JP5924688B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine. More specifically, the present invention relates to an exhaust gas recirculation device for an internal combustion engine including an EGR filter that captures foreign matter flowing into an EGR passage.

Conventionally, there is a technique disclosed in Patent Document 1 as an exhaust gas recirculation device for an internal combustion engine (see Patent Document 1).
In the technique disclosed in Patent Document 1, a compressor in an intake passage is branched from a portion downstream of a diesel particulate filter (hereinafter referred to as DPF) disposed in an exhaust passage of an internal combustion engine in an exhaust flow direction. A low-pressure EGR passage that joins a portion upstream of the intake flow direction. An EGR filter that captures foreign matters such as DPF fragments and metal pieces flowing into the low-pressure EGR passage is disposed at a portion upstream of the low-pressure EGR passage in the exhaust flow direction.

JP 2011-202536 A

By the way, tar products as HC reactants are contained in the exhaust gas and flow into the low pressure EGR passage from the exhaust passage. Further, iron sulfate contained as a fuel component or discharged from the exhaust manifold or DPF enters the condensed water and flows into the EGR passage from the exhaust passage.
Tar products and iron sulfate flow into the low-pressure EGR passage together with the exhaust gas and condensed water, and accumulate on the EGR filter that captures foreign matter disposed in the low-pressure EGR passage. The EGR filter in which tar products and iron sulfate are deposited causes pressure loss in the low-pressure EGR passage when a part of the exhaust gas is recirculated to the internal combustion engine using the low-pressure EGR passage.

On the other hand, if the EGR filter is disposed in the vicinity of the DPF in the low pressure EGR passage, the tar product accumulated on the EGR filter can be burned and removed by the heat during the regeneration control of the DPF.
However, the closer the position of the EGR filter is to the DPF, the more easily the condensed water flowing through the exhaust passage adheres to the EGR filter, and the iron sulfate mixed in the condensed water easily accumulates in the EGR filter. In this case, since iron sulfate cannot be burned and removed by heat during DPF regeneration control, the EGR filter in which a large amount of iron sulfate is deposited causes pressure loss in the low-pressure EGR passage.

  The present invention solves the above-mentioned problems, and the object thereof is to enable removal of both tar products and iron sulfate from the EGR filter, and EGR resulting from deposition of the tar product and iron sulfate on the EGR filter. The purpose is to suppress pressure loss generated in the passage.

  An exhaust gas recirculation device (for example, a low pressure EGR device 10 to be described later) of an internal combustion engine (for example, an engine 1 to be described later) of the present invention is provided in an exhaust passage (for example, an exhaust pipe 4 to be described later) of the internal combustion engine. A filter for collecting the collected PM (for example, DPF 42 described later), and a temperature raising means for regenerating the filter by heating and removing the PM collected by the filter by burning the filter (for example, described later) The DPF regeneration control unit 101) communicates with the exhaust passage immediately after the exhaust flow direction of the filter and an intake passage (for example, an intake pipe 3 described later) of the internal combustion engine, so that a part of the exhaust gas is communicated with the internal combustion engine. An EGR passage (for example, a low pressure EGR passage 11 described later) and a connection portion (for example, a connection portion 9 described later) between the EGR passage and the exhaust passage are provided in the vicinity of the EGR passage. An exhaust gas recirculation device for an internal combustion engine including an EGR filter (for example, an EGR filter 12 to be described later) that captures incoming foreign matter, and a wall surface of the EGR passage (for example, an upstream side of the EGR filter in the exhaust flow direction) On the wall surface of the exhaust passage downstream of the connecting portion and the exhaust passage in the exhaust flow direction to be described later, the exhaust gas and the exhaust gas flow out of the filter at a position against the flow of the exhaust gas that has passed through the filter. A rebound surface (for example, a rebound surface 15 described later) on which condensed water that rebounds from the exhaust flow is provided, and the EGR filter is disposed at a position where the exhaust gas and the condensed water that rebound from the rebound surface directly contact each other. And

  According to this invention, an EGR filter is arrange | positioned in the position where the exhaust and the condensed water which bounced from the bounce surface hit directly. For this reason, since the EGR filter is disposed in the vicinity of the filter so that the exhaust gas and the condensed water bounced from the rebound surface directly contact with each other, tar products accumulated on the EGR filter can be removed by combustion during regeneration of the filter. Further, since the condensed water bounced from the rebound surface directly hits the EGR filter, iron sulfate that easily accumulates on the EGR filter arranged in the vicinity of the filter can be washed away with the condensed water and removed. As a result, iron sulfate that easily deposits on the EGR filter is not deposited on the EGR filter by a predetermined amount or more. Therefore, both the tar product and iron sulfate can be removed from the EGR filter, and the pressure loss generated in the EGR passage due to the tar product and iron sulfate being deposited on the EGR filter can be suppressed.

  It is preferable that the EGR filter is provided at a position where the EGR filter is visible from the rebound surface.

