JP2006037823A - Exhaust emission control device and exhaust emission control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce NOx at low cost. <P>SOLUTION: A predetermined cylinder 2F of each cylinder of an engine 1 is used as a cylinder for NOx emission. Since target air fuel ratio of the cylinder 2F is set rich by ECU 32, exhaust gas containing unburned fuel ingredient is discharged. The exhaust gas is selectively supplied to either of adsorption parts 12, 13 by a switch valve 11. Adsorbed NOx is emitted by unburned fuel ingredient in exhaust gas (S2). Emitted NOx and remaining unburned fuel ingredient are circulated into a combustion chamber 5 via a circulation passage L4 and an intake passage L1 (S3). Part of NOx is reduced by combustion and unburned fuel ingredient is used for combustion and generates part of engine output (S4). Consequently, reduction agent can be used without waste to purify NOx at low cost. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification device and an exhaust gas purification method capable of purifying exhaust gas by removing NOx (nitrogen compounds) in exhaust gas discharged from an engine such as a diesel engine.

  As a method for reducing NOx discharged from a diesel engine or the like, for example, EGR (exhaust gas recirculation) in which exhaust gas is returned to the combustion chamber and burned, an occlusion reduction catalyst method in which exhaust gas is occluded and then reduced are known. ing. Among these, the occlusion reduction catalyst method having a relatively large NOx reduction effect is often used.

  As a first conventional technique, during air-fuel ratio lean operation, NOx is oxidized and stored in the storage material, and during the air-fuel ratio rich operation, unburned fuel (HC) or carbon monoxide in exhaust gas reacts with NOx. There is known a method of reducing and purifying (see, for example, Patent Document 1).

In addition, as a second conventional technique, two storage reduction catalysts are provided in the exhaust passage and are alternately used for switching, while one storage reduction catalyst is used to store NOx and the other storage reduction catalyst is used as the other storage reduction catalyst. A method of supplying a reducing agent to reduce and purify is known (for example, see Patent Document 2).
Japanese Patent No. 2600492 JP-A-62-106826

  In the first prior art, since NOx occlusion and reduction are controlled by changing the air-fuel ratio, it is necessary to perform sophisticated and complicated air-fuel ratio control. A shock may also occur when changing the combustion state. Furthermore, if the stored NOx is reduced and the fuel is excessive and the air-fuel ratio is switched to rich, the fuel efficiency is reduced accordingly. In the first prior art, since the unburned fuel component in the exhaust gas is used as the reducing agent, it is necessary to supply more fuel than necessary as the reducing agent in order to perform the reduction reaction reliably and promptly. However, of the reducing agent supplied more than necessary, the reducing agent that has not been used for the reduction reaction is discharged as exhaust gas, so that fuel is wasted and fuel consumption is deteriorated.

  In the second prior art, a reducing agent such as hydrogen is used to release NOx from the occlusion material and reduce the released NOx, but the reducing agent is consumed only for the reduction reaction. Therefore, the cost increases by the amount of the reducing agent. When fuel is used as a reducing agent instead of hydrogen, as described above, fuel consumption is reduced by the amount of fuel as a reducing agent that does not contribute to combustion.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust gas purification device and an exhaust gas purification method that can efficiently purify NOx without wasting a reducing agent. Other objects of the present invention will become clear from the description of the embodiments described later.

  In order to solve the above problems, an exhaust gas purification apparatus of the present invention selects a storage means for storing NOx in exhaust gas from an engine, and at least one predetermined cylinder among each cylinder of the engine, and this selection By setting the target air-fuel ratio of the predetermined cylinder to be richer than the stoichiometric air-fuel ratio, combustion is performed, and by supplying the rich exhaust gas from the predetermined cylinder to the storage means, the NOx stored in the storage means is reduced. Rich exhaust supply means for releasing, and NOx released from the storage means and reflux means for returning the rich exhaust supplied to the storage means from a predetermined cylinder to the combustion chamber of the engine.

Here, as the storage means, for example, alkali metals (potassium (K), sodium (Na), lithium (Li), cesium (Cs), etc.), alkaline earths (barium (Ba), calcium (Ca), etc.) Rare earth (lanthanum (La), yttrium (Y), etc.) oxides can be used. Alternatively, zirconium oxide (ZrO ₂ ) or aluminum zirconate (ZrO ₂ —Al ₂ O ₃ ) oxide can also be used. The storage means stores NOx in an oxidizing atmosphere and releases the stored NOx in a reducing atmosphere. More precisely, the occlusion means occludes NOx in an atmosphere with little reducing agent and releases NOx in an atmosphere with much reducing agent.

  When exhaust gas from the engine is supplied to the occlusion means, the occlusion means occludes NOx in the exhaust gas. Next, when the rich exhaust gas supply means supplies rich exhaust gas to the storage means, NOx stored in the storage means is released.

  In this specification, rich exhaust means exhaust from a cylinder in which the target air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio, and this rich exhaust is not compared to exhaust from a cylinder that normally burns. It contains more fuel components and carbon monoxide for combustion.

  Here, it should be noted that in the present invention, the unburned fuel component in the rich exhaust is mainly used for NOx emission. In the present invention, the fuel component in the rich exhaust gas is mainly used for releasing NOx from the storage means even if some reduction reaction occurs.

  Of the fuel components in the rich exhaust gas supplied to the storage means, the remaining fuel components that have not been consumed for NOx release (or release and reduction) are returned to the combustion chamber of the engine together with the released NOx by the return means. The That is, in the present invention, a part of the fuel component in the rich exhaust gas is used for NOx release, and the remaining fuel component that has not been consumed for NOx release is sent to the combustion chamber to act as fuel.

  Part of the NOx recirculated to the combustion chamber is purified by combustion. On the other hand, the fuel component in the rich exhaust becomes part of the engine output as fuel. Therefore, even when the fuel component in the rich exhaust gas is larger than the amount necessary for NOx release, the surplus fuel component is reused as fuel in the combustion chamber, so that fuel is not wasted.

  In addition, since the rich exhaust gas containing unburned fuel components is used instead of supplying the reducing agent alone, the gas flow rate used for NOx release can be increased compared to the case where only the reducing agent is supplied. The NOx released from the occlusion material can be quickly removed and recirculated to the combustion chamber.

  The exhaust gas purification method according to the present invention includes a step of guiding exhaust gas from the engine to the storage means, and storing NOx in the exhaust gas in the storage means, and from each cylinder of the engine from a predetermined cylinder set to a rich combustion state Supplying rich exhaust gas to the storage means to release NOx stored in the storage means; and recirculating the released NOx and rich exhaust gas supplied to the storage means to the combustion chamber of the engine. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1st Embodiment is described based on FIGS. 1-3. FIG. 1 is an overall configuration diagram when an exhaust gas purification device is applied to, for example, an automobile engine device or the like.

  The engine 1 is mounted on a passenger car, for example, and is configured as a four-cycle gasoline engine. However, the present invention is not limited to this, and the present invention can be applied to other types of engines such as diesel engines and two-cycle engines.

