Method and system for V8 engine fuel control

Abstract

The invention provides a method and system for V8 engine fuel control. Systems and methods for controlling fuel supplied to cylinders of an internal combustion engine are described. In one example, oxygen sensors are placed in an exhaust system of an engine such that each oxygen sensor may detect exhaust gas from a pair of engine cylinders. The oxygen sensor may then provide feedback to the coupled fuel controller and the decoupled fuel controller.

Description

TECHNICAL FIELD

[0001] The present description relates to systems and methods for controlling fuel supplied to cylinders of an internal combustion engine. The methods can be particularly useful for V8 engines configured with cross-plane crankshafts. BACKGROUND

[0002] An internal combustion engine can operate with a closed loop fuel control system. The closed loop fuel control system operates to drive a measured air-fuel ratio to a requested air-fuel ratio. The measured air-fuel ratio can be inferred via an oxygen sensor that senses exhaust gas. The closed loop fuel control system can include fuel injectors that supply fuel to cylinders. As part of an integrated control system, the closed loop fuel control system can include a diagnosis to assess whether the fuel control system is operating as expected.

[0003] One diagnosis that a fuel system can include is an air-fuel ratio imbalance diagnosis. This diagnosis attempts to determine whether the air-fuel ratio of one cylinder in a cylinder group deviates from the air-fuel ratio of one or more other cylinders in the cylinder group by more than a predetermined amount. This diagnosis helps ensure that each cylinder in the cylinder group operates as requested, even if the cylinders in the cylinder group are averaging to operate at the requested air-fuel ratio. Thus, this diagnosis can enable cylinders that are operating correctly to reduce to leaner or richer than might be expected to compensate for cylinders with deteriorating air-fuel control, while maintaining the average air-fuel ratio of the cylinder group at the requested air-fuel ratio.

[0004] Cylinder firings of a cross-plane crankshaft V8 engine can be unevenly spaced by 90°, 180°, 270°, 180° cylinder firing intervals. These uneven firing intervals can cause exhaust pulses of cylinders in the same cylinder group to vary in residence time at an oxygen sensor. Thus, differences can arise in air-fuel ratio imbalance signals. SUMMARY

[0005] The inventors herein have recognized the above-mentioned shortcomings and have developed a fuel control system comprising: a first cylinder group coupled to an exhaust system, the exhaust system including a first oxygen sensor upstream of a first catalyst and a second oxygen sensor upstream of the first catalyst; a second cylinder group coupled to the exhaust system, the exhaust system including a third oxygen sensor upstream of a second catalyst and a fourth oxygen sensor upstream of the second catalyst; and a controller including executable instructions for a first fuel controller, a second fuel controller, a third fuel controller, and a fourth fuel controller stored in a non-transitory memory.

[0006] By applying an oxygen sensor for each cylinder pair, the difference in air-fuel imbalance signals due to the residence problem of the exhaust pulse can be addressed, allowing for more accurate detection of air-fuel imbalances. Additionally, the additional oxygen sensor enables a coupled controller, which can have the ability to reduce engine emissions via faster convergence to the requested air-fuel ratio. Furthermore, the methods described herein allow the system to apply both a coupled controller and a decoupled controller, such that the features of both controllers can be utilized to provide more sensitive and accurate air-fuel ratio control.

[0007] The present specification can provide several advantages. In particular, the methods can utilize a controller that converges to its requested value faster than other types of controllers to reduce engine emissions. Additionally, the methods can provide more accurate air-fuel ratio control while allowing for detection of air-fuel imbalances. Furthermore, the methods can be applied to both V8 engines and four-cylinder engines.

[0008] The above advantages and other advantages and features of the present specification will be appreciated by reading the following detailed description, with reference to the following figures.

[0009] It is to be understood that the above summary is intended to provide a simplified introduction to a series of concepts further described in the detailed description. It is not intended to identify key features of the claimed subject matter, the scope of which is defined exclusively by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any or all of the disadvantages of any of the problems mentioned in the background or any part of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0010] The advantages described herein will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0011] Figure 1 is a schematic of a single cylinder of an engine;

[0012] Figure 2 is a schematic of an eight-cylinder engine and a presentation of a first air-fuel ratio control system arrangement;

[0013] Figure 3 is a schematic of an eight-cylinder engine and a presentation of a second air-fuel ratio control system arrangement;

[0014] Figure 4 and Figure 5 shows the stability regions of the controller gains for two different air-fuel ratio control methods; and

[0015] Figure 6 is a flowchart for activating different fuel controllers. DETAILED DESCRIPTION

[0016] This specification relates to controlling air-fuel ratios of engine cylinders of a V8 engine comprising four upstream oxygen sensors (e.g., four oxygen sensors in an exhaust system upstream of a catalytic converter). As shown in Figure 1 A single cylinder of an internal combustion engine. In a first example, air-fuel ratios of engine cylinders can be controlled via a first system as shown in Figure 2 A single cylinder of an internal combustion engine. In a second example, air-fuel ratios of engine cylinders can be controlled via a second system as shown in Figure 3 A single cylinder of an internal combustion engine. In a second example, air-fuel ratios of engine cylinders can be controlled via a second system as shown in Figure 4 and Figure 5 A stability plot of the air-fuel control method shown in Figure 2 and Figure 3 A stability plot of the air-fuel control method shown in Figure 6 is a flowchart of a method for activating two different fuel controllers.

