CN110344919B

CN110344919B - Exhaust gas purification device

Info

Publication number: CN110344919B
Application number: CN201910275463.1A
Authority: CN
Inventors: 津田丰史
Original assignee: Suzuki Motor Corp
Current assignee: Suzuki Motor Corp
Priority date: 2018-04-05
Filing date: 2019-04-08
Publication date: 2021-06-25
Anticipated expiration: 2039-04-08
Also published as: JP7125664B2; JP2019183703A; CN110344919A

Abstract

Provided is an exhaust gas purification device capable of reducing the frequency of rich purification and minimizing NOx emission and fuel consumption. An exhaust gas purification apparatus includes a catalyst device disposed in an exhaust gas passage discharged from an internal combustion engine, wherein a three-way catalyst device using a three-way catalyst converter is disposed in the exhaust gas passage, and an occlusion reduction type NOx catalyst device using an occlusion reduction type NOx catalyst converter is disposed on a downstream side of the three-way catalyst device, and wherein the three-way catalyst device is configured such that a low performance OSC material is provided along a longitudinal direction from an inlet to an outlet in a part of a surface orthogonal to an exhaust gas flow, and the low performance OSC material generates a low performance portion in accordance with the low performance portion in the occlusion reduction type NOx catalyst converter disposed on the downstream side of the three-way catalyst converter, and an exhaust NOx amount detection mechanism that estimates or detects an amount of exhaust NOx discharged from the internal combustion engine is provided on the downstream side in an exhaust gas flow direction of the occlusion reduction type NOx catalyst device.

Description

Exhaust gas purification device

Technical Field

The present invention relates to an exhaust gas purification apparatus for an internal combustion engine.

Background

The NOx occlusion catalytic converter is an occlusion type NOx catalytic converter that absorbs NOx (nitrogen oxide) in exhaust gas when the exhaust gas air-fuel ratio is lean (lean) and releases and reduces the occluded NOx when the exhaust gas air-fuel ratio is excessively rich (rich). An occlusion amount estimation device and an estimation method for an NOx occlusion catalytic converter are known as follows (see patent document 1): in the estimation of the NOx occlusion amount of the NOx occluding catalytic converter, the NOx occlusion amount including the NOx occlusion amount remaining in the NOx occluding catalytic converter can be grasped more accurately by the catalytic converter occluding model taking into account the catalytic converter temperature and the flow rate of the exhaust gas at the start time point of the rich operation and the end time point of the rich operation.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2004-270469

Disclosure of Invention

Problems to be solved by the invention

In general, an NOx storage catalytic converter used in an exhaust gas purification apparatus can remove NOx from lean exhaust gas by storing NOx as nitrates, and can store NOx again by switching the exhaust gas air-fuel ratio to rich and reducing and purifying the stored NOx (rich purification for storing NOx). However, in the rich purge for storing NOx, there is a problem that the stored NOx is discharged in a spike (spike) state without being purged at the initial stage of the rich purge. It is known that the amount of spike NOx emission increases as the NOx occlusion amount at the start of rich spike is closer to saturation.

In an internal combustion engine, in order to suppress the NOx emission amount, it is necessary to suppress the emission amount of spike NOx at the initial stage of rich spike purification as low as possible. Therefore, it is necessary to start the rich purge sufficiently early before the NOx occlusion amount reaches saturation.

On the other hand, since the rich purge is an operation using an excessive amount of fuel, if the rich purge is frequently performed, the fuel consumption is significantly deteriorated. Therefore, it is desirable to reduce the number of times of the rich purge as much as possible. In an internal combustion engine, in order to prevent deterioration of fuel consumption while keeping the NOx emission amount low, it is desirable to perform rich purging at a point in time when the NOx is stored up to the upper limit of the allowable storage amount.

The current mainstream is to arrange an NOx sensor at the rear stage of an NOx occluding catalytic converter provided in the exhaust pipe of an internal combustion engine, and start rich purification at the time point when the NOx sensor detects NOx. However, the NOx sensor has a large detection error for NOx having a low concentration of 50ppm or less, and 50ppm can be said to be the lower limit of detection of the NOx sensor. Thus, there is the possibility of: at the time point when NOx is detected by the NOx sensor, the upper limit of the allowable occlusion amount described above is exceeded, and a large amount of NOx is released in a spike-like manner in a state where it is not purified at the initial stage of the subsequent rich purification.

