Diesel Engine Dual-Fuel Injection Strategy

Abstract

The present application relates to a dual fuel injection strategy for a diesel engine. Methods and systems for supplying fuel to a diesel engine during a cycle of a cylinder are described. In one example, fuel is supplied to the cylinder via two fuel injectors having different fuel flow rates. The two fuel injectors can be operated to provide pilot combustion fuel injection, main combustion fuel injection, and post-combustion fuel injection during a cycle of the cylinder.

Description

Technical Field

[0001] The present invention relates to a dual fuel injection strategy for a diesel engine. Background Art

[0002] A diesel engine may include a turbocharger that increases the engine power output performance. The turbocharger may supply pressurized air to the engine so that the cylinder charge mass can be increased to increase the engine output power. However, when the vehicle driver does not request torque to propel the vehicle, the engine may also operate at low engine air flow and boost pressure. Additionally, a diesel engine may operate over a wide range of lean air-fuel ratios. Thus, a diesel fuel injector may have to supply a wide range of fuel amounts to provide a desired air-fuel ratio within a range of operating conditions. Accordingly, the size of the diesel fuel injector is set to supply fuel at high and low engine loads. Even so, due to the kinematics within the fuel injector and due to the fuel injector supplying a wide range of fuel injection amounts, it may be difficult to provide small and precise fuel amounts. It may be desirable to inject one or more small fuel injection amounts into the cylinder during a cylinder cycle to reduce combustion noise and control the heat release of the fuel being burned. The small fuel injection amounts, which may be referred to as pilot injections, may be injected during the cylinder cycle, and during the cylinder cycle the pilot injection may be before the main fuel injection. If the pilot fuel injection amount is not precise, then engine combustion noise and hydrocarbon emissions may increase. Further, it may be desirable to provide these small pilot fuel injections that are very close in time, but the fuel injector has an off dwell time after being immediately closed during which the fuel injector cannot be opened. Thus, the fuel injector cannot provide a pilot fuel injection as close in time as desired. Summary of the Invention

[0003] Herein, the inventors have recognized the above disadvantages and have developed a diesel engine injection method that includes: during a cycle of a cylinder, injecting diesel fuel into the cylinder via a low fuel flow rate diesel fuel injector and injecting diesel fuel into the cylinder via a high fuel flow rate diesel fuel injector by a controller, the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector being positioned in the cylinder.

[0004] By supplying diesel fuel to a diesel engine via two different diesel fuel injectors having two different diesel fuel flow rates, an exact amount of diesel fuel can be supplied during pilot fuel injection and the diesel fuel injection amount at higher engine loads can be met. Specifically, pilot fuel injection can be provided by a lower flow fuel injector, and the main fuel injection amount can be provided by a higher flow fuel injector. Additionally, when the fuel injection time can be short, both the low fuel flow injector and the higher fuel flow injector can supply main fuel injection pulses to provide a desired engine air-fuel ratio at higher engine loads and higher engine speeds. In this way, the accuracy of injecting small and large amounts of fuel during a cylinder cycle can be improved.

[0005] This specification can provide several advantages. In particular, the method can reduce engine emissions by improving the accuracy of the amount of fuel delivered during a cylinder cycle. Additionally, the method can reduce engine combustion noise and / or control peak cylinder pressure. Further, the method can provide more consistent engine operation.

[0006] The above advantages and other advantages, as well as the features of this specification, will become apparent from the following detailed description taken alone or in conjunction with the drawings.

[0007] It should be understood that the above Summary is provided to introduce in a simplified form a selected set of concepts that will be further described in the Detailed Description. This is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the appended claims. Additionally, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A schematic view of an engine is shown;

[0009] Figure 2 A schematic view of fuel injection into a Figure 1 cylinder of the engine shown is shown;

[0010] Figures 3A to 3C A view showing a fuel injection spray pattern of an engine cylinder is shown;

[0011] Figure 4 A cross-sectional view of an opposed-piston engine is shown;

[0012] Figure 5 A sectional view of an opposed-piston engine is shown;

[0013] Figure 6 A view of a piston of an opposed-piston engine is shown;

[0014] Figures 7A to 7H shows an exemplary fuel injection timing;

[0015] Figure 8 shows a flowchart of an exemplary method for adjusting fuel injection timing; and

[0016] Figure 9 shows an exemplary fuel injection sequence having closely coupled pilot fuel injection and post fuel injection.

[0017] Figures 2 to 6 are shown generally to scale. DETAILED DESCRIPTION

[0018] This specification relates to supplying fuel to a diesel engine. Figure 1 shows an example of a boosted diesel engine. Figure 2 and Figure 3A shows two views of a fuel injector spray pattern that can reduce engine emissions and increase engine oil life. Figure 3B and Figure 3C shows two additional fuel spray patterns. Figure 4 shows an opposed piston two - cycle diesel engine in which each engine cylinder includes two fuel injectors. Figure 5 shows Figure 4 a cross - sectional view of the engine shown. Figure 6 shows Figure 4 a detailed view of the engine piston shown. Exemplary fuel injection timing for a diesel engine including two fuel injectors is shown in Figures 7A to 7H . A flowchart of a method for injecting fuel into a diesel engine via two fuel injectors is shown in Figure 8 . Figure 8 The method of Figure 9 can provide closely coupled pilot fuel injection and post fuel injection as shown in

[0019] See Figure 1 , an internal combustion engine 10 (including a plurality of cylinders, one cylinder of the internal combustion engine is shown in Figure 1 ) is controlled by an electronic engine controller 12. The controller 12 receives signals from various sensors of Figure 1 and adjusts engine operation using various actuators of Figure 1 based on the received signals and instructions stored in the controller's memory.

[0020] The engine 10 includes a combustion chamber 30 and a cylinder wall 32, within which a piston 36 is positioned and connected to a crankshaft 40. A cylinder head 13 is fastened to an engine block 14. The illustrated combustion chamber 30 communicates with an intake manifold 44 and an exhaust manifold 48 via respective intake valves 52 and exhaust valves 54. Each intake and exhaust valve can be operated by an intake cam 51 and an exhaust cam 53. However, in other examples, the engine can operate the valves via a single camshaft or pushrods. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57.

[0021] The illustrated fuel injectors 68 and 69 are positioned in the cylinder head 13 to inject fuel directly into the combustion chamber 30, which is known to those skilled in the art as direct injection. Fuel is delivered to the fuel injectors 68 and 69 via 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 varying the position of a valve that regulates the flow to a fuel pump (not shown). Additionally, a metering valve can be located within 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 a high-pressure fuel pump.

[0022] The illustrated intake manifold 44 communicates with an optional electronic throttle 62, which adjusts the position of a throttle plate 64 to control the airflow from an intake plenum 46. A compressor 162 draws air from an air intake device 42 to supply the plenum 46. Exhaust causes a turbine 164 to rotate, which is coupled to the compressor 162 via a shaft 161. In some examples, an intercooler can be provided. The compressor speed can be adjusted by varying the position of a variable vane control 72 or a compressor bypass valve 158. In an alternative example, a wastegate 74 can replace the variable vane control 72, or the wastegate 74 can be used in addition to the variable vane control 72. The variable vane control 72 adjusts the position of variable geometry turbine vanes. When the vanes are in an open position, exhaust can pass through the turbine 164, supplying little energy to rotate the turbine 164. When the vanes are in a closed position, exhaust can pass through the turbine 164 and apply an increased force to the turbine 164. Alternatively, the wastegate 74 or bypass valve allows exhaust to flow around the turbine 164 to reduce the amount of energy supplied to the turbine. The compressor bypass valve 158 allows compressed air at the outlet of the compressor 162 to return to the inlet of the compressor 162. In this way, the efficiency of the compressor 162 can be reduced to affect the flow of the compressor 162 and reduce the likelihood of compressor surge.

[0023] Combustion is initiated in the combustion chamber 30 when the fuel auto-ignites during the compression stroke with the piston 36 near top dead center. In some examples, a universal exhaust gas oxygen (UEGO) sensor 126 may be coupled to the exhaust manifold 48 upstream of the emissions device 70. In other examples, the UEGO sensor may be located downstream of one or more exhaust aftertreatment devices. Additionally, in some examples, the UEGO sensor may be replaced by a NOx sensor having both a NOx sensing element and an oxygen sensing element.

[0024] At lower engine temperatures, the glow plug 66 can convert electrical energy into heat energy to raise the temperature in the combustion chamber 30. By raising the temperature of the combustion chamber 30, the cylinder air-fuel mixture can be more easily ignited via compression.

[0025] In one example, the emissions device 70 may include an oxidation catalyst and a particulate filter. In another example, multiple emissions control devices may be used, each having multiple bricks. In one example, the emissions device 70 may include an oxidation catalyst. In other examples, the emissions device may include a lean NOx trap or a selective catalytic reducer (SCR) and / or a diesel particulate filter (DPF). An exhaust temperature measurement for determining the change in exhaust temperature across the emissions device 70 is provided upstream of the temperature sensor 79 and downstream of the temperature sensor 81.

[0026] Exhaust gas recirculation (EGR) may be provided to the engine via the EGR valve 80. The EGR valve 80 is a valve that closes or allows exhaust to flow from a position downstream of the emissions device 70 to a position upstream of the compressor 162 in the engine air intake system. In an alternative example, the EGR may flow from upstream of the turbine 164 to the intake manifold 44. The EGR may bypass the EGR cooler 85, or alternatively, the EGR may be cooled via passage through the EGR cooler 85. In other examples, a high-pressure EGR system and a low-pressure EGR system may be provided.

