JP2008095599A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control pressure with high accuracy when pressure in a particulate filter in regenerating the particulate filter is controlled higher other than the time of regeneration. <P>SOLUTION: In an exhaust path 3, a first channel 5 set to a first flow channel resistance, a second channel 6 set to a second flow channel resistance greater than the first flow channel resistance, and a flow channel resistance rise regulating means 7 for regulating the flow channel resistance of the second channel from exceeding the second flow channel resistance, are arranged on a further downstream side of the installation position of the particulate filter 4. When regeneration control of the particulate filter is not performed, exhaust gas is led to flow into the first channel between the first and second channels. When regeneration control is performed, exhaust gas is led to flow into the second channel to suppress inflow of exhaust gas into the first channel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine that controls the pressure in the particulate filter at the time of regeneration of the particulate filter to be higher than that at the time of regeneration.

  An exhaust path of an internal combustion engine (for example, a diesel engine) may be provided with a particulate filter (for example, a DPF) that collects particulate matter (PM) generated with combustion of the engine.

  When the amount of PM trapped in the DPF increases, the ventilation resistance in the DPF increases and the back pressure of the engine increases. As a result, the engine load increases and the output decreases. For this reason, regeneration of DPF which removes PM collected in DPF is performed. In regeneration of the DPF, for example, PM collected in the DPF is burned and removed.

  During regeneration of the DPF, control for increasing the temperature of the DPF is performed in order to burn the collected PM. For example, during regeneration of the DPF, control for increasing the fuel injection amount is performed more than in other cases. As a result, the amount of heat generated by the combustion of the fuel increases and the temperature of the exhaust gas rises, so the temperature of the DPF rises. When the temperature of the DPF is raised to a temperature higher than the temperature at which PM burns, the PM collected by the DPF is burned and removed, and the DPF is regenerated.

  In the regeneration control of the DPF that burns and removes the PM collected in the DPF as described above, the combustion of the PM is promoted as the pressure in the DPF is increased, and the regeneration of the DPF is performed in a short time. Is possible.

  FIG. 10 is a diagram showing a correspondence relationship between the absolute pressure in the DPF and the reaction rates of PM and oxygen. FIG. 11 is a diagram illustrating a correspondence relationship between the absolute pressure in the DPF and the time required for regeneration of the DPF (regeneration time).

  As shown in FIG. 10, the reaction rate between PM and oxygen increases in proportion to the absolute pressure in the DPF. This is because as the absolute pressure in the DPF (absolute pressure of the exhaust gas) increases, the oxygen partial pressure in the exhaust gas increases and PM and oxygen are more likely to react. Since the regeneration time of the DPF is generally inversely proportional to the reaction rate between PM and oxygen, as shown in FIG. 11, the regeneration time decreases in inverse proportion to the increase in the absolute pressure in the DPF.

  As a means for increasing the pressure in the DPF in order to shorten the regeneration time when the DPF is regenerated, as shown in FIG. 12, an exhaust pressure adjusting valve (exhaust throttle) is disposed downstream of the DPF installation position in the exhaust path. Valve) may be provided.

  FIG. 12 is a schematic configuration diagram of a main part of an apparatus provided with the exhaust pressure adjusting valve. In FIG. 12, reference numeral 101 denotes an engine. An exhaust manifold 102 is connected to the engine 101. An exhaust pipe (exhaust path) 103 is connected to the exhaust manifold 102. The exhaust pipe 103 is provided with a DPF 104. In the exhaust pipe 103, an exhaust pressure adjustment valve 105 is provided on the downstream side of the installation position of the DPF 104. Exhaust gas discharged from the engine 101 flows through the exhaust pipe 103 through the exhaust manifold 102. PM contained in the exhaust gas is collected in the DPF 104.

  The opening of the exhaust pressure adjusting valve 105 is set to a large opening, for example, fully open so that the exhaust gas can easily flow through the exhaust pipe 103 during normal operation (when regeneration control of the DPF 104 is not performed). On the other hand, when regeneration control of the DPF 104 is performed, the opening of the exhaust pressure adjustment valve 105 is controlled to a predetermined opening that is smaller than the opening during normal operation. By increasing the flow path resistance by the exhaust pressure adjusting valve 105, the pressure of the exhaust gas upstream of the exhaust pressure adjusting valve 105 in the exhaust pipe 103 becomes higher. Thereby, the pressure in the DPF 104 (exhaust gas pressure) increases. Thus, the regeneration time of the DPF 104 can be shortened by increasing the pressure of the exhaust gas during the regeneration of the DPF 104.