This is schematically shown in fig. 5. In fig. 5, X to D respectively show the NOx concentrations in the exhaust gas (outgoing gas) after passing through the NOx occluding catalytic converter. In the case where there is no rich purge, the NOx concentration is very low before the NOx occlusion capacity fails, and the NOx concentration increases after the failure to become approximately equal to the concentration in the intake gas, as indicated by X. When the rich purge is performed, as in A, B, C, when the rich purge is started at a time point (t is ta, tb, tc) when the NOx storage rate is low, the spike NOx discharge amount is suppressed to be low. When the rich purge is started at a time point (t td) when the NOx storage capacity is lost and the downstream NOx sensor detects NOx as in D, a large amount of spike NOx is discharged. Therefore, the NOx emission amounts are D > C > B > A.

On the other hand, the frequency of the rich purge is such that D is the lowest and A is the highest. Therefore, the range of deterioration of fuel consumption due to rich purge is A > B > C > D.

Here, it is assumed that an upper limit (for example, a vehicle destination NOx emission amount limit) for the NOx emission amount is set, C is less than the upper limit, and D exceeds the upper limit. In this case, D is not considered, A, B, C is allowed, and C is optimal in terms of fuel consumption. However, even if it is desired to start the rich purge at the optimum timing (t ═ tc as in C), the NOx sensor cannot sufficiently detect NOx, and therefore the ECU cannot accurately grasp the optimum timing at which the rich purge should be started. Therefore, the rich purge can only be started earlier than the optimum timing like A, B at the sacrifice of fuel consumption.

In order to cope with the exhaust gas restriction and the fuel consumption restriction which become stricter in the future, it is necessary to make the ECU reliably grasp the optimum rich purge start timing.

However, as disclosed in patent document 1, the ECU can calculate the NOx storage amount of the NOx storage catalytic converter. Therefore, it is conceivable that the rich purge may be started at the timing estimated as the optimum timing described above. However, when the operating state of the engine changes every moment, it is extremely difficult to accurately grasp the NOx occlusion amount by calculation alone, and therefore, either the NOx purification rate or the fuel consumption is inferior to the ideal value.

An object of the present invention is to provide an exhaust gas purification device capable of reducing the frequency of rich purification and suppressing the NOx emission amount and fuel consumption to minimum.

Means for solving the problems

In order to solve the above-described problems, the present invention is an exhaust gas purification apparatus including a catalyst device disposed in an exhaust gas passage discharged from an internal combustion engine, wherein a three-way catalyst device using a three-way catalyst converter is disposed in the exhaust gas passage, and an occlusion reduction type NOx catalyst device using an occlusion reduction type NOx catalyst converter is disposed on a downstream side of the three-way catalyst device, and wherein the three-way catalyst device is configured such that a low performance OSC material having a relatively low oxygen Storage capacity is provided along a longitudinal direction from an inlet to an outlet in a part of a surface orthogonal to an exhaust gas flow, and the low performance OSC material causes the occlusion reduction type NOx catalyst converter disposed on the downstream side of the three-way catalyst converter to generate a portion having the same low performance as that of the low performance OSC material on the downstream side in the exhaust gas flow direction of the occlusion reduction type NOx catalyst device, an exhaust NOx amount detection mechanism is provided that estimates or detects the amount of exhaust NOx discharged from the internal combustion engine.

Effects of the invention

According to the present invention, the NOx failure preferentially occurs from the viewpoint of the low-performance NOx occluding catalytic converter. The NOx failure occurs from the viewpoint of the low performance portion, and is detected by a NOx amount detecting mechanism, i.e., a NOx sensor, provided at the rear stage of the catalytic converter. Therefore, by adjusting the proportion of the low performance OSC portion in the end face of the three-way catalytic converter and the OSC capacity of the low performance OSC portion at a low temperature so that the low performance NOx occluding and catalytic converter fails at an optimum timing at which the rich purging should be started, it is possible to detect the NOx concentration in the exhaust gas at the time point at which NOx becomes detectable and the time until the low performance NOx occluding and catalytic converter fails by the NOx amount detecting mechanism arranged downstream of the catalytic converter.

