples, the UEGO sensor may be located downstream of one or more exhaust aftertreatment devices. Further, in some examples, the UEGO sensor may be replaced by a NOx sensor having both NOx and oxygen sensing elements.

[0021] Since engine 10 is a compression ignition engine and does not include a cylinder head, engine 10 does not include glow plugs or spark plugs. Further, engine 10 does not include poppet valves to regulate the flow of air and exhaust gas into and out of cylinder 30.

[0022] Exhaust system 131 takes exhaust away from engine 10 and processes the exhaust. Exhaust valve 140 is shown positioned in exhaust passage 49 downstream of turbine 137a and upstream of exhaust device 70. Alternatively, exhaust valve 140 may be positioned downstream of exhaust device 70. Exhaust valve 140 may be opened and closed to control pressure in exhaust manifold 48. Closing exhaust valve 140 limits flow through exhaust valve 140 and may increase pressure in exhaust manifold 48. Opening exhaust valve 140 may improve flow through exhaust valve 140 and reduce pressure in exhaust manifold 48.

[0023] In one example, the emission device 70 may include an oxidation catalyst 72 and a particulate filter 73. In another example, multiple emission control devices may be used, each with multiple blocks. In one example, the emission device 70 may include an oxidation catalyst. In other examples, the emission device may include a lean NOx trap or a selective catalytic reduction (SCR) device and / or a diesel particulate filter (DPF). The upstream temperature sensor 79 and the downstream temperature sensor 81 provide exhaust temperature measurements for determining changes in exhaust temperature on both sides of the emission device 70. The differential pressure sensor 71 provides a change in the differential pressure on both sides of the emission device 70, which can serve as a basis for determining whether the emission device 70 needs to be regenerated.

[0024] The controller 12 Figure 1 1 is shown as a conventional microcomputer, including: a microprocessor unit 102, input / output ports 104, read-only memory (eg, non-volatile memory) 106, random access memory 108, persistent memory 110, and a conventional data bus. In addition to those signals previously discussed, controller 12 is shown receiving various signals from sensors coupled to engine 10, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling jacket 114; position sensor 134 coupled to accelerator pedal 130 for sensing accelerator position adjusted by a person's foot 132; measurement of engine manifold pressure (MAP) from pressure sensor 121 coupled to intake manifold 44; boost pressure from pressure sensor 122; exhaust oxygen concentration from oxygen sensor 126; engine position sensor from Hall effect sensor 118 sensing position of crankshaft 40b; measurement of air mass entering the engine from sensor 120 (e.g., a hot wire air flow meter); and measurement of throttle position from sensor 58. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, engine position sensor 118 produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined.

[0025] During operation, each cylinder within the engine 10 typically undergoes a two-stroke cycle: the cycle includes a first stroke, in which the intake piston 36a moves toward the exhaust piston 36b and the exhaust piston 36b moves toward the intake piston 36a. In the second stroke, the intake piston 36a moves away from the exhaust piston 36b and the exhaust piston 36b moves away from the intake piston 36a. The intake piston 36a controls the flow through the intake passages 44a and 44b. The exhaust piston 36b controls the flow through the exhaust passages 48a and 48b. In this example, the exhaust piston 36b leads the intake piston 36a by reaching the top dead center position (e.g., the maximum distance of the exhaust piston 36b from the crankshaft 40b) several crankshaft degrees (e.g., depending on the configuration, the difference can be between 0 crankshaft degrees and 20 crankshaft degrees) before the intake piston 36a reaches its top dead center position (e.g., the maximum distance of the exhaust piston 36b from the crankshaft 40b). Therefore, the exhaust piston motion deviates from the intake piston motion by several crankshaft degrees.

