JP2007040129A - Exhaust gas purification system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine provided with an exhaust passage branched into two branch passages on the way and an exhaust purification device provided in each of the two branch passages and having a function of collecting PM in exhaust. In the exhaust gas purification system, a technique capable of more suitably estimating the amount of particulate matter collected in each exhaust gas purification device is provided.
SOLUTION: The pressure upstream of the exhaust gas purifying device and the flow control valve in the vicinity of the upstream side of the two branch passages in the exhaust passage or in the two branch passages, and the downstream of the two branch passages in the exhaust passage Provided in one of the two branch passages with a differential pressure sensor that detects the difference between the exhaust purification device and the pressure downstream of the flow control valve in the vicinity of the side assembly or in the two branch passages Based on the detected value of the differential pressure sensor when the flow rate control valve thus controlled is in the fully closed state, the trapped amount of particulate matter in the exhaust purification device provided in the other branch passage is estimated.
[Selection] Figure 1

Description

  The present invention includes an exhaust passage that is branched into two branch passages, and an exhaust purification device that is provided in each of the two branch passages and has a function of collecting particulate matter in the exhaust. The present invention relates to an exhaust gas purification system for an internal combustion engine.

  In an exhaust gas purification system for an internal combustion engine, an exhaust passage branched into two branch passages and a particulate matter (hereinafter referred to as PM) in the exhaust provided in each of the two branch passages are captured. And an exhaust emission control device having a function of collecting.

  For example, Patent Literature 1 includes an exhaust passage that branches into three branch passages along the way, and a filter that collects PM in two branch passages among the three branch passages is provided as an exhaust purification device. An exhaust purification system for an internal combustion engine is disclosed. In the exhaust gas purification system for an internal combustion engine according to Patent Document 1, an adjustment valve mechanism that adjusts the flow path of exhaust gas is provided at the upstream side of the three branch passages.

Patent Document 2 discloses a technique for estimating the amount of PM trapped in a filter based on the differential pressure between the upstream side and the downstream side of the filter when a filter is provided in the exhaust passage. ing.
JP 2003-343261 A JP 2003-155920 A

  In an exhaust gas purification system for an internal combustion engine comprising: an exhaust passage having two branch passages; and an exhaust purification device provided in each of the two branch passages and having a function of collecting PM in the exhaust gas, It is necessary to estimate the amount of particulate matter collected in each exhaust purification device.

  However, if a differential pressure sensor for detecting the differential pressure between the upstream side and the downstream side of the exhaust purification device is provided in each of the two branch passages, there is a risk of increasing the manufacturing cost. Moreover, there is a possibility that the mounting property on the vehicle may be lowered.

  Further, if the two branch passages communicate with each other upstream of the exhaust purification device and downstream of the exhaust purification device, the pressure upstream of the exhaust purification device in one branch passage and the exhaust purification in the other branch passage The difference between the pressure upstream of the apparatus and the difference between the pressure downstream of the exhaust purification device in one branch passage and the pressure downstream of the exhaust purification device in the other branch passage becomes relatively small. For this reason, even when a differential pressure sensor is provided in each of the two branch passages, the difference in the detected value of each differential pressure sensor becomes relatively small. Therefore, it may be difficult to accurately estimate the amount of PM trapped in each exhaust purification device.

  The present invention has been made in view of the above-described problem, and is provided in each of an exhaust passage branched into two branch passages and two branch passages, and traps PM in the exhaust. It is an object of the present invention to provide a technique capable of more suitably estimating the amount of PM trapped in each exhaust purification device in an exhaust purification system for an internal combustion engine having an exhaust purification device having a function.

  The present invention provides an internal combustion engine comprising: an exhaust passage that is branched into two branch passages; and an exhaust purification device that is provided in each of the two branch passages and has a function of collecting PM in the exhaust. In an engine exhaust gas purification system, one differential pressure sensor is provided in an exhaust passage, and the amount of PM trapped in each exhaust gas purification device is estimated based on a detection value of the differential pressure sensor.

More specifically, the exhaust gas purification system for an internal combustion engine according to the present invention is:
An exhaust passage branched into two branch passages on the way, and the two branch passages gathered downstream thereof;
An exhaust purification device provided in each of the two branch passages and having a function of collecting particulate matter in the exhaust;
A flow rate control valve that is provided in each of the two branch passages and controls the flow rate of the exhaust;
A fully closing means for controlling the flow control valve to a fully closed state when a predetermined condition is satisfied;
A pressure upstream of the exhaust purification device and the flow control valve in the vicinity of the upstream side of the two branch passages in the exhaust passage or in the two branch passages; and the two branches in the exhaust passage. A differential pressure sensor that detects a difference between the pressure on the downstream side of the exhaust purification device and the flow rate control valve in the vicinity of the downstream collecting portion of the passage or in either of the two branch passages;
A collection amount estimating means for estimating the collection amount of particulate matter in each exhaust purification device,
The collected amount estimating means is a detection value of the differential pressure sensor when the flow control valve provided in one of the two branch passages is controlled to a fully closed state by the fully closing means. Based on the above, the amount of trapped particulate matter in the exhaust emission control device provided in the other branch passage is estimated.

  In the present invention, the middle of the exhaust passage branches into two branch passages. Each branch passage is provided with an exhaust purification device having a function of collecting particulate matter in the exhaust gas and a flow rate control valve. As an exhaust emission control device according to the present invention, an exhaust purification device including a particulate filter or a monolith type catalyst can be exemplified.

