WO2013005337A1 - Exhaust purification apparatus for internal combustion engine - Google Patents

Abstract

Provided is an exhaust purification apparatus for an internal combustion engine with a DPF disposed in the exhaust system of the internal combustion engine, such that accumulation of ash in the DPF can be suppressed, and increases in pressure loss and PM regeneration temperature as well as a decrease in fuel efficiency can be suppressed over a long period. A surface of the DPF is coated with a solid acid with an acid strength greater than the acid strength of SO₃ and smaller than the acid strength of SO₄. An SOx adsorbing/releasing catalytic apparatus is provided upstream of the DPF in the exhaust system of the internal combustion engine. The exhaust purification apparatus performs: control for increasing the temperature of the DPF; air-fuel ratio control for the atmosphere within the DPF; and control for causing SO₄ to be released from the SOx adsorbing/releasing catalytic apparatus when the flow rate of exhaust passing through the DPF exceeds a predetermined value during the control for increasing the temperature of the DPF.

Description

Exhaust gas purification device for internal combustion engine

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

In order to reduce the number of particles of particulate matter (hereinafter referred to as “PM”) in the exhaust gas of the internal combustion engine, a diesel particulate filter (hereinafter referred to as “DPF”) is installed in the exhaust gas passage of the internal combustion engine, Generally, PM in exhaust gas is collected and removed.

In this case, since the PM collected in the DPF gradually accumulates, regeneration (hereinafter referred to as “PM regeneration”) is performed periodically or by detecting a decrease in the performance of the DPF and burning and removing the PM collected in the DPF. ”).

PM regeneration operation is usually performed by heating the DPF while supplying a reducing agent such as hydrocarbon (HC) to the DPF.

Various improvements have been proposed to improve the performance and reduce the cost of the PM regeneration operation that collects PM in the exhaust gas using the DPF and burns and removes the PM collected in the DPF. Has been.

However, in the conventional DPF, if the use of the DPF is continued, even if the PM regeneration operation is performed, the pressure loss of the DPF gradually increases, and if the PM regeneration temperature is not gradually increased, sufficient regeneration is achieved. There is a problem that it will not be performed, and fuel consumption deteriorates. This problem is caused by the accumulation of ash inside the DPF.

Ash is generated when the engine oil mixed in the cylinder of the engine burns, and the generated ash particles are covered with PM in the DPF. The ash particles covered with PM are exposed to high temperature conditions during the PM regeneration operation in the DPF, and the PM covering the ash particles is burned and removed. Ash deposition occurs because the ash particles are agglomerated and increased in size by further applying heat to the ash particles from which the PM has been burned and removed.

However, there is no effective solution to the accumulation of ash so far, and in order to minimize the influence of the accumulation of ash on the DPF, for example, a large-capacity DPF is installed in advance. Measures were taken.

That is, the improvement to the conventional DPF and the improvement to the regeneration operation of the DPF are intended to improve the collection efficiency of the DPF and improve the performance of the PM regeneration operation, and not to the accumulation of ash. As an object for improving the performance of the PM regeneration operation, for example, there is an invention disclosed in Patent Document 1, and Patent Document 1 shows a configuration of a DPF capable of burning PM at a relatively low temperature. Yes.

The structure of the DPF disclosed in Patent Document 1 is characterized in that, in the DPF and the exhaust gas purification method using the DPF, a catalyst made of a solid superacid having an active metal supported on the DPF is held on the filter surface. is there.

That is, the invention of Patent Document 1 reduces the combustion temperature of PM with a solid super strong acid carrying an active metal, and regenerates DPF at a lower temperature than before, preferably continuously, and CO, HC, NO, NO ₂ can be removed at the same time.

Therefore, the invention of Patent Document 1 is intended to improve the performance of the PM regeneration operation, and does not correspond to the accumulation of ash. If the use of the DPF is continued, the PM regeneration operation is performed. However, this does not solve the problem that the pressure loss of the DPF gradually increases, and unless the PM regeneration temperature is gradually increased, sufficient regeneration cannot be performed and the fuel consumption deteriorates.

