Diesel engine cold start system and method

Abstract

The present invention relates to a diesel engine cold start system and method. A method and system for supply starting a diesel engine that does not include a glow plug is described. In one example, flow through a cylinder is restricted during engine cranking to heat the charge in the cylinder. In another example, a compressor is activated and air supplied to the engine cylinder is heated and recirculated via the engine and the compressor to improve engine starting.

Description

Technical Field

[0001] The invention relates to a diesel engine cold start system and method. Background Art

[0002] Diesel engines may include glow plugs to heat the air-fuel mixture within the diesel engine so that engine starting during cold conditions can be improved. A glow plug in an engine cylinder can raise the temperature within the engine cylinder so that the air-fuel mixture within the cylinder can ignite under increased cylinder pressure as the piston in the cylinder approaches top dead center compression stroke. Because the engine tends to heat the air-fuel mixture, the glow plug can be deactivated when the engine is warm and restarted. Therefore, it may be desirable to include a glow plug (e.g., an electric heater) in a diesel engine. However, due to the configuration of the engine and because the glow plug typically protrudes into the engine cylinder, it may not be possible to install a glow plug in some diesel engines. Therefore, it is desirable to provide a way to cold start a diesel engine without having to rely on a glow plug. Summary of the invention

[0003] The present inventors have recognized the above-mentioned shortcomings and have developed a diesel engine starting method, which includes: in response to an engine starting request, adjusting a supercharger having multiple drive ratios to a highest drive ratio, cranking the engine, and injecting fuel into the engine during the cranking, wherein injecting fuel during the engine cranking includes injecting a certain amount of fuel into the engine cylinders during the engine cycle, so as to provide that less than 10% of the energy in the fuel injected during the engine cycle is released.

[0004] By adjusting the supercharger ratio in response to an engine start request and injecting a small amount of fuel into the engine cylinder during the engine start rotation, a diesel engine that does not include a glow plug can be reliably cold started. In particular, increasing the supercharger ratio can increase the amount of work done on the air entering the engine cylinder, thereby increasing the temperature in the engine cylinder. In addition, the temperature in the engine cylinder can be increased via the low-temperature heat released from the injected small amount of fuel. Instead of injecting a larger amount of cold fuel into the engine cylinder and significantly cooling the air and fuel mixture in the engine cylinder, a small amount of fuel can be injected into the cylinder, and the small amount of fuel can release its heat into the cylinder when compressed without the need for the small amount of fuel to be completely burned. The heat added to the cylinder can be sufficient to promote the combustion of a larger amount of fuel subsequently injected into the cylinder. The combustion of a larger amount of fuel can accelerate the engine crankshaft, thereby starting the engine. When less than 10% of the injected fuel is burned, the percentage of the injected fuel participating in the first phase of the two-phase diesel fuel combustion is higher than the percentage of the injected fuel participating in the second phase of the two-phase diesel combustion, so that cylinder heating can be improved.

[0005] The present description may provide several advantages. Specifically, the method may allow a diesel engine to be started without a glow plug during cold conditions. Furthermore, in at least one example, the charge in the cylinder may be heated without releasing significant exhaust emissions. Additionally, the method may apply different engine starting procedures for different low engine temperature engine starting conditions.

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

[0007] It should be understood that the above summary is provided to introduce a selection of concepts that are further described in the detailed description in a simplified form. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the appended claims. Furthermore, 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 diagram of an engine is shown.

[0009] Figure 2 and Figure 3 Show Figure 1 The example of an engine shown in FIG. 1 is indicative of an engine starting sequence.

[0010] Figure 4A and Figure 4B Shown for starting Figure 1 An example method for an engine. DETAILED DESCRIPTION

[0011] These instructions relate to starting a diesel engine. Figure 1 An example of a boosted diesel engine is shown that does not include a glow plug. Figure 2 and Figure 3 Two different engine starting sequences are shown for starting an engine from a cold start. FIG. 4A to FIG. 4B Shown for starting Figure 1 The method of the engine shown in FIG.

[0012] Reference Figure 1 , controlled by an electronic engine controller 12, comprising a plurality of cylinders (one of which is Figure 1 10. The controller 12 receives the information from Figure 1 The signals of various sensors are used Figure 1 Various actuators are controlled to adjust engine operation based on received signals and instructions stored in the controller's memory.

[0013] The engine 10 includes a cylinder 30 and a cylinder wall 32 having an intake piston 36a and an exhaust piston 36b positioned therein and connected to a crankshaft 40a and a crankshaft 40b, respectively. The crankshafts 40a and 40b may be coupled together via a belt, a chain, or a gear. The crankshafts 40a and 40b may be rotated by an electric machine 77 (e.g., a starter motor) to start the engine 10. The cylinder 30 shown is in communication with an intake manifold 44 and an exhaust manifold 48 via intake passages 44a and 44b and exhaust passages 48a and 48b.

[0014] Fuel injector 68 and fuel injector 69 are shown positioned in cylinder wall 32, and they can inject fuel directly into cylinder 30, which is known to those skilled in the art as direct injection. Fuel is delivered to fuel injector 68 and fuel injector 69 by a fuel system including fuel tank 95, fuel pump 91, fuel pump control valve 93, and a fuel rail (not shown). The fuel pressure delivered by the fuel system can be adjusted by changing the position valve that regulates the flow to the fuel pump (not shown). In addition, a metering valve can be located in or near the fuel rail for closed-loop fuel control. The pump metering valve can also regulate the fuel flow to the fuel pump, thereby reducing the fuel pumped to the high-pressure fuel pump.

[0015] Intake manifold 44 is shown in communication with optional electronic throttle 62, which adjusts the position of throttle plate 64 to control air flow from intake boost chamber 46. Supercharger compressor 162 is mechanically driven and draws air from downstream of turbocharger compressor 135. Turbocharger compressor 135 draws air from air intake 42. Supercharger compressor 162 supplies air to boost chamber 46. Exhaust gas rotates turbocharger variable geometry turbine 137 coupled to turbocharger compressor 135 via shaft 136. Supercharger compressor 162 is mechanically driven via crankshaft 40b via shaft 161 and gearbox 163, which may be coupled to crankshaft 40b via mechanism 164 (e.g., gears, chain, or belt). Supercharger gearbox 163 includes multiple gear ratios for changing the speed of supercharger compressor 162 relative to the speed of crankshaft 40b. Supercharger compressor speed may be adjusted via selecting and engaging gear 163a of gearbox 163. In one example, a given engine crankshaft speed may rotate supercharger compressor 162 at a first speed and a second speed via switching between a first gear ratio and a second gear ratio in gearbox 163.

[0016] The supercharger compressor bypass valve 158 may be selectively opened to reduce the air pressure in the boost chamber 46 and return air and exhaust gas recirculation (EGR) to the upstream of the supercharger compressor 162. In some examples, a charge air cooler 156 may be disposed downstream of the supercharger compressor 162 to cool the air charge entering the cylinder 30. The air charge cooler bypass valve 157 may be selectively opened to bypass the charge air cooler 156. The position of the vane actuator 137a may be adjusted via the controller 12 to increase or decrease the rotational speed of the turbine 137. In an alternative example, the wastegate 137b may replace the vane actuator 137a or use the wastegate 137b in addition to the vane actuator 137a. The vane actuator 137a adjusts the position of the variable geometry turbine vanes. When the vanes are in the open position, the exhaust gas can pass through the turbine 137 to supply little energy to rotate the turbine 137. When the vanes are in the closed position, exhaust gas is able to pass through turbine 137 and exert increased force on turbine 137. Alternatively, a wastegate 137b or bypass valve allows exhaust gas to flow around turbine 137 to reduce the amount of energy supplied to the turbine.

