JP2019132226A - Exhaust emission control device for engine - Google Patents

Abstract

To provide an exhaust emission control device for an engine, capable of appropriately regenerating a filter while suppressing the worsening of fuel consumption performance.SOLUTION: In the engine which has an exhaust passage 40 provided with an oxidation catalyst 42 and a filter 44 capable of trapping particulate matters, regeneration injection is performed for injecting fuel to regenerate the filter 44. In second operation conditions that main injection is stopped and filter regenerating conditions are established, a fuel injection device 10 is allowed to perform at least compression stroke injection Q1 to be performed in a compression stroke as the regeneration injection, while making the amount of fuel to be injected into a cylinder with the compression stroke injection Q1 smaller when a cylinder pressure as a pressure in the cylinder is high than when it is low.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust purification control apparatus applied to an engine including a cylinder and an engine body including a fuel injection device that injects fuel into the cylinder, and an exhaust passage through which exhaust gas discharged from the engine body flows.

  Conventionally, in an engine, a filter capable of collecting fine particles is provided in an exhaust passage. In this engine, regeneration control for removing the particulates collected by the filter and regenerating the filter is performed.

  For example, Patent Document 1 discloses an engine in which an oxidation catalyst having an oxidation function is provided on the upstream side of the filter, and performs post-injection in which fuel is injected later than main injection for generating engine torque. Then, an unburned fuel is allowed to flow into the oxidation catalyst and react with it in the oxidation catalyst, and the temperature of the exhaust gas passing through the filter is raised by this reaction heat to burn and remove the particulates collected by the filter. It is disclosed.

JP 2004-316441 A

  However, when the main injection is stopped along with the deceleration of the vehicle on which the engine is mounted, the temperature of the exhaust gas discharged from the engine body is significantly lowered. Therefore, in this case, even if the post injection is performed, the temperature of the exhaust gas that passes through the filter cannot be sufficiently increased, and the regeneration time of the filter becomes long and the fuel consumption performance deteriorates.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine exhaust gas purification control device that can appropriately regenerate a filter while suppressing deterioration of fuel consumption performance.

  In order to solve the above-described problems, the present invention is applied to an engine including an engine body including a cylinder and a fuel injection device that injects fuel into the cylinder, and an exhaust passage through which exhaust gas discharged from the engine body flows. An exhaust purification control device for controlling the fuel injection device; an oxidation catalyst provided in the exhaust passage; a filter provided in the exhaust passage and capable of collecting particulates in the exhaust gas; The control means regenerates the filter in a first operating condition in which main injection for injecting fuel into the cylinder at a timing capable of generating engine torque is performed and the regeneration condition for the filter is satisfied The fuel injection device performs the regeneration injection for injecting the fuel for the fuel at a timing delayed from the main injection during the expansion stroke. In a second operating condition that is stopped and the filter regeneration condition is satisfied, the control means performs a compression stroke that is performed during the compression stroke as a re-use injection that injects fuel for regenerating the filter. The fuel injection device performs at least the injection, and the amount of fuel injected into the cylinder by the compression stroke injection is reduced when the in-cylinder pressure, which is the pressure in the cylinder, is higher than when the in-cylinder pressure is low. An exhaust purification control device for an engine is provided.

  According to this device, when main injection is stopped (in the second operating condition), part of the fuel injected into the cylinder to regenerate the filter is injected into the cylinder during the compression stroke. Therefore, the reaction of unburned fuel in the oxidation catalyst can be promoted, and the temperature in the filter can be effectively increased.

  Specifically, the fuel injected into the cylinder in the compression stroke is heated by the compression action of the piston. The fuel becomes lighter (lower molecular weight) and becomes more reactive at higher temperatures. Therefore, according to this apparatus, while the main injection is stopped, the fuel is injected into the cylinder during the compression stroke as described above, so that the fuel can be introduced into the oxidation catalyst in a lightened state. The reaction of the fuel at the catalyst can be promoted, and the temperature of the exhaust can be effectively increased with less fuel. Accordingly, it is possible to appropriately regenerate the filter by increasing the temperature of the filter while suppressing the deterioration of the fuel consumption performance.

  However, when the in-cylinder pressure is high (for example, when the in-cylinder pressure at the compression top dead center is high), the fuel easily burns in the cylinder. Therefore, if a large amount of fuel is injected into the cylinder during the compression stroke when the in-cylinder pressure is high, this fuel may burn and unexpectedly generate engine torque. On the other hand, in this device, the amount of fuel injected into the cylinder during the compression stroke is reduced when the in-cylinder pressure is high than when it is low. Therefore, the engine torque can be prevented from being unexpectedly generated when the in-cylinder pressure is high, and more fuel can be injected into the cylinder in the compression stroke when the in-cylinder pressure is low, thereby promoting the regeneration of the filter.

  In the above configuration, it is preferable that the start timing of the compression stroke injection is advanced when the in-cylinder pressure is high than when it is low (Claim 2).

  According to this configuration, when the main injection is stopped, the compression stroke injection is performed on the more advanced side when the in-cylinder pressure is high and the fuel is easily combusted in the cylinder. Fuel can be diffused into the cylinder, preventing the formation of an air-fuel mixture with high fuel concentration locally in the cylinder and more reliably preventing the fuel related to the compression stroke injection from burning in the cylinder it can.

  In addition, when the in-cylinder pressure is low, the scattering distance of the fuel injected into the cylinder becomes long and adheres to the wall surface of the cylinder and easily leaks to the outside of the cylinder. On the other hand, in this configuration, when the in-cylinder pressure is low, the compression stroke injection is performed at a timing that is more retarded and the in-cylinder pressure is higher. Therefore, leakage of fuel related to the compression stroke injection to the outside of the cylinder can be suppressed.

  In the above-described configuration, the control means includes the compression stroke injection performed in the second half of the compression stroke and the expansion stroke injection performed in the first half of the expansion stroke as the regeneration injection under the second operating condition. It is preferable that the amount of fuel injected into the cylinder by the expansion stroke injection is increased when the in-cylinder pressure is high than when it is low (Claim 3). .

  According to this configuration, when the main injection is stopped, fuel is injected into the cylinder in the expansion stroke in addition to the compression stroke. Therefore, it is possible to increase the total amount of fuel introduced into the oxidation catalyst and to obtain more oxidation reaction heat. In addition, in this configuration, the higher the in-cylinder pressure, the smaller the injection amount of the compression stroke injection, whereas the higher the in-cylinder pressure, the larger the injection amount of the expansion stroke injection. Therefore, the total amount of fuel introduced into the oxidation catalyst can be ensured whether the in-cylinder pressure is high or low.

  In the above-described configuration, the control means further includes, as the regeneration injection, an intermediate injection that is performed before the expansion stroke and before the expansion stroke as the regeneration injection. Preferably, the amount of fuel injected into the cylinder by the intermediate injection is preferably smaller when the in-cylinder pressure is high than when it is low.

