JPH05231131A - Exhaust particulate emission control device - Google Patents

Abstract

PURPOSE:To properly determine the next regeneration starting time when regeneration is suspended midway in the regeneration of a filter. CONSTITUTION:The next regeneration starting time is determined according to the advance degree of the regeration of a filter at the time point where regeneration is suspended. Accordingly, in the illustrated example, the uncombusted quantity of the particulate piled on a filter 1 is detected by a differential pressure detector 12 for each pressure between the fore part and rear part, and when the uncombusted quantity at the time point of the interruption of regeneration is much, the air passing resistance becomes much, and the quantity of the particulates piled on the filter 1 after the restart of the catching of the particulate becomes much, and the temperature in the next regeneration becomes abnormally high, and a control means sets the next regeneration starting time earlier than a standard time, according to the magnitude of the uncombusted quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device provided in an internal combustion engine, and particularly when the filter that collects particulates is regenerated by combustion, the regeneration is performed because the internal combustion engine is stopped during the regeneration. The present invention also relates to an exhaust emission control device capable of performing the next regeneration without trouble even if the fuel consumption is interrupted.

[0002]

2. Description of the Related Art For example, the exhaust gas of a diesel engine contains a large amount of particulates, that is, particulates, mainly carbon particles. Therefore, the exhaust system of the engine contains particulates for collecting the particulates. A filter (hereinafter referred to as a filter) is attached.

This filter is a heat-resistant material typified by, for example, a ceramic material, and is formed of a material having air permeability, and the amount of particulates deposited inside the filter over time has increased. If it increases, the ventilation resistance will gradually increase and the output of the engine will decrease, so it must be regenerated periodically according to the amount of particulates collected.

Regeneration is started by raising the accumulated particulates to a high temperature above the ignition temperature (about 650 ° C.) by a heating means and igniting and burning. As this heating means, an electric heater or a burner system is considered, but FIG. 2 shows an example of the case where an electric heater is used. Figure 2
At the time of regeneration, the entire amount of exhaust gas is bypassed by the bypass pipe 4 by the flow path switching valve 3, and the electric heater 2 embedded in the flow upstream end face of the filter 1 or in the vicinity of the end face is energized. Then, air required for combustion is supplied from the air pump 5.

[0005]

By the way, the inventors of the present invention have found that when the flow rate of this regeneration air is too large, the combustion zone is blown out, so a small amount of air (in the case of a filter having a capacity of about 2 liters, Experiments have confirmed that it is preferable to perform regeneration at about 90 liters per minute). Therefore, since it takes several minutes or tens of minutes to regenerate the filter, the engine may be stopped during parking or the like during the regeneration.

[0006] In such a case, it was confirmed by an experiment that even if the air is not supplied from the air pump 5 due to convection, fresh air enters from the outside even if the system is down and smoldering remains for a considerably long time. Therefore,
During this time, harmful components such as high temperature gas and carbon monoxide generated by combustion are discharged to the outside.

In order to avoid this, shut-off valves 6a and 6b are provided on the upstream side and the downstream side of the filter 1 as shown in FIG. 3, and these valves are closed when the engine is stopped to make the inside of the filter 1 a closed space. It suffices to stop the supply of oxygen to extinguish the fire, but depending on the timing of the fire extinguishing, the range of the unburned residue becomes different as shown in FIGS. 4 (a) and 4 (b).

On the other hand, when collecting again in the state where there is an unburned residue as shown in FIGS. 4 (a) and 4 (b), depending on the magnitude of the ventilation resistance of the unburned portion B and the regeneration completion portion A, respectively. Since particulates are deposited on both parts, the amount of particulates deposited on the part A where regeneration has been completed is smaller than that on the part B where there is an unburned residue, and even if collection is continued, part A continues to be collected. It is not possible to make the deposition amounts of B and B completely the same.

