JPH07127430A - Exhaust gas processing device - Google Patents

Abstract

PURPOSE:To provide an exhaust gas processing device of such constitution as to select a filter, corresponding to the grain diameter of particulates, out of filters with different pore diameters and to collect particulates by the selected filter. CONSTITUTION:Plural filters 2A, 2B, 2C with different pore diameters are disposed parallelly in the width direction in a casing 1. Dampers 3A, 3B, 3C provided at the respective exhaust gas inlets 6A, 6B, 6C of the filters 2 can be opened/closed independently, and the filter 2 with the optimum pore diameter corresponding to the exhaust gas temperature detected by a temperature sensor 9 is selected by a controller 10 to collect particulates. Excessive pressure loss rise is not therefore generated to the filter 2 so as to be able to collect particulates efficiently over many hours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment device having a filter arranged in a casing incorporated in an exhaust system for purifying exhaust gas emitted from a diesel engine.

[0002]

2. Description of the Related Art Combustion of a diesel engine is based on so-called heterogeneous mixing, in which fuel is injected into high temperature, high pressure air. Heterogeneous mixing is different from homogeneous mixture in that air and fuel are not uniformly mixed, so the carbon component in the fuel changes to soot, HC, etc. due to the high temperature heat of combustion, and they aggregate to form particulates, It is released to the outside. Conventionally, carbon, soot, HC contained in exhaust gas exhausted from diesel engines
Collect particulates with a filter and incinerate it D
In a PF, that is, an exhaust gas treatment device, particulates such as carbon, soot, and HC are collected by a filter body or filter, and when particulates are deposited on the filter, they are heated by an ignition glow plug or a heater, and particulates such as soot are collected. The curate is incinerated.

Conventionally, as an exhaust gas treatment device for treating engine exhaust gas, for example, cordierite (2M
An exhaust particulate purifying device for a diesel engine is disclosed in which two sets of filters having a porous honeycomb structure made of gO.2Al ₂ O ₃ .5SiO ₂ ) are arranged in parallel in an exhaust passage. As an exhaust particulate purifying device for such a diesel engine, for example, an actual Kaihei 1-144427
There is one disclosed in the publication. Also, the actual Kaihei 1-13
Japanese Patent No. 4715 discloses a diesel particulate filter that collects particulates discharged from a diesel engine with a single filter.

Further, Japanese Utility Model Laid-Open Publication No. 1-108316 discloses an exhaust particulate treatment device for an internal combustion engine.
The exhaust particulate treatment apparatus for an internal combustion engine has an exhaust passage branched into two branch exhaust passages, one branch exhaust passage provided with a porous trap, and the other branch exhaust passage provided with a lattice trap to obtain an exhaust temperature. And an exhaust gas temperature detecting means for detecting an engine operating condition, an engine load detecting means for detecting an engine load, and the lattice trap for exhaust gas when the detected exhaust temperature is a predetermined value or more and the engine load is a predetermined value or more. And a valve device that opens and closes the branch exhaust passage so that the exhaust gas otherwise flows through the porous trap.

[0005]

By the way, diesel particulate is a compound of carbon and hydrocarbon contained in a diesel engine, and its size is several μm.
To several tens of μm, for example, in the range of 5 μm to 100 μm. The particulate reacts with oxygen and burns easily, but the burning requires a high temperature and cannot be burned completely only by the temperature of the exhaust gas. Therefore, many devices for removing particulates and smoke have been developed from the past, but all have drawbacks.
The current situation is that it cannot be put to practical use.

However, the particle size distribution of the particulates is related to the exhaust gas temperature. In the conventional filter having a single pore diameter, it is necessary to make the pore diameter of the filter fine in order to achieve highly efficient trapping regardless of the exhaust gas temperature. With a single pore size filter, 100 μm particle size particulates must be collected with a filter having a pore size to collect 5 μm particulates, resulting in, for example, the dotted line in FIG. As shown in (2), there is a problem that the exhaust pressure of the filter rises early in the elapsed time of the operation of the filter, and good particulate collection cannot be continued.

Further, the exhaust particulate treatment apparatus for an internal combustion engine disclosed in Japanese Utility Model Laid-Open No. 1-108316 has a pumice-shaped porous trap and a honeycomb-shaped lattice trap arranged in an exhaust passage. The size of the pore size of the filter is not a problem, and either trap is selected according to the exhaust gas temperature, but the combustion start temperature of the particulates of the two ceramic filters with catalyst is different. The selection control based on the temperature is performed by the method, the particulates are burned to prevent melting damage of the trap, and the purpose is not to extend the collection time for the filter.

