JP5846286B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device mounted on an internal combustion engine such as an automobile diesel engine. In particular, the present invention relates to an improvement for optimizing the execution conditions of the exhaust purification filter regeneration process.

  Conventionally, exhaust gas discharged when driving a diesel engine (hereinafter sometimes simply referred to as “engine”) mounted on an automobile or the like includes substances that are not preferably discharged into the atmosphere as they are. It is. In particular, particulate matter containing carbon as a main component (hereinafter referred to as PM (Pattern Matter)) causes air pollution.

  As a device for preventing the PM from being discharged into the atmosphere, a particulate filter (hereinafter sometimes simply referred to as “filter”) disposed in an exhaust passage of a diesel engine is known. That is, PM contained in the exhaust gas passing through the exhaust passage is collected by this filter to purify the exhaust gas.

  As this filter, for example, DPF (Diesel Particulate Filter) and DPNR (Diesel Particulate-NOx Reduction system) catalysts are known.

  By the way, when collecting PM using this kind of filter, if the amount of collected PM increases, the filter will be clogged. In the situation where the filter is clogged, the pressure loss of the exhaust gas passing through the filter increases remarkably, resulting in a decrease in engine output due to an increase in engine exhaust back pressure and a sufficient improvement in fuel consumption rate. There is a possibility of disappearing.

  In order to solve such problems, conventionally, when the amount of collected PM (deposition amount) collected by the filter reaches a predetermined amount, the filter temperature is increased by a method such as raising the exhaust temperature. Therefore, a filter regeneration process is performed to oxidize (combust) and remove the accumulated PM (see, for example, Patent Document 1 and Patent Document 2 below).

  Specific examples of the filter regeneration process include a method in which a small amount of fuel is injected secondary (post injection) after the main fuel injection from the injector (main injection), or a fuel addition valve provided in the exhaust system (additional fuel). That supply the agent). The PM accumulated on the filter can be oxidized (combusted) when the exhaust gas temperature rises as the fuel is supplied to the exhaust system.

JP 2005-90458 A JP 2008-308996 A

  By the way, among the various parts housed in the engine compartment (engine room) of the vehicle, there are parts with relatively low heat resistance. For example, it is a part (for example, a fuse box) molded from a synthetic resin material.

  And in the situation where the temperature in the engine compartment rises, it is not preferable that the ambient temperature exceeds the heat resistance temperature of the component having low heat resistance.

  The temperature in the engine compartment rises when the vehicle stops at a low vehicle speed uphill and the filter regeneration process is performed, and the vehicle stops and the engine stops (so-called dead soak). Is mentioned. In other words, when the vehicle speed is low, the amount of heat dissipated to the outside is small because there is little traveling wind flowing into the engine compartment, and the torque required for the engine when climbing is high, so The amount of heat generated at is increased. During the filter regeneration process, the exhaust gas temperature rises due to the fuel supply to the exhaust system as described above. When the vehicle stops and the engine stops in such a situation, not only is the heat in the engine compartment difficult to be released to the outside, but also the amount of heat radiated into the engine compartment from various parts of the engine and exhaust system increases. The temperature inside the engine compartment tends to rise. In such a situation where the conditions are met, the temperature in the engine compartment may exceed the heat resistance temperature of the component having low heat resistance.

  In particular, in recent years, the grill opening area (opening area of the running wind intake) has been reduced in order to improve the air drag coefficient (CD) of the vehicle, and high-temperature areas and gradients have been increased with the expansion of the vehicle destination. Increasing opportunities for use in regions with many changes are another cause of the above problems.

  Note that Patent Document 2 discloses that the filter regeneration process is interrupted when the filter temperature becomes equal to or higher than a predetermined value during the filter regeneration process and when the vehicle speed is equal to or lower than the predetermined value.

  However, in the technique disclosed in Patent Document 2, since the filter regeneration process is interrupted only by the temperature condition regardless of the PM accumulation amount in the filter, even when the PM accumulation amount is relatively large. There is a possibility that the filter regeneration process cannot be executed, and there still remains a problem in terms of practicality.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an exhaust purification device for an internal combustion engine capable of optimizing execution conditions for regeneration processing of the exhaust purification filter. It is in.

-Solution principle of the invention-
The solution principle of the present invention taken in order to achieve the above object is that the control for suppressing further increase of the temperature in the situation where the temperature in the engine compartment rises or is expected to rise. Like to do. For example, even if the PM accumulation amount in the exhaust purification filter reaches a predetermined amount, the regeneration process of the exhaust purification filter is limited. When the PM accumulation amount in the exhaust purification filter reaches an allowable limit amount larger than the predetermined amount, the regeneration process of the exhaust purification filter is executed regardless of the engine compartment temperature. In other words, the engine compartment temperature is used as an execution condition for the regeneration process of the exhaust purification filter until the PM accumulation amount reaches the allowable limit amount, whereas when the PM accumulation amount reaches the allowable limit amount, this engine compartment is used. The internal temperature is excluded from the conditions for executing the regeneration process of the exhaust purification filter.

-Solution-
Specifically, the present invention includes an exhaust purification filter that collects particulate matter contained in the exhaust gas of an internal combustion engine, and a filter regeneration process that removes the particulate matter collected by the exhaust purification filter is executed. An exhaust gas purification device for an internal combustion engine is assumed. With respect to the exhaust gas purification apparatus for the internal combustion engine, the amount of particulate matter accumulated in the exhaust gas purification filter is not less than the first reference amount and less than the second reference amount, and the engine compartment temperature is increased. In such a case, the temperature increase suppression control is performed so that the filter regeneration process is not executed, and the increase in the temperature in the engine compartment due to the execution of the filter regeneration process is suppressed, while the amount of particulate matter accumulated in the exhaust purification filter is reduced. When the amount exceeds the second reference amount, the filter regeneration process is prioritized and executed over the temperature increase suppression control. In addition, the filter regeneration process is started when the temperature increase suppression control that does not execute the filter regeneration process is continued for a predetermined time.

  When the engine compartment temperature is increased due to this specific matter, the amount of particulate matter accumulated in the exhaust purification filter is not less than the first reference amount and less than the second reference amount. In addition, the temperature increase suppression control (non-execution of the filter regeneration process) is preferentially performed, thereby suppressing an increase in the engine compartment temperature resulting from the execution of the filter regeneration process. For example, when the engine compartment temperature does not increase or when the amount of increase is relatively low, the amount of particulate matter accumulated in the exhaust purification filter is a predetermined amount (for example, the first reference amount). ), The filter regeneration process is executed. On the other hand, when the engine compartment temperature rises, the particulate matter accumulation amount in the exhaust purification filter is greater than or equal to the first reference amount. Even if it exists, the said temperature increase suppression control is preferentially performed on condition that the deposition amount of this particulate matter is less than the 2nd reference amount. As a result, an increase in engine compartment temperature due to the execution of the filter regeneration process is suppressed. As a result, even if the internal combustion engine is subsequently stopped, the engine compartment temperature can be prevented from rising excessively, exceeding the heat resistance temperature of the low heat resistance components disposed in the engine compartment. Can be prevented. In addition, when the amount of particulate matter deposited on the exhaust purification filter exceeds the second reference amount, the filter regeneration process is preferentially executed, so the amount of particulate matter deposited becomes excessive. An adverse effect on the performance of the exhaust purification filter is avoided. In addition, when the temperature rise suppression control that does not execute the filter regeneration process is performed, the state in which the amount of particulate matter accumulated in the exhaust purification filter is equal to or greater than the first reference amount is continued. However, when such a situation continues for a predetermined time, the filter regeneration process is started. For this reason, the situation where a relatively large amount of particulate matter continues to accumulate in the exhaust purification filter can be solved, and the performance of the exhaust purification filter can be recovered early.

  Specifically, when the filter regeneration process is executed when the accumulated amount of the particulate matter is equal to or more than the second reference amount, the removal amount of the particulate matter from the exhaust purification filter is a predetermined filter regeneration. The filter regeneration process is prioritized and executed over the temperature rise suppression control until the process end amount is reached.

