JPH10259711A - Exhaust gas purifying device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent worsening of power performance and fuel consumption by judging regeneration of a trap after catching a specified amount of fine- grains even if an atmospheric pressure or a running load changes and providing stable trap regeneration operation. SOLUTION: This exhaust gas purifying device is formed such that fine-grains in exhaust gas G from an engine 1 are collected by trap devices 2 an 3, the collected fine-grains are removed by regenerating means 4 and 5 to regenerate a trap device, and a correction factor K is set by a control means 17, based on exhaust gas temperature information from exhaust gas temperature detecting means 6 and 8 and an atmospheric pressure information from an atmospheric pressure detecting means 16. Further, a differential pressure ΔP between the fronts and the rears of trap devices 2 and 3 detected by a differential pressure detecting means is corrected by a correction factor K to judge a regeneration timing.

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 an engine which corrects the regeneration timing of a trap device for trapping fine particles in exhaust gas according to the atmospheric pressure and the temperature of exhaust gas.

[0002]

2. Description of the Related Art An exhaust gas passage of a diesel engine, which is one of the internal combustion engines used for vehicles such as buses and trucks, contains carbon particles and the like contained in exhaust gas discharged from the engine as nuclei. An exhaust gas purification device that collects particulates is installed. An exhaust gas purification device, a trap device including a filter for collecting particulates, a regeneration device for burning the particulates collected by the filter to regenerate a trap (filter),
A pressure sensor as a differential pressure detecting means for detecting a differential pressure before and after the filter, a differential pressure calculating circuit, and an exhaust gas flow rate detecting means are provided. In the exhaust gas purification device, the control means determines the regeneration timing and the collection timing based on the relationship between the pressure loss of the filter calculated by obtaining the differential pressure across the filter based on the pressure information from the pressure sensor and the exhaust gas flow rate. When it is determined that the regeneration time is reached, the regeneration device is driven to burn the filter to remove trapped particulates, thereby performing trap regeneration.

[0003]

Vehicles, such as buses and trucks, run at places where there is a change in altitude, and the running load varies depending on the loading conditions of passengers and luggage. Therefore, the specific gravity (density) of the intake air is reduced. The exhaust gas temperature fluctuates due to changes or running conditions. If the altitude changes, the atmospheric pressure changes, and if the running load changes, the exhaust gas temperature changes.If these changes are not taken into account, even if the same amount of particulates is collected by the filter, the atmospheric pressure will change. And the pressure loss of the filter detected due to the difference in exhaust gas temperature changes. Such a change in pressure loss due to a difference in atmospheric pressure or exhaust gas temperature causes early or late filter regeneration time,
This may cause deterioration in power performance and fuel efficiency, or decrease in durability (life) of the battery due to an increase in the number of times of regeneration. The present invention can perform trap regeneration at the optimal time,
Provided is an exhaust gas purification apparatus in which the durability (life) of a battery is extremely low due to deterioration in power performance and fuel efficiency or increase in the number of regenerations.

[0004]

According to the first aspect of the present invention, the differential pressure across the trap device is corrected by the control means by a correction coefficient taking into account the atmospheric pressure and the exhaust gas temperature. The regeneration timing that separates the regeneration zone and the capture zone is determined based on the corrected differential pressure obtained from the differential pressure, so that the regeneration determination is always performed when the amount of collected particulates is constant even if the atmospheric pressure or running load changes. As a result, a stable trap regenerating operation can be obtained, so that deterioration of power performance and fuel efficiency can be suppressed, and an increase in the number of times of trap regenerating can be suppressed to improve battery durability.

[0005] The control means corrects the differential pressure across the trap device by a correction coefficient taking into account the atmospheric pressure and the exhaust gas temperature, and separates the regeneration area and the trapping area by a threshold value set by the correction coefficient. Since the regeneration timing of the device is determined, the regeneration determination is always performed when the trapped amount of particulates is constant even if the atmospheric pressure or running load changes, and a stable trap regeneration operation can be obtained, and power performance and fuel efficiency can be improved. Deterioration can be suppressed, and the durability of the battery can be improved by suppressing an increase in the number of times of trap reproduction.