Therefore, the ECU can accurately grasp the optimum timing at which the rich purge should be started, using the NOx sensor. Therefore, it is possible to suppress the fuel consumption loss to the minimum by rich purification, and quickly reduce and purify the NOx occluded in the catalytic converter.

Drawings

Fig. 1 is a conceptual diagram showing an exhaust purification apparatus in which an occlusion reduction type NOx catalytic converter is provided on the downstream side of a three-way catalytic converter in an exhaust passage provided in an exhaust pipe or the like of an internal combustion engine according to an embodiment of the present invention, and (a) is a conceptual diagram showing an exhaust purification apparatus in which an OSC portion having relatively low-temperature activity is provided in a part of a three-way catalytic converter. (b) Is a conceptual diagram showing a state where the low performance NOx occluding and catalytic converter is formed on the downstream side of the OSC portion due to the flow of the exhaust gas.

Fig. 2 is a system conceptual diagram showing an outline of a system in which a three-way catalytic converter is further provided upstream of an exhaust gas purification device in which an occlusion reduction type NOx catalytic converter is provided on the downstream side of the three-way catalytic converter.

Fig. 3 is a conceptual diagram of an NOx storage reduction catalytic converter provided on the downstream side of a three-way catalytic converter.

Fig. 4 is a characteristic diagram showing the NOx concentration in the exhaust gas after passing through the exhaust gas purification apparatus of the present invention.

Fig. 5 shows the NOx concentration in the exhaust gas (outgoing gas) after passing through the NOx occluding catalytic converter.

Description of the reference numerals

1 exhaust gas purification device

1A exhaust gas purifying apparatus (catalytic apparatus) including three-way catalytic converter

1B exhaust gas purifying apparatus (catalytic apparatus) comprising NOx occlusion reduction catalytic converter

2 exhaust gas passage

2a enlargement part

3 three-way catalytic converter

4 NOx storage catalytic converter

5A Low Performance OSC materials (Low Performance moieties)

5B View Low Performance NOx occluding and catalytic converter (View Low Performance portion)

6 NOx amount detection mechanism (NOx sensor).

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the drawings shown in fig. 1 to 4.

Fig. 1 (a) shows an exhaust gas purification apparatus 1 provided in an exhaust gas passage 2 of an exhaust pipe of an internal combustion engine such as a gasoline engine. An enlarged portion 2a having an enlarged diameter in the middle is provided in an exhaust passage 2 of an exhaust pipe or the like, and an exhaust gas purifying device 1 is provided in the enlarged portion 2 a.

The exhaust gas purification device 1 includes: an exhaust gas purification device (three-way catalyst device using a three-way catalyst converter) 1A including a three-way catalyst converter 3 disposed at the front in the exhaust gas flow direction; and an exhaust gas purification apparatus (an occlusion reduction type NOx catalytic apparatus using an NOx occlusion catalytic converter) 1B including an occlusion reduction type NOx catalytic converter (hereinafter referred to as an NOx occlusion catalytic converter) 4 disposed on the rear side of the exhaust gas purification apparatus 1A including the three-way catalytic converter 3. The three-way catalytic converter 3 is used for simultaneously oxidizing or reducing and removing hydrocarbons, carbon monoxide, and nitrogen oxides contained in exhaust gas, and is formed by atomizing noble metals such as platinum, palladium, and rhodium and attaching the atomized noble metals to the surface of a carrier. The three-way catalytic converter 3 is configured such that a portion (low performance portion) 5A having a relatively low temperature activity of an Oxygen Storage/release Capacity OSC (Oxygen Storage Capacity) is provided along a longitudinal direction from an inlet to an outlet in a part of a surface orthogonal to the exhaust gas flow, and an apparent low performance portion 5B is generated in the occlusion-reduction type NOx catalytic converter 4 disposed on the downstream side of the three-way catalytic converter 3. The above-described three-way catalytic converter 3 includes a honeycomb structure composed of a plurality of cells (cells), which is composed mostly of a basic OSC material, and is provided at a portion thereof with a portion (low-performance OSC portion) 5A where the low-temperature activity of OSC is relatively low. The low-performance OSC portion 5A can be formed by making the noble metal supporting amount in a part thereof smaller than that in the base portion. Reference numeral 6 denotes an NOx sensor as NOx amount detection means provided in the exhaust passage 2 at the rear stage of the exhaust gas purification apparatus 1B. The occlusion-reduction type NOx catalytic converter 4 is disposed on the downstream side of the rear face of the three-way catalytic converter 3 so as to face the three-way catalytic converter 3, and includes a honeycomb structure composed of a plurality of cells. As shown in fig. 1 (B), a portion that partially behaves like a low-performance NOx occlusion catalytic converter (hereinafter referred to as the low-performance NOx occlusion catalytic converter 5B) is formed in the occlusion reduction type NOx catalytic converter 4 located on the rear surface side of the low-performance OSC portion 5A of the three-way catalytic converter 3.

