JP2006226121A - Exhaust emission control device and emission control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device and an exhaust emission control method in which exhaust gas whose temperature is prescribed temperature or higher bypasses a split filter when combusting PM to reproduce DPF, whereby erosion of DPF can be prevented. <P>SOLUTION: A filter of DPF is divided into a plurality of filters. Passage parts 15, 16 to which the split filters 12, 13, 14 are coupled are respectively provided with exhaust gas temperature sensors 17, 18 and connected with bypass flow passages 19, 20 equipped with opening/closing valves 19a, 20a. When the exhaust gas temperature sensors 17, 18 detect that exhaust gas temperatures Tg1, Tg2 reach a predetermined temperature Tc or higher, the opening/closing valves 19a, 20a of the bypass passages 19, 20 connected to passage parts 15, 16 in which the exhaust gas temperature sensors 17, 18 are arranged are operated so as to carry out control for making the exhaust gas bypass the split filters. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification apparatus and an exhaust gas purification method provided with a diesel particulate filter (DPF) that collects particulate matter (PM) in exhaust gas, and more particularly, avoids filter damage. The present invention relates to an exhaust gas purification device and an exhaust gas purification method that can be performed.

  Regulations for particulate matter (hereinafter referred to as PM), NOx, CO, HC, and the like discharged from engines such as diesel engines have been strengthened year by year. Along with this stricter regulation, it has become impossible to meet the regulation value only by improving the engine. Therefore, as shown in FIG. 3, a technique for reducing these substances discharged from the engine 1 by mounting an exhaust gas purification device 10X using a diesel particulate filter (hereinafter referred to as DPF) in the exhaust passage 2 of the engine 1. Is adopted.

  As an apparatus for directly collecting the particulate matter, there are an exhaust gas purification apparatus using a DPF such as a ceramic monolith honeycomb wall flow type or a fiber type filter made of a ceramic or metal fiber.

  When particulate matter is collected by these filters, the exhaust pressure rises corresponding to the amount of collected PM. Therefore, PM is forcibly removed from the filter by burning the collected PM. Need to play the filter.

As a regeneration method of this filter, an electric heater heating method, a burner heating method, a backwashing method, and the like for removing PM by receiving energy supplied from the outside of the filter have been proposed. In addition, an oxidation catalyst such as platinum is installed upstream of the filter (previous stage) so that PM can be oxidized and removed even when the exhaust gas temperature is relatively low, and the exhaust gas rises due to the oxidation reaction heat of the unburned gas in the exhaust gas. There is also a continuous regeneration type DPF that removes PM by utilizing, for example, acceleration of PM oxidation by nitrogen dioxide (NO ₂ ) generated from temperature or nitric oxide (NO).

  In the exhaust gas purifying apparatus equipped with these DPFs, when the exhaust gas temperature continues to be low, PM is continuously collected and accumulated in the DPF, and this PM accumulation causes excessive filter clogging. In order to prevent the engine trouble from progressing, the temperature of the filter is raised above the temperature at which PM starts to oxidize when the clogged state exceeds a predetermined state, and the collected PM is reduced. DPF regeneration that forcibly removes combustion is performed.

As one means for raising the temperature of the DPF, post-injection (post-injection), timing-retarded injection (delayed injection), etc. are performed by fuel injection control into the cylinder of the engine (in-cylinder) to raise the exhaust gas temperature. Or increase the HC concentration in the exhaust gas flowing into the DPF. Then, the unburned fuel such as HC and CO supplied into the exhaust gas is oxidized by the oxidation catalyst on the upstream side of the DPF to raise the exhaust gas temperature, or the NO component in the exhaust gas is oxidized by the oxidation catalyst. There is a method of increasing the NO ₂ component in the exhaust gas to promote PM oxidation by NO ₂ .