Therefore, an object of the present invention is to solve the above-mentioned problems, and paying attention to the fact that the particle size of particulates varies depending on the temperature of exhaust gas discharged from a diesel engine, that is, the combustion state of the engine. For purification, a plurality of filters with different pore diameters are placed in parallel in the width direction inside the casing incorporated in the exhaust system, and the particle size of the generated particulates is detected by measuring the exhaust gas temperature. , A map in which the particle size of particulates corresponding to the exhaust gas temperature is predicted in advance is stored in the controller, and the optimum pore size filter is selected for the particulate form, that is, the particle size of the particulates. It is possible to extend the collection time of the filter by flowing the exhaust gas only into the filter and collecting the particulates. To provide a wear exhaust gas treatment device.

[0009]

In order to achieve the above object, the present invention is constructed as follows. That is, the present invention is, in order to collect the particulates in the exhaust gas, a plurality of filters arranged in parallel in the width direction in the casing in the exhaust system having different pore diameters, the exhaust gas to each filter respectively. Each damper provided at least at the exhaust gas inlet for flowing, a temperature sensor installed on the upstream side of the filter for detecting the exhaust gas temperature, and a particulate corresponding to the exhaust gas temperature detected by the temperature sensor A control is performed to specify the particle size, select the filter having the optimum pore size for collecting particulates of the particle size, open the damper of the selected filter, and close the other dampers. An exhaust gas treatment device, comprising:

Further, in this exhaust gas treatment device, the dampers are provided at the exhaust gas inlet and the exhaust gas outlet of the filter.

Further, in this exhaust gas treatment device, the controller opens the damper of the filter having a small pore diameter and closes the damper of the filter having a large pore diameter when the exhaust gas temperature is high, thereby exhaust gas is exhausted. When the temperature is low, control is performed to close the damper of the filter having a small pore size and open the damper of the filter having a large pore size.

[0012]

The exhaust gas treatment device according to the present invention is constructed as described above and operates as follows. That is, in this exhaust gas treatment device, a plurality of filters having different pore diameters are arranged in parallel in the width direction in the casing of the exhaust system, and a damper is provided at the exhaust gas inlet of each filter, and each damper is The exhaust gas inlets can be opened and closed independently, the particle size of particulates corresponding to the exhaust gas temperature detected by the temperature sensor by the controller is specified, and the optimum pore size for collecting the particulates of the particle size. Since it is possible to perform control to select the filter having the above, open the selected damper, and close the dampers of other filters, an excessive pressure loss increase due to the filter optimal for the particulate particle size can be achieved. It is possible to efficiently collect the particulates for a long time without being generated.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an exhaust gas treatment apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory view showing an embodiment of an exhaust gas treatment apparatus according to the present invention, FIG.
1 is an explanatory diagram showing a rise in exhaust pressure of a filter due to the operation of the exhaust gas treatment apparatus of FIG. 1, and FIG. 3 is a processing flow chart showing an example of operation of the filter due to the operation of the exhaust gas treatment apparatus of FIG. .

This exhaust gas treatment apparatus has a casing 1 arranged in an exhaust passage 5 for discharging exhaust gas from a diesel engine, and a plurality of casings (three in FIG. 1 are shown in parallel in the casing 1 in the width direction). Filters 2A, 2 made of ceramics for collecting particulates such as carbon and smoke contained in the disposed exhaust gas
B, 2C (collective name of filters is 2), filters 2A, 2
B and 2C exhaust gas inlets 6A, 6B and 6C respectively have dampers 3A, 3B and 3C (the damper is generically 3), and filters 2A, 2B and 2C exhaust gas outlet 7
Dampers 4A and 4 provided on A, 7B and 7C, respectively
It has B and 4C (the generic name of the damper is 4). Each filter 2A, 2B, 2C arranged in the casing 1 is blocked by a partition wall 11 and is composed of a porous filter having different pore diameters.

In this exhaust gas treatment device, the relationship between the exhaust gas temperature T _EX measured by the thermocouple 8 and the temperature sensor 9 and the particle size of the particulates is observed in advance, and the data is input to the controller 10, and the exhaust gas is exhausted. It is intended to automatically select the optimum filter 2A, 2B or 2C at the gas temperature T _{EX and} efficiently collect the contained in the exhaust gas. The filter 2 has filters of 2 to 3 kinds of pore diameters (5, 30, 60 μm) arranged in parallel according to the particle size of the particulates, and plural filters 2 having the same kind of pore diameter are arranged in parallel. It's okay.

