JP2006250116A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability of a regeneration condition of an exhaust emission control means 15 determined on the estimation of a passage characteristic by newly adding a means for estimating the passage characteristic in the exhaust emission control means 15 such as a DPF. <P>SOLUTION: An oxygen concentration detection means 16 is disposed downstream of the exhaust emission control means 15 in an exhaust passage 8. Oxygen concentration is detected by the oxygen concentration detection means 16 and, an oxygen concentration changing characteristic is calculated as the passage characteristic using a detection signal outputted from the oxygen concentration detection means. This allows newly estimating the oxygen concentration changing characteristic as the passage characteristic based on the oxygen concentration downstream of the exhaust emission control means 15 in addition to a conventional PM deposition amount based on differential pressure or the like. It is therefore possible to improve the reliability of the regeneration condition based on the estimation of the passage characteristic. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification device that purifies exhaust gas discharged from an engine.

[Conventional technology]
Conventionally, in an exhaust gas purification means such as a catalyst and a filter in an exhaust gas purification device, regeneration processing has been performed in order to prevent the exhaust gas from being obstructed due to clogging with particulates (PM) or the like. In order to effectively perform such regeneration processing, exhaust gas passage characteristics in the exhaust gas purification means are estimated in some form, and regeneration conditions such as regeneration timing are determined based on this estimated value.

  For example, in a filter (DPF) that removes PM discharged from a diesel engine, the PM accumulation amount (PM accumulation amount) is estimated as a passage characteristic based on the differential pressure between the inlet side and the outlet side of the DPF. The playback time is determined based on the value.

  However, with only the estimation based on the differential pressure, there is a risk of erroneous estimation due to detection errors and detection variations of the sensor that detects the differential pressure. Therefore, in addition to the estimation based on the differential pressure, the PM accumulation amount is estimated based on the operating state of the engine, such as the fuel injection amount and the engine speed, and is estimated by two means, so that the reliability for the determination of the regeneration time is improved. (See, for example, Patent Document 1). Furthermore, in this technique, the deposition amount is estimated in consideration of deterioration with time of the fuel injection nozzle and the like, fluctuations in the properties of the fuel, and the like, thereby improving the reliability for determining the regeneration time (for example, Patent Document 2). reference).

[Problems with conventional technology]
However, it is generally very difficult to accurately estimate the passage characteristics as in the estimation of the PM accumulation amount in the DPF. For this reason, even if estimation is performed using two methods as described above, there is a possibility of erroneous estimation. Therefore, the reliability of the reproduction condition based on the estimation of the pass characteristic is insufficient, and further improvement is desired.
JP 2002-256846 A JP 2004-76589 A

  The present invention has been made to solve the above-described problems, and is determined based on estimation of passage characteristics by newly adding means for estimating passage characteristics in exhaust gas purification means such as DPF. It is to improve the reliability of the reproduction conditions.

[Means of Claim 1]
The exhaust gas purification device according to claim 1 is provided with exhaust gas purification means for purifying exhaust gas discharged from the engine, and disposed downstream of the exhaust gas purification means in an exhaust gas exhaust passage, and the exhaust gas purification means. Oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas that has passed through the exhaust gas, and passage characteristic calculation means for calculating the passage characteristics of the exhaust gas in the exhaust gas purification means using the detection signal output from the oxygen concentration detection means Prepare.

  When the operating state of the engine is changed from a predetermined state to another state, the oxygen concentration of the exhaust gas is also switched from a value corresponding to the operating state before the change to a value corresponding to the operating state after the change. Then, downstream of the exhaust gas purification means, the time required for switching the oxygen concentration varies depending on the state of the exhaust gas purification means (for example, the degree of clogging). Therefore, the time required for switching the oxygen concentration downstream of the exhaust gas purification means and the physical quantity corresponding thereto can be regarded as a passage characteristic (hereinafter referred to as “switching of the oxygen concentration downstream of the exhaust gas purification means”). The time required and the physical quantity corresponding thereto are called “oxygen concentration switching characteristics”).

