JP5163964B2 - DPF overheat prevention device - Google Patents

Description

  The present invention relates to a DPF overheating prevention device for preventing an overheating of a DPF that collects particulate matter in exhaust gas provided in an exhaust passage of an internal combustion engine.

  Conventionally, in order to remove harmful substances discharged from an internal combustion engine such as a diesel engine, a DPF (diesel particulate filter) that collects particulate matter in the exhaust gas may be provided in an exhaust passage of the internal combustion engine. . According to this DPF, it is possible to collect particulate matter in the exhaust gas, but there is a problem that the collection ability decreases as the amount of collection increases. Therefore, a temperature raising process is performed in which the particulate matter collected by burning the DPF is burned and removed.

  On the other hand, the DPF may overheat due to the temperature raising process. If the DPF is excessively heated, the DPF may be damaged. Therefore, when there is a possibility that the DPF is excessively heated, a technique for preventing the excessive temperature increase by executing a cooling process for cooling the DPF has been proposed (for example, see Patent Document 1).

  This Patent Document 1 discloses a technique for executing an exhaust cooling process for increasing the exhaust amount flowing into the DPF in order to carry away the heat in the DPF. The exhaust cooling process is performed by, for example, opening an EGR valve that adjusts the opening degree of a throttle valve that adjusts the amount of fresh air taken into the intake system of the internal combustion engine and the EGR amount that is recirculated from the exhaust passage of the internal combustion engine to the intake passage. The exhaust amount is increased by controlling a predetermined exhaust amount adjustment parameter such as a degree.

  In addition to the exhaust cooling process, Patent Document 1 also discloses a technique for executing an oxygen deficient cooling process for reducing the oxygen concentration around the DPF in order to suppress heat generation in the DPF. That is, by making the periphery of the DPF deficient, it is possible to suppress heat generation by suppressing the burning rate of the particulate matter in the DPF. In this oxygen deficient cooling process, for example, the oxygen concentration is decreased by controlling predetermined oxygen adjustment parameters such as the throttle valve opening, the EGR valve opening, the fuel injection amount, and the fuel injection timing. That is, since the opening degree of the throttle valve and the opening degree of the EGR valve affect the fresh air amount, the oxygen concentration can be reduced by controlling the opening degree to reduce the fresh air amount. Further, by executing post injection following the main injection with the fuel injection timing and the fuel injection amount as the oxygen adjustment parameters, oxygen in the cylinder can be consumed and the oxygen concentration can be reduced.

  And in the technique currently disclosed by patent document 1, either one of the said exhaust_gas | exhaustion cooling process and an oxygen deficient cooling process is selectively performed according to a condition. This is aimed at reliably cooling the DPF.

JP 2008-38821 A

  However, depending on the conditions for performing the cooling process such as the operating state of the internal combustion engine, the DPF may not be effectively cooled by either the exhaust cooling process or the oxygen deficient cooling process. For example, depending on the operating state of the internal combustion engine, even if the exhaust amount adjustment parameters such as the opening degree of the throttle valve and the opening degree of the EGR valve are controlled, the new air amount does not increase effectively, so the exhaust amount is effective. There is a case where the amount is not increased. In such a case, even if the exhaust cooling process is executed, the exhaust amount cannot be increased effectively, so that the excessive temperature rise of the DPF cannot be prevented.

  In addition, for example, in-cylinder combustion may not be effectively performed when the ignitability of the fuel is low. In such a case, even if post-injection is performed, oxygen cannot be effectively consumed in the cylinder, and the oxygen concentration cannot be adjusted by increasing or decreasing the post-injection amount. Therefore, even if the oxygen-deficient cooling process is executed, the oxygen concentration cannot be reduced effectively, so that it is not possible to prevent an excessive temperature rise of the DPF. Further, if the combustion in the cylinder is not effectively performed, the amount of unburned fuel that is not burned increases. The unburned fuel may react with an oxidation catalyst that raises the temperature of the exhaust provided to raise the temperature of the DPF, and the oxidation catalyst may overheat.

  The present invention has been made in view of the above problems, and as a cooling process for preventing an excessive temperature rise of the DPF, in an apparatus for preventing an excessive temperature rise of a DPF that performs an exhaust cooling process and an oxygen deficient cooling process, An object is to more reliably prevent overheating.

In order to solve the above problems, the present invention provides a predetermined cooling for preventing an excessive temperature rise of a DPF (diesel particulate filter) that collects particulate matter in exhaust gas provided in an exhaust passage of an internal combustion engine. An apparatus for preventing excessive temperature rise of a DPF that executes processing,
An exhaust cooling means for performing an exhaust cooling process for increasing an exhaust amount flowing into the DPF by controlling a predetermined exhaust amount adjustment parameter in order to take away heat in the DPF as the cooling process;
In the DPF overheating prevention device, comprising the oxygen deficiency cooling means for executing the oxygen deficiency cooling process for reducing the oxygen concentration around the DPF in order to suppress heat generation in the DPF as the cooling process,
A first determination unit for determining whether or not an excessive temperature rise of the DPF can be prevented by the exhaust cooling process by determining whether or not the exhaust amount can be increased effectively;
A second propriety judging means for judging whether or not an excessive temperature rise of the DPF can be prevented by the oxygen deficient cooling treatment by judging whether or not the oxygen concentration can be effectively reduced;
When it is determined by the first and second possibility determination means that the overheating of the DPF cannot be prevented by the exhaust cooling process and the oxygen deficient cooling process, the exhaust cooling process and the oxygen deficient cooling process are used instead. In order to take away the heat in the DPF, the exhaust amount flowing into the DPF is further controlled than the exhaust amount in the exhaust cooling process by controlling a predetermined increase parameter other than the exhaust amount adjustment parameter. And an increase-enhanced cooling means for executing an increased-intensity-enhanced cooling process.

  According to this, the 1st, 2nd possibility judgment means judges whether the excessive temperature rise of DPF can be prevented by exhaust cooling processing and oxygen lack cooling processing. If it is determined that it cannot be prevented, the increase-enhanced cooling means executes an increase-enhanced cooling process in which the exhaust amount flowing into the DPF is further increased from the exhaust amount in the exhaust cooling process. The increase-enhancement cooling means controls the predetermined increase-enhancement parameters other than the exhaust amount adjustment parameter, so even if the new air amount does not increase effectively even if the exhaust amount adjustment parameter is controlled, it is effective. Therefore, the amount of exhaust can be increased. Therefore, it is possible to reduce the possibility that the excessive temperature rise of the DPF due to the exhaust amount shortage cannot be prevented. Even when the oxygen concentration cannot be effectively reduced and the oxygen-deficient cooling process cannot be performed, the heat in the DPF can be taken away by the exhaust amount by the increased and enhanced cooling process. The possibility that overheating of the DPF cannot be prevented can be reduced.

  Further, in the DPF overheat prevention device of the present invention, the exhaust cooling means re-opens the throttle valve opening for adjusting the amount of fresh air taken into the intake system of the internal combustion engine and the exhaust passage from the internal combustion engine to the intake passage. By controlling at least one of the opening degrees of the EGR valve that adjusts the EGR amount to be circulated as the exhaust amount adjustment parameter, the exhaust amount is increased by increasing the fresh air amount and decreasing the EGR amount. .

  Thus, the exhaust amount can be increased by increasing the amount of fresh air. Further, by reducing the amount of EGR, the amount of exhaust gas recirculated to the intake air is reduced, and as a result, the amount of exhaust gas can be increased.

  In the DPF overheat prevention device according to the present invention, the increase-enhancement cooling means increases the displacement by increasing control of at least one of the rotational speed and the intake pressure of the internal combustion engine as the increase-enhancement parameter. Is.

  In this way, the amount of exhaust can be increased by increasing the rotational speed and intake pressure of the internal combustion engine. The rotational speed and intake pressure of the internal combustion engine are easily increased by adjusting the fuel injection amount, fuel injection timing, etc., regardless of the operating state of the internal combustion engine. Therefore, the exhaust amount flowing into the DPF can be further increased from the exhaust amount in the exhaust cooling process by increasing the engine speed and the intake pressure.

If the DPF cannot be effectively cooled by either the exhaust cooling process or the oxygen deficient cooling process, the following may be performed in addition to the above-described increase-intensification cooling process. That is, the present invention relates to a DPF that performs a predetermined cooling process for preventing excessive temperature rise of a DPF (diesel particulate filter) that collects particulate matter in exhaust gas provided in an exhaust passage of an internal combustion engine. An excessive temperature rise prevention device,
Exhaust cooling means for executing an exhaust cooling process for increasing the exhaust amount flowing into the DPF in order to take away heat in the DPF as the cooling process,
As the cooling process, in order to suppress heat generation in the DPF, an oxygen-deficient cooling unit that executes a oxygen-deficient cooling process that controls a predetermined oxygen adjustment parameter to reduce the oxygen concentration around the DPF; In the DPF overheat prevention device provided,
A first determination unit for determining whether or not an excessive temperature rise of the DPF can be prevented by the exhaust cooling process by determining whether or not the exhaust amount can be increased effectively;
A second propriety judging means for judging whether or not an excessive temperature rise of the DPF can be prevented by the oxygen deficient cooling treatment by judging whether or not the oxygen concentration can be effectively reduced;
When it is determined by the first and second possibility determination means that the overheating of the DPF cannot be prevented by the exhaust cooling process and the oxygen deficient cooling process, the exhaust cooling process and the oxygen deficient cooling process are used instead. Correction oxygen deficiency cooling means for correcting the control amount of the oxygen adjustment parameter so that the oxygen concentration can be effectively reduced to reduce the oxygen concentration around the DPF, It is characterized by that.