In this exhaust gas treatment device, the exhaust gas temperature T of the exhaust gas flowing through the exhaust passage 5 is detected according to the detection value from the thermocouple 8 arranged in the exhaust passage 5 on the upstream side of the filter 2.
_It has a temperature sensor 9 for measuring _EX . The signal of the exhaust gas temperature T _EX detected by the temperature sensor 9 is input to the controller 10. The controller 10 specifies the particulate particle size corresponding to the exhaust gas temperature T _EX detected by the temperature sensor 9, and has a filter 2 having an appropriate pore size for collecting the particulate of the particle size.
A, 2B, and 2C are selected, the dampers 3 and 4 of the selected filter 2 are opened, and the dampers 3 and 4 of the other filters 2 are closed.

In this exhaust gas treatment device, the filter 2 can be constructed so that the pore diameters are different as follows, for example. The filter 2A is formed as a porous filter having a large pore size, for example, 60 μm, the filter 2B is formed as a porous filter having an intermediate pore size, for example, 30 μm, and the filter 2C is small. It is formed in a porous filter having a pore size of, for example, 5 μm. Regarding the size of particulates such as carbon and smoke contained in the exhaust gas, the particulates of the particulate matter become large due to the agglomeration of the particulates in an operating state where the exhaust gas temperature is low such as when the engine is idling. Further, at high speed and high load, the exhaust gas temperature becomes high and the particulates have a fine particle size. The exhaust gas temperature T _EX differs depending on such an engine operating state, and the particle size of the particulates also changes. Therefore, these phenomena are grasped and created in a map in advance, and this information is input to the controller 10.

FIG. 2 shows the change over time in the exhaust gas pressure when particulates in the exhaust gas are collected by this exhaust gas treatment device, and has a conventional pore diameter of 5 μm for comparison. For the filter, the change over time in the exhaust gas pressure is shown by the dotted line. Traditional filters are
It can be seen that the exhaust gas pressure rapidly increases in a short time because it has a single pore diameter and collects all the particulates regardless of the particle size of the particulates. On the other hand, the exhaust gas treatment apparatus according to the present invention selects the optimum filter 2A, 2B or 2C for the particle size of the particulates contained in the exhaust gas from the plurality of filters 2A, 2B, 2C. Since exhaust gas is caused to flow through the filter 2, it is possible to prevent an excessive increase in pressure loss in the filters 2A, 2B, 2C. Further, when the vehicle is running, the filter 2A, 2B or 2C that is most suitable for collecting particulates is switched to correspond to the change in the particulate particle size due to the change in the combustion state of the engine, so that the pressure loss increases continuously. It can be suppressed. For example, as shown in FIG. 2, the exhaust gas treatment apparatus according to the present invention has a predetermined pressure reaching time that is about three times longer than that when a conventional filter having a single pore diameter of 5 μm is used, and the trapping time is increased. It has become possible to use it for about three times longer.

In this exhaust gas treatment device, the filter 2 can be made of, for example, non-conductive ceramics or conductive ceramics. When it is made of non-conductive ceramics, the patty collected by the filter 2 is used. A separate heater can be provided to heat and incinerate the curate. As a result, the particulates collected in each filter 2 are regenerated by heating and incinerating them with a heater or the like to release them as gas.

The various filters 2 as described above can exhibit high-temperature strength sufficient to incinerate particulates such as carbon, soot, and HC. For example, undesired carbon contained in exhaust gas of a diesel engine can be removed. The filter 2 is made of a material that can sufficiently collect particulates.
Polyurethane foam is used to impregnate the polyurethane foam with a ceramic slurry or slurry, which is dried and solidified, and then fired to burn off the polyurethane foam to produce a porous ceramic or body having a desired size. it can. Alternatively, a raw material powder of ceramics is mixed to prepare a slurry, and resin particles are added and mixed to the slurry to be dried and solidified, and then this is burned to burn off the resin particles. A porous body can be produced.

The exhaust gas treatment device is constructed as described above and can be operated as follows. Figure 3
As shown in, the engine is started and the exhaust gas temperature T _EX
Is detected by the temperature sensor 9 (step 20). The exhaust gas temperature T _EX detected by the temperature sensor 9 is input to the controller 10, and the controller 10 compares and determines whether or not the exhaust gas temperature T _EX is higher than a preset temperature T ₁ (for example, 250 ° C.) ( Step 21). The exhaust gas temperature T _EX is a preset temperature T ₁ (for example, 250
C)), the particle size of the particulates contained in the exhaust gas is small (for example, about 5 μm to 30 μm), and the dampers 3C and 4C of the filter 2C having a small pore diameter (5 μm) are opened. , The dampers 3A and 4A of the filter 2A having a large pore diameter and the dampers 3B and 4B of the filter 2B having an intermediate pore diameter are closed (step 2).
2). Therefore, the exhaust gas flows only to the filter 2C and does not flow to the filters 2B and 2C.