  Therefore, as in the above configuration, the oxygen concentration detection means is disposed downstream of the exhaust gas purification means in the exhaust gas exhaust passage, and the oxygen concentration detection means detects the oxygen concentration and outputs it from the oxygen concentration detection means. The oxygen concentration switching characteristic as the passage characteristic can be calculated using the detected signal. Thereby, in addition to the PM accumulation amount estimated based on the conventional differential pressure or the like, the oxygen concentration switching characteristic estimated based on the oxygen concentration downstream of the exhaust gas purification means can be newly estimated as the passage characteristic. . For this reason, the reliability of the reproduction conditions determined based on the estimation of the pass characteristic can be improved.

[Means of claim 2]
The passage characteristic calculated by the exhaust gas purifying apparatus according to claim 2 is an oxygen concentration when a predetermined reference time has elapsed since the operating state of the engine was changed.
This means shows one form of the oxygen concentration switching characteristic.

[Means of claim 3]
The passage characteristic calculated by the exhaust gas purification apparatus according to claim 3 is a time from when the operating state of the engine is changed to when the oxygen concentration reaches a predetermined reference value.
This means shows one form of the oxygen concentration switching characteristic.

[Means of claim 4]
The passage characteristic calculation means in the exhaust gas purifying apparatus according to claim 4 is characterized in that the passage characteristic is calculated when the operating state of the engine is changed from a combustion state in which the fuel is combusted to a non-combustion state in which the fuel is not combusted. Is calculated.
In the non-combustion state, the composition of the exhaust gas is the same as the composition of the atmosphere. Therefore, when the combustion state is changed to the non-combustion state, the final oxygen concentration becomes a known value, so that the oxygen concentration switching characteristic can be calculated extremely accurately.

[Means of claim 5]
The exhaust gas purifying means in the exhaust gas purifying apparatus according to claim 5 is a filter that collects particulates contained in the exhaust gas discharged from the diesel engine, and the exhaust gas purifying apparatus has a filter according to the passage characteristics. Change the playback conditions.
A filter that collects PM contained in exhaust gas discharged from a diesel engine, that is, regeneration of the DPF is performed by burning the collected PM. For this reason, in order to prevent the combustion heat from becoming excessive, regeneration is performed before the PM accumulation amount becomes excessive. Therefore, if the amount of accumulated PM is underestimated due to an erroneous estimation and regeneration is performed, an excessive amount of PM is actually burned, and the combustion heat may become excessive.
On the other hand, by adding a new oxygen concentration switching characteristic as a reference characteristic for determining the regeneration condition, the reliability of the regeneration condition based on the estimation of the passage characteristic can be improved. It is possible to reduce the concern.

[Means of claim 6]
The oxygen concentration detecting means in the exhaust gas purifying apparatus according to claim 6 detects the oxygen concentration of the exhaust gas recirculated in the intake passage of the intake air taken into the engine.
In order to reduce the nitrogen oxide content of the exhaust gas, an exhaust gas recirculation device (EGR device) that recirculates part of the exhaust gas to the intake air is provided. This EGR device also requires an oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas. Therefore, if the oxygen concentration detection means required in the EGR device is also used as the oxygen concentration detection means of the exhaust gas purification device, the exhaust gas with improved reliability of the regeneration conditions without newly installing equipment. A purification device can be constructed.

  The exhaust gas purifying device of the best mode 1 is disposed downstream of the exhaust gas purifying means in the exhaust gas purifying means for purifying exhaust gas exhausted from the engine, and the exhaust gas purifying means Oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas that has passed, and passage characteristic calculation means for calculating the passage characteristics of the exhaust gas in the exhaust gas purification means using a detection signal output from the oxygen concentration detection means. .

The passage characteristic is an oxygen concentration when a predetermined reference time has elapsed since the operating state of the engine is changed. The passage characteristic calculation means calculates the passage characteristic when the operating state of the engine is changed from a combustion state in which the fuel is combusted to a non-combustion state in which the fuel is not combusted.
The exhaust gas purification means is a filter that collects particulates contained in the exhaust gas discharged from the diesel engine, and the exhaust gas purification device changes the regeneration condition of the filter according to the passage characteristics.
The oxygen concentration detection means detects the oxygen concentration of the exhaust gas recirculated in the intake passage of the intake air taken into the engine.

