Method and system for operating an engine

Abstract

The present disclosure provides a method and system for operating an engine. The system and method for operating an engine including a compression ratio connecting rod for adjusting the engine's compression ratio are described. The system and method provide different ways to diagnose the presence or absence of engine misfire in response to engine operating regions that may be more or less susceptible to torsional engine crankshaft vibration. In one example, engine misfire may be determined in response to a force applied to the engine's compression ratio changing connecting rod.

Description

Technical Field

[0001] The present disclosure relates to methods and systems for operating an internal combustion engine. The methods and systems may be particularly useful for determining the presence or absence of engine misfire in an engine having a compression ratio adjustment linkage. Background Art

[0002] Due to various operating conditions, an engine may misfire from time to time. For example, the engine may misfire in response to a lean engine air-fuel ratio. Additionally, the engine may misfire in response to an improperly timed ignition spark. One method of determining whether an engine may have misfired may be by monitoring the engine acceleration during an engine cycle. If the engine acceleration during an engine cycle is less than a threshold, then it may be determined that the engine has misfired. However, there may be some engine operating conditions in which it may be difficult to assess whether the engine has misfired because the engine may exhibit torsional vibrations of the engine crankshaft. If engine misfire is not determined during these engine operating conditions, the engine torque output may decrease and undesirable engine emissions may increase. Therefore, it is desirable to provide a way to diagnose the presence or absence of engine misfire over a wider range of engine operating conditions. Summary of the Invention

[0003] The inventors herein have recognized the foregoing problems and have developed an engine operating method comprising adjusting, via a controller, an engine actuator in response to engine misfire indicated by engine crankshaft position when the engine is operated in a first operating region, and adjusting, via the controller, an engine actuator in response to engine misfire indicated by output of a sensor coupled to an engine compression ratio adjustment connecting rod when the engine is operated in a second operating region.

[0004] By adjusting engine actuators in response to engine misfire indicated by engine crankshaft position and the output of a sensor coupled to an engine compression ratio adjustment connecting rod, the presence and absence of engine misfire can be determined over a wide range of engine operating conditions (e.g., engine speed and load ranges). For example, when engine crankshaft torsional vibration is low, engine misfire can be determined by converting engine position to engine speed and differentiating the engine speed to determine engine acceleration during engine operating conditions. Furthermore, when crankshaft torsional vibration is high, engine misfire can be determined by the output of a sensor coupled to an engine compression ratio adjustment connecting rod during engine operating conditions. During some engine operating conditions, the engine compression ratio adjustment connecting rod sensor output may provide a better signal-to-noise ratio than the engine crankshaft position sensor, while during other engine operating conditions, the engine crankshaft position sensor may provide a better signal-to-noise ratio than the engine compression ratio adjustment connecting rod sensor output.

[0005] The present disclosure may provide several advantages. Specifically, the method may provide improved engine misfire detection and mitigation. Furthermore, the method may suspend or alter the method used to determine engine misfire in situations where one engine misfire detection method may be less reliable. Furthermore, if an engine misfire occurs, the method may improve engine emissions and torque production.

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

[0007] It should be understood that the above Summary is provided to introduce in simplified form a series of concepts that are further described in the Detailed Description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the claims that follow the Detailed Description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The advantages described herein will be more fully understood by reading the examples of embodiments herein referred to as detailed description either alone or with reference to the accompanying drawings, in which:

[0009] Figure 1 It is a schematic diagram of the engine;

[0010] Figure 2A and Figure 2B An engine compression ratio changing connecting rod is shown in two positions;

[0011] Figure 3 It shows that according to Figure 4 a diagram of an exemplary engine operating sequence for a method of

[0012] Figure 4 is a method for operating the engine; and

[0013] Figure 5 A graph illustrating an exemplary engine operating range in which engine misfire may be detected. DETAILED DESCRIPTION

[0014] The present description relates to operating a variable compression ratio engine and determining the presence or absence of engine misfire (e.g., no combustion occurring in a cylinder, or wherein less than a threshold amount (15%) of the air-fuel mixture is burning in the cylinder during a cylinder cycle). The engine may be Figure 1 The engine may include one or more cylinder compression ratio changing connecting rods, such as Figure 2A and Figure 2B As shown. Figure 4 The method of operating the engine to provide Figure 3 The engine misfire detection method may be called in response to engine operating conditions, such as Figure 5 shown.

[0015] See also Figure 1 , including multiple cylinders ( Figure 1 Internal combustion engine 10 (one cylinder is shown) is controlled by electronic engine controller 12. Engine 10 includes cylinder head 35 and cylinder block 33, which includes combustion chamber 30 and cylinder walls 32. Piston 36 is positioned therein and reciprocates via rod 117 through connection to crankshaft 40. Flywheel 97 and ring gear 99 are coupled to crankshaft 40. Starter 96 (e.g., a low-voltage (operating at less than 30 volts)) motor includes pinion shaft 98 and pinion gear 95. Pinion shaft 98 can selectively advance pinion gear 95 to engage ring gear 99. Starter 96 can be mounted directly to the front or rear of the engine. In some examples, starter 96 can selectively supply torque to crankshaft 40 via a belt or chain. In one example, when starter 96 is not engaged to engine crankshaft 40, starter 96 is in a base state. Combustion chamber 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Each intake and exhaust valve may be operated by an intake cam 51 and an exhaust cam 53. The position of intake cam 51 may be determined by intake cam sensor 55. The position of exhaust cam 53 may be determined by exhaust cam sensor 57. Intake valve 52 may be selectively activated and deactivated by valve activation device 59. Exhaust valve 54 may be selectively activated and deactivated by valve activation device 58. Valve activation devices 58 and 59 may be electromechanical devices.

[0016] Fuel injector 66 is shown positioned to inject fuel directly into cylinder 30, which is known to those skilled in the art as direct injection. Fuel injector 66 delivers liquid fuel in proportion to the pulse width from controller 12. Fuel is delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail (not shown). In one example, a high-pressure, two-stage fuel system can be used to generate higher fuel pressures.