[0017] In an alternate example, supercharger compressor 162 may be positioned upstream of turbocharger compressor 135. Additionally, an air charge cooler (not shown) may be positioned downstream of where EGR passage 82 joins intake 43 between supercharger compressor 162 and turbocharger compressor 135. The air charge cooler would eliminate the need for an EGR cooler.

[0018] Exhaust gas may be recirculated to cylinder 30 via EGR system 81. The EGR system includes an optional EGR cooler 85, an EGR valve 80, an EGR passage 82, an EGR cooler bypass 84, and a cooled EGR passage 83. Exhaust gas may flow from exhaust manifold 48 to engine air intake 43 between supercharger compressor 162 and turbocharger compressor 135. When the pressure in exhaust manifold 48 is greater than the pressure between turbocharger compressor 135 and supercharger compressor 162, EGR may flow to the engine air intake. EGR may flow through EGR cooler 85 to reduce engine exhaust temperature. When the engine exhaust temperature is low, EGR may bypass EGR cooler 85.

[0019] After intake piston 36a covers intake passages 44a and 44b and exhaust piston 36b covers exhaust passages 48a and 48b, fuel may be injected into cylinder 30 as piston 36a and piston 36b approach each other. The fuel may then combust with the air in cylinder 30 as piston 36 approaches top dead center compression stroke. The fuel and air are ignited via compression ignition. In some examples, universal exhaust gas oxygen (UEGO) sensor 126 may be coupled to exhaust manifold 48 upstream of emissions device 70. In other examples, the UEGO sensor may be located downstream of one or more exhaust aftertreatment devices. Further, in some examples, the UEGO sensor may be replaced by a NOx sensor having both NOx and oxygen sensing elements.

[0020] Because engine 10 is a compression ignition engine and does not include a cylinder head, engine 10 does not include glow plugs or spark plugs. In addition, engine 10 does not include a poppet valve to regulate air and exhaust flow into and out of cylinder 30.

[0021] Exhaust valve 140 is shown positioned in exhaust passage 49 downstream of turbine 137a and upstream of exhaust device 70. Alternatively, exhaust valve 140 may be positioned downstream of exhaust device 70. Exhaust valve 140 may be opened and closed to control pressure in exhaust manifold 48. Closing exhaust valve 140 restricts flow through exhaust valve 140 and may increase pressure in exhaust manifold 48. Opening exhaust valve 140 may improve flow through exhaust valve 140 and reduce pressure in exhaust manifold 48.

[0022] In one example, the emission device 70 may include an oxidation catalyst and a particulate filter. In another example, multiple emission control devices may be used, each with multiple bricks. In one example, the emission device 70 may include an oxidation catalyst. In other examples, the emission device may include a lean NOx trap or a selective catalytic reduction (SCR) and / or a diesel particulate filter (DPF). The upstream temperature sensor 79 and the downstream temperature sensor 81 provide exhaust temperature measurements for determining changes in exhaust temperature across the emission device 70.

[0023] The controller 12 Figure 11 is shown as a conventional microcomputer including: a microprocessor unit (CPU) 102, input / output ports (I / O) 104, read-only memory (ROM) (e.g., non-volatile memory) 106, random access memory (RAM) 108, keep-alive memory (KAM) 110, and a conventional data bus. In addition to those signals previously discussed, controller 12 is shown receiving various signals from sensors coupled to engine 10, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling jacket 114; position sensor 134 coupled to accelerator pedal 130 for sensing accelerator position adjusted by a person's foot 132; a measurement of engine manifold pressure (MAP) from pressure sensor 121 coupled to intake manifold 44; boost pressure from pressure sensor 122; exhaust oxygen concentration from oxygen sensor 126; engine position sensor sensing position of crankshaft 40b from Hall effect sensor 118; a measurement of the mass of air entering the engine from sensor 120 (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor 58. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, engine position sensor 118 produces a predetermined number of equally spaced pulses per revolution of the crankshaft from which engine speed (RPM) may be determined.

[0024] During operation, each cylinder within engine 10 typically undergoes a two-stroke cycle: the cycle includes a first stroke, in which intake piston 36a travels toward exhaust piston 36b and exhaust piston 36b travels toward intake piston 36a. In a second stroke, intake piston 36a travels away from exhaust piston 36b and exhaust piston 36b travels away from intake piston 36a. Intake piston 36a controls flow through intake passages 44a and 44b. Exhaust piston 36b controls flow through exhaust passages 48a and 48b. In this example, exhaust piston 36b leads intake piston 36a by reaching a top dead center position (e.g., the maximum distance of exhaust piston 36b from crankshaft 40b) several crankshaft degrees (e.g., depending on the configuration, the difference can range between 0 crankshaft degrees and 20 crankshaft degrees). Therefore, the exhaust piston motion is offset from the intake piston motion by several crankshaft degrees.

[0025] During the first stroke, generally the intake piston 36a and the exhaust piston 36b move toward each other to compress the air that has entered the cylinder 30. The stroke begins at the bottom dead center (BDC) of the intake piston 36a (the intake piston 36a is at the closest distance to the crankshaft 40a), and it ends at the top dead center of the intake piston 36a (the intake piston 36a is at its farthest distance from the crankshaft 40a). As previously described, the exhaust piston 36b leads the intake piston 36a by several degrees, so that when the intake piston is at BDC, the exhaust piston 36b has already traveled toward its TDC position. In addition, the exhaust piston 36b reaches its TDC position just before the intake piston 36a reaches its TDC position. When the intake piston 36a reaches its TDC position, the exhaust piston 36b is just behind its TDC position. When the intake piston 36a and the exhaust piston 36b are close to their respective TDC positions, the cylinder volume is minimum. As the intake piston 36a and the exhaust piston 36b advance toward their respective TDC positions, air and fuel are compressed in the cylinder 30. When the intake piston 36a and the exhaust piston 36b approach their respective BDC positions, the intake passages 44a and 44b open and pressurized air flows into the cylinder 30. When the intake piston 36a and the exhaust piston 36b approach BDC, the exhaust passages 48a and 48b also open. The supercharger compressor 162 and the turbocharger compressor 135 provide pressurized air to the intake manifold 44, and when the intake passages 44a and 44b are opened, the pressurized air can flow into the cylinder 30. When the intake piston 36a and the exhaust piston 36b move toward their respective TDC positions, the exhaust passages 48a and 48b are closed. The crankshaft continues to rotate, and after a predetermined actual total crankshaft degree, the intake passages 44a and 44b are closed to prevent additional air from entering the cylinder 36. Thus, the exhaust port opens before the intake port, and the exhaust port remains open for substantially the entire duration that the intake port is open. Fuel is injected into cylinder 30 after exhaust ports 44a and 44b are closed, and then the fuel and air mixture is ignited when intake piston 36a and exhaust piston 36b are near their respective TDC positions. The fuel and air mixture is ignited by compression ignition rather than by energy from a spark plug or a glow plug. Fuel may be injected into cylinder 30 via multiple injections, including a pilot injection, a main injection, and a post injection.

