JP2008138537A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

An unburned fuel supply control with high accuracy is possible even when unburned fuel flows out of an oxidation catalyst and burns in a filter while ensuring the responsiveness of unburned fuel supply control.
When an unburned fuel addition amount Qa is larger than a processable amount Qp in an oxidation catalyst (S14), when an exhaust flow rate Qe is equal to or less than a predetermined flow rate Q1, an inlet temperature of the DPF is estimated from an engine operating state. In addition, while feedforward control of the supply of unburned fuel is performed based on the inlet temperature (S10, S20), when the exhaust flow rate Qe is greater than the predetermined flow rate Q1, the DPF inlet temperature is estimated based on the DPF outlet temperature, The supply of unburned fuel is feedback controlled based on the inlet temperature (S10, S16).
[Selection] Figure 2

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine, and more particularly to a technique for controlling the supply of unburned fuel during forced regeneration of a DPF (diesel particulate filter).

  A device having a DPF is known as a device for purifying exhaust gas from a diesel engine. The DPF is provided in the exhaust passage and collects particulates (hereinafter referred to as PM) in the exhaust. In addition, in order to remove the PM collected and accumulated in the DPF, an oxidation catalyst is provided upstream of the DPF, and the unburnt fuel is allowed to flow into the oxidation catalyst to raise the exhaust gas temperature. A forced regeneration device that burns soot, which is the main component of PM, is known.

In addition, a technology is known in which temperature sensors are provided on the upstream side and downstream side of the catalyst, and an appropriate amount of unburned fuel corresponding to the temperature is supplied to the catalyst based on the exhaust temperature detected by these temperature sensors. Yes. Further, there is also known a technique in which when the temperature sensor on the upstream side of the catalyst fails, the temperature of the exhaust gas flowing into the catalyst is estimated based on the operating state of the engine and used as the output of the temperature sensor on the upstream side ( Patent Document 1).
Japanese Patent No. 379927

In view of the technology disclosed in Patent Document 1 and the like described above, a temperature sensor is provided upstream of the DPF in order to properly control the temperature in the DPF in the forced regeneration device, and based on the exhaust temperature detected by the temperature sensor or the engine A method of supplying an appropriate amount of unburned fuel to the oxidation catalyst based on the exhaust temperature estimated from the operating state is conceivable.
However, if, for example, the oxidation function of the oxidation catalyst decreases or the temperature sensor on the upstream side breaks down, and unburned fuel with a flow rate exceeding the oxidation function flows into the oxidation catalyst, the unburned fuel flows in the DPF. May burn. In such a case, it is difficult to properly control the temperature in the DPF from the temperature upstream of the DPF.

  The present invention has been made to solve such problems, and its object is to supply unburned fuel to an oxidation catalyst provided upstream of the filter mainly based on the temperature upstream of the filter. In an exhaust gas purification device for an internal combustion engine that performs control, supply of unburned fuel with high accuracy even when unburned fuel flows out of an oxidation catalyst and burns in a filter while ensuring responsiveness of unburned fuel supply control An object of the present invention is to provide an exhaust emission control device that can be controlled.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a filter provided in an exhaust passage of an internal combustion engine for collecting particulates in exhaust gas, and an oxidation catalyst provided in an exhaust passage upstream of the filter. An unburned fuel supply means for supplying unburned fuel to the oxidation catalyst, an outlet temperature detection means for detecting the outlet temperature of the filter, a flow rate detection means for detecting an exhaust flow rate passing through the filter, and an oxidation treatment in the oxidation catalyst A processable quantity estimation means for estimating a processable quantity, which is a flow rate of possible fuel, and an unburned fuel whose exhaust flow rate detected by the flow rate detection means is larger than a predetermined flow rate and which is supplied to the oxidation catalyst by the unburned fuel supply means When the fuel supply amount is larger than the processable amount estimated by the processable amount estimation means, the inlet temperature of the filter is estimated based on the outlet temperature detected by the outlet temperature detection means. When the exhaust flow rate detected by the flow rate detecting means and the feedback control means for performing feedback control of the unburned fuel supply means so that the inlet temperature becomes the set temperature, An exhaust purification device for an internal combustion engine is configured to include a feedforward control unit that feedforward-controls the unburned fuel supply unit so as to reach a set temperature.