  As a result, it is possible to reliably reduce the amount of particulate matter deposited in the exhaust purification filter, and to ensure a long time (vehicle travel distance) until the amount of particulate matter deposited exceeds the first reference amount. can do. For this reason, it is possible to avoid the situation that the filter regeneration process and the temperature rise suppression control are frequently performed again, and the performance of the exhaust purification filter can be sufficiently exhibited over a long period of time.

  In addition, when the exhaust purification device is mounted on a vehicle, the operating state in which the engine compartment temperature rises may include a case where the vehicle speed is below a predetermined value and the vehicle is traveling on an uphill road that exceeds a predetermined gradient. It is done. In addition, there may be a case where a state where the fuel injection amount of the internal combustion engine is equal to or greater than a predetermined amount is continued for a predetermined time.

  When the vehicle speed is lower than the predetermined value, the amount of heat dissipated to the outside is reduced because the traveling wind flowing into the engine compartment is small. Further, when traveling on an uphill road exceeding a predetermined gradient, the amount of heat generated in the combustion chamber increases because the torque required for the internal combustion engine is high. Further, when the state where the fuel injection amount of the internal combustion engine is equal to or greater than the predetermined amount is continued for a predetermined time, the heat generation amount in the combustion chamber is increased. By determining whether or not the engine compartment temperature is in an operating state based on such a vehicle running state or the operating state of the internal combustion engine, the determination accuracy can be improved, and the temperature rise suppression control is performed. It is possible to optimize the execution period.

  In the present invention, when the accumulation amount of the particulate matter in the exhaust purification filter is within a predetermined range and the engine compartment temperature is in an operating state, the temperature rise suppression control is executed, and the accumulation amount of the particulate matter is predetermined. When it exceeds the range, the filter regeneration process is preferentially executed. For this reason, it can suppress that the temperature in an engine compartment rises excessively, and it can also avoid that the accumulation amount of a particulate matter becomes excessive and exerts a bad influence on an exhaust gas purification filter.

It is a figure which shows schematic structure of the engine which concerns on embodiment, and its control system. It is sectional drawing which shows the combustion chamber of a diesel engine, and its peripheral part. It is a block diagram which shows the structure of control systems, such as ECU. It is a flowchart figure which shows the procedure of the first half of the low vehicle speed uphill determination operation | movement. It is a flowchart figure which shows the procedure of the latter half of the low vehicle speed climbing-up determination operation | movement. It is a flowchart figure which shows the procedure of count operation | movement of a temperature estimation counter. It is a flowchart figure which shows the procedure of DPF regeneration process restriction | limiting operation | movement.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a common rail in-cylinder direct injection multi-cylinder (for example, in-line 4-cylinder) diesel engine (compression self-ignition internal combustion engine) mounted on an automobile will be described.

-Engine configuration-
First, a schematic configuration of a diesel engine (hereinafter simply referred to as an engine) according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of an engine 1 and its control system according to the present embodiment. FIG. 2 is a cross-sectional view showing the combustion chamber 3 of the diesel engine 1 and its periphery.

  As shown in FIG. 1, the engine 1 according to the present embodiment is configured as a diesel engine system having a fuel supply system 2, a combustion chamber 3, an intake system 6, an exhaust system 7 and the like as main parts.

  The fuel supply system 2 includes a supply pump 21, a common rail 22, an injector (fuel injection valve) 23, an engine fuel passage 27, and the like.

  The supply pump 21 pumps fuel from the fuel tank, makes the pumped fuel high pressure, and supplies it to the common rail 22 via the engine fuel passage 27. The common rail 22 has a function as a pressure accumulation chamber that holds (accumulates) high pressure fuel at a predetermined pressure, and distributes the accumulated fuel to the injectors 23, 23,. The injector 23 includes a piezoelectric element (piezo element) therein, and is configured by a piezo injector that is appropriately opened to supply fuel into the combustion chamber 3.

  The intake system 6 includes an intake manifold 63 connected to an intake port 15a formed in the cylinder head 15 (see FIG. 2), and an intake pipe 64 that constitutes an intake passage is connected to the intake manifold 63. Further, an air cleaner 65, an air flow meter 43, and a throttle valve (intake throttle valve) 62 are arranged in this intake passage in order from the upstream side. The air flow meter 43 outputs an electrical signal corresponding to the amount of air flowing into the intake passage via the air cleaner 65.

  The exhaust system 7 includes an exhaust manifold 72 connected to an exhaust port 71 formed in the cylinder head 15, and an exhaust pipe 73 constituting an exhaust passage is connected to the exhaust manifold 72. An exhaust purification unit 77 is disposed in the exhaust passage. The exhaust purification unit 77 is provided with an NSR catalyst (exhaust purification catalyst) 75 as a NOx storage reduction catalyst and a DPF 76 as an exhaust purification filter. A DPNR catalyst may be applied as the exhaust purification unit 77.

  Note that the exhaust purification unit 77 in the present embodiment is disposed in the engine compartment. For this reason, as will be described later, when the vehicle stops and the engine 1 stops in a state where the heat storage amount in the exhaust purification unit 77 is relatively large, the heat storage in the exhaust purification unit 77 is radiated into the engine compartment. The temperature inside the engine compartment tends to rise.

The NSR catalyst 75 stores NOx in a state where a large amount of oxygen is present in the exhaust gas, has a low oxygen concentration in the exhaust gas, and a large amount of reducing component (for example, an unburned component (HC) of fuel). In the existing state, NOx is reduced to NO ₂ or NO and released. NOx released as NO ₂ or NO is further reduced to N ₂ by reacting quickly with HC and CO in the exhaust. Further, HC and CO are oxidized to H ₂ O and CO ₂ by reducing NO ₂ and NO. That is, by appropriately adjusting the oxygen concentration and HC component in the exhaust gas introduced into the NSR catalyst 75, HC, CO, and NOx in the exhaust gas can be purified. In the present embodiment, the oxygen concentration and the HC component in the exhaust gas are adjusted by a fuel injection operation (post injection described later) from the injector 23 and an opening degree control of the throttle valve 62.

  The DPF 76 is made of, for example, a porous ceramic structure, and collects PM (particulate matter) contained in the exhaust gas when the exhaust gas passes through the porous wall. The DPF 76 carries a catalyst (for example, an oxidation catalyst mainly composed of a noble metal such as platinum) that oxidizes and burns the collected PM during the DPF regeneration process.

  Here, the structure of the combustion chamber 3 of a diesel engine and its peripheral part is demonstrated using FIG. As shown in FIG. 2, a cylinder block 11 constituting a part of the engine body is formed with a cylindrical cylinder bore 12 for each cylinder (four cylinders), and a piston 13 is formed inside each cylinder bore 12. Is accommodated so as to be slidable in the vertical direction.

  The combustion chamber 3 is formed above the top surface 13 a of the piston 13. That is, the combustion chamber 3 is defined by the lower surface of the cylinder head 15 attached to the upper portion of the cylinder block 11, the inner wall surface of the cylinder bore 12, and the top surface 13 a of the piston 13. A cavity (concave portion) 13 b is formed in a substantially central portion of the top surface 13 a of the piston 13, and this cavity 13 b also constitutes a part of the combustion chamber 3.

  The piston 13 is connected to a crankshaft, which is an engine output shaft, by a connecting rod 18. As a result, the reciprocating movement of the piston 13 in the cylinder bore 12 is transmitted to the crankshaft via the connecting rod 18, and the engine output is obtained by rotating the crankshaft. Further, a glow plug 19 is disposed toward the combustion chamber 3. The glow plug 19 functions as a start-up assisting device that is heated red when an electric current is applied immediately before the engine 1 is started and a part of the fuel spray is blown onto the glow plug 19 to promote ignition and combustion.

  The cylinder head 15 is formed with an intake port 15a and an exhaust port 71, respectively, and an intake valve 16 for opening and closing the intake port 15a and an exhaust valve 17 for opening and closing the exhaust port 71 are disposed. The cylinder head 15 is provided with the injector 23 that directly injects fuel into the combustion chamber 3. The injector 23 is disposed at a substantially upper center of the combustion chamber 3 in a standing posture along the cylinder center line P, and injects fuel introduced from the common rail 22 toward the combustion chamber 3 at a predetermined timing.