  The flow control valve is controlled to be fully closed by the fully closing means when a predetermined condition is satisfied. Here, the fully closed state is a state in which the opening degree of the flow control valve is as small as possible. Further, the predetermined condition is a condition for determining that it is necessary to reduce the flow rate of the exhaust gas in the branch passage as much as possible.

  In the present invention, one differential pressure sensor is provided in the exhaust passage. This differential pressure sensor has a pressure upstream of the exhaust gas purification device and the flow control valve in the vicinity of the upstream collecting portion of the two branch passages or in one of the two branch passages, and the downstream side of the two branch passages. The difference between the exhaust purification device and the pressure downstream of the flow rate control valve in the vicinity of the collecting portion or in one of the two branch passages is detected.

  In the present invention, the collection amount estimating means detects the differential pressure sensor when the flow control valve provided in one of the two branch passages is controlled to the fully closed state by the fully closing means. Based on the value, the amount of PM trapped in the exhaust emission control device provided in the other branch passage is estimated.

When the flow control valve provided in one branch passage is controlled to a fully closed state, most of the exhaust flowing through the exhaust passage flows through the other branch passage. Therefore, even if the differential pressure sensor detects the differential pressure at any of the above positions, if the flow control valve provided in one branch passage is controlled to be fully closed, the differential pressure sensor Detects the differential pressure between the upstream side and the downstream side of the exhaust gas purification device provided in the other branch passage. Thereby, it is possible to estimate the amount of PM trapped in the exhaust purification device provided in the other branch passage.

  In addition, the collected amount estimating means detects the differential pressure sensor when the flow control valve provided in the other of the two branch passages is controlled to the fully closed state by the fully closing means, as described above. Based on the value, the amount of PM trapped in the exhaust emission control device provided in one branch passage is estimated.

  Therefore, according to the present invention, it is possible to estimate the amount of PM trapped in each exhaust purification device based on the detection value of one differential pressure sensor. Further, if the differential pressure sensor can detect any differential pressure among the above positions, it is possible to estimate the amount of PM trapped in each exhaust purification device, and therefore the installation position of the differential pressure sensor. The degree of freedom is relatively large. As a result, the mountability on the vehicle is further improved.

  In addition, according to the present invention, when estimating the amount of PM collected by the exhaust gas purification device provided in the other branch passage, one branch passage is substantially blocked by the flow path control valve. Therefore, it is possible to estimate the PM collection amount in each exhaust purification device more accurately based on the detection value of the differential pressure sensor.

  As described above, according to the present invention, it is possible to more suitably estimate the amount of PM trapped in each exhaust purification device.

  As described above, in the present invention, the differential pressure sensor has a pressure upstream of the exhaust purification device and the flow control valve in one branch passage, and more than the exhaust purification device and the flow control valve in the one branch passage. A difference from the downstream pressure may be detected. The differential pressure sensor detects the difference between the pressure in the vicinity of the upstream collecting portion of the two branch passages in the exhaust passage and the pressure downstream of the exhaust purification device and the flow control valve in one branch passage. There may be. The differential pressure sensor detects the difference between the pressure upstream of the exhaust purification device and the flow control valve in one branch passage and the pressure in the vicinity of the downstream gathering portion of the two branch passages in the exhaust passage. There may be.

  In any of these cases, the exhaust gas provided in the other branch passage is based on the detected value of the differential pressure sensor when the flow control valve provided in one branch passage is in the closed state. The amount of PM collected in the purification device is estimated. Further, based on the detected value of the differential pressure sensor when the flow control valve provided in the other branch passage is closed, the amount of PM trapped in the exhaust purification device provided in the one branch passage is determined. presume.

  However, when the differential pressure sensor detects the differential pressure at the position as described above and detects the differential pressure between the upstream side and the downstream side of each exhaust purification device by the above-described method, Even if the PM collection amount in the exhaust purification device provided in the passage is the same as the PM collection amount in the exhaust purification device provided in the other branch passage, the pressure detection position for each exhaust purification device is different. Therefore, the detection value of the differential pressure sensor becomes a different value.

  That is, when the PM accumulation amount in each exhaust purification device is the same, the detected value of the differential pressure sensor when the differential pressure between the upstream side and the downstream side of the exhaust purification device provided in one branch passage is detected. However, it becomes larger than the detected value of the differential pressure sensor when the differential pressure between the upstream side and the downstream side of the exhaust purification device provided in the other branch passage is detected.

Therefore, when the differential pressure sensor is for detecting the differential pressure at the position as described above, the collection amount estimation means is configured to estimate the PM collection amount in the exhaust purification device provided in one branch passage. If the detected value of the differential pressure sensor and the detected value of the differential pressure sensor when estimating the amount of PM trapped in the exhaust purification device provided in the other branch passage are the same value, It may be estimated that the amount of collected PM in the provided exhaust purification device is larger than the amount of collected PM in the exhaust purification device provided in one branch passage.

  Thereby, even if a differential pressure sensor detects the differential pressure | voltage of the above positions, PM collection amount in each exhaust gas purification apparatus can be estimated more accurately.

  In the present invention, when the PM collection amount in the exhaust purification device estimated by the collection amount estimating means is equal to or greater than a predetermined collection amount, PM removal control for oxidizing and removing the PM collected in the corresponding exhaust purification device PM removal control execution means for executing the above may be further provided.

  In such a configuration, when PM removal control is continuously executed only for the exhaust purification device provided in one or the other branch passage, it is determined that an abnormality has occurred in the corresponding branch passage. May be.

  In the present invention, usually, PM is collected almost equally in each exhaust purification device. And in the case of the said structure, when PM collection amount will be more than predetermined collection amount, PM removal control will be performed with respect to the applicable exhaust gas purification device, and PM will be oxidized and removed.

