JP2010007634A - Exhaust emission control device for an internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology making a catalyst suitably recover exhaust gas control capacity while avoiding excessive temperature rise of the catalyst and a filter in an exhaust emission control device for an internal combustion engine. <P>SOLUTION: Flow rate of exhaust gas flowing into NSR and DPF is reduced as compared to that before execution of S regeneration or is set to zero when S regeneration is executed by adding fuel from a fuel addition valve arranged in an exhaust gas passage at an upstream side of NSR and DPF, and flow rate of exhaust gas flowing into NSR and DPF is increased as compared to that during execution of S regeneration when S regeneration is completed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

When the vehicle is decelerating, when the air-fuel ratio of the exhaust gas is lowered in order to restore the exhaust purification ability of the catalyst arranged in the exhaust passage of the internal combustion engine, the EGR valve is opened to suck in the EGR gas or Fuel system rich that increases the amount of fuel in the exhaust, such as by intake system rich control that reduces the amount of fresh air by throttling, and post injection in an internal combustion engine or injection in the exhaust passage that supplies fuel directly to the exhaust passage A technique of using both control and control is disclosed (for example, see Patent Document 1).
JP 2006-316757 A JP 2004-60537 A Japanese Patent Laid-Open No. 2007-9810 JP 2007-198145 A JP 2005-113800 A

  In the technique described in Patent Document 1, when the air-fuel ratio of the exhaust gas is lowered in order to recover the exhaust gas purification ability of the catalyst, the amount of fuel to be supplied can be reduced by reducing the fresh air amount. However, if there is a filter that collects particulate matter in the exhaust passage, the filter may be overheated simply by reducing the amount of fresh air.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suitably recover the exhaust purification ability of the catalyst while avoiding excessive temperature rise of the catalyst and the filter in the exhaust purification device of the internal combustion engine. It is to provide the technology to make.

In the first aspect of the present invention, the following configuration is adopted. That is, the present invention
A catalyst that is disposed in the exhaust passage of the internal combustion engine and that can recover the exhaust purification ability when the air-fuel ratio of the inflowing exhaust decreases,
A filter disposed in the exhaust passage and collecting particulate matter;
Reducing agent supply means for supplying a reducing agent upstream of the catalyst and the filter;
An exhaust air / fuel ratio lowering means for supplying a reducing agent by the reducing agent supply means and lowering an air / fuel ratio of exhaust flowing into the catalyst to recover an exhaust purification capability of the catalyst;
Exhaust flow rate adjusting means for adjusting the flow rate of exhaust gas flowing into the catalyst and the filter;
When the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means reduces the exhaust flow rate, and the exhaust air-fuel ratio lowering means decreases the exhaust air flow ratio flowing into the catalyst. When the exhaust air-fuel ratio lowering means finishes reducing the air-fuel ratio of the exhaust gas flowing into the catalyst, the exhaust flow rate adjusting means causes the exhaust flow rate to be reduced. A first control means for increasing the exhaust air / fuel ratio lowering means as compared to the time when the exhaust air / fuel ratio of the exhaust gas flowing into the catalyst is being lowered,
An exhaust emission control device for an internal combustion engine, comprising:

  Even when a catalyst and a filter are provided in the exhaust passage of the internal combustion engine, the reducing agent is supplied by the reducing agent supply means, and the air-fuel ratio of the exhaust gas flowing into the catalyst is lowered to recover the exhaust purification ability of the catalyst. This is implemented by the exhaust air / fuel ratio lowering means.

  Here, when the exhaust air / fuel ratio lowering means lowers the air / fuel ratio of the exhaust flowing into the catalyst, if the flow rate of the exhaust gas is large, it is supplied by the reducing agent supplying means for reducing the air / fuel ratio of the exhaust flowing into the catalyst. The amount of reducing agent supplied increases, the reaction of the reducing agent occurs excessively, and the temperature of a part of the catalyst increases excessively, and the catalyst may partially overheat. However, cooling by the exhaust gas flowing through the filter is superior to oxidation heat generation of the particulate matter due to oxygen supplied to the filter, and the filter does not overheat.

  On the other hand, when the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst, if the flow rate of the exhaust gas is small, the particulate matter due to oxygen supplied to the filter is less than the cooling by the exhaust flowing through the filter. Oxidation heat generation is excellent, and the filter may partially overheat. However, the supply amount of the reducing agent supplied by the reducing agent supply means for reducing the air-fuel ratio of the exhaust gas flowing into the catalyst is reduced, the reaction of the reducing agent is suppressed, and the temperature of the catalyst does not rise excessively. The catalyst does not overheat.

  Therefore, in the present invention, when the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means reduces the exhaust flow rate, and the exhaust air-fuel ratio lowering means flows into the catalyst. It is made to decrease or zero compared with before decreasing. At the same time, when the exhaust air-fuel ratio lowering means finishes reducing the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means changes the exhaust flow rate, and the exhaust air-fuel ratio lowering means reduces the exhaust gas flowing into the catalyst. The air-fuel ratio was increased compared to the time when it was decreasing.

  According to the present invention, when the exhaust air / fuel ratio lowering means lowers the air / fuel ratio of the exhaust gas flowing into the catalyst, the flow rate of the exhaust gas decreases or becomes zero compared to before the exhaust air / fuel ratio decreases. For this reason, when the flow rate of exhaust gas that may cause the filter to partially overheat decreases or becomes zero, the reducing agent is supplied from the upstream side of the filter by the reducing agent supply means and flows into the filter. The air-fuel ratio of the exhaust gas is also decreasing, and the oxygen concentration of the exhaust gas flowing into the filter is decreasing. Thereby, the oxidation heat generation of the particulate matter due to oxygen supplied to the filter does not occur so much, and overheating of the filter can be avoided. In addition, the amount of reducing agent supplied by the reducing agent supply means is decreased in order to reduce the air-fuel ratio of the exhaust gas flowing into the catalyst, so that the reaction of the reducing agent is suppressed and the temperature of the catalyst does not rise excessively. In addition, excessive heating of the catalyst can be avoided. Furthermore, the exhaust gas whose air-fuel ratio has been lowered tends to stay in the catalyst, and the recovery of the exhaust gas purification ability of the catalyst can be promoted, so that the exhaust gas purification capacity of the catalyst can be suitably recovered.

