JP4182281B2 - Exhaust gas purification control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to control for releasing poisonous substances adhering to an exhaust gas purification catalyst.
[0002]
[Prior art]
In Japanese Patent Laid-Open No. 11-303622, when releasing and reducing (releasing) SOx (sulfur oxide), which is a poisonous substance adhering to the exhaust purification catalyst, the air-fuel ratio is made rich and at the same time the exhaust temperature The ignition timing is retarded in order to raise the value, and the period during which the SOx is released is managed by time.
[0003]
[Problems to be solved by the invention]
In the above-described prior art, when the exhaust system temperature differs for each cylinder group, it cannot be quickly raised to the SOx release possible temperature after the start of SOx release. That is, when considering a system (2-in-2 system) in which the exhaust passages of the two cylinder groups are each provided with a catalyst, the higher the exhaust system temperature quickly reaches the SOx release possible temperature, whereas the exhaust system temperature. The lower is the delay in reaching the SOx release possible temperature, causing a cylinder group difference in the release amount.
[0004]
If the SOx release period is uniformly managed by time, the poisoning release time of one cylinder group deviates from the actual release state. That is, if the release time is set to the cylinder group having a low temperature, the fuel consumption is deteriorated, and if the release time is set to a cylinder group having a high temperature, the SOx release of the lower temperature cylinder group becomes insufficient.
Considering the case of a system having a catalyst (2 in 1 system) in the exhaust passage downstream of the joining portion of the exhaust passages of the two cylinder groups (2 in 1 system), the lower the exhaust system temperature, the faster In addition, the temperature cannot be raised to the SOx release possible temperature, and the SOx release period becomes longer and the fuel consumption deteriorates. In addition, exhaust from each cylinder group drifts without being sufficiently mixed and is introduced into the catalyst, resulting in a difference in the poisoning release performance for each region within the catalyst, resulting in a release time as in the case of the 2-in-2 system. If longer, the fuel consumption deteriorates, and if the release time is shortened, SOx release is insufficient and both cannot be achieved.
[0005]
The present invention has been made paying attention to such a conventional problem, and aims to improve the poisoning release performance by eliminating the temperature difference between the cylinder groups when the poisoning release is started. To do.
[0006]
[Means for Solving the Problems]
Therefore, the present invention performs the following control in an internal combustion engine provided with an exhaust purification catalyst for each cylinder group.
That is, when performing the control to release the poisoning substance attached to each catalyst, the cylinder with the lower catalyst temperature is reduced so that the difference in the catalyst temperature between the cylinder groups is reduced before the poisoning substance is released. Control is performed to raise the catalyst temperature of the group.
[0007]
In this way, since the release of poisonous substances starts after the catalyst temperature of each cylinder group becomes equal, there is no difference in release performance between the cylinder groups, and all cylinder groups are reliably poisoned in a short time. Release can be completed.
Another invention performs the following control in an internal combustion engine including an exhaust purification catalyst on the downstream side of the merging portion of the exhaust passage for each cylinder group.
[0008]
That is, when performing the control to release the poisoning substance attached to the catalyst, the temperature difference of the exhaust gas introduced into the catalyst from each cylinder group is reduced before the release of the poisoning substance is started. In addition, control is performed to increase the temperature of the cylinder group having the lower temperature.
In this way, after the exhaust temperature of the low-temperature side cylinder group is raised until it becomes equal to the exhaust temperature of the high-temperature side cylinder group, the release of poisonous substances is started. It can be shortened and fuel economy is improved. Moreover, the performance disparity for each region inside the catalyst is eliminated, and the poisoning release performance is further improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a system diagram according to the first embodiment of the present invention. In an internal combustion engine 1 having an exhaust system for each cylinder group (FIG. 1 shows a V-type 6-cylinder engine as an example), one cylinder group includes an upstream Fr catalyst 3 and a downstream Rr catalyst 4 in an exhaust passage 2. Are arranged in series, and in the other cylinder group, similarly, an upstream Fr catalyst 6 and a downstream Rr catalyst 7 are arranged in series in the exhaust passage 5 (2-in-2 system).
[0010]
The exhaust passage 2 is provided with an EGR passage 8 for extracting EGR gas, and the flow rate of the EGR gas is controlled by an EGR valve 9 interposed in the EGR passage 8. The upstream Fr catalysts 3 and 6 use a three-way catalyst that exhibits good purification performance in the vicinity of the stoichiometric air-fuel ratio, and NOx trap catalysts are used as the downstream Rr catalysts 4 and 7. The NOx trap catalyst traps NOx in the exhaust when the exhaust air-fuel ratio is lean, and releases the trapped NOx when the exhaust air-fuel ratio is rich or is reduced by the three-way catalyst layer A catalyst to be treated (NOx trap type three-way catalyst).