  According to this, when it is determined that the excessive temperature rise of the DPF cannot be prevented by the exhaust cooling process or the oxygen deficient cooling process, the corrected oxygen deficient cooling means effectively sets the control amount of the oxygen adjustment parameter to the oxygen concentration. Correction oxygen deficient cooling processing is executed to correct the oxygen concentration around the DPF and reduce the oxygen concentration around the DPF. Therefore, even when the oxygen concentration cannot be effectively reduced by the oxygen deficient cooling process, such as when combustion in the cylinder is not effectively performed, the corrected oxygen deficient cooling process is executed and the oxygen concentration is reduced. Since the control amount of the adjustment parameter is corrected, the oxygen concentration can be effectively reduced. As a result, it is possible to reduce the possibility that overheating of the DPF due to excessive oxygen concentration cannot be prevented. Further, even if the exhaust cooling process cannot prevent the excessive temperature rise of the DPF due to the fact that the exhaust amount cannot be increased effectively, the corrected oxygen deficient cooling process in which the oxygen concentration is reduced is executed. Heat generation can be suppressed. As a result, it is possible to reduce the possibility that an excessive temperature rise of the DPF due to insufficient exhaust amount cannot be prevented.

  In the DPF overheat prevention device of the present invention, the oxygen deficient cooling means includes an opening of a throttle valve that adjusts the amount of fresh air taken into the intake system of the internal combustion engine and an exhaust passage from the internal combustion engine to the intake passage. The oxygen deficiency cooling process is executed by controlling at least one of the opening degree of the EGR valve, the fuel injection amount, and the fuel injection timing as the oxygen adjustment parameter for adjusting the recirculated EGR amount.

  Thus, the amount of fresh air can be adjusted by controlling the opening of the throttle valve and the opening of the EGR valve. It is considered that the oxygen concentration around the DPF decreases as the amount of fresh air decreases. That is, the oxygen concentration around the DPF can be reduced by controlling the opening of the throttle valve and the opening of the EGR valve. Further, the combustion in the cylinder can be controlled by controlling the fuel injection amount and the fuel injection timing. Oxygen contained in the fresh air taken into the cylinder is consumed by the combustion in the cylinder, so that the oxygen concentration around the DPF can be controlled by controlling the combustion.

Further, in the DPF overheat prevention device according to the present invention, the oxygen deficient cooling means performs post injection subsequent to main injection with the fuel injection amount and fuel injection timing as the oxygen adjustment parameters, and the post injection. The oxygen concentration is reduced by consuming the oxygen in the cylinder by burning it in the cylinder.
The corrected oxygen deficient cooling means performs corrected post injection as the corrected oxygen deficient cooling process in which the fuel injection timing is corrected to a time when the in-cylinder pressure is higher than the fuel injection timing in the post injection during the oxygen deficient cooling process. It is something to execute.

  Thus, by performing post injection, oxygen that could not be consumed by main injection can be consumed, and the oxygen concentration around the DPF can be reduced. At that time, there are cases where the combustion is not effectively performed for reasons such as low ignitability of the fuel. In this case, since the oxygen concentration of the DPF cannot be effectively reduced, the excessive temperature rise of the DPF cannot be prevented by the oxygen deficient cooling treatment. Therefore, the corrected oxygen deficient cooling means corrects the fuel injection timing to a timing when the in-cylinder pressure is high and executes post-injection, so that oxygen can be consumed more easily than when the in-cylinder pressure is low. As a result, the oxygen concentration around the DPF can be effectively reduced. Further, since the amount of unburned fuel is not excessively increased in order for the post injection to burn effectively in the cylinder, the overheating of the oxidation catalyst for raising the temperature of the exhaust gas provided for raising the temperature of the DPF is also caused. Can be suppressed.

  The corrected oxygen deficient cooling means further corrects the fuel injection amount to be larger than the fuel injection amount in the post injection during the oxygen deficient cooling process as the corrected post injection.

  As a result, the amount of fuel in the cylinder increases and oxygen can be consumed more easily than when the amount is small. As a result, the oxygen concentration around the DPF can be more effectively reduced.

  The corrected oxygen deficient cooling means may execute the corrected oxygen deficient cooling process by correcting the opening of the throttle valve as the oxygen adjustment parameter to an opening larger than that during the oxygen deficient cooling process.

  As described above, the oxygen deficient cooling treatment aims to reduce the oxygen concentration around the DPF by reducing the amount of fresh air. However, if the combustion is not performed effectively, such as when the ignitability of the fuel is low, even if the amount of fresh air is reduced, the oxygen contained in the fresh air will not be consumed effectively. The oxygen concentration cannot be reduced effectively. Therefore, in this case, the correction oxygen deficient cooling means increases the throttle valve opening so that the amount of fresh air is increased as compared with that during the oxygen deficient cooling process, so that combustion in the cylinder can be promoted. it can. As a result, the consumption of oxygen contained in fresh air can be promoted, and the oxygen concentration around the DPF can be effectively reduced.

  The corrected oxygen deficient cooling means may execute the corrected oxygen deficient cooling process by correcting the opening degree of the EGR valve as the oxygen adjustment parameter to an opening smaller than that during the oxygen deficient cooling process.

  As described above, the amount of fresh air is reduced in the oxygen deficient cooling process, but the amount of fresh air can be reduced by increasing the amount of EGR. However, as described above, when combustion is not effectively performed, even if the amount of fresh air is reduced, oxygen contained in the fresh air is not effectively consumed. Cannot be reduced. Therefore, in this case, the correction oxygen deficient cooling means decreases the opening of the EGR valve and decreases the EGR amount more than that during the oxygen deficient cooling process, thereby increasing the fresh air amount. Can promote combustion. As a result, the consumption of oxygen contained in fresh air can be promoted, and the oxygen concentration around the DPF can be effectively reduced.

  Further, in the DPF overheat prevention device of the present invention, the second availability determination means determines whether or not the combustion in the cylinder is effectively performed as a determination as to whether or not the oxygen concentration can be effectively reduced. Judge whether or not.

  Thus, by determining whether or not the combustion in the cylinder is effectively performed, it can be used as an index of the amount of oxygen consumed by the combustion. That is, when combustion in the cylinder is not effectively performed, it is determined that the combustion cannot effectively consume oxygen, and the oxygen concentration around the DPF cannot be effectively reduced. be able to.

  And it can be judged as follows whether combustion in a cylinder is made effectively. In other words, an intake air temperature acquisition means for acquiring the intake air temperature is provided, and the second availability determination means determines whether combustion in the cylinder is effectively performed based on the intake air temperature acquired by the intake air temperature acquisition means. Determine whether.

  According to this, since it is considered that combustion in the cylinder is promoted as the intake air temperature is high, it is possible to determine whether or not combustion in the cylinder is effectively performed based on the intake air temperature. it can.

Further, regarding the determination of whether or not the combustion in the cylinder is effectively performed, as an index of the ease of ignition of the fuel, a cetane number acquisition means for acquiring the cetane number of the fuel burned in the cylinder,
The second availability determination unit may determine whether or not combustion in the cylinder is effectively performed based on the cetane number acquired by the cetane number acquisition unit.

  According to this, since it is considered that combustion in the cylinder is promoted as the fuel having a higher cetane number, it is determined whether or not the combustion in the cylinder is effectively performed based on the cetane number. Can do.

Further, regarding the determination of whether or not the combustion in the cylinder is effectively performed, the exhaust temperature acquisition means for acquiring the exhaust temperature is provided,
The second availability determination unit may determine whether combustion in the cylinder is effectively performed based on the exhaust temperature acquired by the exhaust temperature acquisition unit.

  According to this, since it is considered that the exhaust temperature becomes high when the combustion in the cylinder is effectively performed, whether or not the combustion in the cylinder is effectively performed based on the exhaust temperature is determined. Can be judged.

  In the DPF overheating prevention device of the present invention, when the determination by the first availability determination unit is possible, the exhaust cooling process of the exhaust cooling process and the oxygen deficient cooling process is executed. .

  According to this, if the oxygen deficiency cooling process is executed, the oxygen deficiency state may occur and the drivability may be affected. Therefore, if the exhaust cooling process can prevent the overheating of the DPF, the exhaust cooling process is performed. It is designed to be executed with priority.

  Further, when the determination by the first availability determination unit is not possible and the determination by the second availability determination unit is possible, the oxygen deficiency cooling processing of the exhaust cooling processing and the oxygen deficiency cooling processing is performed. Run.

  In this way, when the excessive temperature rise of the DPF cannot be prevented by the exhaust cooling process, the oxygen deficient cooling process is executed, so that the excessive temperature rise of the DPF can be prevented.

In addition, the first availability determination means includes
A required exhaust amount calculating means for calculating a required exhaust amount capable of preventing an excessive temperature rise of the DPF;
A post-increase exhaust amount estimation means for estimating the post-increase exhaust amount in the case of performing the exhaust cooling process based on operating conditions of the internal combustion engine;
A determination unit for determining whether or not the post-increase exhaust amount is smaller than the required exhaust amount, and determining whether or not an excessive temperature rise of the DPF can be prevented.

  According to this, it is considered that how much the exhaust amount increases when the exhaust cooling process is executed depends on the operating state of the internal combustion engine. Therefore, the post-increase exhaust amount estimation means estimates the post-increase exhaust amount when the exhaust cooling process is executed based on the operating conditions of the internal combustion engine. Then, since the availability determining means compares and determines the exhaust amount after the increase and the necessary exhaust amount that can prevent the excessive temperature rise of the DPF, according to the operation state of each internal combustion engine, the excessive temperature increase of the DPF is performed by the exhaust cooling process. It can be determined whether or not it can be prevented.

  The required exhaust amount calculation means calculates the required exhaust amount based on the amount of collected PM, which is the amount of particulate matter collected by the DPF. Thereby, the required exhaust amount according to the amount of collected PM can be calculated.

In the DPF overheat prevention device of the present invention, whether the cooling process needs to be executed based on the amount of PM trapped as the amount of particulate matter trapped by the DPF and the temperature of the DPF. Including execution means for determining whether or not
The cooling process is executed only when it is determined by the execution necessity determination means that the cooling process needs to be executed.

  According to this, it is thought that possibility that DPF overheats will become high, so that PM collection amount and DPF temperature are large. If the cooling process is executed even though the DPF is unlikely to overheat, the exhaust amount increases or an oxygen deficient state occurs, which may adversely affect drivability and the like. Therefore, the execution necessity determination means determines whether or not the cooling process needs to be executed based on the amount of collected PM and the temperature of the DPF, and the cooling process is executed only when it is determined that the execution is necessary. Therefore, unnecessary cooling processing can be prevented.