Therefore, if reproduction is always performed under a constant condition (see a straight line I in FIG. 5 described later) without considering the unburned state, the unburned state is small as shown in FIG. 4B, for example. In this case, if an attempt is made to make the amount of accumulation of the portion A where the regeneration has ended to a degree that allows the regeneration to be performed next favorably, the amount of accumulation becomes too large in the portion B where the particulate remains unburned. It may cause an abnormally high temperature during regeneration. On the contrary, when there is a large amount of unburned residue as shown in FIG. 4A, when the amount of accumulation is set to an extent that good regeneration can be performed in the unburned portion B, the portion where regeneration has ended In A, the next deposition amount is too small, which may cause a regeneration error.

In order to solve this problem, for example, in the prior art disclosed in Japanese Laid-Open Patent Publication No. 3-18614, the amount of particulates trapped in the filter is estimated by the regeneration temperature of the filter, and the next trapping is performed accordingly. I try to determine the amount of data. However, in the case of such a configuration, if the collection amount of the filter is large and the regeneration temperature is low due to other reasons, the next collection amount is set to a value higher than that in the normal case. Therefore, the amount collected in the unburned portion becomes larger than the predetermined amount, and the regeneration temperature at the next time becomes excessively high, which may cause the filter to melt and deteriorate.

Therefore, the present invention has been made in view of the above problems.
(EN) Provided is a device capable of performing good regeneration without generating an abnormally high temperature or an ignition error in the next regeneration when regeneration is interrupted and unburned residue occurs during regeneration combustion of a filter where particulates are accumulated. The purpose is to

[0012]

To achieve the above object, according to the present invention, there is provided a filter provided in an exhaust system of an internal combustion engine for collecting particulates in exhaust gas,
During filter regeneration, an exhaust gas purification device that ignites and burns the collected and accumulated particulates by the heating means and incinerates the accumulated particulates by introducing regeneration gas into the filter. A means to detect the remaining amount of unburned particulate matter, and shorten the period until the next regeneration when the unburned amount is large when the regeneration is interrupted, and lengthen the period until the next regeneration when the unburned amount is small. An exhaust particulate purification device is provided which is provided with a control means for

[0013]

When the regeneration is interrupted for some reason during the regeneration of the filter, the unburned amount of particulates measured by the means for detecting the unburned amount of particulates is stored in the control means. Then, in determining the target collection amount when the collection of particulates starts again, the control means corrects the reference value of the accumulation amount until the next regeneration according to the size of the unburned amount.
In other words, when the amount of unburned fuel is large, the ventilation resistance is large, so if the reference value is set as the target, the amount of deposition will be too large, and the temperature will become excessively high during regeneration.Therefore, lower the value below the reference value. become. In this way, by correcting the reference value according to the degree of the unburned amount, it is possible to avoid troubles due to an abnormal temperature rise at the next regeneration.

[0014]

[Example] During the filter regeneration, for example, when the engine is stopped, it is preferable to immediately terminate the combustion and interrupt the regeneration. However, in the present invention, the unburned amount at that time is detected and the unburned amount is determined according to the unburned amount. And decide the next reproduction time. When there is a large amount of unburned residue, the basic method of determining the regeneration timing is to advance the next regeneration timing standard regeneration timing to reduce the amount of particulates accumulated at the previous regeneration completion portion, and conversely When the amount is small, the next regeneration time is set to be later than the reference regeneration time to increase the amount of particulates accumulated at the previous regeneration completion portion. The concept is shown in FIG.

The abscissa of FIG. 5 represents the unburned residue ratio, that is, the unburned residue / total accumulated amount, and the vertical axis represents the required accumulated amount, that is,
We take the amount of remaining deposition required. If there is no stoppage of the engine during regeneration, m is deposited until the next regeneration to perform regeneration. However, in order to always deposit m according to the unburned amount, This can be used as a reference because it can be set as shown by the straight line I in the figure. For example, if the unburned residue ratio is E, if m _{E is} collected later, m will be deposited on the entire filter.

