JP2005330940A - Exhaust emission control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology making control for raising temperature of an oxidation catalyst by raising exhaust gas temperature of an internal combustion engine before supplying fuel to the oxidation catalyst unnecessary and enabling to perform regeneration treatment of a filter at arbitrary timing in an exhaust emission control system for an internal combustion engine provided with the oxidation catalyst in an exhaust gas passage of the internal combustion engine and provided with a filter on a downstream side of the oxidation catalyst and performing regeneration treatment of the filter by raising temperature of the filter by supplying fuel to the oxidation catalyst. <P>SOLUTION: A bypass passage making exhaust gas discharged from the internal combustion engine bypass the oxidation catalyst is provided. During a period except a period performing the regeneration treatment, exhaust gas from the internal combustion engine is made to pass through the oxidation catalyst to raise and keep temperature of the oxidation catalyst (S105) if the exhaust gas temperature is a predetermined temperature or higher, and exhaust gas from the internal combustion engine is made to pass through the bypass passage to keep the oxidation catalyst warm (S106) if the exhaust gas temperature is lower than the predetermined temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  The exhaust gas of the internal combustion engine contains particulate matter mainly composed of carbon. A technique for providing a particulate filter (hereinafter referred to as “filter”) for collecting particulate matter in an exhaust system of an internal combustion engine is known in order to prevent such particulate matter from being released into the atmosphere.

  In such a filter, when the amount of collected particulate matter increases, the back pressure in the exhaust increases due to clogging of the filter, and the engine performance decreases. On the other hand, by raising the exhaust gas temperature upstream of the filter, the collected particulate matter is oxidized and removed, and the exhaust gas purification performance of the filter is regenerated (hereinafter referred to as “filter regeneration process”). That said.)

  Here, as a method for raising the exhaust temperature upstream of the filter in the regeneration process, an oxidation catalyst having an oxidizing ability is disposed upstream of the filter, and fuel as a reducing agent is supplied to the oxidation catalyst during the regeneration process. How to do is known. As a result, the oxidation reaction of the fuel can occur in the oxidation catalyst, and the exhaust temperature upstream of the filter can be raised.

  However, if fuel is supplied to the oxidation catalyst in a state where the temperature of the oxidation catalyst is low, since the oxidation catalyst is not sufficiently activated, the oxidation reaction cannot be sufficiently caused, and a part of the HC component is generated. In some cases, the oxidation catalyst slips through. As a result, white smoke may be generated or the regeneration processing performance of the filter may deteriorate. Further, the front surface of the oxidation catalyst may be clogged by the HC component before the oxidation reaction and the particulate matter in the exhaust gas.

  Furthermore, when fuel is supplied to the oxidation catalyst in a low temperature state where the temperature of the oxidation catalyst is equal to or lower than the activation temperature (light-off temperature) of the oxidation catalyst, an oxidation reaction does not occur and the filter is regenerated. In some cases, the processing could not be performed.

  On the other hand, the temperature of the oxidation catalyst is sufficiently increased by controlling the operating state of the internal combustion engine before the filter regeneration process and increasing the temperature of the exhaust gas introduced into the oxidation catalyst. From the above, measures for performing the reproduction processing have been taken. However, according to this measure, it is necessary to control the activation of the oxidation catalyst by increasing the temperature of the exhaust gas introduced into the oxidation catalyst before starting the regeneration process of the filter. Therefore, even if the amount of the particulate matter collected by the filter increases, there is a case where the regeneration process cannot be performed immediately even if the regeneration process needs to be performed.

Further, in a configuration in which an oxidation catalyst is provided upstream of the exhaust passage of the internal combustion engine and a filter is provided downstream thereof, the internal combustion engine has a bypass passage that bypasses the oxidation catalyst, and during normal operation other than during the regeneration process of the filter A technique for bypassing the oxidation catalyst to the exhaust gas from the internal combustion engine to suppress deterioration of the oxidation catalyst or the like is disclosed (for example, see Patent Document 1). Even in this case, during normal operation other than during the regeneration process of the filter, the exhaust gas from the internal combustion engine is bypassed by the oxidation catalyst, so the temperature of the exhaust gas introduced into the oxidation catalyst is raised before the regeneration process is started. Therefore, it was necessary to control the activation of the catalyst.
Japanese Patent Publication No. 05-34486 Japanese Patent No. 3012249 Japanese Patent Laid-Open No. 2003-13730 Japanese Unexamined Patent Publication No. 08-31820 JP 2004-44509 A

  An object of the present invention is to have an oxidation catalyst provided in an exhaust passage of an internal combustion engine and a filter provided downstream of the oxidation catalyst, and supply fuel to the oxidation catalyst to raise the temperature of the filter. Therefore, in the exhaust gas purification system for the internal combustion engine that performs the regeneration process of the filter, it is unnecessary to control the temperature of the oxidation catalyst by raising the exhaust temperature of the internal combustion engine before supplying fuel to the oxidation catalyst. It is to provide a technique that enables a reproduction process to be executed at an arbitrary time.

  In order to achieve the above object, the present invention includes an oxidation catalyst provided in an exhaust passage of an internal combustion engine and a filter provided downstream of the oxidation catalyst, and supplies fuel to the oxidation catalyst to supply the filter. An exhaust gas purification system for an internal combustion engine that performs regeneration processing of the filter by raising the temperature of the exhaust gas, further comprising a bypass passage that bypasses the oxidation catalyst to exhaust gas from the internal combustion engine, and performs the regeneration processing When the exhaust gas temperature is equal to or higher than a predetermined temperature other than the time period, the temperature of the oxidation catalyst is raised by passing the oxidation catalyst through the exhaust gas from the internal combustion engine, and the exhaust gas temperature is higher than the predetermined temperature. When the temperature is low, the maximum characteristic is that the oxidation catalyst is kept warm by bypassing the oxidation catalyst to the exhaust gas from the internal combustion engine.