  As shown in FIG. 11, the higher the pressure in the DPF 104, the shorter the regeneration time. Therefore, in order to shorten the regeneration time, the opening of the exhaust pressure adjusting valve 105 is set so that the exhaust gas pressure increases. It is advantageous to set the value as small as possible.

  However, if the exhaust gas pressure, that is, the back pressure of the engine 101 is excessively high, the load on the engine 101 becomes excessive, which is not preferable for the engine 101. Therefore, it is desirable that the target value of the pressure of the exhaust gas in the DPF 104 at the time of regeneration of the DPF 104 (hereinafter referred to as the target pressure at the time of regeneration) be as large as possible within a range lower than the pressure not desirable for the engine 101.

  Here, when the pressure of the exhaust gas in the DPF 104 is controlled by the opening degree of the exhaust pressure adjustment valve 105, the accuracy of the control is limited as described below, and the regeneration target pressure is sufficiently large. There is a problem that the pressure cannot be set.

  In the exhaust pressure adjusting valve 105, the actual opening may be different from the opening instructed by the control command due to the influence of product variations, aging deterioration, and the like. In this case, the actual exhaust gas pressure in the DPF 104 is different from the regeneration target pressure in spite of the generation of the control command for setting the pressure in the DPF 104 to the regeneration target pressure. Therefore, the regeneration target pressure is set to a safe value in consideration of the possibility that the actual pressure in the DPF 104 is different from the regeneration target pressure.

  For example, in the regeneration control of the DPF 104, when the actual opening of the exhaust pressure adjusting valve 105 is smaller than the opening designated by the control command, the actual exhaust gas pressure in the DPF 104 is The value may be larger than the target pressure during regeneration. Even in such a case, it is necessary to suppress the pressure of the exhaust gas from being undesirably higher than the engine 101.

  For this reason, the regeneration target pressure is set to a pressure sufficiently lower than a pressure not desirable for the engine 101. As a result, the regeneration control of the DPF 104 is performed at a pressure lower than the pressure desirable from the viewpoint of shortening the regeneration time. For this reason, there is a problem that the regeneration time of the DPF 104 becomes longer than the regeneration time when the pressure of the exhaust gas is set to the desired pressure.

JP-A-8-170521 JP 2005-282579 A JP 2001-248423 A Japanese Patent No. 3552489

  When the pressure in the particulate filter during regeneration of the particulate filter is controlled to be higher than that during regeneration, it is desired that the pressure in the particulate filter can be accurately controlled.

  Provided is an exhaust gas purifying device for an internal combustion engine capable of accurately controlling the pressure in the particulate filter when controlling the pressure in the particulate filter during regeneration of the particulate filter to a pressure higher than that during regeneration. It is to be.

  An exhaust gas purification apparatus for an internal combustion engine according to the present invention is an exhaust gas purification apparatus for an internal combustion engine having a particulate filter for collecting particulate matter in the exhaust gas in the exhaust path, A first flow channel in which the flow channel resistance is set to the first flow channel resistance on the downstream side of the installation position of the particulate filter in the exhaust channel, and the flow channel resistance is greater than the first flow channel resistance. A second flow path set to a second flow path resistance that is larger than the second flow path, and a flow path resistance increase restricting means for restricting the flow path resistance of the second flow path from exceeding the set second flow path resistance. And the particulate filter is not subjected to regeneration control, exhaust gas is caused to flow through at least the first flow path of the first flow path and the second flow path, and the particulate filter Playback system Is when the reaction is carried out, the exhaust gas is passed through the second flow path, the exhaust gas flows into the first flow path is characterized in that it is suppressed.

  In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the exhaust path is branched into a first pipe having the first flow path and a second pipe having the second flow path.

  In the exhaust gas purifying apparatus for an internal combustion engine of the present invention, the exhaust path has a double pipe structure having an outer pipe and an inner pipe provided inside the outer pipe, and the inner side of the inner pipe A first flow path is formed, and the second flow path is formed between the inner tube and the outer tube.

  In the exhaust gas purifying apparatus for an internal combustion engine of the present invention, when regeneration control of the particulate filter is performed, if the pressure of the exhaust gas in the exhaust path exceeds a predetermined value, the first It is characterized by facilitating the flow of exhaust gas in one flow path.