[0026] Typically, during the first stroke, the intake piston 36a and the exhaust piston 36b move toward each other to compress the air that has entered the cylinder 30. The stroke begins at the bottom dead center (BDC) of the intake piston 36a (the intake piston 36a is at its closest distance to the crankshaft 40a), and ends at the top dead center of the intake piston 36a (the intake piston 36a is at its farthest distance from the crankshaft 40a). As previously described, the exhaust piston 36b leads the intake piston 36a by several degrees, so that when the intake piston is at BDC, the exhaust piston has already traveled toward its TDC position. Further, the exhaust piston 36b reaches its TDC position just before the intake piston 36a reaches its TDC position. When the intake piston 36a reaches its TDC position, the exhaust piston 36b is just behind its TDC position. When the intake piston 36a and the exhaust piston 36b are close to their respective TDC positions, the cylinder volume is minimum. As the intake piston 36a and the exhaust piston 36b advance toward their respective TDC positions, air and fuel are compressed in the cylinder 30. As the intake piston 36a and the exhaust piston 36b approach their respective BDC positions, the intake passages 44a and 44b open and pressurized air flows into the cylinder 30. As the intake piston 36a and the exhaust piston 36b approach BDC, the exhaust passages 48a and 48b also open. The supercharger compressor 162 and the turbocharger compressor 135 provide pressurized air to the intake manifold 44, and the pressurized air can flow into the cylinder 30 when the intake passages 44a and 44b are opened. As the intake piston 36a and the exhaust piston 36b move toward their respective TDC positions, the intake passages 44a and 44b close to prevent additional air from entering the cylinder 36 and to prevent backflow out of the cylinder 36. After the intake passages 44a and 44b are closed, the intake piston 36a and the exhaust piston 36b continue to approach their respective TDC positions. After the intake passages 44a and 44b are closed, the crankshafts 40a and 40b rotate a predetermined angle, and then the exhaust passages 48a and 48b are closed. Therefore, during the entire intake period, the exhaust passages 44a and 44b are open. Fuel is injected into the cylinder 30 after the exhaust passages 44a and 44b are closed, and then the fuel and air mixture is ignited when the intake piston 36a and the exhaust piston 36b are close to their respective TDC positions. The fuel and air mixture is ignited by compression ignition rather than by energy from a spark plug or a glow plug. Fuel can be injected into the cylinder 30 via multiple injections (including pilot injection, main injection, and post injection).

[0027] Typically, during the second stroke, after combustion occurs in the cylinder 30, the intake piston 36a and the exhaust piston 36b move away from each other. The second stroke starts at the TDC of the intake piston 36a and ends at the BDC of the intake piston 36a. The intake piston 36a and the exhaust piston 36b approach their respective BDC positions when they are close to the position where the volume of the cylinder 30 is the largest. The gas expanding in the cylinder 30 pushes the intake piston 36a and the exhaust piston 36b away from each other toward their respective BDC positions. When the exhaust piston 36b moves toward its BDC, the exhaust piston 36b passes through the exhaust passages 48a and 48b. When the top of the exhaust piston 36d passes through the exhaust passages 48a and 48b and the exhaust piston 36b moves toward the crankshaft 40b, the exhaust passages 48a and 48b are exposed (uncovered). After the exhaust piston 36b passes through the exhaust passages 48a and 48b and moves toward the bottom dead center at the same time, the exhaust gas leaves the cylinder 30. Intake piston 36a and exhaust piston 36b further advance toward their respective bottom dead center positions, and after a predetermined actual total crankshaft degree, intake piston 36a exposes intake passages 44a and 44b. When the top of intake piston 36c passes through intake passages 44a and 44b and intake piston 36a advances toward crankshaft 40a, intake passages 44a and 44b are exposed. When intake passages 44a and 44b are exposed, fresh air enters cylinder 30 via intake passages 44a and 44b. Exhaust passages 48a and 48b are opened or exposed during the entire time that intake passages 44a and 44b are opened or exposed. Intake piston 36a and exhaust piston 36b continue to advance toward their respective BDC positions. After the intake piston reaches BDC, the cylinder cycle repeats.

[0028] Thus, the engine cycle includes two strokes, and the engine cycle is one engine revolution. The other engine cylinders operate in a similar manner, but these other cylinders may burn air and fuel out of phase with the cylinders shown. For example, the top dead center compression stroke of one engine cylinder may be at zero crankshaft degrees, while the top dead center of another cylinder may be at one hundred and eighty crankshaft degrees.

