Exhaust emission control system, method for controlling an exhaust emission system and computer program product

Abstract

Exhaust emission control system for an engine, including a NO x Catalyst (45) arranged in an exhaust passage (41) of the engine for storing NO x in the exhaust gas when an air-fuel ratio of the exhaust gas is lean, and for reducing the stored NO x when the air-fuel ratio is approximately stoichiometric or rich, and a catalyst (47) for selective catalytic reduction (SCR) provided in the exhaust passage (41) for purifying NO x is arranged within the exhaust gas by causing a reaction with ammonia, wherein the system comprises a processor (60A) configured to execute: a NO x Reduction control module (60B) for performing when the stored amount of NO x in the NE xcatalyst (45) exceeds a given determination amount, a first NO x Reduction control in which a fuel injection device (20) performs a post-injection of fuel to continuously control the air-fuel ratio to a target air-fuel ratio such that the stored NO x is reduced and the stored amount of NO x falls below a given amount, the target air-fuel ratio being a ratio at which the stored NO x can be reduced, wherein the post-injection causes the injected fuel to burn inside a cylinder, wherein the implementation of the first NO x Reduction control is permitted when an engine load is in a medium load range, where, if the stored amount of NO x in the NE xcatalyst (45) is below the specified amount and the air-fuel ratio becomes rich due to acceleration of a vehicle that emits NO x Reduction control module (60B) also a second NO x Reduction control in which the fuel injection device (20) performs the post-injection to temporarily control the air-fuel ratio to the target air-fuel ratio so that the NO x , which is in the NO x catalyst (45), wherein the post-injection causes the injected fuel to be discharged to the exhaust passage (41) as unburned fuel without being burned inside the cylinder, wherein the implementation of the second NO xReduction control is only permitted when the engine load is within a high load range above a load that defines a higher end of the medium load range, where the SCR catalyst (47) NO x within an engine operating range where the NO x Reduction control module (60B) does not carry out the post-injection by the fuel device (20) in order to reduce the stored NO x to reduce, wherein within a range (R11) where the engine load is higher than a range (R13) where the SCR catalyst (47) NO x cleans, the second NO x Reduction regulation or control is carried out.

Description

BACKGROUND

[0001] The present invention relates to an exhaust emission control system for an engine, and more particularly to an exhaust emission control system provided at an exhaust passage with a NO x Catalyst is provided, which NO x in an exhaust gas. Furthermore, the invention relates to a method for regulating or controlling an exhaust system and to a computer program product.

[0002] Conventionally, NO x Storage catalysts which NO x store (hide) contained in an exhaust gas when an air-fuel ratio of the exhaust gas is lean (i.e., λ>1, greater than a theoretical air-fuel ratio). Such NO x Storage reduction catalysts further reduce the stored NO xwhen the air-fuel ratio is approximately equal to a stoichiometric (i.e., λ≈1, approximately equal to the theoretical air-fuel ratio) or rich (i.e., λ<1, less than the theoretical air-fuel ratio). Within a normal operating range of an engine, the engine is operated at the lean air-fuel ratio (λ>1) to reduce fuel consumption, although if this lean operating condition continues for a while, the stored amount of NO x in the NE x Catalyst reaches a limit and the NO x Catalyst no longer NO x can store, whereby this causes NO x is released. For this reason, the air-fuel ratio is appropriately adjusted to be stoichiometric or richer (λ≤1) to reduce NO x which is present in the NO xcatalyst is stored (the regulation or control for reducing NO x , which is in the NO x catalyst is stored as “NO x Reduction control). It should be noted that “λ” is an index of the air-fuel ratio expressed with reference to the theoretical air-fuel ratio and is a so-called excess air ratio.

[0003] For example, JP 2004-360593 A discloses a prior art for carrying out when a stored amount of NO x in a NO x catalyst exceeds a given amount, a fuel injection control to enrich an air-fuel ratio of exhaust gas to reduce the NO x which is present in the NO x catalyst is stored.

[0004] An example of adjustment methods of an air-fuel ratio of exhaust gas so that NO x , which is in a NO x Catalyst is stored, is reducible (hereinafter, this air-fuel ratio is referred to as the "target air-fuel ratio") is performing a post-injection after a main injection. In the main injection, fuel is injected into a cylinder to deliver a desired engine torque, and in the post-injection, fuel is injected at a timing such that the engine torque output is not affected (typically on an expansion stroke). The fuel injected in the post-injection typically needs to be burned inside the cylinder to achieve the reduction of NO xcatalyst, otherwise unburned fuel will be discharged or discharged and the emission performance of HC (hydrocarbon) etc. will deteriorate.

[0005] However, depending on the operating condition of the engine, combustion of the fuel, which is used in the post-injection of the NO xReduction control or control, smoke (soot) or HC is injected into the interior of the cylinder. For example, within a high engine load range, an in-cylinder temperature rises and the fuel injected in the post injection is ignited without sufficient time from the injection, that is, combustion occurs before air and fuel are properly mixed, and thus smoke may be generated. On the other hand, within a low engine load range, even if the fuel injected in the post injection is to be burned, since the in-cylinder temperature is low and combustion stability is poor, the injected fuel may not be properly burned or misfire may occur. In this case, HC is generated corresponding to unburned fuel.Furthermore, within the range of low engine load, since the temperature of the NO. x catalyst is low, even if the air-fuel ratio is controlled to the target air-fuel ratio, a reduction of NO x Catalyst is not adequately carried out.

[0006] DE 198 47 874 A1 discloses a method for reducing nitrogen oxides in the exhaust gas of a lean-burn internal combustion engine with a downstream NOx storage catalyst. In this method, NOx storage is promoted by measures that increase the exhaust gas temperature and / or reduce the mass flow, and NOx regeneration of the catalyst is controlled to achieve optimal exhaust gas purification. To control NOx regeneration, the nitrogen oxide loading state of the catalyst is determined and / or the catalyst activity is monitored by on-board diagnostics. If a maximum permissible loading is exceeded or if an irregularity in catalyst activity occurs, the admissibility of NOx regeneration is first checked by checking safety-relevant components for proper functioning and / or the current driving situation for compliance with predetermined driving parameters.In addition, it is checked whether compliance with predetermined regeneration parameters allows for NOxT regeneration. If the admissibility requirements are met, the required regeneration parameters are set, if necessary, and NOx regeneration is initiated. This regeneration process continues until either a predetermined degree of regeneration is reached or the current results of the admissibility check require premature termination or interruption of the regeneration process.

[0007] JP 2010-084615 A ​​discloses an engine system control method and an engine system control apparatus that regenerate a NOx absorption catalyst while preventing deterioration of fuel economy.

[0008] DE 10 2014 105 210 A1 describes a system for purifying exhaust gas, comprising: an internal combustion engine with an injector, a lean NOx trap adapted to absorb nitrogen oxide contained in the exhaust gas at a lean air / fuel ratio, release the absorbed nitrogen oxide at a rich air / fuel ratio and reduce the nitrogen oxide contained in the exhaust gas or reduce the released nitrogen oxide, a dosing module adapted to inject reducing agent into the exhaust gas, a selective catalytic reduction catalyst on a diesel particulate filter configured to capture particles and reduce the nitrogen oxide by using the reducing agent injected by the dosing module, and a control device that performs denitrification (DeNOx) by using the lean NOx trap.when the temperature of the exhaust gas is less than a transition temperature and which performs denitrification by using the diesel particulate filter when the temperature of the exhaust gas is greater than or equal to the transition temperature. SUMMARY

[0009] The present invention has been made with a view to solving the objects of the known art described above and aims to appropriately determine whether an exhaust emission control system of an engine generates a NO x Reduction control in which a post-injection is carried out to achieve a target air-fuel ratio at which NO x , which is in a NO x catalyst is stored, is reducible, based on an operating range of the engine.

[0010] This subject matter is achieved by the features of the independent claims. Further developments are defined in the dependent claims.

[0011] According to one aspect of the present invention, there is provided an exhaust emission control system for an engine having a NO x Catalyst which is arranged in an exhaust passage of the engine for storing NO x in the exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NO x when the air-fuel ratio is approximately stoichiometric or rich. The system includes a processor configured to generate a NO x Reduction control module or a NO x Reduction controlling or regulating module to be carried out when the stored amount of NO x in the NE xcatalyst exceeds a given determination quantity, a first NO x Reduction control in which a fuel injector performs a post-injection of fuel to continuously control the air-fuel ratio to a target air-fuel ratio such that the stored NO x is reduced and the stored amount of NO x falls below a given amount, the target air-fuel ratio being a ratio at which the stored NO x can be reduced, wherein the post-injection causes the injected fuel to burn inside a cylinder, wherein the implementation of the first NO x Reduction control is permitted when an engine load is in a medium load range.

[0012] With or with this configuration, since the first NO xReduction control is only carried out within the medium load range, suitable to prevent smoke and HC from being generated by the first NO x Reduction control is carried out outside the medium load range, and due to the combustion of the post-injected fuel in this NO x Reduction regulation or control.

[0013] For example, within a high-load range, smoke may be generated when the post-injected fuel is burned inside the cylinder. According to this configuration, since the first NO xReduction control within such a high-load range is prohibited, smoke generation is properly prevented. Within a low-load range, although the post-injected fuel cannot be properly burned and may generate HC, according to this configuration, since the first NO x Reduction control within such a low load range is prohibited or prevented, HC generation is appropriately prevented. In addition, within the low load range, although the reduction of NO x Catalyst not suitable due to low NO x catalyst temperature can be carried out, according to this configuration the first NO x Reduction regulation or control is prohibited in order to prevent unnecessary post-injection.

[0014] The NO x Reduction control module can carry out the first NO xAllow reduction control when an engine speed is within a medium speed range.

[0015] With or with this configuration, since the first NO x Reduction control is carried out within the medium speed range, suitable prevents smoke and HC from being generated, since the first NO x Reduction control outside the medium speed range and the combustion of the post-injected fuel in this NO x Reduction regulation or control can be carried out.

[0016] The NO x Reduction control module can control the first NO x Cancel reduction control when the engine load moves out of the medium load range and the first NO xReduction control or control will resume when the engine load enters the medium load range again, so that a stored amount of NO x falls below the given amount.

[0017] In this configuration, the execution of the first NO x Reduction regulation or control must be ensured appropriately so that the stored amount of NO x falls below the given amount.

[0018] If a temperature of the NO x catalyst is above a given value, the NO x Reduction control module extends the medium load range towards a higher load side by raising a load that defines a higher end of the medium load range.

[0019] With this configuration, if the NO x Catalyst temperature is comparatively high, a situation in which the first NOx Reduction regulation or control is interrupted and NO x from the NO x Catalyst is removed and released during the interruption.

[0020] If the stored amount of NO x is above a given value, the NO x Reduction control module extends the medium load range towards the higher load side by increasing the load value that defines the higher end of the medium load range.

[0021] With this configuration, if the stored amount of NO x is comparatively large, a situation in which the first NO x Reduction regulation or control is interrupted and thus NO x from the NO x Catalyst is removed and released during the interruption.

[0022] If the temperature of the NO xcatalyst is above a given value, the NO x Reduction control module may extend the medium speed range toward a higher speed side by increasing a speed value that defines a higher end of the medium speed range.

[0023] With this configuration, if the NO x Catalyst temperature is comparatively high, a situation in which the first NO x Reduction regulation or control is interrupted and NO x from the NO x Catalyst is removed and released during the interruption.

[0024] If the stored amount of NO x is above a given value, the NO xReduction control module extends the medium speed range to the higher speed side by increasing the speed value that defines the higher end of the medium speed range.

[0025] With this configuration, if the stored amount of NO x is comparatively large, a situation in which the first NO x Reduction regulation or control is interrupted and NO x from the NO x Catalyst is removed and released during the interruption.

[0026] If the stored amount of NO x in the NE x Catalyst is below the specified amount and the air-fuel ratio becomes rich due to acceleration of a vehicle, the NO x Reduction control module also has a second NO xReduction control in which the fuel injection device performs the post-injection to temporarily control the air-fuel ratio to the target air-fuel ratio so that the NO x , which is in the NO x catalyst is stored, wherein the post-injection causes the injected fuel to be discharged to the exhaust passage as unburned fuel without being burned inside the cylinder, wherein the performance of the second NO x Reduction control is only permitted when the engine load is within a high load range above the load defining the higher end of the medium load range.