  The passage characteristic of the exhaust gas purifying device of the best mode 2 is the time from when the engine operating state is changed until the oxygen concentration reaches a predetermined reference value.

[Configuration of Example 1]
The configuration of the exhaust gas purification apparatus 1 of Embodiment 1 will be described with reference to FIG. The exhaust gas purification apparatus 1 of Example 1 purifies exhaust gas exhausted from a diesel engine 2 (hereinafter referred to as the engine 2).

  As shown in FIG. 1, the engine 2 includes an injector 5 that injects fuel into the air compressed in the cylinder 4 and burns, an intake valve 7 that opens and closes between the intake passage 6 and the cylinder 4, and an exhaust passage 8. An exhaust valve 9 that opens and closes between the cylinder 4, a piston 10 that reciprocates the inside of the cylinder 4, sucks in intake air, compresses or expands exhaust gas, and exhausts, and reciprocates the piston 10. It has a well-known structure provided with a connecting rod 11 or the like that transmits to

  The exhaust gas purification device 1 is disposed downstream of the exhaust gas purification means 15 in the exhaust gas purification means 15 for purifying the exhaust gas discharged from the engine 2, and the exhaust gas purification means 15. Characteristic calculation for calculating the exhaust gas passage characteristic in the exhaust gas purification means 15 using the oxygen concentration detection means 16 for detecting the oxygen concentration of the exhaust gas that has passed through the exhaust gas and the detection signal output from the oxygen concentration detection means 16 Means 17.

  The exhaust gas purification means 15 is composed of a filter (DPF) that collects particulates (PM) generated by the combustion of fuel, and a catalyst that is disposed upstream or downstream of the filter and purifies nitrogen oxides and the like. . The PM collected by the DPF is burned under a regeneration condition determined based on the passage characteristic calculated by the passage characteristic calculating means 17, and thereby the DPF is regenerated. In addition, the combustion of PM operates heating means such as an electric heater or raises the temperature of exhaust gas by post injection (injecting and burning a small amount of fuel into the exhaust gas expanding in the cylinder 4). Can be executed.

  The oxygen concentration detection means 16 is a known oxygen sensor. The oxygen concentration detection means 16 constitutes an exhaust gas purification device 1 and an exhaust gas circulation device (EGR device) 19 that recirculates a part of the exhaust gas to the intake air. That is, an exhaust gas (EGR gas) passage (EGR passage) 20 that recirculates to the intake air branches from the exhaust passage 8 upstream of the exhaust gas purification means 15 and is connected to the intake passage 6. Further, an exhaust gas recirculation valve (EGR valve) 21 is disposed in the EGR passage 20. Then, the recirculation amount of the EGR gas is adjusted by controlling the opening degree of the EGR valve 21 according to the oxygen concentration detected by the oxygen concentration detecting means 16.

  The pass characteristic calculation unit 17 is configured as a part of the function of the ECU 23. The ECU 23 is a computer having a well-known structure including a CPU that performs control processing and arithmetic processing, storage means such as a ROM, RAM, EEPROM, and backup RAM that store various programs and data, an input circuit, an output circuit, and the like. The ECU 23 functions as the passage characteristic calculation unit 17 by calculating the passage characteristic of the exhaust gas in the exhaust gas purification unit 15 using the detection signal output from the oxygen concentration detection unit 16 with the above configuration. Then, the ECU 23 determines regeneration conditions such as the regeneration timing, heating time, and heating rate of the DPF so that the combustion heat due to the DPF regeneration does not become excessive based on the calculated passage characteristics.

  The passage characteristic calculation means 17 estimates the PM accumulation amount (PM accumulation amount) in the DPF based on the differential pressure between the inlet side and the outlet side of the exhaust gas purification means 15. That is, the passage characteristic calculation means 17 calculates the PM accumulation amount as one of the passage characteristics. The estimation of the PM accumulation amount is performed by using a detection signal output from the differential pressure sensor 24 disposed on the inlet side and the outlet side of the exhaust gas purification means 15.

