JP2005061313A - Engine exhaust control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently perform poisoning release while suppressing the deterioration of fuel economy and a manifold catalyst in an upstream side, when it is judged that it is the time to release the poisoning of sulfur adhering to a NOx trapping catalyst provided for an exhaust passage. <P>SOLUTION: At the time of poisoning release, temperature is raised at two stages. Initially, the poisoning release is performed at a relatively low temperature. After sulfur in a state capable of being released at the relatively low temperature is removed, the temperature is further raised to perform the poisoning release at a relatively high temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an engine exhaust purification device that can suitably perform detoxication of sulfur (S) adhering to a catalyst when an exhaust purification catalyst having a NOx trap function is provided in an exhaust passage.

As described in Patent Document 1, as a conventional technique, the detachability (ease of detachment) of sulfur attached to the NOx absorbent (NOx trap catalyst) is determined, and the determination result is determined according to the determination result. There are some which adjust / suppress at least one of the enrichment of the air-fuel ratio and the temperature rise of the exhaust gas for sulfur release.
JP 2002-364348 A

  However, the conventional technology is configured to release the poisoning at a high temperature when sulfur that is difficult to desorb has accumulated to some extent. Since it is necessary to raise the temperature to be able to release poisoning, it takes time to raise the temperature to be able to release poisoning, and the fuel consumption deteriorates during that time. Further, when a three-way catalyst (manifold catalyst) is arranged directly under the exhaust manifold upstream of the NOx trap catalyst, the temperature of the manifold catalyst rises relatively early, and there is a problem that the deterioration thereof becomes large.

  In the present invention, the temperature rise at the time of releasing the poisoning is divided into two stages, and at the time when the low-temperature poisoning release in which the poisoning is released at a relatively low temperature and sulfur in a state that can be released at a relatively low temperature are removed, Further, the temperature is increased, and the high temperature poisoning release for releasing the poisoning at a relatively high temperature is performed.

  According to the present invention, sulfur that can be released at a relatively low temperature (for example, sulfur adhering to a noble metal) is released first, and then sulfur that can only be released at a relatively high temperature (sulfur that adheres to a trapping agent). Therefore, the time during which the catalyst is exposed to high temperature is shorter than when the poisoning is released from the beginning at a high temperature. In addition, since the time during which the temperature is increased is shorter than when the temperature is increased all at once, it is possible to suppress deterioration of fuel consumption and deterioration of the manifold catalyst.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an engine system diagram showing an embodiment of the present invention.
An electric throttle valve 3 for controlling the amount of intake air is installed in the intake passage 2 of the engine (internal combustion engine) 1, and a fuel injection valve 5 and a spark plug 6 are installed in the combustion chamber 4 of the engine 1, These are driven by an engine control unit (hereinafter referred to as ECU) 7.

In addition to the intake air amount Qa detected by the air flow meter 8 provided upstream of the electric throttle valve 3 in the intake passage 2, the ECU 7 detects the accelerator opening Apo detected by the accelerator pedal sensor 9 and the crank angle sensor 10. The engine rotation speed Ne, the engine coolant temperature Tw detected by the water temperature sensor 11, and the like are input.
The ECU 7 calculates a load (required torque) L necessary for the engine 1 mainly based on the accelerator opening Apo. Then, the target air-fuel ratio TFBYA is calculated based on the load L, the engine speed Ne, the engine coolant temperature Tw, and the like. The target air-fuel ratio TFBYA here is the reciprocal of the excess air ratio λ, and takes a value smaller than 1.0 for the stoichiometric air-fuel ratio (stoichiometric) and 1 for the lean air-fuel ratio. Then, the electric throttle valve 3 is driven in order to obtain an air amount necessary to realize the target air-fuel ratio TFBYA. That is, in the case of the same load, the leaner the target air-fuel ratio is, the larger the throttle opening becomes, thereby increasing the intake air amount Qa, and the closer the stoichiometric, the smaller the throttle opening. Reduce intake air amount Qa.