More specifically, a catalyst that is provided in the exhaust passage of the internal combustion engine and has an oxidizing ability;
Provided on the downstream side of the catalyst in the exhaust passage, and collects the particulate matter in the exhaust gas passing through the exhaust passage, and has the ability to collect the particulate matter by a regeneration process for oxidizing and removing the collected particulate matter. A filter to be replayed,
In the regeneration process, a fuel supply means for supplying fuel as a reducing agent to the catalyst from upstream of the catalyst;
A deposition amount estimating means for estimating a deposition amount of the particulate matter collected in the filter into the filter, and
When the accumulation amount of the particulate matter estimated by the accumulation amount estimation means is equal to or greater than a predetermined regeneration processing start accumulation amount, the fuel supply means supplies fuel to the catalyst and the filter An exhaust gas purification system for an internal combustion engine that performs the regeneration process by raising the temperature of
A bypass passage for bypassing the catalyst to exhaust discharged from the internal combustion engine and flowing upstream of the catalyst in the exhaust passage;
An exhaust passage selection means for selecting whether the catalyst passes through the exhaust flowing through the upstream side of the catalyst or the bypass passage;
Exhaust temperature detecting means for detecting the temperature of the exhaust gas flowing upstream of the catalyst,
If the temperature of the exhaust gas flowing upstream of the catalyst detected by the exhaust gas temperature detection means is lower than a predetermined temperature in a period other than the period for performing the regeneration process, the exhaust passage selection means The exhaust gas flowing through the upstream side is passed through the bypass passage.

Here, in the regeneration process, as described above, fuel as a reducing agent is supplied from the fuel supply means to the catalyst. As a result, an oxidation reaction of fuel occurs in the catalyst, and the temperature of the exhaust gas discharged from the catalyst rises due to the reaction heat. And by introducing hot exhaust into the filter, the temperature of the filter can be raised,
The particulate matter collected by the filter can be removed by oxidation.

  However, when the temperature of the catalyst is low and the catalyst is not sufficiently activated at the start of the regeneration process, the fuel supply means cannot sufficiently initiate an oxidation reaction of the fuel. In some cases, a part of the HC component of the fuel supplied by the catalyst slips through the catalyst. In such a case, white smoke may be generated or the efficiency of the regeneration process may be deteriorated. In addition, when the temperature of the catalyst at the start of the regeneration process is equal to or lower than the activation temperature (light-off temperature) of the catalyst, it is difficult to cause an oxidation reaction of the fuel in the catalyst. There was a risk that it would become impossible.

  On the other hand, before the regeneration process is performed, the operating state of the internal combustion engine is controlled, and the temperature of the oxidation catalyst is sufficiently increased by increasing the temperature of the exhaust gas introduced into the oxidation catalyst. It is also possible to perform a reproduction process. This is based on the idea that the temperature of the oxidation catalyst can be controlled by controlling the temperature of the exhaust gas, since the temperature of the oxidation catalyst changes substantially following the temperature of the introduced exhaust gas. However, according to this, it is necessary to control the catalyst to be activated by increasing the temperature of the exhaust gas before the start of the regeneration process. There were cases where it could not be implemented.

  Therefore, in the present invention, a bypass passage for bypassing the catalyst to the exhaust from the internal combustion engine, an exhaust passage selection means for selecting whether the catalyst is passed through the exhaust or the bypass passage, Exhaust temperature detecting means for detecting the temperature of the exhaust, and when the temperature of the exhaust is lower than a predetermined temperature during the period when the regeneration process is not performed, the exhaust is bypassed to the catalyst. It was decided.

  In this way, during the normal operation of the internal combustion engine, when the temperature of the exhaust is high, the temperature of the catalyst is increased by passing the catalyst through the exhaust, and when the temperature of the exhaust is low, By bypassing the exhaust without passing the catalyst through the exhaust, the heat of the catalyst can be suppressed from being taken away by the low-temperature exhaust, and the temperature of the catalyst can be prevented from decreasing. As a result, the temperature of the catalyst can always be kept high, and the regeneration process can be started immediately when the necessity for the regeneration process occurs.

  Here, the predetermined temperature may be a so-called catalyst activation temperature (light-off temperature). Then, when the temperature of the exhaust is equal to or higher than the light-off temperature, the catalyst is passed through the exhaust to raise the temperature of the catalyst to be higher than the light-off temperature, and the temperature of the exhaust is lower than the light-off temperature. Alternatively, the catalyst can be kept warm by bypassing the catalyst to the exhaust. As a result, the temperature of the catalyst can be maintained at or above the light-off temperature during normal operation. Alternatively, the predetermined temperature may be set to a temperature higher than the light-off temperature obtained by adding a margin temperature to a so-called catalyst activation temperature (light-off temperature). In this way, the catalyst can be passed through the exhaust gas only when the temperature of the exhaust gas is higher, and the temperature of the catalyst can be maintained at a higher temperature.

  In the present invention, a catalyst temperature detecting means for detecting the temperature of the catalyst may be further provided, and the predetermined temperature may be the temperature of the catalyst detected by the catalyst temperature detecting means. Then, when the exhaust from the internal combustion engine is equal to or higher than the temperature of the catalyst, the temperature of the catalyst can be raised by passing the catalyst through the exhaust. On the other hand, when the exhaust temperature is equal to or lower than the temperature of the catalyst, the exhaust is bypassed by the catalyst, so that the temperature of the catalyst can be prevented from decreasing.