  The cylinder block of the engine 1 is formed with a plurality of cylinders 2 such as two, four and six, for example, and pistons 3 are slidably provided in each cylinder 2 (description) For convenience, only one cylinder is shown). The opening of each cylinder 2 is covered with a cylinder head 4 in a gas-liquid tight manner, and a combustion chamber 5 is formed above the piston 3. An intake valve 6 is provided at a connection portion between the combustion chamber 5 and the intake manifold 8, and an exhaust valve 7 is provided at a connection portion between the combustion chamber 5 and the exhaust manifold 9 so as to be opened and closed.

  The intake manifold 8 is connected to an intake passage L1 for introducing outside air, and the exhaust manifold 9 is connected to an exhaust passage L2 for releasing the exhaust gas to the atmosphere. Further, an exhaust gas purifying device described later is provided in the middle of the exhaust passage L2.

  As will be described later, the exhaust gas purification apparatus includes an oxidation unit 10, a first switching valve 11, a first storage unit 12, a second storage unit 13, a second switching valve 14, a reducing agent tank 15, and a control unit 16. It is configured.

The oxidation unit 10 has an oxidation catalyst (for example, Pt, Mn ₂ O _3, etc.) that oxidizes nitrogen oxide (NO) in the exhaust gas to nitrogen dioxide (NO ₂ ), and is provided upstream of the exhaust passage L2. It has been. A first switching valve 11 and a second switching valve 14 are provided in the middle of the exhaust passage L2 on the downstream side of the oxidation unit 10.

  The 1st switching valve 11 and the 2nd switching valve 14 can be expressed as a 1st switching means and a 2nd switching means, respectively, for example, are comprised as an electromagnetic valve of 4 port 2 positions. Each switching valve 11, 14 has two switching positions (a), (b), and switches positions in synchronization with each other in accordance with a control signal from the control unit 16. In addition, each switching valve 11 and 14 may be provided with the transient position where each port is not connected anywhere, and in this case, it becomes a 4 port 3 position electromagnetic valve. Moreover, not only a solenoid valve but a pneumatic valve may be used, or a so-called revolver type switching mechanism may be used.

  Between the 1st switching valve 11 and the 2nd switching valve 14, the 1st storage part 12 and the 2nd storage part 13 are provided in parallel. The first occlusion unit 12 is connected to the first switching valve 11 and the second switching valve 14 via the first branch passage L21, and the second occlusion unit 13 performs the first switching via the second branch passage L22. The valve 11 and the second switching valve 14 are connected. Each of the occlusion units 12 and 13 is made of an oxide (specifically, for example, barium oxide (BaO), for example) such as an alkali metal, an alkaline earth metal, or a rare earth. It is occluded and releases NOx in a reducing atmosphere. More precisely, each of the occlusion units 12 and 13 occludes NOx in an atmosphere with little reducing agent and releases NOx in an atmosphere with much reducing agent.

  When each switching valve 11 and 14 is in the first position (a), the upstream side of the first occlusion unit 12 is connected to the oxidation unit 10 via the first branch passage L21, and the downstream side of the first occlusion unit 12 Are open to the atmosphere. On the other hand, the upstream side of the second storage unit 13 is connected to the reducing agent tank 15 via the reducing agent supply passage L3, and the downstream side of the second storage unit 13 is in the middle of the intake passage L1 via the reflux passage L4. Connected. In the present specification, upstream and downstream indicate upstream and downstream in the flow direction of fluid (exhaust gas, reducing agent, outside air), respectively.

  When each switching valve 11 and 14 is in the 1st position (a), exhaust gas is supplied to the 1st occlusion part 12 via the 1st branch passage L21 from the oxidation part 10, and the 1st occlusion part 12 is The NOx in the exhaust gas is occluded (S1). A gaseous reducing agent is supplied to the second storage unit 13 via the reducing agent supply passage L3, and the second storage unit 13 releases the stored NOx (S2).

  The released NOx and the reducing agent remaining not consumed for NOx release flow into the negative pressure intake passage L1 through the recirculation passage L4 and flow into the combustion chamber 5 through the intake passage L1 (S3). . The NOx and the reducing agent that have flowed into the combustion chamber 5 are burned in the combustion chamber 5 (S4). Thereby, NOx is reduced and the reducing agent becomes a part of the engine output as fuel.

  When each of the switching valves 11 and 14 is switched from the first position (a) to the second position (b), the first occlusion unit 12 is connected to the reducing agent tank 15, contrary to the above case. The occlusion unit 13 is connected to the oxidation unit 10. That is, when each switching valve 11 and 14 is in the first position (a), the first storage unit 12 is used in the NOx storage mode, and the second storage unit 13 is used in the NOx release mode. When each of the switching valves 11 and 14 is switched to the second position (b), the first storage unit 12 is switched from the NOx storage mode to the NOx release mode, and the second storage unit 13 is switched from the NOx release mode to the NOx storage mode. Switch.

  As shown in the time chart 16A on the lower side in FIG. 1, by alternately switching the use modes of the respective storage units 12 and 13, NOx is released from the other storage unit while storing NOx in one storage unit. And NOx in the exhaust gas can be continuously stored and purified. In addition, although the example has illustrated the case where the two occlusion parts 12 and 13 are provided, this invention is not restricted to this, It is good also as a structure which switches and uses three or more occlusion parts.

  The reducing agent tank 15 stores the reducing agent, and supplies the reducing agent to either the first occlusion unit 12 or the second occlusion unit 13 via the reducing agent supply passage L3 and the second switching valve 14. Is. As the reducing agent, for example, hydrocarbon, gasoline, light oil, propane, butane, propylene, hydrogen, carbon monoxide and the like can be used. In addition, when providing three or more occlusion parts, a reducing agent is supplied to the several occlusion part used by discharge | release mode.

  The reducing agent tank 15 is configured to supply, for example, a pressurized gaseous reducing agent. Not only this but a liquid reducing agent can also be used. In the case of using a liquid reducing agent, for example, the reducing agent heated and vaporized is supplied to the occlusion unit, or the liquid reducing agent is contained in a gas such as exhaust gas or outside air as in an embodiment described later. The agent may be sprayed and supplied to the occlusion unit.

  When a part of the fuel is used as the reducing agent, it is not necessary to provide the tank 15 dedicated to the reducing agent, and the reducing agent supply passage L3 may be connected to a fuel tank or a fuel pipe to take in the fuel. . In the case of using a liquid reducing agent, a mechanism for vaporizing or atomizing is required. Therefore, a simpler configuration can be achieved by using a gaseous reducing agent. However, when the fuel is used as a reducing agent, a part of the fuel can be taken out from the fuel tank or the fuel pipe and used, so that the trouble of providing the reducing agent tank 15 or replacing the tank 15 can be saved.

  The control unit 16 controls the operation of the switching valves 11 and 14 as shown in the time chart 16A. As described above, the control unit 16 outputs a control signal to the switching valves 11 and 14 at an appropriate time to switch the positions of the switching valves 11 and 14. The control unit 16 can be configured as a microcomputer system or a hardware circuit such as an electromagnetic relay. The control unit 16 can also be realized as a part of an engine control unit (ECU).

  Next, the operation of the present embodiment will be described based on FIG.