[0027] Figure 1The illustrated controller 12 is a conventional microcomputer and includes: a microprocessor unit (CPU) 102, input / output ports (I / O) 104, a read-only memory (ROM) (e.g., non-transitory memory) 106, a random access memory (RAM) 108, a keep-alive memory (KAM) 110, and a conventional data bus. In addition to the signals previously discussed, the illustrated controller 12 receives various signals from sensors coupled to the engine 10, including: engine coolant temperature (ECT) from a temperature sensor 112 coupled to the coolant jacket 114; a position sensor 134 coupled to the accelerator pedal 130 for sensing the accelerator pedal position (PP) adjusted by a human foot 132; a measurement of engine manifold pressure (MAP) from a pressure sensor 121 coupled to the intake manifold 44; boost pressure from a pressure sensor 122; exhaust oxygen concentration from an oxygen sensor 126; an engine position sensor from a Hall effect sensor 118 sensing the position of the crankshaft 40; a measurement of the air mass entering the engine from a sensor 120 (e.g., a hot wire air flow meter); and a measurement of the throttle position from a sensor 58. Atmospheric pressure may also be sensed (sensor not shown) for processing by the controller 12. In a preferred aspect of the present specification, the engine position sensor 118 generates a predetermined number of equally spaced pulses during each rotation of the crankshaft, and the engine speed (RPM) can be determined from these pulses.

[0028] During operation, each cylinder within the engine 10 typically undergoes a four-stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Typically during the intake stroke, the exhaust valve 54 is closed and the intake valve 52 is open. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves to the bottom of the cylinder to increase the volume within the combustion chamber 30. The position of the piston 36 near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its maximum volume) is typically referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the combustion chamber 30. The point at which the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 is at its minimum volume) is typically referred to by those skilled in the art as top dead center (TDC). During what is referred to herein as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected into the cylinder multiple times during a single cylinder cycle.

[0029] In a process referred to herein as ignition, the injected fuel is ignited by compression ignition to cause combustion. During the expansion stroke, the expanding gases push the piston 36 back to BDC. The crankshaft 40 converts the piston motion into a rotational torque of the rotating shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to the exhaust manifold 48, and the piston returns to TDC. Note that the above is only for example, and the intake and exhaust valve opening and / or closing timing may be changed, such as to provide positive or negative valve overlap, delayed intake valve closing, or various other examples. In addition, in some examples, a two-stroke cycle may be used instead of a four-stroke cycle.

[0030] See now Figure 2 , showing the injection of fuel into Figure 1 Detailed schematic diagram of a cylinder of an engine of FIG. In this example, fuel injector 69 and fuel injector 68 are positioned at right angles (e.g., 90 degrees) relative to the longitudinal direction of the two injectors, but the fuel injectors may be positioned at any angle relative to each other that at least partially reduces the spray range of the fuel injectors to reach cylinder wall 32 when both fuel injectors 68 and 69 simultaneously spray fuel. However, in some examples, the fuel injectors may be positioned so that their fuel spray cones do not overlap when the fuel injectors simultaneously spray fuel.

[0031] Air enters combustion chamber 30 via intake valve 52, and exhaust exits combustion chamber 30 via exhaust valve 54. Fuel injector 69 and fuel injector 68 are shown as direct cylinder injectors that inject fuel directly into combustion chamber 30. Fuel injector 69 may be a lower flow fuel injector (e.g., X cc / min@100 bar), and fuel injector 68 may be a higher flow fuel injector (e.g., Y cc / min@100 bar, where Y is greater than X). Alternatively, fuel injector 69 and fuel injector 68 may be fuel injectors having substantially the same fuel injection rate (e.g., injector flow rates within ±2% of each other). Fuel injector 69 may include fewer and / or smaller nozzle holes through which fuel exits than fuel injector 68. Glow plug 66 may be activated during cold engine starting to promote combustion.

[0032] Direct diesel fuel injector 69 delivers diesel fuel that forms a spray cone indicated by dotted line 202. Direct diesel fuel injector 68 delivers diesel fuel that forms a spray cone indicated by dashed line 204. The fuel in the spray cone from fuel injector 69 may intersect and collide with the fuel in the spray cone from fuel injector 68 in the area indicated at 205. In other examples, such as Figure 3B andFigure 3C As shown, the fuel injectors can provide multiple fuel spray cones, and some of the multiple fuel spray cones can intersect and collide when fuel is injected. By intersecting the fuel spray cones, at least some of the fuel range can be reduced or the distance that the fuel travels from each of the fuel injectors 69 and 68 can be reduced. For example, when the fuel from the spray cone 202 collides with the fuel from the spray cone 204, the amount of fuel that exits the nozzle 212 of the fuel injector 68 and travels through the combustion chamber 30 and directly impacts the combustion chamber wall can be reduced. Similarly, the amount of fuel that exits the nozzle 210 of the fuel injector 69 and travels through the combustion chamber 30 and directly impacts the combustion chamber wall can be reduced. The dilution of the engine oil can be reduced by reducing the amount of fuel that flows directly from the injector to the cylinder wall. Additionally, engine emissions can be reduced by reducing the amount of fuel that flows directly from the fuel injector nozzle to the cylinder wall.

[0033] When the piston 36 is in the lower position, the fuel injector 68 can inject fuel that impacts the cylinder wall 32 when fuel is injected only via the fuel injector 68. If the piston 36 is in the higher position, the fuel injected by the fuel injector 68 can impact the first bowl-shaped portion in the top 250 of the piston 36. Similarly, when the piston 36 is in the lower position, the fuel injector 69 can inject fuel that impacts the cylinder wall 32 when fuel is injected only via the fuel injector 69. If the piston 36 is in the higher position, the fuel injected by the fuel injector 69 can impact the second bowl-shaped portion in the top 250 of the piston 36.

[0034] Now referring to Figure 3A , a view of the fuel injector spray pattern of the engine cylinder is shown. Figure 3A The view shown is from Figure 1 and Figure 2 the side of the top 250 of the piston 36 as shown. The injection direction of the nozzle 210 of the fuel injector 69 is at a right angle to the injection direction of the nozzle 212 of the fuel injector 68. The injection direction of each fuel injector is in the longitudinal direction of each fuel injector. In this example, the fuel injector 69 is a low flow rate fuel injector and the fuel injector 69 is a high flow rate fuel injector. Additionally, as indicated at 312 at a predetermined distance 310 from the nozzle 210, the width of the spray cone 202 emitted by injecting fuel from the fuel injector 69 is narrower than the width of the spray cone 204 emitted by injecting fuel from the fuel injector 68 as indicated at 314 at the same predetermined distance 310 from the nozzle 212. The predetermined distance 310 from the nozzle 210 and the nozzle 212 is the same distance. However, in some examples, the widths of the spray cones can be the same.

[0035] If the piston 36 is higher in the cylinder (e.g., closer to top dead center) and fuel is injected via fuel injector 69, the fuel injected from injector 69 can flow directly to bowl 308. Bowl 308 includes a land 306 that can be flush with the top of piston 250. Similarly, if the piston 36 is higher in the cylinder (e.g., closer to top dead center) and fuel is injected via fuel injector 68, the fuel injected from injector 68 can flow directly to bowl 304. Bowl 304 includes a land 302 that can be flush with the top of piston 250. The diameter of bowl 308 is smaller than the diameter of bowl 304 because the size of each bowl can be set to reach the range of the corresponding spray cone (e.g., the diameter of the spray cone). By setting the size of the bowl to the spray cone, the air and fuel mixture can be improved to reduce emissions. Thus, for a narrower spray cone 202, a bowl 308 with a smaller diameter can be set, and for a wider spray cone 204, a bowl 304 with a larger diameter can be set. In this way, the piston geometry can be customized to the size of different fuel spray cones provided by different flow rate fuel injectors. The positions and sizes of bowl 304 and bowl 308 are for illustrative purposes and should not be construed as limiting. Additionally, bowl 304 and bowl 308 can be referred to as cavities.

[0036] Now referring to Figure 3B , an alternative injector position in the cylinder and spray pattern is shown. In this example, the first fuel injector 330 shown is centered in the cylinder and cylinder head 13. The second fuel injector 331 can be positioned along the cylinder wall 32. The first fuel injector 330 provides a circular spray pattern with multiple spray cones indicated by dashed line 334. The second fuel injector 331 provides a fan-shaped spray pattern with multiple spray cones indicated by dotted line 333. When both the first fuel injector 330 and the second fuel injector 331 inject fuel simultaneously, the fuel spray cones indicated by dashed line 334 can intersect and collide with the spray cones indicated by dotted line 333. Thus, the fuel penetration (e.g., the distance the fuel travels in the spray cone) can be at least partially reduced.

[0037] Now referring to Figure 3C, showing alternative injector positions in the cylinder and spray patterns. In this example, the first fuel injector 330 shown is centered in the cylinder and the cylinder head 13. The second fuel injector 331 can be positioned along the cylinder wall 32, and the third fuel injector 335 can also be positioned along the cylinder wall 32. The first fuel injector 330 provides a circular spray pattern with multiple spray cones indicated by the dashed line 334. The second fuel injector 331 provides a fan-shaped spray pattern with multiple spray cones indicated by the dotted line 333. The third fuel injector 335 provides a fan-shaped fuel spray pattern with multiple fuel spray cones indicated by the dash-dotted line 336. When both the first fuel injector 330 and the second fuel injector 331 inject fuel simultaneously, the fuel spray cones indicated by the dashed line 334 can intersect and collide with the spray cones indicated by the dotted line 333. Similarly, when both the first fuel injector 330 and the third fuel injector 335 inject fuel simultaneously, the fuel spray cones indicated by the dashed line 334 can intersect and collide with the spray cones indicated by the dash-dotted line 336. Thus, the fuel spray range (e.g., the distance the fuel travels in the spray cone) can be at least partially reduced.

[0038] Now refer to Figure 4 , showing a schematic cross-section of a cylinder 401 of an opposed-piston two-stroke engine. The two-stroke opposed-piston internal combustion engine 400 (including multiple cylinders, one of which is shown in Figure 4 is controlled by the electronic engine controller 12. The opposed-piston engine system can include Figure 1 the controller 12 shown and sensors and actuators associated with the controller 12. For simplicity Figure 4 some sensors and actuators are omitted. The two-stroke engine includes a compression stroke and an expansion / exhaust stroke. During the compression stroke, the pistons 404 and 406 reciprocate towards the squeeze region 416 and away from the crankshafts 408 and 410, respectively. During the expansion / exhaust stroke, the pistons 404 and 406 reciprocate away from the squeeze region 416 and towards the crankshafts 408 and 410, respectively.