As a result, the temperature of the catalyst can be maintained as high as possible in a period other than the period during which the regeneration process is performed. And even if the temperature of the exhaust does not become higher than the light-off temperature of the catalyst between the end of the previous regeneration process and the start of the next regeneration process, the maximum temperature in that range, The temperature of the catalyst can be maintained. Therefore, even if the conventional control for increasing the exhaust gas temperature introduced into the oxidation catalyst is required before the start of the regeneration process, the time required for the control can be shortened.

  In the present invention, the predetermined temperature may be a lower one of the light-off temperature of the catalyst and the temperature of the catalyst detected by the catalyst temperature detecting means. Then, if the temperature of the catalyst is lower than its light-off temperature, the exhaust will pass the catalyst if the temperature of the exhaust is higher than the temperature of the catalyst even if the temperature of the exhaust is lower than the light-off temperature of the catalyst. By passing the catalyst, the temperature of the catalyst can be raised. On the other hand, when the temperature of the catalyst is higher than its light-off temperature, even if the temperature of the exhaust is lower than the temperature of the catalyst, if the temperature is higher than the light-off temperature, the catalyst is passed through the exhaust. Heat can be positively applied so that the temperature of the catalyst is equal to or higher than the light-off temperature.

  In this way, the temperature of the catalyst can be more reliably maintained at a high temperature during normal operation other than the period of performing the regeneration process.

  Further, in the present invention, the particulate matter detected by the exhaust temperature detection means in a period other than the regeneration period is lower than a predetermined temperature and estimated by the accumulation amount estimation means. When the accumulation amount in the filter is equal to or greater than a predetermined regeneration preparation start accumulation amount that is less than a predetermined regeneration processing start accumulation amount, the exhaust passage selection means allows the exhaust to pass through the bypass passage. It may be.

  Here, the regeneration processing start accumulation amount is a threshold at which when the accumulation amount of the particulate matter in the filter is more than this, the differential pressure in the filter increases, which may affect the operation performance of the internal combustion engine. The amount of particulate matter deposited as. Further, the regeneration preparation start accumulation amount is a value of the accumulation amount smaller than the regeneration treatment start accumulation amount, and if the accumulation amount of the particulate matter in the filter is more than this, the regeneration preparation start amount in the near future. This is the amount of particulate matter deposited as a threshold that is predicted to require treatment.

  Therefore, it is predicted that the regeneration process will be performed in the near future when the amount of particulate matter deposited on the filter is greater than or equal to the regeneration preparation start deposition amount. Therefore, only when the accumulation amount of the particulate matter in the filter is equal to or greater than the regeneration preparation start accumulation amount, when the temperature of the exhaust gas is lower than a predetermined temperature, the exhaust gas is bypassed to the catalyst, and the exhaust gas is exhausted. If the temperature of the catalyst is equal to or higher than a predetermined temperature, it is conceivable to carry out control to pass the catalyst through the exhaust gas.

  In this case, when the possibility that the regeneration process is performed is low, the exhaust gas is bypassed to the exhaust gas when the exhaust gas temperature is lower than the predetermined temperature, and the exhaust gas temperature is set to the predetermined temperature. In the case described above, control for passing the catalyst through the exhaust is not performed. As a result, it is possible to suppress the number of times of operating the exhaust passage selection means for selecting whether to pass the catalyst through the exhaust or the bypass passage, and it is possible to suppress waste of energy.

  Further, in the present invention, when the temperature of the exhaust gas detected by the exhaust gas temperature detecting means is lower than a predetermined temperature in a predetermined period before the start of the regeneration process in a period other than the execution period of the regeneration process. The exhaust passage selection means may allow the exhaust to pass through the bypass passage.

  Here, for example, when the control is performed such that the regeneration process is performed when the travel distance of the vehicle on which the internal combustion engine is mounted reaches a predetermined regeneration process execution distance, the regeneration process is performed. The predetermined period before the start may be defined as a time after the travel distance of the vehicle after the end of the previous regeneration process has reached a regeneration process preparation distance shorter than the regeneration process execution distance. Here, the regeneration processing preparation distance refers to the exhaust gas when the travel distance of the vehicle after the end of the previous regeneration processing reaches this distance and the exhaust gas temperature is lower than a predetermined temperature. By bypassing the catalyst and starting the control to pass the catalyst through the exhaust when the temperature of the exhaust gas is equal to or higher than a predetermined temperature, when the travel distance of the vehicle reaches the regeneration processing execution distance, This is the distance at which it is determined that the temperature of the catalyst can be raised to the predetermined temperature or higher.

  Alternatively, for example, when the control is performed so that the regeneration processing execution interval is a time when a traveling time of a vehicle on which the internal combustion engine is mounted reaches a predetermined regeneration processing execution time, the regeneration processing starts. The previous predetermined period may be defined as a time after the traveling time of the vehicle after the end of the previous regeneration process reaches a regeneration process preparation time shorter than the regeneration process execution time. Here, the regeneration preparation time refers to the above-described exhaust when the vehicle travel time after the end of the previous regeneration process reaches this time and the exhaust temperature is lower than a predetermined temperature. By bypassing the catalyst and starting the control to pass the catalyst through the exhaust when the temperature of the exhaust gas is equal to or higher than a predetermined temperature, when the running time of the vehicle reaches the regeneration processing execution time, This is the time during which it is determined that the temperature of the catalyst can be raised to the predetermined temperature or higher.