[0027] With this configuration, within the high load range above the load that defines the higher end of the medium load range, the second NOx Reduction control in which the post-injected fuel is discharged as unburned fuel without being burned inside the cylinder is carried out. Thus, generation of smoke due to the fact that the post-injected fuel is burned within the high load range is suitably prevented, while execution of NO x Reduction regulation or control is ensured within the high load range.

[0028] The system further includes a selective catalytic reduction (SCR) catalyst installed in the exhaust passage for purifying NO x within the exhaust gas by causing a reaction with ammonia. The SCR catalyst cleans NO x within an engine operating range where the NO xReduction control module does not carry out the post-injection by the fuel injection device in order to reduce the stored NO x Within an area where the engine load is higher than an area where the SCR catalyst NO x cleans, the second NO x Reduction regulation or control is carried out.

[0029] With this configuration, within the area where the first and second NO x Reduction regulation or control is not carried out, NO x The exhaust gas is cleaned appropriately by the SCR catalyst, thus improving emissions performance.

[0030] According to a further aspect, a method for controlling an exhaust system of an engine is provided, comprising the steps of: Saving NO x in the exhaust gas in a NO xCatalyst which is arranged in an exhaust passage of the engine when an air-fuel ratio of the exhaust gas is lean, Cleaning NO x within the exhaust gas in a catalyst for selective catalytic reduction arranged in the exhaust passage by causing a reaction with ammonia, Reducing stored NO x when the air-fuel ratio is approximately stoichiometric or rich, and Carrying out a first NO x Reduction control in which a fuel injector performs a post-injection of fuel to continuously control the air-fuel ratio to a target air-fuel ratio such that the stored NO x is reduced and the stored amount of NO x falls below a given amount when the stored amount of NOx in the NE x catalyst exceeds a given determination quantity, wherein the target air-fuel ratio is a ratio at which the stored NO x can be reduced, whereby the post-injection causes the injected fuel to burn inside a cylinder, where the implementation of the first NO x Reduction control is permitted when an engine load is within a medium load range and / or within a medium speed range, Carrying out a second NO x Reduction control in which the fuel injection device performs the post-injection to temporarily control the air-fuel ratio to the target air-fuel ratio so that the NO x , which is in the NO xCatalyst is reduced when the stored amount of NO x in the NE x catalyst is below the specified amount and the air-fuel ratio becomes rich due to acceleration of a vehicle, wherein the post-injection causes the injected fuel to be discharged to the exhaust passage as unburned fuel without being burned inside the cylinder, wherein the performance of the second NO x Reduction control is only permitted when the engine load is within a high load range above a load that defines a higher end of the medium load range, where the SCR catalyst NO x within an engine operating range where the post-injection by the fuel system is not carried out to remove the stored NO x to reduce, where within a range where the engine load is higher than a range where the SCR catalyst NO x cleans, the second NO x Reduction regulation or control is carried out.

[0031] Preferably, the method further comprises the step of expanding the medium load range towards a higher load side by increasing a load value defining a higher end of the medium load range and / or expanding the medium speed range towards a higher speed side by increasing a speed value defining a higher end of the medium speed range when a temperature of the NO x catalyst is above a given value and / or if the stored amount of NO x is above a given value.

[0032] According to yet another aspect, a computer program product is provided which comprises computer-readable instructions which, when loaded onto and executed on a suitable system, perform or can perform the steps of any of the above-mentioned methods. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view illustrating a schematic configuration of an engine system to which an exhaust emission control system of an engine according to an embodiment of the present invention is applied. Fig. 2 is a block diagram illustrating an electrical configuration of the exhaust emission control system of the engine of the embodiment. Fig. Figure 3 is a diagram illustrating engine operating ranges within which passive DeNO x Regulation or control and an active DeNO xRegulation or control can be carried out in the respective embodiment. Fig. 4 is a view showing a method of expanding an active DeNO x Execution area illustrated in this embodiment. Fig. Figure 5 is a view of a temperature range where a DeNO x Regulation or control is carried out in the embodiment. Fig. 6 is a flowchart illustrating setting an execution flag of a passive DeNO x Regulation or control of the embodiment is illustrated. Fig. 7 is a flowchart showing the passive DeNO x Regulation or control of the embodiment is illustrated. Fig. 8 shows time charts illustrating a specific example of first post injection F / B control of the embodiment. Fig. 9 is a flowchart illustrating setting an execution flag of an active DeNO x Regulation or control of the embodiment is illustrated. Fig. 10 is a flowchart showing the active DeNO x Regulation or control of the embodiment is illustrated. Fig. 11 shows time charts illustrating a specific example of second post injection F / B control of the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENT

[0033] Hereinafter, an exhaust emission control system of an engine according to an embodiment of the present invention will be described with reference to the accompanying drawings. <systemkonfiguration>

[0034] First, an engine system to which the exhaust emission control system of the engine of this embodiment is applied will be described with reference to a schematic view of a configuration of the engine system in Fig. 1 described.

[0035] As this is Fig. 1, an engine system 200 mainly includes a diesel engine as an engine E, an intake system IN for supplying intake air to the engine E, a fuel supply system FS for supplying fuel to the engine E, an exhaust system EX for discharging exhaust gas from the engine E, sensors 100 to 103, 105, 106, and 108 to 119 for detecting various conditions related to the engine system 200, a PCM (Powertrain Control Module; Controller) 60 for controlling the engine system 200, and a DCU (Dosing Control Unit) 70 for executing control regarding a Selective Catalytic Reduction (SCR) catalyst 47.

[0036] First, the intake system IN includes an intake passage 1 through which intake air passes. In the intake passage 1, an air cleaner 3 for cleaning air introduced from the outside, a compressor of a turbocharger 5 for compressing intake air passing therethrough to increase a pressure of the intake air, an intercooler 8 for cooling the intake air with outside air or a coolant, an intake shutoff valve 7 (corresponding to a throttle valve) for adjusting a flow rate of intake air passing therethrough, and a surge tank 12 for temporarily storing intake air to be supplied to the engine E are provided in this order from the upstream side.

[0037] Furthermore, in the intake system IN, an air flow sensor 101 for detecting an intake air quantity and a temperature sensor 102 for detecting an intake air temperature are arranged in the intake passage 1 immediately downstream of the air cleaner 3. A pressure sensor 103 for detecting a pressure of the intake air is provided on the turbocharger 5. A temperature sensor 106 for detecting an intake air temperature is arranged in the intake passage 1 immediately downstream of the intercooler 8. A position sensor 105 for detecting an opening of the intake shutoff valve 7 is provided on the intake shutoff valve 7. A pressure sensor 108 for detecting a pressure of intake air in an intake manifold is provided on the surge tank 12.The various sensors 101 to 103, 105, 106 and 108 provided in the intake system IN output detection signals S101 to S103, S105, S106 and S108 to the PCM 60, respectively, corresponding to the detected parameters.

[0038] Next, the engine E includes an intake valve 15 for introducing the intake air supplied from the intake passage 1 (more specifically, the intake manifold) into a combustion chamber 17, a fuel injector 20 for injecting fuel to the combustion chamber 17, a glow plug 21 provided with a heat generating part 21a for generating heat upon energization, a piston 23 reciprocating due to combustion of an air-fuel mixture within the combustion chamber 17, a crankshaft 25 rotating due to the reciprocating movement of the piston 23, and an exhaust valve 27 discharging the exhaust gas generated by the combustion of the air-fuel mixture within the combustion chamber 17 to an exhaust passage 41.The engine E is also provided with a crankshaft angle sensor 100 for detecting a crankshaft angle, which is a rotation angle of the crankshaft 25 measured with reference to, for example, a top dead center. The crankshaft angle sensor 100 outputs a detection signal S100 corresponding to the detected crankshaft angle to the PCM 60, which obtains an engine speed based on the detection signal S100.

[0039] The fuel supply system FS includes a fuel tank 30 for storing fuel and a fuel supply passage 38 for supplying fuel from the fuel tank 30 to the fuel injector 20. A low-pressure fuel pump 31, a high-pressure fuel pump 33, and a common rail 35 are arranged in this order from the upstream side in the fuel supply passage 38.

[0040] Next, the exhaust system EX includes the exhaust passage 41 through which the exhaust gas passes. A turbine of the turbocharger 5 is arranged in the exhaust passage 41, which is rotated by the exhaust gas passing therethrough and drives the compressor through this rotation. Furthermore, the following components are arranged in the exhaust passage 41 on the downstream side of the turbine in the following order from the upstream side: a NO x Catalyst 45 for cleaning NO x within the exhaust gas; a diesel particulate filter (DPF) 46 for trapping particulate matter (PM) within the exhaust gas; a urea injector 51 for injecting urea into the exhaust passage 41 downstream of the DPF 46; the SCR catalyst 47 for generating ammonia by hydrolyzing urea injected by the urea injector 51 and purifying NO x by causing a reaction (reduction) of this ammonia with NO x within the exhaust gas; and a slip catalyst 48 for oxidizing unreacted ammonia discharged from the SCR catalyst 47 to purify it. Note that the urea injector 51 is controlled to inject urea into the exhaust passage 41 based on a control signal S51 supplied from the DCU 70.

[0041] Here the NO x Catalyst 45 is described in more detail. The NO x Catalyst 45 is a NO x Storage catalyst (NSC), which NO x which is contained in the exhaust gas when an air-fuel ratio of the exhaust gas is lean (i.e., λ>1, greater than a theoretical air-fuel ratio), and the stored NO x reduced when the air-fuel ratio is approximately equal to a stoichiometric one (i.e., λ≈1, approximately equal to the theoretical air-fuel ratio) or rich (i.e., λ<1, less than the theoretical air-fuel ratio). The NO x Catalyst 45 functions not only as the NSC, but also as a diesel oxidation catalyst (DOC), which oxidizes hydrocarbons (HC), carbon monoxide (CO), etc., using oxygen within the exhaust gas to convert them into water and carbon dioxide. For example, the NO x Catalyst 45 is produced by coating a surface of a catalyst material layer of a DOC with a catalyst material of an NSC.

[0042] Furthermore, in the exhaust system EX, a pressure sensor 109 for detecting a pressure of the exhaust gas and a temperature sensor 110 for detecting an exhaust gas temperature are arranged in the exhaust passage 41 upstream of the turbine of the turbocharger 5. An O2 sensor 111 for detecting an oxygen concentration within the exhaust gas is arranged in the exhaust passage 41 immediately downstream of the turbine of the turbocharger 5. Furthermore, the exhaust system EX includes a temperature sensor 112 for detecting an exhaust gas temperature at a position immediately downstream of the NO x catalyst 45, a temperature sensor 113 for detecting an exhaust gas temperature at a position between the NO x Catalyst 45 and the DPF 46, a pressure difference sensor 114 for detecting a pressure difference of exhaust gas between positions immediately upstream and downstream of the DPF 46, a temperature sensor 115 for detecting an exhaust gas temperature at a position immediately downstream of the DPF 46, a NO x Sensor 116 for detecting a concentration of NO x in the exhaust gas at a position immediately downstream of the DPF 46, a temperature sensor 117 for detecting an exhaust gas temperature at a position immediately upstream of the SCR catalyst 47, a NO x Sensor 118 for detecting a concentration of NO x within the exhaust gas at a position immediately downstream of the SCR catalyst 47, and a PM sensor 119 for detecting PM within the exhaust gas at a position immediately upstream of the slip catalyst 48. The various sensors 109 to 119 provided in the exhaust system EX output detection signals S109 to S119 corresponding to the detected parameters to the PCM 60, respectively.

[0043] In this embodiment, the turbocharger 5 is configured as a two-stage turbocharging system capable of obtaining high turbocharging performance in all ranges from low to high engine speed. The exhaust energy is low within the low engine speed range. That is, the turbocharger 5 includes a large turbocharger 5a for supercharging a large amount of air within a high engine speed range, a small turbocharger 5b capable of performing efficient turbocharging even with low exhaust energy, a compressor bypass valve 5c for controlling the flow of intake air to a compressor of the small turbocharger 5b, a regulating valve 5d for controlling the flow of exhaust gas to a turbine of the small turbocharger 5b, and a wastegate valve 5e for regulatingControlling the flow of exhaust gas to a turbine of the large turbocharger 5a. By driving each valve in accordance with the operating state of the engine E (engine speed and load), the actuated turbocharger is switched between the large turbocharger 5a and the small turbocharger 5b.