  In the invention of claim 2, the filter provided in the exhaust passage of the internal combustion engine for collecting particulates in the exhaust, the oxidation catalyst provided in the exhaust passage on the upstream side of the filter, and the oxidation catalyst unburned. Unburned fuel supply means for supplying fuel, outlet temperature detection means for detecting the outlet temperature of the filter, inlet temperature detection means for detecting the inlet temperature of the filter, and flow rate detection means for detecting the exhaust flow rate passing through the filter; An abnormality detecting means for detecting an abnormality of the inlet temperature detecting means or the oxidation catalyst, and an outlet temperature detecting means when the exhaust flow rate detected by the flow rate detecting means is larger than a predetermined flow rate and an abnormality is detected by the abnormality detecting means. The inlet temperature of the filter is estimated on the basis of the outlet temperature detected by, and the unburned fuel supply means is feedback-controlled so that the inlet temperature becomes a set temperature. Feedback control means, and feedforward control means for feedforward controlling the unburned fuel supply means so that the inlet temperature of the filter becomes a set temperature when the exhaust flow rate detected by the flow rate detection means is equal to or lower than a predetermined flow rate. The exhaust gas purification apparatus for an internal combustion engine is configured.

  The invention of claim 3 further comprises an intake air flow rate detecting means for detecting the intake air flow rate of the internal combustion engine and an outside air temperature detecting means for detecting the outside air temperature. 3. The method according to claim 1, wherein the temperature is estimated based on an outlet temperature detected by the outlet temperature detecting means, an intake air flow rate detected by the intake air flow detecting means, and an outside air temperature detected by the outside air temperature detecting means. An exhaust purification device for an internal combustion engine as described.

  According to the exhaust gas purification apparatus for an internal combustion engine of claim 1 of the present invention, when the exhaust flow rate is larger than a predetermined flow rate and the supply amount of unburned fuel is larger than the flow rate that can be oxidized in the oxidation catalyst, the outlet temperature of the filter is increased. Based on this, the inlet temperature is estimated. Since the unburned fuel supply is feedback controlled based on the estimated inlet temperature, the unburned fuel supply amount becomes larger than the oxidation processable amount in the oxidation catalyst, and the unburned fuel flows into the filter. Even if burnt, the supply of unburned fuel is controlled based on the outlet temperature rather than the inlet temperature of the filter, and the temperature in the filter can be controlled appropriately.

On the other hand, when the exhaust gas flow rate is small, the supply of unburned fuel to the filter is feedforward controlled. Therefore, even if the heat capacity in the filter is large, it is possible to control the supply of unburned fuel with good responsiveness.
According to the exhaust gas purification apparatus for an internal combustion engine according to claim 2 of the present invention, when the exhaust gas flow rate is larger than the predetermined flow rate and the inlet temperature detecting means or the oxidation catalyst is abnormal, it is based on the outlet temperature of the filter. The inlet temperature is estimated. Since the unburned fuel supply is feedback controlled based on the estimated inlet temperature, the unburned fuel supply amount becomes larger than the oxidation processable amount in the oxidation catalyst, and the unburned fuel flows into the filter. Even if burnt, the supply of unburned fuel is controlled based on the outlet temperature rather than the inlet temperature of the filter, and the temperature in the filter can be controlled appropriately.

