JP5195287B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

The present invention relates to an exhaust emission control device for an internal combustion engine.

As an exhaust gas purification apparatus for an internal combustion engine, a DPF (Diesel Particulate Filter; Diesel Particulate Filter) that collects PM (Particulate Matter) in exhaust gas is provided in the exhaust passage of the engine, and the PM deposited on the DPF For example, Patent Document 1 discloses a technique for performing purification (DPF regeneration) at a predetermined time. In such a DPF, for example, when driving conditions where DPF regeneration cannot be performed continue, such as during low-speed traveling, and the PM accumulation amount becomes excessive, DPF regeneration starts at a high temperature when DPF regeneration becomes possible thereafter. Then, a large amount of PM may burn at a time and the DPF may be thermally deteriorated due to overheating. Therefore, in order to prevent overheating of the DPF, when the amount of PM accumulated in the DPF increases, the DPF is overheated by changing the operating condition to heat the DPF to a temperature at which PM reacts slowly. A technique is known in which DPF regeneration processing is performed slowly at a temperature that does not cause oxidization.
JP 2006-183599 A

  By the way, in addition to the DPF, NOx trap catalyst (NOx absorption) that traps NOx (nitrogen oxide) in the exhaust flowing in when the exhaust air-fuel ratio is lean and desorbs and purifies the trapped NOx when the exhaust air-fuel ratio is rich. There is also known a technique in which an agent is provided in the exhaust passage, and NOx accumulated on the NOx trap catalyst is purified, that is, NOx regeneration is performed at a predetermined time. The NOx trap catalyst absorbs NOx in the exhaust when the exhaust air-fuel ratio is lean, and also absorbs SOx (sulfur sulfide) in the exhaust. Since the NOx absorption efficiency decreases as the SOx deposition amount increases, when the SOx deposition amount exceeds a predetermined amount, it is necessary to purify the deposited SOx (also referred to as SOx regeneration or S poison removal).

  In general, the above-mentioned NOx regeneration and SOx regeneration are performed by controlling the exhaust air-fuel ratio to be rich. Therefore, during regeneration, the amount of PM discharged from the engine increases, and the amount of PM deposited on the DPF is higher than that in the normal operation state. Will increase quickly. In addition, since the DPF regeneration, the NOx regeneration, and the SOx regeneration have independent start and end conditions, the regeneration times may overlap in some cases.

  Therefore, for example, the DPF regeneration cannot be executed, or the regeneration is terminated before the regeneration is sufficiently performed due to a change in the operating condition of the DPF regeneration started, and a large amount of PM is accumulated in the DPF. If the exhaust air-fuel ratio is simply enriched for NOx regeneration or SOx regeneration, the amount of PM accumulated in the DPF may exceed the DPF trapping capacity, leading to deterioration in exhaust resistance or possibly making it impossible to travel. There is. Alternatively, the PM collection limit is accelerated by the increase in the PM accumulation amount, the DPF regeneration frequency is increased, the fuel consumption is deteriorated, and the fuel adhering to the cylinder wall is scraped to the lower oil pan side due to the reciprocating operation of the piston. May be mixed into the engine oil and increase the amount of oil dilution for diluting the engine oil.

  In the above-mentioned Patent Document 1, rich control is prohibited when the PM accumulation amount is a predetermined amount or more. However, simply prohibiting it prevents NOx regeneration or SOx regeneration from being performed satisfactorily, and avoids performance degradation. I can't.

  SUMMARY OF THE INVENTION Accordingly, the present invention has an object to satisfactorily perform regeneration control of a NOx trap catalyst such as NOx regeneration and SOx regeneration without causing a decrease in performance and suppressing accumulation of a large amount of PM in the DPF. It is said.

  A DPF that is disposed in the exhaust passage of the engine and collects PM in the inflowing exhaust; a PM accumulation amount detection means that detects a PM accumulation amount that accumulates in the DPF; and is disposed in the exhaust passage. A NOx trap catalyst that traps NOx in exhaust flowing when the exhaust air-fuel ratio is lean, desorbs and purifies NOx trapped when the exhaust air-fuel ratio is rich, and a NOx trap that performs regeneration control of the NOx trap catalyst And a catalyst regeneration means. The NOx trap catalyst regeneration means adjusts the target excess air ratio in the regeneration control of the NOx trap catalyst according to the PM accumulation amount.