  Further, the passage characteristic calculation means 17 estimates the oxygen concentration switching characteristic in addition to the estimation of the PM accumulation amount. That is, the passage characteristic calculation means 17 calculates the oxygen concentration switching characteristic as a passage characteristic different from the PM accumulation amount. Here, the oxygen concentration switching characteristic is the time required for switching the oxygen concentration and the physical quantity corresponding to the change in the operating state of the engine 2. Then, by estimating the oxygen concentration switching characteristic while monitoring the switching of the oxygen concentration downstream of the exhaust gas purification means 15, the oxygen concentration switching characteristic has a property as a passage characteristic. That is, the time required for switching the oxygen concentration varies depending on the state of the exhaust gas purification means 15 (for example, the degree of clogging in the DPF) downstream of the exhaust gas purification means 15.

  The oxygen concentration switching characteristic estimated in the first embodiment is an oxygen concentration when a predetermined reference time Tb has elapsed since the operating state of the engine 2 is changed. Here, the reference time Tb is the difference between the oxygen concentration before the operation state of the engine 2 is changed and the target oxygen concentration after the operation state of the engine 2 is changed, that is, the change of the operation state of the engine 2. It is determined according to the change width of the oxygen concentration accompanying the. The oxygen concentration switching characteristic is estimated when the operating state of the engine 2 is changed from a combustion state in which the fuel is combusted to a non-combustion state in which the fuel is not combusted. The time when the combustion state is changed to the non-burning state is, for example, when the accelerator is off.

  That is, as shown in FIG. 2, when the operating state of the engine 2 is changed from the accelerator on to the accelerator off, the oxygen concentration downstream of the exhaust gas purification means 15 changes from the initial value Ci according to the accelerator on to the value of the atmospheric state. It changes toward (atmospheric value Ca). However, this change does not occur in a step shape, and gradually changes from the initial value Ci toward the atmospheric value Ca, for example, as indicated by solid lines L1 and L2, according to the time constant according to the passage characteristics.

  The oxygen concentration switching characteristic is estimated as a measured value of the oxygen concentration when the reference time Tb has elapsed since the accelerator was turned off. For example, when the oxygen concentration changes as indicated by the solid line L1, the estimated value of the oxygen concentration switching characteristic is Ca, and when the oxygen concentration changes as indicated by the solid line L2, the estimated value of the oxygen concentration switching characteristic is C2.

  For such estimation of the oxygen concentration switching characteristic, a danger region D in which combustion heat due to DPF regeneration may be excessive is set. For example, if the oxygen concentration when the reference time Tb elapses after the accelerator is off is greater than the reference value Cb that defines the upper limit on the oxygen concentration axis side of the dangerous region D, such as Ca in the solid line L1, the oxygen concentration is in the dangerous region. The atmospheric value Ca is reached without passing through D. For this reason, it is determined that there is no possibility of excessive combustion heat due to DPF regeneration, and regeneration conditions are determined based on this determination. Here, the reference value Cb is the difference between the oxygen concentration in the accelerator-on state and the target oxygen concentration after the accelerator is off (that is, the atmospheric value Ca), that is, the change range of the oxygen concentration accompanying the change in the operating state of the engine 2. It is decided according to.

  On the other hand, if the oxygen concentration when the reference time Tb elapses after the accelerator is off is smaller than the reference value Cb as indicated by C2 in the solid line L2, the oxygen concentration passes through the danger region D and reaches the atmospheric value Ca. . For this reason, it is determined that the combustion heat due to DPF regeneration may be excessive, and the regeneration condition is determined based on this determination.

[Control Method of Example 1]
A control method of exhaust gas purification by the exhaust gas purification device 1 of Embodiment 1 will be described with reference to a flowchart shown in FIG.
First, in step S1, it is determined whether or not a condition (estimable condition) for which the pass characteristic may be estimated is satisfied. This estimable condition is that the operating state of the engine 2 changes from accelerator on to accelerator off. If the estimable condition is satisfied (YES), the process proceeds to step S2. If the estimable condition is not satisfied (NO), the process is terminated.