According to the second aspect of the present invention, when the atmospheric pressure decreases and the exhaust gas temperature increases, the differential pressure detection value detected by the differential pressure detecting means is greatly corrected or set. Since the threshold value is corrected to a small value by the correction coefficient, it is possible to reduce the delay of the filter regeneration timing for a place having a high altitude or a vehicle having many running states where the exhaust gas temperature is high.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust emission control device according to a first embodiment of the present invention shown in FIG. 1 is applied to a diesel engine 1 (hereinafter referred to as "engine 1") of a vehicle such as a bus or a truck. The exhaust gas purification device includes trap devices 2 and 3 for collecting fine particles in exhaust gas G discharged from the engine 1, regenerating means 4 and 5 for regenerating the trap devices 2 and 3, and detecting the temperature of the exhaust gas G. Exhaust gas temperature sensors 6 and 8 as filter exhaust gas temperature detecting means, and filter temperature sensors 7 and 9
And an atmospheric pressure sensor 16 as atmospheric pressure detecting means, and pressure sensors 10 and 1 for detecting pressures before and after the trap devices 2 and 3.
An engine control unit (hereinafter, referred to as an exhaust gas flow rate detecting means and a control means) comprising a differential pressure detecting circuit 14 for calculating a differential pressure between before and after based on pressure information from the respective pressure sensors; "ECU") 1
7 mainly.

The exhaust gas flow rate detecting means is provided in an intake pipe 18A connected to the engine 1 via an intake manifold 18, and has an air flow sensor 15 having a function of detecting the flow rate, temperature and pressure of intake air A flowing through the intake pipe 18A. , E
It comprises an exhaust gas flow rate calculating means 19 built in the CU 17. The exhaust gas flow rate calculating means 19 calculates the exhaust gas flow rate Gr from the intake / intake air amount, the intake pressure, the intake air temperature, the exhaust gas temperature and the exhaust pressure, and is stored in the ECU 17. The exhaust gas flow rate calculation means 19 may use a characteristic map or a calculation formula created based on the experimental results.
In the present embodiment, the exhaust gas flow rate Gr is searched from a well-known map for calculating the exhaust gas flow rate.

The trap devices 2 and 3 are provided in an exhaust system of the engine 1. In this exhaust system, the downstream side of the main exhaust pipe 21 which is communicated with the exhaust manifold 20 and through which the exhaust gas G flows is divided into two branches to form branch flow paths 21A and 21B. The trap device 2 is provided in the branch channel 21A.
1B is provided with a trap device 3 respectively. The trap devices 2 and 3 include filters 28 and 29 for collecting particulates, and a canister container 3 for storing the filters 28 and 29 via a wire mesh (not shown).
0 and 31 mainly. Filter 28, 2
Reference numeral 9 denotes a ceramic made of a well-known honeycomb structure in which a number of narrow paths are stacked in the same direction, and is configured to filter particulates from exhaust gas passing through side walls of the narrow paths. On the exhaust downstream side of the canister containers 30 and 31, exhaust pipes 21C and 21D to a muffler (not shown) are provided.
Are connected respectively.

On-branch passages 21A and 21B located on the exhaust upstream side of the trap devices 2 and 3 are provided with on-off valves 24 and 25 which are opened and closed by actuators 22 and 23 connected to the ECU 17, respectively. On-off valve 24, 2
5 is a branch flow path 21 according to a drive signal from the ECU 17.
A and 21B are opened and closed. In this embodiment, when the trap device 2 is regenerated, the branch channel 21A is closed, and when the trap device 3 is regenerated, the branch channel 21A is closed.
When B is closed and particulates are being collected by one of the trap units, the corresponding branch flow path is controlled so as not to use the other trap unit.

An introduction passage 26 is provided in the branch passages 21A and 21B located between the trap devices 2 and 3 and the on-off valves 24 and 25 so as to communicate the two. Introductory channel 2
6 is provided with an electromagnetic valve 27 for opening and closing the same flow path. The solenoid valve 27 is connected to the ECU 17 and is normally placed in a state where the introduction flow path 26 is closed, and is operated based on a signal from the ECU 17 at the time of trap regeneration to open the introduction flow path 26 and close the on-off valve. The exhaust gas G for combustion is introduced into the trap device 2 or the trap device 3 which is being regenerated from the branch flow path which is not being used. Since the engine 1 of this embodiment is a diesel engine, the exhaust gas G contains a large amount of oxygen, and the exhaust gas G is used to burn the filter 28 or the filter 29. However, a configuration may be adopted in which secondary air for filter combustion instead of exhaust gas G is introduced into the filter to be regenerated at the time of trap regeneration. In the present embodiment, in order to sufficiently burn and regenerate the filters 28 and 29, the regenerating operation is performed in an engine rotation region where the exhaust gas contains a large amount of oxygen.