  By doing so, only in a predetermined period before the regeneration process is performed, when the temperature of the exhaust gas is lower than a predetermined temperature, the exhaust gas is bypassed to the exhaust gas, and the exhaust gas temperature is set to a predetermined temperature. In the case described above, it is possible to perform control for passing the catalyst through the exhaust gas. As a result, it is possible to suppress the number of times of operating the exhaust passage selection means for selecting whether to pass the catalyst through the exhaust or the bypass passage, and it is possible to suppress waste of energy.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, the regeneration path of the filter is provided by providing an oxidation catalyst in the exhaust passage of the internal combustion engine, providing a filter downstream of the oxidation catalyst, and increasing the temperature of the filter by supplying fuel to the oxidation catalyst. In an exhaust gas purification system for an internal combustion engine that implements the above, there is no need to raise the temperature of the oxidation catalyst by raising the exhaust temperature of the internal combustion engine before supplying fuel to the oxidation catalyst, and the filter regeneration process is executed at any time It becomes possible to do.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine according to the present embodiment and its exhaust system and control system. An internal combustion engine 1 shown in FIG. 1 is a diesel engine. In FIG. 1, the inside of the internal combustion engine 1 and its intake system are omitted.

In FIG. 1, an exhaust pipe 5 through which exhaust gas discharged from the internal combustion engine 1 flows is connected to the internal combustion engine 1, and this exhaust pipe 5 is connected downstream to a muffler (not shown). Further, an exhaust purification device 10 for purifying particulate matter (for example, soot) in the exhaust is disposed in the middle of the exhaust pipe 5. On the upstream side in the exhaust purification device 10, an oxidation catalyst 10a having oxidation ability is provided.
A filter 10b that collects particulate matter (for example, soot) in the exhaust is disposed on the downstream side.

  A fuel addition valve 12 that supplies fuel as a reducing agent to the oxidation catalyst 10a of the exhaust purification device 10 is disposed upstream of the exhaust purification device 10 in the exhaust pipe 5 during the regeneration process of the filter 10b. The fuel injected from the fuel addition valve 12 is introduced into the oxidation catalyst 10a together with the exhaust from the internal combustion engine 1, and causes an oxidation reaction in the oxidation catalyst 10a. As a result, the temperature of the exhaust discharged from the oxidation catalyst 10a increases. The fuel addition valve 12 constitutes a fuel supply means in this embodiment.

  The filter 10b in this embodiment is a wall flow type particulate filter made of a porous base material, an oxidation catalyst typified by platinum (Pt), and NOx occlusion typified by potassium (K) and cesium (Cs). The agent is supported. However, the filter 10b may not necessarily carry a NOx occlusion agent. For example, a NOx catalyst may be provided independently on the upstream side or the downstream side of the exhaust purification device 10 in the exhaust pipe 5.

  Further, from the exhaust pipe 5 in the present embodiment, the bypass pipe 6 is branched upstream of the exhaust purification device 10, and the exhaust pipe 5 on the upstream side is circulated to the connection portion between the exhaust pipe 5 and the bypass pipe 6. A switching valve 15 is provided for selecting whether to introduce exhaust gas to be introduced into the bypass pipe 6 or into the exhaust gas purification device 10. The other end of the bypass pipe 6 is connected between the oxidation catalyst 10a in the exhaust purification device 10 and the filter 10b. That is, it is possible to select whether to pass the oxidation catalyst 10a through the exhaust gas discharged from the internal combustion engine 1 or to bypass the oxidation catalyst 10a by operating the switching valve 15. Here, the switching valve 15 constitutes an exhaust passage selection means in the present embodiment.

  Further, an exhaust temperature sensor 16 for detecting the temperature of the exhaust gas upstream of the filter 10a is provided upstream of the switching valve 15 in the exhaust pipe 5. Further, an upstream exhaust pressure sensor 13 for detecting an exhaust pressure upstream of the filter 10b is provided between the oxidation catalyst 10a and the filter 10b. Further, a downstream side exhaust pressure sensor 18 for detecting an exhaust pressure on the downstream side of the filter 10b is provided in the exhaust pipe 5 on the downstream side of the exhaust purification device 10, that is, on the downstream side of the filter 10b.

  From the output of the exhaust temperature sensor 16, the temperature of the exhaust discharged from the internal combustion engine 1 can be detected. Further, by taking the difference between the output of the upstream exhaust pressure sensor 13 and the output of the downstream exhaust pressure sensor 18, the differential pressure before and after the filter 10b can be acquired, and the filter 10b captures the differential pressure from this differential pressure. The amount of particulate matter collected and deposited can be detected. The exhaust temperature sensor 16 constitutes an exhaust temperature detection means in this embodiment.

  The internal combustion engine 1 configured as described above and its exhaust system are provided with an electronic control unit (ECU) 20 for controlling the internal combustion engine 1 and the exhaust system. 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 driver's request, and performs control related to the exhaust gas purification device 10 of the internal combustion engine 1.

The ECU 20 includes sensors for controlling the operating state of the internal combustion engine 1 such as a crank position sensor and an accelerator position sensor (not shown), an exhaust temperature sensor 16, an upstream exhaust pressure sensor 13, a downstream exhaust sensor in this embodiment. An atmospheric pressure sensor 18 and the like are connected via electrical wiring, and an output signal is input to the ECU 20. On the other hand, a fuel injection valve (not shown) in the internal combustion engine 1 is connected to the ECU 20 via an electrical wiring, and the fuel addition valve 12 and the switching valve 15 in this embodiment are connected via an electrical wiring. Is controlled by.

  The ECU 20 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. A regeneration processing routine (not described) for regenerating the particulate matter collection ability of the filter 10b and a normal operation catalyst temperature control routine in the present invention, which will be described later, are also one of the programs stored in the ROM of the ECU 20. One.

