JPH07139334A - Exhaust gas purification device - Google Patents

Abstract

PURPOSE:To improve the high speed responsiveness of an exhaust gas temperature detection means by estimating a particulate collective quantity based on a corrective pressure loss where the pressure loss of the filter is corrected by an engine rotational speed, exhaust temperature, and acceleration opening, so as to discriminate the regeneration timing of the filter. CONSTITUTION:Exhaust gas discharged from diesel engine 20 is introduced into a case 1 from an exhaust pipe 3, and a particulates in exhaust gas are collected by a filter 2. A solenoid valve 14 is opened at the time of regenerating the filter 2. The particulate collective quantity is calculated by a controller 8 based on respective detection signals from an engine rotational speed sensor 18, an exhaust gas temperature sensor 6, and an acceleration opening sensor 19, etc. Thereafter a heater 11 and a blower 13 are respectively driven when the collective quantity exceeds a threshold value. The collected particulates are thus burned by heating by the heater 11 and air supply by the blower 13.

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 In a conventional exhaust gas purifying apparatus, when the amount of collected particulates reaches a certain level, a heater or a blower is energized in a predetermined order to burn the particulates.
Play the filter.

[0003]

The collected amount of particulates is corrected by the pressure loss of the exhaust gas in the filter to correct the exhaust gas condition, and the corrected pressure loss is calculated as follows. It can be obtained from the map as a value corresponding to the amount of collected particulates. Then, the corrected pressure loss, it is preferable to correct the pressure loss based on the engine speed and the exhaust gas temperature,
Furthermore, the inventors of the present invention calculate the volumetric efficiency of the engine from the rotational speed and the accelerator opening (fuel injection amount), and based on that, further correct the above-mentioned corrected pressure loss to calculate a more accurate particulate. is suggesting.

However, in the above-mentioned particulate trapping amount calculation method, if the exhaust gas temperature is not accurately detected, an error will occur in the calculated particulate trapping amount,
This will cause the filter to be melted and defective. On the other hand, a thermocouple type temperature detecting means is effective for this kind of high temperature measurement application, but it has a protective cover and has a response delay with respect to changes in exhaust temperature. There was a problem that the collected amount of particulates was inaccurate.
This problem also occurs in other types of temperature detecting means.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust gas purifying apparatus capable of improving the high-speed response of the temperature detecting means while avoiding the complication of the apparatus structure. It is a problem to be solved.

[0006]

An exhaust gas purifying apparatus according to the present invention comprises a filter arranged in an exhaust path of a diesel engine for collecting particulates discharged from the diesel engine, and the engine. Rotation speed detecting means for detecting the rotation speed of the filter, electric heating means disposed in the vicinity of the filter for regenerating the filter by burning the particulate by energization, and air is supplied to the filter at the time of regenerating the filter. Air supply means, pressure loss detection means for detecting pressure loss of the filter, temperature detection means arranged upstream of the filter for detecting exhaust temperature of the engine, and accelerator for detecting accelerator opening degree. An opening degree detection means and an exhaust gas temperature sudden change detection means for detecting a sudden change state of the exhaust gas temperature are provided, and the exhaust gas temperature and the rotation are measured when the exhaust gas temperature is stable. The corrected pressure loss is calculated by correcting the pressure loss based on the number, and the corrected pressure loss is calculated by correcting the pressure loss based on the accelerator opening and the rotational speed when the exhaust temperature suddenly changes. It is characterized by comprising a corrected pressure loss calculating means and a filter regeneration timing determining means for determining a filter regeneration timing based on the corrected pressure loss.

In a preferred mode, the exhaust temperature sudden change detection means detects the sudden change in the engine speed.

[0008]

According to the present invention, the particulate collection amount is estimated based on the corrected pressure loss obtained by correcting the pressure loss of the filter with the engine speed, the exhaust temperature and the accelerator opening degree, and the estimated collection amount is estimated. The reproduction time is determined based on. Further, when a sudden change in exhaust gas temperature is detected, the exhaust gas temperature is not used, and the pressure loss is corrected by the accelerator opening and the rotational speed to calculate the corrected pressure loss.

With this configuration, it is possible to prevent an error in calculation of the amount of trapped particulates from occurring due to a temperature detection error caused by a response delay of the temperature detection means when the exhaust temperature suddenly changes.
It is possible to accurately determine the filter regeneration time, and it is possible to avoid problems such as filter damage and regeneration failure caused by the above calculation error.

