JP7172048B2 - Engine exhaust purification control device - Google Patents

Description

The present invention relates to an exhaust purification control device applied to an engine having an engine body including a cylinder and a fuel injection device for injecting 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 is performed to regenerate the filter by removing particulates trapped in the filter.

For example, Patent Document 1 describes an engine provided with an oxidation catalyst having an oxidation function on the upstream side of the filter, in which post injection is performed to inject fuel at a timing later than the main injection for generating engine torque. Then, unburned fuel flows into the oxidation catalyst and reacts in the oxidation catalyst, and the reaction heat raises the temperature of the exhaust gas passing through the filter to burn and remove the fine particles trapped in the filter. disclosed.

JP-A-2004-316441

However, when the main injection is stopped due to deceleration of the vehicle in which the engine is mounted, the temperature of the exhaust gas discharged from the engine body drops significantly. Therefore, in this case, even if the post-injection is performed, the temperature of the exhaust gas passing through the filter cannot be sufficiently increased, and the regeneration time of the filter becomes longer, resulting in deterioration of fuel efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an engine exhaust gas purification control system capable of appropriately regenerating a filter while suppressing deterioration of fuel consumption performance.

In order to solve the above problems, the present invention is applied to an engine having an engine body including a cylinder and a fuel injection device for injecting fuel into the cylinder, and an exhaust passage through which exhaust gas discharged from the engine body flows. an exhaust purification control device comprising: a control means for controlling the fuel injection device; an oxidation catalyst provided in the exhaust passage; and a filter provided in the exhaust passage and capable of collecting particulates in the exhaust gas. and an intake pressure sensor capable of detecting the pressure of the intake air introduced into the engine main body. under the first operating condition, the control means causes the fuel injection device to perform a regeneration injection for injecting fuel for regenerating the filter at a timing later than the main injection during an expansion stroke; Under a second operating condition in which the main injection is stopped and the regeneration condition of the filter is satisfied, the control means performs regeneration injection for injecting fuel for regeneration of the filter in the latter half of the compression stroke. The control means causes the fuel injection device to perform the compression stroke injection performed in the first half of the expansion stroke and the expansion stroke injection performed in the first half of the expansion stroke, and the control means controls the detected value of the intake pressure sensor and the geometric compression of the engine body. The in-cylinder pressure, which is the pressure in the cylinder at the compression top dead center, is estimated by taking the product with the ratio, and under the condition that the total amount of fuel injected into the cylinder by the regeneration injection is the same, the The amount of fuel injected into the cylinder by the compression stroke injection is reduced as the in-cylinder pressure at the compression top dead center estimated by the control means is higher , and the amount of fuel injected into the cylinder by the expansion stroke injection is 2. An exhaust gas purification control device for an engine, characterized in that the higher the in-cylinder pressure at the compression top dead center estimated by the control means is, the higher the cylinder pressure is .

According to this device, part of the fuel injected into the cylinder to regenerate the filter is injected into the cylinder during the compression stroke while the main injection is stopped (under the second operating condition). Therefore, it is possible to promote the reaction of the unburned fuel in the oxidation catalyst and effectively raise the temperature inside the filter.

Specifically, the temperature of the fuel injected into the cylinder during the compression stroke is raised by the compression action of the piston. When the temperature of the fuel becomes high, the fuel becomes lighter (lower in molecular weight) and its reactivity is enhanced. Therefore, according to this device, 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, thereby oxidizing the fuel. By promoting the reaction of the fuel in the catalyst, the temperature of the exhaust gas can be effectively increased with less fuel. Therefore, it is possible to appropriately regenerate the filter by raising the temperature of the filter while suppressing the deterioration of the fuel efficiency performance.

However, when the in-cylinder pressure is high (for example, when the in-cylinder pressure at compression top dead center is high), fuel is likely to burn 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, there is a risk that this fuel will burn and unexpectedly generate engine torque. In contrast, in this device, the amount of fuel injected into the cylinder during the compression stroke is made smaller when the in-cylinder pressure is high than when it is low. Therefore, it is possible to prevent unexpected generation of engine torque when the in-cylinder pressure is high, and it is possible to inject more fuel into the cylinder in the compression stroke when the in-cylinder pressure is low to promote regeneration of the filter.

Further, according to this device , when the main injection is stopped, fuel is injected into the cylinder not only during the compression stroke but also during the expansion stroke. Therefore, a large amount of oxidation reaction heat can be obtained by increasing the total amount of fuel introduced into the oxidation catalyst. Moreover, in this configuration, as described above, the compression stroke injection amount is reduced when the cylinder pressure is high, whereas the expansion stroke injection amount is increased when the cylinder pressure is high. Therefore, the total amount of fuel introduced into the oxidation catalyst can be secured regardless of whether the in-cylinder pressure is high or low.