In step 21, the exhaust gas temperature T
_{When EX} is not higher than the preset temperature T ₁ (for example, 250 ° C.), it is then determined whether or not the exhaust gas temperature T _EX is lower than the preset temperature T ₂ (for example, 150 ° C.) ( Step 23). When the exhaust gas temperature T _EX is lower than a preset temperature T ₂ (for example, 150 ° C.), the particulates contained in the exhaust gas aggregate and grow to a large particle size (for example, larger than 60 μm). There is. Therefore, when the exhaust gas temperature T _EX is low, the dampers 3C and 4C of the filter 2C having a small pore diameter and the dampers 3B and 4B of the filter 2B having an intermediate pore diameter are closed,
Control is performed to open the dampers 3A and 4A of the filter 2A having a large pore diameter (for example, 60 μm) (step 2).
4).

In step 23, the exhaust gas temperature T
_{When EX} is not lower than the preset temperature T ₂ (for example, 150 ° C.), the particulates contained in the exhaust gas have an intermediate particle size (for example, about 30 μm to 60 μm).
Is. Therefore, the exhaust gas temperature T _EX is the intermediate temperature (15
0 ° C to 250 ° C), the filter 2 having a small pore size
C dampers 3C and 4C and large pore size filter 2A
The dampers 3A, 4A of the
The control is performed to open the dampers 3B and 4B of the filter 2B (30 μm) (step 25).

[0024]

The exhaust gas treatment device according to the present invention is constructed as described above and has the following effects.
That is, in this exhaust gas treatment device, a plurality of filters having different pore diameters are arranged in parallel in the width direction in the exhaust system,
A damper is provided at least at the exhaust gas inlet of each filter, and the exhaust gas inlet can be independently opened and closed by the dampers. Further, since the particulate particle size corresponding to the exhaust gas temperature is specified in advance, the particulate particle size corresponding to the exhaust gas temperature detected by the temperature sensor by the controller can be predicted, and the particulate of the particle size can be captured. It is possible to perform control such that the filter having the optimum pore size for collecting is selected, the damper of the filter is opened, and the dampers of the other filters are closed. For example, the controller opens the damper of the filter having a small pore diameter and closes the damper of the filter having a large pore diameter when the exhaust gas temperature is high, and also has the small pore diameter when the exhaust gas temperature is low. It is possible to control to close the damper of the filter and open the damper of the filter having a large pore diameter.

Therefore, this exhaust gas treatment apparatus can efficiently and satisfactorily collect particulates for a long time without causing an excessive increase in pressure loss due to the filter that is optimum for the particle size of particulates. Also,
In this exhaust gas treatment device, the damper can also be provided at the exhaust gas inlet and the exhaust gas outlet of the filter. Then, the particulates are not excessively deposited in the filter, a local high temperature portion is not generated in the filter, and the filter is cracked,
The reliability and durability of the filter can be improved without causing damage such as burning.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of an exhaust gas treatment device according to the present invention.

FIG. 2 is an explanatory diagram showing a state in which the exhaust pressure of the filter rises due to the operation of the exhaust gas treatment device of FIG.

FIG. 3 is a process flow chart showing an embodiment of the operation of the filter by the operation of the exhaust gas treatment device of FIG.

[Explanation of symbols]

1 Casing 2, 2A, 2B, 2C Filter 3, 3A, 3B, 3C Damper (for exhaust gas inlet of filter) 4, 4A, 4B, 4C Damper (for exhaust gas outlet of filter) 5 Exhaust passage 6A, 6B, 6C Exhaust gas inlet of filter 7A, 7B, 7C Exhaust gas outlet of filter 8 Thermocouple 9 Temperature sensor 10 Controller 11 Partition wall

Claims (3)

[Claims] 1. A plurality of filters having different pore diameters arranged in parallel in a width direction in a casing of an exhaust system for collecting particulates in the exhaust gas, and the exhaust gas is caused to flow through the respective filters. Therefore, at least each damper provided at the exhaust gas inlet, a temperature sensor installed on the upstream side of the filter for detecting the exhaust gas temperature, and particulate particles corresponding to the exhaust gas temperature detected by the temperature sensor A control is performed to specify the diameter, select the filter having the optimum pore diameter for collecting particulates of the particle size, open the damper of the selected filter, and close the other dampers. An exhaust gas treatment device comprising a controller. 2. The exhaust gas treatment device according to claim 1, wherein the dampers are provided at the exhaust gas inlet and the exhaust gas outlet of the filter. 3. The controller opens the damper of the filter having a small pore size when the exhaust gas temperature is high and closes the damper of the filter having a large pore size, and the small pore size when the exhaust gas temperature is low. The exhaust gas treatment apparatus according to claim 1, wherein the damper of the filter is closed and the damper of the filter having a large pore size is opened.