  Further, the basic fuel injection amount Tp = K × Qa / Ne (K is a constant) is calculated from the actual intake air amount Qa and the engine speed Ne, and this is multiplied by the target air-fuel ratio TFBYA to obtain a final value. The fuel injection amount Ti = Tp × TFBYA × COEF (COEF is various correction coefficients) is calculated. The fuel injection valve 5 is driven by a fuel injection pulse signal having a pulse width corresponding to Ti. The ignition timing of the spark plug 6 is controlled based on the engine speed Ne and the load L.

  The exhaust passage 12 of the engine 1 is provided with a three-way catalyst 13 as a manifold catalyst on the upstream side, and a NOx trap catalyst 14 as an underfloor catalyst on the downstream side. The downstream NOx trap catalyst 14 is equipped with a catalyst temperature sensor 15 as means for detecting the catalyst temperature, and the signal is input to the ECU 7. The catalyst temperature may be estimated from the exhaust temperature or the like.

The upstream three-way catalyst 13 is, for example, a honeycomb carrier coated with alumina supporting at least one component of a noble metal such as platinum Pt, palladium Pd, rhodium Rh, etc. When the exhaust air-fuel ratio is stoichiometric, HC, CO, It has the characteristic of simultaneously purifying NOx and purifying HC and CO by an oxidation reaction when the exhaust air-fuel ratio is lean.
The downstream NOx trap catalyst 14 further includes at least one component (NOx trapping agent) selected from an alkaline earth represented by barium Ba and an alkali metal represented by cesium Cs in the configuration of the three-way catalyst. In addition to the characteristics of the above three-way catalyst, NOx in the exhaust is trapped when the exhaust air-fuel ratio is lean, and trapped by reducing components (HC, CO) in the exhaust under stoichiometric to rich conditions It has the characteristic of reducing and purifying simultaneously with releasing NOx.

  By the way, in the NOx trap catalyst 14, sulfur poisoning occurs by trapping sulfur in the form of SOx on the same principle as trapping NOx. When sulfur poisoning occurs, the NOx trapping capability decreases, so it is necessary to appropriately cancel sulfur poisoning. In order to release sulfur poisoning, it is necessary to raise the temperature of the NOx trap catalyst 14 in a state where the exhaust is in a reducing atmosphere (exhaust air-fuel ratio is stoichiometric to rich).

Further, the sulfur adhering to the NOx trap catalyst 14 includes those that are easily desorbed and those that are not easily desorbed depending on the adhesion state. It is sulfur that adheres to the noble metal that is easily desorbed and can be released at a relatively low temperature (650 to 700 ° C.). The sulfur that is difficult to desorb is sulfur adhering to the trap material and cannot be released unless the temperature is relatively high (750 ° C. or higher).
Based on such a background, in the present invention, the poisoning release control is performed according to the flowcharts of FIGS. 2 and 3.

  In the following description of the flowchart, sulfur in a state that can be released at a relatively low temperature is referred to as “easy to fly”, and sulfur in a state that cannot be released at a relatively high temperature is referred to as “non-flying sulfur”. Further, the sulfur detoxification release temperature that is easy to fly is called “poisoning release temperature 1”, and the sulfur detoxification release temperature that is difficult to fly is called “poisoning release temperature 2”. It is assumed that the poisoning release temperature 1 <the poisoning release temperature 2, the poisoning release temperature 1 is, for example, 650 ° C., and the poisoning release temperature 2 is, for example, 750 ° C. Further, the sulfur poisoning amount that is easy to fly is referred to as “poisoning amount 1”, and the sulfur poisoning amount that is difficult to fly is referred to as “poisoning amount 2”, which is estimated separately.

FIG. 2 is a flowchart of poisoning amount estimation.
In S1, it is determined whether the air-fuel ratio is stoichiometric or rich. If YES, the process proceeds to S2, and if NO, the process proceeds to S4.
In S2, it is determined whether or not the catalyst temperature exceeds a high-temperature side poisoning release temperature 2 (for example, 750 ° C.). If YES, the process proceeds to S11, and if NO, the process proceeds to S3.

