JPH07180528A - Exhaust emission control device - Google Patents

Abstract

PURPOSE:To detect the unforeseen variation of exhaust gas pressure in the downstream of a filter even if a catalyst honeycomb is clogged by judging faulty the air connection in the downstream of the filter if exhaust gas pressure in the downstream of the filter comes out of a specified threshold range when an engine is operated and sounding alarm. CONSTITUTION:In an exhaust emission control device, a filter storing case 1 is provided between an exhaust pipe 3 in the upstream of a diesel engine 19 and an exhaust pipe 4 in the downstream of it. Also output signals from pressure sensors 7 and 17 in the upstream and downstream in the filter storing case 1, a temperature sensor 6, and a speed sensor 18 installed on the engine 19 are inputted into a controller 8. Then an average compensation pressure based on the input signals into the controller 8 are compared with the specified minimum and maximum threshold pressures stored beforehand and, if it comes out of a specified range, the pressure in the downstream of the filter 1 is judged faulty and an fault alarm lamp 80 will be lit. Thus the device can cope immediately with clogging of catalyst honeycomb 2a and others.

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 components (particulates) contained in the exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-72418, particulates contained in exhaust gas of a diesel engine are collected by a honeycomb ceramic filter (hereinafter, also referred to as a filter). It is known that when the trapped amount reaches a certain level, the filter is heated by a heater to burn the particulates to regenerate the filter. However, although the above filter collects particulates, CO, which is another harmful emission component,
HC is not captured, and SOF (soluble organic component) is also difficult to be captured.

In order to solve this problem, a honeycomb carrying a catalyst (hereinafter referred to as a catalyst honeycomb) is arranged downstream of the filter to remove CO, HC, etc. in the exhaust gas from which particulates have been removed. It has also been proposed to oxidatively decompose SOF.

[0004]

However, the cell diameter of the catalyst honeycomb described above is very fine, for example, 1 mm, because it is necessary to increase the geometric surface area in order to treat high-speed exhaust gas with high SV. Therefore, there is a possibility that clogging may occur due to various causes such as particulate matter and ash leak.

Even when such a catalyst honeycomb is not provided, the exhaust pipe downstream of the filter (for example, muffler or silencer) may be clogged, or the muffler may be broken and the exhaust pressure downstream of the filter may fluctuate. When the exhaust pressure downstream of the filter fluctuates from the normal state due to such factors as clogging of the catalyst honeycomb, there arises a problem that the calculation accuracy of the particulate collection amount calculated by the pressure loss of the filter and the operating condition of the engine decreases. . If the calculation accuracy is seriously deteriorated, filter damage due to an increase in particulate combustion heat amount and filter regeneration failure due to a decrease in particulate combustion heat amount are caused.

Further, the fluctuation (especially increase) of the exhaust pressure on the downstream side of the filter causes deterioration of the operating conditions of the engine, resulting in increase of harmful emission components and reduction of torque. The present invention has been made in view of the above problems, and provides an exhaust gas purification device capable of detecting an unexpected variation in exhaust pressure downstream of a filter such as clogging of a catalyst honeycomb without complicating the device configuration. Is the problem to be solved.

[0007]

An exhaust gas purifying apparatus of the present invention is formed by axially penetrating a porous partition wall made of ceramics, and a downstream end and an upstream end are alternately blind. A filter for collecting particulates, which is provided in the exhaust path of the diesel engine and has a large number of plugged cells, and is disposed in the vicinity of the filter to burn the particulates by energization. An ignition heater, an air supply means for introducing external air into the exhaust path on the upstream side of the ignition heater, a pressure detection means for detecting pressures on the upstream side and the downstream side of the filter, and a pressure detection means of the pressure detection means. Re-estimating the particulate collection amount according to the state amount related to the pressure loss of the filter calculated based on the output, and determining the filter regeneration time based on the particulate collection amount. And a ventilation abnormality warning means for determining the ventilation abnormality on the filter downstream side when the exhaust pressure on the filter downstream side exceeds a predetermined threshold range when the engine is operating. It is characterized by that.

In a preferred embodiment, a catalyst honeycomb is provided downstream of the filter. In a preferred mode, the catalyst honeycomb is housed in the same case as the filter, and the pressure between the catalyst honeycomb and the filter is detected. By doing so, the device configuration can be simplified. In a preferred aspect, the reproduction timing determination means, when the alarm is input,
The estimation of the particulate collection amount based on the pressure loss is interrupted.