In the above configuration, the control means further causes the fuel injection device to perform intermediate injection, which is performed in the first half of an expansion stroke and before the expansion stroke injection, as the regeneration injection under the second operating condition. Under the condition that the total amount of fuel injected into the cylinder by the regeneration injection is the same, the amount of fuel injected into the cylinder by the intermediate injection is the compression top dead center estimated by the control means. is preferably reduced as the in- cylinder pressure is higher (Claim 2 ).

According to this configuration, when the main injection is stopped, the fuel is injected into the cylinder by dividing 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 total amount of fuel introduced into the oxidation catalyst, the injected fuel can be diffused further in the cylinder, thereby promoting the reduction of fuel weight. Therefore, the oxidation reaction of the oxidation catalyst can be further accelerated, and the temperature inside the filter can be increased more reliably. Furthermore, in this configuration, when the in-cylinder pressure is high, the amount of fuel involved in the intermediate injection, which is performed at a time when the compression top dead center is near and combustion is relatively easy in the cylinder, is smaller than when the in-cylinder pressure is low. Therefore, when the cylinder pressure is high, the fuel for the intermediate injection can be prevented from being burned in the cylinder and unexpectedly generating engine torque. Lightening of this can be promoted.

In the above configuration, the total amount of fuel injected into the cylinder by the regeneration injection performed under the second operating condition is constant regardless of the in-cylinder pressure at compression top dead center estimated by the control means . It is preferred that the amount is quantified (Claim 3 ).

According to this configuration, when the main injection is stopped, the amount of fuel introduced into the cylinder and thus 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. It is preferable (claim 4 ).

According to this configuration, when the main injection is stopped, the injection amount of the regeneration injection is reduced, so that it is possible to more reliably suppress the amount of fuel related to the regeneration injection from burning in the cylinder. . On the other hand, when the main injection is being performed, even if part of the fuel for the regeneration injection is burned, the engine torque does not fluctuate at a small rate with respect to the engine torque. In contrast, according to this configuration, the injection amount of the regeneration injection is increased when the main injection is being performed, so that the temperature of the filter can be made higher.

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

1 is a schematic configuration diagram of an engine system to which an engine exhaust purification control device according to an embodiment of the present invention is applied; FIG. 2 is a block diagram showing a control system of the engine system; FIG. 4 is a flowchart showing the flow of DPF regeneration control; FIG. 4 is a diagram showing injection patterns during DPF regeneration control, where (a) is the injection pattern during normal regeneration control, and (b) is the injection pattern during regeneration control during fuel cut. 4 is a flow chart showing a procedure for setting command injection amounts for pre-injection, intermediate injection, and post-injection; 5 is a graph showing the relationship between in-cylinder pressure and respective injection amounts of pre-injection, intermediate injection, and post-injection; 4 is a flow chart showing a procedure for setting command injection timings for pre-injection, intermediate injection, and post-injection; 4 is a graph showing the relationship between in-cylinder pressure and injection timings of front injection, intermediate injection, and rear injection. 4 is a graph showing the relationship between the equivalence ratio and the correction amount for each injection timing of intermediate injection and post-stage injection. 5 is a graph showing the relationship between engine water temperature, intake air temperature, and injection timing correction amounts for intermediate injection and post-stage injection; FIG. 4 is a diagram schematically showing temporal changes of each parameter when DPF regeneration control is performed;

Hereinafter, an engine exhaust gas purification control device 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 an engine exhaust purification control device according to the present embodiment is applied.

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

The engine body 1 has 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 inserted into the cylinder 2 so as to be reciprocally slidable. there is A combustion chamber 6 is defined above the piston 5 .

The engine main body 1 is supplied with engine cooling water for cooling it. Specifically, a water jacket through which engine cooling water flows is formed between the cylinder block 3 and the cylinder head 4, and the engine cooling water is supplied to this water jacket.

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

The cylinder head 4 includes an injector (fuel injection device) 10 for injecting fuel into the combustion chamber 6 (into the cylinder 2), and a glow plug 11 for raising the temperature of the air-fuel mixture in the combustion chamber 6. are provided for each cylinder 2, respectively.

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 at its tip which generates heat when energized, and this heat generating portion is attached to the ceiling surface of the combustion chamber 6 so as to be positioned near the tip of the injector 10. ing. For example, the injector 10 has a plurality of nozzle holes at its tip, and the glow plug 11 is positioned so that its heat-generating portion is located between the plurality of sprays from the plurality of nozzles of the injector 10 and does not come into direct contact with the fuel spray. , are placed.

The cylinder head 4 includes an intake port for introducing air supplied from an intake passage 20 into each combustion chamber 6, an intake valve 12 for opening and closing the intake port, and an exhaust passage through which the exhaust generated in each combustion chamber 6 flows. 40 and an exhaust valve 13 for opening and closing the exhaust port are provided.

