PILOT INJECTION ADJUSTMENT

Abstract

Engine operating procedures that include the following: To receive sensor data in a controller; to assess whether conditions exist for setting a fuel injector transmission function based on sensor data via the control unit; and to activate a glow plug located in a cylinder of an engine via the control system in response to the presence of the appropriate conditions, to operate a fuel injector by means of the control system in response to the presence of the conditions, the operation of the fuel injector includes the supply of pilot injections by means of the fuel injector and to adjust the amount of electrical power delivered to the glow plug, characterized by that the amount of electrical power delivered to the glow plug is based on the pulse width of the pilot injection.

Description

Background / Summary

[0001] Fuel can be delivered to a cylinder of a diesel engine during an engine cycle via one or more fuel injection pulses. A first group of fuel injections provided to an engine cylinder during a cylinder cycle may be referred to as pilot injections. The pilot injections may be followed by a main injection. The main injection may be followed by post-injections during the same cylinder cycle. The pilot injections may be useful to reduce engine noise, while the main injection serves the purpose of generating engine torque. Post-injections may be provided to the engine to transfer thermal energy to emission control devices in the engine's exhaust system or to provide reductant for the emission control devices.The variation in fuel flow for different fuel injectors of the same type can be significantly more pronounced at the narrower fuel pulse widths at which fuel injectors provide pilot injections. Consequently, it may be desirable to periodically update fuel injector transfer functions within a pulse width zone or range where pilot injections are provided. However, it can be difficult to determine fuel injector transfer function errors when an engine is operating with short-duration pilot injections. Consequently, it can be difficult to accurately update the fuel injector transfer function when the engine is operating with short-duration pilot injections.

[0002] JP 2010-43548 A discloses the provision of a fuel supply control device for an internal combustion engine that accurately calculates the correction amount of a fuel supply command value supplied to a fuel supply device under relatively mild conditions. To this end, a glow plug is energized when the conditions for learning the correction amount of the requested fuel injection amount are met. Thereafter, when the conditions for learning execution are met, minute injection for injecting a minute amount is performed by a fuel injection valve. An increase amount of the engine output torque by the minute injection amount is calculated according to an increase amount of the engine speed, and a minute command fuel injection amount that commands the minute injection amount is increased until the torque increase amount reaches a prescribed increased amount.

[0003] A learned value is renewed according to the calculated minute fuel injection amount.

[0004] JP 2009-24500 A describes the provision of an injection quantity learning device for an internal combustion engine capable of accurately completing the learning of an injection quantity by controlling the combustion of the internal combustion engine when a minute injection quantity is learned. This injection quantity learning device of an internal combustion engine is suitably used in the internal combustion engine to perform injection quantity learning. Specifically, the injection quantity learning device performs control to promote combustion of the internal combustion engine when the minute injection quantity is learned. For example, the device controls the variable nozzle of a turbocharger toward the closing side. Since the boost pressure is increased by the turbocharger, the intake air quantity increases, and combustion is promoted.Consequently, since a torque (speed change) corresponding to the injection amount can be properly generated when the minute injection amount is learned, learning can be accurately completed by suppressing the occurrence of erroneous learning.

[0005] DE 10 2008 007 395 A1 relates to a method for detecting a fuel quality and for operating an internal combustion engine and to an engine control unit in which the temperature of at least one glow plug of the engine is controlled, an engine behavior after the temperature change is compared with an engine behavior before the temperature change, and a fuel quality is derived from the result of this comparison.

[0006] JP 2008-280895 A discloses a method for preventing misfires and white smoke due to glow plug wear, wherein an engine system ECU executes combustion performance hold processing to maintain combustion performance during cold start when the glow plug for an engine deteriorates. In this processing, after the fuel injection characteristic of an injector is corrected by micro-injection amount learning processing during fuel cut, cold correction value update processing is executed to update a cold correction value for the injector, which is set to improve combustion performance during cold start during fuel cut, depending on the deterioration state of the glow plug. In this processing, a certain amount of fuel is injected during operation and when the glow plug is not operated, and the torque generated by the engine is calculated, respectively.The cold correction value is updated for each cylinder according to a deviation in the calculated torque generated by the engine. The inventors have recognized the above-mentioned disadvantages and, according to the invention, have provided an engine operating method and an engine system with the features of independent claims 1 and 9.

[0007] It includes the following: Receive sensor data at a controller; assess, based on the sensor data, whether conditions exist for adjusting a fuel injector transfer function via the controller; and activate a glow plug via the controller in response to the conditions being present.

[0008] By selectively operating glow plugs in response to a request to adjust a fuel injector transfer function, it may be possible to provide an improved fuel injector transfer function adjustment as a technical result. For example, one or more engine glow plugs may be activated to provide more stable and repeatable combustion in the engine cylinders during the adjustment of fuel injector transfer functions. The activated glow plugs may heat engine cylinders to improve combustion stability, thereby providing more uniform engine torque production and engine air-fuel ratio.

[0009] The present description can provide several advantages. In particular, the approach can improve the adaptation of fuel injector transfer functions. Additionally, the approach can improve engine emissions and combustion stability by more accurately delivering fuel to the engine. Furthermore, the approach can reduce engine emissions and noise.

[0010] The above advantages and other advantages and features of the present description will be readily apparent from the following detailed description when taken alone or in conjunction with the accompanying drawings.