[0039] The cylinder 401 includes a squish area 416 where air and diesel fuel can be combusted. The shown first piston 404 is mechanically coupled to a first crankshaft 408, and the shown second piston 406 is mechanically coupled to a second crankshaft 410. The first crankshaft 408 can be mechanically coupled to the second crankshaft 410 via a chain or a gear set (not shown). The pistons 404 and 406 reciprocate within the wall 402 of the cylinder 410. The pistons 404 and 406 travel together towards the squish area 416 during their respective compression strokes and away from the squish area 416 after the gas in the cylinder combusts and expands. Air enters the cylinder 401 via an intake passage 412, and exhaust exits the cylinder 401 via an exhaust passage 420.

[0040] The fuel injector 424 is a low flow rate fuel injector and it can have fuel spray characteristics of a fuel injector 69 as Figures 1 to 3A or other fuel injectors described herein. The fuel injector 414 is a high flow rate fuel injector having the same fuel spray characteristics as a fuel injector 68 as Figures 1 to 3A or other fuel injectors described herein. The fuel injector nozzles 417 and 418 are arranged to be directly opposite each other such that the spray cones of the fuel injected from the diesel fuel injector 424 and the diesel fuel injector 414 cause the fuel droplets from each spray cone to collide. The cross-section 450 is shown in Figure 5 and it provides a view of the top of the piston 404 and a view of the fuel injector arrangement. The top 445 of the piston 406 can be the same as the top 490 of the piston 406.

[0041] Now referring to Figure 5 which shows a cross-section 450 of the cylinder 401 as shown in Figure 4 . The shown fuel injector 424 and fuel injector 414 are bisected by a vertical centerline 451. Additionally, the piston 404 is bisected by the vertical centerline 451. The cavity sidewall 457 is the lower sidewall, the sidewall 456 is the intermediate sidewall, and the sidewall 455 is the upper sidewall of the cavity 440. Similarly, the cavity sidewall 462 is the lower sidewall, the sidewall 461 is the intermediate sidewall, and the sidewall 460 is the upper sidewall of the cavity 440. The upper sidewall 460 and the upper sidewall 455 are closer to the top 445 of the piston 404 than the lower sidewalls 462 and 457. The cavity sidewall 455, the cavity sidewall 456, the cavity sidewall 457 and the cavity sidewall 460, the cavity sidewall 461, the cavity sidewall 462 are symmetric about the vertical centerline 451. However, the cavity sidewall 455, the cavity sidewall 456, the cavity sidewall 457, the cavity sidewall 460, the cavity sidewall 461, the cavity sidewall 462 are not symmetric about a horizontal centerline 452. Thus, the cavity 440 is shaped like a pear.

[0042] The cavity 440 is shaped to conform to the spray cones of fuel injector 424 and fuel injector 414. The cavity 440 begins near fuel injector 424 at a first narrow opening 446 at the outer sidewall 491 of piston 404. The cavity 440 includes a second wide opening 444 for fuel injector 414 at the outer sidewall 491 of piston 404. Fuel injector 424 provides a narrower fuel spray cone than fuel injector 414. Thus, compared to the wall boundary 454 of the fuel spray cone of fuel injector 414 disposed between fuel injector nozzle 418 and horizontal centerline 452, the cavity 440 creates a narrower wall boundary 453 between fuel injector nozzle 417 and horizontal centerline 452. Thus, the cavity 440 allows the fuel injector spray cone to increase such that fuel can reach the center of piston 404 to facilitate fuel mixing. By improving fuel mixing, engine emissions can be improved.

[0043] It should be noted that piston 406 can be formed the same as piston 404. Thus, piston 406 can also accommodate the spray cones of fuel injector 414 and fuel injector 424. Additionally, in some examples, piston 406 can be complementary to piston 404 such that the high portion of piston 406 is opposite the low side of piston 404 and vice versa. In some examples, the top of piston 455 can be higher on one side of cavity 440 than on the other side of cavity 440 (e.g., the left side of piston top 445 can be higher than the right side of piston top 445). Further, in some examples, the nozzle of fuel injector 414 can be offset from the nozzle of fuel injector 424.

[0044] Now referring to Figure 6 , a perspective view of piston 404 from Figure 4 is shown. Cavity 440 is shown with upper sidewall 460, middle sidewall 461, and lower sidewall 462 exposed. The shown cavity opening 444 has a depth 610 and a width 612. The shown cavity opening 446 has a depth 622 and a width 608. Depth 622 is less than depth 610, and width 608 is less than width 612. The dimensions of the depth and width of cavity 440 are sized to accommodate the spray cones of fuel injector 414 and fuel injector 424 while maintaining the structural integrity of piston 404. In an alternative example, the depths of opening 446 and opening 444 can be equal such that cavity 440 has a uniform depth.

[0045] Figures 2 to 6Illustrate an example configuration of the relative positioning of various components. In at least one example, if the elements shown are in direct contact or directly coupled to each other, then such elements may be referred to as being in direct contact or directly coupled, respectively. Similarly, in at least one example, elements shown as adjacent or adjoining each other may be adjacent or adjoining each other, respectively. As an example, components placed in coplanar contact with each other may be referred to as being in coplanar contact. As another example, in at least one example, elements that are positioned spaced apart from each other with only space therebetween and no other components may be so referred to. As yet another example, elements shown as above / below each other, on opposite sides of each other, or to the left / right of each other may be so referred to relative to each other. Additionally, as shown in the figure, in at least one example, the highest element or the highest point of an element may be referred to as the "top" of the component, and the lowest element or the lowest point of an element may be referred to as the "bottom" of the component. As used herein, top / bottom, upper / lower, above / below may be relative to the vertical axis of the drawing and are used to describe the positioning of the elements of the drawing relative to each other. Thus, in one example, an element shown above other elements is vertically positioned above the other elements. As yet another example, the shapes of the elements depicted within the drawing may be considered to have those shapes (e.g., such as circular, straight, planar, curved, rounded, chamfered, angled, etc.). Additionally, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or as intersecting each other. Furthermore, in one example, an element shown within another element or shown outside another element may be so referred to.

[0046] Therefore, Figures 1 to 6The system provides an engine system that includes: an engine including at least one cylinder; a first diesel fuel injector that supplies fuel to at least one cylinder; and a second diesel fuel injector that supplies fuel to at least one cylinder, where the second diesel fuel injector is a higher fuel flow rate injector compared to the first diesel fuel injector. The engine system includes where the first diesel fuel injector and the second diesel fuel injector directly inject diesel fuel into at least one cylinder. The engine system further includes positioning the first diesel fuel injector and the second diesel fuel injector in the engine such that a greater than threshold amount of fuel leaving the first diesel fuel injector collides with a greater than threshold amount of fuel leaving the second diesel fuel injector and the fuel from the first diesel fuel injector and the fuel from the second diesel fuel injector do not collide with the surface of the engine (e.g., 75% of the fuel leaving the first fuel injector collides with 75% of the fuel leaving the second fuel injector and no colliding fuel has collided with the cylinder surface). The engine system further includes a piston in at least one cylinder, the piston including a first chamber and a second chamber. The engine system includes where the first chamber is positioned at the top of the piston to receive fuel directly from the fuel spray cone of the fuel injected via the first diesel fuel injector. The engine system includes where the second chamber is positioned in the top of the piston to receive fuel directly from the fuel spray cone of the fuel injected via the second diesel fuel injector. The engine system includes where the first diesel fuel injector and the second diesel fuel injector are coupled to the cylinder head.

[0047] Figures 1 to 6 The system further provides an engine system that includes: an opposed piston engine including at least one cylinder and two pistons positioned within the at least one cylinder; a first diesel fuel injector that supplies diesel fuel to at least one cylinder; and a second diesel fuel injector that supplies diesel fuel to at least one cylinder, where the second diesel fuel injector is a higher fuel flow rate injector compared to the first diesel fuel injector. The engine system further includes a chamber in the first of the two pistons. The engine system includes where the depth of the first chamber changes. The engine system includes where a first opening width of the chamber is less than a second opening width of the chamber. The engine system includes where the first diesel fuel injector and the second diesel fuel injector are positioned to be directly opposite each other. The engine system, where the chamber is asymmetric about a horizontal centerline of the first of the two pistons, the horizontal centerline being perpendicular to the longitudinal direction of the first diesel fuel injector and the second diesel fuel injector. The engine system includes where the chamber includes three side walls.

[0048] Figures 1 to 6The system also provides an engine system, which includes: an engine including at least one cylinder; a first diesel fuel injector that supplies fuel to at least one cylinder; a second diesel fuel injector that supplies fuel to at least one cylinder, and the second diesel fuel injector is a higher fuel flow rate injector compared to the first diesel fuel injector; and a piston that is positioned within at least one cylinder and includes a first chamber and a second chamber, and the first chamber is smaller than the second chamber. The engine system includes wherein the first chamber surrounds a first platform and wherein the second chamber surrounds a second platform. The engine system includes wherein the first chamber is positioned to receive fuel from the first diesel fuel injector. The engine system includes wherein the second chamber is positioned to receive fuel from the second diesel fuel injector. The engine system includes wherein the fuel spray cone of the first diesel fuel injector is narrower than the fuel spray cone of the second diesel fuel injector. The engine system includes wherein diesel fuel is supplied to the first diesel fuel injector and the second diesel fuel injector via the same fuel system.

[0049] Now referring to Figures 7A to 7D , a fuel injection timing diagram for a Figures 1 to 3C four-stroke engine is shown. The fuel injection timing can be provided via the controller 12 and the fuel injectors 68 and 69 or other fuel injectors described herein. The shown fuel injection timing can be provided in the Figures 1 to 3C system. Additionally, the fuel injection timing can be provided via the Figure 8 method in cooperation with the Figures 1 to 3C system. The vertical lines represent the moments of interest during the corresponding sequence curves (e.g., T1 to T4).