  According to the exhaust gas purification apparatus for an internal combustion engine of the present invention, when controlling the pressure in the particulate filter at the time of regeneration of the particulate filter to be higher than that at the time of regeneration, the pressure in the particulate filter is accurately controlled. It becomes possible to do.

  Hereinafter, an embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
The first embodiment will be described with reference to FIGS. 1 to 3. The present embodiment relates to an exhaust gas purification apparatus for an internal combustion engine that controls the pressure in the particulate filter during regeneration of the particulate filter to be higher than that during regeneration.

  In the present embodiment, control is performed so that the pressure of the exhaust gas in the DPF at the time of regeneration of the particulate filter (DPF) is a target value (hereinafter referred to as target pressure at the time of regeneration).

  In the present embodiment, two flow paths (branch pipes) having different flow path resistances are provided on the downstream side of the installation position of the particulate filter in the exhaust path. In the present embodiment, the channel resistances of the two channels are different values depending on the cross-sectional areas of the respective channels. During normal operation (when DPF regeneration control is not performed), the exhaust gas is caused to flow through the first flow path having a relatively small flow path resistance and the second flow path resistance having a relatively large flow path resistance. The exhaust gas does not flow into the flow path. On the other hand, when the regeneration of the DPF is performed, the exhaust gas flows through the second flow path, and the exhaust gas does not flow through the first flow path. As a result, since the pressure in the DPF is increased during regeneration of the DPF compared to during normal operation, the time required for regeneration is shortened.

  As will be described in detail below, according to the present embodiment, as compared with the case where the pressure in the DPF 104 is controlled by the opening of the exhaust pressure regulating valve 105 as described with reference to FIG. The pressure in the DPF 104 can be controlled with high accuracy. As a result, in consideration of the possibility that the actual pressure in the DPF 104 will exceed the regeneration target pressure as in the case where the pressure in the DPF 104 is controlled by the opening of the exhaust pressure regulating valve 105, the regeneration target pressure is reduced. There is no need to set a low pressure. For this reason, since the regeneration target pressure can be set to a higher pressure, the DPF can be regenerated in a shorter time.

  FIG. 1 is a schematic configuration diagram of an apparatus according to the present embodiment. In FIG. 1, reference numeral 1 denotes an engine. An exhaust manifold 2 is connected to the engine 1. An exhaust pipe (exhaust path) 3 is connected to the exhaust manifold 2. The exhaust pipe 3 is provided with a DPF 4.

  The DPF 4 is a filter for collecting particulate matter (PM) in the exhaust gas. Exhaust gas discharged from the engine 1 flows through the exhaust manifold 2 through the exhaust manifold 3 and passes through the DPF 4. PM contained in the exhaust gas is collected in the DPF 4 when passing through the DPF 4.

  The exhaust pipe 3 is provided with a branching portion 8 on the downstream side of the installation position of the DPF 4. The exhaust pipe 3 branches into a first branch pipe (first flow path) 5 and a second branch pipe (second flow path) 6 at the branch portion 8.

  The second branch pipe 6 is provided with a throttle portion (flow path resistance increase restricting means) 7. The diameter of the upstream end portion 7 a in the exhaust gas flow direction in the throttle portion 7 is the same as that of the second branch pipe 6. The throttle portion 7 has a gradually decreasing diameter from the upstream end portion 7a toward the exhaust gas traveling direction. The diameter of the throttle portion 7 is gradually increased from the smallest diameter portion (minimum portion 7b) in the exhaust gas traveling direction, and the second branch pipe 6 is located at the downstream end portion 7c in the exhaust gas flow direction. And the same diameter. The cross-sectional area of the flow path in the minimum part 7 b of the throttle part 7 is set to a value smaller than the cross-sectional area of the flow path of the first branch pipe 5. As a result, the second branch pipe 6 has a flow passage resistance larger than that of the first branch pipe 5 due to the fixed throttle portion 7 having no movable part like the exhaust pressure regulating valve 105 of FIG. It is configured.

  The restricting portion 7 effectively suppresses the cross-sectional area of the second branch pipe 6 from becoming smaller than necessary (the flow path resistance of the second branch pipe 6 exceeds the preset second flow path resistance). Possible fixed structural members. Therefore, it is possible to suppress the flow path resistance from exceeding a preset value as compared with the configuration using the exhaust pressure regulating valve 105 having the movable portion illustrated in FIG.