[0044] The engine system 200 of this embodiment also includes an exhaust gas recirculation (EGR) device 43. The EGR device 43 includes an EGR passage 43a connecting a position of the exhaust passage 41 upstream of the turbine of the turbocharger 5 with a position of the inlet passage 41 downstream of the compressor of the turbocharger 5 (more specifically, downstream of the intercooler 8), an EGR cooler 43b for cooling the exhaust gas passing through the EGR passage 43a, a first EGR valve 43c for adjusting a flow rate of the exhaust gas passing through the EGR passage 43a, an EGR cooler bypass passage 43d for causing the exhaust gas to bypass the EGR cooler 43b, and a second EGR valve 43e for adjusting a flow rate of the exhaust gas passing through the EGR cooler bypass passage 43d.

[0045] Next, an electrical configuration of the exhaust emission control system of the engine of the embodiment will be described with reference to Fig. 2 described.

[0046] Based on the detection signals S100 to S103, S105, S106, and S108 to S119 of the various sensors 100 to 103, 105, 106, and 108 to 119 described above, and detection signals S150 and S151 outputted by an accelerator opening sensor 150 for detecting a position of an accelerator pedal (accelerator opening) and a vehicle speed sensor 151 for detecting a vehicle speed, respectively, the PCM 60 of this embodiment outputs a control signal S20 for mainly controlling the fuel injector 20, a control signal S7 for controlling the intake shutoff valve 7, a control signal S21 for controlling the glow plug 21, and control signals S22 for controlling the intake shutoff valve 7. Control signals S431 and S432 for regulating and controlling the first and second EGR valves 43c and 43e.

[0047] In particular, in this embodiment, the PCM 60 performs a NO x Reduction control in which the fuel injector 20 is controlled to perform post-injection to control the air-fuel ratio of the exhaust gas to a target air-fuel ratio (specifically, a given air-fuel ratio approximately equal to or smaller than a theoretical air-fuel ratio) so that the NO x Catalyst 45 is regulated or controlled in order to remove NO x to reduce. In other words, the PCM 60 performs the post injection after a main injection. In the main injection, the fuel is injected into the cylinder (in the main injection, various adjustments, including a fuel injection amount, are typically performed to obtain a lean air-fuel ratio) to output engine torque according to an accelerator pedal operation by an operator of the vehicle. In the post injection, the fuel is injected at a timing such that the engine torque output is not affected (e.g., expansion stroke) in order to achieve λ≈1 or λ<1 and NO x which is present in the NO x Catalyst 45 is stored. In the following, such a regulation or control for reducing NO x , which is in the NO x Catalyst 45 is stored as “DeNO x Regulation or control". It should be noted that "De" in the word or designation "DeNO x " is an addition or prefix which signifies separation or removal.

[0048] The PCM 60 consists of a processor 60A (e.g., a CPU (central processing unit)), various programs interpreted and executed by the processor 60A (including a basic control program, such as an OS, and an application program activated on the OS and implementing a specific function), and internal memory, such as ROM(s) and / or RAM(s) for storing programs and various data. The processor 60A is configured to include at least one NO x Reduction control module 60B to perform a NO x To perform reduction control. This module is stored in the internal memory as one or more software programs. <Kraftstoffeinspritzungsregelung bzw. -steuerung>

[0049] Next, fuel injection control of this embodiment will be described. This fuel injection control is started when an ignition of the vehicle is turned on and the PCM 60 is supplied with power, and is repeatedly executed at a given cycle.

[0050] First, the PCM 60 obtains an operating state of the vehicle. For example, the PCM 60 obtains at least the accelerator opening detected by the accelerator opening sensor 150, the vehicle speed detected by the vehicle speed sensor 151, the crankshaft angle detected by the crankshaft angle sensor 100, and a gear range currently set in a transmission of the vehicle.

[0051] Next, the PCM 60 sets a target acceleration based on the obtained vehicle operation state. For example, the PCM 60 selects an acceleration characteristic map corresponding to the current vehicle speed and gear range from a plurality of acceleration characteristic maps (which are generated in advance and stored in memory) defined for different vehicle speeds and different gear ranges, and determines the target acceleration corresponding to the current accelerator opening by referring to the selected acceleration characteristic map.

[0052] Next, the PCM 60 determines a target torque of the motor E to achieve the specified target acceleration. In this case, the PCM 60 determines the target torque within a range of torque that the motor E can output based on the current vehicle speed, the gear range, a current road surface inclination, a road surface μ, etc.

[0053] Next, the PCM 60 calculates the fuel injection amount to be injected by the fuel injector 20 based on the target torque and the engine speed to output the determined target torque from the engine E. This fuel injection amount is applied in the main injection (amount of one main injection).

[0054] On the other hand, in parallel with the above processing, the PCM 60 sets a fuel injection pattern according to the operating state of the engine E. For example, when the above DeNO x When control is performed, the PCM 60 determines a fuel injection pattern in which at least the post injection is performed in addition to the main injection. In this case, the PCM 60 also determines the fuel injection amount applied in the post injection (post injection amount) and the timing to perform the post injection (post injection timing, etc.), the details of which will be described later.

[0055] Then, the PCM 60 controls the fuel injector 20 based on the calculated main injection amount and the set fuel injection pattern (including the post injection amount and the post injection timing in the case where the post injection is performed). In other words, the PCM 60 controls the fuel injector 20 such that a desired amount of fuel is injected in a desired fuel injection pattern.

[0056] Next, a method of calculating the post-injection amount used in the DeNO x Regulation or control (hereinafter referred to as “DeNO x post-injection amount") is applied in this embodiment. The PCM 60 repeatedly performs this process at a given cycle in parallel with the above fuel injection control process. In other words, the DeNO x Post-injection quantity is calculated if necessary during fuel injection control.

[0057] First, the PCM 60 obtains the operating state of the engine E. For example, the PCM 60 obtains at least the intake air amount (fresh air amount) detected by the airflow sensor 101, the oxygen concentration within the exhaust gas (exhaust oxygen concentration) detected by the O2 sensor 111, and the main injection amount calculated in the above fuel injection control. The PCM 60 also obtains an exhaust gas amount (EGR gas amount) recirculated to the intake system IN through the EGR device 43, which is obtained, for example, based on a given model.

[0058] Subsequently, the PCM 60 calculates an amount of air to be introduced into the engine E (i.e., charge amount) based on the received fresh air amount and the EGR gas amount. Furthermore, the PCM 60 calculates an oxygen concentration within the air introduced into the engine E based on the calculated charge amount.

[0059] Next, the PCM 60 calculates the post-injection quantity (DeNO x Post-injection quantity) required in the post-injection, which is performed in addition to the main injection, to regulate or control the air-fuel ratio to the target air-fuel ratio (the air-fuel ratio approximately equal to or less than the theoretical air-fuel ratio) in order to reduce the NO x which is present in the NO x Catalyst 45 is stored. In other words, the PCM 60 determines the post-injection amount required in addition to the main injection amount to bring the exhaust air-fuel ratio to the target air-fuel ratio. In this case, the PCM 60 calculates the DeNO x Post-injection amount taking into account the difference between the obtained oxygen concentration (the oxygen concentration detected by the O2 sensor 111) and the calculated oxygen concentration. For example, based on the air-fuel ratio of the exhaust gas generated when the fuel injected in the main injection is combusted, the PCM 60 appropriately performs feedback processing according to the difference between the detected oxygen concentration and the calculated oxygen concentration, and calculates the DeNO x Post-injection quantity for regulating or controlling the air-fuel ratio to the target air-fuel ratio. By calculating the DeNO x Post-injection amount, as described above, the air-fuel ratio of the exhaust gas is precisely adjusted to the target air-fuel ratio by the post-injection in the DeNO x Regulation or control regulated or controlled, and the NO x , which is in the NO x Catalyst 45 is stored and is safely reduced. <DeNO x Regulation or control>

[0060] The DeNO x Regulation or control of this embodiment is described in detail. (Basic concept)

[0061] First, a basic concept of DeNO x Regulation or control of this embodiment is described.

[0062] In this embodiment, when the stored amount of NO x in the NE x Catalyst 45 is above a given amount, typically when the stored amount of NO x approximately equal to a limit value (e.g. the capacity of the NO x Catalyst 45), the PCM 60 the DeNO x Control by which the fuel injection device 20 is controlled to perform the post-injection such that the air-fuel ratio is continuously controlled to the target air-fuel ratio in order to reduce the NO x , which is in the NO x catalyst 45 is stored, essentially to zero (can be used as “first NO x Regulation or control" or "active DeNO x regulation or control"). In this way, a large amount of NO x , which is in the NO x Catalyst 45 is stored, forcibly reduced and the NO x Cleaning performance of the NO x Catalyst 45 is or will be reliably ensured.

[0063] Even if the stored amount of NO x in the NE x Catalyst 45 is below the given amount, when the air-fuel ratio becomes rich due to acceleration of the vehicle, the PCM 60 performs a DeNO x Control in which the fuel injection device 20 is controlled to perform the post-injection to temporarily control the air-fuel ratio to the target air-fuel ratio to reduce NO x which is present in the NO x Catalyst 45 is stored (can be used as “second NO x Reduction control or control" or "passive DeNO x regulation or control"). In passive DeNO x In control, post-injection is performed to control the air-fuel ratio to the target air-fuel ratio approximately equal to or less than the theoretical air-fuel ratio in a situation where the air-fuel ratio decreases due to the increase in the main injection amount, for example, during vehicle acceleration. Therefore, the post-injection amount for controlling the air-fuel ratio to the target air-fuel ratio is smaller compared to a case of executing DeNO. x Control in a situation where the air-fuel ratio is not reduced (ie no acceleration). In addition, since the passive DeNO x If the control or regulation is carried out while the vehicle is accelerating, the frequency of executing this control or regulation is comparatively high.

[0064] In this embodiment, by applying such a passive DeNO x Regulation or control, DeNO x frequently performed, while an increase in fuel consumption due to DeNO x Although the passive DeNO x Control is only carried out for a comparatively short period of time, since it is carried out frequently, the stored amount of NO x in the NE x Catalyst 45 efficiently and effectively reduces the amount of NO stored. As a result, the amount of NO x in the NE x Catalyst 45 does not easily reach the given amount, which is why the execution frequency of the active DeNO x Regulation or control which uses a larger amount of post-injection than in the passive DeNO x Regulation or control requires, is or will be reduced, making it possible to effectively reduce the increase in fuel consumption due to DeNO x to prevent.

[0065] Furthermore, in this embodiment, when the above active DeNO x Control is performed, the fuel injected in the post-injection (hereinafter referred to as "post-injected fuel") is burned inside the cylinder of the engine E to control the air-fuel ratio to the target air-fuel ratio. Here, the PCM 60 performs the post-injection at a timing such that the post-injected fuel is burned inside the cylinder. For example, the PCM 60 sets a given timing in an early half of the expansion stroke of the engine E as the post-injection timing of the active DeNO x Regulation or control. By applying such a post-injection timing of the active DeNO x By controlling the injection or control it is possible to prevent the discharge of the post-injected fuel as unburned fuel (i.e. HC) or oil dilution due to the post-injected fuel.

[0066] On the other hand, in this embodiment, if the passive DeNO x Control is performed, the PCM 60 adjusts the air-fuel ratio to the target air-fuel ratio by discharging the post-injected fuel as unburned fuel into the exhaust passage 41 without burning it inside the cylinder of the engine E. In this case, the PCM 60 performs the post-injection at a timing such that the post-injected fuel is discharged from the cylinder to the exhaust passage 41 as unburned fuel. For example, the PCM 60 sets a given timing in a later half of the expansion stroke of the engine E as the post-injection timing of the passive DeNO x Regulation or control. The post-injection timing of this passive DeNO x Regulation or control is compared with the post-injection timing of the active DeNO x Regulation or control is in principle delayed. By applying such a post-injection timing of the passive DeNO x Regulation or control prevents the generation of smoke (soot) due to the post-injected fuel which is burned inside the cylinder.

[0067] Here, the operating ranges of the engine E, within which the passive DeNO x Regulation or control and the active DeNO x Regulation or control in the embodiment can be carried out with reference to Fig. 3, in which the horizontal axis shows the engine speed and the vertical axis shows the engine load. Furthermore, Fig. 3 the curve L1 represents a line of maximum torque of the motor E.

[0068] As this is Fig. 3, in this embodiment, the PCM 60 performs the active DeNO x Regulation or control by when the engine load is within a medium load range equal to or higher than a first load Lo1, but lower than a second load Lo2 (> first load Lo1) and the engine speed is within a medium speed range equal to or higher than a first speed N1, but lower than a second speed N2 (> first speed N1), ie the engine load and the engine speed are within an operating range indicated by R12 (hereinafter referred to as "active DeNO x Design area R12"). The active DeNO x Execution area R12 is applied for the following reason.