  However, in this method, it is difficult to control the supplied fuel, and there is a problem that the DPF main body may be melted. That is, when the oxidation of PM collected in the DPF proceeds, the heat generated by the oxidation reaction is sequentially transferred to the downstream side, so that the temperature increases as it goes downstream in the DPF, and finally This is because the melting temperature of the DPF filter base material may be reached. In addition, it is difficult to control re-combustion even in a method of regenerating DPF by burning PM using other heat such as an electric heater, instead of supplying unburned fuel into exhaust gas and re-burning PM. There is a possibility that the DPF is melted and there is a similar problem.

  As one countermeasure against this, in the DPF filter, in order to prevent excessive accumulation of PM and excessive increase in the filter temperature during regeneration combustion, it is possible to prevent a decrease in durability due to filter melting damage. The first exhaust outlet and the second exhaust outlet are provided, and the control valve provided in the bypass passage communicating with the second exhaust outlet according to the exhaust pressure or the filter temperature is subjected to on-off valve control. An exhaust aftertreatment device for an internal combustion engine that switches a gas flow between a first permeation path communicating with a first exhaust outlet and a second permeation path communicating with a second exhaust outlet has been proposed (for example, Patent Document 1). reference.).

However, in this exhaust gas aftertreatment device for an internal combustion engine, when the exhaust pressure exceeds the excessive accumulation determination pressure or when the filter temperature is low, the exhaust gas is discharged from the bypass passage to prevent melting, but the first permeation of the filter Since the exhaust gas is allowed to pass through the second permeation passage portion when PM has accumulated in the passage portion, when the abnormal combustion is started, the exhaust gas that has become hot due to the abnormal combustion passes through the filter portion. There is still a problem that the possibility that the entire filter is eventually melted due to melting damage still remains.
JP 2004-116322 A

  The present invention has been made to solve this problem, and an object of the present invention is to form an exhaust gas having a predetermined temperature or higher when the DPF is composed of a plurality of divided filters and PM is burned to regenerate the DPF. Exhaust gas purifying apparatus that prevents the DPF from being melted by bypassing the split filter, and that only the split filter that is a part of the DPF needs to be replaced even if melt occurs. And providing an exhaust gas purification method.

  In order to achieve the above object, an exhaust gas purification apparatus according to the present invention comprises a diesel particulate filter (DPF) that collects particulate matter (PM) discharged from a diesel engine, and regeneration of the diesel particulate filter. In an exhaust gas purification apparatus equipped with a regeneration control device for controlling, a filter is divided into a plurality of parts, and an exhaust gas temperature sensor is provided in each of the passage portions connecting these divided filters, and a bypass flow path with an open / close valve is connected. And when the exhaust gas temperature sensor detects that the exhaust gas temperature has become equal to or higher than a predetermined temperature, the regeneration control device has the bypass passage connected to the passage portion where the exhaust gas temperature sensor is disposed. It is configured to operate the open / close valve so as to bypass the exhaust gas.

  Moreover, the exhaust gas purification method according to the present invention for achieving the above object includes a diesel particulate filter that collects particulate matter discharged from a diesel engine, and a regeneration control that controls regeneration of the diesel particulate filter. In the exhaust gas purification apparatus, the exhaust gas purifying apparatus comprising the apparatus, wherein the filter is divided into a plurality of parts, and an exhaust gas temperature sensor is provided in each of the passage portions connecting the divided filters, and a bypass flow path with an open / close valve is connected to each of the exhaust gas purification apparatuses. When the gas temperature sensor detects that the exhaust gas temperature exceeds a predetermined temperature, the exhaust gas is bypassed by operating the open / close valve of the bypass passage connected to the passage portion where the exhaust gas temperature sensor is disposed. It is characterized by making it.

