JPH07189655A - Exhaust emission control device for engine - Google Patents

Abstract

PURPOSE:To maintain good regenerating condition by at least one filter so as to prevent reduction of output of an engine at the time of a high load. CONSTITUTION:An exhaust emission control device 1 is provided with a plurality of trappers 11, 13, a operation detecting mean 15 for detecting the load condition of an engine 51, a temperature sensor 16 for exhaust gas 81, a flow passage switching means 20, and a controller 40. A flow passage switching means can make switching in a regeneration trapper 13 required for maintaining regenerating condition between a first arranging condition which is arranged in series on the downstream side of the other trapper 11 and a second arranging condition which is placed in series connection by only the regeneration trapper 13. In the controller 40, when engine condition is not under a high load and the temperature T of exhaust gas is a prescribed value To or less, the first arranging condition is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas purification device for collecting and removing particulate matter contained in exhaust gas.

[0002]

2. Description of the Related Art Exhaust gas from internal combustion engines such as automobiles, particularly diesel engines, contains exhaust particulates (particulates) containing carbon as a main component, and causes exhaust black smoke. Therefore, a trapper having a particulate filter (hereinafter, simply referred to as “filter”) made of ceramic or the like is arranged in the exhaust passage of the diesel engine, and the particulate is collected and removed by the trapper.

An exhaust gas purification device using a filter is
In addition to the configuration using a single filter, a configuration using two filters has been proposed. The purpose of using two filters is to avoid an increase in fluid resistance due to clogging of particulates in the filters and to suppress pressure loss in the exhaust passage of the engine. This is because if the pressure loss due to the filter increases, the acceleration performance of the vehicle will decrease significantly.

For example, for the above-mentioned purpose, two filters are used, and when the engine exhaust gas temperature is low, the exhaust gas is allowed to flow only to one filter and the other filter is not allowed to flow. A method has been proposed in which the other filter is kept in a regenerated state (fluid resistance is small) as much as possible (see Japanese Utility Model Laid-Open No. 62-31710).

When the exhaust gas temperature is low, the particulate matter trapped in the filter burns slowly, and the particulate matter is likely to be accumulated to cause clogging of the filter. Therefore, when both filters are operated, both filters are clogged, so that the exhaust gas is prevented from flowing through the other filter. Then, when the exhaust gas temperature is above a predetermined value, such as under high load, the exhaust gas is circulated through both filters to reduce the load on the engine.

[0006]

However, there are the following problems in the above-mentioned conventional exhaust gas purifying apparatus that retracts the other filter from the exhaust passage when the exhaust gas temperature is low. That is, it is extremely difficult to always maintain the other filter in the regenerating state only by not allowing the exhaust gas to flow into the other filter when the exhaust temperature is low.

For example, when the high exhaust gas temperature continues for a short time, the exhaust gas temperature decreases due to the heat capacity of the filter, and the oxidation catalyst does not work. Therefore, the particulates do not burn, and the particulates accumulate on the filter. Even if the other filter is withdrawn from the exhaust passage in this state, the particulates do not decrease. The reason is as follows.

The fact that the exhaust gas does not flow in means that the particulates do not accumulate, but the oxygen necessary for burning the particulates is not supplied, and the combustion of the particulates also stops, and the accumulated particulates are removed. It cannot be reduced. Then, if such a cycle is repeated several times, the amount of particulates deposited gradually increases, and the pressure loss of the filter becomes high.

As a result, the pressure loss of both filters becomes high, so that the back pressure of the engine cannot be kept low, which causes a problem that the output of the engine is lowered at the time of high load such as acceleration. . In view of such conventional problems, the present invention intends to provide an exhaust emission control system for an engine that maintains a good regeneration state for at least one filter and does not overload the engine. It is a thing.