[0069] As described above, in the case of running the active DeNO x Control, with a view to preventing HC generation caused by the post-injected fuel being discharged as it is, oil dilution by the post-injected fuel, etc., the post-injection is performed at the time so that the fuel inside the cylinder is burned. In this case, in this embodiment, when the post-injected fuel is burned, the generation of smoke and also HC (i.e., discharge of unburned fuel due to incomplete combustion) is prevented. For example, the time for combustion of the post-injected fuel is extended as long as possible, i.e., ignition is effected in a state where air and fuel are properly mixed, so that the generation of smoke and HC is prevented. Therefore, in the active DeNO x Control or regulation introduces an appropriate amount of EGR gas in order to effectively delay the ignition of the post-injected fuel.

[0070] It should be noted that the reason for preventing HC generation during active DeNO x The control is to prevent that, in the case where the EGR gas is introduced as described above, HC also recirculates to the intake system IN as EGR gas and this HC serves as a binding agent to combine with soot and clog the gas passage. In addition, when the active DeNO x Regulation or control is carried out within an operating range within which the temperature of the NO x Catalyst 45 is low and HC purification performance (purification performance of HC due to DOC in the NO x Catalyst 45) is not ensured, the reduction of HC generation is carried out to prevent HC from being discharged untreated. The active DeNO x Design area R12 also includes an area where the temperature of the NO x Catalyst 45 is relatively low and therefore cannot ensure such HC purification performance.

[0071] The reason for preventing smoke generation in the active DeNO x Control is to prevent DPF regeneration for burning and removing PM corresponding to smoke trapped by the DPF 46 (control of performing post-injection similar to DeNO x regulation or control) is carried out frequently and fuel consumption increases.

[0072] Furthermore, when the engine load becomes high, since the air introduced into the engine E is reduced to achieve the target air-fuel ratio, the amount of oxygen required for proper combustion of the post-injected fuel becomes insufficient, and smoke and HC tend to be generated. In particular, as the engine load increases, the in-cylinder temperature rises, and the post-injected fuel is ignited without sufficient time from the post-injection of the fuel, i.e., combustion occurs before the air and fuel are properly mixed, causing the generation of smoke and HC. On the other hand, within an operating range where the engine load is quite low, the temperature of the NO x Catalyst 45 low and the NO x Catalyst 45 does not sufficiently remove the NO x reducing function. In addition, within this range, the post-injected fuel does not burn properly, meaning misfire occurs.

[0073] Although the above description describes the phenomenon related to the engine load, the same phenomenon occurs with or at the engine speed or rpm.

[0074] Thus, in this embodiment, the operating range of the engine E corresponding to the medium load range and the medium speed range is defined as the active DeNO x Execution area R12 applied, where the active DeNO x Regulation or control is carried out. In other words, in this embodiment, the active DeNO x Regulation or control only within the active DeNO x execution area R12 and is executed outside the active DeNO x Execution area R12 is prohibited. Within the operating area where the active DeNO x Regulation or control is prohibited, especially where the engine load or engine speed is higher than within the active DeNO x execution area R12 (the area to which the reference symbol "R13" is assigned), cleans, since the NO x Cleaning performance of the SCR catalyst 47 is sufficient, the SCR catalyst 47 NO x , and the application of NO x of the vehicle without performing the DeNO x Regulation or control is prevented.

[0075] Furthermore, in this embodiment, within a range where the engine load is higher than the range R13 where the SCR catalyst 47 NO x cleans (the area to which the reference symbol "R11" is assigned, hereinafter referred to as "passive DeNO x Design area R11"), since the amount of exhaust gas increases and the SCR catalyst 47 does not remove all NO x can clean, the passive DeNO x Control or regulation is carried out. In this passive DeNO x Control, as described above, the post-injection is performed at the time such that the post-injected fuel is discharged from the cylinder to the exhaust passage 41 as unburned fuel. Within the passive DeNO x R11 execution area cleans, since the temperature of the NO x Catalyst 45 is sufficiently high and a suitable cleaning performance of HC (HC cleaning performance of the DOC in the NO x Catalyst 45) ensures that the NO x Catalyst 45 properly or accordingly the unburned fuel, which is discharged as described above.

[0076] It should be noted that if the post-injected fuel is stored inside the cylinder in the passive DeNO x Regulation or control as in the active DeNO x Regulation or control is burned, smoke is produced or generated. The reason for this is similar to the reason for prohibiting the execution of the active DeNO x Control when the engine load becomes high. Therefore, in passive DeNO x Controlling the post-injected fuel from the cylinder to the exhaust passage 41 as unburned fuel.

[0077] Here is a specific example of active DeNO x Regulation or control when the operating state of the engine changes, as indicated by the arrow A11 in Fig. 4 is shown or indicated. First, when the engine operating state changes to active DeNO x Execution area R12 (see the area designated by reference symbol A12), the PCM 60 activates the active DeNO x Regulation or control. Then, when the operating state of the engine changes from the active DeNO x Execution area R12 (see the area designated by reference symbol A13), the PCM 60 activates the active DeNO x Regulation or control and the SCR catalyst 47 cleans NO x . When the engine operating state returns to active DeNO x Execution area R12 (see the area designated by reference symbol A14), the PCM 60 takes the active DeNO x Regulation or control again. In this way, the active DeNO x Regulation or control carried out until NO x , which is in the NO x Catalyst 45 is stored, drops almost to zero.

[0078] Next, a process of expanding the active DeNO x Exercise or execution area R12 in this embodiment with reference to Fig. 4 described. Fig. 4 is a similar view to Fig. 3 and elements which have the same reference numerals as in Fig. 3 have the same meaning as those elements in Fig. 3 on.

[0079] As this is Fig. 4, in this embodiment, when the temperature of the NO x Catalyst 45 is above a given temperature and / or if the stored amount of NO x of the NO x Catalyst 45 is above a given amount, the active DeNO x Execution area R12 is extended to the area designated by the reference symbol R12'. For example, the active DeNO x Execution range R12 is expanded to the higher load side and the higher speed side by increasing a second given load Lo2, which defines the medium load range (see reference symbol Lo2'), and also by increasing a second given engine speed N2, which defines the medium speed range (see reference symbol N2'). In this way, it is prevented that in a situation where the temperature of the NO x Catalyst 45 is comparatively high and / or the stored amount of NO x in the NE x Catalyst 45 is comparatively large, the active DeNO x Regulation or control is interrupted and thus NO x from the NO x Catalyst 45 is removed and released. For example, when the engine operating condition changes, as indicated by arrow A11, the active DeNO x Regulation or control interrupted when the active DeNO x Execution area R12 is not or will not be extended, as in Fig. 3. By expanding the active DeNO x execution area R12 to the higher load side and the higher speed side, as shown in Fig. 4, the active DeNO x Regulation or control is carried out continuously without interruption.

[0080] Next, temperature ranges within which the passive DeNO x Regulation or control and the active DeNO x Regulation or control in the embodiment can be carried out with reference to Fig. 5, which illustrates a relationship between the catalyst temperature (horizontal axis) and an exhaust gas purification rate (vertical axis).

[0081] Specifically, graph G11 shows the relationship between the temperature of the NO x Catalyst 45 (hereinafter referred to as “NO x catalyst temperature") and a NO x NO purification rate x catalyst 45. The graph G12 shows the relationship between the temperature of the SCR catalyst 47 (hereinafter referred to as "SCR temperature") and a NO x cleaning rate of the SCR catalyst 47. The area indicated or designated by the reference symbol R21 designates a temperature range where a higher NO x Cleaning rate as a given value by the NO x Catalyst 45 according to NO x Cleaning characteristics of NO x catalyst 45, which is illustrated in the graph G11. The area designated by the reference symbol R22 denotes a temperature range where a higher NO x Purification rate as a given value by the SCR catalyst 47 according to the NO x Cleaning characteristics of the SCR catalyst 47 are available, which are illustrated in the graph G12. The latter temperature range R22 is defined by a temperature T11 of the SCR catalyst 47. This temperature T11 lies at least within an active temperature range of the SCR catalyst 47 and corresponds, for example, to a lowest value within the temperature range R22 where the NO x A purification rate higher than the given value is achievable by the SCR catalyst 47. Hereinafter, the temperature T11 is appropriately referred to as the "SCR determination temperature."

[0082] As this is Fig. 5, the NO x Catalyst 45 a high NO x cleaning performance within a comparatively low temperature range, and the SCR catalyst 47 performs a high NO x cleaning performance within a comparatively high temperature range. Therefore, NO x in the exhaust gas preferably by the NO x Catalyst 45 cleaned when the temperature of the exhaust gas is comparatively low, and preferably by the SCR catalyst 47 cleaned when the temperature of the exhaust gas is comparatively high.

[0083] In this embodiment, the PCM 60 performs the passive DeNO x Regulation or control and the active DeNO x Control only takes place if the SCR temperature is below the SCR determination temperature T11. If the SCR temperature is above the SCR determination temperature T11, the passive DeNO x Regulation or control and the active DeNO x Regulation or control is prohibited or prevented. The reason for the ban is that, since the SCR catalyst 47 is suitable for NO x in the exhaust gas cleans when the SCR temperature is above the SCR determination temperature T11, the DeNO x Regulation or control is not particularly needed to control the NO x Cleaning performance of the NO x catalyst 45. Therefore, in this embodiment, when the SCR temperature is above the SCR determination temperature T11, an execution of the DeNO x Regulation or control is prohibited in order to prevent an increase in fuel consumption.

[0084] The following describes the passive DeNO x Regulation or control and the active DeNO x Regulation or control of this embodiment is described in detail. (Passive DeNO x Regulation or control)

[0085] The passive DeNO x Control of this embodiment will be specifically described.

[0086] First, an execution flag of the passive DeNO is set or specified. x Regulation or control which is used to determine whether the passive DeNO x Control is to be carried out in this embodiment, with reference to the flowchart (Setting process of the execution flag of the passive DeNO x Regulation or control) of Fig. 6. The PCM 60 repeatedly performs this setting or setting process of the passive DeNO execution flag x Control at a given cycle in parallel with the control of fuel injection and the calculation of DeNO x Post-injection quantity out or through.

[0087] First, at S301, the PCM 60 receives various information from the vehicle. For example, the PCM 60 receives at least one NO x Catalyst temperature, SCR temperature, target torque, which is determined in the fuel injection control system, DeNO x Post-injection quantity used in the calculation of the DeNO x post-injection quantity is calculated, the stored amount of NO x in the NE x Catalyst 45 and a value of an execution flag of the active DeNO x Control which is used to determine whether the active DeNO x Regulation or control is to be carried out. Here the NO x Catalyst temperature is estimated or assessed, for example, based on the temperature detected by the temperature sensor 112, which is located immediately upstream of the NO x Catalyst 45 is arranged (the temperature which is detected by the temperature sensor 113 which is arranged between the NO x catalyst 45 and the DPF 46 may also be used). The SCR temperature is estimated based on, for example, the temperature detected by the temperature sensor 117, which is arranged immediately upstream of the SCR catalyst 47. The stored amount of NO x is determined by estimating the amount of NO x within the exhaust gas based on the operating state of the engine E, the flow rate of the exhaust gas, the temperature of the exhaust gas, etc. and by integrating the NO x Quantities received. The execution flag of the active DeNO x Regulation or control is carried out by a setting process of the execution flag of the active DeNO x Regulation or control is set or determined, which is described later (see Fig. 9).

[0088] In S301, the PCM 60 also receives the execution frequency of the passive DeNO x Control within a given period. For example, the PCM 60 receives the number of times for which the passive DeNO x Control is executed within a given period (e.g. a few seconds or a few minutes) as the execution frequency of the passive DeNO x Regulation or control.

[0089] Next, at S302, the PCM 60 determines whether the SCR temperature obtained at S301 is below an SCR determination temperature T11. If the SCR temperature is below the SCR determination temperature T11 (S302: YES), the process proceeds to S303. On the other hand, if the SCR temperature is above the SCR determination temperature T11 (S302: NO), the process proceeds to S309. In this case, the PCM 60 sets the passive DeNO execution flag. x Regulation or control to "0" in order to execute the passive DeNO x Regulation or control is prohibited (S309), since the NO x in which exhaust gas is suitably cleaned by the SCR catalyst 47. Then the process ends.