  According to this configuration, when the main injection is stopped, the fuel is injected into the cylinder by being divided into the compression stroke injection, the expansion stroke injection, and the intermediate injection. Therefore, while increasing the total amount of fuel injected into the cylinder, that is, the fuel introduced into the oxidation catalyst, the injected fuel can be diffused in the cylinder, thereby promoting the lightening of the fuel. Therefore, the oxidation reaction of the oxidation catalyst can be further promoted to increase the temperature in the filter more reliably. Further, in this configuration, the amount of fuel related to the intermediate injection performed at a time near the compression top dead center and relatively easy to burn in the cylinder is smaller than when the cylinder pressure is high. Therefore, when the in-cylinder pressure is high, the fuel related to the intermediate injection can be prevented from burning in the cylinder and unexpectedly generate engine torque, and when the in-cylinder pressure is low, the fuel related to the intermediate injection is set to a higher temperature. This lightening can be promoted.

  In the above configuration, it is preferable that the total amount of fuel injected into the cylinder by the regeneration injection performed under the second operating condition is a constant amount regardless of the in-cylinder pressure. 5).

  According to this configuration, when the main injection is stopped, the amount of fuel introduced into the cylinder and thus into the oxidation catalyst can be maintained at an appropriate amount.

  In the above configuration, the injection amount of the regeneration injection performed under the second operating condition is made smaller than the injection amount of the regeneration injection performed under the first operating condition. Preferred (claim 6).

  According to this configuration, when the main injection is stopped, the amount of fuel for regeneration injection is reduced, so that the amount of fuel related to this regeneration injection can be more reliably suppressed from burning in the cylinder. . On the other hand, when the main injection is performed, the fluctuation ratio of the engine torque with respect to the engine torque when the fuel according to the regeneration injection does not burn even if a part of the fuel burns is small. On the other hand, according to this configuration, the temperature of the filter can be further increased by increasing the injection amount of the regeneration injection when the main injection is being performed.

  The configuration for detecting the in-cylinder pressure includes a configuration in which an intake pressure sensor capable of detecting the pressure of the intake air introduced into the engine body is provided, and the in-cylinder pressure is estimated using the detected value of the intake pressure sensor ( Claim 7).

  ADVANTAGE OF THE INVENTION According to this invention, a filter can be reproduced | regenerated appropriately, suppressing the deterioration of a fuel consumption performance.

1 is a schematic configuration diagram of an engine system to which an engine exhaust gas purification control apparatus according to an embodiment of the present invention is applied. It is a block diagram which shows the control system of an engine system. It is a flowchart which shows the flow of DPF regeneration control. It is the figure which showed the injection pattern at the time of DPF regeneration control, (a) is the injection pattern at the time of normal regeneration control, (b) is the injection pattern of the regeneration control at the time of fuel cut. It is a flowchart which shows the setting procedure of each command injection quantity of front | former stage injection, intermediate | middle injection, and back | latter stage injection. It is the graph which showed the relationship between cylinder pressure and each injection quantity of front | former stage injection, intermediate | middle injection, and back | latter stage injection. It is a flowchart which shows the setting procedure of each command injection timing of front | former stage injection, intermediate | middle injection, and back | latter stage injection. It is the graph which showed the relationship between cylinder pressure and each injection timing of front | former stage injection, intermediate | middle injection, and back | latter stage injection. It is the graph which showed the relationship between equivalence ratio and the corrected amount of each injection timing of intermediate | middle injection and back | latter stage injection. It is the graph which showed the relationship between engine water temperature and intake air temperature, and the corrected amount of each injection timing of intermediate | middle injection and back | latter stage injection. It is the figure which showed typically the time change of each parameter when implementing DPF regeneration control.

  Hereinafter, an engine exhaust gas purification control apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(1) Overall Configuration FIG. 1 is a schematic configuration diagram of an engine system 100 to which the engine exhaust gas purification control apparatus of the present embodiment is applied.

  The engine system 100 includes a four-stroke engine main body 1, an intake passage 20 for introducing air (intake air) into the engine main body 1, an exhaust passage 40 for discharging exhaust from the engine main body 1 to the outside, a first A turbocharger 51 and a second turbocharger 52 are provided. The engine system 100 is provided in a vehicle, and the engine body 1 is used as a drive source for the vehicle. The engine body 1 is a diesel engine, for example, and has four cylinders 2 arranged in a direction orthogonal to the paper surface of FIG.

  The engine body 1 includes a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 provided on the upper surface of the cylinder block 3, and a piston 5 that is slidably inserted into the cylinder 2. Yes. A combustion chamber 6 is defined above the piston 5.

  Engine cooling water for cooling the engine body 1 is supplied to the engine body 1. Specifically, a water jacket through which engine coolant flows is formed in the cylinder block 3 and the cylinder head 4, and the engine coolant is supplied to the water jacket.

  The piston 5 is connected to the crankshaft 7, and the crankshaft 7 rotates about its central axis in accordance with the reciprocating motion of the piston 5.

  The cylinder head 4 includes an injector (fuel injection device) 10 that injects fuel into the combustion chamber 6 (inside the cylinder 2), and a glow plug 11 that raises the temperature of the fuel / air mixture in the combustion chamber 6. However, one set is provided for each cylinder 2.

  In the example shown in FIG. 1, the injector 10 is provided at the center of the ceiling surface of the combustion chamber 6 so as to face the combustion chamber 6 from above. The glow plug 11 has a heat generating portion that generates heat when energized, and is attached to the ceiling surface of the combustion chamber 6 so that the heat generating portion is located in the vicinity of the front end portion of the injector 10. ing. For example, the injector 10 is provided with a plurality of nozzle holes at its tip, and the glow plug 11 is located between the plurality of sprays from the plurality of nozzles of the injector 10 so that the heat generating portion is not in direct contact with the fuel spray. Have been placed.

  In the cylinder head 4, an intake port for introducing air supplied from the intake passage 20 into each combustion chamber 6, an intake valve 12 that opens and closes the intake port, and exhaust gas generated in each combustion chamber 6 is exhausted through the exhaust passage. An exhaust port for leading to 40 and an exhaust valve 13 for opening and closing the exhaust port are provided.

  In the intake passage 20, the air cleaner 21, the compressor 51 a of the first turbocharger 51 (hereinafter, appropriately referred to as the first compressor 51 a), and the compressor 52 a of the second turbocharger 52 (hereinafter, appropriately) from the upstream side. , A second compressor 52a), an intercooler 22, a throttle valve 23, and a surge tank 24. The intake passage 20 is provided with an intake side bypass passage 25 that bypasses the second compressor 52a and an intake side bypass valve 26 that opens and closes the intake side bypass passage 25. The intake-side bypass valve 26 is switched between a fully closed state and a fully open state by a driving device (not shown).

  In the exhaust passage 40, in order from the upstream side, the turbine 52b of the second turbocharger 52 (hereinafter referred to as the second turbine 52b as appropriate) and the turbine 51b of the first turbocharger 51 (hereinafter referred to as the first of the first as appropriate). Turbine 51 b), first catalyst 43, DPF (Diesel Particulate Filter) 44, urea injector 45 that injects urea into the exhaust passage 40 on the downstream side of the DPF 44, and NOx using urea injected from the urea injector 45. There are provided an SCR (Selective Catalytic Reduction) catalyst 46 for purifying the catalyst, and a slip catalyst 47 for oxidizing and purifying unreacted ammonia discharged from the SCR catalyst 46.