[0011] It should be understood that the above Summary is provided to introduce, in simplified form, a selection of concepts further described in the Detailed Description. It is not intended to identify essential or key features of the claimed subject matter, the scope of which is defined solely by the claims following the Detailed Description. Furthermore, the claimed subject matter is not limited to implementations that mitigate any of the disadvantages mentioned above or in any part of this disclosure. Short description of the characters Fig. 1 shows a schematic representation of an engine; Fig. 2 shows an exemplary engine operating sequence according to the method of the Fig. 3 and Fig. 4; and Fig. 3 - 4 show an exemplary method for adjusting a fuel injector transfer function. Detailed description

[0012] This description relates to adjusting a fuel injector transfer function to reduce engine noise and improve combustion in engine cylinders. Fig. 1 shows an example of a turbocharged diesel engine in which the method of the Fig. 3 and Fig. 4 can adjust glow plug operation and combustion phasing to improve engine torque production, combustion stability, and reduce engine combustion noise. An engine operating sequence is described in Fig. 2, where a fuel injection valve transfer function is set. The Fig. 3 and Fig. 4 show an exemplary method for setting a transfer function that describes fuel injector operation.

[0013] Reference should be made to Fig. 1. The internal combustion engine 10 comprising a plurality of cylinders, one of which is in Fig. 1, is controlled by the electronic engine control unit 12. The engine 10 includes the combustion chamber 30 and cylinder walls 32 with the piston 36 positioned therein, which is connected to a crankshaft 40. The combustion chamber 30 is shown communicating with the intake manifold 44 and the exhaust manifold 48 via the intake valve 52 and the 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 the intake cam 51 may be determined by the intake cam sensor 55. The position of the exhaust cam 53 may be determined by the exhaust cam sensor 57.

[0014] The fuel injector 66 is shown positioned to inject fuel directly into the combustion chamber 30, known to those skilled in the art as direct injection. The fuel injector 66 delivers fuel in proportion to a pulse width from the controller 12. Fuel is delivered to the fuel injector 66 via a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel rail (not shown). The fuel pressure delivered via the fuel system can be adjusted by adjusting a positioner valve controlling flow to a fuel pump (not shown). Additionally, a metering valve may be located in or near the fuel rail for fuel control. A pumping metering valve may also regulate fuel flow to the fuel pump, thereby reducing fuel pumped to a high-pressure fuel pump.

[0015] The intake manifold 44 is shown in conjunction with the optional electronic throttle 62, which adjusts a position of the throttle valve 64 to control airflow out of the intake boost chamber 46. The compressor 162 draws air from the air intake 42 to supply the boost chamber 46. Exhaust gases rotate the turbine 164, which is coupled to the compressor 162 via shaft 161. In some examples, an air charge cooler may be provided. The compressor speed may be adjusted by adjusting a position of a variable geometry guide vane controller 72 or the compressor bypass valve 158. In alternative examples, a wastegate 74 may replace or be used in addition to the variable geometry guide vane controller 72. The variable geometry guide vane controller 72 adjusts a position of variable geometry turbine guide vanes.Exhaust gases may pass through the turbine 164, contributing little power to rotating the turbine 164 when the guide vanes are in an open position. Exhaust gases may pass through the turbine 164 and transfer increased power to the turbine 164 when the guide vanes are in a closed position. Alternatively, the wastegate 74 allows exhaust gases to bypass the turbine 164, thus reducing the amount of power supplied to the turbine. The compressor bypass valve 158 allows compressed air at the outlet of the compressor 162 to be recirculated to the inlet of the compressor 162. In this way, the efficiency of the compressor 162 may be reduced, thereby affecting flow within the compressor 162 and reducing intake manifold pressure.

[0016] Combustion is initiated in combustion chamber 30 when fuel is automatically ignited by compression ignition as piston 36 approaches top dead center on its compression stroke. In some examples, a universal exhaust gas oxygen (UEGO) sensor 126 may be coupled to exhaust manifold 48 upstream of emissions device 70. In other examples, the UEGO sensor may be located downstream of one or more exhaust aftertreatment devices. Further, in some examples, the UEGO sensor may be replaced with a NOx sensor that includes both NOx and oxygen sensing elements.

[0017] At lower engine temperatures, glow plug 68 can convert electrical energy into thermal energy to increase a temperature in combustion chamber 30. By increasing the temperature of combustion chamber 30, it may be easier to ignite a cylinder air-fuel mixture through compression. Controller 12 adjusts the current flow to glow plug 68 and the voltage applied to it. In this way, controller 12 can adjust the amount of electrical power supplied to glow plug 68.

[0018] In one example, the emissions device 70 may include a particulate filter and catalyst bricks. In another example, multiple emission control devices, each with multiple bricks, may be used. In one example, the emissions device 70 may include an oxidation catalyst. In other examples, the emissions device may include a NOx storage catalyst or a selective catalyst reduction (SCR) and / or a diesel particulate filter (DPF).

[0019] Exhaust gas recirculation (EGR) may be provided to the engine via EGR valve 80. EGR valve 80 is a three-way valve that closes or allows exhaust gas to flow from downstream of emissions device 70 to a position in the engine air intake system upstream of compressor 162. In alternative examples, EGR may flow from upstream of turbine 164 to intake manifold 44. EGR may bypass EGR cooler 85, or alternatively, EGR may be cooled by flowing through EGR cooler 85. In other examples, a high-pressure and low-pressure EGR system may be provided.