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

In the exhaust passage 40, in order from the upstream side, a turbine 52b of the second turbocharger 52 (hereinafter referred to as the second turbine 52b) and a turbine 51b of the first turbocharger 51 (hereinafter referred to as the first turbine turbine 51b), a first catalyst 43, a DPF (Diesel Particulate Filter) 44, a urea injector 45 for injecting urea into the exhaust passage 40 on the downstream side of the DPF 44, NOx using the urea injected from the urea injector 45 and a slip catalyst 47 for purifying unreacted ammonia discharged from the SCR catalyst 46 by oxidizing it.

The DPF 44 is a filter for collecting particulate matter (PM) in the exhaust. For example, the DPF 44 is a wall-flow filter made of a heat-resistant ceramic material such as silicon carbide (SiC) or cordierite, or a three-dimensional mesh filter made of heat-resistant ceramic fibers. More specifically, the DPF 44 has a large number of passages made of porous ceramics or the like in a grid pattern. The second passages, which are open on the downstream side, are alternately arranged in a zigzag pattern. Exhaust gas entering the first passage passes through the partition separating 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 by the partition.

There is a limit to the amount of particulate matter that the DPF 44 can collect. Therefore, it is necessary to remove the trapped PM from the DPF 44 as appropriate. The PM trapped in the DPF 44 is burned by exposure to high temperatures and supplied with oxygen, and removed from the DPF 44 . The temperature at which PM is burned and removed is about 600° C., which is relatively high. Therefore, in order to burn PM and remove it from the DPF 44, it is necessary to raise the temperature of the DPF 44 to a high temperature.

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

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

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

The first catalyst 43 is formed, for example, by coating the surface of the DOC catalyst material layer with the 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 this, a wastegate passage 53 that bypasses the first turbine 51b, and a wastegate that opens and closes it. A valve 54 is provided.

The engine system 100 according to this embodiment is capable of executing EGR by recirculating part of the exhaust (EGR gas) to the intake, and has an EGR device 55 for executing this. The EGR device 55 includes an EGR passage 56 that connects a portion of the exhaust passage 40 upstream of the upstream end of the exhaust-side bypass passage 48 and a 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 this, and an EGR cooler 58 that cools the exhaust gas passing through the EGR passage 56 . The EGR device 55 also has an EGR cooler bypass passage 59 that bypasses the EGR cooler 58 and a second EGR valve 60 that opens and closes this passage.

(2) Control system The control system of the engine system will be described with reference to FIG. The engine system 100 of this embodiment is mainly controlled by a PCM (control means, powertrain control module) 200 mounted on the vehicle. The PCM 200 is a microprocessor comprising a CPU, ROM, RAM, I/F, etc., and corresponds to control means 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 for detecting the rotation speed of the crankshaft 7, that is, the engine rotation speed, and an airflow sensor provided near the air cleaner 21 for detecting the amount of intake air (air) flowing through the intake passage 20. SN2, an intake pressure sensor SN3 that detects the pressure of gas flowing into the combustion chamber 6 (cylinder 2), that is, the intake pressure, and oxygen in the portion of the exhaust passage 40 between the first turbine 51b and the first catalyst 43. Exhaust O2 sensor SN4 that detects the concentration, oxidation catalyst temperature sensor SN5 that detects the temperature of the oxidation catalyst 42, differential pressure across the DPF 44 (difference between the pressure in the upstream portion of the exhaust passage 40 and the pressure in the downstream portion of the DPF 41b). and a DPF temperature sensor SN7 for detecting the temperature of the DPF 44 are provided. 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. Further, the cylinder block 3 is provided with an engine water temperature sensor (not shown) for detecting the engine water temperature, which 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, which 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.

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

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

(2-1) Normal Operation Control During normal operation when the DPF regeneration control (regeneration control) described later is not performed, the PCM 200 controls the required torque (requested engine load) mainly based on the engine speed and accelerator opening. is determined, and the main injection is performed by the injector 10 so as to realize the required torque. That is, the main injection is to inject a relatively large amount of fuel into the combustion chamber 6 to generate engine torque. The main injection is performed, for example, near compression top dead center.

The PCM 200 also controls the EGR valves 57 and 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 take appropriate values according to the engine speed, the required torque, and the like. , the opening degree of the exhaust side bypass valve 49 and the like. Then, when the required torque becomes 0 as the vehicle decelerates or the like, the PCM 200 stops the main injection, that is, cuts the fuel. In this embodiment, in order to improve fuel efficiency performance, 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. kept close by. For example, during normal operation, the excess air ratio λ of the air-fuel mixture in the combustion chamber 6 is set to approximately λ=1.7.

(2-2) DPF Control DPF regeneration control for burning and removing PM trapped in the DPF 44 to regenerate the DPF 44 will be described.