  Further, as shown in FIG. 1, the engine 1 is provided with a supercharger (turbocharger) 5. The turbocharger 5 includes a turbine wheel 52 and a compressor wheel 53 that are connected via a turbine shaft 51. The compressor wheel 53 is disposed facing the intake pipe 64, and the turbine wheel 52 is disposed facing the exhaust pipe 73. For this reason, the turbocharger 5 performs a so-called supercharging operation in which the compressor wheel 53 is rotated using the exhaust flow (exhaust pressure) received by the turbine wheel 52 to increase the intake pressure. The turbocharger 5 in the present embodiment is a variable nozzle type turbocharger, and a variable nozzle vane mechanism (not shown) is provided on the turbine wheel 52 side. By adjusting the opening of the variable nozzle vane mechanism, the engine 1 supercharging pressure can be adjusted.

  An intake pipe 64 of the intake system 6 is provided with an intercooler 61 for forcibly cooling the intake air whose temperature has been raised by supercharging in the turbocharger 5.

  Further, the engine 1 is provided with an exhaust gas recirculation passage (EGR passage) 8 that connects the intake system 6 and the exhaust system 7. The EGR passage 8 is configured to reduce the combustion temperature by recirculating a part of the exhaust gas to the intake system 6 and supplying it again to the combustion chamber 3, thereby reducing the amount of NOx generated. Further, the EGR passage 8 is opened and closed steplessly by electronic control, and an exhaust gas flowing through the EGR passage 8 (refluxing) is cooled by an EGR valve 81 that can freely adjust the exhaust flow rate flowing through the passage 8. An EGR cooler 82 is provided. The EGR passage 8, the EGR valve 81, the EGR cooler 82, and the like constitute an EGR device (exhaust gas recirculation device).

-Sensors-
Various sensors are attached to each part of the engine 1, and signals related to the environmental conditions of each part and the operating state of the engine 1 are output.

  For example, the air flow meter 43 outputs a detection signal corresponding to the flow rate of intake air (intake air amount) upstream of the throttle valve 62 in the intake system 6. The intake air temperature sensor 49 is disposed in the intake manifold 63 and outputs a detection signal corresponding to the temperature of the intake air. The intake pressure sensor 48 is disposed in the intake manifold 63 and outputs a detection signal corresponding to the intake air pressure. The rail pressure sensor 41 outputs a detection signal corresponding to the fuel pressure stored in the common rail 22. The throttle opening sensor 42 detects the opening of the throttle valve 62. A / F (air-fuel ratio) sensors 44a and 44b are arranged on the upstream side and the downstream side of the NSR catalyst 75, respectively, and output detection signals that change continuously according to the oxygen concentration in the exhaust gas. The A / F sensor may be disposed only on the upstream side of the NSR catalyst 75 or only on the downstream side of the NSR catalyst 75. That is, the A / F sensor may be any sensor that can detect or estimate the air-fuel ratio of the exhaust gas. Similarly, the exhaust temperature sensors 45a and 45b are arranged on the upstream side and the downstream side of the NSR catalyst 75, respectively, and output detection signals corresponding to the exhaust gas temperature (exhaust temperature). The exhaust temperature sensor may be disposed only on the upstream side of the NSR catalyst 75 or only on the downstream side of the NSR catalyst 75. That is, the exhaust temperature sensor may be any sensor that can detect or estimate the temperature of the exhaust gas. Further, the differential pressure sensor (differential pressure transducer) 4A detects the pressure difference between the upstream side (engine 1 side) and the downstream side of the DPF 76. Based on the differential pressure signal from the differential pressure sensor 4A, the amount of PM trapped by the DPF 76 can be obtained. Specifically, it is determined that the PM collection amount increases as the differential pressure increases.

-ECU-
The ECU 100 includes a microcomputer including a CPU, a ROM, a RAM, and the like (not shown) and an input / output circuit. As shown in FIG. 3, the input circuit of the ECU 100 includes the rail pressure sensor 41, the throttle opening sensor 42, the air flow meter 43, the A / F sensors 44a and 44b, the exhaust temperature sensors 45a and 45b, the intake pressure sensor 48, An intake air temperature sensor 49 and a differential pressure sensor 4A are connected. Further, the input circuit includes a water temperature sensor 46 that outputs a detection signal corresponding to the cooling water temperature of the engine 1, an accelerator opening sensor 47 that outputs a detection signal corresponding to the depression amount of the accelerator pedal, and an output shaft (crank) of the engine 1. A crank position sensor 40 that outputs a detection signal (pulse) every time the shaft rotates by a certain angle, a vehicle speed sensor 4B that detects the traveling speed of the vehicle, and the like are connected.

  On the other hand, the supply circuit 21, the injector 23, the throttle valve 62, the EGR valve 81, and the variable nozzle vane mechanism (actuator for adjusting the opening degree of the variable nozzle vane) 54 of the turbocharger 5 are connected to the output circuit of the ECU 100. ing.

  Then, the ECU 100 executes various controls of the engine 1 based on outputs from the various sensors described above, calculated values obtained by arithmetic expressions using the output values, or various maps stored in the ROM. .

  For example, the ECU 100 executes pilot injection (sub-injection) and main injection (main injection) as fuel injection control of the injector 23.

  The pilot injection is an operation for injecting a small amount of fuel in advance prior to the main injection from the injector 23. The pilot injection is an injection operation for suppressing the ignition delay of fuel due to the main injection and leading to stable diffusion combustion, and is also referred to as sub-injection.

  The main injection is an injection operation (torque generation fuel supply operation) for generating torque of the engine 1. The injection amount in the main injection is basically determined so as to obtain the required torque according to the operating state such as the engine speed, the accelerator operation amount, the coolant temperature, the intake air temperature, and the like. For example, as the engine rotational speed (engine rotational speed calculated based on the output signal of the crank position sensor 40; engine rotational speed) increases, the accelerator operation amount (accelerator pedal depression detected by the accelerator opening sensor 47) increases. The larger the (amount) (the greater the accelerator opening), the higher the required torque value of the engine 1, and the greater the fuel injection amount in the main injection.

  As an example of a specific fuel injection mode, the pilot injection (fuel injection from a plurality of injection holes formed in the injector 23) is performed before the piston 13 reaches the compression top dead center, and the fuel injection is temporarily stopped. After that, the main injection is executed when the piston 13 reaches the vicinity of the compression top dead center after a predetermined interval. As a result, the fuel is combusted by self-ignition, and energy generated by this combustion is kinetic energy for pushing the piston 13 toward the bottom dead center (energy serving as engine output), and heat energy for raising the temperature in the combustion chamber 3. The heat energy is radiated to the outside (for example, cooling water) through the cylinder block 11 and the cylinder head 15.

  The fuel injection pressure when executing the fuel injection is determined by the internal pressure of the common rail 22. As the common rail internal pressure, generally, the target value of the fuel pressure supplied from the common rail 22 to the injector 23, that is, the target rail pressure, increases as the engine load (engine load) increases and the engine speed (engine speed) increases. It will be expensive. This target rail pressure is set according to a fuel pressure setting map stored in the ROM, for example. In the present embodiment, the fuel pressure is adjusted between 30 MPa and 200 MPa according to the engine load and the like.

  Further, the ECU 100 determines the fuel injection amount and the fuel injection form based on the engine operating state. Specifically, the ECU 100 calculates the engine rotation speed based on the detection value of the crank position sensor 40, obtains the amount of depression of the accelerator pedal (accelerator opening) based on the detection value of the accelerator opening sensor 47, The total fuel injection amount (the sum of the injection amount in pilot injection and the injection amount in main injection) is determined based on the engine speed and the accelerator opening.

  In addition to the pilot injection and main injection described above, after injection and post injection are performed as necessary. The function of these injections is well known. In particular, post-injection raises the temperature of exhaust gas in a DPF regeneration process to be described later. The post injection is also used for NOx reduction processing and S poison recovery control.