  The branching unit 8 is provided with a flow path switching valve 9. The exhaust pipe 3 is provided with a first valve seat 10 and a second valve seat 11 corresponding to the flow path switching valve 9. The first valve seat 10 is provided on the inner wall of the exhaust pipe 3 on the first branch pipe 5 side with respect to the central axis. The second valve seat 11 is provided on the inner wall on the second branch pipe 6 side with respect to the central axis of the exhaust pipe 3.

  The flow path switching valve 9 switches the flow path of the exhaust gas flowing out from the DPF 4. 2 and 3 are enlarged views of the vicinity of the flow path switching valve 9.

  FIG. 2 shows a state in which the flow path switching valve 9 is in contact with the second valve seat 11. In this case, as indicated by reference numeral 30 in FIG. 2, the exhaust gas flowing out from the DPF 4 flows to the first branch pipe 5. In a normal operation state, the flow path switching valve 9 is in a state shown in FIG. 2 (a state in which the second valve seat 11 is in contact). As a result, the exhaust gas flows through the first branch pipe 5 having a relatively small channel resistance, so that the exhaust gas is discharged smoothly.

  FIG. 3 shows a state in which the flow path switching valve 9 is in contact with the first valve seat 10. In this case, as indicated by reference numeral 31 in FIG. 3, the exhaust gas flowing out from the DPF 4 flows to the second branch pipe 6. As will be described later, when the regeneration control of the DPF 4 is performed, the flow path switching valve 9 is switched to the state shown in FIG. 3 (the state in contact with the first valve seat 10). Thereby, the inside of the DPF 4 becomes a high pressure, and the regeneration of the DPF 4 can be performed in a shorter time.

  As shown in FIG. 1, a vehicle (not shown) on which the engine 1 is mounted is provided with a vehicle control unit 20 having an ECU (Electronic Control Unit) that controls each part of the vehicle. The flow path switching valve 9 is connected to the vehicle control unit 20, and the operation of the flow path switching valve 9 is controlled by the vehicle control unit 20.

  As described above, PM contained in the exhaust gas is collected in the DPF 4 when passing through the DPF 4. When the amount of PM collected in the DPF 4 increases, the ventilation resistance in the DPF 4 increases and the back pressure of the engine 1 increases. As a result, the engine load increases and the output decreases.

  For this reason, regeneration control of DPF4 which removes PM collected in DPF4 is performed. In the regeneration control of the DPF 4, the temperature of the DPF 4 is increased in order to burn PM.

  More specifically, when the regeneration control of the DPF 4 is performed, the flow path switching valve 9 is switched to a state in which it contacts the first valve seat 10 as shown in FIG. As a result, the exhaust gas flowing out from the DPF 4 flows through the second branch pipe 6. As described above, the flow path resistance of the second branch pipe 6 is larger than the flow path resistance of the first branch pipe 5. For this reason, the pressure of the exhaust gas in the DPF 4 is higher when the exhaust gas is flowed to the second branch pipe 6 (FIG. 3) than when the exhaust gas is flowed to the first branch pipe 5 (FIG. 2).

  When the exhaust gas pressure increases, the load on the engine 1 increases, so the amount of fuel supplied to the engine 1 increases. Thereby, the temperature of the exhaust gas discharged from the engine 1 rises. The DPF 4 is heated by passing the exhaust gas whose temperature has increased. As a result, the temperature of DPF 4 rises above the temperature at which PM burns, and PM is burned and removed.

  As a means for raising the temperature of the exhaust gas, in addition to the above, post-injection in which fuel is injected in the expansion stroke or the exhaust stroke after the main injection of the engine 1 can be performed. In this case, the temperature of the exhaust gas further increases due to the combustion heat of the post-injected fuel, so that the temperature of the DPF 4 is sufficiently increased.

  In the regeneration control of the DPF 4 performed as described above, the regeneration of the DPF 4 is performed in a shorter time as the pressure of the exhaust gas in the DPF 4 is increased as described with reference to FIGS. It becomes possible.

  For this reason, in order to shorten the regeneration time, it is advantageous to increase the pressure of the exhaust gas when the DPF 4 is regenerated.

  However, if the exhaust gas pressure, that is, the back pressure of the engine 1 is excessively increased, the load on the engine 1 becomes excessive, which is not preferable for the engine 1. Therefore, it is desirable that the regeneration target pressure be as large as possible within a range that is less than the undesirable pressure for the engine 1. The regeneration target pressure is set based on the result of an experiment, for example.

