Systems and methods for supplying a gaseous fuel to a power engine

Abstract

Power machine operating procedures (700, 800), which include the following: Direct injection of a gaseous fuel into a power engine in response to a pressure of a gaseous fuel stored in a fuel tank exceeding a threshold pressure; characterized in that the power machine operating method further comprises: Activating a pump for gaseous fuel, adjusting the engagement of the torque converter clutch, and adjusting a gear shift pattern of the transmission in response to the pressure of the gaseous fuel stored in the fuel tank, which is less than or equal to the threshold pressure.

Description

[0001] This description relates to systems and methods for delivering a gaseous fuel to an internal combustion engine. The methods may be particularly useful for vehicles that store pressurized gaseous fuel in a storage vessel.

[0002] Gaseous fuels can provide several advantages over liquid fuels for powering an internal combustion engine. For example, gaseous fuels can be inexpensive, can have a high rated octane number, and can mix more easily with air at colder ambient temperatures. The improved air-fuel mixture can reduce engine emissions and can also improve engine starting at lower ambient temperatures. However, gaseous fuels can also present challenges for powering internal combustion engines. For example, gaseous fuels can be injected into an engine via port injection, but the engine may experience a loss in power output compared to if the same engine were powered by a liquid fuel.On the other hand, if the gaseous fuel is directly injected, it must be stored at a higher pressure so that it can be injected into a cylinder during the cylinder's compression stroke. An engine with direct injection of the gaseous fuel may provide improved power output, but a significant amount of the fuel stored under pressure in a fuel storage vessel may be unusable because the pressure in the storage vessel is reduced as the fuel is consumed by the engine. Consequently, the driving range of the vehicle may be reduced. Systems and methods for supplying a gaseous fuel to an engine are disclosed, for example, in AT 505 960 A1, US 2006 / 0 254 560 A1, and WO 2013 / 075 234 A1.

[0003] The inventor has recognized the above-mentioned disadvantages and, to overcome the disadvantages, has developed an engine operating method according to claim 1 and a vehicle system according to claim 9. Advantageous embodiments are specified in the subclaims.

[0004] By selectively activating a gaseous fuel pump, it may be possible to extend the operating range of a vehicle even when the gaseous fuel stored in a fuel storage tank is at a lower pressure. In particular, a gaseous fuel pump may be activated when a pressure in a gaseous fuel storage tank of the vessel does not reliably support direct injection of the gaseous fuel into the engine cylinders. However, if the pressure in the gaseous fuel tank does support direct injection of the gaseous fuel into the engine cylinders, the gaseous fuel pump may be deactivated and the gaseous fuel may be directed directly from the fuel tank into the engine cylinders.In this manner, the gaseous fuel pump is only operated when the pressure of the gaseous fuel stored in the fuel tank is less than a pressure that supports direct injection of the gaseous fuel into the engine cylinders. Furthermore, the transmission shift schedules and torque converter engagement can be adjusted if the gaseous fuel pump has a flow capacity that is less than desired for operating the engine at all speeds and torque requirements.

[0005] The present description can provide several advantages. For example, the approach can increase a vehicle's driving range. Furthermore, unlike systems that use both port and direct injection, the approach can allow gaseous fuel to be injected only through the direct injectors. Even further, the approach can adjust vehicle operation to accommodate a gaseous fuel pump with a lower flow rate, thus reducing system costs.

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

[0007] It should be understood that the above summary is provided to introduce, in simplified form, a selection of the concepts further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate all of the disadvantages noted above or in any part of this disclosure.

[0008] The advantages described herein will be more fully understood by reading an example of an embodiment, referred to herein as the detailed description, when considered alone or with reference to the drawings, in which: Fig. Figure 1 is a schematic diagram of a power machine; Fig. 2 shows an exemplary configuration of a powertrain of a vehicle; Fig. 3 and Fig. 4 show schematics of exemplary fuel systems; Fig. 5 and Fig. 6 show exemplary operating sequences of a vehicle; and Fig. 7 and Fig. 8 show exemplary methods for operating a vehicle.

[0009] This description relates to the operation of a vehicle including an internal combustion engine. The engine may be configured as described in Fig. 1. The engine may be mechanically coupled to other vehicle components to form a drive train, as shown in Fig. 2. The engine can be controlled via one of the systems described in the Fig. 3 and Fig. 4, gaseous and / or liquid fuel can be supplied. The vehicle can be operated according to the simulated operating sequences shown in the Fig. 5 and Fig. 6. The procedures described in the Fig. 7 and Fig. 8 can be used in the systems according to the Fig. 1-4 and can be used to control the processes in the Fig. 5 and Fig. 6 provide.

[0010] In Fig. 1 is an internal combustion engine 10 comprising several cylinders, one of which is in Fig. 1, is controlled by an electronic engine controller 12. The engine 10 includes a combustion chamber 30 and cylinder walls 32 in which a piston 36 is positioned and connected to a crankshaft 40. A flywheel 97 and a ring gear 99 are coupled to the crankshaft 40. The starter 96 includes a pinion shaft 98 and a pinion gear 95. The pinion shaft 98 can selectively advance the pinion gear 95 to engage the ring gear 99. The starter 96 can be directly attached to the front of the engine or the rear of the engine. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a belt or chain. In one example, the starter 96 is in a base state when not engaged with the engine crankshaft.Combustion chamber 30 is shown communicating with an intake manifold 44 and an exhaust manifold 48 via an intake valve 52 and an exhaust valve 54, respectively. Each intake and exhaust valve may be actuated by an intake cam 51 and an exhaust cam 53. The position of intake cam 51 may be determined by intake cam sensor 55. The position of exhaust cam 53 may be determined by exhaust cam sensor 57.

[0011] A liquid fuel injector 66 is shown positioned to inject fuel directly into the cylinder 30, known to those skilled in the art as direct fuel injection. Alternatively, the liquid fuel may be injected into an intake port, known to those skilled in the art as port fuel injection. The direct gaseous fuel injector 68 delivers gaseous fuel directly into the combustion chamber 30. An engine intake injector (e.g., a central gas manifold injector) 67a injects gas into the intake manifold 44. Alternatively, an engine intake injector (e.g., a port gas injector) 67b injects gaseous fuel into the cylinder intake port 49.Injector 67b is shown as an enhanced version of injector 67a, however, in some examples, injector 67b may enter cylinder intake port 49 directly without entering intake manifold 44. Fuel injectors 66, 67a, 67b, and 68 deliver liquid or gaseous fuel proportional to pulse widths from controller 12. Fuel is delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown). The fuel systems that deliver fuel to injectors 66, 67a, 67b, and 68 are shown in FIGS. Fig. 3 and Fig. 4 shown.

[0012] The intake manifold 44 is shown communicating with an optional electronic throttle 62 that adjusts a position of a throttle plate 64 to control airflow from the air intake 42 to the intake manifold 44. In some examples, the throttle 62 and throttle plate 64 may be positioned between the intake valve 52 and the intake manifold 44 such that the throttle 62 is a port throttle.

[0013] The distributorless ignition system 88 provides an ignition spark to the combustion chamber 30 via a spark plug 92 in response to the controller 12. A universal exhaust gas oxygen (UEGO) sensor 126 is shown coupled to the exhaust manifold 48 upstream of a catalyst 70. Alternatively, the UEGO sensor 126 may be replaced with a dual-state exhaust gas oxygen sensor.

[0014] In one example, the catalyst 70 may include multiple catalyst modules. In another example, multiple emission control devices, each with multiple modules, may be used. In one example, the catalyst 70 may be a three-way catalyst.

[0015] The controller 12 is in Fig. 1 as a conventional microcomputer including a microprocessor unit 102, input / output ports 104, read-only memory 106, random access memory 108, latch 110, and a conventional data bus. Controller 12 is shown receiving, in addition to those signals previously discussed, various signals from sensors coupled to engine 10, including: an engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; an engine manifold pressure (MAP) measurement from a pressure sensor 122 coupled to intake manifold 44; an engine position sensor from a Hall-effect sensor 118 that senses the position of crankshaft 40; a measurement of air mass entering the engine from a sensor 120; and a measurement of the throttle position from a sensor 58.Atmospheric pressure may also be sampled for processing by controller 12 (the sensor not shown). In a preferred aspect of the present description, an engine position sensor 118 generates a predetermined number of equally spaced pulses at each revolution of the crankshaft, from which engine speed (RPM) can be determined.

[0016] During operation, each cylinder in the engine 10 typically undergoes a four-stroke cycle: the cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. Generally, 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 toward the bottom of the cylinder to increase the volume in the combustion chamber 30. The position where the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its largest 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 in the combustion chamber 30.The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at its smallest volume) is typically referred to by those skilled in the art as top dead center (TDC). In a process referred to herein as injection, fuel is introduced into the combustion chamber. In a process referred to herein as ignition, the injected fuel is ignited by known ignition means, such as spark plug 92, resulting in combustion. During the power stroke, expanding gases push piston 36 back to BDC. Crankshaft 40 translates piston motion into rotating shaft torque. Finally, during the exhaust stroke, exhaust valve 54 is open to expel the combusted air-fuel mixture to exhaust manifold 48, returning the piston to TDC.It should be noted that the above has been shown merely as an example and that the opening and / or closing times of the intake and exhaust valves may change, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0017] Fig. 2 is a block diagram of a drivetrain 200 of a vehicle. The drivetrain 200 may be driven by the engine 10 in the vehicle 290. The engine 10 may be connected to a Fig. 1. Furthermore, the engine 10 may generate or adjust torque via a torque actuator 204, such as a fuel injector, a throttle valve, etc.