  The DPF 44 is a filter for collecting particulate matter (PM) in the exhaust gas. For example, the DPF 44 includes a wall flow type filter formed of a heat resistant ceramic material such as silicon carbide (SiC) or cordierite, or a three-dimensional network filter formed of a heat resistant ceramic fiber. More specifically, the DPF 44 is formed with a plurality of passages in a lattice pattern made of porous ceramics or the like. The first passage is opened on the exhaust upstream side and closed on the exhaust downstream side, and the exhaust upstream side is closed on the exhaust. The second passages opened on the downstream side are alternately arranged in a staggered manner. Exhaust gas that has entered the first passage passes through a partition wall that separates the passages and exits to the second passage. At this time, the partition functions as a filter that prevents the particulate matter from escaping into the second passage, and the particulate matter is collected in the partition.

  There is a limit to the amount of particulate matter that can be collected by the DPF 44. Therefore, it is necessary to remove the collected PM from the DPF 44 as appropriate. The PM collected in the DPF 44 is exposed to a high temperature and burned by receiving supply of oxygen, and is removed from the DPF 44. The temperature at which PM is burned and removed is relatively high at about 600 ° C. Therefore, in order to burn PM and remove it from the DPF 44, it is necessary to raise the temperature of the DPF 44.

  The first catalyst 43 includes a NOx catalyst 41 for purifying NOx and an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 42.

  The oxidation catalyst 42 uses oxygen in the exhaust gas to oxidize hydrocarbons (HC), that is, unburned fuel, carbon monoxide (CO), and the like to change them into water and carbon dioxide. The oxidation catalyst 42 is made of, for example, a carrier on which platinum or platinum plus palladium is supported. Here, the oxidation reaction occurring in the oxidation catalyst 42 is an exothermic reaction, and when the oxidation reaction occurs in the oxidation catalyst 42, the temperature of the exhaust is raised.

  The NOx catalyst 41 is in a lean state in which the air-fuel ratio of exhaust (A / F, F: the ratio of air (oxygen) contained in the exhaust gas to the fuel (H) contained in the exhaust gas) is larger than the stoichiometric air-fuel ratio. NOx storage reduction catalyst (NSC: NOx Storage Catalyst) that stores NOx in the exhaust and reduces the stored NOx in a rich state where the air-fuel ratio of the exhaust is in the vicinity of the stoichiometric air-fuel ratio or smaller than the stoichiometric air-fuel ratio. It is.

  The first catalyst 43 is formed, for example, by coating the surface of a DOC catalyst material layer with an NSC catalyst material.

  The exhaust passage 40 includes an exhaust-side bypass passage 48 that bypasses the second turbine 52b, an exhaust-side bypass valve 49 that opens and closes the exhaust passage, a waste gate passage 53 that bypasses the first turbine 51b, and a waste gate that opens and closes the exhaust passage. A valve 54 is provided.

  The engine system 100 according to the present embodiment can execute EGR for recirculating a part of exhaust gas (EGR gas) to intake air, and includes an EGR device 55 for executing the EGR. The EGR device 55 connects the portion of the exhaust passage 40 upstream of the upstream end of the exhaust-side bypass passage 48 and the portion of the intake passage 20 between the throttle valve 23 and the surge tank 24. A first EGR valve 57 that opens and closes it, and an EGR cooler 58 that cools the exhaust gas that passes through the EGR passage 56. Further, the EGR device 55 includes an EGR cooler bypass passage 59 that bypasses the EGR cooler 58 and a second EGR valve 60 that opens and closes the EGR cooler bypass passage 59.

(2) Control system The control system of an engine system is demonstrated using FIG. The engine system 100 of the present embodiment is controlled mainly by a PCM (control means, powertrain control module) 200 mounted on a vehicle. The PCM 200 is a microprocessor including a CPU, a ROM, a RAM, an I / F, and the like, and corresponds to a control unit according to the present invention.

  Information from various sensors is input to the PCM 200.

  For example, the engine system 100 includes a rotation speed sensor SN1 that detects the rotation speed of the crankshaft 7, that is, the engine rotation speed, and an airflow sensor that is provided near the air cleaner 21 and detects the amount of intake air (air) flowing through the intake passage 20. SN2, the gas flowing into the combustion chamber 6 (cylinder 2), that is, the intake pressure sensor SN3 that detects the intake pressure that is the pressure of the intake air, and the oxygen in the portion of the exhaust passage 40 between the first turbine 51b and the first catalyst 43. Exhaust O2 sensor SN4 for detecting the concentration, oxidation catalyst temperature sensor SN5 for detecting the temperature of the oxidation catalyst 42, and differential pressure across the DPF 44 (the difference between the pressure in the exhaust passage 40 upstream of the DPF 41b and the pressure in the downstream portion) There are provided a differential pressure sensor SN6 for detecting the temperature, a DPF temperature sensor SN7 for detecting the temperature of the DPF 44, and the like. The intake pressure sensor SN3 is attached to the surge tank 24, and detects the pressure in the surge tank 24, that is, the pressure of the intake air after being supercharged by the turbochargers 51 and 52. The cylinder block 3 is provided with an engine water temperature sensor (not shown) for detecting the engine water temperature that is the temperature of the engine cooling water. The intake passage 20 is provided with an intake air temperature sensor (not shown) that detects the intake air temperature that is the temperature of the intake air introduced into the combustion chamber 6. The intake air temperature sensor is provided near the air cleaner 21, for example.

  Further, the vehicle is provided with an accelerator opening sensor SN8 that detects an accelerator opening that is an opening of an accelerator pedal (not shown) operated by a driver, a vehicle speed sensor SN9 that detects a vehicle speed, and the like.

  The PCM 200 receives input signals from these sensors SN1 to SN9, etc., executes various calculations based on these signals, and controls the injector 10 and the like.

(2-1) Normal Operation Control During normal operation in which the PCM 200 does not perform DPF regeneration control (regeneration control), which will be described later, the required torque (required engine load) is mainly based on the engine speed and the accelerator opening. And the main injection is performed by the injector 10 so that the required torque is realized. That is, the main injection is a fuel for generating engine torque, and a relatively large amount of fuel is injected into the combustion chamber 6. The main injection is performed, for example, near the compression top dead center.

  Further, the PCM 200 uses the EGR valves 57, 60 so that the EGR rate (the ratio of the EGR gas amount to the total gas amount in the combustion chamber 6) and the intake pressure become appropriate values according to the engine speed, the required torque, and the like. And the opening degree of the exhaust-side bypass valve 49 or the like is changed. Then, the PCM 200 stops the main injection, that is, performs a fuel cut when the required torque becomes 0 with the deceleration of the vehicle or the like. In the present embodiment, in order to improve fuel efficiency, the excess air ratio λ of the air-fuel mixture in the combustion chamber 6 is configured to be greater than 1 during normal operation, and the throttle valve 23 is fully opened during normal operation. Maintained in the vicinity. For example, during normal operation, the excess air ratio λ of the air-fuel mixture in the combustion chamber 6 is set to about λ = 1.7.

(2-2) DPF Control DPF regeneration control for regenerating the DPF 44 by burning and removing the PM collected by the DPF 44 will be described.

  In the present embodiment, unburned fuel is introduced into the oxidation catalyst 42 while making the air-fuel ratio of the air-fuel mixture in the combustion chamber 6 larger than the stoichiometric air-fuel ratio and making the air-fuel ratio of the exhaust gas larger than the stoichiometric air-fuel ratio, By oxidizing this fuel with the oxidation catalyst 42, the temperature of the exhaust gas introduced into the DPF 44 and the temperature of the DPF 44 are set to a high temperature, and the PM trapped in the DPF 44 is removed by combustion. Specifically, the PCM 200 increases the excess air ratio λ of the air-fuel mixture, and thus the excess air ratio λ of the exhaust gas, as DPF regeneration control for regenerating the DPF 44, and unburned fuel in the oxidation catalyst 42. Is supplied to inject the fuel for regenerating the DPF 44 into the combustion chamber 6.