[0026] During the second stroke, usually after combustion occurs in the cylinder 30, the intake piston 36a and the exhaust piston 36b move apart from each other. The second stroke starts at the TDC of the intake piston 36a and ends at the BDC of the intake piston 36a. The intake piston 36a and the exhaust piston 36b approach their respective BDC positions near the maximum volume of the cylinder 30. The gas expanding in the cylinder 30 pushes the intake piston 36a and the exhaust piston 36b apart to their respective BDC positions. When the exhaust piston 36b moves toward its BDC, the exhaust piston 36b passes through the exhaust passages 48a and 48b. When the top of the exhaust piston 36d passes through the exhaust passages 48a and 48b and the exhaust piston 36b moves toward the crankshaft 40b, the exhaust passages 48a and 48b are uncovered. After the exhaust piston 36b passes through the exhaust passages 48a and 48b and moves toward the bottom dead center at the same time, the exhaust gas leaves the cylinder 30. Intake piston 36a and exhaust piston 36b further advance toward their respective bottom dead center positions, and after a predetermined actual total crankshaft degree, intake piston 36a uncovers intake passages 44a and 44b. When the top of intake piston 36c passes through intake passages 44a and 44b while intake piston 36a advances toward crankshaft 40a, intake passages 44a and 44b are uncovered. When intake passages 44a and 44b are uncovered, fresh air enters cylinder 30 via intake passages 44a and 44b. Intake piston 36a and exhaust piston 36b continue to advance toward their respective BDC positions. After the intake piston reaches BDC, the cylinder cycle repeats.

[0027] Thus, an engine cycle consists of two strokes, and an engine cycle is one engine rotation. The other engine cylinders operate in a similar manner, but these other cylinders may combust air and fuel out of phase with the cylinders shown. For example, the top dead center compression stroke of one engine cylinder may be zero crankshaft degrees, while the top dead center of another cylinder may be one hundred and eighty crankshaft degrees.

[0028] Figure 1The system provides an engine system, which includes: an opposed piston diesel engine including a fuel injector and not including a glow plug; a supercharger coupled to the opposed piston diesel engine, the supercharger having a multiple gear ratio; a turbocharger coupled to the opposed piston diesel engine; and a controller, which includes executable instructions stored in a non-transitory memory to adjust the supercharger to a highest gear ratio in response to a request to start the opposed piston diesel engine, crank the opposed piston diesel engine, and open a charge air cooler. The engine system also includes additional instructions to inject fuel into the engine during cranking, wherein injecting fuel during engine cranking includes injecting a certain amount of fuel into the engine cylinder during the engine cycle, so that only a single-phase combustion of the two-phase diesel fuel combustion is provided during the engine cycle. The engine system also includes additional instructions to increase the amount of fuel injected into the engine after the engine cycle is completed while cranking the engine. The engine system also includes additional instructions for adjusting the supercharger with multiple gear ratios to a gear ratio lower than the highest gear ratio in response to the engine temperature exceeding a threshold. The engine system also includes additional instructions to fully open the vanes of the turbocharger in response to a request to start the opposed-piston engine. The engine system also includes additional instructions to fully open the exhaust gas recirculation valve in response to a request to start the opposed-piston diesel engine.

[0029] Reference now Figure 2 , shows a first example engine starting sequence according to method 400 . Figure 2 The engine starting sequence can be used for Figure 1 The engine and system shown in . The vertical lines at time T1 to time T5 represent the times of interest in the sequence. The graphs are aligned in time and occur simultaneously. In this example engine start sequence, work is performed on the air in the engine via the supercharger compressor and engine compression. After the air passes through the engine cylinders via the EGR passage, the air in the engine can be recirculated from the supercharger compressor outlet to the supercharger compressor inlet so that additional work can be performed on the air via the supercharger compressor. As a result, the air temperature in the engine can increase to promote and achieve compression ignition in the engine cylinders.

[0030] since Figure 2 The first graph from the top is a graph of engine intake manifold pressure versus time. Trace 201 represents engine intake manifold pressure. The vertical axis represents engine intake manifold pressure, and engine intake manifold pressure increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0031] since Figure 2The second graph from the top is a graph of engine exhaust manifold pressure versus time. Trace 202 represents engine exhaust manifold pressure. The vertical axis represents engine exhaust manifold pressure, and engine exhaust manifold pressure increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0032] since Figure 2 The third graph from the top is a graph of engine temperature (e.g., engine coolant temperature) versus time. Trace 203 represents engine temperature. The vertical axis represents engine temperature, and engine temperature increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Line 250 represents a threshold temperature, below which the currently shown engine starting procedure is applied to a cold start engine.

[0033] since Figure 2 The fourth graph from the top is a graph of the engine air charge cooler bypass valve state versus time. Trace 204 represents the engine air charge cooler bypass valve state. The vertical axis represents the engine air charge cooler bypass valve state, and when trace 204 is at a higher level near the vertical axis arrow, the engine air charge cooler bypass valve is open. When trace 204 is at a lower level near the horizontal axis, the engine air charge cooler bypass valve is closed. When the engine charge air cooler valve is open, the engine air charge cooler is bypassed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0034] since Figure 2 The fifth graph from the top is a graph of variable geometry turbocharger (VGT) vane position versus time. Trace 205 represents the VGT vane position, and when trace 205 is close to the vertical axis arrow, the VGT vane is fully open. When trace 205 is close to the horizontal axis, the VGT vane is fully closed. When the VGT vane is open, the exhaust exerts a greater force on the VGT vane, allowing the turbocharger compressor to rotate at a higher speed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0035] since Figure 2 The sixth graph from the top is the exhaust valve position (eg, Figure 1 140) versus time. The vertical axis represents exhaust valve position. Trace 206 represents exhaust valve position, and when trace 206 is close to the vertical axis arrow, the exhaust valve is fully open. When trace 206 is close to the horizontal axis, the exhaust valve is fully closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0036] since Figure 2The seventh graph from the top is a graph of the amount of fuel injected into the engine versus time. Trace 207 represents the amount of fuel injected into the engine. The vertical axis represents the amount of fuel injected into the engine, and the amount of fuel injected into the engine increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0037] since Figure 2 The eighth graph from the top is the supercharger bypass valve position (e.g. Figure 1 158) versus time. The vertical axis represents the supercharger bypass valve position. Trace 208 represents the supercharger bypass valve position, and when trace 208 is close to the vertical axis arrow, the supercharger valve is fully open. When trace 208 is close to the horizontal axis, the supercharger bypass valve is fully closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0038] since Figure 2 The ninth graph from the top is a graph of supercharger transmission ratio versus time. The vertical axis represents the supercharger transmission ratio. Trace 209 represents the supercharger transmission ratio. The second supercharger transmission ratio is a higher transmission ratio than the first supercharger transmission ratio, and when the second supercharger transmission ratio is engaged, the supercharger compressor rotates at a higher speed relative to the engine crankshaft speed. When the first supercharger transmission ratio is engaged, the supercharger compressor rotates at a lower speed relative to the engine crankshaft speed. Therefore, by engaging the second supercharger transmission ratio, the supercharger compressor rotates at a higher speed than when the first supercharger transmission ratio is engaged. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0039] since Figure 2 The tenth graph from the top is a graph of engine operating state versus time. The vertical axis represents the engine operating state and the engine operating state of off (no engine rotation), cranking (engine rotation via electric machine), and on (engine rotation under its own torque output). Trace 210 represents the engine operating state. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0040] since Figure 2 The eleventh graph from the top is a graph of EGR valve position versus time. The vertical axis represents EGR valve position. Trace 211 represents EGR valve position, and the EGR valve is fully open when the EGR trace 211 is close to the vertical axis arrow. When the EGR trace 211 is close to the horizontal axis, the EGR valve is fully closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0041] At time T0, the engine is operating and burning air and fuel. The intake manifold pressure is at a high level and the exhaust manifold pressure is at an intermediate level. The engine is operating at a warm temperature and the air charge cooler bypass valve is closed so that the air entering the engine cylinder is cooled. The VGT vane is closed and the exhaust valve is fully open. The fuel injection amount is at a low level and the supercharger bypass valve is partially open. The supercharger gear ratio is at a low ratio and the EGR valve is partially open.

