JP4161887B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust emission control device for processing exhaust particulates of a diesel engine.

In order to process exhaust particulates discharged from diesel engines, a filter that collects particulates is placed in the exhaust system, and when a predetermined amount of particulates is deposited on the filter, the filter temperature is raised and deposited on the filter. Various types of so-called filter regeneration processes have been proposed (see Patent Document 1).
JP-A-5-44437

  By the way, if the rapid deceleration is performed during the regeneration process of the filter, the exhaust gas flow rate rapidly decreases. In this case, the exhaust gas flowing into the filter not only supplies the oxygen necessary for burning the particulates, but also has a cooling function that takes the heat of combustion and discharges it downstream of the filter. If the exhaust flow rate suddenly decreases in the middle of the process, the heat of the filter becomes difficult to escape and the particulates collected by the filter continue to burn, so the bed temperature of the filter may rise rapidly and exceed the limit bed temperature.

  In order to cope with this, it is conceivable to stop the regeneration process when sudden deceleration is performed during the filter regeneration process. However, since there are many opportunities to decelerate during driving, if the regeneration process is stopped at each sudden deceleration, the opportunity for the regeneration process is narrowed.

  In addition, since the sudden rise in bed temperature during deceleration depends on the amount of particulates collected by the filter, if the regeneration process is entered at a stage where the amount of particulates collected is small, that is, the interval of the regeneration process is increased. If the frequency of the regeneration process is increased by shortening it, it can be considered that a sudden rise in bed temperature can be suppressed even if the vehicle is decelerated during the regeneration process. However, for the regeneration process, it is necessary to raise the exhaust gas temperature so that the bed temperature becomes the target bed temperature (in the range of 350 ° C. to 650 ° C.). When the frequency of processing is increased, the opportunity to perform post-injection also increases, leading to deterioration in fuel consumption. Therefore, this method is also not a good idea.

  Therefore, the present invention determines whether or not a predetermined deceleration has occurred during the regeneration process, and when it is determined that the deceleration has occurred during the regeneration process, the exhaust flow rate is controlled to be increased in order to regain the exhaust cooling function. On the other hand, by controlling the exhaust temperature so as to obtain a second target exhaust temperature lower than the first target exhaust temperature in the normal case (meaning excluding a predetermined deceleration time), the vehicle enters a deceleration state during the regeneration process. In this case, it is an object to continue the regeneration process while suppressing an increase in the bed temperature of the filter.

  On the other hand, in the above-described conventional device, when the vehicle is decelerated during the regeneration of the filter, the intake air amount from the outside air is limited to increase the exhaust gas recirculation amount, so that a large amount of high-temperature exhaust gas is mixed into the intake air. Is raised to maintain the temperature rise state of the exhaust. However, the conventional device is only intended to raise the temperature of the exhaust gas, and the technical problem is that the bed temperature of the filter increases due to deceleration during the regeneration process, and an attempt is made to avoid the rise of the bed temperature. The technical idea is different from the present invention. Further, in the present invention, the target value of the exhaust temperature at the time of deceleration is lower than in the normal case, and the control direction of the exhaust temperature is different from that of the conventional apparatus that attempts to increase the exhaust temperature.

The present invention provides an exhaust purification apparatus for an engine which includes a filter for collecting particulates in an exhaust passage, and raises the exhaust temperature to a first target exhaust temperature to perform the regeneration process of the filter at the regeneration time of the filter. It is determined whether or not the vehicle has reached a predetermined deceleration, and from this determination result, when the vehicle is decelerated during the regeneration process, the exhaust temperature is set so that a second target exhaust temperature lower than the first target exhaust temperature is obtained. In addition, when the deceleration occurs during the regeneration process, the exhaust flow rate is controlled to the increase side , and the current temperature of the filter is estimated, and when the deceleration occurs during the regeneration process, the current temperature of the filter The higher the value is, the smaller the delay time is calculated, and the exhaust temperature control and exhaust flow rate control are performed by this delay time from the timing when deceleration occurs during the regeneration process. Make up to Selle so.