[0020] The control 12 is in Fig. 1 as a conventional microcomputer including the microprocessor unit 102, the input / output ports 104, the read-only memory 106, the random access memory 108, the keep-alive memory 110 and a conventional data bus.The controller 12 is shown receiving, in addition to the signals previously discussed, various signals from sensors coupled to the engine 10, including: the engine coolant temperature (ECT) from temperature sensor 112 coupled to the cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 for sensing the accelerator pedal position set by the driver 132; an intake manifold pressure (MAP) measurement from pressure sensor 121 coupled to the intake manifold 44; boost pressure from pressure sensor 122; exhaust gas oxygen concentration from oxygen sensor 126; an engine position sensor from a Hall sensor 118 that senses the position of the crankshaft 40; a measurement of the mass of air entering the engine from sensor 120 (e.g., a hot wire air flow sensor); and a measurement of the throttle position from sensor 58. Atmospheric pressure may also be sensed for processing by controller 12 (sensor not shown).In a preferred aspect of the present description, the engine position sensor 118 generates a predetermined number of evenly spaced pulses for each revolution of the crankshaft from which the engine speed (RPM) can be determined.

[0021] During operation, each cylinder in engine 10 typically undergoes a four-stroke cycle: the cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. During the intake stroke, exhaust valve 54 generally closes and intake valve 52 opens. Air is introduced into combustion chamber 30 via intake manifold 44, and piston 36 moves toward the bottom of the cylinder to increase the volume in combustion chamber 30. The position where piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when 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, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head to compress the air in combustion chamber 30.The point at which the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 is at its smallest volume) is typically referred to by those skilled in the art as top dead center (TDC). In a process referred to below as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected into a cylinder multiple times during a single cylinder cycle. In a process referred to below as ignition, the injected fuel is ignited by compression ignition, resulting in combustion. During the power stroke, the expanding gases push the piston 36 back to BDC. The crankshaft 40 converts piston motion into rotational torque of the rotating shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to the exhaust manifold 48, and the piston returns to TDC.It should be noted that the above description is shown merely as an example, and the timing of intake and exhaust valve opening and / or closing may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. Furthermore, in some examples, a two-stroke cycle may be used instead of a four-stroke cycle.

[0022] Thus, the system Fig. 1 provides an engine system comprising: an engine having a combustion chamber; a fuel injector and a glow plug extending into the combustion chamber; and a controller including instructions for activating the glow plug in response to a request to adjust a fuel injector transfer function in a pulse width range in which the pilot injections are provided. The engine system further includes operating the fuel injector in the pulse width range in which pilot injections are provided in response to the request to adjust the fuel injector transfer function. The engine system further includes additional control instructions for adjusting the fuel injector transfer function in response to an engine air-fuel ratio.The engine system further includes additional control instructions for adjusting the fuel injector transfer function in response to engine torque. The engine system further includes additional control instructions for decreasing the power supplied to the glow plug in response to increasing a pilot injection pulse width. The engine system includes the fuel injector transfer function describing the fuel injector current.

[0023] Reference should now be made to Fig. 2 An exemplary engine operating sequence is shown. The operating sequence can be achieved by the method from the Fig. 3 and Fig. 4, which in conjunction with the system Fig. 1. Vertical lines at times T1 - T8 represent points of interest during the engine operating sequence.

[0024] The first curve image from above in Fig. Figure 2 is a graph of the fuel injection adjustment state over time. The vertical axis represents the fuel injection adjustment state. The fuel injector transfer function is being adjusted or tuned when the graph is at a higher level near the vertical axis arrow. The horizontal axis represents time, and time runs from the left side of the graph to the right side of the graph.

[0025] The second graph from the top in Fig. Figure 2 is a graph of the glow plug operating state over time. The vertical axis represents the glow plug operating state. The glow plug is activated when the curve is at a higher level near the vertical axis arrow. The glow plug is deactivated when the curve is at a lower level near the vertical axis arrow. The horizontal axis represents time, and time runs from the left side of the graph to the right side of the graph.

[0026] The third graph from the top in Fig. Figure 2 is a graph of the electrical power supplied to the glow plug versus time. The vertical axis represents the power supplied to the glow plug, and the power supplied to the glow plug increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time runs from the left side of the graph to the right side of the graph.

[0027] The fourth graph from the top in Fig. Figure 2 is a graph of the fuel injector pulse width versus time. The vertical axis represents the fuel injector pulse width, and the fuel injector pulse width increases in the direction of the vertical axis arrow. The larger the fuel injector pulse width, the greater the amount of fuel injected into a cylinder. The horizontal axis represents time, and time runs from the left side of the graph to the right side of the graph.

[0028] The fifth graph from the top in Fig. Figure 2 is a graph of the number of pilot injections delivered to a cylinder during a single cylinder cycle versus time. The vertical axis represents the number of pilot injections delivered to a cylinder during a single cylinder cycle for a particular cylinder, and the number of pilot injections increases in the direction of the vertical axis arrow. The number of pilot injections is shown along the vertical axis. The horizontal axis represents time, and time runs from the left side of the graph to the right side of the graph.

[0029] At time T0, the fuel injector transfer function adjustment is not activated, as indicated by the fuel injection adjustment state curve being at a lower level near the horizontal axis. The glow plugs are not activated, and the glow plug power is zero. The pilot injection pulse width is at a low-medium level, and the number of pilot injections is one.

[0030] At time T1, fuel injector transfer function adjustment is enabled, as indicated by the fuel injection adjustment state transitioning to a higher level. The main injection pulse width (not shown) is adjusted by a valve based on engine speed and driver torque request (not shown). All fuel injected into a cylinder during the cylinder cycle is injected during the main injection. The engine air-fuel ratio and torque are monitored during fuel injector transfer function adjustment.