  Here, in the internal combustion engine 1, as described above, exhaust gas purification is performed by collecting particulate matter in the exhaust gas by the filter 10b. However, when the accumulation amount of the particulate matter collected in the filter 10b increases, the filter 10b is clogged. As a result, the back pressure of the internal combustion engine 1 increases, and the operation performance may be deteriorated.

  Therefore, in the internal combustion engine 1, a regeneration process for removing the particulate matter in the filter 10b by oxidation every predetermined period or whenever it is detected that a predetermined amount or more of particulate matter has been collected in the filter 10b. Done.

  Here, the above-mentioned predetermined period is a period as a threshold value that is considered that the increase in the back pressure of the filter 10b affects the driving performance when the execution interval of the regeneration process of the filter 10b becomes longer than that. Desired. This predetermined period may be defined as the time traveled by the vehicle equipped with the internal combustion engine 1 after the end of the previous regeneration process, or the distance traveled by the vehicle equipped with the internal combustion engine 1 after the end of the previous regeneration process. It may be defined.

In addition, the predetermined amount of accumulation is the amount of particulate matter as a threshold that is considered to increase the back pressure of the filter 10b when the amount of particulate matter collected by the filter 10b increases. , it determined experimentally as a reproduction process start deposition amount A _0. The amount of particulate matter collected in the filter 10b is detected by detecting that the difference between the output of the upstream exhaust pressure sensor 13 and the output of the downstream exhaust pressure sensor 18 is equal to or greater than a predetermined value. it is possible to detect that but is the reproduction process start deposition amount a ₀ or more.

  In this regeneration process, fuel as a reducing agent is supplied from the fuel addition valve 12 to the oxidation catalyst 10a. As a result, an oxidation reaction of fuel occurs in the oxidation catalyst 10a, and the temperature of the exhaust gas discharged from the oxidation catalyst 10a rises. If it does so, the temperature of the filter 10b will also rise and the temperature of the filter 10b will become more than the ignition temperature of a particulate matter. As a result, the oxidation reaction of the particulate matter is started in the filter 10b, and the particulate matter in the filter 10b can be oxidized and removed.

  Here, when the fuel as the reducing agent is supplied from the fuel addition valve 12 to the oxidation catalyst 10a, if the temperature of the oxidation catalyst 10a is low, the oxidation reaction of the fuel may not be sufficiently performed in the oxidation catalyst 10a. . In this case, a part of the fuel supplied to the oxidation catalyst 10a may not be consumed by the oxidation reaction in the oxidation catalyst 10a, but may pass through the oxidation catalyst 10a as an HC component and cause white smoke. Further, since the temperature of the exhaust gas discharged from the oxidation catalyst 10a is not sufficiently high, the oxidation reaction of the particulate matter in the filter 10b is not sufficiently performed, and the efficiency of the regeneration process of the filter 10b may be deteriorated. As a result, the amount of fuel consumed during the regeneration process increases, and fuel consumption may deteriorate.

On the other hand, before supplying fuel as a reducing agent from the fuel addition valve 12 to the oxidation catalyst 10a, the operating state of the internal combustion engine 1 is controlled so that the temperature of the exhaust discharged from the internal combustion engine 1 rises, Although measures to raise the temperature of the oxidation catalyst 10a is considered, Then, when the amount of particulate matter trapped in the filter 10b is detected to be at play process start deposition amount a ₀ or more, immediately filter 10b May not be able to be performed.

  In addition, depending on the operation state when the regeneration process is to be performed, it is difficult to immediately raise the temperature of the oxidation catalyst 10a. Therefore, the timing of the regeneration process is limited by the operation state of the internal combustion engine 1. was there.

  Therefore, in the present embodiment, the temperature of the exhaust gas discharged from the internal combustion engine 1 is detected by the exhaust gas temperature sensor 16 during normal operation other than during the regeneration process of the filter 10b. Then, only when the detected temperature of the exhaust gas is equal to or higher than the light-off temperature of the oxidation catalyst 10a, the oxidation catalyst 10a is allowed to pass through the exhaust gas, thereby raising the temperature of the oxidation catalyst 10a to be higher than the light-off temperature. On the other hand, when the exhaust gas temperature is lower than the light-off temperature, the switching valve 15 is operated to bypass the oxidation catalyst 10a to the exhaust gas so that the low-temperature exhaust gas does not pass through the oxidation catalyst 10a. This prevents the temperature of the oxidation catalyst 10a from decreasing.

  In this way, exhaust gas from the internal combustion engine 1 can be introduced into the oxidation catalyst 10a only when the exhaust temperature is equal to or higher than the light-off temperature during normal operation other than the period during which the filter 10b is regenerated. It can be maintained above the light-off temperature.

  Next, the temperature control of the oxidation catalyst 10a during the normal operation described above will be described with reference to FIG. FIG. 2 is a flowchart showing a catalyst temperature control routine during normal operation in this embodiment. This routine is a program stored in the ROM of the ECU 20, and is repeatedly executed by the ECU 20 at predetermined intervals during the operation of the internal combustion engine 1.

  When this routine is executed, first, in S101, the amount of particulate matter deposited on the filter 10b is acquired. Specifically, the output signal of the upstream side exhaust pressure sensor 13 and the output signal of the downstream side exhaust pressure sensor 18 are taken into the ECU 20, and the output difference is calculated to calculate the differential pressure before and after the filter 10b. Then, the ECU 20 derives the amount of particulate matter deposited on the filter 10b that has a substantially one-to-one relationship with the calculated differential pressure. Here, the deposition amount of the particulate matter is derived from the map storing the relationship between the differential pressure before and after the filter 10b and the deposition amount of the particulate matter, and the deposition of the particulate matter corresponding to the differential pressure calculated in this process. This may be done by reading the quantity. Note that the upstream side exhaust pressure sensor 13, the downstream side exhaust pressure sensor 18, and the ECU 20 constitute a deposition amount estimating means in the present embodiment. When the processing of S101 ends, the process proceeds to S102.

