JPH06330732A - Exhaust gas cleaner - Google Patents

Abstract

PURPOSE:To estimate the collected amount of particulates highly accurately based on a plurality of factors, and to prevent giving damage to a filter by judging abnormal condition of a pressure sensor, in an exhaust gas cleaner for collecting the particulates in the exhaust and for reactivating. CONSTITUTION:An upstream pressure sensor 7, a temperature sensor 6, a heater 11, a filter 2, a downstream pressure sensor 17 are stored in this order from the upstream side to the downstream side in a case 1. The discharge tube 3 of a diesel engine 20 is connected to the upper end wall of the case 1 and is connected to the outlet of the blower 13 of an air transmitting tube 10 divided from the middle of the air transmitting tube 3, while an air flow sensor is provided on the inlet of the air transmitting tube 10. A rotation speed sensor 18 is provided on a diesel engine 20. The heater 11 and the blower 13 are controlled by a controller 8 based on each detection signal from each sensor 6, 7, 17 and 18. The abnormality of each pressure sensor 7, 17 is judged by the controller 8 based on the relationship between the rotation speed and the pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for collecting and regenerating particulate matter (particulates) contained in the exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Conventionally, a filter provided in an exhaust path of a diesel engine and a heater for igniting particulates collected by the filter are provided, for example, an increase in differential pressure across the filter. The regeneration time is discriminated by and the energization of the heater is started to perform regeneration.

In Japanese Utility Model Publication No. 2-18275, a temperature sensor for detecting a filter temperature is provided, and when the temperature sensor continuously outputs a temperature signal corresponding to a predetermined threshold temperature or more for a predetermined time or more, the filter is used. It is determined that the playback is completed.

[0004]

However, in the above-described conventional filter regeneration system, when the amount of collected particulates is determined only by the differential pressure of the filter as described above, the engine operating condition such as the engine speed or the exhaust gas is exhausted. Since the filter differential pressure also fluctuates depending on the gas temperature, there is a problem in that the error in the estimated particulate collection amount is large.

If the particulate collection amount is estimated to be too small, the maximum temperature during regeneration may cause filter melting damage and cracks, and if the particulate collection amount is estimated to be excessive, regeneration failure occurs. Will end up. Further, if the pressure sensor that detects the differential pressure of the filter becomes defective, an error occurs in the accuracy of the estimated amount of particulate collection, and as in the above case, filter melting loss, cracks, and defective regeneration occur.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an exhaust gas purifying apparatus capable of avoiding filter regeneration failure and filter damage due to an abnormality of a pressure sensor with a simple device configuration. Has an aim.

[0007]

The exhaust gas purifying apparatus of the present invention, as shown in the claim correspondence diagram of FIG. 9, includes a filter arranged in the exhaust path of a diesel engine and a rotational speed of the engine. Rotational speed detection means for detecting, temperature detection means for detecting exhaust gas temperature in the exhaust path, pressure detection means for detecting pressure before and after the filter, and detected rotational speed, exhaust gas temperature and pressure A collection amount estimating means for estimating the particulate collection amount of the filter based on the above; an electric heating means for burning the particulate collected by the filter by heating the filter to regenerate the filter; and Regeneration timing determining means for determining whether or not the estimated collection amount reaches a predetermined level, and input of a filter regeneration command issued when the estimated collection amount reaches the predetermined level. The energization control means for energizing the electric heating means, the storage means for storing the relationship between the pressure and the rotational speed, and the pressure detection means input during the engine operation period in which the energization of the electric heating means is not performed. It is characterized by further comprising a pressure abnormality determining means for determining whether or not the pressure conforms to the above relationship and for issuing an abnormality alarm indicating an abnormality of the pressure detecting means when the pressure is not conforming.

[0008]

In the present invention, not only the pressure on the upstream side of the filter (based on the pressure on the downstream side of the filter or atmospheric pressure; hereinafter also simply referred to as pressure), but also the particulate matter of the filter based on the exhaust gas temperature and the engine speed. -Estimating the collection amount. That is, since the pressure varies depending on the operating state of the engine, for example, the engine speed and the exhaust gas temperature, in addition to the particulate trapping amount, the pressure alone can accurately detect the particulate trapping amount. Can not. According to the present invention, since the amount of collected particulates is determined based on the number of revolutions, the pressure, and the temperature of exhaust gas, the amount of collected particulates can be accurately detected.