In this embodiment, the air-fuel ratio of the air-fuel mixture in the combustion chamber 6 is made higher than the stoichiometric air-fuel ratio to make the air-fuel ratio of the exhaust gas higher than the stoichiometric air-fuel ratio, and unburned fuel is introduced into the oxidation catalyst 42, By causing an oxidation reaction of 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 increased to burn and remove the PM trapped in the DPF 44 . Specifically, as DPF regeneration control for regenerating the DPF 44, the PCM 200 increases the excess air ratio λ of the air-fuel mixture and the excess air ratio λ of the exhaust gas to greater than 1, is supplied to inject fuel into the combustion chamber 6 to regenerate the DPF 44 .

FIG. 3 is a flow chart 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 the exhaust O2 concentration), and the oxygen concentration 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 under which it can be determined that regeneration of the DPF 44 is necessary. The PCM 200 estimates the amount of PM trapped in the DPF 44 using the differential pressure across the DPF 44, etc., and when the estimated amount of PM becomes equal to or greater than a preset first DPF regeneration determination amount, the DPF 44 should be regenerated. Therefore, it is determined that the DPF regeneration condition is satisfied. On the other hand, when 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 met. However, once the PCM 200 determines that the DPF regeneration condition is satisfied, the DPF regeneration condition is not satisfied until the estimated amount of PM becomes less than a preset second DPF regeneration determination amount (<first DPF regeneration determination amount). determined to be

If the determination in step S11 is NO and the DPF regeneration condition is not satisfied, the process is terminated without executing the DPF regeneration control (control during normal operation is executed 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. At step S12, the PCM 200 prohibits EGR. That is, the PCM 200 fully closes the EGR valves 57, 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 due to vehicle deceleration or the like, fuel cut is performed to stop the main injection. The PCM 200 separately determines whether or not the fuel should be cut using the accelerator opening and the like. When 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 the fuel cut, that is, under 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. Enforce controls.

In 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. 4(a), the regeneration injection Qpost is performed only once after the main injection Qm. Hereinafter, the regeneration injection in this normal regeneration control will be referred to as normal regeneration post-injection as appropriate.

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

Hereinafter, the fuel injected into the combustion chamber 6 by XX injection will be referred to as the fuel related to XX injection, and the amount of fuel injected into the combustion chamber 6 by XX injection will be referred to as the injection amount of XX injection. It says. Also, the start timing of XX injection is simply referred to as the injection timing of XX injection.

In the present embodiment, the basic post-injection timing, which is the basic value of the injection timing of the post-injection for normal regeneration, and the basic post-injection amount, which is the basic value of the injection amount of the post-injection for normal regeneration, differ from the engine speed. A map is stored in the PCM 200 in advance according to the required torque, etc. The PCM 200 extracts values corresponding to the current engine speed and required torque from this map. Then, 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, respectively, without correcting them according to the exhaust O2 concentration or the like.

The basic post-injection timing and the basic post-injection amount are set to such timing and amount that the fuel for normal regeneration post-injection does not burn in the combustion chamber 6 . For example, the basic post-injection timing is set to about 80° CA after top dead center of compression (ATDC) to about 120° CA after top dead center of compression (ATDC). Further, the basic post-injection amount is set to an amount that makes the excess air ratio λ of the exhaust gas 1.2 to 1.4, for example, about 10 mm3/st.

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

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

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

On the other hand, when the determination in step S13 is YES and the fuel cut is performed, that is, under the second operating condition in which the fuel cut is performed while 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 minimum temperature at which the oxidation reaction of fuel can occur in the oxidation catalyst 42 and is preset and stored in the PCM 200 .

If the determination in step S16 is NO, the oxidation reaction in the oxidation catalyst 42 cannot be expected, so the process ends without executing the DPF regeneration control (returns to step S10). It is considered that the oxidation catalyst 42 is maintained at a high temperature because the main injection is being performed when the normal regeneration control is performed. Therefore, when the DPF regeneration condition is met while 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, regeneration control during fuel cut is performed.

When the determination in step S16 is YES, the PCM 200 first proceeds to step S17, and closes the opening of the throttle valve 23 more than during normal regeneration control. Specifically, when normal regeneration control is performed or when DPF regeneration control is not performed, the throttle valve 23 is substantially fully opened. On the other hand, in step S17, the opening degree of the throttle valve 23 is set to an opening degree close to fully closed. However, the opening of the throttle valve 23 is such that the excess air ratio λ in the exhaust passage 40 and the excess air ratio λ of the mixture in the combustion chamber 6 are greater than one.

After step S17, the process proceeds to step S18. Here, in the regeneration control during fuel cut, as shown in FIG. 4(b), the regeneration injection is performed three times: the pre-injection (compression stroke injection) Q1, the intermediate injection Q2, and the post-injection (expansion stroke injection) Q3. carried out separately. In step S18, the PCM 200 sets command injection timings, which are command values for the injection timings of the pre-injection Q1, the intermediate injection Q2, and the post-injection Q3. A command injection quantity, which is a command value for the injection quantity, is set. The details of this setting procedure will be described later.