[0018] Engine output torque may be transferred to a torque converter 206 via a shaft 275 and an impeller 285. The torque converter 206 includes a turbine 286 for outputting torque to the transmission input shaft 270. The input shaft 270 mechanically couples the torque converter 206 to an automatic transmission 208. The torque converter 206 also includes a torque converter bypass clutch (TCC) 212. Torque is transferred from the impeller 285 directly to the turbine 286 when the TCC is engaged. The TCC is electrically operated by the controller 12. Alternatively, the TCC may be hydraulically engaged. In one example, the torque converter may be referred to as a component of the transmission.

[0019] When the torque converter clutch 212 is fully disengaged, the torque converter 206 transfers engine torque to the automatic transmission 208 via a fluid connection between the torque converter turbine 286 and the torque converter impeller 285, thereby enabling torque multiplication. Conversely, when the torque converter clutch 212 is fully engaged, the engine output torque is transferred directly to an input shaft 270 of the transmission 208 via the torque converter clutch. Alternatively, the torque converter clutch 212 may be partially engaged, thereby allowing the amount of torque passed directly to the automatic transmission 208 to be adjusted.The controller 12 may be configured to adjust the amount of torque transferred by the torque converter 212 by adjusting the torque converter lock-up clutch in response to various engine operating conditions or based on a driver-based engine operating request.

[0020] The automatic transmission 208 includes gear clutches (e.g., gears 1-6) 211 and a forward clutch 210. The gear clutches 211 and the forward clutch 210 can be selectively engaged to propel a vehicle. The torque output from the automatic transmission 208 can, in turn, be transmitted via an output shaft 260 to the wheels 216 to propel the vehicle. Specifically, the automatic transmission 208 can transmit input drive torque at the input shaft 270 in response to a driving condition of the vehicle before transmitting output drive torque to the wheels 216.

[0021] Furthermore, a frictional force may be applied to the wheels 216 by activating the wheel brakes 218. In one example, the wheel brakes 218 may be activated in response to the driver pressing their foot on a brake pedal (not shown). In other examples, the controller 12 or a controller coupled to the controller 12 may apply the activation of the wheel brakes. Similarly, a frictional force on the wheels 216 may be reduced by releasing the wheel brakes 218 in response to the driver releasing their foot from a brake pedal. Furthermore, the vehicle brakes, via the controller 12, may apply a frictional force to the wheels 216 as part of an automated engine stop procedure.

[0022] The controller 12 may be configured to receive the inputs from the engine 10, as shown in Fig. 1, and accordingly control engine torque output and / or operation of the torque converter, transmission, clutches, and / or brakes. As one example, engine torque output may be controlled by adjusting a combination of spark timing, fuel pulse width, fuel pulse timing, and / or air charge, by controlling throttle opening and / or valve timing, valve lift, and boost for turbocharged or supercharged engines.

[0023] In Fig. 3 is an exemplary fuel system for supplying fuel to the engine 10 according to Fig. 1. The fuel system according to Fig. 3 may be made in accordance with the procedure Fig. 7. Furthermore, the fuel system can be Fig. 3 be part of a system that Fig. 5 provides the operating sequence shown.

[0024] The fuel system 300 includes a liquid fuel tank 301 and a gaseous fuel tank 354. The liquid fuel tank 301 can store gasoline, alcohol, or a mixture of gasoline and alcohol. The gaseous fuel tank 354 can store compressed natural gas (CNG), liquefied petroleum gas (LPG, which changes state to a gas upon injection), hydrogen, or another gaseous fuel.

[0025] The liquid fuel tank 301 includes a fuel level sensor 311 and a fuel pump 302. The fuel pump 302 may be electrically driven via a command from the controller 12. The fuel pump 302 may be a low-pressure fuel pump, supplying fuel to a high-pressure fuel pump 306 via a line 304. The high-pressure fuel pump 306 supplies fuel to the fuel rail 308, distributing the fuel to the fuel injector 66. The high-pressure fuel pump 306 may be driven by the engine 10. The pressure at the fuel rail 308 may be monitored via a pressure sensor 325. The controller 12 may adjust an amount of fuel pumped by the high-pressure fuel pump 306 in response to an output of the pressure sensor 325.

[0026] The gaseous fuel tank 354 includes a pressure sensor 358 for assessing an amount of fuel stored in the fuel tank 354. A regulator 352 adjusts the fuel pressure from the fuel tank 354 to a constant pressure when the fuel pressure in the fuel tank 354 is greater than a threshold pressure. The regulator 352 directs the gaseous fuel to a three-way valve 356. The three-way valve 356 directs the gaseous fuel to the direct fuel injector 68 or the port fuel injector 67a (or alternatively, 67b) based on an output from the controller 12.

[0027] Consequently, the system provides the Fig. 1-3, a vehicle system is provided, comprising: an engine; a gaseous fuel tank; and a controller including non-transitory instructions for increasing engine idle speed and adjusting a transmission shift schedule in response to the amount of gaseous fuel stored in the gaseous fuel tank being less than the threshold level. The vehicle system further includes non-transitory instructions for adjusting a torque converter lock-up schedule in response to the amount of gaseous fuel stored in the gaseous fuel tank being less than the threshold level. The vehicle system further includes a stepped-ratio transmission, wherein adjusting the transmission shift schedule increases a vehicle speed at which the stepped-ratio transmission is shifted. The vehicle system further includes adjusting a torque at which the stepped-ratio transmission is shifted.The vehicle system includes reducing the torque at which the stepped ratio transmission is shifted in response to the amount of gaseous fuel stored in the gaseous fuel tank being less than the threshold level. The vehicle system further includes stopping direct injection of a gaseous fuel into the engine and starting port injection of the gaseous fuel in response to the amount of gaseous fuel stored in the gaseous fuel tank being less than the threshold level. However, the vehicle system of the embodiment of the . Fig. 3 does not fall within independent claim 9, but is rather useful for illustrating the claimed invention.

[0028] In Fig. 4 is a second exemplary fuel system for supplying fuel to the engine 10 according to Fig. 1. The fuel system according to Fig. 4 may be made in accordance with the procedure Fig. 8. Furthermore, the fuel system can be Fig. 4 be part of a system that Fig. 6. The fuel system according to Fig. 4 contains many of the same components as the fuel system according to Fig. 3. Between Fig. 3 and Fig. 4 identical components are in Fig. 4 using the same reference numerals. Therefore, the description of the Fig. 4 For the sake of brevity, the description of identical components has been omitted. However, identical components work as in Fig. 3 is described.

[0029] The fuel system 400 includes a gaseous fuel pump 465 to which gaseous fuel is supplied from the gaseous fuel tank 354. The gaseous fuel pump 465 may be driven by the engine 10 or it may be electrically driven. The gaseous fuel pump 465 may be selectively activated and deactivated by the controller 12 in response to an amount of fuel stored in the gaseous fuel tank 354 and / or an amount of liquid fuel stored in the fuel tank 301. The gaseous fuel pump 465 may supply pressurized gaseous fuel to an accumulator 460 or, alternatively, to a three-way valve 456.The output pressure of accumulator 460 can be adjusted to a desired pressure via a regulator 462, or the pressure of accumulator 460 can be adjusted by modulating the speed or displacement of gaseous fuel pump 465. The operating state (e.g., on / off or pumping capacity) of gaseous fuel pump 465 can be adjusted in response to the pressure sensed in accumulator 460 via pressure sensor 471.

[0030] In one example, the controller 12 supplies gaseous fuel from the gaseous fuel tank 354 to the engine 10 via the pressure regulator 352, the three-way valve 456, and the direct fuel injector 68 when the fuel pressure in the fuel tank 354 is greater than a threshold amount. The gaseous fuel pump 465 is deactivated when the fuel pressure or the amount of gaseous fuel stored in the fuel tank 354 is greater than the threshold amount. Fuel is not supplied to the engine 10 via the regulator 462 when fuel is supplied to the engine 10 via the regulator 352.If the amount of fuel stored in the gaseous fuel tank is less than the threshold amount, the gaseous fuel pump 465 is activated, and the gaseous fuel is delivered from the gaseous fuel tank 354 to the engine 10 via the gaseous fuel pump 465, the accumulator 460, the pressure regulator 462, the three-way valve 456, and the direct fuel injector 68. Fuel is not delivered to the engine 10 via the regulator 352 when the gaseous fuel pump 465 is activated.