[0031] At time T2, pilot injection into the engine is started via the fuel injector so that the fuel injector transfer function can be adjusted to inject a small amount of fuel via the pilot injection. The amount of fuel of the pilot injection is increased to a first amount. The glow plugs are activated, as indicated by the glow plug operating state transitioning to a higher state in response to the activation of the fuel injection during the adjustment of the fuel injector transfer function. The amount of electrical energy supplied to the glow plug is at a higher level in response to the small amount of fuel injected during the pilot injection, so that the fuel injected during the pilot injection can ignite and combust more reliably.The amount of fuel injected during a cylinder cycle by the pilot injection is the amount of fuel taken from the main injection during the cylinder cycle. Thus, if the pilot injection delivers the target amount of fuel, the total amount of fuel injected into the cylinder during a cylinder cycle is equivalent to the amount of fuel delivered to the cylinder at time T1 via the single pulse width of the main injection.

[0032] Between time T2 and time T3, the adaptation state of the fuel injector remains high, and the glow plug continues to operate at a high power level. The pulse width of the pilot injection remains constant, but the number of pilot injections is increased from one to two and then to three. Each time the number of pilot injections increases, an amount of fuel added to the pilot injections is subtracted from the pulse width of the main injections, so that the amount of fuel delivered to the cylinder remains the same as the number of pilot injections increases. By increasing the number of pilot injections and requesting an equal amount of fuel in each pilot injection, it may be possible to increase the signal-to-noise ratio of the amount of fuel injected in the pilot injections.For example, if a single pilot injection is delivered to a cylinder during a cylinder cycle and the main injection in the cylinder cycle is reduced by an amount of fuel expected to come with the pilot injection, a change in engine air-fuel ratio or torque may not be noticeable. However, if the number of pilot injections is increased and an equal amount of requested fuel is injected in each pilot injection, an error in the amount of fuel delivered in the pilot injections may be more noticeable due to the increased number of pilot injections. In this example, a change in engine air-fuel ratio and torque is not noticeable, so the number of pilot injections is incremented until a value of three pilot injections is reached.

[0033] At time T3, the number of pilot injections is adjusted from three to one, and the pilot injection fuel quantity is increased. By increasing the pilot injection fuel quantity, different portions of the fuel injector transfer functions can be adjusted. The pilot injection fuel quantity is increased in response to the number of pilot injections reaching three without a noticeable change in the engine air-fuel ratio or torque. The fuel injection adjustment state is maintained at a higher level, and the glow plugs remain activated. The amount of electrical energy supplied to the glow plug is reduced in response to the increase in the amount of fuel injected in each pilot injection.

[0034] Between time T3 and time T4, the fuel injector's adaptation state remains high, and the glow plug continues to operate at a high power level. The pulse width of the pilot injection remains constant, but the number of pilot injections increases from one to two and then to three. Each time the number of pilot injections increases, the amount of fuel added to the pilot injections is subtracted from the pulse width of the main injections, so the amount of fuel delivered to the cylinder remains the same as the number of pilot injections increases.

[0035] At time T4, the number of pilot injections is adjusted from three to one, and the pilot injection fuel quantity is increased again. The pilot injection fuel quantity is increased in response to the number of pilot injections reaching three without a noticeable change in the engine air-fuel ratio or torque. The fuel injection adjustment state is maintained at a higher level, and the glow plugs remain activated. The amount of electrical energy supplied to the glow plug is reduced in response to the increase in the amount of fuel injected in each pilot injection.

[0036] Between time T4 and time T5, the fuel injector adaptation state remains high, and the glow plug continues to operate at a high power level. The pilot injection pulse width remains constant, but the number of pilot injections is increased from one to two. A change in the engine air-fuel ratio is detected (not shown), so the fuel injector transfer function is adjusted, and then the pilot injection pulse width is increased.

[0037] At time T5, the number of pilot injections is adjusted from two to one, and the pilot injection fuel quantity is increased again. The pilot injection fuel quantity is increased in response to the fuel injector pulse width being adjusted in response to an observed change in the engine air-fuel ratio or a change in engine torque. The fuel injection adjustment state is maintained at a higher level, and the glow plugs remain activated. The amount of electrical energy supplied to the glow plug is reduced again in response to the increase in the amount of fuel injected in each pilot injection.

[0038] Between time T5 and time T6, the fuel injector's adaptation state remains high, and the glow plug continues to operate at a high power level. The pulse width of the pilot injection remains constant, but the number of pilot injections increases from one to two and then to three. Each time the number of pilot injections increases, the amount of fuel added to the pilot injections is subtracted from the pulse width of the main injections, so the amount of fuel delivered to the cylinder remains the same as the number of pilot injections increases.

[0039] At time T6, the number of pilot injections is adjusted from three to one, and the pilot injection fuel quantity is increased again. The pilot injection fuel quantity is increased in response to the number of pilot injections reaching three without a noticeable change in the engine air-fuel ratio or torque. The fuel injection adjustment state is maintained at a higher level, and the glow plugs remain activated. The amount of electrical energy supplied to the glow plug is reduced in response to the increase in the amount of fuel injected in each pilot injection.