  According to the present invention, when the predetermined deceleration is performed during the regeneration process and the bed temperature of the filter is about to rise, the exhaust flow rate is controlled to the increase side, so that the cooling function by the exhaust is regained and the exhaust temperature is reduced. Since the second target temperature, which is lower than that in the case where the vehicle is not decelerated, is controlled, the regeneration process can be continuously performed while suppressing an increase in the bed temperature of the filter.

  Further, since the reproduction process is continued even when deceleration is performed during the reproduction process, the opportunity for the reproduction process can be increased.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a diesel engine. A diaphragm type EGR valve 6 (responsive to a control pressure from a pressure control valve (not shown) is connected to an EGR passage 4 connecting the exhaust passage 2 and the collector portion 3a of the intake passage 3. EGR device). The pressure control valve is driven by a duty control signal from the engine controller 31 and thereby obtains a predetermined EGR rate corresponding to the operating conditions.

  The engine includes a common rail fuel injection device 10. The fuel injection device 10 mainly includes a fuel tank (not shown), a supply pump 14, a common rail (pressure accumulation chamber) 16, and a nozzle 17 provided for each cylinder. The fuel pressurized by the supply pump 14 is accumulated in the pressure accumulation chamber 16. And the high pressure fuel in the pressure accumulating chamber 16 is distributed to the nozzles 17 corresponding to the number of cylinders.

  The nozzle 17 (fuel injection valve) includes a needle valve, a nozzle chamber, a fuel supply passage to the nozzle chamber, a retainer, a hydraulic piston, a return spring, and the like, and a three-way valve (not shown) is interposed in the fuel supply passage to the hydraulic piston. It is disguised. When the three-way valve (solenoid valve) is OFF, the needle valve is seated, but when the three-way valve is turned ON, the needle valve rises and fuel is injected from the nozzle hole at the tip of the nozzle. That is, the fuel injection start timing is adjusted by the switching timing of the three-way valve from OFF to ON, and the fuel injection amount is adjusted by the ON time. If the pressure in the pressure accumulating chamber 16 is the same, the fuel injection amount increases as the ON time increases. Become.

  The exhaust passage 2 downstream of the opening of the EGR passage 4 is provided with a variable capacity turbocharger 21 in which a turbine 22 that converts heat energy of exhaust gas into rotational energy and a compressor 23 that compresses intake air are connected coaxially. A variable nozzle 24 (variable capacity mechanism) driven by an actuator 25 is provided at the scroll inlet of the turbine 22, and the engine controller 31 allows the variable nozzle 24 to obtain a predetermined supercharging pressure from a low rotational speed range. On the low rotational speed side, the nozzle opening degree (tilting state) is increased to increase the flow rate of the exhaust gas introduced into the turbine 22, and on the high rotational speed side, exhaust gas is introduced into the turbine 22 without resistance and controlled to the nozzle opening degree (fully open state).

  The actuator 25 includes a diaphragm actuator 26 that drives the variable nozzle 26 in response to the control pressure, and a pressure control valve 27 that adjusts the control pressure to the diaphragm actuator 26. A duty control signal is generated so as to achieve the target nozzle opening, and this duty control signal is output to the pressure control valve 27.

  An intake throttle valve 42 (intake throttle device) driven by an actuator 43 is provided at the collector 3a inlet. The actuator 43 includes a diaphragm actuator 44 that drives the intake throttle valve 42 in response to the control pressure, and a pressure control valve 45 that adjusts the control pressure to the diaphragm actuator 44, and the intake throttle valve 42 opens the target. A duty control signal is generated so as to be closed to a degree, and this duty control signal is output to the pressure control valve 45.

  In the engine controller 31 to which signals from the accelerator sensor 32, the sensor 33 for detecting the engine speed and the crank angle, the water temperature sensor 34, and the air flow meter 35 are inputted, the target EGR rate and the target supercharging pressure are determined based on these signals. EGR control and supercharging pressure control are performed in a coordinated manner.

  A filter 41 that collects particulates in the exhaust is installed in the exhaust passage 2. When the accumulated amount of particulates on the filter 41 reaches a predetermined value, the exhaust temperature is raised and the particulates accumulated on the filter 41 are burned and removed.