[0050] Figures 7A to 7D The first curve at the top of Figure 7A represents the cylinder stroke of cylinder number one of the engine. The horizontal axis is divided into a series of segments identifying the cylinder stroke that cylinder number one is in as it travels from the left side to the right side of the drawing over time. The exhaust stroke is abbreviated as EXH, while the intake stroke, compression stroke, and expansion stroke are abbreviated as INT, COMP, and EXP, respectively. * indicates the start of combustion of the shown four-stroke cylinder cycle. Thus,

[0051] Figures 7A to 7D The second curve at the top of Figure 1 represents the fuel injection timing during the cylinder cycle of the first fuel injector (e.g., a low flow rate fuel injector such as the

[0052] Figures 7A to 7D The third curve at the top represents the fuel injection timing during the cylinder cycle of the second fuel injector (e.g., a high-flow fuel injector such as Figure 1 the injector 68 shown), and the second fuel injector injects diesel fuel into the first cylinder. The pulse width (e.g., 706) varies in width, and the width is an indication of the amount of fuel injected in the fuel pulse. The wider the pulse, the greater the amount of fuel injected into the cylinder during the pulse. The shorter the pulse, the smaller the amount of fuel injected into the cylinder during the pulse.

[0053] Figure 7A An example fuel injection timing showing a lower-flow fuel injector supplying fuel to an engine cylinder for pilot injection and post-injection is presented. The pilot injection is a fuel injection with a short duration that can be less than 4 mg. The pilot fuel injection starts and ends before top dead center compression stroke in the cylinder cycle in which it is injected. The pilot fuel injection can reduce engine combustion noise, control peak cylinder pressure, and adjust heat release within the cylinder. The main fuel injection is the injection of the largest amount of fuel during the cylinder cycle. The range of the main fuel injection can be within 3 mg to 100 mg per cylinder cycle. The pilot fuel injection is before the main fuel injection. The early post-fuel injection can occur ten crank angles after top dead center compression stroke and after the main fuel injection. The range of the early post-fuel injection can be within 1 mg to 10 mg. During the cylinder cycle, the late post-injection is a fuel injection performed after the combustion of the main fuel injection pulse is completed and before the exhaust valve of the cylinder receiving the fuel closes. The early post-injection and the late post-injection can be used to regenerate an emission control device in the exhaust system of the engine. Figure 7A A main fuel injection pulse via a higher-flow fuel injector is provided. The main fuel injection pulse can provide significant chemical energy to meet the driver demand torque.

[0054] At time T1, the engine is operating at a medium-level engine load (not shown), and the first pilot fuel injection starts via the first fuel injector. The first pilot fuel injection 702 is set during the compression stroke of the first cylinder. Shortly thereafter, the first pilot fuel injection ends. The low-flow fuel injector can be configured to have a smaller moving mass (e.g., the low-flow fuel injector pivot can include a smaller mass), such that the low-fuel-flow injector can be opened and closed in a shorter time compared to the high-flow fuel injector. Alternatively, the low-flow fuel injector can include a nozzle throttle that controls the flow rate, and the nozzle throttle can control the pivot opening and closing rate. Additionally, the low-flow fuel injector can inject a smaller mass of fuel more precisely compared to the high-flow fuel injector. Thus, the low-flow fuel injector is suitable for providing pilot fuel injection. The second higher-flow fuel injector does not inject fuel.

[0055] At time T2, a second pilot fuel injection 704 begins via the first fuel injector. The controller 12 can determine which fuel injector injects the pilot fuel injection in response to the pilot fuel injection quantity and / or the fuel injector minimum pulse width limit. In one example, when the pilot fuel injection quantity is less than a threshold quantity, the controller selects the low-flow fuel injector to inject the pilot fuel injection quantity. The second pilot fuel injection 704 is set during the compression stroke of cylinder number one. Shortly thereafter, the second pilot fuel injection ends.

[0056] At time T3, a main fuel injection 706 begins via the second fuel injector. The main fuel injection 706 is set during the compression stroke of cylinder number one. The main fuel injection pulse ends before top dead center of the compression stroke. The first fuel injector does not inject fuel into cylinder number one.

[0057] At time T4, a first post fuel injection begins. In this example, the post fuel injection is early (e.g., within 30 crankshaft degrees of the end of combustion in cylinder number one). The first post fuel injection is provided via the first fuel injector. The second fuel injector does not inject fuel. Shortly after time T4, the first post fuel injection ends, and fuel delivery to cylinder number one ends for the illustrated cylinder cycle. In other examples, additional or fewer post fuel injections and pilot fuel injections may be provided.

[0058] In this manner, the low-flow fuel injector can supply the smaller fuel quantities for the pilot fuel injection and the post fuel injection. The larger fuel injection quantities can be provided by the higher-flow fuel injector. Thus, fuel injection can be dispatched between the two different fuel injectors in a manner that improves the accuracy of the pilot fuel injection quantity, the post fuel injection quantity, and the main fuel injection quantity.

[0059] Figure 7B A second example fuel injection timing is shown where a lower-flow fuel injector supplies fuel to an engine cylinder for pilot injection, main injection, and post injection. When fueling the cylinder during the cycle of the cylinder, at least one main injection is provided to the cylinder. When the higher-flow fuel injector does not have time to supply a sufficient quantity of fuel to meet the cylinder air-fuel requirements, the lower-flow fuel injector can provide the main fuel injection at higher engine speeds and loads. Figure 7B A main fuel injection pulse via the higher-flow fuel injector is also provided. Two main fuel injection pulses can provide significant chemical energy to meet the driver demand torque.

[0060] At time T5, the engine is operating at a relatively high engine load (not shown), and the first pilot fuel injection starts via the first fuel injector. The first pilot fuel injector 710 starts during the compression stroke of the first cylinder. Shortly thereafter, the first pilot fuel injection ends. The second higher flow fuel injector does not inject fuel.

[0061] At time T6, the second pilot fuel injection 712 starts via the first fuel injector. The second pilot fuel injection 712 is set during the compression stroke of the first cylinder. Shortly thereafter, the second pilot fuel injection ends. The second fuel injector does not supply fuel to the first cylinder.

[0062] At time T7, the main fuel injection 714 starts via the first fuel injector. The main fuel injection is set during the compression stroke of the first cylinder. The first fuel injector can provide the main fuel injection such that a desired engine air-fuel ratio can be provided.

[0063] At time T8, the main fuel injection 716 starts via the second fuel injector. The main fuel injection 716 is set during the compression stroke of the first cylinder. The main fuel injection 714 provided via the first fuel injector and the main fuel injection 716 provided via the second fuel injector overlap. This overlap can be used to reduce the likelihood of the injected fuel impinging on the cylinder wall.

[0064] It should be noted that in other examples, the second fuel injector can start injecting its main fuel injection amount in the cylinder cycle before the first fuel injector starts injecting its main fuel injection amount in the cylinder cycle. The specific timing can depend on the fuel injector specifications and the engine operating conditions. Additionally, if the two fuel injectors have fuel spray patterns that impinge on each other during simultaneous injection, the two fuel injectors can only inject simultaneously during the pilot injection or the post-injection. However, if the two fuel injectors have spray patterns that do not impinge on each other during simultaneous injection, the two fuel injectors can inject simultaneously during the main fuel injection of each fuel injector.

[0065] At time T9, the main fuel pulses 714 provided via the first fuel injector and the main fuel pulses 716 provided via the second fuel injector end. The main fuel injection pulses can end simultaneously to reduce the exhaust temperature and improve the combustion efficiency.

[0066] At time T10, a first post-fuel injection is provided. In this example, the post-fuel injection is late (e.g., close to the closing of the exhaust valve of the first cylinder). The first post-fuel injection is provided via the first fuel injector. Shortly thereafter, the first post-fuel injection ends, and the fuel delivery to the first cylinder ends for the shown cylinder cycle.

[0067] In this manner, a low-flow fuel injector can supply a smaller fuel quantity for pilot fuel injection and post fuel injection. Additionally, the main fuel injection through the second fuel injector can be increased by the main fuel injection from the first fuel injector. Thus, fuel injection can be dispatched between two different fuel injectors in a manner that improves the accuracy of the pilot fuel injection quantity and increases the fuel supplied to meet higher engine loads.

[0068] Figure 7C A third exemplary fuel injection timing is shown where the first fuel injector and the second fuel injector alternate between pilot injection and post injection. Main fuel injection is also provided via the first fuel injector and the second fuel injector. When the higher fuel flow injector does not have time to supply a sufficient amount of fuel to meet the cylinder air-fuel requirement, the lower fuel flow injector can provide main fuel injection at higher engine speeds and loads. Before the fuel injector is reactivated, the pilot fuel injection can alternate between the first fuel injector and the second fuel injector to allow the moving mass within the injector to settle into a desired position (e.g., closed), and to allow the electrical / magnetic components (e.g., the coil) to achieve a desired state (e.g., a magnetic field strength less than a threshold). Thus, the amount of time between the end of fuel injection and the start of a new injection during a cylinder cycle can be increased to improve fuel delivery accuracy and repeatability. Additionally, the amount of time between the end of the first pilot injection and the start of the second pilot fuel injection in a cylinder cycle can be reduced because the fuel injector is less constrained by the off dwell time of each fuel injector. Two main fuel injection pulses can provide significant chemical energy to meet the driver demand torque.

[0069] At time T20, the engine is operating at a partial engine load (not shown), and the first pilot fuel injection 720 starts via the No. 1 fuel injector. The first pilot fuel injection 720 starts during the compression stroke of cylinder No. 1. Shortly thereafter, the first pilot fuel injection ends. The second higher flow fuel injector does not inject fuel.

[0070] At time T21, the second pilot fuel injection 722 starts via the second fuel injector. The second pilot fuel injection 722 is set during the compression stroke of cylinder No. 1. Shortly thereafter, the second pilot fuel injection ends. The first fuel injector does not supply fuel to cylinder No. 1.

[0071] At time T22, the third pilot fuel injection 721 starts via the No. 1 fuel injector. The third pilot fuel injection 721 starts during the compression stroke of cylinder No. 1. Shortly thereafter, the third pilot fuel injection ends. The second higher flow fuel injector does not inject fuel.

[0072] At time T23, the fourth pilot fuel injection 723 starts via the second fuel injector. The fourth pilot fuel injection 723 is set during the compression stroke of the first cylinder. Shortly thereafter, the fourth pilot fuel injection ends. The first fuel injector does not supply fuel to the first cylinder.

[0073] At time T24, the main fuel injections 725 and 726 start via the first fuel injector and the second fuel injector. The main fuel injections are set during the compression stroke of the first cylinder. The first fuel injector and the second fuel injector can provide the main fuel injections such that a desired engine air-fuel ratio can be provided.