[0031] Consequently, the system provides the Fig. 1, Fig. 2 and Fig. 4 provides a vehicle system comprising: an engine; a gaseous fuel tank; a gaseous fuel pump pneumatically communicating with the gaseous fuel tank; and a controller including non-transitory instructions for supplying gaseous fuel to the engine and activating the gaseous fuel pump only when a pressure in the gaseous fuel tank is less than a threshold pressure. The vehicle system further includes non-transitory instructions for adjusting a torque converter lock-up schedule in response to the pressure in the gaseous fuel tank being less than the threshold pressure. The vehicle system further includes a fixed-ratio transmission and non-transitory instructions for adjusting a transmission shift schedule in response to the pressure in the gaseous fuel tank being less than the threshold pressure.The vehicle system may further include an accumulator positioned downstream of the gaseous fuel pump. The vehicle system may further include a pressure regulator positioned downstream of the accumulator. The vehicle system may further include a direct gaseous fuel injector coupled to the engine.

[0032] In Fig. 5 is an exemplary operating sequence of the vehicle according to the method according to Fig. 7. The process according to Fig. 5 can decide on the procedure according to Fig. 7 and the system as it is in the Fig. 1, Fig. 2 and Fig. 3 is shown.

[0033] The first graphic representation from top to Fig. 5 is a graphical representation of the pressure of gaseous fuel in the gaseous fuel tank versus time. The Y-axis represents the pressure of the gaseous fuel, with pressure increasing in the direction of the Y-axis arrow. The X-axis represents time, with time increasing from the left side of the figure to the right side of the figure. The horizontal line 502 represents a first threshold level below which the engine operates with the port or air intake gaseous fuel injectors. The engine operates with the direct fuel injectors when the amount of gaseous fuel stored is greater than a threshold level 502. The horizontal line 504 represents a second threshold level below which the engine operates exclusively with liquid fuel unless the amount of stored liquid fuel is less than a threshold level.

[0034] The second graphical representation from top to Fig. Figure 5 is a graphical representation of the state of the active gaseous fuel injector versus time. The active gaseous fuel injector may be a port injector for injecting gaseous fuel into the intake manifold or intake ports, or alternatively, the active gaseous fuel injector may be a direct fuel injector for injecting the fuel directly into an engine cylinder. The active gaseous fuel injector is the direct fuel injector when the trace is near the Y-axis arrow. The active gaseous fuel injector is the port fuel injector when the trace is near the X-axis. The X-axis represents time, with time increasing from the left side of the figure to the right side of the figure.

[0035] The third graphic representation from top to Fig. Figure 5 is an example plot of a scheduled vehicle speed at which the first to second gear upshift occurs versus time. The Y-axis represents the scheduled vehicle speed for the first to second gear upshifts, with vehicle speed increasing in the direction of the Y-axis arrow. The X-axis represents time, with time increasing from the left side of the figure to the right side of the figure. It will be appreciated that a gearshift strategy is also a function of engine torque (or a surrogate for torque, such as intake manifold pressure or accelerator pedal position). This plot represents the upshift speed for a typical engine torque, although the upshift speed would behave in a similar manner for other torques.Likewise, the vehicle speeds for upshifting from second gear to third gear would behave in a similar manner, and so on.

[0036] The fourth graphic representation from top to Fig. Figure 5 is a graphical representation of scheduled vehicle speed at which the torque converter clutch is engaged for a particular selected gear versus time. The Y-axis represents the scheduled vehicle speed at which the torque converter clutch is engaged for a particular selected gear, with vehicle speed increasing in the direction of the Y-axis arrow. The X-axis represents time, with time increasing from the left side of the figure to the right side of the figure. It will be appreciated that torque converter clutch lockup can be scheduled as a function of engine speed instead of vehicle speed with similar results.

[0037] The fifth graphic representation from top to Fig. Figure 5 is a graph of the liquid fuel utilization factor versus time. The Y-axis represents the liquid fuel utilization factor, with the liquid fuel utilization factor increasing in the direction of the Y-axis arrow. The X-axis represents time, with time increasing from the left side of the figure to the right side of the figure.

[0038] At time T0, the pressure of the gaseous fuel stored in the gaseous fuel tank is at a higher level. In response to the pressure of the gaseous fuel stored in the gaseous fuel tank, direct injection of the gaseous fuel is activated. The vehicle speed at which an upshift from first gear to second gear is scheduled is scheduled at a lower vehicle speed so that the upshift occurs earlier in time for a vehicle that is accelerating. The vehicle speed at which the torque converter clutch is engaged is scheduled at a lower vehicle speed so that torque converter lock-up occurs earlier in time for a vehicle that is accelerating.The liquid fuel utilization factor is at a lower level, indicating that only a small portion of the total amount of fuel supplied to the engine during an engine cycle is liquid fuel.

[0039] Between time T0 and time T1, the pressure of the gaseous fuel stored in the gaseous fuel tank is reduced in response to the engine consuming fuel. The direct gaseous fuel injectors remain active, so the first-to-second upshift schedule remains unchanged, the vehicle speed at which the torque converter clutch is engaged remains the same, and the liquid fuel utilization factor remains the same.

[0040] At time T1, the pressure of the gaseous fuel stored in the gaseous fuel tank is reduced to less than the threshold level 502 because the engine consumes gaseous fuel. Therefore, the active gaseous fuel injector is switched from direct fuel injection to port or intake fuel injection. Further, the vehicle speed at which an upshift from first gear to second gear occurs is increased. Likewise, the vehicle speed at which the torque converter clutch is engaged is increased in response to the pressure of the gaseous fuel stored in the gaseous fuel tank. Additionally, the liquid fuel utilization factor is increased so that a larger proportion of the total fuel quantity delivered to the engine during an engine cycle is liquid fuel.

[0041] Between time T1 and time T2, the pressure of the gaseous fuel stored in the gaseous fuel tank continues to decrease in response to the engine consuming fuel. The port gaseous fuel injectors remain active, the first-to-second upshift schedule remains unchanged, the vehicle speed at which the torque converter clutch is engaged remains the same, and the liquid fuel utilization factor remains the same.

[0042] At time T2, the pressure of the gaseous fuel stored in the gaseous fuel tank is reduced to less than the threshold level 504. Consequently, the active gaseous fuel injectors remain the port fuel injectors, but gaseous fuel injection is stopped because there is sufficient liquid fuel (not shown) available to operate the engine. Further, the vehicle speed at which the first-to-second upshift occurs is reduced to its previous level. Likewise, the vehicle speed at which the torque converter clutch is engaged is reduced to its previous level in response to switching to injecting only liquid fuel. The liquid fuel utilization factor is increased so that only liquid fuel is delivered to the engine.

[0043] At time T3, the gaseous fuel storage tank is refilled. Consequently, the active gaseous fuel injector is switched to direct injection. The direct gaseous fuel injectors are activated, the port gaseous fuel injectors are deactivated, and the liquid fuel utilization factor is reduced so that the proportion of liquid fuel delivered to the engine is reduced in response to the gaseous fuel tank being filled to a level greater than 502. The vehicle speed at which a first-to-second upshift occurs is at the same level as if only liquid fuel is injected into the engine.Likewise, the vehicle speed at which the torque converter clutch is engaged is maintained at the same level as if only liquid fuel were injected into the engine.

[0044] Consequently, the fuel injector type, gear shift schedule, and torque converter engagement schedule are adjusted in response to the pressure of the fuel stored in the gaseous fuel tank. By switching from direct gaseous fuel injection to port injection of the gaseous fuel, a greater amount of the gaseous fuel stored in the gaseous fuel tank can be used because the gaseous fuel can be port injected at a lower fuel pressure; however, the available amount of engine torque output may be reduced because a portion of the cylinder volume is occupied by gaseous fuel drawn into the cylinder from the engine air intake.Additionally, adjusting the transmission shift schedule and torque converter clutch lock-up schedule allows the engine to produce additional power when port injection of the gaseous fuel is used, so there is less chance that the engine will produce less than desired power after a shift or after the torque converter engages.

[0045] In Fig. 6 is an exemplary operating sequence of the vehicle according to the method according to Fig. 8. The process according to Fig. 6 can decide on the procedure according to Fig. 8 and the system as it is in the Fig. 1, Fig. 2 and Fig. 4 is shown. Fig. 6 contains graphical representations which correspond to the graphical representations according to Fig. 5 are similar, except that the second graphical representation is Fig. 6 is a graphical representation of the gaseous fuel pump status versus time instead of the fuel injection type. Therefore, for the sake of brevity, the description of the graphical representations is Fig. 5, which leads to the graphical representations according to Fig. 6 are similar, are not repeated. The description of the variable from Fig. 5 applies to the same variables in Fig. 6.

[0046] The second graphical representation from top to Fig. Figure 6 is a graphical representation of the state of the gaseous fuel pump versus time. The gaseous fuel pump is activated when the trace is at a higher level. The gaseous fuel pump is deactivated when the trace is at a lower level.

[0047] At time T10, the pressure of the gaseous fuel stored in the gaseous fuel tank is at a higher level. The gaseous fuel pump is not activated in response to the pressure of the gaseous fuel stored in the gaseous fuel tank. The vehicle speed at which an upshift from first gear to second gear is scheduled is at the default vehicle speed. The vehicle speed at which the torque converter clutch is engaged is scheduled at a default vehicle speed. The liquid fuel utilization factor is at a lower level, indicating that only a small portion of the total fuel quantity delivered to the engine during an engine cycle is liquid fuel.