  In order to detect the pressure loss of the filter 41 (the pressure difference between the upstream and downstream of the filter 41), a differential pressure sensor 36 is provided in the differential pressure detection passage that bypasses the filter 41.

  The pressure loss ΔP of the filter 41 detected by the differential pressure sensor 36 is sent to the engine controller 31 together with the filter inlet temperature T1 from the temperature sensor 37 and the filter outlet temperature T2 from the temperature sensor 38, and is mainly composed of a microprocessor. The engine controller 31 that is to perform the regeneration processing of the filter 41 based on these.

On the premise of such an engine that performs the regeneration processing of the filter 41, in the present invention, (1) it is determined whether or not sudden deceleration has occurred during the regeneration processing,
(2) Target exhaust temperature (second target exhaust temperature) lower than the target exhaust temperature (first target exhaust temperature) in the normal case (meaning excluding sudden deceleration) when sudden deceleration occurs during the regeneration process Set
(3) The exhaust gas temperature is controlled so that the second target exhaust gas temperature is obtained while controlling the exhaust gas flow rate to the increase side.

  This will be further described. In this embodiment, the regeneration processing flag is set according to FIG. 3 described later, but in this case, the time of deceleration is excluded from the regeneration execution condition in step 4 of FIG. That is, even if the pressure loss ΔP of the filter 41 detected by the differential pressure sensor 36 exceeds the regeneration start determination value ΔPHmax, the regeneration process flag = 1 is not set during deceleration. The reason why the regeneration process is not performed during deceleration is to avoid a sudden rise in the bed temperature of the filter 41 when sudden deceleration is performed during the regeneration process. This will be described with reference to FIG. 2. FIG. 2 shows, as a model, movements of the exhaust gas flow rate, the exhaust gas temperature, and the bed temperature when sudden deceleration is performed during the regeneration process.

  The case where the regeneration process is started at the time of deceleration is not exactly the same as the case where the sudden deceleration is performed in the middle of the regeneration as shown in FIG. 2, but the effect of the sudden deceleration on the bed temperature of the filter 41 is the same. . That is, if the accelerator pedal is quickly returned for rapid deceleration during the regeneration process of the filter 41, the exhaust gas flow rate rapidly decreases (see the broken line in the third stage in FIG. 2). The exhaust gas flowing into the filter 41 supplies oxygen necessary for burning particulates in the filter 41, and also has a cooling function of taking away the burned heat and discharging it downstream of the filter 41. If the exhaust flow rate suddenly decreases during the process, the heat of the filter 41 becomes difficult to escape and the particulates collected by the filter 41 continue to burn, so the bed temperature of the filter 41 rises rapidly and the limit bed temperature is increased. (See the broken line at the bottom of FIG. 2).

  The same applies to the case where the regeneration process is started at the time of deceleration, and the bed temperature of the filter 41 rapidly rises due to the decrease in the exhaust flow rate due to the deceleration and may exceed the limit bed temperature. Therefore, in order not to enter the reproduction process at the time of deceleration, the condition at the time of deceleration is excluded from the reproduction execution condition at step 4 in FIG.

  However, since there are many opportunities to decelerate during driving, if the driving conditions are set so that regeneration processing is not performed during deceleration, the opportunity for regeneration processing is narrowed.

  In addition, when rapid deceleration is performed during the regeneration process, the bed temperature of the filter 41 may rapidly increase and exceed the limit bed temperature due to the decrease in the exhaust flow rate due to deceleration as described above with reference to FIG.

  Therefore, even when a sudden deceleration is performed during the regeneration process, the inventor of the present invention may confirm that the regeneration process can be continuously performed while considering that the bed temperature of the filter 41 does not exceed the limit bed temperature. As a result of the above consideration, the present invention has been created. In other words, in the present invention, when the sudden deceleration is determined (when the sudden deceleration flag is 1 as in the second stage in FIG. 2), the exhaust flow rate is controlled to the increase side so that the value before the sudden deceleration is maintained. However, the target exhaust temperature is lower than the normal value (see the first target exhaust temperature tTexh1 in the fourth stage in FIG. 2) (see the fourth stage in the second stage in FIG. 2). 2), and the exhaust gas temperature is controlled to reach the second target exhaust gas temperature tTexh2, so that the bed temperature of the filter 41 can be reduced even if sudden deceleration is performed during the regeneration process. The regeneration process is to be continued without exceeding the limit bed temperature.

