JP2005048741A - Control device of diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a diesel engine, controlling the EGR according to the amount of exhaust particulates deposited in a DPF. <P>SOLUTION: This control device of a diesel engine calculates the amount of exhaust particulates scavenged by the DPF, calculates the passage area of the DPF proportional to the amount of exhaust particulates deposited, calculates the passage area of an EGR valve on the basis of the flow velocity of EGR gas passing through the EGR valve, and corrects the opening of the EGR valve so that the ratio of the passage area of the DPF to the passage area of the EGR valve is constant. Thus, increase in residual gas in a combustion chamber (a cylinder) due to a pressure rise in the exhaust passage can be restrained so as to restrain the exhaust performance deterioration due to the transition of the combustion state to the rich side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for a diesel engine.

In Patent Document 1, an exhaust turbine having an exhaust turbine and a compressor coaxially, an EGR passage and an EGR valve for performing EGR (exhaust gas recirculation), an oxidation catalyst and exhaust particulates provided on the downstream side of the exhaust turbine are disclosed. A diesel engine exhaust purification device that controls the valve opening of an EGR valve in accordance with the exhaust temperature in order to continuously burn exhaust particulates collected in the DPF is disclosed. Yes.
JP 2002-276405 A

  However, in such an exhaust emission control device for a diesel engine, when exhaust particulates accumulate on the DPF, the passage area of the DPF decreases and the pressure on the suction side of the DPF increases, so the amount of residual gas in the cylinder increases. It will be different. That is, even if the EGR rate based on the valve opening degree of the EGR valve is kept constant, the actual combustion state shifts to the rich side, which causes a problem that exhaust performance deteriorates.

  Therefore, the control device for a diesel engine according to the present invention calculates the accumulation amount of exhaust particulates collected in the DPF, calculates the passage area of the DPF proportional to the accumulation amount of exhaust particulates, and passes through the EGR valve. The EGR valve passage area is calculated based on the gas flow velocity, and the EGR valve opening is corrected so that the ratio of the DPF passage area to the EGR valve passage area is constant.

  ADVANTAGE OF THE INVENTION According to this invention, the increase in the residual gas in a combustion chamber (cylinder) accompanying the pressure rise in an exhaust passage is suppressed, and exhaust gas performance deterioration accompanying a combustion state shifting to the rich side can be suppressed.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an overall configuration of a diesel engine 1 to which the present invention is applied. The diesel engine 1 performs a relatively large amount of exhaust gas recirculation (EGR). The opening degree of the diesel engine 1 is continuously increased, for example, by a stepping motor in an EGR passage 4 connecting the exhaust passage 2 and the collector portion 3a of the intake passage 3. An EGR valve 6 is provided as an exhaust gas recirculation means that can be variably controlled.

  The opening degree of the EGR valve 6 is controlled by the control unit 5 so as to obtain a predetermined EGR rate corresponding to operating conditions. For example, the EGR rate becomes maximum in the low speed and low load region, and the EGR rate decreases as the rotational speed and load increase.

  In the vicinity of the intake port of the intake passage 3, a swirl control valve 9 that generates a swirl in the combustion chamber according to operating conditions is provided. The swirl control valve 9 is opened and closed in accordance with a control signal from the control unit via an actuator (not shown). For example, the swirl control valve 9 is closed in a low-speed and low-load region, and a swirl is generated in the combustion chamber.

  The diesel engine 1 includes a common rail fuel injection device 10. In the common rail type fuel injection device 10, the fuel pressurized by the supply pump 11 is temporarily stored in the pressure accumulating chamber (common rail) 13 through the high pressure fuel supply passage 12, and then, from the pressure accumulating chamber 13 to each cylinder. The fuel is distributed to the fuel injection nozzles 14 and injected according to the opening and closing of the fuel injection nozzles 14. The fuel pressure in the pressure accumulating chamber 13 is variably adjusted by a pressure regulator (not shown), and the pressure accumulating chamber 13 is provided with a fuel pressure sensor 15 for detecting the fuel pressure. . Further, a fuel temperature sensor 16 for detecting the fuel temperature is disposed on the upstream side of the supply pump 11. A known glow plug 18 is disposed in the combustion chamber.

