JP2023170812A - Control system of internal combustion engine - Google Patents

Abstract

To provide a control system of an internal combustion engine including: a fuel addition valve for injecting (adding) a fuel to an exhaust gas flowing in an exhaust passage from one end of a connection passage branched at a branch position located upstream with respect to an exhaust emission control device disposed on the exhaust passage of the internal combustion engine; and a control device allowing the injection of the fuel to the fuel addition valve when a fuel addition condition is established, and preventing accumulation of deposit near the branch position.SOLUTION: When a branch temperature correlation value correlating to a temperature of an exhaust gas flowing at a branch position is higher than a prescribed correlation value threshold, injection of a fuel by a fuel addition valve is forbidden. The correlation value threshold is a value for estimating accumulation of the fuel injected from the fuel addition valve and attached near the branch position as deposit, when the branch temperature correlation value becomes higher than the correlation value threshold.SELECTED DRAWING: Figure 2

Description

The present invention relates to a control system for an internal combustion engine. For example, the present invention relates to a control system for an internal combustion engine that includes a fuel addition valve that injects (adds) fuel to exhaust gas flowing into an exhaust gas purification device.

One of these types of internal combustion engines has a fuel addition valve installed at one end of a "connecting passage" that branches off at a position upstream of the exhaust purification device (specifically, the oxidation catalyst device) in the exhaust path. There is. That is, fuel injected from the fuel addition valve is added to the exhaust gas flowing through the exhaust path via the connection passage. By disposing the fuel addition valve in the connection passage, the nozzle hole of the fuel addition valve is prevented from being directly exposed to the exhaust gas flowing through the exhaust passage and becoming high temperature. Therefore, fuel adhering to the nozzle is prevented from accumulating as a deposit (see, for example, Patent Document 1).

JP 2018-13095 Publication

However, there is a possibility that deposits may accumulate near the branching position of the connection passage and the exhaust passage. Specifically, there is a possibility that a portion of the fuel injected from the fuel addition valve may adhere to the inner wall surface near the branching position and become a solidified deposit together with soot contained in the exhaust gas. When the amount of deposit increases, the connecting passage becomes blocked at the branch position, and there is a possibility that the fuel injected from the fuel addition valve cannot be added to the exhaust gas flowing through the exhaust path.

The present invention was devised in view of these points, and provides a control system for an internal combustion engine that can avoid an increase in the amount of deposits accumulated in the vicinity of the branching position between the connection passage and the exhaust passage. The purpose is to

In order to solve the above problems, a control system for an internal combustion engine according to a first aspect of the present invention includes an exhaust gas purification device disposed in an exhaust path of an internal combustion engine, and an exhaust gas purification device located upstream of the exhaust gas purification device in the exhaust path. a fuel addition valve that injects and adds fuel to the exhaust gas flowing through the exhaust path from one end of a connecting passage branched at a certain branching position; A control device that executes fuel addition control to inject fuel.

Furthermore, the control system for an internal combustion engine includes a temperature correlation value detection device that obtains a branch temperature correlation value that correlates with the temperature of the exhaust gas flowing through the branch position, and the control device is configured to detect a branch temperature correlation value that is correlated to the temperature of the exhaust gas flowing through the branch position, and the control device is configured to detect a temperature correlation value that is correlated with the temperature of the exhaust gas flowing through the branch position. If the branch temperature correlation value is higher than a predetermined correlation value threshold, execution of the fuel addition control is prohibited. The correlation value threshold is a value at which it is predicted that when the branch temperature correlation value becomes higher than the correlation value threshold, fuel injected from the fuel addition valve and deposited near the branch position will accumulate as a deposit. .

A second invention of the present invention is the control system for an internal combustion engine according to the first invention, wherein the control device is configured to inject fuel from the fuel addition valve per unit time when executing the fuel addition control. The amount of fuel added, which is the amount of fuel, is determined to be equal to or greater than the lower limit value of addition amount determined according to the branch temperature correlation value. The lower limit of the addition amount is a value at which it is predicted that when the fuel addition amount becomes smaller than the lower limit of the addition amount, the fuel injected from the fuel addition valve and attached to the vicinity of the branch position will accumulate as a deposit. be.