  On the other hand, according to the present invention, when the exhaust air / fuel ratio lowering means finishes decreasing the air / fuel ratio of the exhaust gas flowing into the catalyst, the flow rate of the exhaust gas increases as compared with the exhaust air / fuel ratio decreasing. For this reason, the reducing agent is not supplied from the upstream side of the filter by the reducing agent supply means, the air-fuel ratio of the exhaust gas flowing into the filter starts to rise, and the oxygen concentration of the exhaust gas flowing into the filter increases. However, at this time, the flow rate of the exhaust gas increases. Thereby, the cooling by the exhaust gas flowing through the filter is superior to the oxidation heat generation of the particulate matter due to oxygen supplied to the filter, and the excessive temperature rise of the filter can be avoided. Further, when the exhaust gas flow rate increases, the reduction of the exhaust air-fuel ratio is completed, so that the reaction of the reducing agent does not occur, the catalyst is not excessively heated, and the excessive temperature increase of the catalyst can be avoided.

  Therefore, the exhaust gas purification ability of the catalyst can be suitably recovered while avoiding excessive temperature rise of the catalyst and the filter.

  The catalyst may be disposed in an exhaust passage upstream of the filter, and the catalyst may be disposed in an exhaust passage downstream of the filter.

In the second present invention, the following configuration is adopted. That is, the present invention
A catalyst that is disposed in the exhaust passage of the internal combustion engine and can recover the exhaust purification ability when the air-fuel ratio of the inflowing exhaust gas decreases,
A filter that is disposed in an exhaust passage upstream of the catalyst and collects particulate matter;
Reducing agent supply means for supplying a reducing agent downstream from the filter and upstream from the catalyst;
An exhaust air / fuel ratio lowering means for supplying a reducing agent by the reducing agent supply means and lowering an air / fuel ratio of exhaust flowing into the catalyst to recover an exhaust purification capability of the catalyst;
Exhaust flow rate adjusting means for adjusting the flow rate of exhaust gas flowing into the catalyst and the filter;
Oxygen concentration adjusting means for adjusting the oxygen concentration of the exhaust gas upstream of the filter;
When the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means reduces the exhaust flow rate, and the exhaust air-fuel ratio lowering means decreases the exhaust air flow ratio flowing into the catalyst. The oxygen concentration of the exhaust gas is reduced or reduced to zero as compared with before the reduction, and the oxygen concentration of the exhaust gas is compared with that before the exhaust air / fuel ratio reduction device reduces the air / fuel ratio of the exhaust gas flowing into the catalyst. And when the exhaust air-fuel ratio reducing means finishes reducing the air-fuel ratio of the exhaust gas flowing into the catalyst, the exhaust air-fuel ratio reducing means reduces the exhaust flow rate by the exhaust flow rate adjusting means. The air-fuel ratio of the exhaust gas flowing into the catalyst is increased as compared with the time when the exhaust gas was being lowered, and the oxygen concentration of the exhaust gas is decreased by the oxygen concentration adjusting means, and the exhaust air-fuel ratio decreasing means flows into the catalyst A second control means for increasing compared during the air-fuel ratio of the exhaust gas was reduced that,
An exhaust emission control device for an internal combustion engine, comprising:

  Therefore, in the present invention, when the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means reduces the exhaust flow rate, and the exhaust air-fuel ratio lowering means flows into the catalyst. The oxygen concentration of the exhaust gas is reduced by the oxygen concentration adjusting means, and the oxygen concentration of the exhaust gas is reduced by the oxygen concentration adjusting means as compared with that before the exhaust air / fuel ratio reducing means lowers the air / fuel ratio of the exhaust gas flowing into the catalyst. I tried to make it. At the same time, when the exhaust air-fuel ratio lowering means finishes reducing the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means changes the exhaust flow rate, and the exhaust air-fuel ratio lowering means reduces the exhaust gas flowing into the catalyst. While the air-fuel ratio is being decreased, the oxygen concentration of the exhaust gas is increased by the oxygen concentration adjusting means, and the air-fuel ratio of the exhaust gas flowing into the catalyst is reduced by the exhaust air-fuel ratio reducing means. It was made to increase compared with.

  According to the present invention, when the exhaust air / fuel ratio lowering means lowers the air / fuel ratio of the exhaust gas flowing into the catalyst, the flow rate of the exhaust gas decreases or becomes zero as compared to before the exhaust air / fuel ratio decreases and flows into the filter. The oxygen concentration of the exhaust gas is reduced as compared with that before the exhaust air-fuel ratio is lowered. For this reason, when the flow rate of the exhaust gas, which may cause the filter to partially overheat, decreases or becomes zero, the oxygen concentration of the exhaust gas upstream of the filter is reduced by the oxygen concentration adjusting means, The oxygen concentration in the inflowing exhaust is decreasing. Thereby, the oxidation heat generation of the particulate matter due to oxygen supplied to the filter does not occur so much, and overheating of the filter can be avoided. In addition, the amount of reducing agent supplied by the reducing agent supply means is decreased in order to reduce the air-fuel ratio of the exhaust gas flowing into the catalyst, so that the reaction of the reducing agent is suppressed and the temperature of the catalyst does not rise excessively. In addition, excessive heating of the catalyst can be avoided. Furthermore, the exhaust gas whose air-fuel ratio has been lowered tends to stay in the catalyst, and the recovery of the exhaust gas purification ability of the catalyst can be promoted, so that the exhaust gas purification capacity of the catalyst can be suitably recovered.

On the other hand, according to the present invention, when the exhaust air-fuel ratio lowering means finishes reducing the air-fuel ratio of the exhaust flowing into the catalyst, the flow rate of the exhaust increases as compared with the exhaust air-fuel ratio decreasing, and the filter The oxygen concentration of the exhaust gas flowing into the exhaust gas increases as compared to when the exhaust air-fuel ratio is decreasing. For this reason, when the exhaust air-fuel ratio is finished lowering, the oxygen concentration of the exhaust gas is increased by the oxygen concentration adjusting means compared to when the exhaust air-fuel ratio is being lowered, and the oxygen concentration of the exhaust gas flowing into the filter is increased. However, at this time, the flow rate of the exhaust gas increases. Thereby, the cooling by the exhaust gas flowing through the filter is superior to the oxidation heat generation of the particulate matter due to oxygen supplied to the filter, and the excessive temperature rise of the filter can be avoided. Further, when the exhaust gas flow rate increases, the reduction of the exhaust air-fuel ratio is completed, so that the reaction of the reducing agent does not occur, the catalyst is not excessively heated, and the excessive temperature increase of the catalyst can be avoided.

  Therefore, the exhaust gas purification ability of the catalyst can be suitably recovered while avoiding excessive temperature rise of the catalyst and the filter.

  The reducing agent supply means may supply the reducing agent by at least one of an increase in the amount of fuel supplied to the internal combustion engine or an addition of the reducing agent to the exhaust by a reducing agent addition valve arranged in the exhaust passage. . According to the present invention, the reducing agent can be supplied and the air-fuel ratio of the exhaust can be lowered.