  FIG. 3 is a flowchart showing the flow of DPF regeneration control.

  First, in step S10, the PCM 200 detects the intake pressure detected by the intake pressure sensor SN3, the oxygen concentration detected by the exhaust O2 sensor SN4 (hereinafter referred to as exhaust O2 concentration), and the oxidation detected by the oxidation catalyst temperature sensor SN5. Various information such as the temperature of the catalyst 42, the differential pressure across the DPF 42 detected by the differential pressure sensor SN6, and the temperature of the DPF 44 detected by the DPF temperature sensor SN7 are read.

  Next, in step S11, the PCM 200 determines whether or not the DPF regeneration condition (filter regeneration condition) is satisfied.

  The DPF regeneration condition is a condition where it can be determined that regeneration of the DPF 44 is necessary. The PCM 200 estimates the amount of PM collected in the DPF 44 using the differential pressure before and after the DPF 44, and when the estimated amount of PM exceeds a preset first DPF regeneration determination amount, the DPF 44 should be regenerated. It is determined that the DPF regeneration condition is satisfied. On the other hand, if the estimated amount of PM is less than the preset first DPF regeneration determination amount, the PCM 200 determines that the DPF regeneration condition is not satisfied. However, once the PCM 200 determines that the DPF regeneration condition is satisfied, the DPF regeneration condition is satisfied until the estimated amount of PM becomes less than a preset second DPF regeneration determination amount (<first DPF regeneration determination amount). It is determined that

  If the determination in step S11 is NO and the DPF regeneration condition is not satisfied, the DPF regeneration control is not performed, and the process is terminated (control during normal operation is performed and the process returns to step S10).

  On the other hand, when the determination in step S11 is YES and the DPF regeneration condition is satisfied, the PCM 200 proceeds to step S12. In step S12, the PCM 200 prohibits EGR. That is, the PCM 200 fully closes the EGR valves 57 and 60.

  After step S12, the process proceeds to step S13. In step S13, the PCM 200 determines whether or not the fuel is cut. As described above, when the required torque becomes 0 or less with the deceleration of the vehicle or the like, the fuel cut that stops the main injection is performed. The PCM 200 separately determines whether or not the fuel should be cut using the accelerator opening or the like. If it is determined that the fuel should be cut, the main injection is stopped and the determination in step S13 is YES. And

  When the determination in step S13 is NO and the main injection is performed instead of when the fuel is cut, that is, in the first operating condition in which the main injection is performed and the regeneration condition of the DPF 44 is satisfied, the PCM 200 performs normal regeneration. Implement control.

  In the normal regeneration control, regeneration injection is performed after the main injection and during the expansion stroke. That is, the PCM 200 causes the injector 10 to inject fuel into the combustion chamber 6 after the main injection and during the expansion stroke. In the normal regeneration control, as shown in FIG. 4A, after the main injection Qm, the regeneration injection Qpost is performed only once. Hereinafter, the regeneration injection in the normal regeneration control is referred to as normal regeneration post-injection as appropriate.

  Specifically, the PCM 200 proceeds to step S14 when the determination in step S13 is NO. In step S14, the PCM 200 sets a command injection timing that is a command value for the start timing of normal regeneration post-injection and a command injection amount that is the amount of fuel injected into the combustion chamber 6 by the normal regeneration post-injection.

  In the following, the fuel injected into the combustion chamber 6 by the O injection is referred to as the fuel related to the O injection, and the amount of fuel injected into the combustion chamber 6 by the O injection is referred to as the injection amount of the O injection. That's it. In addition, the start timing of 00 injection is simply referred to as injection timing of 00 injection.

  In the present embodiment, the basic post injection timing, which is the basic value of the injection timing of the normal regeneration post injection, and the basic post injection amount, which is the basic value of the injection amount of the normal regeneration post injection, are determined as the engine speed. The PCM 200 is preset according to the required torque and stored in the PCM 200 as a map, and the PCM 200 extracts values corresponding to the engine speed, the required torque, and the like at this time (when step S14 is performed) from the map. The PCM 200 sets the basic post injection timing and the basic post injection amount as the command injection timing and the command injection amount of the normal regeneration post injection without correcting the basic post injection timing and the basic post injection amount by the exhaust O2 concentration or the like, respectively.

  The basic post-injection timing and the basic post-injection amount are set to such a time and amount that the fuel related to the normal regeneration post-injection does not burn in the combustion chamber 6. For example, the basic post injection timing is set to approximately 80 ° CA after compression top dead center (ATDC) to 120 ° CA after compression top dead center (ATDC). Further, the basic post injection amount is set to an amount that causes the excess air ratio λ of the exhaust gas to be 1.2 to 1.4, for example, about 10 mm 3 / st.

  After step S14, the PCM 200 proceeds to step S15 and performs normal regeneration post-injection. At this time, the PCM 200 causes the injector 10 to inject the fuel of the command injection amount set in step S15 at the command injection timing set in step S15. As described above, in step S15, the main injection is performed, and the normal regeneration post-injection is performed after the main injection.

  In this way, when the DPF regeneration control is performed in a state where the main injection is performed instead of at the time of fuel cut, the normal regeneration post-injection is performed once after the main injection and during the expansion stroke. As a result, the fuel introduced into the combustion chamber 6 by the normal regeneration post-injection remains unburned and is discharged to the exhaust passage 40, and the unburned fuel undergoes an oxidation reaction in the oxidation catalyst 42.

  As described above, when the normal regeneration post injection is performed (when the normal regeneration control is performed), the air excess ratio λ of the air-fuel mixture in the combustion chamber 6 and the air excess ratio in the exhaust passage 40 are larger than 1. As described above, the opening degree of the throttle valve 23, the exhaust-side bypass valve 49, etc. is adjusted so that the excess air ratio λ of the exhaust gas is about 1.2 to 1.4.

  On the other hand, when the determination in step S13 is YES and the fuel cut is performed, that is, in the second operating condition in which the fuel cut is performed in a state where the DPF regeneration condition is satisfied, the PCN 200 proceeds to step S16. move on.

  In step S16, the PCM 200 determines whether or not the temperature of the oxidation catalyst 42 is equal to or higher than the activation temperature. The activation temperature is the lowest temperature at which the fuel can cause an oxidation reaction in the oxidation catalyst 42, and is preset and stored in the PCM 200.

  If the determination in step S16 is NO, since the oxidation reaction at the oxidation catalyst 42 cannot be expected, the process ends without performing the DPF regeneration control (return to step S10). Note that it is considered that the oxidation catalyst 42 is maintained at a high temperature because the main injection is performed when the normal regeneration control is performed. Therefore, when the DPF regeneration condition is satisfied in a state where the main injection is being performed, the determination in step S16 is not performed.

  On the other hand, if the determination in step S16 is YES and the temperature of the oxidation catalyst 42 is equal to or higher than the activation temperature, the regeneration control at the time of fuel cut is performed.