  Therefore, if the exhaust purification device and the flow control valve are in a normal state in each branch passage, when PM removal control is performed on the exhaust purification device provided in one branch passage, the other branch passage PM removal control is also executed for the provided exhaust purification device. That is, PM removal control is executed alternately for each exhaust purification device. Therefore, when PM removal control is continuously executed only for the exhaust purification device provided in one or the other branch passage, it can be determined that an abnormality has occurred in the corresponding branch passage.

  In the present invention, each exhaust purification device may include a catalyst having an oxidation function. Also, a reducing agent supply means for supplying a reducing agent to the catalyst provided in each of the two branch passages, and PM removal control execution for executing PM removal control for oxidizing and removing the PM collected in the exhaust purification device And a means.

  In this case, the PM removal control means executes the PM removal control by controlling the flow rate control valve in the valve closing direction and supplying the reducing agent to the catalyst by the reducing agent supply means. That is, by controlling the flow rate control valve in the valve closing direction, the flow rate of the exhaust gas flowing through the exhaust purification device is decreased, and further, the reducing agent is supplied to the catalyst to oxidize the reducing agent. The exhaust gas purification device is heated by the oxidation heat generated at this time to oxidize and remove PM. In this case, the temperature of the exhaust emission control device is controlled to a target temperature by controlling the opening degree of the flow control valve and the supply amount of the reducing agent.

  Here, in the present invention, the flow rate of the exhaust gas flowing through one branch passage varies depending on the amount of PM trapped in the exhaust gas purification device provided in the other branch passage.

  Therefore, in the case of the above configuration, when the PM removal control execution means executes the PM removal control to oxidize and remove the PM collected in the exhaust gas purification device provided in one branch passage, Based on the amount of collected PM in the provided exhaust purification device, the opening degree of the flow control valve in one branch passage and / or the reducing agent supply amount by the reducing agent supply means may be controlled.

  As a result, the temperature of the exhaust gas purification device that is subject to PM removal control can be controlled to a target temperature with higher accuracy.

In the present invention, each exhaust purification device may include an NOx storage reduction catalyst (hereinafter simply referred to as a NOx catalyst). Further, a reducing agent supply means for supplying a reducing agent to the NOx catalyst provided in each of the two branch passages, and an SOx poisoning regeneration control for executing SOx poisoning regeneration control for reducing SOx stored in the NOx catalyst. Execution means.

  In this case, the SOx poisoning regeneration control execution unit controls the flow rate control valve in the valve closing direction and supplies the reducing agent to the NOx catalyst by the reducing agent supply unit, thereby executing the SOx poisoning regeneration control. That is, by controlling the flow rate control valve in the valve closing direction, the flow rate of the exhaust gas flowing through the NOx catalyst is decreased, and further, the reducing agent is supplied to the NOx catalyst, whereby the ambient atmosphere of the NOx catalyst is made the reducing atmosphere. Thereby, SOx is reduced. In this case, by controlling the opening of the flow control valve and the supply amount of the reducing agent, the temperature of the NOx catalyst is controlled to a target temperature, and the air-fuel ratio in the ambient atmosphere of the NOx catalyst is set as a target. To control.

  Here, in the present invention, as in the case of PM removal control, the flow rate of the exhaust gas flowing through one branch passage varies depending on the amount of PM trapped in the exhaust gas purification device provided in the other branch passage.

  Therefore, in the case of the above configuration, when the SOx poisoning regeneration control execution means executes SOx poisoning regeneration control to reduce the SOx occluded in the NOx catalyst of the exhaust purification device provided in one branch passage, Based on the amount of PM collected in the exhaust gas purification device provided in the branch passage, the opening of the flow control valve in the one branch passage and / or the reducing agent supply amount by the reducing agent supply means may be controlled.

  Thereby, it becomes possible to control the temperature of the NOx catalyst to be subjected to SOx poisoning regeneration control to a target temperature with higher accuracy. In addition, the air-fuel ratio of the atmosphere surrounding the NOx catalyst can be controlled to the target air-fuel ratio with higher accuracy.

  According to the present invention, there are provided an exhaust passage that is branched into two branch passages, and an exhaust purification device that is provided in each of the two branch passages and has a function of collecting PM in the exhaust. In the exhaust gas purification system for an internal combustion engine, the amount of PM trapped in each exhaust gas purification device can be estimated more suitably.

  Hereinafter, specific embodiments of an exhaust gas purification system for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Schematic configuration of intake and exhaust system of internal combustion engine>
Here, the case where the present invention is applied to a diesel engine for driving a vehicle will be described as an example. FIG. 1 is a diagram showing a schematic configuration of an intake / exhaust system of an internal combustion engine according to the present embodiment.

  The internal combustion engine 1 is a diesel engine for driving a vehicle. An intake passage 3 and an exhaust passage 2 are connected to the internal combustion engine 1. An air flow meter 4 is provided in the intake passage 3.

The exhaust passage 2 is branched into two branch passages on the way, and these branch passages are gathered downstream thereof. In this embodiment, one of the two branch passages is a first branch passage 2a, and the other is a second branch passage 2b. Further, an upstream portion of the exhaust passage 2 upstream of the first and second branch passages 2a and 2b is referred to as an upstream passage 2c. Further, a downstream portion of the first and second branch passages 2a and 2b in the exhaust passage 2 is defined as a downstream passage 2d.

  The first branch passage 2a is provided with a filter 6a that collects PM in the exhaust gas. An oxidation catalyst 5a is provided on the upstream side of the filter 6a in the first branch passage 2a. The oxidation catalyst 5a may be a catalyst having an oxidation function, and may be a NOx catalyst, for example.