  The exhaust flow rate adjusting means includes an opening degree of a throttle valve disposed in an intake passage of the internal combustion engine, an EGR valve disposed in an EGR passage that recirculates a part of exhaust gas from the exhaust passage to the intake passage as EGR gas. The flow rate of the exhaust gas may be adjusted by at least one of the opening degree, the opening degree of the exhaust throttle valve disposed in the exhaust passage, the opening degree of the nozzle vane provided in the turbine of the turbocharger, or the engine stop of the internal combustion engine. . According to the present invention, the flow rate of the exhaust gas flowing into the catalyst and the filter can be adjusted.

  The period during which the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst is the air-fuel ratio of the exhaust downstream of the catalyst, the NOx storage amount of the catalyst, the SOx storage amount of the catalyst, or the It may be controlled based on at least any change in the bed temperature of the catalyst. According to the present invention, it is possible to set a suitable period for reducing the air-fuel ratio of the exhaust gas flowing into the catalyst.

  The oxygen concentration adjusting means is at least one of an increase in the amount of fuel supplied to the internal combustion engine or the addition of a reducing agent to the exhaust by a reducing agent addition valve disposed in the exhaust passage upstream of the filter. The oxygen concentration of the exhaust may be adjusted by According to the present invention, the oxygen concentration in the exhaust gas upstream of the filter can be adjusted.

  According to the present invention, in the exhaust gas purification apparatus for an internal combustion engine, the exhaust gas purification ability of the catalyst can be suitably recovered while avoiding excessive temperature rise of the catalyst and the filter.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus for an internal combustion engine according to the present embodiment is applied and an intake system / exhaust system thereof. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders. The internal combustion engine 1 is mounted on a vehicle. An intake passage 2 and an exhaust passage 3 are connected to the internal combustion engine 1.

  In the middle of the intake passage 2 connected to the internal combustion engine 1, a compressor 4a of a turbocharger 4 that operates using exhaust energy as a drive source is disposed. An air flow meter 5 for detecting the flow rate of fresh intake air (fresh air) flowing through the intake passage 2 is disposed in the intake passage 2 upstream of the compressor 4a. A fresh air amount (intake amount) of the internal combustion engine 1 is measured by the air flow meter 5.

A throttle valve 6 for adjusting the flow rate of the intake air flowing through the intake passage 2 is disposed in the intake passage 2 downstream of the compressor 4a. The throttle valve 6 is opened and closed by an electric actuator. The throttle valve 6 in this embodiment corresponds to the exhaust flow rate adjusting means of the present invention. The intake passage 2 and the devices disposed in the intake passage 2 constitute an intake system of the internal combustion engine 1.

  On the other hand, a turbine 4 b of the turbocharger 4 is arranged in the middle of the exhaust passage 3 connected to the internal combustion engine 1. The turbine 4b is driven by exhaust gas flowing through the exhaust passage 3, and the compressor 4a rotates together with the driven turbine 4b to supercharge intake air flowing through the intake passage 2. A plurality of variable nozzle vanes 4c are provided in a turbine chamber that accommodates the turbine 4b so as to surround the entire circumference of the turbine 4b, and a nozzle passage formed between the variable nozzle vanes 4c by rotating each of these variable nozzle vanes 4c. The cross-sectional area is changed. When the nozzle passage cross-sectional area is reduced by rotating the variable nozzle vane 4c, the supercharging pressure of the turbocharger 4 can be increased and the flow rate of the exhaust gas flowing to the exhaust passage 3 downstream of the turbine 4b is reduced. it can. The variable nozzle vane 4c is rotated by an electric actuator. The variable nozzle vane 4c of this embodiment corresponds to the exhaust flow rate adjusting means of the present invention.

  An NOx storage reduction catalyst (hereinafter referred to as NSR) 7 is disposed in the exhaust passage 3 downstream of the turbine 4b. The NSR 7 occludes NOx in the exhaust when the internal combustion engine 1 is in a normal operation state when the oxygen concentration of the exhaust is high, and the air-fuel ratio of the exhaust flowing in decreases to reduce the oxygen concentration of the exhaust. When the reducing agent is present, it has a characteristic of releasing and reducing the stored NOx to recover the NOx storage capacity. Further, when the oxygen concentration of the exhaust gas flowing into the internal combustion engine 1 is high as in the normal operation state, SOx is also occluded together with NOx in the exhaust gas, the temperature is raised to a high temperature, and the air-fuel ratio of the exhaust gas flowing in decreases. When the oxygen concentration in the exhaust gas is reduced and a reducing agent is present, the stored SOx is released and reduced to restore the NOx storage capacity. The NSR 7 in this embodiment corresponds to the catalyst of the present invention, and the NOx storage capacity of the NSR 7 corresponds to the exhaust purification capacity of the present invention.

  The catalyst of the present invention may be any catalyst that can recover the exhaust purification ability when the air-fuel ratio of the inflowing exhaust gas decreases, and may be a NOx direct reduction type catalyst or an ammonia selective reduction type NOx catalyst. Even with these catalysts, when the air-fuel ratio of the inflowing exhaust gas decreases, the adsorbed SOx can be released and reduced, and the exhaust gas purification ability can be recovered.

A diesel particulate filter (hereinafter referred to as DPF) 8 that collects particulate matter (PM) in the exhaust is disposed in the exhaust passage 3 downstream of the NSR 7.

  An exhaust throttle valve 9 that adjusts the flow rate of the exhaust gas flowing through the exhaust passage 3 is disposed in the exhaust passage 3 downstream of the DPF 8. The exhaust throttle valve 9 is opened and closed by an electric actuator. The exhaust throttle valve 9 in this embodiment corresponds to the exhaust flow rate adjusting means of the present invention.

  An exhaust air / fuel ratio sensor 10 for detecting the air / fuel ratio of the exhaust gas flowing out from the NSR 7 is disposed in the exhaust passage 3 immediately downstream of the NSR 7 and upstream of the DPF 8.

  In the exhaust passage 3 downstream of the turbine 4b and upstream of the NSR 7, a fuel addition valve 11 for adding fuel (light oil) as a reducing agent to the exhaust gas flowing through the exhaust passage 3 is disposed. The fuel added from the fuel addition valve 11 into the exhaust gas in the exhaust passage 3 lowers the exhaust air / fuel ratio flowing into the NSR 7 to release and reduce NOx and SOx stored in the NSR 7 or flows into the DPF 8. The temperature of the DPF 8 can be raised to oxidize and remove PM. The exhaust passage 3 and the devices arranged in the exhaust passage 3 constitute an exhaust system of the internal combustion engine 1.