[0011]
In the above system, the EGR gas may be introduced from the upstream side of the Fr catalyst 3 or from the downstream exhaust passage thereof, but the EGR gas is introduced from the upstream side of the Rr catalyst 4 constituted by the NOx trap catalyst of one bank. By being exploited, the temperature of the Rr catalyst 4 becomes lower as the flow rate of the exhaust gas flowing through the catalyst is reduced by the amount of EGR gas than the Rr catalyst 7 in the other bank where the EGR gas is not exploited.
[0012]
Therefore, the control for releasing SOx (poisonous substances) adhering to the catalyst (mainly the downstream side catalysts 4 and 7 which are NOx trap catalysts) while eliminating the influence of the catalyst temperature difference between the banks is as follows. Execute.
The poisoning release control in the above system will be described according to the flowchart shown in FIG.
[0013]
FIG. 2 shows a main flow of a series of controls for executing the poisoning release control at a predetermined timing while estimating the SOx adhesion amount (hereinafter referred to as poisoning amount) of each catalyst.
In step 101, the amount of poisoning of each catalyst is estimated, whether or not it is necessary to cancel the poisoning, the value of the flag SOXFUL is set, and in step 102, the poisoning cancellation is performed based on the value of the flag SOXFUL. Whether or not is necessary is determined.
[0014]
If it is determined in step 102 that it is necessary to cancel the poisoning, it is determined in step 103 whether or not it is possible to shift to the poisoning cancellation control, and the value of the flag FSOXLS is set. In step 104, the poisoning is determined based on the value of the flag FSOXLS. It is determined whether or not the engine is in an operating state that allows the transition to the poison release control.
If it is determined in step 104 that the shift to the poisoning cancellation control is possible, the poisoning cancellation control is started in step 105. Here, the exhaust temperature is raised and the exhaust air-fuel ratio is enriched.
[0015]
In step 106, it is determined whether or not the poisoning amount counter can be subtracted. Here, the value of the flag FSOXCD is set by determining whether or not the poisoning amount counter can be subtracted depending on the temperature state of the NOx trap catalyst.
In step 107, it is determined whether or not the poisoning amount counter can be subtracted based on the value of the flag FSOXCD. If it is determined that subtraction is possible, the end of poisoning cancellation is determined in step 108. Specifically, the poisoning release control is terminated when the poisoning release amount per unit time is calculated and the estimated value of the poisoning amount is subtracted and the estimated value of the poisoning amount falls below a predetermined value. And flag SOXFUL is set to 1.
[0016]
In step 108, the end of the poisoning release control is determined based on the value of the flag SOXFUL. When the flag SOXFUL = 1, this flow is ended.
FIG. 3 shows a poisoning release timing determination flow in step 101 of FIG.
In step 201, the vehicle speed (VSP), the engine rotation speed (RPM), and the load (T) are read as the engine operation state.
[0017]
In Step 202, the poisoning amount ΔSOX of the catalyst per unit time is integrated based on the operating state, and this integrated value is calculated as the current poisoning amount TSOX.
In step 203, the poisoning amount TSOX is compared with the poisoning determination amount SOXFUL, and when it is determined that TSOX ≧ SOXFUL, it is determined that the poisoning amount has reached an amount that requires the poisoning release control, and the process proceeds to step 204. Then, the poisoning release request flag FSOXFUL = 1 is set and a poisoning release control request is set.
[0018]
If it is determined in step 203 that TSOX <SOXFUL, it is determined that the poisoning amount has not reached the amount that requires the poisoning cancellation control, and the routine proceeds to step 205 where the flag FSOXFUL = 0 and the poisoning cancellation control is performed. Reject the request.
FIG. 4 shows a poisoning release control transition determination flow in step 103 of FIG. In step 301, the vehicle speed (VSP), the engine speed (RPM), and the load (T) are read as the engine operating state.
[0019]
In steps 302, 303, and 304, it is determined whether or not the vehicle speed, the engine speed, and the load are within the range where the control can be shifted to the poisoning release control.
If all the conditions are affirmed (determined to be in the area), the poisoning cancellation execution flag FSOXRLS is set to 1 in step 305 to permit the cancellation control execution.