On the other hand, when the exhaust gas flow rate is small, the supply of unburned fuel to the filter is feedforward controlled. Therefore, even if the heat capacity in the filter is large, it is possible to control the supply of unburned fuel with good responsiveness.
According to the exhaust gas purification apparatus for an internal combustion engine of claim 3 of the present invention, when the inlet temperature is estimated from the outlet temperature of the filter, the outside temperature is also taken into consideration, so that the inlet temperature can be obtained with high accuracy.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an overall configuration diagram of an engine (internal combustion engine) 1 to which an exhaust emission control device according to an embodiment of the present invention is applied.
The engine 1 is, for example, a common rail type in-line multi-cylinder diesel engine. The cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection nozzle (unburned fuel supply means) 4 for each cylinder facing the combustion chamber 3. Each fuel injection nozzle 4 is connected to a common rail 6 by a high-pressure pipe 5, and the common rail 6 is connected to a high-pressure pump 8 via a high-pressure pipe 7. The high-pressure pump 8 has a function of supplying the fuel (light oil) stored in the fuel tank 9 to the common rail 6. The fuel supplied to the common rail 6 is stored in a high-pressure state and burns from each fuel injection nozzle 4. It is injected into the chamber 3.

The cylinder head 2 is formed with an intake port 10 and an exhaust port 11 communicating with the combustion chamber for each cylinder. An intake pipe 12 is connected to the intake port 10, and an exhaust pipe 13 is connected to the exhaust port 11. ing. The cylinder head 2 is provided with an intake valve 14 that opens and closes the intake port 10 and an exhaust valve 15 that opens and closes the exhaust port 11.
The intake pipe 12 is provided with an electromagnetic intake throttle valve 16 that adjusts the amount of intake air, and an airflow sensor 17 that detects the intake flow rate upstream thereof.

Between the exhaust pipe 13 and the intake pipe 12, an EGR pipe 18 in which an EGR valve 19 that is an electromagnetic on-off valve is inserted is provided. One end of the EGR pipe 18 is connected to the exhaust pipe 13 in the vicinity of the exhaust port 11, and the other end is connected to the intake pipe 12 in the vicinity of the intake port 10, and the exhaust pipe 13 and the intake pipe 12 are communicated.
A catalyst unit 20 and a DPF (corresponding to the filter of the present invention) 21 are interposed in the exhaust pipe 13 in order from the upstream side. The catalyst unit 20 is formed by accommodating a first oxidation catalyst 22 and a second oxidation catalyst 23 in a cylindrical case. The first oxidation catalyst 22 is provided on the exhaust upstream side, and the second oxidation catalyst 23 is provided downstream from the first oxidation catalyst 22. The first oxidation catalyst 22 and the second oxidation catalyst 23 function to oxidize CO and HC in exhaust gas to convert them into CO ₂ and H ₂ O, and to oxidize NO in exhaust gas to generate NO _2. Have

  The DPF 21 of the present embodiment has an oxidation catalyst function (oxidation catalyst support type). For example, the DPF 21 is formed by alternately closing the upstream side and the downstream side of the honeycomb carrier passage with plugs and oxidizing platinum (Pt), palladium (Pd), rhodium (Rh), etc. on the porous wall forming the passage. It is formed by supporting a catalytic noble metal having a function, and has a function of collecting PM in exhaust gas.

  A first temperature sensor 24 that detects an exhaust temperature Tf1 immediately before flowing into the first oxidation catalyst 22 is provided in the vicinity of the upstream side of the first oxidation catalyst 22. Between the first oxidation catalyst 22 and the second oxidation catalyst 23, a second temperature sensor (inlet temperature detection means) 25 for detecting the exhaust temperature Tf2 immediately after passing through the first oxidation catalyst 22 is provided. It has been. A third temperature sensor (exit temperature detection means) 26 that detects the exhaust gas temperature Tf3 immediately after passing through the DPF 21 is provided on the downstream side of the DPF 21. Furthermore, a differential pressure sensor 27 that detects a differential pressure Pd between the upstream side and the downstream side of the DPF 21 is provided on the upstream side and the downstream side of the DPF 21.

The ECU 30 is a control device for performing comprehensive control including operation control of the engine 1, and includes an input / output device, a storage device (ROM, RAM, nonvolatile RAM, etc.), a central processing unit (CPU), and the like. It consists of
On the input side of the ECU 30, in addition to the airflow sensor 17, the first temperature sensor 24, the second temperature sensor 25, the third temperature sensor 26, and the differential pressure sensor 27 described above, the crank angle of the engine 1 is detected. A crank angle sensor 31, an accelerator position sensor 32 that detects the amount of depression of the accelerator pedal, a vehicle speed sensor 33 that detects the vehicle speed, and the like are connected, and detection information from these sensors is input.