  According to the present invention, by adjusting the target excess air ratio in the regeneration control of the NOx trap catalyst according to the PM deposition amount, the regeneration control of the NOx trap catalyst is favorably performed without causing excessive deposition of the PM deposition amount. It can be carried out.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram to which an example of an exhaust emission control device for an internal combustion engine (here, a diesel engine) according to the present invention is applied. The intake passage 2 of the diesel engine 1 is provided with an intake compressor of a variable nozzle type turbocharger 3. The intake air is supercharged by the intake compressor, cooled by the intercooler 4, passed through the intake throttle valve 5, and then the collector. 6 and then flows into the combustion chamber of each cylinder. The fuel is increased in pressure by the common rail type fuel injection device, that is, by the high pressure fuel pump 7, sent to the common rail 8, and directly injected from the fuel injection valve 9 of each cylinder into the combustion chamber. The air that has flowed into the combustion chamber and the injected fuel are combusted by compression ignition, and the exhaust gas flows out to the exhaust passage 10.

  Part of the exhaust gas flowing into the exhaust passage 10 is recirculated to the intake side via the EGR valve 12 through the EGR passage 11 as EGR gas. The remainder of the exhaust passes through the exhaust turbine of the variable nozzle type turbocharger 3 and drives it. Here, downstream of the exhaust turbine in the exhaust passage 10, for exhaust purification, NOx in the exhaust flowing in when the exhaust air-fuel ratio is lean is trapped, and when the exhaust air-fuel ratio is rich, the trapped NOx is desorbed and purified. A NOx trap catalyst 13 is disposed. Further, the NOx trap catalyst 13 carries an oxidation catalyst (noble metal) and has a function of oxidizing the exhaust components (HC, CO) flowing in.

  Further, a DPF 14 that collects PM in the exhaust gas is disposed downstream of the NOx trap catalyst 13. The DPF 14 also has a function of supporting an oxidation catalyst (noble metal) and oxidizing exhaust components (HC, CO) flowing in. Note that the NOx trap catalyst 13 and the DPF 14 may be disposed in reverse, or may be configured integrally by supporting the NOx trap catalyst on the DPF.

  Signals are input to the control unit 20 from the rotational speed sensor 21 for detecting the engine rotational speed Ne and the accelerator opening sensor 22 for detecting the accelerator opening APO for controlling the engine 1. Further, a catalyst temperature sensor 23 for detecting the temperature of the NOx trap catalyst 13 (catalyst temperature), an exhaust pressure sensor 24 for detecting the exhaust pressure on the DPF 14 inlet side of the exhaust passage 10, and a DPF for detecting the temperature of the DPF 14 (DPF temperature). A temperature sensor 25 and an air / fuel ratio sensor 26 for detecting an exhaust air / fuel ratio (hereinafter referred to as exhaust λ, which is expressed as an excess air ratio) are provided on the outlet side of the DPF 14 in the exhaust passage 10, and these signals are also controlled. Input to the unit 20. However, the temperature of the NOx trap catalyst 13 and the temperature of the DPF 14 may be detected indirectly from the exhaust temperature by providing an exhaust temperature sensor downstream thereof.

  Based on these input signals, the control unit 20 performs the main injection by the fuel injection valve 9 and the post-injection after the main injection (expansion stroke or exhaust stroke) under predetermined operating conditions, that is, the fuel injection amount and the injection timing of the post injection. A fuel injection command signal to the fuel injection valve 9 for control, an opening command signal to the intake throttle valve 5, an opening command signal to the EGR valve 12, and the like are output.

  Here, the control unit 20 purifies the PM collected and accumulated in the DPF 14 (DPF regeneration), purifies the NOx trapped and accumulated in the NOx trap catalyst 13 (NOx regeneration), and SOx poisoning of the NOx trap catalyst 13. Therefore, the exhaust purification control for purifying the SOx deposited thereon (SOx regeneration) is performed by controlling the excess air ratio in the exhaust, that is, the exhaust λ. The relationship between the exhaust λ and the PM emission amount (g / h) from the engine 1 increases as the exhaust λ becomes richer. In particular, when the exhaust λ is richer than the stoichiometric (exhaust λ = 1.0), normal operation is performed. Significant increase compared to state.

  Next, NOx regeneration control according to the first embodiment of the present invention will be described.

  FIG. 2 is a flowchart showing the flow of rich spike control according to the present embodiment. In S11, it is determined whether there is a NOx regeneration request according to the NOx accumulation amount. For example, the unit time NOx adsorption amount (ΔSNOx) is calculated from the fuel injection amount and the engine speed using a control map (not shown), and the unit time NOx adsorption amount is integrated to thereby accumulate the current NOx accumulation amount (S_NOx (n)). When the NOx adsorption / deposition amount reaches a predetermined amount, it is determined that the adsorbed / deposited NOx needs to be desorbed / reduced and regenerated, that is, there is a NOx regeneration request.