  The contents of these controls performed by the engine controller 31 will be described in detail below based on a flowchart.

  FIG. 3 is for setting a reproduction processing flag, and is executed at regular intervals (for example, every 10 ms).

  In FIG. 3, in step 1, the pressure loss ΔP of the filter 41 is read from the output of the differential pressure sensor 36.

  In step 2, the reproduction processing flag is checked. The reproduction processing flag is a flag that becomes 1 when a reproduction processing condition described later is satisfied. Since the engine is initially set to zero when the engine is started, the process proceeds to steps 3 and 4 before the regeneration process condition is satisfied, and the regeneration process condition is checked. The establishment of the regeneration process condition is that the pressure loss ΔP of the filter 41 exceeds the regeneration start determination value ΔPHmax and is in the regeneration execution condition.

  Here, the regeneration execution condition is a condition for determining whether or not the engine operating condition is suitable for the regeneration of the filter 41. Here, the regeneration execution condition is satisfied when the operating condition determined by the engine speed and the fuel injection amount (corresponding to the engine load) is in a predetermined region.

  It is assumed that the regeneration execution condition is not established in the idle region (or including a low load region close to idle). This is because the exhaust temperature is originally low in the idle region, and the exhaust temperature cannot be raised to the first target exhaust temperature tTbed1 even if post injection and intake throttling are performed. Here, the first target exhaust temperature tTbed1 is a temperature at which the particulates deposited on the filter 41 are self-ignited and burned quickly, and is in the range of 450 ° C to 650 ° C.

  Further, even when the engine rotation speed and the fuel injection amount are in a predetermined region, it is determined that the regeneration execution condition is not satisfied when the engine is decelerated.

  For this reason, when the pressure loss ΔP is equal to or smaller than the regeneration start determination value ΔPHmax or when the engine operating condition is not in the regeneration execution condition, the current process is terminated.

  When the pressure loss ΔP of the filter 41 exceeds the regeneration start determination value ΔPHmax and the operation condition determined by the engine speed and the fuel injection amount is the regeneration execution condition, it is determined that the regeneration process can be performed, and the process proceeds to Step 5 for regeneration. Process flag = 1.

  Since the reproduction processing flag = 1 cannot proceed from step 2 to step 3 from the next time, the processing is ended as it is. That is, after the reproduction processing flag is set to 1 in step 5, it is reset to zero at the timing of completion of the reproduction processing described later (see step 37 in FIG. 5).

  FIG. 4 is for setting the rapid deceleration flag, and is executed at regular intervals (for example, every 10 ms).

  In step 11, the reproduction processing flag is checked. When the reproduction process flag = 0, the current process is terminated as it is.

  When the regeneration processing flag = 1, the routine proceeds to step 12 where the rapid deceleration flag (initially set to zero) is viewed. Here, assuming that the rapid deceleration flag = 0, at this time, the routine proceeds to step 13 and thereafter.

  In step 13, the engine rotational speed Ne detected by the sensor 33 is read, and in step 14, a deviation from the previous engine rotational speed (that is, the amount of change per rotational speed calculation period) ΔNe is calculated. If ΔNe is a positive value, it indicates that the vehicle is decelerating, and if it is a positive or negative value, it indicates that the vehicle is accelerating or in a steady state.

  In step 15, ΔNe is compared with a predetermined value α (positive value). When ΔNe is less than α, it is determined that the vehicle is not rapidly decelerating, that is, during moderate deceleration, steady state or acceleration, and the current process is terminated.

  When ΔNe is greater than or equal to α, it is determined that rapid deceleration is in progress, and the routine proceeds to step 16 where the rapid deceleration flag = 1.