  According to the present invention, since the EGR filter is provided at a position where it can be seen from the rebound surface, there is no obstacle between the rebound surface and the EGR filter, and exhaust and condensed water can be directly applied to the EGR filter from the rebound surface. .

  It is preferable that the rebound surface is provided at a position that can be viewed from an upstream position of the exhaust passage in the exhaust flow direction, and the EGR filter is provided at a position that cannot be viewed from an upstream position of the exhaust passage in the exhaust flow direction. .

According to the present invention, the rebound surface is provided at a position where it can be seen from the position upstream of the exhaust passage in the exhaust flow direction, so that the exhaust and condensed water flowing through the exhaust passage directly collide with the rebound surface, You can bounce on the bounce surface.
In addition, since the EGR filter is provided at a position where it cannot be seen from the upstream side in the exhaust flow direction of the exhaust passage, the exhaust gas flowing through the exhaust passage hardly hits the EGR filter directly, and tar generation as an HC reactant contained in the exhaust is generated. Things are difficult to deposit on the EGR filter.

  Exhaust pressure acquisition means (for example, an exhaust pressure sensor 44 described later) for acquiring the exhaust pressure of the exhaust passage, intake pressure acquisition means (for example, an intake pressure sensor 21 described later) for acquiring the intake pressure of the intake passage, First determination means (for example, Steps S1 and S2 to be described later) for determining whether or not a pressure abnormality of the EGR passage including the EGR filter has occurred based on the acquired exhaust pressure and intake pressure; When it is determined by the first determination means that a pressure abnormality has occurred, regeneration of the filter is performed using the temperature raising means, and determination is performed again using the first determination means after regeneration of the filter. And determining that a pressure abnormality has occurred in the EGR passage when the first determination means determines again that a pressure abnormality has occurred (for example, described later) Step S1, S2, S3, S4, S5, S6) and, preferably further comprising a.

  According to the present invention, when it is determined by the first determination means that a pressure abnormality has occurred, the regeneration of the filter is performed using the temperature raising means, and after the regeneration of the filter, the first determination means is used again. Make a decision. For this reason, the tar product is burned and removed from the EGR filter by regenerating the filter, so that the pressure abnormality in the EGR passage caused by the accumulation of the tar product on the EGR filter can be solved immediately. As a result, the pressure abnormality of the EGR passage that can be resolved immediately and the pressure abnormality of the EGR passage that cannot be resolved immediately can be separated, and the pressure abnormality of the EGR passage that cannot be resolved immediately can be reliably detected.

  The second determination means determines that a pressure abnormality has occurred in the EGR passage excluding the EGR filter when it is determined that a pressure abnormality has occurred by the second determination of the first determination means. It is preferable.

  According to the present invention, the second determining means burns and removes the tar product from the EGR filter by performing the regeneration of the filter, thereby detecting the pressure abnormality in the EGR passage caused by the accumulation of the tar product on the EGR filter. Eliminate immediately. Thereby, when it is determined that the pressure abnormality has occurred by the second determination by the first determination means, the pressure abnormality of the EGR passage due to the accumulation of the tar product on the EGR filter does not occur. As a result, the second determination means can identify the part where the abnormality has occurred as the part of the EGR passage excluding the EGR filter, and can improve the accuracy of the abnormality determination.

  When the travel distance of the vehicle on which the internal combustion engine is mounted or the operation time of the internal combustion engine is less than or equal to a predetermined value from the previous regeneration of the filter using the temperature raising means, the first determination means causes a pressure abnormality. It is preferable to further include third determination means (for example, step S3 to be described later) that determines that a pressure abnormality has occurred in the EGR passage.

  If the travel distance of the vehicle on which the internal combustion engine is mounted or the operation time of the internal combustion engine is less than or equal to a predetermined value from the previous regeneration of the filter, tar products have not yet accumulated on the EGR filter. According to the present invention, from the previous regeneration of the filter, it can be determined that the travel distance of the vehicle on which the internal combustion engine is mounted or the operation time of the internal combustion engine is less than or equal to a predetermined value and that tar products are not yet accumulated on the EGR filter. In this case, the filter regeneration by the second determination unit is not performed, and unnecessary filter regeneration is avoided. Further, it is possible to quickly determine an abnormal pressure in the EGR passage by omitting an extra filter regeneration time and the like. Further, since unnecessary regeneration of the filter is avoided, it is possible to suppress deterioration of fuel consumption and exhaust emission.

  According to the present invention, both the tar product and iron sulfate can be removed from the EGR filter, and the pressure loss generated in the EGR passage caused by the tar product and iron sulfate being deposited on the EGR filter can be suppressed. .