A third invention of the present invention is the control system for an internal combustion engine according to the first or second invention, wherein the internal combustion engine is located at a position between the branch position in the exhaust path and the exhaust purification device. The exhaust purification device includes an oxidation catalyst device and a particulate matter collection device downstream of the oxidation catalyst device.

When some of the fuel injected from the fuel addition valve adheres to the inner surface near the branch point, some of the components evaporate and become a highly viscous binder that adsorbs soot contained in the exhaust gas flowing through the exhaust path. . Fuel components containing soot build up as deposits when exposed to high temperature exhaust gas. Therefore, in the control system for an internal combustion engine according to the first invention, if the temperature of the exhaust gas flowing through the branch position is high (specifically, even when the fuel addition condition is met, the branch temperature correlation value is set to the correlation value threshold value). ), fuel injection by the fuel addition valve is prohibited. That is, even if the fuel addition conditions are met, if there is a high possibility that the fuel injected by the fuel addition valve will accumulate as a deposit near the branch position, the fuel addition valve will not inject fuel.

In the second aspect of the invention, since fuel is injected from the fuel addition valve so that the amount of fuel added is equal to or greater than the lower limit of addition amount, there is a high possibility that the binder containing soot described above will be washed away. Therefore, according to the second invention, it is possible to more reliably prevent the amount of deposits accumulated near the branching position from increasing.

In the third invention, since the branch position is on the upstream side of the turbine in the exhaust path, the fuel injected from the fuel addition valve is transferred to the exhaust gas before it flows into the turbine (i.e., before the temperature decreases through the turbine). (exhaust gas). Therefore, the vaporization and atomization of the fuel injected by the fuel addition valve is promoted, which further increases the possibility of avoiding an increase in the amount of deposits accumulated near the branching position.

1 is a schematic configuration diagram of a vehicle to which an internal combustion engine control system according to the present invention is applied. 1 is a schematic configuration diagram of a fuel addition valve disposed in an exhaust path of an internal combustion engine. FIG. 3 is a diagram showing combinations of a turbine outlet temperature of an internal combustion engine and a fuel addition amount of a fuel addition valve. 2 is a flowchart showing a "DPF regeneration processing routine" executed by a control device of a control system for an internal combustion engine.

Embodiments of the present invention will be described with reference to FIGS. 1 to 4. The same reference numbers in the description refer to the same elements having the same function without redundant description. The internal combustion engine control system according to this embodiment is applied to a vehicle 1 shown in FIG. The vehicle 1 includes an internal combustion engine 2 as a driving force source, a supercharger 3, an intake system 4, an exhaust system 5, an EGR system 6, and an ECU 7. Note that illustration of the external appearance of the vehicle 1 is omitted.

Internal combustion engine 2 is a multi-cylinder diesel engine. Internal combustion engine 2 includes a plurality of fuel injection valves 21. Each of the fuel injection valves 21 injects high-pressure fuel supplied from a pressure accumulation chamber of a common rail device (not shown) into the cylinder in response to instructions from the ECU 7.

The supercharger 3 includes a turbine 31 and a compressor 32. The turbine 31 is operated (rotated) by the pressure of exhaust gas (combustion gas) discharged from each cylinder of the internal combustion engine 2 . The compressor 32 operates (rotates) in conjunction with the turbine 31 and pressurizes the air (intake) taken into each cylinder of the internal combustion engine 2 .

The intake system 4 includes intake pipes 41a to 41b, which are intake passages, an intake manifold 42, an intercooler 43, a throttle valve 44, and a throttle actuator 44a. The intake pipe 41a introduces intake air (fresh air) drawn from the outside (outside the vehicle) into the compressor 32. The intake pipe 41b introduces intake air discharged from the compressor 32 into the intake manifold 42. The intake manifold 42 introduces intake air into each cylinder of the internal combustion engine 2. The intake pipes 41a to 41b and the intake manifold 42 form an intake path of the internal combustion engine 2.

The intercooler 43 is arranged in the intake pipe 41b. The intercooler 43 cools the intake air which has been pressurized by the compressor 32 and whose temperature has increased. The throttle valve 44 is interposed at a position downstream of the intercooler 43 in the intake pipe 41b. The throttle valve 44 adjusts the opening degree of the intake pipe 41b according to its rotational position. The throttle actuator 44a changes the rotational position (valve open state) of the throttle valve 44 between a predetermined fully open position (fully open state) and a fully closed position (fully closed state) in response to instructions from the ECU 7.