[0017] In addition, intake manifold 44 is shown in communication with turbocharger compressor 162 and engine air intake 42. In other examples, compressor 162 may be a supercharger compressor. Shaft 161 mechanically couples turbocharger turbine 164 to turbocharger compressor 162. Optional electronic throttle 62 adjusts the position of throttle plate 64 to control air flow from compressor 162 to intake manifold 44. The pressure in boost chamber 45 may be referred to as the throttle inlet pressure because the inlet of throttle 62 is located within boost chamber 45. The throttle outlet is located in intake manifold 44. In some examples, throttle 62 and throttle plate 64 may be positioned between intake valve 52 and intake manifold 44, such that throttle 62 is a gate throttle. Compressor recirculation valve 47 can be selectively adjusted to a plurality of positions between fully open and fully closed. Wastegate 163 may be adjusted by controller 12 to allow exhaust to selectively bypass turbine 164 to control the speed of compressor 162. Air filter 43 cleans air entering engine air intake 42.

[0018] Distributorless ignition system 88 provides an ignition spark to combustion chamber 30 via ignition coil 89 and spark plug 92 in response to spark timing signals from controller 12. Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled to exhaust manifold 48 upstream of catalytic converter 70. Alternatively, a two-state exhaust gas oxygen sensor may be used in place of UEGO sensor 126.

[0019] Engine torque can be adjusted by adjusting spark timing, the amount of fuel supplied through the fuel injectors, fuel timing, throttle plate position, intake and exhaust valve timing, boost pressure, spark energy, and the amount of air supplied to the engine. Thus, engine torque can be adjusted by adjusting the operation of actuators such as ignition coil 89, the position of throttle valve 62, the position of wastegate 163, the position of compressor recirculation valve 47, intake valve activation device 59, and exhaust valve activation device 58.

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

[0021] The controller 12 Figure 11 is a conventional microcomputer including a microprocessor unit 102, input / output ports 104, read-only memory 106 (eg, non-volatile memory), random access memory 108, keep alive memory 110, and a conventional data bus. Controller 12 is also shown receiving various signals from sensors coupled to engine 10 (in addition to those previously discussed), including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling jacket 114; position sensor 134 coupled to accelerator pedal 130 for sensing force applied by a human foot 132; position sensor 154 coupled to brake pedal 150 for sensing force applied by a human foot 132; measurement of engine manifold pressure (MAP) from pressure sensor 122 coupled to intake manifold 44; an engine position sensor from Hall effect sensor 118 sensing the position of crankshaft 40; measurement of air mass entering the engine from sensor 120; and measurement of throttle position from sensor 68. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, engine position sensor 118 generates a predetermined number of equally spaced pulses for each revolution of the crankshaft, from which engine speed (revolutions per minute, RPM) can be determined. Additionally, controller 12 can communicate with human / machine interface 91 to indicate the status of diagnostics and provide feedback to vehicle occupants.

[0022] During operation, each cylinder within 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, typically, exhaust valve 54 closes and intake valve 52 opens. Air is introduced into combustion chamber 30 via intake manifold 44, and piston 36 moves to the bottom of the cylinder so as to increase the volume within combustion chamber 30. The position at which 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 of skill in the art as bottom dead center (BDC).

[0023] During the compression stroke, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head so as to compress the air within combustion chamber 30. The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process herein referred to as injection, fuel is introduced into the combustion chamber. In a process herein referred to as ignition, the injected fuel is ignited by known ignition means, such as spark plug 92, resulting in combustion.

[0024] During the expansion stroke, the expanding gases push piston 36 back to bottom dead center (BDC). Crankshaft 40 converts the piston's motion into rotational torque of the rotating shaft. Finally, during the exhaust stroke, exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48, and the piston returns to top dead center (TDC). It should be noted that the above is shown only as an example, and the intake and exhaust valve opening and / or closing timing can be varied, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0025] Figure 2A and Figure 2B A cylinder compression ratio changing connecting rod for changing the compression ratio of the engine is shown. Figure 2A Compression ratio varying connecting rod 200 is shown in a first position, which increases the compression ratio of cylinder 30 . Figure 2B Compression ratio varying connecting rod 200 is shown in a second position that reduces the compression ratio of cylinder 30. Controller 12 may include non-transient executable instructions for operating the cylinder compression ratio varying connecting rod in the illustrated position, as well as other positions, to adjust the compression ratio of the engine.

[0026] Connecting rod 117 is shown mechanically coupled to upper tie rod 203 via connecting pin 202. Upper tie rod 203 is coupled to crank pin 204, which is part of crankshaft 40. Crank journal 218 is supported by engine block 33, and crank pin 204 is offset from crank journal 218. Upper tie rod 203 is mechanically coupled to lower tie rod 215 via connecting pin 206. Lower tie rod 215 is mechanically coupled to control tie rod 216 via connecting pin 208. Motor 212 is mechanically coupled to control tie rod 216 via connecting pin 209. Shaft 210 of motor 212 can be selectively rotated clockwise or counterclockwise to advance or retract control tie rod 216. Controller 12 can selectively supply current to motor 212, and the current can be monitored via current sensor 250c. The current supplied to motor 212 to maintain the position of control link 216 can indicate the force applied to rod 117 because rod 117 is mechanically coupled to control link 216. Therefore, motor 212 can be implemented as a force sensor coupled to control link 216. In some examples, strain gauge 250b can be mechanically coupled to lower control link 215 to determine the force applied to rod 117. Alternatively, strain gauge 250a can be mechanically coupled to control link 216 to determine the force applied to rod 117.

[0027] Figure 2A The control link 216 is shown in an extended position by the counterclockwise rotation of the motor shaft 210 which causes the upper link 203 to rotate, thereby changing the angle between the rod 117 and the upper link 203 . Figure 2B The control rod 216 is shown in a retracted state by the clockwise rotation of the motor shaft 210 which causes the upper rod 203 to rotate and change the angle between the rod 117 and the upper rod 203 . Figure 2A The compression ratio changing connecting rod 200 is shown in a high compression state (e.g., a compression ratio of 12:1), and Figure 2B The compression ratio changing connecting rod 200 is shown in a low compression state (eg, an 8:1 compression ratio).