[0010]

FIG. 1 shows an embodiment of an exhaust gas purifying apparatus according to the present invention.
Shown in. This exhaust gas purifying apparatus has a filter housing case 1 whose both ends are hermetically sealed, and an upstream side pressure sensor for detecting exhaust pressure (pressure loss detecting means in the present invention) from the upstream side to the downstream side in the filter housing case 1. ) 7, a temperature sensor (temperature detection means) 6, a heater (electric heating means) 11, a filter 2, and a downstream pressure sensor (pressure loss detection means in the present invention) 17 for detecting filter downstream pressure are arranged in order. . The exhaust pipe 3 of the diesel engine 20 is arranged on the upstream end wall of the filter housing case 1.
The air supply pipe 10 is branched from the middle of. The air supply pipe 10 is connected to an outlet of a blower 13 for supplying air via an opening / closing valve 14. Reference numeral 15 is an air supply flow rate detection sensor used for feedback controlling the air supply flow rate of the blower 13.

On the other hand, the above-mentioned heater 11, on-off valve 14,
The blower (air supply means) 13 is drive-controlled by a controller (corrected pressure loss calculation means, filter regeneration timing determination means, exhaust gas temperature sudden change detection means in the present invention) 8. Also,
For the diesel engine 20, a rotation speed sensor (rotation speed detecting means in the present invention) 18 and an accelerator opening sensor (accelerator opening detecting means, here, an injection amount sensor of the fuel injection device is used as a substitute, but the accelerator opening is performed. 9 may be directly detected), and their output signals are output to the controller 8.

The controller 8 is equipped with a microcomputer (not shown) with a built-in A / D converter, processes various data, controls the heater 11, the on-off valve 14 and the blower 13 to execute regeneration, thereby generating an abnormality. Occasionally, the abnormality alarm lamp 9 is turned on. Reference numeral 91 is a reproduction time display lamp. Filter 2
Is a honeycomb ceramic filter (manufactured by Nippon Insulator kk, diameter 5.66 inches × length 6 inches), which is a porous core.
It is fired into a cylindrical shape using gellite as a material. The filter 2 has a large number of ventilation holes penetrating both end surfaces 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.

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 applied to the high end of each of the heater 11 and the blower drive motor M, and the low end of the heater 11 is grounded through the relay switch 56. The lower end of the relay is grounded through the relay switch 55.

The heater 11 is composed of an electrothermal resistor made of nichrome wire, and is arranged close to the end face of the filter 2 which is located on the upstream side during regeneration. 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 Regeneration Operation) The regeneration operation of the filter 2 will be described with reference to the flowchart 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. This filter regeneration operation is performed by a filter regeneration determination routine (steps 100 to 11) performed during engine operation.
1) and a filter regeneration execution routine (steps 112 to 116) executed while the engine is stopped.

First, the filter regeneration discrimination routine will be described. When the engine 20 is started, the filter regeneration determination routine is started, and in step 100, the exhaust pressures P1 and P2 detected by the pressure sensors 7 and 17, the engine rotation speed n detected by the rotation speed sensor 18, and the temperature sensor 6 are detected. Based on the detected exhaust gas temperature T and the accelerator opening A detected by the accelerator opening sensor 19, the particulate amount is determined.
Calculate the collected amount.

The calculation of the amount G of collected particulates is
This will be described in detail with reference to the subroutine of FIG. First, in step 1001, the engine speed sensor 18, the pressure sensors 7 and 17, the temperature sensor 6, and the accelerator opening sensor 19 provided in the engine 20 are used to exhaust gas pressure P1 on the upstream side of the filter and exhaust gas P1 on the downstream side of the filter. The atmospheric pressure P2, the rotation speed n, the exhaust gas temperature T, and the accelerator opening A are input.

At the next step 200, a later-described subroutine (exhaust temperature sudden change detection means in the present invention) corresponding to the exhaust temperature sudden change, which is a feature of this embodiment, is executed. In the next step 1002, the corrected differential pressure ΔPeqi is obtained by the following correction formula 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. .

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.

In 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.
The steps 1003 and 1004 can be omitted.

In the next step 1006, an average of the 64 calculated values immediately before, out of the corrected differential pressures ΔPeqi ′ input every 50 msec in the past, is calculated, and this is set as the average corrected differential pressure ΔPeqm. Next, in step 1007, 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. And then returns 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. If it does not exceed, the process returns to step 100, and if it exceeds, the process returns to step 111. move on. In step 111, the lamp 91 for instructing filter regeneration is turned on, and the routine ends.

After that, when the driver visually recognizes the lighting of the lamp 91 for instructing the filter regeneration and turns on the 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), and the heater 11 and the blower 13 are timer-controlled in a predetermined order to perform the regenerating operation (11
6) The reproduction is ended.