Next, in step S2, it is determined whether or not the reference time Tb has elapsed since the accelerator was turned off. If the reference time Tb has elapsed since the accelerator was turned off (YES), the process proceeds to step S3. If the reference time Tb has not elapsed since the accelerator was turned off (NO), the process waits until it elapses.
In step S 3, the oxygen concentration is detected by the oxygen concentration detection unit 16, and the oxygen concentration is measured using the detection signal output from the oxygen concentration detection unit 16.

  Next, in step S4, it is determined whether or not the measured value of the oxygen concentration is equal to or less than the reference value Cb. If the measured value is less than or equal to the reference value Cb (YES), the process proceeds to step S5. If the measured value is greater than the reference value Cb (NO), the process proceeds to step S6.

  In step S5, the abnormal mode is selected as the DPF regeneration condition, and in step S6, the normal mode is selected as the DPF regeneration condition. Here, the normal mode is a uniform regeneration condition set to burn out all PMs based on the determination that there is no risk of excessive combustion heat. In addition, the abnormal mode is based on the determination that the combustion heat may be excessive, and the regeneration condition is set so that the combustion becomes slower than the normal mode in order to prevent the DPF from overheating due to the excessive combustion heat. It is.

[Effect of Example 1]
The exhaust gas purification apparatus 1 according to the first embodiment is disposed downstream of the exhaust gas purification means 15 in the exhaust gas exhaust passage 8 and detects the oxygen concentration of the exhaust gas that has passed through the exhaust gas purification means 15. Means 16 and passage characteristic calculation means 17 for calculating an oxygen concentration switching characteristic as the passage characteristic of the exhaust gas in the exhaust gas purification means 15 using the detection signal output from the oxygen concentration detection means 16. Then, the exhaust gas purification device 1 calculates the oxygen concentration when the reference time Tb has elapsed since the operating state of the engine 2 was changed as the oxygen concentration switching characteristic.

  When the operating state of the engine 2 is changed from a predetermined state to another state, the oxygen concentration of the exhaust gas is also switched from a value corresponding to the operating state before the change to a value corresponding to the operating state after the change. Then, downstream of the exhaust gas purification means 15, the time required for switching the oxygen concentration varies depending on the state of the exhaust gas purification means 15 (for example, the degree of clogging). Therefore, the oxygen concentration switching characteristic downstream of the exhaust gas purification means 15 can be regarded as a passage characteristic.

  Therefore, as described above, the oxygen concentration detection means 16 is disposed downstream of the exhaust gas purification means 15 in the exhaust passage 8, and the oxygen concentration is detected by the oxygen concentration detection means 16. It is possible to calculate the oxygen concentration switching characteristic as the pass characteristic. Thereby, in addition to the conventional PM accumulation amount based on the differential pressure or the like, the oxygen concentration switching characteristic based on the oxygen concentration downstream of the exhaust gas purification means 15 can be newly estimated as the passage characteristic. For this reason, the reliability of the reproduction conditions based on the estimation of the pass characteristic can be improved.

The passage characteristic calculation means 17 calculates the oxygen concentration switching characteristic when the operating state of the engine 2 is changed from accelerator on to accelerator off.
The accelerator off state is a non-combustion state, and the composition of the exhaust gas is the same as the composition of the atmosphere. Therefore, when the operating state of the engine 2 is changed from accelerator on to accelerator off, the final oxygen concentration becomes a known value, so that the oxygen concentration switching characteristic can be calculated very accurately.

The exhaust gas purification means 15 incorporates a DPF as one of the components.
The regeneration of the DPF is performed by burning the collected PM. For this reason, in order to prevent the combustion heat from becoming excessive, regeneration is performed before the PM accumulation amount becomes excessive. For this reason, if the amount of accumulated PM as a passing characteristic is excessively estimated due to erroneous estimation and regeneration is performed, an excessive amount of PM is actually burned, and the combustion heat may be excessive.
On the other hand, since the reliability of the regeneration condition based on the estimation of the passage characteristic can be improved by newly adding the oxygen concentration switching characteristic as the passage characteristic serving as the reference of the regeneration condition, there is a possibility of the above Can be reduced.