1 is a schematic configuration diagram showing an internal combustion engine according to an embodiment of the present invention. It is a figure which shows the vicinity of the connection part of the exhaust pipe which concerns on the said embodiment, and a low voltage | pressure EGR channel | path. It is sectional drawing in the AA line of FIG. 2 which shows the vicinity of the connection part of the exhaust pipe which concerns on the said embodiment, and a low voltage | pressure EGR channel | path. It is sectional drawing in the BB line of FIG. 2 which shows the vicinity of the connection part of the exhaust pipe which concerns on the said embodiment, and a low voltage | pressure EGR channel | path. It is sectional drawing in the CC line of FIG. 2 which shows the vicinity of the connection part of the exhaust pipe which concerns on the said embodiment, and a low voltage | pressure EGR channel | path. It is a figure which shows the tar product combustion characteristic at the time of DPF regeneration control which concerns on the said embodiment. It is a figure which shows the temperature change of the vicinity of the connection part of the exhaust pipe and low pressure EGR channel | path at the time of DPF regeneration control which concerns on the said embodiment. It is a figure which shows the temperature change of the EGR filter at the time of engine operation which concerns on the said embodiment. It is a figure which shows the flow of the condensed water in the vicinity of the connection part of the exhaust pipe at the time of engine starting which concerns on the said embodiment, and a low voltage | pressure EGR channel | path. It is a flowchart which shows the process sequence of the low voltage | pressure EGR abnormality detection by ECU which concerns on the said embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

First, the configuration of the internal combustion engine 1 according to the present embodiment will be described.
FIG. 1 is a schematic configuration diagram showing an internal combustion engine 1 according to the present embodiment.

An internal combustion engine (hereinafter referred to as an engine) 1 is a diesel engine that is mounted on a vehicle and injects fuel directly into a combustion chamber of each cylinder 2. Each cylinder 2 of the engine 1 is provided with a fuel injection valve (not shown).
The engine 1 includes an electronic control unit (hereinafter, ECU) 100 that is electrically connected to a fuel injection valve. The valve opening time and valve closing time of the fuel injection valve are controlled by the ECU 100.

  The engine 1 includes an intake pipe 3, an exhaust pipe 4, a supercharger 5, and a low pressure EGR device 10.

  The intake pipe 3 functions as an intake passage through which intake air flows, and is connected to the intake port of each cylinder 2 of the engine 1 via a plurality of branch portions of the intake manifold 7.

An intake pressure sensor 31 is provided in the intake pipe 3.
The intake pressure sensor 31 detects the pressure of intake air flowing through the intake pipe 3.
The intake pressure sensor 31 is electrically connected to the ECU 100 and transmits a detection signal of the pressure of intake air flowing through the intake pipe 3 to the ECU 100.

  The exhaust pipe 4 functions as an exhaust passage through which exhaust flows, and is connected to the exhaust port of each cylinder 2 of the engine 1 through a plurality of branch portions of the exhaust manifold 8.

The supercharger 5 pumps intake air to the intake pipe 3.
The supercharger 5 includes a turbine 51 and a compressor 52.

The turbine 51 is disposed in the middle of the exhaust pipe 4 and is driven by the kinetic energy of the exhaust gas that flows through the exhaust pipe 4.
The turbine 51 has a plurality of variable vanes (not shown), and is configured to be able to change the rotational speed of the turbine 51 by changing the opening of the variable vanes. The opening degree of the variable vane is electromagnetically controlled by the ECU 100.

  The compressor 52 is disposed in the middle of the intake pipe 3, is rotated by the rotation of the turbine 51, pressurizes the intake air, and pumps it to the intake pipe 3.

  An oxidation catalyst 41 and a DPF 42 are provided in the case 43 (see FIG. 2) in this order from the upstream side in the exhaust flow direction in a portion of the exhaust pipe 4 on the downstream side in the exhaust flow direction of the turbine 51.

The oxidation catalyst 41 raises the temperature of the exhaust gas with heat generated by the reaction with the exhaust gas and the fuel.
As the oxidation catalyst 41, for example, platinum (Pt) acting as a catalyst is supported on an alumina (Al ₂ O ₃ ) carrier, zeolite having excellent HC adsorption action, and HC steam reforming action. The one composed of excellent rhodium (Rh) is used.

When the exhaust gas passes through the fine holes in the filter wall, the DPF 42 collects PM by depositing PM on the surface of the filter wall and the holes in the filter wall. As a constituent material of the filter wall, for example, a ceramic porous body such as silicon carbide is used.
When the DPF 42 collects PM up to the limit of the collection capability, that is, the accumulation limit, the pressure loss of the exhaust pipe 4 becomes large. Therefore, DPF regeneration control for burning and removing the PM collected in the DPF 42 is executed.

An exhaust pressure sensor 44 is provided in a portion of the exhaust pipe 4 downstream of the oxidation catalyst 41 in the exhaust flow direction and upstream of the DPF 42 in the exhaust flow direction.
The exhaust pressure sensor 44 detects the pressure at the upstream side in the exhaust flow direction of the DPF 42 in the exhaust pipe 4.
The exhaust pressure sensor 44 is electrically connected to the ECU 100 and transmits a pressure detection signal to the ECU 100 at a position upstream of the DPF 42 in the exhaust pipe 4 in the exhaust flow direction.