[0042] At time T1, the engine is stopped. The engine can be stopped via a human driver or an autonomous driver. As the engine is stopped, the intake manifold pressure and the exhaust manifold pressure decrease. The VGT vane remains closed, and the air charge cooler bypass valve remains closed. The exhaust valve remains open and no fuel is injected into the engine. The supercharger bypass valve is fully closed, and the supercharger gear ratio is maintained at the first gear ratio. The EGR valve is fully closed.

[0043] Between time T1 and time T2, the intake manifold pressure and the exhaust manifold pressure drop. The engine temperature drops to less than the threshold 250 and the exhaust valve remains fully open. Fuel is not injected into the engine and the supercharger bypass valve is closed. The EGR valve also remains closed.

[0044] At time T2, the engine is cranked in response to a request to start the engine (not shown). The supercharger gear ratio is engaged with the second ratio to increase the work done on the air within the engine and its intake system. By engaging the second ratio, a greater amount of work can be done on the air in the engine intake system. The EGR valve is fully open and the exhaust valve is fully closed so that air warmed by the supercharger compressor can be circulated through the engine, where compression work can be added to further heat the air. The air then returns to the supercharger compressor, where additional work is done on the air, further increasing the air temperature in preparation for combustion of the starting fuel supply injected into the engine cylinders (e.g., a fuel supply to complete two-phase combustion). The VGT vanes are also fully open, so that the exhaust valves (e.g., Figure 1 140) controls the exhaust manifold exhaust pressure. The supercharger bypass valve is closed so that air flowing through the supercharger is not directly recirculated back to the supercharger input without having to flow through the engine. The air charge cooler bypass valve is opened to reduce the cooling of the air flowing through the engine.

[0045] Between time T2 and time T3, a small amount of fuel is injected into each engine cylinder. Alternatively, fuel injection can be disabled. If fuel is injected, the amount of fuel injected is less than the amount of two-phase combustion of the injected fuel caused during the engine cycle of the injected fuel. Diesel fuel is a fuel that exhibits two-phase combustion. During the first phase of combustion (e.g., low-temperature exothermic phase), larger chain hydrocarbons decompose into smaller chain hydrocarbons in an exothermic reaction. The first phase of combustion can be characterized by the presence of formaldehyde formation and the absence of OH radicals and CO2. The second phase of fuel combustion is identified by CO2 formation and OH radical formation. Subjecting the fuel to multiple compression events provides more time for the fuel to react chemically and reach the second stage ignition. If the combustion chamber is subjected to the second stage ignition, both a small amount of fuel and a large amount of fuel will heat the combustion chamber. However, in the second compression event or the third compression event, a large amount of fuel is more likely to ignite prematurely. In addition, if ignition occurs very early with a small amount of fuel, the piston will not be significantly slowed, but if the second stage ignition occurs very early in the compression stroke, the large amount of fuel will not provide enough force to slow the starting rotation speed, but it may also cause a change in the direction of rotation. However, by injecting a small amount of fuel, first phase combustion and heat release can be achieved even if second phase combustion is not achieved. Because the air-fuel mixture in the cylinder is too lean to support second phase combustion, the second phase of fuel combustion is prevented when a small amount of fuel is injected into the cylinder. However, the heat released during the first phase of combustion can further heat the air and the remaining fuel mixture to prepare for the engine starting fuel supply (e.g., the first fuel supply delivered to the engine cylinder, which participates in the first instance of two-phase combustion in the cylinder since the most recent engine starting rotation segment). The small amount of fuel injection that only achieves first phase combustion in the engine cylinder can be referred to as an engine supply warming fuel supply or a pre-start fuel supply.

[0046] The intake manifold pressure is greater than the exhaust manifold pressure so that gas can circulate from the supercharger compressor to the engine cylinders, then to the EGR passage and back to the supercharger compressor inlet. Since the exhaust valve is closed, the intake manifold pressure increases via the supercharger compressor and the exhaust pressure is at a higher level. The engine temperature remains below the threshold 250 and the air charge cooler bypass valve remains open. The VGT vane remains fully open and the supercharger bypass valve remains fully closed. The supercharger gear ratio remains at a high level and the EGR valve is fully open.

[0047] At time T3, the amount of fuel injected is increased to deliver the engine start fuel supply. The time interval between time T2 and time T3 may be a function of the engine temperature and the actual total number of engine charge warming fuel supplies delivered to the engine since the most recent engine start cranking began. The actual number of engine charge warming fuel supplies may indicate a temperature increase within the engine. In this way, the actual number of engine charge warming fuel supplies may be used to determine when the engine start fuel supply may be delivered and expected to provide two-phase combustion and engine acceleration. The intake manifold pressure and the exhaust manifold pressure are maintained at previous levels, and the air charge cooler bypass valve is maintained open. The VGT vane is maintained fully open and the exhaust valve is open. The supercharger bypass valve is maintained closed and the supercharger gear ratio is maintained at level 2. The engine continues to be cranked and the EGR valve is maintained open.

[0048] At time T4, the last engine start fuel supply is delivered (at least one engine start fuel supply is provided to each engine cylinder) and the engine is accelerated (not shown). As the engine accelerates, the engine intake manifold pressure increases and the exhaust pressure also rises. The exhaust valve remains open. Because it is no longer necessary to recirculate the heated charge via the supercharger compressor to start the engine, the EGR valve is closed. The engine is switched to the running state and the VGT vane is partially closed to activate the turbocharger compressor. The charge air cooler bypass valve remains open so that the charge air is not cooled and the amount of fuel injected is reduced to allow the engine to rotate at idle speed. Because the engine boost pressure is sufficient, the supercharger bypass valve is also partially opened. The supercharger gear ratio is maintained at the second ratio.

