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  Cold start emission reduction monitoring system and methodUSPTO Application #: 20070283682Title: Cold start emission reduction monitoring system and method Abstract: An engine emissions diagnostic is disclosed that utilizes parameters correlating to catalyst temperature to identify when an indication of degraded performance may be generated. (end of abstract)
Agent: Alleman Hall Mccoy Russell & Tuttle, LLP - Portland, OR, US Inventors: Michael J. Cullen, John Rollinger, Marsha Kapolnek, Robert Baskins, Karen Willard USPTO Applicaton #: 20070283682 - Class: 60284 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070283682. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND AND SUMMARY [0001]Vehicles may be required to meet certain emission thresholds. As such, some vehicles may use emission control devices, such as catalytic converters, to reduce engine emissions. These devices may provide various levels of emission reduction depending on exhaust temperature. As such, engine operation may be adjusted during an engine start to increase temperature of the device to thereby reduce emissions by achieving earlier catalyst light-off, for example. [0002]However, the various factors can affect performance of the above adjustments to increase catalyst temperature. For example, degradation of components may result in less airflow than desired, for example, which may reduce exhaust gas heat. Further, engine speed control operation may result in adjustment of spark timing to such a degree that spark retard is sufficiently reduced or eliminated thus resulting in reduced exhaust gas temperature and delayed catalyst light-off. [0003]As such, in one example, the above conditions causing reduced catalyst light-off performance via reduced catalyst temperature may be detected and utilized to indicate that vehicle emission control performance has degraded. DESCRIPTION OF THE FIGURES [0004]FIG. 1 shows a schematic engine diagram; [0005]FIG. 2 shows an example cold start emissions reduction monitoring routine; and [0006]FIG. 3 shows an example graph plotting the catalyst delta ratio against the engine coolant temperature at start. DETAILED DESCRIPTION [0007]Internal combustion engine 10 comprising a plurality of cylinders, one cylinder of which is shown in FIG. 1, is controlled by electronic engine controller 12. Engine 10 includes combustion chamber 30 and cylinder walls 32 with piston 36 positioned therein and connected to crankshaft 13. Combustion chamber 30 communicates with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Exhaust gas oxygen sensor 16 is coupled to exhaust manifold 48 of engine 10 upstream of catalytic converter 20. [0008]Intake manifold 44 communicates with throttle body 64 via throttle plate 66. Throttle plate 66 is controlled by electric motor 67, which receives a signal from ETC driver 69. ETC driver 69 receives control signal (DC) from controller 12. Intake manifold 44 is also shown having fuel injector 68 coupled thereto for delivering fuel in proportion to the pulse width of signal (fpw) from controller 12. Fuel is delivered to fuel injector 68 by a conventional fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown). [0009]Engine 10 further includes conventional distributorless ignition system 88 to provide ignition spark to combustion chamber 30 via spark plug 92 in response to controller 12. In the embodiment described herein, controller 12 is a conventional microcomputer including: microprocessor unit 102, input/output ports 104, electronic memory chip 106, which is an electronically programmable memory in this particular example, random access memory 108, and a conventional data bus. The controller may further include a keep alive memory (not shown) for storing adaptive parameters. [0010]Controller 12 receives various signals from sensors coupled to engine 10, in addition to those signals previously discussed, including: measurements of inducted mass air flow (MAF) from mass air flow sensor 110 coupled to throttle body 64; engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling jacket 114; a measurement of throttle position (TP) from throttle position sensor 117 coupled to throttle plate 66; a measurement of turbine speed (Wt) from turbine speed sensor 119, where turbine speed measures the speed of a torque converter output shaft, and a profile ignition pickup signal (PIP) from Hall effect sensor 118 coupled to crankshaft 13 indicating an engine speed (N). Alternatively, turbine speed may be determined from vehicle speed and gear ratio. [0011]Controller 12 may include various control routines, such as cold start rapid catalyst heating routines that adjust various engine and/or vehicle operating parameters to more rapidly raise exhaust gas temperature. For example, ignition timing of one or more cylinders may be retarded from peak torque timing during cold starting operating to increase exhaust gas heat generation. Further, engine idle speed may be temporarily elevated after a cold start to further increase exhaust gas heat generation. Still other actions may be taken, such as air-fuel ratio adjustments, valve timing adjustments, fuel injection timing adjustments, and the like. In one particular embodiment, engine idle speed, spark timing, and engine airflow, may be adjusted during a cold start to increase exhaust gas temperature. In another embodiment, intake valve advance and/or retard may be used, along with spark retard and fuel injection