JPH05149126A - Diesel particulate after-treatment device - Google Patents

Abstract

PURPOSE:To provide a diesel particulate after treatment device which does not cause cracking, dissolution damage and is favourable in scavenging reliabil ity and durability whatever filter temperature at the time of completion of particulate scavenging is. CONSTITUTION:In a diesel particulate after treatment device provided with a particulate scavenging filter 9, a by-pass pipe 15 for exhaust isolation at the time of regeneration, a regenerated gas supply means 16 and an ignition means 11, a temperature sensor 22 as a filter temperature detection means, a filter temperature up cooling means and a control means 18 are furnished. The control means 18 judges whether the particulate scavenging filter 9 is within a regeneration start temperature range by a signal from the temperature detection means after completion of scavenging particulates, the particulate scavenging filter 9 is raised in temperature or cooled by the temperature up cooling means, the ignition means 11 and the regenerated gas supply means 16 are actuated in the case when it comes to be within the regeneration start temperature range and are made to carry out combustive removal of particulates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of optimizing the regeneration start temperature of a filter and is excellent in collection reliability.
The present invention relates to a diesel particulate aftertreatment device.

[0002]

2. Description of the Related Art Diesel engine exhaust contains a large amount of fine particles such as carbon. From the viewpoint of recent environmental pollution prevention, it is necessary to remove these fine particles before they are released into the atmosphere as exhaust gas. Various methods have been proposed as a method for treating the fine particles, and a diesel particulate post-treatment device is one example. As shown in FIG. 5, the diesel particulate post-treatment device filters the exhaust gas 99 with a filter 9 and collects the particulates in the exhaust gas 99 with the filter 9, and an electric heater when a specified amount of particulates is collected. The ignition means 11 such as the above is operated to ignite and propagate and burn the fine particles. Reference numeral 10 is a clamshell.

As a method of regenerating the filter in the above apparatus, there has been proposed a method of regenerating the exhaust gas while filtering the exhaust gas, or a method of regenerating the exhaust gas while filtering a part thereof. This method has an advantage that a regeneration gas supply device such as an air pump is unnecessary because the propagating combustion is performed by using the exhaust gas. However, on the other hand, the exhaust flow rate and exhaust temperature of the engine during filter regeneration change depending on the operating conditions. As a result, a sudden combustion heat generation may occur, which may cause local cracking or melting damage in the filter, which may deteriorate the filter collecting performance.

In addition, unburned residue may occur due to ignition failure or misfire, which may increase the collection / regeneration cycle due to unburned residue and an error in collecting amount estimation (fine particles above the estimated value may be collected). Therefore, in this respect as well, the filter cracks,
It becomes an indirect factor such as melting loss, leading to a decrease in the reliability of particulate collection. Therefore, as a countermeasure against this, a diesel particulate post-treatment device has been already proposed, in which the flow rate of the regeneration gas sent to the filter at the time of regeneration is made constant and the regeneration is stably performed repeatedly.

This diesel particulate post-treatment device is also disclosed in Japanese Patent Laid-Open No. 63-71511. In this device, the filter is separated from the exhaust passage during regeneration, and the regeneration gas supplied from a regeneration gas supply device other than exhaust gas is used as the gas used for combustion propagation during regeneration. This regeneration gas is supplied by supplying the atmosphere with an air pump. By using such a device, the gas flow rate at the time of filter regeneration is optimized and stabilized, and the reliability of the device is improved.

[0006]

However, the above conventional device has the following problems. That is, in the above device, the filter temperature at the start of ignition is not managed. Therefore, as shown in FIG. 6, when the filter temperature is equal to or lower than a predetermined value, that is, when the regeneration is started at a temperature lower than the reproducible range A, the unburned residue is generated and the unburned particle amount B (the ratio of the removed particles by burning) is satisfied. Can not. When the temperature of the filter is equal to or higher than the crack limit value E, cracking / melting loss has occurred.

Incidentally, in FIG. 6, a curve C shows the filter maximum temperature characteristic at the time of regeneration with respect to the filter temperature at the time of regeneration start. Further, the curve F shows the characteristics of the unburned particulate amount with respect to the filter temperature at the start of regeneration. Therefore, from both curves C and F, there is a trade-off relationship between the maximum temperature during regeneration and the amount of unburned residue, and the temperature at which regeneration is possible at the beginning of regeneration that satisfies both conditions is within a limited range. Recognize. As described above, in the conventional diesel particulate post-treatment device, there is a possibility that the filter may be cracked or melted when the filter is regenerated, and there is a problem in collection reliability and durability. In view of the above problems, the present invention does not suffer from damage such as filter cracking or melting damage at any engine exhaust temperature at the time of completion of collection, and is a diesel particulate post-treatment excellent in collection reliability and durability. It is intended to provide a device.