In S3, it is determined whether or not the catalyst temperature exceeds the low temperature side poisoning release temperature 1 (for example, 650 ° C.). If YES, the process proceeds to S8, and if NO, the process proceeds to S4.
Therefore, if the air-fuel ratio is lean as determined in S1, or if the catalyst temperature is lower than the low-temperature poisoning release temperature 1 as determined in S3, the process proceeds to S4. In these cases, poisoning is not released and the amount of poisoning increases.

In S4, the fuel injection amount Ti is multiplied by a predetermined coefficient 1 to calculate a sulfur poisoning increase amount 1 that is easy to fly. In S5, the fuel injection amount Ti is multiplied by a predetermined coefficient 2 to calculate the sulfur poisoning increase amount 2 that is difficult to fly.
In the next S6, the sulfur poisoning amount 1 that is easy to fly is calculated by adding the poisoning increase amount 1 to the previous value (old). In S7, the poisoning amount 2 of sulfur which is difficult to fly is calculated by adding the poisoning increase amount 2 to the previous value (old).

  That is, when lean or catalyst temperature <poisoning release temperature 1, since poisonous substances accumulate, they are added, but the poisonous substances are discharged in proportion to the fuel injection amount, and combustion exhaust Since the gas is carried to the catalyst, the poisoning amount is added by a value obtained by multiplying the fuel injection amount by a coefficient. In addition, although the releasable temperature differs between sulfur adhering to precious metals and sulfur adhering to the trapping agent, since the accumulation ratio is constant, there is an increase in the amount of sulfur poisoning that is easy to fly and the amount of sulfur poisoning that is difficult to fly The ratio is constant (coefficient 1: coefficient 2 = constant ratio).

Although the air-fuel ratio is stoichiometric to rich in the determination in S1, and the catalyst temperature does not exceed the high-temperature side poisoning release temperature 2 in the determination in S2 and S3, it exceeds the low-temperature side poisoning release temperature 1. If so, the process proceeds to S8. In this case, only the sulfur that is easy to fly is detoxified.
In S8, it is determined whether or not the sulfur poisoning amount 1 which is easy to fly is equal to or greater than a fixed value 1, and the process proceeds to S9 only in the case of YES.

In S9, as a function of the poisoning amount 1, a release rate 2 at a low temperature of sulfur which is difficult to fly is calculated. Specifically, the release speed 2 is calculated from the poisoning amount 1 based on the characteristics of the release speed 2 in FIG.
FIG. 4 shows the relationship between the poisoning amount and the release speed for each case. “Release speed 1” is the release speed at high temperature of sulfur which is difficult to fly, and “Release speed 2” is low temperature of sulfur which is easy to fly. “Release speed 3” indicates the release speed at a high temperature of sulfur which is easy to fly. In any case, the release rate increases as the poisoning amount increases. However, with the same poisoning amount, the release speed 1 <release speed 2 <release speed 3 is obtained.

In the next S10, the sulfur poisoning amount 1 which is easy to fly is updated by subtracting the release rate 2 which is the poisoning reduction amount per unit time from the previous value (old).
That is, when stoichiometric to rich and poisoning release temperature 1 <catalyst temperature <poisoning release temperature 2, only the sulfur that can easily fly is detoxified, so only the poisoning amount 1 of sulfur that can easily fly is subtracted. To go.

If the air-fuel ratio is stoichiometric to rich in the determination in S1 and the catalyst temperature exceeds the high-temperature poisoning release temperature 2 in the determination in S2, the process proceeds to S11. In this case, it is a case where the poisoning of sulfur which is easy to fly and sulfur which is difficult to fly is released.
In S11, it is determined whether or not the sulfur poisoning amount 1 that is easy to fly is equal to or greater than a predetermined value 1. If YES, the process proceeds to S12.