Further, as a disclosure of a catalyst structure similar to the invention of Patent Document 1, there is an invention of Patent Document 2, which is selected from platinum, palladium and rhodium as a catalyst for a diesel engine exhaust gas purification device. By using a catalyst having at least one kind of noble metal and a solid super strong acid, it is possible to purify SOF (Soluable Organic Fraction), unburned hydrocarbons, etc. contained in particulate matter in diesel engine exhaust gas from a low temperature range. Further, it is described that the effect of suppressing oxidation of sulfur dioxide is exhibited even in a high temperature range, and the invention of Patent Document 2 aims at an effect similar to the invention of Patent Document 1 and does not relate to DPF. Therefore, it does not correspond to the accumulation of ash on the DPF. If the use of the DPF is continued, the pressure loss of the DPF gradually increases and the PM regeneration temperature gradually increases even if the PM regeneration operation is performed. If this is not done, it will not solve the problem that sufficient regeneration will not be performed and fuel consumption will deteriorate.

JP 2006-289175 A Japanese Patent Laid-Open No. 10-033985

The present invention provides an exhaust emission control device for an internal combustion engine that can suppress the accumulation of ash on the DPF and suppress an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption over a long period of time. It is aimed.

That is, the present invention provides a configuration in which the ash deposited on the DPF is discharged after being reduced in particle size to regenerate the DPF (hereinafter referred to as “ash regeneration”), and the CaSO ₄ having a reduced particle size is retained. As the ash regeneration operation proceeds effectively and the ash is removed at a high release rate, it is possible to suppress an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption over a long period of time. It is an object of the present invention to provide an epoch-making DPF that has the advantageous effect of being able to be made.

According to the present invention, the accumulated ash can be discharged with a reduced particle size. As a further effect, a DPF that is smaller than the conventional DPF can be used from the beginning of the installation of the DPF. Not only cost reduction, but also energy cost of PM regeneration operation can be reduced. In addition, the fact that a small DPF can be used means that the space for mounting the DPF on the vehicle can be reduced, and the weight of the vehicle on which the DPF is mounted can be reduced.

The inventor of the present application studied the problem of ash accumulation inside the DPF, analyzed the cause of ash accumulation, and the main components of ash were calcium (Ca) contained in engine oil and SOx in exhaust gas. It was found that ash is ion-bonded, CaSO ₄ is the main component, and Ca salt has a high melting point, so that in the exhaust gas, ash flows into the DPF as a solid and aggregates to increase the particle size.

Furthermore, the inventors of the present application have confirmed by experiments that the size of ash is on the order of submicrons, and that the ash slips through the DPF when the ash size is reduced to the order of nanomicrons.

Furthermore, the inventors of the present application, a CaSO ₄ that large grain size to the size of submicron, when placed in a reducing atmosphere, it becomes SO ₃ SO ₄ of CaSO ₄ is reduced, the bond between Ca weakened, At this time, if an acid stronger than SO ₃ is present on the surface of the DPF, the bond between Ca and SO _{3 in} the CaSO ₃ is cleaved, and the Ca ions are stronger than the SO ₃ on the surface of the DPF. It was confirmed by experiments that the atoms were dispersed and bonded in an atomic form.

Furthermore, the inventors of the present application, Ca ions associated with stronger acid than SO ₃ on the surface of the DPF is different from the stronger acid than SO ₃ on the surface of the DPF, if a stronger acid is present in the atmosphere It was confirmed by an experiment that it binds to a stronger acid in the atmosphere, is released from the DPF, and passes through the DPF to be discharged.

To summarize the above, if the acid strength of this acid is stronger than SO ₃ on the surface of the DPF and the acid strength of this acid is stronger than SO ₃ and weaker than SO ₄ , the particle size will be submicron. CaSO ₄ deposited in the DPF turned into, in a reducing atmosphere, becomes CaSO ₃ SO ₄ is reduced in CaSO _4, Ca ions CaSO ₃ is bonded with the acid on the surface of the DPF, on the surface of the DPF Disperse in atomic form. Next, if SO ₄ is present in the atmosphere, the Ca on the surface of the DPF combines with the SO _{4 in} the atmosphere and becomes sub-nanometer-sized CaSO ₄ and is released from the DPF.

When the exhaust gas atmosphere is a stoichiometric or rich atmosphere, it is the above-described reducing atmosphere, and when it is a lean atmosphere, the lean atmosphere contains SO ₄ . Therefore, if control for making the atmosphere stoichiometric or rich and control for making the lean atmosphere next are performed on the above-mentioned DPF, ash Ca ions deposited on the DPF in the stoichiometric or rich atmosphere are converted to DPF. Then, in a lean atmosphere, Ca on the surface of the DPF is combined with SO ₄ in the lean atmosphere and released from the DPF, and the fine particle size is reduced to a sub-nanometer size. CaSO ₄ is converted to pass through the DPF and discharged.

