JP2004183525A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfy three requirements of regeneration treatment by using regeneration treatment of three stages. <P>SOLUTION: In this exhaust emission control device, a filter 41 for collecting particulates is provided to an exhaust passage 2, and the regeneration treatment of the filter 41 is performed at a regeneration time. The device has regeneration treatment means 31, 10, and 42 for performing two post injections and two oxygen concentration controls per one cycle of an engine so as to obtain a constant target regeneration speed during the regeneration treatment of the filter 41. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purification device for treating exhaust particulates of a diesel engine.
[0002]
[Prior art]
To treat the exhaust particulates discharged from the diesel engine, a filter is installed in the exhaust system to collect the particulates.When a predetermined amount of particulates accumulates on the filter, the filter temperature is raised and accumulated on the filter. There are various proposals for performing a so-called filter regeneration process in which burning of the particulates is performed (see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-7-259533
[0004]
[Problems to be solved by the invention]
By the way, the following three requirements generally have to be satisfied for the filter regeneration processing.
[0005]
(1) At the start of the regeneration process, it is necessary to quickly raise the bed temperature of the filter to the self-ignition temperature of the particulates deposited on the filter. For example, post injection or fuel injection timing is retarded in order to raise the temperature of the filter bed.However, rapid temperature rise is required because the longer the filter bed temperature rise period, the worse the fuel economy. is there.
[0006]
(2) When the bed temperature of the filter reaches the particulate auto-ignition temperature and the particulates burn, it is necessary to suppress the burning speed of the particulates so that the bed temperature of the filter does not exceed the allowable maximum temperature. . This is because if the burning speed of the particulates (regeneration speed of the filter) is high, a large amount of particulates deposited on the filter will burn rapidly, and the bed temperature of the filter will exceed the maximum allowable temperature, thereby causing the filter to deteriorate due to heat. This may cause durability to decrease.
[0007]
(3) It is necessary to prevent unburned particulates from remaining in the filter near the end of the regeneration process. This is because the following problem arises when unburned residue occurs in the filter.
[0008]
{Circle around (1)} Since the pressure loss of the filter does not completely disappear, the fuel efficiency deteriorates.
[0009]
{Circle around (2)} When particulates accumulate in the unburned portion, an imbalance in the accumulation distribution occurs, and the durability of the filter is reduced due to rapid combustion in that portion during the next regeneration treatment.
You.
[0010]
Therefore, the present invention provides an apparatus that satisfies the above three requirements for regeneration processing by performing two post-injections per cycle and oxygen concentration control so as to obtain a constant target regeneration speed during filter regeneration processing. The purpose is to provide.
[0011]
On the other hand, in the above-described conventional apparatus, one post-injection is performed per cycle before the catalyst is activated, and two post-injections are performed per cycle after the catalyst is activated.
[0012]
However, the conventional apparatus cannot merely meet the requirement (1) above, that is, only raise the bed temperature of the filter, and therefore cannot meet the requirement (2). That is, when the bed temperature of the filter reaches the self-ignition temperature of the particulate, the particulate burns vigorously and the regeneration speed of the filter rapidly increases. Even at this stage, if the post-injection is performed twice per cycle as in the conventional apparatus, the regeneration speed may be too high beyond the target, and the bed temperature of the filter may rise above the limit temperature. On the other hand, in the present invention, after the filter bed temperature reaches the auto-ignition temperature of the particulates, two post-injections per cycle are stopped to perform one post-injection per cycle, and exhaust gas is exhausted. By performing the first oxygen concentration control in which the target oxygen concentration in the medium is set to a low concentration, the regeneration speed is prevented from exceeding the target regeneration speed, and thus the bed temperature of the filter is increased by the catalytic reaction. The technical idea is different between the conventional device that attempts to make it work and the present invention that focuses on the regeneration speed of the filter.