The oxygen concentration detection means 16 detects the oxygen concentration of the EGR gas that is recirculated to the intake passage 6 for the intake air drawn into the engine 2.
In order to reduce the nitrogen oxide content of the exhaust gas, an EGR device 19 for recirculating a part of the exhaust gas to the intake air is provided. This EGR device 19 also requires the oxygen concentration detection means 16 in order to detect the oxygen concentration of the EGR gas. Therefore, if the oxygen concentration detection means 16 required in the EGR device 19 is also used as the oxygen concentration detection means 16 of the exhaust gas purification device 1, the reliability of the regeneration conditions can be improved without newly installing equipment. An improved exhaust gas purification device 1 can be configured.

[Configuration of Example 2]
The oxygen concentration switching characteristic estimated in the second embodiment is the time from when the operating state of the engine 2 is changed until the oxygen concentration reaches the reference value Cb. As in the first embodiment, the oxygen concentration switching characteristic is estimated when the accelerator is off. The oxygen concentration is gradually increased from the initial value Ci as indicated by solid lines L3 and L4 shown in FIG. It changes toward the atmospheric value Ca.

  The oxygen concentration switching characteristic is estimated as a count value of the time from when the accelerator is turned off until the oxygen concentration reaches the reference value Cb. For example, when the oxygen concentration changes as indicated by a solid line L3, the estimated value of the oxygen concentration switching characteristic is T3, and when the oxygen concentration changes as indicated by a solid line L4, the estimated value of the oxygen concentration switching characteristic is T4.

  For such estimation of the oxygen concentration switching characteristic, a dangerous region D similar to that in the first embodiment is set. For example, if the time from when the accelerator is off until the oxygen concentration reaches the reference value Cb is shorter than the reference time Tb corresponding to the lower limit on the time axis side of the danger region D, as indicated by T3 in the solid line L3, the oxygen concentration is The atmospheric value Ca is reached without passing through the dangerous area D. For this reason, it is determined that there is no possibility of excessive combustion heat due to DPF regeneration, and regeneration conditions are determined based on this determination.

  On the other hand, if the time from when the accelerator is off until the oxygen concentration reaches the reference value Cb is longer than the reference time Tb as indicated by T4 in the solid line L4, the oxygen concentration passes through the danger region D and reaches the atmospheric value Ca. To reach. For this reason, it is determined that the combustion heat due to DPF regeneration may be excessive, and the regeneration condition is determined based on this determination.

[Control Method of Example 2]
A control method of exhaust gas purification by the exhaust gas purification device 1 of Embodiment 2 will be described with reference to a flowchart shown in FIG.
First, in step S11, it is determined whether or not a condition (estimable condition) where the pass characteristic may be estimated is satisfied. This estimable condition is that the operating state of the engine 2 changes from accelerator on to accelerator off. If the estimable condition is satisfied (YES), the process proceeds to step S12. If the estimable condition is not satisfied (NO), the process ends.

  Next, in step S12, time counting is started. In step S13, it is determined whether or not the oxygen concentration has reached the reference value Cb. The oxygen concentration is detected by the oxygen concentration detecting means 16 and the oxygen concentration is measured using the detection signal output from the oxygen concentration detecting means 16. If the oxygen concentration reaches the reference value Cb (YES), the process proceeds to step S14. If the oxygen concentration has not reached the reference value Cb (NO), the process waits until it reaches. In step S14, the time counting ends.

  Next, in step S15, it is determined whether or not the time count value is larger than the reference time Tb. If the count value is equal to or greater than the reference time Tb (YES), the process proceeds to step S16. If the count value is smaller than the reference time Tb (NO), the process proceeds to step S17. In step S16, the abnormal mode is selected as the DPF regeneration condition. In step S17, the normal mode is selected as the DPF regeneration condition.

[Modification]
Although the oxygen concentration switching characteristics of the present embodiment were estimated when the accelerator was off, if the state change of the engine 2 is such that the oxygen concentration becomes a steady value before and after switching, it is not limited by the state change state. For example, even when the oxygen concentration decreases and stabilizes at a steady value, the oxygen concentration switching characteristics can be estimated.