[0040] Between time T6 and time T7, the fuel injector adaptation state remains high, and the glow plug continues to operate at a high power level. The pilot injection pulse width remains constant, but the number of pilot injections is increased from one to two. A change in the engine air-fuel ratio is detected (not shown), so the fuel injector transfer function is readjusted, and then the pilot injection pulse width is increased.

[0041] At time T7, the number of pilot injections is adjusted from two to one, and the pilot injection fuel amount is increased again. The pilot injection amount is increased in response to the fuel injector pulse width being adjusted in response to an observed change in the engine air-fuel ratio or a change in engine torque. The fuel injection adjustment state is maintained at a higher level; however, the glow plug is deactivated in response to the pilot injection being greater than a threshold amount. The amount of electrical energy supplied to the glow plug is reduced to zero in response to the amount of fuel injected in each pilot injection increasing.

[0042] Between time T7 and time T8, only one pilot injection is provided because the amount of fuel in the pilot injection is greater than a threshold. In this example, no change in the engine air-fuel ratio or engine torque is noticeable. Therefore, the fuel injector transfer function is not adjusted.

[0043] At time T8, the sequence ends with the fuel injection adjustment state transitioning to a lower level. The glow plug remains deactivated, and a single pilot injection is delivered to the engine cylinder.

[0044] In this way, the fuel injector transfer function can be adjusted to improve the accuracy of the injected fuel quantity. Because small amounts of fuel are injected during the pilot injection, a small error in the fuel injector transfer function can result in a large percentage increase or decrease in the injected fuel. Thus, it may be desirable to adjust the fuel injector transfer function for small fuel injection quantities. Furthermore, by increasing the number of pilot injections, it may be possible to improve air-fuel ratio error detection.

[0045] Now let us refer to the Fig. 3 and Fig. 4: A method for adjusting a fuel injector transfer function is shown. The method from the Fig. 3 and Fig. 4 can be at least partly in the system of Fig. 1 as executable instructions stored in non-volatile memory. Furthermore, the method from the Fig. 3 and Fig. 4 actions that are performed in the physical world. The procedure from the Fig. 3 and Fig. 4 can the Fig. 3 provide the operating sequence shown.

[0046] In step 302, method 300 determines vehicle operating conditions. Vehicle operating conditions may be determined by receiving outputs from sensors and actuators in the vehicle system. In one example, vehicle operating conditions include, but are not limited to, engine temperature, driver demand torque, engine speed, vehicle speed, engine air-fuel ratio, and distance traveled by the vehicle. Method 300 continues to step 304 after the vehicle operating conditions are determined.

[0047] In step 304, method 300 assesses whether conditions exist for adjusting a fuel injector transfer function. The fuel injector transfer function describes the fuel flow through a fuel injector versus the pulse width or activated time of the fuel injector. In one example, the conditions include the engine operating within a prescribed engine speed and load range. It may also be desirable for the engine temperature to be within a desired temperature range. It may still be desirable for the vehicle in which the engine is operating to have traveled a predetermined distance.If method 300 determines that conditions exist to adjust a fuel injector transfer function, the answer is yes, and method 300 proceeds to step 306 based on a request to adjust the fuel injector transfer function. Otherwise, the answer is no, and method 300 proceeds to exit. Additionally, method 300 may end if operating conditions change after the request to adjust the fuel injector transfer function. For example, method 300 may end if a driver applies an accelerator pedal to increase a driver demand.

[0048] In step 306, method 300 determines a desired amount of fuel to be injected into one or more engine cylinders. In one example, the desired amount of fuel may be based on the accelerator pedal position and the vehicle speed and / or the engine speed. In particular, the desired amount of fuel to be injected into an engine cylinder is determined empirically and stored in a table or function. The table or function is indexed by a desired engine torque, as determined from the accelerator pedal position and the vehicle speed and / or the engine speed. Method 300 continues to step 308 after the desired amount of fuel to be injected into the engine cylinders is determined.

[0049] In step 308, method 300 injects the desired amount of fuel into one or more engine cylinders. For example, the desired amount of fuel may be injected into each engine cylinder. The desired amount of fuel is injected in one main injection without pilot injections. By injecting the desired amount of fuel in one main injection, the pulse width of the fuel injection may be much larger than the pulse width of a pilot injection, so that a base engine air-fuel ratio and base engine torque can be established in response to the amount of fuel provided in the one main injection. The start of fuel injection for a cylinder receiving the one main injection during a cycle of the cylinder may also be adjusted to provide maximum cylinder pressure for the cylinder at a predetermined crankshaft angle.The method 300 continues to step 310 after the desired amount of fuel has been injected into one or more engine cylinders.

[0050] In step 310, method 300 determines the engine air-fuel ratio. The engine air-fuel ratio may be determined in an exhaust manifold that carries exhaust from a single cylinder to a confluence region where exhaust from more than one engine cylinder is carried. Alternatively, the engine air-fuel ratio may be determined in the confluence region. Further, in some examples, engine torque may be determined. In one example, torque from a cylinder may be estimated based on engine acceleration during a power stroke of the cylinder receiving the fuel (e.g., T = jω̇, where T is the torque, j is the observed inertia at the engine crankshaft, and ω̇ is the angular acceleration).The engine air-fuel ratio without pilot injections provides a baseline air-fuel ratio for determining whether or not to provide a desired fuel amount during subsequent engine cycles when pilot injection is enabled. Method 300 proceeds to step 312 after the engine and / or cylinder air-fuel ratio has been determined.