[0049] Between time T4 and time T5, the engine temperature begins to increase and the remaining control parameters remain unchanged. At time T5, the engine temperature exceeds the threshold 250 and the supercharger gear ratio is reduced in response to the engine temperature exceeding the threshold 250. The air charge cooler bypass valve is also closed, and the supercharger gear ratio is reduced in response to the engine temperature exceeding the threshold 250. The EGR valve is also partially opened to provide external EGR to the engine.

[0050] In this way, the gas (e.g., air) in the engine can be heated via the work produced by the supercharger compressor. The gas can be recirculated through the supercharger compressor to provide additional heating to the gas, and a small amount of fuel can be injected to further heat the gas circulating in the engine during the engine cranking. Then, after the engine starting fuel amount is injected into the engine cylinders, the engine can be accelerated under its own power. Therefore, instead of heating the air entering the engine via the glow plug, the supercharger compressor and the small amount of fuel injection can heat the gas in the engine so that two-stage combustion can be supported.

[0051] Reference now Figure 3 , a second example engine starting sequence according to method 400 is shown. Figure 2 The engine starting sequence can be used for Figure 1 The engine and system shown in . The vertical lines at time T10 to time T15 represent times of interest in the sequence. The graphs are aligned in time and occur simultaneously. In this example engine starting sequence, during at least a portion of the engine starting rotation, the intake manifold pressure and the exhaust manifold pressure are adjusted to substantially the same average pressure (e.g., within +5% of each other) in the engine cycle. By maintaining a substantially constant average pressure between the engine intake manifold and the engine exhaust manifold, work can be performed on the gases in the engine cylinders, thereby heating the contents of the engine cylinders so that combustion can be initiated without glow plugs. In addition, a small amount of fuel can be injected into the engine cylinders so that low temperature heat release from the fuel can further heat the contents of the engine cylinders and support combustion within the engine cylinders.

[0052] since Figure 3 The first graph from the top is a graph of engine intake manifold pressure versus time. Trace 301 represents engine intake manifold pressure. The vertical axis represents engine intake manifold pressure, and engine intake manifold pressure increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0053] since Figure 3 The second graph from the top is a graph of engine exhaust manifold pressure versus time. Trace 302 represents engine exhaust manifold pressure. The vertical axis represents engine exhaust manifold pressure, and engine exhaust manifold pressure increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0054] since Figure 3 The third graph from the top is a graph of engine temperature (e.g., engine coolant temperature) versus time. Trace 303 represents engine temperature. The vertical axis represents engine temperature, and engine temperature increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Line 350 represents a threshold temperature, below which the currently shown engine starting procedure is applied to a cold start engine.

[0055] since Figure 3The fourth graph from the top is a graph of the engine air charge cooler bypass valve state versus time. Trace 304 represents the engine air charge cooler bypass valve state. The vertical axis represents the engine air charge cooler bypass valve state, and when trace 304 is at a higher level near the vertical axis arrow, the engine air charge cooler bypass valve is open. When trace 304 is at a lower level near the horizontal axis, the engine air charge cooler bypass valve is closed. When the engine charge air cooler valve is open, the engine air charge cooler is bypassed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0056] since Figure 3 The fifth graph from the top is a graph of variable geometry turbocharger (VGT) vane position versus time. Trace 305 represents the VGT vane position, and when trace 305 is close to the vertical axis arrow, the VGT vane is fully open. When trace 305 is close to the horizontal axis, the VGT vane is fully closed. When the VGT vane is open, the exhaust exerts a greater force on the VGT vane, allowing the turbocharger compressor to rotate at a higher speed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0057] since Figure 3 The sixth graph from the top is the exhaust valve position (eg, Figure 1 140) versus time. The vertical axis represents exhaust valve position. Trace 306 represents exhaust valve position, and when trace 306 is close to the vertical axis arrow, the exhaust valve is fully open. When trace 306 is close to the horizontal axis, the exhaust valve is fully closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0058] since Figure 3 The seventh graph from the top is a graph of the amount of fuel injected into the engine versus time. Trace 307 represents the amount of fuel injected into the engine. The vertical axis represents the amount of fuel injected into the engine, and the amount of fuel injected into the engine increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0059] since Figure 3 The eighth graph from the top is the supercharger bypass valve position (e.g. Figure 1 158) versus time. The vertical axis represents the supercharger bypass valve position. Trace 308 represents the supercharger bypass valve position, and when trace 308 is close to the vertical axis arrow, the supercharger valve is fully open. When trace 308 is close to the horizontal axis, the supercharger bypass valve is fully closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0060] since Figure 3 The ninth graph from the top is a graph of supercharger transmission ratio versus time. The vertical axis represents the supercharger transmission ratio. Trace 309 represents the supercharger transmission ratio. The second supercharger transmission ratio is a higher transmission ratio than the first supercharger transmission ratio, and when the second supercharger transmission ratio is engaged, the supercharger compressor rotates at a higher speed relative to the engine crankshaft speed. When the first supercharger transmission ratio is engaged, the supercharger compressor rotates at a lower speed relative to the engine crankshaft speed. Therefore, by engaging the second supercharger transmission ratio, the supercharger compressor rotates at a higher speed than when the first supercharger transmission ratio is engaged. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0061] since Figure 3 The tenth graph from the top is a graph of engine operating state versus time. The vertical axis represents the engine operating state and the engine operating state of off (no engine rotation), cranking (engine rotation via electric machine), and on (engine rotation under its own torque output). Trace 310 represents the engine operating state. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0062] since Figure 3 The eleventh graph from the top is a graph of EGR valve position versus time. The vertical axis represents EGR valve position. Trace 311 represents EGR valve position, and the EGR valve is fully open when the EGR trace 311 is close to the vertical axis arrow. When the EGR trace 311 is close to the horizontal axis, the EGR valve is fully closed. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0063] At time T10, the engine is operating and burning air and fuel. The intake manifold pressure is at a high level and the exhaust manifold pressure is at an intermediate level. The engine is operating at a warm temperature and the air charge cooler bypass valve is partially open so that the air entering the engine cylinder is partially cooled. The VGT vane is closed and the exhaust valve is fully open. The fuel injection amount is at a low level and the supercharger bypass valve is partially open. The supercharger gear ratio is at a low ratio and the EGR valve is partially open.

[0064] At time T11, the engine is stopped. The engine may be stopped by a human driver or an autonomous driver. As the engine is stopped, the intake manifold pressure and the exhaust manifold pressure decrease. The VGT vane remains closed and the air charge cooler bypass valve is closed. The exhaust valve remains open and no fuel is injected into the engine. The supercharger bypass valve is fully closed and the supercharger gear ratio is maintained at the first gear ratio. The EGR valve is fully closed.

[0065] Between time T11 and time T12, the intake manifold pressure and the exhaust manifold pressure drop. The engine temperature drops below threshold 350 and the exhaust valve remains fully open. Fuel is not injected into the engine and the supercharger bypass valve is closed. The EGR valve also remains closed.