  On the other hand, various output devices such as the fuel injection nozzle 4, the intake throttle valve 16, and the EGR valve 19 are connected to the output side of the ECU 30. These various output devices output the fuel injection amount, the fuel injection timing, the EGR amount, etc., calculated by the ECU 30 based on the detection information from various sensors, respectively. Control of the nozzle 4, the EGR valve 19 and the like is performed.

As described above, by disposing the first oxidation catalyst 22 and the second oxidation catalyst 23 upstream of the DPF 21, NO ₂ flows into the DPF 21 from the downstream second oxidation catalyst 23 and is collected in the DPF 21. It reacts and oxidizes with soot, which is a carbon component in the deposited PM. The oxidized soot becomes CO _{2 and} is removed from the DPF 21, and the DPF 21 is continuously regenerated (continuous regeneration).

  In the continuous regeneration described above, the DPF 21 may not be sufficiently regenerated depending on the operating condition of the engine 1. Therefore, the ECU 30 performs forced regeneration when a predetermined amount or more of PM is accumulated in the DPF 21. The forced regeneration is performed by performing post-injection after main fuel injection during engine operation, discharging unburned fuel from the engine 1 together with exhaust, and supplying it to the first oxidation catalyst 22. The unburned fuel supplied to the first oxidation catalyst 22 is oxidized and raises the exhaust temperature. Thereby, the soot in PM deposited on the DPF 21 is burned to regenerate the DPF 21.

The exhaust emission control device according to the present invention further includes an outside air temperature sensor 35 for detecting an outside air temperature To in the vicinity of the DPF 21. Control the supply of unburned fuel during regeneration. Hereinafter, the control content of the exhaust emission control device according to the present invention will be described.
FIG. 2 is a flowchart showing the first embodiment of the unburned fuel supply control procedure at the time of forced regeneration. Hereinafter, the unburned fuel supply control at the time of forced regeneration according to the present invention will be described along the flowchart. To do.

This routine starts when forced regeneration starts, and is repeatedly executed at appropriate intervals during forced regeneration.
First, in step S12, the processing is the maximum flow rate of unburned fuel that can be oxidized in the first oxidation catalyst 22 and the second oxidation catalyst 23 from the exhaust temperature Tf2 detected by the second temperature sensor 25 and the exhaust flow rate Qe. Estimate the possible quantity Qp. The estimation of the processable amount Qp is read out based on the exhaust temperature Tf2 detected by the second temperature sensor 25 and the exhaust flow rate Qe, for example, from a map confirmed in advance by experiments or the like and stored in the storage device of the ECU 30. Is done by. Then, the process proceeds to step S14.

  In step S14, the amount of unburned fuel added (the amount of unburned fuel supplied to the first oxidation catalyst 22) that is the flow rate of unburned fuel (set in the ECU 30) injected from the fuel injection nozzle 4 immediately before. It is determined whether or not Qa is larger than the processable amount Qp estimated in step S12. When the unburned fuel addition amount Qa is larger than the processable amount Qp, the process proceeds to step S10.

In step S10, it is determined whether or not the exhaust flow rate Qe is greater than a predetermined flow rate Q1. If the exhaust flow rate Qe is greater than the predetermined flow rate Q1, the process proceeds to step S16. The exhaust flow rate Qe may be obtained, for example, by calculating from the intake flow rate Qi detected by the air flow sensor 17 or by directly detecting the exhaust pipe 13 by providing a flow meter (flow rate detection means).
In step S16, based on the exhaust temperature (exit temperature) Tf3 input from the third temperature sensor 26, the intake air flow rate Qi input from the airflow sensor 17, and the outside air temperature To input from the outside air temperature sensor 35, the inlet side of the DPF 21 is set. The exhaust temperature (inlet temperature) Ti1 is estimated. Then, the fuel injection amount injected from the fuel injection nozzle 4 is feedback-controlled (estimated DPF inlet temperature F / B control) so that the inlet temperature Ti1 of the DPF becomes the set temperature T2, and this routine ends. The set temperature T2 may be set to a temperature at which PM deposited on the DPF 21 at the time of forced regeneration burns efficiently.

