JP5698706B2 - Internal combustion engine system - Google Patents

Description

  The present invention relates to an internal combustion engine. More specifically, the present invention relates to a compression ignition (diesel) internal combustion engine that is configured to reduce emissions of harmful exhaust gases.

  There are many uses for internal combustion engines. Internal combustion engines burn fossil fuels in the engine's cylinders, which emits gases that can be harmful to both human health and the environment. Over the past decades, the use of internal combustion engines has increased dramatically with increasing environmental pollution.

  The main concern gases emitted from the vehicle exhaust system include i) unburned fuel or partially burned fuel, which in addition to being toxic, is a significant factor in urban smog Hydrocarbons (HC) and nitrogen in the engine air stream, which is generated when it reacts with high-temperature and high-pressure oxygen inside the combustion cylinder, and causes nitrogen oxides (NOx) that cause both smog and acid rain, Carbon monoxide (CO), a product of incomplete combustion, which is also harmful to humans, and carbon dioxide (CO2), which is a byproduct of the combustion process and is considered one of the most important greenhouse gases And particulate matter (PM), also called soot.

The most widely used types of internal combustion engines for road and non-road applications are spark ignition engines (gasoline fuel) and compression ignition (diesel) engines.
In a spark ignition engine, the throttle valve controls the rate of air supplied to the engine in response to the output required by the vehicle driver, so that the fuel supply system obtains the desired air / fuel ratio. A certain amount of fuel is supplied based on the supply rate. In order to reduce emissions from such engines, a catalytic converter that has the functionality of a reduction catalyst that reduces NO2 to nitrogen and an oxidation catalyst that oxidizes CO to carbon dioxide and HC to water and CO2. It is known to use. In order for the catalytic converter to operate optimally, the spark ignition engine is at the exact amount required to completely burn the amount of fuel supplied to the engine cylinder. Operated under stoichiometric operating conditions. In the gasoline case, the stoichiometric air / fuel ratio is about 14.7: 1, but the exact value depends on the fuel composition.

  In contrast to spark ignition engines, diesel engines are operated under diesel combustion conditions where the air / fuel ratio is much leaner than spark ignition engines, usually between 20: 1 and 40: 1. The

  In a diesel engine, air is introduced into the cylinder head via an intake valve and is compressed during the compression stroke of a piston that compresses and heats the introduced air. The fuel is injected directly into the cylinder near the top dead center piston location and ignited by heated air, thereby causing combustion and a corresponding rapid expansion of the compressed air / fuel mixture. Occurs, driving the piston of the output stroke. As a result, diesel engines operate at much higher air / fuel ratios because the air introduced into the cylinders is not throttled as in gasoline engines.

  Diesel engines have many advantages. For example, as a result of leaner combustion regimes and higher compression ratios, diesel engines have higher thermal efficiency over gasoline engines that convert to higher torque at relatively low engine speeds and better fuel economy. ing.

  One of the characteristic emissions of diesel engines is the production of particulate matter or soot in addition to emissions of hydrocarbons, carbon dioxide and the like. In order to combat the emissions of diesel engines, it is known to wear various devices for the purpose of purifying exhaust gases. For example, it is known to install a diesel particulate removal device (DPF) in the exhaust system to reduce about 80% to 100% of particulate matter entrained in the exhaust gas flow.

  Similarly, the use of diesel oxidation catalysts (DOCs) that utilize excess oxygen in the exhaust gas flow to oxidize CO to CO2 and HC to water and CO2 is also known. However, such an apparatus cannot sufficiently reduce the NOx present in the gas flow.

A major challenge facing the future of diesel engines is to reduce NOx production in a cost-effective manner.
In general, two major approaches are used in efforts to reduce NOx emissions. First, diesel engines are operated at extremely high exhaust gas recirculation (EGR) rates with the aim of reducing the combustion temperature of the cylinders and reducing the generation of NOx. A high EGR rate is effective when the engine is idling and at relatively low engine load conditions, but a relatively large amount of fresh air is required for combustion in medium to high load conditions, such as in the vehicle acceleration phase. Therefore, it is difficult to obtain a high EGR rate. Second, it is known to use devices commonly referred to as NOx absorbers (“NOx traps” or “NOx absorbers”) and selective catalytic reduction (“SCR”) devices, both technologies Are well known to those skilled in the art of diesel engine technology.