  Further, the execution necessity determination means is based on whether the internal combustion engine is in a predetermined operating state in which excessive temperature rise of the DPF is likely to occur in addition to the amount of collected PM and the temperature of the DPF. It is determined whether or not the cooling process needs to be executed.

  According to this, it is considered that whether or not the DPF is excessively heated depends on the operating state of the internal combustion engine. Therefore, the execution necessity determination means performs the cooling process based on the operating state of the internal combustion engine. Since it is determined whether or not execution is necessary, the determination can be made more accurately.

  Predetermined operation state in which overheating of the DPF is likely to occur The predetermined operation state can be a deceleration state. Thus, it can be said that when the internal combustion engine is in a decelerating state, the amount of exhaust gas flowing into the DPF decreases due to a decrease in the rotational speed of the internal combustion engine, and the DPF tends to overheat. Therefore, the cooling process can be executed at a more appropriate time.

Further, in the DPF overheating prevention apparatus of the present invention, during the execution of the cooling process, it is determined whether or not the ongoing cooling process needs to be continued based on the temperature of the DPF. When,
A cooling process ending unit for ending the cooling process being executed when the continuation necessity determining unit determines that continuation is unnecessary.

  According to this, it is possible to prevent the cooling process from being continued unnecessarily even though the cooling process is executed and the temperature of the DPF is lowered.

1 is a diagram showing a schematic configuration of an engine system 1. FIG. It is the flowchart which showed the procedure of the excessive temperature rising prevention process. It is the flowchart which showed the detail of the procedure of the exhaust-cooling possibility determination of S30 of FIG. It is the figure which showed an example of the map for determining required displacement Q0. It is the flowchart which showed the detail of the procedure of the oxygen deficiency cooling possibility determination of S60 of FIG. It is a figure for demonstrating the effect of the increase reinforcement | strengthening cooling process of 1st embodiment. It is the flowchart which showed the procedure of the correction | amendment oxygen lack cooling process of 2nd embodiment. It is a figure for demonstrating the correction | amendment post injection of 2nd embodiment. It is a figure for demonstrating the effect of the correction | amendment oxygen deficient cooling process of 2nd embodiment.

(First embodiment)
Hereinafter, a first embodiment of a DPF overheat prevention device of the present invention will be described with reference to the drawings. This embodiment is an embodiment according to the invention according to the invention that executes an increase-intensified cooling process when excessive temperature rise cannot be prevented by the exhaust cooling process and the oxygen deficient cooling process.

  FIG. 1 is a diagram showing a schematic configuration of an engine system 1 to which the DPF overheat prevention device of the present embodiment is applied. The engine 10 to be controlled by the system 1 is assumed to be a multi-cylinder (for example, in-line four-cylinder) diesel engine (internal combustion engine) mounted on a four-wheeled vehicle (for example, an AT vehicle). In the diesel engine 10 (hereinafter referred to as an engine), fuel injected from an injector (not shown) into a combustion chamber (not shown) self-ignites in the combustion chamber to generate power.

  The engine 10 is provided with an in-cylinder pressure sensor 66 that detects a pressure (in-cylinder pressure) in a cylinder (not shown), for example, integrally with a glow plug as an ignition assist device. This makes it possible to grasp the combustion state in the cylinder, that is, to estimate the ignition timing and combustion temperature, to detect knocking, to detect the peak position of the combustion pressure, to detect misfire, and the like. The in-cylinder pressure detected by the in-cylinder pressure sensor 66 is input to the ECU 70.

  A diesel particulate filter (DPF) 30 is installed in the exhaust passage 51 of the engine 10, and an oxidation catalyst (DOC) 20 is installed upstream thereof. The DPF 30 is a ceramic filter having a known structure. For example, a heat-resistant ceramic such as cordierite is formed into a honeycomb structure so that a large number of cells serving as gas flow paths are staggered on the inlet side or the outlet side. It ’s sealed. The exhaust discharged from the engine 10 flows downstream while passing through the porous partition wall of the DPF 30, and particulates (particulate matter, PM) are collected and gradually accumulated therebetween.

  When the amount of PM collected by the DPF 30 increases, the PM collection capability of the DPF 30 decreases. Therefore, the temperature rise process is executed regularly (or irregularly according to the amount of collected PM), and the collected PM is burned, oxidized, and discharged as harmless carbon dioxide. ing. That is, the DPF 30 is regenerated. In this temperature raising process, for example, post injection of one time or multistage injection is executed at a time delayed by a predetermined time from the main fuel injection (main injection) which is performed to obtain power of the engine 10 (generate output torque). Is done by. Specifically, the exhaust temperature is raised by this post-injection, and unburned fuel (hydrocarbon, HC) is added to the DOC 20, which will be described later, and the collected PM is burned by the reaction heat, and the DPF 30 is regenerated. I am doing so.

  The DOC 20 has a known structure and is formed by supporting an oxidation catalyst on the surface of a ceramic carrier made of a cordierite honeycomb structure or the like. The DOC 20 burns hydrocarbons (HC) supplied to the exhaust passage 51 by a catalytic reaction to increase the exhaust temperature, and raises the DPF 30 temperature. The DPF 30 may or may not carry an oxidation catalyst. In the present embodiment, description will be made assuming that the oxidation catalyst is not supported on the DPF 30. Alternatively, a system configuration in which the DPF 30 supporting the oxidation catalyst is used and the DOC 20 is not installed upstream thereof can be used.

  An exhaust temperature sensor 61 as a temperature sensor is installed on the upstream side of the DOC 20 in the exhaust passage 51. The exhaust temperature sensor 61 is connected to the ECU 70, detects the inlet gas temperature of the DOC 20, and outputs it to the ECU 70. For example, the ECU 70 estimates the temperature (center temperature) of the DPF 30 based on the output of the exhaust temperature sensor 61. Even if an exhaust temperature sensor for detecting the outlet gas temperature of the DPF 30 is provided downstream of the DPF 30 and the temperature of the DPF 30 is estimated based on the outlet gas temperature and the inlet gas temperature detected by the exhaust temperature sensor 61. Good.

  In addition, a differential pressure sensor 67 that detects a differential pressure across the DPF 30 is connected to the exhaust passage 51 in order to know the amount of PM collected by the DPF 30. One end of the differential pressure sensor 67 is connected to the exhaust passage 51 upstream of the DPF 30, and the other end is connected to the exhaust passage 51 downstream of the DPF 30, and outputs a signal corresponding to the differential pressure across the DPF 30 to the ECU 70.

  Further, an A / F sensor 62 (air-fuel ratio sensor) is disposed in the exhaust passage 51, and the numerical value of the A / F value measured by the sensor 62 is sent to the ECU 70. The A / F sensor 62 is used, for example, to control the A / F value of exhaust gas in order to reduce NOx occluded by an occlusion reduction type NOx catalyst (not shown) or for EGR control described later. Or used.

  Further, an EGR passage 41 for recirculating exhaust gas from the exhaust passage 51 to the intake passage 52 is provided as an exhaust gas recirculation system. An EGR valve 42 is disposed on the EGR passage 41, and its opening degree is controlled by a command from the ECU 70, thereby adjusting an EGR amount that is an exhaust gas recirculation amount. Further, an EGR cooler for cooling the EGR gas or the like is also provided for the EGR passage 41 as necessary. Based on such a configuration, a part of the exhaust gas is recirculated to the intake system through the EGR passage 41, thereby lowering the combustion temperature and reducing the generation of NOx.

  An intake air temperature sensor 63 for detecting the intake air temperature and an air flow meter 64 for detecting the fresh air amount are installed in the intake passage 52 of the engine 10 so as to output the intake air temperature and the fresh air amount to the ECU 70. The intake passage 52 downstream of the air flow meter 64 is provided with a throttle valve 65 (intake throttle valve) that adjusts the increase / decrease in the amount of fresh air taken into the engine 10, and the amount of fresh air is increased / decreased by a command from the ECU 70. .

  Further, in the present embodiment, a compressor 66 for sending compressed fresh air to the engine 10 is provided in the intake passage 52 upstream of the throttle valve 65. The compressor 66 is driven by the rotational force of a turbine (not shown) rotated at high speed using the energy of the exhaust, and compresses fresh air, that is, increases intake air pressure to bring the fresh air into the engine 10. It is what you send in. As a result, an output exceeding the apparent displacement can be obtained. In addition, the structure which consists of these turbines and the compressor 66 is what is called what is called a turbocharger, Comprising: A turbine and the compressor 66 are connected to ECU70, and compress fresh air based on the instruction | command of ECU70.

  The ECU 70 is connected to a rotation speed sensor 81 that detects the engine rotation speed NE. The rotation speed sensor 81 may be a crank angle sensor that measures the rotation angle of a crank (not shown) connected from the engine 10, for example. Then, the detected value of the crank angle sensor is sent to the ECU 70, and the ECU 70 calculates the rotational speed NE of the engine 10.

  Further, the ECU 70 is connected to an accelerator sensor 82 that detects the state (displacement amount) of an accelerator pedal corresponding to a driving operation unit for notifying the vehicle side of the driver's required torque. These rotational speed sensor 81 and accelerator sensor 82 are used, for example, to detect the operating state (acceleration state, deceleration state, etc.) of engine 10.

  The ECU 70 has a normal computer structure, and includes a CPU (not shown) for performing various calculations and a memory (not shown) for storing various information. The ECU 70 detects an operating state based on detection signals from the various sensors, calculates an optimal fuel injection amount, injection timing, injection pressure, etc. according to the operating state, and controls fuel injection to the engine 10. To do. Further, the amount of fresh air is adjusted by controlling the opening of the throttle valve 65, or the amount of EGR is adjusted by controlling the opening of the EGR valve 42. Further, the ECU 70 performs a temperature increasing process for the DPF 30 to regenerate the DPF 30.