[0013]
[Means for Solving the Problems]
According to the present invention, in an exhaust gas purifying apparatus for an engine that includes a filter for collecting particulates in an exhaust passage, and performs a filter regeneration process when the filter regeneration time comes, a constant target regeneration speed can be obtained during the filter regeneration process. Thus, the regeneration processing means for performing the post injection twice per one cycle of the engine and controlling the oxygen concentration of the exhaust gas is provided. Specifically, the filter regeneration processing period is composed of the first half, the middle half, and the second half, and in the first half, the temperature rise control is performed to control the first target bed temperature so that the regeneration speed increases to the target regeneration speed. The first target bed temperature maintenance control for maintaining the first target bed temperature so that the regeneration speed becomes smaller than the target regeneration speed and the first oxygen concentration control for setting the target oxygen concentration in the exhaust gas to a low concentration are performed. Second target bed temperature maintenance control for maintaining a second target bed temperature higher than the first target bed temperature so that the regeneration speed increases to the target regeneration speed, and second oxygen in which the target oxygen concentration in the exhaust gas is set to a high concentration Perform density control.
[0014]
【The invention's effect】
According to the reproduction processing means of the present invention, the following effects can be obtained.
[0015]
(1) In the first period, the bed temperature of the filter can be rapidly raised to the first target bed temperature, which is the temperature at which the particulates self-ignite.
[0016]
(2) In the middle period, the first oxygen concentration control is performed in a state where the bed temperature of the filter is maintained at the first target bed temperature at which the particulates self-ignite. The target oxygen concentration in the exhaust is set to a low oxygen concentration so that a large amount of particulates deposited on the filter does not burn rapidly, so that the filter bed temperature does not exceed the maximum allowable temperature. This does not impair the durability of the filter.
[0017]
There is also a method of suppressing the burning rate of particulates by lowering the exhaust gas temperature. However, with this method of controlling the burning rate of particulates based on the exhaust gas temperature, the response of the control is affected by the thermal inertia of the exhaust gas and the filter. Poor, it is difficult for the particulates to burn rapidly, and controllability is poor. On the other hand, in the present invention, since the particulate combustion speed control method is not based on the exhaust gas temperature, the influence of the thermal inertia of the exhaust gas and the filter can be eliminated, and the control response is good and the control reliability is high.
[0018]
(3) In the latter period, the target oxygen concentration is made higher than that at the time of the first oxygen concentration control and sufficient oxygen is supplied while maintaining the second target bed temperature higher than the first target bed temperature, so that the regeneration process is performed. The particulates remaining in the filter near the end can be quickly and reliably burned out.
[0019]
As described above, the present invention satisfies all of the requirements in the first, middle, and late stages of the regeneration process, so that the regeneration process period can be shortened and almost complete filter regeneration can be achieved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.
[0022]
In FIG. 1, reference numeral 1 denotes a diesel engine, and a diaphragm type EGR valve 6 responsive to a control pressure from a pressure control valve (not shown) is provided in an EGR passage 4 connecting an exhaust passage 2 and a collector portion 3a of an intake passage 3. Have. The pressure control valve is driven by a duty control signal from the engine controller 31 so as to obtain a predetermined EGR rate according to the operating conditions.
[0023]
The engine includes a common rail type fuel injection device 10. The fuel injection device 10 mainly includes a fuel tank (not shown), a supply pump 14, a common rail (pressure accumulating chamber) 16, and a nozzle 17 provided for each cylinder. And the high-pressure fuel in the accumulator 16 is distributed to the nozzles 17 for the number of cylinders.
[0024]
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. A three-way valve (not shown) is provided in the fuel supply passage to the hydraulic piston. Is equipped. When the three-way valve (electromagnetic valve) is OFF, the needle valve is in a seated state, but when the three-way valve is ON, the needle valve rises and fuel is injected from the injection 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 accumulator 16 is the same, the longer the ON time, the larger the fuel injection amount. Become.
[0025]
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 driven by an actuator 25 is provided at a scroll inlet of the turbine 22. The variable nozzle 24 is controlled by the engine controller 31 so that a predetermined supercharging pressure is obtained from a low rotation speed range. The nozzle opening (inclined state) for increasing the flow rate of the exhaust gas introduced into the turbine 22 is controlled to the nozzle opening degree (fully opened state) by introducing the exhaust gas to the turbine 22 without resistance on the high rotational speed side.