[0090] It should be noted that at S302, whether the exhaust gas flow rate is above a given amount may be determined in addition to whether the SCR temperature is below the SCR determination temperature T11. In this case, even if the SCR temperature is above the SCR determination temperature T11, as long as the exhaust gas flow rate is determined to be above the given amount, the passive DeNO execution flag will be x Regulation or control preferably not set to "0". The reason for this is to ensure the passive DeNO x to carry out regulation or control and the NO x Cleaning performance of the NO x Catalyst 45 taking into account that the NO x Cleaning rate of the SCR catalyst 47 decreases when or as the exhaust gas quantity increases.

[0091] At S303, the PCM 60 determines whether the target torque obtained at S301 is above a given torque. This determination is equivalent to determining whether the air-fuel ratio, when the fuel corresponding to the target torque is injected, falls below a given value on the rich side. In other words, it is equivalent to determining whether the current operating state is an operating state where passive DeNO x Control is executable while preventing the increase in fuel consumption (given acceleration condition). If the target torque is higher than the given torque (S303: YES), the process proceeds to S304. On the other hand, if the target torque is lower than the given torque (S303: NO), the process proceeds to S309. In this case, the PCM 60 sets the passive DeNO execution flag. x Regulation or control to "0" in order to execute the passive DeNO x To prohibit regulation and prevent an increase in fuel consumption (S309). Then the process ends.

[0092] At S304, the PCM 60 determines whether the execution frequency of the passive DeNO x Control obtained at S301 is below a given frequency determination value. If this execution frequency is below the frequency determination value (S304: YES), the process proceeds to S305. On the other hand, if the execution frequency is above the frequency determination value (S304: NO), the process proceeds to S309. In this case, the PCM 60 sets the passive DeNO execution flag. x Regulation or control to "0" in order to execute the passive DeNO x To prohibit regulation or control (S309).

[0093] If the passive DeNO x Control is carried out in a situation where the passive DeNO x Control has been executed comparatively frequently, there is a high possibility that oil dilution occurs due to the post-injection. Therefore, in this embodiment, when the execution frequency of the passive DeNO x Regulation or control is above the frequency determination value (S304: NO), an execution of the passive DeNO x Regulation or control prohibited in order to avoid oil dilution due to the post-injection of the passive DeNO x On the other hand, even if the passive DeNO x Control is carried out in a situation where the passive DeNO x Regulation or control was hardly carried out (ie the exercise frequency of the passive DeNO x control is comparatively low), the possibility of oil dilution due to post-injection is low. Therefore, in this embodiment, when the execution frequency of the passive DeNO x Regulation or control is lower than the frequency determination value (S304: YES), an execution of the passive DeNO x Regulation or control permitted.

[0094] Next, at S305, the PCM 60 determines whether the stored amount of NO x , which is obtained at S301, is above a first stored quantity determination value. For example, the first stored quantity determination value is set to a value which is approximately one half of the limit value of the storable amount of NO x As a result of this determination, if the stored amount of NO x is above the first determination value of the stored amount (S305: YES), the process proceeds to S306. On the other hand, if the stored amount of NO x is lower than the first determination value of the stored quantity (S305: NO), the process goes to S309. In this case, the PCM 60 sets the passive DeNO execution flag x Regulation or control to "0" to avoid unnecessary execution of the passive DeNO x To prohibit regulation and prevent an increase in fuel consumption (S309). Then the process ends.

[0095] At S306, the PCM 60 determines whether the execution flag of the active DeNO x control obtained at S301 is "0". In other words, the PCM 60 determines whether the active DeNO x Regulation or control is to be executed. If the execution flag of the active DeNO x Control is "0" (S306: YES), the process goes to S307. On the other hand, if the execution flag of the active DeNO x control is not "0", ie if it is "1" (S306: NO), the process goes to S309. In this case, the PCM 60 sets the execution flag of the passive DeNO x Regulation or control to "0" in order to execute the passive DeNO x To prohibit regulation or control and preferably to use the active DeNO x control (S309). In other words, even if the execution condition of the passive DeNO x Regulation or control is fulfilled if the execution condition of the active DeNO x Regulation or control is fulfilled, the active DeNO x Regulation or control is preferably carried out. Then the process ends.

[0096] At S307, the PCM 60 determines whether the DeNO x Post-injection amount obtained at S301 is smaller than a first determination value of the post-injection amount. If the DeNO x If the post-injection amount is smaller than the first post-injection amount determination value (S307: YES), the process proceeds to S308. Typically, this condition is met at S307 when the vehicle is accelerating (more specifically, a prerequisite for meeting this condition is that the vehicle is accelerating). In this case, since all of the conditions in S302 to S307 are met, the PCM 60 sets the passive DeNO execution flag. x Regulation or control to "1" to execute the passive DeNO x to allow regulation or control (S308). Then the process ends. On the other hand, if the DeNO x Post-injection amount is above the first determination value of the post-injection amount (S307: NO), the process proceeds to S309. In this case, since the post-injection is performed with a comparatively large amount of fuel and there is a high possibility of oil dilution, the PCM 60 sets the passive DeNO execution flag. x Regulation or control to "0" in order to execute the passive DeNO x To prohibit regulation and prevent oil dilution (S309). Then the process ends.

[0097] It should be noted that, in one example, the first determination value of the post-injection amount used in the determination of S307 is preferably set with reference to a post-injection amount that is likely to cause oil dilution. In another example, the first determination value of the post-injection amount may be set with consideration of preventing, in addition to oil dilution, the increase in fuel consumption caused by execution of the passive DeNO x In such a case, it is necessary to determine whether the DeNO x Post-injection amount is below the first determination value of the post-injection amount, at S307 is equivalent to determining whether the air-fuel ratio when the amount of fuel corresponding to the target torque is injected falls below the given value. In other words, it is essentially the same as determining whether the target torque obtained above is the given torque at S303. Therefore, since the determination at S303 and the determination at S307 are redundant, the passive DeNO execution flag x Regulation or control can be set, for example, by carrying out the determination at S307 without carrying out the determination at S303.

[0098] Furthermore, the first determination value of the post-injection amount is not limited to being a fixed value and can be changed according to an in-cylinder temperature. For example, the first determination value of a post-injection amount can be increased as the in-cylinder temperature increases. Since evaporation of the post-injected fuel progresses and oil dilution is less likely to occur as the in-cylinder temperature increases, the restriction on DeNO x Post-injection quantity when performing passive DeNO x Regulation or control should be relaxed, ie an upper limit of the DeNO x Post-injection quantity can be increased.

[0099] Next, the passive DeNO x Control of this embodiment, which is based on the execution flag of the passive DeNO x Control is carried out, which is set as described above, with reference to the flowchart (process of passive DeNO x Regulation or control) of Fig. 7. The PCM 60 repeatedly performs this process of passive DeNO x Control at a given cycle in parallel with the control of fuel injection, the calculation of DeNO x Post-injection quantity and the setting process of the passive DeNO execution flag x Regulation or control by which in Fig. 6 is illustrated.

[0100] First, at S401, the PCM 60 receives various information from the vehicle. For example, the PCM 60 receives at least the DeNO x Post-injection quantity used in the calculation of the DeNO x post-injection quantity is calculated, and the value of the execution flag of the passive DeNO x Control or control, which in the setting process of the execution flag of the passive DeNO x Regulation or control is set, which is in Fig. 6 is illustrated.

[0101] Next, at S402, the PCM 60 determines whether the passive DeNO execution flag x control obtained at S401 is "1". In other words, the PCM 60 determines whether the passive DeNO x Control is to be executed. If the execution flag of the passive DeNO x Control is "1" (S402: YES), the process goes to S403. On the other hand, if the execution flag of the passive DeNO x Regulation or control is "0" (S402: NO), the process ends without the passive DeNO x To carry out regulation or control.

[0102] At S403, the PCM 60 sets the timing of the post-injection, which in the passive DeNO x Regulation or control is applied. The procedure for this setting or adjustment is described in detail.

[0103] As described above, in this embodiment, when performing the passive DeNO x Control with a view to preventing smoke generation due to combustion of the post-injected fuel, the air-fuel ratio is controlled to the target air-fuel ratio by discharging the post-injected fuel to the exhaust passage 41 as unburned fuel. In order to discharge the post-injected fuel as unburned fuel, the post-injection may be performed at a comparatively retarded timing in the expansion stroke. However, if the post-injection timing is excessively retarded, oil dilution occurs due to the post-injection. Therefore, in this embodiment, with a view to preventing smoke generation and oil dilution, a suitable timing in the latter half of the expansion stroke is typically selected as the post-injection timing of the passive DeNO. x Control is applied. In this embodiment, the more the in-cylinder temperature rises, the more the post-injection timing is retarded, at least in the latter half of the expansion stroke. This is because, as the in-cylinder temperature rises, even if the post-injection timing is retarded, vaporization of the post-injected fuel progresses, and oil dilution becomes less likely to occur.

[0104] It should be noted that since it is difficult to detect the in-cylinder temperature with a sensor or estimate it with high accuracy, the PCM 60 can set the post-injection timing by using various indices that reflect the in-cylinder temperature. For example, the PCM 60 sets the post-injection timing based on the engine water temperature and / or the intake air temperature. In this example, the PCM 60 retards the post-injection timing when the engine water temperature rises or retards the post-injection timing when the intake air temperature rises.

[0105] Although in the above description the post injection timing is changed according to the in-cylinder temperature, in another example the post injection timing does not need to be changed according to the in-cylinder temperature, etc., and a fixed value for the post injection timing may be applied (ie, a fixed timing in the later half of the expansion stroke).

[0106] Next, at S404, the PCM 60 controls the fuel injector 20 to adjust the DeNO x Post-injection amount obtained at S401 at the post-injection timing set at S403 to control the air-fuel ratio to the target air-fuel ratio and to reduce the NO x which is present in the NO x Catalyst 45 is stored. For example, due to changes in detections of the various sensors, changes in the fuel injection amount of the fuel injector 20, etc., based on the air-fuel ratio corresponding to the detection value of the O2 sensor 111 arranged in the exhaust passage 41 (actual air-fuel ratio) and the target air-fuel ratio, the PCM 60 performs F / B (feedback) control of the post-injection amount injected from the fuel injector 20 to match the actual air-fuel ratio with the target air-fuel ratio. Subsequently, the F / B control of the fuel injection amount used in the passive DeNO x Control is executed is appropriately referred to as "first post-injection F / B control". Although in this first post-injection F / B control, F / F control (feed-forward control) is preferably executed in addition to the F / B control, since the F / B control is mainly executed, the term "F / B control" is used for the sake of simplicity.

[0107] More specifically, the PCM 60 first sets a comparatively low air-fuel ratio (comparatively rich air-fuel ratio) as a target value and executes the F / F control of the post-injection amount from the fuel injector 20. Then, the PCM 60 executes the F / B control of the post-injection amount from the fuel injector 20 by using a comparatively large F / B slope based on the actual air-fuel ratio and the target air-fuel ratio. In this way, the actual air-fuel ratio is caused to quickly match the target air-fuel ratio in the passive DeNO x Regulation or control which is carried out for a comparatively short period of time.

[0108] It should be noted that in practice, the PCM 60 performs the processing of S404 in the fuel injection control.

[0109] Next, at S405, the PCM 60 determines whether the passive DeNO execution flag x Regulation or control is "0". In other words, the PCM 60 determines whether the passive DeNO x Regulation or control is to be terminated. If the execution flag of the passive DeNO x control is "0" (S405: YES), the process ends. In this case, the PCM 60 ends the passive DeNO x Regulation or control. On the other hand, if the execution flag of the passive DeNO x Regulation or control is not "0" (S405: NO), ie if the execution flag of the passive DeNO x control is maintained at "1", the process returns to S403 to execute the process of S403 again. In this way, the PCM 60 resets the passive DeNO x Regulation or control continues. In other words, the PCM 60 continues the passive DeNO x Control continues until the execution flag of the passive DeNO x Regulation or control of 11 1 11 switches to "0".

[0110] Next, a specific example of the first post-injection F / B control used in the passive DeNO x Control of this embodiment is carried out with reference to the timing charts of Fig. 8 described. Fig. 8 shows the execution flag of the passive DeNO x Control, the post-injection quantity and the current or actual air-fuel ratio (λ) in this order from the top.