[0066] At time T12, the engine is cranked in response to a request to start the engine (not shown). The supercharger gear ratio is engaged with the second ratio to increase the work done on the air in the engine and its intake system. By engaging the second ratio, a greater amount of work can be done on the air in the engine intake system. The EGR valve is fully closed and the exhaust valve is fully closed. The supercharger bypass valve is fully opened so that most of the air pumped by the supercharger compressor returns to the supercharger compressor inlet. By closing the exhaust valve and opening the supercharger compressor valve, the intake manifold pressure and the exhaust manifold pressure can be maintained substantially the same. The air in the engine cylinder can be maintained in the engine cylinder and heated via the compression work provided by the engine when the engine is cranked. The VGT vane is also fully closed. The air charge cooler bypass valve is opened to reduce the cooling of the air flowing through the engine.

[0067] Between time T12 and time T13, a small amount of fuel is injected into each engine cylinder. Alternatively, fuel injection can be disabled. If fuel is injected, the amount of fuel injected is less than the amount that causes two-phase combustion of the injected fuel during the engine cycle in which the fuel is injected. By injecting a small amount of fuel, first-phase combustion and heat release can be achieved even if second-phase combustion is not achieved. Because the air-fuel mixture in the cylinder is too lean to support the second phase of combustion, the second phase of fuel combustion is prevented when a small amount of fuel is injected into the cylinder. However, the heat released during the first phase of combustion can further heat the air and the remaining fuel mixture to prepare for the engine start fuel supply (e.g., the first fuel supply delivered to the engine cylinder, which participates in the first instance of two-phase combustion in the cylinder since the most recent engine start rotation segment). The small amount of fuel injection that only achieves first-phase combustion in the engine cylinder can be referred to as an engine charge warming fuel supply or a pre-start fuel supply.

[0068] The engine temperature remains below threshold 350 and the air charge cooler bypass valve remains open. The VGT vane remains fully closed and the supercharger bypass valve remains fully open. The supercharger gear ratio remains at a high level and the EGR valve is fully open.

[0069] At time T13, the amount of fuel injected is increased to deliver the engine start fuel supply. The time interval between time T12 and time T13 may be a function of the engine temperature and the actual total number of engine charge heating fuel supplies delivered to the engine since the most recent engine start rotation began. The actual number of engine charge warming fuel supplies may indicate a temperature rise within the engine. In this way, the actual number of engine charge warming fuel supplies may be used to determine when the engine start fuel supply may be delivered and expected to provide two combustion phases and engine acceleration. The intake manifold pressure and the exhaust manifold pressure are maintained at their previous levels, and the air charge cooler bypass valve is maintained open. The VGT vane is maintained fully closed and the exhaust valve is open. The supercharger bypass valve is partially closed to provide air to the engine cylinders. The supercharger gear ratio is maintained at level 2. The engine continues to be started and the EGR valve is maintained closed.

[0070] At time T14, the last engine start fuel supply is delivered (at least one engine start fuel supply is provided to each engine cylinder) and the engine is accelerated (not shown). As the engine accelerates and the exhaust pressure also rises, the engine intake manifold pressure increases, but the exhaust pressure rise is limited by the partial opening of the exhaust valve. The EGR valve closes and the engine switches to the running state. The VGT vane remains closed to activate the turbocharger compressor. The charge air cooler bypass valve remains open so that the charge air is not cooled and the amount of fuel injected is reduced to allow the engine to rotate at idle speed. Because the engine boost pressure is sufficient, the supercharger bypass valve is also partially opened. The supercharger gear ratio maintains a second ratio.

[0071] Between time T14 and time T15, the engine temperature begins to increase and the remaining control parameters remain unchanged. At time T15, the engine temperature exceeds the threshold 350 and the supercharger gear ratio is reduced in response to the engine temperature exceeding the threshold 350. The air charge cooler bypass valve is also closed, and the supercharger gear ratio is reduced in response to the engine temperature exceeding the threshold 350. The EGR valve is also partially opened to provide external EGR to the engine.

[0072] In this way, the gas (e.g., air) in the engine can be heated via the work produced by engine compression. The gas can be compressed several times to promote combustion in the cylinder. In addition, a small amount of fuel can be injected during the engine cranking to further heat the gas in the cylinder. Then, after the engine starting fuel amount is injected into the engine cylinder, the engine can be accelerated under its own power. Therefore, instead of heating the air entering the engine via a glow plug, engine compression heating can be used to heat the cylinder contents.

[0073] Reference now FIG. 4A to FIG. 4B, a method for adjusting fuel injection timing is shown. FIG. 4A to FIG. 4B The method can be stored as executable instructions in a program such as Figure 1 A flow chart showing a method for starting a diesel engine that does not include a glow plug is shown. FIG. 4A to FIG. 4B The method can be combined with Figure 1 in the system and can be used with Figure 1 In addition, FIG. 4A to FIG. 4B At least a portion of the method may be incorporated as executable instructions stored in a non-transitory memory, while other portions of the method may be performed via a controller that transforms operating states of devices and actuators in the physical world. According to the method described below, the controller may employ engine actuators of an engine system to adjust engine operation.

[0074] At 402, method 400 determines whether engine operation (e.g., rotation and combustion) is desired. In one example, if a human or autonomous driver supplies an input to the controller indicating the desire for engine operation (e.g., inserting a key into a switch or pressing a button), method 400 determines that engine operation is desired. If method 400 determines that engine operation is desired, the answer is yes and method 400 proceeds to 404. Otherwise, the answer is no and method 400 proceeds to 422.

[0075] At 422, if the engine is operating, method 400 terminates injecting fuel to the engine. In addition, method 400 may adjust the selected actuator to a predetermined state to reduce engine start time if the engine is operating. For example, if the operating conditions indicate that Figure 2 If the engine start shown is desired, method 400 may adjust the charge cooler bypass valve to an open state, the VGT vane fully open, the exhaust valve closed, the supercharger to a second gear ratio, and the EGR valve open. Similarly, if operating conditions indicate that Figure 3 If the engine start shown is desired, method 400 may adjust the air charge cooler bypass valve to an open state, the VGT vane fully closed, the exhaust valve closed, the supercharger to a second gear ratio, the supercharger bypass valve open, and the EGR valve closed. In one example, when the engine temperature is within a first temperature range, it is desired Figure 2 The engine starting sequence shown is used to start the engine and when the engine temperature is in the second temperature range, it is expected that Figure 3 The engine start sequence shown is used to start the engine. The engine start temperature may be estimated from the ambient temperature and the amount of time the engine is expected to be inoperative. Alternatively, the engine actuators may be pre-set to a predetermined state regardless of the expected engine start temperature. After pre-setting the engine actuators, method 400 proceeds to exit.

[0076] At 404, method 400 determines whether the engine is operating. If the engine speed is greater than a threshold speed (e.g., 300 RPM), method 400 may determine that the engine is operating. If method 400 determines that the engine is operating, the answer is yes and method 400 proceeds to 420. Otherwise, the answer is no and method 400 proceeds to 406.

[0077] At 420 , method 400 adjusts engine actuators in response to vehicle operating conditions. For example, engine throttle position, EGR valve position, supercharger gear ratio, and fuel injection timing in response to driver demand torque and engine speed. Method 400 proceeds to exit.