However, on such a linear basis, as described with reference to FIG. 4, the accumulation amount of the portion A where the regeneration is completed is smaller than that of the portion B where the unburned portion is left, and the unburned portion ratio of the unburned portion is increased. In the case of Fig. 4 (b) where the range is small, that is, the range where the regeneration is completed is wide (about L in Fig. 5), when the collection is restarted, the accumulation of particulates on the regeneration completed portion A is small, that is, over a wide range. Since the amount of deposition is small, it causes ignition mistakes. Therefore, in the preferred embodiment of the present invention, the collection time obtained from the straight line I in FIG. 5 serving as a reference is set longer so that the amount of deposition on the portion where the regeneration is completed becomes the target amount of deposition. In addition, the total deposition amount is set to a value m _E ′ obtained from the points on the curve II, and the deposition amount is increased by ΔE to prevent ignition mistakes. In this case, the accumulated amount of the unburned portion B becomes larger than the target value, and there is a concern that the temperature may rise in that portion, but the amount of unburned portion is small from the beginning, that is, the portion where the accumulated amount is large. The effect is small, since there are few.

On the other hand, in the case of FIG. 4 (a) in which the range where the regeneration is finished is relatively narrow (about H in FIG. 5), the control such as the straight line I as the reference causes burning when the collection is restarted. Since the amount of deposition on the remaining portion B increases, that is, the amount of deposition increases over a wide range, an abnormally high temperature state is caused especially at the center of the filter. Therefore, when the unburned residue ratio is H, the subsequent accumulation amount is m _H from the point on the straight line I.
What should be done is to shorten the collection time so that m _H ′ obtained from the point on the curve II, so that the amount of deposition in the portion B where there is unburned residue is about the target amount of deposition. That is, the collection amount as a whole is reduced by ΔH to prevent the occurrence of an abnormally high temperature state. In this case, the amount of deposition in the part A where the regeneration was finished becomes smaller than the target value,
There is concern about ignition mistakes in that area, but it has already been regenerated.
Is relatively small, that is, there are relatively few portions where the amount of deposition is small, and since the portion A where regeneration has been completed is in the upstream range near the electric heater 2, the heat of the electric heater 2 is easily transferred. The impact is small.

As another embodiment, when giving priority to absolutely avoiding heat damage to the filter, even if the engine is stopped during regeneration and the unburned residue ratio is small as indicated by E in FIG. 5, Without increasing the deposition amount as in the above m _E ′, the reference deposition amount m _E is kept as it is, and the deposition amount is reduced as in m _H ′ only when the unburned residue ratio is high as in _H. Then, regardless of the size of the unburned portion B, the control may be performed such that the next trap amount is always reduced.

FIG. 1 shows an example of a specific system configuration of an exhaust particulate purifying apparatus capable of executing the above control. As in FIG. 2, 1 is a filter, 2 is an electric heater for regeneration,
3 is a flow path switching valve, 4 is a bypass pipe, 5 is an air pump, a flow path switching valve 7 is also provided on the downstream side of the filter 1, and air 8 sent from the air pump 5 is fed by the flow path switching valves 3 and 7. The filter 1 is supplied from the downstream side toward the upstream side while being bypassed from the exhaust flow.
Therefore, the electric heater 2 for regeneration is also provided on the downstream end surface of the filter 1. In this case, the flow path switching valve 3 operates so as to switch between the regeneration exhaust pipe 9 and the exhaust inlet pipe 10. In the regeneration state shown in FIG. 1, exhaust 11
All flow through the bypass pipe 4. The differential pressure detection device 12 for detecting the differential pressure across the filter 1 inputs the detected value to the control device 13. The control device 13 includes an engine stop detection device 1 such as a key switch for detecting the stop of the engine.
The signal of No. 4 is also input, and the control device 13 performs calculation based on these signals, and as a result, supplies the control signal to the actuators 15 and 16 of the flow path switching valves 3 and 7 and the air flow rate control device 17 of the air pump 5. And the electric heater 8 is energized.