  FIG. 2A shows a case where NOx is stored by the first storage unit 12 and NOx is released by the second storage unit 13. In this case, as described above, the exhaust gas generated in the combustion chamber 5 is oxidized by the oxidation unit 10 and then introduced from the first switching valve 11 to the first storage unit 12. The exhaust gas from which NOx has been removed by the first storage unit 12 is discharged from the exhaust passage L2 into the atmosphere via the second switching valve 14. A three-way catalyst or the like may be further provided in the middle of the exhaust passage L2 on the downstream side of the second switching valve 14.

  Next, as shown in FIG. 2B, when the switching valves 11 and 14 are respectively switched, the reducing agent from the reducing agent tank 15 is supplied through the reducing agent supply passage L3 and the second switching valve 14 to the first. It flows into the storage unit 12. Part of the reducing agent that has flowed into the first storage unit 12 releases NOx stored in the first storage unit 12. The NOx released from the first storage unit 12 and the remaining reducing agent flow into the intake passage L1 through the first branch passage L21, the first switching valve 11, and the return passage L4, and through the intake passage L1, the combustion chamber 5 Is refluxed in. Part of the NOx is reduced in the combustion chamber 5, while the reducing agent is burned as part of the fuel.

  The operation of the second storage unit 13 is opposite to the operation of the first storage unit 12. While the 1st occlusion part 12 occludes NOx, the 2nd occlusion part 13 discharge | releases NOx, and the 2nd occlusion part 13 occludes NOx while the 1st occlusion part 12 discharge | releases NOx.

  Next, chemical reactions occurring in each part will be described. First, the oxidation reaction in the oxidation part 10 is shown in the following chemical formula 1.

NO + 1 / 2O ₂ → NO ₂ (Chemical formula 1)

Next, the reaction formula when the occlusion material occludes NO ₂ is shown in the following chemical formula 2 (MO is occlusion material, M is Ba, for example).

NO ₂ + 1 / 2MO + 1 / 4O ₂ → 1 / 2M (NO ₃ ) ₂ ... (Chemical formula 2)

Respectively a reducing agent (CH ₂₎ n and NO2 emission reaction of the storage material when expressed 3, the formula 4. Chemical formula 3 shows the case where it is released as NO ₂ , and chemical formula 4 shows the case where it is released as NO ₂ .

1 / 2M (NO ₃ ) ₂ + 1 / 6n (CH ₂ ) _n → NO ₂ + 1 / 2MO + 1 / 6CO ₂ + 1 / 6H ₂ O ... (Chemical formula 3)

1 / 2M (NO ₃ ) ₂ + 1 / 2n (CH ₂ ) _n → NO + 1 / 2MO + 1 / 2CO ₂ + 1 / 2H ₂ O (Chemical formula 4)

Summarizing the above reaction formula, the case where NO ₂ is released is shown in Chemical Formula 5, and the case where NO is released is shown in Chemical Formula 6.

NO + 1 / 6n (CH ₂ ) _n + 3 / 4O ₂ → NO ₂ +1/6 CO ₂ + 1 / 6H ₂ O (Chemical formula 5)

1 / 2n (CH ₂ ) _n + 3 / 4O ₂ → 1 / 2CO ₂ + 1 / 2H ₂ O (Chemical formula 6)

As shown in Chemical Formula 5, the amount of hydrocarbon (HC) required to occlude and release 1 mol of NO (number of moles of C) is 1/6 mol when released as NO ₂ and discharged as NO. When it is done, it becomes 1/2 mol.

For comparison, when the chemical reaction in the case of further reducing the released NOx with a reducing agent is examined, the reaction formula in the case of being released as NO ₂ is shown in Chemical Formula 7, and the case of being released as NO The reaction formula is shown in Chemical Formula 8.

NO ₂ + 2 / 3n (CH ₂ ) _n → 1 / 2N ₂ + 2 / 3CO ₂ + 2 / 3H ₂ O (Chemical formula 7)

NO + 1 / 3n (CH ₂ ) _n → 1 / 2N ₂ + 1 / 3CO ₂ + 1 / 3H ₂ O (Chemical formula 8)

Therefore, in both cases of releasing as NO ₂ and releasing as NO, the overall reaction formula is as shown in Chemical Formula 9,

NO + 5 / 6n (CH ₂ ) _n + 3 / 4O ₂ → 1 / 2N ₂ + 5 / 6CO ₂ + 5 / 6H ₂ O ... (Chemical formula 9)
The amount of hydrocarbon (HC) required to release 1 mol of NO from the storage material and further reduce it is 5/6 mol.

FIG. 3 is a characteristic diagram showing the NOx reduction effect according to the present embodiment. Using a diesel combustion device, the relationship between the amount of NOx recirculated to the combustion chamber and the amount of NOx discharged from the combustion chamber was examined. The NOx reduction effect was measured when the fuel injection amount into the combustion chamber was 60 mm ³ (square) and when the fuel injection amount was 120 mm ³ (circle). In addition, CLA (chemiluminescence method) was used for NOx measurement.

  The dotted line in FIG. 3 is a theoretical value when there is no NOx reduction effect. As shown at the left end of the graph, when the NOx reflux amount is 0, about 500 ppm of NOx is generated. This is the amount of NOx produced by normal combustion. Assuming that there is no NOx reduction effect according to the present embodiment, NOx accumulates as shown by the oblique dotted line.

However, the solid lines connecting the circle marks or the square marks are all at positions lower than the oblique dotted lines, and a certain NOx reduction effect is observed. When the fuel injection amount is 120 mm ³ , the NOx reduction effect increases as the NOx recirculation amount increases. Further, when the fuel injection amount is 60 mm ^3, a certain amount of NOx is reduced when the NOx recirculation amount exceeds about 1000 ppm, and when the fuel injection amount is 120 mm ³ , the NOx reduction effect is greater.

  As described above in detail, according to the present embodiment, the reducing agent is used for NOx release without being used in the active (or substantial) reduction reaction, and the remaining reduction that did not contribute to NOx release. Since the agent is recirculated to the combustion chamber 5 together with NOx, the reducing agent can be burned as fuel while reducing NOx in the combustion chamber 5 to be a part of the engine output.

  Therefore, compared with the case where the reducing agent is exclusively used for the reduction reaction, the reducing agent is not consumed wastefully, and the NOx reduction cost can be reduced. Further, when fuel is used as a reducing agent, fuel consumption is not deteriorated.

  Next, a second embodiment of the present invention will be described with reference to FIG. The feature of this embodiment is that an occlusion part having an oxidation function is used.

  As in the first embodiment, the exhaust gas purifying apparatus according to the present embodiment includes the switching valves 11 and 14 and the storage units 21 and 22, and alternately uses the storage units 21 and 22. However, in this embodiment, the independent oxidation part 10 is abolished and each of the storage parts 21 and 22 is provided with oxidation parts 21A and 22A, respectively. That is, each of the storage units 21 and 22 has a configuration in which an oxidation catalyst is supported on the storage material, and includes the oxidation units 21A and 22A and the storage materials 21B and 22B. In addition, it is preferable that the oxidation catalyst has a characteristic that a reduction reaction hardly occurs even in an oxygen-poor atmosphere.