The exhaust system 5 includes an exhaust manifold 51, exhaust pipes 52a to 52b, a connecting passage 53, a fuel addition valve 54, a first oxidation catalyst 55, a DPF (Diesel Particulate Filter) 56, an SCR (Selective Catalytic Reduction) 57, and a second oxidation catalyst. Contains 58. The exhaust manifold 51 and the exhaust pipes 52a to 52b form an exhaust path of the internal combustion engine 2. The first oxidation catalyst 55, DPF 56, SCR 57, and second oxidation catalyst 58 are also collectively referred to as an "exhaust purification device."

The exhaust manifold 51 introduces exhaust gas (combustion gas) discharged from each cylinder of the internal combustion engine 2 into the exhaust pipe 52a. The exhaust pipe 52a introduces exhaust gas into the turbine 31. The exhaust pipe 52b discharges the exhaust gas discharged from the turbine 31 to the outside (outside the vehicle).

The connection passage 53 is a branch passage that joins the exhaust path at the exhaust pipe 52a. For convenience, the position where the exhaust pipe 52a and the connection passage 53 join is also referred to as a "branch position." The fuel addition valve 54 is disposed at the other end of the connection passage 53 (that is, at the end of the connection passage 53 opposite to the branch position). The fuel addition valve 54 injects fuel supplied from a fuel pump (not shown) toward the branch position (that is, the exhaust pipe 52a) according to instructions from the ECU 7.

FIG. 2 shows how the fuel injected from the fuel addition valve 54 is added to the exhaust gas flowing through the exhaust pipe 52a. As will be described later, the exhaust gas to which fuel has been added flows into the first oxidation catalyst 55 via the turbine 31, and as a result, the temperature of the exhaust gas discharged from the first oxidation catalyst 55 (that is, the exhaust gas flowing into the DPF 56) rises.

The cooling water channels 59a and 59b shown in FIG. 2 are channels (water jackets) through which cooling water (coolant liquid) supplied from a water pump (not shown) flows. The fuel addition valve 54 (specifically, the nozzle hole formed at the tip of the fuel addition valve 54) is cooled by the cooling water flowing through the cooling water channels 59a and 59b. Therefore, after a portion of the fuel injected from the fuel addition valve 54 adheres to the nozzle hole, the possibility that the adhered fuel becomes a deposit due to being exposed to a high temperature environment is reduced.

The first oxidation catalyst 55 shown in FIG. 1 is an oxidation catalyst device (DOC: Diesel Oxidation Catalyst) that oxidizes and purifies carbon monoxide (CO), hydrocarbons (HC), etc. contained in exhaust gas. The DPF 56 is a well-known particulate matter collection device that collects (captures) particulate matter (PM) contained in exhaust gas.

The SCR 57 uses ammonia gas generated by hydrolysis of urea water injected from a urea water addition valve (not shown) to reduce and purify nitrogen oxides (NOx) contained in the exhaust gas. The second oxidation catalyst 58 oxidizes and purifies the residual ammonia gas discharged from the SCR 57.

The EGR system 6 includes an EGR pipe 61 and an EGR valve 62. The EGR pipe 61 communicates the exhaust pipe 52a and the intake pipe 41b. The EGR valve 62 is interposed in the EGR pipe 61. The open state of the EGR valve 62 changes between a predetermined fully open position (fully open state) and a fully closed position (fully closed state) according to instructions from the ECU 7, and as a result, the valve is opened from the exhaust pipe 52a to the intake pipe 41b. The amount of EGR gas that is refluxed is adjusted.

The ECU 7 is an electronic control unit that includes a CPU, ROM, RAM, and EEPROM, and is a control device (control unit) of the control system of the internal combustion engine 2. The CPU reads data, performs numerical calculations, and outputs calculation results by sequentially executing predetermined programs. The ROM stores programs executed by the CPU, maps (lookup tables), and the like. The RAM temporarily stores data referenced by the CPU. The EEPROM stores data referenced by the CPU, and further retains the stored data even if the ECU 7 stops operating.

The ECU 7 is connected to a crank angle sensor 71, a cam position sensor 72, an air flow meter 73, temperature sensors 74a to 74b, a differential pressure sensor 75, and an accelerator opening sensor 76.