[0017] Referring to Figure 1 , an internal combustion engine 10 (comprising a plurality of cylinders, Figure 1 one of which is shown in FIG. 1) is controlled by an electronic engine controller 12. The engine 10 includes a combustion chamber 30 and a cylinder wall 32 with a piston 36 positioned therein and connected to a crankshaft 40. A flywheel 97 and a ring gear 99 are coupled to the crankshaft 40. A 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 mounted directly to the front of the engine or to the rear of the engine. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a chain. In one example, the starter 96 is in a base state when not engaged to the engine crankshaft. The combustion chamber 30 is shown in communication with an intake manifold 44 and an exhaust manifold 48 via respective intake valves 52 and exhaust valves 54. Each intake and exhaust valve can be operated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57.

[0018] Direct fuel injectors 66 are shown positioned to inject fuel directly into the cylinders 35, which is referred to by those skilled in the art as direct injection. The fuel injectors 66 deliver liquid fuel in proportion to the voltage pulse width of the signals from the controller 12 or fuel injector pulse width. Fuel is delivered to the fuel injectors 66 by a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel rail (not shown). Additionally, the intake manifold 44 is shown in communication with an optional electronic throttle 62 that adjusts the position of a throttle plate 64 to control the flow of air from the air intake 42 to the intake manifold 44. In some examples, the throttle 62 and throttle plate 64 can be positioned between the intake valves 52 and the intake manifold 44 such that the throttle 62 is an intake runner throttle.

[0019] A non-distributor ignition system 88 provides an ignition spark to the combustion chambers 30 via a spark plug 92 in response to the controller 12. A first oxygen sensor 126, such as a universal exhaust gas oxygen (UEGO) sensor, is shown coupled to the exhaust manifold 48 upstream of the catalytic converter 70. Alternatively, the first oxygen sensor 126 can be replaced with a two-state exhaust gas oxygen sensor.

[0020] In one example, the catalytic converter 70 can include multiple catalytic bricks. In another example, multiple emission control devices each having multiple bricks can be used. In one example, the catalytic converter 70 can be a three-way catalytic converter.

[0021] The controller 12 is shown in Figure 1 a conventional microcomputer that includes a microprocessor unit 102, input / output ports 104, read only memory 106 (e.g., non-transitory memory), random access memory 108, keep-alive memory 110, and a conventional data bus. The controller 12 is shown receiving various signals from sensors coupled to the engine 10 in addition to those previously discussed, including engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling jacket 114, a position sensor 134 coupled to a driver demand pedal 130 to sense the distance a human 132 displaces, a position sensor 154 coupled to a brake caliper application pedal 150 to sense the distance a human 132 displaces, a measurement of engine manifold pressure (MAP) from a pressure sensor 122 coupled to the intake manifold 44, an engine position sensor 118 that senses the position of the crankshaft 40, a measurement of mass of air entering the engine from a sensor 120, and a measurement of throttle position from a sensor 58. Atmospheric pressure can also be sensed (sensor not shown) for processing by the controller 12. In the preferred aspects of the present description, the engine position sensor 118 produces a predetermined number of equally spaced pulses per revolution of the crankshaft, from which the engine rotational speed (RPM) can be determined.

[0022] In some examples, the engine can be coupled to an electric motor / battery system in a hybrid vehicle. Further, in some examples, other engine configurations can be employed, such as a diesel engine with multiple fuel injectors. Further, the controller 12 can receive inputs and communicate conditions such as component degradation to a light, or alternatively to a human / machine interface 171.

[0023] During operation, each cylinder within the engine 10 typically undergoes a four stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, generally the exhaust valve 54 is closed and the intake valve 52 is open. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves to the bottom of the cylinder to increase the volume within the combustion chamber 30. The position of the piston 36 near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its maximum volume) is commonly referred to by those skilled in the art as the bottom dead center (BDC). During the compression stroke, both the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the combustion chamber 30. The point at which the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 is at its minimum volume) is commonly referred to by those skilled in the art as the top dead center (TDC). During a process referred to hereafter as injection, fuel is introduced into the combustion chamber. During a process referred to hereafter as ignition, the injected fuel is ignited by a known ignition device, such as the spark plug 92, resulting in combustion. During the expansion stroke, the expanding gases push the piston 36 back to the BDC. The crankshaft 40 converts the piston movement into rotational torque of the rotational 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 the TDC. It should be noted that the above is shown merely by way of example, and the intake and exhaust valve opening and / or closing timing can vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0024] Reference is now made to Figure 2 , which shows a plan view 200 of the engine 10. The engine 10 is the same engine as shown in Figure 1 , but in Figure 2In this example, all of the engine cylinders are shown. In this example, the engine has cylinders numbered 1 through 8. Air is supplied to the cylinders via intake manifold 44. A first cylinder group includes cylinders 1 through 4, and a second cylinder group includes cylinders 5 through 8. Cylinders 1 through 4 are shown in fluid communication with exhaust manifold 48, and cylinders 5 through 8 are shown in fluid communication with exhaust manifold 220. Exhaust system 275 includes exhaust manifold 220, and catalyst 270 processes gases from cylinders 5-8. However, in other examples, a separate catalyst can be provided to process gases from cylinder pair [5, 6], and another separate catalyst can be provided to process gases from cylinder pair [7, 8]. Exhaust system 276 includes exhaust manifold 48, and catalytic converter 70 processes gases from cylinders 1-4. However, in other examples, a separate catalyst can be provided to process gases from cylinder pair [1, 3], and another separate catalyst can be provided to process gases from cylinder pair [2, 4]. Each of cylinders 1 through 8 includes a fuel injector, a spark plug, and an intake / exhaust valve, as shown in Figure 1