If each condition is denied in steps 302, 303, and 304, the poisoning release execution flag FSOXRLS = 0 is set in step 306, and the release execution is rejected.
[0020]
FIG. 5 shows a poisoning release control flow according to the present invention executed in step 105 of FIG.
In step 401, the vehicle speed (VSP), the engine speed (RPM), the load (T), and the intake air amount (Q) are read as the engine operating state.
In step 402, the ignition timing of the EGR exploitation side cylinder group (hereinafter referred to as bank 1) is retarded. At this time, the ignition timing retard amount is set to a retard amount at which the NOx trap poisoning can be released. The calculation of the retard amount is determined by the engine operating state read in step 401.
[0021]
In step 403, the ignition timing of the EGR non-introduced cylinder group (hereinafter referred to as bank 2) is retarded. The ignition timing retard amount is also determined in the same manner as in bank 1.
Simultaneously with the ignition timing retard, EGR is stopped at step 404 and the exhaust air-fuel ratio is enriched at step 405.
In step 406, the temperature TEMP1 of the Fr catalyst 3 in the bank 1 is calculated. The calculation of TEMP1 can be estimated based on the engine operating state read in step 401, but it may be estimated from the exhaust temperature by a temperature sensor provided upstream or downstream of the catalyst, and the temperature of the catalyst is directly measured by the sensor. The value may be used.
[0022]
In step 407, the catalyst temperature TEMP2 of the Fr catalyst 6 in the bank 2 is calculated. Similarly to TEMP1, this TEMP2 is calculated by an engine operating state or a temperature sensor.
In step 408, the temperature of each bank is compared based on the calculated TEMP1 and TEMP2. Specifically, when the temperature difference (TEMP2−TEMP1) between the temperature TEMP2 of the high temperature side bank and the temperature TEMP1 of the low temperature side bank is equal to or greater than a predetermined value TEMPA, the temperature difference is large and is less than the predetermined value TEMPA. Judge that the temperature is almost the same.
[0023]
If it is determined in step 408 that the catalyst temperature difference between the banks is large after the start of the poisoning release control, the routine proceeds to step 409, where the ignition timing retard amount of the low temperature side bank 1 is further added, and only the bank 1 is changed. When the ignition timing control is performed to raise the temperature further, and it is determined that the temperatures are almost the same, step 409 is jumped to stop adding the ignition timing retard amount of the low temperature side bank 1, and the retard set in step 402 Return the amount to the same retard amount as the high temperature bank.
[0024]
FIG. 6 shows a flow of determining whether or not the poisoning amount can be subtracted, which is executed in step 106 of FIG.
In step 601, the vehicle speed (VSP), the engine speed (RPM), the load (T), and the intake air amount (Q) are read as engine operating states.
In step 602, the catalyst temperature TEMPR of the Rr catalyst that is the NOx trap catalyst is estimated based on the engine operating state read in step 601. Here, the catalyst temperature estimated in step 602 can be estimated based on the engine operating state read in step 601, but may be estimated from the exhaust temperature by a temperature sensor provided upstream or downstream of the catalyst, or directly You may use the value which measured temperature of this with the sensor.
[0025]
In step 603, the estimated catalyst temperature TEMPR is compared with the poisoning amount subtraction permission temperature SOXTEMP.
If it is determined in step 603 that the catalyst temperature TEMPR is lower than the poisoning amount subtraction permission temperature SOXTEMP, the subtraction permission flag FSOXCD is set to 0 in step 605 to disable the counter subtraction.
[0026]
If it is determined in step 603 that the catalyst temperature TEMPR is equal to or higher than the poisoning amount subtraction permission temperature SOXTEMP, the subtraction permission flag FSOXCD is set to 1 in step 604, and the subtraction of the poisoning amount counter is permitted.
FIG. 7 shows an end determination flow of the poisoning release control.
In step 701, the vehicle speed (VSP), the engine speed (RPM), the load (T), and the intake air amount (Q) are read as engine operating states.
[0027]
In step 702, a poisoning release amount MSOX per unit time is calculated based on the engine operating state.
In step 703, the poisoning amount TSOX is calculated by the following equation.
TSOX = TSOXold + ΔSOX−MSOX
Here, TSOXold is the previous calculated value of the poisoning amount TSOX. Since the poisoning release amount MSOX is a very large value with respect to the poisoning amount ΔSOX during the poisoning release control, TSOX is subtracted.