Fig. 2 shows the configuration of an exhaust gas purification apparatus 1 mounted to an actual internal combustion engine.

It is provided with: an exhaust gas purification device 1A that includes a three-way catalytic converter 3; and an exhaust gas purification device 1A₂An exhaust gas passage 2 including another three-way catalytic converter 3 on the upstream side of an exhaust gas purification apparatus 1B including an occlusion-reduction type NOx catalytic converter 4₂. 7 is a gasoline engine. Comprising a three-way catalytic converter 3₂Exhaust gas purifying device 1A₂Is an engine direct-under catalytic converter disposed directly below the engine, and the exhaust gas purification apparatus 1 is an underfloor catalytic converter. Comprising a further three-way catalytic converter 3₂Exhaust gas purifying device 1A₂Provided for exhaust gas at the start of the gasoline engine 7.

Next, the operation of the present invention will be described with reference to fig. 3 and 4.

As shown in fig. 3, a portion of a site (referred to as a low-performance NOx occluding and catalytic converter) 5B which appears like a low-performance NOx occluding and catalytic converter is formed on the downstream side of the low-performance OSC material 5A in the NOx occluding and catalytic converter 4.

As shown by the Y waveform of fig. 4, the low performance NOx occluding catalytic converter 5B fails before the basic NOx occluding catalytic converter 4 fails. That is, two levels of failure occur: before the basic NOx occluding catalytic converter 4 fails, the NOx occluding catalytic converter 5B regarded as low performance first fails at the level of C1 on the downstream side of the catalytic converter, and then the basic NOx occluding catalytic converter 4 fails at the level of C2. That is, NOx can be detected with the NOx sensor 6 on the downstream side of the catalytic converter before the basic NOx occluding catalytic converter 4 fails.

Therefore, for example, if it is adjusted so that t ═ tc, which is the optimum timing at which the rich purge should be started, fails depending on the low-performance NOx occluding catalytic converter 5B as shown in E in fig. 4, there is obtained an effect that the electronic control unit ECU can accurately grasp the optimum timing at which the rich purge should be started, using the NOx sensor 6.

When a transition from the rich purge or stoichiometric operation shown in fig. 1 (a) to the lean state shown in fig. 1 (b) is considered, the stoichiometric exhaust gas rather than the lean exhaust gas flows into the NOx storing catalytic converter 4 for a certain period from the transition due to the OSC function of the three-way catalytic converter 3. This is because the three-way catalytic converter 3 occludes excess oxygen for the theoretical ratio. Therefore, the larger the oxygen storage capacity of the three-way catalytic converter 3 is, the longer the period during which the stoichiometric exhaust gas flows into the NOx storage catalytic converter 4 after the shift to lean becomes. In the present invention, by replacing a part of the three-way catalytic converter 3 with the low-performance OSC material 5A, the period during which the stoichiometric exhaust gas flows after the transition to lean is shortened only downstream of the low-performance OSC material 5A. In other words, since the NOx occluding catalytic converter 4 downstream of the low performance OSC material 5A starts to occlude NOx earlier than other portions, the amount of NOx which can be occluded until the failure is smaller than other portions at the time point when the entire NOx occluding catalytic converter 4 starts to occlude NOx. That is, a portion that can be regarded as the low-performance NOx occluding and catalytic converter 5B is formed downstream of the low-performance OSC material 5A (see fig. 1 (B)).

Further, the low performance OSC material 5A has low temperature activity, and therefore, the amount of oxygen that can be occluded in a low temperature exhaust gas such as during lean burn operation is smaller than that of the basic OSC material, but when the temperature is sufficiently high, the OSC capacity becomes large. Therefore, even though the low performance OSC material 5A is mentioned, it shows an OSC activity at a high engine load operation at a theoretical ratio not inferior to that of the basic OSC material 3, and therefore, the underfloor three-way catalytic converter shows a sufficiently high NOx purification rate. That is, when the underfloor three-way catalytic converter is to function as a purification device, there is no particular problem in replacing a part of the low-performance OSC material 5A.