  The diesel engine 1 also includes a turbocharger 21 that is provided with an exhaust turbine 22 and a compressor 23 on the same axis. The exhaust turbine 22 is located downstream of the EGR passage 4 branch point of the exhaust passage 2 and has a variable displacement type structure in which a variable nozzle 24 as a capacity adjusting means is provided at the scroll inlet of the exhaust turbine 22. ing. That is, when the opening of the variable nozzle 24 is small, the characteristics of the small capacity are suitable for conditions with a small exhaust flow rate such as a low speed region, and when the opening of the variable nozzle 24 is large, the characteristic is as in the high speed region. Large capacity characteristics suitable for conditions with a large exhaust flow rate. The variable nozzle 24 is driven by a diaphragm actuator 25 that responds to a control pressure (control negative pressure), and the control pressure is generated through a pressure control valve 26 that is duty-controlled. A wide-range air-fuel ratio sensor 17 that detects the exhaust air-fuel ratio is disposed upstream of the exhaust turbine 22.

  Further, in the exhaust passage 2 downstream of the exhaust turbine 22, an oxidation catalyst 27 that oxidizes CO, HC, and the like in the exhaust, and a NOx trap catalyst 28 that performs NOx treatment are sequentially arranged. The NOx trap catalyst 28 adsorbs NOx when the exhaust air-fuel ratio of the inflowing exhaust gas is lean, and releases the adsorbed NOx when the oxygen concentration of the inflowing exhaust gas is reduced, thereby purifying the catalyst. To do. On the downstream side of the NOx trap catalyst 28, a particulate collection filter (Diesel particulate filter: DPF) 29 with a catalyst for collecting and removing exhaust particulate (PM) is further provided. As the particulate collection filter 29, for example, a wall flow honeycomb structure (so-called plugging) is formed by forming a large number of honeycomb-like fine passages in a filter material such as cordierite and closing the ends alternately. Type) filter is used. A filter inlet side temperature sensor 30 and a filter outlet side temperature sensor 31 for detecting exhaust temperatures on the inlet side and the outlet side, respectively, are arranged on the inlet side and the outlet side of the particulate collection filter 29. Further, since the pressure loss of the particulate collection filter 29 changes with the accumulation of exhaust particulates, a differential pressure sensor 32 for detecting the pressure difference between the inlet side and the outlet side of the particulate collection filter 29 is provided. . Of course, instead of the differential pressure sensor 32 that directly detects the pressure difference, a pressure sensor may be provided on each of the inlet side and the outlet side to obtain the pressure difference. Note that an exhaust silencer (not shown) is disposed further downstream of the particulate collection filter 29.

  An air flow meter 35 for detecting the amount of intake air, that is, the amount of fresh air is disposed upstream of the compressor 23 interposed in the intake passage 3, and an air cleaner 36 is positioned further upstream. At the inlet side of the air cleaner 36, an atmospheric pressure sensor 37 for detecting an external atmospheric pressure, that is, an atmospheric pressure, is disposed. An intercooler 38 is provided between the compressor 23 and the collector 3a to cool the supercharged high-temperature air.

  Furthermore, an intake throttle valve 41 for limiting the amount of fresh air is interposed on the inlet side of the collector portion 3a of the intake passage 3. The intake throttle valve 41 is driven to open and close by a control signal from the control unit 5 via an actuator 42 formed of a stepping motor or the like. The collector 3a is provided with a supercharging pressure sensor 44 that detects a supercharging pressure and an intake air temperature sensor 45 that detects an intake air temperature.

  The control unit 5 that controls the injection amount and injection timing of the fuel injection device 10, the opening degree of the EGR valve 6, the opening degree of the variable nozzle 24, etc., includes the depression amount of the accelerator pedal in addition to the sensors described above. Detection signals of sensors such as an accelerator opening sensor 46 to detect, a rotation speed sensor 47 to detect engine rotation speed, and a water temperature sensor 48 to detect cooling water temperature are input.