  In other words, in an exhaust gas purification apparatus that regenerates DPF by burning PM, the filter is composed of several divided filters in the flow direction, and the temperature of the exhaust gas flowing into the second and subsequent divided filters from the most upstream is determined. Each exhaust gas temperature sensor is configured to include a bypass flow path with an open / close valve that bypasses most of the exhaust gas flowing into the second and subsequent divided filters from the most upstream, and detection of these exhaust gas temperature sensors. The opening / closing control of the opening / closing valve based on the detected temperature and the detected exhaust gas temperature causes most of the exhaust gas having a temperature equal to or higher than a predetermined temperature to flow through the bypass passage to bypass the split filter, so that the split filter becomes an abnormally high temperature. It is possible to prevent the DPF from being melted.

  Furthermore, even if a melting loss should occur, it is only necessary to replace the divided filter that is a part of the DPF. Therefore, even if a partial melting is caused, the entire DPF is replaced. It becomes economical.

  Further, the DPF device constituting the exhaust gas purification device includes a filter only DPF, a device in which an oxidation catalyst is arranged upstream of the DPF, a device in which an oxidation catalyst is arranged upstream of the catalyst-carrying DPF, There are an apparatus in which a catalyst is supported, a continuous regeneration type DPF in which an oxidation catalyst and a PM oxidation catalyst are supported on a DPF, and the like.

  According to the exhaust gas purification device and the exhaust gas purification method of the present invention, when PM is burned and the DPF is regenerated, the DPF can be prevented from being melted. It is possible to replace only the divided filter.

  Next, an embodiment of an exhaust gas purification device and an exhaust gas purification method according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the exhaust gas purification apparatus 10 includes a plurality (three in FIG. 1) of first to first PMs that collect PM (particulate matter) discharged from an upstream side oxidation catalyst 11 and a diesel engine. A third divided DPF (diesel particulate filter) 12, 13, and 14 and a regeneration control device 30 that controls regeneration of the DPF are provided, and these first to third divided filters 12, 13, and 14 are connected. First and second exhaust gas temperature sensors 17 and 18 are provided in the first and second passage portions 15 and 16, respectively, and first and second bypass passages having first and second on-off valves 19a and 20a are provided. 19 and 20 are connected. The exhaust gas purification device 10 is disposed in the exhaust passage 2 of the engine.

  In addition, when the first exhaust gas temperature sensor 17 detects that the first exhaust gas temperature Tg1 has become equal to or higher than the predetermined temperature Tc, the regeneration control device 30 is provided with the first exhaust gas temperature sensor 17. Exhaust gas is operated so that exhaust gas having a temperature equal to or higher than a predetermined temperature Tc does not flow into the second divided filter 13 and the third divided filter 14 by operating the first opening / closing valve 19a of the first bypass passage 19 connected to the first passage portion 15. It is comprised so that the control which bypasses most may be performed.

  In addition, when the second exhaust gas temperature sensor 18 detects that the second exhaust gas temperature Tg2 has become equal to or higher than the predetermined temperature Tc, the regeneration control device 30 is provided with the second exhaust gas temperature sensor 18. By operating the second opening / closing valve 20a of the second bypass passage 20 connected to the second passage portion 16, most of the exhaust gas is bypassed so that the exhaust gas having a predetermined temperature Tc or higher does not flow into the third divided filter 14. It is configured to perform control.

  The predetermined temperature Tc is set to, for example, 650 ° C., but is a value adjusted depending on the vehicle type, the type of the DPF base material, and the number of divided filters is three in FIG. It is selected according to the usage type of the vehicle type.

  In the exhaust gas purification device 10, during normal operation, the regeneration control device 30 controls the first and second on-off valves 19a and 20a of the first and second bypass passages 19 and 20 to close, The exhaust gas is allowed to pass through all of the first to third divided filters 12, 13, and 14 to collect PM in the exhaust gas.

When the regeneration control device 30 detects that the amount of collected PM exceeds a predetermined limit value, the regeneration control device 30 starts the regeneration control with the first and second on-off valves 19a and 20a being closed. In the cylinder (in-cylinder) fuel injection control, post injection is performed to increase the exhaust gas temperature or to increase the HC concentration in the exhaust gas flowing into the exhaust gas purification device 10. Then, unburned fuel such as HC and CO supplied into the exhaust gas is oxidized by the oxidation catalyst 11, and the exhaust gas temperature is raised to, for example, the DPF front inlet temperature to 600 ° C. by the combustion heat, or the exhaust gas The NO component in the exhaust gas is oxidized by the oxidation catalyst 11 to increase the NO ₂ component in the exhaust gas. As a result, PM composed of soot (SOOT) and the like accumulated in the first to third divided filters 12, 13, and 14 is reburned.