[0028]
In step 704, the end of the release control is determined based on whether the calculated poisoning amount TSOX is equal to or less than the release control end determination value SOXMIN.
If it is determined in step 704 that TSOX> SOXMIN, that is, the release control has not been completed yet, the process returns to step 701 to continue the poisoning release control.
[0029]
If it is determined in step 704 that TSOX ≦ SOXMIN, that is, the release control is still finished, the flags SOXFUL, FSOXRSL, and FSOXCD are sequentially set to 0 in steps 705 to 707, and the poisoning release control is finished.
FIG. 8 shows a state during poisoning release control in the first embodiment. The EGR is stopped simultaneously with the request for the poisoning cancellation control, and the exhaust air-fuel ratio is enriched by performing the air-fuel ratio enrichment control, and the ignition timing is retarded to start the poisoning cancellation control. In parallel with the poisoning release control, the ignition timing retard amount on the EGR exploitation side is made larger than the retard amount on the non-EGR exploitation side to raise the exhaust gas temperature. As a result, the temperature difference between the Rr catalyst 4 and the Rr catalyst 7 which are NOx trap catalysts in both banks (cylinder group) is quickly reduced while the temperature difference disappears, and then reaches a temperature at which poisoning can be released. Poison release is started simultaneously in both cylinder groups.
[0030]
Therefore, the poisoning release performance is equal among the cylinder groups, and the poisoning release control can be started quickly and the poisoning release control can be completed in a short time, and thus exhaust purification while maintaining good fuel efficiency. The performance can be improved sufficiently.
FIG. 9 shows a state in which the same control is performed without performing the control for eliminating the catalyst temperature difference in each cylinder group after requesting the poisoning cancellation without considering the influence of the catalyst temperature difference between the cylinder groups. It shows as a comparative example. In this case, the Rr catalyst of the EGR non-exploitation side cylinder group reaches the poisoning releaseable temperature earlier than the Rr catalyst of the EGR extraction side cylinder group, and the poisoning cancellation of the air-fuel ratio rich control and the ignition timing retard control is performed. Since the control has already started, the actual poisoning release starts from this time. On the other hand, since the Rr catalyst of the EGR extraction side cylinder group has not yet reached the poisoning releaseable temperature, the poisoning release is not started, and the performance between the cylinder groups is different. If the catalyst temperature is not taken into account in calculating the poisoning amount TSOX, the subtraction starts at the same time as the poisoning release control request, so that it differs from the actual value. Even if it is calculated correctly, the calculated value of the poisoning amount TSOX is not changed. Based on this, the poisoning release control is terminated simultaneously in both cylinder groups, so that the Rr catalyst poisoning release control time of the EGR exploitation side cylinder group is insufficient, or the poisoning release amount is insufficient, or conversely, Poison release control is prolonged and fuel consumption and driving performance are deteriorated.
[0031]
Further, in the above embodiment, the ignition timing of the cylinder group with the lower temperature (bank 1) is retarded than the cylinder group with the higher temperature (bank 2) for a predetermined period, so that the responsiveness is high. By increasing the exhaust temperature, the catalyst temperature on the low temperature side can be quickly brought close to the catalyst temperature on the high temperature side.
In particular, until the catalyst temperature of each cylinder group becomes substantially the same, the ignition timing of the cylinder group with the lower temperature is retarded than the cylinder group with the higher temperature, so that it is necessary and sufficient. Control with a difference in retard is performed, and the driving performance can be satisfactorily satisfied.
[0032]
Each cylinder group (bank 1, 2) further includes a front catalyst (Fr catalysts 3, 6) upstream of the catalyst (Rr catalysts 4, 7), and the temperatures of these front catalysts are substantially the same. Until now, by setting the ignition timing of the cylinder group having the lower temperature to be retarded than the details of the cylinder having the higher temperature, the temperature of the downstream side catalyst (Rr catalysts 4 and 7) for releasing the poisoning is also increased. Until the two become substantially the same, the control with a difference in the retard is performed.
[0033]
Further, on the condition that the catalyst temperature difference between the cylinder groups is equal to or greater than a predetermined value (TEMPA), the ignition timing of the lower temperature cylinder group is retarded than the higher temperature cylinder group for a predetermined period. As a result, control with a difference in retard is performed only for the minimum necessary period without being affected by variations in temperature detection.
In addition, as a control to release poisonous substances, the ignition timing retard and the air-fuel ratio enrichment are adopted, so that the conditions for temperature rise and reducing agent supply necessary for the poisoning cancellation are satisfied and good performance is achieved. Can be obtained.