In S102, the deposition amount of particulate matter to the filter 10b derived at S101 whether reproduction preparation start deposition amount A ₁ or more is determined. Here, the reproduction preparation start deposition amount A _1, is an amount less than the reproduction process start deposition amount A ₀ described above, when the deposition amount of the particulate matter to the filter 10b is reproduction preparation start deposition amount A ₁ or more , the deposition amount of the threshold value time at which the particulate matter deposit amount of the filter 10b is reproduction process start deposition amount a ₀ is determined to close. Therefore, the deposition amount of particulate matter to the filter 10b acquired at S101 is, when it is determined that less than the reproduction preparation start deposition amount A ₁ is still, it is determined that the time when the reproduction process is required not close Therefore, it progresses to S107. On the other hand, if it is determined that the regeneration preparation start accumulation amount A1 is greater than or equal to ₁ , the time when the regeneration process is necessary is near and it is determined that preparation needs to be started, and thus the process proceeds to S103.

  In S107, the flow path of the exhaust is selected by the switching valve 15 so that the exhaust from the internal combustion engine 1 is introduced into the oxidation catalyst 10a. Therefore, the temperature of the oxidation catalyst 10a continues to change with the temperature of the exhaust from the internal combustion engine 1. When the process of S107 ends, this routine is temporarily ended.

  In S103, the temperature of the exhaust discharged from the internal combustion engine 1 and flowing upstream of the oxidation catalyst 10b is acquired. Specifically, the exhaust gas temperature is acquired by taking the output signal of the exhaust gas temperature sensor 16 into the ECU 20. When the process of S103 ends, the process proceeds to S104.

In S104, the temperature of the obtained exhaust in S103 whether above _{T 1} is determined. Here, T ₁ is a temperature at which the oxidation catalyst 10a should be maintained at the start of the regeneration process, and may be set to the light-off temperature, or a margin temperature considering the heat capacity of the oxidation catalyst 10a is added to the light-off temperature. It may be set to a different temperature. Here, it determines that when the exhaust temperature from the internal combustion engine 1 is determined to be above T _1, by passing the oxidation catalyst 10a in the exhaust, can maintain the temperature of the oxidation catalyst 10a above T ₁ to Therefore, the process proceeds to S105.

  In S105, the switching valve 15 is operated so that the exhaust catalyst from the internal combustion engine 1 passes through the oxidation catalyst 10a. When the processing of S105 ends, this routine is once ended.

On the other hand, in S104, when the exhaust temperature obtained in S103 is determined to be lower than T _1, when passing the oxidation catalyst 10a in the exhaust gas from the internal combustion engine 1, the temperature of the oxidation catalyst 10a T ₁ or more It is judged that it may be difficult to maintain. Therefore, in this case, the process proceeds to S106.

In S106, the switching valve 15 is operated so that the exhaust from the internal combustion engine 1 passes through the bypass pipe 6. Thus, the exhaust of cold temperature is T ₁ or less, it is possible to suppress the heat of the oxidation catalyst 10a is taken away, the oxidation catalyst 10a can be suppressed to low temperatures. When the processing of S106 is completed, this routine is once ended.

As described above, according typically to the operation time of the catalyst temperature control routine in the present embodiment, when the temperature of the exhaust gas discharged from the internal combustion engine 1 is above T ₁ is passed through the oxidation catalyst 10a in the exhaust, the exhaust of when the temperature is lower than T _1, in order to bypass the oxidation catalyst 10a in the exhaust, it is possible to maintain the temperature of the oxidation catalyst 10a higher than T _1, when the implementation of the regeneration process need arises, immediately The playback process can be performed.

In the present embodiment, to detect the deposition amount of particulate matter to the filter 10b, the deposit amount only if the reproduction preparation start deposition amount A ₁ or more, to select the distribution channels of the exhaust by the switching valve 15 Implement control. Therefore, the switching valve 15 can be operated only when the regeneration process is nearly executed, and waste of energy can be suppressed.

In the present embodiment, the deposition amount of particulate matter to the filter 10b is, when it is determined that less than the reproduction preparation start deposition amount A ₁ is the switching valve 15, the exhaust gas from the internal combustion engine 1 is an oxidation catalyst 10a The flow path of the exhaust is selected as introduced in In this case, NO in the exhaust gas is oxidized in the oxidation catalyst 10a NO ₂ is produced, the NO ₂ is introduced into the filter 10b. Then, it is possible to promote the oxidation of the particulate matter deposited in the filter 10b by the NO _2. That is, so-called natural regeneration of the filter 10b can be expected even when the exhaust passage is selected so that the exhaust from the internal combustion engine 1 is introduced into the oxidation catalyst 10a in S107.

Next, a second embodiment of the present invention will be described. Since the hardware configuration of the exhaust system of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment, the description thereof is omitted. In the normal operation catalyst temperature control routine in this embodiment, the switching valve 15 causes the internal combustion engine 1 to
The control for selecting whether the exhaust gas from the exhaust gas passes through the oxidation catalyst 10a or the bypass pipe 6 is performed only for a predetermined period before the regeneration process is performed. The normal operation medium temperature control routine in the present embodiment is suitably applied when the execution interval of the regeneration process is determined based on the travel distance or travel time of the vehicle.