[0111] As this is Fig. 8, starts when the exercise or execution flag of the passive DeNO x regulation or control is switched from "0" to "1", the PCM 60 the passive DeNO x Control in which the fuel injection valve 20 is controlled to perform the post-injection to control the actual air-fuel ratio to the target air-fuel ratio to produce NO x , which is in the NO x catalyst 45 is stored. For example, the PCM 60 performs the first post-injection F / B control such that the actual air-fuel ratio promptly agrees with the target air-fuel ratio based on the actual air-fuel ratio and the target air-fuel ratio. More specifically, the PCM 60 first sets a comparatively small air-fuel ratio (comparatively rich air-fuel ratio) as a target value and performs F / F control of the post-injection amount from the fuel injector 20 (see the arrow A21). As a result, the post-injection amount sharply increases, and the actual air-fuel ratio rapidly changes to the richer side. Then, the PCM 60 performs the F / B control.Control (see arrow A22) the post-injection amount from the fuel injector 20 by using a comparatively large F / B gain based on the actual air-fuel ratio and the target air-fuel ratio. In this way, the actual air-fuel ratio agrees with the target air-fuel ratio once the actual air-fuel ratio becomes richer than the target air-fuel ratio, that is, the actual air-fuel ratio temporarily falls below the target air-fuel ratio (see arrow A23) due to the large change in the post-injection amount.

[0112] As described above, in this embodiment, by performing the first post-injection F / B control in the passive DeNO x The post-injection amount is greatly changed during control so that the actual air-fuel ratio quickly matches the target air-fuel ratio. In this way, the actual air-fuel ratio is immediately controlled to the target air-fuel ratio in a short period of time during which the passive DeNO x Regulation or control is carried out so that NO x , which is in the NO x Catalyst 45 is stored, is safely reduced.

[0113] It should be noted that although the amount of unburned fuel discharged from the engine E to the exhaust passage 41 increases when the actual air-fuel ratio falls below the target air-fuel ratio as described above, this does not particularly cause a problem because in the passive DeNO x Regulation or control of sufficient HC cleaning performance of the NO x Catalyst 45 (HC cleaning performance of DOC in the NO x Catalyst 45) is ensured and also the execution period of the passive DeNO x Regulation or control is relatively short, and thus the NO x Catalyst 45 is suitable for cleaning the unburned fuel, which is discharged as described above. (Active DeNO x Regulation or control)

[0114] Next, the active DeNO x Regulation or control according to this embodiment is specifically described.

[0115] First, the execution flag of the active DeNO is set. x Control which is used to determine whether the active DeNO x Control of the embodiment is to be carried out, with reference to the flowchart (setting process of the execution flag of the active DeNO x Regulation or control) of Fig. 9. The PCM 60 repeatedly performs this process of setting the execution flag of the active DeNO x Control at a given cycle in parallel with the fuel injection control, the calculation of the DeNO x Post-injection quantity, the setting process of the passive DeNO execution flag x Regulation or control, which in Fig. 6 is illustrated, etc.

[0116] First, at S501, the PCM 60 receives various information from the vehicle. For example, the PCM 60 receives at least the NO x Catalyst temperature, SCR temperature and the stored amount of NO x in the NE x Catalyst 45. It should be noted that the processes for obtaining the NO x Catalyst temperature, SCR temperature and the amount of NO stored x for S301 in the above section of the “passive DeNO x Regulation or control".

[0117] Next, at S502, the PCM 60 determines whether the SCR temperature obtained at S501 is below the SCR determination temperature T11. If the SCR temperature is below the SCR determination temperature T11 (S502: YES), the process proceeds to S503. On the other hand, if the SCR temperature is above the SCR determination temperature T11 (S502: NO), the process proceeds to S509. In this case, since the SCR catalyst 47 is suitable for NO x in the exhaust gas cleans, the PCM 60 sets the execution flag of the active DeNO x Regulation or control to "0" in order to execute the active DeNO x To prohibit regulation or control (S509). Then the process ends.

[0118] At S503, the PCM 60 determines whether the NO x Catalyst temperature, which is obtained at S501, is above a given temperature. If the NO x Catalyst temperature is low, even if the air-fuel ratio is controlled to the target air-fuel ratio, the NO x Catalyst 45 hardly stores the NO x Therefore, at S503 it is determined whether the NO x Catalyst 45 stored NO x The given temperature used in the determination of S503 is determined based on the NO x Catalyst temperature at which the NO x , which is in the NO x Catalyst 45 is stored, can be reduced. If the NO x If the catalyst temperature is above the given temperature (S503: YES), the process proceeds to S504. On the other hand, if the NO x catalyst temperature is below the given temperature (S503: NO), the process goes to S509. In this case, the PCM 60 sets the active DeNO execution flag x Regulation or control to "0" in order to execute the active DeNO x To prohibit regulation or control (S509).

[0119] At S504, the PCM 60 determines whether the active DeNO x The control itself has been executed only once after an engine start. The determination of S504 is carried out so that when the active DeNO x Regulation or control was not carried out after the engine start, the execution condition of the active DeNO x Regulation or control is relaxed compared to the case where the active DeNO x Regulation or control was carried out to preferentially the active DeNO x For example, if the active DeNO x Control has been executed (S504: NO), the execution condition of S507 and the execution condition of S508, which are comparatively strict, are used, while when the active DeNO x control has not been executed, only the execution condition of S505, which is comparatively loose, is used (these will be described in detail later). If the active DeNO x If the control has not been executed (S504: YES), the process goes to S505.

[0120] At S505, the PCM 60 determines whether the stored amount of NO x , which is obtained at S501, is above a second stored quantity determination value or a second stored quantity determination value. For example, the second stored quantity determination value is set to a value slightly lower than the limit value of the stored quantity of NO x set or fixed. If the stored amount of NO x is above the second determination value of a stored quantity (S505: YES), the process proceeds to S506. In this case, the PCM 60 sets the execution flag of the active DeNO x Regulation or control to "1" in order to execute the active DeNO x to allow regulation or control (S506). In this way, by executing the active DeNO x Regulation or control after the engine start, for example to force the NO x which is present in the NO x Catalyst 45 is stored, the NO x Cleaning performance of the NO x Catalyst 45 reliably ensures this. On the other hand, if the stored amount of NO x is smaller than the second determination value of the stored quantity (S505: NO), the process goes to S509. In this case, the PCM 60 sets the execution flag of the active DeNO x Regulation or control to "0" to avoid unnecessary execution of the active DeNO x To prohibit regulation or control (S509). Then the process ends.

[0121] On the other hand, if the active DeNO x Control has been executed after the engine start (S504: NO), the process goes to S507, where the PCM 60 determines whether the stored amount of NO x obtained at S501 is above a third stored amount determination value (a value greater than the second stored amount determination value). For example, the third stored amount determination value is set to a value close to the limit value of the stored amount of NO x set or fixed. If the stored amount of NO x is above the third determination value of the stored amount (S507: YES), the process proceeds to S508. On the other hand, if the stored amount of NO x is smaller than the third determination value of the stored quantity (S507: NO), the process goes to S509. In this case, the PCM 60 sets the execution flag of the active DeNO x Regulation or control to "0" to avoid unnecessary execution of the active DeNO x To prohibit regulation or control (S509). Then the process ends.

[0122] At S508, the PCM 60 determines whether a travel distance of the vehicle from the previous execution time of the active DeNO x Control is longer than a given destination distance. If this travel distance is longer than the destination distance (S508: YES), the process proceeds to S506. In this case, the PCM 60 sets the active DeNO execution flag. x Regulation or control to "1" in order to execute the active DeNO x to allow regulation or control (S506). By doing this, the active DeNO x Control or regulation is carried out to force a large amount of NO x which is present in the NO x Catalyst 45 is stored so that the NO x Cleaning performance of the NO x catalyst 45 is reliably ensured. On the other hand, if the travel distance is less than the determination distance (S508: NO), the process proceeds to S509. In this case, the PCM 60 sets the active DeNO execution flag. x Regulation or control to "0" in order to execute the active DeNO x To prohibit regulation or control (S509). Then the process ends.

[0123] If the active DeNO x Control is carried out in a situation where the travel distance from the previous execution time of the active DeNO x Regulation or control is short (ie the execution interval of the active DeNO x control is short), the possibility of oil dilution due to the occurrence of post-injection becomes high. Therefore, in this embodiment, if this travel distance is shorter than the determination distance (S508: NO), execution of the active DeNO x Regulation or control is prohibited and the oil dilution due to the post-injection in the active DeNO x Regulation or control is prevented. On the other hand, if the travel distance from the previous execution time of the active DeNO x Regulation or control is long (ie the execution interval of the active DeNO x regulation or control is long), even if the active DeNO x Control is to be performed, the possibility of oil dilution due to post-injection is low. Therefore, in this embodiment, when the travel distance from the previous execution time of the active DeNO x Regulation or control is longer than the determination distance (S508: YES), an execution of the active DeNO x Regulation or control permitted.

[0124] Next, the active DeNO x Regulation or control of this embodiment, which is based on the execution flag of the active DeNO x Control is carried out, which is set as described above, with reference to the flowchart (process of active DeNO x Regulation or control) of Fig. 10. The PCM 60 repeatedly performs this process of active DeNO x Control at a given cycle in parallel with the fuel injection control, the calculation of the DeNO x Post-injection quantity and the setting process of the execution flag of the active DeNO x Regulation or control, which in Fig. 9 is illustrated.

[0125] In the process of active DeNO x In this embodiment, the control of the glow plug 21 (glow control) and the control of the EGR gas (EGR control) are carried out in parallel with the fuel injection control in the active DeNO x Control (the fuel injection control for performing the post-injection to control the air-fuel ratio to the target air-fuel ratio) is performed. Glow control is performed to operate the glow plug 21 in the active DeNO x to excite or supply energy to the control system in order to ensure the ignitability of the post-injected fuel in the active DeNO x Control by the heat of the glow plug 21. The EGR control is carried out to maintain a suitable amount of EGR gas in the active DeNO x Control to recirculate the fuel to delay the ignition of the post-injected fuel, thus ensuring the combustion stability of the post-injected fuel and preventing smoke generation. In this embodiment, the fuel injection control in the active DeNO x Control is started after the state of the glow plug 21 and the state of the EGR gas are stabilized by the glow control and the EGR control, respectively.

[0126] The process of active DeNO x Regulation or control in Fig. 10 is described in detail. First, at S601, the PCM 60 receives various information from the vehicle. For example, the PCM 60 receives at least the engine load, the engine speed or rpm, the NO x Catalyst temperature, the DeNO x Post-injection quantity used in the calculation of the DeNO x post-injection quantity is calculated, and the value of the execution flag of the active DeNO x Regulation or control, which in the setting process of the execution flag of the active DeNO x Regulation or control is determined or set, which in Fig. 9. In addition, the PCM 60 receives an oxygen concentration inside the cylinder (in-cylinder oxygen concentration), which is obtained by estimation.

[0127] Next, at S602, the PCM 60 determines whether the execution flag of the active DeNO x control obtained at S601 is "1". In other words, the PCM 60 determines whether the active DeNO x Regulation or control is to be executed. If the execution flag of the active DeNO x Control is "1" (S602: YES), the process goes to S603. On the other hand, if the execution flag of the active DeNO x Regulation or control is "0" (S602: NO), the process without executing the active DeNO x Regulation or control ended.

[0128] At S603, the PCM 60 determines whether the engine operating condition (engine load and engine speed or rpm) is within the active DeNO x execution area R12 is or lies (see Fig. 3). Here, if the NO x Catalyst temperature is above a given temperature and / or the stored amount of NO x is above a given amount, the PCM 60 the active DeNO x Extend the execution range R12 to the higher load side and to the higher speed side. If the engine operating state is within the active DeNO x execution range R12 (S603: YES), the process goes to S605. On the other hand, if the engine operating state is outside the active DeNO x execution area R12 (S603: NO), the process goes to S604.

[0129] At S604, without executing the active DeNO x Control, that is, without executing the fuel injection control including the post injection, the PCM 60 executes normal fuel injection control not including the post injection to control the air-fuel ratio to the target air-fuel ratio. Typically, the PCM 60 only executes the control to effect the main injection with the fuel injection amount corresponding to the target torque. The PCM 60 actually executes the processing of S604 in the above-described fuel injection control. Then, the process returns to S603 to perform the determination again. In other words, when the execution flag of the active DeNO x Control is "1", the PCM 60 performs normal fuel injection control while the engine operating state is outside of active DeNO x execution area R12 remains. When the operating state changes to the active DeNO x Execution area R12 is entered, the PCM 60 switches the control from the normal fuel injection control to the fuel injection control in the active DeNO x Regulation or control. For example, if the operating state of the engine is changed from the active DeNO x Execution area R12 during fuel injection control in active DeNO x control, the PCM 60 stops the fuel injection control and performs the normal fuel injection control. Thus, when the operating state enters the active DeNO x Execution area R12 is entered, the PCM 60 the fuel injection control in the active DeNO x Regulation or control again.