  Further, the ECU 100 controls the opening degree of the EGR valve 81 according to the operating state of the engine 1 to adjust the exhaust gas recirculation amount (EGR amount) toward the intake manifold 63. This EGR amount is set in accordance with an EGR map that is created in advance by experiments, simulations, or the like and stored in the ROM. This EGR map is a map for determining the EGR amount (EGR rate) using the engine speed and the engine load as parameters.

  Next, various processing operations for the exhaust purification unit 77 will be described. As this processing operation, there are NOx reduction processing, S poison recovery control, and DPF regeneration processing which is the characteristic feature of this embodiment. Hereinafter, these various processing operations will be described in order.

-NOx reduction treatment-
In general, in the diesel engine 1, the oxygen concentration of the mixture of fuel and air used for combustion in the combustion chamber 3 is in a high concentration state in most operating regions. The oxygen concentration of the air-fuel mixture supplied for combustion is usually reflected in the oxygen concentration in the exhaust gas as it is after subtracting the oxygen supplied for combustion, and the oxygen concentration in the air-fuel mixture (air-fuel ratio: combustion A / If F) is high, the oxygen concentration in the exhaust gas (air-fuel ratio: exhaust A / F) basically becomes similarly high. On the other hand, as described above, the NSR catalyst 75 has a characteristic of storing NOx when the oxygen concentration in the exhaust gas is high, and reducing NOx to NO ₂ or NO and releasing it when the oxygen concentration is low. As long as is in a high concentration state, NOx is occluded. However, there is a limit amount in the NOx occlusion amount of the NSR catalyst 75. When the NSR catalyst 75 occludes the limit amount of NOx, NOx in the exhaust gas is not occluded in the NSR catalyst 75 and passes through the catalyst casing. It becomes.

Therefore, the ECU 100 executes post injection by the injector 23, thereby temporarily reducing the oxygen concentration in the exhaust gas and increasing the amount of reducing components (HC and the like). Thus, the NSR catalyst 75 reduces and releases the stored NOx to NO ₂ or NO, and recovers (regenerates) its own NOx storage capability.

  Note that the NOx amount stored in the NSR catalyst 75 is estimated by recognizing the total NOx generation amount based on the history information of the engine speed and the fuel injection amount into each cylinder. When the estimated NOx amount exceeds a predetermined value set in advance (appropriate value before the NOx storage capacity of the NSR catalyst 75 is saturated), NOx reduction processing is performed by executing the post injection. As described above, the NOx storage capacity of the NSR catalyst 75 is recovered (regenerated).

-S poison recovery control-
As described above, by making the air-fuel ratio of the exhaust gas flowing into the NSR catalyst 75 a target rich air-fuel ratio in a spike manner, NOx held in the NSR catalyst 75 can be reduced. However, in the NSR catalyst 75, SOx is absorbed by the same mechanism as in the case of holding NOx, and once held, SOx is less likely to desorb than NOx, and NOx is released in a reducing atmosphere with a reduced oxygen concentration. Even if it is performed, SOx does not leave and gradually accumulates in the NSR catalyst 75. Such sulfur poisoning (S poisoning) causes a reduction in the NOx purification rate of the NSR catalyst 75.

As a method of eliminating S poisoning of the NSR catalyst 75, the ambient temperature of the NSR catalyst 75 is raised to a high temperature range of approximately 600 ° C. to 700 ° C., and the oxygen concentration of the exhaust gas flowing into the NSR catalyst 75 is lowered. Accordingly, the barium sulfate (BaSO ₄₎ absorbed in the NSR catalyst 75 SO ₃ ^- and SO ₄ ^- and pyrolyzed, followed by SO ₃ ^- and SO ₄ ^- hydrocarbons (HC) and carbon monoxide in the exhaust gas (CO) and reacted gaseous SO ₂ ^- method of reducing is mentioned.

  In the present embodiment, the post-injection and the opening degree control of the throttle valve 62 described above are used to oxidize unburned fuel components in the NSR catalyst 75, and to increase the bed temperature of the NSR catalyst 75 by the heat generated during the oxidation. In addition, the exhaust A / F is made rich so as to eliminate S poisoning.

-DPF regeneration process-
The ECU 100 detects a state in which PM is collected in the DPF 76 by detecting a differential pressure before and after the DPF 76. Specifically, the differential pressure sensor 4A detects the pressure difference between the upstream side (engine 1 side) and the downstream side of the DPF 76 formed of a porous ceramic structure for removing PM in the exhaust gas. Based on the differential pressure signal from the sensor 4A, the amount of PM trapped by the DPF 76 is obtained by calculation or a map stored in the ECU 100. Specifically, it is determined that the PM collection amount increases as the differential pressure increases.

  As a basic operation of the DPF regeneration process, when the amount of PM accumulated in the DPF 76 becomes equal to or greater than a predetermined amount, which is a threshold value for determining that it is necessary to remove PM (the value of the differential pressure is predetermined When the value is equal to or greater than the value), the post-injection of the injector 23 is executed. As a result, the reducing agent such as fuel supplied to the exhaust pipe 73 is oxidized by the NSR catalyst 75. The DPF 76 is heated by the oxidation heat at that time (for example, heated to about 650 ° C.), and the PM collected by the DPF 76 can be burned and removed. Specifically, the proximity post injection is executed after the pilot injection and the main injection are executed. After the temperature of the exhaust gas rises to a predetermined temperature by this proximity post injection, late post injection, which is retarded side post injection, is executed. Thereby, the temperature of the exhaust gas further rises, and the PM accumulated in the DPF 76 can be oxidized (combusted) and removed. The proximity post injection is started, for example, at 30 ° after the compression top dead center of the piston 13. The late post injection is started at 100 ° after the compression top dead center of the piston 13, for example. The injection timings of the proximity post injection and the late post injection are not limited to those described above, and are set as appropriate.

  During the DPF regeneration process, PM removal is performed using the exhaust gas temperature detected by the exhaust temperature sensors 45a and 45b, the intake air amount detected by the air flow meter 43, and the execution time of the DPF regeneration process as parameters. The amount is calculated, and the DPF regeneration process is terminated when the amount of PM removal reaches a predetermined amount. That is, each post injection is terminated and the normal fuel injection control is resumed.

(DPF regeneration processing restriction control)
Next, DPF regeneration processing restriction control, which is a characteristic feature of this embodiment, will be described. This DPF regeneration processing restriction control restricts (prohibits) DPF regeneration processing when a predetermined condition is satisfied in each of the values (a temperature estimation counter described later) correlated with the PM accumulation amount in the DPF 76 and the temperature in the engine compartment. )

  First, an outline of the DPF regeneration process restriction control will be described. Among the various parts housed in the engine compartment of a vehicle, there are parts with relatively low heat resistance. For example, a part molded from a synthetic resin material. And in the situation where the temperature in the engine compartment rises, it is not preferable that the ambient temperature exceeds the heat resistance temperature of the component having low heat resistance.

  The situation in which the temperature in the engine compartment rises includes a case where the vehicle is stopped and the engine 1 is stopped from the state where the filter regeneration process is being performed while the vehicle is traveling at a low vehicle speed. In such a situation, the temperature in the engine compartment may exceed the heat resistance temperature of the component having low heat resistance.

  Therefore, in the present embodiment, a situation in which the temperature in the engine compartment rises is estimated by a count value of a temperature estimation counter described later, and the count value of the temperature estimation counter is equal to or greater than a predetermined value, and the PM accumulation amount in the DPF 76 Is within the predetermined range, the DPF regeneration process is restricted (DPF regeneration process is prohibited), and the situation in which the temperature in the engine compartment rises is avoided, so that the vehicle stops and the engine 1 Even if the engine stops, the temperature in the engine compartment does not exceed the heat resistance temperature of the component having low heat resistance (temperature increase suppression control in the present invention). Even when the DPF regeneration process is limited in this way, the DPF regeneration process is forcibly executed when the PM accumulation amount in the DPF 76 reaches a predetermined allowable limit value. . That is, the filter regeneration process is executed with priority over the temperature rise suppression control. This will be specifically described below.