timing and amount variations. For example, the controller may adjust a variable valve timing system to increase positive valve overlap (e.g., via an intake only variable valve timing unit) of at least one cylinder during a cold start, and then adjust a fuel injection amount and/or timing and/or spark timing. [0012]However, other control routines may be present which may limit or vary the above exhaust heat generation adjustments. For example, detection of low fuel quality, such as hesitation fuel, may reduce or eliminate spark retard (in order to maintain combustion and minimum engine speed). As another example, flow blockages or plugs, may limit airflow increases. As still another example, variable valve unit degradation may limit or affect valve timing adjustments or positive overlap generation. As such, diagnostic routines may be used to detect such system overrides and the corresponding effects on exhaust gas temperature and/or catalyst light off during at least the first 15 seconds of vehicle operation from a cold start under selected conditions, such as standard air temperatures near 70 degrees F. and barometric pressure near sea level. [0013]Continuing with FIG. 1, accelerator pedal 130 is shown communicating with the driver's foot 132. Accelerator pedal position (PP) is measured by pedal position sensor 134 and sent to controller 12. [0014]In an alternative embodiment, where an electronically controlled throttle is not used, an air bypass valve (not shown) can be installed to allow a controlled amount of air to bypass throttle plate 62. In this alternative embodiment, the air bypass valve (not shown) receives a control signal (not shown) from controller 12. In another alternative embodiment, where a mass air flow sensor is not used, inducted mass air flow may be determined using a variety of computational methods. [0015]In an exemplary embodiment, electronic engine controller 12 may further include an on-board diagnostic (OBD) system (not shown). The OBD system may detect operating component degradation through various diagnostic routines. In some instances, if a routine detects degradation, the routine may set a diagnostic trouble code (alternatively referred to as a service code) in the electronic engine controller. Many routines within the on-board diagnostics system may detect emission related degradations in a range of operating condition of the engine. [0016]One embodiment advantageously implements a routine to monitor hydrocarbon emissions during various operating conditions, such as during engine cold start conditions. Such a monitoring routine may detect, whether various cold start emissions reduction (CSER) engine control strategies are effective in heating a catalyst to a desired light-off temperature and reducing hydrocarbon emissions. Specifically, the routine may determine if particular ignition spark retard and/or elevated idle speed strategies are effectively reducing cold start emissions. However, it should be appreciated that in some embodiments the routine may demonstrate the effectiveness of other CSER control strategies as well. [0017]Referring to FIG. 2, an exemplary cold start emissions reduction (CSER) monitoring routine is shown. Specifically, routine 200 monitors catalyst temperature via a catalyst temperature warm-up index calculation. Furthermore the monitoring system may make a degradation determination regarding CSER related components based on whether actual emissions exceed a predetermined threshold when compared to reference emissions standards. The determined degradation may result in setting a CSER service code in the electronic engine controller. Additionally, in some embodiments the degradation determination may result in a change in operating parameter. [0018]Referring back to FIG. 2, the routine begins at 210 where it is determined if the engine is in a start condition. In one embodiment, the CSER monitor routine may be configured to monitor emissions conditions for fifteen seconds following the start of the engine. Thus, the determination made at 210 may judge whether or not fifteen seconds have elapsed since the start of the engine. In some embodiments, the CSER monitor routine may further be limited to running only when the engine is started and the transmission is in a neutral position. As such, the engine may be judged to be in a start condition only when the transmission is in neutral and less than fifteen seconds have elapsed since the start of the engine. [0019]It should be appreciated that in some embodiment, the CSER monitor routine may run for a desired longer or shorter amount of time, and/or may run during driving conditions as well. [0020]Continuing with 210, if it is determined that the engine is not in a start condition, the routine ends, otherwise the routine moves to 220. In the illustrated embodiment, the routine may be configured to make diagnostic calculations at predetermined intervals during the CSER monitoring time period, for example, a calculation cycle may be carried out every one hundred milliseconds. In some embodiments, the diagnostic interval may be adjusted to desired longer or shorter lengths based on a desired diagnostic resolution. [0021]Continuing with 220, if it is determined that the predetermined amount of time has not elapsed, the routine loops until it is determined that the predetermined amount of time has elapsed. Once the predetermined amount of time has elapsed the routine moves to 230. 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