[0028] therefore, Figures 1 to 2BA vehicle system is provided, comprising: an engine including a crankshaft position sensor, a compression ratio adjustment connecting rod, and a sensor coupled to the compression ratio adjustment connecting rod; an actuator coupled to the engine; and a controller including executable instructions stored in non-transitory memory for diagnosing engine misfire in response to crankshaft position when the engine is operating in a low torsional vibration engine operating range, and in response to force applied to the compression ratio adjustment connecting rod when the engine is operating in a high torsional vibration engine operating range. The system includes the following: wherein diagnosing engine misfire in response to force applied to the compression ratio adjustment connecting rod comprises determining misfire in response to a maximum force applied to the compression ratio adjustment connecting rod occurring within a predetermined crankshaft angle range of a top dead center compression stroke of a cylinder during a cylinder cycle. The system also includes diagnosing engine misfire not in response to force applied to the compression ratio adjustment connecting rod when the controller adjusts the compression ratio of the engine. The system also includes additional instructions for adjusting the actuator in response to diagnosing cylinder misfire in the engine (e.g., determining that an engine cylinder misfire exists). The system includes: wherein the actuator is an ignition coil. The system includes: wherein the actuator is a fuel injector.

[0029] See now Figure 3 , shows a diagram showing a predictive cylinder misfire detection sequence. Figure 1 and the system in Figure 2 Figure 4 Collaboration to provide Figure 3 sequence. Figure 3 The graphs are time aligned and occur simultaneously. The vertical lines at times t0 to t7 represent the times of interest in the sequence. The controller 12 may include non-transient executable instructions for Figure 3 The engine is operated under the conditions shown and discussed in the description of FIG.

[0030] Figure 3 The first graph is a graph of cylinder compression ratio versus time. The vertical axis represents cylinder compression ratio, and cylinder compression ratio increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Curve 302 represents cylinder compression ratio.

[0031] Figure 3The second graph is a graph of engine load versus time. The vertical axis represents engine load, and engine load increases in the direction of the vertical axis arrow. Trace 304 represents engine load. Engine load can be represented as a value ranging from 0 to 1, where 0 represents no engine load and 1 represents full engine load. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Horizontal line 322 represents a first, lower engine load. Horizontal line 320 represents a second, higher engine load threshold. When the engine load is greater than the level of horizontal line 322 or less than the level of horizontal line 320, engine misfire is determined by engine position and speed measurements. When the engine load is at a load between the engine loads represented by horizontal lines 320 and 322, engine misfire is determined by the force applied to the engine compression ratio changing connecting rod.

[0032] Figure 3 The third graph is a graph of a cylinder misfire detection method versus time. The vertical axis represents the cylinder misfire detection method, and when trace 306 is at a lower level near the horizontal axis, the cylinder misfire detection method is implemented using engine crankshaft acceleration. When trace 306 is at a higher level near the vertical axis arrow, the cylinder misfire detection method detects engine misfire by changing the connecting rod due to the engine compression ratio. Trace 306 represents the cylinder misfire detection method. The horizontal axis represents time, with time increasing from the left side of the graph to the right side.

[0033] Figure 3 The fourth graph is a graph of engine misfire indication versus time. The vertical axis represents engine misfire indication, and an engine misfire is indicated when trace 308 is at a higher level near the vertical axis arrow. When trace 308 is at a lower level near the horizontal axis, an engine misfire is not indicated. Trace 308 indicates an engine misfire. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. If a misfire is indicated, certain mitigating actions can be taken. For example, the engine air-fuel ratio can be increased, the spark timing can be adjusted (e.g., retarded), and the amount of spark energy can be increased as indicated in the fifth graph.

[0034] Figure 3 The fifth graph is a graph of spark energy supplied to an engine cylinder versus time. The vertical axis represents spark energy, and spark energy increases in the direction of the vertical axis arrow. Spark energy is zero at the horizontal axis. Trace 310 represents the amount of spark energy supplied to the engine cylinder. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0035] At time t0, the engine is operating at a high load (e.g., burning air and fuel) and the engine compression ratio is at a low level. Engine misfire detection is based on crankshaft acceleration and no engine misfire is indicated. In other words, the presence or absence of engine misfire is determined based on engine acceleration. The spark energy supplied to the engine cylinders is at a low level. At time t1, engine misfire is indicated by engine acceleration. In response to the engine acceleration being less than a threshold amount or level, engine misfire may be indicated. In response to the indication of engine misfire, the amount of spark energy (e.g., joules) supplied to the engine cylinders is increased. The engine spark energy may be increased to all engine cylinders, or the engine spark energy may be increased only to one or more engine cylinders in which misfire is detected. The engine load is at a high level, above threshold 320. Therefore, engine misfire detection is performed based on engine crankshaft acceleration.

[0036] At time t2, the engine load decreases to less than threshold 320, and the cylinder misfire detection method switches from crankshaft acceleration-based engine misfire detection to engine misfire detection based on engine compression ratio change connecting rods. In response to a decrease in driver demand torque (e.g., a partial release of the accelerator pedal), the engine load can be reduced. The amount of spark energy supplied to the engine cylinders remains at its previous level, and no engine misfire is indicated. Between time t2 and time t3, the engine load further decreases, and in response to the change in engine operating conditions, the amount of spark energy supplied to the engine cylinders decreases. No engine misfire is indicated, and the engine compression ratio remains at a lower level.

[0037] At time t3, engine misfire is indicated by detecting engine misfire based on the engine compression ratio by changing the connecting rod. Figure 4In one example, described in greater detail in the description of the method, engine misfire can be detected in response to a motor current supplied to maintain an engine compression ratio changing connecting rod in a specific position that provides a specific engine compression ratio. If the current supplied to motor 212 for a cylinder cycle is maximum at top dead center (TDC) of the cylinder's compression stroke, then it can be determined that the cylinder has misfired. This is because the highest motor current near TDC of the cylinder's compression stroke indicates that the maximum pressure in the cylinder during the cylinder cycle is due to compression of the gas in the cylinder, rather than combustion in the cylinder, which may significantly increase the pressure in the cylinder more than compression. In other words, if the force measured by the current supplied to motor 212 when the cylinder's piston is at TDC of the cylinder's compression stroke within a predetermined crankshaft angle range (e.g., within ±2 crankshaft degrees) is greater than the force measured by the current supplied to the motor to maintain the engine compression ratio changing connecting rod position at other crankshaft angles in the cylinder cycle, then it can be determined that the cylinder has misfired. In response to the indication of engine misfire, the spark energy supplied to the engine cylinder is increased. By increasing the amount of spark energy provided to the engine cylinders, the engine's tolerance to lean air-fuel mixtures can be improved, thereby reducing the likelihood of engine misfire. The engine load is maintained between the first threshold 322 and the second threshold 320. The engine compression ratio is maintained at a low level.