  However, SCR devices tend to be expensive and require a minimum temperature to operate efficiently, and as a result, require a regime to warm the device, usually to increase the temperature. , By delayed injection of fuel leading to oxidation of the fuel in the SCR device. SCR devices are generally undesirable due to the complexity of the instrument itself, the attendant control system, and the fact that it adversely affects engine fuel consumption. With respect to NOx absorbers, it requires periodic regeneration to maintain effectiveness, which also adversely affects engine fuel consumption. In addition, the presence of sulfur in diesel fuel can degrade the performance of the NOx absorber, thus limiting its use to geographical areas where the fuel supply meets acceptable quality.

  As you can see, installing some of these devices aimed at combating the various emissions from diesel engines results in an overly expensive system, typically small vehicles for commercial vehicles and private drivers. Lacks wide feasibility for use.

  It is an object of the present invention to provide a diesel engine system that avoids or at least mitigates some of the problems described above.

  In contrast to the above-described background art, the present invention provides a compression ignition engine system having a compression ignition engine, an exhaust passage, and an exhaust gas treatment device including a three-way catalytic converter.

Preferably, the diesel engine is operated in a substantially stoichiometric combustion mode.
The first advantage of the present invention directed to an alternative emission management system for a compression ignition engine is its simplicity. For example, a three-way catalytic converter is technically less complex than an SCR system that requires a urea storage, supply, and cooling subsystem. Such a reduction in complexity results in a reduction in overall engine system weight and cost. This provides further benefits with respect to engine fuel economy.

  In order to operate a three way catalytic converter at or near optimal efficiency, it is desirable to operate a compression ignition internal combustion engine within a small window near the stoichiometric air / fuel ratio. A special control regime is preferred because this is not a common way of operating a diesel engine without incurring significant drawbacks regarding fuel consumption and particulate emissions.

  As such, in some embodiments of the invention, the engine controls the flow rate of gas flowing into one or more combustion chambers of the engine and / or over a range of engine loads. Operated to control injection of fuel toward the one or more combustion chambers to provide stoichiometric combustion. For example, in the first mode with low engine load, the engine is operated at a high EGR rate in normal diesel combustion conditions to reduce NOx emissions, and in the second mode with medium to high engine load, the engine In a third mode with very high engine load and / or engine speed, which is operated in a stoichiometric state where the original catalytic converter can be used to reduce NOx emissions, the engine has to Operates at normal diesel combustion conditions and low EGR ratio.

  Further, to control the engine to operate in a narrow air / fuel ratio range at certain engine conditions, the engine is operated in an air lead mode, whereby the intake air flow rate achieves the required torque. The amount of fuel injected is controlled to obtain a target air / fuel ratio based on the intake air flow rate.

  In yet another embodiment, the exhaust subsystem comprises a diesel particulate filter installed downstream of the three way catalytic converter in the exhaust gas flow direction. In addition to removing hydrocarbons, nitrogen oxides, and carbon monoxide from the exhaust flow by deploying a particulate filter, the system can remove particulate matter from the exhaust gas flow with high efficiency. become. Furthermore, by disposing downstream of the three-way catalytic converter, the particulate filter can be installed in an environment that is advantageous with respect to the exhaust temperature. A further advantage is that during lean operating conditions, the three-way catalytic converter functions in the same way as a diesel oxidation catalyst, thus creating heat by an exothermic reaction, for regeneration of the particulate filter. Helps to raise exhaust gas temperature.

  The first oxygen sensor (also known as a lambda sensor or lambda probe) monitors the exhaust gas components and allows precise control of the air / fuel ratio supplied to the engine cylinders. In order to be able to maintain optimum efficiency, it is arranged downstream of the exhaust passage of the engine and upstream of the three-way catalytic converter.