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

(command injection amount)
The procedure for setting the commanded injection amounts of the pre-injection Q1, the intermediate injection Q2, and the post-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 the in-cylinder pressure, which is the pressure inside the combustion chamber 6 . In this embodiment, the intake pressure detected by the intake pressure sensor SN3 is used to estimate the in-cylinder pressure at compression top dead center. Specifically, the in-cylinder pressure at compression top dead center is calculated by taking the product of the intake pressure and the geometrical compression ratio of the engine body 1 .

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

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

The basic pre-injection amount Mq0_Q1, the basic intermediate injection amount Mq0_Q2, and the basic post-injection amount Mq0_Q3 are set so that the sum of them becomes the total basic injection amount during fuel cut Mq0_total calculated in step S21.

Basic pre-injection amount Mq0_Q1, basic intermediate injection amount Mq0_Q2, and basic post-injection amount Mq0_Q3 are set according to the in-cylinder pressure estimated in step S20.

Specifically, as shown in FIG. 6, the basic pre-injection amount Mq0_Q1 and the basic intermediate injection amount Mq0_Q2 are set to smaller values when the in-cylinder pressure is high than when it is low. On the other hand, the basic post-injection amount Mq0_Q3 is set to a larger value when the in-cylinder pressure is high than when it is low. The total amount of the basic pre-injection amount Mq0_Q1, the basic intermediate injection amount Mq0_Q2, and the basic post-injection amount Mq0_Q3, that is, the total basic injection amount during fuel cut Mq0_total is a constant amount regardless of the in-cylinder pressure.

FIG. 6 shows the basic pre-injection amount Mq0_Q1 and the basic intermediate injection amount when the total basic injection amount Mq0_total during fuel cut is 3 mm3/st (amount of fuel injected into one combustion chamber 6 in one combustion cycle). FIG. 4 is a diagram showing the relationship between Mq0_Q2 and basic post-injection amount Mq0_Q3 and in-cylinder pressure; In the example of FIG. 6, the basic pre-injection amount Mq0_Q1 and the basic intermediate injection amount Mq0_Q2 are set to the same value at each in-cylinder pressure. Further, 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 mm3/st and maintained at a constant value regardless of the in-cylinder pressure. On the other hand, when the in-cylinder pressure is equal to or higher than a predetermined value, the basic pre-injection amount Mq0_Q1 and the basic intermediate injection amount Mq0_Q2 are decreased in proportion to the in-cylinder pressure, and the basic post-injection amount Mq0_Q3 is increased in proportion to the in-cylinder pressure.

In the PCM 200, the relationship between the in-cylinder pressure and the respective injection amounts Mq0_Q1, Mq0_Q2, Mq0_Q3 as shown in FIG. When the total basic injection amount Mq0_total during fuel cut 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 injection amount of each of the pre-injection Q1, the intermediate injection Q2, and the post-injection Q3 that have already been performed, that is, the actual value of the total injection amount at the time of fuel cut, and the total injection amount when this injection was performed. The amount of deviation from the command value of the total injection amount during fuel cut is calculated.

Specifically, the PCM 200 estimates the actual value of the total injection amount during fuel cut based on the exhaust O2 concentration and the exhaust flow rate. Then, the PCM 200 calculates a value obtained by subtracting the actual value of the estimated total injection amount during fuel cut from the command value of the total injection amount during fuel cut as the deviation amount. Here, the estimated actual value of the total injection amount at the time of fuel cut is a predetermined time after the timing at which the exhaust O2 concentration used for estimation is detected by the exhaust O2 sensor (the fuel injected into the combustion chamber 6 is The amount of fuel injected into the combustion chamber 6 before reaching the sensor) is the amount of fuel injected into the combustion chamber 6, and the command value to be compared with this is the command value of the total injection amount during fuel cut set a predetermined time before. It is a 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 pre-injection amount Mq0_Q1 set in step S22 as the command injection amount for the pre-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 post-injection amount Mq0_Q3 set in step S22 using the amount of deviation calculated in step S23, and corrects the intermediate injection Q2 and the post-injection Q3. Calculate quantity.

As described above, in this embodiment, the injection amount of the pre-injection Q1 is not corrected based on the exhaust O2 concentration, and only the injection amounts of the intermediate injection Q2 and the post-injection Q3 are corrected based on the exhaust O2 concentration. conduct.

In the present embodiment, half the deviation amount 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 equal to 1/2 of the deviation amount is added to the basic post-injection amount Mq0_Q3, and the resulting value is used as the command injection amount for the post-injection Q3.

For example, when the deviation amount is 2 mm3/st and it is calculated that the actual total injection amount at the time of fuel cut is short of the command value by 2 mm3/st, the command injection amount of the intermediate injection Q2 is the basic value. 1 mm3/st is added to (basic intermediate injection amount Mq0_Q2), and the command injection amount of post-injection Q3 is a value obtained by adding 1 mm3/st to the basic value (basic post-injection amount Mq0_Q3).

