JPH08210122A - Exhaust emission control device for diesel engine - Google Patents

Abstract

PURPOSE: To enable sensing of a capturing rate according to an operation condition by providing a means for calculating a ratio between a multiplying value of a rotational speed of an engine and a reference multiplying value to a pressure difference on a capturing rate sensing means, and sensing the capturing rate based on the ratio of the multiplying values and the pressure difference. CONSTITUTION: Pressure difference in respect to a filter 7 is sensed by means of a front pressure sensor 11, a rear pressure sensor 12, an inlet gas temperature sensor 13, and an outlet gas temperature sensor 14. Based on the pressure difference, a particulate capturing rate of the filter 7 is sensed. A ratio between a multiplying value of a rotational speed of a diesel engine to the time that the pressure difference is sensed, and a reference multiplying value to the pressure difference are obtained. Based on the ratio between the multiplying values and the pressure difference a capturing rate is sensed. Even when a particulate component is varied according to an operation condition at the capturing time, regeneration control can be started so as to detect the weight at a proper time, and the filter can be stably regenerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control system for a diesel engine equipped with a filter for collecting particulates discharged from the diesel engine.

[0002]

2. Description of the Related Art Conventionally, in this type of exhaust emission control device, as disclosed in Japanese Patent Laid-Open No. 4-325707,
Detects the pressure loss (pressure difference between filters) caused by the collection of particulates (particulates) in the filter, and corrects this pressure difference to the value in the standard state based on the exhaust temperature before and after the filter and the intake air amount. The collection amount of the filter is obtained from this corrected differential pressure, and the filter is regenerated when this value reaches a predetermined value.

[0003]

In the detection of the filter trapping amount in this device, the relationship between the correction differential pressure and the trapping amount (weight) has a one-to-one relationship as shown in FIG. It is a premise. However, in reality, depending on the engine operating conditions, the injected fuel does not all burn during high load operation, and part of it is carbonized, and the proportion of carbon in the composition of fine particles increases, resulting in a unit volume (unit correction differential pressure). The collection amount per unit increases. Conversely, during low load operation, engine oil and unburned fuel are discharged, and the amount of trapped per unit correction differential pressure becomes small.

Therefore, the relationship between the corrected differential pressure and the trapped amount is influenced by the operating conditions during trapping and becomes as shown in FIG. Therefore, if the collected amount is detected as the correction differential pressure like the above-mentioned conventional one, the collected amount cannot be accurately detected, and a large error occurs in the collected amount detection. When such an error occurs, the regeneration control of the filter is not performed at an appropriate time, so that the regeneration temperature in the filter does not reach an appropriate temperature and stable regeneration cannot be performed.

The present invention has been made in view of the above problems, and it is an object of the present invention to detect a trapping amount more accurately in consideration of operating conditions.

[0006]

In order to achieve the above-mentioned object, in the invention described in claim 1, a filter (7) provided in an exhaust passage (4) of a diesel engine (1) for collecting particulates. And a differential pressure detection means (11-14, 502) for detecting a differential pressure (ΔP1) before and after the filter in the exhaust passage, and a particulate trap of the filter based on the detected differential pressure before and after the filter. A collection amount detecting means for detecting a collection amount, and in a diesel engine exhaust gas purification device configured to regenerate the filter when the detected particulate collection amount becomes a predetermined amount or more, Quantity detection means (502
˜507) are integrated values (ΣNe) obtained by integrating the number of revolutions of the diesel engine until the differential pressure is detected by the differential pressure detecting means and a reference integrated value (Σ) for the differential pressure.
Neref) and means (503-505) for obtaining the ratio, and based on the ratio of the integrated value and the differential pressure (ΔP1
× (ΣNeref / ΣNe)) The feature is that the trapped amount is detected.

According to a second aspect of the present invention, in the exhaust gas purification apparatus for a diesel engine according to the first aspect, the trapping amount detecting means is a ratio of the trapping amount according to the engine load to the ratio of the integrated value. Has a means (506) for obtaining a correction coefficient (α) indicating the above, and the correction coefficient obtained by this means is multiplied by the ratio of the integrated value and the differential pressure (ΔP1 × (ΣN
eref / ΣNe) × α) It is characterized by detecting the collection amount.

The symbols in parentheses for the above means are as follows:
It shows a correspondence relationship with a specific means described in the embodiments described later.

[0009]

According to the first and second aspects of the present invention, the integrated value obtained by integrating the number of revolutions of the diesel engine until the differential pressure is detected by the differential pressure detecting means and the reference integrated value for the differential pressure. And the collection amount is detected based on the ratio of the integrated value and the differential pressure.

Therefore, since the ratio of the integrated value corresponds to the operating condition up to the time of collection, the collected amount is detected based on the ratio of the integrated value and the differential pressure, so that the operating condition can be adjusted. It is possible to detect the collected amount. Further, in the invention described in claim 2, a correction coefficient indicating the ratio of the collection amount according to the engine load to the ratio of the integrated value is obtained, and the correction coefficient is multiplied by the ratio of the integrated value and the differential pressure to collect. I try to detect the quantity.