[0010]

According to a first aspect of the present invention, there are provided a plurality of trappers with an oxidation catalyst, which are provided in an exhaust passage of an engine and collect particulates in exhaust gas, and an operation detecting means for detecting a load state of the engine. A temperature sensor for detecting the exhaust temperature of the engine, a flow path switching means for changing the arrangement of the plurality of trappers in the exhaust passage, and a controller connected to the operation detecting means and the temperature sensor for operating the flow path switching means. In the exhaust gas purifying apparatus for an engine, the plurality of trappers are composed of a regeneration trapper that always tries to maintain a regeneration state and an ordinary trapper, and the flow path switching means is different from the regeneration trapper. The first array state in which the trapper is arranged in series downstream of the trapper, and the second arrangement state in which the trapper is arranged alone or in series by only the reproduction trapper. The controller can operate the flow path switching means so that the regeneration trapper is in the first arrangement state when the engine is not in a high load operating state and the exhaust gas temperature is below a predetermined value. It is a characteristic engine exhaust purification system.

What is most noticeable in the present invention is that the reproduction trapper, which always tries to maintain the reproduction state,
The controller has a flow path switching means capable of switching between two arrangement states of a first arrangement state and a second arrangement state. When the engine is not in a high load operation state and the exhaust temperature is below a predetermined value, the regeneration is performed. Switching the trapper to the first arrangement state.

In the above, the first arrangement state means that the regeneration trapper is arranged in series downstream of another trapper, and the other trapper upstream at this time may be a normal trapper or a regeneration trapper. The second arrangement state is that the reproduction trappers are arranged in series, but it is more preferable that the second arrangement state is independent.

When there are a plurality of trappers that can be reproduction trappers, it is not always necessary that all the trappers have the same arrangement state. That is, when there are a large number of replay trappers, one may be the replay trapper and the other may be the normal trapper. Therefore, it is allowed that one trapper is in the first arrangement state and another trapper is in the second arrangement state.

The controller can know the high load state of the engine by the operation detecting means and the exhaust gas temperature by the temperature sensor. The exhaust temperature can also be estimated from the operating state of the engine detected by the operation detecting means. Further, a part of the function of the operation detecting means and the controller can be configured on a common microprocessor or ECU.

When the exhaust emission control device is composed of two trappers, it is preferable to configure the flow path switching means so that both trappers can be regenerated trappers. That is, there are three flow path states, that is, a flow path state in which two trappers are arranged in parallel, a series state in which one is upstream and the other is in downstream, and a series state in which one is upstream and one is in downstream. It constitutes a switching means.

According to this structure, a trapper having a small fluid resistance and a small amount of particulates accumulated can be selected as the regenerating trapper, and the other can be selected as the normal trapper, so that a better regenerating state can be maintained. Because you can

On the other hand, according to the second invention of the present application, first and second trappers with an oxidation catalyst for collecting particulates in the exhaust gas, which are provided in the exhaust passage of the engine, and a temperature for detecting the exhaust gas temperature of the engine. An exhaust emission control device for an engine, comprising: a sensor; a flow passage switching means for changing the arrangement of the first and second trappers in the exhaust passage; and a controller connected to the temperature sensor for operating the flow passage switching means. When the exhaust temperature is below a predetermined value, the first
And the second trapper is arranged in series with each other,
When the exhaust temperature is above a predetermined value, the first and second
An exhaust emission control system for an engine, wherein the trappers are arranged in parallel with each other.

The second invention, unlike the first invention, does not have an operation detecting means. When the exhaust temperature detected using the temperature sensor is below a predetermined value, both trappers are arranged in series regardless of the load condition, and when the exhaust temperature is above the predetermined value, both trappers are arranged in parallel. To do. Others are the same as the first invention.

[0019]

In the exhaust gas purifying apparatus of the first invention of the present application, when the engine is not in a high load operating state and the exhaust gas temperature is low, that is, in a state where high output is not required, particulates are hard to burn and accumulate. In the easy state, the regeneration trapper is placed in the first arrangement, i.e. downstream of the other trappers.

In the regeneration trapper in the first arrangement state as described above, since the particulates are captured by the upstream particulates, the particulate traps do not increase and only the burning of the particulates is promoted. Therefore, the particulates are reduced and a good reproduction state is advanced. On the other hand, when the engine is not in the above state, that is, when the exhaust temperature is not low, the combustion of particulates is promoted and the combustion amount of particulates is larger than the accumulation amount, as shown in FIG. Therefore, the reproduction state does not deteriorate and the reproduction trapper can always maintain a good reproduction state.