  In the present invention, the first and second exhaust gas temperature sensors 17 and 18 monitor the first and second exhaust gas temperatures Tg1 and Tg2 during the regeneration control. If the temperature does not exceed the predetermined temperature Tc, the regeneration control is performed as it is. The regeneration control is terminated when a predetermined regeneration time elapses or when the pressure difference across the exhaust gas purification device 10 is restored.

  This control can be performed by a control flow as exemplified in FIG. This control flow is shown as a control flow in which the DPF regeneration control is started, and at the same time, repeatedly called in parallel with various controls for DPF regeneration such as fuel injection control, and the control contents are executed and returned. No longer called with the end of playback control. In addition to DPF regeneration control, when preventing high-temperature exhaust gas from flowing into the second and third divided filters 13 and 14, it is called repeatedly in parallel with engine operation regardless of DPF regeneration control. The control flow may be executed after the control content is executed.

  In the control flow of FIG. 2, when called and started, in step S11, the first exhaust gas temperature Tg1 is checked. If the first exhaust gas temperature Tg1 is lower than the predetermined temperature Tc, the process goes to step S13. When the first exhaust gas temperature Tg1 is equal to or higher than the predetermined temperature Tc, the process goes to step S12, the first opening / closing valve 19a is opened, the second opening / closing valve 20a is closed, and the process goes to step S16.

  In step S13, the second exhaust gas temperature Tg2 is checked. If the second exhaust gas temperature Tg2 is smaller than the predetermined temperature Tc, the process goes to step S15, the first opening / closing valve 19a is closed, and the second opening / closing valve is closed. 20a is closed and the process goes to step S16. If the second exhaust gas temperature Tg2 is equal to or higher than the predetermined temperature Tc in step S13, the process goes to step S14, the first opening / closing valve 19a is closed, the second opening / closing valve 20a is opened, and the process goes to step S16. go.

  In step S16, the open / close state of each open / close valve is maintained for a predetermined time related to the interval of checking the exhaust gas temperature. When a predetermined time has elapsed, the process returns. The period from start to return is repeatedly executed during regeneration control (or during engine operation).

  Then, the first exhaust gas temperature sensor 17 detects that the first exhaust gas temperature Tg1 has exceeded the predetermined temperature Tc before the regeneration control is ended by the valve opening / closing control by the control flow of FIG. Sometimes, the first on-off valve 19a of the first bypass passage 19 connected to the first passage portion 15 where the first exhaust gas temperature sensor 17 is disposed is controlled to open. By this control, most of the exhaust gas flows to the first bypass passage 19 side having a smaller flow resistance than the passages on the second and third divided filters 13 and 14 side having a larger flow resistance. As a result, most of the exhaust gas is bypassed, and the exhaust gas having a temperature equal to or higher than the predetermined temperature Tc is prevented from flowing into the second and third divided filters 13 and 14. Then, the regeneration control is continued as it is, and the regeneration control is terminated when a predetermined regeneration time elapses or when the pressure difference between the exhaust gas purification device 10 is restored. If the first exhaust gas temperature Tg1 becomes equal to or lower than the predetermined temperature Tc during the regeneration control, the first on-off valve 19a is controlled to be closed to restore the exhaust gas flow.