[0130] Next, at S605, the PCM 60 determines whether the glow plug 21 has been energized by the glow control for a given period of time, that is, whether the energization time of the glow plug 21 has reached the given period of time, to determine whether the energized glow plug 21 has become stable. The given period of time used at S605 is set based on the energization time required for the glow plug 21 to reach a desired temperature, for example. If the energization time of the glow plug 21 has reached the given period of time (S605: YES), the process proceeds to S606. On the other hand, if the energization time of the glow plug 21 has not reached the given period of time (S605: NO), the process returns to S603. In this case, the PCM 60 waits until the excitation time of the glow plug 21 reaches the given time period.

[0131] At S606, the PCM 60 determines whether the estimated in-cylinder oxygen concentration substantially exceeds a target in-cylinder oxygen concentration for fuel injection control (including post-injection) in active DeNO x Control by the EGR control. For example, the PCM 60 determines whether a difference (absolute value) between the in-cylinder oxygen concentration and the target in-cylinder oxygen concentration is below a given value. At S606, it is determined whether the amount of EGR gas introduced by the EGR control is stable, in other words, whether a desired flow rate of EGR gas is introduced. If the in-cylinder oxygen concentration has substantially reached the target in-cylinder oxygen concentration by the EGR control (S606: YES), the process proceeds to S607. On the other hand, if the in-cylinder oxygen concentration has not reached the target in-cylinder oxygen concentration (S606: NO), the process returns to S603.In this case, the PCM 60 waits until the oxygen concentration in the cylinder substantially reaches the target oxygen concentration in the cylinder through the EGR control.

[0132] At S607, the PCM 60 sets the timing of the post-injection, which in the active DeNO x The regulation or control is to be applied. The procedure for this setting or setting is described in detail.

[0133] As described above, in this embodiment, when performing the active DeNO x Control the air-fuel ratio to the target air-fuel ratio by burning the post-injected fuel inside the cylinder. In order to burn the post-injected fuel inside the cylinder, the post-injection may be performed at a comparatively advanced timing in the expansion stroke. However, if the post-injection timing is excessively advanced, ignition occurs before air and fuel are properly mixed, and smoke is generated. Therefore, in this embodiment, the post-injection timing is appropriately set on the advance side, specifically, an appropriate timing in the early half of the expansion stroke is selected as the post-injection timing of the active DeNO. x Control is applied and a suitable amount of EGR gas is added to the active DeNO x Control is introduced. Thus, the ignition of the post-injected fuel is retarded to prevent the generation of smoke, etc. In this embodiment, the post-injection timing is retarded at least in the early half of the expansion stroke as the engine load becomes higher. This is because, since the fuel injection amount increases and the generation of smoke becomes easier as the engine load increases, the post-injection timing is retarded as much as possible. In this case, if the post-injection timing is excessively retarded, it becomes easier for the post-injected fuel to be burned (misfire), and HC is generated. Therefore, in this embodiment, the post-injection timing is appropriately retarded.

[0134] Furthermore, in this embodiment, the post-injection timing is advanced, that is, the retarding amount of the post-injection timing is reduced as the engine speed increases. When the engine speed is high, if the fuel is injected at the same crankshaft angle as when the engine speed is low, since misfire may occur due to the short time period for fuel ignition, in this embodiment, the post-injection timing is advanced as the engine speed increases to ensure combustion stability.

[0135] At S608, the PCM 60 determines whether the DeNO x Post-injection amount obtained at S601 is smaller than the second determination value of the post-injection amount. The second determination value of the post-injection amount is set larger than the first determination value of the post-injection amount obtained in the passive DeNO x regulation or control is used (see S307 in Fig. 6). In this way, it is possible to achieve a larger post-injection quantity in the active DeNO x Regulation or control than in passive DeNO x control, and the air-fuel ratio becomes controllable to the target air-fuel ratio regardless of the operating state of the engine E (e.g., even if it is not in a state where the air-fuel ratio reduces, such as during acceleration).

[0136] If the DeNO x post-injection amount is smaller than the second determination value of the post-injection amount (S608: YES), the process goes to S609, where the PCM 60 controls the fuel injector 20 to adjust the DeNO x post-injection amount obtained at S601 at the post-injection timing set at S607, and control the air-fuel ratio to the target air-fuel ratio to reduce NO x which is present in the NO x Catalyst 45 is stored. For example, due to changes in detections from various sensors, changes in the fuel injection amount of the fuel injector 20, etc., based on the air-fuel ratio corresponding to the detection value of the O2 sensor 111 arranged in the exhaust passage 41 (actual air-fuel ratio) and the target air-fuel ratio, the PCM 60 performs F / B (feedback) control of the post-injection amount injected from the fuel injector 20 to match the actual air-fuel ratio with the target air-fuel ratio. Subsequently, the F / B control of the fuel injection amount used in the active DeNO x Control is executed, appropriately referred to as "second post-injection F / B control". Although in this second post-injection F / B control, F / F control (feed-forward control) is preferably executed in addition to the F / B control, since the F / B control is mainly executed, the term "F / B control" is used for the sake of simplicity.

[0137] More specifically, the PCM 60 sets a comparatively large air-fuel ratio (comparatively less rich air-fuel ratio) as a target value and executes the F / F control of the post-injection amount from the fuel injector 20. Then, the PCM 60 executes the F / B control of the post-injection amount from the fuel injector 20 by using a comparatively small F / B slope based on the actual air-fuel ratio and the target air-fuel ratio. In this way, the actual air-fuel ratio is smoothly adjusted toward the target air-fuel ratio in the active DeNO. x Control is changed to prevent the actual air-fuel ratio from becoming richer than the target air-fuel ratio, ie the actual air-fuel ratio from falling below the target air-fuel ratio.

[0138] It should be noted that the PCM 60 actually executes the processing of S609 in the fuel injection control.

[0139] On the other hand, if the DeNO x Post-injection amount is above the second determination value of the post-injection amount (S608: NO), the process goes to S610. At S610, the PCM 60 reduces the oxygen concentration of air introduced into the engine E to control the air-fuel ratio to the target air-fuel ratio by using the post-injection amount that is below the second determination value of the post-injection amount (specifically, the second determination value of the post-injection amount itself is referred to as the DeNO x Post-injection amount applied). In this case, the PCM 60 performs at least one of a control for decreasing the opening of the intake shut-off valve 7, a control for increasing the EGR gas amount, and a control for lowering the turbocharging pressure by the turbocharger 5 in order to reduce the oxygen concentration of the air introduced into the engine E, i.e., to reduce the charging amount. For example, the PCM 60 obtains the turbocharging pressure required for controlling the air-fuel ratio to the target air-fuel ratio by using the DeNO x Post-injection amount to which the second determination value of the post-injection amount is applied. The PCM 60 reduces the opening of the intake shutoff valve 7 to a desired opening based on the actual turbocharger pressure (the pressure detected by the pressure sensor 108) and the EGR gas amount to achieve this turbocharger pressure. Then, the process proceeds to S611.

[0140] It should be noted that the intake shut-off valve 7 is substantially fully open in the normal operating state of the engine E, whereas during a DeNO x , DPF regeneration, idle operation, etc., the opening of the intake shutoff valve 7 is typically a given base opening. In the operating state where the EGR gas is not introduced, the intake shutoff valve 7 is feedback-controlled based on the turbocharger pressure.

[0141] Next, at S611, the PCM 60 applies the second determination value of the post-injection amount to the DeNO x post-injection quantity, ie sets the DeNO x post-injection amount to be the second determination value of the post-injection amount. In addition, the PCM 60 controls the fuel injector 20 to determine this DeNO x Post-injection fuel quantity at the post-injection timing set at S607 to control the air-fuel ratio to the target air-fuel ratio and to reduce the NO x which is present in the NO x Catalyst 45 is stored. For example, similar to S609, the PCM 60 performs the second post-injection F / B control. That is, the PCM 60 first sets a comparatively large air-fuel ratio (comparatively less rich air-fuel ratio) as a target value and performs F / F control of the post-injection amount from the fuel injector 20. Then, the PCM 60 performs F / B control of the fuel injection amount injected from the fuel injector 20 by using a comparatively small F / B slope based on the actual air-fuel ratio and the target air-fuel ratio. Note that the PCM 60 actually performs the processing of S611 in the fuel injection control.

[0142] After S609 or S611, the process proceeds to S612, where the PCM 60 determines whether the stored amount of NO x in the NE x catalyst 45 is essentially zero. For example, the PCM 60 determines that the amount of NO x is essentially zero when the stored amount of NO x , which is estimated or judged based on the operating state of the engine E, the flow rate of the exhaust gas, the temperature of the exhaust gas, etc., becomes substantially zero and the detection value of NO x sensor 116, which is located immediately downstream of the DPF 46, changes (S612: YES). Then the process ends. Here, the PCM 60 stops the active DeNO x Regulation or control. The PCM 60 also determines the stored amount of NO x which in the process of active DeNO x Regulation or control and the setting process of the execution flag of the active DeNO x Regulation or control in Fig. 7 is used, again set to zero.

[0143] On the other hand, if the stored amount of NO x is not essentially zero (S612: NO), the process returns to S603. In this case, the PCM 60 resets the active DeNO x In other words, the PCM 60 continues the active DeNO x Regulation or control continues until the stored amount of NO x becomes almost zero. In particular, even if the execution condition of the active DeNO x Regulation or control (e.g. the condition of S603) not during the active DeNO x Regulation or control is or will be fulfilled and the active DeNO x Regulation or control is cancelled if the execution condition of the active DeNO x Regulation or control is then fulfilled, the PCM 60 promptly or immediately activates the active DeNO x Regulation or control in turn to control the stored amount of NO x essentially to zero.

[0144] Here is the stored amount of NO x essentially as zero based on the detection value of NO x Sensor 116 can be determined for the following reason. Since the NO x Sensor 116 also functions as an oxygen concentration sensor, the detection value of NO x Sensor 116 the air-fuel ratio, which determines the NO x Sensor 116 is reached. During the NO x Catalyst 45 performs a reduction, ie when the stored amount of NO x is not essentially zero, oxygen reaches, which is reduced by reducing NO x generated or produced, the NO x Sensor 116. On the other hand, when the stored amount of NO x becomes essentially zero, such oxygen produced or generated by reduction no longer contains the NO x Sensor 116. Therefore, at the time when the stored amount of NO x becomes essentially zero, the air-fuel ratio, which determines the NO x Sensor 116 is reached, which increases the detection value of the NO x Sensor 116 changes.

[0145] It should be noted that the second determination value of the post-injection quantity, which is used in the process of active DeNO x The second determination value of the post-injection amount used for control is not limited to a fixed value and can be changed according to the in-cylinder temperature. For example, similar to the first determination value of the post-injection amount described above, considering that vaporization of post-injected fuel progresses and oil dilution is less likely to occur as the in-cylinder temperature increases, the second determination value of the post-injection amount can be increased as the in-cylinder temperature increases.

[0146] Next, a specific example of the second post-injection F / B control, which is used in the active DeNO x Control of this embodiment is carried out with reference to the timing charts of Fig. 11 described. Fig. 11 shows the execution flag of the active DeNO x Control, the post-injection quantity and the actual air-fuel ratio (λ) in this order from the top.

[0147] As this is Fig. 11, starts when the execution flag of the active DeNO x regulation or control is switched from "0" to "1", the PCM 60 activates the active DeNO x Control in which the fuel injection valve 20 is controlled to perform the post-injection to control the actual air-fuel ratio to the target air-fuel ratio to produce NO x , which is in the NO x catalyst 45 is stored. For example, the PCM 60 performs the second post-injection F / B control such that the actual air-fuel ratio gradually changes to agree with the target air-fuel ratio based on the actual air-fuel ratio and the target air-fuel ratio. More specifically, the PCM 60 first sets a comparatively low air-fuel ratio (comparatively rich air-fuel ratio) as a target value and performs the F / F control of the post-injection amount from the fuel injector 20 (see the arrow A31). Thus, the post-injection amount gradually increases, and the actual air-fuel ratio gradually changes to the richer side (see the arrow A33). Then, the PCM 60 performs the F / B control.Control of the post-injection amount from the fuel injector 20 by using a smaller F / B gain than in the first post-injection F / B control (see . Fig. 8) based on the actual air-fuel ratio and the target air-fuel ratio (see arrow A32). In this way, the post-injection amount increases even more gradually and the actual air-fuel ratio changes progressively, making the actual air-fuel ratio consistent with the target air-fuel ratio without falling below the target air-fuel ratio (see arrow A34).