  FIG. 3 shows a normal operation catalyst temperature control routine in this embodiment. This routine is a program stored in the ROM of the ECU 20, and is repeatedly executed by the ECU 20 at predetermined intervals during the operation of the internal combustion engine 1.

When the normal operation catalyst temperature control routine in FIG. 3 is executed, it is first determined in S201 whether or not it is in the regeneration processing preparation period. Here, the reproduction process preparation period is a period before the reproduction process is performed, and is a period in which preparation for the reproduction process is necessary. Specifically, for example, the reproduction process in the present embodiment is programmed to perform the next reproduction process when the mileage of the vehicle becomes D ₀ or more after the previous reproduction process ends. in this case, when the travel distance of the vehicle is shorter D ₁ or more than D ₀ after the previous regeneration processing ends, it is determined that the regeneration process preparation period. Here, D ₀ indicates that when the vehicle travels a distance longer than this, the back pressure of the internal combustion engine 1 increases due to the accumulation of particulate matter on the filter 10b, which may affect the operating performance of the internal combustion engine 1. It is a travel distance as a threshold value.

D ₁ is a distance shorter than D ₀ , and after the travel distance of the vehicle reaches D ₁ , the exhaust from the internal combustion engine 1 is changed by the switching valve 15 based on the temperature of the exhaust. either it passes, by starting the control for selecting whether to pass the bypass pipe 6, when the travel distance of the vehicle becomes D _0, a distance considered as the temperature of the oxidation catalyst 10a becomes sufficiently high temperature. This may be obtained experimentally.

On the other hand, for example, when the reproduction process in the present embodiment is programmed to perform the next reproduction process when the traveling time of the vehicle becomes equal to or greater than t ₀ after the end of the previous reproduction process. When the running time of the vehicle after the end of the previous regeneration process becomes t ₁ or more shorter than t _0, it is determined that the regeneration process preparation period is reached. Here, t ₀ is a threshold value that may cause the particulate matter to accumulate on the filter 10b and increase the back pressure of the internal combustion engine 1 and affect the operation performance of the internal combustion engine 1 when the vehicle travels beyond this time. Is the travel time. Further, t ₁ is a travel time shorter than t ₀ , and after the travel time of the vehicle reaches t ₁ , the oxidation from the internal combustion engine 1 to the oxidation catalyst 10a is made by the switching valve 15 based on the exhaust temperature. whether to pass, by starting the control for selecting whether to pass the bypass pipe 6, when the travel distance of the vehicle becomes t _0, the temperature of the oxidation catalyst 10a is transit time is considered to be a sufficiently high temperature. This may be obtained experimentally.

  Since the processing after S103 is the same as the processing described in the first embodiment, the description thereof is omitted here.

  As described above, in this embodiment, it is determined whether or not it is the regeneration process preparation period from the travel distance or travel time of the vehicle, and only when it is determined that the regeneration process preparation period is in progress, the switching valve 15 The control which selects the distribution route of exhaust by is carried out. Therefore, it can be detected by a simple process that the reproduction process is about to be performed. Since the switching valve 15 is operated only when it is determined that the regeneration process preparation period is in progress, waste of energy can be suppressed.

Next, a third embodiment of the present invention will be described. The difference between the hardware configuration of the exhaust system of the internal combustion engine 1 in the present embodiment and that described in the first embodiment is that, in the present embodiment, in addition to the exhaust temperature sensor 16 that detects the temperature of the exhaust from the internal combustion engine 1. In addition, a catalyst temperature sensor (not shown) that detects the temperature of the oxidation catalyst 10a by acquiring the temperature of the exhaust gas immediately after being discharged from the oxidation catalyst 10a is provided. This catalyst temperature sensor is provided in the exhaust pipe 5 on the downstream side of the oxidation catalyst 10a and is located in the immediate vicinity of the oxidation catalyst 10a. The catalyst temperature sensor constitutes catalyst temperature detection means in the present embodiment.

  In the present embodiment, the temperature of the exhaust gas from the internal combustion engine 1 and the temperature of the oxidation catalyst 10a are acquired, and when the temperature of the exhaust gas from the internal combustion engine 1 is higher than the temperature of the oxidation catalyst 10a, the internal combustion engine The oxidation catalyst 10a is passed through the exhaust from the engine 1; otherwise, the bypass pipe 6 is passed through the exhaust.

  FIG. 4 is a flowchart showing a normal operation catalyst temperature control routine in the present embodiment. This routine is a program stored in the ROM of the ECU 20, and is repeatedly executed by the ECU 20 at predetermined intervals during the operation of the internal combustion engine 1.

When this routine is executed, first, the amount of particulate matter deposited on the filter 10b is acquired in S101. Then, in S102, the deposition amount of the obtained particulate matter whether reproduction preparation start deposition amount A ₁ or more it is determined. Since the above processing has already been described in the description of FIG. Then, in S102, when the deposition amount of particulate matter is determined to playback preparation start deposition amount A ₁ or more, the process proceeds to S103.

  In S103, the temperature of the exhaust discharged from the internal combustion engine 1 is acquired from the output signal of the exhaust temperature sensor 16. This is also the same as the content already described in FIG. When the process of S103 ends, the process proceeds to S301.

  In S301, the temperature of the oxidation catalyst 10a is acquired. Specifically, it is acquired by taking the output signal of the catalyst temperature sensor into the ECU 20. When the process of S301 ends, the process proceeds to S302.