  FIG. 5 shows a third embodiment of the present invention. The feature of this embodiment is that NOx is released using a mixed gas of outside air and a reducing agent.

  In the middle of the reducing agent supply passage L3, an outside air introduction passage L5 is connected. The reducing agent flowing out from the reducing agent tank 15 is mixed with the outside air introduced from the outside air introduction passage L5 and supplied to one of the storage units 12 and 13.

  Therefore, according to the present embodiment, the amount of the gas mixture used for NOx release can be made larger than when the reducing agent is supplied alone, and the NOx released from the occlusion material can be quickly carried away to the intake passage. It can be refluxed to L1.

  FIG. 6 illustrates a fourth embodiment of the present invention. A feature of this embodiment is that NOx is released using a mixed gas of exhaust gas and a reducing agent.

  An exhaust gas introduction passage L6 is connected in the middle of the reducing agent supply passage L3, and the reducing agent from the reducing agent tank 15 is mixed with the exhaust gas introduced from the exhaust gas introduction passage L6 and supplied to the occlusion unit. .

  Thereby, similarly to the case where the outside air and the reducing agent are mixed, the amount of the gas mixture used for the release can be increased, and NOx can be quickly carried away. Moreover, according to this embodiment, the temperature of the occlusion parts 12 and 13 does not change substantially at the time of occlusion and at the time of omission, and the temperature of the occlusion material can be kept substantially constant. Therefore, the temperature drop during NOx release can be prevented and the release effect can be enhanced (in general, the higher the storage material, the higher the NOx release effect), and the heat due to the temperature difference between the storage and release Fatigue and deterioration can be prevented.

  The fifth embodiment of the present invention will be described based on FIG. The feature of this embodiment is that a mixed gas of a reducing agent and outside air is supplied to the occlusion unit with an oxidation function.

  Each occlusion part 21 and 22 by this embodiment is provided with oxidation parts 21A and 22A, respectively, similarly to the second embodiment. And the external air introduction channel | path L5 is connected to the reducing agent supply channel | path L3 similarly to 3rd Embodiment.

  In this embodiment, since NOx occluded in the occlusion unit is released by a large amount of gas mixed with outside air and a reducing agent, the released NOx is reduced on the catalyst in a reducing atmosphere with little oxygen. This is particularly effective when a platinum catalyst having the above is used. That is, by mixing the outside air and the reducing agent, an oxygen-rich atmosphere can be formed, and NOx is released while suppressing the reduction reaction in the oxygen-rich atmosphere, and the remaining NOx and the reducing agent are returned to the combustion chamber 5. It can be refluxed.

  A sixth embodiment of the present invention will be described based on FIG. The feature of this embodiment is that a mixed gas of a reducing agent and exhaust gas is supplied to the occlusion unit with an oxidation function.

  Each occlusion part 21 and 22 by this embodiment is provided with oxidation parts 21A and 22A, respectively, similarly to the second embodiment. Further, an exhaust gas introduction passage L6 branched from the exhaust passage L2 is connected to the reducing agent supply passage L3.

  As a result, the amount of gas mixture used for release can be increased to quickly carry away NOx, the temperature difference between NOx storage and NOx release can be reduced, the NOx release effect can be enhanced, and thermal fatigue and deterioration can be achieved. Etc. can be prevented. Further, even when a platinum catalyst is used, NOx is released in a relatively oxygen-rich atmosphere, so that the released NOx can be prevented from being reduced on the platinum catalyst.

  A seventh embodiment of the present invention will be described with reference to FIGS. The feature of this embodiment is that unburned fuel in exhaust gas is used as the NOx releasing agent.

  FIG. 9 is an overall configuration diagram when an exhaust gas purification apparatus is applied to an automobile engine. In the present embodiment, the engine 1 includes, for example, six cylinders 2A to 2F. Each cylinder 2 </ b> A to 2 </ b> F is provided with an electronic fuel injection device 31 so as to face the combustion chamber 5.

  The fuel sucked from the fuel tank by the fuel pump is supplied to these fuel injectors 31 through fuel supply pipes (both not shown). Each fuel injection device 31 is opened based on a control signal from the ECU 32 and discharges a predetermined amount of fuel toward the combustion chamber 5.

  The ECU 32 controls the operation of each fuel injection device 31, ignition device (not shown), and the like. The ECU 32 can control the fuel injection amount by controlling the valve opening timing and the valve opening time of the fuel injection device 31, for example. Here, in general, the target air-fuel ratio of each of the cylinders 2A to 2F is set to about 14.7. However, not only the stoichiometric air-fuel ratio, but, for example, when improving fuel efficiency or reducing exhaust emissions, the fuel injection amount may be reduced below the stoichiometric air-fuel ratio and burned in a so-called lean state. Or, in order to improve the engine output, the fuel injection amount may be increased more than the stoichiometric air-fuel ratio, and combustion may be performed in a so-called rich state.

  The ECU 32 can set the target air-fuel ratio of each of the cylinders 2A to 2F in accordance with, for example, the operating state (steady running state, acceleration / deceleration state, etc.) and can individually control the fuel injection amount. Further, the ECU 32 sets the target air-fuel ratio of a predetermined cylinder 2F to be rich and performs combustion in a rich state for exhaust gas purification. The cylinder burned in the rich state may be any of the cylinders 2A to 2F, but in the present embodiment, the cylinder 2F is used as an example. The target air-fuel ratios of the other cylinders 2A to 2E can be set to a leaner state than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio.

  Since the target air-fuel ratio of the cylinder 2F as a predetermined cylinder is set to be rich, the exhaust gas from the cylinder 2F contains more unburned fuel components than when it is burned at the stoichiometric air-fuel ratio. It is. In addition, as a component that exhibits the NOx releasing effect, the exhaust gas contains carbon monoxide in addition to the unburned fuel component. However, in the following description, the unburned fuel component will be mainly described.

  Note that the cylinder 2F does not necessarily need to be always in the rich combustion state, and the target air-fuel ratio of the cylinder 2F is set to the theoretical air in accordance with at least the period during which NOx is released from either one of the storage units 12 and 13. It is sufficient to set it richer than the fuel ratio. In a period other than the NOx releasing period, the target air-fuel ratio of the cylinder 2F can be set similarly to the other cylinders 2A to 2E.

  The predetermined cylinder 2F that realizes the function as the reducing agent supply means is connected to the first switching valve 11 via the exhaust gas supply passage L31. When the first switching valve 11 is in the switching position (a), the predetermined cylinder 2F and the second storage unit 13 are connected via the exhaust gas supply passage L31 and the first switching valve 11, and the other cylinders 2A to 2E. And the first storage part 12 are connected via an exhaust manifold 9, an exhaust passage L2, and a first switching valve 11.

  When the second switching valve 14 is in the switching position (a), the second storage unit 13 is connected to the intake passage L1 via the second switching valve 14 and the return passage L4, and the first storage unit 12 is The air is released to the atmosphere via the second switching valve 14 and the exhaust passage L2. When the first switching valve 11 and the second switching valve 14 are respectively in the switching position (b), the exhaust gas in the cylinder 2F recirculates to the intake passage L1 via the first occlusion unit 12 etc. The exhaust gases in the cylinders 2A to 2E are released into the atmosphere via the second storage part 13 and the like.