  If it is determined that the NOx trap catalyst 13 has a NOx regeneration request, the routine proceeds to S12 and the rich spike control is executed. In this embodiment, rich spike control is performed step by step by two enrichments. First, in S12, first enrichment described later is performed, and in S13, it is determined whether or not the first enrichment process is completed. The determination of the end of the first enrichment process may be performed by, for example, detecting or estimating the exhaust air excess ratio, and determining the end when the exhaust air excess ratio reaches the first target air excess ratio λ1. Alternatively, the end timing, that is, the first enrichment operation time may be set based on the value of the first target excess air ratio λ1. If it is determined that the first enrichment is completed, the process proceeds from S13 to S14, and a second enrichment described later is performed. If it is determined in S15 that the NOx regeneration process has been completed, this routine is terminated. This termination determination is terminated when, for example, the above-described NOx desorption amount (ΔNOx0) becomes equal to or smaller than a predetermined value, that is, when the NOx accumulation amount becomes sufficiently small.

  The first enrichment and the second enrichment will be described with reference to FIG. Lamda is the excess air ratio λ, QAC is the intake air amount, and PostQ is the post injection amount. In FIG. 3, the solid line shows the characteristics of the present embodiment in which enrichment is performed by using both the intake throttle and the post injection, and the broken line is a comparative example in which enrichment is performed only by the intake throttle without using the post injection. The characteristics are shown. Although not shown, the intake throttle is larger in the comparative example than in the present embodiment.

  The first enrichment described above is a enrichment that lowers the excess air ratio in the NOx trap catalyst 13 to an excess air ratio suitable for desorption of NOx, and the excess air ratio at that time is reduced to the first target excess air. The rate is λ1. As described above, the NOx trap catalyst starts desorbing the adsorbed and deposited NOx when λ becomes around a predetermined value. Therefore, in the first enrichment, enrichment is performed for the purpose of desorbing NOx from the NOx trap catalyst. In the present embodiment, the first enrichment means is the intake throttle valve 5 and / or the EGR valve 10, and the first enrichment is performed using these. This may be performed by the intake throttle valve 5 or the EGR valve 10. Both the intake throttle valve 5 and the EGR valve 10 may be used. In particular, it is not limited to these two, and any oxygen amount reducing means for widely reducing the amount of inhaled oxygen may be used. In other words, the first enrichment is performed only by reducing the intake oxygen amount without performing post injection.

  That is, the above-mentioned first target excess air ratio λ1 is an excess air ratio at which NOx is desorbed from the NOx trap catalyst 13, and can be said to be an excess air ratio suitable for starting the reduction of NOx. This λ1 is not limited to one value, and may be in a range (desorption range) suitable for NOx desorption. The NOx desorption rate is relatively fast in the range of the excess air ratio that is equal to or less than the excess air ratio λ0 corresponding to the theoretical air-fuel ratio. Further, if λ is reduced to a value smaller than λ0 before NOx is sufficiently desorbed, the exhaust performance may be deteriorated. Therefore, λ1 is an excess air ratio of λ0 or less, and is preferably a value relatively close to λ0 (= 1.0).

  Next, the second enrichment is enrichment for reducing NOx accumulated on the NOx trap catalyst 13 without excess or deficiency. The target excess air ratio at that time is defined as a second target excess air ratio λ2. In the present embodiment, rich spike control is performed in which NOx accumulated on the NOx trap catalyst 13 is sufficiently desorbed by the first enrichment and the desorbed NOx is reduced by the second enrichment.

  Here, the second enrichment means is a common rail fuel injection valve system, and the second enrichment is performed by post (POST) injection by the common rail fuel injection system. Although the post-injection is used in this embodiment, the present invention is not limited to this, and any fuel injection that is injected in the expansion stroke or / and the exhaust stroke and does not contribute to torque generation may be used. That is, the second target excess air ratio λ2 is an excess air ratio sufficient to reduce NOx desorbed from the NOx trap catalyst 13, and is an excess air ratio smaller than λ1. The value of λ2 is a relatively small value of about 0.8, for example, but of course is not limited to 0.8, and any excess air ratio that can reduce NOx satisfactorily suffices.