  The first branch passage 2a upstream of the oxidation catalyst 5a is provided with a fuel addition valve 7a for adding fuel as a reducing agent into the exhaust gas. The first branch passage 2a on the downstream side of the filter 6a is provided with a flow rate control valve 8a for controlling the flow rate of the exhaust gas flowing through the first branch passage 2a.

  An upstream exhaust temperature sensor 10a is provided downstream of the oxidation catalyst 5a and upstream of the filter 6a in the first branch passage 2a. A downstream exhaust temperature sensor 11a is provided in the first branch passage 2a downstream from the filter 6a and upstream from the flow control valve 8a.

  Also, the second branch passage 2b has the same arrangement as the first branch passage 2a, and the filter 6b and the oxidation catalyst 5b, the fuel addition valve 7b, the flow control valve 8b, the upstream side exhaust temperature sensor 10b, and the downstream side exhaust temperature sensor. 11b is provided. Thus, in this embodiment, the exhaust emission control device according to the present invention is constituted by the oxidation catalysts 5a and 5b and the filters 6a and 6b.

  An engine side exhaust temperature sensor 12 is provided in the upstream side passage 2c. Further, the exhaust passage 2 includes a pressure in the upstream passage 2c in the vicinity of the upstream collecting portion of the first and second branch passages 2a and 2b, and a downstream of the first and second branch passages 2a and 2b in the downstream passage 2d. A differential pressure sensor 9 that detects a difference from the pressure in the vicinity of the side assembly portion is provided.

  The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 20 for controlling the internal combustion engine 1. The ECU 20 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.

  The ECU 20 includes an air flow meter 4 and upstream exhaust temperature sensors 10a and 10b, downstream exhaust temperature sensors 11a and 11b, an engine exhaust temperature sensor 12, a differential pressure sensor 9, and a rotation of a crankshaft of the internal combustion engine 1. A crank position sensor 13 that outputs an electrical signal corresponding to a corner and an accelerator opening sensor 14 that outputs an electrical signal corresponding to the accelerator opening of a vehicle equipped with the internal combustion engine 1 are electrically connected. These output signals are input to the ECU 20.

  The ECU 20 calculates the rotational speed of the internal combustion engine 1 based on the detection value of the crank position sensor 14 and calculates the load of the internal combustion engine 1 based on the detection value of the accelerator opening sensor 15. Further, the ECU 20 estimates the temperatures of the oxidation catalysts 5a and 5b based on the detected values of the upstream side exhaust temperature sensors 10a and 10b. Further, the ECU 20 estimates the temperature of each of the filters 6a and 6b based on the detected value of each of the downstream side exhaust temperature sensors 11a and 11b.

  Further, the ECU 10 is electrically connected to the fuel addition valves 7a and 7b and the flow control valves 8a and 8b. These are controlled by the ECU 10.

<Filter regeneration control>
In the present embodiment, when the amount of PM trapped in the filter 6a or 6b becomes equal to or greater than the first specified amount of collection, filter regeneration control for oxidizing / removing PM trapped in the corresponding filter is executed. In this embodiment, this filter regeneration control corresponds to PM removal control according to the present invention.

  For example, when the PM collected by the filter 6a is oxidized and removed, the filter regeneration control is executed by controlling the flow control valve 8a in the valve closing direction and adding fuel from the fuel addition valve 7a. By controlling the flow rate control valve 8a in the valve closing direction, the flow rate of the exhaust gas flowing through the oxidation catalyst 5a and the filter 6a decreases. Moreover, fuel is supplied to the oxidation catalyst 5a by adding fuel from the fuel addition valve 7a. The filter 6a is heated by the oxidation heat generated when the fuel is oxidized by the oxidation catalyst 5a, and the PM is oxidized and removed.

  At this time, the temperature of the filter 6a is controlled to the target filter temperature by controlling the opening degree of the flow control valve 8a and the amount of fuel added by the fuel addition valve 7a. Here, the target filter temperature is a temperature at which PM can be oxidized and the deterioration of the filter 6a can be suppressed. This target filter temperature is determined in advance by experiments or the like.

  Also in the case of oxidizing and removing the PM collected by the filter 6b, the filter regeneration control is executed by controlling the flow control valve 8b in the valve closing direction and adding fuel from the fuel addition valve 7b as described above. .

<PM collection amount estimation method>
Next, a method for estimating the amount of collected PM in the filters 6a and 6b will be described. In this embodiment, the flow control valves 8a and 8b are controlled to be fully closed when a predetermined condition is satisfied. Here, the fully closed state is a state in which the opening degree of the flow control valves 8a and 8b is as small as possible. In addition, the predetermined condition is a condition for determining that it is necessary to reduce the flow rate of the exhaust gas in the first or second branch passages 2a and 2b as much as possible.

  In the present embodiment, when the filter regeneration control is executed when the internal combustion engine 1 is operated at a low load, it is provided in the branch passage provided with the filter to be subjected to the filter regeneration control. It is assumed that the flow rate control valve is controlled to be fully closed, and at this time, it may be determined that the predetermined condition is satisfied. In the present embodiment, when one of the flow control valves 8a and 8b is controlled to be fully closed, the other is open.

  In this embodiment, the filter 6b provided in the second branch passage 2b is based on the detected value of the differential pressure sensor 9 when the flow control valve 8a provided in the first branch passage 2a is in the fully closed state. Estimate the amount of collected PM. Further, based on the detected value of the differential pressure sensor 9 when the flow control valve 8b provided in the second branch passage 2b is in the fully closed state, the amount of PM trapped in the filter 6a provided in the first branch passage 2a. Is estimated.