[0026]
The actuator 25 includes a diaphragm actuator 26 that drives a variable nozzle 26 in response to a control pressure, and a pressure control valve 27 that adjusts a control pressure applied to the diaphragm actuator 26. A duty control signal is generated so as to achieve the target nozzle opening, and the duty control signal is output to the pressure control valve 27.
[0027]
The engine controller 31 to which signals from the accelerator sensor 32, the sensor 33 for detecting the engine rotational speed and the crank angle, the water temperature sensor 34, and the air flow meter 35 are input, the target EGR rate, the target supercharging pressure, EGR control and supercharging pressure control are performed in a coordinated manner so that
[0028]
A filter 41 for collecting particulates in the exhaust gas is installed in the exhaust passage 2. The filter 41 carries an oxidation catalyst. When the amount of particulates accumulated in the filter 41 reaches a predetermined value, the exhaust gas temperature is raised to burn and remove the particulates accumulated in the filter 41.
[0029]
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 a differential pressure detection passage that bypasses the filter 41.
[0030]
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 mainly includes a microprocessor. The engine controller 31 performs the regeneration processing of the filter 41 based on these. That is, although the period of the reproduction process of the filter 41 is divided in time series into three periods of the first period (time of t1), the middle period (time of t2), and the second period (time of t3) as shown in FIG. Two post-injections with different functions per cycle and oxygen concentration control are performed per cycle so that a constant target regeneration speed can be obtained throughout the entire regeneration process.
[0031]
This will be further described with reference to FIGS. In FIG. 3, the fourth stage shows the characteristics of the post-injection according to this embodiment, and the bottom stage shows the characteristics of the target oxygen concentration in the exhaust gas according to this embodiment.
[0032]
Here, a post injection having a different function is introduced (see the upper part of FIG. 4). That is, the post-injection 1 is set at an injection timing (TDC to ATDC 60 deg) close to the main injection for the purpose of directly increasing the exhaust gas temperature by burning in the cylinder. On the other hand, the post-injection 2 supplies HC to the oxidation catalyst carried on the filter 41, burns HC by the catalytic reaction, and raises the bed temperature of the filter 41. It is set at the time when no combustion occurs (ATDC 60 deg or later).
[0033]
<1> First half:
In the former stage where the bed temperature of the filter 41 is lower than the catalyst activation temperature (approximately 240 ° C.), post-injection 1 is executed in order to activate the catalyst earlier (see the lower left of FIG. 4). At this time, the post injection 2 is not performed because the reaction of HC is not performed by the catalyst.
[0034]
When the bed temperature of the filter 41 becomes later than the catalyst activation temperature, the post-injection 2 is executed in addition to the post-injection 1 to further raise the bed temperature. When the bed temperature of the filter 41 rises and reaches the first target bed temperature (about 600 ° C.) tTbed1, the first period is ended and the next stage is shifted to the middle period.
[0035]
Here, the transition from the former stage to the latter stage is performed based on whether or not the actual bed temperature rTbed of the filter 41 has reached the catalyst activation temperature. The actual bed temperature of the filter 41 is estimated based on signals from temperature sensors 37 and 38 provided before and after the filter 41.
[0036]
However, the target oxygen concentration in the exhaust gas is not determined during the period of the first half, and therefore, the oxygen concentration control is not performed.
[0037]
<2> Medium term:
In order to suppress the burning speed of particulates deposited on the filter 41 (regeneration speed of the filter), the target oxygen concentration in the exhaust gas is set to a low concentration as shown in the lowermost part of FIG. The oxygen concentration control (first oxygen concentration control) is performed so as to obtain the oxygen concentration.
[0038]
In addition, the post-injection amount of the post-injection 1 is feedback-controlled so that the actual bed temperature of the filter 41 matches the first target bed temperature tTbed1 (see the lower part of FIG. 4). When the particulates in the filter 41 are actively burning and the first target bed temperature is maintained, the post-injection 1 is not performed.
[0039]
By controlling the oxygen concentration in the exhaust gas so as to obtain the target oxygen concentration set at a low concentration and controlling the temperature to maintain the first target bed temperature, the particulates deposited on the filter 41 burn rapidly. Burning proceeds without.