That is, in the above process, the first CaSO ₄ having a large particle size of submicron and deposited on the DPF is finally released again from the DPF as CaSO _4. No. ₄ is reduced in size to a sub-nanometer size and passes through the DPF and is discharged.

However, when the above ash regeneration operation is performed, if the flow rate of the exhaust gas passing through the DPF is low, the CaSO ₄ having a reduced particle size stays and re-aggregates, which makes it difficult to release from the DPF. is there.

In order to solve this problem, the present invention supplies SO ₄ required for the release of ash when the flow rate of exhaust gas passing through the DPF is high, and CaSO ₄ having a reduced particle size is effectively used. It is intended to be released. That is, according to the present invention, CaSO ₄ having a reduced particle size is released without stagnation, and the ash regeneration operation proceeds effectively.

Moreover, when performing the above ash reproduction | regeneration operation | movement, normally, the ash is in the state buried in PM deposited in DPF. Therefore, even trying to ash reproduced in this state, in order to CaSO ₄ deposited in the DPF with large grain size to the size of the sub-micron can not be in contact with a reducing atmosphere, SO ₄ of CaSO ₄ is reduced Not. Alternatively, the ash reduced to CaSO ₃ cannot contact the solid acid on the surface of the DPF. Therefore, in order to effectively decompose the ash, it is preferable to perform the ash regeneration operation after burning and removing PM by the PM regeneration operation.

The ash regeneration operation and the PM regeneration operation are performed in accordance with the ash accumulation state and the PM accumulation state, respectively. Usually, the frequency of the ash regeneration operation may be less than the frequency of the PM regeneration operation. In addition, since the ash regeneration operation and the PM regeneration operation can be performed at substantially the same temperature, the ash regeneration operation is performed as one of a plurality of PM regeneration operations using the temperature increase of the PM regeneration operation. It is efficient to carry out it subsequently.

Further, when the operating state of the internal combustion engine is in an accelerated state, the condition that the flow rate of the exhaust gas is high is likely to occur. Therefore, when performing the above-described ash regeneration operation, when the operation state of the internal combustion engine is in the acceleration state, it is determined whether the flow rate of the exhaust gas is fast, and control for supplying SO ₄ is performed. The timing of operation can be determined efficiently.

According to the first aspect of the present invention, there is provided an exhaust purification device for an internal combustion engine in which a DPF is disposed in an exhaust system of the internal combustion engine, wherein the DPF is a DPF whose surface is coated with a solid acid, The acid strength is higher than the acid strength of SO ₃ and lower than the acid strength of SO ₄ , and in the exhaust system of the internal combustion engine, SO ₄ is increased by raising the temperature upstream of the DPF whose surface is coated with a solid acid. An SOx absorption / release catalyst device having a characteristic of releasing ash, and further, an ash regeneration operation control that removes ash accumulated in the DPF, and the control of the ash regeneration operation increases the temperature of the DPF; The control of the air-fuel ratio of the atmosphere in the DPF and the control of releasing SO ₄ from the SOx adsorption / release catalyst device are provided, and the control of the air-fuel ratio of the atmosphere in the DPF increases the temperature of the DPF. In this control, the stoichiometric or air-fuel ratio rich atmosphere is first changed to the air-fuel ratio lean atmosphere, and the control for releasing SO ₄ from the SOx adsorption / release catalyst device increases the DPF temperature. During this time, there is provided an exhaust gas purification apparatus for an internal combustion engine, which is control for releasing SO ₄ from the SOx absorption / release catalyst device when the flow rate of the exhaust gas passing through the DPF exceeds a predetermined value.