  Here, when exhaust particulates accumulate on the particulate collection filter 29, the passage area of the particulate collection filter 29 decreases, and the pressure in the exhaust passage 2 increases. Thus, when the pressure in the exhaust passage 2 increases, the residual gas in the combustion chamber (cylinder) increases, and even if the EGR rate is kept constant, the combustion state shifts to the rich side and the exhaust gas is exhausted. Performance will deteriorate. Therefore, in the present embodiment, the EGR flow rate and the target air-fuel ratio are corrected according to the accumulation amount of the exhaust particulates accumulated on the particulate collection filter 29, and the exhaust performance deterioration is suppressed.

  FIG. 2 and FIG. 3 show processing for obtaining the exhaust particulate accumulation amount in the particulate collection filter 29 among the contents of the control executed by the control unit 5 as a block diagram, which will be described below. . Many of these functions are processed by software.

  As a basic idea of this processing, the passage area (equivalent area) of the particulate collection filter 29 is obtained from the relationship based on Bernoulli's theorem, and this is compared with the passage area when the accumulation amount is 0. The rate is obtained, and the amount of deposited fine particles is finally obtained from the area reduction rate. According to Bernoulli's theorem, there is a relationship represented by the following equation (1) among the passage area A, the flow rate Q, the front-rear differential pressure ΔP, and the fluid density ρ of the portion that becomes the throttle.

(Equation 1)
A = Q / √ (2ρ · ΔP) (1)
In the following processing, the equivalent area A of the particulate collection filter 29 at that time is obtained from the relationship of the equation (1).

  First, FIG. 2 shows the flow of processing for obtaining the exhaust flow rate QEXH. The fresh air amount QAC flowing into the cylinder and the fuel amount QFTRQ injected into the cylinder are added in S1, and this is added in S2. By multiplying the engine speed NE, the exhaust flow rate QEXH is obtained.

  The value of the exhaust flow rate QEXH obtained sequentially in this way is subjected to a weighted average process in S3 shown in FIG. 3, and is output as an exhaust flow rate QEXHD having an appropriate response. Here, as the filter constant (weighting coefficient) TC at the time of weighted average, the value obtained from the predetermined map TTC_DPFLT in S4 according to the engine speed NE is used. This map TTC_DPFLT has characteristics as shown in FIG. 4 and has low responsiveness in the low speed region and high responsiveness in the high speed region.

  The above-described output value PF_D of the differential pressure sensor 32 is weighted and averaged in S5 using a filter constant (weighting factor) TC corresponding to the engine speed NE obtained in S4, and has a differential pressure DP_DPF_FLT having appropriate responsiveness. Is output as

  Further, the output value PF_Pre of the filter inlet side temperature sensor 30 is subjected to weighted average processing in S6, and the output value PF_Pst of the filter outlet side temperature sensor 31 is subjected to weighted average processing in S7. A certain constant KTC_TEXH is used as the constant (weight coefficient) TC. Then, the sum of the respective weighted average temperatures is obtained in S8, and is divided by a constant “2” in S9, whereby the temperature TMP_DPF of the particulate collection filter 29 is obtained as an average value of the inlet side and outlet side temperatures. . The temperature TMP_DPF is an absolute temperature.

  When engine operating conditions change suddenly, for example, when the accelerator pedal opening changes stepwise, changes in parameters, that is, changes in the exhaust flow rate QEXH, the inlet side and outlet of the particulate collection filter 29 The change in the exhaust gas temperature on the side and the change in the differential pressure across the particulate collection filter 29 have different responsiveness. Specifically, changes in the differential pressure before and after and the exhaust flow rate QEXH occur relatively quickly, while the temperature changes occur relatively slowly. Therefore, if these detected values are read as they are and the amount of exhaust particulate accumulation is estimated, a large error occurs transiently. The step response of these parameters also changes depending on the engine speed NE. Therefore, in the present embodiment, as described above, by appropriately providing the filter constant TC when performing the weighted average processing of each detection value, the estimation accuracy of the amount of deposited particulates due to the variation in the responsiveness of each parameter is reduced. Try to avoid. In particular, the filter constant is changed according to the engine speed NE when measuring the change in the exhaust gas flow rate QEXH and the change in the pressure, with the change in the temperature having the slowest response as a reference.