On the other hand, if it is determined in step S10 that the exhaust flow rate Qe is equal to or less than the predetermined flow rate Q1, the process proceeds to step S20.
In step S20, for example, the exhaust temperature (inlet temperature) Ti1 on the inlet side of the DPF 21 is estimated based on the engine operating condition (engine speed, load, etc.), and the fuel is set so that the inlet temperature Ti1 becomes the set temperature T2. Feed forward control (F / F control) is performed on the amount of fuel injected from the injection nozzle 4. Here, the estimation of the inlet temperature Ti1 may be performed by, for example, reading from a map that has been confirmed in advance by experiments or the like and stored in the storage device of the ECU 30 based on the engine operating state. Then, this routine ends.

On the other hand, when it is determined in step S14 that the unburned fuel addition amount Qa is equal to or less than the processable amount Qp, the process proceeds to step S40.
In step S40, feedback control (detected DPF inlet temperature F / B control) is performed on the fuel injection amount injected from the fuel injection nozzle 4 so that the exhaust temperature Tf2 input from the second temperature sensor 25 becomes the set temperature T2. This routine ends.

In addition, control of step S10-16 in this control corresponds to the feedback control means of this invention, and control of step S10-14, 20 corresponds to the feedforward control means of this invention.
FIG. 3 is a block diagram showing the estimation control of the inlet temperature Ti1 of the DPF 21 performed in step S16.

The temperature gradient calculation unit 40 calculates the temperature gradient Dt based on the exhaust temperature Tf3 input from the third temperature sensor 24.
The multiplication unit 42 multiplies the temperature gradient Dt calculated by the temperature gradient calculation unit 40 and the gain obtained by gaining the intake air amount Qi detected by the airflow sensor 17 in the gain unit 44, thereby increasing (decreasing) the temperature. A correction amount Tc due to the delay is calculated. In the calculation of the correction amount Tc, the intake flow rate Qi is taken into account because the intake flow rate correlates with the exhaust flow rate. When the exhaust flow rate is large, the temperature rise (decrease) delay is reduced, while the exhaust flow rate is reduced. This is because if the amount is small, the temperature increase (decrease) delay increases.

On the other hand, the temperature decrease amount calculation unit 46 calculates the temperature decrease amount Td of the exhaust when passing through the DPF 21 based on the exhaust temperature Tf3, the intake air flow rate Qi, and the outside air temperature To.
The adder 48 adds the correction amount Tc calculated by the multiplier 42 and the temperature decrease Td calculated by the temperature decrease calculator 46 to the exhaust temperature Tf3.
The first-order lag processor 50 performs first-order lag processing on the addition result in the adder 48 with a processing amount based on the intake flow rate Qi, and calculates the inlet temperature Ti1 of the DPF 21.

  In the exhaust gas purification apparatus for an internal combustion engine as described above, when more unburned fuel is added than the flow rate that can be oxidized by the first oxidation catalyst 22 and the second oxidation catalyst 23 (processable amount Qp). In the case where the exhaust flow rate Qe is equal to or less than the predetermined flow rate Q1, for example, the inlet temperature Ti1 of the DPF 21 is estimated based on the engine operating condition, and feedforward control is performed so that the inlet temperature Ti1 becomes the set temperature T2. Thus, by performing feedforward control of fuel injection based on the engine operating state, fuel injection control with good responsiveness is possible.