The low pressure EGR device 10 recirculates a part of the exhaust gas flowing through the exhaust pipe 4 to the engine 1 as low pressure EGR gas.
The low pressure EGR device 10 includes a low pressure EGR passage 11, an EGR filter 12, a low pressure EGR cooler 13, and a low pressure EGR valve 14.

  The low-pressure EGR passage 11 communicates a portion (cone portion 45 (see FIG. 2)) immediately after the DPF 42 in the exhaust pipe 4 in the exhaust pipe 4 and a portion upstream of the compressor 52 in the intake pipe 3 using a tubular body. Then, a part of the exhaust gas immediately after the exhaust flow direction of the DPF 42 is returned to a portion of the intake pipe 3 upstream in the exhaust flow direction of the compressor 52 as low-pressure EGR gas.

  The EGR filter 12 is provided in the vicinity of the connection portion 9 (see FIG. 4) with the exhaust pipe 4 in the low pressure EGR passage 11, and captures foreign matters such as DPF 42 fragments and metal pieces flowing into the low pressure EGR passage 11. When foreign matter such as a piece of DPF 42 or a metal piece flows through the low pressure EGR passage 11 and reaches the upstream side of the compressor 52 in the intake flow direction, the foreign matter may flow into the compressor 52 and damage the compressor 52. 12 is arranged.

The low pressure EGR cooler 13 reduces the temperature of the low pressure EGR gas that flows back through the low pressure EGR passage 11.
The low-pressure EGR cooler 13 is a water-cooled type, and exchanges heat between the low-pressure EGR gas flowing through the low-pressure EGR passage 11 and the engine coolant.

The low pressure EGR valve 14 controls the flow rate of the low pressure EGR gas that flows back through the low pressure EGR passage 11.
The low pressure EGR valve 14 is connected to the ECU 100 via an actuator (not shown), and the valve opening degree is electromagnetically controlled by the ECU 100.

ECU 100 includes an input circuit, a central processing unit (hereinafter referred to as CPU), a storage circuit, and an output circuit.
The input circuit has functions such as shaping input signal waveforms from various sensors, correcting a voltage level to a predetermined level, and converting an analog signal value into a digital signal value.
The storage circuit stores various calculation programs executed by the CPU, calculation results, and the like.
The output circuit outputs a control signal to the low pressure EGR valve 14 and the fuel injection valve of the engine 1.

The ECU 100 includes a module including a DPF regeneration control unit 101 and a low-pressure EGR control unit 102 with the hardware configuration described above.
Hereinafter, the function of each module will be described.

The DPF regeneration control unit 101 includes a deposition amount parameter calculation unit, a filtering unit, a regeneration determination unit, and a regeneration execution unit (all not shown).
The accumulation amount parameter calculation unit calculates an accumulation amount parameter that serves as an index of the accumulation amount of PM accumulated on the DPF 42.
The filtering unit performs a filtering process on the deposition amount parameter calculated by the deposition amount parameter calculation unit.
The regeneration determination unit determines whether to execute DPF regeneration control based on the filtered accumulation amount parameter.
The regeneration executing unit executes DPF regeneration control. In the DPF regeneration control, post-injection is executed by the fuel injection valve, and unburned fuel is burned by the oxidation catalyst 41, whereby the temperature of the exhaust gas flowing into the DPF 42 is raised and PM accumulated in the DPF 42 is removed by combustion.

  The low-pressure EGR control unit 102 controls the opening degree of the low-pressure EGR valve 14, adjusts the flow rate of the low-pressure EGR gas that is recirculated through the low-pressure EGR passage 11, and controls the recirculation of the exhaust gas to the engine 1.

Next, details of the vicinity of the connection portion 9 between the exhaust pipe 4 and the low-pressure EGR passage 11 will be described.
FIG. 2 is a view showing the vicinity of the connection portion 9 between the exhaust pipe 4 and the low pressure EGR passage 11 according to the present embodiment. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, showing the vicinity of the connection portion 9 between the exhaust pipe 4 and the low pressure EGR passage 11 according to the present embodiment. FIG. 4 is a cross-sectional view taken along line BB in FIG. 2, showing the vicinity of the connection portion 9 between the exhaust pipe 4 and the low pressure EGR passage 11 according to the present embodiment. FIG. 5 is a cross-sectional view taken along the line CC of FIG. 2 showing the vicinity of the connection portion 9 between the exhaust pipe 4 and the low-pressure EGR passage 11 according to the present embodiment.

As shown in FIG. 2, the low-pressure EGR passage 11 has a cone portion 45 whose diameter is reduced toward the downstream side, which is a portion immediately after the exhaust flow direction of the DPF 42 in the exhaust pipe 4 with the exhaust flow direction downward along the side surface of the engine 1. Has a connecting portion 9.
The connecting portion 9 extends sideways from the middle of the cone portion 45 while tilting the low pressure EGR passage 11 slightly upward.
In the vicinity of the connecting portion 9, a rebound surface 15 and an EGR filter 12 are provided.