[0048] Between time T10 and time T11, the pressure of the gaseous fuel stored in the gaseous fuel tank is reduced in response to the engine consuming fuel. The gaseous fuel pump remains active, the first-to-second gear upshift schedule remains unchanged, the vehicle speed at which the torque converter clutch is engaged remains the same, and the liquid fuel utilization factor remains the same.

[0049] At time T11, the pressure of the gaseous fuel stored in the gaseous fuel tank is reduced to less than the threshold level 502. Therefore, the active gaseous fuel pump is activated so that the gaseous fuel is delivered to the direct injectors at sufficient pressure to enter the cylinder. The vehicle speed at which a first-to-second upshift occurs is reduced because the engine speed may be limited by the flow capacity of the gaseous fuel pump. Likewise, the vehicle speed at which the torque converter clutch is engaged is reduced because the engine speed may be limited while the gaseous fuel pump is activated.In addition, the liquid fuel utilization factor is increased so that a larger proportion of a total amount of fuel supplied to the engine during an engine cycle consists of liquid fuel.

[0050] Between time T11 and time T12, the pressure of the gaseous fuel stored in the gaseous fuel tank continues to decrease in response to the engine consuming fuel. The gaseous fuel pump remains active, the first-to-second upshift schedule remains unchanged, the vehicle speed at which the torque converter clutch is engaged remains the same, and the liquid fuel utilization factor remains the same.

[0051] At time T12, the amount of gaseous fuel stored in the gaseous fuel tank is reduced to less than the threshold level 504. As a result, the gaseous fuel pump is deactivated (not shown) and the liquid fuel portion is increased so that only liquid fuel is supplied to the engine. In addition, the vehicle speed at which a first-to-second upshift occurs is increased to its previous level when the gaseous fuel pump was not active. Likewise, the vehicle speed at which the torque converter clutch is engaged is increased to its previous level in response to transitioning to only liquid fuel injection.

[0052] At time T13, the gaseous fuel storage tank is refilled. Consequently, the direct gaseous fuel injectors are activated, and the liquid fuel utilization factor is reduced, thus reducing the proportion of liquid fuel delivered to the engine. In this manner, the gaseous fuel injection and the liquid fuel injection are adjusted in response to the gaseous fuel tank being filled to a pressure greater than 502. The vehicle speed at which an upshift from first gear to second gear occurs is at the same level as if the gaseous fuel tank had been filled to a pressure greater than 502.Likewise, the vehicle speed at which the torque converter clutch is engaged is maintained at the same level as if the gaseous fuel tank had been filled to a pressure greater than 502.

[0053] Consequently, the gaseous fuel pump may be activated and deactivated in response to a pressure of the gaseous fuel stored in a fuel tank. By operating the gaseous fuel pump, the gaseous fuel at a lower pressure may be converted to gaseous fuel at a high pressure suitable for direct injection. However, in one example, the flow rate of the gaseous fuel may be limited, so it may be desirable to adjust the gear shift schedules and the torque converter engagement schedule to shift and engage at lower vehicle speeds.

[0054] In Fig. 7 shows a method for operating a vehicle. The method can be incorporated into the system as executable instructions stored in a non-volatile memory according to the Fig. 1-3. The procedure according to Fig. 7 can Fig. Provide the operating procedure shown in Figure 5.

[0055] At 702, method 700 determines engine and fuel tank conditions. Engine conditions may include, but are not limited to, engine speed, driver torque request, a currently injected fuel type, and engine temperature. Fuel tank conditions may include, but are not limited to, a fuel level or amount of fuel stored in a fuel tank, fuel temperature, fuel pressure, fuel pump state (e.g., on or off), and a fuel delivery path (e.g., port injection / direct injection). After engine and fuel tank conditions are determined, method 700 proceeds to 704.

[0056] At 704, method 700 judges whether the gaseous fuel tank pressure is less than (LT) a first threshold pressure. The first threshold pressure may indicate a fuel pressure to overcome cylinder pressure to allow fuel into the cylinder while injecting fuel directly into a cylinder. Further, the first threshold pressure may change with engine operating conditions (e.g., fuel injection timing, engine speed, and torque request). If method 700 judges that the gaseous fuel tank pressure is less than the first threshold pressure, the answer is yes, and method 700 proceeds to 706. Otherwise, the answer is no, and method 700 proceeds to 708.

[0057] At 706, method 700 deactivates the direct gaseous fuel injectors and activates the port or intake manifold gaseous fuel injectors. The port or intake manifold gas injectors are activated so that the gaseous fuel can be delivered to the engine cylinders even if the pressure in the gaseous fuel tank is too low to support direct injection. Consequently, the driving range of the vehicle may be extended compared to if the engine were operating with only direct injection of the gaseous fuel. After the port gaseous fuel injectors are activated, method 700 proceeds to 710.

[0058] Additionally, when method 700 transitions from direct gaseous fuel injection to port or intake manifold gas injection, method 700 adjusts the engine idle speed, transmission gear shift schedules, and torque converter lock-up scheduling. In one example, the engine idle speed is increased when port gaseous fuel injection is enabled and direct gaseous fuel injection is disabled. The amount of increase in engine idle speed may be based on the type of gaseous fuel being injected. For example, if method 700 transitions from direct gaseous fuel injection to port gaseous fuel injection, the idle speed may be increased by 200 rpm. -1increased. By increasing the idle speed, the time required to increase engine torque from a time when an increase in torque is requested until the engine produces the requested torque can be reduced. The higher idle speed increases the number of combustion events per second. Therefore, engine torque can be increased quickly because torque is provided at each combustion event and because a higher idle speed provides more combustion events per second, even when a portion of the cylinder volume is displaced by gaseous fuel instead of air. In addition, the engine idle speed can be further increased in response to operating the engine at a lower atmospheric pressure. For example, if the engineoperating at increasing altitude, the engine idle speed may be further increased to improve engine torque response while the engine is operating on port-injected gaseous fuel.

[0059] The transmission gear shift schedule is also adjusted based on the gaseous fuel injection method. For example, if the engine transitions from direct gaseous fuel injection to port gas injection, the vehicle speed at which each transmission gear upshift occurs is increased. Consequently, a first-to-second gear upshift at an initial engine torque request may be increased from a vehicle speed of 16 kilometers per hour (km / h) to a vehicle speed of 22 km / h, allowing engine speed to be maintained at a higher speed after a transmission gear shift.Operating the engine at a higher speed after a shift may allow the engine to produce more power and provide improved performance compared to if the transmission were shifted at lower vehicle speeds during a period when gaseous fuel is port injected into the engine. The upshift schedule for higher gears of the transmission may be similarly adjusted. The downshift schedules may also be adjusted so that the transmission downshifts at a higher vehicle speed when port injected with gaseous fuel compared to when the engine and vehicle are operating under similar conditions with direct injection of the gaseous fuel. For example, downshifting from third gear to second gear mayat a vehicle speed of 48 km / h when the engine is operating with port injection of the gaseous fuel, and at a vehicle speed of 42 km / h when the engine is operating with direct injection of the gaseous fuel. The downshift schedule for other transmission gears can be set similarly.

[0060] Additionally, in some examples, the engine or wheel torque at which the gear upshifts and downshifts occur may be adjusted similarly to the way the vehicle speed gear upshifts are adjusted. If the engine transmission is scheduled to upshift from first gear to second gear at 16 km / h and 65 Nm of driver torque request or wheel torque when the gaseous fuel is injected directly into the engine, the same first gear to second gear upshift may be scheduled at 22 km / h and 80 Nm of driver torque request or wheel torque when the gaseous fuel is port injected into the engine. Similar shift schedules may be applied to all gears of the transmission.

[0061] The transmission torque converter lock-up schedule is also adjusted based on the gaseous fuel injection method. For example, if the engine transitions from direct gaseous fuel injection to port gaseous fuel injection, the vehicle speed (or engine speed) at which torque converter lock-up occurs is increased. Consequently, torque converter lock-up may be scheduled for a vehicle speed of 88 km / h if the engine is receiving port-injected gaseous fuel while a transmission is in fourth gear. Conversely, torque converter lock-up may be scheduled for a vehicle speed of 80 km / h if the engine is receiving directly injected gaseous fuel while the transmission is in fourth gear.Increasing the torque converter lock-up speed allows the engine speed to be a higher speed after the torque converter is engaged, allowing the engine to operate at a speed where the engine has the capacity to produce more power. Consequently, the engine may provide more power in a shorter period of time compared to if the engine were operating at a lower speed and receiving fuel via port injection of gaseous fuel. However, in some examples, the torque converter clutch may be held open while port injection of gaseous fuel is enabled, allowing the torque converter impeller speed and engine speed to be greater than if the torque converter clutch were engaged, thereby improving engine performance.