  On the other hand, when more unburned fuel than the processable amount Qp is added and the exhaust flow rate Qe is larger than the predetermined flow rate Q1, the inlet temperature Ti1 is estimated from the outlet temperature Tf3 of the DPF 21, and this inlet temperature Ti1 is set. Feedback control is performed so that the temperature becomes T2. Thus, since the inlet temperature Ti1 is estimated from the outlet temperature Tf3 of the DPF 21, even if unburned fuel that has not been oxidized by the first oxidation catalyst 22 and the second oxidation catalyst 23 flows into the DPF 21, The temperature in the DPF 21 can be maintained within the allowable temperature range, and melting of the DPF 21 can be prevented. Further, since the fuel injection amount is feedback-controlled based on the outlet temperature Tf3 of the DPF 21, accurate fuel injection can be performed. Here, the condition that the exhaust flow rate Qe is larger than the predetermined flow rate Q1 is that when the exhaust flow rate Qe is not secured to some extent, the responsiveness of the exhaust temperature at the DPF outlet side is low, This is to avoid a decrease in the accuracy of unburned fuel supply control during the transient operation of the engine 1.

FIG. 4 shows an example of changes in the outlet temperature Tf3 of the DPF 21, the inlet temperature Ti1 of the DPF 21 estimated based on the outlet temperature Tf3, and the actual exhaust gas temperature Ti2 on the DPF 21 inlet side in the above embodiment.
As shown in FIG. 4, the inlet temperature Ti1 estimated based on the outlet temperature Tf3 is substantially the same as the actual exhaust temperature Ti2, although there is a slight delay. Thus, the exhaust gas purification apparatus of the present invention can accurately estimate the inlet temperature Ti1 based on the outlet temperature Tf3 of the DPF 21.

In this embodiment, the second oxidation catalyst is ensured while ensuring the responsiveness of the unburned fuel supply control by switching the estimation method of the inlet temperature of the DPF 21 according to the unburned fuel addition amount Qa and the exhaust gas flow rate Qe. Even when unburned fuel flows out of the fuel 23 and burns in the DPF 21, it is possible to control the supply of unburned fuel with high accuracy.
FIG. 5 is a flowchart showing a second embodiment of the unburned fuel supply control procedure during forced regeneration. Only the differences from the first embodiment will be described below.

  In the present embodiment, first, in step S32, it is determined whether or not the first oxidation catalyst 22 and the second oxidation catalyst 23 are abnormal (the oxidation function of the oxidation catalyst is reduced). If these oxidation catalysts 22 and 23 are abnormal, the process proceeds to step S10. If the oxidation catalysts 22 and 23 are not abnormal, the process proceeds to step S36. Whether or not the oxidation catalysts 22 and 23 are abnormal, that is, whether or not the oxidation function of the oxidation catalysts 22 and 23 is lowered is, for example, the first after a lapse of a predetermined time from the start of supply of unburned fuel. Based on the temperature Tf1 of the exhaust gas flowing into the oxidation catalyst 22 and the temperature Tf2 of the exhaust gas flowing out of the first oxidation catalyst 22 or the temperature Tf3 of the exhaust gas discharged from the DPF 21, the determination is made based on the degree of temperature rise at the oxidation catalysts 22, do it.

In step S36, it is determined whether or not the first temperature sensor 24 or the second temperature sensor 25 is abnormal. If the first temperature sensor 24 or the second temperature sensor 25 is abnormal, the process proceeds to step S10. If the first temperature sensor 24 or the second temperature sensor 25 is not abnormal, the process proceeds to step S40.
In addition, control of step S10, S32, S36, S16 in this control corresponds to the feedback control means of this invention.

  As described above, in this embodiment, when the oxidation catalysts 22 and 23 are abnormal or when the first or second temperature sensors 24 and 25 are abnormal, the exhaust flow rate Qe is required to be larger than the predetermined flow rate Q1. The unburned fuel supply control is performed based on the outlet temperature Tf3 of the DPF 21. When the oxidation catalysts 22 and 23 are abnormal, most of the unburned fuel flows out of the oxidation catalysts 22 and 23 and burns in the DPF 21, but the supply control of the unburned fuel is performed based on the temperature of the exhaust gas discharged from the DPF 21. By doing so, it is possible to monitor the rise in the exhaust temperature due to the combustion of the unburned fuel amount in the DPF 21 and to prevent the DPF 21 from being damaged due to excessive supply of unburned fuel. Further, when the first temperature sensor 24 or the second temperature sensor 25 is abnormal, supply control of unburned fuel is possible without using this temperature sensor, and reliability of supply control of unburned fuel is ensured. can do.