The regenerating devices 4 and 5 include canister containers 30 and
The filter 31 is disposed on the exhaust upstream side of the filters 28 and 29. The regenerating devices 4 and 5 are provided with electric heaters 32 and 33 for heating the filters 28 and 29 to burn the collected particulates, and a heat source formed with a large number of ventilation holes disposed further forward of the electric heaters 32 and 33. Reflectors 34, 35
Respectively. Electric heaters 32 and 33
Is connected to a battery 38 via electromagnetic switches 36 and 37, and generates heat for a certain period of time when the trap devices 2 and 3 are reproduced. The switching input terminals of the electromagnetic switches 36 and 37 are connected to the ECU 17, respectively. When the ECU 17 is energized, the switches are closed to connect the battery 38 and the electric heaters 32 and 33, respectively. The electric heaters 32 and 33 are formed so as to be substantially uniformly distributed in the cross-sectional direction of the exhaust gas flow path, and the generated heat energy is reflected by the heat reflecting plates 34 and 35, respectively, and collected by the filters 28 and 29. Quickly burns particulates. The heat reflecting plates 34 and 35
Reflects heat radiated on the opposite side of the filters 28 and 29,
Alternatively, it is returned to the exhaust gas G which has been absorbed once and then flows to promote the combustion of the particulates. An alternator 39 is connected to the battery 38.

The pressure sensors 10 and 12 are filters 28 and 2
The pressure sensors 11 and 13 are provided in the canister containers 30 and 31 on the downstream side of the filters 28 and 29, respectively.
EC by detecting front pressure and rear pressure of 8, 29 respectively
It is sent to U17 as pressure information.

The exhaust gas temperature sensors 6 and 8 are a filter 2
8 and 29 are provided in the canister containers 30 and 31 on the upstream side. The filter temperature sensors 7 and 9 include the filter 2
8 and 29 for detecting the temperatures of the filters 28 and 29.
It is provided in the canister containers 30 and 31 on the downstream side. The temperature information from the filter temperature sensors 7 and 9 is E
The data is input to the CU 17.

The ECU 17 is an engine control device mainly including a microcomputer, and detects rotation information N from a rotation sensor 40 serving as engine rotation information detection means.
e, the atmospheric pressure information P from the atmospheric pressure sensor 16, the exhaust gas temperature information Gt from the exhaust gas temperature sensors 6 and 8, the intake air amount from the air flow sensor 15, and various information such as the intake temperature and the intake pressure. . The ECU 17 stores various maps and programs.
2, 23, the electromagnetic valve 27 and the electromagnetic switches 36 and 37 are controlled.

The program and the map include a correction coefficient K selected based on the exhaust gas temperature information Gt from the exhaust gas temperature sensors 6 and 8 and the atmospheric pressure information P from the atmospheric pressure sensor 16, Reproduction means 4, 5 according to coefficient K
And a program for judging the regenerative time of the trap devices 2 and 3 based on the above.

The correction coefficient K is selected from a map 41 as a correction coefficient setting means shown in FIG.
As shown in FIG. 3, the map 41 has a characteristic that the correction coefficient K increases as the exhaust gas temperature Gt increases and the atmospheric pressure decreases. The threshold value P1 that separates the regeneration region and the collection region serving as the regeneration reference of the filters 28 and 29 shown in FIG. 4 is the differential pressure when the amount of particulates that does not exceed the endurance temperature of the filters 28 and 29 is collected. I have. The threshold value P1 is experimentally obtained in advance and stored on the map 42 in FIG.
The map 42 determines the regeneration timing of the filters 28 and 29 from the exhaust gas flow rate Gr and the corrected differential pressure KΔP.

When it is determined that the trap device 2 or the trap device 3 is to be regenerated, the ECU 17 drives one of the electromagnetic switches 36 and 37 and the actuators 22 and 23 corresponding to the trap device determined to be regenerated. It has become. The ECU 17 includes filters 28 and 29
When the combustion temperature of the filter is set in advance and the temperature information from the filter temperature sensors 7 and 9 exceeds the set temperature, it is determined that each filter has become higher than the combustion temperature of the particulates and the electromagnetic valve 27 is driven. The introduction channel 26 is opened.