  In the present embodiment, when the flow control valve 8a or 8b provided in one of the first and second branch passages 2a and 2b is controlled to be fully closed, most of the exhaust flowing through the exhaust passage 2 is controlled. Flows through the other branch passage. Therefore, when the flow control valve 8a or 8b provided in one branch passage is controlled to be fully closed, the differential pressure sensor 9 is connected to the upstream side and the downstream side of the filter 6a or 6b provided in the other branch passage. The differential pressure with the side will be detected. Therefore, the amount of PM trapped in each filter 6a, 6b can be estimated by the method as described above.

Here, a control routine of PM collection amount estimation control for estimating the PM collection amount in the filters 6a and 6b will be described based on a flowchart shown in FIG. Here, a control routine for estimating the PM collection amount Qpma in the filter 6a provided in the first branch passage 2a will be described as an example. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, first, in S101, the ECU 20 determines whether or not the flow control valve 8b provided in the second branch passage 2b is in a fully closed state. If an affirmative determination is made in S101, the ECU 20 proceeds to S102, and if a negative determination is made, the ECU 20 once ends the execution of this routine.

  In S102, the ECU 20 reads the detection value ΔPf of the differential pressure sensor 9.

  Next, the ECU 20 derives the PM collection amount Qpma in the filter 6a based on the detection value ΔPf of the differential pressure sensor 9. The relationship between the detected value ΔPf of the differential pressure sensor 9 and the PM trapping amount Qpma is stored in advance in the ECU 20 as a map. After deriving the PM collection amount Qpma, the ECU 20 once terminates execution of this routine.

  A control routine for estimating the amount of PM trapped in the filter 6b provided in the second branch passage 2b is a similar control routine.

<Differential pressure sensor installation position>
Next, a modified example of the installation position of the differential pressure sensor 9 according to the present embodiment will be described with reference to FIG.

  In the present embodiment, as shown in FIG. 3A, the pressure upstream of the oxidation catalyst 5a in the first branch passage 2a and the pressure downstream of the flow control valve 8a in the first branch passage 2a. You may install the differential pressure sensor 9 in the position which detects a difference.

  Even when the differential pressure sensor 9 is installed at such a position, when the flow control valve 8a provided in the first branch passage 2a is in a fully closed state, the differential pressure sensor 9 is located upstream of the filter 6b. The differential pressure between the downstream side and the downstream side is detected. When the flow control valve 8b provided in the second branch passage 2b is in a fully closed state, the differential pressure sensor 9 detects the differential pressure between the upstream side and the downstream side of the filter 6a.

  Similarly, the differential pressure sensor 9 is installed at a position that detects the difference between the pressure upstream of the oxidation catalyst 5b in the second branch passage 2b and the pressure downstream of the flow control valve 8b in the second branch passage 2b. You may do it.

  Further, in the present embodiment, as shown in FIG. 3B, the pressure in the vicinity of the upstream gathering portion of the first and second branch passages 2a and 2b in the upstream passage 2c and the first branch passage 2a. You may install the differential pressure sensor 9 in the position which detects the difference with the pressure downstream from the flow control valve 8a.

  Even when the differential pressure sensor 9 is installed at such a position, as described above, when the flow control valve 8a provided in the first branch passage 2a is in a fully closed state, the differential pressure sensor 9 is not filtered. The differential pressure between the upstream side and the downstream side of 6b is detected. When the flow control valve 8b provided in the second branch passage 2b is in a fully closed state, the differential pressure sensor 9 detects the differential pressure between the upstream side and the downstream side of the filter 6a.

Similarly, the difference between the pressure in the upstream passage 2c near the upstream collecting portion of the first and second branch passages 2a, 2b and the pressure downstream of the flow control valve 8b in the second branch passage 2b is detected. The differential pressure sensor 9 may be installed at any position. Further, a position for detecting the difference between the pressure upstream of the oxidation catalyst 5a in the first branch passage 2a and the pressure in the downstream passage 2d near the downstream gathering portion of the first and second branch passages 2a, 2b. Alternatively, the differential pressure sensor 9 may be installed. Further, the difference between the pressure upstream of the oxidation catalyst 5b in the second branch passage 2b and the pressure in the vicinity of the connecting portion of the downstream passage 2d between the first and second branch passages 2a, 2b in the downstream passage is detected. The differential pressure sensor 9 may be installed at such a position.

  According to this embodiment, it is possible to estimate the amount of PM trapped in each of the filters 6a and 6b based on the detection value of one differential pressure sensor 9. Further, if the differential pressure sensor 9 can detect any differential pressure among the above positions, it is possible to estimate the amount of PM trapped in each filter 6a, 6b. The degree of freedom of installation position is relatively large. As a result, the mountability on the vehicle is further improved.

  Further, according to the present embodiment, when estimating the amount of PM trapped by the filter 6a provided in the first branch passage 2a, the second branch passage 2b is substantially blocked by the flow path control valve 8b. . Similarly, when estimating the amount of PM collected by the filter 6b provided in the second branch passage 2b, the first branch passage 2a is substantially blocked by the flow path control valve 8a. Therefore, it is possible to estimate the PM collection amount in each of the filters 6a and 6b with higher accuracy based on the detection value of the differential pressure sensor 9.

  As described above, according to this embodiment, it is possible to more suitably estimate the amount of PM trapped in each of the filters 6a and 6b.