  It should be noted that any one of the determination controls as described above, such as whether or not the oxidation catalysts 22 and 23 are abnormal and whether or not the first temperature sensor 24 or the second temperature sensor 25 is abnormal. You may do only one. Further, these determination controls may be combined with the determination control for determining whether or not the unburned fuel addition amount Qa in the first embodiment is equal to or greater than the processable amount Qp. For example, the reliability of unburned fuel supply control can be improved.

1 is an overall configuration diagram of an internal combustion engine according to the present invention. It is a flowchart which shows 1st Embodiment of the supply control procedure of unburned fuel. It is a block diagram which shows the estimation control of the inlet_port | entrance temperature of DPF. It is a graph which shows an example of transition of DPF exit temperature, DPF entrance temperature estimated based on exit temperature, and actual entrance temperature of DPF. It is a flowchart which shows 2nd Embodiment of the supply control procedure of unburned fuel.

Explanation of symbols

1 Engine 4 Fuel injection nozzle 21 DPF
17 air flow sensor 22 first oxidation catalyst 23 second oxidation catalyst 24 first temperature sensor 25 second temperature sensor 26 third temperature sensor 30 ECU

Claims (3)

A filter provided in an exhaust passage of the internal combustion engine for collecting particulates in the exhaust;
An oxidation catalyst provided in the exhaust passage upstream of the filter;
Unburned fuel supply means for supplying unburned fuel to the oxidation catalyst;
Outlet temperature detecting means for detecting the outlet temperature of the filter;
A flow rate detecting means for detecting an exhaust flow rate passing through the filter;
A processable amount estimating means for estimating a processable amount that is a flow rate of fuel that can be oxidized in the oxidation catalyst;
A processable amount in which the exhaust gas flow rate detected by the flow rate detection unit is larger than a predetermined flow rate, and the supply amount of unburned fuel supplied to the oxidation catalyst by the unburnt fuel supply unit is estimated by the processable amount estimation unit. When it is larger, feedback is performed to estimate the inlet temperature of the filter based on the outlet temperature detected by the outlet temperature detecting means, and to feedback-control the unburned fuel supply means so that the inlet temperature becomes a set temperature. Control means;
A feedforward control means for feedforward controlling the unburned fuel supply means so that an inlet temperature of the filter becomes a set temperature when an exhaust flow rate detected by the flow rate detection means is equal to or lower than a predetermined flow rate;
An exhaust emission control device for an internal combustion engine, comprising: A filter provided in an exhaust passage of the internal combustion engine for collecting particulates in the exhaust;
An oxidation catalyst provided in the exhaust passage upstream of the filter;
Unburned fuel supply means for supplying unburned fuel to the oxidation catalyst;
Outlet temperature detecting means for detecting the outlet temperature of the filter;
An inlet temperature detecting means for detecting an inlet temperature of the filter;
A flow rate detecting means for detecting an exhaust flow rate passing through the filter;
An abnormality detecting means for detecting an abnormality of the inlet temperature detecting means or the oxidation catalyst;
When the exhaust flow rate detected by the flow rate detection means is larger than a predetermined flow rate and an abnormality is detected by the abnormality detection means, the inlet temperature of the filter is set based on the outlet temperature detected by the outlet temperature detection means. A feedback control means for performing feedback control of the unburned fuel supply means so that the inlet temperature becomes a set temperature,
A feedforward control means for feedforward controlling the unburned fuel supply means so that an inlet temperature of the filter becomes a set temperature when an exhaust flow rate detected by the flow rate detection means is equal to or lower than a predetermined flow rate;
An exhaust emission control device for an internal combustion engine, comprising: An intake flow rate detecting means for detecting an intake flow rate of the internal combustion engine;
An outside air temperature detecting means for detecting the outside air temperature,
The inlet temperature is estimated based on the outlet temperature detected by the outlet temperature detection means, the intake air flow rate detected by the intake flow rate detection means, and the outside air temperature detected by the outside air temperature detection means. The exhaust emission control device for an internal combustion engine according to claim 1 or 2.

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