Partial Engine View

Figure 1 depicts an example embodiment of a combustion chamber or cylinder of internal combustioninternal combustion engine 100. Internal combustion engine 100 may receive control parameters from a control system including controller 126 and input from a vehicle operator 130 via an input device 132. In this example, input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal 102. Cylinder 182 of internal combustion engine 100 may include combustion chamber walls 136 with piston 138 positioned therein. Piston 138 may be coupled to crankshaft 140 so that reciprocating motion of the piston is translated into rotational motion of the crankshaft. Crankshaft 140 may be coupled to at least one drive wheel of the passenger vehicle via a transmission system. Further, a starter motor may be coupled to crankshaft 140 via a flywheel to enable a starting operation of internal combustion engine 100. 

Cylinder 182 can receive intake air via a series of intake air passage 1 142, intake air passage 2 144, and intake air passage 3 146. Intake air passage 3 146 can communicate with other cylinders of internal combustion engine 100 in addition to cylinder 182. In some embodiments, one or more of the intake passages may include a boosting device such as a turbocharger or a supercharger. For example, Figure 1 shows internal combustion engine 100 configured with a turbocharger including a compressor 174 arranged between intake air passage 1 142 and intake air passage 2 144, and an exhaust turbine 176 arranged along exhaust passage 148. Compressor 174 may be at least partially powered by exhaust turbine 176 via a shaft 180 where the boosting device is configured as a turbocharger. However, in other examples, such as where internal combustion engine 100 is provided with a supercharger, exhaust turbine 176 may be optionally omitted, where compressor 174 may be powered by mechanical input from a motor or the engine. A throttle 188 including a throttle plate 164 may be provided along an intake passage of the engine for varying the flow rate and/or pressure of intake air provided to the engine cylinders. For example, throttle 188 may be disposed downstream of compressor 174 as shown in Figure 1, or alternatively may be provided upstream of compressor 174. 

Exhaust passage 148 can receive exhaust gases from other cylinders of internal combustion engine 100 in addition to cylinder 182. Exhaust gas sensor(s) 128 is shown coupled to exhaust passage 148 upstream of emission control device 178. Exhaust gas sensor(s) 128 may be selected from among various suitable sensors for providing an indication of exhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO 196 (as depicted), a HEGO (heated EGO), a NOx, HC, or CO sensor, for example. Emission control device 178 may be a three waycatalyst (TWC), NOx trap, various other emission control devices, or combinations thereof. 

Exhaust temperature may be estimated by one or more temperature sensors (not shown) located in exhaust passage 148. Alternatively, exhaust temperature may be inferred based on engine operating conditions such as speed, load, air-fuel ratio (AFR), spark retard, etc. Further, exhaust temperature may be computed by one or more exhaust gas sensor(s) 128. It may be appreciated that the exhaust gas temperature may alternatively be estimated by any combination of temperature estimation methods listed herein. 

Each cylinder of internal combustion engine 100 may include one or more intake valves and one or more exhaust valves. For example, cylinder 182 is shown including at least one intake valve 150 and at least one exhaust valve 156 located at an upper region of cylinder 182. In some embodiments, each cylinder of internal combustion engine 100, including cylinder 182, may include at least two intake poppet valves and at least two exhaust poppet valves located at an upper region of the cylinder. 

Intake valve 150 may be controlled by controller 126 by cam actuation via cam actuation system 1 152. Similarly, exhaust valve 156 may be controlled by controller 126 via cam actuation system 2 154. Cam actuation system 1 152 and cam actuation system 2 154 may each include one or more cams and may utilize one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT) and/or variable valve lift (VVL) systems that may be operated by controller 126 to vary valve operation. The position of intake valve 150 and exhaust valve 156 may be determined by valve position sensor 1 158 and position sensor 2 160, respectively. In alternative embodiments, the intake and/or exhaust valve may be controlled by electric valve actuation. For example, cylinder 182 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and/or VCT systems. In still other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system. 

Cylinder 182 can have a compression ratio, which is the ratio of volumes when piston 138 is at bottom center to top center. Conventionally, the compression ratio is in the range of 9:1 to 10:1. However, in some examples where different fuels are used, the compression ratio may be increased. This may happen, for example, when higher octane fuels or fuels with higher latent enthalpy of vaporization are used. The compression ratio may also be increased if direct injection is used due to its effect on engine knock. 