  In addition, before the regeneration control is finished, the first exhaust gas temperature sensor 17 does not detect that the first exhaust gas temperature Tg1 exceeds the predetermined temperature Tc, and the second exhaust gas temperature Tg2 becomes the predetermined temperature Tc. When the second exhaust gas temperature sensor 18 detects that the second exhaust gas temperature sensor 18 has been exceeded, the second on-off valve 20a of the second bypass passage 20 connected to the second passage portion 16 where the second exhaust gas temperature sensor 18 is disposed is operated. Thus, most of the exhaust gas is bypassed so that the exhaust gas having a temperature equal to or higher than the predetermined temperature Tc does not flow into the third divided filter 14. Then, the regeneration control is continued as it is, and the regeneration control is terminated when a predetermined regeneration time elapses or when the pressure difference between the exhaust gas purification device 10 is restored. If the second exhaust gas temperature Tg2 becomes equal to or lower than the predetermined temperature Tc during the regeneration control, the second open / close valve 20a is controlled to be closed to restore the exhaust gas flow.

  According to the exhaust gas purification device 10 and the exhaust gas purification method described above, the exhaust gas having a temperature equal to or higher than the predetermined temperature Tc is caused to flow through the first bypass passage 15 or the second bypass passage 16 and the second divided filter 13 and the third divided filter or Since the third divided filter 14 is bypassed, the second divided filter 13 and the third divided filter or the third divided filter 14 are prevented from becoming abnormally high temperatures, and the second and The temperature of the 3rd division filters 13 and 14 can be controlled, and the melting loss of DPF can be prevented. Furthermore, even if a melting loss should occur, it is only necessary to replace one of the first to third divided filters 12, 13, and 14 as a part of the DPF. Compared to economics.

  The DPF device constituting the exhaust gas purification device 10 includes a filter only DPF, a device in which an oxidation catalyst is arranged on the upstream side of the DPF, a device in which an oxidation catalyst is arranged on the upstream side of the catalyst-carrying DPF, and a DPF. There are an apparatus in which an oxidation catalyst is supported, a continuous regeneration type DPF in which an oxidation catalyst and a PM oxidation catalyst are supported on a DPF, and the like.

It is a figure which shows the exhaust-gas purification apparatus of embodiment which concerns on this invention. It is a figure which shows the example of the control flow of the exhaust gas purification method of embodiment which concerns on this invention. It is a figure which shows the structure of the vehicle engine provided with the exhaust-gas purification apparatus.

Explanation of symbols

1 Diesel Engine 2 Exhaust Passage 10, 10X Exhaust Gas Purifier 11 Oxidation Catalyst 12, 13, 14 Divided DPF
15, 16 Passage portion 17, 18 Exhaust gas temperature sensor 19, 20 Bypass passage 19a, 20a Open / close valve 30 Regeneration control device Tg1, Tg2 Exhaust gas temperature Tc Predetermined temperature

Claims (2)

  In an exhaust gas purification apparatus provided with a diesel particulate filter that collects particulate matter discharged from a diesel engine and a regeneration control device that controls regeneration of the diesel particulate filter, the filter is divided into a plurality of parts, An exhaust gas temperature sensor is provided in each of the passage portions connecting the filters, and a bypass flow path with an open / close valve is connected, and the regeneration control device is configured so that the exhaust gas temperature sensor has an exhaust gas temperature equal to or higher than a predetermined temperature. When this is detected, the exhaust gas purifying apparatus is characterized in that the exhaust gas is controlled to be bypassed by operating the on-off valve of the bypass passage connected to the passage portion where the exhaust gas temperature sensor is disposed. A passage having a diesel particulate filter that collects particulate matter discharged from a diesel engine and a regeneration control device that controls regeneration of the diesel particulate filter, the filter is divided into a plurality of parts, and the divided filters are connected to each other In each of the exhaust gas purifying devices provided with an exhaust gas temperature sensor and connected to a bypass flow path with an opening / closing valve, when the exhaust gas temperature sensor detects that the exhaust gas temperature is equal to or higher than a predetermined temperature. A method for purifying exhaust gas, wherein the exhaust gas is bypassed by operating the on-off valve of the bypass passage connected to a passage portion where the exhaust gas temperature sensor is disposed.

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