[0062] Additionally, in some examples, a portion of liquid fuel delivered to the engine during an engine cycle may be increased in response to a driver torque request or wheel torque exceeding a threshold torque. By increasing the portion of liquid fuel when the gaseous fuel is injected via port injection, it may be possible to increase engine torque output even if the gaseous fuel may displace some air from the engine cylinders.

[0063] At 710, method 700 judges whether or not the gaseous fuel tank pressure is less than (LT) a second threshold pressure. The second threshold pressure is less than the first threshold pressure. If so, the answer is yes, and method 700 proceeds to 712. Otherwise, the answer is no, and method 700 proceeds to 714.

[0064] At 712, method 700 uses the fuel remaining in the gaseous and liquid fuel tanks to extend the driving range of the vehicle, even when the amount of fuel stored in the gaseous and liquid fuel tanks is low. In one example, method 700 selects a fuel type with which to operate the engine based on the fuel tank that has the largest amount of stored fuel. For example, if the gaseous fuel tank is one-quarter full and the liquid fuel tank is one-eighth full, method 700 selects the gaseous fuel to operate the engine with, injecting the gaseous fuel via the port gaseous fuel injectors. In one example, method 700 operates the engine with the selected fuel for a predetermined duration (e.g.,a period of time or distance of travel), and then transitions to the previously unselected fuel. For example, if the gaseous fuel is selected first, the engine operates on the gaseous fuel for ten minutes, then transitions to operating the engine using the liquid fuel for ten minutes, and then the engine operates on gaseous fuel for another ten minutes. If the engine loses power while operating on one fuel, the engine transitions to the other fuel and continues to operate on the selected fuel until the vehicle is refueled or runs out of fuel. After selecting the fuel with which to operate the engine, method 700 proceeds to exit.

[0065] At 708, method 700 activates the gaseous fuel direct injectors while deactivating the port or intake manifold gaseous fuel injectors. The gaseous fuel direct injectors are activated so that the gaseous fuel may be delivered to an engine cylinder during the cylinder's compression stroke when the intake valves are closed. Consequently, engine power loss due to gaseous fuel injection may be reduced because the air in the cylinder is not displaced by the gaseous fuel. After the gaseous fuel direct injectors are activated, method 700 proceeds to 714.

[0066] When method 700 transitions from gas port injection to gas direct injection, method 700 adjusts the engine idle speed, transmission gear shift schedules, and torque converter lockup scheduling. In particular, the engine idle speed is decreased when gas direct injection is enabled and port injection of gaseous fuel is disabled. The amount of decrease in engine idle speed may be based on the type of gaseous fuel being injected. For example, if method 700 transitions from port injection of gaseous fuel to direct injection of gaseous fuel, the idle speed may be decreased by 200 rpm. -1 By reducing the idle speed, it may be possible to reduce the engine's fuel consumption under idle conditions.

[0067] The transmission shift schedule is also adjusted based on the gaseous fuel injection method. Specifically, if the engine switches from port injection of the gaseous fuel to direct gas injection, the vehicle speed at which each transmission gear upshift occurs is reduced. Consequently, a first-to-second upshift at an initial engine torque request may be reduced from a vehicle speed of 22 kilometers per hour (km / h) to a vehicle speed of 16 km / h, allowing the engine speed to be maintained at a lower speed after the transmission gear shift.Operating the engine at a lower speed after a shift may allow the engine to operate at a lower level of fuel consumption compared to if the transmission were shifted at higher vehicle speeds during a period when gaseous fuel is injected into the engine. The upshift schedule for higher transmission gears may be adjusted similarly. The downshift schedules may also be adjusted so that the transmission downshifts at a lower vehicle speed when using direct injection of the gaseous fuel compared to when the engine and vehicle are operating under similar conditions with port injection of the gaseous fuel. For example, a downshift from third gear to second gear mayat a vehicle speed of 42 km / h when the engine is operating with direct injection of the gaseous fuel, and at a vehicle speed of 48 km / h when the engine is operating with port injection of the gaseous fuel. The downshift schedule for other transmission gears can be set similarly.

[0068] The transmission torque converter lock-up schedule is also adjusted based on the gaseous fuel injection method. For example, if the engine transitions from port injection of gaseous fuel to direct gas injection, the vehicle speed (or engine speed) at which torque converter lock-up occurs is reduced. Consequently, torque converter lock-up may be scheduled for a vehicle speed of 80 km / h if the engine is receiving directly injected gaseous fuel while the transmission is in fourth gear. Conversely, torque converter lock-up may be scheduled for a vehicle speed of 88 km / h if the engine is receiving port injection of gaseous fuel while the transmission is in fourth gear.Reducing the torque converter lock-up speed allows the engine speed to be at a lower speed after the torque converter has engaged, which can improve fuel economy.

[0069] At 714, method 700 judges whether a level or amount of fuel in the liquid fuel storage tank is less than (LT) a threshold level or amount. If so, the answer is yes, and method 700 proceeds to 716. Otherwise, the answer is no, and method 700 proceeds to 718.

[0070] At 716, method 700 deactivates the injection of the liquid fuel. The liquid fuel may be deactivated until the liquid fuel tank is refilled or until the pressure of the gaseous fuel stored in the gaseous fuel tank is less than a second threshold level. After the liquid fuel is deactivated, method 700 proceeds to 710.

[0071] At 718, method 700 judges whether a desired driver torque request is greater than (GT) a threshold torque and whether port injection of the gaseous fuel is enabled. If method 700 judges that port or intake manifold injection of the gaseous fuel is active and a driver torque request is greater than the threshold torque, the answer is yes, and method 700 proceeds to 720. Otherwise, the answer is no, and method 700 proceeds to 722.

[0072] At 720, method 700 increases the liquid fraction of a total amount of fuel supplied to the engine. For example, if a total amount of fuel supplied to the engine consists of 10 mass% of liquid fuel and 90 mass% of gaseous fuel, the mass of liquid fuel may be increased to 15% of the total fuel mass. In other examples, the fuel fraction may be increased based on energy density rather than fuel mass. For example, if the liquid fuel supplies 20% of the energy supplied to the engine in an engine cycle, the supplied liquid energy may be increased to 25% of the energy supplied to the engine during an engine cycle (e.g., two engine revolutions for a four-stroke engine).In one example, the liquid fuel fraction delivered to the engine during a cylinder cycle is increased by a predetermined amount (e.g., 5%). After the liquid fuel fraction is increased, method 700 proceeds to the exit.

[0073] At 722, method 700 judges whether the engine is currently knock-limited. In one example, method 700 judges that the engine is knock-limited based on predetermined engine knock limits stored based on engine speed and load. In other examples, method 700 judges whether or not the engine is currently knock-limited based on the output of a knock sensor. If method 700 judges that the engine is knock-limited, the answer is yes, and method 700 proceeds to 723. Otherwise, the answer is no, and method 700 proceeds to 724.

[0074] At 723, method 700 increases the portion of fuel having a higher effective octane number delivered to the engine. The effective octane number of the fuel is based on the injected fuel and the injection route (e.g., direct injection or port injection). For example, the gaseous fuel may have a port injection effective octane number of 130 RON and a direct injection effective octane number of 140 RON due to the improved charge cooling via direct injection and injection timing. On the other hand, the liquid fuel may have a nominal octane number of 89. Consequently, the portion of gaseous fuel delivered to the engine is increased. For example, the portion of gaseous fuel may be increased from 80% to 85% of the total amount of fuel delivered to the engine during an engine cycle.After the proportion of fuel having a higher effective octane number has been increased, method 700 proceeds to the exit.

[0075] The base proportions of each fuel delivered to the engine can be determined empirically and stored in memory. The base proportions of fuel can be indexed based on the engine speed and load or the requested torque. At 1500 rpm -1 At 0.2 and 0.2 load, the fuel supplied to the engine during an engine cycle may consist of 95% gaseous fuel and 5% liquid fuel. The proportion of gaseous fuel may decrease as engine load increases, and vice versa for the proportion of liquid fuel.

[0076] At 724, method 700 assesses whether the relative costs of the respective fuels are known. In one example, the driver may enter the costs of the liquid and gaseous fuels into controller 12 via a keypad or user interface. In other examples, the internet or a fuel pump may provide the fuel cost information to controller 12 via a wireless interface. If the cost of each fuel supplied to the engine is known, the answer is yes, and method 700 proceeds to 725. Otherwise, the answer is no, and method 700 proceeds to 726.

[0077] At 725, method 700 increases the fuel portion of the lower-cost fuel delivered to the engine. In one example, the cost of each fuel is converted into a gasoline gallon equivalent (GGE) based on the cost and energy in the fuel delivered to the engine. For example, it may be determined that a given mass of gaseous fuel has an equivalent amount of energy as one gallon of gasoline. The given mass of gaseous fuel is then multiplied by the cost per unit mass to determine the GGE price of the gaseous fuel. Once the GGE cost of each fuel has been determined, method 700 increases the portion of the low-cost fuel delivered to the engine relative to the total fuel delivered to the engine.The increase in the proportion of lower-cost fuel delivered to the engine may be a predetermined amount up to a predetermined limit. For example, if the gaseous fuel delivered to the engine is 10% cheaper than the liquid fuel delivered to the engine, the proportion of gaseous fuel may be increased by 5% up to a maximum increase of 20%. After the proportion of lower-cost fuel has been increased, method 700 proceeds to the exit.