  As this DPF regeneration process restriction control, a low vehicle speed climbing judgment operation, a temperature estimation counter counting operation, and a DPF regeneration process restriction operation are performed.

  The low vehicle speed climb determination operation determines whether the vehicle is traveling at a low vehicle speed and traveling on an uphill road. That is, the amount of heat generated in the combustion chamber 3 is large because the amount of heat radiated to the outside is small because the traveling wind flowing into the engine compartment is small and the torque required for the engine 1 is high. Determine if you are in the situation.

  The counting operation of the temperature estimation counter is an operation for estimating the temperature in the engine compartment. In a situation where the temperature in the engine compartment rises, the count value of the temperature estimation counter is increased (incremented). To go. Specifically, when the vehicle travels at a low vehicle speed and the DPF regeneration process is being executed, the count value of the temperature estimation counter is increased assuming that the temperature in the engine compartment is rising. Further, when the vehicle is not traveling at a low vehicle speed uphill or when the DPF regeneration process is not executed, the count value of the temperature estimation counter is subtracted.

  In the DPF regeneration processing limiting operation, when the temperature in the engine compartment is estimated to be at a predetermined temperature because the count value of the temperature estimation counter has reached a predetermined value, the PM accumulation amount in the DPF 76 is set to the allowable upper limit. The DPF regeneration process is prohibited only when it is within a predetermined range less than the value (allowable upper limit accumulation amount).

  Each operation will be described below with reference to flowcharts.

<Low vehicle speed climbing judgment operation>
4 and 5 are flowcharts showing the procedure of the low vehicle speed climbing judgment operation. This flowchart is executed every predetermined time after the ignition switch (start switch) is turned on.

  First, in step ST1, it is determined whether or not the current fuel instruction injection amount (injection amount command value from the ECU 100) for the injector 23 exceeds a predetermined amount INJ1. The predetermined amount INJ1 is set in advance based on experiments and simulations as a value for obtaining torque required when the vehicle travels on an uphill road having a predetermined slope or more. Further, as described above, the fuel command injection amount is determined in the ECU 100 so as to obtain the required torque in accordance with the operation state such as the engine speed, the accelerator operation amount, the coolant temperature, the intake air temperature, and the like.

  If the fuel command injection amount is equal to or less than the predetermined amount INJ1, and a NO determination is made in step ST1, the operation proceeds to step ST10 (FIG. 5) and later described later.

  If the fuel command injection amount exceeds the predetermined amount INJ1, and a YES determination is made in step ST1, the process proceeds to step ST2, where a first timer provided in advance in the ECU 100 is turned on, and the first timer Start counting. The first timer is timed up in 5 seconds, for example. This time is not limited to this, and can be set arbitrarily.

  Thereafter, the process proceeds to step ST3, where it is determined whether or not the fuel command injection amount for the injector 23 is equal to or less than the predetermined amount INJ1.

  If the fuel commanded injection amount does not become equal to or less than the predetermined amount INJ1 (the fuel commanded injection amount exceeding the predetermined amount INJ1 is maintained) and NO is determined in step ST3, the process proceeds to step ST4, and the first Determine whether the timer has expired. That is, it is determined whether or not the fuel command injection amount exceeding the predetermined amount INJ1 is maintained for a predetermined time (5 sec).

  If the predetermined time has not yet elapsed and NO is determined in step ST4, the process returns to step ST3 to determine again whether or not the fuel command injection amount for the injector 23 has become equal to or less than the predetermined amount INJ1. .

  Then, if the predetermined time has elapsed and the first timer has expired without the fuel command injection amount becoming equal to or less than the predetermined amount INJ1, a YES determination is made in step ST4 and the process proceeds to step ST5 described later.

  On the other hand, if the fuel command injection amount becomes equal to or less than the predetermined amount INJ1 before the predetermined time elapses (before the first timer expires), a YES determination is made in step ST3, and operations after step ST10 described later are performed. Move on.

  In step ST5, it is determined whether or not the current slope of the road surface exceeds a predetermined slope SL1. The predetermined gradient SL1 can be set to an arbitrary value. Further, the climbing slope of the road surface is calculated by an arithmetic expression stored in the ROM of the ECU 100 with the vehicle acceleration and the fuel command injection amount from the injector 23 as parameters. Moreover, you may make it obtain | require the climbing gradient of a road surface with G sensor.

  If the climbing gradient of the road surface exceeds the predetermined gradient SL1, and YES is determined in step ST5, the process proceeds to step ST6. On the other hand, if the climbing slope of the road surface is equal to or smaller than the predetermined slope SL1, and a NO determination is made in step ST5, the operation proceeds to step ST10 and later described later.

  In step ST6, it is determined whether or not the current vehicle speed is less than a predetermined vehicle speed V1. The predetermined vehicle speed V1 is a value such that the traveling wind cannot sufficiently flow into the engine compartment (cannot sufficiently release the heat in the engine compartment), and is obtained by an arbitrary value or an experiment or simulation in advance. Is set as the specified value. The vehicle speed is detected by the vehicle speed sensor 4B.

  If the vehicle speed is less than the predetermined vehicle speed V1, and YES is determined in step ST6, the process proceeds to step ST7. On the other hand, when the vehicle speed is equal to or higher than the predetermined vehicle speed V1 and NO is determined in step ST6, the operation proceeds to step ST10 and later described later.

  In step ST7, it is determined whether or not the current intake air temperature exceeds a predetermined intake air temperature Tha1. The predetermined intake air temperature Tha1 can be set to an arbitrary value. The intake air temperature is detected by the intake air temperature sensor 49.

  If the intake air temperature exceeds the predetermined intake air temperature Tha1, and YES is determined in step ST7, the process proceeds to step ST8. On the other hand, if the intake air temperature is equal to or lower than the predetermined intake air temperature Tha1, and a NO determination is made in step ST7, the operation proceeds to the operation after step ST10 described later.

  In step ST8, it is determined whether or not the current cooling water temperature exceeds a predetermined cooling water temperature Thw1. The predetermined cooling water temperature Thw1 can be set to an arbitrary value. The cooling water temperature is detected by the water temperature sensor 46.

  When the cooling water temperature exceeds the predetermined cooling water temperature Thw1 and YES is determined in step ST8, the process proceeds to step ST9, and the low vehicle speed climbing flag stored in the ECU 100 is set to ON.

  On the other hand, when the cooling water temperature is equal to or lower than the predetermined cooling water temperature Thw1 and a NO determination is made in step ST8, the operation proceeds to the operation after step ST10 described later.

  As described above, in the operations of steps ST1 to ST9, the state in which the fuel instruction injection amount exceeds the predetermined amount INJ1 has continued for a predetermined time, the climbing gradient of the road surface exceeds the predetermined gradient SL1, and the vehicle speed is the predetermined vehicle speed. In step ST9, when all the conditions (AND condition) that the temperature is less than V1, the intake air temperature exceeds the predetermined intake water temperature Thal, and the cooling water temperature exceeds the predetermined cooling water temperature Thw1 are satisfied. The low vehicle speed climbing flag is set to ON. That is, the low vehicle speed climbing flag is set to ON when the temperature in the engine compartment is likely to rise as the vehicle state, the driving state of the engine 1, and the environmental conditions.

  Next, the operation after step ST10 when NO is determined in any of steps ST1, ST5, ST6, ST7, ST8, or when YES is determined in step ST3 will be described.

  In step ST10 (FIG. 5), it is determined whether or not the current climbing gradient of the road surface is less than a predetermined gradient SL2. The predetermined gradient SL2 can be set to an arbitrary value, and is set to a value smaller than the predetermined gradient SL1 in step ST5 or the same value as the predetermined gradient SL1.

  If the climbing slope of the road surface is less than the predetermined slope SL2, and YES is determined in step ST10, the process proceeds to step ST16, and the low vehicle speed climbing flag is set to OFF.