In S12, as a function of the poisoning amount 1, a release speed 3 at a high temperature of sulfur which is easy to fly is calculated. Specifically, the release speed 3 is calculated from the poisoning amount 1 based on the characteristics of the release speed 3 in FIG. In the next S13, the sulfur poisoning amount 1 which is easy to fly is updated by subtracting the release rate 3 which is the poisoning reduction amount per unit time from the previous value (old).
If the poisoning amount 1 is less than the fixed value 1 in the determination in S11, the process proceeds to S14.

In S14, it is determined whether or not the sulfur poisoning amount 2 that is difficult to fly is equal to or greater than a predetermined value 2, and the process proceeds to S15 only in the case of YES.
In S15, as a function of the poisoning amount 2, a release speed 1 at a high temperature of sulfur that is difficult to fly is calculated. Specifically, the release speed 1 is calculated from the poisoning amount 2 based on the characteristics of the release speed 1 in FIG. In the next S16, the sulfur poisoning amount 2 which is difficult to fly is updated by subtracting the release speed 1 which is the poisoning reduction amount per unit time from the previous value (old).

In the next S17, it is determined whether or not the sulfur poisoning amount 1 which is easy to fly is equal to or greater than a certain value 3 (<constant value 1), and the process proceeds to S18 only in the case of YES.
In S18, as a function of the poisoning amount 1, a release speed 3 at a high temperature of sulfur which is easy to fly is calculated. Specifically, the release speed 3 is calculated from the poisoning amount 1 based on the characteristics of the release speed 3 in FIG. The release speed 3 calculated here is smaller than that calculated in S12 because the poisoning amount 1 is reduced. In the next S19, the sulfur poisoning amount 1 which is easy to fly is updated by subtracting the release speed 3 which is the poisoning reduction amount per unit time from the previous value (old).

  That is, when stoichiometric to rich and the catalyst temperature is greater than the poisoning release temperature 2, if the sulfur poisoning amount 1 that is easy to fly is equal to or greater than a certain value 1, the sulfur that is easy to fly is released first. 1 is subtracted (S12, S13). When the poisoning amount 1 becomes less than a certain value 1, the sulfur poisoning release that is easy to fly is almost finished, and the sulfur that is difficult to fly can be released, so the sulfur poisoning amount 2 that is difficult to fly is subtracted. (S15, S16). At this time, sulfur which is easy to fly is also released, although it is small. If the poisoning amount 1 is 3 or more, the poisoning amount 1 is also subtracted (S18, S19).

FIG. 3 is a flowchart of poisoning release control including poisoning release timing determination.
In S21, it is determined whether or not the poisoning cancellation request flag has already been set. If the poisoning release request flag = 1, the process proceeds to S25 for the removal of poisoning. If the poisoning release request flag = 0, the process proceeds to S22 for determining the poisoning release time.
In S22, the sum of the poisoning amount 1 of sulfur that is easy to fly and the poisoning amount 2 of sulfur that is difficult to fly (the poisoning amount 1 + 2) estimated by the flowchart of poisoning amount estimation is calculated. It is determined whether or not the set poisoning release requirement amount 1 is exceeded.

If the amount of poisoning 1 + 2> the amount required for detoxification is 1, there is a possibility of affecting the emission. Therefore, it is determined that it is time to detoxify, proceed to S24, set the poisoning release request flag, Proceed to S25 to cancel the poison.
If the poisoning amount 1 + 2 <the poisoning cancellation necessary amount 1, the process proceeds to S23.
In S23, it is determined whether or not the sulfur poisoning amount 2 which is difficult to fly is equal to or greater than a predetermined value (C22), and the poisoning amount 1 + 2 exceeds the poisoning release required amount 2 set smaller than the poisoning release required amount 1 Determine.