The proportion occupied by the low performance OSC material 5A in the end faces of the three-way catalytic converter 3 can be adjusted by adjusting the proportion occupied by the low performance NOx occluding and catalytic converter 5B, and the apparent NOx occluding capacity (the amount of NOx that can be occluded from the start of occlusion of NOx by the apparent low performance NOx occluding and catalytic converter 5B to the time of failure of the apparent low performance NOx occluding and catalytic converter 5B) of the apparent low performance NOx occluding and catalytic converter 5B can be adjusted by adjusting the OSC capacity of the low performance OSC material 5A at low temperature. Further, the NOx concentration in the exhaust gas at the time when the NOx sensor 6 becomes able to detect NOx can be adjusted by adjusting the proportion of the compatible low performance NOx storage catalytic converter 5B, and the time until the compatible low performance NOx storage catalytic converter 5B fails can be adjusted by adjusting the compatible NOx storage capacity. Therefore, for example, as shown by E in fig. 4, if it is adjusted so that the NOx occluding and catalytic converter 5B fails at t ═ tc, which is the optimum timing at which the rich purge should be started, as viewed from the low performance, the ECU can accurately grasp the optimum timing at which the rich purge should be started, by the NOx sensor 6.

According to the above embodiment, as shown in fig. 1 (a), the exhaust gas purification apparatus 1 includes a catalytic converter disposed in an exhaust gas passage 2 from an internal combustion engine, wherein the exhaust gas purification apparatus 1A including a three-way catalytic converter 3 is disposed in the exhaust gas passage 2, and the exhaust gas purification apparatus 1B including an NOx storage reduction catalytic converter 4 is disposed downstream of the three-way catalytic converter 3. The three-way catalytic converter 3 is provided with a portion (low-performance portion) 5A having a relatively low-temperature activity of the oxygen Storage release capacity osc (oxygen Storage capacity) in a portion of a surface perpendicular to the exhaust gas flow indicated by an arrow along a longitudinal direction from the inlet to the outlet. As shown in fig. 1 (B), the NOx storage-reduction catalytic converter 4 disposed on the downstream side of the three-way catalytic converter 3 is configured to generate the visually low-performance portion 5B. In this way, the NOx sensor 6 as the exhaust NOx amount detecting means is provided on the downstream side in the exhaust gas flow direction of the occlusion reduction type NOx catalytic converter 4 to estimate or detect the amount of exhaust NOx discharged from the internal combustion engine, and therefore, the following effects can be obtained.

The NOx failure occurs preferentially from the viewpoint of the NOx occluding catalytic converter 5B. The NOx failure occurs from the viewpoint of the low performance portion 5B, and is detected by the NOx amount detecting mechanism, i.e., the NOx sensor 6, provided at the rear stage of the catalytic converter. Therefore, by adjusting the proportion of the low-performance OSC portion 5A in the end face of the three-way catalytic converter 3 and the OSC capacity of the low-performance OSC portion 5A at a low temperature so that the low-performance NOx occluding and catalytic converter 5B fails at an optimum timing at which the rich purification should be started, it is possible to detect the NOx concentration in the exhaust gas at a point in time when it becomes possible to detect NOx and the time until the low-performance NOx occluding and catalytic converter 5B fails by means of the NOx amount detecting mechanism arranged downstream of the catalytic converter.

Therefore, the ECU can accurately grasp the optimum timing at which the rich purge should be started, using the NOx sensor 6. Therefore, it is possible to suppress the fuel consumption loss to the minimum by rich purification, and quickly reduce and purify the NOx occluded in the catalytic converter.

The low performance OSC material 5A is configured to have an increased OSC capacity at 500 ℃ to 900 ℃ inclusive, and therefore can exhibit an OSC activity equivalent to that of the basic OSC material at the time of a stoichiometric engine high load operation. Therefore, a sufficiently high NOx purification rate can be obtained also in the combination of the low performance OSC portion 5A and the NOx storage catalytic converter 4.