  On the other hand, if the climbing gradient of the road surface is equal to or greater than the predetermined gradient SL2 and NO is determined in step ST10, the process proceeds to step ST11, and it is determined whether or not the current vehicle speed exceeds the predetermined vehicle speed V2. The predetermined vehicle speed V2 is a value that allows the traveling wind to sufficiently flow into the engine compartment (can sufficiently release the heat in the engine compartment), and is obtained by an arbitrary value or by experiments or simulations in advance. Is set to a value higher than the vehicle speed V1 in step ST6 or the same value as the vehicle speed V1.

  If the vehicle speed exceeds the predetermined vehicle speed V2 and YES is determined in step ST11, the process proceeds to step ST16, and the low vehicle speed climbing flag is set to OFF.

  On the other hand, if the vehicle speed is less than the predetermined vehicle speed V2 and NO is determined in step ST11, the process proceeds to step ST12, and it is determined whether or not the current fuel instruction injection amount for the injector 23 is less than the predetermined amount INJ2. . The predetermined amount INJ2 is set in advance through experiments and simulations as a value smaller than a value for obtaining torque required when the vehicle travels on an uphill road. Further, as described above, the fuel command injection amount is determined so as to obtain the required torque in accordance with the operation state such as the engine speed, the accelerator operation amount, the coolant temperature, the intake air temperature, and the like.

  If the fuel command injection amount is equal to or greater than the predetermined amount INJ2, and a NO determination is made in step ST12, the process directly returns.

  If the fuel command injection amount is less than the predetermined amount INJ2 and YES is determined in step ST12, the process proceeds to step ST13, the second timer provided in advance in the ECU 100 is turned on, and the count of the second timer is counted. To start. Similar to the first timer, the second timer is timed up in 5 seconds, for example. This time is not limited to this, and can be set arbitrarily.

  Thereafter, the process proceeds to step ST14, where it is determined whether or not the fuel command injection amount for the injector 23 is equal to or greater than the predetermined amount INJ2.

  If the fuel instruction injection amount does not become equal to or greater than the predetermined amount INJ2 (the fuel instruction injection amount less than the predetermined amount INJ2 is maintained) and if NO is determined in step ST14, the process proceeds to step ST15, and the second timer It is determined whether or not the time is up. That is, it is determined whether or not the fuel command injection amount less than the predetermined amount INJ2 is maintained for a predetermined time (5 sec).

  If the predetermined time has not yet elapsed and NO is determined in step ST15, the process returns to step ST14, and it is determined again whether or not the fuel command injection amount for the injector 23 is equal to or greater than the predetermined amount INJ2. .

  Then, if the predetermined time has elapsed and the second timer has expired without the fuel command injection amount becoming equal to or greater than the predetermined amount INJ2, a YES determination is made in step ST15 and the process proceeds to step ST16, where the low vehicle speed climbing flag is set. Set to OFF.

  On the other hand, if the fuel command injection amount becomes equal to or greater than the predetermined amount INJ2 before the predetermined time elapses (before the second timer expires), a YES determination is made in step ST14 and the low vehicle speed climbing flag is turned OFF. Returns without being set.

  As described above, in the operations of steps ST10 to ST16, the road climb gradient is less than the predetermined gradient SL2, the vehicle speed exceeds the predetermined vehicle speed V2, and the fuel command injection amount is less than the predetermined amount INJ2. When any condition (OR condition) of continuing for a predetermined time is satisfied, the low vehicle speed climbing flag is set to OFF in step ST16. That is, the low vehicle speed climbing flag is set to OFF when the temperature in the engine compartment is unlikely to rise as the vehicle state and the engine 1 drive state.

  By repeating the above routine, a low vehicle speed climbing operation is performed to determine whether the vehicle is traveling at a low vehicle speed and traveling on an uphill road. When it is determined that the vehicle is in the state, the low vehicle speed climbing flag is set to ON. On the other hand, when it is determined that the vehicle is not in the low vehicle speed climbing state, the low vehicle speed climbing flag is set to OFF.

<Counting operation of temperature estimation counter>
Next, the counting operation of the temperature estimation counter will be described.

  FIG. 6 is a flowchart showing the procedure of the counting operation of the temperature estimation counter. This flowchart is executed every predetermined time (for example, every 1 sec) after the ignition switch (start switch) is turned on. The counting operation of the temperature estimation counter is performed in parallel with the low vehicle speed climbing determination operation described above.

  First, in step ST21, the low vehicle speed climb flag information set in the low vehicle speed climb determination operation is read, and it is determined whether or not the low vehicle speed climb flag is ON. That is, it is determined whether or not the current vehicle traveling state is a state in which the vehicle speed is low and the vehicle is traveling on an uphill road (the temperature in the engine compartment is likely to rise).

  If the low vehicle speed climbing flag is ON and the determination in step ST21 is YES, the process proceeds to step ST22, and it is determined whether the DPF regeneration process is currently being executed. This determination is performed by recognizing the DPF regeneration processing command signal from the ECU 100 or determining whether fuel injection (post injection) for increasing the exhaust gas temperature is being performed.

  If the DPF regeneration process is being executed and it is determined YES in step ST22, the process proceeds to step ST23, where it is determined whether the count value of the temperature estimation counter provided in advance in the ECU 100 has reached the upper limit value. judge. As described above, this temperature estimation counter is used to estimate the temperature in the engine compartment, and the temperature in the engine compartment increases or the temperature in the engine compartment is expected to increase. The more the situation is, the larger the count value becomes. Accordingly, when the temperature in the engine compartment is low, such as when the engine is started, the count value of the temperature estimation counter is “0”. The upper limit value of the count value is set to “200”, for example. This value is not limited to this and is set as appropriate.

  If the count value of the temperature estimation counter has not reached the upper limit value and NO is determined in step ST23, the count value is incremented (incremented) by “1” in step ST24, and the process returns.

  On the other hand, if the count value of the temperature estimation counter has reached the upper limit value and a YES determination is made in step ST23, the count value of the temperature estimation counter is not counted up and the process returns directly.

  In this way, when the low vehicle speed climbing flag is ON and the DPF regeneration process is being executed, the temperature in the engine compartment rises (if the current operating state is continued) When the vehicle stops and the engine 1 stops, the temperature in the engine compartment may exceed the heat resistance temperature of the low heat resistance component), and the count value of the temperature estimation counter counts up. It will be done.

  On the other hand, if the low vehicle speed climbing flag is OFF and NO is determined in step ST21, the process proceeds to step ST25, where the count value of the temperature estimation counter is “0” which is the lower limit value. Determine whether.

  If the count value of the temperature estimation counter is not “0” and NO is determined in step ST25, the count value is counted down by “1” in step ST26, and the process returns.

  On the other hand, if the count value of the temperature estimation counter is “0” and a YES determination is made in step ST25, the count value of the temperature estimation counter is returned without being counted down.

  Even if the low vehicle speed climbing flag is ON (even if YES is determined in step ST21), if the DPF regeneration process is not being executed, a NO determination is made in step ST22. In addition, the operation proceeds to the operation after step ST25 described above. That is, in step ST25, it is determined whether or not the count value of the temperature estimation counter is the lower limit value “0”. The count value of the temperature estimation counter is not “0”, and NO determination is made in step ST25. If this is the case, in step ST26, the count value is counted down by "1" and the process returns. On the other hand, if the count value of the temperature estimation counter is “0” and a YES determination is made in step ST25, the count value of the temperature estimation counter is returned without being counted down.

  In this way, when the low vehicle speed climbing flag is OFF, or when the DPF regeneration process is not being executed (not being executed), the temperature in the engine compartment does not increase or increases. Is relatively small, and the count value of the temperature estimation counter is counted down on condition that the count value of the temperature estimation counter is not “0”.

  By repeating the above routine, the count operation of the temperature estimation counter is performed in which the count value of the temperature estimation counter is changed according to the state of the low vehicle speed climb flag and the execution state of the DPF regeneration process.

<DPF regeneration processing restriction operation>
Next, the DPF regeneration processing restriction operation will be described.