[0029] therefore, Figure 1The system provides an engine system, comprising: an opposed piston diesel engine, comprising a cylinder having a first fuel injector and a second fuel injector; a supercharger coupled to the opposed piston diesel engine, the supercharger having a plurality of gear ratios; a turbocharger coupled to the opposed piston diesel engine; and a controller, comprising executable instructions stored in a non-volatile memory to provide a late post injection amount during a cylinder cycle only via the second fuel injector, and to provide a main fuel injection amount during a cylinder cycle only via the first fuel injector. The engine system further comprises additional instructions to adjust the post injection amount in response to an internal residual amount in the cylinder. The engine system comprises advancing the start of the post injection in response to an increase in the internal residual amount. The engine system comprises advancing the end of the post injection in response to an increase in the internal residual amount. The engine system comprises delaying the start of the post injection in response to a decrease in the internal residual amount. The engine system further comprises additional instructions to adjust internal exhaust gas recirculation in response to engine speed and load.

[0030] Reference now Figure 2 , which shows an example particulate filter regeneration sequence according to method 400 . Figure 2 The particulate filter regeneration sequence can be used for Figure 1 The engine and system shown in FIG. 1 . The vertical lines at time t0 to time t3 represent times of interest in the sequence. The graphs are aligned in time and occur simultaneously. In this example particulate filter regeneration sequence, the post fuel injection amount is adjusted in response to internal residuals within the engine cylinder. Internal residuals are byproducts of combustion (e.g., exhaust CO, HC, NOx) that may remain in the cylinder from one combustion event (e.g., compression ignition and combustion of air and fuel in the cylinder) to the next subsequent combustion event in the cylinder.

[0031] from Figure 2 The first graph from the top is a graph of a diesel particulate filter (DPF) regeneration request versus time. Trace 201 represents the diesel particulate filter regeneration state. The vertical axis represents the diesel particulate filter regeneration state, and when trace 201 is at a high level near the vertical axis arrow, the diesel particulate filter regeneration request is asserted. When trace 201 is at a lower level near the horizontal axis, the diesel particulate filter regeneration request is not asserted. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0032] from Figure 2The second graph from the top is a graph of the post fuel injection amount of fuel injected into the cylinder versus time. Trace 202 represents the post fuel injection amount. The vertical axis represents the post fuel injection amount, and the post fuel injection amount increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0033] from Figure 2 The third graph from the top is a graph of internal exhaust gas recirculation (IEGR) amount versus time. Trace 204 represents the IEGR amount. The vertical axis represents the IEGR amount, and the IEGR amount increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0034] from Figure 2 The fourth graph from the top is a graph of engine speed versus time. Trace 205 represents engine speed. The vertical axis represents engine speed, and engine speed increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0035] from Figure 2 The fifth graph from the top is a graph of engine load versus time. Trace 207 represents engine load. The vertical axis represents engine load, and engine load increases in the direction of the vertical axis. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0036] from Figure 2 The sixth graph from the top is a graph of the amount of soot accumulated in the particulate filter versus time. The vertical axis represents the amount of soot accumulated in the particulate filter. Trace 206 represents the amount of particulate matter accumulated in the particulate filter. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0037] At time t0, the engine is operating at a medium speed and load and burning air and fuel. DPF regeneration is not required, but the soot stored in the DPF is at a high level. The IEGR amount is at a medium level, and the post fuel injection amount is zero.

[0038] At time t1, in response to the amount of accumulated soot and vehicle operating conditions, a DPF regeneration request is asserted. In response to the particulate filter regeneration request being asserted, the post fuel injection amount begins to increase. In response to the increase in engine load, the IEGR amount decreases. In response to the increase in engine load, the engine speed begins to increase. The engine load may increase based on a higher driver demand torque (not shown). The amount of soot accumulated on the particulate filter begins to decrease.

[0039] Between time t1 and time t2, the engine speed continues to increase and the engine load also increases. In response to the engine speed and load, the IEGR amount is reduced. In response to the reduced IEGR amount, the post fuel injection amount is increased. Because the reduced IEGR amount may indicate that less post fuel injection fuel may remain in the cylinder until the next cylinder cycle, the post fuel injection amount may be increased in response to the reduced IEGR amount. Therefore, an increased amount of fuel may be post injected into the cylinder and sprayed into the engine exhaust system so as not to remain in the cylinder during the next cycle of the cylinder. The post injected fuel may then increase the exhaust temperature to regenerate the particulate filter. As the engine exhaust temperature increases, the particulate filter soot amount decreases (not shown).