The relationship between the atmospheric temperature and its specific gravity will be described with reference to FIG. In general, the specific gravity of the atmosphere decreases as the atmospheric temperature increases, and decreases as the atmospheric pressure decreases.
In general, this relationship is based on Bernoulli's theorem, ΔP = A (γ / g) q ² A: drag coefficient g: dynamic acceleration q: flow velocity γ: specific weight, and ΔP is the same because γ is a function of temperature and pressure. Becomes This relationship is obtained by mapping in advance. For this reason, in the present embodiment, as shown in FIG. 3, the correction coefficient K is set to increase as the exhaust gas temperature increases and the atmospheric pressure decreases.

In this embodiment, the correction coefficient K is obtained not from the temperature of the intake air flow but from the exhaust gas temperature Gt and the atmospheric pressure. The reason is that the particulate collection amount of the filters 28 and 29 is estimated from the differential pressure ΔP before and after the filters 28 and 29, and that vehicles such as buses and trucks
This is because the exhaust gas temperature increases due to the load and the specific gravity of the atmosphere. When the pressure loss before and after the filters 28 and 29 is obtained to obtain the pressure loss of each filter due to the collection of particulates, the optimum temperature is obtained as compared with the case where the pressure loss is obtained based only on the information on the intake side. And the flow rate and the differential pressure can be detected with high accuracy.

The operation of the first embodiment will be described with reference to the trap regeneration control flowchart shown in FIG. When a starter switch (not shown) is turned on, the engine 1 and the ECU 1
7 and various sensors are activated to enter a trap regeneration control routine, and the air A sucked into the engine 1 is burned together with fuel injected from an injection device (not shown) to exhaust the exhaust gas G from the engine 1. . This exhaust gas G
The particulate matter (PM) is mainly collected from the main exhaust passage 21 through the branch passage 21A or the branch passage 21B by the filters 28 and 29, and is collected from the exhaust pipes 21C and 21D into the atmosphere via a muffler (not shown). Is discharged. In this embodiment, the trap device 3 is used from the trap device 2 and is used.
The description will be continued below assuming that the trap device 2 is regenerated earlier.

In the trap regeneration control routine shown in FIG. 2, the rotation signal Ne from the rotation sensor 40 is
Is determined, and if the rotation signal Ne is input, the process proceeds to step B2, and if there is no rotation information Ne, the process returns as the engine is stopped. In step B2, the intake flow rate signal and the temperature / pressure information from the air flow sensor 15 and the pressure information from the pressure sensor 10 are taken in, and the exhaust gas flow rate Gr is calculated using a well-known exhaust gas flow rate calculation map. Step B
In step 3, the pressure information before and after the filter from the pressure sensors 10 and 11 is taken in to calculate the differential pressure ΔP. In step B4, the atmospheric pressure information P from the atmospheric pressure sensor 16 and the exhaust gas temperature information Gt from the exhaust gas temperature sensor 6 are fetched, and the map 41 shown in FIG. 3 is used according to the current atmospheric pressure and the exhaust gas temperature information Gt. Search for an optimal correction coefficient K.

In step B5, the differential pressure ΔP calculated in step B3 is corrected by multiplying by a correction coefficient K, and the corrected differential pressure KΔ
Calculate P. In step B6, the corrected differential pressure KΔP
Is greater than the threshold value P1, that is, it is determined whether the trapped amount of particulates has reached the pressure of the specified amount and the filter 28 is in the regeneration period. And the corrected differential pressure KΔP
If the threshold value exceeds the threshold value P1 of the map shown in FIG. 4 and is on the reproduction area side, it is regarded as trap reproduction and the process proceeds to step B7 to perform trap reproduction. Returns as possible to collect.