The crank angle sensor 71 outputs a pulse signal to the ECU 7 every time a crankshaft (not shown) of the internal combustion engine 2 rotates by a predetermined angle. The cam position sensor 72 outputs a signal to the ECU 7 according to the rotational position of a camshaft (not shown) of the internal combustion engine 2 . The ECU 7 obtains the engine rotation speed NE of the internal combustion engine 2 based on the signal input from the crank angle sensor 71. The ECU 7 acquires the crank angle CA of a specific cylinder included in the internal combustion engine 2 based on signals input from the crank angle sensor 71 and the cam position sensor 72.

The air flow meter 73 detects the amount of intake air flowing through the intake pipe 41a as an intake air amount Ga, and outputs a signal representing the intake air amount Ga to the ECU 7. The temperature sensor 74a is arranged at a position between the turbine 31 and the first oxidation catalyst 55 in the exhaust pipe 52b. The temperature sensor 74a detects the temperature of the exhaust gas flowing out from the turbine 31 as a turbine outlet temperature T6, and outputs a signal representing the turbine outlet temperature T6 to the ECU 7.

The temperature sensor 74b is arranged at a position between the first oxidation catalyst 55 and the DPF 56 in the exhaust pipe 52b. The temperature sensor 74b detects the temperature of the exhaust gas flowing out from the first oxidation catalyst 55 as the catalyst outlet temperature T7, and outputs a signal representing the catalyst outlet temperature T7 to the ECU 7. The differential pressure sensor 75 detects the differential pressure Pd, which is the pressure difference between the pressure of the exhaust gas flowing into the DPF 56 and the pressure of the exhaust gas flowing out from the DPF 56, and outputs a signal representing the differential pressure Pd to the ECU 7.

The accelerator opening sensor 76 detects the accelerator pedal opening Ap, which is the opening of an accelerator pedal (not shown) operated by the driver of the vehicle 1 to control the acceleration of the vehicle 1, and detects the accelerator pedal opening Ap. A signal representing this is output to the ECU 7. When the driver accelerates the vehicle 1 (that is, when the required load on the internal combustion engine 2 increases), the accelerator pedal opening degree Ap increases.

The ECU 7 controls the engine rotation speed NE based on the accelerator pedal opening Ap. When increasing the engine rotational speed NE, the ECU 7 increases the fuel injection amount Qi, which is the amount of fuel injected from the fuel injection valve 21. The ECU 7 determines the fuel injection amount Qi based on the accelerator pedal opening Ap, the engine rotational speed NE, the intake air amount Ga, and the like.

When the fuel injection amount Qi is determined, the ECU 7 sets the fuel injection pattern to the fuel injection amount Qi, which includes (a plurality of) combinations of the fuel injection timing represented by the crank angle CA and the fuel injection amount at that timing. Decide accordingly. The ECU 7 causes the fuel injection valves 21 of each cylinder to inject fuel according to the fuel injection pattern.

(DPF regeneration processing)
When the "regeneration start condition" is satisfied, the ECU 7 starts a "DPF regeneration process" that causes the fuel addition valve 54 to inject fuel. The regeneration start condition is established when there is a high possibility that the amount of particulate matter collected by the DPF 56 (hereinafter also referred to as "filter deposition amount") exceeds a predetermined amount of deposition threshold. The regeneration start condition in this embodiment is satisfied when the differential pressure Pd becomes larger than a predetermined difference threshold Pth (ie, Pd>Pth).

When the DPF regeneration process is executed, the fuel injected from the fuel addition valve 54 and added to the exhaust gas is oxidized at the first oxidation catalyst 55, so that the temperature of the exhaust gas discharged from the first oxidation catalyst 55 and flowing into the DPF 56 increases. Rise. As a result, the particulate matter deposited on the DPF 56 is burned away. That is, the DPF regeneration process is a process in which high-temperature exhaust gas flows into the DPF 56 by injecting fuel into the fuel addition valve 54, thereby reducing the amount of filter accumulation.

When the "regeneration end condition" is satisfied after the regeneration start condition is satisfied, the ECU 7 ends the DPF regeneration process. The regeneration end condition in this embodiment is satisfied when the catalyst outlet temperature T7 remains higher than the predetermined regeneration processing execution temperature Tr for longer than a predetermined time threshold Eth.