  Here, this control is not performed even during deceleration other than rapid deceleration. This is because it is determined that the bed temperature of the filter 41 does not increase so much due to the decrease in the exhaust flow rate at the time of slow deceleration, and therefore the bed temperature does not exceed the limit bed temperature. Finally, α is determined by matching.

  Due to this rapid deceleration flag = 1, it is not possible to proceed from step 12 to step 13 onward from the next time.

  FIG. 5 shows a control for sudden deceleration during the reproduction process, which is executed at regular time intervals (for example, every 10 ms). Here, the control at the time of sudden deceleration is the control of the above (3), which consists of exhaust temperature control and exhaust flow rate control, and when the exhaust temperature control flag = 1 as will be described later, the exhaust temperature control is performed according to the flow of FIG. When the exhaust flow rate control flag = 1, the exhaust flow rate control is performed according to the flow of FIG.

  In step 21, the reproduction processing flag is checked. When the reproduction processing flag = 1, the process proceeds to step 22 and subsequent steps.

  Steps 22 and 23 look at the current and previous rapid deceleration flags. If the rapid deceleration flag = 0 at this time, it is determined that the regeneration process of the filter 41 is necessary but the rapid deceleration control is not necessary, and the routine proceeds to step 39 where the normal exhaust temperature control, that is, the exhaust temperature is set to the first target. Control to increase the exhaust temperature to tTexh1 is performed, and the current process is terminated.

When the rapid deceleration flag = 1 at this time and the rapid deceleration flag = 0 at the previous time, that is, when the rapid deceleration flag = 1 at this time for the first time, the process proceeds to Steps 24-28. That is, in step 24, the filter inlet temperature T1 and the filter outlet temperature T2 detected by the temperature sensors 37 and 38 are read, and in step 25, using these temperatures T1 and T2,
rTbed = b1 × T1 + b2 × T2 (1)
Where b1, b2: constants,
The current bed temperature r Tbed of the filter 41 is calculated (estimated) by the following equation. In formula (1), b1 and b2 are values determined by experiments.

  In step 26, a delay time tdly for switching the target exhaust temperature from the first target exhaust temperature tTbed1 to the lower second target exhaust temperature tTbed2 is calculated by searching a table having the contents shown in FIG. 6 from the actual bed temperature rTbed. . As shown in FIG. 6, the delay time tdly is a value that decreases as the actual bed temperature rTbed increases. When the actual bed temperature rTbed is low, it is preferable that the delay time tdly is set large so as not to prevent the bed temperature from rising. On the other hand, when the actual bed temperature rTbed is high, it is necessary to prevent the upper limit temperature of the bed temperature from being exceeded by reducing the delay time tdly as much as possible. The delay time tdly is set to a value that satisfies these requirements.

  In step 27, a timer is started. This timer is for measuring the elapsed time after the rapid deceleration flag is switched from zero to one.

  At this time, if the rapid deceleration flag = 1 in both cases, the process proceeds from step 22 and step 23 to step 29 and subsequent steps. In steps 29 and 30, it is checked whether or not the timer value is equal to or longer than the delay time at this time, and whether or not the timer value was equal to or longer than the delay time last time. If the timer value is less than the delay time this time, the current process is terminated.

  When the timer value is now greater than or equal to the delay time and the timer value was less than the delay time last time, that is, when the timer value has reached the delay time for the first time, the process proceeds to steps 31 and 32, and the exhaust gas temperature control flag (initially set to zero) = 1 and the exhaust flow control flag (initially set to zero) = 1.

  Here, the exhaust temperature control flag is used in the flow of FIG. 7 described later, and the exhaust flow rate control flag is used in the flow of FIG. 11 described later.

  At this time, when the timer value is equal to or longer than the delay time in the previous time, the process proceeds from Steps 29 and 30 to Steps 33 and 34, and similarly to Steps 24 and 25, the filter inlet temperature T1 and the filter outlet temperature detected by the temperature sensors 37 and 38. Using T2, the current bed temperature rTbed of the filter 41 is calculated by the above-described equation (1).