On the other hand, in a high load state such as during acceleration of the engine, the regeneration trapper is arranged in the second arrangement state, so that the pressure loss in the exhaust passage of the engine is suppressed and the engine exhibits good acceleration performance. it can. As described above, according to the first aspect of the present invention, there is provided an engine exhaust gas purification device that maintains a good regeneration state for at least one filter (regeneration filter) and does not reduce the output of the engine under high load. can do.

On the other hand, in the second invention of the present application, when the exhaust temperature is lower than the predetermined value, the trappers are arranged in series. Therefore, the trapper (regeneration trapper) arranged downstream at this time always has a good regeneration state. Can be held.
When the trappers are arranged in series, the back pressure of the engine increases, but when the engine load is small,
Even if the engine back pressure is high, the decrease in engine output is slight and causes almost no problem. Also, when the engine load is large, the exhaust temperature rises in a short time, and as a result, the trappers are arranged in parallel, so this does not pose a problem for practical operation.

Further, it is cheaper than the first invention in that the operation detecting means is not provided. Others are the same as the first invention. As described above, according to the second invention, at least one of the filters maintains a good reproduction state,
It is possible to provide an exhaust gas purification device that does not place an excessive load on the engine.

[0024]

【Example】

Embodiment 1 An exhaust emission control device according to an embodiment of the present invention will be described with reference to FIGS. In this example, as shown in FIGS. 1 and 2, two trappers 11 and 13 with an oxidation catalyst, which are installed in the exhaust passage 31 of the engine 51 and collect particulates in the exhaust 81, and the load of the engine 51. The operation detecting means 15 for detecting the state, the temperature sensor 16 for detecting the exhaust temperature of the engine 51, and the flow path switching means 20 for changing the arrangement of the two trappers 11, 13 in the exhaust passage 31.
The exhaust gas purifying apparatus 1 further includes a controller 40 that is connected to the operation detecting unit 15 and the temperature sensor 16 and operates the flow path switching unit 20.

The two trappers 11 and 13 are composed of a regeneration trapper 13 and an ordinary trapper 11 which always try to maintain a regeneration state, and the flow path switching means 2
Regarding 0, the reproduction trapper 13 has a first arrangement state (FIG. 1) arranged in series downstream of the ordinary trapper 11 and a second arrangement state (FIG. 2) arranged only in series with the reproduction trapper.
It can be switched to and. Further, the controller 40 operates the flow path switching means 20 so that the regeneration trapper 13 is in the first arrangement state shown in FIG. 1 when the engine 51 is not in the high load operation state and the exhaust gas temperature is below the predetermined value.

A supplementary explanation will be added below. The engine 51 of this example is a diesel engine, and as shown in FIGS. 1 and 2, an intake throttle valve 35 is arranged in the middle of an intake pipe 32 of the engine 51. The exhaust passage 31 branches into the first, second, and third branch pipes 311, 312, 313 on the way, and then merges with the exhaust pipe 33 again.
Emitted from.

Trappers 11 and 13 having filters 110 and 130 carrying an oxidation catalyst are inserted into the first and third branch pipes 311 and 313, respectively. And the exhaust passage 3
The first and second switching valves 2 are provided at the branch portion and the merging portion, respectively.
1, 22 are provided. A temperature sensor 16 is inserted between the first switching valve 21 and the engine 51.

The controller 40 is formed in the ECU 4 for controlling the engine, and the controller 40 includes the intake throttle valve 35, the temperature sensor 16, the first and second switching valves 2.
1, 22 are connected. The operation detecting means 15 is also formed in the ECU 4, and the operation detecting means 15
Are connected to the engine speed sensor 151 and the accelerator opening sensor 152.