  Further, the ECU 70 functions as a “DPF excessive temperature rise prevention device” of the present invention, and executes a predetermined cooling process for preventing the DPF 30 from being excessively heated due to the temperature increase process or the like. Specifically, as a cooling process, in order to take away heat in the DPF 30, the amount of exhaust flowing into the DPF 30 is increased by controlling the opening of the throttle valve 65 and the opening of the EGR valve 42 (displacement adjustment parameter). Exhaust cooling processing is executed. Further, as another cooling process, in order to suppress heat generation in the DPF 30, the opening of the throttle valve 65, the opening of the EGR valve 42, the fuel injection amount, and the fuel injection timing (oxygen adjustment parameter) are controlled, and the vicinity of the DPF 30 is controlled. An oxygen deficient cooling process is performed to reduce the oxygen concentration of the water. The exhaust cooling process and the oxygen deficient cooling process are selectively used depending on the operating state of the engine 10 and the like. Details and timing of the exhaust cooling process and the oxygen deficient cooling process will be described later with reference to flowcharts.

  Further, in the present embodiment, the ECU 70 increases the exhaust amount flowing into the DPF 30 as a cooling process, which is different from the exhaust cooling process and the oxygen deficient cooling process, further than the exhaust amount in the exhaust cooling process, and in the DPF 30 Execute the enhanced cooling process to remove heat. This increase-intensified cooling process is executed when it is determined that the excessive temperature rise of the DPF 30 cannot be prevented by either the exhaust cooling process or the oxygen deficient cooling process. These cooling processes are specifically executed according to the flowchart of FIG.

  Here, FIG. 2 is a flowchart showing a procedure of an excessive temperature rise prevention process for preventing the excessive temperature rise of the DPF 30 executed by the ECU 70. This excessive temperature rise prevention process is repeatedly executed at regular intervals, for example. Hereinafter, the excessive temperature rise prevention process will be described with reference to FIG.

  First, in step S10, the temperature of the DPF 30, the amount of PM trapped in the DPF 30, and the operating state (acceleration / deceleration state) of the engine 10 are acquired. Specifically, the exhaust temperature detected by the exhaust temperature sensor 61 is acquired as the temperature of the DPF 30. Further, a relationship between the exhaust temperature and the temperature (center temperature) of the DPF 30 is obtained in advance by experiments or the like, and a map defining the relationship is stored in a memory or the like in the ECU 70. Then, based on the acquired exhaust temperature and the stored map, the temperature of the DPF 30 is estimated.

  Further, the amount of PM collected is the differential pressure across the DPF 30 detected by the differential pressure sensor 67. Here, it is considered that as the amount of PM collected by the DPF 30 increases and the DPF 30 becomes clogged, the differential pressure across the DPF 30 increases. Therefore, the relationship between the differential pressure across the DPF 30 and the amount of PM trapped is obtained in advance through experiments or the like, and a map defining the relationship is stored in a memory or the like in the ECU 70. Then, the PM trap amount is estimated based on the acquired differential pressure across the DPF 30 and the stored map.

  Further, as the operating state (acceleration / deceleration state) of the engine 10, the engine speed NE detected by the speed sensor 81 and the operation amount of the accelerator pedal detected by the accelerator sensor 82 are acquired. The engine speed NE and the amount of operation of the accelerator pedal are information corresponding to the operating state (acceleration / deceleration state) of the engine 10. That is, for example, it can be said that the engine 10 is in an accelerated state as the engine speed NE is large, and the engine 10 is in an accelerated state as the operation amount of the accelerator pedal is large.

  In the subsequent step S20, it is determined whether or not it is necessary to execute a cooling process for preventing an excessive temperature rise of the DPF 30 based on the temperature of the DPF 30 acquired in step S10, the amount of collected PM, and the operating state of the engine 10. . Specifically, for example, the determination is made in the same manner as the method described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-38821). That is, (1) the amount of collected PM is greater than a predetermined threshold (for example, “10 g”, a variable value if necessary) (PM collected amount> threshold), and (2) the temperature of the DPF 30 is a predetermined threshold T0 (for example, “ It is determined whether or not three conditions of “600 ° C.” (variable value as necessary) (DPF temperature> threshold value T0) and (3) the engine 10 is in a decelerating state are satisfied simultaneously. If all the conditions are satisfied at the same time, it is determined that the cooling process of the DPF 30 is necessary. If one of the three conditions is not satisfied, it is determined that the cooling process is not necessary. .

  As described above, the necessity of performing the cooling process is determined in consideration of the amount of collected PM. If the amount of collected PM is small, the amount of PM burned in the DPF 30 during the temperature raising process is small. This is because the possibility that the DPF 30 will be overheated is low. Further, the necessity of executing the cooling process is determined in consideration of the temperature of the DPF 30. If the temperature of the DPF 30 is originally low, the DPF 30 may be excessively heated even if the temperature increasing process is executed. Because it is low. In addition, the necessity of executing the cooling process is determined in consideration of the operation state of the engine 10 because the engine 10 is in the acceleration state, because the exhaust amount is large, the temperature increasing process is executed. However, heat does not stay in the DPF 30 indefinitely, and the possibility that the DPF 30 will be overheated is low. As described above, it is possible to execute the cooling process at an appropriate time by determining whether or not the cooling process needs to be executed according to the three conditions. The ECU 70 that executes step S20 corresponds to the “execution necessity determination unit” of the present invention.

  Here, in step S20, when even one of the conditions (1) to (3) is not satisfied, the process proceeds to step S100. In step S100, the cooling process is not required to be executed. If the cooling process is currently being executed, the cooling process is terminated. If the cooling process is not currently being executed, the state is maintained. To do. Thereafter, the excessive temperature rise prevention process of FIG. In this way, by not performing the cooling process when it is not necessary, it is not possible to forcibly increase the exhaust amount or to be in an oxygen deficient state as will be described later, thereby preventing a change in drivability and the like. it can.

  On the other hand, if all of the above conditions (1) to (3) are satisfied in step S20, it is determined that the cooling process is necessary, and the process proceeds to step S30 and subsequent steps. In this case, an exhaust cooling process, an oxygen deficient cooling process, or an increased amount enhanced cooling process is executed as the cooling process. In step S30, therefore, an exhaust cooling permission determination is performed to determine whether or not the excessive temperature rise of the DPF 30 can be prevented when the exhaust cooling processing is executed. FIG. 3 is a flowchart showing details of the procedure for determining whether or not exhaust cooling is possible. The determination of whether or not exhaust cooling is possible is basically the same as the method described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-38821).

  That is, first, in step S31, when exhaust cooling processing is performed, in order to remove the heat of the DPF 30 by exhaust and prevent excessive temperature rise, a necessary exhaust amount Q0 that can prevent excessive temperature rise of the DPF 30 is calculated. Here, when the required exhaust amount Q0 is set to the exhaust amount necessary for reducing the temperature of the DPF 30 to a safe predetermined temperature T1 at which the DPF 30 does not overheat, the higher the PM collection amount, the higher the temperature increasing process. As a result, the amount of PM that burns increases and the temperature of the DPF 30 tends to rise. That is, as the amount of collected PM increases, the temperature of the DPF 30 is less likely to decrease, so it is considered that a larger required displacement Q0 is necessary. In addition, the higher the temperature of the DPF 30, the greater the amount of temperature decrease when the temperature is decreased to the predetermined temperature T1, so that it is considered that a larger required displacement Q0 is necessary. That is, the necessary exhaust amount Q0 can be determined based on the amount of PM trapped and the temperature of the DPF 30.

  Here, FIG. 4 is a diagram showing an example of a map of conformity values as the necessary exhaust amount Q0 with respect to the PM collection amount and the temperature of the DPF 30. FIG. In FIG. 4, curves L <b> 1 to L <b> 4 indicate the relationship between the required displacement Q0 and the temperature of the DPF 30 for each different PM collection amount (PM collection amount is “L1> L2> L3> L4”). ing. That is, according to this map, as the temperature of the DPF 30 is higher and the amount of collected PM is larger, a larger value is associated with the required exhaust amount Q0. In step S31, the required exhaust amount Q0 is calculated based on the amount of collected PM, the temperature of the DPF 30, and this map. Note that the map of FIG. 4 may be obtained in advance by experiments or the like and stored in a memory or the like in the ECU 70. The ECU 70 that executes step S31 corresponds to the “necessary exhaust amount calculation means” of the present invention.

  In the subsequent step S32, the post-increase exhaust amount Qu when the exhaust cooling process is executed is estimated based on the operating conditions of the engine 10. Specifically, in the present embodiment, as an example of the exhaust amount increase operation in the exhaust cooling process, the throttle valve 65 is fully opened and the EGR valve 42 is fully closed so that fresh air taken into the intake system of the engine 10 is taken. The amount is increased, and the amount of EGR recirculated from the exhaust passage 51 of the engine 10 to the intake passage 52 is reduced. Therefore, in this step S32, the exhaust amount (= the increased exhaust amount Qu) obtained when the throttle valve 65 is fully opened and the EGR valve 42 is fully closed is calculated based on the operating state of the engine 10. Become. At this time, the increased exhaust amount Qu can be calculated based on the current fresh air amount detected by the air flow meter 64, for example. The ECU 70 that executes step S32 corresponds to the “post-increase exhaust amount estimation means” of the present invention.

  In the subsequent step S33, the required exhaust amount Q0 and the increased exhaust amount Qu are compared to determine whether or not the increased exhaust amount Qu is larger than the required exhaust amount Q0. If it is larger (S33: YES), it is determined that the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process, and in step S34, the cooling availability determination flag F1 indicating that the exhaust cooling process can be performed is turned on (F1 = 1). ), This cooling availability determination flag F1 is stored in a memory or the like in the ECU 70. Thereafter, the process of FIG. 3 is exited and the process returns to the process of FIG. On the other hand, if the increased exhaust amount Qu is smaller than the required exhaust amount Q0 in step 33 (S33: NO), the cooling permission determination flag F1 is turned off (F1 = 0) in step S35, and this cooling permission determination is made. The flag F1 is stored in a memory or the like in the ECU 70. Thereafter, the process of FIG. 3 is exited and the process returns to the process of FIG. Note that the ECU 70 that executes steps S33 to S35 corresponds to “availability determination unit” of the present invention. Moreover, ECU70 which performs step S30 (= S31-S35 of FIG. 3) of FIG. 2 is equivalent to the "first availability determination means" of the present invention.