  As shown in FIG. 10A, when the first switching valve 11 and the second switching valve 14 are in the switching position (a), the exhaust gas from the cylinder 2 </ b> F is guided to the second occlusion unit 13. NOx stored in the second storage unit 13 is released by the unburned fuel component contained in the exhaust gas. The released NOx flows together with the exhaust gas from the cylinder 2F into the combustion chambers 5 of the cylinders 2A to 2F via the recirculation passage L4, the intake passage L1, and the like. As a result, the remaining fuel components that have not contributed to NOx release are reused as fuel. On the other hand, the exhaust gas from the other cylinders 2A to 2E in the normal combustion state is guided to the first occlusion unit 12 to remove NOx and released into the atmosphere.

  As shown in FIG. 10 (b), when the first switching valve 11 and the second switching valve 14 are switched to the switching position (b), the exhaust gas from the cylinder 2F is guided to the first occlusion part 12, and the other cylinders The exhaust gas from 2A to 2E is guided to the second storage unit 13. Then, the NOx stored in the first storage unit 12 is released and returned to the combustion chambers 5 of the cylinders 2A to 2F together with unburned fuel components. On the other hand, the 2nd occlusion part 13 removes NOx from the exhaust gas from cylinder 2A-2E, and discharges normal exhaust gas in air | atmosphere.

  As described above, in the present embodiment, the target air-fuel ratio of the predetermined cylinder 2F among the cylinders 2A to 2F of the engine 1 is set to be richer than the stoichiometric air-fuel ratio, and combustion is performed. By alternately supplying the storage units 12 and 13, the NOx stored in each of the storage units 12 and 13 is released and recirculated to the combustion chambers 5 of the respective cylinders 2 </ b> A to 2 </ b> F. Therefore, the unburned fuel component contained in the exhaust gas from the predetermined cylinder 2F can be used for NOx release of the storage units 12 and 13, and the remaining fuel component that has not contributed to NOx release can be used as fuel. . Thereby, NOx purification cost can be reduced and fuel consumption can be prevented from deteriorating.

  In addition to this, in the present embodiment, the existing engine structure can be used almost as it is without using the reducing agent tank, and the target air-fuel ratio of the predetermined cylinder 2F can be set to rich and used for NOx release. The fuel component can be easily obtained. Further, the amount of the unburned fuel component used for NOx release can be controlled only by adjusting the target air-fuel ratio of the predetermined cylinder 2F. Furthermore, the rich combustion of the predetermined cylinder 2F not only generates exhaust gas in a rich atmosphere as a NOx release agent, but also constitutes a part of the output of the engine 1, so that the combustion of the cylinder 2F can be used effectively. it can.

  Further, when the engine 1 is a construction machine engine, the construction machine engine is used in a plurality of output modes, for example, a heavy load mode, a light load mode, a light load mode, etc. according to the purpose of use. Is done. Thus, for example, in the light load mode and the heavy load mode, all the cylinders 2A to 2F can be normally burned, and in the light load mode, one or a plurality of cylinders can be selected and richly burned. Thus, the release and storage of NOx can be controlled according to the purpose of use of the engine.

  An eighth embodiment of the present invention will be described based on FIG. The feature of this embodiment is that a plurality of cylinders 2E and 2F are used as the cylinder for rich combustion.

  FIG. 11 is an overall configuration diagram of the present embodiment. As shown in FIG. 11, in this embodiment, two adjacent cylinders 2F and 2E are selected as dedicated cylinders for releasing NOx, and the target air-fuel ratios of these cylinders 2E and 2F are respectively It is set richer than the theoretical air-fuel ratio. The NOx releasing cylinders 2E and 2F do not necessarily have to be adjacent to each other, but the adjacent ones are easier to install and route the piping, which is advantageous in terms of the mechanical structure.

  The exhaust gas supply passage of the present embodiment includes a first branch passage L31A connected to one cylinder 2E, a second branch passage L31B connected to the other cylinder 2F, these branch passages, and L31A and L31B. It is comprised from the confluence | merging channel | path L31C which joins. Exhaust gas from the cylinders 2E and 2F flows into the first switching valve 11 via the merge passage L31C, and is selectively supplied from the first switching valve 11 to one of the storage units 12 and 13.

  Since this embodiment is configured as described above, the same operational effects as those of the seventh embodiment described above can be obtained. In addition to this, in the present embodiment, a configuration is used in which a plurality of cylinders 2E and 2F are used as NOx release dedicated cylinders, and exhaust gases for NOx release are obtained from the cylinders 2E and 2F, respectively. Therefore, as compared with the above-described embodiment in which the single cylinder 2F is used as the NOx releasing cylinder, the unburned fuel components necessary for NOx releasing may be generated by sharing each of the cylinders 2E and 2F. The target air-fuel ratio of 2E and 2F can be made closer to the theoretical air-fuel ratio side.

  Based on FIGS. 12-15, the 9th Embodiment of this invention is described. The feature of this embodiment is that the three occlusion units 43 to 45 are used while being switched in order.

  FIG. 12 is an explanatory diagram showing the overall configuration of the present embodiment. In each said embodiment, although the case where two occlusion parts were switched and used was illustrated, you may use three or more occlusion parts 43-45 like this embodiment. In addition, although the case where three occlusion parts are provided is described as an example, as will be apparent from other embodiments described later, four or more occlusion parts may be provided.

  Similar to the seventh embodiment, the predetermined cylinder 2F is used as a dedicated cylinder for releasing NOx, and its target air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio. The other cylinders 2A to 2E are used as normal cylinders for generating engine output, and the target air-fuel ratio can be set to be close to the stoichiometric air-fuel ratio or leaner than the stoichiometric air-fuel ratio. Note that the NOx releasing cylinder is not limited to 2F, and any one or a plurality of cylinders among the cylinders 2A to 2F can be used.

  A first switching valve 41 is provided on the upstream side (gas inflow side) of each of the storage units 43 to 45, and the second switching valve 42 is provided on the downstream side (gas outflow side) of each of the storage units 43 to 45. Is provided. Each of these switching valves 41 and 42 can be configured as, for example, a 6-port 3-position electromagnetic valve or a pneumatic valve.

  Each switching valve 41, 42 has three switching positions (a), (b), and (c), respectively, and is switched in accordance with a control signal from the control unit 16. The exhaust gas from the NOx releasing cylinder 2F and the exhaust gas from the other normal cylinders 2A to 2E are input to the first switching valve 41, respectively. Exhaust gases from the other cylinders 2A to 2E are input from the two inlets. This is because any one of the three storage units 43 to 45 is used in the NOx release mode, and the other two storage units are used in the NOx storage mode. The outlets of the first switching valve 41 are connected to the inlets of the storage parts 45, 44, 43 through branch passages L21, L22, L23, respectively.

  Each inflow port of the 2nd switching valve 42 is connected to the outflow port of each occlusion part 45, 44, 43 via branch passage L21, L22, L23, respectively. Of the outlets of the second switching valve 42, one outlet is connected to the intake passage L1 via the reflux passage L4, and the remaining two outlets are connected to the atmosphere via the exhaust passage L2. It is open.