  The rebound surface 15 is a wall surface on the upstream side in the exhaust flow direction of the EGR filter 12 in the low pressure EGR passage 11 and is provided at a position that resists the flow of exhaust gas that has passed through the DPF 42, that is, on the lower surface 91 of the connection portion 9. At the same time, the condensed water flowing out from the DPF 42 is rebounded against the exhaust flow (see FIGS. 7 and 9).

As shown in FIG. 3, when the rebound surface 15 is viewed from the position upstream of the rebound surface 15 in the exhaust flow direction (arrow D in FIG. 2), the position and the rebound surface. There is no obstacle between 15 and visible.
When the condensed water flowing out from the DPF 42 is rebounded, the rebound surface 15 is disposed at an angle that causes the condensate that has bounced off once to fly upward and toward the downstream side in the exhaust gas flow direction (EGR filter 12 side) in the low-pressure EGR passage 11. Is done.

As shown in FIGS. 4 and 5, the EGR filter 12 is made of a hemispherical metal mesh (particularly SUS material).
As shown in FIG. 4, the EGR filter 12 projects a hemispherical convex portion upstream in the exhaust flow direction so as to be orthogonal to the exhaust pipe 4 extending in the vertical direction (see FIGS. 7 and 9) and bounces. The exhaust and the condensed water bounced off from the surface 15 are arranged at positions where they directly hit each other.
Here, the position where the exhaust gas and the condensed water bounced from the bounce surface 15 directly hit each other is a position where the condensed water bounced off the bounce surface 15 and flew upward falls on the entire surface.

  The lower surface 91 including the rebound surface 15 is configured as an inclined surface in which the exhaust pipe 4 side is inclined downward.

As shown in FIG. 5, the EGR filter 12 is provided at a position where there is no obstacle between the rebound surface 15 and the EGR filter 12 when viewed from the rebound surface 15 (arrow E in FIG. 2).
On the other hand, as shown in FIG. 3, when the EGR filter 12 is viewed from the position upstream of the rebound surface 15 in the exhaust flow direction (arrow D in FIG. 2), The wall surface 45a of the cone part 45 becomes an obstacle and cannot be visually observed. For this reason, the exhaust gas flowing through the DPF 42 does not easily hit the EGR filter 12, and the tar product as the HC reactant contained in the exhaust gas is difficult to deposit on the EGR filter 12.

Next, a method for burning and removing the tar product deposited on the EGR filter 12 will be described.
FIG. 6 is a graph showing tar product combustion characteristics during DPF regeneration control according to the present embodiment. FIG. 6 is a graph showing time on the horizontal axis and temperature and tar product weight change on the vertical axis.
At the time of DPF regeneration control, as shown in FIG. 6, the tar product is burned and completely extinguished when heated to 530 ° C. or higher in consideration of the regeneration time of DPF 42 of about 10 minutes. For this reason, in order to burn and remove the tar product accumulated on the EGR filter 12, the EGR filter 12 needs to be heated to 530 ° C. or higher during the DPF regeneration control.

FIG. 7 is a view showing a temperature change in the vicinity of the connection portion between the exhaust pipe 4 and the low-pressure EGR passage 11 during the DPF regeneration control according to the present embodiment.
At the time of DPF regeneration control, the DPF 42 is heated to about 600 ° C. and burns and removes PM, so that a temperature change as shown in FIG.
That is, the upstream portion of the cone portion 45 in the exhaust flow direction is about 600 ° C. during DPF regeneration control. The connecting portion 9 close to the cone portion 45 is about 580 ° C. during DPF regeneration control. The position where the EGR filter 12 is disposed is about 530 ° C. during DPF regeneration control. A portion of the low pressure EGR passage 11 on the downstream side of the EGR filter 12 in the exhaust flow direction is about 480 ° C. during DPF regeneration control.

  As shown in FIG. 7, the position where the EGR filter 12 is arranged is heated to about 530 ° C. during the DPF regeneration control. Thereby, the tar product deposited on the EGR filter 12 is removed by combustion.

On the other hand, in the DPF regeneration control, the connecting portion 9 upstream of the EGR filter 12 adjacent to the cone portion 45 in the exhaust flow direction is heated to about 580 ° C.
When the position where the EGR filter 12 is disposed is heated to a temperature exceeding 600 ° C., the EGR filter 12 becomes sensitized and causes a deterioration phenomenon of corrosion resistance. For this reason, in consideration of safety, the EGR filter 12 needs to be heated so as to be kept at 550 ° C. or lower even when the DPF regeneration control is performed or when the engine operation is at full load.
For this reason, the EGR filter 12 cannot be disposed at this portion heated to about 580 ° C. because the above-described adverse effects occur.

FIG. 8 is a diagram showing a temperature change of the EGR filter 12 during engine operation according to the present embodiment. FIG. 8 is a graph in which the horizontal axis indicates the distance from the current position to the upstream and downstream sides in the exhaust flow direction with respect to the position of the EGR filter 12, and the vertical axis indicates the temperature.
As shown in FIG. 8, even when the engine speed is 2000 or 3000 rpm and the engine is operating at full load, the temperature tends to rise as the position becomes upstream in the exhaust flow direction.
The EGR filter 12 is heated to not less than 530 ° C. and not more than 550 ° C. not only at the time of DPF regeneration control but also when the engine is operating at an engine speed of 2000 or 3000 rpm and full load.