The filters 110 and 130 are cylindrical members as shown in FIG. 5, and the inside thereof is formed in a honeycomb shape by a large number of rectangular channels 111 divided by thin partition walls as shown in FIG. Has been done. Then, one end of the inlet or outlet of the rectangular flow passage 111 of the filters 110 and 130 is sealed with a plug material 112.

Then, the plug member 1 of the adjacent rectangular channel 111
Reference numeral 12 denotes an inflow port and an outflow port, which are provided on opposite sides of each other. As a result, as shown in FIG. 5, at the inflow port 113 and the outflow port 114, the assembly of the plug members 112 has a checkered pattern. The partition wall of the filter that defines the rectangular channel 111 is formed of ceramic such as cordierite or high temperature resistant metal powder, and its surface is coated with γ-alumina or the like. An oxidation catalyst such as Pt, Pd or Cu is carried on the surface of the coating layer.

Next, an outline of the control operation of the exhaust gas purification device will be described. During normal engine operation,
As shown in FIG. 2, by increasing the opening of the intake throttle valve 35,
The first and second switching valves 21 and 22 close both ends of the second branch pipe 312. As a result, the two trappers 11, 13 are
It is connected in parallel to the exhaust passage 31.

For this reason, the exhaust 81 is supplied to both trappers 1
1 and 13, the particulates are in the rectangular channel 1
The exhaust gas 81 collected and purified by the partition wall 11 is the muffler 3
Inflow to 4. At this time, if the exhaust temperature is high, the particulates trapped by the filters 110 and 130 burn by the action of the oxidation catalyst. That is, the filter 11
0 and 130 will burn while collecting particulates. Then, when the burning particulates is relatively larger than the collected particulates, the particulates of the filters 110 and 130 decrease.

On the other hand, when the amount of collected particulates is relatively large, the particulates of the filters 110 and 130 gradually increase, and the back pressure of the engine 51 rises due to the pressure loss of the filters, and the output Is reduced. Therefore, the back pressure of the engine is measured by a pressure sensor (not shown), or the filter 110,
The differential pressure (pressure loss) before and after 130 is measured, the accumulation state of particulates is detected, the temperature of exhaust gas is raised, and combustion of particulates is promoted.

The rise of the exhaust gas temperature can be realized by reducing the opening of the intake throttle valve 35 by the controller 40 to throttle the intake air. This is because if the intake air is reduced, the excess air amount will decrease and the exhaust temperature will rise. Then, if the exhaust gas temperature rises, as shown in FIG. 3, the burning velocity v _{c of the} particulates increases.

As a result, the collecting speed v of the particulates
_The combustion velocity v _c (g / sec) becomes relatively larger than _t (g / sec) (v _c > v _t ), and the filter 110,
The particulates of 130 are reduced. However the above condition (v _c> v _t) is achieved, it is necessary that the exhaust gas temperature becomes a predetermined value T ₀ or more.

That is, for example, when the particulate collection velocity v _t is a shown in FIG. 3, the particulate combustion velocity v _c must exceed 430 ° at which it becomes a. That is, the exhaust gas temperature T is required to be equal to or higher than the combustion speed v _{c and the} trapping speed v _t (v _c = v _t critical temperature T ₀ ).

Here, there is a problem that when the engine is in a low load operation state, even if the intake throttle is throttled, the temperature rise of the exhaust gas is small and the critical temperature T ₀ is not reached. In this example, when the exhaust temperature T does not reach the critical temperature T ₀ , the regeneration trapper 13 is placed in the second arrangement state shown in FIG. 1 to avoid the accumulation of particulates in the regeneration trapper 13.

The above control procedure will be described more specifically with reference to the control flow chart shown in FIG. First, in step 601, the operation detecting means 15 reads the accelerator opening and the engine speed from the respective sensors 151, 152. Then, in step 602, the operation detecting means 15
From the above two sensor information, it is determined whether the engine is in a high load operation state (for example, an acceleration operation state). If the determination result is affirmative (YES), the process proceeds to step 606, and no (N
If it is O), go to step 603.