  As shown in FIG. 13, when each switching valve 41, 42 is in the switching position (a), the exhaust gas from the cylinders 2 </ b> A to 2 </ b> E in the normal combustion state is stored in the first storage unit 43 and the second storage unit 44. Supplied. Each of the occlusion units 43 and 44 occludes and removes NOx in the exhaust gas, and discharges the clean exhaust gas into the atmosphere.

  The third storage unit 45 is supplied with exhaust gas from the NOx releasing cylinder 2F. The third storage unit 45 uses the exhaust gas containing the unburned fuel component to release the stored NOx. The released NOx is recirculated to the combustion chamber 5 through the recirculation passage L4 and the intake passage L1 together with other fuel components not used for NOx release.

  As shown in FIG. 14, when each switching valve 41, 42 is in the switching position (b), the exhaust gas from the cylinders 2 </ b> A to 2 </ b> E in the normal combustion state is respectively stored in the first storage unit 43 and the third storage unit 45. Supplied. The 1st occlusion part 43 and the 3rd occlusion part 45 occlude NOx in exhaust gas, and purify exhaust gas. On the other hand, the exhaust gas containing the unburned fuel component from the cylinder 2 </ b> F is supplied only to the second storage unit 44. The second storage unit 44 releases the stored NOx, and the released NOx returns to the combustion chamber 5 together with the remaining fuel component.

  As shown in FIG. 15, when each switching valve 41, 42 is in the switching position (c), exhaust gas from the cylinders 2 </ b> A to 2 </ b> E in the normal combustion state is stored in the second storage unit 44 and the third storage unit 45. Supplied respectively. The exhaust gas from the cylinder 2 </ b> F is supplied only to the first storage unit 43. Accordingly, the second and third storage units 44 and 45 store NOx in the exhaust gas, and the first storage unit 43 releases the stored NOx. The correspondence relationship between the valve switching position and the operation mode of each storage unit is not limited to the above example.

  In this way, three or more occlusion units 43 to 45 are provided, and can be used alternately while switching in a predetermined order. Thus, NOx can be shared and stored by the two storage units. In addition, it is also possible to use any one of the three storage units 43 to 45 in the NOx storage mode and the other two in the NOx release mode. Furthermore, for example, when four or more occlusion parts are provided, any two occlusion parts can be used in the NOx occlusion mode, and the remaining two occlusion parts can be used in the NOx release mode.

  A tenth embodiment of the present invention will be described with reference to FIGS. The feature of this embodiment is that each cylinder 2A to 2F is divided into two groups each having the same number, and either one of the cylinders is alternately richly burned to obtain NOx releasing gas. .

  FIG. 16 is an explanatory diagram showing the overall configuration. Each cylinder 2A-2F of this embodiment is grouped into 1st cylinder group 2A-2C and 2nd cylinder group 2D-2F. The first cylinder groups 2A to 2C are connected to the first storage unit 12 via the first exhaust manifold 9A. The second cylinder groups 2D to 2F are connected to the second occlusion unit 13 via the second exhaust manifold 9B. Each of the exhaust manifolds 9A and 9B functions as an exhaust supply passage that is an example of a rich exhaust supply unit during a period in which the target air-fuel ratio of the cylinder group to which the exhaust manifold 9B is connected is set to be rich. During other periods, it functions as a normal exhaust manifold.

  In the present embodiment, it should be noted that the first switching valve located on the upstream side of each of the storage units 12 and 13 is abolished and only the second switching valve 14 is provided. That is, each of the occlusion units 12 and 13 is directly connected to each cylinder group. In the present embodiment, the six cylinders 2A to 2F are grouped into two cylinder groups, and each cylinder group is directly connected to each of the occlusion units 12 and 13, respectively. Then, the ECU 32 sets the target air-fuel ratio of one of the cylinder groups to be richer than the theoretical air-fuel ratio, and normally burns the other cylinder group. That is, in the present embodiment, the first switching valve is not required by switching the target air-fuel ratio of each cylinder group alternately.

  In addition, each cylinder group and each occlusion part 12,13 being connected directly means that the switching valve 11 is unnecessary, and between each cylinder group and each occlusion part 12,13, It does not mean that no equipment is involved. Between each cylinder group and each occlusion part 12,13, an oxidation part, a check valve, etc. can be provided as needed.

  FIG. 16 shows a case where the first cylinder groups 2A to 2C are in the normal combustion state and the second cylinder groups 2D to 2F are in the rich combustion state. Thereby, the normal exhaust gas from the first cylinder groups 2A to 2C is supplied to the first storage unit 12 via the first exhaust manifold 9A, and after the NOx is removed by the first storage unit 12, the exhaust passage It is discharged into the atmosphere via L2. On the other hand, the exhaust gas containing unburned fuel components from the second cylinder groups 2D to 2F is supplied to the second storage unit 13 via the second exhaust manifold 9B, and the NOx released from the second storage unit 13 is released. Used for. The released NOx and unburned fuel components that have not been used for NOx release are recirculated to the combustion chambers 5 of the respective cylinders 2A to 2F via the recirculation passage L4 and the intake passage L1.

  FIG. 17 shows a case where the first cylinder groups 2A to 2C are richly burned and the second cylinder groups 2D to 2F are normally burned, contrary to the case shown in FIG. As a result, exhaust gas containing an unburned fuel component is supplied to the first storage unit 12, and NOx stored in the first storage unit 12 is released. On the other hand, normal exhaust gas is supplied to the second storage unit 13 from the second cylinder groups 2D to 2F, and the second storage unit 13 removes NOx from the exhaust gas and cleans it.

  FIG. 18 is a flowchart showing an outline of control according to the present embodiment. First, it is assumed that the first cylinder groups 2A to 2C are operated in a rich combustion state and the second cylinder groups 2D to 2F are operated in a normal combustion state at a certain time (S11, S12). In this case, as shown in FIG. 17, the first storage unit 12 is used in the NOx release mode (S13), and the second storage unit 13 is used in the NOx storage mode (S14). .

  The ECU 32 monitors whether or not the target air-fuel ratio setting switching timing has arrived (S15), and when it is determined that the predetermined timing has arrived (S15: YES), a switching instruction is transmitted to the control unit 16. (S16). Here, as the predetermined time, for example, a certain time can be given. When a preset fixed or variable predetermined time has elapsed, it can be determined that the target air-fuel ratio setting switching timing has arrived. Further, for example, the switching determination can be performed based on the current or past operating state of the engine, such as performing NOx release during steady running. Alternatively, a sensor for monitoring the NOx occlusion amount may be provided, and it may be determined whether or not it is the switching time in consideration of an output signal from this sensor.

  When receiving the switching instruction from the ECU 32, the control unit 16 outputs a control signal to the switching valve 14 and switches the position of the switching valve 14 (S17). The ECU 32 changes the target air-fuel ratio of the first cylinder groups 2A to 2C from the rich state to the vicinity of the theoretical air-fuel ratio (S18), and changes the target air-fuel ratio of the second cylinder groups 2D to 2F from the vicinity of the theoretical air-fuel ratio to the rich state. (S19).