Therefore, by multiplying the ratio of the integrated value by the correction coefficient showing the ratio of the collected amount according to the engine load to the ratio of the integrated value, the ratio of the collected amount according to the engine load can be obtained. Based on this and the differential pressure, it is possible to accurately detect the trapped amount with correction for the deviation due to the difference in operating conditions.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an exhaust gas purification apparatus for a diesel internal combustion engine according to an embodiment of the present invention. An air cleaner 2 is provided on the intake side of the diesel engine 1,
A hot-wire type flow sensor 3 for detecting the intake flow rate is provided in the flow path from the air cleaner 2 to the diesel engine 1. Further, an engine speed sensor (engine speed detection means) 15 for detecting the speed (Ne) of the diesel engine 1 is provided.

The exhaust pipe 4 of the diesel engine 1 is provided with an exhaust purification device 5. This exhaust gas purification device 5
It has a housing 6 connected to the exhaust pipe 4,
A filter 7 made of porous ceramic is installed in the housing 6. When the exhaust gas passes through the filter 7, the fine particles contained in the exhaust gas are collected.

The diesel engine 1 side of the filter 7 is provided with a pressure sensor 11 for detecting an absolute pressure (pre-pressure) and a temperature sensor 13 for detecting an absolute temperature of exhaust gas (inlet gas temperature) flowing into the filter 7 from the diesel engine 1. Has been. Further, on the exhaust side of the filter 7, a pressure sensor 12 that detects an absolute pressure (post pressure) and a temperature sensor 14 that detects an absolute temperature of exhaust gas (gas temperature) flowing out from the filter 7 are provided.

Further, a heating device (electric heater) 8 for igniting the fine particles trapped in the filter 7 at the time of combustion regeneration of the filter 7 is installed in the filter 7, and the secondary air for combustion is also provided at the time of this combustion regeneration. An air pump 9 and a valve 10 for supplying the air are provided. Signals from the above sensors are input to an electronic control unit (ECU) 16. In order to prevent the filter 7 from being clogged, the ECU 16 detects the collection amount of fine particles in the filter 7, and when the collection amount reaches a certain value, the electric heater 8 is operated to collect the fine particles in the filter 7. The fine particles are ignited, the valve 10 is opened, and the secondary air for combustion is filtered from the air pump 9 by the filter 7.
Is controlled to burn and regenerate the filter 7.

Next, the concept of trapped amount detection in this embodiment will be described. As described above, the corrected differential pressure is obtained by correcting the pressure difference between the filters based on the exhaust temperature before and after the filter, the intake air amount, and the like. Here, the collection amount (hereinafter, referred to as a calibration curve) with respect to the corrected differential pressure is as shown in FIG.
Determined by engine load. Therefore, the deviation from the calibration curve when collected under the standard operating condition is determined by the ratio of the engine load to the standard load.

The relationship between the Ne integrated value and the corrected differential pressure when the operating condition during collection is used as a parameter is as shown in FIG.
The engine load can be specified from the Ne integrated value and the corrected differential pressure.
From the above two points, the deviation of the calibration curve from the reference value can be derived from the Ne integrated value and the corrected differential pressure. Therefore, by correcting the corrected differential pressure by the amount of deviation of the calibration curve from the reference value, it is possible to detect the trapped amount in consideration of operating conditions.

Next, an EC constructed based on the above examination
The operation of the exhaust emission control device according to the present embodiment will be described with reference to the flowchart of FIG. 5 showing the calculation process of U16.
FIG. 5 shows a calculation process of a regeneration timing determination routine for determining the regeneration timing of the filter 7. First, step 5
In 01, it is determined whether or not the reproduction is currently being performed, and if the reproduction is being performed, this routine is ended. If not playing, step 5
The arithmetic processing after 02 is executed.

In step 502, the intake air amount Ga, the front pressure P1, and the rear pressure P2 detected by the hot wire type flow sensor 3, the front pressure sensor 11, the rear pressure sensor 12, the inlet gas temperature sensor 13 and the outlet gas temperature sensor 14, respectively. , The exhaust gas temperatures Tin and Tout before and after the filter,
P (= P1-P2), filter internal temperature T [= (Ti
n + Tout) / 2] is used to calculate the corrected differential pressure ΔP1 using the equation 1.

[0020]

## EQU00001 ## .DELTA.P1 = .DELTA.P.multidot.f (Ga, T) Note that the method of calculating the corrected differential pressure .DELTA.P1 is known. In addition, the heat wire type flow sensor 3 and the incoming gas temperature sensor 1
3. The output gas temperature sensor 14 and the process for correcting the filter front-rear differential pressure ΔP based on the signals detected by the output gas temperature sensor 14 constitute a pressure difference correcting unit for correcting the filter front-rear differential pressure ΔP.