  FIG. 7 is a flowchart showing the procedure of the DPF regeneration processing restriction operation. This flowchart is executed every predetermined time after the ignition switch (start switch) is turned on. The DPF regeneration process limiting operation is performed in parallel with the low vehicle speed climbing determination operation and the temperature estimation counter counting operation described above.

  First, in step ST31, it is determined whether or not the PM accumulation amount in the DPF 76 is equal to or greater than a second reference amount that is an allowable upper limit value. The second reference amount is set in advance based on experiments and simulations, and is changed according to the atmospheric pressure. Specifically, when the next DPF regeneration process is executed, the temperature gradient in the DPF 76 (temperature difference per unit length inside the DPF 76, and if this temperature gradient is equal to or greater than a predetermined value, the DPF regeneration process The second reference amount is set so that a crack may occur in the DPF 76 during the execution of (1) does not exceed a predetermined amount. Further, since the air density is lower as the atmospheric pressure is lower, the cooling effect of the DPF 76 due to the air flowing into the exhaust system is reduced. Therefore, the temperature of the DPF 76 is likely to be higher as the atmospheric pressure is lower. For this reason, the lower the atmospheric pressure, the lower the second reference amount is set.

  If the PM accumulation amount in the DPF 76 is less than the second reference amount and a NO determination is made in step ST31, the process proceeds to step ST32, and whether the third timer provided in advance in the ECU 100 is counting (past In step ST38, the third timer starts counting in step ST38, and whether or not the counting is continuing is determined.

  If the third timer is not counting and NO is determined in step ST32, the process proceeds to step ST33, and the count value of the temperature estimation counter counted in the counting operation of the temperature estimation counter is equal to or greater than a predetermined value B. It is determined whether or not. The predetermined value B is an arbitrary value and is set to “100”, for example. This value is not limited to this.

  If the count value of the temperature estimation counter is less than the predetermined value B, that is, the temperature in the engine compartment is still low, and if NO is determined in step ST33, the process proceeds to step ST34, and the PM accumulation amount in the DPF 76 is increased. It is determined whether or not the first reference amount is exceeded. The first reference amount is set to a value smaller than the second reference amount. Specifically, this first reference amount is also set in advance based on experiments and simulations, and is changed according to the atmospheric pressure.

  If the PM accumulation amount in the DPF 76 is less than the first reference amount, a NO determination is made in step ST34, and the process proceeds to step ST35 and the DPF regeneration process is not executed. That is, as the amount of PM accumulated in the DPF 76, the DPF regeneration process is not executed because it has not yet reached the amount that requires the DPF regeneration process.

  On the other hand, when the PM accumulation amount in the DPF 76 is equal to or larger than the first reference amount, a YES determination is made in step ST34, and the process proceeds to step ST40 to execute the DPF regeneration process. In other words, when the count value of the temperature estimation counter is less than the predetermined value B, even if the DPF regeneration process is executed, the temperature in the engine compartment will exceed the heat resistance temperature of the parts having low heat resistance. Therefore, this DPF regeneration process is permitted.

  After the DPF regeneration process is executed in this way, when the PM accumulation amount in the DPF 76 decreases to less than the first reference amount, a NO determination is made in step ST34, and the process proceeds to step ST35 to end the DPF regeneration process. .

  On the other hand, if the count value of the temperature estimation counter is equal to or greater than the predetermined value B, YES is determined in step ST33 and the process proceeds to step ST36, where the PM accumulation amount in the DPF 76 is equal to or greater than the first reference amount and the first value. It is determined whether or not it is within a range less than 2 reference amounts (first reference amount ≦ PM deposition amount <second reference amount).

  Here, when the PM accumulation amount in the DPF 76 is not within the above range, that is, when the count value of the temperature estimation counter is not less than the predetermined value B, but the PM accumulation amount in the DPF 76 is less than the first reference amount (the above step) Since the NO determination is made in ST31, the PM accumulation amount in the DPF 76 is not equal to or greater than the second reference amount), the process proceeds to step ST35, and the DPF regeneration process is not executed. That is, even if the count value of the temperature estimation counter is equal to or greater than the predetermined value B, the DPF regeneration process is not executed because the PM accumulation amount in the DPF 76 has not yet reached the amount that requires the DPF regeneration process.

  On the other hand, if the PM accumulation amount in the DPF 76 is within the above range and YES is determined in step ST36, that is, the count value of the temperature estimation counter is not less than the predetermined value B, and the PM accumulation amount in the DPF 76 is within the above range. If (first reference amount ≦ PM deposition amount <second reference amount), the process proceeds to step ST37, and DPF regeneration processing is prohibited (not executed). That is, when the count value of the temperature estimation counter is equal to or greater than the predetermined value B, the temperature in the engine compartment is likely to rise, and when the DPF regeneration process is executed in such a situation, the vehicle subsequently stops and When the engine 1 is stopped, the DPF regeneration process is prohibited on the assumption that the temperature in the engine compartment may exceed the heat resistance temperature of the parts having low heat resistance.

  After prohibiting the DPF regeneration process in this way, the process proceeds to step ST38, where a third timer provided in advance in the ECU 100 is turned on, and counting of the third timer is started. This third timer is timed up in 600 seconds, for example. This time is not limited to this, and can be set arbitrarily.

  However, it is necessary to set the third timer as a value that secures a time sufficient for the count value of the temperature estimation counter to be subtracted to “0” or a value close to “0” until the time is up. . That is, when the DPF regeneration process is prohibited in step ST37, the count value of the temperature estimation counter is counted down in the count operation of the temperature estimation counter (the flowchart of FIG. 6) (step ST25). The third timer is set so as to secure time for the count value of the temperature estimation counter that has risen to the value B to be subtracted to “0” or a value close to “0”.

  After the third timer is turned on, the process proceeds to step ST39, where it is determined whether or not the third timer has expired. That is, it is determined whether or not the state where the DPF regeneration process is prohibited is maintained for a predetermined time.

  If the predetermined time has not yet elapsed and NO is determined in step ST39, the process returns. In this case, in the next routine, a YES determination is made in step ST32 (when the PM accumulation amount does not reach the second reference amount), and the DPF regeneration process is performed without performing the determinations in steps ST33 and ST36. In the prohibited state, it waits for the third timer to expire.

  When such a state (a state in which the DPF regeneration process is prohibited) is continued and the predetermined time has elapsed and the third timer has timed out, a YES determination is made in step ST39 and the process proceeds to step ST40, where the DPF regeneration process is performed. Run. That is, the DPF regeneration process is executed in order to eliminate the continuing state where the PM accumulation amount in the DPF 76 is equal to or greater than the first reference amount.

  When the DPF regeneration process is executed in this way, the count value of the temperature estimation counter is less than the predetermined value B, so that a NO determination is made in step ST33, and the operation after step ST34 described above is performed. The DPF regeneration process is continued until the PM accumulation amount in the DPF 76 becomes less than the first reference amount.

  On the other hand, if the PM accumulation amount in the DPF 76 is equal to or greater than the second reference amount and YES is determined in step ST31, the process proceeds to step ST41, and the DPF regeneration process is forcibly started. That is, the DPF regeneration process is executed regardless of the count value of the temperature estimation counter.

  Thereafter, the process proceeds to step ST42, and it is determined whether or not the PM combustion amount (PM removal amount) in the DPF regeneration process is equal to or greater than a predetermined amount A (filter regeneration process end amount in the present invention). The predetermined amount A can be set to an arbitrary value. Further, as described above, the PM combustion amount in the DPF regeneration process uses the exhaust gas temperature detected by the exhaust temperature sensors 45a and 45b, the intake air amount detected by the air flow meter 43, and the execution time of the DPF regeneration process as parameters. Calculated.

  Then, it waits for the PM combustion amount in the DPF regeneration process to reach the predetermined amount A or more. When the PM combustion amount reaches the predetermined amount A or more, a YES determination is made in step ST42, and the DPF regeneration process ends in step ST43. .

  The above DPF regeneration process limiting operation is repeated, and the DPF regeneration process is executed according to the count value of the temperature estimation counter and the PM accumulation amount in the DPF 76.