  On the other hand, in S13, a predetermined map TPEXH_MFLR is used to determine the pressure increase due to the ventilation resistance of an exhaust silencer (not shown) according to the exhaust flow rate QEXHD. This increase in pressure basically increases as the exhaust flow rate QEXHD increases. In S14, the above pressure increase is added to the differential pressure DP_DPF_FLT before and after the particulate collection filter 29, and this output PEXH_DPFIN (this corresponds to the pressure difference between the exhaust silencer and the particulate collection filter 29), In S15, the atmospheric pressure pATM is added. Therefore, the output of S15 corresponds to the exhaust pressure on the inlet side of the particulate collection filter 29. In S16, the value corresponding to the pressure is multiplied by a predetermined constant (S17) corresponding to the gas constant R, and in S18, the value is divided by the temperature TMP_DPF (absolute temperature) of the particulate collection filter 29. Thereby, the density ρ, that is, the specific gravity ROUEXH of the exhaust gas is obtained as the output of S16. In S19, the constant “2” (S20) is multiplied and the differential pressure DP_DPF_FLT is multiplied so as to correspond to the above-described equation (1).

  Furthermore, the square root of the output value of S19 is obtained in S21. This is obtained by referring to a predetermined map TROOT_VEXH for convenience of arithmetic processing. As a result, a value corresponding to the denominator of the equation (1), that is, the exhaust flow velocity VEXH is obtained. In S22, the exhaust flow rate QEXHD is divided by the exhaust flow velocity VEXH. Therefore, this gives a value corresponding to the area A in the above equation (1), that is, a basic value of the equivalent area of the particulate collection filter 29. In this embodiment, in order to increase the estimation accuracy, necessary correction corresponding to the exhaust gas flow rate and the temperature of the particulate collection filter 29 is added by multiplying the correction coefficient KADPF in S23.

  That is, the correction coefficient KADPF is given by the map MAP_KADPF in S24 in which the reciprocal of the exhaust flow rate QEXHD and the temperature TMP_DPF of the particulate collection filter 29 are input. The reciprocal of the exhaust flow rate QEXHD is obtained by dividing the constant “1.0” by the exhaust flow rate QEXHD in S36. FIG. 5 shows the characteristics of the map MAP_KADPF. A correction coefficient KADPF is given corresponding to the reciprocal of the exhaust gas flow rate QEXHD, and varies in the range of 0.5 to 2.5, for example. This is to offset the influence of the fact that the passage utilization factor is considered to change substantially when the exhaust flow rate, that is, the exhaust pressure changes, even with the same particulate collection filter 29. Further, although the change of the correction coefficient KADPF is relatively small with respect to the temperature TMP_DPF, the correction coefficient KADPF tends to be smaller as the temperature is higher. This offsets the influence of the fact that when the temperature of the particulate collection filter 29 rises, the bulk density of the particulate collection filter 29 increases and the area of the fine passage is physically reduced. is there. Therefore, by multiplying the correction coefficient KADPF based on these factors by S23, the equivalent area of the particulate collection filter 29 can be obtained with higher accuracy.

  The values sequentially obtained in this manner are subjected to weighted average processing in S25 and output as the equivalent area ADPFD of the particulate collection filter 29.

  On the other hand, in S27, an initial equivalent area of the particulate collection filter 29, that is, an equivalent area ADPF_INIT when exhaust particulates are not deposited is obtained. In particular, here, as described above, the temperature TMP_DPF is determined using the predetermined map TBL_ADPF_INIT in consideration of the change in the bulk density of the particulate collection filter 29 and the passage area due to the temperature change of the particulate collection filter 29. The corrected initial equivalent area ADPF_INIT is output. This map TBL_ADPF_INIT has characteristics as shown in FIG. 6, that is, characteristics that become slightly smaller at high temperatures with reference to an equivalent area at low temperatures.