  When the position of the switching valve 14 is switched and the target air-fuel ratio of each cylinder group is set and changed, the normal exhaust gas discharged from the first cylinder groups 2A to 2C, as shown in FIG. After NOx is removed by the 1 occlusion unit 12, it is discharged into the atmosphere from the exhaust passage L2 (S20). On the other hand, the exhaust gas containing unburned fuel components discharged from the second cylinder groups 2D to 2F is used for releasing NOx occluded in the second occlusion unit 13 and returns to the combustion chamber 5 together with the released NOx ( S21). Note that the target air-fuel ratio setting change timing of each cylinder group and the switching timing of the switching valve 14 are appropriately adjusted so that the exhaust gas from which NOx has not been removed is not released into the atmosphere by switching the operation mode.

  Then, the ECU 32 again determines whether or not the switching time has come (S22), and when the switching time has come, outputs a switching instruction to the control unit 16 (S23). The control unit 16 switches the position of the switching valve 14 in response to the switching instruction (S24). Further, the ECU 32 changes the setting of the target air-fuel ratio of the first cylinder groups 2A to 2C to be rich and the target air-fuel ratio of the second cylinder groups 2D to 2F to be close to the theoretical air-fuel ratio (S25, S26). Thus, as shown in FIG. 17, the first storage unit 12 is used in the NOx release mode (S27), and the second storage unit 13 is used in the NOx storage mode (S28).

  Since this embodiment is configured as described above, the same effects as those of the seventh embodiment are exhibited. In addition, in the present embodiment, the cylinders 2A to 2F of the engine 1 are grouped into first cylinder groups 2A to 2C and second cylinder groups 2D to 2F, and the first cylinder groups 2A to 2C store the first occlusion. The part 12 is directly connected, the second storage part 13 is directly connected to the second cylinder groups 2D to 2F, and the outlets of the storage parts 12 and 13 are provided downstream of the storage parts 12 and 13, respectively. Since the switching valve 14 connected to either the atmosphere or the combustion chamber 5 is provided and the target air-fuel ratio of each cylinder group is alternately set to be rich, the space between each of the storage units 12 and 13 and each cylinder group is set. It is not necessary to provide the switching valve 11 in the configuration, and the configuration can be simplified.

  The eleventh embodiment of the present invention will be described with reference to FIGS. The feature of this embodiment is that the storage portions 61 to 66 are directly connected to the cylinders 2A to 2F, respectively, and rich combustion is performed while switching the cylinders 2A to 2F in order.

  As shown in the overall configuration diagram of FIG. 19, the cylinders 2 </ b> A to 2 </ b> F of the engine 1 of the present embodiment are connected to the storage units 61 to 66 via exhaust gas supply passages L <b> 31 </ b> A to L <b> 31 </ b> F, respectively. That is, dedicated storage parts 61 to 66 are directly connected to the cylinders 2A to 2F, respectively.

  On the downstream side of each of the storage units 61 to 66, a switching valve 70 is provided for connecting the outlet of each of the storage units 61 to 66 to either the combustion chamber 5 or the atmosphere. This switching valve 70 can be realized by providing, for example, two-way switching valves 71 to 76 corresponding to the number of cylinders.

  The inflow ports of the respective two-way switching valves 71 to 76 are connected to the respective storage portions 61 to 66, respectively. One outflow ports of the respective two-way switching valves 71 to 76 are connected to the reflux passage L4, respectively. The other outlets of the direction switching valves 71 to 76 are connected to the exhaust passage L2. Accordingly, by switching the valve positions of the two-way switching valves 71 to 76, the two-way switching valves 71 to 76 can be individually connected to either the combustion chamber 5 or the atmosphere.

  FIG. 19 shows a case where only the cylinder 2F is richly burned and the other cylinders 2A to 2E are each normally burned. In this case, only the sixth storage unit 66 connected to the cylinder 2F is used in the NOx release mode, and the other storage units 61 to 65 are each used in the NOx storage mode. And the 6th occlusion part 66 is connected to the combustion chamber 5 of each cylinder 2A-2F via the recirculation | reflux passage L4 and the intake passage L1 by the switching valve 76 connected to the 6th occlusion part 66, respectively. As a result, NOx released from the sixth storage unit 66 and the remaining unburned fuel components recirculate to the combustion chambers 5 respectively. Other occlusion parts 61-65 remove NOx from exhaust gas from each cylinder 2A-2E, respectively. The exhaust gas purified by removing NOx is discharged into the atmosphere from the switching valves 71 to 75 through the exhaust passage L2.

  FIG. 20 shows a state where only the cylinder 2E is richly burned. In this case, only the fifth storage unit 65 connected to the cylinder 2E is used in the NOx release mode, and the other storage units 61 to 64 and 66 are used in the NOx storage mode.

  Similarly, FIG. 21 shows a case where only the cylinder 2A is richly burned. Only the first storage section 61 connected to the cylinder 2A is used in the NOx release mode, and the other storage sections 62 to 66 are used in the NOx storage mode.

  FIG. 22 is a flowchart showing an outline of operations of the ECU 32 and the control unit 16. First, the ECU 32 sets “1” as an initial value to the cylinder number CN for selecting any one of the cylinders 2A to 2F (S31). Similarly, the control part 16 sets "1" as an initial value to the occlusion part number AN for selecting any one occlusion part among the occlusion parts 61-66 (S32).

  The ECU 32 sets the target air-fuel ratio of the cylinder designated by the cylinder number CN to be richer than the theoretical air-fuel ratio (S33). The control unit 16 outputs a control signal to the switching valve 70, thereby connecting the storage unit designated by the storage unit number AN to the reflux passage L4 (S34).

  Further, the ECU 32 sets the target air-fuel ratio of the other cylinders in the vicinity of the theoretical air-fuel ratio (S35), and the control unit 16 connects the other storage units to the exhaust passage L2 (S36). Thereby, any one occlusion part can be used in NOx release mode, and another occlusion part can be used in NOx occlusion mode.

  Then, the ECU 32 determines whether or not the switching time has come (S37). The determination as to whether or not the switching time has arrived can be made based on the passage of time, engine operating conditions, and the like, as described in the above embodiment.

  When it is determined that the switching time has come (S37: YES), the ECU 32 outputs a switching instruction to the control unit 16 (S38). When receiving the switching instruction, the control unit 16 increments the storage unit selection number AN by one (S39). The ECU 32 also increments the cylinder selection number CN by one (S40).

  Here, the ECU 32 determines whether or not the cylinder selection number CN exceeds the upper limit value CNmax (S41). In the present embodiment, a 6-cylinder engine is illustrated, so the upper limit value CNmax is “6” as the number of cylinders. As a result of incrementing the cylinder selection number CN by 1 in S40, when the value of the cylinder selection number CN exceeds the upper limit value CNmax (S41: YES, ie, CN = 7), the cylinder selection number CN is an initial value “1”. (S42). When the value of the cylinder selection number CN does not exceed the upper limit value CNmax (S41: NO), the process returns to S33. In this way, each time the CN reaches a predetermined number, the counter is reset so that each cylinder is repeated in order and selected periodically.