  If the poisoning amount 2> the constant value and the poisoning amount 1 + 2> the required amount 2 of poisoning cancellation, it is determined that the poisoning cancellation time is reached, the process proceeds to S24, and the poisoning cancellation request flag is set, and then the poisoning is performed. Proceed to S25 for release. When the poisoning amount 2 of sulfur that is difficult to fly is larger than a certain value (relatively large), the required amount of detoxication for determining the detoxication timing is changed to the smaller side (the necessary amount of detoxication 1 → 2) This is to increase the frequency of release of poisoning.

On the other hand, if all of the determinations in S21 to S23 are NO, it is not the poisoning release timing, so the poisoning release is not performed.
In S25, it is determined whether or not it is a poisoning release 1 possible region where low temperature poisoning release is possible. Specifically, referring to FIG. 5, it is determined from the engine speed Ne and the load (torque) L whether or not the region is on the higher rotation / high load side (high exhaust temperature side) than the boundary line L1. This is because it is difficult to raise the temperature to the poisoning release temperature 1 even if the ignition timing is retarded in an area on the low rotation / low load side (for example, low vehicle speed conditions). If it is the poisoning release 1 possible area, the process proceeds to S26, and if not, it waits to enter the poisoning release 1 possible area.

In S26, it is determined whether or not the sulfur poisoning amount 1 which is easy to fly is equal to or less than a predetermined value (C10) for judging the end of the low-temperature poisoning. If NO, go to S27. If YES, Proceed to S28. That is, since the sulfur poisoning release which is easy to fly is performed at a low temperature at first, if the poisoning amount 1 is not less than a certain value, the process proceeds to S27.
In S27, the ignition timing is retarded to cancel the poisoning. However, in order to cancel the poisoning at a low temperature, a map as shown in FIG. 6 prepared in advance by setting the target catalyst temperature to 650 to 700 ° C. is used. The low-temperature retard amount is searched from the engine speed Ne and the load (torque) L, the ignition timing is retarded by the retard amount, and the exhaust temperature is raised. FIG. 6 shows the tendency of the retard amount of the ignition timing for obtaining a certain target catalyst temperature (target exhaust temperature) using the engine speed Ne and the load (torque) L as parameters.

  When the sulfur poisoning amount 1 that is easy to fly becomes equal to or less than a certain value due to the low temperature poisoning cancellation, the process proceeds from S26 to S28. When the amount of sulfur poisoning 1 that is easy to fly becomes a certain value or less due to the low temperature poisoning cancellation, the high temperature poisoning is canceled in principle. To reduce the high temperature poisoning cancellation once every n times, or once every n times, the high temperature poisoning cancellation is executed (n-1 times n times, high temperature poisoning cancellation canceled) . Note that n ≧ 2.

For this reason, in S28, if high temperature poisoning cancellation is to be executed once every n times, it is determined whether or not the number of consecutive cancellations has reached n-1 times. If YES, the high temperature poisoning cancellation is executed. Therefore, the process proceeds to S29. If NO, the process proceeds to S33 for cancellation.
In S29, it is determined whether or not the sulfur poisoning amount 2 that is difficult to fly is equal to or greater than a predetermined value (C20). This constant value is a value for determining the end of the high temperature poisoning cancellation when it becomes less than this. Accordingly, in the case of YES, the process proceeds to S30 for executing the high temperature poisoning cancellation, and in the case of NO, the process proceeds to S33 for completing the high temperature poisoning cancellation.

  In S30, it is determined whether or not it is a poisoning release 2 possible region where high temperature poisoning release is possible. Specifically, referring to FIG. 5, it is determined from the engine speed Ne and the load (torque) L whether or not the region is on the higher rotation / high load side (high exhaust temperature side) than the boundary line L2. This is because it is difficult to raise the temperature to the poisoning release temperature 2 even if the ignition timing is retarded in the low rotation / low load region. The poisoning release 2 possible area is an area including the poisoning release 1 possible area. If it is the poisoning release 2 possible region, the process proceeds to S31, and if not, the process proceeds to S32.