On the other hand, the internal combustion engine 1 is provided with an EGR (Exhaust Gas Recirculation) passage 12 that recirculates (recirculates) part of the exhaust gas flowing through the exhaust passage 3 to the intake passage 2. In this embodiment, the exhaust gas recirculated by the EGR passage 12 is referred to as EGR gas. The EGR passage 12 connects the exhaust passage 3 upstream of the turbine 4 b and the intake passage 2 downstream of the throttle valve 6. Through this EGR passage 12, a part of the exhaust is sent to the internal combustion engine 1 as EGR gas. The EGR passage 12 is provided with an EGR valve 13 for adjusting the flow rate of the EGR gas flowing through the EGR passage 12 by adjusting the passage sectional area of the EGR passage 12. The EGR valve 13 is opened and closed by an electric actuator. The EGR valve 13 of this embodiment corresponds to the exhaust flow rate adjusting means of the present invention.

  Further, the internal combustion engine 1 is provided with a fuel injection valve 14 for supplying fuel into the cylinder of the internal combustion engine 1.

  The internal combustion engine 1 configured as described above is provided with an ECU 15 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 15 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  In addition to the air flow meter 5 and the exhaust air / fuel ratio sensor 10, the ECU 15 includes an accelerator opening sensor 16 that outputs an electrical signal corresponding to the amount of depression of the accelerator pedal, and a crank position sensor that detects the engine speed of the internal combustion engine 1. Various sensors such as 17 are connected via electric wiring, and output signals of these various sensors are input to the ECU 15.

  On the other hand, the variable nozzle vane 4c, the throttle valve 6, the exhaust throttle valve 9, and the electric actuator of the EGR valve 13, the fuel addition valve 11 and the fuel injection valve 14 are connected to the ECU 15 via electric wiring. By controlling these devices.

  By the way, in the NSR 7 disposed in the exhaust passage 3, the stored NOx increases with the operation time of the internal combustion engine 1. And when NSR7 occluded NOx increases, the NOx occlusion capability will decrease. Eventually, the NOx storage capacity of the NSR 7 is saturated, and NOx in the exhaust may be released into the atmosphere without being stored in the NSR 7. Therefore, in order to restore the NOx storage capacity of the NSR 7, when the NOx storage amount stored in the NSR 7 exceeds a predetermined amount, fuel is added from the fuel addition valve 11. As a result, there is a case where the air-fuel ratio of the exhaust gas flowing into the NSR 7 disposed in the exhaust passage 3 on the downstream side of the fuel addition valve 11 is reduced, and NOx reduction for releasing and reducing NOx from the NSR 7 may be performed. The ECU 15 that performs NOx reduction in this embodiment corresponds to the exhaust air-fuel ratio lowering means of the present invention.

  In NSR 7, SOx stored together with NOx increases with the operating time of the internal combustion engine 1. And as NSR7 occluded SOx increases, the NOx occlusion capability decreases. Therefore, in order to restore the NOx storage capacity of the NSR 7, when the SOx storage amount stored in the NSR 7 exceeds a predetermined amount, fuel is added from the fuel addition valve 11. As a result, the NSR 7 disposed in the exhaust passage 3 downstream of the fuel addition valve 11 is heated to a high temperature, the air-fuel ratio of the exhaust gas flowing into the NSR 7 is lowered, and S regeneration is performed in which SOx is released and reduced from the NSR 7. There is a case. The ECU 15 that executes S regeneration in this embodiment corresponds to the exhaust air-fuel ratio lowering means of the present invention. Hereinafter, the S reproduction will be described as an example. However, similar control is performed in NOx reduction.

Such S regeneration is performed when the vehicle on which the internal combustion engine 1 is mounted is decelerated. Here, when the S regeneration is performed, if the flow rate of the exhaust gas flowing into the NSR 7 is large, as shown by the solid line in FIG. 2, the fuel supply valve 11 supplies the exhaust gas flowing into the NSR 7 to reduce the air-fuel ratio. The amount of added fuel increases, the fuel reaction occurs excessively, and a part of the NSR 7 rises excessively,
NSR7 may partially overheat. However, when the S regeneration is performed, if the flow rate of the exhaust gas flowing into the DPF 8 is large, as shown by the broken line in FIG. 2, the exhaust gas flowing through the DPF 8 rather than the oxidative heat generation of PM due to the oxygen supplied to the DPF 8. Cooling is superior and the DPF 8 does not overheat.

  On the other hand, when performing the S regeneration, if the flow rate of the exhaust gas flowing into the DPF 8 is small, the oxidation of PM by the oxygen supplied to the DPF 8 rather than the cooling by the exhaust gas flowing through the DPF 8 as shown by the broken line in FIG. There is a possibility that the heat generation is excellent and the DPF 8 partially overheats. However, when performing the S regeneration, if the flow rate of the exhaust gas flowing into the NSR 7 is small, it is added by the fuel addition valve 11 in order to reduce the air-fuel ratio of the exhaust gas flowing into the NSR 7 as shown by the solid line in FIG. The amount of added fuel is reduced, the reaction of the fuel is suppressed, and the NSR 7 does not excessively rise in temperature, and the NSR 7 does not overheat.

  Therefore, in this embodiment, as shown in FIG. 4, when performing S regeneration on the NSR 7, the flow rate of the exhaust gas flowing into the NSR 7 and the DPF 8 is reduced or reduced to zero compared to before performing S regeneration. I tried to do it. At the same time, when the S regeneration is terminated, the flow rate of the exhaust gas flowing into the NSR 7 and the DPF 8 is increased as compared with the execution of the S regeneration.

  Here, the timing at which the flow rate of the exhaust gas is reduced or made zero when performing the S regeneration may be the timing after the S regeneration is performed and the fuel is added from the fuel addition valve 11, or the fuel addition valve 11 The timing just before the fuel is added may be used and is not limited. That is, when the exhaust gas flow rate is reduced or zero, the air-fuel ratio of the exhaust gas is lowered by the fuel added from the fuel addition valve 11, and the oxygen concentration of the exhaust gas is reduced. That's fine. In this embodiment, as shown in FIG. 4, immediately after the flow rate of the exhaust gas is reduced to a predetermined flow rate or less, S regeneration is started and fuel is added from the fuel addition valve 11. This is because if the fuel is added from the fuel addition valve 11 in a state where the flow rate of the exhaust gas is reduced, the amount of fuel addition required for lowering the air-fuel ratio of the exhaust gas can be reduced.

  The air-fuel ratio of the exhaust gas that is lowered when the S regeneration is performed is a desired rich air-fuel ratio by feeding back the detection value detected by the exhaust air-fuel ratio sensor 10 to control the amount of fuel added from the fuel addition valve 11. I am doing so.