  The oxygen concentration switching characteristics of this embodiment were used to determine the regeneration conditions of the exhaust gas purification means 15 such as DPF, but should be used to estimate the shape stability of the catalyst such as cracking and melting. You can also. When performing regeneration in the abnormal mode, the operating condition of the engine 2 may be switched to a condition for performing a specific safe traveling (for example, retreat traveling).

  In this embodiment, the oxygen concentration reference value Cb and the reference time Tb for selecting the abnormal mode or the normal mode are determined according to the change range of the oxygen concentration accompanying the change in the operating state of the engine 2. For example, it is stored as a map of the differential pressure between the inlet side and the outlet side of the exhaust gas purification means 15 when the accelerator is off, the actual injection amount, the engine speed, etc., and the differential pressure, the actual injection amount, the engine speed, etc. It can also be changed according to. Further, this map can be corrected according to the deterioration with time of the oxygen concentration detection means 16 or the like.

Although the exhaust gas purification means 15 of the present embodiment is composed of DPF and a catalyst, it may be a catalyst alone or a DPF alone.
In the present embodiment, the passage characteristic (other passage characteristics) estimated in addition to the oxygen concentration switching characteristic is the PM accumulation amount estimated based on the differential pressure between the inlet side and the outlet side of the exhaust gas purification means 15. For example, the PM accumulation amount estimated based on the actual injection amount and the engine speed may be substituted for other passage characteristics, or may be added as other passage characteristics.
Although the exhaust gas purification apparatus 1 of the present embodiment is applied to the purification of exhaust gas from a diesel engine, it can also be applied to the case of purifying exhaust gas from a gasoline engine.

1 is a configuration diagram of an exhaust gas purification device (Example 1). FIG. (A) is a time chart which shows the state of an accelerator, (b) is a time chart which shows transition of oxygen concentration (Example 1). 3 is a flowchart showing processing by an exhaust gas purification device (Example 1). (A) is a time chart which shows the state of an accelerator, (b) is a time chart which shows transition of oxygen concentration (Example 2). 10 is a flowchart showing processing by an exhaust gas purification device (Example 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2 Diesel engine, engine 6 Intake passage 8 Exhaust passage 15 Exhaust gas purification means 16 Oxygen concentration detection means 17 Passage characteristic calculation means Tb Reference time Cb Reference value

Claims (6)

Exhaust gas purification means for purifying exhaust gas discharged from the engine;
An oxygen concentration detection unit that is disposed downstream of the exhaust gas purification unit in the exhaust passage of the exhaust gas and detects an oxygen concentration of the exhaust gas that has passed through the exhaust gas purification unit;
An exhaust gas purification apparatus comprising: passage characteristic calculation means for calculating a passage characteristic of exhaust gas in the exhaust gas purification means using a detection signal output from the oxygen concentration detection means. The exhaust gas purification device according to claim 1,
The exhaust gas purifying device according to claim 1, wherein the passage characteristic is an oxygen concentration when a predetermined reference time has elapsed after the operating state of the engine is changed. The exhaust gas purification device according to claim 1,
The exhaust gas purification device according to claim 1, wherein the passage characteristic is a time from when the operating state of the engine is changed to when the oxygen concentration reaches a predetermined reference value. The exhaust gas purification device according to claim 2 or claim 3,
The passage characteristic calculation means calculates the passage characteristic when the operating state of the engine is changed from a combustion state in which fuel is combusted to a non-combustion state in which fuel is not combusted. Exhaust gas purification device. The exhaust gas purification device according to claim 1,
The exhaust gas purification means is a filter that collects particulates contained in exhaust gas discharged from a diesel engine,
An exhaust gas purifying apparatus, wherein a regeneration condition of the filter is changed according to the passage characteristic. The exhaust gas purification device according to claim 1,
The exhaust gas purifying apparatus according to claim 1, wherein the oxygen concentration detecting means detects an oxygen concentration of exhaust gas recirculated in an intake passage of intake air sucked into the engine.

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