[0074] At time T25, the main fuel pulses 725 provided via the first fuel injector and the main fuel pulse 726 provided via the second fuel injector end. The main fuel injection pulses can end simultaneously to improve engine emissions and regulate the heat release during combustion. Additionally, by stopping the fuel injection via the first fuel injector and the second fuel injector simultaneously, the possibility of fuel impinging on the cylinder wall can be reduced.

[0075] At time T26, the first post fuel injection starts. In this example, the post fuel injection is late. The first post fuel injection is provided via the first fuel injector. Shortly thereafter, the first post fuel injection ends.

[0076] At time T27, the second post fuel injection starts. The second post fuel injection is provided via the second fuel injector. Shortly thereafter, the second post fuel injection ends.

[0077] At time T28, a third post fuel injection is provided. The third post fuel injection is provided via the first fuel injector. Shortly thereafter, the third post fuel injection ends, and the fuel delivery to the first cylinder ends for the illustrated cylinder cycle. Thus, the post fuel injections can alternate between the first fuel injector and the second fuel injector to allow the mechanical and electro / magnetic components of the fuel injectors to operate stably, thereby improving fuel delivery accuracy.

[0078] Alternative pilot fuel injection and post fuel injection are also available when the flow rates of the first fuel injector and the second fuel injector are equal or different. In this way, a short recovery time between fuel injections can be provided for each fuel injector of the engine. Additionally, the main fuel injection through the second fuel injector can be increased by the main fuel injection from the first fuel injector. Thus, fuel injection can be dispatched between two different fuel injectors in a way that improves the accuracy of the pilot fuel injection amount and increases the fuel supplied to meet higher engine loads. Furthermore, injecting fuel with two fuel injectors allows the fuel to be injected via the second fuel injector shortly after the first injector stops injecting fuel, such that the second fuel injector injects during the closed dwell time of the first fuel injector. This allows for a more tightly coupled injection, which can improve engine noise reduction and engine emissions.

[0079] Figure 7D A fourth exemplary fuel injection timing is shown in which a lower flow rate fuel injector (e.g., fuel injector number one) supplies fuel to an engine cylinder for main injection and post injection. The lower flow rate fuel injector can provide one or two main fuel injections at higher engine speeds and loads such that the pressure rise in the cylinder can be controlled and limited with an early start of the injection of the main fuel pulse. Figure 7D Pilot fuel injection and main fuel injection pulses via a higher flow rate fuel injector (e.g., fuel injector number two) are also provided. When the second fuel injector is a higher flow rate fuel injector, the second fuel injector can supply pilot fuel injection at higher engine loads. Three main fuel injection pulses can provide significant chemical energy to meet the driver demand torque.

[0080] At time T30, the engine is operating at a higher level engine load (not shown), and a first pilot fuel injection starts via the second fuel injector. The first pilot fuel injection 742 starts during the compression stroke of cylinder number one and shortly thereafter, the first pilot fuel injection ends. The first lower flow rate fuel injector does not inject fuel at time T30.

[0081] At time T31, a second pilot fuel injection 743 starts via the second fuel injector. The second pilot fuel injection 743 is set during the compression stroke of cylinder number one. Shortly thereafter, the second pilot fuel injection ends. The first fuel injector does not supply fuel to cylinder number one.

[0082] At time T32, the main fuel injection 740 starts via the first fuel injector. The main fuel injection 740 is provided during the compression stroke of the first cylinder. The first fuel injector can provide the main fuel injection such that a desired engine air-fuel ratio can be provided. Additionally, compared to the case where the first fuel injector is a higher flow rate fuel injector, when the first fuel injector is a lower flow rate fuel injector, the combustion heat release can be controlled to provide a slower heat release.

[0083] At time T33, the main fuel injection 744 starts via the second fuel injector. The main fuel injection 744 is provided during the compression stroke of the first cylinder. The main fuel injection 740 provided via the first fuel injector and the main fuel injection 744 provided via the second fuel injector do not overlap, but in other examples they can overlap. The second main fuel injection 741 is provided via the first fuel injector shortly after time T33.

[0084] At time T34, the first post fuel injection 745 is provided via the first injector, and the second post fuel injection 746 is provided via the second injector. The first injection and the second injection are simultaneous and contemporaneous to reduce the likelihood of the fuel impinging on the cylinder wall. In this example, the post fuel injection is late (e.g., close to the exhaust valve closing of the first cylinder). The first post fuel injection and the second post fuel injection end, and the fuel delivery to the first cylinder ends for the shown cylinder cycle.

[0085] In this way, when a larger pilot fuel injection amount is desired, the higher flow rate fuel injector can supply the pilot fuel injection at a higher engine load. Additionally, the main fuel injection through the second fuel injector can be increased by the main fuel injection from the first fuel injector. Thus, the fuel injection can be dispatched between two different fuel injectors in a manner that improves the accuracy of the pilot fuel injection amount and increases the fuel supplied to meet a higher engine load.

[0086] Now referring to Figures 7E to 7H shows a fuel injection timing diagram for a two-stroke engine for Figures 4 to 6 . The fuel injection timing can be provided via the controller 12 and the fuel injectors 414 and 424. The shown fuel injection timing can be provided in the system of Figures 4 to 6 . Additionally, the fuel injection timing can be provided via the method of Figure 8 in cooperation with the system of Figures 4 to 6 . The vertical lines represent the moments of interest during the corresponding sequence curves (e.g., T40 to T43).

[0087] Figures 7E to 7HThe first curve at the top represents the cylinder stroke of cylinder number one of the engine. The horizontal axis is divided into a series of segments identifying the cylinder stroke of cylinder number one as it progresses from the left side to the right side of the drawing over time. The expansion / exhaust stroke is abbreviated as EXP, and the compression stroke is abbreviated as COMP. *Indicates the start of combustion of the shown two-stroke cylinder cycle. Thus, Figure 7E Shows the development of the cylinder cycle over time. Thus, the fuel injection of one cycle (e.g., one revolution) of the two-stroke cylinder number one is shown.

[0088] Figures 7E to 7H The second curve at the top represents the fuel injection timing during the cylinder cycle of the first fuel injector (e.g., a low-flow fuel injector such as Figure 4 the 424 shown) that injects diesel fuel into cylinder number one. The pulse widths (e.g., 750, 754, 756, and 758) vary in width, and the width is an indication of the amount of fuel injected in the fuel pulse. The wider the pulse, the greater the amount of fuel injected into the cylinder during the pulse.

[0089] Figures 7E to 7H The third curve at the top represents the fuel injection timing during the cylinder cycle of the second fuel injector (e.g., a higher-flow fuel injector such as Figure 4 the 414 shown) that injects diesel fuel into cylinder number one. The pulse width (e.g., 756) varies in width, and the width is an indication of the amount of fuel injected in the fuel pulse. The wider the pulse, the greater the amount of fuel injected into the cylinder during the pulse. The shorter the pulse, the smaller the amount of fuel injected into the cylinder during the pulse.

[0090] Figure 7E Shows an example fuel injection timing for a low-flow fuel injector to supply fuel to the engine cylinder for pilot injection and post-injection. Pilot injection is a fuel injection of short duration less than a threshold amount of time (e.g., less than 1 millisecond). Pilot fuel injection can reduce engine combustion noise, control peak cylinder pressure, and adjust heat release within the cylinder. Post-injection is a fuel injection performed after the combustion of the main fuel injection pulse is complete and after the piston passes the exhaust port during the expansion / exhaust stroke of the cylinder that receives fuel during the cylinder cycle. Post-injection can be used to regenerate the emission control device in the engine's exhaust system. Figure 7E A main fuel injection pulse 756 via the higher-flow fuel injector is provided. The main fuel injection pulse 756 can provide significant chemical energy to meet the driver demand torque.

[0091] At time T40, the engine is operating at a medium engine load (not shown), and the first pilot fuel injection 750 starts via the first fuel injector. The first pilot fuel injection 750 is set during the compression stroke of the first cylinder. Shortly thereafter, the first pilot fuel injection ends. The low flow rate fuel injector can be configured to have a smaller moving mass (e.g., the low flow rate fuel injector pivot can include a smaller mass), such that the low fuel flow injector can be opened and closed in a shorter time compared to a higher flow rate fuel injector. Additionally, the low flow rate fuel injector can inject a smaller mass of fuel more precisely compared to a higher flow rate fuel injector. Thus, the low flow rate fuel injector can be adapted to provide the pilot fuel injection. The second higher flow rate fuel injector does not inject fuel.

[0092] At time T41, the second pilot fuel injection 754 starts via the first fuel injector. The second pilot fuel injection 754 is set during the compression stroke of the first cylinder. Shortly thereafter, the second pilot fuel injection ends.

[0093] At time T42, the main fuel injection 756 starts via the second fuel injector. The main fuel injection 756 can be set during the compression stroke of the first cylinder after the cylinder passes through the exhaust port. The main fuel injection pulse ends before top dead center of the compression stroke. The first fuel injector does not inject fuel into the first cylinder.

[0094] At time T43, the first post fuel injection 758 starts. The first post fuel injection is provided via the first fuel injector. The second fuel injector does not inject fuel. Shortly after time T43, the first post fuel injection ends, and the fuel delivery to the first cylinder ends for the illustrated cylinder cycle. In other examples, additional or fewer post fuel injections and pilot fuel injections can be provided.

[0095] In this manner, the low flow rate fuel injector can supply a smaller fuel quantity for pilot fuel injection and post fuel injection. A larger fuel injection quantity can be provided by the higher flow rate fuel injector. Thus, fuel injection can be dispatched between two different fuel injectors in a manner that improves the accuracy of the pilot fuel injection quantity, the post fuel injection quantity, and the main fuel injection quantity.

[0096] Figure 7F A second example fuel injection timing is shown where a lower flow rate fuel injector supplies fuel to an engine cylinder for pilot injection, main injection, and post injection. The main fuel injection is a longer duration fuel injection greater than a threshold time amount (e.g., greater than 1 millisecond). The lower flow rate fuel injector can provide the main fuel injection at higher engine speeds and loads when the higher flow rate fuel injector does not have time to supply a sufficient quantity of fuel to meet the cylinder air - fuel requirements. Figure 7FMain fuel injection via a higher flow fuel injector is also provided. Two main fuel injection pulses can provide significant chemical energy to meet the driver demand torque.