<PM collection amount estimation method in a modified example>
In the case where the installation position of the differential pressure sensor 9 is the position as in the above-described modification, and the differential pressure between the upstream side and the downstream side of each filter 6a, 6b is detected by the above-described method, the first branch Even if the amount of PM trapped in the filter 6a provided in the passage 2a is the same as the amount of PM collected in the filter 6b provided in the second branch passage 2b, the pressure detection positions for the filters 6a and 6b are the same. Because of the difference, the detection value of the differential pressure sensor 9 becomes a different value.

  That is, when the PM accumulation amounts in the filters 6a and 6b are the same, the detection of the differential pressure sensor 9 when the differential pressure between the upstream side and the downstream side of the filter 6a is detected when the flow control valve 8b is in the fully closed state. The value is larger than the detected value of the differential pressure sensor 9 when the differential pressure between the upstream side and the downstream side of the filter 6b is detected when the flow control valve 8a is in the fully closed state.

  Therefore, when the installation position of the differential pressure sensor 9 is the position as in the above-described modification, a map showing the relationship between the detected value of the differential pressure sensor 9 and the amount of PM trapped in the filter 6a, A map showing the relationship between the detected value and the amount of PM trapped in the filter 6b is stored separately in the ECU 20.

  In these maps, the detection value of the differential pressure sensor 9 when estimating the amount of PM trapped in the filter 6a is the same as the detection value of the differential pressure sensor 9 when estimating the amount of PM trapped in the filter 6b. When the value is a value, the amount of PM collected by the filter 6b is larger than the amount of PM collected by the filter 6a.

  By deriving the PM trapping amount in the filter 6a and the PM trapping amount in the filter 6b from these two maps, the PM trapping amount in each of the filters 6a and 6b can be estimated more accurately.

In the present embodiment, normally, PM is collected almost equally in each of the filters 6a and 6b. When the PM collection amount is equal to or greater than the first collection amount, filter regeneration control is executed on the corresponding filter, and PM is oxidized and removed.

  Therefore, if the filters 5a and 5b and the flow rate control valves 8a and 8b are normal in the first and second branch passages 2a and 2b, filter regeneration control is executed alternately for the filters 5a and 5b. It will be.

  Therefore, in the present embodiment, when only the PM collection amount in one of the filters 6a and 6b is continuously estimated to be equal to or more than the first collection amount, that is, continuous only for one of the filters. When the filter regeneration control is executed, it is determined that an abnormality has occurred in the branch path provided with the corresponding filter.

  Examples of abnormalities here include sticking of the flow control valves 8a and 8b, and the fact that PM that cannot be oxidized and removed even when filter regeneration control is executed has accumulated in the filters 6a and 6b. I can do it.

  In this embodiment, when the oxidation catalysts 5a and 5b are monolithic catalysts, PM is also collected on the front end face of the oxidation catalyst. In such a case, the amount of PM trapped in each of the oxidation catalysts 5a and 5b and the filters 6a and 6b is estimated by the same method as the method of estimating the amount of PM trapped in each of the filters 6a and 6b according to the present embodiment. I can do it. The same applies when a monolithic NOx catalyst is installed in place of the oxidation catalysts 5a and 5b.

  In addition, when each of the branch passages 2a and 2b is provided only with a filter carrying an oxidation catalyst or NOx catalyst, or when only a monolithic oxidation catalyst or NOx catalyst is provided, The amount of PM trapped in each filter or catalyst can be estimated by a method similar to the method of estimating the amount of PM trapped by the filters 6a and 6b.

  Since the schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted. In this embodiment, the same filter regeneration control as that in the first embodiment is executed.

<Control of fuel addition amount by flow control valve opening and fuel addition valve>
As described above, when the filter regeneration control is executed, the temperature of the filters 6a and 6b is controlled to the target filter temperature by controlling the opening degree of the flow rate control valves 8a and 8b and the fuel addition amount by the fuel addition valves 7a and 7b. To do.

  Here, the flow rate of the exhaust gas flowing through the first branch passage 2a varies depending on the amount of PM trapped in the filter 6b provided in the second branch passage 2b. Further, the flow rate of the exhaust gas flowing through the second branch passage 2b varies depending on the amount of PM trapped in the filter 6a provided in the first branch passage 2a.

  Therefore, in the present embodiment, when the PM collected by the filter 6a is oxidized and removed, the opening degree of the flow control valve 8a is controlled based on the amount of PM collected by the filter 6b. That is, the larger the amount of PM trapped in the filter 6b, the smaller the opening degree of the flow control valve 8a. Similarly, when the PM collected by the filter 6b is oxidized and removed, the opening degree of the flow control valve 8b is controlled based on the amount of PM collected by the filter 6a.

<Control routine for filter regeneration control>
Here, the control routine of the filter regeneration control according to the present embodiment will be described based on the flowchart shown in FIG. Here, a case where PM collected by the filter 6a is oxidized and removed will be described as an example. This routine is stored in advance in the ECU 20 and is executed at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, first, in S201, the ECU 20 determines whether or not the PM collection amount Qpma in the filter 6a is equal to or greater than the first collection amount Qpm1. If an affirmative determination is made in S201, the ECU 20 proceeds to S202, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  In S202, the ECU 20 determines the reference target opening Rvbase and the fuel addition valve of the flow control valve 8a based on the rotational speed and load of the internal combustion engine 1, the intake air amount, the exhaust temperature detected by the engine side exhaust temperature sensor 12, and the like. The fuel addition amount Qadd from 7a is calculated.