The regeneration processing execution temperature Tr is adjusted in advance so that particulate matter within the DPF 56 is burned (reduced) when the catalyst outlet temperature T7 becomes higher than the regeneration processing execution temperature Tr. The time threshold Eth is pre-adapted to be equal to the time required to burn off most of the particulate matter within the DPF 56.

For convenience, the conditions that are satisfied during the period from when the regeneration start condition is satisfied until the regeneration end condition is satisfied (that is, the period during which the DPF regeneration process is executed) are also referred to as "fuel addition conditions." For convenience, the control that causes the fuel addition valve 54 to inject fuel when the fuel addition conditions are met is also referred to as "fuel addition control."

During execution of the DPF regeneration process, the ECU 7 determines a fuel addition amount Di representing the amount of fuel injected from the fuel addition valve 54 per unit time. To be more specific, the ECU 7 sets the fuel addition amount Di to a region R1 (i.e., a region with downward hatching to the right) where the combination of the turbine outlet temperature T6 and the fuel addition amount Di is shown in FIG. Decide to include.

In the region R1, if the combination of the turbine outlet temperature T6 and the fuel addition amount Di is included in the region R1, particulate matter in the DPF 56 will be burnt out in a relatively short time when the DPF regeneration process is executed, and the temperature will be excessive. The adjustment is made in advance so that the possibility of damage to the DPF 56 due to the rise is not increased.

(DPF regeneration process - fuel addition prohibition process)
By the way, the inventor of the present application has determined that the fuel addition amount Di is determined from the value (hereinafter also referred to as the "addition amount lower limit value") determined with respect to the temperature of the exhaust gas flowing through the branch position in the exhaust pipe 52a (branch position temperature). It was found that the smaller the value, the more likely the amount of deposits deposited near the branch position will increase.

The lower limit of the addition amount in this embodiment is shown by the curve L1 in FIG. 3 (that is, a set of combinations of the turbine outlet temperature T6 and the fuel addition amount Di). Since the turbine outlet temperature T6 detected by the temperature sensor 74a is correlated with the branch position temperature (that is, the higher the branch position temperature, the higher the turbine outlet temperature T6), for convenience, it is also referred to as a "branch temperature correlation value". be called. For convenience, the temperature sensor 74a is also referred to as a "temperature correlation value detection device."

Deposits deposited near the branch position will be explained. When fuel is injected from the fuel addition valve 54, a portion of the injected fuel adheres to the inner surface near the branch position. The fuel adhering to the vicinity of the branching position becomes a highly viscous binder as some of its components evaporate and adsorbs soot contained in the exhaust gas flowing through the exhaust pipe 52a. When the fuel components containing soot are exposed to the high-temperature exhaust gas flowing through the exhaust pipe 52a, they accumulate as deposits. Examples of deposits that adhere to and accumulate on the inner surfaces of the exhaust pipe 52a and the connecting passage 53 near the branching positions are shown by deposits D1 and D2 in FIG.

On the other hand, when the fuel addition amount Di becomes larger than the amount represented by the curve L1 with respect to the turbine outlet temperature T6 at that time (that is, the value of the fuel addition amount Di shown by the point on the curve L1), the fuel component is not sufficiently evaporated (that is, the viscosity does not increase), and the soot in the exhaust gas is no longer adsorbed. In addition, as the fuel addition amount Di increases, the soot that has already been adsorbed is removed from the inner surface near the branching position. That is, the fuel components, soot, etc. that have not yet become fixed as deposits are washed away by the fuel newly injected from the fuel addition valve 54.

In other words, fuel adhering to the nozzle holes of the fuel addition valve 54 does not accumulate as deposits because the nozzle holes are housed in the connection passage 53 and do not come into direct contact with the high-temperature exhaust gas, and the cooling water flow path 59a , 59b, the nozzle holes are cooled by the cooling water flowing through them. However, since the fuel adhering to the inner surface near the branch position is directly heated by the high-temperature exhaust gas flowing through the exhaust pipe 52a, if the fuel addition amount Di is smaller than the lower limit value of addition amount, fuel will accumulate near the branch position. The amount of deposits is likely to increase. That is, the addition amount lower limit value is a value at which it is predicted that when the fuel addition amount Di becomes smaller than the addition amount lower limit value, the fuel injected from the fuel addition valve 54 and deposited near the branch position will accumulate as a deposit. .