  The method of reducing or reducing the exhaust flow rate when executing the S regeneration is to control the opening degree of the throttle valve 6 to the closed side to reduce the intake air amount, thereby reducing the flow rate of the exhaust gas discharged from the internal combustion engine 1. It may be allowed to. The flow rate of the exhaust gas in the exhaust passage 3 on the downstream side of the turbine 4b may be decreased by controlling the opening of the variable nozzle vane 4c to the closed side. The flow rate of the exhaust gas flowing through the exhaust passage 3 may be reduced or made zero by controlling the exhaust throttle valve 9 to the closed side. The engine exhausted from the internal combustion engine 1 may be made zero by stopping the internal combustion engine 1. The EGR valve 13 may be controlled to open to recirculate much of the exhaust gas to the EGR passage 12 so that the flow rate of the exhaust gas in the exhaust passage 3 downstream from the connection portion with the EGR passage 12 may be reduced. In this embodiment, the flow rate of the exhaust gas can be reduced or zero by combining one or more of the above-described methods. It is desirable that the flow rate of the exhaust gas be reduced as much as possible or zero so that the exhaust gas whose air-fuel ratio has been lowered tends to stay in the NSR 7 and the recovery of the NOx storage capacity of the NSR 7 can be promoted.

On the other hand, the timing of increasing the exhaust gas flow rate when S regeneration ends may be the timing after S regeneration ends and the addition of fuel from the fuel addition valve 11 ends, or the fuel is added from the fuel addition valve 11 It may be the timing just before the end, and is not limited. That is, when the addition of fuel from the fuel addition valve 11 is completed and the air-fuel ratio of the exhaust gas is increased and the oxygen concentration of the exhaust gas is increased, the flow rate of the exhaust gas is increased. Just do it. In the present embodiment, as shown in FIG. 4, when the detected value of the exhaust air / fuel ratio sensor 10 becomes equal to or higher than a predetermined air / fuel ratio after S regeneration is completed and fuel is added from the fuel addition valve 11, the flow rate of the exhaust gas is increased. Try to increase.

  The method of increasing the exhaust gas flow rate when the S regeneration is finished may be to increase the intake air flow rate by controlling the opening of the throttle valve 6 to the open side to increase the exhaust gas flow rate discharged from the internal combustion engine 1. . The flow rate of the exhaust gas in the exhaust passage 3 on the downstream side of the turbine 4b may be increased by controlling the opening of the variable nozzle vane 4c to the opening side. It is also possible to increase the flow rate of exhaust by controlling the exhaust throttle valve 9 to the open side. The internal combustion engine 1 that has been stopped may be restarted to exhaust the exhaust gas from the internal combustion engine 1. It is also possible to control the EGR valve 13 to the closed side and increase the flow rate of the exhaust gas in the exhaust gas passage 3 on the downstream side of the connection portion with the EGR passage 12 without causing the exhaust gas to recirculate so much in the EGR passage 12. In the present embodiment, the flow rate of the exhaust gas can be increased by combining one or more of the methods listed above. The flow rate of the exhaust gas may be a flow rate that is discharged when the internal combustion engine 1 is normally operated during deceleration of the vehicle.

  According to the present embodiment, when the S regeneration is executed, the flow rate of the exhaust gas flowing into the NSR 7 and the DPF 8 is reduced or becomes zero as compared with that before the S regeneration is executed. For this reason, when the flow rate of the exhaust gas, which may cause the DPF 8 to partially overheat, decreases or becomes zero, fuel is added from the upstream side of the DPF 8 by the fuel addition valve 11 and the exhaust gas flowing into the DPF 8 The air-fuel ratio of the exhaust gas also decreases, and the oxygen concentration of the exhaust gas flowing into the DPF 8 decreases. Then, as shown by the solid line in FIG. 5, when the flow rate of the exhaust gas decreases or becomes zero, the oxygen concentration of the exhaust gas flowing into the DPF 8 is low, so the oxidation heat of PM due to the oxygen supplied to the DPF 8 does not occur so much. Overheating of the DPF 8 can be avoided. Further, in order to reduce the air-fuel ratio of the exhaust gas flowing into the NSR 7, the amount of fuel added by the fuel addition valve 11 is reduced, the reaction of the fuel is suppressed, and the NSR 7 does not rise excessively. It is possible to avoid excessive temperature rise. Further, the exhaust gas whose air-fuel ratio has been lowered tends to stay in the NSR 7, and the recovery of the NOx storage capacity of the NSR 7 can be promoted, so that the NOx storage capacity of the NSR 7 can be recovered appropriately.

  On the other hand, according to the present embodiment, when the S regeneration is terminated, the flow rate of the exhaust gas is increased as compared with the execution of the S regeneration. For this reason, fuel is not added from the upstream side of the DPF 8 by the fuel addition valve 11, the air-fuel ratio of the exhaust gas flowing into the DPF 8 starts to rise, and the oxygen concentration of the exhaust gas flowing into the DPF increases. However, at this time, the flow rate of the exhaust gas flowing into the DPF 8 increases. Thereby, the cooling by the exhaust gas flowing through the DPF 8 is superior to the oxidation heat generation of the PM by the oxygen supplied to the DPF 8, and the excessive temperature rise of the DPF 8 can be avoided. Further, when the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 increases, the S regeneration is completed and the exhaust air-fuel ratio is finished decreasing. Therefore, the reaction of the fuel does not occur, the NSR 7 is not excessively heated, and the NSR 7 Overheating can also be avoided.

  Therefore, according to the present embodiment, it is possible to suitably recover the NOx storage capability of the NSR 7 while avoiding excessive temperature rise of the NSR 7 and the DPF 8.

  Next, the S regeneration control routine 1 according to this embodiment will be described. FIG. 6 is a flowchart showing the S regeneration control routine 1 according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 15 that executes this routine corresponds to the first control means of the present invention.

  In step S101, it is determined whether or not there is an S reproduction execution request. It can be determined that there is an S regeneration execution request when the S regeneration execution condition is established from the operating state of the internal combustion engine 1 detected by various sensors during deceleration of the vehicle or the like.

  If it is determined in step S101 that there is an S regeneration execution request, the process proceeds to step S102. If it is determined in step S101 that there is no S regeneration execution request, this routine is temporarily terminated.

  In step S102, the exhaust flow rate is decreased or made zero. By combining one or more of the above listed techniques, the exhaust flow rate is reduced or zeroed.

  In step S103, it is determined whether the exhaust flow rate is equal to or lower than a predetermined flow rate. The exhaust flow rate is estimated from the intake air amount detected by the air flow meter 5 and the operating state of the internal combustion engine 1 detected by various sensors, and it is determined whether or not the estimated exhaust flow rate is equal to or less than a predetermined flow rate. The predetermined flow rate is a predetermined flow rate, and is a flow rate that is reduced as compared to before performing the process of step S102.