Since the amount of noble metal supported in the low performance OSC material 5A is reduced by 10 to 40% as compared with the other portions, the apparent NOx storage capacity of the apparent low performance NOx storage catalytic converter 5B (the amount of NOx which can be stored from when the apparent low performance NOx storage catalytic converter 5B starts storing NOx to when the apparent low performance NOx storage catalytic converter 5B fails) can be adjusted by adjusting the OSC capacity.

In the present invention, the heat treatment temperature of the low performance OSC material 5A can be set higher than other portions.

The proportion of the low-performance OSC material 5A in the area of the end faces of the entire catalytic converter can be set to 5 to 12%.

The cell density of the honeycomb structure in the above-described low-performance OSC material 5A can be set smaller than the basal part.

On the upstream side of the three-way catalytic converter 3 and the NOx storage reduction catalytic converter 4 disposed in the exhaust gas passage 2, the three-way catalytic converter 3 can be further disposed₂。

The exhaust NOx amount detection means may detect the amount of NOx in the exhaust NOx amount, and the fuel injection means may be configured to inject the fuel quickly.

Industrial applicability of the invention

The present invention is not limited to the above-described embodiments, and can be carried out, for example, by exposing only a part of the low performance OSC material (low performance portion) 5A provided in the three-way catalytic converter 3 to a high temperature of about 950 ℃.

Claims

1. An exhaust gas purification device (1) comprising a catalyst device disposed in an exhaust gas passage (2) for exhaust gas discharged from an internal combustion engine,

an expansion part (2a) with an expanded diameter at the middle part is arranged on the exhaust passage (2),

the exhaust gas purification device (1) disposed in the enlarged portion (2a) is provided with a three-way catalyst device (1A) using a three-way catalyst converter (3), and an occlusion-reduction type NOx catalyst device (1B) located on the downstream side of the three-way catalyst device (1A) and using an occlusion-reduction type NOx catalyst converter (4), and is configured so that the occlusion-reduction type NOx catalyst converter (4) is disposed on the downstream side of the rear face of the three-way catalyst converter (3) so as to face the three-way catalyst converter (3),

the three-way catalytic device (1A) is configured such that a low performance OSC material (5A) having a relatively low OSC low temperature activity is provided along a longitudinal direction from an inlet of the three-way catalytic converter (3) to an outlet of the three-way catalytic converter (3) in a part of a surface of the three-way catalytic converter (3) perpendicular to an exhaust gas flow, whereby an apparently low performance NOx occlusion catalytic converter (5B) located downstream of the low performance OSC material (5A) is generated in the occlusion reduction type NOx catalytic converter (4),

the above-described occlusion reduction type NOx catalytic converter (5B) is generated so as to start occlusion of NOx earlier than the other portions of the occlusion reduction type NOx catalytic converter (4), thereby making the amount of NOx which can be occluded until failure smaller than the other portions of the occlusion reduction type NOx catalytic converter (4) when the whole occlusion reduction type NOx catalytic converter (4) starts occlusion of NOx,

an exhaust NOx amount detection means (6) for estimating or detecting the amount of exhaust NOx discharged from the internal combustion engine is provided on the downstream side in the exhaust gas flow direction of the NOx storage-reduction catalyst device (1B).

2. The exhaust gas purification apparatus according to claim 1,

the low performance OSC material is configured such that the OSC capacity increases at 500 ℃ to 900 ℃.

3. The exhaust gas purification apparatus according to claim 1,

the amount of noble metal supported in the low-performance OSC material is 10 to 40% less than that in the other part.

4. The exhaust gas purification apparatus according to claim 1,

the heat treatment temperature of the above low performance OSC material is higher than that of the other portions.

5. The exhaust gas purification apparatus according to claim 1,

the proportion of the low-performance OSC material in the area of the end face of the entire catalytic converter is set to 5 to 10%.

6. The exhaust gas purification apparatus according to claim 1,

the cell density of the honeycomb structure in the above low-performance OSC material is smaller than that of the base portion.

7. The exhaust gas purification apparatus according to claim 1,

a three-way catalytic converter is further disposed upstream of the three-way catalytic converter (3) and the NOx storage reduction catalytic converter (4) disposed in the exhaust gas passage.

8. The exhaust gas purification apparatus according to claim 2,

9. The exhaust gas purification device according to any one of claims 1 to 8,

the exhaust NOx amount detection means detects the amount of NOx and the fuel injection means is set to inject fuel.