[0040] At time t2, the engine load decreases in response to the reduced driver demand torque (not shown). In response to the reduction in engine load, the engine speed begins to decrease. The IEGR amount increases in response to the reduced engine load. The post-injection fuel amount decreases in response to the increase in IEGR amount so that less fuel can be carried in the cylinder until the next cylinder cycle. The soot amount continues to decrease and the particulate filter regeneration request remains in effect.

[0041] Between time t2 and time t3, the engine load increases after it decreases, and the engine speed begins to increase. In response to the increase in engine load and the increase in engine speed, the IEGR amount increases. The post-fuel injection fuel amount increases in response to the decrease in IEGR, and the soot stored in the particulate filter continues to decrease. The particulate filter regeneration request is still in effect.

[0042] At time t3, soot stored in the particulate filter is less than a threshold, so the particulate filter regeneration request is withdrawn. The post fuel injection fuel amount is adjusted to zero, and the IEGR amount is based on engine speed and load. The engine speed and load are responsive to the driver demand torque (not shown).

[0043] In this way, the post-injection fuel amount may be adjusted in response to the IEGR amount. Further, the start of injection timing and the end of injection timing of the post-injection fuel may also be adjusted in response to the IEGR amount. By adjusting the post-injection fuel amount in response to the IEGR amount, the amount of fuel supplied to the oxidation catalyst may be adjusted while controlling the amount of post-injection fuel that may remain in the cylinder during the next cylinder cycle. Thus, particulate filter regeneration may be promoted by increasing the temperature of the gas leaving the oxidation catalyst while reducing the likelihood of igniting the post-injection fuel in the cylinder during a subsequent cycle of the cylinder.

[0044] Reference now Figure 3 , which shows an example fuel injection sequence according to method 400. The example fuel injection sequence occurs during particulate filter regeneration. Figure 3The fuel injection sequence can be used for Figure 1 The engine and system shown in FIG. 10 and FIG. 15. The vertical line at time t10 to time t15 represents the time of interest in the sequence. The graphs are aligned in time and occur simultaneously. In this example, the post fuel injection is performed by a second fuel injector having a nozzle pointed directly into the exhaust passage.

[0045] from Figure 3 The first graph from the top is via a first fuel injector (eg, Figure 1 69) to a cylinder. A fuel pulse is delivered during regeneration of a particulate filter. Trace 302 represents a fuel injection pulse from a first fuel injector. As the pulse width increases, the amount of fuel injected into the cylinder increases, and as the pulse width decreases, the amount of fuel injected into the cylinder decreases. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0046] from Figure 3 The second graph from the top is via a second fuel injector (e.g., Figure 1 FIG. 3 is a graph of a fuel injection pulse delivered to a cylinder by a second fuel injector 68 of FIG. 3. A fuel pulse is delivered during regeneration of a particulate filter. Trace 304 represents a fuel injection pulse from a second fuel injector. As the pulse width increases, the amount of fuel injected into the cylinder increases, and as the pulse width decreases, the amount of fuel injected into the cylinder decreases. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. The nozzle of the second fuel injector is pointed directly at the exhaust passage, so that the fuel spray cone from the second fuel injector impinges directly on the exhaust passage.