  In S302, it is determined whether or not the exhaust gas temperature acquired in S103 is equal to or higher than the catalyst temperature acquired in S301. Here, when it is determined that the exhaust temperature is equal to or higher than the catalyst temperature, it is determined that the temperature of the oxidation catalyst 10b can be increased or maintained by passing the oxidation catalyst 10b through the exhaust from the internal combustion engine 1. The Therefore, it progresses to S105, the switching valve 15 is operated, and the oxidation catalyst 10b is allowed to pass through the exhaust from the internal combustion engine 1. On the other hand, when it is determined in S302 that the exhaust gas temperature is lower than the catalyst temperature, if the oxidation catalyst 10b is passed through the exhaust gas from the internal combustion engine 1, the heat of the oxidation catalyst 10b is carried away to the exhaust gas, and the oxidation catalyst 10b. It is determined that there is a risk that the temperature of the battery will decrease. Therefore, in this case, the process proceeds to S106, the switching valve 15 is operated, and the bypass pipe 6 is passed through the exhaust gas from the internal combustion engine 1.

  Other processes are the same as those in the flowchart shown in FIG.

  As described above, in the present embodiment, when both the temperature of the exhaust gas from the internal combustion engine 1 and the temperature of the oxidation catalyst 10a are acquired and the temperature of the exhaust gas is equal to or higher than the temperature of the oxidation catalyst 10a, When the oxidation catalyst 10a is passed through the exhaust gas and the temperature of the exhaust gas is lower than the temperature of the oxidation catalyst 10a, the oxidation catalyst 10a is kept warm by bypassing the oxidation catalyst 10a to the exhaust gas.

Accordingly, in S102, since the deposition amount of particulate matter to the filter 10b is determined that the reproduction preparation start deposition amount A ₁ or more, until the reproduction processing is carried out, the temperature of the exhaust gas is higher than T ₁ Even if not, the oxidation catalyst 10a can be kept as high as possible. Therefore, even if it is necessary to control the temperature of the oxidation catalyst 10a to be raised by raising the temperature of the exhaust gas from the internal combustion engine 1 before performing the regeneration process, the period and energy related to the temperature rise are required. Can be reduced.

It is the figure which showed schematic structure of the internal combustion engine which concerns on the Example of this invention, its exhaust system, and a control system. It is a flowchart which shows the catalyst temperature control routine at the time of normal operation which concerns on Example 1 of this invention. It is a flowchart which shows the catalyst temperature control routine at the time of normal operation which concerns on Example 2 of this invention. It is a flowchart which shows the catalyst temperature control routine at the time of normal operation which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 5 ... Exhaust pipe 6 ... Bypass pipe 10 ... Exhaust gas purification device 10a ... Oxidation catalyst 10b ... Filter 12 ... Fuel addition valve 13 ... Upstream exhaust Pressure sensor 15 ... Switching valve 16 ... Exhaust temperature sensor 18 ... Downstream exhaust pressure sensor 20 ... ECU

Claims (5)

A catalyst provided in the exhaust passage of the internal combustion engine and having an oxidizing ability;
Provided on the downstream side of the catalyst in the exhaust passage, and collects the particulate matter in the exhaust gas passing through the exhaust passage, and has the ability to collect the particulate matter by a regeneration process for oxidizing and removing the collected particulate matter. A filter to be replayed,
In the regeneration process, a fuel supply means for supplying fuel as a reducing agent to the catalyst from upstream of the catalyst;
A deposition amount estimating means for estimating a deposition amount of the particulate matter collected in the filter into the filter, and
When the accumulation amount of the particulate matter estimated by the accumulation amount estimation means is equal to or greater than a predetermined regeneration processing start accumulation amount, the fuel supply means supplies fuel to the catalyst and the filter An exhaust gas purification system for an internal combustion engine that performs the regeneration process by raising the temperature of
A bypass passage for bypassing the catalyst to exhaust discharged from the internal combustion engine and flowing upstream of the catalyst in the exhaust passage;
An exhaust passage selection means for selecting whether the catalyst passes through the exhaust flowing through the upstream side of the catalyst or the bypass passage;
Exhaust temperature detecting means for detecting the temperature of the exhaust gas flowing upstream of the catalyst,
If the temperature of the exhaust gas flowing upstream of the catalyst detected by the exhaust gas temperature detection means is lower than a predetermined temperature in a period other than the period for performing the regeneration process, the exhaust passage selection means An exhaust gas purification system for an internal combustion engine, characterized in that the bypass passage is passed through exhaust gas that circulates upstream. A catalyst temperature detecting means for detecting the temperature of the catalyst;
2. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the predetermined temperature is a temperature of the catalyst detected by the catalyst temperature detecting means.   The fine particles estimated by the accumulation amount estimating means in which the temperature of the exhaust gas flowing through the upstream side of the catalyst detected by the exhaust temperature detecting means is lower than the predetermined temperature in a period other than the execution period of the regeneration process. When the accumulation amount of the substance in the filter is equal to or greater than a predetermined regeneration preparation start accumulation amount that is less than the regeneration treatment start accumulation amount, the exhaust passage selection means is configured to exhaust the exhaust that circulates upstream of the catalyst. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the bypass passage is passed.   When the temperature of the exhaust gas flowing upstream of the catalyst detected by the exhaust gas temperature detecting means is lower than a predetermined temperature in a predetermined period before the start of the regeneration process in a period other than the execution period of the regeneration process. 2. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the exhaust passage selecting means allows the exhaust gas flowing upstream of the catalyst to pass through the bypass passage.   The exhaust passage selection means allows the catalyst to pass through the exhaust flowing through the upstream side of the catalyst during a period other than the period during which the exhaust passage selection means passes the bypass passage through the exhaust flowing through the upstream side of the catalyst. The exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 4.

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