[0040]
<3> Second term:
In order to completely burn out the particulates remaining in the filter 41 near the end of the regeneration process, the target oxygen concentration in the exhaust gas is set higher than that in the middle stage as shown in the lowermost part of FIG. Control (second oxygen concentration control) is performed so that is obtained.
[0041]
In the latter period, post-injection 2 is performed in addition to post-injection 1, so that the actual bed temperature of the filter 41 matches the second target bed temperature tTbed2 (about 650 ° C.) higher than the first target bed temperature tTbed1. The post-injection amount of post-injection 2 is feedback-controlled (see the lower right in FIG. 4).
[0042]
By controlling the oxygen concentration in the exhaust gas so as to obtain the target oxygen concentration set at a high concentration as described above and performing control to maintain the second target bed temperature higher than in the middle period, the regeneration efficiency is increased, and the complete regeneration is achieved. Approaching 100%.
[0043]
The following is the basis of this idea. That is, when the exhaust gas temperature is kept constant, the particulates deposited on the filter gradually start to burn at the start of the regeneration process, and eventually burn as a lump, and then fall down and the combustion ends. I do. The regeneration speed represents this combustion state. Therefore, as shown by the solid line at the top of FIG. 3, the reproduction speed gradually increases from the start of the reproduction process to a peak, and thereafter decreases. The bed temperature of the filter changes as if to match such a change in the regeneration speed (see the broken line in the second row in FIG. 3).
[0044]
Here, the uppermost part of FIG. 3 shows a temporal change in the regeneration speed when the filter is viewed as a lump, but in actuality, the particulate distribution and gas flow distribution in the filter are not uniform, and the spatial distribution is not uniform. Also, the reproduction speed is uneven.
[0045]
What is troublesome when there is a change (unevenness) in the reproduction speed over time or space is that unburned particulates occur in the filter 41. If there is unburned particulates, the unburned particulates will be generated during the next regeneration process. The remaining particulates also burn, and the bed temperature of the filter rises by that much. Therefore, a regeneration speed (depending on the material and capacity of the filter, but, for example, 2 to 3 g / min) is selected as a target value (target regeneration speed) such that no unburned portion is generated and combustion is not excessively intense. Then, it is desirable to control the target reproduction speed to the target reproduction speed over the entire section of the reproduction process. Then, the playback speed must be increased in the latter half of the playback process, the playback speed decreases in the middle stage of the playback process, and the playback speed increases in the later stage of the playback process (see FIG. 3 See the top row). In the present invention, post-injection and oxygen concentration control are used in combination to obtain such a constant target regeneration speed.
[0046]
Next, the details of these controls performed by the engine controller 31 will be described in detail.
[0047]
The flowchart in FIG. 5 is a main routine for performing the reproduction process, and this flow is executed at regular intervals (for example, every 10 ms).
[0048]
In step 1, the reproduction processing flag is checked. The setting of the reproduction processing flag will be described with reference to the flow of FIG.
[0049]
The flow of FIG. 6 is executed every predetermined time (for example, every 10 ms) separately from FIG. In FIG. 6, in step 11, the pressure loss ΔP of the filter 41 is read from the output of the differential pressure sensor 36.
[0050]
In step 12, 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 initial value is set to zero when the engine is started, the process proceeds to steps 13 and 14 before the regeneration processing conditions are satisfied, and the regeneration processing conditions are checked. The satisfaction of the regeneration processing 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.
[0051]
Here, the regeneration execution condition is satisfied, for example, when the operating condition determined by the engine speed and the fuel injection amount (corresponding to the engine load) is in a predetermined region excluding a low load region near idling or idle.
[0052]
The reason that the regeneration execution condition is not satisfied in the region that is a low load region near idling or idling is that the exhaust temperature is originally low during idling, and the bed temperature of the filter 41 is reduced even after performing post injection and intake throttle. This is because the temperature cannot be increased to the first target bed temperature tTbed1.
[0053]
Therefore, when the pressure loss ΔP is equal to or less than the regeneration start determination value ΔPHmax or when the operating condition of the engine is not the regeneration execution condition, the current process is terminated as it is.