[0047] from Figure 3 The third graph from the top is a graph of cylinder intake port opening and closing versus time. Trace 303 represents intake port state. The vertical axis represents cylinder intake port state, and when trace 303 is at a higher level near the vertical axis arrow, the cylinder intake port is open. When trace 303 is at a lower level near the horizontal axis, the intake port is closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0048] from Figure 3 The fourth graph from the top is a graph of cylinder exhaust port state versus time. Trace 304 represents exhaust port state. The vertical axis represents exhaust port state, and when trace 304 is at a higher level near the vertical axis arrow, the exhaust port is open. When trace 304 is near the horizontal axis, the exhaust port is closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0049] from Figure 3The fifth graph from the top is a graph of piston position versus time. Trace 305 represents the piston position of intake piston 36a. When trace 305 is at the level of the vertical axis marked TDC, the piston is at its top dead center position. When trace 305 is at the level of the vertical axis marked BDC, the piston is at its bottom dead center position. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0050] At time t10, the piston is at BDC and the intake and exhaust ports are open. No fuel is injected via the first fuel injector and the second fuel injector. The engine rotates, and at time t11, the exhaust port is closed, while the intake port remains open. No fuel is injected via the first fuel injector and the second fuel injector. The engine continues to rotate, and then the intake port is closed at time t12. No fuel is still injected at time t12, and as time increases, the engine continues to rotate. The exhaust port remains closed. As the piston approaches TDC, a pilot fuel injection is provided at time t13. In this example, a pilot fuel injection is provided via the first fuel injector and the second fuel injector, but in some examples, a pilot fuel injection may be provided only by the first fuel injector. Two pilot fuel injections are provided. Then at time t14, a main fuel injection pulse is provided via the first fuel injector. However, in other examples, a main fuel injection pulse may also be provided via the second injector. The engine compresses the injected fuel and the air-fuel mixture ignites.

[0051] At time t15, post-fuel injection is provided only via the second fuel injector so that a greater percentage of the post-injected fuel can be ejected from the cylinder so that it can reach the oxidation catalyst to promote particulate filter regeneration. In this example, a single post-fuel injection fuel pulse is provided, but additional fuel pulses can be provided. When the exhaust port opens at time t15, the post-fuel injection fuel is injected with a delay so that a higher percentage of the injected fuel flows out of the cylinder. However, the post-fuel injection can be provided after the main injection and before the exhaust port opens. Further, if the post-fuel injection time is earlier (e.g., close to the end of ignition), the first fuel injector can also provide the post-fuel injection. The post-fuel injection is completed before the intake port opens at time t16. The cylinder cycle is repeated shortly after time t16.

[0052] In this way, fuel may be post-injected during a cylinder cycle to facilitate particulate filter regeneration. The post fuel injection pulse width is timed to increase the flow of post injected fuel to the oxidation catalyst so that less fuel may remain in the cylinder during the next cylinder cycle.

[0053] Reference now Figure 4 , which shows a method for regenerating a particulate filter positioned in the exhaust system downstream of a two-stroke diesel engine. Figure 4 The method can be stored as executable instructions in a file such as Figure 1 The non-transitory memory in the system shown. Figure 4 The method can be combined with Figure 1 in the system and can be used with Figure 1 Further, Figure 4 At least a portion of the method may be incorporated as executable instructions stored in a non-volatile memory, while other portions of the method may be performed via a controller that transforms operating states of devices and actuators in the physical world. According to the method described below, the controller may employ an engine actuator of an engine system to adjust engine operation.

[0054] At 402, method 400 determines vehicle operating conditions. Vehicle operating conditions may include, but are not limited to, the amount of soot stored in the particulate filter, the amount of internal residual, the particulate filter temperature, the engine speed, the engine load, and the driver's demand torque. Figure 1 The vehicle operating conditions are determined or inferred from sensor data received by the controller 12 shown in . For example, the internal residual can be estimated in response to the engine speed, engine load, intake manifold pressure, and exhaust valve position. The engine speed, engine load, intake manifold pressure, and exhaust valve position can refer to one or more tables and functions including empirically determined internal residual values. The table or function outputs the cylinder residual estimate. The driver demand torque can be determined from the accelerator pedal position and the vehicle speed, which refers to a table or function that maintains the empirically determined driver demand torque value. The function or table outputs the driver demand torque. Method 400 proceeds to 404.

[0055] At 404, method 400 operates the engine according to the operating conditions determined at 402. The fuel injection timing of the pilot injection and the main injection is based on the vehicle operating conditions determined at 402. The pilot fuel injection is a short duration fuel injection that can be less than 4 mg. The pilot fuel injection starts and ends before the top dead center compression stroke in the cylinder cycle in which the injection is performed. The pilot fuel injection can reduce engine combustion noise, control peak cylinder pressure, and adjust heat release in the cylinder. The main fuel injection is the injection of the maximum amount of fuel injected during the cylinder cycle. The main fuel injection can be in the range of 3 mg per cylinder cycle to 100 mg per cylinder cycle. The pilot fuel injection is performed before the main fuel injection. The first fuel injector can supply the pilot fuel injection, the main fuel injection, and the early post-fuel injection. The second fuel injector can provide the pilot fuel injection, the main fuel injection, and the early and late post-injections. The boost pressure, throttle position, exhaust throttle position, the timing of the pilot fuel injection and the main fuel injection, and the external EGR adjustment can be based on the engine speed and load. Method 400 proceeds to 406 .