  As described above, in this embodiment, the count value of the temperature estimation counter is equal to or greater than the predetermined value B, and the PM accumulation amount in the DPF 76 is within the above range (first reference amount ≦ PM deposition amount <second reference amount). In such a case, the DPF regeneration process is prohibited (not executed). In other words, in a situation where the temperature in the engine compartment is likely to rise, when the vehicle subsequently stops and the engine 1 stops, the temperature in the engine compartment exceeds the heat resistance temperature of the parts having low heat resistance. The DPF regeneration process is prohibited in consideration of the possibility of a failure. For this reason, it is possible to avoid a situation in which the temperature in the engine compartment exceeds the heat resistance temperature of the component having low heat resistance. When the PM accumulation amount in the DPF 76 is equal to or greater than the second reference amount, the DPF regeneration process is executed regardless of the count value of the temperature estimation counter. As a result, the PM accumulation amount is prevented from being excessive due to the prohibition of the DPF regeneration process, and the performance of the DPF 76 can be maintained high.

(Modification 1)
Next, Modification 1 will be described. In the above-described embodiment, the DPF regeneration process is not executed (prohibited) as the temperature rise suppression control for suppressing the temperature increase in the engine compartment. In this modified example, a radiator fan (not shown) disposed in the engine compartment is driven in place of or in addition thereto, and outside air is introduced into the engine compartment.

  That is, if YES is determined in step ST36 in the flowchart shown in FIG. 7, that is, the count value of the temperature estimation counter is equal to or greater than the predetermined value B, and the PM accumulation amount in the DPF 76 is within the above range (first reference amount ≦ PM If the accumulated amount is less than the second reference amount, the process proceeds to step ST37 to prohibit (non-execute) the DPF regeneration process and forcibly drive the radiator fan to introduce outside air into the engine compartment. . Alternatively, without prohibiting the DPF regeneration process (permitting execution), the radiator fan is forcibly driven to introduce outside air into the engine compartment.

  Thereby, even if the temperature in the engine compartment is likely to rise because the count value of the temperature estimation counter is equal to or greater than the predetermined value B, the temperature in the engine compartment is reduced by introducing the outside air by driving the radiator fan. Can be reduced. For this reason, even if a vehicle stops after that and the engine 1 stops, the temperature in an engine compartment can be restrained below the heat-resistant temperature of the said component with low heat resistance.

(Modification 2)
Next, Modification 2 will be described. In the above-described embodiment, the operating state in which the temperature in the engine compartment rises is determined based on the fuel instruction injection amount, the road slope, the vehicle speed, the intake air temperature, and the coolant temperature. Instead of this, in this modification, a temperature sensor is disposed in the engine compartment, and it is determined whether or not the engine compartment is in an operating state in which the temperature in the engine compartment rises based on the temperature measured by the temperature sensor. To do.

  Specifically, the location of the temperature sensor is around the part with low heat resistance, and the temperature inside the engine compartment rises when the ambient temperature of this part reaches near the heat-resistant temperature. The temperature estimation counter is incremented on the condition that the DPF regeneration process is being executed.

  Further, the position of the temperature sensor is not limited to the above, and may be, for example, around the engine or around the exhaust system parts. In this case, it is preferable to estimate the ambient temperature of the component having low heat resistance based on the measured temperature.

-Other embodiments-
In the above-described embodiment and each modification, the case where the present invention is applied to an in-line four-cylinder diesel engine has been described. Etc.) is not particularly limited.

  In the above-described embodiment and each modification, fuel for DPF regeneration processing is supplied by post injection from the injector 23. The present invention is not limited to this, and a fuel addition valve that supplies fuel directly to the exhaust system 7 (for example, the exhaust manifold 72) is provided, and DPF regeneration processing is performed using the fuel supplied from the fuel addition valve. May be.

  Further, in the above-described embodiment and each modification, the PM accumulation amount for starting the DPF regeneration process when the count value of the temperature estimation counter is less than a predetermined value (B) and the count value of the temperature estimation counter are predetermined. When the value is equal to or greater than the value (above B), the lower limit amount of the PM accumulation amount that prohibits the DPF regeneration process is set to be the same (the first reference amount). The present invention is not limited to this, and these values may be different from each other. For example, the former PM accumulation amount may be set to a larger value than the latter PM accumulation amount.

  Further, in the embodiment and each modification, the second reference amount is set as the allowable upper limit value of the PM deposition amount. The present invention is not limited to this, and an amount smaller than the allowable upper limit value of the PM accumulation amount by a predetermined amount may be set as the second reference amount so that damage to the DPF 76 and the like can be reliably prevented.

  Further, in the above-described embodiment and each modified example, the condition that the low vehicle speed climbing flag is set to ON is that the state in which the fuel instruction injection amount exceeds the predetermined amount INJ1 has continued for a predetermined time, and the road slope is predetermined. All conditions (the slope SL1 is exceeded, the vehicle speed is less than the predetermined vehicle speed V1, the intake air temperature exceeds the predetermined intake air temperature Tha1, and the cooling water temperature exceeds the predetermined cooling water temperature Thw1) The AND condition is satisfied. The present invention is not limited to this, the state in which the fuel commanded injection amount exceeds the predetermined amount INJ1 has continued for a predetermined time, the climbing slope of the road surface exceeds the predetermined gradient SL1, and the vehicle speed is less than the predetermined vehicle speed V1. When each of these conditions (AND condition) is satisfied, the low vehicle speed climbing flag may be set to ON.

  Moreover, although the said embodiment and each modification demonstrated the engine 1 which applied the piezo injector 23 which changes a fuel-injection rate by becoming a valve opening state of full open only during an electricity supply period, this invention is variable injection rate. Application to an engine to which an injector is applied is also possible.

  The present invention is applicable to regeneration processing of a DPF provided in an exhaust system in a common rail in-cylinder direct injection multi-cylinder diesel engine mounted on an automobile.

1 engine (internal combustion engine)
12 Cylinder bore 23 Injector 3 Combustion chamber 46 Water temperature sensor 49 Intake air temperature sensor 4A Differential pressure sensor 4B Vehicle speed sensor 7 Exhaust system 76 DPF (Exhaust purification filter)
77 Exhaust gas purification unit 100 ECU

Claims (4)

An exhaust gas purification apparatus for an internal combustion engine that includes an exhaust gas purification filter that collects particulate matter contained in the exhaust gas of the internal combustion engine and that can perform filter regeneration processing to remove the particulate matter collected by the exhaust gas purification filter In
When the accumulated amount of particulate matter in the exhaust purification filter is not less than the first reference amount and less than the second reference amount, and the engine compartment temperature is in an operating state, the filter regeneration process is not executed. While suppressing the temperature rise in the engine compartment due to the execution of the filter regeneration process by performing the temperature rise suppression control to
When the amount of particulate matter accumulated in the exhaust purification filter is equal to or greater than the second reference amount, the filter regeneration process is prioritized and executed over the temperature rise suppression control,
The exhaust gas purification apparatus for an internal combustion engine is characterized in that the filter regeneration process is started when the temperature increase suppression control that does not execute the filter regeneration process is continued for a predetermined time. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
When the amount of particulate matter accumulated in the exhaust purification filter is equal to or greater than the second reference amount and the filter regeneration process is executed, the removal amount of the particulate matter from the exhaust purification filter is a predetermined filter regeneration process completion amount. The exhaust gas purification apparatus for an internal combustion engine is configured to execute the filter regeneration process with priority over the temperature rise suppression control until the temperature reaches the control value. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2,
Mounted on the vehicle,
The operating state in which the temperature in the engine compartment rises is a case where the vehicle speed is below a predetermined value and the vehicle is traveling on an uphill road exceeding a predetermined gradient. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2,
Mounted on the vehicle,
The operating state in which the temperature in the engine compartment rises is a state in which the vehicle speed is below a predetermined value, the vehicle is traveling on an uphill road exceeding a predetermined gradient, and the fuel injection amount of the internal combustion engine is a predetermined amount or more. An exhaust gas purification apparatus for an internal combustion engine, characterized in that the exhaust gas purification apparatus is continued for a time.

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