[0054]
When the pressure loss ΔP of the filter 41 exceeds the regeneration start determination value ΔPHmax and the operating 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 15 to perform regeneration. It is assumed that the processing flag = 1.
[0055]
Because the reproduction process flag = 1, it is not possible to proceed from step 12 to step 13 from the next time, so the process is terminated.
[0056]
Returning to FIG. 5, when the reproduction processing flag is 1 in step 1, the processing proceeds to step 2 and subsequent steps to perform the reproduction processing. In step 2, a reproduction phase is set. The setting of the reproduction phase will be described with reference to the flow of FIG.
[0057]
The flow of FIG. 7 (the subroutine of step 2 in FIG. 5) is for comparing the elapsed time T from the start of the reproduction process with the set times t1, t2, and t3 to set the first, middle, and late stages of the reproduction phase. It is.
[0058]
In step 21, the reproduction end flag is checked. Since the reproduction end flag is initially set to zero, the process proceeds to step 22 to check the reproduction processing flag. When the reproduction processing flag is 0, the current processing is terminated.
[0059]
When the reproduction processing flag is 1, the routine proceeds to step 23, where the timer value T (initial setting to zero) is
T = Tz + ΔT (1)
Where ΔT: calculation cycle (= 10 ms),
Tz: previous value of the timer value,
Is incremented by the following equation. This timer is for measuring the elapsed time from the start of the reproduction processing (that is, the reproduction processing time).
[0060]
In steps 24 and 25, each period of the regeneration phase is set as follows based on the timer value T and the set times t1, t2 and t3 (see FIG. 2).
[0061]
(1) When T <t1:
The process proceeds from step 24 to step 26 to set the regeneration phase to the first half.
[0062]
(2) When t1 ≦ T <t1 + t2:
The process proceeds from step 24 to step 27, where the regeneration phase is set to the middle stage.
[0063]
(3) When t1 + t2 ≦ T <t1 + t2 + t3:
The process proceeds from Steps 24 and 25 to Step 28 to set the reproduction phase to the latter period.
[0064]
(4) When t1 + t2 + t3 ≦ T:
At this time, it is determined that the reproduction process has been completed, and the process proceeds from Steps 24 and 25 to Step 29 to set the reproduction end flag = 1. Further, in order to prepare for the next reproduction process, the reproduction process flag = 0 and the timer value T = 0 in steps 30 and 31.
[0065]
The set times t1, t2, and t3 used in step 24 may be constant values, but here, t1 and t2 are set as variable values as follows.
[0066]
FIG. 8 is an example of setting t1 with respect to the actual bed temperature at the start of the regeneration process. In order to regenerate the filter 41, it is necessary to increase the temperature to a first target bed temperature tTbed1, which is a temperature at which the particulates accumulated on the filter 41 can self-ignite and burn. This is the time required to raise the temperature to one target bed temperature tTbed1. This time t1 becomes smaller as the bed temperature at the start of the reproduction process becomes higher as shown in FIG. This is because if the bed temperature at the start of the regeneration process is high, the time required to raise the bed temperature of the filter 41 to the first target bed temperature tTbed1 may be short.
[0067]
In a temperature range equal to or higher than tTbed1, t1 = 0. This is because the particulates deposited on the filter 41 self-ignite and burn in the temperature range of tTbed1 or higher without performing the temperature increase control. At this time, t1 is set to zero and the process immediately shifts to the middle stage of the next stage. That's why.
[0068]
Further, the bed temperature at the start of the regeneration process is a constant value in a temperature range lower than the predetermined value Ta. This is a constant value because the temperature of the filter 41 cannot be raised to the target bed temperature tTbed1 in the temperature range lower than Ta even if the filter 41 is heated.
[0069]
In FIG. 8, the actual bed temperature at the start of the regeneration process on the horizontal axis is based on two temperatures T1 and T2 detected by temperature sensors 37 and 38 provided before and after the filter 41 at the start of the regeneration process.
rTbed = b1 · T1 + b2 · T2 (2)
Here, Tbed: bed temperature at the start of the regeneration process,
b1, b2: constants,
It may be estimated (calculated) by the following equation. B1 and b2 in the equation (2) are values determined by experiments.