Next, the subroutine 200 for sudden temperature change, which is the main part of this embodiment, will be described with reference to the flowchart of FIG. First, in step 2002, it is checked whether the engine speed n exceeds 1300 rpm or more. If it is below, it is determined that there is no sudden change in exhaust temperature, and the process returns to step 1002. The maximum value nmax and the minimum value nmin of the engine speed n for 7 seconds are extracted (200
4). Note that this subroutine is executed about every 50 msec, each data of the read engine speed n is held in the register for 7 seconds, and the maximum value nmax and the minimum value nmin are extracted from the held data. And

Next, the rotational speed change Δn = in the past 7 seconds
nmax-nmin is calculated (2006), and it is checked whether or not this rotation speed change Δn is larger than 50 rpm (20
08), if it is below, it is determined that there is no sudden change in temperature change, and the process returns to step 1002. On the other hand, if Δn exceeds 50 rpm in step 2008, it is determined that the temperature sudden change has occurred, and the exhaust temperature Ta corresponding to the current engine speed n and accelerator opening A is searched from the map. (2010).

Next, the corrected pressure loss ΔPeqi is calculated based on the searched exhaust temperature Ta and the engine speed n (2012), and the process returns to step 1003. The calculation of the corrected pressure loss ΔPeqi is the same as in the case of step 1002, and the pressure loss ΔP = P1−P of the filter 2
For 2, the correction differential pressure ΔPeqi is calculated by the following correction formula.
The calculation formula is ΔPeqi = ΔP × (523 / Ta) × (2600 /
n).

The map used in the above step 2008 is a three-dimensional map, and the value of the exhaust gas temperature Ta for each value of the engine speed n and the accelerator opening A is stored. That is, here, the exhaust gas temperature Ta is determined by the engine speed n and the accelerator opening A (or the fuel injection amount). Of course, the exhaust temperature Ta may be further corrected by parameters such as the outside air temperature and the elapsed time from the start of engine operation.

In this embodiment, the change in the number of revolutions is measured for 7 seconds, but this is set based on the delay time constant of the temperature sensor 6 composed of a thermocouple, but it can be changed as a matter of course. By doing so, the exhaust temperature T detected when the temperature suddenly changes and estimated from the accelerator opening A and the rotational speed n instead of the temperature detected by the temperature sensor 6 when the temperature suddenly changes
Since a is adopted, it is possible to prevent erroneous estimation of the particulate trapped amount due to the response delay of the temperature sensor 6.

Further, in this embodiment, since the judgment of the sudden temperature change is detected by the sudden change of the engine speed n, the rapid temperature change can be detected accurately and easily. In the above embodiment, the exhaust gas temperature Ta is estimated from the accelerator opening or the state quantity A corresponding to the accelerator opening amount and the rotation speed n, and the exhaust gas temperature Ta is estimated.
Although the pressure loss ΔP is corrected based on the above, it is also possible to directly correct ΔP from these A and n using a three-dimensional map of A and n and ΔP.

[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 a subroutine for sudden temperature change.

[Explanation of symbols]

2 is a filter, 6 is a temperature sensor (temperature detecting means), 7,
Reference numeral 17 is a pressure sensor (pressure loss detection means), 8 is a controller (correction pressure loss calculation means, regeneration timing determination means, exhaust gas temperature sudden change detection means), 11 is an ignition heater (electric heating means), and 13 is a blower (air supply means). ), 18 is a rotation speed sensor (rotation speed detection means), and 19 is an accelerator opening sensor (accelerator opening detection means).

Claims (2)

[Claims] 1. A filter disposed in an exhaust path of a diesel engine for collecting particulates discharged from the diesel engine; a rotation speed detecting means for detecting a rotation speed of the engine; An electric heating means disposed near the filter to regenerate the filter by burning the particulate by energization, an air supply means for supplying air to the filter when the filter is regenerated, and a pressure loss of the filter is detected. Pressure loss detecting means, a temperature detecting means arranged upstream of the filter for detecting the exhaust temperature of the engine, an accelerator opening detecting means for detecting an accelerator opening, and a sudden change state of the exhaust temperature. Exhaust gas temperature sudden change detection means for detecting, and filter regeneration timing determining means for determining filter regeneration timing based on the corrected pressure loss. Exhaust gas purifying device, characterized in that. 2. The exhaust gas purifying apparatus according to claim 1, wherein the exhaust gas temperature sudden change detecting means detects the sudden change in the engine speed.