When the trap is regenerated in step B7, a drive signal is issued from the ECU 17 to drive the actuators 22 and 23, and the branch flow path 21A is closed by the on-off valve 24 as shown in FIG. The branch flow path 21B is opened, the branch flow path and the filter are switched, and the collection of particulates by the filter 29 is started. The ECU 17 closes the electromagnetic switch 36 and energizes the electric heater 32 to generate heat and heat the filter 28. When the temperature signal from the filter temperature sensor 7 exceeds a set temperature at which it can be considered that the temperature has reached the temperature at which the particulates can be burned, the solenoid valve 27 is driven. When the electromagnetic valve 27 is driven, the introduction flow path 26 is opened, and a part of the exhaust gas G flowing in the branch flow path 21B enters the trap device 2 through the introduction flow path 26 as shown by a broken line in FIG. The gas is introduced, the filter 28 is burned, particulates are removed, and the trap device 2 is regenerated.

When the trap device 3 is to be regenerated, in step B2, the intake flow rate signal and the temperature / pressure information from the air flow sensor 15 and the pressure information from the pressure sensor 8 are fetched and the exhaust gas flow rate is calculated using a well-known exhaust gas flow rate calculation map. The flow rate Gr is calculated, and in step B3, the pressure information before and after the filter from the pressure sensors 12, 13 is taken in to calculate the differential pressure ΔP. At step B4, the atmospheric pressure sensor 1
6 and the exhaust gas temperature information Gt from the exhaust gas temperature sensor 8 are taken in, and a map 41 shown in FIG.
Search for the optimum correction coefficient K according to the current atmospheric pressure and the exhaust gas temperature information Gt.

In step B5, the differential pressure ΔP calculated in step B3 is corrected by multiplying by a correction coefficient K, and the corrected differential pressure KΔ
Calculate P. In step B6, the corrected differential pressure KΔP
Is greater than the threshold value P1, that is, it is determined whether the amount of trapped particulates has reached the prescribed amount of pressure and the filter 29 has entered the regeneration period. And the corrected differential pressure KΔP
If it is more than the threshold value P1 of the map shown in FIG. 4 and it is in the reproduction area side, it is regarded as trap reproduction, and the process proceeds to step B7 to perform trap reproduction. Returns as possible to collect.

When trap regeneration is performed in step B7, a drive signal is issued from the ECU 17 and the actuator 2
2 and 23, the branch flow path 21B is closed by the on-off valve 25, and the branch flow path 21A is opened by the on-off valve 24 to switch the branch flow path and the filter.
8 starts collection of particulates. next,
The ECU 17 closes the electromagnetic switch 37 to release the electric heater 3.
3 is energized to generate heat, and the filter 29 is heated. When the temperature signal from the filter temperature sensor 9 exceeds a set temperature at which it can be considered that the temperature has reached the temperature at which the particulates can be burned, the solenoid valve 27 is driven. When the solenoid valve 27 is driven, the introduction flow path 26 is opened, a part of the exhaust gas G flowing in the branch flow path 21A is introduced into the filter 29 through the introduction flow path 26, and the combustion of the filter 29 is performed. Then, the particulates are removed and the trap device 3 is regenerated.

As described above, the differential pressure ΔP before and after the trap devices 2 and 3 is corrected by the correction coefficient K obtained from the atmospheric pressure P and the exhaust gas temperature Gt in consideration of the specific gravity of the atmosphere.
Since the regeneration timing of the trap devices 2 and 3 is determined according to the correction coefficient K, the regeneration determination is always performed at the same particulate collection amount even if the atmospheric pressure or running conditions change, The stable regenerating operation of the trap devices 2 and 3 can be performed. The correction coefficient K is calculated based on the running state and the exhaust gas temperature where the vehicle travels on an ascending road or a high altitude road with a large running load, the particulates are collected more than on a flat ground, and the differential pressure ΔP is smaller than on a flat ground. At this time, the pressure difference ΔP is corrected to a large value, so that the pressure loss due to the filters 28 and 29 does not become too high or too low. This means
The deterioration of power performance and fuel consumption can be suppressed, and the increase in the number of times of trap regeneration can be suppressed to improve the durability of the battery.

An exhaust gas purifying apparatus according to a second embodiment of the present invention will be described. In the second embodiment, the regeneration of the trap devices 2 and 3 by the regeneration means 4 and 5 is performed by comparing a threshold value P2 set by a correction coefficient K selected in consideration of the atmospheric pressure and the exhaust gas temperature Gt with the differential pressure ΔP. Control means for judging timing is provided. The exhaust gas purifying apparatus according to the second mode is the first type.
The configuration other than the control means has the same configuration as that of the first embodiment.