[0009]

The ventilation abnormality alarming means determines that the filter downstream is clogged or damaged when the exhaust pressure downstream of the filter during operation of the engine deviates from a predetermined threshold range and issues an alarm. For this reason, even if the downstream side of the filter is clogged or damaged, it is possible to prevent the calculation accuracy of the particulate collection amount calculated from the pressure loss of the filter and the operating condition of the engine from decreasing. Also,
It is possible to prevent the deterioration of engine operating conditions and the resulting increase in harmful emission components and torque reduction.
The exhaust pressure on the downstream side of the filter can use the pressure detecting means for detecting the pressure loss of the filter, and it is not necessary to add an expensive pressure sensor, and the complexity of the device configuration can be prevented.

In a preferred embodiment, a catalyst honeycomb is arranged downstream of the filter. By doing so, it is possible to prevent an increase in the particulate matter estimation error and an engine malfunction due to the clogging of the catalyst honeycomb.

[0011]

FIG. 1 shows an embodiment of an exhaust gas purifying apparatus according to the present invention.
Shown in. This exhaust gas purification device is a diesel engine 1
9 has a filter housing case 1 interposed between an exhaust pipe 3 on the upstream side and an exhaust pipe 4 on the downstream side, and the filter housing case 1 has a filter upstream side pressure from the upstream side to the downstream side. The upstream pressure sensor 7 for detection, the temperature sensor 6, the ignition heater 9, the filter 2, the downstream pressure sensor 17 for pressure detection on the filter downstream side, and the catalyst honeycomb 2a are arranged in order. An air supply pipe 30 is branched from the middle of the exhaust pipe 3, the air supply pipe 30 is connected to an outlet of an air supply blower 13 through a solenoid valve 14, and an inlet of the air supply blower 13 is connected through an air flow sensor 15 to the outside. It is open to.

On the other hand, the ignition heater 9 and the blower 1 described above
The motor M of No. 3 is drive-controlled by the controller 8, and the output signal of the rotation speed sensor 18 mounted on the diesel engine 19 is output to the controller 8. The controller 8 is a microcomputer with an A / D converter (not shown)
The switch 55, 56 is controlled to open and close to control the ignition heater 9 and the blower 13, and the abnormality warning lamp 80 is turned on when an abnormality occurs. The controller 8 uses the blower 1 based on the signal from the air flow sensor 15.
The duty ratio control (feedback control) of the voltage applied to the blower 3 precisely controls the supply flow rate of the blower 13 to the target level. Reference numeral 81 is a lamp for instructing reproduction.

Reference numeral 5 denotes a power feeding device, which includes a plug 51 connected to a commercial ground power source (not shown), a step-down transformer 52,
The full-wave rectifier 53 is provided, and the DC voltage output from the full-wave rectifier 53 is supplied to the ignition heater 9 and the blower drive motor M through the semiconductor power switches 55 and 56. The filter 2 is a honeycomb ceramic filter (Japanese insulator kk).
Made of porous cordierite as a raw material, and is fired into a cylindrical shape. The filter 2 has a large number of cells (ventilation holes) penetrating both end surfaces thereof. These cells are an upstream cell whose downstream open end is sealed by a plug made of ceramic,
The upstream side open end is sealed by the plug and the downstream side cell is formed. The upstream side cell and the downstream side cell are alternately arranged with a porous partition wall made of porous cordierite separated. As a result, the exhaust gas permeates from the upstream side cell to the adjacent downstream side cell through the porous partition wall, and only the particulates are collected by the porous partition wall.

The catalyst honeycomb 2a is composed of CO in exhaust gas,
This catalyst honeycomb 2 comprises a honeycomb made of ceramic or metal that carries catalyst particles that oxidize HC.
a has a large number of ventilation holes (cells) in the axial direction. In this embodiment, the cell density is 400 cells / inch and the cell diameter is about 1 mm. The catalyst honeycomb 2a is housed on the downstream side of the filter 2 via a mat made of expandable ceramic.

The ignition heater 9 uses almost the same material and the same structure as the filter 2 described above, but does not carry catalyst particles. The ignition heater 9 is arranged close to the end surface of the filter 2 which is located on the upstream side during regeneration.
The pressure sensors 7 and 17 employ a configuration in which the strain of the diaphragm due to the pressure difference is transmitted to the semiconductor pressure sensor through the heat insulating member.

The operation of this exhaust gas purifying apparatus will be described below. (Particulate collection operation) Diesel engine 19
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 further converted into CO, HC, etc. in the catalyst honeycomb 2a. After being purified, it is discharged to the outside.

(Filter Regeneration Operation) The regeneration operation of the filter 2 will be described with reference to the flow chart of FIG. It should be noted that in this device, the filter regeneration operation is started by receiving power from an external power source while the engine is stopped and starting it by a manual operation. The solenoid valve 14 is opened immediately before the start of reproduction.