[0008]

According to the present invention, a filter provided in an exhaust passage for collecting fine particles in exhaust gas, an isolation means for isolating the filter from the exhaust gas, and a regeneration gas for supplying a regeneration gas into the filter after isolation. In a diesel particulate post-treatment device equipped with a supply means and an ignition means for heating the particles to regenerate the filter, a temperature detecting means for detecting the temperature of the filter, a temperature raising / cooling means for heating or cooling the filter, A control means for controlling the temperature raising / cooling means by a signal from the temperature detecting means to adjust the filter to a predetermined regeneration start temperature range, and then activating the ignition means and the regeneration gas supply means. The diesel particulate post-treatment device is characterized by:

What is most noticeable in the present invention is that the filter is provided with a temperature detecting means for detecting its temperature and a temperature raising / cooling means and a control means, and the filter is heated or cooled after the completion of the collection of the particulates to obtain a predetermined temperature. There is no regeneration start temperature range, and then the ignition means is driven. The regeneration gas is a gas for feeding into a filter that collects fine particles to burn and remove the fine particles, and air, oxygen-containing gas or the like is used. Further, as the regenerated gas supply means, there are an air pump, a gas cylinder and the like. An electric heater burner or the like is used as the ignition means.

Further, the temperature raising / cooling means is means for raising or cooling the temperature of the filter after collecting the fine particles so as to bring it into a regeneration start temperature range. As the temperature raising means, the above ignition means can be used in combination. Also, as the cooling means,
There is a combined use of the above-mentioned regenerated gas in a state of almost room temperature. That is, these igniting means and regeneration gas are originally used to burn and remove the particulates trapped in the filter, but prior to their original use, the filter is heated to the regeneration start temperature range or cooled. It is used to do.

The above-mentioned regeneration start temperature range is a temperature at which the filter is not damaged as described above and can be efficiently regenerated prior to heat regeneration of the filter, that is, combustion removal of fine particles. This regeneration start temperature range varies depending on the material, structure, etc. of the filter, but when a ceramic honeycomb filter is used, the temperature range is from 200 ° C to 40 ° C.
The temperature is preferably 0 ° C.

[0012]

In the diesel particulate aftertreatment device of the present invention, the temperature detecting means detects whether or not the temperature of the filter is within the regeneration start temperature range when the collection of the particulates is completed. If the temperature is within the regeneration start temperature range, the ignition means is heated by the control means, and the regeneration gas is sent from the regeneration gas supply means to the filter to burn and remove fine particles. On the other hand, if the temperature of the filter is lower or higher than the regeneration start temperature range, the temperature raising / cooling means raises or cools the filter to the regeneration start temperature range. In this case, as described above, the ignition means or the regeneration gas is used as the temperature raising / cooling means.

Then, after confirming that the temperature of the filter has reached the regeneration start temperature range by the temperature detecting means, the ignition means and the regeneration gas supply means are operated by the control means to burn and remove the fine particles as described above. As described above, in the present invention, the filter temperature detecting means is controlled within the regeneration start temperature range prior to the combustion and removal of the collected particulates, and then the regeneration heating is performed. Therefore, it is possible to prevent damage such as cracking and melting of the filter due to abnormal combustion of fine particles. Therefore, no unburned particles are left unburned.

Therefore, also in collecting fine particles after regeneration, the full collection ability of the filter can be exerted, and the collection reliability and durability are excellent. Therefore, according to the present invention, regardless of the engine exhaust temperature and the filter temperature at the time of completion of particulate collection, there is no damage such as filter cracking or melting loss, and the particulate diesel is excellent in collection reliability and durability. An aftertreatment device can be provided.

[0015]

EXAMPLE A diesel particulate post-treatment device according to an example of the present invention will be described with reference to FIGS. First,
As shown in FIG. 1, the diesel particulate post-treatment device of the present embodiment is provided with a filter 9 for trapping particulates provided in the exhaust passage 7 of the engine 6 and a separating means for isolating the filter 9 from exhaust gas. And a bypass pipe 15.
Further, it has a regeneration gas supply means 16 for supplying a regeneration gas after exhaust gas isolation and an ignition means 11 for heating fine particles to regenerate the filter.