In another embodiment, the system further includes an oxygen sensor disposed downstream of the three-way catalytic converter and upstream of the diesel particulate filter. By placing another oxygen sensor in the exhaust system in this way, all the fuel reacts with free oxygen downstream of the catalytic converter, and the actual air / fuel ratio can be measured more accurately, The engine air / fuel ratio can be adjusted accurately. Further, when the second oxygen sensor is provided, a diagnostic function based on the oxygen storage capacity of the three-way catalytic converter can be used. The oxygen storage capacity of a catalytic converter indicates how efficiently the converter is operating. As the oxygen storage capacity decreases over time, the conversion efficiency of the catalytic converter decreases. The oxygen storage capacity of the catalytic converter is measured by introducing an air / fuel ratio that varies near the stoichiometry on the inlet side of the converter detected by the first oxygen sensor. When the converter is operating correctly, it absorbs excess oxygen received during lean conditions and releases oxygen during rich conditions. Thus, the second oxygen sensor detects a substantially constant air / fuel ratio. However, when the oxygen storage function of the converter deteriorates, the second oxygen sensor starts to detect a change in the air fuel ratio. The engine control unit may monitor the first and second oxygen sensors and derive a health indicator for the catalytic converter based on the signal ratio from the first and second oxygen sensors.

  The oxygen sensor may be a binary oxygen sensor or a wide range oxygen sensor depending on the adjustment requirements. A wide range sensor can determine the oxygen content in the exhaust gas over a wide range, but the air / fuel ratio is i) substantially equivalent to stoichiometric, ii) rich, or iii) lean. More expensive than a binary oxygen sensor that outputs a signal indicating that.

  In another embodiment, the exhaust subsystem further includes a fuel injector installed upstream of the three-way catalytic converter and thus intermediate the catalytic converter and the engine. Fuel injectors operate an engine at a leaner air / fuel ratio than stoichiometric while providing a way to enrich the fuel content in the exhaust gas and improve the performance of the three way catalytic converter It is convenient because it allows In effect, the converter “detects” a richer mixture than the current engine fuel mode. Furthermore, the provision of additional fuel injectors avoids the increase in particulate emissions typically associated with operating a diesel engine under a rich fuel mode.

1 is a schematic diagram of a compression ignition internal combustion engine system according to an embodiment of the present invention. FIG. 2 is a graph of engine load versus engine speed according to a method of operating the engine system of FIG. It is a compression ignition internal combustion engine system by the 2nd Embodiment of this invention. It is a compression ignition internal combustion engine system by the 3rd Embodiment of this invention. It is a compression ignition internal combustion engine system by the 4th Embodiment of this invention.

For a better understanding, the invention will now be described, by way of example only, in conjunction with the accompanying drawings.
FIG. 1 shows a compression ignition internal combustion engine 2 according to the invention which collects exhaust gas flow from individual cylinders (not shown) of the engine and directs the gas into an exhaust passage or pipe 8. It includes an engine unit 4 to which a manifold 6 is attached. The exhaust passage 8 communicates from the engine 4 to the exhaust gas processing device 10.

  The exhaust gas treatment device includes a three-way catalytic converter 12 and a diesel particulate filter (DPF) 14. The three-way catalytic converter 12 functions to perform the following processing on the exhaust gas discharged from the engine, that is, first, it functions to reduce nitrogen oxides (NOx) to nitrogen and oxygen, and then It works to oxidize carbon monoxide to carbon dioxide, and thirdly it works to oxidize hydrocarbons to carbon dioxide and water.

  The diesel particulate filter 14 is entrained in the exhaust gas flow and serves to reduce particulate matter and soot levels that are not reduced by the three way catalytic converter 14. Such particulate filters are known in the art and may take the form of, for example, a cordierite wall flow filter or a silicon carbide wall flow filter. Downstream of the particulate filter 14 is an exhaust outlet nozzle 15 from which the treated exhaust gas flow exits the engine system 2 to the external environment.