  When the determination in step S16 is YES, the PCM 200 first proceeds to step S17, and sets the opening of the throttle valve 23 to the closed side compared to when the normal regeneration control is performed. Specifically, the throttle valve 23 is almost fully opened when the normal regeneration control is performed or when the DPF regeneration control is not performed. On the other hand, in step S17, the opening degree of the throttle valve 23 is set to an opening degree close to full closing. However, the opening degree of the throttle valve 23 is set so that the excess air ratio λ in the exhaust passage 40 and thus the excess air ratio λ of the air-fuel mixture in the combustion chamber 6 becomes larger than 1.

  After step S17, the process proceeds to step S18. Here, in the regeneration control at the time of fuel cut, as shown in FIG. 4B, the regeneration injection is performed three times, that is, the front injection (compression stroke injection) Q1, the intermediate injection Q2, and the rear injection (expansion stroke injection) Q3. Implemented separately. In step S18, the PCM 200 sets command injection timings that are command values for the respective injection timings of the upstream injection Q1, the intermediate injection Q2, and the post-injection Q3, and each of the upstream injection Q1, the intermediate injection Q2, and the post-injection Q3. A command injection amount that is a command value of the injection amount is set. Details of this setting procedure will be described later.

  After step S18, the PCM 200 proceeds to step S19. In step S19, the PCM 200 performs each injection Q1, Q2, Q3 at each command injection timing and each command injection amount set in step S18. Following step S19, the process ends (returns to step S10).

(Commanded injection amount)
The procedure for setting the command injection amounts for the front injection Q1, the intermediate injection Q2, and the rear injection Q3 performed in step S18 will be described with reference to the flowchart of FIG.

  First, in step S <b> 20, the PCM 200 estimates an in-cylinder pressure that is a pressure in the combustion chamber 6. In the present embodiment, the in-cylinder pressure at the compression top dead center is estimated using the intake pressure detected by the intake pressure sensor SN3. Specifically, the integrated value of the intake pressure and the geometric compression ratio of the engine body 1 is calculated as the in-cylinder pressure at the compression top dead center.

  After step S20, the PCM 200 proceeds to step S21. In step S21, the PCM 200 determines the total injection amount of the front injection Q1, the intermediate injection Q2, and the rear injection Q3, that is, the total injection amount of the regeneration injection in the fuel cut regeneration control (hereinafter referred to as the fuel cut total injection). The fuel cut total basic injection amount Mq0_total, which is a basic value), is set.

  After step S21, the PCM 200 proceeds to step S22. In step S22, the PCM 200 performs basic basic injection amount Mq0_Q1, which is a basic value of the injection amount of the front injection Q1, basic basic injection amount Mq0_Q2, which is a basic value of the injection amount of the intermediate injection Q2, and basic injection amount of the post injection Q3. The basic post-injection amount Mq0_Q3, which is a value, is set.

  These basic pre-stage injection amount Mq0_Q1, basic intermediate injection amount Mq0_Q2, and basic post-stage injection amount Mq0_Q3 are set such that the sum is the fuel cut total basic injection amount Mq0_total calculated in step S21.

  The basic front injection amount Mq0_Q1, the basic intermediate injection amount Mq0_Q2, and the basic rear injection amount Mq0_Q3 are set according to the in-cylinder pressure estimated in step S20.

Specifically, as shown in FIG. 6, the basic upstream injection amount Mq0_Q1 and the basic intermediate injection amount Mq0_Q2 are set to values smaller when the in-cylinder pressure is higher than when it is lower. On the other hand, the basic post-stage injection amount Mq0_Q3 is set to a larger value when the in-cylinder pressure is higher than when it is lower. And, the total amount, that the fuel cut during total basic injection amount Mq0_total of the basic stage injection amount Mq0_Q1 the basic intermediate injection amount Mq0_Q2 and basic succeeding injection amount Mq0_Q3 is a certain amount regardless of the cylinder pressure.

  FIG. 6 shows a basic pre-stage injection quantity Mq0_Q1 and a basic intermediate injection quantity when the total basic injection quantity Mq0_total during fuel cut is 3 mm 3 / st (amount of fuel injected into one combustion chamber 6 in one combustion cycle). It is the figure which showed the relationship between Mq0_Q2, basic back injection quantity Mq0_Q3, and in-cylinder pressure. In the example of FIG. 6, the basic upstream injection amount Mq0_Q1 and the basic intermediate injection amount Mq0_Q2 are set to the same value at each in-cylinder pressure. In this example, when the in-cylinder pressure is less than the predetermined value, the three injection amounts Mq0_Q1, Mq0_Q2, and Mq0_Q3 are all set to the same 1 mm 3 / st and are maintained at a constant value regardless of the in-cylinder pressure. On the other hand, when the in-cylinder pressure is greater than or equal to a predetermined value, the basic front injection amount Mq0_Q1 and the basic intermediate injection amount Mq0_Q2 are reduced in proportion to the in-cylinder pressure, and the basic rear injection amount Mq0_Q3 is increased in proportion to the in-cylinder pressure.

  The PCM 200 stores a map of the relationship between the in-cylinder pressure and the injection amounts Mq0_Q1, Mq0_Q2, and Mq0_Q3 as shown in FIG. 6 for a plurality of fuel cut total basic injection amounts Mq0_total. When the fuel cut total basic injection amount Mq0_total is set in step S21, the PCM 200 extracts a map corresponding to this, and further extracts each injection amount Mq0_Q1, Mq0_Q2, Mq0_Q3 corresponding to the in-cylinder pressure from this map. .

  Returning to FIG. 5, after step S22, the PCM 200 proceeds to step S23. In step S23, the PCM 200 determines the total amount of each injection amount of the front injection Q1, the intermediate injection Q2 and the rear injection Q3 that has already been performed, that is, the actual value of the total injection amount at the time of fuel cut, and when this injection is performed. The amount of deviation from the command value of the total injection amount at the time of fuel cut is calculated.

  Specifically, the PCM 200 estimates the actual value of the total injection amount at the time of fuel cut based on the exhaust O2 concentration and the exhaust gas flow rate. Then, the PCM 200 calculates, as a deviation amount, a value obtained by subtracting the estimated actual value of the fuel injection total injection amount from the command value of the fuel injection total injection amount. Here, the actual value of the estimated total injection amount at the time of fuel cut is a predetermined time (the fuel injected into the combustion chamber 6 is exhausted O 2) than the timing at which the exhaust O 2 concentration used for estimation is detected by the exhaust O 2 sensor. The amount of fuel injected into the combustion chamber 6 before the time until the sensor is reached, and the command value to be compared with this is the command value of the total injection amount at the time of fuel cut set a predetermined time ago. The value calculated in step S26, which will be described later, performed a predetermined time before.

  After step S23, the PCM 200 proceeds to step S24. In step S24, the PCM 200 sets the basic upstream injection amount Mq0_Q1 set in step S22 to the command injection amount of the upstream injection Q1.

  After step S24, the PCM 200 proceeds to step S25. In step S25, the PCM 200 corrects the basic intermediate injection amount Mq0_Q2 and the basic rear-stage injection amount Mq0_Q3 set in step S22 using the deviation amount calculated in step S23, and command injection of these intermediate injection Q2 and subsequent-stage injection Q3. Calculate the amount.

  Thus, in this embodiment, the correction based on the exhaust O2 concentration is not performed on the injection amount of the upstream injection Q1, and the correction based on the exhaust O2 concentration is performed only on the injection amounts of the intermediate injection Q2 and the subsequent injection Q3. Do.