  As described above, since the EGR filter 12 is heated to 530 ° C. or more and 550 ° C. or less when the DPF regeneration control is performed and the engine operation is at full load, the tar product deposited on the EGR filter 12 is used in those cases. To burn off.

Next, a method for removing iron sulfate deposited on the EGR filter 12 will be described.
FIG. 9 is a view showing the flow of condensed water in the vicinity of the connection portion 9 between the exhaust pipe 4 and the low-pressure EGR passage 11 when the engine is started according to the present embodiment.
When the engine is stopped, the moisture in the exhaust gas, which is lowered in temperature after the engine is stopped, is condensed, and a large amount of condensed water is held inside the DPF 42. For this reason, at the time of starting the engine, a large amount of condensed water held inside the DPF 42 by the exhaust pressure at the start of the engine flows out together with the exhaust gas in the exhaust flow direction downstream. At this time, as shown in FIG. 9, the condensed water flowing out in a large amount from the DPF 42 collides with the rebound surface 15 together with the exhaust gas, rebounds against the exhaust flow, and directly hits the EGR filter 12.

  Specifically, as shown in FIG. 3, when the downstream side in the exhaust flow direction is viewed from the position upstream of the rebound surface 15 (arrow D in FIG. 2), the position and the rebound surface Since there is no obstacle between 15 and 15, the condensed water bounces back and collides directly with the surface 15.

As shown in FIG. 5, since the EGR filter 12 is visible when viewed from the rebound surface 15 (arrow E in FIG. 2), the condensed water rebounding from the rebound surface 15 flies upward and the entire EGR filter 12 is seen. Get down directly to.
The condensed water that has fallen directly on the EGR filter 12 flows through the lower surface 91 inclined downward from the EGR filter 12 toward the exhaust pipe 4 and returns to the exhaust pipe 4 to be discharged again.

As described above, when a large amount of condensate flows out of the DPF 42 together with the exhaust gas in the exhaust flow direction at the time of starting the engine, the large amount of condensate rebounds on the rebound surface 15 to wet the entire EGR filter 12 and accumulates on the EGR filter 12. Wash away and remove the ferrous sulfate.
Thereby, since the iron sulfate deposited on the EGR filter 12 is washed away every time the engine is started, iron sulfate is not continuously deposited on the EGR filter 12 by a predetermined amount or more.

Next, control of low pressure EGR abnormality detection by the ECU 100 will be described.
FIG. 10 is a flowchart showing a processing procedure of low-pressure EGR abnormality detection by the ECU 100 according to the present embodiment. This process is executed every predetermined control cycle.

In step S1, low pressure EGR abnormality detection is performed.
The low-pressure EGR abnormality detection uses the detection signal of the exhaust pressure sensor 44 and the detection signal of the intake pressure sensor 31 to calculate a differential pressure between the exhaust pressure and the intake pressure.

In step S2, it is determined whether a differential pressure abnormality has occurred.
Whether or not the differential pressure abnormality has occurred is determined that the differential pressure abnormality has occurred when the differential pressure between the exhaust pressure and the intake pressure calculated in step S1 exceeds a predetermined value.
In step S2, if an affirmative determination is made that a differential pressure abnormality has occurred, the process proceeds to step S3. If a negative determination is made, the process proceeds to step S9 and is determined to be normal.
Here, the process of step S1, S2 comprises a 1st determination means.

In step S3, it is determined from the previous DPF regeneration control whether the travel distance of the vehicle is equal to or less than a predetermined value.
In step S3, when it is affirmatively determined from the previous DPF regeneration control that the travel distance of the vehicle is equal to or less than the predetermined value, the process proceeds to step S7 to determine that there is an abnormality, and further proceeds to step S8 for warning. Turn on the lamp. On the other hand, if a negative determination is made, the process proceeds to step S4.
Here, the process of step S3 constitutes a third determination unit.

In step S4, DPF regeneration control is performed.
In the DPF regeneration control, the DPF regeneration control unit 101 performs post injection with the fuel injection valve, and burns unburned fuel with the oxidation catalyst 41, thereby raising the temperature of the exhaust gas flowing into the DPF 42 and accumulating in the DPF 42. PM is burned off. At this time, the tar product deposited on the EGR filter 12 is also removed by combustion.

In step S5, low-pressure EGR abnormality detection is performed again.
In the low pressure EGR abnormality detection again, the differential pressure between the exhaust pressure and the intake pressure is calculated using the detection signal of the exhaust pressure sensor 44 and the detection signal of the intake pressure sensor 31 as in step S1.