  If it is determined in step S103 that the exhaust gas flow rate is equal to or lower than the predetermined flow rate, the process proceeds to step S104. If it is determined in step S103 that the exhaust gas flow rate is greater than the predetermined flow rate, the process loops and returns to step S103.

  In step S104, S reproduction is executed. That is, fuel is added from the fuel addition valve 11, the temperature of the NSR 7 is raised to a high temperature, the air-fuel ratio of the exhaust gas flowing into the NSR 7 is lowered, and SOx is released and reduced from the NSR 7.

  Here, the execution period of S regeneration is based on a change in at least one of the air-fuel ratio of the exhaust downstream of the NSR 7 detected by the exhaust air-fuel ratio sensor 10, the SOx occlusion amount of the NSR 7, or the bed temperature of the NSR 7. It should be controlled. Thereby, the execution time of S reproduction can be optimized.

  In step S105, it is determined whether or not the detected value of the exhaust air / fuel ratio sensor 10 is equal to or greater than a predetermined air / fuel ratio. The predetermined air-fuel ratio is a predetermined air-fuel ratio, for example, not a low air-fuel ratio that would be detected by air-fuel ratio fluctuations during S regeneration, but when S air regeneration ends and the exhaust air-fuel ratio rises An air-fuel ratio that can be detected is set.

  If it is determined in step S105 that the detected value of the exhaust air-fuel ratio sensor 10 is equal to or greater than the predetermined air-fuel ratio, the process proceeds to step S106. If it is determined in step S105 that the detected value of the exhaust air-fuel ratio sensor 10 is lower than the predetermined air-fuel ratio, the process loops and returns to step S105.

  In step S106, the exhaust gas flow rate is increased. The exhaust flow rate is increased by combining one or more of the methods listed above.

  According to this routine described above, the flow rate of the exhaust gas flowing into the NSR 7 and the DPF 8 can be reduced or zero immediately before the S regeneration is performed, and the NSR 7 and the DPF 8 are immediately restored after the S regeneration is finished. The flow rate of the inflowing exhaust gas can be increased. Thereby, it is possible to avoid the excessive temperature rise of the NSR 7 and the DPF 8 and execute the S regeneration.

  In the above embodiment, the S regeneration has been described, but the same applies to NOx reduction. The NOx reduction execution period is controlled based on a change in at least one of the air-fuel ratio of the exhaust downstream of the NSR 7 detected by the exhaust air-fuel ratio sensor 10, the NOx occlusion amount of the NSR 7, or the bed temperature of the NSR 7. Good. Thereby, the execution time of NOx reduction can be optimized.

In the above embodiment, the air-fuel ratio of the exhaust gas is reduced by adding fuel from the fuel addition valve 11 when performing the S regeneration. However, the present invention is not limited to this. For example, the amount of fuel supplied from the fuel injection valve 14 to the internal combustion engine 1, such as main injection increase, after injection, or post injection, may be increased, and the air-fuel ratio of the exhaust may be reduced when S regeneration is performed.

  Further, the exhaust flow rate adjusting means listed in the above embodiment is not limited. For example, as shown in FIG. 7, in a configuration in which the exhaust passages 3 of the two internal combustion engines 1 once merge in the middle and branch again, NSR 7 and DPF 8 are arranged in the exhaust passage 3 that branches again, and the NSR 7 and DPF 8 Alternatively, the flow rate of the exhaust gas flowing into the NSR 7 and the DPF 8 may be adjusted by opening and closing the exhaust control valve 18 disposed upstream. Further, as shown in FIG. 8, NSR 7 and DPF 8 are arranged in the exhaust passage 3 of the internal combustion engine 1, and a bypass passage 19 is provided that bypasses the exhaust passage 3 upstream from the NSR 7 to the exhaust passage 3 downstream of the DPF 8. In this configuration, the flow rate of the exhaust gas flowing into the NSR 7 and the DPF 8 is switched by switching the exhaust circulation route selection valve 20 that selects the exhaust passage 3 in which the NSR 7 and the DPF 8 are arranged or the bypass passage 19. May be adjusted. Further, as shown in FIG. 9, NSR 7 and DPF 8 are arranged in the exhaust passage 3 of the internal combustion engine 1, and a bypass passage 21 that bypasses the exhaust passage 3 upstream of the NSR 7 to the exhaust passage 3 upstream of the DPF 8 is provided. In this configuration, the flow rate of the exhaust gas flowing into the NSR 7 is adjusted by switching the exhaust gas flow route selection valve 22 that selects the exhaust passage 3 where the NSR 7 is disposed or the bypass passage 21 as the exhaust passage route. It may be. In these cases, the exhaust control valve 18 and the exhaust flow path selection valves 20 and 21 correspond to the exhaust flow rate adjusting means of the present invention.

  Moreover, in the said Example, NSR7 was arrange | positioned in the exhaust passage 3 upstream from DPF8. However, the present invention is not limited to this. As shown in FIG. 10, the NSR 7 may be disposed in the exhaust passage 3 on the downstream side of the DPF 8. Even in this case, if fuel is supplied from the fuel addition valve 11 or the internal combustion engine 1 upstream of the DPF 8 to the exhaust gas flowing into the NSR 7 and the DPF 8 when the S regeneration is performed, the same as in the above embodiment. Control becomes possible.

  In the above embodiment, the exhaust air / fuel ratio is detected using the detected value of the exhaust air / fuel ratio sensor 10. However, the present invention is not limited to this. For example, the exhaust air / fuel ratio may be detected by an HC sensor, an oxygen concentration sensor, or the like disposed at the same position as the exhaust air / fuel ratio sensor 10. Further, the exhaust air / fuel ratio may be estimated from a map based on the operating state of the internal combustion engine 1 without using these sensors.

<Example 2>
In the present embodiment, the case where the NSR 7 is arranged in the exhaust passage 3 downstream of the DPF 8 and the fuel addition valve 11 is arranged between the DPF 8 and the NSR 7 will be described. In the present embodiment, the characteristic part will be described, and the other configurations are the same as those in the above embodiment, and the description thereof will be omitted.

  In this embodiment, as shown in FIG. 11, the NSR 7 is arranged in the exhaust passage 3 on the downstream side of the DPF 8. A fuel addition valve 11 is disposed in the exhaust passage 3 downstream of the DPF 8 and upstream of the NSR 7.