If the load is high, step 6
At 06, the switching valves 21 and 22 are operated to operate the device in the second arrangement state of the trappers 13 shown in FIG. on the other hand,
If it is not in the high load state at step 602, the routine proceeds to step 603, where the controller 40 reads the exhaust temperature T from the temperature sensor 16.

Then, in step 604, it is compared whether or not the exhaust temperature T is equal to or higher than a predetermined value T ₀ . Step 60
If the result in 4 is affirmative (YES), step 606.
Then, the switching valves 21 and 22 are operated to set the second arrangement state. If the comparison result in step 604 is NO (NO), the flow proceeds to step 605, the switching valves 21, 22 are operated, and the regeneration trapper 13 is brought into the first arrangement state as shown in FIG.

That is, when the exhaust gas is at a low temperature (T <T ₀ ) instead of in the high load operation state, the connection state shown in FIG.
Most of the particulates are normally trapped by the trapper 11. As a result, since only the particulate combustion is performed in the regeneration trapper 13, the particulate burning speed v _c is equal to the particulate collecting speed v.
_{It exceeds t} (≈0), and the particulates decrease.
Then, the reproduction trapper 13 can hold the reproduction state.

As shown in FIG. 1, the trapper 11,
When 13 are connected in series, the back pressure of the engine is large and the output of the engine 51 is reduced. However, when this arrangement (FIG. 1) is taken, the load of the engine 51 is small (step 60
(No in 2), so this is hardly a problem.

On the other hand, at the time of high load such as acceleration, the routine proceeds from step 602 to step 606, and the arrangement state shown in FIG. 2, that is, the trappers 11 and 13 are arranged in parallel, so that the back pressure of the engine is always maintained by the regeneration trapper. The engine 51 becomes lower, and the engine 51 can fully exert its ability.

Further, in this case, since the exhaust temperature is high under a high load and the burning rate of particulates is higher than the trapping rate of particulates (v _c > v _t ), the trappers 11, 1 are
The amount of particulates in 3 does not increase. As described above, according to the present example, in any case, the regeneration trapper 13 provides an exhaust purification device that maintains a good regeneration state and does not reduce the output of the engine under high load. You can

Embodiment 2 In this embodiment, as shown in FIGS. 6 and 7, as compared with Embodiment 1, the arrangement of the branch pipes 311 to 313 and the switching valves 211 and 22 are compared.
It is another embodiment in which the operation mode of 1 is changed. That is, in the first array state (FIG. 1) in the first embodiment,
The downstream side of the ordinary trapper 11 was connected to the upstream side of the regenerating trapper 13 in the second arrangement state (FIG. 2), but in the first arrangement state (FIG. 7) in this example, the downstream side of the ordinary trapper 11 is changed to the second arrangement state. Playback trapper 13 in the state (FIG. 6)
To the downstream side of.

As a result, the flow direction of the exhaust 81 of the regeneration trapper 13 is reversed depending on the first and second arrangement states. With this configuration, it becomes possible to shorten the length of the flow path between the normal trapper 11 and the regeneration trapper 13 in the first arrangement state (FIG. 7) in which both the trappers 11 and 13 are in series. It is possible to suppress a decrease in exhaust temperature during that time. Therefore, the particulate burning velocity v _c of the regenerating trapper 13 can be maintained at a higher level. Others are the same as those in the first embodiment.

Third Embodiment In this embodiment, as shown in FIGS. 8 and 9, the switching mode of the switching valve 23 is changed as compared with the first embodiment, and the exhaust passage 3 is changed.
This is another embodiment in which the connection mode of the branch pipes 315 to 317 branched from 1 is changed, and the flow of the exhaust gas of the ordinary trapper 11 is reversed depending on the arrangement state so as to flow in both directions.

That is, the reproduction trapper 13 shown in FIG.
The direction of the flow of the exhaust gas 81 in the ordinary trapper 11 is reversed between the time of the arrangement state and the time of the first arrangement state shown in FIG. Therefore, in the ordinary trapper 11, the particulates can be collected on both sides of the partition wall of the rectangular flow passage 111 of the filter 110, and the combustion performance of the particulates can be significantly increased.