[0051] In step 312, method 300 schedules and activates the pilot injection for each engine cylinder. Method 300 begins by providing a single pilot injection during each cylinder cycle of the cylinder receiving the pilot injection. The first pulse width duration of the pilot injection is a minimum pulse width expected to provide a steady or repeatable fuel injection amount. The main injection delivered during the cylinder cycle in which the pilot injection is provided is reduced by a pulse width duration corresponding to an amount of fuel commanded to be injected during the pilot injection during the same cylinder cycle.For example, if the pilot injection is expected to inject X grams of fuel during a cylinder cycle, the main injection is reduced by X grams of fuel during the cylinder cycle, so that the engine air-fuel ratio and torque are expected to be constant. Method 300 proceeds to step 314 after the pilot injection is enabled and the pilot injection begins.

[0052] In step 314, the method 300 activates glow plugs in cylinders that receive the pilot injection quantity, as in Fig. 4. The glow plugs are activated to improve combustion by providing a heat source that may improve ignition. Furthermore, activating the glow plugs may provide smoother and more consistent engine torque. Method 300 proceeds to step 316 after the glow plugs are activated.

[0053] In step 316, method 300 assesses whether there is a change in engine air-fuel ratio. In some examples, method 300 may determine that there is a change in engine air-fuel ratio if the air-fuel ratio of the engine or an individual cylinder changes by more than a predetermined amount. Alternatively, method 300 may assess whether there is a change in engine torque production. In some examples, method 300 may determine that there is a change in engine torque production if the torque production of the engine or an individual cylinder changes by more than a predetermined amount. If method 300 determines that there is a change in engine air-fuel ratio or if there is a change in engine torque production, the answer is yes, and method 300 proceeds to step 318.Otherwise, the answer is no, and method 300 continues to step 330.

[0054] In step 318, method 300 increments or decrements the value in the fuel injector transfer function corresponding to the pulse width provided to generate the current pilot injection. For example, if the air-fuel ratio is leaner than expected, the value in the fuel injector transfer function corresponding to the pulse width of the pilot injection is increased to enrich the engine and / or cylinder air-fuel ratio. If the air-fuel ratio is richer than expected, the value in the fuel injector transfer function corresponding to the pulse width of the pilot injection is decreased to lean the engine and / or cylinder air-fuel ratio. The change in the engine air-fuel ratio or engine torque may indicate that an undesirable value is stored in the fuel injector transfer function.Similarly, if the engine torque is less than expected, the value in the fuel injector transfer function corresponding to the pilot injection pulse width is increased to increase engine torque. If the engine torque is greater than expected, the value in the fuel injector transfer function corresponding to the pilot injection pulse width is decreased to reduce engine torque. Method 300 proceeds to step 336 after the fuel injector transfer function has been adjusted.

[0055] In step 336, method 300 increments the pilot injection pulse width and continues injecting fuel into engine cylinders with a single pilot injection and a main injection pulse width. The pilot injection amount injected during a cylinder cycle increases by increasing an opening time of the fuel injector, as shown in Fig. 2. The pilot injection amount injected during a cylinder cycle may be increased by a predetermined amount. The total amount of fuel injected into the engine during one engine cycle (e.g., two engine revolutions) is the same as determined in step 306. Thus, the pilot injection amount plus the main injection amount during a cylinder cycle is equal to the amount of fuel injected into the engine in the main injection at 308. Method 300 returns to step 314 after the pilot injection fuel amount has been increased.

[0056] In step 330, method 300 increments the number of pilot injections provided to one or more engine cylinders. For example, if only one pilot injection is currently provided to a cylinder by a fuel injector, two pilot injections must be provided via the fuel injector. Similarly, the pilot injections for other engine cylinders are also incremented. All pilot injections provided to a cylinder or engine cylinders during an engine cycle have the same pulse width. By increasing the number of pilot injections, errors in the fuel injector transfer function may be more prominent or detectable because additional pilot injections increase the engine air-fuel error and torque error if the fuel injector does not inject a desired amount of fuel during the pilot injections.Method 300 continues to step 332 after the number of pilot injections has been increased.

[0057] In step 332, method 300 judges whether the number of pilot injections is greater than a threshold number of pilot injections. In one example, the number is three, however, other numbers are considered. If method 300 determines that the number of pilot injections is greater than a threshold number, the answer is yes, and method 300 continues to step 334. Otherwise, the answer is no, and method 300 returns to step 314.

[0058] In step 332, method 300 judges whether the number of pilot injections is greater than (e.g., greater than) a threshold number of pilot injections. In one example, the number is three, however, other numbers are considered. If method 300 determines that the number of pilot injections is greater than a threshold number, the answer is yes, and method 300 proceeds to step 334. Otherwise, the answer is no, and method 300 returns to step 314.

[0059] In step 334, method 300 assesses whether the pilot injections are occurring at a maximum pilot injection pulse width. If method 300 determines that the pilot injections are occurring at or greater than the maximum pilot injection pulse width, the answer is yes, and method 300 continues to step 340. Otherwise, the answer is no, and method 300 continues to step 336.

[0060] In step 340, method 300 returns to the base pilot injection amount and the base main injection amount. However, the pilot injection amounts are delivered with pulse widths determined by the adjusted or adjusted fuel injector transfer function. In this way, the pilot injections are adjusted after the fuel injector transfer function has been adjusted. Method 300 continues to step 342 after fuel injection has returned to the base amounts.

[0061] In step 342, method 300 deactivates the glow plugs. The glow plugs are deactivated to reduce electrical power consumption and increase glow plug life. Method 300 continues to exit after the glow plugs are deactivated.