  Similarly, after incrementing the storage unit selection number AN by 1 (S39), the control unit 16 also determines whether or not the value of the storage unit selection number AN has exceeded the upper limit value ANmax (S43). In this embodiment, each cylinder is provided with a dedicated occlusion portion, and each cylinder and each occlusion portion correspond one-to-one, so the upper limit value ANmax of the occlusion portion selection number AN is the same value as CNmax. That is, it is “6”. When the value of the occlusion part selection number AN does not exceed the upper limit value ANmax (S43: NO), the process returns to S34. On the other hand, when the value of the occlusion unit selection number AN exceeds the upper limit value ANmax (S43: YES, ie, AN = 7), the control unit 16 sets the occlusion unit selection number AN to the initial value “1”. (S44).

  As described above, the control of the cylinder for rich combustion and the mode control (switching valve control) of the storage unit can be synchronized. As a result, a predetermined cylinder is brought into a rich combustion state in accordance with a predetermined order, and only the storage portion connected to the cylinder is used in the NOx releasing mode. In addition, although the case where only any one occlusion part is used in NOx discharge | release mode was demonstrated, you may use not only this but a several occlusion part in NOx discharge | release mode, respectively.

  As described above, in the present embodiment, the dedicated storage units 61 to 66 are directly connected to the respective cylinders 2A to 2F, and the respective storage units 61 to 66 are connected to the downstream side of the storage units 61 to 66. A switching valve 70 that can be individually connected to either the combustion chamber 5 or the atmosphere is provided, and any one or a plurality of cylinders among the cylinders 2A to 2F are sequentially richly burned. Therefore, it is possible to flexibly set which storage unit is used in the NOx release mode and which storage unit is used in the NOx storage mode.

  A person skilled in the art can make various additions and modifications within the scope of the gist of the present invention described in each embodiment. For example, those skilled in the art can appropriately combine the above embodiments.

  For example, a configuration in which a conventional reduction catalyst, a three-way catalyst, or the like is further added to the exhaust gas purification apparatus of the present invention is also possible.

  Further, the present invention is not limited to passenger car engines, and can be applied to various engines such as construction machinery engines, marine engines, agricultural machinery engines, and power generation engines.

1 is an overall configuration diagram of an exhaust gas purification apparatus according to a first embodiment of the present invention. It is explanatory drawing which shows the switching operation | movement of each occlusion part, (a) is the state which occludes NOx in a 1st occlusion part, and discharge | releases NOx in a 2nd occlusion part, (b) is NOx in a 1st occlusion part. The state of releasing and storing NOx in the second storage part is shown respectively. It is a characteristic view which shows the NOx reduction effect by this embodiment. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 2nd Embodiment of this invention. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 3rd Embodiment of this invention. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 4th Embodiment of this invention. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 5th Embodiment of this invention. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 6th Embodiment of this invention. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 7th Embodiment of this invention. It is explanatory drawing which shows the switching operation | movement of each occlusion part, (a) is the state which occludes NOx in a 1st occlusion part, and discharge | releases NOx in a 2nd occlusion part, (b) is NOx in a 1st occlusion part. The state of releasing and storing NOx in the second storage part is shown respectively. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 8th Embodiment of this invention. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 9th Embodiment of this invention. It is explanatory drawing which shows a mode that a 1st and 2nd occlusion part occludes NOx and a 3rd occlusion part discharge | releases NOx. It is explanatory drawing which shows a mode that a 1st and 3rd storage part occludes NOx and a 2nd occlusion part discharge | releases NOx. It is explanatory drawing which shows a mode that a 2nd and 3rd occlusion part occludes NOx and a 1st occlusion part discharge | releases NOx. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 10th Embodiment of this invention. It is explanatory drawing at the time of changing the cylinder group made to carry out rich combustion. It is a flowchart which shows the relationship between target air fuel ratio control and switching control of a switching valve. It is a whole block diagram of the exhaust gas purification apparatus which concerns on the 11th Embodiment of this invention. It is explanatory drawing in the case of releasing NOx in the 5th storage part and storing NOx in another storage part. It is explanatory drawing in the case of discharging | emitting NOx in a 1st storage part and storing NOx in another storage part. It is a flowchart which shows the relationship between target air fuel ratio control and switching control of a switching valve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder, 5 ... Combustion chamber, 8 ... Intake manifold, 9 ... Exhaust manifold, 10 ... Oxidizing part, 11 ... 1st switching valve, 12 ... 1st occlusion part, 13 ... 2nd occlusion part, 14 DESCRIPTION OF SYMBOLS 2nd switching valve, 15 ... Reducing agent tank, 16 ... Control part, L1 ... Intake passage, L2 ... Exhaust passage, L3 ... Reducing agent supply passage, L4 ... Recirculation passage, 21 ... 1st occlusion part, 21A ... Oxidation part , 21B ... occlusion material, 22 ... second occlusion part, 22A ... oxidation part, 22B ... occlusion material, L5 ... outside air introduction passage, L6 ... exhaust gas introduction passage, 2A-2F ... cylinder, 31 ... fuel injection device, 32 ... engine Control unit, L31 ... exhaust gas supply passage, 41 ... first switching valve, 42 ... second switching valve, 43 ... first occlusion part, 44 ... second occlusion part, 45 ... third occlusion part, 61-66 ... occlusion part , 71-76 ... 2-way switching valve

Claims (4)

Occlusion means (12, 13) for occluding NOx in the exhaust gas from the engine (1);
At least one or more predetermined cylinders are selected from the cylinders (2A to 2F) of the engine (1), and the target air-fuel ratio of the selected predetermined cylinder is set to be richer than the theoretical air-fuel ratio and burned. Engine control means (32);
Rich exhaust gas supply means (L31) for releasing NOx occluded in the occlusion means by supplying rich exhaust gas from the predetermined cylinder to the occlusion means (12, 13);
The NOx released from the storage means (12, 13) and the rich exhaust gas supplied from the predetermined cylinder to the storage means (12, 13) are recirculated to the combustion chamber (5) of the engine (1). Reflux means (L4);
An exhaust gas purification apparatus comprising:   The exhaust gas purification device according to claim 1, wherein the engine control means (32) selects any one or a plurality of cylinders among the cylinders (2A to 2F) while switching in a predetermined order.   The engine control means (32) switches one cylinder group (2A to 2C) and the other cylinder group (2D to 2F) among the cylinders (2A to 2F). The exhaust gas purifying apparatus according to claim 1, wherein the exhaust gas purifying apparatus is selected and burned by setting the target air-fuel ratio of the selected cylinder group to be richer than the stoichiometric air-fuel ratio. Guiding the exhaust gas from the engine to the storage means, and storing the NOx in the exhaust gas in the storage means (S1);
A step (S2) of releasing NOx occluded in the occlusion means by supplying rich occlusion from a predetermined cylinder set in a rich combustion state among the cylinders of the engine to the occlusion means;
Recirculating the released NOx and the rich exhaust gas supplied to the storage means to the combustion chamber of the engine (S3);
An exhaust gas purification method comprising:

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