  In step 35, the actual bed temperature rTbed is compared with the limit bed temperature. Since the actual bed temperature rTbed does not exceed the limit bed temperature at the beginning of the exhaust gas temperature control and the exhaust gas flow control, the process proceeds to step 36. In response to this, the exhaust temperature control and the exhaust gas flow control are started for some reason. When the bed temperature rTbed exceeds the limit bed temperature, the regeneration process is stopped, and the process proceeds to an end operation of the regeneration process in steps 37 and 38.

  In step 36, it is checked whether or not the reproduction is finished. Various methods for determining the end of reproduction are disclosed. Either method is acceptable. For example, since the time required for the reproduction is known in advance, the reproduction may be determined to end when the timer value started at the start of the reproduction process exceeds this time.

  When the regeneration end timing has not been reached, the operations of steps 31 and 32 are executed in order to continue the exhaust gas temperature control and the exhaust gas flow rate control.

  On the other hand, when the regeneration end timing is reached, the regeneration process is terminated, so that the process proceeds from step 36 to step 37 where the regeneration process flag = 0, and in order to prepare for sudden deceleration during the next regeneration process, the exhaust temperature control flag at step 38. The exhaust flow control flag and the rapid deceleration flag are all returned to zero.

  FIG. 7 is for exhaust gas temperature control, and is executed at regular intervals (for example, every 10 ms).

  In step 41, the exhaust temperature control flag is checked. When the exhaust gas temperature control flag = 0, the current process is terminated.

  When the exhaust gas temperature control flag = 1, the routine proceeds to step 42, where the engine speed Ne and the fuel injection amount Qf as the engine load are read, and the operating conditions determined by these Ne and Qf are the exhaust gas temperature by the post injection and the second target exhaust gas temperature. Whether it is in the region where the temperature is increased to tTexh2 (post injection region) or whether it is in the region where the exhaust temperature is increased to the second target exhaust temperature tTexh2 due to the delay of the main injection timing (main injection timing delay region) See at 43. These post-injection region and main injection timing retardation region are predetermined as shown in FIG. 8 using the engine speed Ne and the fuel injection amount Qf as parameters.

  When the operating condition is in the post-injection region, the routine proceeds to step 44, where the post-injection amount is calculated by searching a map having the contents shown in FIG. 9 from the engine speed Ne and the fuel injection amount Qf. When in the injection timing retardation region, the routine proceeds from step 43 to step 45, where the main injection timing retardation amount is calculated by searching a map having the contents shown in FIG. 10 from the engine speed Ne and the fuel injection amount Qf.

  The characteristics shown in FIGS. 9 and 10 are set in advance so as to obtain the second target exhaust temperature tTexh2. The second target exhaust temperature tTexh2 is a constant value, and the post-injection amount and the main injection timing retardation amount are reduced as the load decreases so that a constant second target exhaust temperature tTexh2 can be obtained even if the operating conditions are different. The value is set so as to increase as the rotational speed decreases.

  The post injection amount and the main injection timing retardation amount calculated in this way are used in a flow (not shown) for calculating the fuel injection amount and the fuel injection timing, and the post injection and the main injection timing are retarded. .

  FIG. 11 is for exhaust gas flow rate control, and is executed at regular intervals (for example, every 10 ms).

  In step 51, the exhaust flow control flag is checked. If the exhaust flow control flag = 0, the current process is terminated.

  When the exhaust gas flow rate control flag = 1, the routine proceeds to step 52 where the EGR valve opening degree (the opening degree of the EGR valve 6) and the variable nozzle opening degree (the variable nozzle 24 of the variable nozzle 24) are increased. Nozzle opening) and intake throttle valve opening (opening of intake throttle valve 42) are controlled.

  There is a relationship shown in FIG. 12 between the EGR valve opening, the variable nozzle opening, the intake throttle valve opening, and the exhaust flow rate, and the characteristics of the figure change depending on the operating conditions (Ne, Qf). Finally, as shown in FIG. 13, the characteristics of the target EGR valve opening, the target variable nozzle opening, and the target intake throttle valve opening are obtained in accordance with the operating conditions, and these are plotted on a map. By searching the map according to the conditions, the target EGR valve opening, the target variable nozzle opening, and the target intake throttle valve opening may be calculated.