  In S31, the ignition timing is retarded to cancel the poisoning. However, in order to cancel the poisoning at a high temperature, a map as shown in FIG. 6 prepared in advance by setting the target catalyst temperature to 750 ° C. or higher is used. From the engine speed Ne and the load (torque) L, the high-temperature retard amount is searched, the ignition timing is retarded by the retard amount, and the exhaust temperature is raised. The map used in S27 and the map used in S31 have the same tendency, but the target catalyst temperature is different. Therefore, the map used in S31 has a larger retardation amount than the map used in S27 under the same operating conditions. Become.

If the sulfur poisoning amount 2 that is difficult to fly becomes equal to or less than a certain value due to the high temperature poisoning cancellation, the process proceeds from S29 to S33, where the poisoning request flag = 0 and the poisoning cancellation is terminated.
On the other hand, if the number of consecutive cancellations has not reached n-1 in the determination in S28 and the process proceeds to S33 for canceling the high temperature poisoning cancellation, the poisoning cancellation request flag = 0 is set and the high temperature poisoning cancellation is performed. To cancel the poisoning release.

  If it is determined in S30 that the poisoning release 2 possible area is not reached, the process proceeds to S32. However, in S32, the sulfur poisoning amount 2 that is difficult to fly is equal to or less than a predetermined value (C21) and is outside the poisoning removal 2 possible area. It is determined whether or not the continuous elapsed time at has reached a certain time. The constant value (C21) for the poisoning amount 2 here is a value that does not affect the emission, and is set to a value larger than the constant value (C20) in S29. In the case of YES, it progresses to S33, sets poisoning cancellation | release request flag = 0, cancels high temperature poisoning cancellation | release, and completes poisoning cancellation | release. If the continuous elapsed time outside the poisoning release 2 possible area becomes longer, the catalyst temperature decreases, and it takes time to raise the temperature again. Therefore, the poisoning amount 2 is less than the value that does not affect the emission. This is to end the poisoning release on the condition. In the case of NO, it waits to enter the poisoning release 2 possible area.

  FIG. 7 is a conceptual diagram of the temperature rise when the poisoning is released. At the time point (t1) when it is determined that the poisoning release time is reached, first, the catalyst temperature is raised to the low-temperature side poisoning release temperature 1 (for example, 650 to 750 ° C.), and the low-temperature poisoning release is performed. Process. After that, when the easy-to-fly sulfur is treated to some extent (t2), the catalyst temperature is further raised to the high-temperature-side poisoning release temperature 2 (750 ° C. or higher) to release the high-temperature poisoning, and the sulfur that is difficult to fly is treated. To do. This continues until the point (t3) at which the hard-to-fly sulfur is treated.

FIG. 8 is a diagram comparing the prior art and the present invention. In any case, the manifold catalyst is provided upstream of the exhaust passage and the NOx trap catalyst is provided downstream. As for the manifold catalyst, the temperature (referred to as the manifold contact temperature) is measured at the inlet side. The temperature (called trap temperature) was measured at the outlet side.
FIG. 8A shows the case of the prior art, in which high temperature poisoning is released at once. In this case, the trap temperature rises from the trap normal temperature to the trap temperature when the high temperature is released. The manifold contact temperature rises from the manifold contact normal temperature higher than the trap normal temperature to the high temperature release manifold contact temperature higher than the high temperature release trap temperature.

FIG. 8B shows the case of the present invention, in which the high temperature poisoning release is performed following the low temperature poisoning release. In this case, the trap temperature rises from the trap temperature when the low temperature is released to the trap temperature when the high temperature is released. The manifold contact temperature rises from the low temperature release manifold contact temperature higher than the low temperature release trap temperature to the high temperature release release manifold contact temperature higher than the high temperature release trap temperature.
What can be said by comparing the two is that, as indicated by a in FIG. 8A, when the trap temperature is the trap temperature at low temperature release, the manifold contact temperature is higher than that of the present invention. Will reach the manifold contact temperature when the high temperature is released, and the waiting time from when the manifold contact temperature reaches the manifold contact temperature when the high temperature is released until the trap temperature reaches the trap temperature when the high temperature is released is increased. .