[0038] At time t4, the engine load is further reduced by the vehicle operator partially releasing the accelerator pedal (not shown). In response to the reduced engine load, the cylinder compression ratio is increased, thereby improving engine efficiency. The engine misfire detection mode is changed to detect engine misfire using engine crankshaft acceleration. When the engine compression ratio changes, engine misfire is not detected using the engine compression ratio changing link, as changing the engine compression ratio may render engine misfire assessment using the engine compression ratio changing link less reliable. Between time t4 and time t5, no engine misfire is detected, and engine spark energy is reduced in response to the change in engine operating conditions.

[0039] At time t5, the engine compression ratio stabilizes at an intermediate level, and the cylinder misfire detection method transitions back to detecting engine misfire via the engine compression ratio change linkage because the engine compression ratio has not changed and because the engine load is greater than the first threshold 322. Between time t5 and time t6, no engine misfire is detected, and the spark energy supplied to the engine cylinders remains at an intermediate level. The engine maintains these conditions until time t6, when the engine load decreases again in response to the vehicle operator partially releasing the accelerator pedal. In response to the change in the engine compression ratio, the cylinder misfire detection method transitions to detecting engine misfire via engine crankshaft acceleration. In response to the engine being at a lower load, the engine compression ratio begins to change. Between time t6 and time t7, no engine misfire is detected, and the spark energy supplied to the engine cylinders remains at an intermediate level.

[0040] At time t7, in response to the engine load being less than threshold 322, the cylinder misfire detection method remains at the engine crankshaft acceleration method. The engine remains at a low load and no engine misfire is detected. The engine spark energy remains at a medium level.

[0041] In this way, the method for detecting engine misfire can be changed in response to the crankshaft torsional vibration being greater than the expected engine operating region. In addition, the engine misfire detection method can be changed or shifted in response to changing the engine compression ratio, thereby reducing the possibility of false misfire detection.

[0042] See now Figure 4 , showing a flow chart for operating an engine. Figure 4 At least a portion of the method may be combined as stored in Figure 1 and executable instructions in the non-transitory memory of the system shown in FIG2. In addition, Figure 4 Portions of the methods may occur in the physical world as operations or actions performed by a controller to transform the operating state of one or more devices. Some of the control parameters described herein may be determined by receiving input from the sensors and actuators described herein. Figure 4 The method can also provide Figure 3 Furthermore, the engine may be operated under the conditions mentioned in method 400. The engine controller may also include executable instructions stored in the non-transitory memory for operating the engine under the conditions mentioned in method 400.

[0043] At 402, method 400 determines engine operating conditions. Engine operating conditions may include engine speed, engine load, engine acceleration rate, engine position, ambient temperature, engine temperature, force applied to the engine compression ratio changing connecting rod, and driver demand torque. Engine position can be determined by an engine position sensor, and engine speed can be determined from engine position. For example, engine speed can be determined by dividing the angular distance the engine travels from a first engine position to a second engine position by the amount of time it takes for the engine to rotate from the first engine position to the second engine position. Engine acceleration rate can be determined by differentiating the engine speed. Engine load can be determined by dividing the current engine airflow by the theoretical maximum engine airflow. The force applied to the engine compression ratio changing connecting rod can be determined from the strain gauge sensor output or the motor current by converting the strain gauge output or the motor current into a force value using a function or a lookup table. Other engine operating conditions can be determined by receiving data from various engine sensors. Method 400 proceeds to 404.

[0044] At 404 , method 400 judges whether an engine compression ratio change is in progress. Figure 2A and Figure 2B As discussed, engine compression ratio changes can be performed by rotating motor 212 and adjusting the position of the engine compression ratio changing connecting rod. If controller 12 commands motor 212 to change the position of control rod 216, method 400 may determine that an engine compression ratio change is in progress. Alternatively, if motor 212 is rotating, method 400 may determine that an engine compression ratio change is in progress. If method 400 determines that an engine compression ratio change is in progress, the answer is yes and method 400 proceeds to 430. Otherwise, the answer is no and method 400 proceeds to 406.

[0045] At 430, method 400 ignores and / or discards the engine cylinder compression ratio changing connecting rod force data. The engine cylinder compression ratio changing connecting rod force data can be provided by a strain gauge mechanically coupled to the engine cylinder compression ratio changing connecting rod, or it can be the amount of current supplied to motor 212 to maintain the position of the engine cylinder compression ratio changing connecting rod. If the data is provided by a strain gauge, the output of the strain gauge can be converted into a force. The force can indicate the pressure in the engine cylinder during the cycle of the cylinder having a compression ratio that can be adjusted by the engine cylinder compression ratio changing connecting rod. The strain gauge output can be input into a function, and the function outputs a force that is proportional to or equal to the force applied to the piston of the cylinder having a compression ratio that can be adjusted by the engine cylinder compression ratio changing connecting rod. The values ​​in the function can be determined empirically and stored in the controller memory.

[0046] On the other hand, the position of motor 212 can be closed-loop controlled to a desired position that provides the desired compression ratio for the engine cylinder. The current supplied to motor 212 can be continuously adjusted to maintain the desired compression ratio, whether the desired compression ratio is constant or varying. The current supplied to maintain the position of the compression ratio changing connecting rod can indicate the force applied to the piston of a cylinder having a compression ratio adjustable by the compression ratio changing connecting rod. The current supplied to motor 212 to maintain the position of the compression ratio changing connecting rod can be converted into a force applied to the piston of the cylinder by a function having inputs including the motor current and the position of the compression ratio changing connecting rod. The function outputs a force value, which can indicate cylinder pressure. Cylinder pressure can indicate whether misfire has occurred in the cylinder during the cylinder cycle. However, because the compression ratio changing connecting rod is constantly moving to different positions, data output from a sensor electrically or mechanically connected to the compression ratio changing connecting rod may be less reliable. Therefore, the compression ratio changing connecting rod sensor data can be ignored and / or discarded. Method 400 proceeds to 432 .