[0034]
If a control request to release the poisonous substance is issued, the ignition timing of the higher temperature cylinder group is set to the retard amount for the control to release the poisonous substance before the release of the poisonous substance is started. By setting the ignition timing of the cylinder group with the lower temperature to the retard side than this, the ignition timing retard control is performed before the release of poisonous substances is started in both the high temperature side and low temperature side cylinder groups. By increasing the exhaust gas temperature and increasing the exhaust temperature, the low temperature side catalyst temperature can be quickly brought close to the high temperature side catalyst temperature by increasing the retard amount on the low temperature side while accelerating the start of detoxication. it can.
[0035]
In addition, after the catalyst temperature of each cylinder group becomes substantially the same, the retard amount is returned to the ignition timing of the control of the cylinder group whose temperature is lower until the control timing of releasing the poisonous substance, thereby reducing the temperature. After the side cylinder group is in the same temperature state as the high temperature side cylinder group, the retard amount appropriate for releasing poisoning is controlled to obtain good releasing performance.
Moreover, after the catalyst temperature of each cylinder group becomes substantially the same, the same poisoning release performance can be obtained in each cylinder group by making the retard amount of the ignition timing of each cylinder group the same.
[0036]
Further, by applying to an engine having an EGR device that recirculates exhaust gas from one cylinder group to the intake system, the poisoning release performance due to the EGR exploitation side cylinder group becoming lower temperature than the EGR nonexploit cylinder group Can be effectively prevented.
In addition, when a request to release the poisonous substance is issued, EGR is stopped before the release of the poisonous substance is started, and the ignition timing of the cylinder group having the higher temperature is released. Is set to the retard amount, and the ignition timing of the higher temperature cylinder group is set to the retard side than this, so that the EGR stop and ignition timing retard causing the low temperature side cylinder group to decrease in temperature. By increasing the amount, the temperature of the high temperature side cylinder group can be quickly brought close to.
[0037]
Further, when a request to release the poisoning substance is made, the EGR is stopped, and after the predetermined period has elapsed, the release of the poisoning substance is started. After the difference is reduced, the poisoning release is started, and the performance among the cylinder groups can be equalized.
In particular, when a request to release the poisonous substance is made, the EGR is stopped, and after the catalyst temperature of each cylinder group becomes substantially the same, the release of the poisonous substance is started. The performance among the cylinder groups can be more equalized.
[0038]
In the above-described embodiment, the air-fuel ratio enrichment control is started at the same time as the control request for releasing the poisonous substance is issued. However, as shown by the one-dot chain line in FIG. When they become the same, the air-fuel ratio enrichment control may be started to enrich the exhaust air-fuel ratio. In this case, since enrichment is waited until the catalyst temperature of each cylinder group becomes substantially equal, deterioration of fuel consumption can be suppressed.
[0039]
Next, a second embodiment that performs poisoning release control different from that of the first embodiment will be described. In the first embodiment, as the control for eliminating the catalyst temperature difference between the cylinder groups simultaneously with the start of the poisoning release control, the control for stopping the EGR and increasing the ignition timing retard amount of the low temperature side cylinder group is performed. The temperature difference between the two cylinder groups is eliminated before the poison release is started. However, in the second embodiment, when the request for the poisoning release control is generated, only the EGR that is the cause of the catalyst temperature difference is stopped. The poisoning release control is started when the catalyst temperature difference is almost eliminated after the elapse of a predetermined time due to the EGR stop.
[0040]
FIG. 10 shows a poisoning release control flow according to the second embodiment (the system and other flows are the same as those of the first embodiment).
In response to the request for the poisoning release control, the vehicle speed (VSP), the engine rotational speed (RPM), the load (T), and the intake air amount (Q) are read as the engine operating state in Step 501, and the EGR is stopped in Step 502, In step 503, the temperature TEMP1 of the Fr catalyst 3 in the bank 1 is calculated, and in step 504, the catalyst temperature TEMP2 of the Fr catalyst 6 in the bank 2 is calculated as in the first embodiment. The release control is not yet started, and in step 505, the calculated temperature difference between TEMP1 and TEMP2 (TEMP2-TEMP1) is compared with a predetermined value TEMPA to determine the timing for starting the poisoning release control.
[0041]
That is, while it is determined in step 505 that the catalyst temperature difference between the banks is large, the process returns to step 502 to wait for the catalyst temperature increase in the low temperature side bank 1 due to the EGR stop of the EGR extraction side cylinder group.