Control means (ECU) according to the second embodiment
Is an engine control device mainly composed of a microcomputer, and includes rotation information Ne from a rotation sensor 40 serving as engine rotation information detection means, and an atmospheric pressure sensor 16.
Atmospheric pressure information P from the exhaust gas temperature information Gt from the exhaust gas temperature sensors 6 and 8, the intake air supply amount from the air flow sensor 15, the intake air temperature, the intake pressure, and other various information are taken in, as well as various maps and programs. Is stored, and has a function of controlling the actuators 22 and 23, the electromagnetic valve 27, and the electromagnetic switches 36 and 37.

A correction coefficient K selected based on the exhaust gas temperature information Gt from the exhaust gas temperature sensors 6 and 8 and the atmospheric pressure information P from the atmospheric pressure sensor 16 and a correction coefficient K A program for judging the regeneration time of the trap devices 2 and 3 by the regeneration means 4 and 5 according to K is included.

The correction coefficient K is selected from a map 41 serving as correction coefficient setting means shown in FIG.
As shown in FIG. 3, the map 41 has a characteristic that the correction coefficient K increases as the exhaust gas temperature Gt increases and the atmospheric pressure decreases. The threshold value P2 that separates the regeneration region and the collection region serving as the regeneration reference of the filters 28 and 29 shown in FIG. 6 is defined as the differential pressure when the amount of particulates that does not exceed the endurance temperature of the filters 28 and 29 is collected. It is obtained experimentally and stored in the map 43 of FIG. That is, the control unit according to the second embodiment basically has the same configuration as the control unit of the first embodiment except for the map 43 and the program shown in FIG.

The map 43 shows the exhaust gas flow rate Gr and the differential pressure Δ
This is to judge the regeneration timing of the filters 28 and 29 from P, and the threshold value P2 is changed within the range indicated by the two-dot chain line according to the correction coefficient K. More specifically, a plurality of correction threshold values corresponding to the correction coefficient K are set within the range indicated by the two-dot chain line, depending on the specific gravity (air density). A correction threshold is selected and a map corresponding to the correction coefficient K is set. That is, the threshold value is corrected to be smaller as the atmospheric pressure is lower or the exhaust gas temperature Gt is higher.

In the control means according to the second embodiment, a preset temperature for burning the filters 28 and 29 is preset, and when the temperature information from the filter temperature sensors 8 and 9 exceeds the preset temperature, The electromagnetic valve 27 is driven to open the introduction flow path 26 assuming that each filter has reached a temperature higher than the particulate combustion temperature. When the control unit determines that the trap unit 2 or the trap unit 3 is to be regenerated, the control unit drives the electromagnetic switch 37 and the actuator 22, 23 corresponding to the trap unit determined to be the regenerative time. ing.

The operation of the exhaust gas purifying apparatus having such a configuration will be described with reference to the trap regeneration control flowchart shown in FIG. When a starter switch (not shown) is turned on, the engine 1, the control means and various sensors operate to enter a trap regeneration control routine, and the air A taken into the engine 1 is burned together with fuel injected from an injection device (not shown). Then, the exhaust gas G is discharged. This exhaust gas G
The filter (28) mainly collects particulates (PM) from the main exhaust passage (21) through the branch passage (21A) or the branch passage (21B), and from the muffler (not shown) to the atmosphere via the exhaust pipes (21C, 21D). Is discharged. In this embodiment, the trap device 3 is used from the trap device 2 and is used.
The description will be continued below assuming that the trap device 2 is regenerated earlier.

In the trap regeneration control routine shown in FIG. 5, the rotation information Ne from the rotation sensor 40 is obtained in step C1.
Is determined, and if the rotation information Ne is input, the process proceeds to step C2, and if there is no rotation information Ne, the routine returns as the engine is stopped. In step C2, the intake gas flow rate signal and the temperature / pressure information from the air flow sensor 15 and the pressure information from the pressure sensor 10 are taken in, and the exhaust gas flow rate Gr is calculated using a well-known exhaust gas flow rate calculation map. Step C
In step 3, the pressure information before and after the filter from the pressure sensors 10 and 11 is taken in to calculate the differential pressure ΔP.