  In S28, the equivalent area ADPFD at that time obtained in S25 is divided by the initial equivalent area ADPF_INIT obtained in S27, thereby obtaining the reduction ratio of the passage area, that is, the “ratio” RTO_ADPF due to exhaust particulates. In S29, the exhaust particulate accumulation amount (weight) SPMact is obtained from the value of the ratio RTO_ADPF with reference to a predetermined map Tbl_SPMact along the known characteristics.

  In S33, a predetermined map TPEXH_CATS is used to obtain the pressure increase due to the ventilation resistance of the catalyst device (NOx trap catalyst 28 and oxidation catalyst 27) upstream of the particulate collection filter 29 according to the exhaust flow rate QEXHD. . This increase in pressure basically increases as the exhaust flow rate QEXHD increases. In S34, the pressure increase is added to the output PEXH_DPFIN in S14 described above. Therefore, the output PEXH_TCOUT in S34 corresponds to the pressure upstream of the oxidation catalyst 27, that is, the pressure on the outlet side of the exhaust turbine 22.

  FIG. 7 is a block diagram showing processing for obtaining the valve opening of the EGR valve 6, that is, the EGR flow rate, among the contents of the control executed by the control unit 5.

  In S41, the basic passage area AEVO of the EGR valve 6 is calculated by dividing the target EGR flow rate TQEC by the flow rate Cqe of the EGR gas passing through the EGR valve 6. The target EGR flow rate TQEC is given by the following equation (2). In the following equation (2), QAC is a fresh air amount detected by the air flow meter 35, and MEGR is a target EGR rate determined in accordance with operating conditions.

(Equation 2)
TQEC = QAC × (MEGR / 100) (2)
The flow velocity Cqe may be given by the following equation (3) using, for example, the pressure Pin in the collector 3a and the pressure Pexh in the intake passage 2 on the combustion chamber side with respect to the exhaust turbine 22.

(Equation 3)
Cqe = {2ρ (Pexh-Pin)} ^1/2 (3)
In S42, the map TBL_KAEV_ADPF is used, that is, a correction coefficient corresponding to the ratio RTO_ADPF is calculated. This map TBL_KAEV_ADPF determines whether exhaust gas should flow positively toward the particulate collection filter 29 or be distributed to EGR when exhaust particulate accumulates in the particulate collection filter 29. Specifically, as shown in FIG. 8, the correction coefficient is calculated so that the ratio between the passage area ADPFD of the particulate collection filter 29 and the passage area AEV of the EGR valve 6 is constant.

  In S43, the passage area AEV of the EGR valve 6 is calculated by multiplying the basic passage area AEVO of the EGR valve 6 by the correction coefficient obtained in S42, and output to S44.

  The map MAVSTP of S44 converts the passage area AEV of the EGR valve 6 into the number of motor rotation steps of a step motor (not shown) that drives the EGR valve 6, and outputs the step number STPD corresponding to the passage area AEV. .

  That is, the opening degree of the EGR valve 6 is corrected by the correction coefficient calculated by the map TBL_KAEV_ADPF of S42 described above so that the ratio of the passage area ADPFD of the particulate collection filter 29 and the passage area AEV of the EGR valve 6 is constant. Is done.

  FIG. 9 is a block diagram showing a process for obtaining the target air-fuel ratio among the contents of the control executed by the control unit 5.

  In the present embodiment, when the EGR valve 6 is opened and EGR is performed, the variable capacity adjustment by the variable nozzle 24 of the exhaust turbine 22 is not performed, and the EGR valve 6 is closed and EGR is performed. It is assumed that the variable capacity adjustment by the variable nozzle 24 of the exhaust turbine 22 is performed when there is not.

In the map tLambda_map_w_pilot in S51, the target air-fuel ratio λ ₀ is calculated according to the fuel injection amount QFDRV_DC determined by the accelerator opening and the engine speed NE.