  In the present embodiment, a value that is ½ of the deviation is added to the basic intermediate injection amount Mq0_Q2, and the obtained value is used as the command injection amount for the intermediate injection Q2. Similarly, a value ½ of the deviation is added to the basic rear injection amount Mq0_Q3, and the obtained value is used as the command injection amount for the rear injection Q3.

  For example, when it is calculated that the deviation amount is 2 mm 3 / st and the actual fuel cut total injection amount is 2 mm 3 / st short of the command value, the command injection amount of the intermediate injection Q 2 is its basic value. A value obtained by adding 1 mm 3 / st to (basic intermediate injection amount Mq 0 _Q 2), and a command injection amount for the rear injection Q 3 is a value obtained by adding 1 mm 3 / st to the basic value (basic rear injection amount Mq 0 _Q 3).

  Instead of this, the deviation amount may be distributed to the basic intermediate injection amount Mq0_Q2 and the basic rear injection amount Mq0_Q3 according to the ratio of these basic amounts.

  Further, the injection amount of the post-stage injection Q3 may be corrected according to the temperature of the DPF 44 after step S25. For example, you may correct | amend so that the command injection quantity of back | latter stage injection Q3 may become larger when the temperature of DPF44 is high than when it is low.

  After step S25, the PCM 200 proceeds to step S26. In step S26, the PCM 200 instructs the command injection amount of the front injection Q1 set in step S24, the command injection amount of the intermediate injection Q2 set in step S25, and the command injection amount of the subsequent injection Q3 set in step S25. Is calculated as a command value for the total injection amount at the time of fuel cut.

  Note that the total injection amount at the time of fuel cut is set to be smaller than the post injection amount at the time of normal regeneration control, and is, for example, about 5 mm 3 / st or less.

(Injection timing)
A procedure for setting the command injection timings of the front injection Q1, the intermediate injection Q2, and the rear injection Q3 performed in step S18 will be described with reference to the flowchart of FIG.

  First, in step S31, the PCM 200 performs basic basic injection timing Ti0_Q1, which is the basic value of the injection timing of the front injection Q1, basic intermediate injection timing Ti0_Q2, which is the basic value of the injection timing of the intermediate injection Q2, and injection timing of the post injection Q3. Is set according to the in-cylinder pressure estimated in step S20.

  FIG. 8 is a graph showing the relationship between the basic values Ti0_Q1, Ti0_Q2, Ti0_Q3 of the injection timing and the in-cylinder pressure. FIG. 8 is a diagram in which the horizontal axis is the in-cylinder pressure and the vertical axis is the injection timing. The vertical axis in FIG. 8 indicates the value of the crank angle before the compression top dead center, where 0 is the compression top dead center, the positive value is the angle before the compression top dead center, and the negative value. Represents the angle after compression top dead center.

  As shown in FIG. 8, in the present embodiment, the difference ΔT2 between the basic intermediate injection timing Ti0_Q2 and the basic rear injection timing Ti0_Q3 is maintained constant regardless of the in-cylinder pressure. On the other hand, the difference ΔT1 between the basic pre-stage injection timing Ti0_Q1 and the basic intermediate injection timing Ti0_Q2 and the difference ΔT3 between the basic pre-stage injection timing Ti0_Q1 and the basic post-stage injection timing Ti0_Q3 are made longer as the in-cylinder pressure is higher. In the present embodiment, the injection periods of the front injection Q1, the intermediate injection Q2, and the rear injection Q3 are approximately the same, and the difference between the injection timings is the interval between the injections (the next injection is completed after the previous injection ends). The period until the start).

  In the present embodiment, the basic pre-injection timing Ti0_Q1 is advanced when the in-cylinder pressure is high than when it is low. On the other hand, the basic intermediate injection timing Ti0_Q2 and the basic rear injection timing Ti0_Q3 are retarded when the in-cylinder pressure is high than when it is low.

  The PCM 200 stores the relationship between the in-cylinder pressure and the basic values Ti0_Q1, Ti0_Q2, Ti0_Q3 of each injection timing as shown in FIG. 8, and the PCM 200 corresponds to the in-cylinder pressure estimated in step S20 from this map. To extract the value to be

  After step S31, the PCM 200 proceeds to step S32. In step S32, the PCM 200 sets the command injection timing of the upstream injection Q1 to the basic upstream injection timing Ti0_Q1 set in step S31.

  After step S32, the PCM 200 proceeds to step S33. In step S33, the PCM 200 corrects the basic intermediate injection timing Ti0_Q2 and the basic rear injection timing Ti0_Q3 based on the equivalence ratio of the air-fuel mixture in the combustion chamber 6, the engine water temperature, and the intake air temperature, and the intermediate injection Q2 and The command injection timing of the post injection Q3 is calculated.

  Specifically, the engine water temperature is set so that the command injection timings of the intermediate injection Q2 and the subsequent injection Q3 are retarded when the equivalence ratio of the air-fuel mixture in the combustion chamber 6 is higher than when it is lower. The basic intermediate injection timing Ti0_Q2 and the timing of the retarded angle when the intake gas is high, and the timing of the retarded angle when the intake air temperature is high, The basic post injection timing Ti0_Q3 is corrected.

  The equivalence ratio of the air-fuel mixture in the combustion chamber 6 is the ratio of the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio, and is the reciprocal of the excess air ratio λ. The equivalence ratio of the air-fuel mixture in the combustion chamber 6 is the detected value of the air flow sensor SN2 or the amount of air in the combustion chamber 6 estimated based on this detected value and the total injection amount at the time of fuel cut calculated in step S26. It is calculated based on the command value, that is, the total amount of fuel injected into the combustion chamber 6. Further, the detected value of the engine water temperature sensor is used as the engine water temperature. As the intake air temperature, the detection value of the intake air temperature sensor is used.

  In the present embodiment, the correction amounts set based on the equivalence ratio of the air-fuel mixture in the combustion chamber 6, the engine water temperature, and the intake air temperature are the basic values of the injection timings of the intermediate injection Q2 and the subsequent injection Q3. By adding, the command injection timing of these injections Q2 and Q3 is determined. At this time, the correction amount of the injection timing of the intermediate injection Q2 is the same as the correction amount of the injection timing of the post-stage injection Q3. That is, the difference ΔT2 between the injection timing of the intermediate injection Q2 and the injection timing of the post-stage injection Q3 is kept constant regardless of the equivalence ratio, the engine water temperature, and the intake air temperature.

  FIG. 9 is a diagram showing the relationship between the equivalence ratio in the combustion chamber 6 and the correction amount of the injection timing of the intermediate injection Q2 and the subsequent injection Q3. FIG. 10 is a graph showing the relationship between the engine water temperature and the intake air temperature and the injection timing correction amount. In FIG. 10, the lines W1, W2, W3, and W4 are correction amounts when the engine water temperature is 40, 60, 80, and 100 ° C., respectively. The vertical axis in FIGS. 9 and 10 is the crank angle. In this vertical axis, the value on the plus side of 0 is the advance side correction amount, and the value on the minus side of 0 is the retard side correction amount. That is, when a value on the plus side of 0 is extracted as the correction amount, a value obtained by advancing the extracted value with respect to the basic value of the injection timing is set as the command injection timing. On the other hand, when a value on the minus side of 0 is selected, a value obtained by retarding the absolute value of the extracted value with respect to the basic value of the injection timing is set as the command injection timing.