Then, when the temperature difference between both banks becomes less than the predetermined value TEMPA, the poisoning release control is started. That is, the ignition timing retard control (same retard amount) of the banks 1 and 2 is started in steps 506 and 507, and the rich control of the air-fuel ratio (riching of the exhaust air-fuel ratio) is started in step 508.
[0042]
FIG. 11 shows a state during poisoning release control in the second embodiment. The EGR is stopped simultaneously with the request for the poisoning release control, but the air-fuel ratio enrichment control and the ignition timing retard control are not started. Due to the EGR stop, the temperature of the Rr catalyst 4 which is the NOx trap catalyst of the bank 1 on the EGR exploitation side rises, and the temperature difference from the bank 2 on the non-EGR exploitation side is reduced. After the temperature difference between banks 1 and 2 disappears, poisoning release control by air-fuel ratio rich control and ignition timing retard control is started, and the catalyst temperatures of both banks 1 and 2 rise while maintaining the same temperature state simultaneously. The poisoning release starts when the poisoning release possible temperature is reached.
[0043]
Therefore, even in the second embodiment, the poisoning release performance is equal between the cylinder groups, and it is possible to perform the poisoning release control without excess or deficiency, and to sufficiently improve the exhaust purification performance while maintaining good fuel efficiency. . In the second embodiment, the timing at which the poisoning release temperature is reached and the poisoning release starts is delayed from that in the first embodiment, but the catalyst temperature at the start of the poisoning release control is lower than that in the first embodiment. Since the temperature is high, the period from the start to the end of the poisoning release control is shortened, and the fuel consumption can be further improved.
[0044]
Next, an embodiment applied to a system having a form different from the first and second embodiments will be described.
FIG. 12 shows a V-type 6-cylinder engine as in FIG. 1, but Fr catalysts 3 and 6 composed of one three-way catalyst are arranged in the exhaust passages 2 and 5 of each cylinder group. One Rr catalyst 4 composed of a NOx trap catalyst is disposed in an exhaust passage 10 that merges downstream of the exhaust passages 2 and 5.
[0045]
FIG. 13 shows an in-line internal combustion engine 20 having an exhaust system for each cylinder group (FIG. 3 shows an in-line four-cylinder engine as an example), but is connected to one cylinder group (# 1, 4 cylinders) as described above. The exhaust passage 2 and the exhaust passage 5 connected to the other cylinder group (# 2, 3 cylinder) are provided with Fr catalysts 3, 6 each composed of a three-way catalyst. , 5, one Rr catalyst 4 composed of a NOx trap catalyst is disposed in the exhaust passage 10 that merges downstream of the exhaust passage 10.
[0046]
In these 2-in-1 systems, EGR gas is introduced from the exhaust passage 2 in the same manner as in FIG.
For these 2-in-1 systems, poisoning release control can be performed in exactly the same manner as in the first embodiment. FIG. 14 shows a state during poisoning release control in the third embodiment.
[0047]
In the 2-in-1 system as in the present embodiment, there is one Rr catalyst 6 composed of a NOx trap catalyst. However, as shown in the comparative example of FIG. If the same poisoning release control is started for both cylinder groups at the same time as the poisoning release control request without considering the exhaust gas temperature difference, the temperature of the exhaust gas introduced into the Rr catalyst 6 from the EGR exploitation cylinder group is low. The temperature of the exhaust gas that joins the exhaust gas from the exploitation cylinder group and is introduced into the Rr catalyst 6 is also lowered. As a result, the Rr catalyst 6 reaches the poisoning decomposable temperature and delays the start of the poisoning release, and the poisoning release control period is prolonged and the fuel consumption is deteriorated.
[0048]
On the other hand, in this embodiment, the ignition timing retard amount of the EGR exploitation cylinder group is made larger than the ignition timing retard amount of the EGR non exploitation cylinder group, and the exhaust gas temperature from the combustion chamber is further increased to increase the EGR exploitation cylinder group. By approaching the exhaust gas temperature from the exhaust gas, it is possible to quickly reach the poisoning release possible temperature, complete the poisoning release in the minimum necessary poisoning release control period, and maintain good fuel efficiency. Further, since the exhaust temperatures from both cylinder groups become equal before reaching the poisonable release temperature, there is no difference in performance within the catalyst.