[0025] First oxygen sensor 126 is shown configured to sense exhaust from cylinders numbered 1 and 3. Second oxygen sensor 204 is shown configured to sense exhaust from cylinders 2 and 4. Third oxygen sensor 206 is shown configured to sense exhaust from cylinders numbered 5 and 6. Fourth oxygen sensor 208 is shown configured to sense exhaust from cylinders 7 and 8. From the flow of exhaust from the cylinders as indicated by arrows 230 and 240, no cylinders are downstream of any of the exhaust sensors.

[0026] The output of first oxygen sensor 126 can be applied as an air-to-fuel or equivalence ratio (e.g., λ = air-to-fuel ratio / stoichiometric air-to-fuel ratio) feedback for controlling fuel supplied to cylinders numbered 1 and 3. The output of third oxygen sensor 204 can be applied as air-to-fuel or equivalence ratio feedback for controlling fuel supplied to cylinders numbered 2 and 4. The output of third oxygen sensor 206 can be applied as air-to-fuel or equivalence ratio feedback for controlling fuel supplied to cylinders numbered 5 and 6. The output of fourth oxygen sensor 208 can be applied as air-to-fuel or equivalence ratio feedback for controlling fuel supplied to cylinders numbered 7 and 8.

[0027] Figure 2 ​Four decoupled lambda ratio controllers, or alternatively, fuel controllers, for an eight cylinder engine with four upstream oxygen sensors are also shown. A first decoupled lambda ratio controller is indicated as controller CI 250. Controller CI 250, controller C2 252, controller C3 254, and controller C4 256 can be proportional / integral controllers, proportional / integral / derivative controllers, Smith predictors, linear controllers, or can also include non-linear controllers with adaptive learning. These controllers, as well as difference or summation points (e.g., 260-266) can be incorporated as part of a method as executable instructions stored in a non-transitory memory of the controller.

[0028] Controller CI controls fueling to the first pair of cylinders [1, 3] to produce a fuel mass modification value (mi) based on or in response to a difference between a lambda (l) derived from the first oxygen sensor output of the first pair of cylinders and a target Controller C2 controls fueling to the second pair of cylinders [2, 4] to produce a fuel mass modification value (m2) based on or in response to a difference between a lambda (l) derived from the second oxygen sensor output of the second pair of cylinders and a target Controller C3 controls fueling to the third pair of cylinders [5, 6] to produce a fuel mass modification value (m3) based on or in response to a difference between a lambda (l) derived from the third oxygen sensor output of the third pair of cylinders and a target Controller C4 controls fueling to the fourth pair of cylinders [7, 8] to produce a fuel mass modification value (m4) based on or in response to a difference between a lambda (l) derived from the fourth oxygen sensor output of the fourth pair of cylinders and a target Controller C4 controls fueling to the fourth pair of cylinders [7, 8] to produce a fuel mass modification value (m4) based on or in response to a difference between a lambda (l) derived from the fourth oxygen sensor output of the fourth pair of cylinders and a target

[0029] The four controllers are decoupled in that each controller outputs a fuel mass correction for a unique pair of cylinders that is based on the output of an oxygen sensor that senses exhaust from the unique pair of cylinders. Each of the controllers does not receive feedback from other upstream oxygen sensors that are not associated with the cylinders for which the controller adjusts fuel mass. For example, controller CI adjusts fuel mass mi to adjust the amount of fuel supplied to cylinders 1 and 3. Controller CI does not receive feedback from oxygen sensors 204, 206, and 208, and controller CI does not adjust fuel supplied to cylinders 2, 4, 5, 6, 7, and 8. Upstream is based on the direction of exhaust flow, and an upstream oxygen sensor is an oxygen sensor that is upstream of an exhaust system catalyst, not downstream of an exhaust system catalyst.

[0030] Turning now to Figure 3 , which shows coupled lambda ratio controllers, or alternatively, fuel controllers, for an eight cylinder engine with four upstream oxygen sensors. A first coupled lambda ratio controller is indicated as controller 352. Controller 352, controller C Δ12 356, controller 361 and controller C Δ34 365 can be a proportional / integral controller, a proportional / integral / derivative controller, a Smith predictor, a linear controller, or a nonlinear controller that can also include adaptive learning. These controllers, as well as the difference or summing point (e.g., 351), the bisection (e.g., 366), and the averaging function (e.g., 350) can be incorporated as part of a method as executable instructions stored in a non-transitory memory of the controller.

[0031] controller 352 controls the average fuel supply of the first pair of cylinders [1, 3] and the second pair of cylinders [2, 4] as a function of the average of the lambda values derived from the outputs of the two oxygen sensors determined at block 350 (e.g., where where λ1is the lambda value derived from the output of the first oxygen sensor 126, and where λ2is the lambda value derived from the output of the second oxygen sensor 204) and the average of the oxygen sensor outputs of the first pair of cylinders and the second pair of cylinders as determined at difference or summing point 351. to a target average .