  The first enrichment is performed by the intake throttle valve 5 and / or the EGR valve 10. However, as shown in the figure, the enrichment by these inevitably involves a time delay. On the other hand, since the second enrichment is performed by post injection, unlike the first enrichment, there is substantially no time delay as shown in FIG.

  The first enrichment, that is, the intake throttle, is continued during the second enrichment. That is, as shown in FIG. 3, when the first enrichment is performed by the intake throttle valve 5, for example, the opening degree is maintained until the second enrichment is completed.

  Here, in the present embodiment, the control contents of the first enrichment and the second enrichment are changed according to the PM accumulation amount. This point will be described with reference to FIGS.

  As the PM accumulation amount increases, the first target excess air ratio λ1 due to the first enrichment is leaned as shown by the arrow 1 in FIG. 4, that is, the intake throttle amount is suppressed as shown by the arrow Y3. As a result, the smoke discharge amount is reduced, and the increase in the PM deposition amount is suppressed. As the rich operation time becomes longer as shown in FIG. 5, the NOx purification amount increases in proportion to this, so that the amount of NOx desorption / purification, that is, the reduction in the purge amount due to the leaning of λ1 is compensated. In addition, as shown by the arrow Y2 in FIG. 4 and FIG. 6, the operation time by the second enrichment is extended. Alternatively, as shown in FIG. 6, the second target air excess ratio λ <b> 2 in the second enrichment may be enriched as the PM accumulation amount increases. Alternatively, the extension of the operation time by the second enrichment and the enrichment of the second target excess air ratio λ2 may be used in combination.

  Referring to FIG. 7, when the deviation Δλ (λ1-λ2) between the first target excess air ratio λ1 and the second target excess air ratio λ2 is large, in order to suppress rapid NOx desorption, Slowly perform post-injection in line with the enrichment. In other words, post-injection processing such as first-order lag processing is performed so that post-injection ramp time (period until the post-injection amount is increased to the target value) ΔT becomes longer as deviation Δλ increases. The rise (inclination) of is intentionally gentle.

  As shown in FIG. 8, when the post injection amount increases due to the enrichment to the second target excess air ratio λ2, the oil dilution amount described above may be excessively increased. Therefore, preferably, when the post-injection amount exceeds a predetermined dilution limit α, the number of post-injection injections (number of stages) is divided into a plurality (two in this example) in order to suppress the oil dilution amount. By dividing the post-injection into a plurality of times in this way, the fuel pressure in each post-injection, that is, the penetration of the spray, is reduced, the amount of fuel adhering to the cylinder wall surface is reduced, and consequently the oil dilution amount is reduced. Can be reduced.

  The function and effect of the first embodiment will be described.

  When rich spike control is performed using only the intake throttle, an increase in exhaust HC can be suppressed, but smoke will increase. The same applies when rich spike control is performed only by EGR control. That is, as the exhaust gas λ is reduced, the amount of smoke discharged increases. On the other hand, when rich spike control is performed only by post injection, the amount of smoke discharged does not increase, but the amount of exhaust HC and oil dilution may increase because the amount of fuel injection increases. That is, regardless of which method is used to perform rich spike control, exhaust performance may be deteriorated if the excess air ratio is immediately reduced and enriched.

  On the other hand, in this embodiment, after enriching to the state where NOx is desorbed from the NOx trap catalyst 13 by the first enrichment, it is enriched to a relatively high richness by the second enrichment and reduces NOx. doing. Therefore, rich spike control can be performed without deteriorating the exhaust performance.

  In particular, by setting the first target excess air ratio λ1 resulting from the first enrichment to a range of excess air ratio (desorption range) in which desorption from the NOx trap catalyst 13 is promoted, desorption of NOx is ensured. Can be done.

  Further, the NOx trap catalyst 13 can be desorbed without deteriorating the fuel consumption rate by performing the first enrichment by reducing the amount of oxygen such as an intake throttle. Then, after shifting to the desorption range (after NOx is desorbed), fuel injection for reduction is performed, so that reduction can be performed without waste. Therefore, the exhaust HC and the oil dilution amount are not increased.

  In particular, the first enrichment means is the intake throttle valve 5, and the first enrichment is performed by the intake throttle valve 5, thereby suppressing an increase in exhaust HC. On the other hand, by performing the first enrichment by the EGR valve 10, it is possible to perform a good rich spike control without causing deterioration of the fuel consumption rate. Furthermore, since the second enrichment is performed by fuel injection, NOx reduction can be started at an appropriate timing without a time delay.