  Next, the ECU 20 proceeds to S203 and calculates a correction coefficient c for correcting the opening degree of the flow control valve 8a based on the PM collection amount Qpmb in the filter 6b. The relationship between the PM collection amount Qpmb and the correction coefficient c is stored in advance in the ECU 20 as a map. In this map, the correction coefficient c becomes smaller as the PM collection amount Qpmb increases.

  Next, the ECU 20 proceeds to S204, and calculates the target opening degree Rv of the flow control valve 8a by multiplying the reference target opening degree Rvbase by the correction coefficient c.

  Next, the ECU 20 proceeds to S205, controls the flow rate control valve 8a in the valve closing direction to control the opening degree to the target opening degree Rv, and executes fuel addition from the fuel addition valve 7a. That is, filter regeneration control is executed. As a result, the temperature of the filter 6a rises to the target filter temperature, and PM is oxidized and removed.

  Next, the ECU 20 proceeds to S206 and determines whether or not the PM collection amount Qpma in the filter 6a has decreased to the second collection amount Qpm2 or less. Here, the second collection amount Qpm2 is an amount smaller than the first collection amount Qpm1, and is a threshold at which it can be determined that it takes some time before the PM collection amount becomes the first collection amount Qpm1 again. This is the amount. This second collection amount Qpm2 is also a predetermined amount by experiment or the like. If an affirmative determination is made in S206, the ECU 20 proceeds to S207, and if a negative determination is made, the ECU 20 returns to S202.

  In S207, the ECU 20 stops the execution of the filter regeneration control. That is, the flow control valve 8a is controlled in the valve opening direction, and fuel addition from the fuel addition valve 7a is stopped. Thereafter, the ECU 20 once terminates execution of this routine.

  The control routine of the filter regeneration control when oxidizing and removing the PM collected by the filter 6b provided in the second branch passage 2b is the same as the control routine described above.

  As described above, according to the present embodiment, when the filter regeneration control is executed, the openings of the flow control valves 8a and 8b are based on the flow rates of the exhaust gas flowing through the oxidation catalysts 5a and 5b and the filters 6a and 6b. Is controlled. Therefore, it is possible to control the temperature of the filters 6a and 6b to be subjected to filter regeneration control to the target filter temperature with higher accuracy.

  In this embodiment, when the PM collected by the filter 6a is oxidized and removed, the amount of fuel added by the fuel addition valve 8a may be corrected based on the amount of PM collected Qpmb in the filter 6b. Similarly, when the PM collected by the filter 6b is oxidized and removed, the fuel addition amount by the fuel addition valve 8b may be corrected based on the PM collection amount Qpma in the filter 6a.

  Also by such control, the temperature of the filters 6a and 6b to be subjected to the filter regeneration control can be controlled to the target filter temperature with higher accuracy.

<Modification>
Here, a modified example of the present embodiment will be described. In this modified example, a NOx catalyst 5a ′ is provided instead of the oxidation catalyst 5a, and a NOx catalyst 5b ′ is provided instead of the oxidation catalyst 5b. The NOx catalysts 5a ′ and 5b ′ are catalysts that store NOx in the exhaust when the ambient atmosphere is an oxidizing atmosphere, and reduce the NOx that is stored when the ambient atmosphere is a reducing atmosphere. Other configurations are the same as described above.

  In the case of such a configuration, SOx poisoning regeneration control is executed to reduce the SOx stored in the NOx catalysts 5a ′ and 5b ′. This SOx poisoning regeneration control is performed by controlling the flow rate control valves 8a and 8b in the valve closing direction and adding fuel from the fuel addition valves 7a and 7b, similarly to the filter regeneration control.

  Then, the temperature of the NOx catalysts 5a ′ and 5b ′ is controlled to the target catalyst temperature by controlling the opening of the flow rate control valves 8a and 8b and the amount of fuel added by the fuel addition valves 7a and 7b, and the NOx catalyst 5a. The air-fuel ratio of the ambient atmosphere of '5b' is controlled to the target air-fuel ratio.

  Therefore, in the SOx poisoning regeneration control according to this modified example, when SOx occluded in the NOx catalyst 5a ′ provided in the first branch passage 2a is reduced as in the case of executing the filter regeneration control, PM trapping in the filter 6b is performed. The opening degree of the flow control valve 8a is controlled based on the collected amount. That is, the larger the amount of PM trapped in the filter 6b, the smaller the opening degree of the flow control valve 8a. Similarly, when the SOx stored in the NOx catalyst 5b ′ provided in the second branch passage 2b is reduced, the opening degree of the flow rate control valve 8b is controlled based on the amount of PM trapped in the filter 6a.

  As a result, the temperatures of the NOx catalysts 5a ′ and 5b ′ that are subject to SOx poisoning regeneration control can be controlled to the target catalyst temperature with higher accuracy. In addition, the air-fuel ratio of the atmosphere around the NOx catalysts 5a ′ and 5b ′ that is the target of SOx poisoning regeneration control can be controlled to the target air-fuel ratio with higher accuracy.

  Further, in this modified example, when SOx stored in the NOx catalyst 5a ′ is reduced, the amount of fuel added by the fuel addition valve 8a is based on the PM trapping amount Qpmb in the filter 6b as in the case of executing the filter regeneration control. It may be corrected. Similarly, when the SOx stored in the NOx catalyst 5b ′ is reduced, the amount of fuel added by the fuel addition valve 8b may be corrected based on the PM collection amount Qpma in the filter 6a.

  Also by such control, the temperature of the NOx catalysts 5a ′ and 5b ′ that are targets of SOx poisoning regeneration control can be controlled to the target catalyst temperature with higher accuracy. In addition, the air-fuel ratio of the atmosphere around the NOx catalysts 5a ′ and 5b ′ that is the target of SOx poisoning regeneration control can be controlled to the target air-fuel ratio with higher accuracy.