  Based on the set regeneration target pressure, the flow path resistance of the throttle portion 7 is set. In this case, the flow path resistance of the throttle portion 7 is set to a value such that the pressure of the exhaust gas in the DPF 4 when the regeneration control of the DPF 4 is performed becomes approximately the target pressure during regeneration. The flow path resistance of the throttle unit 7 is set based on the result of an experiment, for example.

  In the present embodiment, when the DPF 4 is regenerated, the pressure in the DPF 4 is controlled by switching the flow path to the second branch pipe 6 having the throttle portion 7 in which the flow path resistance is set to a fixed value. For this reason, the pressure in the DPF 4 is controlled with higher accuracy than in the case where the pressure in the DPF 104 is controlled by the exhaust pressure regulating valve 105 having a movable part as in the conventional technique (FIG. 12).

  Further, when the pressure in the DPF 104 is controlled by the opening degree of the exhaust pressure adjusting valve 105 as in the prior art (FIG. 12), if the movable part of the exhaust pressure adjusting valve 105 fails, Although the pressure may increase beyond the target pressure during regeneration, since the second branch pipe 6 of the present embodiment does not include a movable part, the possibility that the pressure increases as described above is small. Therefore, it is suitably suppressed that the pressure of the exhaust gas in the DPF 4 increases excessively during the regeneration of the DPF 4 and becomes a pressure not preferable for the engine 1.

  In the unlikely event that particulate matter or the like adheres to the throttle portion 7, the flow path resistance of the throttle portion 7 may change. On the other hand, in the present embodiment, since the throttle portion 7 is provided downstream of the DPF 4 in the flow of exhaust gas, the exhaust gas passing through the throttle portion 7 may contain particulate matter or the like. Is small. For this reason, the possibility that the flow path resistance of the throttle portion 7 changes as described above is small.

(First modification of the first embodiment)
In the present embodiment, the second branch pipe 6 is provided with the narrowed portion 7 having a flow path cross-sectional area smaller than that of the first branch pipe 5, but instead of this, the second branch pipe 6. Can be set to a uniform value smaller than the cross-sectional area of the first branch pipe 5. In this case, since it is not necessary to provide a structure like the throttle portion 7, it is possible to reduce manufacturing costs and manufacturing errors compared to the case where the throttle portion 7 is provided in the second branch pipe 6.

(Second modification of the first embodiment)
In the present embodiment, the flow path switching valve 9 is provided in the branch portion 8 in order to switch the flow of the exhaust gas. Instead of this, an opening / closing valve for opening and closing the first branch pipe 5 is provided in the first branch pipe 5. Can be provided. In the normal operation state, the on-off valve is opened. In this case, the exhaust gas flows through each of the first branch pipe 5 and the second branch pipe 6. When the DPF 4 is regenerated, the on-off valve is completely closed. In this case, the exhaust gas does not flow to the first branch pipe 5 and flows through the second branch pipe 6.

  In the present embodiment, the second branch pipe 6 is provided with a fixed throttle portion 7 so that the flow resistance of the second branch pipe 6 is larger than the flow resistance of the first branch pipe 5. However, the structure for increasing the flow path resistance of the second branch pipe 6 is not limited to this. The flow resistance of the second branch pipe 6 can be made larger than the flow resistance of the first branch pipe 5 by a conventionally known fixed structure having no movable part.

(Second Embodiment)
The second embodiment will be described with reference to FIGS. 4 to 6. In the second embodiment, only differences from the first embodiment will be described.

  In the first embodiment (FIG. 1), two branch pipes (5, 6) having different flow path resistances are provided, and the first branch pipe 5 having a relatively low flow path resistance except when the DPF 4 is regenerated. The exhaust gas was caused to flow through the second branch pipe 6 having a relatively large flow path resistance when the DPF 4 was regenerated (FIG. 3). Instead, in this embodiment, as shown in FIG. 4, a part of the exhaust pipe 3 on the downstream side of the installation position of the DPF 4 has a double pipe structure. An on-off valve (flow path resistance increase restricting means) 12 is provided inside the inner pipe in the double pipe structure. When the DPF 4 is regenerated, the on-off valve 12 is completely closed, and control for increasing the flow path resistance of the exhaust pipe 3 is performed.