  An oxygen sensor 16 is attached to the exhaust passage 8 between the engine and the three-way catalytic converter 12. The oxygen sensor 16, also known in the art as a lambda probe / sensor, is a linear sensor that is inserted into the exhaust passage 8 to measure the oxygen concentration remaining in the exhaust gas flow. Yes. The oxygen sensor 16 may be a narrow band (also known as a binary sensor) or a broadband sensor to accurately measure the oxygen content of the exhaust gas. The oxygen sensor 16 provides a signal to an engine control system (not shown) that ensures an efficient combustion process and thus efficient operation of the three way catalytic converter 12. The engine 4 can be controlled.

  The three-way catalytic converter 12 operates most effectively when it receives exhaust gas flow from the engine 4 while the engine 4 is operating near a stoichiometric operating point, which is the case with a diesel engine. Corresponds to an air / fuel ratio of between about 20 and 40 air to 1 ratio fuel. The exact value depends on the type of fuel used.

  When there is more oxygen than needed at the air / fuel ratio, the engine system is said to be operating lean and the system is in an oxidized state. In such an environment, the two oxidation reactions of the three-way catalytic converter (converting carbon monoxide into carbon dioxide and converting hydrocarbons into carbon dioxide and water) are reduced reactions (nitrogen oxides into nitrogen and oxygen). More efficient).

  In contrast, when there is excess fuel in the air / fuel ratio, the engine system is said to be operating rich and nitrogen oxide reduction has an advantage while sacrificing low efficiency oxidation reactions. ing.

  Thus, in order for the three-way catalytic converter to operate most efficiently for both oxidation and reduction reactions, the compression ignition engine 4 is operated at a stoichiometric operating point for at least some of the engine operating region. It is necessary to make it.

  FIG. 2 illustrates a method of operating a diesel engine that is particularly beneficial in the operation of the engine system shown in FIG. In the first or low load mode (indicated as mode “A”), the engine is operated on a conventional diesel engine to reduce NOx emissions when the engine is in a relatively low load condition, such as light acceleration or substantially steady running. It is operating in a very high EGR ratio (greater than the typical 50%) in the combustion state (lean burn; lambda> 1).

  In the first engine mode, the operating characteristics of the engine 4, especially in the PCCI mode (premixed charge compression ignition), the engine NOx emissions are very low (regions below about 15 parts per million) so that after the exhaust gas No processing is required or minimal post-processing is required. Therefore, it is not necessary to operate the engine 4 stoichiometrically in such a low load region.

  The second combustion mode (indicated as mode “B”) is effective when the engine 4 is subjected to a medium to high engine load, for example, during moderate acceleration or high steady state running speed. In the second combustion mode, the engine is operating stoichiometrically. In this second mode, when the engine 4 is working harder than mode A, a higher EGR rate cannot be achieved (since more fresh air is needed for the fuel), so in the normal diesel combustion state Below, the NOx emissions of the engine 4 increase considerably. In this region, therefore, the fuel condition is modified so that the air / fuel ratio is stoichiometric. Accordingly, in this second region, the three-way catalytic converter 12 is operating at maximum efficiency to reduce the NOx content of the exhaust gas in addition to hydrocarbons and carbon monoxide. Further, the three-way catalytic converter 12 is easily operated efficiently due to the high exhaust temperature accompanying the high engine load.

  In order to operate the diesel engine 4 stoichiometrically in a second mode with limited soot emissions, the engine 4 is operated in normal diesel combustion with a PCCI fuel regime or high EGR and one or more post-injections. Need to be activated. However, operation with post-injection will slightly worsen fuel economy (in the range of 4% to 5%).

  In the third combustion mode (designated as mode “C”), the engine 4 is operating under very high loads and / or engine speeds, for example maximum acceleration and / or very high running speed. In this combustion mode, the engine 4 operates at a low EGR in a normal diesel combustion state in order to obtain the maximum torque.