In some embodiments, each cylinder of internal combustion engine 100 may include a spark plug 192 for initiating combustion. Ignition system 190 can provide an ignition spark to cylinder 182 via spark plug 192 in response to spark advance signal 162 from controller 126, under select operating modes. However, in some embodiments, spark plug 192 may be omitted, such as where internal combustion engine 100 may initiate combustion by auto-ignition or by injection of fuel as may be the case with some diesel engines. 

In some embodiments, each cylinder of internal combustion engine 100 may be configured with one or more fuel injectors for providing fuel thereto. As a non-limiting example, cylinder 182 is shown including one fuel injector 166. Fuel injector 166 is shown coupled directly to cylinder 182 for injecting fuel directly therein in proportion to the pulse width of signal FPW 170 received from controller 126 via electronic driver 168. In this manner, fuel injector 166 provides what is known as direct injection (hereafter also referred to as “DI”) of fuel into combustion cylinder 182. While Figure 1 shows fuel injector 166 as a side injector, it may also be located overhead of the piston, such as near the position of spark plug 192. Such a position may improve mixing and combustion when operating the engine with an alcohol-based fuel due to the lower volatility of some alcohol-based fuels. Alternatively, the injector may be located overhead and near the intake valve to improve mixing. Fuel may be delivered to fuel injector 166 from a high pressure fuel system 104 including fuel tanks, fuel pumps, and a fuel rail. Alternatively, fuel may be delivered by a single stage fuel pump at lower pressure, in which case the timing of the direct fuel injection may be more limited during the compression stroke than if a high pressure fuel system is used. Further, while not shown, the fuel tanks may have a pressure transducer providing a signal to controller 126. It will be appreciated that, in an alternate embodiment, fuel injector 166 may be a port injector providing fuel into the intake port upstream of cylinder 182. 

It will also be appreciated that while the depicted embodiment illustrates the engine being operated by injecting fuel via a single direct injector; in alternate embodiments, the engine may be operated by using two injectors (for example, a direct injector and a port injector) and varying a relative amount of injection from each injector. 

Fuel may be delivered by the injector to the cylinder during a single cycle of the cylinder. Further, the distribution and/or relative amount of fuel delivered from the injector may vary with operating conditions. Furthermore, for a single combustion event, multiple injections of the delivered fuel may be performed per cycle. The multiple injections may be performed during the compression stroke, intake stroke, or any appropriate combination thereof. Also, fuel may be injected during the cycle to adjust the air-to-injected fuel ratio (AFR) of the combustion. For example, fuel may be injected to provide a stoichiometric AFR. An AFR sensor may be included to provide an estimate of the in-cylinder AFR. In one example, the AFR sensor may be an exhaust gas sensor, such as exhaust gas sensor(s) 128. By measuring an amount of residual oxygen (for lean mixtures) or unburned hydrocarbons (for rich mixtures) in the exhaust gas, the sensor may determine the AFR. As such, the AFR may be provided as a lambda (.lamda.) Value, that is, as a ratio of actual AFR to stoichiometry for a given mixture. Thus, a lambda of 1.0 indicates a stoichiometric mixture, richer than stoichiometry mixtures may have a lambda value less than 1.0, and leaner than stoichiometry mixtures may have a lambda value greater than 1. 

As described above, Figure 1 shows only one cylinder of a multi-cylinder engine. As such each cylinder may similarly include its own set of intake/exhaust valves, fuel injector(s), spark plug, etc. 

Fuel tanks in fuel system 104 may hold fuel with different fuel qualities, such as different fuel compositions. These differences may include different alcohol content, different octane, different heat of vaporizations, different fuel blends, and/or combinations thereof etc. 

Internal combustion engine 100 may further include a knock sensor(s) 194 coupled to each cylinder 182 for identifying abnormal cylinder combustion events. In alternate embodiments, one or more knock sensor(s) 194 may be coupled to selected locations of the engine block. The knock sensor may be an accelerometer on the cylinder block, or an ionization sensor configured in the spark plug of each cylinder. The output of the knock sensor may be combined with the output of a crankshaft acceleration sensor to indicate an abnormal combustion event in the cylinder. In one example, based on the output of knock sensor(s) 194 in a one or more defined windows (e.g., crank angle timing windows), abnormal combustion due to one or more of knock and pre-ignition may be addressed. In particular, the severity of a mitigating action applied may be adjusted to address an occurrence of knock and pre-ignition, as well as to reduce the likelihood of further knock or pre-ignition events. 