The figure which shows schematic structure of the intake / exhaust system of the internal combustion engine which concerns on the Example of this invention. The flowchart which shows the control routine of PM collection amount estimation control which concerns on Example 1 of this invention. The figure which shows the modification of the installation position of the differential pressure sensor which concerns on Example 1 of this invention. 9 is a flowchart showing a control routine for filter regeneration control according to Embodiment 2 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust passage 2a ... First branch passage 2b ... Second branch passage 2c ... Upstream side passage 2d ... Downstream side passage 3 ... Intake passage 4 ... Air flow meter 5a ·· Oxidation catalyst 5b · · Oxidation catalyst 5a '· · NOx catalyst 5b' · · NOx catalyst 6a · · Filter 6b · · Filter 7a · · Fuel addition valve 7b · · Fuel addition valve 8a · · Flow control valve 8b · -Flow control valve 9 ... Differential pressure sensor 20-ECU

Claims (5)

An exhaust passage branched into two branch passages on the way, and the two branch passages gathered downstream thereof;
An exhaust purification device provided in each of the two branch passages and having a function of collecting particulate matter in the exhaust;
A flow rate control valve that is provided in each of the two branch passages and controls the flow rate of the exhaust;
A fully closing means for controlling the flow control valve to a fully closed state when a predetermined condition is satisfied;
A pressure upstream of the exhaust purification device and the flow control valve in the vicinity of the upstream side of the two branch passages in the exhaust passage or in the two branch passages; and the two branches in the exhaust passage. A differential pressure sensor that detects a difference between the pressure on the downstream side of the exhaust purification device and the flow rate control valve in the vicinity of the downstream collecting portion of the passage or in either of the two branch passages;
A collection amount estimating means for estimating the collection amount of particulate matter in each exhaust purification device,
The collected amount estimating means is a detection value of the differential pressure sensor when the flow control valve provided in one of the two branch passages is controlled to a fully closed state by the fully closing means. The exhaust gas purification system for an internal combustion engine is characterized in that the trapped amount of particulate matter in the exhaust gas purification device provided in the other branch passage is estimated based on the above. The differential pressure sensor is
A difference between the pressure upstream of the exhaust purification device and the flow control valve in the one branch passage and the pressure downstream of the exhaust purification device and the flow control valve in the one branch passage is detected. Or
Alternatively, it detects a difference between the pressure in the vicinity of the upstream collecting portion of the two branch passages in the exhaust passage and the pressure downstream of the exhaust purification device and the flow rate control valve in the one branch passage. Is there
Alternatively, it detects a difference between the pressure upstream of the exhaust purification device and the flow rate control valve in the one branch passage and the pressure in the vicinity of the downstream collecting portion of the two branch passages in the exhaust passage. Yes,
The collected amount estimating means is provided in the detected value of the differential pressure sensor when estimating the collected amount of particulate matter in the exhaust gas purification device provided in the one branch passage, and provided in the other branch passage. When the detected value of the differential pressure sensor when estimating the trapped amount of particulate matter in the exhaust purification device is the same value, the exhaust purification device provided in the other branch passage 2. The internal combustion engine according to claim 1, wherein the amount of collected particulate matter is estimated to be greater than the amount of collected particulate matter in the exhaust gas purification device provided in the one branch passage. Exhaust purification system. PM that oxidizes and removes the particulate matter collected by the exhaust purification device when the collected amount of the particulate matter in the exhaust purification device estimated by the collection amount estimation means is equal to or greater than a predetermined collection amount. PM removal control execution means for executing removal control is further provided,
2. When PM removal control is continuously executed only for the exhaust purification device provided in the one or the other branch passage, it is determined that an abnormality has occurred in the corresponding branch passage. 3. An exhaust gas purification system for an internal combustion engine according to 1 or 2. Each of the exhaust purification devices includes a catalyst having an oxidation function,
A reducing agent supply means provided in each of the two branch passages for supplying a reducing agent to the catalyst;
PM that controls the flow rate control valve in the valve closing direction and supplies the reducing agent to the catalyst by the reducing agent supply means, thereby oxidizing and removing the particulate matter collected in the exhaust purification device
PM removal control execution means for executing the removal control,
When the PM removal control execution means executes the PM removal control to oxidize and remove the particulate matter collected by the exhaust gas purification device provided in the one branch passage, the PM removal control execution means Controlling the opening of the flow control valve and / or the reducing agent supply amount by the reducing agent supply means in the one branch passage based on the amount of particulate matter collected in the provided exhaust purification device. 3. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the exhaust gas purification system is an internal combustion engine. Each of the exhaust purification devices includes an NOx storage reduction catalyst,
Reducing agent supply means provided in each of the two branch passages for supplying a reducing agent to the NOx storage reduction catalyst;
SOx poisoning that controls the flow control valve in the valve closing direction and reduces the SOx stored in the NOx storage reduction catalyst by supplying the reducing agent to the NOx storage reduction catalyst by the reducing agent supply means. SOx poisoning regeneration control execution means for executing regeneration control,
When the SOx poisoning regeneration control execution means executes the SOx poisoning regeneration control to reduce SOx stored in the NOx storage reduction catalyst of the exhaust purification device provided in the one branch passage, Based on the trapped amount of particulate matter in the exhaust purification device provided in the other branch passage, the opening of the flow control valve in the one branch passage and / or the reducing agent supply by the reducing agent supply means The exhaust gas purification system for an internal combustion engine according to claim 1 or 2, wherein the amount is controlled.

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