[0097] At time T44, the engine is operating at a higher level engine load (not shown), and the first pilot fuel injection starts via the No. 1 fuel injector. The first pilot fuel injection 760 starts during the compression stroke of the No. 1 cylinder. Shortly thereafter, the first pilot fuel injection ends. The second higher flow fuel injector does not inject fuel.

[0098] At time T45, the second pilot fuel injection 762 starts via the first fuel injector. The second pilot fuel injection 762 is set during the compression stroke of the No. 1 cylinder. Shortly thereafter, the second pilot fuel injection ends. The second fuel injector does not supply fuel to the No. 1 cylinder.

[0099] At time T46, the main fuel injection 764 starts via the first fuel injector. The main fuel injection is set during the compression stroke of the No. 1 cylinder. The first fuel injector can provide the main fuel injection such that a desired engine air-fuel ratio can be provided.

[0100] At time T47, the main fuel injection 766 starts via the second fuel injector. The main fuel injection 766 is set during the compression stroke of the No. 1 cylinder. The main fuel injection 746 provided via the first fuel injector and the main fuel injection 766 provided via the second fuel injector overlap. This overlap can be used to reduce the likelihood of the injected fuel impacting the cylinder wall.

[0101] At time T48, the main fuel pulse 764 provided via the first fuel injector and the main fuel pulse 766 provided via the second fuel injector end. The main fuel injection pulses can end simultaneously to improve engine emissions and regulate the heat release during combustion. Additionally, by simultaneously stopping the fuel injection via the first fuel injector and the second fuel injector, the likelihood of the fuel impacting the cylinder wall can be reduced.

[0102] At time T49, a first post-fuel injection is provided. The first post-fuel injection is provided via the first fuel injector. Shortly thereafter, the first post-fuel injection ends, and the fuel delivery to the No. 1 cylinder ends for the shown cylinder cycle.

[0103] In this manner, the low-flow fuel injector can supply a smaller fuel quantity for pilot fuel injection and post fuel injection. Additionally, the main fuel injection through the second fuel injector can be increased by the main fuel injection from the first fuel injector. Thus, fuel injection can be dispatched between two different fuel injectors in a manner that improves the accuracy of the pilot fuel injection quantity and increases the fuel supplied to meet higher engine loads. In other examples, additional or fewer post fuel injections and pilot fuel injections can be provided.

[0104] Figure 7G A third exemplary fuel injection timing is shown where the first fuel injector and the second fuel injector alternate pilot injection and post injection. Main fuel injection is also provided via the first fuel injector and the second fuel injector. When the higher-flow fuel injector does not have time to supply a sufficient quantity of fuel to meet the cylinder air-fuel requirement, the lower-flow fuel injector can provide the main fuel injection at higher engine speeds and loads. Before the fuel injector is reactivated, the pilot fuel injection can alternate between the first fuel injector and the second fuel injector to allow the moving mass within the injector to settle into a desired position (e.g., closed) and allow the electrical / magnetic components (e.g., the coil) to achieve a desired state (e.g., a magnetic field strength less than a threshold). Thus, the amount of time between the end of fuel injection and the start of a new injection during a cylinder cycle can be increased to improve fuel delivery accuracy and repeatability. Additionally, the amount of time between the end of the first pilot injection and the start of the second pilot fuel injection in a cylinder cycle can be reduced because the fuel injector is less constrained by the off-time of each fuel injector. Two main fuel injection pulses can provide significant chemical energy to meet the driver demand torque.

[0105] At time T50, the engine is operating at a partial engine load (not shown), and the first fuel injection 770 starts via the first fuel injector. The first pilot fuel injection 770 starts during the compression stroke of cylinder number one. Shortly thereafter, the first pilot fuel injection ends. The second higher-flow fuel injector does not inject fuel.

[0106] At time T51, the second pilot fuel injection 772 starts via the second fuel injector. The second pilot fuel injection 772 is set during the compression stroke of cylinder number one. Shortly thereafter, the second pilot fuel injection ends. The first fuel injector does not supply fuel to cylinder number one.

[0107] At time T52, the third pilot fuel injection 771 starts via the first fuel injector. The third pilot fuel injection 771 starts during the compression stroke of cylinder number one. Shortly thereafter, the third pilot fuel injection ends. The second higher-flow fuel injector does not inject fuel.

[0108] At time T53, the fourth pilot fuel injection 773 starts via the second fuel injector. The fourth pilot fuel injection 773 is set during the compression stroke of cylinder number one. Shortly thereafter, the fourth pilot fuel injection ends. The first fuel injector does not supply fuel to cylinder number one.

[0109] At time T54, the main fuel injections 775 and 776 start via the first fuel injector and the second fuel injector. The main fuel injections are set during the compression stroke of cylinder number one. The first fuel injector and the second fuel injector can provide the main fuel injections such that a desired engine air-fuel ratio can be provided.

[0110] At time T55, the main fuel pulses 775 provided via the first fuel injector and the main fuel pulse 776 provided via the second fuel injector end. The main fuel injection pulses can end simultaneously to improve engine emissions and regulate the heat release during combustion. Additionally, by stopping the fuel injection via the first fuel injector and the second fuel injector simultaneously, the possibility of fuel impinging on the cylinder wall can be reduced.

[0111] At time T56, the first post fuel injection starts. In this example, the post fuel injection is late. The first post fuel injection is provided via the first fuel injector. Shortly thereafter, the first post fuel injection ends.

[0112] At time T57, the second post fuel injection starts. The second post fuel injection is provided via the second fuel injector. Shortly thereafter, the second post fuel injection ends.

[0113] At time T58, a third post fuel injection is provided. The third post fuel injection is provided via the first fuel injector. Shortly thereafter, the third post fuel injection ends, and the fuel delivery to cylinder number one ends for the indicated cylinder cycle. Thus, the post fuel injections can alternate between the first fuel injector and the second fuel injector to allow the mechanical and electro / magnetic components of the fuel injectors to operate stably, thereby improving fuel delivery accuracy.

[0114] Alternative pilot fuel injection and post fuel injection are also available when the flow rates of the first fuel injector and the second fuel injector are equal or different. In this way, a short recovery time between fuel injections can be provided for each fuel injector of the engine. Additionally, the main fuel injection through the second fuel injector can be increased by the main fuel injection from the first fuel injector. Thus, fuel injection can be dispatched between two different fuel injectors in a way that improves the accuracy of the pilot fuel injection quantity and increases the fuel supplied to meet higher engine loads. Furthermore, injecting fuel with two fuel injectors allows fuel to be injected via the second fuel injector shortly after the first injector stops injecting fuel, such that the second fuel injector injects during the closed dwell time of the first fuel injector. This allows for a more tightly coupled injection, which can improve engine noise reduction and engine emissions.

[0115] Figure 7H A fourth exemplary fuel injection timing is shown in which a lower flow rate fuel injector (e.g., fuel injector number one) supplies fuel to an engine cylinder for main injection and post injection. The lower flow rate fuel injector can provide one or two main fuel injections at higher engine speeds and loads such that the pressure rise in the cylinder can be controlled and limited with an early start of the injection of the main fuel pulse. Figure 7H Pilot fuel injection and main fuel injection pulses are also provided via a higher flow rate fuel injector (e.g., fuel injector number two). When the second fuel injector is a higher flow rate fuel injector, the second fuel injector can supply pilot fuel injection at higher engine loads. Three main fuel injection pulses can provide significant chemical energy to meet the driver demand torque.

[0116] At time T60, the engine is operating at a higher level engine load (not shown), and a first pilot fuel injection starts via the second fuel injector. The first pilot fuel injection 792 starts during the compression stroke of cylinder number one. Shortly thereafter, the first pilot fuel injection ends. At time T60, the first lower flow rate fuel injector is not injecting fuel.

[0117] At time T61, a second pilot fuel injection 793 starts via the second fuel injector. The second pilot fuel injection 793 is set during the compression stroke of cylinder number one. Shortly thereafter, the second pilot fuel injection ends. At time T61, the first fuel injector is not supplying fuel to cylinder number one.

[0118] At time 62, the main fuel injection 790 starts via the first fuel injector. The main fuel injection 790 is set during the compression stroke of cylinder number one. The first fuel injector can provide the main fuel injection such that a desired air-fuel ratio can be provided. Additionally, compared to the case where the first fuel injector is a high-flow fuel injector, when the first fuel injector is a low-flow fuel injector, the combustion heat release can be controlled to provide a slower heat release.

[0119] At time T63, the main fuel injection 794 starts via the second fuel injector. The main fuel injection 794 is set during the compression stroke of cylinder number one. The main fuel injection 790 provided via the first fuel injector and the main fuel injection 794 provided via the second fuel injector overlap. This overlap can be used to reduce the likelihood of the injected fuel hitting the cylinder wall, and can also increase the heat release within the cylinder. The main fuel injection pulse ends earlier during the expansion stroke.

[0120] At time T64, a first post-fuel injection is provided. The first post-fuel injection is provided via the first fuel injector because only a small fuel injection amount is desired. Shortly thereafter, the first post-fuel injection ends, and the fuel delivery to cylinder number one ends for the illustrated cylinder cycle.

[0121] In this way, when a larger pilot fuel injection amount is desired, the high-flow fuel injector can supply the pilot fuel injection at a higher engine load. Additionally, the main fuel injection through the second fuel injector can be increased by the main fuel injection from the first fuel injector. Thus, the fuel injection can be dispatched between two different fuel injectors in a way that improves the accuracy of the pilot fuel injection amount and increases the fuel supplied to meet a higher engine load. In other examples, additional or fewer post-fuel injections and pilot fuel injections can be provided.

[0122] Now refer to Figure 8 , which shows a method for adjusting fuel injection timing. Figure 8 The method of Figures 1 to 6 can be stored as executable instructions in a non-transitory memory in a system such as Figure 8 shown. A flowchart of a method for adjusting the fuel injection timing of an internal combustion engine is shown. Figures 1 to 6 The method of Figures 1 to 6 can be incorporated into the system of Figure 8 and can cooperate with the system of

[0123] At 802, method 800 determines the engine operating condition. The engine operating condition can include, but is not limited to, engine temperature, accelerator pedal position, and engine speed. The engine operating condition can be determined via engine sensors and an engine controller. Method 800 proceeds to 804.