  Referring once again to the mode B described above, the engine 4 is operating under stoichiometric conditions in order to maximize the efficiency of the three way catalytic converter 12. One way that can be operated to help maintain the desired lambda value during the quasi / semi-steady state is to operate the engine 4 under a so-called “air lead” condition. In this state, the EGR ratio is calculated by the engine control system so that there is just enough outside air left to allow the engine to produce the torque required by the driver at the desired air / fuel ratio. However, since the response speed of the EGR control ratio valve of the engine is finite, for example, in the case of a rapidly changing torque request, for example, due to a slight change in the driver's pedal position or a change in the road surface condition, Can not respond.

  By way of illustration, if the torque demand is reduced in steps, the fuel that needs to be injected is likewise reduced in a step-wise manner. In order to keep the air / fuel ratio (lambda value) at the same desired value (preferably stoichiometric value), the outside air drawn into the engine must be reduced. This is accomplished by operating the EGR valve to circulate a greater amount of exhaust gas from the exhaust side of the engine 4 back to the air intake of the engine 4. However, since this does not happen instantaneously, for some time the air / fuel ratio will deviate significantly from the desired value.

  In order to avoid deviations that may occur from the target air / fuel ratio (in this case lambda = 1), the engine can control the air / fuel ratio within narrow boundaries during steady engine conditions. Operated based on the “Air Lead” regime.

  When the engine is operated according to the air lead regime, the desired air mass flow rate into the engine 4 is calculated by the engine control system, as calculated under normal diesel combustion conditions, and the desired air mass rate into the engine. The flow rate is controlled by controlling the EGR ratio. The fuel actually injected into the engine is calculated from the available outside air and the desired air / fuel ratio.

  Since the torque response of the air lead regime is limited to the response speed of the change in EGR value, the air lead regime is operating between the regions of limited engine conditions. For example, when the engine 4 is operating in Mode B where a stoichiometric air / fuel ratio is required, the amount of fuel injected will be accurate to the target air based on the actual amount of outside air entering the engine. The fuel / fuel ratio is adjusted to obtain, in other words, air “leads” the fuel. The calculated EGR ratio will guide the air / fuel ratio close to the desired air / fuel ratio, theoretically exactly to the target air / fuel ratio.

  The engine control system calculates the air / fuel ratio that would be obtained when the desired fuel (based on the torque required by the driver) is injected into the available outside air. If this calculated air / fuel ratio exceeds the target air / fuel ratio by a predetermined and calibratable amount, then the outside air / lead regime is not feasible and the engine will Is operated in a “fuel lead” regime until it returns again to a predetermined threshold away from the desired air / fuel ratio.

  The above control regime allows the actual air / fuel ratio to accurately follow the target air / fuel ratio, where the dynamics of torque change required by the driver is greater than a predetermined value. Does not result in an air / fuel ratio.

  A particular advantage of the system of the present invention over known compression ignition internal combustion engine systems that include exhaust gas treatment strategies such as NOX absorbers and / or SCR technology is the simplicity, which further includes the engine This will reduce the overall unit cost of the system. In addition, by installing the DPF 14 downstream of the three-way catalytic converter, the DPF 14 is concerned with respect to the temperature of the exhaust gas flow when the exhaust gas flow reaches the DPF 14 and with respect to exhaust gas compensation to reduce particulate emissions. Beneficial environmental conditions are guaranteed.

  In the embodiment of FIG. 3, similar parts are represented by similar reference numbers, and the compression ignition engine system 2 is further installed downstream of the three-way catalytic converter 12 and upstream of the DPF 14, ie, between them. The oxygen sensor 18 is included. In this embodiment, another oxygen sensor 18 is a binary sensor that takes two states to indicate that an amount of oxygen greater or less than a predetermined threshold is present.