[0056] At 406, method 400 judges whether particulate filter (PF) regeneration is desired. Method 400 may judge that particulate filter regeneration is desired in response to the amount of soot stored in the particulate filter exceeding a threshold amount and the engine load being greater than a threshold load. If method 400 judges that particulate filter regeneration is desired, the answer is yes and method 400 proceeds to 408. Otherwise, the answer is no and method 400 proceeds to 440.

[0057] At 440 , method 400 stops PF regeneration by stopping injection of post-injection fuel. Further, method 400 may adjust engine boost pressure and exhaust throttle position to stop particulate filter regeneration. Method 400 proceeds to exit.

[0058] At 408 , method 400 begins increasing PF temperature. Method 400 may increase boost pressure and at least partially close the exhaust throttle to increase exhaust temperature to begin PF regeneration. Method 400 proceeds to 410 .

[0059] At 410, method 400 estimates internal residuals within the engine cylinder. Internal residuals are residuals (HC, NOx, and CO) that remain in the cylinder from a first combustion event in the cylinder (e.g., combustion of air and fuel in the cylinder) to a next second combustion event. Internal residuals leave the cylinder during the period from the first combustion event to the next or second combustion event, except that the internal residuals may include residuals that leave the exhaust passage and are drawn back into the cylinder from the exhaust passage prior to the second combustion event. The internal residuals do not include residuals that leave the exhaust passage and re-enter the cylinder via the intake passage.

[0060] In one example, method 400 estimates an amount of internal exhaust gas residual (IEGR) in a cylinder. In one example, the internal residual can be estimated by referencing one or more tables or functions via engine speed, engine load, boost pressure, and exhaust throttle position. The table or function maintains empirically determined estimates of the internal residual. The table or function outputs the internal residual. Method 400 proceeds to 412.

[0061] At 412, method 400 determines the post fuel injection amount, the start of the post injection pulse width, and the end of the post injection pulse width. Early post fuel injection may occur after the top dead center compression stroke and ten crankshaft degrees after the main fuel injection. Early post fuel injection may be in the range of 1 mg to 10 mg. Late post injection is a fuel injection performed after the combustion of the main fuel injection pulse is complete and before the exhaust port of the cylinder receiving fuel during the cycle of the cylinder is closed. Early post injection and late post injection may be beneficial for regenerating an emission control device (e.g., PF) in the exhaust system of the engine.

[0062] In one example, method 400 refers to one or more functions and / or tables, which include a post-fuel injection fuel amount, a start of a post-fuel injection pulse width, and an end of a fuel injection pulse width. The values ​​in the table are determined empirically and stored in the controller memory. The table and / or function can be referenced via the desired PF temperature, engine speed, engine load, and IEGR amount. When the IEGR amount decreases, the table and / or function increases the post-fuel injection amount. Because a larger fraction of the post-injected fuel can leave the cylinder when the IEGR amount is small, the post-fuel injection amount can be increased when the IEGR amount decreases. When the IEGR amount increases, the table and / or function also reduces the post-fuel injection amount, so that less fuel is trapped in the cylinder during the first cycle of the cylinder to the next second cycle of the cylinder. In one example, the end of the post-injection pulse width is within five crankshaft degrees of the exhaust port opening, so that cylinder discharge helps to empty the fuel injected into the cylinder. Additionally, the start of the post fuel injection can be advanced in response to an increase in the IEGR amount such that the end of the post fuel injection can also be advanced, thereby allowing all of the post injected fuel to be injected before the exhaust port opens during the cylinder cycle so that more of the post injected fuel can exit the exhaust port before the next cylinder cycle. The start of the post fuel injection can be delayed in response to a decrease in the IEGR amount such that the end of the post fuel injection can also be delayed, thereby allowing a larger post injected fuel pulse to end before the exhaust port opens. A larger fuel pulse width can increase the temperature in the oxidation catalyst, thereby increasing the exhaust temperature reaching the PF. In one example, the post fuel injection pulse begins before or when the exhaust port of the cylinder opens. As Figure 3 As shown, the post fuel injection fuel pulse ends before the intake port opens during the cylinder stroke in which fuel is injected. Method 400 proceeds to 414 .