That is, in the invention of claim 1, the DPF is constituted by applying a solid acid having an acid strength stronger than SO _{3 and} weaker than SO ₄ on the surface of the DPF. Relative thus constituted DPF, when passing the exhaust gas in a reducing atmosphere, CaSO ₄ deposited on the DPF with large grain size is in a reducing atmosphere, SO ₄ of CaSO ₄ is reduced CaSO ₃ If the Ca ions of CaSO ₃ bind to the solid acid on the surface of the DPF, and then SO ₄ is present in the atmosphere, the Ca on the surface of the DPF binds to SO _{4 in} the atmosphere. , CaSO ₄ is released from the DPF. Since the CaSO ₄ released through this process has a reduced particle size, the first large-sized CaSO ₄ is released from the DPF as a reduced particle size CaSO ₄ and passes through the DPF. Discharged. Here, in order to avoid the fact that CaSO ₄ having a reduced particle size stays and re-aggregates, and the release from the DPF is less likely to occur, the ash is released when the flow rate of the exhaust gas passing through the DPF is high. Necessary SO ₄ is supplied so that CaSO ₄ having a reduced particle size is effectively released. Therefore, CaSO ₄ having a reduced particle size is released without stagnation, the ash regeneration operation effectively proceeds, and the ash is removed at a high release rate, thereby suppressing the accumulation of ash on the DPF, An exhaust purification device for an internal combustion engine that can suppress an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption over a long period of time is provided.

According to the second aspect of the present invention, there is further provided a PM regeneration operation control in which the PM accumulated in the DPF is combusted and removed by raising the temperature of the DPF, and the ash regeneration operation is controlled in a plurality of ways. The exhaust emission control device for an internal combustion engine according to claim 1, which is performed subsequent to one of the PM regeneration operations.

That is, in the invention of claim 2, the ash regeneration operation is controlled following one of the plurality of PM regeneration operations. Usually, the frequency of the ash regeneration operation may be less than the frequency of the PM regeneration operation, and the ash regeneration operation and the PM regeneration operation can be performed at substantially the same temperature. When carried out following one of the plurality of PM regeneration operations, the CaSO ₄ having a large particle size that has been buried in the PM comes to be exposed to a reducing atmosphere and is reduced to CaSO _{4. The} ash that becomes ₃ comes into contact with the solid acid on the surface of the DPF, and the ash regeneration operation following the PM regeneration operation effectively proceeds. Further, when the flow rate of the exhaust gas passing through the DPF is high, SO ₄ necessary for ash release is supplied so that CaSO ₄ having a reduced particle size is effectively released. Therefore, CaSO ₄ having a reduced particle size is released without stagnation, the ash regeneration operation effectively proceeds, and the ash is removed at a high release rate, thereby suppressing the accumulation of ash on the DPF, An exhaust purification device for an internal combustion engine that can suppress an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption over a long period of time is provided.

According to the third aspect of the present invention, the control for releasing SO ₄ from the SOx adsorption / release catalyst device is further performed when the operating state of the internal combustion engine is in an acceleration state. An exhaust gas purification device for an internal combustion engine according to 2, is provided.

That is, in the third aspect of the invention, when the operating state of the internal combustion engine is in an accelerated state, the condition that the flow rate of the exhaust gas is high is likely to occur. Therefore, when the operating state of the internal combustion engine is in the accelerated state, the exhaust gas It is possible to determine whether the flow rate of the ash is high and control to supply SO ₄ to efficiently determine the timing of the ash regeneration operation. Therefore, CaSO ₄ having a reduced particle size is released without stagnation, the ash regeneration operation effectively proceeds, and the ash is removed at a high release rate, thereby suppressing the accumulation of ash on the DPF, An exhaust purification device for an internal combustion engine that can suppress an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption over a long period of time is provided.

According to the invention described in each claim, an ash regeneration configuration is provided, and in the ash regeneration operation, the CaSO ₄ having a reduced particle size is released without stagnation, and the ash regeneration operation proceeds effectively. Since the ash is removed at a high release rate, the accumulation of ash on the DPF is suppressed, and an increase in pressure loss, an increase in PM regeneration temperature, and a decrease in fuel consumption can be suppressed over a long period of time. There is a common effect that the exhaust purification device provides.

FIG. 1 is a diagram for explaining a schematic configuration of an embodiment of an apparatus arrangement when the present invention is applied to an exhaust gas purification apparatus for an internal combustion engine.
FIG. 2 is a diagram for explaining the effect of implementing the present invention.
FIG. 3 is a flowchart illustrating a schematic configuration of an embodiment of control according to the present invention.
FIG. 4 is a diagram for explaining the principle of the present invention.
FIG. 5 is a diagram for explaining the principle of the present invention.
FIG. 6 is a diagram for explaining the principle of the present invention.
FIG. 7 is a diagram for explaining the principle of control of the present invention.
FIG. 8 is a diagram for explaining an embodiment of the control of the present invention.
FIG. 9 is a diagram for explaining another embodiment of the control of the present invention.
FIG. 10 is a diagram for explaining still another embodiment of the control of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the plurality of accompanying drawings, the same or corresponding members are denoted by the same reference numerals.

