JP2002180821A - Method for controlling diesel particulate filter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a diesel particulate filter device to enable the use of an inexpensive pressure sensor and reduce a temperature influence besides and high efficient purification of exhaust gas by using a clogging deciding value capable of high-precisely estimating a clogging state of a filter approximately in the whole area of the operation state of an engine. SOLUTION: In a diesel particulate filter device to purify exhaust gas G as collection and regeneration are repeated by a plurality of filters 11A and 11B interconnected through a passage switching means 20 on the side situated downstream of an exhaust passage 2, a clogging decision value for operation of the passage switching means 20 is set to a pressure index (Cp=P1/(P1-P2)) dividing a first pressure (P1) by a difference pressure (P1-P2) the first pressure P1 upper stream from the passage switching means 20 and a second pressure P2 between the passage switching means 30 and a filter 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel particulate filter (D) for collecting particulates (PM) of an internal combustion engine such as a diesel engine.
PF) A method for controlling a device.

[0002]

2. Description of the Related Art Conventionally, exhaust gas discharged from a diesel engine mounted on a vehicle or the like contains particulate matter called particulate matter (PM), and a diesel particulate filter (DP) is used to remove the particulate matter.
F) Apparatus is used.

[0003] In this diesel particulate filter device, a plurality of filters made of non-woven fabric such as ceramic fiber such as alumina are mounted on the downstream side of the exhaust of a diesel engine, and the exhaust gas is alternately passed through the filter to remove the particulates discharged from the engine. Collect curate.

[0004] That is, as shown in FIG. 3, this diesel particulate filter device 10X comprises two first
A first filter is formed having a filter 11A and a second filter 11B.
First inlet-side branch passage 12A communicating with filter 11A
And the second inlet-side branch passage 12B communicating with the second filter 11B.

[0005] An upstream pressure sensor 31 is provided in the exhaust gas passage 2 upstream of the switching valve 20, and a first outlet branch passage 13A downstream of the first filter 11A is provided in the first outlet branch passage 13A.
The downstream pressure sensor 33A is connected to the second filter 11B.
The second downstream-side pressure sensor 33B is disposed in the second outlet-side branch passage 13B on the downstream side.

Further, each of the pressure sensors 31, 33A, 33B
The outputs P1, P3A and P3B are input to control the switching valve 20 and to control the power supplied to the heater electrode 13A for regeneration of the first filter 11A and the heater electrode 13B for regeneration of the second filter 11B. A control device 40 for performing control is provided.

Then, the differential pressure before and after the first filter 11A (DpA = P1-P3A) and the differential pressure before and after the second filter 11B (DpB = P1-P3B), or the pressure ratio before and after (RpA = P1 / P1) P3A) and (RpB = P1 / P3
When each of B) reaches a predetermined determination value, it is determined that the filter 11A or 11B has become clogged, the flow of exhaust gas is switched, and the clogged filter 11A or 11B is heated and collected. The burned particulates are incinerated to regenerate the filter 11A or 11B.

However, when the clogging of the filter is determined based on the differential pressure Dp before and after the filter, the operation state of the engine changes moment by moment, so that there is a problem that the control is complicated, and the filter before and after the filter is complicated. Is determined based on the pressure ratio Rp.

[0009]

However, even in the case where clogging is detected and determined by the pressure ratio Rp before and after the filter, the pressure on the downstream side of the filter is about 0 Pa to
Since the pressure is as low as about 70 Pa (about 0 mmHg to 7 mmHg), there are the following problems.

First, in the case where the engine is operating while idling or performing EGR under a load of 20% or less, about 10 Pa or less, which is equal to or less than the lower limit of the measurement of the pressure sensor.
(Approximately 1 mmHg) or less, there is a problem that the clogged state cannot be detected and the operating range of the engine that can detect the clogged filter is narrow.

Further, the pressure on the downstream side is lower than the pressure on the upstream side of the filter by about one fifth to one tenth, so that the measurement of the pressure on the downstream side requires high precision. Since the pressure sensor described above is required, there is a problem that the cost is increased.