In step S6, it is determined whether a differential pressure abnormality has occurred.
Whether or not the differential pressure abnormality has occurred is determined that the differential pressure abnormality has occurred when the differential pressure between the exhaust pressure and the intake pressure calculated in step S5 exceeds a predetermined value.
In step S6, when an affirmative determination is made that a differential pressure abnormality has occurred, the process proceeds to step S7 to determine the abnormality, and further to step S8 to turn on the warning lamp. On the other hand, if a negative determination is made, the process proceeds to step S9 and is determined to be normal.
Here, the process of step S5, S6 comprises a 1st determination means. Moreover, the process of step S1, S2, S3, S4, S5, S6 comprises a 2nd determination means.

  According to the low pressure EGR device 10 according to the above-described embodiment, the following effects are obtained.

  (1) According to the present embodiment, the EGR filter 12 is disposed at a position where exhaust and boiled water bounced from the bounce surface 15 directly hit. For this reason, since the EGR filter 12 is disposed in the vicinity of the DPF 42 where the exhaust gas and the condensed water bounced from the rebound surface 15 directly hit, the tar product accumulated on the EGR filter 12 is controlled during DPF regeneration control and engine operation. Combustion can be removed at full load. Further, since the condensed water that has flowed out of the DPF 42 and bounced off the rebound surface 15 directly hits the EGR filter 12 when the engine is started, iron sulfate that easily accumulates on the EGR filter 12 disposed in the vicinity of the DPF 42 is used. It can be removed by washing away with condensed water. As a result, iron sulfate that easily deposits on the EGR filter 12 is not deposited on the EGR filter 12 by a predetermined amount or more. Therefore, both the tar product and iron sulfate can be removed from the EGR filter 12, and the pressure loss generated in the low pressure EGR passage 11 due to the tar product and iron sulfate being deposited on the EGR filter 12 can be suppressed. .

  (2) According to this embodiment, since the EGR filter 12 is provided at a position where it can be seen from the rebound surface 15 (arrow E in FIG. 2), there is no obstacle between the rebound surface 15 and the EGR filter 12, and the exhaust gas is exhausted. The condensed water can be directly applied to the EGR filter 12 from the rebound surface 15.

(3) According to the present embodiment, the rebound surface 15 is provided at a position that can be seen from the position upstream of the position of the rebound surface 15 in the exhaust flow direction (arrow D in FIG. 2), and therefore flows through the exhaust pipe 4. The exhaust gas and the condensed water can directly collide with the rebound surface 15, and the exhaust gas and the condensed water can be rebound at the rebound surface 15.
Further, since the EGR filter 12 is provided at a position where it cannot be seen from the position upstream of the rebound surface 15 in the exhaust flow direction (arrow D in FIG. 2), the exhaust gas flowing out from the DPF 42 is difficult to directly hit the EGR filter 12. The tar product generated from the HC contained in the exhaust gas is difficult to deposit on the EGR filter 12.

  (4) According to the present embodiment, when it is determined that the pressure abnormality has occurred in the processes of steps S1 and S2, the DPF regeneration control is performed by the process of step S4, and the steps S5 and S6 are performed after the DPF regeneration control. The determination is performed again by the above process. For this reason, the pressure of the low pressure EGR passage 11 caused by the tar product accumulated on the EGR filter 12 by burning and removing the tar product from the EGR filter 12 by performing the DPF regeneration control in the process of step S4. Abnormalities can be resolved immediately. Thereby, the pressure abnormality of the low-pressure EGR passage 11 that can be resolved immediately and the pressure abnormality of the low-pressure EGR passage 11 that cannot be resolved immediately can be separated, and the pressure abnormality of the low-pressure EGR passage 11 that can not be solved immediately can be reliably detected.

  (5) According to the present embodiment, the tar product is burned and removed from the EGR filter 12 by performing the DPF regeneration control in the process of step S4, so that the low pressure caused by the tar product accumulated on the EGR filter 12 is a factor. The pressure abnormality in the EGR passage 11 is immediately resolved. As a result, when it is determined that a pressure abnormality has occurred by re-determining the processing in steps S5 and S6, the pressure abnormality in the low-pressure EGR passage 11 caused by the accumulation of tar products on the EGR filter 12 is caused. Does not occur. As a result, in the process of step S6, the part where the abnormality has occurred can be identified as the part of the low pressure EGR passage 11 excluding the EGR filter 12, and the accuracy of abnormality determination can be improved.

  (6) From the previous DPF regeneration control, when the travel distance of the vehicle on which the engine 1 is mounted is equal to or less than the predetermined value, the tar product has not yet accumulated on the EGR filter 12. According to the present embodiment, when the travel distance of the vehicle on which the engine 1 is mounted is less than or equal to a predetermined value and the tar product has not yet accumulated on the EGR filter 12 from the previous DPF regeneration control by the process of step S3. If it can be determined, the DPF regeneration control in step S4 is not performed, and unnecessary DPF regeneration control is avoided. Then, unnecessary time for performing the DPF regeneration control or the like is omitted, and the process proceeds to step S7, where the pressure abnormality in the low pressure EGR passage 11 can be quickly determined. Moreover, since unnecessary DPF regeneration control is avoided, deterioration of fuel consumption and exhaust emission can be suppressed.