  Returning to the description of FIG. 2, when the determination in step S <b> 30 ends, the process proceeds to step S <b> 40. In step S40, it is determined based on the previous cooling enable / disable determination flag F1 whether the determination result in step S30 is whether or not exhaust cooling can be performed. Here, if the coolability determination flag F1 is turned on and the exhaust cooling process can be executed, the process proceeds to step S50.

  In step S50, as the exhaust cooling process, the throttle valve 65 is fully opened and the EGR valve 42 is fully closed to increase the exhaust amount. As a result, the exhaust amount is increased to a larger exhaust amount than the necessary exhaust amount Q0 (= the increased exhaust amount Qu), and the heat of the DPF 30 can be taken away. Therefore, excessive temperature rise of the DPF 30 can be prevented. The opening of the throttle valve 65 and the opening of the EGR valve 42 correspond to the “displacement adjustment parameter” of the present invention. Further, the ECU 70 that executes step S50 corresponds to the “exhaust cooling means” of the present invention. Thereafter, the process returns to step S10.

  As described above, if the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process, the exhaust cooling process is executed in preference to the oxygen deficient cooling process described later. Since the oxygen deficiency cooling process is forced to be in an oxygen deficient state, drivability may be deteriorated. Therefore, the exhaust cooling process is prioritized.

  On the other hand, if the exhaust cooling process cannot be performed in step S40, the process proceeds to step S60. Then, in step S60, it is determined whether or not oxygen concentration can be effectively reduced, thereby performing oxygen deficiency cooling availability determination that determines whether or not excessive temperature rise of the DPF 30 can be prevented by the oxygen deficiency cooling processing. To do. FIG. 5 is a flowchart showing details of the procedure for determining whether or not oxygen deficiency cooling is possible.

  First, in step S61, the intake air temperature Ta is obtained from the intake air temperature sensor 63, the exhaust gas temperature Te is obtained from the exhaust gas temperature sensor 61, and the fuel (light oil) to be combusted in the cylinder is used as an index of the ease of ignition of the fuel. Get cetane number C. The cetane number C is obtained, for example, by measuring the in-cylinder pressure in the cylinder of the engine 10 with the in-cylinder pressure sensor 66 and determining the in-cylinder pressure. For this purpose, the relationship between the in-cylinder pressure and the cetane number C may be obtained in advance by experiments or the like and stored in a memory or the like in the ECU 70. If the in-cylinder pressure of the engine 10 is, for example, a pressure change value due to main injection near the top dead center, the heat generation rate is high, and therefore the cetane number C can be estimated with high accuracy. Note that the ignitability of the fuel may correspond to any of the rate of pressure increase of the in-cylinder pressure at the time of fuel combustion, the maximum value of the in-cylinder pressure at the time of combustion, and the period from when fuel is injected until ignition occurs. Good. The ECU 70 that executes step S61 corresponds to the “intake temperature acquisition means”, “exhaust temperature acquisition means”, and “cetane number acquisition means” of the present invention.

  In the following step S62, (4) the intake air temperature Ta is higher than a predetermined reference intake air temperature Ta0 (Ta> Ta0), (5) the exhaust air temperature Te is higher than a predetermined reference exhaust air temperature Te0 (Te> Te0), (6 ) By determining whether or not the three conditions of cetane number C being greater than a predetermined reference cetane number C0 are satisfied at the same time, the oxygen concentration can be effectively reduced when the oxygen-deficient cooling process is performed. Determine if you can. That is, it is determined whether or not the excessive temperature rise of the DPF 30 can be prevented by the oxygen deficient cooling process. If all the conditions are satisfied at the same time, it is determined that the excessive temperature rise of the DPF 30 can be prevented by the oxygen deficiency cooling process. If one of the three conditions is not satisfied, the deficiency cooling process determines that the DPF 30 It is judged that overheating cannot be prevented.

  As described above, the determination is made in consideration of the intake air temperature Ta because the larger the intake air temperature Ta is, the more the combustion in the cylinder is promoted and the more oxygen is consumed in the cylinder. That is, if the intake air temperature Ta is equal to or higher than a predetermined value, it can be considered that the oxygen concentration around the DPF 30 is effectively reduced.

  In addition, it is considered that whether or not the oxygen concentration is effectively reduced in consideration of the exhaust temperature Te is considered to be that combustion in the cylinder is effectively performed if the exhaust temperature Te is large. This is because the amount of oxygen consumed in the inside increases. That is, if the exhaust temperature Te is equal to or higher than a predetermined value, it can be considered that the oxygen concentration around the DPF 30 can be effectively reduced.

  In addition, it is determined whether or not the oxygen concentration is effectively reduced in consideration of the cetane number C. If the cetane number C is large, the fuel is easily ignited, so that combustion in the cylinder is effective. This is because the amount of oxygen consumed in the cylinder increases. That is, if the cetane number C is greater than or equal to a predetermined value, it can be considered that the oxygen concentration around the DPF 30 can be effectively reduced.

  As described above, whether or not the oxygen concentration around the DPF 30 can be effectively reduced by determining whether or not oxygen can be effectively consumed by combustion in the cylinder, that is, in the oxygen-deficient cooling process. It is determined whether or not excessive temperature rise of the DPF 30 can be prevented. Therefore, the reference intake air temperature Ta0, the reference exhaust gas temperature Te0, and the reference cetane number C0 are determined as threshold values as to whether combustion in the cylinder is effectively performed. The cetane number C is a detection value that can be detected before the execution of the oxygen deficiency cooling process, and the intake air temperature Ta and the exhaust gas temperature Te are detection values that are appropriately detected during the execution of the oxygen deficiency cooling process.

  In step S62, if all of the above conditions (4) to (6) are satisfied (S62: YES), it is possible to prevent excessive temperature rise of the DPF 30 by the oxygen deficient cooling process. A cooling availability determination flag F2 indicating that processing can be performed is turned on (F2 = 1), and the cooling availability determination flag F2 is stored in a memory or the like in the ECU 70. Thereafter, the process of FIG. 5 is exited and the process returns to the process of FIG. On the other hand, if at least one of the above conditions (4) to (6) is not satisfied in step S62 (S62: NO), it is assumed that excessive temperature rise of the DPF 30 cannot be prevented by the oxygen deficient cooling process. The cooling permission determination flag F2 is turned off (F2 = 0), and the cooling permission determination flag F2 is stored in a memory or the like in the ECU 70. Thereafter, the process of FIG. 5 is exited and the process returns to the process of FIG. Note that the ECU 70 that executes step S60 of FIG. 2 (= S61 to 64 of FIG. 5) corresponds to the “second availability determination unit” of the present invention.

  Returning to the description of FIG. 2, when the determination in step S <b> 60 ends, the process proceeds to step S <b> 70. In step S70, it is determined based on the previous cooling availability determination flag F2 whether the determination result in step S60 indicates whether or not the lack of oxygen cooling can be performed. Here, when the cooling availability determination flag F2 is turned on and the oxygen deficient cooling process can be executed, the process proceeds to step S80.

  In step S80, an oxygen deficiency operation for reducing the oxygen concentration around the DPF is executed as an oxygen deficiency cooling process. Specifically, post injection subsequent to main injection is executed to consume surplus oxygen in the cylinder. Note that the combustion injection timing (hereinafter referred to as “post injection timing”) and the fuel injection amount (hereinafter referred to as “post injection amount”) in the post injection are appropriately determined according to the operating state of the engine 10 or the like. The fuel injection timing and the fuel injection amount can be set as a reference. Further, in step S80, at least one of opening the EGR valve 42 and throttle the throttle valve 65 is executed as an oxygen deficiency cooling process, thereby reducing the amount of fresh air taken into the engine 10 and reducing the engine 10 The amount of oxygen taken in is reduced. This is because if the amount of oxygen itself is reduced, the amount of oxygen exhausted is also reduced, and the oxygen concentration around the DPF 30 can be reduced. When the EGR valve 42 is fully opened, the amount of EGR recirculated to the intake system increases, and as a result, the amount of fresh air can be reduced.

  As described above, by performing the oxygen deficient cooling process, the oxygen concentration around the DPF 30 can be reduced, and heat generation in the DPF 30 can be suppressed. Therefore, excessive temperature rise of the DPF 30 can be prevented. Further, even if the excessive temperature rise of the DPF 30 cannot be prevented by the exhaust cooling process, the excessive temperature rise of the DPF 30 can be prevented by the oxygen deficient cooling process. The post-injection timing, post-injection amount, opening degree of the EGR valve 42 and opening degree of the throttle valve 65 that are controlled during the oxygen deficient cooling process correspond to the “oxygen adjustment parameter” of the present invention. The ECU 70 that executes step S80 corresponds to the “oxygen deficient cooling means” of the present invention. If the process of step S80 is performed, it will return to the process of step S10.

  On the other hand, if it is determined in step S70 that the cooling availability determination flag F2 is off and the oxygen deficiency cooling process cannot be performed, the process proceeds to step S90. In this case, even if post injection is performed, combustion is not effectively performed, so that oxygen cannot be consumed effectively. Further, even if the amount of fresh air is reduced by controlling the EGR valve 42 and the throttle valve 65, the combustion in the cylinder is not effectively performed, so that the oxygen contained in the fresh air is not consumed. Will increase. That is, the excessive temperature rise of the DPF 30 cannot be prevented not only by the exhaust cooling process but also by the oxygen deficient cooling process.

  Therefore, in step S90, in order to carry away the heat in the DPF 30, an increase-intensified cooling process in which the exhaust amount flowing into the DPF 30 is further increased from the exhaust amount in the exhaust cooling process is executed. Specifically, the exhaust amount adjustment parameters (the opening degree of the throttle valve 65 and the opening degree of the EGR valve 42) are controlled to increase the exhaust amount in the same manner as during the exhaust cooling process, and as an increase enhancement parameter. The engine displacement NE and the intake pressure are forcibly increased to further increase the displacement. Here, the engine speed NE can be increased, for example, by controlling the fuel injection timing and the fuel injection amount in the main injection. The intake pressure can be increased by operating the compressor 66 to compress fresh air. The extent to which the engine speed NE and the intake pressure are increased depends on the difference (S31, S32 in FIG. 3) between the required exhaust amount Q0 calculated by the above-described determination of whether or not exhaust cooling is possible and the increased exhaust amount Qu. To decide. That is, the engine speed NE and the intake pressure are increased so that the required exhaust amount Q0 can be secured with the increased exhaust amount Qu as a reference.