[0032] controller C Δ12 356 controls the delta or difference fuel supply of the first pair of cylinders [1, 3] and the second pair of cylinders [2, 4] as a function of the difference between the delta lambda (δ) of the first pair of cylinders and the second pair of cylinders as determined at difference or summing point 355 (e.g., where the output of summing point 355 is ) and a target difference between the delta lambda (δ) of the first pair of cylinders and the second pair of cylinders as determined at difference or summing point 355. Δ12 The output of controller C 1 / 2 at block 357. The output of block 357 is added to the output of block 352 (the output of controller C ) at summing point 353 to generate a fuel mass modification (m1) value for the first pair of cylinders. The output of block 352 (the output of controller C ) is subtracted from the output of block 357 at summing point 358 to generate a fuel mass modification (m2) value for the second pair of cylinders.

[0033] controller 361 controls the average fuel supply of the first pair of cylinders [1, 3] and the second pair of cylinders [2, 4] as a function of the average of the lambda values derived from the outputs of the two oxygen sensors determined at block 359 (e.g., where where λ3 is the lambda value derived from the output of the third oxygen sensor 206, and where λ4 is the lambda value derived from the output of the fourth oxygen sensor 208) and the difference between the average of the third pair of cylinders and the fourth pair of cylinders as determined at difference point or summing point 360 and the target average control the average fuel supply to the third pair of cylinders [5, 6] and the fourth pair of cylinders [7, 8].

[0034] Controller C Δ34 365 the difference between the lambda values derived from the two oxygen sensors as determined at summing point 363 (e.g., where the output of summing point 363 is δ = λ3 - λ4) and the difference between the delta lambda (δ) of the third pair of cylinders and the fourth pair of cylinders of the third pair of cylinders and the fourth pair of cylinders as determined at difference point or summing point 364 and the target difference ) control the delta or difference fuel supply to the third pair of cylinders [5, 6] and the fourth pair of cylinders [7, 8]. At block 366, the output of controller C Δ34 is multiplied by 1 / 2. The output of block 366 is added to the output of block 361 (the output of controller C at summing point 362 to generate the fuel mass modification (m3) value for the third pair of cylinders. The output of block 366 is subtracted from the output of block 361 (the output of controller C at summing point 367 to generate the fuel mass modification (m4) value for the fourth pair of cylinders.

[0035] Thus, Figure 3 the controller of controller C controls the fuel delivered to the cylinders to an average lambda value, and it also controls the fuel to reduce the difference in lambda values between the cylinder groups. In this example, the left cylinder group and the right cylinder group can be independently controlled.

[0036] Although the system is described in terms of a V8 engine, Figure 2 and Figure 3 it will be appreciated that the method described herein can be applied to a four cylinder engine, where two oxygen sensors are placed in the exhaust system upstream of the catalyst. The four cylinder engine can utilize a coupled controller and a decoupled controller as shown herein.

[0037] Figures 1 to 3A system of the present disclosure provides a fuel control system, the fuel control system comprising: a first bank of cylinders coupled to an exhaust system, the exhaust system comprising a first oxygen sensor upstream of a first catalyst and a second oxygen sensor upstream of the first catalyst; a second bank of cylinders coupled to the exhaust system, the exhaust system comprising a third oxygen sensor upstream of a second catalyst and a fourth oxygen sensor upstream of the second catalyst; and a controller comprising executable instructions for a first fuel controller, a second fuel controller, a third fuel controller, and a fourth fuel controller stored in a non-transitory memory. In a first example, the fuel control system comprises: wherein the first fuel controller causes an adjustment to a first fuel mass, wherein the second fuel controller causes an adjustment to a second fuel mass, wherein the third fuel controller causes an adjustment to a third fuel mass, and wherein the fourth fuel controller causes an adjustment to a fourth fuel mass. In a second example, which can include the first example, the fuel control system comprises: wherein the first fuel mass is supplied to a first pair of cylinders, wherein the second fuel mass is supplied to a second pair of cylinders, wherein the third fuel mass is supplied to a third pair of cylinders, and wherein the fourth fuel mass is supplied to a fourth pair of cylinders. In a third example, which can include one or both of the first example and the second example, the fuel control system comprises: wherein the first fuel controller adjusts the first fuel mass in response to a first difference between a first target lambda value and a first lambda value determined via the first oxygen sensor, wherein the second fuel controller adjusts the second fuel mass in response to a second difference between a second target lambda value and a second lambda value determined via the second oxygen sensor, wherein the third fuel controller adjusts the third fuel mass in response to a third difference between a third target lambda value and a third lambda value determined via the third oxygen sensor, wherein the fourth fuel controller adjusts the fourth fuel mass in response to a fourth difference between a fourth target lambda value and a fourth lambda value determined via the fourth oxygen sensor. In a fourth example, which can include one or more of the first example through the third example, the fuel control system comprises: wherein the first fuel controller adjusts a first fuel mass in response to a first average lambda determined via the first oxygen sensor and the second oxygen sensor, wherein the second fuel controller adjusts a second fuel mass in response to a first difference between a lambda determined via the first oxygen sensor and a lambda determined via the second oxygen sensor, wherein the third fuel controller adjusts a third fuel mass in response to a second average lambda determined via the third oxygen sensor and the fourth oxygen sensor, wherein the fourth fuel controller adjusts a fourth fuel mass in response to a second difference between a lambda determined via the third oxygen sensor and a lambda determined via the fourth oxygen sensor.In a fifth example, which can include one or more of the first example through the fourth example, the fuel control system includes: where the first fuel mass is supplied to a first pair of cylinders and a second pair of cylinders, where the second fuel mass adds fuel to the first pair of cylinders and subtracts fuel from the second pair of cylinders, where the third fuel mass is supplied to a third pair of cylinders and a fourth pair of cylinders, and where the fourth fuel mass adds fuel to the third pair of cylinders and subtracts fuel from the fourth pair of cylinders. In a sixth example, which can include one or more of the first example through the fifth example, the fuel control system includes: where each of the first oxygen sensor, the second oxygen sensor, the third oxygen sensor, and the fourth oxygen sensor is positioned at an exhaust convergence location of two engine cylinders.