  As shown in FIGS. 9 and 10, the PCM 200 stores a map of the equivalence ratio and the correction amount of the injection timing, and a map of the engine water temperature, the intake air temperature and the correction amount of the injection timing. The PCM 200 extracts a correction amount corresponding to the equivalence ratio of the air-fuel mixture in the combustion chamber 6 at the present time (when step S33 is performed) from these maps, and at the present time (when step S33 is performed). A correction amount corresponding to the engine water temperature and the intake air temperature is extracted. Then, the PCM 200 adds a value obtained by adding the total value of these correction amounts and the basic value of the injection timing set in step S31 (when the total value of correction amounts is positive, the amount of correction amount is calculated from the basic value of the injection timing. When the total value of the correction amount is negative, a value obtained by retarding the correction amount from the basic value of the injection timing) is set as the command injection timing.

  Thus, the command injection timing of each injection, that is, the injection timing is set using the in-cylinder pressure or the like. However, the injection timing of the front injection Q1 is set to be included in the latter half of the compression stroke (between 90 ° CA before compression top dead center and the compression top dead center), and the injection timing of the intermediate injection Q2 and the rear injection Q3. Is set to be included in the first half of the expansion stroke (from compression top dead center to 90 ° CA after compression top dead center).

(3) Operation, etc. FIG. 11 is a diagram schematically showing a time change of each parameter when the DPF regeneration control is performed. Specifically, in FIG. 11, in order from the top, the vehicle speed, the engine speed, the main injection amount that is the injection amount of the main injection, the DPF regeneration flag, and the normal regeneration post injection that is the injection amount of the normal regeneration post injection. The total post-injection amount, which is the amount obtained by subtracting the main injection amount from the total amount of fuel injected into the combustion chamber 6. A time change of the injection amount of the normal regeneration post injection or the total injection amount at the time of fuel cut is shown. The DPF regeneration flag is a flag that is set to 1 when a request for DPF regeneration control is issued, and is set to 0 at other times.

  As shown in FIG. 11, in the present embodiment, when the DPF regeneration flag is 1 and the injection amount of the main injection is greater than 0 during the period up to time t1, The normal regeneration post-injection amount is set to a value larger than 0, and the normal regeneration post-injection is performed. On the other hand, at this time, the front injection Q1, the intermediate injection Q2, and the rear injection Q3 are stopped. If the DPF regeneration flag is maintained at 1 even when the fuel cut is performed as the vehicle is decelerated at time t1 and the injection amount of the main injection is 0, the normal regeneration post-injection amount is 0. However, the injection amounts of the front injection Q1, the intermediate injection Q2, and the rear injection Q3 are set to values larger than 0, and the injections Q1, Q2, and Q3 are performed. The fuel continues to be supplied into the combustion chamber 6. However, at this time, the total amount of each injection amount of the front injection Q1, the intermediate injection Q2, and the rear injection Q3 is made smaller than the injection amount of the post injection when the main injection is performed. Further, when the main injection is resumed at time t2 due to the acceleration of the vehicle and the like, the DPF regeneration flag is 1, so that the normal regeneration post-injection is performed again, and the pre-stage injection Q1 and the intermediate injection Q2 are performed again. Then, the post injection Q3 is stopped.

  Thus, in this embodiment, when a request for DPF regeneration control is issued, fuel is supplied to the combustion chamber 6 even if the main injection is stopped. Therefore, the DPF 44 can be regenerated by raising the temperature in a shorter time.

  In this embodiment, when the main injection is stopped in a state where the request for the DPF regeneration control is issued, a part of the regeneration injection (pre-stage injection Q1) is performed during the compression stroke, and the fuel is combusted. It is injected into the chamber 6. Therefore, the fuel can be lightened and efficiently oxidized by the oxidation catalyst 42, and even when the main injection is stopped and the temperature of the exhaust gas tends to be low, the exhaust gas is suppressed while suppressing the deterioration of the fuel efficiency. The DPF 44 can be appropriately regenerated while maintaining the temperature high.

  Specifically, when the main injection is stopped, it is conceivable that the DPF 44 is regenerated by performing the post injection only once in the expansion stroke, as in the case of the normal regeneration control. However, since the temperature of the exhaust tends to be low because the main injection is stopped, it is necessary to increase the temperature of the exhaust by increasing the amount of post-injection more than at the time of performing the main injection. is there. However, even if a large amount of fuel is injected during the expansion stroke, the fuel is led to the exhaust passage in a state where the temperature is low and heavy. That is, most of the hydrocarbons constituting the fuel are led out to the exhaust passage in the state of hydrocarbons having many carbon atoms and high molecular weight. Therefore, the reactivity of the fuel in the oxidation catalyst 42 is poor, and the fuel consumption performance may be remarkably deteriorated, or the temperature of the DPF 44 may not be sufficiently increased.

  On the other hand, in the present embodiment, in the DPF regeneration control that is performed at the time of fuel cut as described above, fuel is injected into the combustion chamber 6 during the compression stroke. Here, the temperature of the fuel injected during the compression stroke is raised by the compression action of the piston 5. As the temperature rises, the fuel becomes lighter. That is, the carbon bonds of the hydrocarbons constituting the fuel are cut off, and the proportion of low molecular weight components contained in the fuel increases. For example, by being injected during the compression stroke, most of the hydrocarbons contained in the fuel change from high molecular weight hydrocarbons having 16 or more carbon atoms to low molecular weight hydrocarbons having less than 16 carbon atoms. And when it becomes lighter, the reactivity of the fuel increases. Therefore, as described above, fuel is injected into the combustion chamber 6 during the compression stroke, so that the reactivity of the fuel can be increased, and more fuel can be appropriately oxidized by the oxidation catalyst 42. it can.

  Moreover, in the present embodiment, in addition to the front injection Q1, the intermediate injection Q2 and the rear injection Q3 are performed, and fuel is also injected into the combustion chamber 6 during the expansion stroke. Therefore, it is possible to increase the total amount of fuel injected into the combustion chamber 6 while suppressing the injection amount of the pre-stage injection Q1 to prevent an unexpected engine torque from occurring while the main injection is stopped. In addition, the temperature of the DPF 44 can be effectively increased. That is, in order to increase the temperature of the exhaust gas and the DPF 44, it is preferable to increase the total amount of fuel injected into the combustion chamber 6. However, if the injection amount of the pre-stage injection Q1 performed during the compression stroke is increased, the air-fuel ratio of the air-fuel mixture in the vicinity of the compression top dead center is increased, and the injected fuel may be burned, resulting in unexpected engine torque. There is. On the other hand, by configuring as described above, the total amount of fuel injected into the combustion chamber 6 can be increased, and the injection amount of the pre-stage injection Q1 can be reduced to prevent the unexpected generation of engine torque. Here, as described above, since the fuel related to the front injection Q1 is efficiently oxidized, the exhaust gas and the DPF 44 are heated at least effectively by the injection amount of the front injection Q1.

  In particular, in the present embodiment, the fuel injection performed during the expansion stroke is divided into the intermediate injection Q2 and the rear injection Q3. Therefore, when the main injection is stopped, a large amount of fuel is injected into the combustion chamber 6 at a time while maintaining a large total amount of fuel introduced into the oxidation catalyst 42, and the fuel concentration in the combustion chamber 6 is locally rich. Thus, unexpected engine torque can be prevented. Further, the fuel can be diffused and lighter than when a large amount of fuel is injected into the combustion chamber 6 at a time.