  At this time, a map showing how much the exhaust amount can be increased by increasing the engine speed NE and a map showing how much the exhaust amount can be increased by increasing the intake pressure. Is obtained in advance by experiments or the like and stored in a memory or the like in the ECU 70. The target engine speed NE and the target intake pressure are determined on the basis of these maps, the required exhaust amount Q0 and the increased exhaust amount Qu, and the fuel injection timing is set so as to be the target engine speed NE and the target intake pressure. The fuel injection amount and the compressor 66 are controlled.

  By executing the increase-intensified cooling process in this way, the necessary exhaust amount Q0 that can prevent the excessive temperature rise of the DPF 30 can be secured, and therefore the excessive temperature increase of the DPF 30 can be prevented. If the process of step S90 is performed, it will return to the process of step S10. The ECU 70 that executes step S90 corresponds to the “increase-intensified cooling means” of the present invention.

  Here, FIG. 6 is a diagram for explaining the effect of the present invention for executing the increase-intensification cooling process. FIG. 6A is a diagram of the vehicle determined based on the engine speed NE, the operation amount of the accelerator pedal, and the like. The figure which showed the time change of the vehicle speed, the figure (b) the figure which showed the time change of the displacement, the figure (c) the figure which showed the time change of the oxygen concentration around DPF30, the figure (d) It is the figure which showed the time change of the temperature of DPF30. And the time axis of these Fig.6 (a)-(d) is common. FIG. 6 also shows a time change (one-dot chain line) of the conventional invention for comparison with the present invention.

  As shown in FIG. 6 (a), the vehicle speed is above a certain level in the section from time t1 to t2, but decelerates in the section from time t2 to t3, and cooling processing is necessary at the time t4. Suppose that it is determined (S20 in FIG. 2). Therefore, it is determined whether or not the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process, but as shown in FIG. 6B, the current exhaust amount (solid line) is the time t4. It is assumed that the required exhaust amount Q0 is smaller, and the increased exhaust amount Qu is also smaller than the required exhaust amount Q0. Therefore, it is determined that the excessive temperature rise of the DPF 30 cannot be prevented by the exhaust cooling process (S30 and S40 in FIG. 2).

  In this case, conventionally, an oxygen deficiency cooling process is performed as the cooling process. However, as shown in FIG. 6C, even if the oxygen deficiency cooling process is performed, for reasons such as fuel ignitability, In some cases, the oxygen concentration cannot be reduced to an oxygen concentration level n0 where combustion is not effectively performed in the cylinder and overheating is prevented. In this case, the temperature of the DPF 30 cannot be effectively reduced, and as shown in FIG. 6D, the temperature of the DPF 30 is reduced during the period from time t4 to t5 when the oxygen deficient cooling process is performed. It becomes higher than the breakage temperature Tx that may break, and the DPF 30 is overheated.

  On the other hand, in the present invention, when it is determined that the excessive temperature rise of the DPF 30 cannot be prevented by the exhaust cooling process, it is next determined whether or not the excessive temperature rise of the DPF 30 can be prevented by the oxygen deficient cooling process. (S60 in FIG. 2). If it is determined that the excessive temperature rise of the DPF 30 cannot be prevented even in the oxygen deficient cooling process (S60 and S70 in FIG. 2), instead of the exhaust cooling process and the oxygen deficient cooling process, the exhaust amount in the exhaust cooling process is used. (Step S90 in FIG. 2), the interval between time t4 and t5 in which the increase-intensification cooling process is executed is executed as shown in FIG. 6 (b). As a result, the temperature of the DPF 30 can be made lower than the breakage temperature Tx as shown in FIG. Note that even if the increased amount enhanced cooling process is executed, as shown in FIG. 6C, the oxygen concentration is still higher than the oxygen concentration level n0 that can prevent overheating, Necessary exhaust Since secured many emissions than Q0, considered possible to prevent excessive temperature rise of the DPF 30.

  Returning to the description of FIG. 2, when any of the exhaust cooling process (S50), the oxygen deficient cooling process (S80), and the increased amount enhanced cooling process (S90) is performed as the cooling process, the process of step S10 is performed thereafter. Will return. In step S10, the current temperature of the DPF 30 and the like are acquired. In step S20, it is determined whether or not it is necessary to execute a cooling process based on the acquired temperature of the DPF 30 and the like. At this time, if the temperature of the DPF 30 decreases due to the cooling process being executed, it is determined in step S20 that the cooling process is unnecessary. In this case, the process proceeds to step S100. In step S100, the execution of the cooling process being executed is terminated, and the process of the flowchart of FIG. 2 is terminated. Accordingly, it is possible to prevent the cooling process from being continued unnecessarily even though the cooling process is executed and the temperature of the DPF 30 is decreased. The ECU 70 that executes step S20 corresponds to the “continuation necessity determination unit” of the present invention. The ECU 70 that executes step S100 corresponds to the “cooling processing end means” of the present invention.

  On the other hand, if it is determined in step S20 that the temperature of the DPF 30 is still high and that the cooling process needs to be performed, the process proceeds to step S30 and subsequent steps. In this case, the execution of the cooling process is continued. At this time, if the cooling process being executed is the exhaust cooling process, it is determined again whether or not the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process (S30). If it is determined that the excessive temperature rise of the DPF 30 can still be prevented by the exhaust cooling process (S40), the execution of the exhaust cooling process is continued (S50). On the other hand, if it is determined that the excessive temperature rise of the DPF 30 cannot be prevented by the exhaust cooling process due to a change in the operation state of the engine 10 or the like thereafter (S40), the process proceeds to step S60 and subsequent steps, and the exhaust cooling process starts. Then, the process is switched to either an oxygen deficient cooling process or an increase in quantity enhancement process (S80 or S90). Thereby, it is possible to prevent the excessive temperature rise of the DPF 30 even if the operating state of the engine 10 thereafter changes.

  When the cooling process being executed is the oxygen deficient cooling process, it is determined again whether or not the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process (S30). Then, when it is determined that the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process due to a change in the operating state of the engine 10 thereafter (S40), the oxygen deficient cooling process is switched to the exhaust cooling process (S50). . As a result, the oxygen deficiency cooling process is forced into an oxygen deficient state, which may adversely affect drivability. However, since the exhaust cooling process is preferentially executed, it is possible to prevent the drivability from being deteriorated. On the other hand, when it is determined that the excessive temperature rise of the DPF 30 cannot be prevented by the exhaust cooling process (S40), it is determined again whether the excessive temperature rise of the DPF 30 can be prevented by the oxygen deficient cooling process. (S60). When it is determined that the excessive temperature rise can still be prevented (S70), the execution of the oxygen deficiency cooling process is continued (S80). On the other hand, if it is determined that the excessive temperature rise of the DPF 30 cannot be prevented by the oxygen deficiency cooling process due to a change in the operating state of the engine 10 thereafter (S70), the oxygen deficient cooling process is switched to the increase-intensified cooling process ( S90). As a result, even if the excessive temperature rise cannot be prevented by either the exhaust cooling process or the oxygen deficient cooling process due to subsequent changes in the operating state of the engine 10, the excessive temperature rise of the DPF 30 is prevented by the increase-intensified cooling process. it can.

  When the cooling process being executed is the increase-intensity cooling process, it is determined again whether or not the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process or the oxygen deficient cooling process (S30, S60). If it is determined that the excessive temperature rise of the DPF 30 can be prevented by the exhaust cooling process or the oxygen deficient cooling process due to a change in the operating state of the engine 10 or the like thereafter, the exhaust cooling process or the oxygen deficient process is increased from the increase in the enhanced cooling process. Switching to the cooling process (S50 or S80). If it is determined that the excessive temperature rise of the DPF 30 cannot be prevented by either the exhaust cooling process or the oxygen deficient cooling process, the increase-intensified cooling process is continued (S90).

  As described above, in the present embodiment, the engine speed NE or the like is set even if the excessive temperature rise of the DPF 30 cannot be prevented not only by the exhaust cooling process but also by the oxygen deficient cooling process due to the ignitability of the fuel. Since the increase-enhanced cooling process forcibly increasing the required exhaust amount Q0 is executed, it is possible to prevent an excessive temperature rise of the DPF 30.

  Further, regarding the determination of whether or not the excessive temperature rise of the DPF 30 can be prevented by the oxygen deficient cooling process, it is determined whether or not the combustion in the cylinder is effectively performed by taking the cetane number C of the fuel into consideration. can do. If the combustion in the cylinder is not effectively performed, it is determined that the combustion cannot effectively consume oxygen and the oxygen concentration around the DPF 30 cannot be effectively reduced. be able to.

(Second embodiment)
Next, a second embodiment of the DPF overheat prevention device of the present invention will be described focusing on the differences from the first embodiment. In addition, this embodiment is an embodiment which concerns on the invention which performs a correction | amendment oxygen deficiency cooling process among the invention which concerns on a claim, when an excessive temperature rise cannot be prevented by an exhaust_gas | exhaustion cooling process and an oxygen deficiency cooling process.

  The configuration of the invention according to this embodiment is the same as that of the first embodiment shown in FIG. Further, the excessive temperature rise prevention process for preventing the excessive temperature rise of the DPF 30 in the present embodiment is obtained by replacing step S90 with another process step in the flowchart of FIG. Here, FIG. 7 is a flowchart showing the procedure of the corrected oxygen deficient cooling process executed in place of step S90. That is, if it is determined in step S70 of FIG. 2 that the excessive temperature rise of the DPF 30 cannot be prevented by the oxygen deficient cooling process, the process proceeds to the corrected oxygen deficient cooling process of FIG. Hereinafter, the corrected oxygen deficient cooling process will be described, but before that, post injection during the oxygen deficient cooling process will be described.