Further, there is a problem that an error due to the temperature is large with respect to the pressure value in the use range, and it is difficult to accurately estimate the clogged state of the filter. For example,
The measurable range is about 0 kPa to 6.5 kPa (about 0 mm
Hg to 50 mmHg) and the operating pressure range is about 0 kPa
In a pressure sensor of 0.9 kPa (approximately 0 mmHg to 7 mmHg), an error of approximately 0.3 kPa (approximately 2.5 mmHg) may occur depending on a use temperature, and an error of a determination value of clogging increases.

Furthermore, the pressure downstream of the filter is about 0 P
a to 70 Pa (approximately 0 mmHg to 7 mmHg), and when the shape of the tail pipe provided on the downstream side of the filter changes, the pressure on the downstream side changes. Is different from the condition of the actual vehicle, it is necessary to confirm the validity of the determination value by actually running a test after mounting the diesel particulate filter device on the actual vehicle, which is not suitable for mass production.

In particular, it is necessary to set a different judgment value for each change in the vehicle type in which the shape of the tail pipe changes.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to use an inexpensive pressure sensor, have a small influence on temperature, and cover almost the entire operating state of the engine. By using a clogging determination value capable of accurately estimating the clogging state of the filter, the filter that collects particulates and the filter that burns and removes and collects the collected particulates are alternately switched, and the exhaust gas is removed. An object of the present invention is to provide a method for controlling a diesel particulate filter device that can efficiently purify the diesel particulate filter device.

[0016]

A control method for a diesel particulate filter device for achieving the above object has a plurality of filters connected downstream of an exhaust passage via passage switching means. A diesel particulate that captures particulates in exhaust gas while alternately switching a filter that captures particulates in exhaust gas and a filter that burns the captured particulates by the passage switching means. In the filter device, a clogging determination value for switching the filter is determined by a first pressure (P1) upstream of the passage switching means of the exhaust passage provided upstream of the filter and the passage switching. The pressure difference (P1-P2) from the second pressure (P2) in the exhaust gas passage between the means and the filter collecting particulates. Configured to the first pressure (P1) divided by the pressure exponent (Cp = P1 / (P1-P2)).

With this configuration, the pressure index Cp exhibits the same behavior as the pressure ratio Rp before and after the filter as shown in FIG. 2, so that clogging detection similar to the pressure ratio Rp can be performed using a low-cost pressure sensor. Can be done using

The pressure used in the pressure index Cp is the pressure on the upstream side of the filter, and the value of the pressure is larger than the pressure on the downstream side of the filter used in the prior art.

Therefore, the measurement can be performed accurately with an inexpensive sensor, and the clogging of the filter can be detected in almost the entire operating state of the engine.

In addition, in the case of the pressure index Cp, the influence of the pressure measurement error due to the temperature of the pressure sensor is reduced, so that the clogging of the filter can be accurately determined.

Furthermore, even if the shape of the tail pipe downstream of the filter changes, the numerical value of the pressure index Cp at the time of clogging is small, and the clogging upper limit value is determined using the clogging determination value of the bench test. Cp0 can be set. Therefore, it is not necessary to adjust the set value for each actual vehicle, and the vehicle can be shipped immediately. In addition, since the influence of the difference in the shape of the tail pipe depending on the vehicle type is small, the setting change of the determination value due to the difference in the vehicle type can be omitted.

In the method for controlling the diesel particulate filter device, a numerical value used as the clogging determination value is a numerical value obtained by moving-averaging the pressure index during a predetermined time or a predetermined count number.

By using the moving average value, clogging can be determined with higher accuracy.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for controlling a diesel particulate filter device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a device and the arrangement of pressure sensors in a method for controlling a diesel particulate filter device according to an embodiment of the present invention.

[Configuration of Diesel Particulate Filter Apparatus] As shown in FIG. 1, this diesel particulate filter apparatus 10 includes two first filters 11
A and a second filter 11B, and a first inlet-side branch passage 12A communicating with the first filter 11A through a switching valve (passage switching means) 20 to the exhaust passage 2 of the engine.
And the second inlet-side branch passage 12B communicating with the second filter 11B.