Alternatively, the deviation amount may be distributed between the basic intermediate injection amount Mq0_Q2 and the basic post-injection amount Mq0_Q3 according to the ratio of these basic amounts.

Further, the injection amount of the post-injection Q3 may be further corrected according to the temperature of the DPF 44 after step S25. For example, the commanded injection amount of the post-injection Q3 may be corrected to be larger when the temperature of the DPF 44 is high than when it is low.

After step S25, the PCM 200 proceeds to step S26. In step S26, the PCM 200 outputs the commanded injection amount for the pre-injection Q1 set in step S24, the commanded injection amount for the intermediate injection Q2 set in step S25, and the commanded injection amount for the post-injection Q3 set in step S25. is calculated as the command value for the total injection amount during fuel cut.

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

(Injection timing)
The procedure for setting the commanded injection timings of the pre-injection Q1, the intermediate injection Q2 and the post-injection Q3 performed in step S18 will be described with reference to the flowchart of FIG.

First, in step S31, the PCM 200 sets the basic pre-injection timing Ti0_Q1 that is the basic value of the injection timing of the pre-injection Q1, the basic intermediate injection timing Ti0_Q2 that is the basic value of the injection timing of the intermediate injection Q2, and the 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 injection timing values Ti0_Q1, Ti0_Q2, and Ti0_Q3 and the in-cylinder pressure. FIG. 8 is a graph 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, 0 being the compression top dead center, the positive value being the angle before the compression top dead center, and the negative value being the angle before the compression top dead center. represents the angle after compression top dead center.

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

Further, in the present embodiment, the basic front injection timing Ti0_Q1 is advanced more 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 late injection timing Ti0_Q3 are retarded more 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, and Ti0_Q3 of each injection timing as shown in FIG. extract the value that

After step S31, the PCM 200 proceeds to step S32. In step S32, the PCM 200 sets the command injection timing of the pre-injection Q1 to the basic pre-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 late 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. A command injection timing for the post-injection Q3 is calculated.

Specifically, the commanded injection timings of the intermediate injection Q2 and the post-injection Q3 are set to be retarded when the equivalence ratio of the air-fuel mixture in the combustion chamber 6 is high, rather than when the equivalence ratio of the air-fuel mixture in the combustion chamber 6 is low. The basic intermediate injection timing Ti0_Q2 and the basic intermediate injection timing Ti0_Q2 and 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 sum of the detected value of the airflow sensor SN2 or the amount of air in the combustion chamber 6 estimated based on this detected value and the total injection amount during 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 . A detected value of an engine water temperature sensor is used as the engine water temperature. A detected value of an intake air temperature sensor is used as the intake air temperature.

In this 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 used as base values for the injection timings of the intermediate injection Q2 and the post-injection Q3. The command injection timings of these injections Q2 and Q3 are determined by the addition. At this time, the correction amount of the injection timing of the intermediate injection Q2 and the correction amount of the injection timing of the post-injection Q3 are set to the same amount. That is, the difference ΔT2 between the injection timing of the intermediate injection Q2 and the injection timing of the post-injection Q3 is maintained constant regardless of the equivalence ratio, engine water temperature, and intake air temperature.

FIG. 9 is a diagram showing the relationship between the equivalence ratio in the combustion chamber 6 and the injection timing correction amounts of the intermediate injection Q2 and the post-stage injection Q3. FIG. 10 is a diagram showing the relationship between the engine water temperature, the intake air temperature, and the injection timing correction amount. In FIG. 10, lines W1, W2, W3, and W4 represent correction amounts at engine water temperatures of 40, 60, 80, and 100° C., respectively. The vertical axis in FIGS. 9 and 10 is the crank angle. On the vertical axis, the value on the plus side of 0 is the advance side correction amount, and the minus side of 0 is the retardation side correction amount. In other words, when a value on the positive side of 0 is extracted as the correction amount, a value obtained by advancing the base value of the injection timing by the extracted value is used 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 basic value of the injection timing by the absolute value of the extracted value is used as the command injection timing.

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

In this manner, the commanded injection timing for each injection, that is, the injection timing is set using the in-cylinder pressure or the like. However, the injection timing of the pre-stage injection Q1 is set so as to be included in the latter half of the compression stroke (between 90° CA before the top dead center of the compression stroke and the top dead center of the compression stroke), and the injection timings of the intermediate injection Q2 and the post-stage injection Q3 are set. is set to be included in the first half of the expansion stroke (from top dead center of compression to 90° CA after top dead center of compression).