[0078] At 726, method 700 judges whether or not the engine is currently throttled by more than a predetermined amount. In one example, method 700 judges whether or not the engine is throttled based on intake manifold pressure. If intake manifold pressure is less than a predetermined amount, it may be determined that the engine is throttled by more than a predetermined amount. If method 700 judges that the engine is throttled by more than a predetermined amount, the answer is yes and method 700 proceeds to 727. Otherwise, the answer is no and method 700 proceeds to 728.

[0079] At 727, method 700 increases the portion of gaseous fuel injected via port or intake manifold injection that is delivered to the engine. Further, if gaseous fuel is currently being injected directly into the engine, port injection of the gaseous fuel may be enabled. The portion of gaseous fuel injected via port or intake manifold injection may be increased by a predetermined amount (e.g., 5%) up to a threshold amount (e.g., 95%). By increasing the portion or proportion of fuel injected via port or intake manifold injection, the engine may be operated less throttled, so that engine pumping losses may be reduced.Note that the engine throttle may be opened when increasing the portion of gaseous fuel injected via port injection to provide equivalent torque and air-fuel ratio compared to when gaseous fuel is injected directly into the engine at the same engine speed and torque demand. After increasing the portion of port injection of gaseous fuel, method 700 proceeds to the exit.

[0080] At 728, method 700 assesses whether the carbon intensities of the fuel stored onboard the vehicle are known. Carbon intensity may be referred to as a mass of carbon dioxide emissions from a fuel relative to the energy in the fuel. CNG typically equates to 62 g of CO2 per megajoule of energy, while gasoline typically equates to 73 g of CO2 per megajoule of energy. In one example, the carbon intensity of the fuels stored on the vehicle may be based on information supplied from the internet or a gas station via a wireless transmitter. If method 700 assesses that the relative carbon intensities of the fuels stored within the vehicle are known, the answer is yes, and method 700 proceeds to 729. Otherwise, method 700 ends.

[0081] At 729, method 700 increases the proportion of lower carbon fuel delivered to the engine. For example, if the liquid fuel stored in the vehicle has X grams of carbon per gram of fuel and a gaseous fuel stored in the vehicle has X-Y grams of carbon, method 700 increases the proportion of gaseous fuel in the total amount of fuel delivered during an engine cycle. The proportion of gaseous fuel may be increased by a predetermined amount up to a limit. For example, the proportion of gaseous fuel delivered to the engine may increase from 25% to 35% during an engine cycle. After the proportion of low carbon fuel delivered to the engine during an engine cycle is increased, method 700 proceeds to exit.

[0082] Consequently, the procedure under Fig. 7 provides an engine operating method comprising: directly injecting a gaseous fuel into an engine in response to the pressure of the gaseous fuel stored in a fuel tank exceeding a threshold level; and increasing the idle speed of the engine and injecting the gaseous fuel into an engine air intake in response to the pressure of the gaseous fuel stored in the fuel tank being less than the threshold level.

[0083] In one example, the method includes operating the engine at a first idle speed while injecting fuel directly into the engine, operating the engine at a second idle speed while injecting fuel into the engine air intake, and the first idle speed being less than the second idle speed. The method further includes decreasing the engine idle speed in response to the pressure of gaseous fuel stored in the fuel tank being greater than the threshold level. The method further includes increasing the proportion of a liquid fuel in a total amount of fuel delivered to the engine during an engine cycle in response to a desired engine torque exceeding a threshold level.The method further includes increasing a proportion of a liquid fuel in a total amount of fuel delivered to the engine during an engine cycle in response to activating the engine air intake injector. The method includes injecting the gaseous fuel into the engine air intake including injecting the gaseous fuel into an engine intake manifold. The method includes injecting the gaseous fuel into the engine air intake including injecting the gaseous fuel into a cylinder intake port.

[0084] The procedure according to Fig. 7 also provides an engine operating method comprising: directly injecting a gaseous fuel into an engine in response to the pressure of a gaseous fuel stored in a fuel tank exceeding a threshold level; and increasing an engine idle speed, adjusting engagement of the torque converter clutch, and injecting the gaseous fuel into the engine air intake in the engine in response to the amount of gaseous fuel stored in the fuel tank being less than the threshold level. The method includes maintaining the torque converter clutch in an open state without engagement while injecting the gaseous fuel into the engine air intake.The method includes where direct injection of the gaseous fuel is disabled while the gaseous fuel is injected into the engine air intake. The method further includes where injection of the gaseous fuel into the engine air intake is disabled while the gaseous fuel is directly injected. The method includes where adjusting engagement of the torque converter clutch includes increasing vehicle speed, wherein the torque converter clutch is engaged in response to the amount of gaseous fuel stored in the fuel tank being less than the threshold level. The method further includes increasing a portion of the liquid fuel in a total amount of fuel delivered to the engine during an engine cycle in response to a desired engine torque exceeding a threshold level.

[0085] In Fig. 8 shows a method for operating a vehicle. The method can be integrated into the system according to the Fig. 1-2 and 4 as executable instructions stored in a non-volatile memory. The method according to Fig. 8 can Fig. 6 provide the operating procedure shown.

[0086] At 802, method 800 determines engine and fuel tank conditions. Engine conditions may include, but are not limited to, engine speed, driver torque request, a current injected fuel type, and engine temperature. Fuel tank conditions may include, but are not limited to, a fuel level or amount of fuel stored in a fuel tank, fuel temperature, fuel pressure, fuel pump state (e.g., on or off), and fuel delivery path (e.g., port injection / direct injection). After engine and fuel tank conditions are determined, method 800 proceeds to 804.

[0087] At 804, method 800 judges whether or not the gaseous fuel tank pressure is less (LT) than a first threshold pressure. The first threshold pressure may indicate a fuel pressure to directly introduce fuel into a cylinder during a compression stroke of the cylinder. Further, the first threshold pressure may change with engine operating conditions (e.g., engine speed and torque demand). If method 800 judges that the gaseous fuel tank pressure is less than the first threshold pressure, the answer is yes, and method 800 proceeds to 806. Otherwise, the answer is no, and method 800 proceeds to 808.

[0088] At 806, method 800 activates a gaseous fuel pump to increase the pressure of the fuel supplied to the direct injectors. The gaseous fuel pump is pneumatically connected to the gaseous fuel storage tank, as shown in Fig. 4. The gaseous fuel pump may supply the gaseous fuel to the direct fuel injectors via a control valve. In one example, the control valve is a three-way valve that selects between the output of the gaseous fuel storage tank and the output of the gaseous fuel pump. The gaseous fuel pump may supply pressurized gaseous fuel to a pressurized storage tank, where the output from the pressurized storage tank may be directed to the direct fuel injectors. The gaseous fuel pump may be selectively activated and deactivated depending on the pressure at the fuel pump outlet and / or the pressure in the accumulator. In examples where the gaseous fuel pump has variable pumping capacity, the capacity of the pump may be reduced when the pressure in the accumulator is at or above a target pressure.The capacity of the gaseous fuel pump can be increased if the pressure in the accumulator is lower than desired. The pressure at the accumulator outlet can be regulated by a pressure regulator.

[0089] In some examples, the gaseous fuel pump may be sized to operate the engine at rated load. However, in other examples, the gaseous fuel pump may be sized with an output capacity less than the fuel flow rate to operate the engine at wide-open throttle with a slightly rich air-fuel ratio (e.g., an air-fuel ratio 0.15 richer than stoichiometry).

[0090] The transmission gear shift schedule may also be adjusted based on the activation state of the gaseous fuel pump and the amount of gaseous fuel stored in the gaseous fuel storage tank. For example, if the gaseous fuel pump is activated, the engine speed at which each transmission gear upshift occurs may be reduced to avoid exceeding the flow capacity of the gaseous fuel pump. Consequently, a first-to-second gear upshift at a first engine torque request may be reduced from a vehicle speed of 22 kilometers per hour (km / h) to a vehicle speed of 16 km / h, so that the gaseous fuel flow rate may be reduced.In some examples, the throttle opening amount, cam timing, or boost pressure may be adjusted to limit engine airflow and engine torque so that a smaller capacity gaseous fuel pump can deliver the gaseous fuel to the engine. The upshift schedule for higher transmission gears may be adjusted similarly. Downshift schedules may also be adjusted so that the transmission downshifts at a lower vehicle speed when using the gaseous fuel pump compared to when gaseous fuel is delivered to the engine without the use of a gaseous fuel pump. For example, downshifting from third gear to second gear mayat a vehicle speed of 42 km / h when the engine is operating with the gaseous fuel pump, and at a vehicle speed of 48 km / h when the engine is operating without the gaseous fuel pump. The downshift schedule for other transmission gears can be set similarly.