  FIG. 4 is a schematic configuration diagram of an apparatus according to the second embodiment. The apparatus according to the present embodiment differs from the apparatus according to the first embodiment (FIG. 1) in the configuration on the downstream side of the installation position of the DPF 4. A double pipe structure is provided downstream of the DPF 4 installation position in the exhaust pipe 3. The double pipe structure includes an inner exhaust pipe (inner pipe) 13 and an outer exhaust pipe (outer pipe) 19 (exhaust pipe 3). In the present embodiment, the outer exhaust pipe 19 forms a part of the exhaust pipe 3. The diameter of the inner exhaust pipe 13 is set to a value smaller than the diameter of the outer exhaust pipe 19. The inner exhaust pipe 13 is installed inside the outer exhaust pipe 19.

  An outer flow path (second flow path) 15 is formed between the outer exhaust pipe 19 and the inner exhaust pipe 13. The configuration of the outer flow path 15 does not have a movable part, and the flow path resistance is set to a fixed value. An inner flow path (first flow path) 14 is formed inside the inner exhaust pipe 13. An open / close valve 12 is provided in the inner exhaust pipe 13. The on-off valve 12 opens and closes the inner exhaust pipe 13 (inner flow path 14).

  Instead of the vehicle control unit 20 of the first embodiment, a vehicle control unit 40 is provided. The on-off valve 12 is connected to the vehicle control unit 40, and the operation of the on-off valve 12 is controlled by the vehicle control unit 40.

  The on / off valve 12 switches the flow path of the exhaust gas flowing out from the DPF 4. 5 and 6 are enlarged views of the vicinity of the on-off valve 12.

  FIG. 5 shows a state where the on-off valve 12 is opened. In this case, as indicated by reference numeral 32, the exhaust gas flowing out from the DPF 4 flows through the inner flow path 14 and the outer flow path 15. In a normal operation state (when the regeneration control of the DPF 4 is not performed), the on-off valve 12 is in the state shown in FIG. 5 (open state). Thereby, since the flow path resistance of the exhaust pipe 3 becomes the smallest state, the exhaust gas is discharged smoothly.

  FIG. 6 shows a state in which the on-off valve 12 is completely closed. In this case, as indicated by reference numeral 33, the exhaust gas flowing out from the DPF 4 flows through the outer flow path 15. When regeneration control of the DPF 4 is performed, the on-off valve 12 is switched to the state shown in FIG. 6 (completely closed state). As a result, the flow path resistance is increased as compared to the state in which the on-off valve 12 is open, so that the pressure inside the DPF 4 becomes high, and the regeneration of the DPF 4 is completed in a shorter time.

  Similar to the first embodiment, the regeneration target pressure is set to be as large as possible within a range that does not exceed the pressure not desirable for the engine 1. The channel resistance of the outer channel 15 is set based on the regeneration target pressure. The channel resistance of the outer channel 15 is set based on the result of an experiment, for example.

  According to the second embodiment, when the DPF 4 is regenerated, the pressure in the DPF 4 is controlled by completely closing the on-off valve 12 provided in the inner exhaust pipe 13 and flowing the exhaust gas to the outer flow path 15. The Compared to the case where the pressure in the DPF 104 is controlled by adjusting the opening degree of the exhaust pressure adjusting valve 105 to the intermediate opening degree as in the prior art (FIG. 12), the pressure in the DPF 4 is controlled with higher accuracy. The

  Further, the opening degree of the on-off valve 12 at the time of regeneration of the DPF 4 is in a completely closed state (fully closed). For this reason, even if the actual opening of the on / off valve 12 deviates from the command value of the opening, the channel resistance is the channel resistance (second channel resistance) with the on / off valve 12 completely closed. ) Is unlikely to be larger.

  For this reason, as shown in FIG. 12, compared with the case where the pressure in the DPF 104 is controlled by the opening of the exhaust pressure regulating valve 105, the actual exhaust gas pressure in the DPF 4 is suppressed from exceeding the regeneration target pressure. Is done.

  In the present embodiment, the inner flow path 14 formed inside the inner exhaust pipe 13 is the first flow path, but instead, the first flow path is formed by combining the inner flow path 14 and the outer flow path 15. Can be considered.

  In the present embodiment, a double pipe structure is formed by the inner exhaust pipe 13 and the outer exhaust pipe 19 and the inside of the exhaust pipe 3 is partitioned, but the partitioning method in the exhaust pipe 3 is not limited to this. Various configurations may be employed in which the inside of the exhaust pipe 3 is partitioned and a plurality of flow paths having different flow path resistances are formed.