(3) Effects, etc. FIG. 11 is a diagram schematically showing temporal changes of each parameter when the DPF regeneration control is performed. Specifically, FIG. 11 shows, from top to bottom, vehicle speed, engine speed, main injection amount, which is the injection amount of main injection, DPF regeneration flag, normal regeneration post-injection, which is the injection amount of normal regeneration post-injection. injection quantity of pre-injection Q1, injection quantity of intermediate injection Q2, injection quantity of post-injection Q3, and total post-injection quantity which is the total quantity of fuel injected into the combustion chamber 6 minus the injection quantity of main injection. The change over time in the injection amount of post-injection for normal regeneration or the total injection amount during fuel cut is shown. The DPF regeneration flag is set to 1 when a request for DPF regeneration control is issued, and set to 0 otherwise.

As shown in FIG. 11, in the present embodiment, during the period up to time t1, when the DPF regeneration flag is 1 and the injection amount of main injection is greater than 0 and main injection is being performed, The post-injection amount for normal regeneration is set to a value greater than 0, and the post-injection for normal regeneration is performed. On the other hand, at this time, the pre-injection Q1, the intermediate injection Q2, and the post-injection Q3 are stopped. At time t1, even if the fuel is cut as the vehicle decelerates and the injection amount of the main injection becomes 0, if the DPF regeneration flag is maintained at 1, the post injection amount for normal regeneration remains 0. However, each of the injection amounts of the pre-stage injection Q1, the intermediate injection Q2, and the post-stage injection Q3 is set to a value greater than 0, and these injections Q1, Q2, and Q3 are carried out. Fuel continues to be supplied into the combustion chamber 6 . However, at this time, the total injection amount of each of the pre-injection Q1, the intermediate injection Q2, and the post-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 acceleration of the vehicle, etc., the DPF regeneration flag is set to 1, and post-injection for normal regeneration is performed again to perform pre-injection Q1 and intermediate injection Q2. , 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 heated and regenerated in a shorter time.

In the present embodiment, when the main injection is stopped while the DPF regeneration control request is issued, part of the regeneration injection (pre-stage injection Q1) is performed during the compression stroke to burn the fuel. Injected into 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 tends to decrease, the deterioration of the fuel efficiency is suppressed and the exhaust is reduced. The DPF 44 can be properly regenerated by keeping the temperature high.

Specifically, even when the main injection is stopped, it is conceivable to try to regenerate the DPF 44 by performing the post-injection only once in the expansion stroke, as in the normal regeneration control. However, since the temperature of the exhaust gas tends to drop when the main injection is stopped, it is necessary to raise the temperature of the exhaust gas by increasing the injection amount of the post injection compared to when the main injection is performed. be. However, even if a large amount of fuel is injected during the expansion stroke, the fuel is discharged to the exhaust passage in a state of being low in temperature and heavy. That is, most of the hydrocarbons that make up the fuel are led out to the exhaust passage in the form of hydrocarbons having a large number of carbon atoms and a 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.

In contrast, in the present embodiment, fuel is injected into the combustion chamber 6 during the compression stroke in the DPF regeneration control that is performed when the fuel is cut as described above. 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. In other words, the carbon bonds of the hydrocarbons that make up the fuel are cut off, and the ratio 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 with 16 or more carbon atoms to low molecular weight hydrocarbons with less than 16 carbon atoms. And when lightened, the reactivity of the fuel increases. Therefore, as described above, by injecting fuel into the combustion chamber 6 during the compression stroke, the reactivity of the fuel can be enhanced, and more fuel can be appropriately oxidized by the oxidation catalyst 42. can.

Moreover, in this embodiment, in addition to the pre-injection Q1, the intermediate injection Q2 and the post-injection Q3 are performed to inject fuel into the combustion chamber 6 also in 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-injection Q1 to a small amount to prevent unexpected engine torque from being generated while the main injection is stopped. and the temperature of the DPF 44 can be effectively increased. That is, it is preferable to increase the total amount of fuel injected into the combustion chamber 6 in order to increase the temperature of the exhaust gas and the DPF 44 . However, if the injection amount of the pre-injection Q1 performed during the compression stroke is increased, the air-fuel ratio of the air-fuel mixture in the vicinity of the top dead center of the compression stroke becomes high, and the injected fuel may be burned, resulting in unexpected engine torque. There is On the other hand, by configuring as described above, it is possible to increase the total amount of fuel injected into the combustion chamber 6 and reduce the injection amount of the pre-injection Q1, thereby preventing unexpected generation of engine torque. Here, as described above, since the fuel related to the pre-injection Q1 is efficiently oxidized, the temperature of the exhaust gas and the DPF 44 is raised at least effectively by the injection amount of the pre-injection Q1.

In particular, in this embodiment, the fuel injection during the expansion stroke is divided into an intermediate injection Q2 and a post-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, so that the fuel concentration in the combustion chamber 6 becomes locally rich. Therefore, it is possible to prevent unexpected generation of engine torque. Further, the fuel can be diffused and made lighter than when a large amount of fuel is injected into the combustion chamber 6 at once.