[0091] The transmission torque converter lock-up schedule may also be adjusted based on the operating state of the gaseous fuel pump. For example, if the engine transitions from operating without the gaseous fuel pump to operating with the gaseous fuel pump, the vehicle speed (or engine speed) at which torque converter lock-up occurs may be reduced to avoid exceeding the flow capacity of the gaseous fuel pump. Consequently, torque converter lock-up may be scheduled for a vehicle speed of 80 km / h (50 mph) when the engine is receiving gaseous fuel via the gaseous fuel pump while a transmission is in fourth gear.On the other hand, torque converter lockup may be scheduled for a vehicle speed of 88 km / h (55 mph) when the engine is receiving gaseous fuel directly from the gaseous fuel tank while the transmission is in fourth gear. Reducing the torque converter lockup speed allows the engine speed to be at a lower speed after the torque converter is engaged, allowing the engine to operate at a lower speed to reduce the gaseous fuel flow rate.

[0092] At 810, method 800 judges whether the gaseous fuel tank pressure is less than (LT) a second threshold pressure. The second threshold pressure is less than the first threshold pressure. If yes, the answer is yes, and method 800 proceeds to 812. Otherwise, the answer is no, and method 800 proceeds to 814.

[0093] At 812, method 800 uses the fuel remaining in the gaseous and liquid fuel tanks to extend the driving range of the vehicle, even when the amount of fuel stored in the gaseous and liquid fuel tanks is low. In one example, method 800 selects a fuel type with which to operate the engine based on the fuel tank that has the largest amount of stored fuel. For example, if the gaseous fuel tank is one-quarter full and the liquid fuel tank is one-eighth full, method 800 selects the gaseous fuel to operate the engine with, injecting the gaseous fuel via the gaseous fuel port injectors. In one example, method 800 operates the engine with the selected fuel for a predetermined duration (e.g.,a period of time or distance of travel), and then transitions to the previously unselected fuel. For example, if the gaseous fuel is selected first, the engine operates on the gaseous fuel for ten minutes, then transitions to operating the engine using the liquid fuel for ten minutes, and then operates the engine on the gaseous fuel for another ten minutes. If the engine loses power while operating on one fuel, the engine transitions to the other fuel and continues to operate on the selected fuel until the vehicle is refueled or runs out of fuel. After selecting the fuel with which to operate the engine, method 800 proceeds to exit.

[0094] At 808, method 800 deactivates the gaseous fuel pump, delivering the gaseous fuel to the engine without a gaseous fuel pump and directly from the gaseous fuel storage tank. After the direct gaseous fuel injectors are activated, method 800 proceeds to 814.

[0095] When method 800 turns off the gaseous fuel pump, method 800 may further adjust the transmission gear shift schedules and the torque converter lock-up scheduling. In particular, the transmission gear shift schedule may also be adjusted based on the operating state of the gaseous fuel pump. Specifically, if the engine transitions from operating with the gaseous fuel pump to operating without the gaseous fuel pump, the vehicle speed at which each transmission gear upshift occurs may be increased. Consequently, a first-to-second upshift at a first engine torque request may be increased from a vehicle speed of 16 kilometers per hour (km / h) to a vehicle speed of 22 km / h, so that the engine power output may be increased if desired.The upshift schedule for higher transmission gears can be adjusted similarly. The throttle opening amount can be allowed to open to its full extent because the gaseous fuel pump does not limit fuel flow to the engine. Downshift schedules can also be adjusted so that the transmission downshifts at a higher vehicle speed when operating without the gaseous fuel pump compared to when the engine and vehicle are operating under similar conditions with the gaseous fuel pump. For example, a downshift from third gear to second gear can be scheduled at a vehicle speed of 48 km / h when the engine is operating without the gaseous fuel pump and at a vehicle speed of 42 km / h when the engine is operating with the gaseous fuel pump.The downshift schedule for other transmission gears can be set similarly.

[0096] The transmission torque converter lock-up schedule may also be adjusted based on the gaseous fuel pump stopping. For example, if the engine transitions from operating the gaseous fuel pump to operating the engine without the gaseous fuel pump, the vehicle speed at which torque converter lock-up occurs may be increased. Consequently, torque converter lock-up may be scheduled for a vehicle speed of 88 km / h when the engine is receiving gaseous fuel without the gaseous fuel pump while a transmission is in fourth gear. Conversely, torque converter lock-up may be scheduled for a vehicle speed of 80 km / h when the engine is receiving gaseous fuel from the gaseous fuel pump while the transmission is in fourth gear.Increasing the torque converter lock-up speed allows the engine to be at a higher speed after the torque converter has been engaged, allowing the engine to operate at an engine speed where the engine torque capacity is increased.

[0097] At 814, method 800 judges whether a level or amount of fuel in the liquid fuel storage tank is less than (LT) a threshold level or amount. If so, the answer is yes, and method 800 proceeds to 816. Otherwise, the answer is no, and method 800 proceeds to 818.

[0098] At 816, method 800 deactivates the injection of the liquid fuel. The liquid fuel may be deactivated until the liquid fuel tank is refilled or until the pressure of the gaseous fuel stored in the gaseous fuel tank is less than a second threshold level. After the liquid fuel is deactivated, method 800 proceeds to 810.

[0099] At 818, method 800 judges whether a gaseous fuel flow rate is greater than (GT) a threshold flow and whether the gaseous fuel pump is activated. If method 800 judges that the gaseous fuel flow rate is greater than the threshold rate and that the gaseous fuel pump is active, the answer is yes, and method 800 proceeds to 820. Otherwise, the answer is no, and method 800 proceeds to 822.

[0100] At 820, method 800 increases a liquid fraction of a total amount of fuel delivered to the engine. In one example, the liquid fraction of fuel delivered to the engine during a cylinder cycle is increased by a predetermined amount (e.g., 5%). After the liquid fuel fraction is increased, method 800 proceeds to the exit.

[0101] At 822, method 800 judges whether the engine is currently knock-limited. In one example, method 800 judges that the engine is knock-limited based on predetermined engine knock limits stored based on engine speed and load. In other examples, method 800 judges whether the engine is currently knock-limited based on the output of a knock sensor. If method 800 judges that the engine is knock-limited, the answer is yes, and method 800 proceeds to 823. Otherwise, the answer is no, and method 800 proceeds to 824.

[0102] At 823, method 800 increases the portion of fuel having a higher effective octane number delivered to the engine. The effective octane number of the fuel is based on the injected fuel and the injection route (e.g., direct injection or port injection). For example, a gaseous fuel may have a port injection effective octane number of 130 RON and a direct injection effective octane number of 140 RON due to improved charge cooling via direct injection and injection timing. On the other hand, the liquid fuel may have a nominal octane number of 89. Consequently, the portion of gaseous fuel delivered to the engine is increased. For example, the portion of gaseous fuel may be increased from 80% to 85% of the total amount of fuel delivered to the engine during an engine cycle.After the proportion of the fuel with the higher effective octane number has been increased, the method 800 proceeds to the exit.

[0103] At 824, method 800 assesses whether the relative costs of the respective fuels are known or not. In one example, the driver may enter the costs of the liquid and gaseous fuels into controller 12 via a keypad or user interface. In other examples, the internet or a fuel pump may provide the fuel cost information to controller 12 via a wireless interface. If the cost of each fuel supplied to the engine is known, the answer is yes, and method 800 proceeds to 825. Otherwise, the answer is no, and method 800 proceeds to 826.

[0104] At 825, method 800 increases the fuel portion of the lower-cost fuel delivered to the engine. In one example, the cost of each fuel is converted into a gasoline gallon equivalent (GGE) based on the cost and energy in the fuel delivered to the engine. For example, it may be determined that a given mass of gaseous fuel has an equivalent amount of energy as one gallon of gasoline. The given mass of gaseous fuel is then multiplied by the cost per unit mass to determine the GGE price of the gaseous fuel. Once the GGE cost of each fuel has been determined, method 800 increases the portion of the low-cost fuel delivered to the engine relative to the total fuel delivered to the engine.The increase in the proportion of low-cost fuel supplied to the engine may be a predetermined amount up to a predetermined limit. For example, if the gaseous fuel supplied to the engine is 10% cheaper than the liquid fuel supplied to the engine, the proportion of gaseous fuel may be increased by 5% up to a maximum increase of 20%. After the proportion of lower-cost fuel has been increased, method 800 proceeds to the exit.

[0105] At 826, method 800 judges whether or not the engine is currently throttled by more than a predetermined amount. In one example, method 800 judges whether or not the engine is throttled based on intake manifold pressure. If intake manifold pressure is less than a predetermined amount, it may be determined that the engine is throttled by more than a predetermined amount. If method 800 judges that the engine is throttled by more than a predetermined amount, the answer is yes and method 800 proceeds to 827. Otherwise, the answer is no and method 800 proceeds to 828.

[0106] At 827, method 800 increases the portion of gaseous fuel injected via port or intake manifold injection that is delivered to the engine. Further, if the gaseous fuel is currently injected directly into the engine, port injection of the gaseous fuel may be enabled. The portion of gaseous fuel injected via port or intake manifold injection may be increased by a predetermined amount (e.g., 5%) up to a threshold amount (e.g., 95%). By increasing the portion or proportion of fuel injected via port or intake manifold injection, the engine may be operated less throttled, so that engine pumping losses may be reduced.Note that the engine throttle may be opened when increasing the portion of port-injected gaseous fuel to provide equivalent torque and air-fuel ratio compared to when the gaseous fuel is directly injected into the engine at the same engine speed and torque demand. After increasing the portion of port-injected gaseous fuel, method 800 proceeds to the exit.