At step C4, the atmospheric pressure information P from the atmospheric pressure sensor 16 and the exhaust gas temperature information Gt from the exhaust gas temperature sensor 6 are fetched, and the current atmospheric pressure and the exhaust gas temperature information Gt are obtained from the map 41 shown in FIG. Is determined by searching for the optimum correction coefficient K according to. In step C5, the threshold value P2
Is corrected, a correction threshold corresponding to the determined correction coefficient K is selected from the range of the map 43 shown in FIG. 6, and the correction threshold is set as the current threshold P2. In step C6, the corrected threshold value P2 is compared with the differential pressure ΔP corresponding to the exhaust gas flow rate Gr to determine whether or not the differential pressure ΔP has exceeded the threshold value P2, that is, whether the amount of trapped particulates is the specified amount. It is determined whether the pressure has reached and the regeneration time of the filter 28 has entered. If the differential pressure ΔP is in the reproduction area beyond the threshold value P2 in the map shown in FIG. 6, the flow is regarded as reproduction, and the process proceeds to step C7 where trap regeneration is performed. Returns as it is possible to collect curate.

When trap regeneration is performed in step C7, a drive signal is issued from the control means to drive the actuators 22 and 23, and the branch passage 21A is closed by the on-off valve 24 as shown in FIG. The branch passage 21B is opened, the branch passage and the filter are switched, and the collection of particulates by the filter 29 is started. The control means closes the electromagnetic switch 36 and energizes the electric heater 32 to generate heat and heat the filter 28. When the temperature signal from the filter temperature sensor 7 exceeds a set temperature at which it can be considered that the temperature has reached the temperature at which the particulates can be burned, the solenoid valve 27 is driven.

When the solenoid valve 27 is driven, the introduction passage 26 is opened, and a part of the exhaust gas G flowing in the branch passage 21B is trapped through the introduction passage 26 as shown by a broken line in FIG. The filter 28 is burned to remove particulates, and the trap device 2 is regenerated.

When the trap device 3 is to be regenerated, in step C2, the intake flow rate signal and the temperature / pressure information from the air flow sensor 15 and the pressure information from the pressure sensor 8 are taken in and the exhaust gas flow rate calculation map is used. The flow rate Gr is calculated, and in step C3, the pressure information before and after the filter from the pressure sensors 12, 13 is taken in to calculate the differential pressure ΔP. In step C4, the atmospheric pressure sensor 1
6 and the exhaust gas temperature information Gt from the exhaust gas temperature sensor 8 are taken in, and a map 41 shown in FIG.
Then, the optimum correction coefficient K is searched and determined according to the current atmospheric pressure and the exhaust gas temperature information Gt. In step C5, in order to correct the threshold value P2, a correction threshold value corresponding to the determined correction coefficient K is selected from the range of the map 43 shown in FIG. 6, and the correction threshold value is set as the current threshold value P2. In step C6, the corrected threshold value P2 and the differential pressure Δ corresponding to the exhaust gas flow rate Gr are used.
P to determine whether the differential pressure ΔP has exceeded a threshold value P2,
That is, it is determined whether or not the filter 29 has reached the regeneration time at which the trapped amount of particulates becomes the specified amount. And
If the pressure difference ΔP is in the reproduction area beyond the threshold value P2 of the map shown in FIG. 6, it is regarded as the reproduction time and the process proceeds to step C7 to perform trap regeneration. Returns as it is possible to collect curate.

When the trap is regenerated in step C7, a drive signal is issued from the control means to drive the actuators 22 and 23. In contrast to FIG. The branch passage 21A is opened, the branch passage and the filter are switched, and the collection of particulates by the filter 28 is started. The control means closes the electromagnetic switch 37 and energizes the electric heater 33 to generate heat, thereby heating the filter 29. Then, the temperature signal from the filter temperature sensor 9 is
When the temperature exceeds a set temperature at which it can be considered that the temperature has reached the temperature at which particulates can be burned, the solenoid valve 27 is driven.

When the solenoid valve 27 is driven, the introduction passage 26 is opened, and a part of the exhaust gas G flowing in the branch passage 21A is introduced into the trap device 3 through the introduction passage 26, and the filter 29 Combustion is performed to remove particulates, and trap regeneration is performed.