FIG. 1 is a diagram showing a basic configuration of the present invention. A solid acid corresponding to an acid strength of SO ₃ or more and SO ₄ or less is formed on the surface of DPF 2, specifically, on the surface of a DPF substrate of DPF 2. Apply. Further, an SOx absorption / release catalyst device 30 is provided upstream of the DPF 2 in the exhaust system of the internal combustion engine 1. The exhaust gas of the internal combustion engine 1 is guided to the DPF 2 via the SOx absorption / release catalyst device 30, SOx in the exhaust gas is collected and removed by the SOx absorption / release catalyst device 30, and PM in the exhaust gas is captured by the DPF 2. The exhaust gas that has been collected and removed and from which SOx and PM have been removed is discharged. Since PM collected in the DPF 2 is gradually accumulated, a PM regeneration operation is performed periodically or by detecting a decrease in the performance of the DPF 2 and burning and removing the PM collected in the DPF 2.

However, when the PM regeneration operation is repeatedly performed, as shown in FIG. 4, the ash 3 accumulates in the DPF, and even when the PM regeneration operation is performed, the pressure loss of the DPF gradually increases, and the PM regeneration temperature is increased. There is a problem that sufficient regeneration cannot be performed unless the value is gradually increased, and fuel consumption deteriorates.

In the present invention, as shown in FIG. 5, the ash 3 deposited in the DPF is reduced in size, so that the particles reduced in size pass through the filter gap of the DPF and are discharged together with the exhaust gas.

The present invention will be described in detail with reference to FIG. 6. First, as shown in FIG. 6A, when the DPF is continuously used, the ash particles generated by the engine and covered with the PM are regenerated into the PM within the DPF. Ashes 3 exposed to high temperature conditions during operation are burned and removed from the PM particles that have covered the ash particles, and heat is further applied to the ash particles from which the PM has been burned and removed to aggregate the ash particles, thereby increasing the particle size. accumulate. At this time, the particles of ash 3 are mainly composed of calcium sulfate (CaSO ₄ ). However, when the atmosphere is a reducing atmosphere, for example, a stoichiometric atmosphere or a rich atmosphere in FIG. It is reduced to calcium (CaSO ₃ ). Therefore, when the solid acid 6 having an acid strength of SO ₃ or more is present on the DPF substrate 5, as shown in FIG. 6B, calcium (Ca) in the ash particles is stronger than SO _3. It binds to solid acid 6 which is an acid, and ash 3 decomposes. At this time, Ca is dispersed atomically on the solid acid 6. Next, when Ca dispersed atomically on the solid acid 6 is exposed to an atmosphere containing SO ₄ , for example, the exhaust from the internal combustion engine usually contains SOx, and the lean atmosphere in order to sO ₄ is contained in a large amount, when exposed to a lean atmosphere, as shown in FIG. 6 (c), Ca dispersed in atomic form on the solid acid 6, sO ₄ is stronger acid than the solid acid 6 And is sulfated again to form calcium sulfate (CaSO ₄ ), which is released from the solid acid. Calcium sulfate (CaSO ₄ ) at this time is a particle having a fine particle size of 1 nanometer or less, and the fine particle size passes through the DPF as an aerosol. The accumulated ash is removed.

In this case, the acid strength of the solid acid 6 applied on the DPF substrate 5 must be larger than the acid strength of SO ₃ and smaller than the acid strength of SO ₄ . When the acid strength of the solid acid 6 is equal to or lower than the acid strength of SO ₃ , Ca in the ash particles reduced to CaSO ₃ does not bind to the solid acid 6 and therefore ash 3 does not decompose, and This is because when the solid acid 6 is a super strong acid that is equal to or higher than the acid strength of SO ₄ , even if SO ₄ exists in the atmosphere, Ca is not released from the solid acid 6.

Therefore, a solid acid corresponding to an acid strength of SO ₃ or more and SO ₄ or less is applied on the DPF base 5 and the air-fuel ratio of the atmosphere in the DPF is set to the stoichiometric or air-fuel ratio first during the ash regeneration operation. When control is performed so as to change to a rich atmosphere and then change to an air-fuel ratio lean atmosphere, the ash having a large particle size in the DPF becomes ash particles having a fine particle size, passes through the DPF, and is discharged.