Step S52 the map TBL_KLAMB_ADPF_WOEGR, it calculates a correction coefficient K ₁ depending on the clogging ratio RTO_ADPF described above. This map TBL_KLAMB_ADPF_WOEGR calculates the correction amount of the air-fuel ratio when the capacity variable adjustment by the variable nozzle 24 of the exhaust turbine 22 is performed, and as shown in FIG. 10, that is, the ratio RTO_ADPF is the diesel engine 1 and K ₁ <1 in the region A ₁ smaller than the threshold determined by the capacity of the particulate collection filter 29, and K ₁ = 1 in the region B ₁ greater than or equal to the threshold.

In S53 in map TBL_KLAMB_ADPF_WEGR, depending on the clogging ratio RTO_ADPF described above, it calculates the correction factor K _2. This map TBL_KLAMB_ADPF_WEGR is for calculating the correction amount of the air-fuel ratio when EGR is performed. As shown in FIG. 11, the ratio RTO_ADPF is determined by the capacity of the diesel engine 1 and the particulate collection filter 29. In the region A ₂ smaller than the threshold value, K ₂ > 1, and when the accumulation of exhaust particulates in the particulate collection filter 29 becomes significant, the air-fuel ratio is set to the lean side and exhaust particulate emissions from the combustion chamber (cylinder). Reduce the amount. In other words, K ₂ = 1 in the region B ₂ where the ratio RTO_ADPF is larger than the threshold value.

In other words, when the amount of exhaust particulate deposited on the particulate collection filter 29 is greater than or equal to a predetermined amount, the correction coefficient K ₂ (K ₂ > 1) for setting the target air-fuel ratio λ ₀ to the lean side is the exhaust particulate. When the amount of exhaust particulate deposited on the particulate collection filter 29 is less than a predetermined amount, the value of the correction coefficient K ₂ is “1”, resulting in the amount of exhaust particulate deposited. The corresponding target air-fuel ratio λ ₀ is not corrected.

In S54, by multiplying the target air-fuel ratio lambda ₀ calculated by the correction factor K ₁ and S51 calculated in S52, and outputs the S56.

In S55, by multiplying the target air-fuel ratio lambda ₀ calculated by the correction factor K ₂ and S51 calculated in S53, and outputs the S56.

The S56, opening information STPD of the EGR valve 6 is input, when the EGR valve 6 is fully closed, multiplies the target air-fuel ratio lambda ₀ calculated by the correction factor K ₁ and S51 calculated in S52 The obtained value is output to S57 as the air-fuel ratio target value λ ₁ , and when the EGR valve 6 is open, the target value is the product of the correction coefficient K ₂ calculated in S53 and the air-fuel ratio λ ₀ calculated in S51. The air-fuel ratio λ ₁ is output to S57.

That is, when the air-fuel ratio is corrected according to the condition of the particulate collection filter 29 when the EGR is not performed and the capacity variable adjustment by the variable nozzle 24 of the exhaust turbine 22 is performed, in S52, the air-fuel ratio is corrected. When the target air-fuel ratio λ ₀ is corrected using the calculated correction coefficient K ₁ and the air-fuel ratio is corrected according to the condition of the particulate collection filter 29 during EGR, the calculation is made in S53. The target air-fuel ratio λ ₀ is corrected using the corrected correction coefficient K ₂ .

On the other hand, in the map tLambda_map_dpf_reg in S58, the target air-fuel ratio λ ₂ required for regenerating the particulate collection filter 29 is calculated according to the fuel injection amount QFDRV_DC determined by the accelerator opening and the engine speed NE. The target air-fuel ratio λ ₂ is output to S57.

In S57, the regeneration request signal state_ATS of the particulate collection filter 29 is input, and when there is a regeneration request of the particulate collection filter 29, that is, during regeneration of the particulate collection filter 29, that is, according to the ratio RTO_ADPF. Without correcting the air-fuel ratio, the target air-fuel ratio λ ₂ calculated in S58 is output as the target air-fuel ratio λ. Then, if there is no request for reproducing the particulate collection filter 29, i.e. the particulate collection filter 29 is when not being played and outputs the target air-fuel ratio lambda ₁ output from S56 as the target air-fuel ratio lambda.