[0038] Moving to Figure 4 which shows Figure 2 a plot 400 of a gain map for the decoupled controllers C1 and C2. Gain can describe a proportional relationship between an input or an integral of an input to a controller and an output of the controller. A larger gain can tend to cause the controller to drive a facility being controlled to its target value more quickly than a smaller gain. However, a larger gain can cause instability (e.g., an engine fuel supply can oscillate around a target value rather than converging to the target value).

[0039] The plot 400 includes a vertical axis representing gain values for controller C2, and the gain values for controller C2 increase in the direction of the vertical axis. The plot 400 also includes a horizontal axis representing gain values for controller C1, and the controller C1 gain values increase from the left side of the plot to the right side of the plot.

[0040] A dashed background region 402 represents a region of gains for controllers C1 and C2 that result in stable lambda control of an engine. A diagonal background region 404 represents a region of gains for controllers C1 and C2 that result in unstable operation of a facility. A G* gain value represents a threshold gain value for controllers C1 and C2 that should not be exceeded for stable operation of a facility. The G* gain value can be based on an oxygen sensor that exhibits a delayed response.

[0041] Referring now to Figure 5 which shows Figure 3 a plot 500 of a gain map for the coupled controllers C1 and C2. The plot 500 includes a vertical axis representing gain values for controller C1, and the gain values for controller C1 increase in the direction of the vertical axis. The plot 500 also includes a horizontal axis representing gain values for controller C2, and the gain values for controller C2 increase in the direction of the horizontal axis. Δ12 Δ12 The plot 500 includes a vertical axis representing gain values for controller C1, and the gain values for controller C1 increase in the direction of the vertical axis. The plot 500 also includes a horizontal axis representing gain values for controller C2, and the gain values for controller C2 increase in the direction of the horizontal axis. Δ12 Δ12 Δ12 The plot 500 includes a vertical axis representing gain values for controller C1, and the gain values for controller C1 increase in the direction of the vertical axis. The plot 500 also includes a horizontal axis representing gain values for controller C2, and the gain values for controller C2 increase in the direction of the horizontal axis.​ The gain value increases from the left side of the curve to the right side of the curve.

[0042] The background area with horizontal line 502 represents the controller. and C Δ12 The gain results in a region where the facility operates stably. The slashed background area 504 indicates the controller. and C Δ12 The gain leads to regions of unstable facility operation. For comparison purposes, the G* gain values ​​of controller C1 and controller C2 are also included. Note that the intersection of the gain G* of controller C2 and the gain G* of controller C1 intersects the gain boundary of the coupled controller (e.g., line 550). Therefore, it can be observed that the coupled controller vertically and horizontally expands the stable operating region without shrinking the stable region along the diagonal direction (y = x) of the graph.

[0043] Now for reference Figure 6 The flowchart illustrates a method for selecting and activating one of two fuel control systems based on vehicle operating conditions. Figure 6 The method can be incorporated via executable instructions stored in the controller's non-transitory memory. Figures 1 to 3 The system. Figure 6 This method can be applied to engine systems where cylinder pairs share the same catalyst for processing the gases from the cylinder pair.

[0044] At 602, method 600 determines the operating condition. The operating condition may include, but is not limited to, engine speed, engine load, ambient air temperature, catalytic converter temperature, engine temperature, and driver load requirements. Method 600 may determine the operating condition via the sensors described herein. Method 600 proceeds to 604.

[0045] At 604, method 600 determines whether the engine is operating under cold start conditions (e.g., engine temperature below a threshold, catalytic converter temperature below a threshold, time since the last engine start less than a threshold time, etc.). If method 600 determines that the engine is starting or operating under cold start conditions, the answer is yes, and method 600 proceeds to 606. Otherwise, the answer is no, and method 600 proceeds to 608.

[0046] At 606, method 600 activates the decoupling controller (e.g., as...) Figure 2 Method 600 activates the decoupled fuel control using C1, C2, C3, and C4 (as shown). If the coupled controller is activated, method 600 also deactivates the coupled controller. The decoupled controller can be activated such that the λ value for each cylinder pair converges to one faster than when the coupled controller is applied. This can reduce NOx and HC emissions. Method 600 then proceeds to exit.