  As described in the first embodiment, in the oxygen deficient cooling process, in order to reduce the oxygen concentration around the DPF 30, post injection following the main injection is executed to consume excess oxygen in the cylinder. Here, FIG. 8A is a diagram for explaining the post injection timing and the post injection amount of the post injection. In addition, the horizontal axis of Fig.8 (a) has shown the crank angle CA as an injection timing, and the magnitude | size of the peak which showed each injection has shown the fuel quantity in each injection. As shown in FIG. 8A, the main injection is performed near the top dead center TDC. Note that pre-injection is executed prior to main injection in order to promote combustion in main injection. And at the time of an oxygen deficient cooling process, post injection is performed following main injection. The post-injection timing x1 and post-injection amount y1 of this post-injection are appropriately determined according to, for example, the operating state of the engine 10, or are determined with reference to the fuel injection timing and fuel injection amount of the main injection. Further, in the oxygen deficient cooling process, the amount of fresh air taken into the engine 10 is reduced by executing at least one of the operations of opening the EGR valve 42 and throttle the throttle valve 65. At this time, the opening degree of the EGR valve 42 is Z1, and the opening degree of the throttle valve 65 is W1.

  Under such a premise, when the process shifts to the corrected oxygen deficient cooling process of FIG. 7, first, in step S111, the post injection timing x1 of the post injection when the oxygen deficient cooling process is executed is advanced by a predetermined angle x. A corrected post-injection timing x2 is calculated.

  In subsequent step S112, as the corrected oxygen deficient cooling process, the corrected post injection is executed at the corrected injection timing x2 subsequent to the main injection to reduce the oxygen concentration around the DPF 30. The fuel injection amount at this time is the post injection amount y1 during the oxygen deficient cooling process. Here, FIG. 8B is a diagram for explaining the injection timing and the injection amount of the corrected post-injection. As shown in FIG. 8B, it can be seen that the corrected post-injection is executed at the corrected post-injection timing x2. The corrected post-injection timing x2 is on the advance side of the main injection with respect to the post-injection timing x1 in FIG. 8A, and the difference between them is a predetermined angle x. Thus, it is considered that the corrected post-injection executed at the correction post-injection timing x2 from the main injection is burned in a state where the in-cylinder pressure is higher than that at the time of normal post-injection execution. Therefore, the fuel can be effectively burned in the cylinder and consumed more oxygen than when normal post-injection is executed, and as a result, the oxygen concentration around the DPF 30 can be further reduced.

  On the other hand, even if the injection timing of the post injection is corrected to a fixed angle advance side, depending on the ignitability of the fuel and the operating state of the engine 10, combustion in the cylinder is still not effective, and oxygen around the DPF 30 There may be cases where the concentration cannot be effectively reduced. Therefore, in the following step 113, it is determined whether or not oxygen consumption in the cylinder is sufficient by the corrected post injection. Specifically, for example, the determination is made based on the exhaust temperature detected by the exhaust temperature sensor 61 or the in-cylinder pressure detected by the in-cylinder pressure sensor 66. That is, when the combustion is effectively performed by the corrected post-injection, the exhaust temperature becomes high. Therefore, if the exhaust temperature is equal to or higher than a predetermined value, it can be determined that the combustion is effectively performed. Further, if the in-cylinder pressure at the time of the corrected post injection is high, it can be determined that the combustion at the corrected post injection is effectively performed. And if combustion is made effectively, it can be judged that oxygen consumption is enough. Whether or not the oxygen consumption is sufficient is determined from the viewpoint of whether or not the oxygen concentration can be reduced to an excessive temperature rise of the DPF 30.

  If it is determined in step S113 that the oxygen consumption in the corrected post-injection is sufficient (S113: YES), the corrected oxygen deficient cooling process in FIG. 7 is exited and the process returns to the process in FIG. In this case, the corrected oxygen deficient cooling process by the corrected post injection is executed.

  On the other hand, if it is determined in step S113 that the oxygen consumption in the corrected post-injection is insufficient (S113: NO), in step S114, the injection timing is further corrected to a predetermined angle advance side, and the correction post is corrected. The post injection amount y1 of the injection is corrected to a corrected post injection amount y2 that is increased by a predetermined amount. At this time, the amount to be increased is, for example, a predetermined percentage of the original post injection amount y1, or a predetermined absolute amount regardless of the original post injection amount y1. As a result, as shown in FIG. 8C, the combustion scale of the corrected post-injection increases and the oxygen consumption amount also increases.

  Furthermore, in step S114, the opening degree of the throttle valve 65 is corrected to an opening degree W2 that is larger than the opening degree W1 in the oxygen deficient cooling process. Accordingly, the amount of fresh air is increased from that during the oxygen-deficient cooling process, so that combustion in the cylinder can be promoted. As a result, the consumption of oxygen contained in fresh air can be promoted, and the oxygen concentration around the DPF can be effectively reduced.

  Furthermore, in step S114, the opening degree of the EGR valve 42 is corrected to an opening degree Z2 that is smaller than the opening degree Z1 during the oxygen deficient cooling process. Accordingly, the amount of fresh air can be increased by reducing the EGR amount as compared with the time of the oxygen-deficient cooling process, so that combustion in the cylinder can be promoted. As a result, the consumption of oxygen contained in fresh air can be promoted, and the oxygen concentration around the DPF can be effectively reduced.

  Note that the opening W2 of the throttle valve 65 and the opening Z2 of the EGR valve 42 at this time may be determined, for example, as a predetermined opening, or based on the original opening W1, Z1.

  Thus, in step S114, not only the corrected post-injection timing x2, but also the corrected post-injection amount y2, the opening W2 of the throttle valve, and the opening Z2 of the EGR valve 42 are corrected to execute corrected post-injection. Therefore, combustion in the cylinder can be promoted, and the oxygen concentration around the DPF 30 can be effectively reduced.

  Thereafter, the process returns to step S113, and it is determined again whether or not the oxygen consumption amount in the corrected post-injection is sufficient based on the exhaust temperature Te, the in-cylinder pressure, and the like (S113). If it is sufficient (S113: YES), the correction oxygen deficient cooling process of FIG. 7 is exited and the process returns to the process of FIG.

  On the other hand, if it is still insufficient (S113: NO), the corrected post-injection amount y2, the opening W2 of the throttle valve, and the opening Z2 of the EGR valve 42 are corrected again. The correction amount is determined in advance as an absolute amount, or is set to a predetermined percentage of the original values y2, W2, and Z2. In this way, by looping the processing of steps S113 and S114, it is possible to finally reduce the oxygen concentration level to n0 that can prevent the excessive temperature rise of the DPF 30. As a result, excessive temperature rise of the DPF 30 can be prevented. The ECU 70 that executes steps S111 to S114 corresponds to the “corrected oxygen deficient cooling means” of the present invention.

  Here, FIG. 9 is a diagram for explaining the effect of the present invention for executing the corrected oxygen deficient cooling process. FIG. 9 (a) is a vehicle determined based on the engine speed NE, the operation amount of the accelerator pedal, and the like. The figure which showed the time change of the vehicle speed of this, the figure (b) the figure which showed the time change of displacement, the figure (c) the figure which showed the time change of the oxygen concentration around DPF30, the figure (d) FIG. 6 is a diagram showing a change over time in the temperature of the DPF 30. The time axes of FIGS. 9A to 9D are common. In addition, FIG. 9 also shows a time change (one-dot chain line) of the conventional invention for comparison with the present invention.

  Similar to FIG. 6 described above, it is determined that the cooling process needs to be performed at time t4 in FIG. 9, and the DPF 30 is excessively heated by either the exhaust cooling process or the oxygen deficient cooling process. If it is determined that it cannot be prevented, a corrected oxygen deficient cooling process is executed (FIG. 8). As a result, as shown in FIG. 9C, the oxygen concentration around the DPF 30 is lower than the oxygen concentration level n0 that can prevent the excessive temperature rise of the DPF 30 during the period from time t4 to t5 when the corrected oxygen deficient cooling process is executed. Can be reduced to levels of. As a result, as shown in FIG. 9D, the temperature of the DPF 30 can be made lower than the breakage temperature Tx, so that an excessive temperature rise of the DPF 30 can be prevented.

  Conventionally, the exhaust amount is smaller than the required exhaust amount Q0, and the oxygen concentration is higher than the oxygen concentration level n0 that can prevent the excessive temperature rise of the DPF 30, so that either the exhaust cooling process or the oxygen deficient cooling process is executed. The temperature of the DPF 30 cannot be effectively reduced. Therefore, as shown in FIG. 9D, the temperature of the DPF 30 becomes higher than the breakage temperature Tx.

  As described above, in the present embodiment, even when the excessive temperature rise of the DPF 30 cannot be prevented by either the exhaust cooling process or the oxygen deficient cooling process, the oxygen adjustment parameters (post injection timing, post injection amount, throttle) A corrected oxygen deficiency cooling process in which the control amounts of the opening degree of the valve 65 and the opening degree of the EGR valve 42 are corrected from the control amounts during the oxygen deficiency cooling process is executed. Therefore, regardless of the ignitability of the fuel and the like, the oxygen concentration around the DPF 30 can be effectively reduced, and the excessive temperature rise of the DPF 30 can be prevented.

  Note that the DPF overheat prevention device of the present invention is not limited to the first and second embodiments, and can be variously modified without departing from the scope of the claims. For example, in the above-described embodiment, whether or not the excessive temperature rise of the DPF 30 can be prevented by the oxygen deficient cooling process is determined by considering the cetane number C of the fuel, etc., and whether combustion in the cylinder is effectively performed. Judging from the point of view. However, the present invention is not limited to this. For example, the oxygen deficiency cooling process is temporarily performed, and the oxygen concentration in the cylinder or around the DPF 30 at that time is directly measured, and the oxygen deficiency cooling process is performed based on the magnitude of the oxygen concentration. It may be determined whether or not excessive temperature rise of the DPF 30 can be prevented. However, in this case, as in the above embodiment, since it is not determined whether or not combustion in the cylinder is effectively performed, how to correct the amount of fresh air, post injection, etc. There is a drawback that it is difficult to determine whether it can be effectively reduced.