  Note that the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the scope of the present invention.

  In the present embodiment, the rebound surface 15 is provided on the lower surface 91 that is the wall surface on the upstream side in the exhaust flow direction of the EGR filter 12 in the low pressure EGR passage 11, but is not limited thereto. For example, the rebound surface 15 may be provided on the wall surface of the exhaust pipe 4 on the downstream side in the exhaust flow direction at the connection portion 9.

  In the present embodiment, the exhaust pressure sensor 44 detects the exhaust pressure and the intake pressure sensor 31 detects the intake pressure. However, the present invention is not limited to this. For example, the exhaust pressure and the intake pressure may be estimated by calculation.

  In the present embodiment, in step S3, it can be determined from the previous DPF regeneration control that the travel distance of the vehicle on which the engine 1 is mounted is equal to or less than a predetermined value, and the tar product has not yet accumulated on the EGR filter 12. The DPF regeneration control in step S4 was not performed. However, it is not limited to this. For example, in step S3, when it can be determined from the previous DPF regeneration control that the operation time of the engine 1 is less than or equal to a predetermined value and the tar product has not yet accumulated on the EGR filter 12, the same processing is performed in step S4. The DPF regeneration control may not be performed.

1. Engine (internal combustion engine)
3 ... Intake pipe (intake passage)
4 ... Exhaust pipe (exhaust passage)
9 ... Connection 10 ... Low pressure EGR device (exhaust gas recirculation device)
11 ... Low pressure EGR passage (EGR passage)
DESCRIPTION OF SYMBOLS 12 ... EGR filter 15 ... Rebound surface 21 ... Intake pressure sensor (intake pressure acquisition means)
42 ... DPF (filter)
44. Exhaust sensor (exhaust pressure acquisition means)
91 ... Lower surface (wall surface)
101 ... DPF regeneration control unit (temperature raising means)
S1, S2 (first determination means)
S5, S6 (first determination means)
S1, S2, S3, S4, S5, S6 (second determination means)
S3 (third determination means)

Claims (6)

A filter provided in the exhaust passage of the internal combustion engine for collecting PM contained in the exhaust;
A temperature raising means for regenerating the filter by heating and removing the PM collected by the filter by heating the filter;
An EGR passage that recirculates part of the exhaust to the internal combustion engine by communicating the exhaust passage immediately after the exhaust flow direction of the filter with the intake passage of the internal combustion engine;
An exhaust gas recirculation device for an internal combustion engine, comprising: an EGR filter provided in the vicinity of a connection portion of the EGR passage with the exhaust passage and capturing foreign matter flowing into the EGR passage,
The wall surface of the EGR passage on the upstream side in the exhaust flow direction of the EGR filter and / or the wall surface of the exhaust passage on the downstream side in the exhaust flow direction of the connecting portion is positioned against the flow of exhaust gas that has passed through the filter. And a rebound surface on which the condensed water flowing out of the filter together with the exhaust gas rebounds against the exhaust flow,
The exhaust gas recirculation device for an internal combustion engine, wherein the EGR filter is disposed at a position where exhaust gas and condensed water bounced from the rebound surface directly contact each other.   2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the EGR filter is provided at a position where the EGR filter can be seen from the rebound surface. The rebound surface is provided at a position that can be seen from a position upstream of the exhaust passage in the exhaust flow direction,
3. The exhaust gas recirculation device for an internal combustion engine according to claim 2, wherein the EGR filter is provided at a position where it cannot be seen from a position upstream of the exhaust passage in the exhaust flow direction. Exhaust pressure acquisition means for acquiring the exhaust pressure of the exhaust passage;
Intake pressure acquisition means for acquiring the intake pressure of the intake passage;
First determination means for determining whether a pressure abnormality of the EGR passage including the EGR filter has occurred based on the acquired exhaust pressure and intake pressure;
When it is determined by the first determination means that a pressure abnormality has occurred, regeneration of the filter is performed using the temperature raising means, and after the regeneration of the filter, the first determination means is used again. A second determination unit that performs a determination and determines that a pressure abnormality has occurred in the EGR passage when it is determined that a pressure abnormality has occurred by the second determination of the first determination unit; The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 3, further comprising:   The second determination means determines that a pressure abnormality has occurred in the EGR passage excluding the EGR filter when it is determined that a pressure abnormality has occurred by the second determination of the first determination means. The exhaust gas recirculation device for an internal combustion engine according to claim 4.   When the travel distance of the vehicle on which the internal combustion engine is mounted or the operation time of the internal combustion engine is less than or equal to a predetermined value from the previous regeneration of the filter using the temperature raising means, the first determination means causes a pressure abnormality. 6. The exhaust of an internal combustion engine according to claim 4, further comprising a third determination means for determining that a pressure abnormality has occurred in the EGR passage when it is determined that the EGR has occurred. Reflux apparatus.

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