[0047] At 608, the method 600 activates coupled fuel control via activation of a coupled controller (e.g., the coupled controller 208) and deactivation of the decoupled controller (e.g., the decoupled controller 210). The coupled controller is configured to operate in a manner that is different than the decoupled controller. For example, the coupled controller can be configured to operate in a manner that is different than the decoupled controller in terms of the manner in which the coupled controller controls the fueling of the engine and / or the manner in which the coupled controller controls the air intake of the engine. Figure 3 of the C Δ12 , and the C Δ34 ) to activate coupled fuel control. Activating the coupled controller allows the cylinder lambda values to converge to the average value faster than when the decoupled controller is activated. Thus, once the catalyst reaches its light-off temperature, the coupled controller can operate to provide lower exhaust tailpipe emissions than when the decoupled controller is activated. If the decoupled controller is activated, the method 600 can also deactivate the decoupled controller. The method 600 proceeds to exit.

[0048] Thus, the method 600 can select and activate the coupled controller or the decoupled controller depending on whether the engine is cold-starting and whether the catalyst temperature is below the light-off temperature. Selecting the active controller in this manner can reduce emissions and take advantage of the benefits of both types of controllers.

[0049] Thus, the method 600 and the Figure 2 and Figure 3At least portions of the illustrated system can provide a method for operating an engine, the method comprising supplying fuel to the engine via first, second, third, and fourth fuel controllers in response to a first lambda value determined via a first oxygen sensor, a second lambda value determined via a second oxygen sensor, a third lambda value determined via a third oxygen sensor, and a fourth lambda value determined via a fourth oxygen sensor. In a first example, the method further comprises adjusting a first fuel mass supplied to the engine via the first fuel controller in response to a first difference between a first target lambda and the first lambda value, adjusting a second fuel mass supplied to the engine via the second fuel controller in response to a second difference between a second target lambda and the second lambda value, adjusting a third fuel mass supplied to the engine via the third fuel controller in response to a third difference between a third target lambda and the third lambda value, and adjusting a fourth fuel mass supplied to the engine via the fourth fuel controller in response to a fourth difference between a fourth target lambda and the fourth lambda value. In a second example, which can include the first example, the method further comprises averaging the first lambda value and the second lambda value to generate a first result, and inputting a first difference to the first fuel controller, the first difference being a difference between the first result and a first target average lambda value. In a third example, which can include one or both of the first example and the second example, the method further comprises generating a second difference between the first lambda value and the second lambda value, and inputting a third difference between the second difference and a first target difference lambda value to the second fuel controller. In a fourth example, which can include one or more of the first through third examples, the method further comprises averaging the third lambda value and the fourth lambda value to generate a second result, and inputting a fourth difference to the third fuel controller, the fourth difference being a difference between the second result and a second target average lambda value. In a fifth example, which can include one or more of the first through fourth examples, the method further comprises generating a fifth difference between the third lambda value and the fourth lambda value, and inputting a sixth difference between the fifth difference and a second target difference lambda value to the fourth fuel controller. In a sixth example, which can include one or more of the first through fifth examples, the method comprises wherein the first fuel controller and the second fuel controller adjust fuel supplied exclusively to cylinders in a first cylinder group, and wherein the third fuel controller and the fourth fuel controller adjust fuel supplied exclusively to cylinders in a second cylinder group.In a seventh example, which can include one or more of the first example through the sixth example, the method includes wherein the first fuel controller, the second fuel controller, the third fuel controller, and the fourth fuel controller are included as executable instructions stored in a memory of a controller.

[0050] Accordingly, the method 600 and Figure 2 and Figure 3 At least portions of the system shown can provide a method for operating an engine, the method including operating the engine with decoupled fuel controllers active and coupled fuel controllers inactive in a first mode, and operating the engine with decoupled fuel controllers inactive and coupled fuel controllers active in a second mode. In a first example, the method includes activating the first mode in response to a catalyst temperature being below a threshold temperature. In a second example, which can include the first example, the method includes activating the second mode in response to a catalyst temperature being above a threshold temperature. In a third example, which can include one or both of the first example and the second example, the method includes wherein each of the activated decoupled fuel controllers controls fuel exclusively supplied to a pair of cylinders of the engine. In a fourth example, which can include one or more of the first example through the third example, the method includes wherein each of the activated coupled fuel controllers controls fuel supplied to two pairs of cylinders of the engine.

[0051] It should be noted that the example control and estimation routines included herein can be used with a variety of engine and / or vehicle system configurations. Additionally, although the methods included herein relate to lambda control, the methods herein can be applied with other units. For example, the methods herein describe lambda control, but in other examples, the control and methods can be configured for air-fuel ratio control. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The particular routines described herein can represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and so on. As such, various acts, operations, and / or functions illustrated can be performed in the manner shown, in parallel, or in some cases omitted. Likewise, the sequence in which various acts, operations, and / or functions are described is not necessarily the sequence in which they are to be performed, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions can be repeated, regardless of whether they are illustrated as a single function, multiple functions, or skipped between subsequent iterations. Further, the illustrated acts, operations, and / or functions can be programmed into non-transitory memory of a computer readable storage medium graphically represented in an engine control system, where the described acts are implemented by executing instructions in conjunction with an electronic controller in a system including various engine hardware components.

[0052] This specification concludes with claims particularly pointing out the scope of the present disclosure. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is appreciated. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations can benefit from the present specification.