As described above, by taking into account the specific gravity of the atmosphere, the threshold value P2 for separating the regeneration region and the collection region is changed according to the correction coefficient K by the correction coefficient K obtained from the atmospheric pressure P and the exhaust gas temperature Gt. Since the regeneration timing of the trap devices 2 and 3 is appropriately changed in accordance with the atmospheric pressure P and the exhaust gas temperature Gt, the regeneration determination is always performed at the same particulate collection amount even when the atmospheric pressure and the running conditions change. As a result, the regenerating operation of the trap devices 2 and 3 can be performed stably. In other words, the correction coefficient K is higher than the level when the vehicle is traveling on an ascending road or a high altitude road with a high running load, and the particulate matter is collected at a higher pressure than the level.
Differential pressure ΔP when running at low exhaust gas temperature
Is corrected to a large value, so that the pressure loss due to the filters 28 and 29 does not become too high or too low. As a result, deterioration of power performance and fuel efficiency can be suppressed, and an increase in the number of times of regeneration of the trap devices 2 and 3 is suppressed, thereby improving the durability of the battery.

[0044]

According to the first aspect of the present invention, the control means corrects the differential pressure across the trap device with a correction coefficient taking into account the atmospheric pressure and the exhaust gas temperature. Since the regeneration time for separating the regeneration area and the collection area is determined based on the corrected differential pressure determined from
Even if the atmospheric pressure or running load changes, the regeneration judgment is always made at the same particle collection amount, and a stable trap regeneration operation can be obtained, and the deterioration of power performance and fuel efficiency can be suppressed,
The durability of the battery is improved by suppressing the increase in the number of times of trap reproduction. Further, the control device corrects a differential pressure across the trap device by a correction coefficient considering the atmospheric pressure and the exhaust gas temperature, and separates the regeneration region and the collection region by a threshold value set by the correction coefficient. The regeneration timing is determined, so even if the atmospheric pressure or running load changes, the regeneration is always determined when the amount of collected particulates is the same, and a stable trap regeneration operation can be obtained to reduce the power performance and fuel consumption. In addition to suppressing the number of times of trap reproduction, the durability of the battery is improved.

According to the second aspect of the present invention, when the atmospheric pressure decreases and when the temperature of the exhaust gas increases, the differential pressure detection value detected by the differential pressure detecting means is greatly corrected or the threshold value is corrected. Since the correction is made small by the coefficient, it is possible to reduce the delay of the filter regeneration timing for a place having a high altitude or a vehicle in which the exhaust gas temperature is high and the running state is high.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust gas purification device for an engine according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control procedure of trap regeneration in the first embodiment.

FIG. 3 is a characteristic diagram of a correction coefficient.

FIG. 4 is a switching characteristic diagram of trap regeneration in the first embodiment.

FIG. 5 is a flowchart showing a control procedure for trap regeneration in the second embodiment.

FIG. 6 is a switching characteristic diagram of trap regeneration in the second embodiment.

FIG. 7 is a characteristic diagram of the specific gravity of the atmosphere.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2,3 Trap device 4,5 Regeneration means 6,8 Exhaust gas temperature detecting means 10,11,12,13 Pressure sensor 14 Differential pressure detecting means 16 Atmospheric pressure detecting means 17 Control means G Exhaust gas Gt Exhaust gas temperature information P Atmospheric pressure information K Correction coefficient ΔP Differential pressure KΔP Corrected differential pressure P2 Threshold

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 312 F02D 45/00 312Z

Claims (2)

[Claims] 1. A trap device for collecting fine particles in exhaust gas from an engine, a regenerating means for removing the fine particles collected by the trap device and regenerating the trap device, and controlling a temperature of the exhaust gas. Exhaust gas temperature detecting means for detecting; atmospheric pressure detecting means for detecting atmospheric pressure; differential pressure detecting means for detecting a differential pressure across the trap device; and exhaust gas temperature information from the exhaust gas temperature detecting means. A correction coefficient is set based on the atmospheric pressure information from the atmospheric pressure detecting means, and the reproduction area is captured by a correction differential pressure obtained by correcting the differential pressure with the correction coefficient or a threshold set by the correction coefficient. And a control means for judging the regeneration time of the trap device which separates the trap region from the collection region. 2. The exhaust gas purifying apparatus for an engine according to claim 1, wherein the correction coefficient is a difference detected by the differential pressure detecting means when the atmospheric pressure is reduced and when the temperature of the exhaust gas is increased. An exhaust gas purification apparatus for an engine, wherein the detected pressure value is corrected to be large or the threshold value is corrected to be small.