When the estimated trapped amount reaches a predetermined level, the electric heating means is instructed to energize (issues a filter regeneration command), and the electric heating means ignites the particulates of the filter to regenerate the filter. Further, in the present invention, the relationship between the engine speed and the exhaust gas pressure is detected during non-regeneration (non-energization) by using the rotation speed detection means and the pressure detection means used for estimating the amount of collected particulates. Checking whether the relationship between the detected engine speed and exhaust gas pressure matches the previously stored relationship between engine speed and exhaust gas pressure, and if not, determine that the pressure detection means is abnormal. .

[0010]

As described above, in the exhaust gas purifying apparatus of the present invention, the particulate collection amount of the filter is estimated on the basis of the engine speed, the exhaust gas temperature and the exhaust gas pressure. It is possible to accurately estimate the amount of trapped particulate matter, prevent damage to the filter and defective regeneration, and obtain it from the rotational speed detection means and pressure detection means used for estimating the amount of trapped particulates. By comparing the data with the data stored in advance, it is possible to check the abnormality of the pressure detecting means, and as a result, the amount of the particulate trapped due to the abnormality of the pressure detecting means can be checked without complicating the structure. Erroneous estimation can be prevented, and filter damage and regeneration failure based on erroneous estimation of the amount of collected particulates can be suppressed.

[0011]

【Example】

(Embodiment 1) An embodiment of the exhaust gas purifying apparatus of the present invention is shown in FIG. This exhaust gas purifying apparatus has a filter housing case 1 whose both ends are hermetically sealed, and an upstream pressure sensor 7 for detecting exhaust pressure and a temperature sensor 6 (in the present invention) from the upstream side to the downstream side in the filter housing case 1. The temperature detecting means), the heater (electric heating means in the present invention) 11, the filter 2, and the downstream pressure sensor 17 for detecting the filter downstream pressure are sequentially arranged. The exhaust pipe 3 of the diesel engine 20 is provided on the upstream end wall of the filter housing case 1,
The air supply pipe 10 is branched from the middle of the exhaust pipe 3. The air supply pipe 10 is connected to the outlet of a blower 13 for supplying air.

On the other hand, the above-mentioned heater 11 and blower 13 are drive-controlled by the controller 8, and the signals of the rotation speed sensor 18 and the accelerator opening sensor 19 mounted on the diesel engine 20 are output to the controller 8. The filter 2 is a honeycomb ceramic filter (manufactured by Nippon Insulator kk, diameter 5.66 inches × length 6 inches), which is fired into a cylindrical shape using cordierite as a material. The filter 2 has a large number of vent holes penetrating both end faces thereof, one of the adjacent vent holes is plugged at the upstream end, and the other is plugged at the downstream end. The exhaust gas passes through the porous partition wall between the adjacent vent holes, and only the particulates are trapped in the vent holes. Both end faces of the filter 2 face the both end faces of the case 1 with a predetermined distance.

The heater 3 is composed of an electrothermal resistor made of nichrome wire, and is arranged close to the end surface of the filter 2 which is located on the upstream side during regeneration. The controller 8 is equipped with a microcomputer (not shown) with a built-in A / D converter, processes various data, controls the heater 11 and the blower 13 to execute regeneration, and also activates an abnormality warning lamp 9 when an abnormality occurs. Lights up (an abnormal signal is output).

The operation of this device will be described below. (Particulate collection operation) Diesel engine 20
The exhaust gas discharged from the exhaust gas is introduced into the case 1 through the exhaust pipe 3, particulates in the exhaust gas are collected by the filter 2, and the purified exhaust gas is discharged to the outside from the tail pipe 4.

(Filter Regenerating Operation) Next, the regenerating operation of the filter 2 will be described with reference to the flow charts shown in FIGS. In this device, the filter regeneration operation is performed while the engine is stopped. FIG. 2 is a filter determination routine. First, in step 100, the exhaust pressures P1 and P2 detected by the pressure sensors 7 and 17, the engine speed n detected by the rotation speed sensor 18, and the exhaust gas temperature T are detected. The particulate collection amount G is calculated based on the detected temperature sensor 6.