Although not shown in the drawing, the ECU 16 executes a routine different from that shown in FIG. 5 from the time when the filter 7 starts collecting (that is, the time when the filter 7 shifts to the collecting state after the regeneration is completed). Based on a signal from the engine speed sensor 15, the engine speed is integrated to calculate a current integrated value ΣNe. In step 503, the current integrated value ΣNe of the engine speed calculated in that routine is monitored.

In step 504, the correction differential pressure ΔP1 calculated in step 502, and the relational map between the Ne integrated value and the correction differential pressure when collected under the standard operating conditions stored in advance in the ECU 16 ( (Shown in FIG. 4), the reference integrated value ΣNeref when the correction differential pressure is collected up to ΔP1 under the standard operating conditions is calculated. And next step 5
At 05, ΣNeref / ΣNe is calculated. This indicates the ratio of the Ne integrated value when the gas is collected until it reaches the corrected differential pressure ΔP1 to the reference.

Next, in step 506, step 50
The ratio of the Ne integrated value when collecting until the corrected differential pressure ΔP1 calculated in 2 is obtained (ΣNeref / ΣN
e) is the ratio (PM / PMre) of the collection amount (particulate weight) to the correction differential pressure due to the difference in the composition of the particles caused by the difference in the operating condition (load) during collection
Find the coefficient α to convert to f).

This coefficient α is (PM / PMref) / (Σ
Neref / ΣNe), and the ECU 16
It is obtained by using a table in which ΣNeref / ΣNe is stored as a parameter. Next, in step 507, the collected amount PM is calculated by the equation 2.

[0025]

## EQU00002 ## PM = .DELTA.P1.times. (. SIGMA.Neref / .SIGMA.Ne) .times..alpha..beta..beta., Where .beta. Is the collection amount per unit correction differential pressure when collecting under the standard operating conditions. Next, in step 508, it is determined whether or not the trapped amount PM detected in step 507 is equal to or greater than the set value. If it is greater than or equal to the set value, step 509
Then, the reproduction control is instructed by a flag or the like, and the process shifts to the reproduction control process.

Since this regeneration control process is well known, its specific calculation process is not shown, but the electric heater 8 is operated to ignite the fine particles trapped in the filter 7, and the valve 10 is opened. The secondary air for combustion is supplied from the air pump 9 to the filter 7 so that the filter 7 is burned and regenerated. By performing the collection amount detection as described above, the weight of the fine particles is detected even if the fine particle component changes due to the operating condition at the time of collection, so that the regeneration control can be started at an appropriate time and the filter stability can be improved. Playback can be performed.

As shown in FIG. 4, since ΣNeref / ΣNe corresponds to the operating conditions up to that point, the process of step 506 is eliminated and ΔP1 × (ΣNe
Even if the collection amount is detected by a simplified arithmetic expression of (ref / ΣNe) × β, compared to the conventional one which does not consider the operating condition, the more accurate detection of the collected amount corresponding to the operating condition can be performed. It can be carried out.

Further, each step of the flowchart shown in FIG. 5 is configured as means for realizing each function.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing a relationship between a corrected differential pressure and a collection amount.

FIG. 3 is a characteristic diagram showing a relationship between a corrected differential pressure and a trapped amount when operating conditions are used as parameters.

FIG. 4 is a characteristic diagram showing a relationship between a Ne integrated value and a corrected differential pressure when operating conditions are used as parameters.

5 is a flowchart showing a calculation process of a regeneration timing determination routine in the ECU in FIG.

[Explanation of symbols]

1 ... Diesel engine, 4 ... Exhaust pipe, 5 ... Exhaust gas purification device, 7 ... Filter, 8 ... Electric heater, 9 ... Valve, 10
… Air pump, 15… Engine speed sensor, 16… E
CU.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Kato 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihondenso Co., Ltd.

Claims (2)

[Claims] 1. A filter provided in an exhaust passage of a diesel engine for collecting particulates, a differential pressure detecting means for detecting a differential pressure before and after the filter in the exhaust passage, and a difference before and after the detected filter. Diesel equipped with a collection amount detection means for detecting the particulate collection amount of the filter based on the pressure, and the filter is regenerated when the detected particulate collection amount becomes a predetermined amount or more. In the exhaust gas purifying apparatus for an engine, the trapped amount detecting means is a reference integrated value for the differential value and the integrated value obtained by integrating the number of revolutions of the diesel engine until the differential pressure is detected by the differential pressure detecting means. And a means for determining the ratio of the integrated value, and the trapped amount is detected based on the ratio of the integrated value and the differential pressure. Gas purification equipment. 2. The collection amount detection means has means for obtaining a correction coefficient indicating a ratio of the collection amount according to an engine load with respect to a ratio of the integrated value, and the correction coefficient obtained by this means is used as the correction coefficient. The exhaust emission control device for a diesel engine according to claim 1, wherein the trapped amount is detected by multiplying the ratio of integrated values and the differential pressure.