(Third embodiment)
A third embodiment will be described with reference to FIGS. In the third embodiment, only differences from the above embodiment will be described.

  In each of the above-described embodiments, control is performed in which the pressure in the DPF 4 at the time of regeneration of the DPF 4 is used as the regeneration target pressure. In this embodiment, when the pressure of the exhaust gas in the DPF 4 becomes higher than the target pressure at the time of regeneration when the DPF 4 is regenerated, control is performed to reduce the pressure of the exhaust gas. When the pressure of the exhaust gas in the DPF 4 becomes higher than the regeneration target pressure, such as when an abnormality occurs, the flow path resistance is reduced, and an increase in the exhaust gas pressure is suppressed. As a result, the pressure of the exhaust gas at the time of regeneration of the DPF 4 is more reliably suppressed from becoming an unfavorable pressure for the engine 1.

  FIG. 7 is a schematic configuration diagram of an apparatus according to the present embodiment. Instead of the flow path switching valve 9 of the first embodiment (FIG. 1), a flow path control valve 17 is provided. The valve position of the flow path control valve 17 can be set to an arbitrary position (intermediate opening) between the state in contact with the first valve seat 10 and the state in contact with the second valve seat 11. .

  Instead of the vehicle control unit 20 of the first embodiment, a vehicle control unit 50 is provided. The flow path control valve 17 is connected to the vehicle control unit 50, and the operation of the flow path control valve 17 is controlled by the vehicle control unit 50. Further, a pressure sensor 16 is provided on the exhaust pipe 3 upstream of the installation position of the DPF 4. The pressure of the exhaust gas in the exhaust pipe 3 is detected by the pressure sensor 16. The pressure sensor 16 is connected to the vehicle control unit 50, and the measurement result by the pressure sensor 16 is input to the vehicle control unit 50.

  In the normal operation state, the flow path control valve 17 is in contact with the second valve seat 11 in the same manner as the flow path switching valve 9 of the first embodiment (FIG. 2).

  When regeneration control of the DPF 4 is performed, the flow path control valve 17 is controlled as follows. First, at the start of regeneration control, the flow path control valve 17 is brought into contact with the first valve seat 10 in the same manner as the flow path switching valve 9 of the first embodiment (FIG. 3). Thereby, the exhaust gas flowing out from the DPF 4 flows through the second branch pipe 6. For this reason, the pressure of the exhaust gas in the DPF 4 is higher than that in a normal operation state in which the exhaust gas flows to the first branch pipe 5.

  When the flow path control valve 17 is brought into contact with the first valve seat 10, the control is performed according to the flowchart shown in FIG.

  First, the pressure of the exhaust gas detected by the pressure sensor 16 in step S10 is taken. Next, in step S20, it is determined whether or not the pressure of the exhaust gas taken in in step S10 is greater than a predetermined pressure. The predetermined pressure can be, for example, a regeneration target pressure.

  As a result of the determination in step S20, when it is determined that the pressure of the exhaust gas is larger than the predetermined pressure (Yes in step S20), the process proceeds to step S30.

  In step S30, control for reducing the flow path resistance is performed. Specifically, the flow path control valve 17 is moved toward the second valve seat 11 to an intermediate opening. As a result, as indicated by arrows 34 and 35 in FIG. 9, the exhaust gas flows to the second branch pipe 6 and to the first branch pipe 5. Since the flow path resistance is smaller than the state in which the flow path control valve 17 is in contact with the first valve seat 10, the pressure of the exhaust gas is reduced.

  On the other hand, as a result of the determination in step S20, when it is determined that the exhaust gas pressure is equal to or lower than the predetermined pressure (No in step S20), the control flow is reset.

  According to the third embodiment, when the pressure of the exhaust gas is higher than the predetermined pressure (Yes at Step S20), the flow path resistance is reduced (Step S30). As a result, the pressure of the exhaust gas is suppressed from becoming higher than the predetermined pressure, so that the back pressure of the engine 1 is preferably suppressed to an unfavorable pressure for the engine 1 during regeneration of the DPF 4. In the present embodiment, the opening degree of the flow path control valve 17 is set to the intermediate opening degree in step S30. Instead, the flow path control valve 17 is in contact with the second valve seat 11. be able to.