[0047] At 432 , method 400 monitors engine crankshaft acceleration. Method 400 monitors engine crankshaft acceleration and determines the presence or absence of cylinder misfire based on the engine crankshaft acceleration.

[0048] The engine crankshaft acceleration may be determined over an entire engine cycle (e.g., two revolutions of a four-stroke engine), or alternatively, method 400 may determine the engine crankshaft acceleration only within a predetermined engine crankshaft angle region. For example, for a first cylinder, method 400 may monitor the engine crankshaft acceleration within a crankshaft angle region extending from 10 degrees before the top dead center compression stroke of the first cylinder to 90 crankshaft degrees after the top dead center compression stroke of the first cylinder. Method 400 may also monitor the engine acceleration within similar crankshaft angle regions for other cylinders of the engine (e.g., cylinders 2 through 4). Method 400 may determine the engine acceleration by differentiating the engine speed. Method 400 stores the engine acceleration data in controller memory and proceeds to 434.

[0049] At 434, method 400 judges whether the engine acceleration within the predetermined crankshaft angle region corresponding to the specific engine cylinder is less than a threshold engine acceleration. If so, the answer is yes and method 400 proceeds to 440. Otherwise, the answer is no and method 400 proceeds to 436.

[0050] An engine acceleration less than a threshold engine acceleration between predetermined crankshaft angle regions for a specific engine cylinder may indicate misfire in the engine cylinder. For example, if the engine acceleration in a crankshaft angle region extending from 10 degrees before top dead center compression stroke of a first cylinder to 90 crankshaft degrees after top dead center compression stroke of the first cylinder is less than X crankshaft degrees per square second, then misfire may be present in the first cylinder. An engine angular acceleration greater than X crankshaft degrees per square second may indicate the absence of misfire in the engine cylinder. The threshold engine acceleration value may be determined empirically and stored in controller memory. In one example, the threshold engine acceleration value may be determined by operating the engine on a dynamometer and determining the difference between engine acceleration values ​​when misfire is absent and when misfire is present in one or more engine cylinders.

[0051] At 436, method 400 clears the cylinder misfire indication from the controller memory. In one example, a bit or word of the controller memory may store a value indicating whether misfire in a particular engine cylinder was detected during a previous engine cycle. Method 400 clears the value of the memory location so that misfire in a particular engine cylinder is no longer indicated after no misfire is detected during the cylinder's cycle. If misfire is not detected in each engine cylinder, the variable storing the cylinder misfire status for each cylinder may be cleared. Method 400 proceeds to 416.

[0052] At 440, method 400 records and reports to memory the engine misfire for cylinders in which the engine acceleration is less than a threshold engine acceleration between predetermined crankshaft angle regions of the engine cylinders. The engine misfire may be reported to a human / machine interface (e.g., a display panel, a light, or other human / machine interface) to provide an indication of the engine misfire to a vehicle occupant. Additionally, the indication of the engine misfire may be stored in memory to provide a historical record of engine misfires. Method 400 proceeds to 442.

[0053] At 442, method 400 adjusts engine operation in response to engine misfire. Method 400 adjusts one or more actuators in response to engine misfire. In one example, method 400 increases spark energy by increasing the dwell time during which voltage is supplied to the ignition coil to increase the amount of energy provided by the spark to the engine cylinder indicating the misfire. By increasing the dwell (e.g., duration) time of the voltage applied to the ignition coil, the charge stored in the ignition coil increases and the increased charge stored in the ignition coil is delivered to the cylinder to ignite the air-fuel mixture in the cylinder. The additional spark energy can improve the engine's tolerance to lean burn. Additionally, method 400 can increase the amount of fuel supplied to the engine in response to the indication of misfire, particularly when the engine air-fuel ratio is indicated as lean by the engine's oxygen sensor. After adjusting the engine actuators in response to the engine misfire, method 400 proceeds to 416.

[0054] At 406, method 400 determines whether the engine is operating within a predetermined engine operating range. In one example, method 400 may determine whether the engine load is greater than a first engine load and less than a second engine load. Additionally, in some examples, method 400 may determine whether the engine speed is greater than a first engine speed and less than a second engine speed. In one example, the predetermined engine operating range may be as follows: Figure 5 However, the predetermined engine operating range may include Figure 5 The operating range shown is different from the operating range shown. In addition, there may be multiple engine operating regions included in the predetermined engine operating range. Method 400 can determine whether the engine is within the predetermined operating range by receiving input from engine position and airflow sensors. If method 400 determines that the engine is operating within the predetermined operating range, the answer is yes and method 400 proceeds to 408. Otherwise, the answer is no and method 400 proceeds to 432.

[0055] At 408, method 400 monitors the force applied to the engine compression ratio changing connecting rod via current supplied to motor 212 or a sensor mechanically coupled to the engine compression ratio changing connecting rod. In one example, method 400 monitors the current supplied to motor 212 to maintain the position of the engine compression ratio changing connecting rod. The amount of current supplied to the motor is converted to a force applied to the piston by an empirically determined function that is referenced by the motor current and the engine compression ratio changing connecting rod position. If the force applied to the engine compression ratio changing connecting rod is determined by a strain gauge, the force applied to the piston is output by a function referenced by the strain gauge output and the engine compression ratio changing connecting rod position, the piston having a compression ratio that can be adjusted by the engine compression ratio changing connecting rod. The force applied to the cylinder piston can be a force applied to the cylinder piston within a predetermined crankshaft angle range of the piston. For example, if determining the force applied to the piston of the first cylinder, the force applied to the piston of the first cylinder can be determined for a crankshaft angle region between ten crankshaft degrees before top dead center of the first cylinder's compression stroke and 90 degrees after top dead center of the first cylinder's compression stroke. It should be noted that the crankshaft angle regions described herein are merely exemplary in nature and should not be considered limiting of the present disclosure. Method 400 proceeds to 410.