[0063] At 414, method 400 provides a post fuel injection pulse to one or more engine cylinders via the first and second injectors or only via the second fuel injector. When the post fuel injection is an early fuel injection, the post fuel injection may be provided by both the first and second fuel injectors. The second fuel injector may be the only fuel injector supplying the late post injection. After providing the post fuel injection at the timing determined at 412, method 400 proceeds to 416.

[0064] At 416, method 400 judges whether PF filter regeneration is complete. In one example, differential pressure sensor 71 outputs data indicating whether soot stored in the PF is less than a threshold amount. If method 400 judges that PF filter regeneration is complete, the answer is "yes" and method 400 proceeds to exit. Otherwise, the answer is "no" and method 400 returns to 410.

[0065] therefore, Figure 4 A method of regenerating a particulate filter is provided, comprising: receiving sensor data to a controller; and adjusting, via the controller, a post-injection fuel pulse width of a second fuel injector provided to the cylinder in response to an estimated amount of internal residual in the cylinder based on the sensor data. The particulate filter regeneration method comprises estimating the internal residual based on engine speed and engine boost pressure, and providing the post-injection fuel pulse width during a cylinder cycle before the exhaust port is opened. The method comprises wherein the second fuel injector is angled relative to a wall of the cylinder so that a fuel spray from the second fuel injector is directed to an exhaust piston, and the method further comprises: adjusting, via the controller, a post-injection fuel pulse width of a first fuel injector provided to the cylinder in response to an estimated amount of residual in the cylinder based on the sensor data. The particulate filter regeneration method comprises wherein the internal residual is estimated based on engine speed and a position of a valve in an exhaust system. The particulate filter regeneration method comprises: wherein adjusting the post-injection fuel pulse width comprises increasing the post-injection fuel pulse in response to a decrease in the amount of internal residual in the engine cylinder. The particulate filter regeneration method comprises: wherein adjusting the post-injection fuel pulse width comprises decreasing the post-injection fuel pulse in response to an increase in the amount of internal residual in the cylinder.

[0066] Additionally, the particulate filter regeneration method includes where a post-injection fuel pulse width is injected directly into the cylinder during a cylinder stroke where the piston exposes the exhaust and intake ports. The particulate filter regeneration method includes where the exhaust port is open the entire time the intake port is open during the stroke. The particulate filter regeneration method includes where a post-injection fuel pulse width is provided to a second fuel injector of the cylinder during a cylinder cycle, and where a main fuel injection pulse width is provided to a first fuel injector of the cylinder during a cylinder cycle.

[0067] Figure 4The method also provides a particulate filter regeneration method, which includes: receiving sensor data to a controller; adjusting a post-injection fuel pulse width of a second fuel injector provided to the cylinder via the controller in response to an internal residual amount in the cylinder estimated based on the sensor data; and injecting the post-injection fuel amount into the cylinder via the second fuel injector, the second fuel injector including a spray cone that directly impinges on the exhaust port of the cylinder. The particulate filter regeneration method includes: wherein injecting the post-injection fuel amount includes injecting fuel via the second fuel injector between the time when the exhaust port of the cylinder is opened and the intake port is opened. The particulate filter regeneration method includes wherein the piston opens the intake port and the exhaust port. The particulate filter regeneration method further includes injecting the main injection fuel amount into the cylinder via the first fuel injector. The particulate filter regeneration method further includes adjusting the internal residual amount in response to engine speed and load. The particulate filter regeneration method includes wherein the internal residual amount is adjusted by adjusting the boost pressure of the cylinder.