  In this embodiment, the control mode of the first enrichment and the second enrichment is changed according to the PM accumulation amount, that is, the first target air excess ratio λ1 and the second target air excess. The deviation Δλ from the rate λ2 is changed. Specifically, as the PM accumulation amount increases, the first target excess air ratio λ1 is leaned, and accordingly, the operation time by the second enrichment and the second target excess air ratio λ2 are enriched. As a result, while ensuring the desired NOx purification performance, it is possible to reduce smoke in a situation where the PM deposition amount is excessive, and to suppress / prevent further increase in the PM deposition amount. Further, in a situation where the PM accumulation amount is relatively small, the exhaust gas HC and the oil dilution amount are increased by relatively leaning the second enrichment, that is, the post injection operation time and the second target excess air ratio λ2. Can be suppressed. That is, it is possible to satisfactorily balance the reduction of the smoke emission amount during NOx regeneration and the reduction of the exhaust HC and the oil dilution amount without causing an excessive increase in the PM accumulation amount.

  When the deviation Δλ (λ1−λ2) between the first target excess air ratio λ1 and the second target excess air ratio λ2 is large, the post injection ramp time is lengthened and the post injection is performed slowly. , Rapid NOx desorption can be suppressed.

  Furthermore, if the rich degree by the second enrichment is increased, an increase in the amount of oil dilution becomes a problem, but when the rich degree exceeds a predetermined oil dilution limit, by increasing the number of post injections, An increase in the amount of oil dilution can be effectively suppressed.

  Next, a second embodiment in which the present invention is applied to the SOx regeneration process will be described. When it is determined that it is the SOx regeneration timing at which the NOx trap catalyst 13 should be released from sulfur poisoning, that is, SOx regeneration should be performed based on the engine operating state, SOx regeneration control to make the exhaust air-fuel ratio rich is performed. In the present embodiment, an appropriate air-fuel ratio in SOx regeneration, that is, sulfur (S) poisoning release, based on the PM accumulation amount of the DPF 14 and the oil dilution rate O / D that is a parameter corresponding to the oil dilution amount of the engine. Control is performed.

  FIG. 9A shows the pros and cons of various techniques for canceling S poisoning. In the first method I, S poisoning is canceled only by adjusting the intake air amount by the intake throttle valve 5 and the EGR valve 12, that is, by the oxygen amount reducing means for reducing the intake oxygen amount described above, without performing post injection. In this case, although the smoke discharge amount increases and the smoke performance deteriorates, the oil dilution amount is sufficiently suppressed and the oil dilution performance is improved. In the second method II and the third method III, the intake air amount adjustment and the post-injection are used together. In this case, the oil dilution performance is lower than that of the first means I only by adjusting the intake air amount. However, smoke performance is improved. In the second method II, as compared with the third method III, the target excess air ratio λair is set to the lean side, the post injection amount qPost is increased, and the smoke reduction is emphasized. In the third method III, as compared with the second method II, the target excess air ratio λair is set to the rich side, the post injection amount qPost is reduced, and the oil dilution characteristics are set as important.

  In this embodiment, these three methods I to III are switched according to the operating conditions. That is, as shown in FIG. 9B, based on the oil dilution amount (rate) and the PM accumulation amount, post injection ON / OFF, post injection amount qPost, and interval (time) from main injection to post injection. IT_Post, EGR amount, etc. are controlled.

  As shown in FIG. 9C, the first method I is used under operating conditions exceeding the oil dilution limit value. In the region where the oil dilution limit is not exceeded, the second method II and the third method III are switched. As shown in FIG. 9 (D), as the post injection amount qPost increases, the overall target air excess ratio λair is set to the lean side and the smoke discharge amount is reduced to improve the smoke reduction effect. As the amount qPost increases, the oil dilution amount increases and the oil dilution characteristics deteriorate. Also, smoke and oil dilution change depending on the injection timing of post-injection, that is, the interval IT_Post with the main injection, and as IT_Post increases, the smoke discharge amount decreases and the oil dilution amount (rate) increases.

  Therefore, when the PM accumulation amount is large, the second method II that emphasizes the smoke reduction by increasing the post injection amount is used. When the oil dilution rate is large, the second method II that emphasizes the oil dilution characteristic by decreasing the post injection amount is used. Method 3 of III is used. More preferably, as the PM accumulation amount increases, at least one of an increase in the post-injection amount and an increase in the post-injection interval is performed. As the oil dilution rate corresponding to the oil dilution amount increases, the decrease in the post-injection amount and the post-injection interval. At least one of the shortening. As a result, the improvement of the oil dilution characteristic and the reduction of the smoke discharge amount, that is, the suppression of the PM accumulation amount can be achieved at a high level.