[0078] At 406, method 400 judges whether the first starting mode is selected. In one example, the first starting mode may be selected in response to the engine temperature. If the engine temperature is within a first predetermined range (e.g., less than 20°C), the answer is yes and method 400 proceeds to 408. Otherwise, the answer is no and method 400 proceeds to 430 to start the engine via a second engine starting method.

[0079] At 408, method 400 fully opens the charge air cooler bypass valve, fully opens the VGT vane, fully closes the exhaust valve, fully closes the supercharger bypass valve, fully opens the EGR valve, and adjusts the supercharger gear ratio to a second gear ratio (e.g., a high gear ratio) in response to a request to start the engine. The supercharger gear ratio is engaged at the second gear ratio to increase the supercharger compressor output, which may increase charge heating within the engine system. The air charge cooler is bypassed and the supercharger is not bypassed to increase charge heating in the engine. The sequence is as follows Figure 2 The method 400 proceeds to 410 .

[0080] At 410, method 400 cranks the engine (e.g., rotating the engine via an electric machine) and flows pressurized air from a supercharger compressor to the engine cylinders. Additionally, method 400 begins injecting a small amount of fuel (e.g., a fuel amount less than a threshold amount to provide two-phase combustion of the fuel). As the engine rotates, the small amount of fuel is compressed, and the small amount of fuel provides low temperature heat release to the gases in the engine. Figure 2As discussed above with respect to the injected fuel, a small amount of fuel supports only the first phase of combustion. A small amount of fuel injected is insufficient to support two-phase combustion of the injected fuel. The small amount of fuel injected is an engine charge warming fuel supply or a pre-start fuel supply. When the engine start fuel supply is injected, fuel that is not burned in the first phase of combustion may be burned. While the engine is cranking, a predetermined amount of the engine charge warming fuel supply may be injected. The predetermined amounts of the engine charge warming fuel supply or injection may be determined empirically and may be a function of the engine temperature. Fuel may be injected when the piston approaches top dead center.

[0081] Method 400 injects an engine starting fuel supply or propellant to the engine cylinders after a predetermined actual total number of engine charge warming fuel injections have been injected or after a predetermined amount of time has passed since the most recent engine cranking. The engine starting fuel supply may be determined empirically and may be a function of engine temperature and engine intake manifold pressure. Figure 2 As discussed in the description of , the engine starting fuel supply burns the injected fuel in two combustion phases, and the engine can be accelerated due to the combustion. The mass of the engine starting fuel injector is greater than the mass of the engine charge warming fuel injector. In addition, the exhaust valve is fully opened to allow combustion gases to pass from the exhaust system. Method 400 proceeds to 412.

[0082] At 412, method 400 determines whether the engine is firing or whether a predetermined engine cranking time has elapsed since the most recent engine cranking began. If the engine speed exceeds a threshold speed (e.g., 300 RPM), method 400 may determine that the engine is firing. If the engine is not firing or the engine cranking time has not elapsed, the answer is no and method 400 returns to 412 and continues to inject fuel to the engine. If the engine is firing (e.g., burning air and fuel) or if the engine cranking time has been exceeded, the answer is yes and method 400 proceeds to 414.

[0083] At 414, if the engine is not firing and the threshold engine cranking time has been exceeded, method 400 terminates cranking the engine and supplying air and fuel to the engine cylinders. If the engine is firing, method 400 proceeds to 416 without adjusting the engine fuel and air supplied to the engine.

[0084] At 416 , method 400 continues to hold the exhaust valve open, partially close the VGT vane to accelerate the turbocharger turbine, adjust the amount of fuel delivered to the engine cylinders in response to driver demand torque, and partially open the supercharger bypass valve because operating the supercharger compressor in the second drive mode may provide excess air flow. Figure 2 This phase of the engine starting sequence is shown.

[0085] At 418 , method 400 reduces supercharger gear ratio, closes the charge air cooler bypass valve, and partially opens the EGR valve in response to engine temperature exceeding a threshold temperature. In one example, the threshold temperature may be a warm engine temperature (eg, 60° C.).

[0086] In this way, if Figure 2 As shown, the engine's charge may be heated via engine compression work done by cranking the engine, supercharger compressor work done on the air in the engine, and low temperature heat release provided solely by the first stage combustion of fuel injected during the engine cycle.

[0087] At 430, method 400 responds to Figure 3 The illustrated engine start request opens the charge air cooler bypass valve, fully closes the VGT vane, fully closes the exhaust valve, fully opens the supercharger bypass valve, adjusts the supercharger gear ratio to a maximum value (e.g., a second ratio), and fully closes the EGR valve. Figure 3 As discussed in the discussion of , the supercharger bypass valve is opened and the exhaust valve is closed to maintain substantially equal intake manifold pressure and exhaust manifold pressure during engine cranking. This allows the engine to compress and heat the charge in the engine cylinder multiple times. Method 400 proceeds to 432.

[0088] At 432 , method 400 cranks the engine via electric machine starting, restricts air flow through the engine cylinders, and injects a small amount of fuel (e.g., Figure 3 The small amount of fuel releases heat to the charge in the engine cylinder, thereby heating the contents of the engine cylinder. The small amount of fuel participates only in the first combustion phase in the cylinder cycle. When the engine starting fuel supply is injected into the engine cylinder, the fuel that was not burned in the first phase of combustion can be burned. Method 400 proceeds to 434.

[0089] At 434, method 400 determines whether a predetermined actual total number of engine charge warming fuel injections have been injected. By determining whether a predetermined actual total number of engine charge warming fuel injections have been performed, it can be estimated that the charge heating and charge temperature are sufficient to support two-phase fuel combustion in the engine cylinders. Alternatively, method 400 may determine whether the engine has been cranked for an amount of time exceeding a threshold value (e.g., 20 seconds) since the most recent engine crank. If method 400 determines that the engine crank time has exceeded the threshold value or if a predetermined actual total number of engine charge warming fuel injections has been exceeded, the answer is yes and method 400 proceeds to 436. Otherwise, the answer is no and method 400 returns to 432.

[0090] At 436, method 400 increases the amount of fuel injected so that the injected fuel participates in two-phase combustion during the engine cycle in which the fuel is injected. The injected fuel may be referred to as an engine starting fuel supply. The amount of fuel may be determined empirically and may be a function of engine temperature and atmospheric pressure. At time T13, as Figure 3 The method 400 may be configured to inject engine starting fuel. The injected fuel may burn and may accelerate the engine. In addition, the method 400 may open an exhaust valve to release combustion byproducts from the exhaust system of the engine. The engine may continue to be cranked while the fuel is injected. The method 400 may proceed to 438.

[0091] At 438, method 400 judges whether the engine is firing (e.g., burning air and fuel in two-phase combustion) or whether the engine has been cranked for an extended period of time and has exceeded an engine cranking threshold (e.g., 30 seconds). If the engine cranking threshold has been exceeded by cranking the engine for an extended period of time or if the engine is firing, the answer is yes and method 400 proceeds to 440. Otherwise, the answer is no and method 400 returns to 436.

[0092] At 440, if the engine is not firing and the threshold engine cranking time has been exceeded, method 400 terminates cranking the engine and supplying air and fuel to the engine cylinders. If the engine is firing, method 400 proceeds to 442 without adjusting the engine fuel and air supplied to the engine.