  In addition, as indicated by b in FIG. 8B, in the present invention, the temperature of the upstream portion has already increased during the release of the low temperature, so the trap temperature rises quickly (the inclination is larger than that of the prior art). Therefore, the trap temperature reaches the trap temperature when the high temperature is released faster, and the waiting time until the trap temperature reaches the trap temperature when the high temperature is released after the manifold contact temperature reaches the manifold temperature when the high temperature is released is shortened. That is.

  Therefore, according to the present embodiment, the temperature rise at the time of the release of poisoning is divided into two stages, the low temperature poisoning release (S27) in which the poisoning release is first performed at a relatively low temperature, and the state in which the release can be performed at a relatively low temperature. When the sulfur is removed, the temperature is further increased, and the high temperature poisoning release (S31) for releasing the poisoning at a relatively high temperature is performed. Since the time required for the (NOx trap catalyst) to reach a high temperature is shortened and the time during which the (NOx trap catalyst) is exposed to the high temperature is shortened, deterioration of fuel consumption and deterioration of the catalyst (particularly, the upstream manifold catalyst) can be suppressed.

Further, according to the present embodiment, the first poisoning amount (the poisoning amount 1), which is the sulfur poisoning amount that can be released at a relatively low temperature, and the sulfur poisoning state that can only be released at a relatively high temperature. A second poisoning amount (a poisoning amount 2) that is a poisoning amount is estimated separately, and the determination of the poisoning release time is performed based on the first poisoning amount and the second poisoning amount. Therefore, it is possible to accurately determine the poisoning release time.
In addition, according to the present embodiment, when the poisoning amount is estimated, the poisoning increase amount corresponding to the operating condition (fuel injection amount Ti) is added except when the poisoning is released, and when the poisoning is released, the catalyst temperature is increased. The poisoning amount can be accurately estimated by subtracting the poisoning reduction amount (release speed) corresponding to (and the poisoning amount) and calculating the first and second poisoning amounts.

According to the present embodiment, the increase in poisoning for calculating the first poisoning amount and the increase in poisoning for calculating the second poisoning amount are considered to have a constant accumulation ratio. Based on this, by setting a certain ratio (coefficient 1: coefficient 2), it is possible to estimate each poisoning amount relatively easily and accurately.
Further, according to the present embodiment, the poisoning reduction amount (release speed) for calculating the first poisoning amount and the poisoning reduction amount (release speed) for calculating the second poisoning amount, By calculating with different characteristics with respect to the catalyst temperature, it is possible to accurately estimate each poisoning amount in consideration of the characteristics of sulfur that is likely to fly and sulfur that is difficult to fly.

Further, according to the present embodiment, the determination of the poisoning release time is performed based on the sum of the first poisoning amount and the second poisoning amount (the poisoning amount 1 + 2), and the sum is a predetermined amount of poisoning. By determining that it is the poisoning release time when it is larger than the poison removal requirement amount (poisoning removal requirement amount 1) (S22), the poisoning release time can be accurately determined.
Further, according to the present embodiment, when the second poisoning amount (poisoning amount 2) is larger than a certain value, the poisoning release required amount for determining the poisoning release timing is changed to a smaller side. (Detoxication required amount 1 → 2) (S23) When there is a lot of sulfur that is difficult to fly, the chance of release can be increased, and the release of sulfur that is difficult to fly becomes easier.

Further, according to the present embodiment, when the operating conditions (parameters related to the engine speed, load, and further the vehicle speed) are lower than the predetermined conditions, the high temperature poisoning cancellation is canceled. (S30) It is possible to prevent a significant deterioration in fuel consumption due to an excessive increase in the control amount (ignition timing retardation amount) for increasing the exhaust gas temperature.
Further, according to the present embodiment, by canceling the high temperature poisoning cancellation at a predetermined rate with respect to the low temperature poisoning cancellation (S28), the frequency of the high temperature poisoning cancellation is reduced, the fuel consumption is deteriorated, the manifold It becomes possible to suppress deterioration of the catalyst.