The calculation of the amount G of collected particulates is
This will be described in detail with reference to the subroutine shown in FIG. First, in step 1001, the exhaust pressures P1 and P2, the rotation speed n, and the exhaust gas temperature T are input. Next, in step 1002, in order to eliminate the influence of the rotational speed n and the exhaust gas temperature T on the pressure loss (differential pressure) ΔP = P1-P2 of the filter 2, the corrected differential pressure ΔPeqi is calculated by the following correction formula. Ask.

ΔPeqi = ΔP × (523 / T) × (2600 / n) The exhaust gas temperature T is an absolute temperature, and the unit of the rotation speed n is r.
pm. That is, the measured differential pressure ΔP is calculated by the above equation, and the corrected differential pressure ΔPeqi corresponding to the differential pressure when the absolute temperature T is 523 and the rotation speed n is 2600 is calculated. Therefore, in this embodiment, the differential pressure is the exhaust gas temperature T or the rotation speed n.
Is inversely proportional to the fluctuation of. This corrected differential pressure ΔPeqi is calculated every 50 msec.

Next, at step 1003, the corrected differential pressure Δ
The average of the 64 calculated values immediately before Peqi is calculated, and this is set as the average correction differential pressure ΔPeqm. Next, step 100
At 4, the collection amount G is searched from a table stored in a memory (not shown) built in the microcomputer type controller 8 and storing the relationship between the average correction differential pressure ΔPeqm and the collection amount G.

Next, at step 101, the rotational speed n is integrated to calculate the cumulative rotational speed. The counter for accumulating the number of revolutions n is reset in step 118, which will be described later, and then the number of revolutions n read in step 1001 is multiplied by a time Δt from the start time of the previous step 1001 to the start time of this step 1001. This is performed by adding this integrated value n × Δt to the integrated value (cumulative rotation speed) up to the previous time to obtain the current cumulative rotation speed.

In step 101, the cumulative engine operating time (hereinafter simply referred to as operating time) after the end of the previous filter regeneration is also counted. This operating time uses a timer (not shown) that operates during engine operation, and this timer is reset at step 118. Further, in step 101, the average cumulative rotation speed is calculated. For this average cumulative rotation speed, the average value (moving average value) of the five above-mentioned cumulative rotation speeds calculated n times in the past (here, five times) is obtained, and this is taken as the average cumulative rotation speed. In the first four routines, a predetermined constant value is adopted as the average cumulative rotation speed.

In the next step 102, the pressure sensor 7,
The pressure check subroutine for checking 17 is executed. This pressure check subroutine will be described with reference to the flowchart of FIG. First, the engine speed is 750
It is checked whether it is 2500 rpm (1021). If NO, the process bypasses to step 1023, and if YES, the filter upstream pressure Pf output from the pressure sensor 7 is 750 to 1300.
It is checked whether or not the filter downstream pressure Pb output from the pressure sensor 71 is 700 to 780 mHg in mHg (1022). According to a preliminary investigation, if the engine speed is 750 to 2500 rpm, the filter upstream pressure Pf is 750 to 1300 mHg in the expected fluctuation range of the amount of particulate trapped in the filter 2.
It is known that the filter downstream pressure Pb becomes 700 to 780 mHg. Therefore, only when the determination condition of step 1022 is satisfied, it is determined that the pressure sensors 7 and 17 are normal, and the process proceeds to step 1023. Otherwise, the process proceeds to step 1025.

In step 1023, it is checked whether the engine speed continuously changes from 750 rpm to 2500 rpm. If NO, the process bypasses step 1023 and proceeds to step 1029. If YES, the filter upstream pressure due to this speed change is detected. The change ΔPf is 70 mHg or more, and the change ΔPb in the filter downstream pressure Pb is 20 m.
It is checked whether or not it is equal to or higher than Hg (1024). According to a preliminary investigation, the engine speed will be 750 rpm to 250
When continuously increasing to 0 rpm, ΔPf is 70 mHg
As described above, it is known that ΔPb is 20 mHg or more. Therefore, only when the determination condition of step 1024 is satisfied, the pressure sensors 7 and 17 are regarded as normal, the timer described later is reset to 0 (1029), and the process returns to the main routine, otherwise the process proceeds to step 1025.