[0062] In an alternative example, the fuel injector transfer function may be adjusted in response to the vehicle and engine entering deceleration fuel shutoff (DFSO). The vehicle may enter DFSO in response to a driver releasing the accelerator pedal and the vehicle decelerating from a speed greater than a threshold speed. During DFSO, a selected fuel injector may be reactivated while other fuel injectors remain off. The amount of fuel injected during the DFSO event may be estimated via an oxygen sensor, engine acceleration, or cylinder pressure.In one example, a small amount of fuel is injected via the reactivated fuel injector, and the amount of fuel is estimated based on the oxygen concentration in the cylinder exhaust, the engine acceleration during a power stroke of the cylinder, or the maximum cylinder pressure during the power stroke of the cylinder.

[0063] If cylinder pressure transducers are used to determine the amount of fuel injected into a single cylinder during DFSO, the cumulative heat released during combustion can be determined using thermodynamics, and the total energy released from the combusted fuel can be quantified. Knowing the energy density or heating value of the fuel—that is, the energy contained in the fuel per unit volume or mass or number of molecules—or using a standard energy density, the total energy released can be converted into a quantity of fuel burned. The quantity of fuel burned can further be adjusted based on the engine's thermal efficiency at the prevailing operating conditions.

[0064] If engine acceleration is the basis for determining the amount of fuel injected into a single cylinder during DFSO, positive changes in the acceleration / deceleration of the engine crankshaft are a direct result of work done by the fuel being burned and are proportional to the amount of fuel burned. The rate of change of the crankshaft rotational speed, or crankshaft acceleration, can be detected using the derivative of the crankshaft speed as determined by a position sensor. The engine controller can adjust the fuel injector pulse width to match a predetermined crankshaft acceleration that has been calibrated to correspond to a known target amount.The accuracy of estimating an amount of injected fuel may be improved by activating a glow plug in the cylinder receiving the fuel. Furthermore, in some examples, glow plugs may be activated in cylinders not receiving fuel to conserve heat in cylinders not combusting air and fuel. Furthermore, the cylinder receiving fuel may combust a larger amount of fuel during each of a predetermined number of combustion events before the fuel injector injects a small amount of fuel and adjusts the fuel injector transfer function based on the small injection amount so that the cylinder is at a desired temperature when transfer function adjustment begins during DFSO.

[0065] A glow plug is activated during DFSO in the cylinder receiving fuel to promote combustion stability and improve the accuracy of estimating the amount of fuel injected into the cylinder during DFSO. Furthermore, the operation of a glow plug during fuel injector adjustment during DFSO in the cylinder receiving fuel can also reduce variability in the combustion event and combustion efficiency due to noise factors, including, but not limited to, intake air temperature, intake air humidity, intake manifold temperature, intake manifold pressure, intake manifold humidity, intake manifold composition, the presence of EGR in the intake manifold, engine coolant temperature, engine oil temperature, and fuel properties, especially cetane number.After the adjustment of a fuel injector in one cylinder is complete, fuel is injected into another cylinder, while fuel is deactivated in all other cylinders. The glow plug in the cylinder receiving fuel is also activated.

[0066] Now reference is made to Fig. 4. The procedure from Fig. 4 can be at least partly in the system of Fig. 1 as executable instructions stored in non-volatile memory. Furthermore, the method of Fig. 4 actions performed in the physical world.

[0067] In step 402, method 400 activates glow plugs. The glow plugs are activated by supplying electrical current and voltage to the glow plugs. Controller 12 may supply electrical power to the glow plugs, or alternatively, controller 12 may command a glow plug controller to activate glow plugs. Method 400 continues to step 404 after the glow plugs are activated.

[0068] In step 404, method 400 adjusts an amount of electrical power provided to a glow plug based on a pulse width of a pilot injection provided to a cylinder. Method 400 increases an amount of electrical power supplied to the glow plug as the pulse width of the pilot injection decreases. Method 400 decreases an amount of electrical power supplied to the glow plug as the pulse width of the pilot injection increases. In one example, the amount of electrical power supplied to the glow plug is empirically determined based on the pulse width of the pilot injection and stored in memory. The memory is indexed by the pulse width of the pilot injection, and the memory outputs an amount of electrical power to supply to a glow plug. The total electrical power of the engine glow plug may be adjusted in the same manner.Method 400 ends after the glow plug power has been adjusted.

[0069] Thus, the procedure ensures Fig. 3 and Fig. 4 for an engine operating method, comprising: receiving sensor data at a controller; assessing, based on the sensor data, whether conditions for adjusting a fuel injector transfer function exist via the controller; and activating a glow plug via the controller in response to the conditions being met. The method includes adjusting the fuel injector transfer function based on an engine air-to-fuel ratio sensed via an oxygen sensor. The method includes adjusting the fuel injector transfer function based on engine torque.

[0070] In some examples, the method further comprises operating a fuel injector via the controller in response to the conditions being met. The method includes operating the fuel injector including delivering pilot injections via the fuel injector. The method includes the transfer function describing current through a fuel injector. The method includes the transfer function describing current through the fuel injector as a function of the fuel injector activation period.