  The EGR valve 6, the variable nozzle 24, and the intake throttle valve 42 are exhaust flow rate control means in the exhaust flow rate control of FIG. 11, and here, three exhaust flow rate control means are simultaneously operated. One exhaust flow rate control means may be used.

In step 53, the intake air flow rate Qa detected by the air flow meter 35, the fuel injection amount Qf, the filter inlet temperature T1 [° C.] detected by the temperature sensor 37, and the pressure loss ΔP detected by the differential pressure sensor 36 are read. Using these, rQexh = A × (Qa + σ2 × σ1 × Qf)
× {P0 / (273 + 20)} × {(273 + T1) / (P0 + ΔP)} (2)
Where A is a constant,
σ1: Fuel density (constant value),
σ2: exhaust density (constant value),
P0: atmospheric pressure,
The actual exhaust flow rate rQexh is calculated (estimated) by the following formula. In the equation (2), the term {P0 / (273 + 20)} × {(273 + T1) / (P0 + ΔP)} is a conversion factor to the reference state (20 ° C., atmospheric pressure).

  In step 55, the actual exhaust flow rate rQexh is compared with the upper limit value Qmax. Here, the upper limit value Qmax is determined as shown in FIG. That is, there is a relationship shown in FIG. 14 between the exhaust flow rate and the bed temperature during the regeneration process. The exhaust flow rate does not have to be increased. If the exhaust flow rate is excessively increased, the bed temperature during the regeneration process is lowered. I will let you. Therefore, an upper limit value Qmax is set for the exhaust flow rate control, and the range between the upper limit value Qmax and the exhaust flow rate (lower limit value) with respect to the limit bed temperature is set as the control range.

  If the actual exhaust flow rate rQexh is below the upper limit value Qmax, the current process is terminated. The degree of opening is corrected in the increasing direction and the opening degree of the target throttle valve is reduced in the decreasing direction, and the EGR valve opening degree, the variable nozzle opening degree, and the intake throttle valve opening degree are controlled in accordance with the corrected target values.

  Each correction amount at this time is determined as follows. That is, the difference rQexh−Qmax between the actual exhaust flow rate rQexh and the upper limit value Qmax is calculated. Then, based on the difference rQexh−Qmax, the table of characteristics shown in FIGS. 15 to 17 stored in advance in the memory of the engine controller 31 is searched to determine the EGR valve opening, the variable nozzle opening, and the intake throttle valve opening. Each correction amount is determined.

  In each of the maps of the target EGR valve opening, the target variable nozzle opening, and the target intake throttle valve opening in FIG. 13 used for increasing the exhaust flow rate in step 52, the exhaust flow rate is within the upper limit value Qmax. It has established. However, even when the map of FIG. 13 is applied, steps 55 and 56 are added to ensure that the actual exhaust flow rate does not exceed the upper limit value Qmax for some reason.

  Here, the operation of the present embodiment will be described.

  According to the present embodiment (the invention described in claim 1), when the deceleration is suddenly performed during the regeneration process and the bed temperature of the filter 41 is about to rise rapidly, the exhaust flow rate is controlled to the increase side (see FIG. 2 (see the solid line in the third stage), the cooling function by exhaust gas is recovered, and the exhaust gas temperature is lower than the first target exhaust gas temperature tTbed1, which is a value when the exhaust gas temperature is not suddenly decelerated. Since the target exhaust temperature tTbed2 is controlled (refer to the solid line in the fourth stage in FIG. 2), the regeneration process can be continued while suppressing the rapid rise in the bed temperature of the filter 41.

  In addition, since the reproduction process is continued even when sudden deceleration is performed during the reproduction process, the opportunity for the reproduction process can be increased.