First, FIG. 2 shows a filter regeneration routine consisting of a filter regeneration determination routine (steps 100 to 111) executed during engine operation and a filter regeneration execution routine (steps 112 to 116) executed during engine stop. . First, the filter regeneration determination routine is started when the engine 19 is started, and step 1
00, the exhaust pressure P detected by the pressure sensors 7 and 17
1, P2, the engine rotation speed n detected by the rotation speed sensor 18, and the exhaust gas temperature T detected by the temperature sensor 6, the particulate trapping amount is calculated.

Calculation of this particulate collection amount G
This will be described in detail with reference to the subroutine of FIG. First, at step 1001, the engine speed sensor 18, the pressure sensors 7 and 17, and the temperature sensor 6, the accelerator opening sensor (not shown) provided in the engine 19, the exhaust pressure P1 on the filter upstream side, the filter. The downstream exhaust pressure P2, the rotational speed n, the exhaust gas temperature T, and the accelerator opening A are input.

In the next step 200, a filter downstream pressure determination subroutine, which will be described later, for determining whether or not the filter downstream pressure is normal is executed (200). Next Step 10
In 02, the pressure loss (measured differential pressure) of the filter 2 ΔP = P
1-P2 In order to eliminate the influence of the rotation speed n and the exhaust gas temperature T, the correction differential pressure ΔPeq is calculated by the following correction formula.
Find i.

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 corrected by the above equation to the corrected differential pressure ΔPeqi when the absolute temperature T is 523 and the rotation speed n is 2600. Therefore, in this embodiment,
The measured differential pressure ΔP is approximated to be inversely proportional to the fluctuation of the exhaust gas temperature T or the rotational speed n. This correction differential pressure ΔP
eqi is calculated every 50 msec.

At the next step 1003, the engine load is obtained from the rotational speed n and the accelerator opening A based on a calculation formula or map stored in advance. Next, by introducing the rotational speed n and the engine load into a three-dimensional map stored in advance,
The volume efficiency η linked to the rotation speed n and the load is searched.
In the next step 1004, in order to compensate the change in the correction differential pressure ΔPeqi due to the change in volume efficiency, the above ΔPeq is corrected.
The corrected pressure loss ΔPeqi ′ is calculated by multiplying i by η.

In the next step 1004, the average of the immediately preceding 64 calculated values out of the corrected differential pressures ΔPeqi ′ input every 50 msec in the past is calculated, and this is taken as the average corrected differential pressure ΔPeqm. In the next step 1004, of the correction differential pressures ΔPeqi input every 50 msec in the past, the average of the immediately previous 64 calculated values is calculated, and this is set as the average correction differential pressure ΔPeqm.

Next, at step 1007, a collection amount is stored 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. Search G and return to the main routine. Next, in step 108, it is checked whether or not the searched particulate collection amount G exceeds a predetermined threshold value Gt, and if not, step 10
When it returns to 0 and exceeds it, it proceeds to step 111.

In step 111, the lamp 81 for instructing the filter regeneration is turned on and the routine ends. After that, when the driver visually recognizes that the lamp 81 for instructing the filter regeneration is turned on and turns on a regeneration switch (not shown) while the engine is stopped, the filter regeneration execution routine is started.

In this routine, first, the blower 13 is started in step 112, then the built-in timer is started (114), the timer control subroutine is executed to perform the reproducing operation (116), and the reproducing is ended. . The timer control subroutine described above will be described below with reference to FIG.

This subroutine is for carrying out energization and blowing control using the time from the start of energization of the blower 13 as a parameter, first after energizing the blower 13 and after time Ta (here, 1 minute) has elapsed (1161), The energization of preheating power to the heater 11 is started (1162). Next, after the time Tb ′ has passed after the start of the preheating power to the heater 11, the ignition power is turned on, and after the time Tb has passed after the start of the power to the heater 11 (1163), the power to the heater 11 is turned on. Switch from ignition power to continuous combustion power (116
4). Next, after the time Tb has elapsed, the time Tc (here, 15
After a lapse of minutes (1165), the power supply is stopped (116).
6). Next, after the power supply is stopped, time Td (here, 10 minutes)
When the time has passed (1167), the ventilation is stopped (116
8).

As described above, in this embodiment, first,
In order to eliminate the influence of the rotational speed n and the exhaust gas temperature T on the pressure loss (measured differential pressure) ΔP = P1-P2 of the filter 2, the corrected differential pressure ΔPeqi = ΔP × (523 / T) × (2
600 / n), the engine load is calculated from the rotation speed n and the accelerator opening A, and the engine load and the rotation speed are introduced into a three-dimensional map that is stored in advance, and is linked to the rotation speed n and the load. The volumetric efficiency η1 is searched, and ΔPeqi is multiplied by the volumetric efficiency η1 to calculate a corrected pressure loss ΔPeqi ′ that compensates for the variation of the pressure loss due to the volumetric efficiency, and the particulate collection amount is calculated from the calculated corrected pressure loss ΔPeqi ′. presume.