  The purpose of another oxygen sensor 18 is to allow a finer control of the air / fuel ratio to ensure that the three way catalytic converter 12 operates most efficiently. In addition, another oxygen sensor 18 allows the engine control system to monitor the amount of oxygen stored in the three-way catalytic converter 12 by comparing the response of the first oxygen sensor 16 and the second oxygen sensor 18. It becomes like this. By placing another oxygen sensor in the exhaust system in this way, all the fuel reacts with free oxygen downstream of the catalytic converter and the actual air / fuel ratio can be measured more accurately, Allows precise adjustment of the engine air / fuel ratio. Further, when the second oxygen sensor is provided, a diagnostic function based on the oxygen storage capacity of the three-way catalytic converter can be used. The oxygen storage capacity of a catalytic converter indicates how efficiently the converter is operating. As the oxygen storage capacity decreases over time, the conversion efficiency of the catalytic converter decreases. The oxygen storage capacity of the catalytic converter is measured by introducing an air / fuel ratio that varies near the stoichiometry on the inlet side of the converter detected by the first oxygen sensor. When the converter is operating correctly, it absorbs excess oxygen received during lean conditions and releases oxygen during rich conditions. Thus, the second oxygen sensor detects a substantially constant air / fuel ratio. However, when the oxygen storage function of the converter deteriorates, the second oxygen sensor starts to detect a change in the air fuel ratio. The engine control unit may monitor the first and second oxygen sensors and determine a health indicator for the catalytic converter based on a signal ratio from the first and second oxygen sensors.

  The second oxygen sensor 18 is a binary sensor that provides an exhaust gas analysis sufficient to allow diagnosis of the three-way catalytic converter 12. However, it should be understood that broadband sensors can also be used here, although more expensive. Alternatively, a NOX sensor can be placed at this location to measure the proportion of NOX in the exhaust gas flow, thus providing a direct indication of the NOx reduction function of the three way catalytic converter. .

Another alternative embodiment of the present invention is shown in Table 4, where like parts are designated with like reference numbers. In the embodiment of FIG. 4, in the engine system 2, a fuel injector 30 is installed in the exhaust passage 8 between the engine 4 and the three-way catalytic converter 12. In this embodiment, the compression ignition internal combustion engine 4 can be operated at a lean operating point (lower than the stoichiometric value) while the fuel injector 30 is used to change the composition of the exhaust gas. Therefore, the operation of the three-way catalytic converter 12 is optimized in a more balanced state. This is effective in reducing the production of particulate emissions (because lean air / fuel ratios produce less particulate matter), while three-way catalytic converters can be used for nitrogen oxides, monoxide It operates at high efficiency to reduce carbon and hydrocarbon emissions.

  FIG. 5 shows another alternative embodiment where the functions of the three way catalytic converter 12 and the DPF 14 are combined in a single unitized diesel engine exhaust treatment package 40. Such a composite catalytic converter / DPF package 40 provides benefits in terms of layout, temperature management and cost. In the composite exhaust treatment package 40, since the diesel particulate filter 14 is close to the engine necessary for regeneration purposes, the temperature of the diesel particulate filter 14 can be maintained at a high level, so the temperature management problem is particularly important. is there.

  It should be appreciated by those skilled in the art that various alternatives and modifications can be made to the embodiments described above.

2 Compression ignition internal combustion engine 4 Engine 6 Exhaust manifold 8 Exhaust passage and pipe 10 Exhaust gas treatment device 12 Three-way catalytic converter 14 Diesel particulate filter (DPF)
15 Exhaust outlet nozzle 16 Oxygen sensor 18 Second oxygen sensor 30 Fuel injector 40 Diesel engine exhaust treatment package

Claims (7)