[0053] According to the present disclosure, a fuel control system is provided having a first cylinder bank coupled to an exhaust system including a first oxygen sensor upstream of a first catalyst and a second oxygen sensor upstream of the first catalyst, a second cylinder bank coupled to the exhaust system including a third oxygen sensor upstream of a second catalyst and a fourth oxygen sensor upstream of the second catalyst, and a controller including executable instructions for a first fuel controller, a second fuel controller, a third fuel controller, and a fourth fuel controller stored in non-transitory memory.

[0054] According to embodiments, the first fuel controller causes an adjustment to a first fuel mass, wherein the second fuel controller causes an adjustment to a second fuel mass, wherein the third fuel controller causes an adjustment to a third fuel mass, and wherein the fourth fuel controller causes an adjustment to a fourth fuel mass.

[0055] According to an embodiment, the first fuel mass is supplied to a first pair of cylinders, wherein the second fuel mass is supplied to a second pair of cylinders, wherein the third fuel mass is supplied to a third pair of cylinders, and wherein the fourth fuel mass is supplied to a fourth pair of cylinders.

[0056] According to an embodiment, the first fuel controller adjusts the first fuel mass in response to a first difference between a first target lambda value and a first lambda value determined via the first oxygen sensor, wherein the second fuel controller adjusts the second fuel mass in response to a second difference between a second target lambda value and a second lambda value determined via the second oxygen sensor, wherein the third fuel controller adjusts the third fuel mass in response to a third difference between a third target lambda value and a third lambda value determined via the third oxygen sensor, wherein the fourth fuel controller adjusts the fourth fuel mass in response to a fourth difference between a fourth target lambda value and a fourth lambda value determined via the fourth oxygen sensor.

[0057] According to an embodiment, the first fuel controller adjusts the first fuel mass in response to a first average lambda determined via the first oxygen sensor and the second oxygen sensor, wherein the second fuel controller adjusts the second fuel mass in response to a first difference between a lambda determined via the first oxygen sensor and a lambda determined via the second oxygen sensor, wherein the third fuel controller adjusts the third fuel mass in response to a second average lambda determined via the third oxygen sensor and the fourth oxygen sensor, wherein the fourth fuel controller adjusts the fourth fuel mass in response to a second difference between a lambda determined via the third oxygen sensor and a lambda determined via the fourth oxygen sensor.

[0058] According to an embodiment, the first fuel mass is supplied to a first pair of cylinders and a second pair of cylinders, wherein the second fuel mass is added to the first pair of cylinders and subtracted from the second pair of cylinders, wherein the third fuel mass is supplied to a third pair of cylinders and a fourth pair of cylinders, and wherein the fourth fuel mass is added to the third pair of cylinders and subtracted from the fourth pair of cylinders.

[0059] According to an embodiment, each of the first oxygen sensor, the second oxygen sensor, the third oxygen sensor, and the fourth oxygen sensor is positioned at an exhaust convergence location of two engine cylinders.

[0060] According to the present invention, a method for operating an engine comprises supplying fuel to the engine via a first fuel controller, a second fuel controller, a third fuel controller, and a fourth fuel controller in response to a first lambda value determined via a first oxygen sensor, a second lambda value determined via a second oxygen sensor, a third lambda value determined via a third oxygen sensor, and a fourth lambda value determined via a fourth oxygen sensor.

[0061] In one aspect of the application, the method includes adjusting a first fuel mass supplied to the engine via the first fuel controller in response to a first difference between a first target lambda and the first lambda value; adjusting a second fuel mass supplied to the engine via the second fuel controller in response to a second difference between a second target lambda and the second lambda value; adjusting a third fuel mass supplied to the engine via the third fuel controller in response to a third difference between a third target lambda and the third lambda value; and adjusting a fourth fuel mass supplied to the engine via the fourth fuel controller in response to a fourth difference between a fourth target lambda and the fourth lambda value.

[0062] In one aspect of the application, the method includes averaging the first lambda value and the second lambda value to generate a first result; and inputting a first difference to the first fuel controller, the first difference being a difference between the first result and a first target average lambda value.

[0063] In one aspect of the application, the method includes generating a second difference between the first lambda value and the second lambda value; and inputting a third difference between the second difference and a first target difference lambda value to the second fuel controller.

[0064] In one aspect of the application, the method includes averaging the third lambda value and the fourth lambda value to generate a second result; and inputting a fourth difference to the third fuel controller, the fourth difference being a difference between the second result and a second target average lambda value.

[0065] In one aspect of the application, the method includes generating a fifth difference between the third lambda value and the fourth lambda value; and inputting a sixth difference between the fifth difference and a second target difference lambda value to the fourth fuel controller.

[0066] In one aspect of the application, the first fuel controller and the second fuel controller adjust fuel supplied exclusively to cylinders in a first cylinder group, and wherein the third fuel controller and the fourth fuel controller adjust fuel supplied exclusively to cylinders in a second cylinder group.

[0067] In one aspect of the application, the first fuel controller, the second fuel controller, the third fuel controller, and the fourth fuel controller are included as executable instructions stored in a memory of a controller.

[0068] According to the invention, a method for operating an engine includes operating the engine in a first mode with a decoupled fuel controller active and a coupled fuel controller inactive, and operating the engine in a second mode with the decoupled fuel controller inactive and the coupled fuel controller active.

[0069] In one aspect of the invention, the first mode is activated in response to a catalyst temperature being below a threshold temperature.

[0070] In one aspect of the invention, the second mode is activated in response to a catalyst temperature being above a threshold temperature.

