JP3116549B2 - Engine exhaust purification device - Google Patents

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 a diesel engine.

[0002]

2. Description of the Related Art There is an exhaust gas purifying apparatus in which an exhaust passage of a diesel engine is branched into a plurality of passages, each of which is provided with a filter for trapping fine particles (particulates) such as carbon in exhaust gas.

[0003] When the filter is regenerated, the valve in the corresponding passage is closed so that exhaust gas does not flow through the filter, and a temperature increasing device such as a heater provided in the filter is operated, thereby accumulating on the filter. The particulates are burned and removed. At this time, the exhaust gas is passed through another filter to collect the particulates at all times (JP-A-59-20515, JP-A-59-85417, 63-134808, etc.).

[0004]

However, in such a conventional apparatus, in order to determine the regeneration time of each filter,
A pressure sensor is provided for each filter, whereby the amount of accumulated particulates in each filter is detected to determine the regeneration time. Therefore, an increase in the number of pressure sensors increases the cost. .

[0005] On the other hand, there is a type in which the pressure of the entire filter is detected by a single pressure sensor and the regeneration of each filter is sequentially performed. In this case, the determination of the regeneration timing for each filter is ambiguous. Becomes In other words, it is possible to detect the regeneration time by increasing the sum of the pressures of a plurality of filters. However, considering individual filters, even when almost the same amount of particulates is deposited on the plurality of filters, a certain Even if a large amount of particulates accumulates in the filter, the same phenomenon will occur. Therefore, detecting the regeneration time of a plurality of filters with one pressure sensor is not always an appropriate detection considering the regeneration of each filter. Can not do. For this reason, the filter is overheated by starting the regeneration in a state where the accumulation amount is excessive, or the efficiency is deteriorated by performing the regeneration when the accumulation amount is small, and the fuel efficiency is also deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exhaust gas purifying apparatus capable of judging the amount of particulates accumulated in each filter without using a pressure sensor, and accurately regenerating each filter.

[0007]

According to the present invention, as shown in FIG. 1, filters 3 and 4 for collecting particulates in exhaust gas are interposed in a plurality of branch exhaust passages 1 and 2, respectively. Means for detecting the operating condition of the engine; and means for detecting the operating condition of the engine; And a collection control means 1 for operating the valve devices 7 and 8 to flow exhaust gas to all the filters 3 and 4 when the regeneration conditions are not satisfied.
1, a particulate distribution ratio calculating means 12 for calculating a distribution ratio of the particulates distributed and flowing into each of the filters 3 and 4 based on the accumulated amount of the particulates in each of the filters 3 and 4; Filters 3 and 4 based on curated distribution ratio
New deposition amount calculating means 13 for calculating the particulate new deposition amount, and particulate deposition amount calculating means 14 for calculating the particulate deposition amount of each of the filters 3 and 4 based on the particulate deposition amount and the new deposition amount. When the amount of accumulated particulates reaches a predetermined value, the temperature of the corresponding filter is raised and the temperature raising devices 5, 6,
Filter regeneration means 15 for operating the valve devices 7 and 8 is provided.

[0008]

According to the present invention, the exhaust gas of the engine is distributed into and flows into each of the filters which are not being regenerated in accordance with the passage resistance of each of the filters based on the amount of particulates already deposited on each of the filters.

That is, the particulates discharged from the engine are distributed and collected by the respective filters in accordance with the branch ratio of the exhaust gas, and are accumulated.

Thus, the amount of particulate emissions of the engine is determined based on the operating conditions of the engine, the distribution ratio of particulates is determined based on the amount of accumulated particulates in each filter, and the distribution ratio of particulates is determined based on the distribution ratio of particulate emissions and particulates. By calculating the new deposition amount of the filter, the particulate deposition amount of each filter is calculated based on the existing deposition amount and the new deposition amount. By operating the temperature raising device and the valve device to raise the temperature of the filter and restrict the flow of exhaust gas to the filter, the filter can be properly regenerated.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, reference numeral 20 denotes a diesel engine (engine body), and reference numeral 21 denotes an exhaust passage.

The exhaust passage 21 is branched in the middle into two parts.
Filters 24 and 25 for collecting particulates are interposed in the branch exhaust passages 22 and 23, respectively.

The filters 24 and 25 are formed of a porous ceramic foam or the like, and heaters 26 and 27 as heating devices are installed around the filters 24 and 25, respectively.

Upstream of the filters 24 and 25, the branch exhaust passages 22 and 23 are respectively provided with an on-off valve 2 as a valve device.
8, 29 are interposed.