  FIG. 10 is a block diagram schematically showing the setting process of the post injection amount qPost and the post injection interval (time) IT_Post when the S poisoning is released. In B11, the oil dilution rate O / D is estimated based on the engine operating conditions. For example, it is calculated based on an integrated value during traveling of the oil dilution amount obtained from the engine speed and the fuel injection amount.

  In B12, the PM accumulation amount massPM is estimated according to the engine operating conditions. In B13, the average vehicle speed from the previous DPF regeneration is obtained. In B14, a target DPF regeneration interval is obtained from this average vehicle speed. In B15, the travel distance from the previous DPF regeneration is obtained. In B14A, the target travel distance until the next DPF regeneration is obtained based on the target DPF regeneration interval and the travel distance from the previous DPF regeneration. In B16, based on the oil dilution rate O / D and the PM accumulation amount massPM, it is determined whether or not to perform POST injection.

  In B18, based on the oil dilution amount limit value O / D_max in B17, the oil dilution rate O / D, and the target travel distance until the next DPF regeneration, the oil dilution increase rate at the time of S poison release (SOx regeneration) The limit value O / D_limit is calculated.

  In B20, when the S poison is released based on the smoke limit value SML corresponding to the PM deposit amount limit value of the DPF 14 in B19, the PM deposit amount massPM, and the target travel distance until the next DPF regeneration. The smoke emission limit value smoke_limit is calculated.

  In B21, the post injection amount qPost is calculated based on the oil dilution increase rate limit value O / D_limit and the smoke discharge limit value smoke_limit.

  In B22, a post injection interval (time) IT_Post is calculated based on the oil dilution increase rate limit value O / D_limit and the smoke discharge limit value smoke_limit.

In B23, when the post-injection prohibition determination is output in B16, the post-injection amount qPost is set to 0 (zero) and post-injection is prohibited.
As described above, in this embodiment, the PM accumulation amount massPM is excessively controlled by performing the air-fuel ratio control in the SOx regeneration based on the PM accumulation amount massPM and the oil dilution rate O / D that is a parameter corresponding to the oil dilution amount. Without causing a significant increase, it is possible to satisfactorily achieve both suppression of the oil dilution amount and suppression of the smoke discharge amount during SOx regeneration.

  Next, characteristic configurations of the present embodiment are listed below.

  [1] The NOx trap catalyst 13 and the DPF 14 are provided in the exhaust passage of the internal combustion engine, and the PM accumulation amount detection means (B12) for detecting the PM accumulation amount massPM accumulated on the DPF 14, and the oil dilution amount An oil dilution estimation means (B11) for estimating / calculating the parameter O / D to be performed, and an SOx regeneration means for purifying the SOx deposited on the NOx trap catalyst 13. Then, the SOx regeneration means appropriately performs air-fuel ratio control in the SOx regeneration control based on the PM accumulation amount and the parameter corresponding to the oil dilution amount.

  [2] The SOx regeneration means adjusts the intake air amount, that is, the intake oxygen amount by the intake throttle valve 5, the EGR valve 12, etc., and post-injection (post-injection) that is injected in the expansion stroke or exhaust stroke and does not contribute to torque generation. , At least one of the above.

  [3] The SOx regeneration means determines whether or not to use post-injection based on parameters corresponding to the PM accumulation amount and oil dilution amount at that time (B16).

  [4] The air-fuel ratio control amount for calculating the post-injection amount qPost and the injection timing of the post-injection, that is, the interval (interval) IT_Post with the main injection, when the SOx regeneration means determines that post-injection is to be performed. It has a calculation means (B21, B22).

  [5] The air-fuel ratio control amount calculation means calculates a post-injection amount and a post-injection timing based on parameters corresponding to the PM accumulation amount and the oil dilution amount at that time.

  [6] The air-fuel ratio control amount calculation means performs at least one of increasing the post-injection amount and expanding the post-injection interval when the PM accumulation amount is large, and when the parameter corresponding to the oil dilution amount is large, the post-injection At least one of reducing the amount and shortening the post-injection interval is performed.

  [7] The SOx regeneration means sets a target exhaust temperature at the time of air-fuel ratio control in the SOx regeneration control, and sets an engine control parameter so as to be the target exhaust temperature.

  [8] For detecting the exhaust temperature, for example, the catalyst temperature sensor 23 for detecting the temperature (catalyst temperature) of the NOx trap catalyst 13 or the DPF temperature sensor 25 for detecting the temperature (DPF temperature) of the DPF 14 is used. A temperature sensor provided before or after the charger (supercharger) 3 or before or after the catalyst may be used.