[0148] As described above, by executing the second post-injection F / B control in the active DeNO x Control or open-loop control restricts or limits the rate of change of the post-injection quantity, i.e. the rate of change of the post-injection quantity is controlled or closed-loop controlled so as not to exceed a given speed. In particular, in this second post-injection F / B control or open-loop control, the rate of change of the post-injection quantity is restricted or limited so that the actual air-fuel ratio does not fall below the target air-fuel ratio. In the second post-injection F / B control or open-loop control, which is used in the active DeNO x Control is carried out, the change rate of the post-injection quantity becomes lower than that of the first post-injection F / B control, which is carried out in the passive DeNO x Control is carried out, in principle (in other words, in the first post-injection F / B control, which in the passive DeNO x Control is carried out, the rate of change of the post-injection quantity is made larger than that of the second post-injection F / B control, which is carried out in the active DeNO x Control is performed). In this embodiment, by performing such second post injection F / B control, generation of a large amount of smoke and HC due to the fact that the actual air-fuel ratio exceeds the target air-fuel ratio during the active DeNO x Regulation or control falls below, safely prevents. <Betrieb und Effekte>

[0149] Next, the operation and effects of the exhaust emission control system of the engine of this embodiment will be described.

[0150] According to this embodiment, since the active DeNO x Regulation or control only within the active DeNO x Execution range R12 as the area of ​​medium load and medium speed, smoke and HC are likely to arise due to the fact that the first NO x Reduction control is carried out outside the medium load range, and the combustion of the post-injected fuel in this NO x Reduction regulation or control is hindered.

[0151] For example, within the high load and high speed ranges, smoke may be generated when the post-injected fuel is burned inside the cylinder. According to this embodiment, since the active DeNO x Control within such ranges is prohibited, smoke generation is suitably prevented. Within the low load range and the low speed range, although the post-injected fuel cannot be properly combusted and may generate HC, according to this embodiment, since the active DeNO x Control is prohibited, HC generation is appropriately prevented. In addition, within the low load and low speed range, although the reduction of NO x Catalyst 45 not suitable due to the low NO x catalyst temperature, according to this embodiment, the active DeNO x Regulation or control prohibited in order to prevent unnecessary post-injection.

[0152] According to this embodiment, the execution of the active DeNO x Regulation or control is canceled when the engine load is reduced by the active DeNO x Execution range R12, and is resumed when the engine load returns to active DeNO x Execution area R12 is entered. Thus, the stored amount of NO x reliably reduced to essentially zero.

[0153] According to this embodiment, when the NO x Catalyst temperature is or is above the given temperature and / or the stored amount of NO x is above the given amount, the active DeNO x The design area R12 is extended to the higher load side and the higher speed side. In this way, when the NO x Catalyst temperature is comparatively high and / or the stored amount of NO x is comparatively large, a situation is prevented where the active DeNO x Regulation or control is interrupted and thus NO x from the NO x Catalyst 45 is removed and released or released.

[0154] According to this embodiment, within the passive DeNO x Execution area R11 on the higher load side of the active DeNO x Execution area R12 the passive DeNO x Control in which the post-injected fuel is discharged as unburned fuel without being burned inside the cylinder is carried out. Thus, smoke generation due to the fact that the post-injected fuel is burned within the high-load range is appropriately prevented, while performing DeNO x within the high load range. In passive DeNO x Regulation or control is carried out, although the post-injected fuel is discharged or discharged as unburned fuel, since the NO x Catalyst temperature is sufficiently high and the HC cleaning performance within the passive DeNO x Execution area R11 is ensured, unburned fuel, which is applied as described above, suitable by the NO x Catalyst 45 cleaned.

[0155] According to this embodiment, since the SCR catalyst 47 is provided in the exhaust passage 41 in addition to the NO x Catalyst 45 is arranged within the area where the passive DeNO x Regulation or control and the active DeNO x Regulation or control is not carried out, NO x within the exhaust gas is suitably cleaned by the SCR catalyst 47. This ensures the exhaust gas cleaning performance. <modifikationen>

[0156] In the above embodiment, the permission or prohibition of active DeNO x Regulation or control based on the driving distance from the previous execution time of the active DeNO x Regulation or control. Alternatively, a modification or amendment can permit or prohibit active DeNO x Control based on an elapsed time from the previous execution time of the active DeNO x regulation or control. In other words, the active DeNO x Regulation or control may be prohibited if the elapsed time from the previous execution time of the active DeNO x Control is less than a given determination time. Also, in this modification, the determination time can be set similarly to the determination distance. For example, the determination time can be set shorter as the in-cylinder temperature rises. Furthermore, the engine water temperature or the intake air temperature can be used as an index reflecting the in-cylinder temperature, so that the determination time is set shorter as the engine water temperature rises or the intake air temperature rises.

[0157] As described above, even in the modification of a determination of the permission or prohibition of active DeNO x Control based on the elapsed time from the previous execution time of the active DeNO x Control, the same effects as those described in the above section "Operation and Effects" are obtained. In other words, oil dilution due to the post-injected fuel in the active DeNO x Regulation or control is appropriately prevented.

[0158] In the above embodiment, an implementation of the passive DeNO x Regulation or control is completely prohibited if the execution or exercise frequency of the passive DeNO x Control is above the frequency determination value; however, this is not limited to this. Compared to when the execution frequency of the passive DeNO x control is lower than the frequency determination value, an execution of the passive DeNO x Regulation or control can be easily limited if the execution frequency of the passive DeNO x Control is above the frequency determination value. For example, if the execution frequency of the passive DeNO x Control is above the frequency determination value, the number of times of performing the post-injection can be reduced to less than when the execution frequency of the passive DeNO x Regulation or control is less than the frequency determination value.

[0159] Similarly, if the driving distance from the previous execution of the active DeNO x control is less than the determination distance, or if the elapsed time from the previous execution of the active DeNO x Regulation or control is less than the determination time, the execution of the active DeNO x Regulation or control should be appropriately restricted without being completely prohibited.

[0160] Although in the above embodiment, the recirculation of the EGR gas to the intake system IN is completely in the passive DeNO x Control is prohibited to the extent that the deposit caused by the recirculation of the EGR gas does not block the passage, a small amount of EGR gas may be released during passive DeNO x regulation or control. In this case, at least in the passive DeNO x Regulation or control of the EGR gas quantity preferably to less than in the active DeNO x Regulation or control reduced. DESCRIPTION OF REFERENCE SYMBOLS 1 inlet passage 5 turbochargers 7 Inlet shut-off valve 17 Combustion chamber 20 Fuel injection device 41 Outlet passage 43 EGR device 43a EGR passage 43b EGR cooling device 43c first EGR valve 43d EGR cooling device bypass passage 43e second EGR valve 45 NO x catalyst 46 DPF 47 SCR catalyst 60 PCM (control device or controller) 111 O2 Sensor 116 NO x sensor 200 engine system Electric motor EX exhaust or exhaust system IN intake system< / modifikationen> < / systemkonfiguration>

Claims

[1] Exhaust emission control system for an engine, including a NO x Catalyst (45) arranged in an exhaust passage (41) of the engine for storing NO x in the exhaust gas when an air-fuel ratio of the exhaust gas is lean, and for reducing the stored NO x when the air-fuel ratio is approximately stoichiometric or rich, and a catalyst (47) for selective catalytic reduction (SCR) provided in the exhaust passage (41) for purifying NO x is arranged within the exhaust gas by causing a reaction with ammonia, wherein the system comprises a processor (60A) configured to execute: a NO x Reduction control module (60B) for performing when the stored amount of NO x in the NE xcatalyst (45) exceeds a given determination amount, a first NO x Reduction control in which a fuel injection device (20) performs a post-injection of fuel to continuously control the air-fuel ratio to a target air-fuel ratio such that the stored NO x is reduced and the stored amount of NO x falls below a given amount, the target air-fuel ratio being a ratio at which the stored NO x can be reduced, wherein the post-injection causes the injected fuel to burn inside a cylinder, wherein the implementation of the first NO x Reduction control is permitted when an engine load is in a medium load range, where, if the stored amount of NO x in the NE xcatalyst (45) is below the specified amount and the air-fuel ratio becomes rich due to acceleration of a vehicle that emits NO x Reduction control module (60B) also a second NO x Reduction control in which the fuel injection device (20) performs the post-injection to temporarily control the air-fuel ratio to the target air-fuel ratio so that the NO x , which is in the NO x catalyst (45), wherein the post-injection causes the injected fuel to be discharged to the exhaust passage (41) as unburned fuel without being burned inside the cylinder, wherein the implementation of the second NO xReduction control is only permitted when the engine load is within a high load range above a load that defines a higher end of the medium load range, where the SCR catalyst (47) NO x within an engine operating range where the NO x Reduction control module (60B) does not carry out the post-injection by the fuel device (20) in order to reduce the stored NO x to reduce, wherein within a range (R11) where the engine load is higher than a range (R13) where the SCR catalyst (47) NO x cleans, the second NO x Reduction regulation or control is carried out. [2] The system of claim 1, wherein the NO x Reduction control module (60B) the implementation of the first NO xReduction control is permitted when an engine speed is in a medium speed range. [3] System according to claim 1 or 2, wherein the NO x Reduction control module (60B) the first NO x Reduction control is canceled when the engine load moves out of the medium load range and the first NO x Reduction control or control takes up again when the engine load again enters the medium load range, so that a stored amount of NO x falls below the given amount. [4] System according to one of the preceding claims, wherein when a temperature of the NO x catalyst (45) is above a given value, and / or if the stored amount of NO x is above a given value, the NO xReduction control module (60B) extends the medium load range toward a higher load side by increasing a load value that defines a higher end of the medium load range. [5] System according to one of the preceding claims 2 to 4, wherein when a temperature of the NO x catalyst is above a given value and / or if the stored amount of NO x is above a given value, the NO x Reduction control module (60B) extends the medium speed range toward a higher speed side by increasing a speed value defining a higher end of the medium speed range. [6] A method for controlling an exhaust system of an engine, comprising the steps of: Saving NO x in the exhaust gas in a NO xCatalyst (45) which is arranged in an exhaust passage (41) of the engine when an air-fuel ratio of the exhaust gas is lean, Cleaning NO x within the exhaust gas in a catalyst (47) for selective catalytic reduction (SCR) arranged in the outlet passage (41) by causing a reaction with ammonia, Reducing stored NO x when the air-fuel ratio is approximately stoichiometric or rich, and Carrying out a first NO x Reduction control in which a fuel injection device (20) performs a post-injection of fuel to continuously control the air-fuel ratio to a target air-fuel ratio such that the stored NO x is reduced and the stored amount of NO xfalls below a given amount when the stored amount of NO x in the NE x catalyst (45) exceeds a given determination quantity, wherein the target air-fuel ratio is a ratio at which the stored NO x can be reduced, whereby the post-injection causes the injected fuel to burn inside a cylinder, where the implementation of the first NO x Reduction control is permitted when an engine load is within a medium load range and / or within a medium speed range, Carrying out a second NO x Reduction control in which the fuel injection device (20) performs the post-injection to temporarily control the air-fuel ratio to the target air-fuel ratio so that the NO x, which is in the NO x Catalyst (45) is reduced when the stored amount of NO x in the NE x catalyst (45) is below the specified amount and the air-fuel ratio becomes rich due to acceleration of a vehicle, wherein the post-injection causes the injected fuel to be discharged to the exhaust passage (41) as unburned fuel without being burned inside the cylinder, wherein the performance of the second NO x Reduction control is only permitted when the engine load is within a high load range above a load that defines a higher end of the medium load range, where the SCR catalyst (47) NO x within an engine operating range where the post-injection by the fuel device (20) is not carried out in order to remove the stored NO x to reduce, wherein within a range (R11) where the engine load is higher than a range (R13) where the SCR catalyst (47) NO x cleans, the second NO x Reduction regulation or control is carried out. [7] The method according to claim 6, further comprising the step of expanding the medium load range towards a higher load side by increasing a load value defining a higher end of the medium load range and / or expanding the medium speed range towards a higher speed side by increasing a speed value defining a higher end of the medium speed range when a temperature of the NO x catalyst is above a given value and / or if the stored amount of NO x is above a given value. [8] A computer program product comprising computer-readable instructions which, when loaded onto and executed on a suitable system, can perform the steps of a method according to claim 6 or 7.

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