At the rear of the filters 24 and 25, temperature sensors 30 and 31 for detecting the temperatures of the filters 24 and 25 are provided.

On the other hand, the engine operating condition detecting means includes a rotational speed sensor 32 for detecting the rotational speed of the engine, an accelerator opening sensor 33 for detecting the opening of the accelerator, a water temperature sensor 34 for detecting the cooling water temperature of the engine, and the like. These signals are provided to the control unit 35 together with the signals from the temperature sensors 30 and 31.

The control unit 35 is composed of a microcomputer, and controls the open / close valves 28 and 29 and the heaters 26 and 27 based on signals from the respective sensors.

Next, the control contents of the control unit 35 will be described with reference to the flowcharts of FIGS.

First, in S101 and S102, the engine speed Ne and the accelerator opening / closing C / L are read, and the engine speed per unit time is obtained from a map set as shown in FIG. 6 based on the engine speed Ne and the accelerator opening / closing C / L. To find the total emission of particulates. In this case, depending on the characteristics of the engine, if the particulate emission amount differs between the time of cooling and the time of warming up, the particulate emission amount correction value set as shown in FIG. 9 based on the water temperature is read out, and the particulate emission amount is determined. to correct.

In step S103, the amounts of the particulates deposited on the filters 24 and 25 are read from the memory storing the previous values. After the end of the reproduction, a predetermined initial value is set.

In step S104, a distribution ratio of the particulates (with reference to the filter 24) is retrieved from a distribution ratio map set as shown in FIG. 7 based on the accumulated amounts of the particulates in the filters 24 and 25.

The passing resistance of the filters 24 and 25 is determined by the amount of particulates accumulated in the filters 24 and 25, and the exhaust of the engine is diverted to the filters 24 and 25 according to the passing resistance. The distribution ratio of the particulates of the filters 24 and 25 can be obtained from the amount of deposition.

When the filter is being reproduced, the distribution ratio between the filter being reproduced and the filter not being reproduced is 0: 1.
It is.

In step S105, the amount of particulates discharged from the engine, the distribution ratio of particulates, and the amount of particulates deposited on the filters 24 and 25 are determined.
The amount of particulates deposited on the filters 24 and 25 is calculated.

In this case, the filter 2 is determined from the particulate emission amount of the engine and the distribution ratio of the particulate.
A new particulate accumulation amount of the filters 24 and 25 that are distributed and collected by the filters 4 and 25 is obtained, and this is added to the already-deposited amount to obtain a particulate accumulation amount of the filters 24 and 25.

When the particulate emission amount of the engine is, for example, S, if the distribution ratio is 0.5, the new accumulation amount of the filter 24 is 1, and the new accumulation amount of the filter 25 is 0.5. The new deposition amount of the filter 24 is 2 / 3S, and the new deposition amount of the filter 25 is 1 / 3S.

When the filter is being regenerated, the discharged particulates are collected and deposited on the filter that is not being regenerated. By adding the particulate discharge amount to the already deposited amount, the particulate matter of the filter that is not being regenerated is added. The amount of curated deposition is determined.

The amount of newly deposited particulate is corrected by the collection efficiency based on the operating conditions of the engine, the state of the particulate, and the like.

Steps S106 to S108 show a routine for subtracting accumulated particulates during the regeneration of the filter and when the temperature of the exhaust gas is high (high rotation and high load range).

In S106 and S107, the temperature sensor 30,
The temperature of the filters 24 and 25 is read from 31, and the reproduction amount (per unit time) of the filters 24 and 25 is searched from the reproduction speed map set as shown in FIG.

In S108, the regeneration amount of the filters 24 and 25, that is, the amount of particulate incineration is corrected by the accumulation amount and the like, and the regeneration amount of the filters 24 and 25 is obtained.

Next, in step S109, the regeneration amount of the filters 24 and 25 is subtracted from the particulate accumulation amount of the filters 24 and 25 obtained in step S105, to obtain the total particulate accumulation amount of the filters 24 and 25.

Steps S110 to S113 are for judging the reproduction start time and the reproduction end time of the filter 24.
4 is compared with a predetermined regeneration start threshold value, and when the total particulate amount exceeds the regeneration start threshold value, the regeneration flag of the filter 24 is set so that the filter 24 is regenerated. Set A.

Further, the total amount of particulates accumulated in the filter 24 is compared with a predetermined regeneration end threshold value. When the total amount of particulates falls below the regeneration end threshold value, regeneration of the filter 24 is terminated. , Filter 2
4 is reset.