Further, there are provided a temperature sensor 22 as a temperature detecting means for detecting the temperature of the filter 9, and an ignition means 11 and a regeneration gas supply means 16 as a temperature raising / cooling means for raising or lowering the temperature of the filter 9. Further, the ECU as the control means 18 for controlling the temperature raising / cooling means by the signal from the temperature detecting means to bring the filter 9 into a predetermined regeneration start temperature range and then actuating the ignition means 11 and the regeneration gas supply means 16 Have. Further, in the bypass pipe 15 as the isolation means, exhaust switching valves 12 and 14 having valves 121 and 141 are provided between the upstream and downstream sides of the bypass pipe 15 and the exhaust passage 7. Further, in the exhaust passage 7, a regeneration gas exhaust pipe 17 for exhausting regeneration gas at the time of regeneration is connected between the upstream branch point of the bypass pipe 15 and the filter 9, and an exhaust switching having a valve 131 is provided. A valve 13 is provided.

The filter 9 is arranged in the clam shell 10. An exhaust gas temperature sensor 20 is provided in front of the filter 9.
Also, the pressure sensor 23 and the exhaust temperature sensor 21 and the pressure sensor 24 are attached to the rear of the filter 9. A silencer 8 is attached to the rear of the exhaust passage 7. An engine speed sensor 19 is arranged in the engine 6. Then, as shown in FIG. 1, various sensors such as the temperature sensor 22, the ignition means 11, the regenerated gas supply means 1
6, the exhaust switching valves 12, 13, 14, etc. are electrically connected to the control means 18.

Next, the function and effect of the diesel particulate aftertreatment device will be described. First, as shown in FIG. 1, the exhaust gas of the engine 6 enters the filter 9 through the exhaust passage 7,
Here, the fine particles are collected. Then, the exhaust gas is discharged from the silencer 8. When the amount of collected particulates in the filter 9 reaches a predetermined value, the exhaust switching valve 12 opens the bypass pipe 15 side, and the exhaust switching valve 13 closes the exhaust passage 17. Also, the exhaust switching valve 1 behind the filter
The exhaust passage is closed by 4, and the exhaust is configured to pass through the bypass pipe. The detection of the amount of collected fine particles is performed by the pressure sensors 23, 24 and the exhaust temperature sensors 20, 21 and the like.

Next, the temperature sensor 22 is used to filter the filter 9
Is within the regeneration start temperature range, and the ignition means 11 of the filter is detected as shown in the flow chart described later.
Further, the regenerating gas supply means 16 raises or cools the temperature.
Then, after reaching the regeneration start temperature range, the ignition means 1
1 and the regeneration gas supply means 16 perform heating regeneration of the filter. These control means are performed by the control means 18 based on the signals from the various sensors.

At the time of the above-mentioned regeneration, the air as the regeneration gas supply means 16 sends the air as the regeneration gas to the filter. The same applies when cooling to the above regeneration start temperature range. Further, at the time of regeneration, the electric heater as the ignition means 11 is heated. The same applies when heating up to the regeneration start temperature range. After the regeneration, the operations of the ignition means 11 and the regeneration gas supply means 16 are stopped, and the exhaust switching valves 12, 13, 1
4 is returned to its original position and the exhaust gas is passed through the filter 9.

Next, the control algorithm in the diesel particulate post-treatment device of this example will be described using the flow charts of FIGS. 2 and 3 and the relationship diagram between various operations and filter temperature in FIG. The control is started when the engine 6 is started. First, step 101
At 103, the amount of particulates collected on the filter is estimated. The collection amount is estimated from the pressure loss in the filter. That is, the output P ₁ of the pressure sensor 23 at the upstream portion of the filter and the output P ₂ of the pressure sensor 24 at the downstream portion thereof are obtained. Further, correction is performed using the engine speed N _E , the output T _EX1 of the exhaust gas temperature sensor 20 at the upstream portion of the filter, and the output T _EX2 of the exhaust gas temperature sensor 21 at the downstream portion thereof to calculate the trapped amount estimated value m.

Next, at step 104, the estimated collection amount m is compared with the reproducible predetermined collection amount m _O. If m ≧ m _O in this step, it is judged that the collection is completed,
Go to step 105 and subsequent steps. On the other hand, m <m _O
If so, the process returns to step 101 again, and the collection is continued until a predetermined collection amount is reached. Also, in step 105,
The exhaust switching valves 12, 13, 14 are provided to separate the collected filter from the exhaust passage and connect the regeneration means to the passage.
Is driven to switch the interlocking valves 121, 131, 141 as described above.

Next, steps 106 to 111 are a control part to which the present invention is applied. First, in step 106,
The filter temperature T _F is detected by the temperature sensor 22. Next, in steps 107 and 110 (FIG. 3), the relationship between the filter temperature T _F and the regeneration start temperature range (lower limit T ₁ , upper limit T ₂ ) is compared. Here, if the filter temperature T _F is within the regeneration start temperature range, the process proceeds to step 112 to start regeneration.