[0056] At 410, method 400 judges whether the maximum force applied to the engine compression ratio changing connecting rod (which is a function of the maximum force applied to the cylinder piston) within a predetermined crankshaft angle range of the monitored cylinder is within a predetermined crankshaft angle range of the top dead center (TDC) compression stroke of the monitored cylinder. If so, the answer is yes and method 400 proceeds to 412. Otherwise, the answer is no and method 400 proceeds to 436.

[0057] If a misfire occurs in a monitored cylinder, the cylinder pressure may be maximum near the top dead center compression stroke during the cylinder cycle, as there may be no pressure in the cylinder due to combustion during the cylinder cycle. Since the engine compression ratio changing connecting rod is mechanically coupled to the cylinder's piston, the force exerted on the piston by the cylinder pressure can be transmitted to the engine compression ratio changing connecting rod. Therefore, when a misfire occurs during the cylinder cycle, the maximum cylinder pressure during the cylinder cycle may be within ±2 crankshaft degrees of the cylinder's top dead center compression stroke. The actual cylinder pressure at the cylinder's top dead center compression stroke may be a function of the airflow entering the cylinder during the cylinder cycle. However, if combustion occurs within the engine cylinder, the maximum pressure may be exerted on the piston after the cylinder's top dead center compression stroke (e.g., 15 crankshaft degrees after the cylinder's top dead center compression stroke). Therefore, if the peak cylinder pressure and the maximum force applied to the engine compression ratio changing connecting rod during a cylinder cycle are near the top dead center compression stroke of the cylinder, it can be determined that cylinder misfire has occurred during the cylinder cycle. On the other hand, if the maximum cylinder pressure and / or the maximum force applied to the engine compression ratio changing connecting rod are not during the top dead center compression stroke of the cylinder, it can be determined that misfire has not occurred in the cylinder. In other words, if the force applied to the engine compression ratio changing connecting rod during the cylinder cycle at the top dead center compression stroke of the cylinder is greater than the force applied to the engine compression ratio changing connecting rod during the cylinder cycle at a crankshaft angle other than the top dead center compression stroke of the cylinder (e.g., a crankshaft angle greater than ±2 crankshaft degrees from the top dead center compression stroke of the cylinder), it can be determined that cylinder misfire has occurred during the cylinder cycle. However, if the force applied to the engine compression ratio changing connecting rod at the top dead center compression stroke of the cylinder during the cylinder cycle is less than the force applied to the engine compression ratio changing connecting rod at a crankshaft angle other than the top dead center compression stroke of the cylinder during the cylinder cycle, it can be determined that cylinder misfire has not occurred during the cylinder cycle.

[0058] At 412, method 400 reports a cylinder misfire. A cylinder misfire may be reported to a vehicle occupant via a human / machine interface. Additionally, a cylinder misfire may be reported by changing the value of a variable stored in controller memory. The misfire indication may be transmitted to a remote computer or stored in controller memory in a vehicle history file. Method 400 proceeds to 414.

[0059] At 414, method 400 adjusts engine operation in response to engine misfire. Method 400 adjusts one or more actuators in response to engine misfire. In one example, method 400 increases spark energy by increasing the dwell time during which voltage is supplied to the ignition coil to increase the amount of energy provided by the spark to the engine cylinder indicating the misfire. By increasing the dwell (e.g., duration) time of the voltage applied to the ignition coil, the charge stored in the ignition coil increases and the increased charge stored in the ignition coil is delivered to the cylinder to ignite the air-fuel mixture in the cylinder. The additional spark energy can improve the engine's tolerance to lean burn. Additionally, method 400 can increase the amount of fuel supplied to the engine in response to the indication of misfire, particularly when the engine air-fuel ratio is indicated as lean by the engine's oxygen sensor. After adjusting the engine actuators in response to the engine misfire, method 400 proceeds to 416.

[0060] At 416 , method 400 estimates engine torque based on the force applied to the engine compression ratio changing connecting rod. As previously described, the engine compression ratio changing connecting rod is mechanically coupled to one or more engine pistons. Therefore, the force applied to the engine compression ratio changing connecting rod can indicate the engine torque during the engine cycle. The engine compression ratio changing connecting rod can be held in position by current supplied to a motor, and the current supplied to the motor can indicate the force applied to the engine compression ratio changing connecting rod. Because the connecting rod is mechanically coupled to one or more engine pistons, the current holding the connecting rod in position can be proportional to the force applied to the connecting rod by the pistons. The force applied to the pistons can indicate engine torque generation. Alternatively, the output of a strain gauge coupled to the engine compression ratio changing connecting rod can indicate engine torque, because the force applied to the engine compression ratio changing connecting rod can indicate cylinder pressure and engine torque. Therefore, the motor current or strain gauge output can be converted into an estimated engine torque. For example, the motor torque and the engine compression ratio changing connecting rod position can be input into a function that outputs an estimate of engine torque. An estimate of engine torque can be determined empirically by operating the engine on a dynamometer and monitoring engine compression ratio change motor current, engine compression ratio change connecting rod position, and engine torque. Alternatively, engine compression ratio change connecting rod strain gauge output and engine compression ratio change connecting rod position can be input into a function that outputs an estimate of engine torque. An estimate of engine torque can be determined empirically by operating the engine on a dynamometer and monitoring engine compression ratio change connecting rod strain gauge output, engine compression ratio change connecting rod position, and engine torque. The torque estimate can serve as the basis for providing closed-loop control of engine torque. Method 400 proceeds to exit.

[0061] In this manner, method 400 can determine the presence or absence of engine misfire. Engine misfire can be determined during some conditions by engine crankshaft acceleration and during other conditions by the engine compression ratio connecting rod. Sensor signals from the engine compression ratio connecting rod can provide an improved basis for engine misfire detection during some engine operating conditions, such as when engine torsional vibrations may be present.