  As described above, in this embodiment, when exhaust particulates accumulate in the particulate collection filter 29, the pressure in the exhaust passage 2 increases, and the residual gas in the combustion chamber (cylinder) increases. Furthermore, since the opening degree of the EGR valve 6 is corrected so that the ratio of the passage area ADPFD of the particulate collection filter 29 and the passage area AEV of the EGR valve 6 is constant, combustion associated with a rise in pressure in the exhaust passage 2 An increase in residual gas in the chamber (cylinder) is suppressed, and exhaust performance deterioration due to the shift of the combustion state to the rich side can be suppressed.

Further, when exhaust particulates of a predetermined amount or more are accumulated in the particulate collection filter 29, the target air-fuel ratio λ ₀ is corrected to the lean side, so that the exhaust particulate discharge amount discharged from the combustion chamber (cylinder). Can be further suppressed.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

  (1) A control device for a diesel engine includes an EGR passage that connects an exhaust passage and an intake passage, an EGR valve that is provided in the EGR passage, a DPF that is provided in the exhaust passage and collects exhaust particulates, and an operating state of the engine An operating state detecting means for detecting exhaust gas, an exhaust particulate amount calculating means for calculating the amount of exhaust particulates collected in the DPF based on the operating conditions, and a passage area of the DPF proportional to the amount of exhaust particulates accumulated And a DGR passage area calculating means for calculating a passage area of the EGR valve based on a flow rate of the EGR gas passing through the EGR valve, and a passage area of the DPF and a passage area of the EGR valve The EGR valve opening is corrected so that the ratio to As a result, an increase in residual gas in the combustion chamber (cylinder) due to an increase in pressure in the exhaust passage is suppressed, and deterioration in exhaust performance due to the shift of the combustion state to the rich side can be suppressed.

  (2) In the diesel engine control device configuration described in (1) above, when a predetermined amount or more of exhaust particulate accumulates in the DPF, the target air-fuel ratio is corrected to the lean side. As a result, the target air-fuel ratio is corrected to the lean side, so that the amount of exhaust particulate discharged from the combustion chamber (cylinder) can be further suppressed.

Explanatory drawing which shows the whole structure of the diesel engine provided with the control apparatus which concerns on this invention. The block diagram which shows the process which calculates | requires exhaust flow volume. The block diagram which shows the process which calculates | requires exhaust particulate amount. The characteristic view which shows the characteristic of filter constant TC. The characteristic view which shows the characteristic of the correction coefficient KADPF. The characteristic view which shows the characteristic of equivalent area ADPF_INIT. The block diagram which shows the process which calculates | requires the valve opening degree of an EGR valve. Correlation between the passage area ADPFD of the particulate collection filter, the passage area AEV of the EGR valve, and the EGR rate when controlled by the target air-fuel ratio corrected using the correction coefficient obtained in S42 of FIG. FIG. The block diagram which shows the process which calculates | requires a target air fuel ratio. Characteristic diagram showing the characteristics of a correction coefficient K _1. Characteristic diagram showing the characteristic of the correction factor K _2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diesel engine 5 ... Control unit 6 ... EGR valve 21 ... Turbocharger 29 ... Fine particle collection filter (DPF)

Claims (2)

An EGR passage connecting the exhaust passage and the intake passage;
An EGR valve provided in the EGR passage, a DPF provided in the exhaust passage and collecting exhaust particulates;
An operating state detecting means for detecting the operating state of the engine;
Exhaust particulate amount calculation means for calculating the amount of exhaust particulates collected in the DPF based on operating conditions;
DPF passage area calculating means for calculating the passage area of the DPF proportional to the amount of exhaust particulates deposited;
EGR valve passage area calculating means for calculating the passage area of the EGR valve based on the flow rate of the EGR gas passing through the EGR valve,
A control device for a diesel engine, wherein the EGR valve opening is corrected so that a ratio of a passage area of the DPF and a passage area of the EGR valve is constant. 2. The diesel engine control device according to claim 1, wherein when a predetermined amount or more of exhaust particulate accumulates in the DPF, the target air-fuel ratio is corrected to the lean side.

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