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

Further, in the present embodiment, as described with reference to FIG. 6, the injection amount of the pre-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 likely to burn in the combustion chamber 6, it is possible to prevent the fuel related to the pre-injection Q1 from burning in the combustion chamber 6. Therefore, it is possible to more reliably prevent the generation of engine torque.

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

Further, in the present embodiment, the fuel injection amount of the intermediate injection Q2, which is performed at a timing closer to the compression top dead center in the expansion stroke, is increased when the cylinder internal pressure is high than when it is low. be. Therefore, as described above, it is possible to prevent the fuel related to the intermediate injection Q2 from burning 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, when the main injection is stopped, the injection amount of each of the pre-stage injection Q1 and the intermediate injection Q2 is changed according to the cylinder pressure, and the total amount of fuel supplied to the combustion chamber 6 is The total injection amount at the time of fuel cut is designed not to change depending on 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) Modification In the above embodiment, the post-injection is performed by dividing the post-injection into the intermediate injection Q2 and the post-injection Q3, but the intermediate injection Q2 is omitted and the post-injection Q3 is performed only once during the expansion stroke. you can go However, if it is divided into two times as in the above-described embodiment, it is possible to prevent unexpected engine torque from being generated and to make the fuel lighter.

Further, in the above embodiment, the case where the in-cylinder pressure is estimated using the intake pressure sensor has been described, but a sensor capable of detecting the in-cylinder pressure may be used to directly detect the in-cylinder pressure.

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 upstream of the DPF 44), the more retarded the timing. may Specifically, it is a map showing the relationship between the preset temperature of the DPF 44 and the lightening rate of the fuel (a parameter that becomes a higher value as the fuel is more easily lightened). is stored in the PCM 200, and the lightening rate corresponding to the current temperature of the DPF 44 is extracted from this map. This may be corrected so that the timing is retarded. Further, the injection amount of the post-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 (as the fuel is more easily lightened), the temperature of the DPF 44 is raised to a higher temperature, and the fuel is more likely to burn in the combustion chamber 6. It can definitely be prevented. Further, as described above, if the injection amount of the post-injection Q3 is made smaller as the lightening rate is higher, deterioration of the fuel efficiency can be suppressed.

Further, in the above-described embodiment, the post-injection is performed only once after the main injection 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 (4)

An exhaust purification control device applied to an engine comprising an engine body including a cylinder and a fuel injection device for injecting 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 ;
Equipped with an intake pressure sensor capable of detecting the pressure of intake air introduced into the engine body ,
Under a first operating condition in which main injection is performed to inject fuel into the cylinder at a timing at which engine torque can be generated and the filter regeneration condition is satisfied, the control means supplies fuel to regenerate the filter. causing the fuel injection device to perform the regeneration injection at a timing later than the main injection during the expansion stroke;
Under a second operating condition in which the main injection is stopped and the regeneration condition of the filter is satisfied, the control means performs regeneration injection for injecting fuel for regeneration of the filter in the latter half of the compression stroke. causing the fuel injection device to perform the compression stroke injection performed during the first half of the expansion stroke and the expansion stroke injection performed in the first half of the expansion stroke ;
The control means estimates the in-cylinder pressure, which is the pressure in the cylinder at compression top dead center, by taking the product of the detected value of the intake pressure sensor and the geometric compression ratio of the engine body,
Under the condition that the total amount of fuel injected into the cylinder by the regeneration injection is the same, the amount of fuel injected into the cylinder by the compression stroke injection is the compression top dead center estimated by the control means. is reduced as the in- cylinder pressure increases, and the amount of fuel injected into the cylinder by the expansion stroke injection is increased as the in-cylinder pressure at compression top dead center estimated by the control means increases. engine exhaust purification control device. In the engine exhaust gas purification control device according to claim 1 ,
The control means causes the fuel injection device to further perform, as the regeneration injection under the second operating condition, an intermediate injection that is performed in the first half of an expansion stroke and before the expansion stroke injection, and
Under the condition that the total amount of fuel injected into the cylinder by the regeneration injection is the same, the amount of fuel injected into the cylinder by the intermediate injection is the in-cylinder pressure at the compression top dead center estimated by the control means. An exhaust gas purification control device for an engine, characterized in that the higher is , the lower is. In the engine exhaust gas purification control device according to claim 1 or 2 ,
The total amount of fuel injected into the cylinder by the regeneration injection performed under the second operating condition is kept constant regardless of the in-cylinder pressure at compression top dead center estimated by the control means. , an engine exhaust purification control device characterized by: In the engine exhaust purification control device according to any one of claims 1 to 3 ,
The engine, wherein the injection amount of the regeneration injection performed under the second operating condition is smaller than the injection amount of the regeneration injection performed under the first operating condition. exhaust purification control device.

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