In step 1025, it is checked whether the timer built in the microcomputer is operating. If it is not operating, this timer is started (1026). If it is operating, step 1
It detours to 026 and proceeds to step 1027. As a result, if the pressure sensor 7 or 17 is in an abnormal state, the timer will start. In the next step 1027, it is checked whether or not the above-mentioned timer has elapsed for 3 seconds, and if it has not elapsed, it returns to the main routine, and if it has elapsed, the abnormal state of the pressure sensor 7 or 17 continues for 3 seconds or more. As a matter of course, the abnormality display lamp 9 is turned on (102
8) The subroutine for calculating and replacing the temporary particulate collection amount G'for emergency regeneration is executed and the process returns to the main routine.

This temporary collection amount calculation and replacement subroutine will be described with reference to FIG. First, in step 1031, it is checked whether or not the cumulative rotation speed calculated in step 101 is equal to or greater than the average cumulative rotation speed + predetermined value α, and if it is above, it is estimated that the filter regeneration time has been reached, and the routine proceeds to step 1034. On the other hand, if less than, the operating time calculated in step 101 in step 1032 is the average operating time + predetermined value β
Whether or not it is above is checked, and if it is above, it is estimated that the filter regeneration time has been reached, and the routine proceeds to step 1034. In addition,
The average operating time is calculated in step 101 as a moving average value of the operating time of each time as with the average cumulative rotation speed.

In step 100, the differential pressure Δ
The particulate collection amount G was calculated based on P, but when the pressure sensor 17 is abnormal, the pressure difference ΔP can be replaced by the value of the pressure sensor 7. If you do this,
Even if one or both of the pressure sensors 7 and 17 are out of order, the regeneration time can be discriminated and the command can be issued, and it can be warned that the particulate collection amount becomes excessive.

In the next step 108, it is checked whether or not the searched particulate collection amount G exceeds a predetermined threshold value Gt. If it does not exceed the predetermined threshold value Gt, the process returns to step 100, and if it does, the process proceeds to step 109. The reproduction instruction display lamp 91 is turned on and the routine ends. Next, the filter regeneration routine will be described with reference to FIG.

Lamp 9 for driver commanding filter regeneration
When the regeneration switch (not shown) is turned on while the engine is stopped, the filter regeneration routine is started. In this routine, first, in step 112, the blower 13 is activated, and the built-in timer is activated (11
4), a timer control subroutine is executed to perform a reproduction operation (116), and after the reproduction is completed, a rotation speed integration counter (for cumulative rotation speed integration) and an operating time built in a microcomputer (not shown) in the controller 8 A cumulative timer (for cumulative engine operating time) is reset (118).

The timer control subroutine will be described below with reference to FIG. This subroutine controls energization and blowing by using the time from energization of the blower 13 as a parameter. First, after energizing the blower 13, the time Ta
After (1 minute in this case) (1161), the heater 11
The energization of the preheating power is started (1162). Next, after the heater 11 is energized, the energized power is increased to the ignition power when the time Tb 'has passed, and thereafter, when the time Tb has passed since the heater 11 was energized (1163), the power supplied to the heater 11 is changed from the ignition power to the combustion continuous power. Switch (1164). Next, after a lapse of Tb, when a time Tc (here, 15 minutes) has elapsed (1165), energization is stopped (1166). next,
When the time Td (here, 10 minutes) elapses after the energization is stopped (1167), the blowing is stopped (1168).

FIG. 8 shows a timing chart in this subroutine. In the above routine, step 100 is the collection amount estimation means in the present invention, step 108 is the regeneration timing determination means in the present invention, energization control means in steps 112 to 116, and steps 1022 and 1024 are A storage means and an abnormality determination means.

As described above, in this embodiment, the particulate trapped amount of the filter is accurately estimated based on the engine speed, the exhaust gas temperature and the exhaust gas pressure, and the detected pressure is the rotational speed. It is possible to realize accurate and highly reliable filter regeneration since it is checked whether or not there is a deviation from the relationship between the pressure and the pressure, and it is possible to prevent the filter from melting or cracking due to an error in the estimation of the amount of collected particulates. Reproduction failure can be prevented.