[0070]
FIG. 9 is an example of setting t2 with respect to the particulate accumulation amount (abbreviated as PM accumulation amount in the figure) at the start of the regeneration process. After raising the bed temperature of the filter 41 to the first target bed temperature tTbed1, the particulates accumulated on the filter 41 self-ignite and burn. In this case, when the oxygen concentration in the exhaust gas is sufficiently large (in terms of the air-fuel ratio, the predetermined value A leaner than the stoichiometric air-fuel ratio), a large amount of particulates deposited on the filter 41 burns rapidly. As a result, the bed temperature of the filter 41 rises above the allowable maximum temperature Tmax, and the filter 41 may be thermally degraded and the durability may be reduced. Therefore, the oxygen concentration is low enough that a large amount of particulates deposited on the filter 41 does not rapidly burn (the predetermined value B on the lean side of the stoichiometric air-fuel ratio on the lean side of the stoichiometric air-fuel ratio and on the rich side of the above A). ) Is t2. This time t2 becomes longer as the amount of particulates accumulated at the start of regeneration increases.
[0071]
When the particulate accumulation amount at the start of the regeneration process is equal to or larger than the maximum particulate accumulation amount pmax, t2 is fixed.
[0072]
Further, when the particulate accumulation amount at the start of the regeneration process is equal to or less than the predetermined value p, t2 = 0. This is because, in the case of a particulate accumulation amount equal to or less than p, the middle stage is omitted and the process shifts to the latter stage, and even if all of them are burned at once, the rise in the bed temperature of the filter 41 is small, and the bed temperature of the filter 41 is low. Since the maximum allowable temperature Tmax is not reached, the middle stage is omitted and the process immediately shifts to the second stage. That is, the predetermined value p is set near the maximum amount of the particulate deposition amount in which the bed temperature of the filter 41 does not exceed the allowable maximum temperature in the latter period without passing through the middle period.
[0073]
In FIG. 9, the particulate accumulation amount at the start of the regeneration process on the horizontal axis may be calculated by searching a table having the contents shown in FIG. 10 from the pressure loss of the filter at the start of the regeneration process.
[0074]
When the setting of each stage of the reproduction phase of FIG. 7 has been completed in this way, the process returns to FIG. 5. In step 3, it is determined which stage of the reproduction phase the current processing timing is, and each control is performed as follows. I do. That is, in the first half, the process proceeds to step 4 to perform a temperature increase control for controlling the first target bed temperature tTbed1 so that the regeneration speed increases to the target regeneration speed.
[0075]
In the middle period, the process proceeds to steps 5 and 7, and the first target bed maintenance control for maintaining the first target bed temperature tTbed1 so that the regeneration speed decreases to the target regeneration speed, and the target oxygen concentration in the exhaust gas is set to a low concentration. First oxygen concentration control is performed. In the latter period, the process proceeds to steps 6 and 7, the second target bed maintenance control for maintaining the second target bed temperature tTbed2 higher than the first target bed temperature tTbed1 such that the regeneration speed increases to the target regeneration speed, and the target oxygen in the exhaust gas. The second oxygen concentration control in which the concentration is set to a high concentration is performed.
[0076]
Here, the control in steps 4 to 8 in FIG. 5 will be further described separately for post-injection and oxygen concentration control.
[0077]
[1] Post injection:
[1] -1. Temperature control:
The flow of FIG. 11 (subroutine of step 4 in FIG. 5) is for performing the temperature rise control.
[0078]
In step 31, the engine speed Ne detected by the crank angle sensor 33, the main fuel injection amount Qf, the filter inlet temperature T1 detected by the temperature sensor 37, and the filter outlet temperature T2 detected by the temperature sensor 38 are read.
[0079]
In step 32, the actual bed temperature rTbed of the filter 41 is calculated from the filter inlet temperature T1 and the filter outlet temperature T2 using the above-described equation (2).
[0080]
In step 33, the post-stage flag (initial setting to zero) is checked. Here, a description will be given assuming that the post-stage flag = 0. At this time, the process proceeds to steps 34 and 35 of the pre-stage, and a map having contents shown in FIGS. 12 and 13 is obtained from the engine speed Ne and the main fuel injection amount Qf. The first post-injection amount 1 and the first post-injection timing 1 are calculated by searching.