  In the present embodiment, the pressure of the exhaust gas is detected, but instead, the pressure of the exhaust gas can be estimated based on the flow rate of the exhaust gas. In this case, a sensor for detecting the flow rate of the exhaust gas is provided in the exhaust pipe 3. Based on the detected flow rate of the exhaust gas and the opening degree of the flow path control valve 17, the relationship between the flow rate of the exhaust gas, the opening degree of the flow path control valve 17 and the pressure of the exhaust gas, which was obtained in advance by experiments, was determined. The map is referenced to estimate the exhaust gas pressure.

1 is a schematic configuration diagram of an apparatus according to a first embodiment of an exhaust gas purification apparatus for an internal combustion engine of the present invention. It is a figure which shows the state at the time of normal operation of the apparatus which concerns on 1st Embodiment of the exhaust gas purification apparatus of the internal combustion engine of this invention. It is a figure which shows the state at the time of DPF reproduction | regeneration of the apparatus which concerns on 1st Embodiment of the exhaust-gas purification apparatus of the internal combustion engine of this invention. It is a schematic block diagram of the apparatus which concerns on 2nd Embodiment of the exhaust-gas purification apparatus of the internal combustion engine of this invention. It is a figure which shows the state at the time of normal operation of the apparatus which concerns on 2nd Embodiment of the exhaust gas purification apparatus of the internal combustion engine of this invention. It is a figure which shows the state at the time of DPF reproduction | regeneration of the apparatus which concerns on 2nd Embodiment of the exhaust gas purification apparatus of the internal combustion engine of this invention. It is a schematic block diagram of the apparatus which concerns on 3rd Embodiment of the exhaust-gas purification apparatus of the internal combustion engine of this invention. It is a flowchart which shows operation | movement of 3rd Embodiment of the exhaust-gas purification apparatus of the internal combustion engine of this invention. It is a figure which shows the state at the time of DPF reproduction | regeneration of the apparatus which concerns on 3rd Embodiment of the exhaust gas purification apparatus of the internal combustion engine of this invention. It is a figure which shows the relationship between the absolute pressure in DPF, and the reaction rate of PM and oxygen. It is a figure which shows the relationship between the absolute pressure in DPF, and regeneration time. It is a figure which shows an example of the apparatus provided with the exhaust pressure adjustment valve in the downstream of DPF.

Explanation of symbols

1 Engine 2 Exhaust manifold 3 Exhaust pipe 4 DPF
DESCRIPTION OF SYMBOLS 5 1st branch pipe 6 2nd branch pipe 7 Restriction part 8 Branch part 9 Flow path switching valve 10 1st valve seat 11 2nd valve seat 12 On-off valve 13 Inner exhaust pipe 14 Inner flow path 15 Outer flow path 16 Pressure sensor 17 Flow control valve 19 Outer exhaust pipe 20 Vehicle control unit 30 Flow of exhaust gas 31 Flow of exhaust gas 32 Flow of exhaust gas 33 Flow of exhaust gas 34 Flow of exhaust gas 35 Flow of exhaust gas 40 Vehicle control unit 50 Vehicle control unit 101 Engine 102 Exhaust manifold 103 Exhaust pipe 104 DPF
105 Exhaust pressure adjustment valve

Claims (4)

An exhaust gas purifying device for an internal combustion engine comprising a particulate filter for collecting particulate matter in exhaust gas in an exhaust path,
In the exhaust path, on the downstream side of the installation position of the particulate filter in the exhaust path,
A first channel having a channel resistance set to the first channel resistance;
A second channel having a channel resistance set to a second channel resistance greater than the first channel resistance;
A flow path resistance increase restricting means for restricting the flow path resistance of the second flow path from exceeding the set second flow path resistance;
When regeneration control of the particulate filter is not performed, exhaust gas is caused to flow through at least the first flow path among the first flow path and the second flow path,
When the regeneration control of the particulate filter is performed, exhaust gas is allowed to flow through the second flow path, and exhaust gas is prevented from flowing into the first flow path. Gas purification device. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
The exhaust gas purification apparatus for an internal combustion engine, wherein the exhaust path is branched into a first pipe having the first flow path and a second pipe having the second flow path. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
The exhaust path has a double pipe structure having an outer pipe and an inner pipe provided inside the outer pipe,
The first flow path is formed inside the inner tube;
The exhaust gas purifying device for an internal combustion engine, wherein the second flow path is formed between the inner pipe and the outer pipe. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3,
When regeneration control of the particulate filter is performed, if the pressure of the exhaust gas in the exhaust path exceeds a predetermined value, it is promoted that the exhaust gas flows through the first flow path. An exhaust gas purifying device for an internal combustion engine.

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