  [9] The engine control parameter is at least one of the opening degree of the EGR valve 12, the vane opening degree of the variable nozzle type turbocharger 3, the injection timing of the preliminary injection and the main injection, and the opening degree of the intake throttle valve 5. is there.

  [10] The SOx regeneration means includes a smoke emission limit value calculation means (B20) for calculating a smoke emission limit value smoke_limit discharged from the internal combustion engine, and an oil dilution increase value for calculating an oil dilution increase rate limit value O / D_limit. A rate limit value calculation means (B18), and based on one or both of the smoke discharge limit value smoke_limit and the oil dilution increase rate limit value O / D_limit, the post-injection amount qPost and the post-injection timing IT_Post Is calculated.

  [11] The smoke emission limit value calculating means (B20) is based on the target travel distance until the next DPF regeneration, the PM accumulation amount limit value SML (B19) of the DPF, and the current PM accumulation amount massPM (B12). The smoke emission limit value smoke_limit is calculated.

  [12] The oil dilution increase rate limit value calculation means (B18) is a parameter corresponding to the target travel distance until the next DPF regeneration, the oil dilution amount limit value O / D_limit (B17) of the internal combustion engine, and the current oil dilution amount. Based on O / D (B11), an oil dilution increase rate limit value O / D_limit is calculated.

  [13] A travel distance calculating means (B15) for calculating a travel distance from the previous DPF regeneration, and a target DPF regeneration interval calculating means (B14) for calculating an interval (distance) until the target DPF regeneration. The target travel distance until the next DPF regeneration is calculated based on the target DPF regeneration interval and the travel distance from the previous DPF regeneration (B14A).

  [14] The target DPF regeneration interval is calculated using the average vehicle speed (B13) from the previous DPF regeneration (B14).

  [15] The PM accumulation amount massPM is calculated based on the differential pressure before and after the DPF detected by the DPF differential pressure detecting means such as the exhaust pressure sensor 24 (B12).

  [16] Alternatively, the PM accumulation amount massPM is calculated based on an integrated value during traveling of the soot emission amount obtained from the engine speed and the fuel injection amount (B12).

  [17] The parameter O / D corresponding to the oil dilution amount is calculated based on, for example, an integrated value during traveling of the oil dilution amount obtained from the engine speed and the fuel injection amount (B11).

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, the present invention is not limited to a diesel internal combustion engine, and can be applied to a gasoline internal combustion engine that performs lean combustion, that is, a spark ignition internal combustion engine. In the case of a gasoline internal combustion engine, a known three-way catalyst is disposed in the exhaust passage 10 in addition to the NOx trap catalyst 13 and the DPF 14 described above.

1 is a system diagram to which an example of an exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied. The flowchart which shows the flow of the rich spike control in NOx reproduction | regeneration based on 1st Example of this invention. The timing chart at the time of NOx reproduction | regeneration concerning 1st Example. The timing chart which shows an example of the content of control when PM accumulation amount is excessive according to the first embodiment. The characteristic view which shows the relationship between the NOx purification amount which concerns on 1st Example, and 2nd rich operation time. Explanatory drawing which shows an example of the control content according to PM deposition amount which concerns on 1st Example. The characteristic view which shows the relationship between the deviation of the target excess air ratio which concerns on 1st Example, and post injection lamp time. The characteristic view which shows the relationship between the post injection quantity which concerns on 1st Example, and the post injection stage number (number of times). Explanatory drawing which shows the pros and cons by the technique of sulfur poisoning cancellation | release which concerns on 2nd Example. The block diagram which shows simply the setting process of the post injection quantity at the time of the sulfur poisoning cancellation | release which concerns on 2nd Example, and the interval of post injection.