[0049]
Further, in the third embodiment applied to the 2-in-1 system, the ignition timing of the lower temperature cylinder group (bank 1) is retarded than the higher temperature cylinder group (bank 2) for a predetermined period. With this configuration, it is possible to raise the exhaust temperature with high responsiveness and bring the exhaust temperature introduced from the low temperature side cylinder group into the catalyst closer to the exhaust temperature introduced into the catalyst from the high temperature side cylinder group.
[0050]
In particular, the ignition timing of the cylinder group with the lower temperature is retarded than the cylinder group with the higher temperature until the temperature of each cylinder group becomes substantially the same, so that the necessary and sufficient retardance is achieved. The control with a difference is performed, and the driving performance can be satisfactorily satisfied.
Each cylinder group (bank 1, 2) further includes a front catalyst (Fr catalysts 3, 6) upstream of the catalyst (Rr catalysts 4, 7), and the temperatures of these front catalysts are substantially the same. Until downstream, the downstream side catalyst that releases the poison from each cylinder group (banks 1 and 2) by retarding the ignition timing of the cylinder group having the lower temperature than the details of the cylinder having the higher temperature. Control is performed with a difference in retard until the exhaust gas temperature introduced into the (Rr catalyst 4) becomes substantially the same.
[0051]
If a control request to release the poisonous substance is issued, the ignition timing of the higher temperature cylinder group is set to the retard amount for the control to release the poisonous substance before the release of the poisonous substance is started. By setting the ignition timing of the cylinder group with the lower temperature to the retard side than this, the ignition timing retard control is performed before the release of poisonous substances is started in both the high temperature side and low temperature side cylinder groups. By increasing the exhaust temperature by increasing the exhaust temperature by increasing the retard amount on the low temperature side while increasing the exhaust temperature, the low temperature side catalyst introduction exhaust temperature can be quickly increased. Can be approached.
[0052]
In addition, after the catalyst introduction exhaust temperature from each cylinder group becomes substantially the same, the ignition amount of the cylinder group having the lower temperature is returned to the ignition timing of the control for releasing the poisonous substance. Thus, after the low temperature side cylinder group becomes the same temperature state as the high temperature side cylinder group, the retard amount is controlled to be appropriate for the poisoning release, and a good release performance is obtained.
In addition, after the temperature of each cylinder group becomes almost the same, the retard amount of the ignition timing of each cylinder group is made the same, so that good detoxification performance is maintained while maintaining the same temperature state thereafter. Is obtained.
[0053]
Also, the 2-in-1 system is applied to an engine having an EGR device that recirculates exhaust gas from one cylinder group to the intake system, so that the EGR exploitation-side cylinder group becomes lower in temperature than the EGR non-exploit cylinder group. It is possible to effectively prevent deterioration of the poisoning release performance due to.
In addition, when a request to release the poisonous substance is issued, EGR is stopped before the release of the poisonous substance is started, and the ignition timing of the cylinder group having the higher temperature is released. Is set to the retard amount, and the ignition timing of the higher temperature cylinder group is set to the retard side than this, so that the EGR stop and ignition timing retard causing the low temperature side cylinder group to decrease in temperature. By increasing the amount, the temperature of the high temperature side cylinder group can be quickly brought close to.
[0054]
In addition, when a request to release the poisonous substance is made, the EGR is stopped, and after the predetermined period has elapsed, the release of the poisonous substance is started. After the temperature difference of the catalyst introduction exhaust gas is reduced, the poisoning release is started, and the poisoning release can be performed efficiently and efficiently.
In particular, when a request to release the poisonous substance is made, the EGR is stopped, and after the catalyst temperature of each cylinder group becomes substantially the same, the release of the poisonous substance is started. Good and efficient removal of poisoning.
[0055]
Further, the poisoning release control can be performed on the 2-in-1 system shown in FIGS. 12 and 13 in the same manner as in the second embodiment. FIG. 16 shows the poisoning release control in the fourth embodiment. Shows the state of time. In this embodiment, the EGR is stopped only at the same time as the request for the poisoning release control to increase the temperature of the Rr catalyst 4 that is the NOx trap catalyst on the EGR exploitation cylinder group side, and the bank 2 on the non-EGR exploitation side After the temperature difference is reduced and the temperature difference disappears, poisoning release control by air-fuel ratio rich control and ignition timing retard control is started. Thereby, the temperature of the exhaust gas from both cylinder groups introduced into the Rr catalyst 4 rises while maintaining the same temperature state at the same time, and the poisoning release is started when the poisoning release possible temperature is reached. Also in this embodiment, the poisoning release control is started after the exhaust temperature after joining is sufficiently increased until it becomes the same. The poison release control period can be shortened as much as possible to further improve fuel efficiency. Further, since the poisoning release control is started after the exhaust temperatures from the two cylinder groups become equal, there is no performance difference within the catalyst.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a V-type internal combustion engine common to first and second embodiments of the present invention.