[0071] In one aspect of the invention, each of the activated decoupled fuel controllers controls fuel exclusively to one pair of cylinders of the engine.

[0072] In one aspect of the invention, each of the activated coupled fuel controllers controls fuel to two pairs of cylinders of the engine.

Claims

1. A fuel control system, comprising: A first cylinder bank is connected to an exhaust system, the exhaust system including a first oxygen sensor upstream of a first catalyst and a second oxygen sensor upstream of the first catalyst; A second cylinder bank is connected to the exhaust system, the exhaust system including a third oxygen sensor upstream of the second catalytic converter and a fourth oxygen sensor upstream of the second catalytic converter; and The controller includes executable instructions for a first fuel controller, a second fuel controller, a third fuel controller, and a fourth fuel controller stored in a non-transitory memory.

2. The fuel control system according to claim 1, wherein the first fuel controller causes an adjustment to a first fuel quality, wherein the second fuel controller causes an adjustment to a second fuel quality, wherein the third fuel controller causes an adjustment to a third fuel quality, and wherein the fourth fuel controller causes an adjustment to a fourth fuel quality.

3. The fuel control system according to claim 2, wherein the first fuel mass is supplied to the first pair of cylinders, wherein the second fuel mass is supplied to the second pair of cylinders, wherein the third fuel mass is supplied to the third pair of cylinders, and wherein the fourth fuel mass is supplied to the fourth pair of cylinders.

4. The fuel control system of claim 2, wherein the first fuel controller adjusts the first fuel mass in response to a first difference between a first target λ value and a first λ value determined via the first oxygen sensor, wherein the second fuel controller adjusts the second fuel mass in response to a second difference between a second target λ value and a second λ value determined via the second oxygen sensor, wherein the third fuel controller adjusts the third fuel mass in response to a third difference between a third target λ value and a third λ value determined via the third oxygen sensor, and wherein the fourth fuel controller adjusts the fourth fuel mass in response to a fourth difference between a fourth target λ value and a fourth λ value determined via the fourth oxygen sensor.

5. The fuel control system of claim 1, wherein the first fuel controller adjusts the first fuel mass in response to a first average λ determined via the first oxygen sensor and the second oxygen sensor, wherein the second fuel controller adjusts the second fuel mass in response to a first difference between λ determined via the first oxygen sensor and λ determined via the second oxygen sensor, wherein the third fuel controller adjusts the third fuel mass in response to a second average λ determined via the third oxygen sensor and the fourth oxygen sensor, wherein the fourth fuel controller adjusts the fourth fuel mass in response to a second difference between λ determined via the third oxygen sensor and λ determined via the fourth oxygen sensor.

6. The fuel control system of claim 5, wherein the first fuel mass is supplied to a first pair of cylinders and a second pair of cylinders, wherein the second fuel mass is added to the first pair of cylinders and subtracted from the second pair of cylinders, wherein the third fuel mass is supplied to a third pair of cylinders and a fourth pair of cylinders, and wherein the fourth fuel mass is added to the third pair of cylinders and subtracted from the fourth pair of cylinders.

7. The fuel control system according to claim 1, wherein each of the first oxygen sensor, the second oxygen sensor, the third oxygen sensor and the fourth oxygen sensor is located at the exhaust junction of two engine cylinders.

8. A method for operating an engine, comprising: Fuel is supplied to the engine via a first fuel controller, a second fuel controller, a third fuel controller, and a fourth fuel controller in response to a first λ value determined by a first oxygen sensor, a second λ value determined by a second oxygen sensor, a third λ value determined by a third oxygen sensor, and a fourth λ value determined by a fourth oxygen sensor.

9. The method of claim 8, further comprising: The first fuel mass supplied to the engine via the first fuel controller is adjusted in response to a first difference between a first target λ and the first λ value; The second fuel mass supplied to the engine via the second fuel controller is adjusted in response to a second difference between a second target λ and a second λ value. The third fuel mass supplied to the engine via the third fuel controller is adjusted in response to a third difference between the third target λ and the third λ value. And in response to a fourth difference between a fourth target λ and the fourth λ value, adjust the fourth fuel mass supplied to the engine via the fourth fuel controller.

10. The method of claim 8, further comprising: The first λ value and the second λ value are averaged to generate a first result; And inputting a first difference to the first fuel controller, the first difference being the difference between the first result and the first target average value λ.

11. The method of claim 10, further comprising: Generate a second difference between the first λ value and the second λ value; And input a third difference between the second difference and the first target difference λ value into the second fuel controller.

12. The method of claim 11, further comprising: The second result is generated by averaging the third λ value and the fourth λ value. And input a fourth difference to the third fuel controller, the fourth difference being the difference between the second result and the second target average value λ.

13. The method of claim 12, further comprising: Generate a fifth difference between the third λ value and the fourth λ value; And input the sixth difference between the fifth difference and the second target difference λ value into the fourth fuel controller.

14. The method of claim 8, wherein the first fuel controller and the second fuel controller adjust the fuel supplied specifically to the cylinders in the first cylinder bank, and wherein the third fuel controller and the fourth fuel controller adjust the fuel supplied specifically to the cylinders in the second cylinder bank.

15. The method of claim 8, wherein the first fuel controller, the second fuel controller, the third fuel controller, and the fourth fuel controller are included as executable instructions stored in the memory of the controller.

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