  In the present embodiment, as described above, the total injection amount at the time of fuel cut, which is the total amount of fuel supplied to the combustion chamber 6 when the main injection is stopped, is smaller than the post injection amount at the time of normal regeneration control. Is set to Therefore, it is possible to more reliably prevent the engine torque from being unexpectedly generated when the main injection is stopped.

  Moreover, in this embodiment, as demonstrated using FIG. 6, the injection quantity of the pre-stage injection Q1 is made smaller when the in-cylinder pressure is high than when it is low. Therefore, even when the in-cylinder pressure is high and the fuel is easily combusted in the combustion chamber 6, it is possible to prevent the fuel related to the pre-injection Q1 from being combusted in the combustion chamber 6 and to expect when the main injection is stopped. Without generating engine torque more reliably.

  On the other hand, in the present embodiment, the injection amount of the post-stage injection Q3 is increased when the in-cylinder pressure is high than when it is low. Therefore, when the main injection is stopped, the total amount of fuel supplied to the combustion chamber 6 when the main injection is stopped can be ensured regardless of whether the in-cylinder pressure is high or low, and the DPF 44 is appropriately increased. Can be warmed.

  Further, in the present embodiment, the amount of fuel injection that is performed during the intermediate injection Q2 and closer to the compression top dead center in the expansion stroke is increased when the in-cylinder pressure is high than when it is low. The Therefore, as described above, it is possible to prevent the fuel related to the intermediate injection Q2 from being burned in the combustion chamber 6 due to the high in-cylinder pressure while obtaining the effect of performing the intermediate injection.

  Further, in the present embodiment, as described above, the total amount of fuel supplied to the combustion chamber 6 while changing the injection amounts of the front injection Q1 and the intermediate injection Q2 by the in-cylinder pressure when the main injection is stopped. The total injection amount at the time of fuel cut is not changed by the in-cylinder pressure. Therefore, when the main injection is stopped, the amount of fuel introduced into the combustion chamber 6 and thus the oxidation catalyst 42 can be maintained at an appropriate amount.

(4) Modified Example In the above embodiment, the case where the post-injection is performed separately for the intermediate injection Q2 and the post-injection Q3 has been described. You may go. However, if divided into two times as in the above-described embodiment, unexpected generation of engine torque can be prevented as described above, and the fuel can be made lighter.

  In the above embodiment, the case where the in-cylinder pressure is estimated using the intake pressure sensor has been described. However, a sensor capable of detecting the in-cylinder pressure may be used, and the in-cylinder pressure may be directly detected by this sensor.

  Further, the injection timing of the post-injection Q3 is corrected so that the higher the temperature of the DPF 44 (for example, the temperature of the exhaust gas detected by the temperature sensor provided on the upstream side of the DPF 44) is the retarded timing. May be. Specifically, it is a map showing a relationship between a preset temperature of the DPF 44 and the lightening rate of the fuel (a parameter that becomes higher as the fuel is easily lightened), and the lightening rate becomes higher as the temperature of the DPF 44 is higher. The map set so as to increase is stored in the PCM 200, the lightening rate corresponding to the current temperature of the DPF 44 is extracted from this map, and the injection timing of the post-stage injection Q3 becomes higher as the lightening rate becomes higher. You may correct | amend this so that it may become the time of a retard side. Further, the injection amount of the post-stage injection Q3 may be corrected so that the higher the lightening rate, the smaller the injection amount. In this way, if the injection timing of the post-injection Q3 is retarded as the lightening rate is higher (the fuel is more easily lightened), the fuel is more combusted in the combustion chamber 6 while the temperature of the DPF 44 is kept high. It can be surely prevented. Further, as described above, if the injection amount of the post-stage injection Q3 is decreased as the lightening rate is higher, deterioration of fuel efficiency can be suppressed.

  In the above embodiment, the case where the post injection is performed only once after the main injection during the normal regeneration control has been described. However, the post injection may be performed in a plurality of times during the normal regeneration control. Good.

1 Engine body 10 Injector (fuel injection device)
40 Exhaust passage 41 NOx catalyst 42 Oxidation catalyst 44 DPF (filter)
200 PCM (control means)
SN4 Exhaust O2 sensor (oxygen concentration sensor)

Claims (7)

An exhaust purification control device applied to an engine including a cylinder and an engine body including a fuel injection device that injects fuel into the cylinder, and an exhaust passage through which exhaust gas discharged from the engine body flows,
Control means for controlling the fuel injection device;
An oxidation catalyst provided in the exhaust passage;
A filter provided in the exhaust passage and capable of collecting particulates in the exhaust gas;
In a first operating condition in which main injection for injecting fuel into a cylinder at a timing at which engine torque can be generated and the regeneration condition for the filter is satisfied, the control means is a fuel for regenerating the filter. The fuel injection device performs the regenerative injection for injecting the fuel at a timing delayed from the main injection during the expansion stroke,
In the second operating condition in which the main injection is stopped and the regeneration condition for the filter is satisfied, the control means is implemented during the compression stroke as a re-use injection for injecting fuel for regenerating the filter. At least the fuel injection device performs the compression stroke injection,
An engine exhaust gas purification control apparatus according to claim 1, wherein the amount of fuel injected into the cylinder by the compression stroke injection is reduced when the in-cylinder pressure, which is the pressure in the cylinder, is higher than when the in-cylinder pressure is low. The engine exhaust gas purification control device according to claim 1,
The engine exhaust gas purification control apparatus according to claim 1, wherein the start timing of the compression stroke injection is advanced when the in-cylinder pressure is high than when the cylinder pressure is low. The engine exhaust gas purification control device according to claim 1 or 2,
The control means, under the second operating condition, performs the fuel injection with the compression stroke injection performed in the second half of the compression stroke and the expansion stroke injection performed in the first half of the expansion stroke as the regeneration injection. Let the device carry out,
The engine exhaust gas purification control apparatus according to claim 1, wherein the amount of fuel injected into the cylinder by the expansion stroke injection is increased when the in-cylinder pressure is high than when it is low. The engine exhaust gas purification control device according to claim 3,
The control means causes the fuel injection device to further perform an intermediate injection that is performed as the regeneration injection under the second operating condition, the first half of the expansion stroke and before the expansion stroke injection,
The engine exhaust gas purification control apparatus according to claim 1, wherein the amount of fuel injected into the cylinder by the intermediate injection is reduced when the in-cylinder pressure is high than when it is low. The engine exhaust gas purification control apparatus according to claim 3 or 4,
Exhaust gas purification control for an engine characterized in that the total amount of fuel injected into the cylinder by the regeneration injection performed under the second operating condition is made constant regardless of the in-cylinder pressure. apparatus. The engine exhaust gas purification control apparatus according to any one of claims 1 to 5,
An engine in which the injection amount of the regeneration injection performed under the second operation condition is made smaller than the injection amount of the regeneration injection performed under the first operation condition. Exhaust purification control device. The engine exhaust gas purification control apparatus according to any one of claims 1 to 6,
It has an intake pressure sensor that can detect the pressure of intake air introduced into the engine body,
The engine exhaust purification control apparatus, wherein the in-cylinder pressure is estimated using a detection value of the intake pressure sensor.

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