Explanation of symbols

1. Engine (internal combustion engine)
5 ... Intake throttle valve 9 ... Fuel injection valve 10 ... Exhaust passage 12 ... EGR valve 13 ... NOx trap catalyst 14 ... Diesel particulate filter (DPF)
20 ... Control unit 23 ... Catalyst temperature sensor 25 ... DPF temperature sensor

Claims (7)

A DPF that is disposed in the exhaust passage of the engine and collects PM in the inflowing exhaust;
PM deposition amount detection means for detecting the PM deposition amount deposited on the DPF;
A NOx trap catalyst that is disposed in the exhaust passage and traps NOx in exhaust flowing when the exhaust air-fuel ratio is lean, and desorbs and purifies NOx trapped when the exhaust air-fuel ratio is rich;
NOx trap catalyst regeneration means for performing regeneration control of the NOx trap catalyst;
NOx accumulation amount detection means for detecting the NOx accumulation amount accumulated on the NOx trap catalyst;
Have
The NOx trap catalyst regeneration means adjusts the target excess air ratio in the regeneration control of the NOx trap catalyst according to the PM accumulation amount,
The NOx trap catalyst regeneration means has NOx regeneration means for purifying NOx deposited on the NOx trap catalyst in accordance with the NOx accumulation amount,
The NOx regeneration means includes a first enrichment means for reducing the excess air ratio to a first target excess air ratio in the desorption range where NOx is desorbed from the NOx trap catalyst,
In order to reduce NOx desorbed by the first enrichment means after the first enrichment, the second target air excess ratio is lower than the first target air excess ratio. It possesses a second enrichment means for enriching, and to,
The exhaust gas purification apparatus for an internal combustion engine, wherein the NOx regeneration means changes a deviation between the first target air excess rate and the second target air excess rate according to the PM accumulation amount . A DPF that is disposed in the exhaust passage of the engine and collects PM in the inflowing exhaust;
PM deposition amount detection means for detecting the PM deposition amount deposited on the DPF;
A NOx trap catalyst that is disposed in the exhaust passage and traps NOx in exhaust flowing when the exhaust air-fuel ratio is lean, and desorbs and purifies NOx trapped when the exhaust air-fuel ratio is rich;
NOx trap catalyst regeneration means for performing regeneration control of the NOx trap catalyst;
NOx accumulation amount detection means for detecting the NOx accumulation amount accumulated on the NOx trap catalyst;
Have
The NOx trap catalyst regeneration means adjusts the target excess air ratio in the regeneration control of the NOx trap catalyst according to the PM accumulation amount,
The NOx trap catalyst regeneration means has NOx regeneration means for purifying NOx deposited on the NOx trap catalyst in accordance with the NOx accumulation amount,
The NOx regeneration means includes a first enrichment means for reducing the excess air ratio to a first target excess air ratio in the desorption range where NOx is desorbed from the NOx trap catalyst,
In order to reduce NOx desorbed by the first enrichment means after the first enrichment, the second target air excess ratio is lower than the first target air excess ratio. It possesses a second enrichment means for enriching, and to,
The NOx regeneration means increases the first target excess air ratio as the PM deposition amount increases, and at least one of the extension of the second enrichment operation time or the decrease of the second target excess air ratio. exhaust purification system of an internal combustion engine which comprises carrying out the. The second enrichment means performs post-injection that is injected in an expansion stroke or an exhaust stroke and does not contribute to torque generation;
The exhaust purification device for an internal combustion engine according to claim 1 or 2 , wherein when the deviation is larger than a predetermined value, the post-injection is performed gently. The second enrichment means performs post-injection that is injected in an expansion stroke or an exhaust stroke and does not contribute to torque generation;
The exhaust purification of an internal combustion engine according to any one of claims 1 to 3 , wherein the number of post-injection injections is increased when the rich degree due to the second enrichment exceeds a predetermined oil dilution limit. apparatus. Oil dilution estimation means for estimating a parameter corresponding to the oil dilution amount is provided,
The NOx trap catalyst regeneration means has SOx regeneration means for purifying SOx deposited on the NOx trap catalyst,
The SOx regeneration means, and the PM accumulation amount, the parameter corresponding to the oil dilution amount, based on, according to any one of claims 1 to 4, characterized in that the air-fuel ratio control in the SOx regeneration control Exhaust gas purification device for internal combustion engine. The SOx regeneration means includes a method of performing post-injection that is injected in an expansion stroke or an exhaust stroke and does not contribute to torque generation, and is based on the PM accumulation amount and a parameter corresponding to the oil dilution amount. 6. The exhaust gas purification apparatus for an internal combustion engine according to claim 5 , wherein it is determined whether or not the post-injection is performed. The SOx regeneration means includes a method of performing post-injection that is injected in an expansion stroke or an exhaust stroke and does not contribute to torque generation.
In addition, when the PM accumulation amount is large, at least one of the increase of the post injection amount and the expansion of the post injection interval is performed. When the parameter corresponding to the oil dilution amount is large, the decrease of the post injection amount and the post injection are performed. The exhaust emission control device for an internal combustion engine according to claim 5 or 6 , wherein at least one of the intervals is shortened.

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