  Further, according to the present embodiment, the low temperature poisoning release and the high temperature poisoning release can be easily performed by performing retarding of the ignition timing and varying the retard amount. However, post injection may be performed in the expansion stroke or exhaust stroke, and the post injection amount may be controlled.

Engine system diagram showing an embodiment of the present invention Flow chart of poisoning amount estimation Flow chart of poisoning release control including poisoning release time judgment The figure which shows the relationship between poisoning quantity and poisoning release speed Diagram showing poisonable release possible area Diagram showing retard amount calculation map Conceptual diagram of temperature rise at the time of release of poisoning Diagram comparing the prior art and the present invention

Explanation of symbols

1 engine
2 Intake passage
3 Electric throttle valve
4 Combustion chamber
5 Fuel injection valve
6 Spark plug
7 ECU
12 Exhaust passage
13 Three-way catalyst (manifold catalyst)
14 NOx trap catalyst
15 Catalyst temperature sensor

Claims (10)

An engine having an exhaust gas purification catalyst having a NOx trap function in an exhaust passage, determining the timing of detoxication of sulfur adhering to the catalyst, and increasing the exhaust temperature when it is determined to be the detoxication timing, thereby detoxicating the engine In the exhaust purification device of
The temperature rise at the time of release of poisoning is divided into two stages. At first, when the release of low-temperature poisoning that removes poisoning at a relatively low temperature and when sulfur that can be released at a relatively low temperature is removed, the temperature is further raised. An exhaust purification device for an engine, characterized in that the high temperature poisoning release for releasing the poisoning at a relatively high temperature is performed. A first poisoning amount that is a sulfur poisoning amount that can be released at a relatively low temperature and a second poisoning amount that is a sulfur poisoning amount that can be released only at a relatively high temperature are separately estimated. Having poisoning amount estimation means,
The engine exhaust gas purification apparatus according to claim 1, wherein the determination of the poisoning release timing is performed based on the first poisoning amount and the second poisoning amount.   The poisoning amount estimation means adds the poisoning increase amount according to the operating conditions except when the poisoning is released, and subtracts the poisoning reduction amount according to the catalyst temperature when the poisoning is released. 3. The engine exhaust gas purification apparatus according to claim 2, wherein the second poisoning amount is calculated.   The poisoning amount estimation means sets the poisoning increase amount for calculating the first poisoning amount and the poisoning increase amount for calculating the second poisoning amount at a constant ratio. The exhaust emission control device for an engine according to claim 3.   The poisoning amount estimation means calculates a poisoning reduction amount for calculating the first poisoning amount and a poisoning reduction amount for calculating the second poisoning amount with different characteristics with respect to the catalyst temperature. The exhaust emission control device for an engine according to claim 3 or 4,   The determination of the poisoning release time is performed based on the sum of the first poisoning amount and the second poisoning amount, and when the sum is larger than a predetermined required amount of poisoning removal, it is determined that the poisoning release time is reached. The engine exhaust gas purification apparatus according to any one of claims 2 to 5, wherein:   7. The engine exhaust gas purification apparatus according to claim 6, wherein when the second poisoning amount is larger than a predetermined value, the poisoning cancellation required amount for determining the poisoning cancellation timing is changed to a smaller side. .   The engine exhaust gas purification apparatus according to any one of claims 1 to 7, wherein the high-temperature poisoning cancellation is canceled when an operating condition is on a lower exhaust temperature side than a predetermined condition. .   The engine exhaust purification device according to any one of claims 1 to 8, wherein the high temperature poisoning cancellation is canceled at a predetermined rate with respect to the low temperature poisoning cancellation.   The engine exhaust gas purification according to any one of claims 1 to 9, wherein the low temperature poisoning release and the high temperature poisoning release are performed by retarding the ignition timing, and varying the retard amount. apparatus.

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