Therefore, in order to avoid an increase in deposits near the branching position, the ECU 7 in this embodiment is configured to ( That is, if Tth<T6), the fuel addition valve 54 is not injected with fuel. For convenience, the temperature threshold Tth is also referred to as a "correlation value threshold."

On the other hand, if the turbine outlet temperature T6 is equal to or lower than the temperature threshold Tth when the fuel addition condition is satisfied (i.e., T6≦Tth), the ECU 7 controls the temperature in the region R2 shown in FIG. ) is determined to include the fuel addition amount Di. In addition, the ECU 7 causes the fuel addition valve 54 to inject fuel according to the determined fuel addition amount Di.

Region R2 is a region formed by a set of combinations of turbine outlet temperature T6 smaller than temperature threshold Tth and fuel addition amount Di included in region R1. In other words, the ECU 7 sets the fuel addition amount Di to be equal to or greater than the lower limit value of the addition amount determined according to the turbine outlet temperature T6 (that is, the value of the fuel addition amount Di determined by the curve L1 with respect to the turbine outlet temperature T6). Decide as follows. This means that in FIG. 3, line segment L2 that defines the lower end of region R2 (that is, the line segment from point P1 to point P2, which is the point corresponding to temperature threshold Tth on curve L1) and curve L1 It can be understood from the positional relationship (vertical relationship) of .

Note that in this embodiment, the temperature threshold Tth is approximately equal to the regeneration processing execution temperature Tr. Therefore, even if the injection of fuel by the fuel addition valve 54 is stopped (interrupted) due to the turbine outlet temperature T6 being higher than the temperature threshold Tth, the particulate matter in the DPF 56 is reduced as fuel. .

In addition, when the turbine outlet temperature T6 is higher than the temperature threshold value Tth, if the fuel addition amount Di is set to a value larger than the addition amount lower limit value and then the fuel addition valve 54 is injected with fuel, the temperature of the DPF 56 increases rapidly. Therefore, the fuel addition valve 54 cannot be made to continuously inject fuel. In other words, when the turbine outlet temperature T6 is higher than the temperature threshold Tth, the fuel addition valve 54 can be made to inject fuel while avoiding the possibility that the amount of deposits deposited near the branch position will increase. becomes difficult. That is, the temperature threshold Tth is a value at which it is predicted that when the turbine outlet temperature T6 becomes higher than the temperature threshold Tth, the fuel injected from the fuel addition valve 54 and deposited near the branch position will accumulate as a deposit. Therefore, the ECU 7 does not cause the fuel addition valve 54 to inject fuel when the turbine outlet temperature T6 is higher than the temperature threshold Tth.

(Specific operation)
Next, the specific operation of the ECU 7 will be explained. The CPU of the ECU 7 (hereinafter also referred to as a unit "CPU") executes the "DPF regeneration processing routine" shown in the flowchart in FIG. 4 every time a predetermined time period ΔT elapses.

In this routine, the value of the playback flag Xr is set and referenced. The regeneration flag Xr is set to "0" by an initial routine (not shown) that is executed when the ECU 7 starts operating. The regeneration flag Xr is set to "1" when the fuel addition condition is satisfied (that is, in the period from when the regeneration start condition is satisfied until the regeneration end condition is satisfied).

When the timing is appropriate, the CPU starts processing from step 400 in FIG. 4, proceeds to step 405, and determines whether the value of the reproduction flag Xr is "0". If the value of the reproduction flag Xr is "0", the CPU determines "Yes" in step 405, proceeds to step 410, and determines whether the reproduction start condition is satisfied. That is, the CPU determines whether the differential pressure Pd is greater than the differential threshold Pth.

If the differential pressure Pd is larger than the differential threshold Pth, the CPU determines "Yes" in step 410, proceeds to step 415, and sets the value of the regeneration flag Xr to "1". Next, the CPU proceeds to step 420 and sets the value of the cumulative time Et to "0".