  Further, by increasing the exhaust flow rate, it is possible to suppress an increase in the bed temperature of the filter 41. However, if the exhaust flow rate is excessively high, the filter bed temperature is lowered, and the regeneration efficiency is reduced. Although the regeneration of the filter may end in an incomplete state, according to the present embodiment (the invention described in claim 2), a predetermined upper limit value is set when the exhaust gas flow rate is controlled to be increased. Since Qmax is not exceeded (steps 55 and 56 in FIG. 11), it is possible to prevent the bed temperature of the filter 41 from being excessively lowered and increase the regeneration efficiency.

  The function of the sudden deceleration determination means according to claim 1 is the flow of FIG. 4, the function of the exhaust temperature control means is the flow of FIGS. 5 and 7, and the function of the exhaust flow control means is the flow of FIGS. Has been fulfilled.

The schematic block diagram which shows one Embodiment of this invention. The wave form diagram for demonstrating the effect | action of this embodiment. The flowchart for demonstrating the setting of a reproduction | regeneration processing flag. The flowchart for demonstrating the setting of the rapid deceleration flag. The flowchart for demonstrating the control at the time of rapid deceleration during filter reproduction | regeneration processing. The characteristic diagram of delay time. The flowchart for demonstrating exhaust gas temperature control. Operation region diagram. The characteristic figure of post injection quantity. The characteristic diagram of the main injection timing retard amount. The flowchart for demonstrating exhaust flow control. The characteristic view which shows the relationship between an EGR valve opening degree, a variable nozzle opening degree, an intake throttle valve opening degree, and an exhaust flow rate. FIG. 4 is a characteristic diagram of a target EGR valve opening, a target variable nozzle opening, and a target intake throttle valve opening. The characteristic view which shows the relationship between exhaust flow volume and the bed temperature in a regeneration process. The characteristic view of the EGR valve opening correction amount. The characteristic diagram of variable nozzle opening correction amount. The characteristic diagram of the intake throttle valve opening correction amount.

Explanation of symbols

1 Engine 6 EGR valve (EGR device)
17 Nozzle (fuel injection valve)
21 Variable capacity turbocharger 24 Variable nozzle (variable capacity mechanism)
31 Engine controller 33 Crank angle sensor 36 Differential pressure sensor 37, 38 Temperature sensor 41 Filter 42 Inlet throttle valve

Claims (7)

It has a filter that collects particulates in the exhaust passage,
In an exhaust emission control device for an engine that performs a regeneration process of a filter by increasing the exhaust temperature to a first target exhaust temperature when the regeneration time of the filter is reached,
A deceleration determination means for determining whether or not a predetermined deceleration has occurred during the reproduction process;
An exhaust temperature control means for controlling the exhaust temperature so as to obtain a second target exhaust temperature lower than the first target exhaust temperature when deceleration occurs during the regeneration process from the determination result;
Similarly, an exhaust flow rate control means for controlling the exhaust flow rate to the increase side when deceleration occurs during the regeneration process ,
Filter temperature estimating means for estimating a current temperature of the filter;
Similarly, when the deceleration time is reached during the regeneration process, a delay time calculating means for calculating a delay time having a value that decreases as the current temperature of the filter increases.
Similarly , the exhaust gas purification system includes a delay processing means for delaying the operation of the exhaust temperature control means and the exhaust flow rate control means by this delay time from the timing when the deceleration is reached during the regeneration process. apparatus.   The exhaust emission control device according to claim 1, wherein when the exhaust flow rate control means controls the exhaust flow rate to the increase side, the exhaust flow rate is limited so as not to exceed a predetermined upper limit value. 2. The exhaust emission control device according to claim 1, wherein the reduction of the exhaust temperature to the second target exhaust temperature is achieved by retarding the fuel injection timing. The exhaust emission control device according to claim 1, wherein the exhaust temperature is lowered to the second target exhaust temperature by post injection.   2. The exhaust emission control device according to claim 1, wherein when the intake throttle valve is provided, the exhaust flow rate control means is the intake throttle valve.   The exhaust emission control device according to claim 1, wherein when the turbocharger having a variable capacity mechanism is provided, the exhaust flow rate control means is the variable capacity mechanism.   The exhaust emission control device according to claim 1, wherein when the EGR device is provided, the exhaust gas flow rate control means is the EGR device.

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