That is, the exhaust passage 2 is connected to the first inlet side branch passage 1
2A and a second inlet-side branch passage 12B, and a switching valve 20 is arranged at the branch point so that a passage communicating with the exhaust passage 2 can be switched.

An upstream pressure sensor 31 is disposed in the exhaust gas passage 2 upstream of the switching valve 20, and a first inlet downstream of the switching valve 20 and upstream of the first filter 11A. The first inlet pressure sensor 3 is connected to the side branch passage 12A.
2A, and a second inlet pressure sensor 32B in the second inlet branch passage 12B downstream of the switching valve 20 and upstream of the second filter 11B.

The pressures P2A, P2B measured by the first inlet side pressure sensor 32A and the second inlet side pressure sensor 32B.
Is less affected by the shape of the tail pipe provided on the downstream side of the first filter 11A and the second filter 11B, and the value itself is substantially the same order as the measurement value P1 of the upstream pressure sensor 31. Therefore, although it is an example, the working pressure range is about 2.6 kPa to 29.9 kPa.
(About 20 mmHg to 230 mmHg), and the measurable range is about 0 kPa to 39 kPa (about 0 mmHg to 30 kPa).
0 mmHg) pressure sensor can be used.

Each of the pressure sensors 31, 32A, 32
B outputs P1, P2A and P2B as inputs and the switching valve 20
Control device 40 for controlling the power supply to the heater electrode 13A for regenerating the first filter 11A and the heater electrode 13B for regenerating the second filter 11B.
Is provided. The control device 40 is usually incorporated in a part of an engine controller (ECU) that controls the entire engine.

[Control Method of Diesel Particulate Filter Device] In this diesel particulate filter device 10, whether the first filter 11A is clogged is determined by an upstream pressure value P1, which is a pressure detected by the upstream pressure sensor 31, and The differential pressure (P1) with the downstream first pressure value P2A
-P2A), the first pressure index CpA (= P1 / (P1-P2A)) obtained by dividing the upstream pressure value P1.

The clogging of the second filter 11B is determined by dividing the upstream pressure value P1 by the differential pressure (P1−P2B) between the upstream pressure value P1 and the downstream second pressure value P2B. It is performed with a pressure index CpB (= P1 / (P1-P2B)).

Further, with respect to the first pressure index CpA and the second pressure index CpB, a predetermined time (for example, 30 s to 1
The clogging can be determined with higher accuracy than when a moving average of about 80 s) or a predetermined count number is employed.

That is, when the switching valve 20 is operated so that the exhaust passage 2 communicates with the first inlet-side branch passage 12A, and the first filter 11A collects particulates, the first pressure index increases. Until CpA exceeds a predetermined determination value Cp0, particulate collection is continued, and the first pressure index C
When pA exceeds a predetermined determination value Cp0, the exhaust passage 2
Is connected to the second inlet-side branch passage 12B.
0 to operate the second filter 1
1B, power is supplied to the heater electrode 13A of the first filter 11A to heat the first filter 11A and burn and remove the collected particulates.

At this time, it is necessary to supply oxygen for the combustion of the particulates. This is achieved by supplying air to the first filter 11A by an air pump (not shown), or by using the switching valve 20 to supply the inlet-side branch passages 11A and 12B. Is performed by partially supplying the exhaust gas G to the first filter 11A without completely closing the first filter 11A.

Next, when the second pressure index CpB exceeds a predetermined judgment value Cp0, the switching valve 20 is operated so as to connect the exhaust passage 2 to the first inlet side branch passage 12A, and the The curated collection is performed by the first filter 11A, and electric power is supplied to the heater electrode 13B of the second filter 11B to heat the second filter unit 11B to burn and remove the collected particulates.

By repeating this, the particulates in the exhaust gas G are continuously collected, and the purified gases Gc are discharged by burning and removing the particulates.