[0081]
Since the function of the first post-injection 1 is to increase the exhaust gas temperature to the catalyst temperature, the first post-injection amount 1 basically includes the exhaust gas temperature (base exhaust gas temperature) and the catalyst activity based on only the main fuel injection amount. What is necessary is just to give a value proportional to the temperature difference. That is, the larger the difference from the catalyst activation temperature is, the larger the preceding post-injection amount 1 is given. Here, since the exhaust temperature of the base is lower on the low-load low-rotational-speed side, the front-stage post-injection amount 1 is correspondingly increased toward the low-load low-rotational-speed side (see FIG. 12).
[0082]
In step 36, the actual bed temperature rTbed of the filter 41 is compared with the catalyst activation temperature (about 240 ° C.). When the actual bed temperature rTbed is lower than 240 ° C., the current process is terminated.
[0083]
If the pre-stage post-injection amount 1 continues to be given according to the operating conditions (Ne, Qf), the actual bed temperature rTbed eventually becomes 240 ° C. or higher. At this time, the process proceeds to step 37 and the post-stage flag = 1.
[0084]
With the latter flag = 1, the process proceeds from the next step to the subsequent steps from step 33 to step 38 and thereafter.
[0085]
In steps 38, 39, 40, and 41, a post-stage post-injection amount 1, a post-stage post-injection amount are searched for from the engine rotational speed Ne and the main fuel injection amount Qf by searching a map having the contents shown in FIGS. 14, 15, 16, and 17. An injection timing 1, a basic post-stage post-injection amount 2, and a post-stage post-injection timing 2 are calculated.
[0086]
The post-stage post-injection amount 1 is the same as the post-stage post-injection amount 1, and gives a value proportional to the difference between the base exhaust temperature and the catalyst activation temperature.
[0087]
On the other hand, the function of the post-injection 2 is to supply HC to the catalyst and burn it to raise the bed temperature to the first target bed temperature. A value proportional to the difference between T1 and the first target bed temperature tTbed1 is given. That is, the larger the difference from the first target bed temperature tTbed1 is, the larger the value of the basic post-stage injection amount 2 is given. Here, since the filter inlet temperature T1 is lower on the low-load low-rotational-speed side, the basic post-stage injection amount 2 is correspondingly increased toward the low-load low-rotational-speed side (see FIG. 16).
[0088]
Steps 42 to 45 calculate the feedback amount FB21 of the post-stage post-injection amount 2 such that the actual bed temperature rTbed matches the first target bed temperature tTbed1. That is, the actual bed temperature rTbed in step 42 and the first target bed temperature upper limit (tTbed1 + ε), which is the value obtained by adding the allowable value ε (positive value) to the first target bed temperature tTbed1, and the actual bed temperature in step 43. The temperature rTbed is compared with a first target bed temperature lower limit (tTbed1-ε), which is a value obtained by subtracting the allowable value ε from the first target bed temperature tTbed1. When the actual bed temperature rTbed exceeds the first target bed temperature upper limit (tTbed1 + ε), the routine proceeds to step 44, where the feedback amount (initial value is zero) FB21 is reduced by a predetermined value Δ21 (positive value). When the actual bed temperature rTbed is lower than the first target bed temperature lower limit value (tTbed1-ε), the routine proceeds to step 45, where the feedback amount FB21 is increased by a predetermined value Δ21. On the other hand, when the actual bed temperature rTbed falls between the first target bed temperature upper limit value and the first target bed temperature lower limit value, the routine proceeds to step 46, where the feedback amount FB is maintained as it is.
[0089]
The predetermined value Δ21 may be a constant value, or may be given in proportion to the difference between the actual bed temperature rTbed and the first target bed temperature tTbed1.
[0090]
In step 47, a value obtained by adding the feedback amount FB21 thus obtained to the basic post-stage post-injection amount 2 is calculated as the post-stage post-injection amount 2.