Further, the CPU proceeds to step 425 and determines whether the turbine outlet temperature T6 is equal to or lower than the temperature threshold Tth. If the turbine outlet temperature T6 is equal to or lower than the temperature threshold Tth, the CPU determines "Yes" in step 425, proceeds to step 430, and determines the fuel addition amount Di. Specifically, the CPU determines the fuel addition amount Di such that the combination of the turbine outlet temperature T6 and the fuel addition amount Di is included in the region R2 shown in FIG. Next, the CPU proceeds to step 435 and causes the fuel addition valve 54 to inject fuel equal to the fuel addition amount Di. Furthermore, the CPU proceeds to step 440.

On the other hand, if the turbine outlet temperature T6 is higher than the temperature threshold Tth, the CPU determines "No" in step 425 and directly proceeds to step 440. That is, in this case, fuel injection (addition) by the fuel addition valve 54 is not performed.

In step 440, the CPU determines whether the catalyst outlet temperature T7 is higher than the regeneration processing execution temperature Tr. If the catalyst outlet temperature T7 is higher than the regeneration processing execution temperature Tr, the CPU determines "Yes" in step 440, proceeds to step 445, and increases the value of the integrated time Et by the time period ΔT.

Next, the CPU proceeds to step 450 and determines whether the playback end condition is satisfied. That is, the CPU determines whether or not the cumulative time Et has become longer than the time threshold Eth as a result of the cumulative time Et being increased by the process of step 445.

If the reproduction end condition is satisfied, the CPU makes a "Yes" determination in step 450, proceeds to step 455, and sets the value of the reproduction flag Xr to "0". Next, the CPU proceeds to step 495 and ends the processing of this routine.

On the other hand, if the reproduction end condition is not satisfied, the CPU makes a "No" determination in step 450 and directly proceeds to step 495.

Note that if the determination condition in step 405 is not satisfied (that is, if the value of the reproduction flag Xr is "1"), the CPU determines "No" in step 405 and directly proceeds to step 425. If the determination condition in step 410 is not satisfied (that is, if the playback start condition is not satisfied), the CPU makes a "No" determination in step 410 and directly proceeds to step 495.

If the determination condition in step 440 is not satisfied (that is, if the catalyst outlet temperature T7 is equal to or lower than the regeneration processing execution temperature Tr), the CPU makes a "No" determination in step 440 and directly proceeds to step 495. That is, in this case, since the catalyst outlet temperature T7 has not risen sufficiently, burning out of the particulate matter in the DPF 56 is not promoted, and therefore the cumulative time Et does not increase.

As described above, according to the internal combustion engine control system according to the present embodiment, fuel addition control is executed when the fuel addition condition is met. That is, fuel is injected from the fuel addition valve 54 and the DPF regeneration process is executed. However, when the turbine outlet temperature T6 is higher than the temperature threshold Tth, execution of the fuel addition control is prohibited. That is, in this case, fuel is not injected from the fuel addition valve 54. Therefore, it is possible to avoid an increase in the amount of deposits accumulated in the vicinity of the branch position between the exhaust pipe 52a and the connecting passage 53 due to the injection from the fuel addition valve 54 when the turbine outlet temperature T6 is high. becomes higher.

In addition, when fuel is injected from the fuel addition valve 54, the fuel addition amount Di is determined to be equal to or greater than the lower limit of addition amount, so that the fuel injected from the fuel addition valve 54 connects the exhaust pipe 52a and the connecting passage. There is a high possibility that an increase in the amount of deposits accumulated in the vicinity of the branch position with 53 can be avoided.

Furthermore, since the branch position is located upstream of the turbine 31 in the exhaust path, the fuel injected from the fuel addition valve 54 is added to the exhaust gas before it flows into the turbine 31. In other words, since the fuel addition valve 54 injects (adds) fuel to the exhaust gas before its temperature decreases after passing through the turbine 31, vaporization and atomization of the injected fuel is promoted and deposits near the branch position. This increases the possibility that increased deposit amounts will be avoided.

Although the embodiments of the present invention have been described above with reference to the above structure, it will be apparent to those skilled in the art that many alterations, improvements, and changes can be made without departing from the purpose of the present invention. Accordingly, forms of the invention may include all alterations, modifications, and changes that do not depart from the spirit and purpose of the appended claims. The form of the present invention is not limited to the above-mentioned special structure, and can be modified, for example, as described below.