Next, FIG. 2 shows the above-mentioned pressure index Cp (= P1 / (P1-P
The change of 2)) and the change of the pressure ratio Rp in the related art are shown in comparison. (Cp is CpA, CpB, Pp
2 represents P2A and P2B as representatives, respectively. 2) The pressure index Cp in FIG. 2 shows almost the same behavior as the pressure ratio Rp, and it can be seen that the clogging determination of the filter can be performed substantially the same as the pressure ratio Rp by using the pressure index Cp.

Therefore, according to the above-described control method for the diesel particulate filter device, clogging of the first filter 11A and the second filter 11B can be detected in almost the entire operating state of the engine, and the shape of the tail pipe can be detected. Changes in the value of the pressure index Cp at the time of clogging is small, so that the clogging upper limit value Cp0 can be set using the clogging judgment value in the bench test performed in advance, so that it is shipped immediately. It becomes possible.

Further, the influence of the pressure measurement error due to the temperature of the pressure sensors 31, 32A, 32B is reduced in the form of the pressure index Cp, and the influence of the error due to the temperature is reduced.

Therefore, the measurable range is about 0 kPa to 3 kPa.
At 9 kPa (about 0 mmHg to 300 mmHg), the operating pressure range is about 2.6 kPa to 29.9 kPa (about 20 to 2
In a pressure sensor having a pressure of 30 mmHg, an error of about 0.4 kPa (about 3 mmHg) may occur depending on the operating temperature, but such a pressure sensor can also be used.

[0042]

As described above, according to the method for controlling a diesel particulate filter device according to the present invention, the following effects can be obtained.

First, since the pressure used in the pressure index is the pressure on the upstream side of the filter, the value of the pressure is larger than the pressure on the downstream side of the filter used in the prior art. Can be measured with high accuracy, and clogging of the filter can be detected in almost the entire operating state of the engine.

Further, since the influence of the pressure measurement error due to the temperature of the pressure sensor is reduced in the form of the pressure index, the influence of the error due to the temperature can be reduced, and the clogging of the filter can be accurately determined.

In addition, even if the shape of the tail pipe changes, the change in the numerical value of the pressure index at the time of clogging is small.
By using the clogging judgment value in the bench test that was performed in advance,
Since the upper limit of clogging can be set, it can be shipped immediately. Further, since the influence of the difference in the shape of the tail pipe depending on the vehicle type is small, it is possible to omit the change in the setting of the determination value due to the difference in the vehicle type.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a device and an arrangement of a pressure sensor in a control method of a diesel particulate filter device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a pressure index Cp according to the present invention and a pressure ratio Rp used in the related art.

FIG. 3 is a schematic configuration diagram showing a configuration of a device and an arrangement of a pressure sensor in a conventional method for controlling a diesel particulate filter device.

[Explanation of symbols]

 2 Exhaust passage 10 Diesel particulate filter device 11A First filter 11B Second filter 20 Switching valve (passage switching means) P1 First pressure P2, P2A, P2B Second pressure Cp, CpA, CpB Pressure index (clogging determination value) G Exhaust gas Gc Purified gas

Claims (2)

[Claims] 1. A filter for collecting particulates in exhaust gas, comprising: a plurality of filters connected downstream of an exhaust passage via a passage switching means; and a filter for performing a combustion process on the collected particulates. In a diesel particulate filter device that captures particulates in exhaust gas while alternately switching between them by the passage switching means, a clogging determination value for switching the filter is set to an upstream side of the filter. A first pressure (P1) on the upstream side of the passage switching means of the provided exhaust passage, and a second pressure (P1) of an exhaust gas passage between the passage switching means and a filter for collecting particulates. P2) and differential pressure (P1)
-P2), wherein a pressure index (Cp = P1 / (P1-P2)) obtained by dividing the first pressure (P1) is obtained. 2. The diesel particulate filter according to claim 1, wherein the numerical value adopted as the clogging determination value is a numerical value obtained by moving-averaging the pressure index during a predetermined time or a predetermined count number. How to control the device.