[0071] The procedure from the Fig. 3 and Fig. 4 also provides for an engine operating method, comprising: receiving sensor data at a controller; assessing, based on the sensor data, whether conditions exist for adjusting a fuel injector transfer function, via the controller, based on the sensor data, within a pulse width range in which pilot injections are delivered; and activating, via the controller, a glow plug in response to the conditions being met. The method further includes adjusting an amount of electrical power delivered to the glow plug. The method includes basing the amount of electrical power delivered to the glow plug on the pulse width of the pilot injection. The method includes decreasing the amount of electrical power delivered to the glow plug as the pulse width of the pilot injection is increased.

[0072] In some examples, the method further includes increasing a value of the transfer function if an engine air-fuel ratio is less than desired. The method further includes decreasing a value of the transfer function if engine torque is greater than desired. The method further includes deactivating the glow plug when adjusting the fuel injector transfer function.

[0073] As is obvious to an average expert, this can be Fig. 3 and Fig. 4 may represent one or more processing strategies of any number, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, various illustrated steps or functions may be performed in the order illustrated, in parallel, or in some cases omitted. Likewise, the processing order may not necessarily achieve the objects, features, and advantages described herein, but is provided for convenience of illustration and description. Furthermore, the methods described herein may be a combination of actions of a controller in the physical world and instructions within the controller.At least portions of the control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and executed by the control system, which includes the controller in combination with the various sensors, actuators, and other engine hardware. Although not explicitly illustrated, it will be apparent to one of ordinary skill in the art that one or more of the illustrated steps, methods, or functions may be performed repeatedly, depending on the strategy used.

[0074] This concludes the description. A reading of it by one skilled in the art would reveal many changes and modifications without departing from the spirit and scope of the description. For example, single-cylinder, I2, I3, I4, I5, V6, V8, V10, V12, and V16 engines powered by natural gas, gasoline, diesel, or alternative fuel configurations could advantageously utilize the present description. Key to symbols:

[0075] Fig. 3: 302 DETERMINE VEHICLE OPERATING CONDITIONS 304 ARE THERE CONDITIONS TO ADJUST THE FUEL INJECTOR TRANSFER FUNCTION FOR PILOT INJECTIONS? 306 DETERMINE TARGET FUEL AMOUNT 308 INJECTING FUEL WITHOUT PILOT INJECTIONS 310 DETERMINE ENGINE AIR-FUEL RATIO 312 Schedule first pilot injection for each engine cylinder at expected, repeatable minimum fuel injector pulse width and reduce main injection by the equivalent pulse width 314 GLOW PLUGS OPERATION SEE Fig. 4 340 RETURN TO BASE PILOT INJECTIONS AND MAIN INJECTION 316 CHANGE IN ENGINE AIR-FUEL RATIO? 318 INCREMENT OR DECREMENT FUEL INJECTOR TRANSMISSION AT SPECIFIED PULSE WIDTH 332 NUMBER OF PILOT INJECTIONS GREATER THAN THRESHOLD? 336 INCREMENT PILOT INJECTION PULSE WIDTH AND CONTINUE WITH A SINGLE PILOT INJECTION 334 PILOT INJECTIONS AT MAXIMUM PULSE WIDTH? 342 DEACTIVATE GLOW PLUGS 330 INCREMENT NUMBER OF PILOT INJECTIONS AND DECREASE MAIN INJECTION BY THE EQUIVALENT PULSE WIDTH

Claims

[1] Engine operating procedure which includes: to receive sensor data in a controller; to assess whether conditions exist for setting a fuel injector transfer function based on the sensor data via the controller; and to activate a glow plug arranged in a cylinder of an engine via the controller in response to the conditions being met, to operate a fuel injector by means of the controller in response to the existence of the conditions, wherein operating the fuel injector includes delivering pilot injections by means of the fuel injector, and to adjust the amount of electrical power delivered to the glow plug, characterized by , that the amount of electrical power delivered to the glow plug is based on the pulse width of the pilot injection. [2] The method of claim 1, wherein the fuel injector transfer function is adjusted based on an engine air-fuel ratio sensed by an oxygen sensor. [3] The method of claim 1, wherein the fuel injector transfer function is adjusted based on engine torque. [4] The method of claim 1, wherein the fuel injector transfer function describes the current through a fuel injector. [5] The method of claim 4, wherein the fuel injector transfer function describes the current through the fuel injector as a function of the activation period of the fuel injector. [6] The method of claim 1, wherein the amount of electrical power delivered to the glow plug is reduced as the pulse width of the pilot injection is increased. [7] The method of claim 6, further comprising increasing a value of the fuel injector transfer function if an engine air-fuel ratio is less than desired. [8] The method of claim 7, further comprising decreasing a value of the fuel injector transfer function if the engine torque is greater than desired. [9] Engine system comprising: an engine with a combustion chamber; a fuel injection valve and a glow plug extending into the combustion chamber; and a controller including instructions to activate the glow plug in response to a request to set a fuel injector transfer function in a pulse width range in which pilot injections are provided, to operate the fuel injector in the pulse width range in which pilot injections are provided in response to the request to adjust the fuel injector transfer function, to adjust the amount of electrical power delivered to the glow plug, whereby the amount of electrical power delivered to the glow plug is based on the pulse width of the pilot injection. [10] The engine system of claim 9, further comprising additional control instructions for adjusting the fuel injector transfer function in response to an engine air-fuel ratio. [11] The engine system of claim 9, further comprising additional control instructions for adjusting the fuel injector transfer function in response to engine torque. [12] The engine system of claim 9, further comprising additional control instructions for decreasing power supplied to the glow plug in response to increasing a pulse width of the pilot injection. [13] The engine system of claim 9, wherein the fuel injector transfer function describes the fuel injector current.

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