  With the configuration of this embodiment, when performing S regeneration on the NSR 7, the DPF 8 disposed in the exhaust passage 3 upstream of the fuel addition valve 11 even if fuel is added from the fuel addition valve 11. The air-fuel ratio of the exhaust gas flowing into the exhaust gas does not decrease, and the oxygen concentration of the exhaust gas flowing into the DPF 8 does not decrease. In this case, when the S regeneration is executed, if the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 is reduced or made zero compared to before the execution of the S regeneration, the supply to the DPF 8 is performed rather than the cooling by the exhaust gas flowing through the DPF 8. There is a possibility that the oxidation heat of PM by the oxygen that is generated is superior and the DPF 8 partially overheats.

Therefore, in this embodiment, when performing the S regeneration, the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 is reduced or made zero as compared to before performing the S regeneration, and the exhaust gas flowing into the DPF 8 is reduced. The oxygen concentration was decreased as compared to before performing S regeneration. At the same time, when the S regeneration is finished, the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 is increased as compared to the time during the S regeneration, and the oxygen concentration of the exhaust gas flowing into the DPF 8 is increased. Increased compared to running.

  Here, the method of reducing the oxygen concentration of the exhaust gas flowing into the DPF 8 is to increase the amount of fuel supplied from the fuel injection valve 14 to the internal combustion engine 1 such as main injection increase, after injection, or post injection. While reducing the air-fuel ratio of the exhaust gas discharged, the oxygen concentration of the exhaust gas is decreased. In this method, the main purpose is to reduce the oxygen concentration of the exhaust gas flowing into the DPF 8, and therefore it is not necessary to reduce the air-fuel ratio of the exhaust gas as the S regeneration is performed on the NSR 7.

  The method for increasing the oxygen concentration of the exhaust gas flowing into the DPF 8 is to stop the increase in the amount of fuel supplied from the fuel injection valve 14 to the internal combustion engine 1, such as main injection increase, after injection, or post injection, and to be discharged from the internal combustion engine 1. The oxygen concentration of the exhaust gas is increased while the air-fuel ratio of the exhaust gas is increased. The amount of increase in the oxygen concentration of the exhaust may be an amount that is discharged when the internal combustion engine 1 is normally operated during deceleration of the vehicle. For this reason, the internal combustion engine 1 of the present embodiment corresponds to the oxygen concentration adjusting means of the present invention.

  According to the present embodiment, when performing S regeneration, the flow rate of the exhaust gas flowing into the DPF 8 and NSR 7 decreases or becomes zero as compared to before performing the S regeneration, and the oxygen concentration of the exhaust gas flowing into the DPF 8 is Reduced compared to before S regeneration. For this reason, when the flow rate of the exhaust gas, which may cause the DPF 8 to partially overheat, decreases or becomes zero, the fuel supply amount from the fuel injection valve 14 to the internal combustion engine 1 increases, and the exhaust gas flowing into the DPF 8 The oxygen concentration is decreasing. Thereby, the oxidation heat generation of PM due to oxygen supplied to the DPF 8 does not occur so much, and excessive temperature rise of the DPF 8 can be avoided. In addition, the amount of fuel added by the fuel addition valve 11 is reduced to reduce the air-fuel ratio of the exhaust gas flowing into the NSR 7, the reaction of the fuel is suppressed, and the NSR 7 does not rise excessively. It is possible to avoid excessive temperature rise. Further, the exhaust gas whose air-fuel ratio has been lowered is likely to stay in the NSR, and the recovery of the NOx storage capability of the NSR 7 can be promoted, and the NOx storage capability of the NSR 7 can be preferably recovered.

  On the other hand, according to the present embodiment, when the S regeneration is finished, the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 increases as compared with the execution of the S regeneration, and the oxygen concentration of the exhaust gas flowing into the DPF 8 is S Increased during playback. For this reason, when the S regeneration is completed and the decrease in the exhaust air-fuel ratio is completed, the amount of fuel supplied from the fuel injection valve 14 to the internal combustion engine 1 decreases, and the oxygen concentration of the exhaust gas flowing into the DPF 8 increases. However, at this time, the flow rate of the exhaust gas flowing into the DPF 8 increases. Thereby, the cooling by the exhaust gas flowing through the DPF 8 is superior to the oxidation heat generation of the PM by the oxygen supplied to the DPF 8, and the excessive temperature rise of the DPF 8 can be avoided. Further, when the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 increases, the S regeneration is completed and the exhaust air-fuel ratio is finished decreasing. Therefore, the reaction of the fuel does not occur, the NSR 7 is not excessively heated, and the NSR 7 Overheating can also be avoided.

  Therefore, the NOx occlusion capability of NSR 7 can be suitably recovered while avoiding excessive temperature rise of DPF 8 and NSR 7.

  Next, the S regeneration control routine 2 according to this embodiment will be described. FIG. 12 is a flowchart showing the S regeneration control routine 2 according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 15 that executes this routine corresponds to the second control means of the present invention. In this routine, the description of the same processing as that of the S regeneration control routine 1 of the above embodiment is omitted.

  If it is determined in step S103 that the exhaust gas flow rate is equal to or lower than the predetermined flow rate, the process proceeds to step S201. If it is determined in step S103 that the exhaust gas flow rate is greater than the predetermined flow rate, the process loops and returns to step S103.

  In step S201, the oxygen concentration of the exhaust gas flowing into the DPF 8 is decreased. That is, the amount of fuel supplied from the fuel injection valve 14 to the internal combustion engine 1 is increased by the method described above.

  If it is determined in step S105 that the detected value of the exhaust air-fuel ratio sensor 10 is equal to or greater than the predetermined air-fuel ratio, the process proceeds to step S202. If it is determined in step S105 that the detected value of the exhaust air-fuel ratio sensor 10 is lower than the predetermined air-fuel ratio, the process loops and returns to step S105.

  In step S202, the oxygen concentration of the exhaust gas flowing into the DPF 8 is increased. That is, the amount of fuel supplied from the fuel injection valve 14 to the internal combustion engine 1 is reduced.

  According to the routine described above, immediately before the S regeneration is executed, the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 can be reduced or made zero, and the oxygen concentration of the exhaust gas flowing into the DPF 8 can be decreased. Immediately after the completion of the S regeneration, the flow rate of the exhaust gas flowing into the DPF 8 and the NSR 7 can be increased, and the oxygen concentration of the exhaust gas flowing into the DPF 8 can be increased. Thereby, it is possible to avoid the excessive temperature rise of the DPF 8 and the NSR 7 and execute the S regeneration.

  In the above embodiment, the oxygen concentration of the exhaust gas flowing into the DPF 8 is reduced or increased by adjusting the amount of fuel supplied from the fuel injection valve 14 to the internal combustion engine 1. However, the present invention is not limited to this. For example, an upstream fuel addition valve may be disposed in the exhaust passage 3 upstream of the DPF 8, and fuel may be added from the upstream fuel addition valve to reduce the oxygen concentration of the exhaust flowing into the DPF 8. In this case, the upstream fuel addition valve corresponds to the oxygen concentration adjusting means of the present invention.