Steps S114 to S117 determine the start time and the end time of the regeneration of the filter 25.
5 is compared with a predetermined regeneration start threshold value. If the total particulate accumulation amount exceeds the regeneration start threshold value, the regeneration flag of the filter 25 is controlled so that the filter 25 is regenerated. Set B.

Further, the total amount of particulates accumulated in the filter 25 is compared with a predetermined regeneration end threshold, and when the total amount of particulates falls below the regeneration end threshold, regeneration of the filter 25 is terminated. , Filter 2
5 is reset.

Then, the engine operating conditions are determined in S118.
Proceeding to 4, the on / off valves 28, 29 of the filters 24, 25 are closed according to the setting of the regeneration flags A, B, and the heaters 26, 27 of the filters 24, 25 are energized.

On the other hand, in the high rotation and high load range, S125
The process proceeds to １２８128, and regardless of the regeneration flags A and B, the open / close valves 28 and 29 are opened (normal state), and the heaters 26 and 27 are turned off (normal state).

As described above, the discharged particulates are collected by the filters 24 and 25,
25, the distribution ratio of the discharged particulates is determined from the exhaust gas diverted according to the particulate deposition amount of each of the filters 24 and 25, and each filter is determined based on the particulate new deposition amount determined from the distribution ratio. Since the amount of accumulated particulates of the filters 24 and 25 is obtained, each filter 24 and 25 can be used without using a pressure sensor or the like.
The amount of accumulated particulates can be accurately grasped.

Accordingly, the regeneration timing of each of the filters 24 and 25 can be set accurately, and the regeneration is started in a state where the accumulation amount is excessive as in the conventional example, so that the filter is overheated or the regeneration is performed when the accumulation amount is small. By doing so, fuel efficiency does not deteriorate and there is no cost increase.
4, 25 can be reproduced accurately, and high reliability can be secured.

On the other hand, when the filters 24 and 25 are reproduced,
Since the incineration amount of the particulates is obtained based on the temperature, it is possible to accurately set the regeneration end time of the filters 24 and 25.

Also, in the high-speed and high-load region of the engine, the exhaust gas flows through both filters 24 and 25 without performing regeneration.
The exhaust resistance does not increase, and the amount of particulates incinerated is determined based on the temperature, so that the amount of particulates deposited on each of the filters 24 and 25 can be accurately determined even in a high rotation and high load region. .

[0044]

As described above, according to the present invention, the distribution ratio of the discharged particulates is determined based on the particulate deposition amount of each of the plurality of filters, and the particulate deposition amount of each filter is determined based on the distribution ratio. Without using a pressure sensor or the like, the amount of accumulated particulates in each filter can be accurately grasped. Therefore, while reducing the cost, the regeneration of each filter can be accurately performed at an appropriate time, and high reliability can be secured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment.

FIG. 3 is a flowchart showing control contents.

FIG. 4 is a flowchart showing control contents.

FIG. 5 is a flowchart showing control contents.

FIG. 6 is a characteristic diagram of control data.

FIG. 7 is a characteristic diagram of control data.

FIG. 8 is a characteristic diagram of control data.

FIG. 9 is a characteristic diagram of control data.

[Explanation of symbols]

 Reference Signs List 21 exhaust passage 22, 23 branch exhaust passage 24, 25 filter 26, 27 heater 28, 29 opening / closing valve 30, 31 temperature sensor 32 rotation speed sensor 33 accelerator opening sensor 34 water temperature sensor 35 control unit

Claims (1)

(57) [Claims] A filter for collecting particulates in exhaust gas is interposed in each of a plurality of branch exhaust passages, and a temperature raising device for each filter and a valve device for controlling the flow of exhaust gas into each filter are provided. Means for detecting the operating conditions of the engine, particulate emission calculating means for calculating the particulate emissions of the engine based on the operating conditions of the engine, and means for flowing exhaust gas to all filters when the regeneration conditions are not satisfied. Collection control means for operating the valve device, particulate distribution ratio calculating means for calculating the distribution ratio of the particulates distributed and flowing into each filter based on the particulate accumulated amount of each filter, and the particulate emission amount of the engine. A parameter for calculating the amount of newly deposited particulate in each filter based on the distribution ratio of particulates Means for calculating a particulate accumulation amount, a particulate accumulation amount calculating means for calculating the particulate accumulation amount of each filter based on the particulate accumulation amount and the new accumulation amount, and a case where the particulate accumulation amount reaches a predetermined value. An exhaust gas purifying apparatus for an engine, comprising: a temperature raising device for raising the temperature of a filter and restricting the flow of exhaust gas into the filter.