Further, when performing the above ash regeneration operation, if the flow rate of the exhaust gas passing through the DPF is slow, the CaSO ₄ having a reduced particle size stays and re-aggregates, which makes it difficult to release from the DPF. is there. That is, in FIG. 5, when the ash 3 deposited in the DPF has a small particle size, if the flow rate of the exhaust gas passing through the DPF is slow, the CaSO ₄ having a small particle size re-aggregates and the release from the DPF Less likely to occur.

Therefore, the present invention supplies SO ₄ necessary for ash release when the flow rate of exhaust gas passing through the DPF is high, so that CaSO ₄ having a reduced particle size can be effectively released. .

This will be described with reference to FIG. 7. In the two uppermost graphs in FIG. 7, the thin line graph indicates the vehicle speed indicated by the left vertical axis, and the bold line graph indicates the right vertical axis. Exhaust gas flow rate, but when the exhaust gas flow rate Ga exceeds the threshold value, as shown by the oblique line, the air-fuel ratio in the third graph from the top is close to the stoichiometric value on the rich side of the threshold value, that is, the lean region. At the same time, release of SO ₄ from the SOx adsorption / release catalyst device is started (in the control of FIG. 3 described later, this is referred to as “acceleration rich control”). The lowermost graph in FIG. 7 is a graph showing the SOx release concentration from the SOx absorption / release catalyst device, and when the exhaust gas flow rate Ga exceeds the threshold value, the release of SO ₄ from the SOx absorption / release catalyst device starts. It is shown that.

Doing the above control, as shown by D _P3 of FIG. 2, also the pressure loss of the DPF forever can constitute the DPF does not increase. That is, D _P1 in FIG. 2 indicates an increase in pressure loss of the DPF when the ash regeneration control of the present invention is not performed, and D _P2 performs the ash regeneration control of the present invention, but the flow rate of the exhaust gas passing through the DPF in the case where the not controlled supplying SO ₄ needed for the release of ash in accordance with the time fast, shows an increase in the pressure loss of the DPF, D _P3, the control supplies SO ₄ of the present invention, D It shows that it is more advantageous than _P1 and _DP2 .

Figure 3 is obtained by the flow chart of the control described above, at step 100, if it is determined to perform the ash regeneration, i.e., when entering the ash reproducing area Z _A in FIG. 7, the process proceeds to step 200, Start control of ash regeneration operation. In step 300, it is determined whether or not the exhaust gas flow rate Ga exceeds a threshold value during the ash regeneration operation. If the threshold value is exceeded, the process proceeds to step 400, where acceleration rich control is performed. As described above, the acceleration rich control is a control in which the air-fuel ratio is controlled to a region close to the stoichiometric range in the lean region, and at the same time, the release of SO ₄ from the SOx adsorption / release catalyst device is started.

In step 300, if the exhaust gas flow rate Ga does not exceed the threshold value, it is determined whether to continue the ash regeneration operation, whether in the case of ash reproducing area Z _A is exceeded further exhaust gas flow rate Ga is the threshold This determination is repeated, and the acceleration rich control is repeated when the exhaust gas flow rate Ga exceeds the threshold value.

The acceleration rich control in the description of the flowchart of FIG. 3, that is, the control of controlling the air-fuel ratio in FIG. 7 to a region close to the stoichiometric in the lean region and simultaneously starting the release of SO ₄ from the SOx adsorption / release catalyst device, FIG. 8 illustrates in more detail, and FIG. 8 shows the relationship of the supplied SOx with respect to the air-fuel ratio in the DPF and the temperature. That is, in FIG. 8, “small” and “many” indicate that “the supply amount of SOx is small” and “the supply amount of SOx is large”, respectively, and the relationship of FIG. 8 is controlled. A map is incorporated into the control system, and combined control of the air-fuel ratio and the SOx supply amount is performed.

FIG. 9 shows another embodiment of the control according to the present invention. The control is the same as that shown in FIG. 7, but shows the control when combined with the afterburn control of the internal combustion engine. Among the two graphs, the graph a indicated by a thin line is the case without after injection, the graph b indicated by the thick line is the case with after injection, and when the after injection is present, the exhaust gas flow rate Ga is When the threshold value is exceeded, after-injection is performed, and the air-fuel ratio of the environment in the DPF is shifted to a region close to stoichiometry in the lean region, and the same control effect as the control of FIG. 7 is obtained. .