[0062] therefore, Figure 4 A method for operating an engine includes: adjusting an engine actuator via a controller in response to engine misfire indicated by engine crankshaft position when the engine is operated in a first operating region; and adjusting the engine actuator via the controller in response to engine misfire indicated by output of a sensor coupled to an engine compression ratio adjustment connecting rod when the engine is operated in a second operating region. The method includes operating the engine in both the first and second operating regions. The method also includes determining engine misfire in response to a force measured by the sensor being maximum within a predetermined crankshaft angle of a top dead center compression stroke of a cylinder during a cylinder cycle, and wherein the predetermined crankshaft angle varies based on the engine compression ratio. The method includes: the first operating region includes an engine load less than a first threshold engine load. The method includes: the first operating region includes an engine load greater than a second threshold. The method also includes adjusting the engine compression ratio via the engine compression ratio adjustment connecting rod, and disregarding the output of the sensor for purposes of determining engine misfire when adjusting the engine compression ratio. The method includes wherein the engine actuator is an ignition coil, and further includes adjusting spark energy provided by the ignition coil in response to engine misfire indicated by engine crankshaft position and engine misfire indicated by the output of the sensor.

[0063] Figure 4The method also provides an engine operating method, comprising: adjusting a compression ratio of a cylinder by adjusting a position of a control rod in response to an output of a controller; receiving input from a sensor positioned along the control rod to the controller; and adjusting an engine actuator in response to engine misfire determined by the output of the sensor when the controller is not adjusting the compression ratio, and not adjusting the engine actuator in response to the output of the sensor when the controller is adjusting the compression ratio. In other words, engine misfire can be determined by the sensor only when the engine compression ratio is not adjusted. Similarly, engine misfire can be determined by changing the current supplied to the motor by adjusting the engine compression ratio only when the engine compression ratio is unchanged. The method includes wherein the sensor is a strain gauge, and wherein the control rod extends from the motor to the engine piston. The method further includes adjusting the engine actuator in response to the output of the sensor, wherein the output of the sensor is determined within a predetermined crankshaft angle range. The method includes wherein the engine actuator is an ignition coil. The method further includes increasing spark energy by increasing the dwell time of the ignition coil. The method further includes determining the presence or absence of engine misfire by determining a crankshaft angle during a cylinder cycle in which a force applied to the control rod is greatest. The method further includes determining the presence of misfire within a predetermined crankshaft angle range of a top dead center compression stroke of the cylinder in response to the crankshaft angle. The method includes wherein the controller ignores the output of the sensor regarding engine misfire when adjusting the compression ratio.

[0064] See now Figure 5 , showing exemplary engine operating ranges for applying different methods for detecting engine misfire. Figure 5 The engine operating range shown can be applied to Figure 4 in the method.

[0065] Figure 5A graph of engine speed versus engine load is shown. The vertical axis represents engine load, and engine load increases in the direction of the vertical axis arrow. The horizontal axis represents engine speed, and engine speed increases from the left side of the graph to the right side of the graph. The unshaded area or zone 502 is an engine operating region in which engine crankshaft acceleration is the basis for determining the presence or absence of engine misfire. The force applied to the engine compression ratio adjustment connecting rod is not the basis for determining the presence or absence of engine misfire in region 502. The shaded area or zone 504 is an engine operating region in which the force applied to the engine compression ratio adjustment connecting rod can be the basis for determining the presence or absence of engine misfire. When the engine is operating in this region, engine crankshaft acceleration is not the basis for determining the presence or absence of engine misfire in region 502 unless the engine compression ratio is changing.

[0066] A first engine speed threshold 522 is a lower engine speed below which the force that can be applied to the engine compression ratio changing connecting rod is not used to determine engine misfire. A second engine speed threshold 524 is a higher engine speed above which the force that can be applied to the engine compression ratio changing connecting rod is not used to determine engine misfire. A first engine load (e.g., engine airflow divided by the maximum theoretical maximum engine airflow) threshold 512 is a lower engine load below which the force that can be applied to the engine compression ratio changing connecting rod is not used to determine engine misfire. A second engine load threshold 510 is a higher engine load above which the force that can be applied to the engine compression ratio changing connecting rod is not used to determine engine misfire.

[0067] In other examples, two or more regions may be provided, where the force applied to the engine compression ratio changing connecting rod is the basis for determining the presence or absence of engine misfire. Furthermore, the shape of the engine operating region need not be rectangular. Rather, the region may be circular, elliptical, triangular, or free-form. The engine operating region may be based on torsional crankshaft vibration levels at various engine speeds and loads.

[0068] It should be noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc. Thus, the various actions, operations, and / or functions shown can be performed in parallel in the sequence shown or omitted in some cases. Similarly, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly performed depending on the specific strategy used. In addition, at least a portion of the described actions, operations, and / or functions can graphically represent code to be programmed into the non-transitory memory of a computer-readable storage medium in the control system. When the described actions are implemented by executing instructions in a system including various engine hardware components in combination with one or more controllers, the control actions can also transform the operating states of one or more sensors or actuators in the physical world.

[0069] This specification ends here. A reading of this specification will enable those skilled in the art to devise numerous changes and modifications without departing from the spirit and scope of this specification. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations may benefit from using this specification.

[0070] According to the present invention, an engine operating method includes adjusting an engine actuator by a controller in response to engine misfire indicated by engine crankshaft position when the engine is operated in a first operating region; and adjusting the engine actuator by the controller in response to engine misfire indicated by an output result of a sensor coupled to an engine compression ratio adjustment connecting rod when the engine is operated in a second operating region.

[0071] According to one embodiment, the above invention is further characterized by: determining that the engine misfires in response to the force measured by the sensor being the largest during the cylinder cycle within a predetermined crankshaft angle of the top dead center compression stroke of the cylinder during the cylinder cycle, and wherein the predetermined crankshaft angle varies according to the engine compression ratio.

[0072] According to one embodiment, the first operating region includes an engine load less than a first threshold engine load; and the embodiment further includes operating the engine in the first operating region; and operating the engine in the second operating region.

[0073] According to one embodiment, the first operating region includes engine loads greater than a second threshold.

[0074] According to one embodiment, the above invention is further characterized in that the compression ratio of the engine is adjusted by the engine compression ratio adjusting connecting rod, and when adjusting the compression ratio of the engine, the output result of the sensor for the purpose of determining engine misfire is ignored.