[0093] At 442 , method 400 partially closes the VGT vane to initiate turbocharger compressor operation, continues to hold the charge cooler bypass valve open, partially opens the supercharger bypass valve to reduce air pressure in the boost chamber, and continues to hold the EGR valve closed. Method 400 proceeds to 444 .

[0094] At 444 , method 400 closes the charge cooler bypass valve, partially opens the EGR valve, and reduces the supercharger gear ratio in response to the engine reaching a threshold temperature (eg, an engine temperature indicative of a warm engine, such as 60° C.) Method 400 then proceeds to exit.

[0095] therefore, FIG. 4A to FIG. 4BThe method provides a diesel engine starting method, which includes: in response to an engine start request, adjusting a supercharger with multiple gear ratios to a highest gear ratio, cranking the engine, and injecting fuel into the engine during the cranking, wherein injecting fuel during the engine cranking includes injecting a certain amount of fuel into the engine cylinder during the engine cycle, which provides a percentage of injected fuel participating in a first phase of two-phase diesel fuel combustion that is greater than a percentage of injected fuel participating in a second phase of the two-phase diesel fuel combustion. The diesel engine starting method includes wherein the first phase of combustion is characterized by the absence of CO formation and OH radical formation during the first phase of the two-phase combustion.

[0096] In some examples, the diesel engine starting method also includes completely closing the exhaust valve in response to the engine start request, opening the air charge cooler bypass valve and opening the EGR valve. The diesel engine starting method includes wherein injecting fuel during the start rotation includes injecting fuel when the two pistons of the cylinder are close to the top dead center. The diesel engine starting method also includes increasing the amount of fuel injected into the engine after the engine cycle is completed (for example, during a subsequent engine cycle) while the engine is started. The diesel engine starting method includes wherein increasing the amount of fuel injected into the engine after the engine cycle is completed includes injecting a fuel amount sufficient to produce two-phase diesel fuel combustion during a subsequent engine cycle. The diesel engine starting method also includes adjusting a mechanical supercharger with a multi-speed ratio to a speed ratio lower than the highest speed ratio in response to the engine temperature exceeding a threshold.

[0097] FIG. 4A to FIG. 4BThe method also provides a diesel engine starting method, which includes: in response to an engine start request, adjusting a supercharger with a multi-speed ratio to a highest speed ratio, starting the engine, closing an exhaust valve in an exhaust system located downstream of a turbocharger turbine, and fully opening a supercharger bypass valve. The diesel engine starting method also includes injecting fuel to the engine during the starting rotation, wherein injecting fuel during the engine starting rotation includes injecting a certain amount of fuel into the engine cylinder during the engine cycle, so that only a single-phase combustion of two-phase diesel combustion is provided during the engine cycle. The diesel engine starting method also includes increasing the amount of fuel injected to the engine after the engine cycle is completed while starting the engine. The diesel engine starting method includes increasing the amount of fuel injected to the engine after the engine cycle is completed, including injecting an amount of fuel sufficient to produce two-phase diesel fuel combustion during the subsequent engine cycle. The diesel engine starting method also includes providing substantially equal average intake manifold pressure and average exhaust manifold pressure during the engine starting rotation for at least one engine cycle. The diesel engine starting method includes wherein at least one engine cycle is one engine rotation. The diesel engine starting method further includes injecting fuel into the engine when the first piston of the cylinder and the second piston of the cylinder are approaching top dead center.

[0098] Note that the example control and estimation routines included herein can be used with various 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 can be implemented by a control system including a controller in combination with various sensors, actuators, and other engine hardware. In addition, parts of these methods can be physical actions taken in the real world to change the state of the device. The specific routines described herein may represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). In this way, the various actions, operations, and / or functions shown can be performed in the order shown, in parallel, or omitted in some cases. Similarly, the order of processing is not necessarily required to achieve 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 may be repeated depending on the specific strategy used. In addition, the described actions, operations, and / or functions can graphically represent the code in the non-transitory memory of a computer-readable storage medium to be programmed into the engine control system, wherein the described actions are performed by implementing instructions in a system including various engine hardware components combined with an electronic controller. If desired, one or more of the method steps described herein may be omitted.

[0099] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and because many variations are possible, these specific examples should not be construed in a limiting sense. For example, the above-described techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or properties disclosed herein.

[0100] The appended claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also deemed to be included within the subject matter of the present disclosure.

Claims

1. A diesel engine starting method, comprising: In response to an engine start request, a multi-ratio supercharger is adjusted to a highest ratio, the engine is cranked, and fuel is injected into the engine during the cranking, wherein injecting fuel during the engine cranking includes: injecting a certain amount of fuel into the engine cylinder during the engine cycle to provide a percentage of the injected fuel participating in a first phase of two-phase diesel fuel combustion that is greater than the percentage of the injected fuel participating in a second phase of the two-phase diesel fuel combustion, wherein the first phase of combustion is characterized by the absence of CO formation and OH free radical formation during the first phase of the two-phase combustion.

2. The diesel engine starting method according to claim 1, further comprising: In response to the engine start request, the exhaust valve is fully closed, the air charge cooler bypass valve is opened, and the EGR valve is opened.

3. The diesel engine starting method of claim 1 , wherein injecting fuel during cranking comprises: Fuel is injected when both pistons in the cylinder approach top dead center.

4. The diesel engine starting method according to claim 1, further comprising: While cranking the engine, an amount of fuel injected into the engine during a subsequent engine cycle is increased.

5. The diesel engine starting method of claim 4, wherein increasing the amount of fuel injected into the engine after the engine cycle is completed comprises: An amount of fuel sufficient to produce two-phase diesel fuel combustion is injected during a subsequent engine cycle.

6. The diesel engine starting method according to claim 1, further comprising: In response to an engine temperature exceeding a threshold, the multi-ratio supercharger is adjusted to a gear ratio lower than the highest gear ratio.

7. An engine system, comprising: an opposed-piston diesel engine including a fuel injector and not including a glow plug; a supercharger coupled to the opposed-piston diesel engine, the supercharger having a multiple gear ratio; a turbocharger coupled to the opposed-piston diesel engine; as well as A controller including executable instructions stored in a non-transitory memory to: in response to a request to start the opposed-piston diesel engine, adjust the supercharger to a highest gear ratio, crank the opposed-piston diesel engine and open a charge air cooler, and also including: additional instructions to inject fuel into the engine during cranking, wherein injecting fuel during engine cranking includes: injecting a certain amount of fuel into the engine cylinder during the engine cycle to provide less than 10% of the energy in the injected fuel to be released during the engine cycle.

8. The engine system of claim 7, further comprising: Additional instructions to increase the amount of fuel injected to the engine during a subsequent engine cycle while cranking the engine.

9. The engine system of claim 7, further comprising: In response to an engine temperature exceeding a threshold, an additional command is provided to adjust the multi-ratio supercharger to a gear ratio lower than the highest gear ratio.

10. The engine system of claim 7, further comprising: In response to the request to start the opposed-piston diesel engine, an additional command to fully open the vanes of the turbocharger is provided.

11. The engine system of claim 7, further comprising: In response to the request to start the opposed-piston diesel engine, an additional command to fully open an exhaust gas recirculation valve is provided.

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