In a compression ignition internal combustion engine system (2) having a compression ignition engine (4), an exhaust passage (8), and an exhaust gas treatment device (10),
The exhaust gas treatment device (10) includes a three-way catalytic converter (12) and a diesel particulate filter (14) installed downstream of the three-way catalytic converter (12) in the direction of exhaust gas flow. And
Furthermore, the target air / fuel ratio at which lambda = 1 and the calculated air / fuel ratio obtained when the desired fuel based on the torque required by the driver is injected into the available outside air Equipped with an engine control system that can determine
In a second mode in which the engine is subjected to medium to high engine loads, the engine controls the flow rate of gas supplied to one or more combustion chambers of the engine and / or the one or It is operated in a stoichiometric combustion state, controlling the fuel injection into the further combustion chamber,
In the second mode,
(A) The engine controls the intake air flow rate to provide the required torque during engine conditions when the calculated air / fuel ratio does not exceed the target air / fuel ratio by a predetermined amount. Operated in an air lead mode so that the target air / fuel ratio can be achieved based on the intake air flow rate by controlling the amount of fuel injected
(B) The engine injects into the combustion chamber during a condition where the calculated air / fuel ratio exceeds the target air / fuel ratio by a predetermined amount and the torque demand changes rapidly. A compression ignition internal combustion engine system that is operated in a fuel lead mode so that the required fuel can be controlled to achieve the required torque. The compression ignition internal combustion engine system according to claim 1,
Compression ignition internal combustion, when the engine (4) is operated in stoichiometric combustion, corresponding to an air / fuel ratio of about 20 to 40 air to 1 ratio fuel Institution system. The compression ignition internal combustion engine system according to claim 1 or 2,
The exhaust gas treatment device (10) is supplied to the engine (4) so as to monitor the components of the exhaust gas and maintain the optimum performance of the three-way catalytic converter (12). In order to be able to accurately control the air / fuel ratio, a first installed in the exhaust passage (8) downstream of the engine (4) and upstream of the three-way catalytic converter (12). A compression ignition internal combustion engine system including an oxygen sensor (16). The compression ignition internal combustion engine system according to any one of claims 1 to 3,
The exhaust gas treatment device (10) includes a second oxygen sensor (18) installed downstream of the three-way catalytic converter (12) and upstream of the diesel particulate filter (14). Ignition internal combustion engine system. The compression ignition internal combustion engine system according to claim 3 ,
In order to inject fuel into the exhaust passage (8), further includes a fuel injector (30) installed upstream of the three-way catalytic converter (12) and the first oxygen sensor (16). A compression ignition internal combustion engine system. The compression ignition internal combustion engine system according to any one of claims 1 to 5,
In the second mode, the engine is operating under stoichiometric conditions where NOx emissions can be reduced using the three-way catalytic converter;
The compression ignition internal combustion engine system further comprises a first mode at low engine load and a third mode under very high engine load and / or engine speed,
In the first mode, the engine is operated at a high EGR ratio under normal diesel combustion to reduce NOx emissions;
In the third mode, the compression ignition internal combustion engine system, wherein the engine is operated under normal diesel combustion conditions and a low EGR ratio to obtain maximum torque. In a compression ignition internal combustion engine system (2) having a compression ignition engine (4), an exhaust passage (8), and an exhaust gas treatment device (10),
The exhaust gas treatment device (10) includes a three-way catalytic converter (12) and a diesel particulate filter (14) installed in the direction of the exhaust gas flow,
Furthermore, the target air / fuel ratio at which lambda = 1 and the calculated air / fuel ratio obtained when the desired fuel based on the torque required by the driver is injected into the available outside air Equipped with an engine control system that can determine
In a second mode in which the engine is subjected to medium to high engine loads, the engine controls the flow rate of gas supplied to one or more combustion chambers of the engine and / or the one or It is operated in a stoichiometric combustion state, controlling the fuel injection into the further combustion chamber,
In the second mode,
(A) The engine controls the intake air flow rate to provide the required torque during engine conditions when the calculated air / fuel ratio does not exceed the target air / fuel ratio by a predetermined amount. Operated in an air lead mode so that the target air / fuel ratio can be achieved based on the intake air flow rate by controlling the amount of fuel injected
(B) The engine injects into the combustion chamber during a condition where the calculated air / fuel ratio exceeds the target air / fuel ratio by a predetermined amount and the torque demand changes rapidly. Operated in fuel lead mode so that the required torque can be controlled by controlling the fuel
The compression ignition internal combustion engine system, wherein the three-way catalytic converter (12) and the diesel particulate filter (14) are combined into a single unit (40).

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