Based on the knock sensor signal, such as a signal timing, amplitude, intensity, frequency, etc., and further based on the crankshaft acceleration signal, the controller may address abnormal cylinder combustion events. For example, the controller may identify and differentiate abnormal combustion due to knock and/or pre-ignition. As an example, pre-ignition may be indicated in response to knock sensor signals that are generated in an earlier window (e.g., before a cylinder spark event) while knock may be indicated in response to knock sensor signals that are generated in a later window (e.g., after the cylinder spark event). Further, pre-ignition may be indicated in response to knock sensor outputsensor output signals that are larger (e.g., higher than a first threshold), and/or less frequent while knock may be indicated in response to knock sensor outputsensor output signals that are smaller (e.g., higher than a second threshold, the second threshold lower than the first threshold) and/or more frequent. Additionally, pre-ignition may be distinguished from knock based on the engine operating conditions at the time of abnormal combustion detection. For example, high knock intensities at low engine speed may be indicative of low speed pre-ignition. In other embodiments, abnormal combustion due to knock and pre-ignition may be distinguished based on the output of the knock sensor in a single defined window. For example, pre-ignition may be indicated based on the output of the knock sensor being above a threshold in an earlier part of the window while knock is indicated based on the output of the knock sensor being higher than the threshold in a later part of the window. Furthermore, each window may have differing thresholds. For example, a first higher threshold may be applied in the first (earlier) pre-ignitionwindow while a second, lower threshold is applied in the second (later) knock window. 

Mitigating actions taken to address knock may differ from those taken by the controller to address pre-ignition. For example, knock may be addressed using spark retard and EGR while pre-ignition is addressed using cylinder enrichment, cylinder enleanment, engine load limiting, and/or delivery of cooled external EGR. 

As elaborated with reference to FIGS. 2-4, the inventors have recognized that instead of detecting and differentiating abnormal combustion events, and then adjusting a mitigating action based on the nature of the abnormal combustion, mitigating actions may be performed based on an output intensity of the knock sensor in the one or more windows. Specifically, a nature of the mitigating action applied may be selected based on the knock sensor output intensity in the one or more windows, and furthermore, a severity of the mitigating action(s) applied may be increased as the knock sensor output intensity in the defined window increases. The mitigating action may also be adjusted based on the engine speed at which the knock sensor output is detected. For example, knock sensor output generated in the first window may be addressed via cylinder enrichment, while knock sensor output generated in the second window may be addressed via spark timing retard. As another example, the cylinder enrichment may be increased as the knock sensor output intensity in the first window increases, while the spark timing may be retarded further from MBT as the knock sensor output intensity in the second window exceeds a threshold. 

Returning to Figure 1, controller 126 is shown as a microcomputer, including microprocessor unit 106, input/output ports 108, an electronic storage medium for executable programs and calibration values shown as read-only memory 110 in this particular example, random access memory 112, keep alive memory 114, and a data bus. Controller 126 may receive various signals from sensors coupled to internal combustion engine 100, in addition to those signals previously discussed, including measurement of inducted mass air flow 198 from mass air flow sensor 122; engine coolant temperature 172 from temperature sensor 116 coupled to cooling sleeve 118; a profile ignition pickup signal 200 from hall effect sensor 120 (or other type) coupled to crankshaft 140; throttle position 184 from a throttle position sensor; absolute manifold pressure signal 186 from sensor 124, cylinder AFR from exhaust gas sensor(s) 128, and abnormal combustion from knock sensor(s) 194 and a crankshaft acceleration sensor. Engine speed signal, RPM, may be generated by controller 126 from profile ignition pickup signal 200. Manifold pressure signal 186 from a manifold pressure sensor may be used to provide an indication of vacuum, or pressure, in the intake manifold. 

Storage medium read-only memory 110 can be programmed with computer readable data representing instructions executable by microprocessor unit 106 for performing the methods described below as well as other variants that are anticipated but not specifically listed. Example