In step 107, the filter temperature T
_{If F} is equal to or lower than the lower limit T ₁ of the regeneration start temperature range, in step 108, the ignition means 11 located downstream of the filter is operated as the temperature raising means of the filter. At the same time, at step 109, a small amount of gas is supplied from the regeneration gas supply means 16 to promote heat propagation. Then, the process returns to step 107, and the temperature of the filter is raised until the filter temperature T _F falls within the regeneration start temperature range as shown in FIG.

If the filter temperature T _F is higher than the upper limit T ₂ of the regeneration start temperature range, the process proceeds to step 111,
Operate the air pump as the regeneration gas supply means 16,
The electric heater of the ignition means 11 is not energized, but a large amount of gas is supplied to cool the filter. And step 1
Returning to 07, the filter is cooled until it falls within the regeneration start temperature range. If the filter temperature T _F becomes equal to or lower than the upper limit T ₂ of the regeneration start temperature range, that is, within the reproducible initial temperature range, as shown in the diagram of FIG.
Playback will be performed later.

Through the above steps, the filter temperature at the start of regeneration is managed. Then, steps 112 to 120
In FIG. 3, the filter is regenerated. That is, in step 112, the regeneration gas supply means 16 is controlled to a predetermined air flow rate, and in step 113, ignition power is supplied to the ignition means 11 to ignite the fine particles. And step 1
At 14 and 115, the filter temperature T _F is detected again. Then, when the particulate ignition completion temperature T ₃ shown in FIG. 4 or higher is reached, the operation of the ignition means 11 is stopped. Further, in steps 117 and 118, when the filter temperature T _F becomes equal to or lower than the regeneration completion temperature T ₄ shown in FIG. 4, it is judged that the regeneration of the filter 9 is completed.

Then, in step 119, the air pump of the regeneration gas supply means 16 is stopped, and in step 120,
Valves 121, 13 linked to the exhaust switching valves 12, 13, 14
1, 141 are driven to collect the particulates in the exhaust gas again.
As is known from the above, in the diesel particulate aftertreatment device of this example, prior to the combustion removal of the collected particulates,
The filter temperature detection means is controlled within the regeneration start temperature range, and then regeneration heating is performed. Therefore, it is possible to prevent damage such as cracking and melting of the filter due to abnormal combustion of fine particles. Therefore, no unburned particles are left unburned.

Also, with respect to the collection of fine particles after regeneration, the full collection ability of the filter can be exerted, and the collection reliability and durability are excellent. The configuration of the present invention is not limited to that shown in the present embodiment, and for example, the regeneration gas supply means 16 is not limited to the air pump and may be any device capable of controlling the gas flow rate. Also, regarding the detection of the filter temperature, a value that correlates with the filter temperature,
For example, the temperature of the exhaust gas temperature sensor 20 when gas is supplied by the regeneration gas supply means 16 may be used. Further, in this example, the ignition means 11 is also used as the filter temperature raising device, but a temperature raising means may be separately provided.

[Brief description of drawings]

FIG. 1 is an overall explanatory view of a diesel particulate post-treatment device according to an embodiment.

FIG. 2 is a flowchart showing the steps of detecting the amount of collected particulates, filter temperature, etc. in the embodiment.

FIG. 3 is a flowchart showing steps such as filter regeneration heating following FIG. 2;

FIG. 4 is an explanatory view showing the relationship between various operations and filter temperature in the embodiment.

FIG. 5 is an explanatory diagram of a conventional particulate collection filter.

FIG. 6 is an explanatory diagram of problems in a conventional diesel particulate post-treatment device.

[Explanation of Codes] 6. ． ． Engine, 7. ． ． Exhaust passage, 8. ． ． Silencer, 9. ． ． Filter, 11. ． ． Ignition means, 12, 13, 14. ． ． Exhaust gas switching valve, 15. ． ． Bypass pipe, 16. ． ． Regeneration gas supply means, 18. ． ． Control means, 20, 21. ． ． Exhaust temperature sensor, 22. ． ． Temperature sensor, 23, 24. ． ． Pressure sensor,

Claims (1)

[Claims] 1. A filter provided in an exhaust passage for collecting fine particles in exhaust gas, an isolation means for isolating the filter from the exhaust gas, a regeneration gas supply means for supplying a regeneration gas into the filter after isolation, and a fine particle. In a diesel particulate aftertreatment device equipped with an ignition means for heating a filter to regenerate the filter, a temperature detecting means for detecting the temperature of the filter, a temperature raising / cooling means for heating or cooling the filter, and a temperature detecting means The control means for controlling the temperature raising / cooling means by the signal to adjust the filter to a predetermined regeneration start temperature range, and thereafter operating the ignition means and the regeneration gas supply means. Fine particle aftertreatment device.