The branch temperature correlation value in this embodiment was the turbine outlet temperature T6. Alternatively, the branch temperature correlation value may be the temperature of the exhaust gas detected by a temperature sensor that is disposed in the exhaust pipe 52a and directly detects the temperature of the exhaust gas flowing through the branch position in the exhaust pipe 52a. .

Alternatively, the branch temperature correlation value may be the exhaust temperature estimated based on the fuel injection amount Qi and the engine rotation speed NE. In this case, the crank angle sensor 71 and cam position sensor 72 used to obtain the engine rotational speed NE, and the ECU 7 that executes the exhaust temperature estimation process serve as a temperature correlation value detection device.

The connecting passage 53 was connected to the exhaust pipe 52a. Alternatively, the connection passage 53 may be connected to a position between the turbine 31 and the first oxidation catalyst 55 in the exhaust pipe 52b. That is, in this case, the branch position is between the turbine 31 and the first oxidation catalyst 55 in the exhaust pipe 52b, and the fuel addition valve 54 adds fuel to the exhaust gas flowing out from the turbine 31.

The fuel addition condition was satisfied during the period from when the above-described regeneration start condition was satisfied until when the regeneration end condition was satisfied. Alternatively, the fuel addition condition may be satisfied during the period from when the driver of the vehicle 1 performs a predetermined "on operation" until he performs a predetermined "off operation." For example, the on operation is an operation to switch the DPF regeneration button disposed on the driver's seat of the vehicle 1 from an off state to an on state, and the off operation is an operation to switch the DPF regeneration button from an on state to an off state.

The processing realized by the ECU 7 described above may be executed by a plurality of ECUs (control devices, control units).

1...Vehicle 2...Internal combustion engine 3...Supercharger 4...Intake system 5...Exhaust system 6...EGR system 7...ECU
21... Fuel injection valve 31... Turbine 32... Compressor 41a, 41b... Intake pipe 42... Intake manifold 43... Intercooler 44... Throttle valve 44a... Throttle actuator 51... Exhaust manifold 52a, 52b... Exhaust pipe 53... Connection passage 54... Fuel Addition valve 55...first oxidation catalyst 56...DPF
57...SCR
58...Second oxidation catalyst 59a, 59b...Cooling water flow path 61...EGR pipe 62...EGR valve 71...Crank angle sensor 72...Cam position sensor 73...Air flow meter 74a, 74b...Temperature sensor 75...Differential pressure sensor 76...Accelerator open degree sensor D1, D2...deposit

Claims (3)

An exhaust purification device installed in the exhaust path of an internal combustion engine;
a fuel addition valve that injects and adds fuel to exhaust gas flowing through the exhaust route from one end of a connecting passage branched at a branch position upstream of the exhaust gas purification device in the exhaust route;
a control device that executes fuel addition control that causes the fuel addition valve to inject fuel when a predetermined fuel addition condition is satisfied;
A control system for an internal combustion engine, comprising:
comprising a temperature correlation value detection device that obtains a branch temperature correlation value that correlates with the temperature of the exhaust gas flowing through the branch position;
The control device includes:
Prohibiting execution of the fuel addition control if the branch temperature correlation value is higher than a predetermined correlation value threshold when the fuel addition condition is met;
The correlation value threshold is
When the branch temperature correlation value becomes higher than the correlation value threshold, it is predicted that fuel injected from the fuel addition valve and attached to the vicinity of the branch position will accumulate as a deposit;
Internal combustion engine control system. The internal combustion engine control system according to claim 1,
The control device includes:
When the fuel addition control is executed, the fuel addition amount, which is the amount of fuel injected from the fuel addition valve per unit time, is set to be equal to or greater than the addition amount lower limit value determined according to the branch temperature correlation value. decided,
The lower limit of the addition amount is
It is a value that is predicted to cause fuel injected from the fuel addition valve and attached to the vicinity of the branch position to accumulate as a deposit when the fuel addition amount becomes smaller than the addition amount lower limit value;
Internal combustion engine control system. The internal combustion engine control system according to claim 1 or 2,
The internal combustion engine is
a supercharger including a turbine disposed at a position between the branch position in the exhaust path and the exhaust purification device,
The exhaust purification device includes:
an oxidation catalyst device and a particulate matter collection device downstream of the oxidation catalyst device;
Internal combustion engine control system.

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