  The exhaust gas purification apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram showing a schematic configuration of an internal combustion engine and an intake system / exhaust system thereof according to Embodiment 1. FIG. The figure which shows the NSR floor temperature and DPF floor temperature in case there are many exhaust gas flow rates. The figure which shows the NSR floor temperature and DPF floor temperature when there are few exhaust gas flow rates. FIG. 3 is a diagram showing an exhaust air-fuel ratio and an exhaust flow rate during S regeneration according to the first embodiment. The figure which shows the DPF bed temperature which changes with the oxygen concentration of exhaust when there are few exhaust gas flow rates. 3 is a flowchart showing an S regeneration control routine 1 according to the first embodiment. FIG. 3 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to another example of the first embodiment. FIG. 3 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to another example of the first embodiment. FIG. 3 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to another example of the first embodiment. FIG. 3 is a diagram illustrating a schematic configuration of an internal combustion engine and an intake system / exhaust system thereof according to another example of the first embodiment. FIG. 3 is a diagram illustrating a schematic configuration of an internal combustion engine and an intake system and an exhaust system thereof according to a second embodiment. 9 is a flowchart showing an S regeneration control routine 2 according to the second embodiment.

Explanation of symbols

1 Internal combustion engine 2 Intake passage 3 Exhaust passage 4 Turbocharger 4a Compressor 4b Turbine 4c Variable nozzle vane 5 Air flow meter 6 Throttle valve 7 NSR
8 DPF
9 Exhaust throttle valve 10 Exhaust air / fuel ratio sensor 11 Fuel addition valve 12 EGR passage 13 EGR valve 14 Fuel injection valve 15 ECU
16 Accelerator opening sensor 17 Crank position sensor 18 Exhaust control valve 19 Bypass passage 20 Exhaust flow path selection valve 21 Bypass path 22 Exhaust flow path selection valve

Claims (8)

A catalyst that is disposed in the exhaust passage of the internal combustion engine and can recover the exhaust purification ability when the air-fuel ratio of the inflowing exhaust gas decreases,
A filter disposed in the exhaust passage and collecting particulate matter;
Reducing agent supply means for supplying a reducing agent upstream of the catalyst and the filter;
An exhaust air / fuel ratio lowering means for supplying a reducing agent by the reducing agent supply means and lowering an air / fuel ratio of exhaust flowing into the catalyst to recover an exhaust purification capability of the catalyst;
Exhaust flow rate adjusting means for adjusting the flow rate of exhaust gas flowing into the catalyst and the filter;
When the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means reduces the exhaust flow rate, and the exhaust air-fuel ratio lowering means decreases the exhaust air flow ratio flowing into the catalyst. When the exhaust air-fuel ratio lowering means finishes reducing the air-fuel ratio of the exhaust gas flowing into the catalyst, the exhaust flow rate adjusting means causes the exhaust flow rate to be reduced. A first control means for increasing the exhaust air / fuel ratio lowering means compared to the time when the exhaust air / fuel ratio of the exhaust flowing into the catalyst is being lowered,
An exhaust emission control device for an internal combustion engine, comprising:   The exhaust purification device for an internal combustion engine according to claim 1, wherein the catalyst is disposed in an exhaust passage upstream of the filter.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the catalyst is arranged in an exhaust passage downstream of the filter. A catalyst that is disposed in the exhaust passage of the internal combustion engine and can recover the exhaust purification ability when the air-fuel ratio of the inflowing exhaust gas decreases,
A filter that is disposed in an exhaust passage upstream of the catalyst and collects particulate matter;
Reducing agent supply means for supplying a reducing agent downstream from the filter and upstream from the catalyst;
An exhaust air / fuel ratio lowering means for supplying a reducing agent by the reducing agent supply means and lowering an air / fuel ratio of exhaust flowing into the catalyst to recover an exhaust purification capability of the catalyst;
Exhaust flow rate adjusting means for adjusting the flow rate of exhaust gas flowing into the catalyst and the filter;
Oxygen concentration adjusting means for adjusting the oxygen concentration of the exhaust gas upstream of the filter;
When the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst, the exhaust flow rate adjusting means reduces the exhaust flow rate, and the exhaust air-fuel ratio lowering means decreases the exhaust air flow ratio flowing into the catalyst. The oxygen concentration of the exhaust gas is reduced or reduced to zero as compared with before the reduction, and the oxygen concentration of the exhaust gas is compared with that before the exhaust air / fuel ratio reduction device reduces the air / fuel ratio of the exhaust gas flowing into the catalyst. And when the exhaust air-fuel ratio reducing means finishes reducing the air-fuel ratio of the exhaust gas flowing into the catalyst, the exhaust air-fuel ratio reducing means reduces the exhaust flow rate by the exhaust flow rate adjusting means. The air-fuel ratio of the exhaust gas flowing into the catalyst is increased as compared with the time when the exhaust gas was being lowered, and the oxygen concentration of the exhaust gas is decreased by the oxygen concentration adjusting means, and the exhaust air-fuel ratio decreasing means flows into the catalyst A second control means for increasing compared during the air-fuel ratio of the exhaust gas was reduced that,
An exhaust emission control device for an internal combustion engine, comprising:   The reducing agent supply means supplies the reducing agent by at least one of an increase in the amount of fuel supplied to the internal combustion engine or an addition of the reducing agent to the exhaust by a reducing agent addition valve disposed in the exhaust passage. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 4, wherein: The exhaust flow rate adjusting means includes an opening degree of a throttle valve disposed in an intake passage of the internal combustion engine,
An opening degree of an EGR valve arranged in an EGR passage for recirculating a part of the exhaust gas from the exhaust passage to the intake passage as EGR gas, an opening degree of an exhaust throttle valve arranged in the exhaust passage, and provided in a turbine of a turbocharger The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the flow rate of the exhaust gas is adjusted by at least one of an opening degree of the nozzle vane provided or an engine stop of the internal combustion engine. .   The period during which the exhaust air-fuel ratio lowering means lowers the air-fuel ratio of the exhaust flowing into the catalyst is the air-fuel ratio of the exhaust downstream of the catalyst, the NOx storage amount of the catalyst, the SOx storage amount of the catalyst, or the The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust gas purification device is controlled based on at least any change in the bed temperature of the catalyst.   The oxygen concentration adjusting means is at least one of an increase in the amount of fuel supplied to the internal combustion engine or the addition of a reducing agent to the exhaust by a reducing agent addition valve disposed in the exhaust passage upstream of the filter. The exhaust gas purification apparatus for an internal combustion engine according to claim 4, wherein the oxygen concentration of the exhaust gas is adjusted by the control.

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