Next, the filter downstream pressure determination subroutine 200, which is the main part of this embodiment, will be described with reference to the flowchart of FIG. First in step 2002,
In order to eliminate the influence of the rotational speed n and the exhaust gas temperature T on the input exhaust pressure P2 on the downstream side of the filter, the correction pressure P2eqi is calculated by the following correction formula.

P2eqi = P2 × (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 corrected to the correction pressure P2eqi when the absolute temperature T is 523 and the rotation speed n is 2600 by the above formula. This correction pressure P2eqi is 5
It is calculated every 0 msec.

At the next step 2004, the engine load is obtained from the rotational speed n and the accelerator opening A based on a previously stored calculation formula or map. Next, by introducing the rotational speed n and the engine load into a three-dimensional map stored in advance,
The volume efficiency η linked to the rotation speed n and the load is searched.
In the next step 2006, in order to compensate for the change in the correction pressure P2eqi due to the change in volume efficiency, P2eqi is multiplied by η to calculate the correction pressure P2eqi ′.

In the next step 2008, the average value of the immediately preceding 64 calculated values out of the corrected pressures P2eqi 'input every 50 msec in the past is calculated, and this is set as the average corrected pressure P2eqm. In the next step 2010, the average corrected pressure P2eqm is stored in advance as a predetermined minimum threshold pressure Pt1 and maximum threshold pressure Pt2.
It is determined whether or not P2eqm is within this range. If it is within the range, it is determined that the filter downstream pressure is normal and the process proceeds to step 1002. If it is out of the range, the filter downstream pressure is abnormal (for example, the catalyst honeycomb 2a). No clogging of the muffler, breakage of the muffler, etc.), the process proceeds to step 2012, the abnormality alarm lamp 80 is turned on, and an alarm is issued by voice, and the routine ends.

In this way, the filter downstream pressure determination subroutine 200 (ventilation abnormality warning means in the present invention) gives an alarm when clogging or damage occurs in the filter downstream, so the amount of particulate collection. It is possible to promptly cope with the deterioration of the calculation accuracy of the above and the deterioration of the operating condition of the engine. (Modification) The exhaust pressure P2 downstream of the filter 2 is
Since it also varies depending on the amount of particulate collection of the filter 2, the correction pressure P2eqi or P2eqm is multiplied by the coefficient obtained from the map by the amount of particulate collection ΔPeqm estimated in the flowchart of FIG. It is also possible to correct the exhaust pressure downstream of the filter under the trapping condition.

[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 an operation of estimating the amount of collected particulates,

FIG. 4 is a flowchart showing the reproduction operation,

FIG. 5 is a flowchart for determining an exhaust pressure abnormality downstream of the filter.

[Explanation of symbols]

2 is a filter, 6 is a temperature sensor, 7 and 17 are pressure sensors (pressure detection means), 8 is a controller (ventilation abnormality warning means, regeneration timing determination means), 11 is an ignition heater (electric heating means), and 13 is a blower ( 18 is a rotation speed sensor, and 19 is an engine.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01M 15/00 Z

Claims (4)

[Claims] 1. A disk comprising a large number of cells formed by axially penetrating a porous partition wall made of ceramics and having blind ends alternately arranged on the downstream side and the upstream side.
A filter for collecting particulates that is installed in the exhaust path of the Zel engine, an ignition heater that is disposed in the vicinity of the filter and burns the particulates by energization, and an upstream side of the ignition heater. Air supply means for introducing external air into the exhaust path, pressure detection means for detecting pressure on the upstream side and downstream side of the filter, and pressure loss of the filter calculated based on the output of the pressure detection means Depending on the state quantity
And a regeneration timing determining means for estimating a trapped trapping amount and determining a filter regeneration timing based on the particulate trapped amount, and an exhaust pressure on the downstream side of the filter when the engine is operating is within a predetermined threshold range. And a ventilation abnormality alarming unit that gives a warning when the ventilation abnormality on the downstream side of the filter is detected. 2. The exhaust gas purifying apparatus according to claim 1, further comprising a catalyst honeycomb downstream of the filter. 3. The catalyst honeycomb is housed in the same case as the filter, and the pressure detecting means detects the pressure between the catalyst honeycomb and the filter as the pressure on the downstream side of the filter. 2. The exhaust gas purification device according to 2. 4. The exhaust gas purifying apparatus according to claim 1, wherein the regeneration timing determining means suspends estimation of the particulate trapped amount based on the pressure loss when the alarm is input.