FIG. 10 shows still another embodiment of the control according to the present invention. The control is the same as the control in FIG. 7 except that an exhaust fuel addition valve is provided and combined with the control of the fuel addition valve. In the lower graph of FIG. 9, the graph c indicated by a thin line of the two graphs is a case where the fuel addition valve control is not performed, and the graph d indicated by a bold line is a case where the fuel addition valve control is performed. Yes, when fuel addition valve control is performed, when the exhaust gas flow rate Ga exceeds a threshold value, the fuel addition valve control is performed to shift the air-fuel ratio of the environment in the DPF to a region close to stoichiometry in the lean region. Thus, it is shown that the same control effect as the control of FIG. 7 is obtained.

As described above, a solid acid corresponding to an acid strength of SO ₃ or higher and SO ₄ or lower is applied on the DPF base material, and the air-fuel ratio of the atmosphere in the DPF is first stoichiometrically or during the ash regeneration operation. When the air-fuel ratio rich atmosphere is set and the flow rate of the exhaust gas passing through the DPF exceeds a predetermined value, the air-fuel ratio is changed to a lean atmosphere close to the stoichiometric so as to release SO ₄ from the SOx adsorption / release catalyst device. When controlled, the ash having a large particle size in the DPF 2 is completely removed, and an exhaust gas purification apparatus for an internal combustion engine having a DPF whose performance does not deteriorate indefinitely can be configured. The advantageous effect that it can be improved automatically. Furthermore, as a further effect that accompanies this effect, a DPF smaller than the conventional one can be used from the beginning of the installation of the DPF, which not only reduces the manufacturing cost of the DPF but also reduces the energy cost of the PM regeneration operation. be able to. Furthermore, the fact that a small DPF can be used has the effect that the space for mounting the DPF on the vehicle can be reduced, and the weight of the vehicle on which the DPF is mounted can be reduced. It should be noted.

1 Internal combustion engine 2 DPF
3 Ash 4 Fine particle 5 DPF base material 6 Solid acid 30 SOx absorption / release catalyst device L ₁ : SOx absorption / release catalyst device inlet L ₂ : DPF inlet L ₃ : DPF outlet Z _A : Ash regeneration operation Z _NOR : Normal Operation Z _R : Air-fuel ratio rich operation

Claims (3)

1. An exhaust purification device for an internal combustion engine in which a DPF is disposed in an exhaust system of the internal combustion engine,
   The DPF is a DPF having a surface coated with a solid acid,
   The acid strength of the solid acid is greater than the acid strength of SO ₃ and less than the acid strength of SO ₄ ;
   In the exhaust system of the internal combustion engine, an SOx absorption / release catalyst device having a characteristic of releasing SO ₄ by raising the temperature is provided upstream of the DPF whose surface is coated with a solid acid,
   Furthermore, the ash regeneration operation control for removing the ash accumulated in the DPF is provided,
   The control of the ash regeneration operation is
   Control to increase the temperature of the DPF;
   Control of the air-fuel ratio of the atmosphere in the DPF;
   Control for releasing SO ₄ from the SOx absorption / release catalyst device,
   The control of the air-fuel ratio of the atmosphere in the DPF is a control for changing the atmosphere to the stoichiometric or air-fuel ratio rich atmosphere first and then changing to the air-fuel ratio lean atmosphere during the control to increase the temperature of the DPF.
   When the control for releasing SO ₄ from the SOx adsorption / release catalyst device increases the temperature of the DPF, and the flow rate of the exhaust gas passing through the DPF exceeds a predetermined value, the SOx adsorption / release catalyst device Control to release SO ₄ ,
   An exhaust purification device for an internal combustion engine.
2. Furthermore, it comprises control of PM regeneration operation that raises the temperature of the DPF to burn and remove PM accumulated in the DPF,
   Control of the ash regeneration operation is performed following one of the plurality of PM regeneration operations.
   The exhaust emission control device for an internal combustion engine according to claim 1.
3. The control for releasing SO ₄ from the SOx absorption / release catalyst device is control performed when the operating state of the internal combustion engine is in an accelerated state.
   The exhaust emission control device for an internal combustion engine according to claim 1 or 2.

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