FIG. 2 is a flowchart showing a main flow of poisoning release control common to the embodiments of the present invention.
FIG. 3 is a flowchart for determining a poisoning amount that is also a condition for starting poisoning release control.
FIG. 4 is a flowchart for determining the shift of the poisoning release control.
FIG. 5 is a flowchart of poisoning release control common to the first and third embodiments.
FIG. 6 is a flowchart for determining whether or not the poisoning amount subtraction is common to each embodiment of the present invention.
FIG. 7 is a flowchart for performing poisoning release control end determination common to the embodiments of the present invention.
FIG. 8 is a time chart showing a state during poisoning release control in the first embodiment.
FIG. 9 is a time chart showing a state of poisoning release control of a comparative example with respect to the first embodiment.
FIG. 10 is a flowchart of poisoning release control common to the second and fourth embodiments.
FIG. 11 is a time chart showing a state during poisoning release control in the second embodiment.
FIG. 12 is a system configuration diagram of a V-type internal combustion engine applied to the third and fourth embodiments of the present invention.
FIG. 13 is a system configuration diagram of a series internal combustion engine applied to the third and fourth embodiments of the present invention.
FIG. 14 is a time chart showing a state during poisoning release control in the third embodiment.
FIG. 15 is a time chart showing a state of poisoning release control of a comparative example with respect to the third embodiment.
FIG. 16 is a time chart showing a state during poisoning release control in the fourth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... V-type internal combustion engine 2 ... Exhaust passage of one cylinder group 3 ... Fr catalyst (three-way catalyst) of one cylinder group 4 ... Rr catalyst (NOx trap catalyst) 5 ... Exhaust passage of other cylinder group 6 ... Other Fr catalyst (three-way catalyst) 7 ... Rr catalyst (NOx trap catalyst) 20 ... In-line internal combustion engine

Claims (6)

In the exhaust gas purification apparatus for an internal combustion engine that includes an exhaust purification catalyst for each cylinder group of the internal combustion engine and simultaneously releases poisonous substances adhering to each catalyst ,
An EGR device for recirculating exhaust gas to an intake system of the one cylinder group;
When a request to release the poisonous substance is issued, the EGR is stopped before the release of the poisonous substance is started, and after the catalyst temperature of each cylinder group becomes substantially the same, the exhaust temperature of each cylinder group is changed. An exhaust purification control apparatus for an internal combustion engine, which performs poisoning release control for raising the poisoning substance to a catalyst temperature for releasing the poisoning substance . When a request to release the poisoning substance is issued, the EGR is stopped, and the ignition timing of the cylinder group having a lower exhaust temperature than that of the cylinder group having a higher exhaust temperature is set to the retard side. Item 2. An exhaust gas purification control apparatus for an internal combustion engine according to Item 1 . 3. The exhaust gas purification control apparatus for an internal combustion engine according to claim 1, wherein the control for releasing the poisoning substance includes at least ignition timing retard and air-fuel ratio enrichment . In the exhaust gas purification apparatus for an internal combustion engine, which includes an exhaust purification catalyst downstream of the merging portion of the exhaust passage for each cylinder group of the internal combustion engine and releases the poisonous substances attached to the catalyst by increasing the exhaust temperature,
An EGR device for recirculating exhaust gas to an intake system of the one cylinder group;
When a request to release the poisonous substance is issued, the EGR is stopped before the release of the poisonous substance is started, and after the exhaust temperature of each cylinder group becomes substantially the same, the exhaust temperature of each cylinder group is changed. An exhaust purification control apparatus for an internal combustion engine, which performs poisoning release control for raising the poisoning substance to a catalyst temperature for releasing the poisoning substance . When a request to release the poisoning substance is issued, the EGR is stopped, and the ignition timing of the cylinder group having a lower exhaust temperature than that of the cylinder group having a higher exhaust temperature is set to the retard side. Item 5. An exhaust gas purification control apparatus for an internal combustion engine according to Item 4 . 6. The exhaust gas purification control apparatus for an internal combustion engine according to claim 5, wherein the control for releasing the poisonous substance includes at least ignition timing retard and air-fuel ratio enrichment .

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