  Further, in the second embodiment, in the corrected oxygen deficient cooling process of FIG. 7, as the corrected post-injection, first the post-injection time is corrected by a predetermined time x, and then the post-injection amount and the throttle according to the combustion state. The opening degree of the valve 65 and the opening degree of the EGR valve 42 were appropriately adjusted. However, these oxygen adjustment parameters (post injection timing, post injection amount, opening of the throttle valve 65, EGR valve, etc.) can be reduced to an oxygen concentration lower than the oxygen concentration level n0 that can prevent overheating of the DPF 30. 42) may be corrected in any way.

1 Engine system 10 Diesel engine (internal combustion engine)
20 DOC
30 DPF
42 EGR valve 51 Exhaust passage 52 Intake passage 61 Exhaust temperature sensor 62 A / F sensor 63 Intake temperature sensor 64 Air flow meter 65 Throttle valve 66 Compressor 67 Differential pressure sensor 70 ECU (DPF excessive temperature rise prevention device)
81 Rotational speed sensor 82 Accelerator sensor S20 Execution necessity determination means, continuation necessity determination means S30 First availability determination means S31 Required exhaust amount calculation means S32 Increased exhaust amount estimation means S33 to S35 Availability determination means S50 Exhaust cooling means S60 Second availability determination means S61 Intake air temperature acquisition means, exhaust temperature acquisition means, cetane number acquisition means S80 Oxygen deficiency cooling means S90 Increase intensification cooling means S100 Cooling processing end means S111 to S114 Correction oxygen deficiency cooling means

Claims (21)

An apparatus for preventing excessive temperature rise of a DPF that performs a predetermined cooling process for preventing excessive temperature rise of a DPF (diesel particulate filter) that collects particulate matter in exhaust gas provided in an exhaust passage of an internal combustion engine Yes,
An exhaust cooling means for performing an exhaust cooling process for increasing an exhaust amount flowing into the DPF by controlling a predetermined exhaust amount adjustment parameter in order to take away heat in the DPF as the cooling process;
In the DPF overheating prevention device, comprising the oxygen deficiency cooling means for executing the oxygen deficiency cooling process for reducing the oxygen concentration around the DPF in order to suppress heat generation in the DPF as the cooling process,
A first determination unit for determining whether or not an excessive temperature rise of the DPF can be prevented by the exhaust cooling process by determining whether or not the exhaust amount can be increased effectively;
A second propriety judging means for judging whether or not an excessive temperature rise of the DPF can be prevented by the oxygen deficient cooling treatment by judging whether or not the oxygen concentration can be effectively reduced;
When it is determined by the first and second possibility determination means that the overheating of the DPF cannot be prevented by the exhaust cooling process and the oxygen deficient cooling process, the exhaust cooling process and the oxygen deficient cooling process are used instead. In order to take away the heat in the DPF, the exhaust amount flowing into the DPF is further controlled than the exhaust amount in the exhaust cooling process by controlling a predetermined increase parameter other than the exhaust amount adjustment parameter. A DPF overheating prevention device, comprising: an increase-enhanced cooling means for executing an increased-intensity-enhanced cooling process.   The exhaust cooling means includes an opening of a throttle valve that adjusts the amount of fresh air taken into the intake system of the internal combustion engine and an opening of an EGR valve that adjusts the amount of EGR recirculated from the exhaust passage of the internal combustion engine to the intake passage. 2. The excess of the DPF according to claim 1, wherein at least one is controlled as the displacement adjustment parameter to increase the exhaust amount by increasing the fresh air amount and decreasing the EGR amount. Temperature rise prevention device.   3. The engine according to claim 1, wherein the increase-enhancement cooling means is configured to increase the displacement by increasing control of at least one of the rotational speed and the intake pressure of the internal combustion engine as the increase-enhancement parameter. The overheat prevention device of DPF of description. An apparatus for preventing excessive temperature rise of a DPF that performs a predetermined cooling process for preventing excessive temperature rise of a DPF (diesel particulate filter) that collects particulate matter in exhaust gas provided in an exhaust passage of an internal combustion engine Yes,
Exhaust cooling means for executing an exhaust cooling process for increasing the exhaust amount flowing into the DPF in order to carry away heat in the DPF as the cooling process;
As the cooling process, in order to suppress heat generation in the DPF, an oxygen-deficient cooling unit that executes a oxygen-deficient cooling process that controls a predetermined oxygen adjustment parameter to reduce the oxygen concentration around the DPF; In the DPF overheat prevention device provided,
A first determination unit for determining whether or not an excessive temperature rise of the DPF can be prevented by the exhaust cooling process by determining whether or not the exhaust amount can be increased effectively;
A second propriety judging means for judging whether or not an excessive temperature rise of the DPF can be prevented by the oxygen deficient cooling treatment by judging whether or not the oxygen concentration can be effectively reduced;
When it is determined by the first and second possibility determination means that the overheating of the DPF cannot be prevented by the exhaust cooling process and the oxygen deficient cooling process, the exhaust cooling process and the oxygen deficient cooling process are used instead. Correction oxygen deficiency cooling means for correcting the control amount of the oxygen adjustment parameter so that the oxygen concentration can be effectively reduced to reduce the oxygen concentration around the DPF, An apparatus for preventing excessive temperature rise of a DPF, characterized in that   The oxygen deficient cooling means includes an opening of a throttle valve for adjusting the amount of fresh air taken into the intake system of the internal combustion engine and an opening of an EGR valve for adjusting the amount of EGR recirculated from the exhaust passage of the internal combustion engine to the intake passage. 5. The DPF overheating according to claim 4, wherein the oxygen deficient cooling process is performed by controlling at least one of a fuel injection amount and a fuel injection timing as the oxygen adjustment parameter. Prevention device. The oxygen deficient cooling means performs post injection following the main injection with the fuel injection amount and fuel injection timing as the oxygen adjustment parameters, and burns the post injection in the cylinder, thereby reducing oxygen in the cylinder. By reducing the oxygen concentration,
The corrected oxygen deficient cooling means performs corrected post injection as the corrected oxygen deficient cooling process in which the fuel injection timing is corrected to a time when the in-cylinder pressure is higher than the fuel injection timing in the post injection during the oxygen deficient cooling process. The apparatus for preventing excessive temperature rise of the DPF according to claim 5, wherein the apparatus is executed.   The corrected oxygen deficient cooling means further corrects the fuel injection amount to an amount larger than the fuel injection amount in the post injection during the oxygen deficient cooling process as the corrected post injection. The overheat prevention device of DPF as described in 2.   The corrected oxygen deficient cooling means corrects the opening of the throttle valve as the oxygen adjustment parameter to an opening larger than that during the oxygen deficient cooling process, and executes the corrected oxygen deficient cooling process. The overheat prevention device for a DPF according to any one of claims 5 to 7,   The corrected oxygen deficient cooling means executes the corrected oxygen deficient cooling process by correcting the opening of the EGR valve as the oxygen adjustment parameter to a smaller opening than that during the oxygen deficient cooling process. The apparatus for preventing excessive temperature rise of a DPF according to any one of claims 5 to 8.   The second availability determination means determines whether or not combustion in the cylinder is effectively performed as a determination as to whether or not the oxygen concentration can be effectively reduced. The overheat prevention device for a DPF as described in any one of 9 above. Intake temperature acquisition means to acquire intake temperature,
11. The second availability determination unit determines whether or not combustion in a cylinder is effectively performed based on the intake air temperature acquired by the intake air temperature acquisition unit. DPF overheat prevention device. A cetane number acquisition means for acquiring the cetane number of the fuel burned in the cylinder as an index of ease of ignition of the fuel,
12. The second determination unit for determining whether or not combustion in a cylinder is effectively performed based on the cetane number acquired by the cetane number acquisition unit. The overheat prevention device of DPF as described in 2. An exhaust temperature acquisition means for acquiring the exhaust temperature is provided,
The second possibility determination unit determines whether or not combustion in the cylinder is effectively performed based on the exhaust temperature acquired by the exhaust temperature acquisition unit. The overheating prevention apparatus of DPF of any one of these.   14. The exhaust gas cooling process of the exhaust gas cooling process and the oxygen deficient cooling process is executed when the determination by the first availability determination unit is possible. The overheat prevention device for DPF as described in the item.   If the determination by the first availability determination unit is negative and the determination by the second availability determination unit is possible, the oxygen deficiency cooling processing of the exhaust cooling processing and the oxygen deficiency cooling processing is executed. The overheat prevention device for a DPF according to any one of claims 1 to 14, wherein: The first availability determination means includes:
A required exhaust amount calculating means for calculating a required exhaust amount capable of preventing an excessive temperature rise of the DPF;
A post-increase exhaust amount estimation means for estimating the post-increase exhaust amount in the case of performing the exhaust cooling process based on operating conditions of the internal combustion engine;
And a determination unit for determining whether or not an excessive increase in temperature of the DPF can be prevented by comparing and determining whether or not the exhaust amount after the increase is smaller than the necessary exhaust amount. The overheating prevention apparatus of DPF of any one of 1-15.   The DPF excess amount according to claim 16, wherein the required exhaust amount calculating means calculates the required exhaust amount based on a PM trapped amount that is an amount of particulate matter trapped by the DPF. Temperature rise prevention device. Based on the amount of particulate matter collected by the DPF and the amount of PM collected and the temperature of the DPF, an execution necessity determination unit is provided that determines whether or not the cooling process is necessary.
The overheating temperature of the DPF according to any one of claims 1 to 17, wherein the cooling process is executed only when it is determined by the execution necessity determination means that the cooling process is necessary. Prevention device.   The execution necessity determination unit is configured to determine whether the internal combustion engine is in a predetermined operation state in which excessive temperature rise of the DPF is likely to occur, in addition to the amount of collected PM and the temperature of the DPF. The apparatus for preventing excessive temperature rise of the DPF according to claim 18, wherein it is determined whether or not execution of processing is necessary.   20. The DPF overheat prevention device according to claim 19, wherein the predetermined operation state is a deceleration state. Continuation necessity determination means for determining whether or not the continuation of the cooling process being executed is necessary based on the temperature of the DPF during the execution of the cooling process;
21. A cooling process ending unit for ending a cooling process being executed when the continuation necessity determining unit determines that continuation is unnecessary. The overheat prevention device of DPF of description.

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