[0124] At 804, method 800 determines the driver demand torque. In one example, method 800 determines the driver torque demand by retrieving or referring to a table or function that stores empirically determined values of the driver demand torque. The table or function can be retrieved or referred to via engine speed and accelerator pedal position. The table outputs the driver demand torque. Method 800 proceeds to 806.

[0125] At 806, method 800 determines the amount of fuel injected into the cylinder during a cycle of the cylinder. In one example, the amount of fuel injected into the cylinder during a cylinder cycle can be determined by retrieving or referring to a table of empirically determined fuel amounts. The table can be referred to via the driver demand torque and engine speed. The table outputs the empirically determined amount of fuel injected during the cylinder cycle. Method 800 proceeds to 808.

[0126] At 808, method 800 determines the pilot fuel injection amount and the main fuel injection amount. In one example, the amount of fuel injected during a cycle of the cylinder determined at 806 is divided into the pilot fuel injection amount and the main fuel injection amount. Specifically, a portion of the amount of fuel injected into the cylinder during the cylinder cycle is output from a table or function of an empirically determined pilot fuel injection portion. The table or function can be referred to via engine speed and driver demand torque. The main fuel injection amount is the amount of fuel determined at 806 minus a predetermined amount of fuel allocated to the pilot fuel injection during the cylinder cycle. For example, if X grams of fuel are to be injected into the cylinder during a cycle of the cylinder, 10% of X grams of fuel are to be pilot injected, and the main fuel injection amount is X - (X·0.1) or 90% of X.

[0127] Alternatively, a predetermined amount of fuel can be allocated to the pilot fuel injection during the cylinder cycle. The predetermined amount can be determined empirically and can be stored in a table or function. The table or function can be referred to via engine speed and driver demand torque. The table outputs the predetermined amount of fuel to be pilot injected. The main fuel injection amount is the amount of fuel determined at 806 minus the predetermined amount of fuel allocated to the pilot fuel injection during the cylinder cycle. Method 800 proceeds to 810.

[0128] At 810, method 800 determines the actual total number of pilot fuel injections during a cycle of the cylinder. In one example, a table or function stores the value of the total number of pilot fuel injections provided to the cylinder during a cycle of the cylinder. This value can be determined empirically. The table or function can be retrieved or referenced via engine speed and driver demand torque. The amount of pilot fuel to be injected can be divided by the actual total number of pilot fuel injections to determine the amount of fuel in each pilot fuel injection. Alternatively, the amount of fuel in each pilot injection can be a portion / fraction of the amount of pilot injection fuel determined at 808. Method 800 proceeds to 812.

[0129] At 812, method 800 determines the actual total number of main fuel injections during a cycle of the cylinder. In one example, a table or function stores the value of the total number of main fuel injections provided to the cylinder during a cycle of the cylinder. This value can be determined empirically. The table or function can be retrieved or referenced via engine speed and driver demand torque. When fueling the cylinder during a cylinder cycle, the actual total number of main fuel injections can be one or two values. The amount of main injection fuel to be injected can be divided by the actual total number of main fuel injections to determine the amount of fuel in each main fuel injection. Alternatively, the amount of fuel in each main injection can be a portion of the amount of main injection fuel determined at 808. Method 800 proceeds to 814.

[0130] At 814, method 800 determines the amount of post - combustion fuel injected into the cylinder during a cycle of the cylinder. In one example, the amount of post - combustion fuel injected into the cylinder during a cycle of the cylinder can be determined by retrieving or referencing a table of post - combustion fuel injection amounts determined empirically. The table can be referenced via catalyst temperature and engine air flow. The table outputs the amount of fuel injected for post - combustion in the cylinder during a cycle of the cylinder. Additionally, method 800 can determine the actual total number of post - fuel injections from a table or function that stores the empirically determined post - fuel injection quantity. The table or function can be referenced via engine speed and driver demand torque. The amount of fuel injected in each post - combustion fuel injection can be the post - fuel injection amount for the cylinder cycle divided by the actual total number of post - combustion injections during the cylinder cycle. Method 800 proceeds to 816.

[0131] At 816, method 800 determines the timings of the pilot fuel injection, the main fuel injection, and the post fuel injection. In one example, the start of the injection timing of the pilot injection is determined empirically and stored in a table or function. The table or function is referenced by engine speed and driver demand torque. The table or function outputs the start of the pilot injection time in engine crankshaft degrees. The pilot fuel injection starts at the start of the pilot fuel injection time. Similarly, the start of the injection timings of the main combustion injection and the post combustion injection are determined empirically and stored in a table or function. The table or function is referenced by engine speed and driver demand torque. The table or function outputs the start of the main injection time and the start of the post combustion injection time in engine crankshaft degrees. The main combustion fuel injection and the post combustion fuel injection start at the respective starts of the injection times. Alternatively, method 800 can determine the end of the injection times of the pilot combustion injection, the main combustion injection, and the post combustion injection. The start of the injection time is then determined from the injector flow rate, the engine of the injection time, and the amount of fuel injected.

[0132] Method 800 also allocates the injections to each of the fuel injectors. In one example, which fuel injectors are allocated the pilot injection, the main injection, and the post injection can be determined empirically and stored in a table or function. The fuel injector allocation is output from the table or function and the table or function can be retrieved or referenced via engine speed and driver demand torque. For example, at lower engine speeds and loads, the table can allocate lower flow rate fuel injectors to output the pilot fuel injection and the main fuel injection. At medium engine speeds and loads, the table or function can allocate lower flow rate fuel injectors to output the pilot fuel injection and allocate higher flow rate fuel injectors to output the main pulse injection. The table can also allocate the post fuel injection to lower flow rate fuel injectors. At higher engine speeds and loads, the table or function can allocate higher flow rate fuel injectors to output the pilot fuel injection and the main pulse injection. The table or function can also alternate the pilot injection and the main injection between lower flow rate injectors and higher flow rate injectors as shown. The table or function can provide all of the fuel injector allocations and their combinations described in Figures 7A to 7H what follows. Figures 7A to 7H

[0133] Alternatively, which fuel injectors are assigned to inject fuel can be based on the amount of fuel injected during pilot injection, main injection, and post injection. For example, if the amount of fuel to be delivered as pilot injection fuel is less than or equal to a threshold, a lower flow rate fuel injector can be assigned to inject pilot fuel. If the amount of fuel to be delivered as pilot injection fuel is greater than the threshold, a higher flow rate fuel injector can be assigned to inject pilot fuel. Similarly, if the amount of fuel to be delivered as main injection fuel is less than or equal to a threshold, a lower flow rate fuel injector can be assigned to inject main pulse fuel. If the amount of fuel to be delivered as main injection fuel is greater than the threshold, a higher flow rate fuel injector can be assigned to inject main pulse fuel. Likewise, if the amount of fuel to be delivered as post combustion injection fuel is less than or equal to a threshold, a lower flow rate fuel injector can be assigned to inject post combustion fuel. If the amount of fuel to be delivered as post combustion injection fuel is greater than the threshold, a higher flow rate fuel injector can be assigned to inject post combustion fuel. Method 800 proceeds to 818.

[0134] At 818, method 800 injects a pilot fuel injection amount, a main fuel injection amount, and a post fuel injection amount. Fuel can be injected via the lower flow rate fuel injector and the higher flow rate fuel injector. Alternatively, in some examples, the fuel injectors can have substantially the same flow rate (e.g., the flow rates are within 2% of each other). Method 800 proceeds to exit.

[0135] Figure 8 The method can be performed for each engine cylinder such that fuel can be supplied to multiple engine cylinders via dual diesel fuel injectors. Additionally, if desired, a unique fuel injection timing can be assigned to each engine cylinder.

[0136] Thus, Figure 8 The method provides a diesel fuel injection method that includes: during a cycle of a cylinder, injecting diesel fuel into the cylinder via a low fuel flow rate diesel fuel injector and via a high fuel flow rate diesel fuel injector by a controller, the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector being positioned in the cylinder. The diesel fuel injection method includes where the low fuel flow rate diesel fuel injector provides a pilot fuel injection during the cycle of the cylinder. The diesel fuel injection method includes where the high fuel flow rate diesel fuel injector provides a main fuel injection during the cycle of the cylinder.

[0137] In some examples, diesel fuel injection also includes providing post-combustion fuel injection via a low flow rate diesel fuel injector during a cycle of a cylinder. The diesel fuel injection method includes where the cylinder is included in a four-stroke engine. The diesel fuel injection method includes where the cylinder is included in a two-stroke opposed piston engine. The diesel fuel injection method includes where injecting diesel fuel into the cylinder via a low fuel flow rate diesel fuel injector and injecting diesel fuel into the cylinder via a high fuel flow rate diesel fuel injector includes injecting a main fuel pulse via the low fuel flow rate diesel fuel injector and injecting a main fuel pulse via the high fuel flow rate diesel fuel injector.

[0138] Figure 8 The method also provides a diesel fuel injection method that includes: during a cycle of a cylinder, alternating pilot fuel injection between a first diesel fuel injector and a second diesel fuel injector by a controller, the first diesel fuel injector and the second diesel fuel injector being positioned in the cylinder, opening the second diesel fuel injector after providing a first pilot injection in the cycle to provide a second pilot fuel injection in the cycle after the first diesel fuel injector is closed, and starting to open the second diesel fuel injector after the expiration of the first pilot injection for the second pilot fuel injection before a shut-off dwell time of the first pilot fuel injector. The diesel fuel injection method includes where the first diesel fuel injector is a lower fuel flow rate diesel fuel injector and where the second diesel fuel injector is a higher fuel flow rate diesel fuel injector. The diesel fuel injection method includes where the first diesel fuel injector and the second diesel fuel injector provide substantially equal fuel flow rates.