The amount of particulates deposited on the filter 1 is detected by the differential pressure detector 12 before and after the filter 1 in this example. When the filter 1 is regenerated, the control device 13 controls the flow path switching valves 3 and 7 provided upstream of the filter 1 by the valve actuators 15 and 16.
At this position, all the exhaust gas is bypassed through the bypass pipe 4, the electric heater 2 is simultaneously energized, and the air 8 required for combustion of the accumulated particulates is supplied from the air pump 5 through the air flow rate control device 17. To do. If an engine stop operation is performed during this regeneration, the engine stop detection device 1
In the control device 13 that monitors the engine stop signal of No. 4 (key switch OFF signal, etc.), the engine speed is increased by the detection value of the filter front-back differential pressure detection device 12 when the signal is input. Can be detected, that is, how much the unburned residue ratio is.

In accordance with this unburned residue ratio, the control device 13
For example, a map having the contents shown in the curve II of FIG. 5 is used. When the unburned residue ratio is large, the differential pressure before and after the filter (corresponding to the accumulated amount) for the next regeneration is set to the target differential pressure ( (Derived from the straight line I), and conversely, a large value when the unburned residue ratio is small, a value different from the reference value is set. Then, after the engine is restarted, when the differential pressure across the filter 1 reaches the above-mentioned set value, the flow path switching valves 3 and 7 are switched to energize the electric heater 2 to cause red heat and the air pump 5 Drive to start playback.

The amount of accumulated particulate matter may be detected based on the integrated value of the engine speed instead of the differential pressure. Depending on the unburned residue ratio calculated based on the integrated value of the engine speed, for example, if the unburned residue ratio is large, set the engine speed integrated value for the next regeneration to a value smaller than the target value, and burn it in reverse. When the remaining ratio is large, the control means 13 controls the value so that it becomes a large value. In this case, the regeneration condition that is better suited to the actual state can be obtained by using not only the engine speed integrated value but also the engine load as a criterion.

[0023]

According to the present invention, even if the regeneration is interrupted during the regeneration of the filter, the next regeneration time can be adjusted according to the state of the unburned particulates, so that the unburned amount of the unburned particulates can be adjusted. Regardless of this, it is always possible for the filter to perform good regeneration, thereby extending the service life of the filter and allowing the exhaust gas purification to continue satisfactorily for a long period of time.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an exhaust particulate purifying apparatus according to an embodiment of the present invention.

FIG. 2 is a system configuration diagram showing a conventional technique.

FIG. 3 is a cross-sectional view of a filter for explaining the problems of the conventional technique.

FIG. 4 is a cross-sectional view of the inside of the filter for explaining the difference in the unburned state.

FIG. 5 is a diagram for explaining a control example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Filter 2 ... Electric heater 3 ... Flow passage switching valve 4 ... Bypass pipe 5 ... Air pump 6a, 6b ... Shutoff valve 7 ... Flow passage switching valve 8 ... Air 9 ... Regeneration exhaust pipe 10 ... Exhaust inlet pipe 11 ... Exhaust gas 12 ... Front-rear differential pressure detection device 13 ... Control device 14 ... Engine stop detection device 15, 16 ... Actuator 17 ... Air flow control device A ... Part where regeneration is finished B ... Part where unburned remains

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinji Miyoshi 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute (72) Inventor Kenji Arakawa 1 Toyota-cho, Toyota-shi, Aichi Toyota Auto Car Co., Ltd.

Claims (2)

[Claims] 1. An exhaust system of an internal combustion engine, comprising a filter for collecting particulates in exhaust gas, and during the regeneration of the filter, the collected particulates are ignited and burned by a heating means, and at the same time, the filter is filtered. Is an exhaust gas purification device that incinerates the accumulated particulates by introducing the regeneration gas, a means for detecting the unburned amount of particulates after the filter regeneration operation, and the unburned amount when regeneration is interrupted. The exhaust particulate purifying apparatus is provided with a control means for shortening the period until the next regeneration when there is a large amount of fuel and for increasing the period until the next regeneration when there is little unburned amount. 2. The exhaust particulate purifying apparatus according to claim 1, wherein the means for detecting the amount of unburned residue is means for measuring the differential pressure across the filter.