[0107] At 828, method 800 assesses whether the carbon intensities of the fuels stored onboard the vehicle are known. Carbon intensity may be referred to as a mass of carbon dioxide emissions from a fuel relative to the energy in the fuel. In one example, the carbon intensity of the fuels stored on the vehicle may be based on information supplied from the internet or a gas station via a wireless transmitter. If method 800 assesses that the relative carbon intensities of the fuels stored within the vehicle are known, the answer is yes, and method 800 proceeds to 829. Otherwise, method 800 ends.

[0108] At 829, method 800 increases the proportion of lower carbon fuel delivered to the engine. For example, if the liquid fuel stored in the vehicle has X grams of carbon per gram of fuel and a gaseous fuel stored in the vehicle has X-Y grams of carbon, method 800 increases the proportion of gaseous fuel in a total amount of fuel delivered during an engine cycle. The proportion of gaseous fuel may be increased by a predetermined amount up to a limit. After the proportion of low carbon fuel delivered to the engine during an engine cycle is increased, method 800 proceeds to exit.

[0109] Consequently, the procedure under Fig. 8 provides an engine operating method comprising: directly injecting a gaseous fuel into an engine in response to a pressure of a gaseous fuel stored in a fuel tank exceeding a threshold pressure; and activating a gaseous fuel pump only when the pressure of the gaseous fuel stored in the fuel tank is less than or equal to the threshold level. The method includes supplying fuel from the fuel tank to the direct injector without a gaseous fuel pump in response to the pressure of the gaseous fuel stored in the fuel tank exceeding the threshold pressure.

[0110] In one example, the method includes supplying fuel from the gaseous fuel pump to the direct injector in response to the pressure of gaseous fuel stored in the fuel tank being less than or equal to the threshold level. The method further includes a three-way valve and adjusting a state of the three-way valve in response to the pressure of gaseous fuel stored in the fuel tank. The method further includes regulating the output of the gaseous fuel pump to a desired pressure. The method includes varying the threshold pressure with engine operating conditions.

[0111] The procedure according to Fig. 8 also provides an engine operating method comprising: directly injecting a gaseous fuel into an engine in response to a pressure of a gaseous fuel stored in a fuel tank exceeding a threshold pressure; and activating a gaseous fuel pump, adjusting engagement of the torque converter clutch, and adjusting a gear shift schedule of the transmission in response to the pressure of the gaseous fuel stored in the fuel tank being less than or equal to the threshold pressure. The method includes where adjusting the gear shift schedule of the transmission includes adjusting a vehicle speed at which a transmission shifts gears. The method includes decreasing the vehicle speed at which the transmission shifts gears in response to activating the gaseous fuel pump.The method includes adjusting the engagement of the torque converter clutch including adjusting a vehicle speed at which the torque converter clutch engages.

[0112] In some examples, the method includes decreasing the vehicle speed at which the torque converter engages in response to activating the gaseous fuel pump. The method further includes setting an operating state of a three-way valve fluidly in communication with the gaseous fuel pump and the fuel tank. The method includes the gaseous fuel pump supplying the fuel to a direct fuel injector. The method includes supplying the gaseous fuel to the direct fuel injector via the fuel tank without passing the fuel through the gaseous fuel pump.

[0113] As will be recognized by one of ordinary skill in the art, this may Fig. 7 and Fig. 8 may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, the various steps or functions illustrated may be performed in the order illustrated, performed in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the objects, features, and advantages described herein, but is provided for ease of illustration and description. Although not explicitly illustrated, one of ordinary skill in the art will recognize that one or more of the illustrated steps or functions may be repeatedly performed depending on the particular strategy employed.Furthermore, the described acts, operations, methods, and / or functions may graphically represent code to be programmed into the non-transitory memory of the computer-readable storage medium in the engine control system.

[0114] For example, I3, I4, I5, V6, V8, V10, and V12 engines operating on natural gas, gasoline, diesel, or alternative fuel configurations could advantageously utilize the present description. KEY TO SYMBOLS

[0115] Fig. 7 Beginning 702 The conditions of the engine and the fuel tank determine 704 Gaseous fuel tank pressure less than 1st threshold? N NO 706 Enable gaseous fuel PFI and disable gaseous fuel DI 708 Enable gaseous fuel DI and disable gaseous fuel PFI 710 Gaseous fuel tank pressure less than 2nd threshold? 712 Use the fuel stored in the largest quantity; if gaseous fuel, activate the PFI, otherwise deactivate the PFI of the gaseous fuel and activate the injection of the liquid fuel 714 Level in liquid fuel tank less than threshold level? 716 Deactivate the liquid fuel injection 718 Target torque greater than threshold and throttle PFI active? 720 Increase the proportion of liquid fuel supplied to the engine 722 engine currently knock limited? 723 Increase the proportion of higher effective octane fuel supplied to the engine 724 Relative fuel costs known? 725 Increase the proportion of lower-cost fuel supplied to the engine 726 Engine currently throttled greater than a threshold amount? 727 Increase the proportion of gaseous PFI fuel supplied to the engine 728 Relative carbon intensity of fuels known? 729 Increase the proportion of lower carbon fuel supplied to the engine Output

[0116] Fig. 8 Beginning 802 The conditions of the engine and the fuel tank determine 804 Gaseous fuel tank pressure less than 1st threshold? N NO 806 Activate the DI pump for gaseous fuel 808 Disable the DI pump for gaseous fuel 810 Gaseous fuel tank pressure less than 2nd threshold? 812 Use the fuel stored in the largest quantity; if gaseous fuel, activate the PFI, otherwise deactivate the PFI of the gaseous fuel and activate the injection of the liquid fuel 814 Level in liquid fuel tank less than threshold level? 816 Deactivate the liquid fuel injection 818 Fuel target flow greater than threshold and DI pump for gaseous fuel active? 820 Increase the proportion of liquid fuel supplied to the engine 822 engine currently knock limited? 823 Increase the proportion of higher effective octane fuel supplied to the engine 824 Relative fuel costs known? 825 Increase the proportion of lower-cost fuel supplied to the engine 826 Engine currently throttled greater than a threshold amount? 827 Increase the proportion of gaseous PFI fuel supplied to the engine 828 Relative carbon intensity of fuels known? 829 Increase the proportion of lower carbon fuel supplied to the engine Output

Claims

[1] Engine operating method (700, 800) comprising: Direct injection of a gaseous fuel into an engine in response to a pressure of a gaseous fuel stored in a fuel tank exceeding a threshold pressure; characterized by that the engine operating method further comprises: Activating a gaseous fuel pump, adjusting torque converter clutch engagement, and adjusting a transmission gear shift schedule in response to the pressure of gaseous fuel stored in the fuel tank being less than or equal to the threshold pressure. [2] The method (700, 800) of claim 1, wherein adjusting the gear shift schedule of the transmission includes adjusting a vehicle speed at which a transmission shifts gears. [3] The method (700, 800) of claim 2, wherein the vehicle speed at which the transmission shifts gears is reduced in response to activating the gaseous fuel pump. [4] The method (700, 800) of claim 1, wherein adjusting engagement of the torque converter clutch includes adjusting a vehicle speed at which the torque converter clutch engages. [5] The method (700, 800) of claim 4, wherein the vehicle speed at which the torque converter engages is reduced in response to activating the gaseous fuel pump. [6] The method (700, 800) of claim 1, further comprising setting an operating state of a three-way valve fluidly connected to the gaseous fuel pump and the fuel tank. [7] The method (700, 800) of claim 1, wherein the gaseous fuel pump supplies the fuel to a direct fuel injector. [8] The method (700, 800) of claim 7, wherein the gaseous fuel is supplied to the direct injector via the fuel tank without passing the fuel through the gaseous fuel pump. [9] Vehicle system comprising: a power machine (10); a tank (354) for gaseous fuel; a gaseous fuel pump (465) pneumatically connected to the gaseous fuel tank (354); and a controller (12) containing non-transitory instructions for supplying gaseous fuel to the engine (10) and for activating the gaseous fuel pump (465) only when a pressure in the gaseous fuel tank (354) is less than a threshold pressure (502), characterized by , that the non-transitory instructions for setting a lock-up schedule of a torque converter (206) in response to the pressure in the gaseous fuel tank (354) being less than the threshold pressure (502), or that the vehicle system further comprises a stepped ratio transmission and non-transitory instructions for adjusting a transmission shift schedule in response to the pressure in the gaseous fuel tank (354) being less than the threshold pressure (502). [10] The vehicle system of claim 9, further comprising an accumulator (460) positioned downstream of the gaseous fuel pump (465). [11] The vehicle system of claim 10, further comprising a pressure regulator (462) positioned downstream of the accumulator (460). [12] The vehicle system of claim 9, further comprising a direct gaseous fuel injector (66) coupled to the engine (10).

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