[0139] In some examples, the diesel fuel injection method also includes providing alternating post-combustion fuel injection via the first diesel fuel injector and the second diesel fuel injector during a cycle of the cylinder. The diesel fuel injection method also includes providing a first main fuel injection via the first diesel fuel injector during a cycle of the cylinder. The diesel fuel injection method also includes providing a second main fuel injection via the second diesel fuel injector during a cycle of the cylinder. The diesel fuel injection method includes where alternating pilot fuel injection between the first diesel fuel injector and the second diesel fuel injector includes providing a series of pilot fuel injections via the first diesel fuel injector and the second diesel fuel injector, where the first diesel fuel injector does not inject diesel fuel when the second diesel fuel injector injects diesel fuel.

[0140] Figure 8The method also provides a diesel fuel injection method, which includes: during a cycle of a cylinder, via a controller, simultaneously providing a main fuel injection via a first diesel fuel injector and a second diesel fuel injector, the first diesel fuel injector and the second diesel fuel injector being positioned in the cylinder, the first diesel fuel injector being a low fuel flow diesel fuel injector, and the second diesel fuel injector being a high fuel flow diesel fuel injector. The diesel fuel injection method includes where the cylinder includes two pistons. The diesel fuel injection method includes where the cylinder is included in a two-stroke engine.

[0141] In some examples, the diesel fuel injection method includes where the main fuel injection occurs during the cylinder cycle, and the main fuel injection includes a main fuel injection injected via the first diesel fuel injector and a main fuel injection injected via the second diesel fuel injector, and where the main fuel injection injected via the first diesel fuel injector starts before the main fuel injection injected via the second fuel injector starts, and the method further includes ending the main fuel injection provided via the first diesel fuel injector and the main fuel injection provided via the second diesel fuel injector at the same time. The diesel fuel injection method further includes ending the main fuel injection provided via the first diesel fuel injector and the main fuel injection provided via the second diesel fuel injector at different times. The diesel fuel injection method further includes alternating pilot fuel injection between the first diesel fuel injector and the second diesel fuel injector.

[0142] Now referring to Figure 9 , a curve of the cylinder cycle is shown, which shows closely coupled pilot fuel injection and post fuel injection during the cylinder cycle according to Figure 8 's method. It can be provided via Figures 1 to 6 's shown system Figure 9 's sequence. Figure 9 A fuel injection timing diagram of a four-stroke engine or a two-stroke engine is shown. The fuel injection timing can be provided via the controller and fuel injectors described herein. The vertical lines represent the moments of interest (e.g., T70 to T86) during the corresponding sequence curves.

[0143] Figure 9 The first curve at the top of

[0144] Figure 9 represents the cylinder stroke of cylinder No. 1 of the engine. The horizontal axis is divided into a series of segments identifying the cylinder stroke where cylinder No. 1 is located as it travels from the left side to the right side of the drawing over time. The compression stroke is abbreviated as COMP, and the expansion stroke is abbreviated as EXP. * indicates the start of combustion of the shown cylinder cycle. Figure 1The fuel injection timing during a cylinder cycle of the fuel injector (69) shown, which injects diesel fuel into the first cylinder. The pulse widths (e.g., 901 and 903) vary in width, and the width is an indication of the amount of fuel injected in the fuel pulse. The wider the pulse, the greater the amount of fuel injected into the cylinder during the pulse. The thick line 998 represents the injector off-time during which the first fuel injector cannot open to inject fuel after being recently closed. The fuel injector off-time can be related to the physical properties of the first fuel injector and / or the driver circuit.

[0145] Figure 9 The third curve at the top of () represents the fuel injection timing during a cylinder cycle of the second fuel injector (e.g., a high-flow fuel injector such as Figure 1 The fuel injection timing during a cylinder cycle of the fuel injector (68) shown, which injects diesel fuel into the first cylinder. The pulse widths (e.g., 906 and 908) vary in width, and the width is an indication of the amount of fuel injected in the fuel pulse. The wider the pulse, the greater the amount of fuel injected into the cylinder during the pulse. The shorter the pulse, the smaller the amount of fuel injected into the cylinder during the pulse. The thick line 999 represents the injector off-time during which the second fuel injector cannot open to inject fuel after being recently closed. The fuel injector off-time can be related to the physical properties of the second fuel injector and / or the driver circuit.

[0146] At time T70, the fuel injector begins injecting a first pilot fuel injection 901 during the cylinder cycle. The second fuel injector does not inject fuel. The first fuel injector stops injecting fuel at time T71, and the injector off-time 998 of the first fuel injector begins. At time T72, the second fuel injector begins injecting a second pilot fuel injection 906 during the fuel injection off-time of the first fuel injector. The second fuel injector stops injecting fuel at time T73, and the off-time 999 of the second fuel injector begins. While the off-time of the second fuel injector is in progress, the first fuel injector provides a third pilot fuel injection 902 at time T74. The third pilot fuel injection provided by the first fuel injector stops at time T75. While the off-time of the first fuel injector is active, the second fuel injector begins a fourth pilot injection 907 at time T76. Thus, by staggering the fuel injection times of the two fuel injectors, a closer pilot fuel injection can be provided than can be provided by using a single fuel injector.

[0147] Between time T76 and time T80, the first fuel injector and the second fuel injector each provide a main fuel injection, and their respective closing dwell times are after the main fuel injection. The closing dwell time ends well before the post fuel injection starts at time T80.

[0148] At time T80, the fuel injector starts to inject the first post fuel injection 904 during the cylinder cycle. The second fuel injector does not inject fuel. The first fuel injector stops injecting fuel at time T81, and the injector closing dwell time 998 of the first fuel injector starts. At time T82, the second fuel injector starts to inject the second post fuel injection 909 during the fuel injection closing dwell time of the first fuel injector. The second fuel injector stops injecting fuel at time T83, and the closing dwell time 999 of the second fuel injector starts. When the closing dwell time of the second fuel injector is in progress, the first fuel injector provides the third post fuel injection 905 at time T84. The third pilot fuel injection provided by the first fuel injector stops at time T85. When the closing dwell time of the first fuel injector is activated, the second fuel injector starts the fourth post injection 910 at time T86. Thus, by staggering the fuel injection times of the two fuel injectors, a closer post fuel injection can be provided than can be provided by using a single fuel injector.

[0149] In addition, the main injection through the other injector can be started during the closing dwell time of an injector after that injector has completed the pilot fuel injection, such that the main fuel injection can be closely coupled to the pilot fuel injection. For example, during the closing dwell time of the first fuel injector after the first fuel injector has completed the pilot fuel injection, the main injection from the second fuel injector can be started. Similarly, the post fuel injection through the other injector can be started during the closing dwell time of an injector after that injector has completed the main fuel injection, such that the post fuel injection can be closely coupled to the main fuel injection. For example, during the closing dwell time of the second fuel injector after the second fuel injector has completed the main fuel injection, the post injection from the first fuel injector can be started.

[0150] Note that the example control and estimation routines included herein can be used with a variety of engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transitory memory and implemented by a control system including a controller in combination with various sensors, actuators, and other engine hardware. Additionally, portions of the method can be actual actions taken in the real world to change the state of the device. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc. As such, the various actions, operations, and / or functions shown can be executed in the sequence shown, executed in parallel, or omitted in some cases. Similarly, the order of processing is not necessary to implement the features and advantages of the examples described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeated in accordance with the particular strategy being used. Additionally, the actions, operations, and / or functions described can represent code to be programmed into the non-transitory memory of a computer-readable storage medium for an engine control system, where the described actions are implemented by executing instructions in a system including various engine hardware components. One or more of the method steps described herein can be omitted if desired.

[0151] It should be understood that, because there can be many variations, the configurations and routines disclosed herein are exemplary in nature and these specific examples should not be considered limiting. For example, the above techniques can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, 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 disclosed herein, as well as other features, functions, and / or properties.

[0152] The appended claims particularly point out certain combinations and sub-combinations that are regarded as novel and non-obvious. These claims can refer to "a" element or "a first" element or the equivalent thereof. Such claims should be understood to include the combination of one or more such elements, neither requiring nor precluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties can be claimed by amendment of the claims of this application or by the presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal to, or different in scope from the original claims, are also regarded as included within the subject matter of the present disclosure.

Claims

1. A diesel fuel injection method, comprising: During a cycle of a cylinder, injecting diesel fuel into the cylinder via a low fuel flow rate diesel fuel injector and injecting diesel fuel into the cylinder via a high fuel flow rate diesel fuel injector by a controller, the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector being positioned in the cylinder; and During the cycle of the cylinder, alternately performing pilot fuel injection between the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector by the controller, after providing a first pilot fuel injection in the cycle, opening the high fuel flow rate diesel fuel injector to provide a second pilot fuel injection in the cycle after the low fuel flow rate diesel fuel injector is closed, and after the first pilot fuel injection, starting to open the high fuel flow rate diesel fuel injector for the second pilot fuel injection before the expiration of the off dwell time of the low fuel flow rate diesel fuel injector.

2. The diesel fuel injection method according to claim 1, wherein injecting diesel fuel into the cylinder via a low fuel flow rate diesel fuel injector and injecting diesel fuel into the cylinder via a high fuel flow rate diesel fuel injector includes injecting a main fuel pulse via the low fuel flow rate diesel fuel injector and injecting a main fuel pulse via the high fuel flow rate diesel fuel injector.

3. The diesel fuel injection method according to claim 1, further comprising providing alternate post-combustion fuel injection via the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector during the cycle of the cylinder.

4. The diesel fuel injection method according to claim 1, further comprising providing a first main fuel injection via the low fuel flow rate diesel fuel injector during the cycle of the cylinder.

5. The diesel fuel injection method according to claim 4, further comprising providing a second main fuel injection via the high fuel flow rate diesel fuel injector during the cycle of the cylinder.

6. The diesel fuel injection method according to claim 1, wherein alternately performing pilot fuel injection between the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector includes providing a series of pilot fuel injections via the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector, wherein when the high fuel flow rate diesel fuel injector is injecting diesel fuel, the low fuel flow rate diesel fuel injector does not inject diesel fuel.

7. The diesel fuel injection method according to claim 1, further comprising: During the cycle of the cylinder, providing main fuel injection simultaneously via the low fuel flow rate diesel fuel injector and the high fuel flow rate diesel fuel injector by a controller.

8. The diesel fuel injection method according to claim 7, wherein the cylinder includes two pistons.

9. The diesel fuel injection method according to claim 8, wherein the cylinder is included in a two-stroke engine.

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