[0068] Note that the example control and estimation procedures included herein can be used with various engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-volatile memory and can be implemented by a control system including a controller in combination with various sensors, actuators, and other engine hardware. Further, a portion of these methods can be a physical action taken in the real world to change the state of a device. The specific procedures described herein can represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). Therefore, the various actions, operations, and / or functions shown may have been executed in the order shown, executed in parallel, or omitted in some cases. Similarly, the processing order is not necessary to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly performed according to the specific strategy used. Further, the described actions, operations, and / or functions can graphically represent the code in the non-volatile memory of a computer-readable storage medium to be programmed into the engine control system, wherein the actions are executed by executing instructions in a system including various engine hardware components in combination with an electronic controller. If necessary, one or more method steps described herein can be omitted.

[0069] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific examples should not be considered limiting, as many variations are possible. For example, the above-described techniques can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0070] The appended claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. The claims may refer to "an" element or a "first" element or their equivalent. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or characteristics may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope to the original claims, are deemed to be included in the subject matter of the present disclosure.

Claims

1. A particulate filter regeneration method, comprising: Receive sensor data to the controller; as well as In response to an internal residual amount in the cylinder estimated based on the sensor data, a post-injection fuel pulse width of a second fuel injector provided to the cylinder is adjusted via the controller, wherein the internal residual amount is an amount of residual remaining in the cylinder from one combustion event in the cylinder to a next combustion event.

2. The particulate filter regeneration method of claim 1 , wherein the internal residual is estimated based on engine speed and engine boost pressure, and wherein the second fuel injector is angled relative to a wall of the cylinder such that a fuel spray from the second fuel injector is directed toward an exhaust piston.

3. The particulate filter regeneration method of claim 1 , wherein the internal residual amount is estimated based on engine speed and a position of a valve in an exhaust system, and wherein the post-injection fuel pulse width is provided during a cylinder cycle before an exhaust port opening is opened.

4. The particulate filter regeneration method of claim 1 , wherein adjusting the post injection fuel pulse width comprises increasing the post injection fuel pulse in response to a decrease in the internal residual amount in the cylinder, and the method further comprises: A post-injection fuel pulse width provided to a first fuel injector of the cylinder is adjusted via the controller in response to the internal residual amount in the cylinder estimated based on the sensor data. 5 . The particulate filter regeneration method of claim 1 , wherein adjusting the post injection fuel pulse width comprises decreasing the post injection fuel pulse in response to an increase in the internal residual amount in the cylinder. 6 . The particulate filter regeneration method of claim 1 , wherein the post-injection fuel pulse width is injected directly into the cylinder during a cylinder stroke where a piston exposes an exhaust port and an intake port. 7 . The particulate filter regeneration method of claim 6 , wherein the post injection fuel pulse width is provided during a cylinder cycle before an intake port is opened.

8. The particulate filter regeneration method of claim 1 , wherein the post injection fuel pulse width is provided to the second fuel injector of the cylinder during a cylinder cycle, and wherein a main fuel injection pulse width is provided to the first fuel injector of the cylinder during the cylinder cycle.

9. An engine system comprising: an opposed piston diesel engine including a cylinder having a first fuel injector and a second fuel injector; a supercharger coupled to the opposed-piston diesel engine, the supercharger having a plurality of gear ratios; a turbocharger coupled to the opposed-piston diesel engine; as well as A controller comprising executable instructions stored in a non-volatile memory to receive sensor data to the controller and, in response to an internal residual amount in the cylinder estimated based on the sensor data, adjust a post-injection fuel pulse width provided to a second fuel injector of the cylinder, wherein the internal residual amount is an amount of residual remaining in the cylinder from one combustion event in the cylinder to a next combustion event; wherein a late post fuel injection amount is provided only via the second fuel injector during a cycle of the cylinder, and a main fuel injection amount is provided only via the first fuel injector during the cycle of the cylinder. 10 . The engine system of claim 9 , wherein the start of post fuel injection is advanced in response to an increase in the internal residual amount. 11 . The engine system of claim 9 , wherein the end of post fuel injection is advanced in response to an increase in the internal residual amount. 12 . The engine system of claim 9 , wherein initiation of post fuel injection is delayed in response to a decrease in the internal residual amount.

13. The engine system of claim 9 further comprising additional instructions to adjust internal exhaust gas recirculation in response to engine speed and load.

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