[0075] According to one embodiment, the engine actuator is an ignition coil and the method further comprises adjusting spark energy provided by the ignition coil in response to engine misfire indicated by engine crankshaft position and engine misfire indicated by the output of the sensor.

[0076] According to the present invention, a method of operating an engine includes adjusting a compression ratio of a cylinder by adjusting a position of a control rod in response to an output of a controller; receiving input from a sensor positioned along the control rod to the controller; and adjusting an engine actuator in response to an engine misfire determined by the output of the sensor when the controller is not adjusting the compression ratio, and not adjusting the engine actuator in response to the output of the sensor when the controller is adjusting the compression ratio.

[0077] According to one embodiment, the sensor is a strain gauge, and wherein the control rod extends from the motor to the engine piston.

[0078] According to one embodiment, the above invention is further characterized by adjusting the engine actuator in response to an output of the sensor, the output of the sensor being within a predetermined crankshaft angle range.

[0079] According to one embodiment, the engine actuator is an ignition coil.

[0080] According to one embodiment, the above invention is further characterized in that the spark energy is increased by increasing the dwell time of the ignition coil.

[0081] According to one embodiment, the above invention is further characterized by determining the presence or absence of engine misfire by determining the crankshaft angle during the cylinder cycle in which the force applied to the control rod is greatest.

[0082] According to one embodiment, the above invention is further characterized by determining the presence of misfire in response to the crankshaft angle being within a predetermined crankshaft angle range of a top dead center compression stroke of the cylinder.

[0083] According to one embodiment, when the controller adjusts the compression ratio, the controller ignores the output of the sensor regarding engine misfire.

[0084] According to the present invention, a vehicle system is provided having: an engine including a crankshaft position sensor, a compression ratio adjusting connecting rod, and a sensor coupled to the compression ratio adjusting connecting rod; an actuator coupled to the engine; and a controller including executable instructions stored in a non-volatile memory for diagnosing engine misfire in response to the crankshaft position when the engine is operated in a low torsional vibration engine operating range, and diagnosing engine misfire in response to a force applied to the compression ratio adjusting connecting rod when the engine is operated in a high torsional vibration engine operating range.

[0085] According to one embodiment, diagnosing engine misfire in response to force applied to a compression ratio adjusting connecting rod includes determining misfire in response to a maximum force applied to the compression ratio adjusting connecting rod occurring within a predetermined crankshaft angle range of a top dead center compression stroke of the cylinder during a cylinder cycle.

[0086] According to one embodiment, the above invention is further characterized by diagnosing engine misfire not in response to a force applied to a compression ratio adjustment connecting rod when the controller adjusts the compression ratio of the engine.

[0087] According to one embodiment, the above invention is further characterized by additional instructions for adjusting the actuator in response to diagnosing cylinder misfire in the engine. According to one embodiment, the actuator is an ignition coil. According to one embodiment, the actuator is a fuel injector.

Claims

1. A method for operating an engine, comprising: adjusting, by the controller, an engine actuator in response to engine misfire indicated by an engine crankshaft position while operating the engine in the first operating region; as well as The engine actuators are adjusted by the controller in response to engine misfire indicated by an output of a sensor coupled to an engine compression ratio adjustment linkage when the engine is operated in a second operating region.

2. The method of claim 1, further comprising: The engine misfire is determined in response to the force measured by the sensor being maximum during a cylinder cycle within a predetermined crankshaft angle at top dead center of a compression stroke of a cylinder, and wherein the predetermined crankshaft angle varies according to an engine compression ratio.

3. The method of claim 1 , wherein the first operating region includes an engine load less than a first threshold engine load, and the method further comprises: operating the engine in the first operating region; as well as The engine is operated in the second operating region. The method of claim 1 , wherein the first operating region includes an engine load greater than a second threshold.

5. The method of claim 1 , further comprising: The compression ratio of the engine is adjusted by the engine compression ratio adjusting connecting rod, and when the compression ratio of the engine is adjusted, the output result of the sensor for the purpose of determining engine misfire is ignored.

6. The method of claim 1 , wherein the engine actuator is an ignition coil, and further comprising: Spark energy provided by the ignition coil is adjusted in response to engine misfire indicated by engine crankshaft position and engine misfire indicated by the output of the sensor.

7. The method of claim 1 , further comprising: adjusting a compression ratio of the cylinder by adjusting a position of a control rod in response to an output of the controller; receiving input from the sensor; as well as When the controller is not adjusting the compression ratio, engine actuators are adjusted in response to engine misfire determined by the output of the sensor, and when the controller is adjusting the compression ratio, the engine actuators are not adjusted in response to the output of the sensor.

8. The method of claim 7, wherein the sensor is a strain gauge, and wherein the control rod extends from a motor to an engine piston.

9. The method of claim 7, further comprising: The engine actuator is adjusted in response to an output of the sensor, the output of the sensor being within a predetermined crankshaft angle range.

10. A vehicle system comprising: An engine comprising a crankshaft position sensor, a compression ratio adjusting connecting rod, and a sensor coupled to the compression ratio adjusting connecting rod; an actuator coupled to the engine; as well as A controller including executable instructions stored in non-transitory memory for diagnosing engine misfire in response to crankshaft position when the engine is operated in a low torsional vibration engine operating range and in response to force applied to the compression ratio adjustment connecting rod when the engine is operated in a high torsional vibration engine operating range.

11. The system of claim 10, wherein diagnosing engine misfire in response to the force applied to the compression ratio adjustment connecting rod comprises: Misfire is determined in response to a maximum force applied to the compression ratio adjusting connecting rod within a predetermined crankshaft angle range occurring at top dead center of a compression stroke of the cylinder during a cylinder cycle.

12. The system of claim 10, further comprising: When the controller adjusts a compression ratio of the engine, an engine misfire is not diagnosed in response to a force applied to the compression ratio adjustment link.

13. The system of claim 10 further comprising additional instructions for adjusting the actuator in response to diagnosing cylinder misfire in the engine.

14. The system of claim 10, wherein the actuator is an ignition coil.

15. The system of claim 10, wherein the actuator is a fuel injector.

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