It should be noted that a more detailed relationship between the engine speed and the pressure than that in the above embodiment is stored as a map, and the reference pressure obtained from this map is compared with the detected pressure to determine whether the pressure sensor is good or defective. It is also possible to detect

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an exhaust gas purification device of the present invention,

FIG. 2 is a flowchart showing the reproducing operation,

FIG. 3 is a flowchart showing the reproducing operation,

FIG. 4 is a flowchart showing the reproduction operation,

FIG. 5 is a flowchart showing the reproducing operation,

FIG. 6 is a flowchart showing the reproducing operation,

FIG. 7 is a flowchart showing the reproducing operation,

FIG. 8 is a timing chart showing the reproduction mode,

FIG. 9 is a complaint correspondence diagram.

[Explanation of symbols]

2 is a filter, 6 is a temperature sensor (temperature detecting means), 7,
Reference numeral 17 is a pressure sensor (pressure detection means), 8 is a controller (collection amount detection means, regeneration timing determination means, storage means, energization control means, abnormality determination means), 11 is a heater (electric heating means), and 18 is a rotation speed sensor. (Rotation speed detection means).

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[Procedure amendment]

[Submission date] September 20, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011]

EXAMPLE 1 An example of an exhaust gas purifying apparatus of the present invention is shown in FIG. This exhaust gas purifying apparatus has a filter housing case 1 whose both ends are hermetically sealed, and an upstream pressure sensor 7 for detecting exhaust pressure and a temperature sensor 6 (in the present invention) from the upstream side to the downstream side in the filter housing case 1. The temperature detecting means), the heater (electric heating means in the present invention) 11, the filter 2, and the downstream pressure sensor 17 for detecting the filter downstream pressure are sequentially arranged. The exhaust pipe 3 of the diesel engine 20 is provided on the upstream end wall of the filter housing case 1,
The air supply pipe 10 is branched from the middle of the exhaust pipe 3. The air supply pipe 10 is provided with a valve 14 at the outlet of the blower 13 for supplying air.
It is connected Te.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

On the other hand, the above-mentioned heater 11, blower 13 and
The drive of the valve 14 and the valve 14 is controlled by the controller 8, and the signals of the rotation speed sensor 18 and the accelerator opening sensor 19 mounted on the diesel engine 20 are output to the controller 8. The filter 2 is a honeycomb ceramic filter (manufactured by Nippon Insulator kk, diameter 5.66 inches × length 6 inches), which is fired into a cylindrical shape using cordierite as a material. The filter 2 has a large number of vent holes penetrating both end faces thereof, one of the adjacent vent holes is plugged at the upstream end, and the other is plugged at the downstream end. The exhaust gas passes through the porous partition wall between the adjacent vent holes, and only the particulates are trapped in the vent holes. Both end faces of the filter 2 face the both end faces of the case 1 with a predetermined distance.

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (1)

[Claims] 1. A filter arranged in an exhaust passage of a diesel engine, a rotation speed detecting means for detecting a rotation speed of the engine, and a temperature detecting means for detecting an exhaust gas temperature in the exhaust passage. Pressure detection means for detecting the pressure on the upstream side of the filter, collection amount estimation means for estimating the particulate collection amount of the filter based on the detected rotation speed, exhaust gas temperature and pressure, and the filter Heating means for burning the particulates trapped in the filter to regenerate the filter, regeneration timing discriminating means for discriminating whether or not the estimated trap amount reaches a predetermined level, and the estimated trap. The relationship between the pressure and the rotation speed is stored, and an energization control unit that energizes the electric heating unit by inputting a filter regeneration command that is issued when the collection amount reaches the predetermined level. And a storage unit for determining whether or not the pressure input from the pressure detection unit during the engine operation period in which the power supply to the electric heating unit is not performed conforms to the relationship, and detects the pressure when the relation is not satisfied. An exhaust gas purifying apparatus, comprising: a pressure abnormality determination means for issuing an abnormality alarm indicating an abnormality of the means.