That is, the catalyst is supported on both sides of the partition wall, and the contact area with the particulates can be doubled, whereby the burning rate v _{c of the} particulates can be greatly increased. Others are described in Example 1.
Is the same as.

Embodiment 4 As shown in FIGS. 10 and 11, this embodiment is another embodiment in which two ordinary trappers 11 and 12 are used as compared with the first embodiment. That is, the ordinary trappers 11 and 12 are arranged in parallel with the separate branch pipes 318 and 319.

In the second arrangement state shown in FIG. 10, the reproduction trapper 13 is arranged in parallel with both trappers 11 and 12, and in the first arrangement state shown in FIG. 11, the reproduction trapper 13 is arranged.
Are arranged in series with both trappers 11 and 12. Others are the same as those in the first embodiment.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an exhaust emission control device according to a first embodiment (first array state).

FIG. 2 is another system configuration diagram (second arrangement state) of the exhaust emission control device of the first embodiment.

FIG. 3 is a graph showing the relationship between exhaust gas temperature and particulate burning speed in the trapper of the first embodiment.

FIG. 4 is a control flowchart of the exhaust emission control device according to the first embodiment.

FIG. 5 is a perspective view of the filter according to the first embodiment.

FIG. 6 is a system configuration diagram of an exhaust emission control device according to a second embodiment (second array state).

FIG. 7 is a system configuration diagram of an exhaust emission control device of a second embodiment (first arrangement state).

FIG. 8 is a system configuration diagram of an exhaust emission control device of a third embodiment (second array state).

FIG. 9 is a system configuration diagram (first array state) of the exhaust emission control device of the third embodiment.

FIG. 10 is a system configuration diagram of an exhaust emission control device of a fourth embodiment (second array state).

FIG. 11 is a system configuration diagram (first array state) of the exhaust emission control device of the fourth embodiment.

[Explanation of symbols]

 1. ． ． Exhaust gas purification device, 11, 13. ． ． Trapper, 15. ． ． Operation detection means, 16. ． ． Temperature sensor, 20. ． ． Flow path switching means, 40. ． ． Controller, 51. ． ． Engine, 81. ． ． exhaust,

Claims (3)

[Claims] 1. A plurality of trappers with an oxidation catalyst, which are provided in an exhaust passage of an engine and collect particulates in the exhaust, an operation detecting means for detecting a load state of the engine, and an exhaust temperature of the engine. An exhaust gas purifying apparatus for an engine having a temperature sensor, a flow path switching means for changing the arrangement of the plurality of trappers in the exhaust passage, and a controller connected to the operation detecting means and the temperature sensor for operating the flow path switching means. The plurality of trappers are composed of a regeneration trapper that always tries to maintain a regeneration state and an ordinary trapper, and the flow path switching means is arranged in series downstream of the other trappers with respect to the regeneration trapper. It is possible to switch between the first arrangement state in which the first arrangement state and the second arrangement state in which the reproduction arrangement is arranged in series by only the reproduction trapper. The controller operates the flow passage switching means so that the regeneration trapper is in the first arrangement state when the engine is not in a high load operating state and the exhaust temperature is below a predetermined value. Purification device. 2. The plurality of trappers according to claim 1, wherein the plurality of trappers are composed of two trappers, and the flow path switching means takes the first and second arrangement states in which any of the trappers is a regeneration trapper. An exhaust emission control device for an engine, characterized in that the flow path can be changed so that 3. A first and a second trapper with an oxidation catalyst, which is provided in an exhaust passage of an engine and collects particulates in the exhaust, a temperature sensor for detecting an exhaust temperature of the engine, and the exhaust passage in the exhaust passage. An exhaust gas purifying apparatus for an engine, comprising: a flow path switching means for changing the arrangement of the first and second trappers; and a controller connected to the temperature sensor for operating the flow path switching means, wherein the exhaust gas temperature is predetermined. When the value is less than or equal to a value, the first and second trappers are arranged in series with each other, and when the exhaust temperature is equal to or higher than a predetermined value, the first and second trappers are arranged in parallel with each other. Exhaust gas purification device for engines.