[0091]
In the fuel injection control flow (not shown), the pre-stage post-injection (one post-injection per cycle) is performed using the pre-stage post-injection amount 1 and the pre-stage post-injection timing 1 obtained as described above. The post-injection in the post-stage (two post-injections per cycle) is performed using the obtained post-post-injection amount 1, post-post-injection timing 1, post-post-injection amount 2 and post-post-injection timing 2 obtained.
[0092]
[1] -2. Maintenance control to the first target bed temperature:
The flow in FIG. 18 (the subroutine of step 6 in FIG. 5) is for performing control to maintain the first target bed temperature tTbed1.
[0093]
Steps 51 and 52 are the same as steps 31 and 32 in FIG. 11, and calculate the actual bed temperature rTbed. In steps 53 and 54, a basic post-injection amount 1 and a post-injection timing 1 are calculated by searching a map having contents shown in FIGS. 19 and 20 from the engine rotation speed Ne and the main fuel injection amount Qf.
[0094]
The basic post-injection amount 1 (post-injection amount in the middle period) is a value smaller than the post-injection amount 1 in the first half (pre-post injection amount 1, post-post injection amount 2) (see FIG. 3). This is because if the post-injection amount in the middle period is reduced from the post-injection amount 1 in the previous period, the filter inlet temperature decreases and the filter 41 is cooled, so that the regeneration speed of the filter 41 is reduced.
[0095]
Steps 55 to 58 are for calculating the feedback amount FB1 of the post-injection amount 1 so that the actual bed temperature rTbed of the filter 41 matches the first target bed temperature tTbed1. That is, in step 55, the actual bed temperature rTbed of the filter 41 and the first target bed temperature upper limit value (tTbed1 + ε), and in step 56, the actual bed temperature rTbed of the filter 41 and the first target bed temperature lower limit value (tTbed1-ε). Compare with When the actual bed temperature rTbed exceeds the first target bed temperature upper limit (tTbed1 + ε), the routine proceeds to step 57, where the feedback amount (the initial value is zero) FB1 is reduced by a predetermined value Δ1, and the actual bed temperature rTbed Is lower than the first target bed temperature lower limit value (tTbed1-ε), the routine proceeds to step 58, where the feedback amount FB1 is increased by a predetermined value Δ1. On the other hand, when the actual bed temperature rTbed falls between the first target bed temperature upper limit value and the first target bed temperature lower limit value, the routine proceeds to step 59, where the feedback amount FB1 is maintained as it is.
[0096]
The predetermined value Δ1 may be a constant value, or may be given in proportion to the difference between the actual bed temperature rTbed and the first target bed temperature tTbed1.
[0097]
In step 60, a value obtained by adding the feedback amount FB1 thus obtained to the basic post injection amount 1 is calculated as the post injection amount 1.
[0098]
In a fuel injection control flow (not shown), the post injection in the middle term (one post injection per cycle) is performed using the post injection amount 1 and the post injection timing 1 obtained as described above. Here, since the feedback amount FB1 can take a negative value, the post-injection amount 1 can be zero (steps 57 and 60). At this time, it means that the particulates in the filter 41 are actively combusted, and it is not necessary to perform the exhaust temperature increase control by the post injection 1.
[0099]
[1] -3. Maintenance control to the second target bed temperature:
The flow of FIG. 21 (the subroutine of step 8 in FIG. 5) is for performing control to maintain the second target bed temperature tTbed2.
[0100]
Steps 71 and 72 are the same as steps 31 and 32 in FIG. 11, and calculate the actual bed temperature rTbed. In steps 73, 74, 75, and 76, the post injection amount 1, the post injection timing are obtained by searching maps containing the contents of FIGS. 22, 23, 24, and 25 from the engine speed Ne and the main fuel injection amount Qf. 1. A basic post injection amount 2 and a post injection timing 2 are calculated.
[0101]
The post-injection amount 1 is the same as the post-injection amount in the first half (first post-injection amount 1, second post-injection amount 1), and gives a value proportional to the difference between the base exhaust temperature and the catalyst activation temperature. In relation to the post-injection amount 1 in the middle period, the post-injection amount 1 in the latter period is larger (see the lower part in FIG. 3), whereby the exhaust gas temperature is increased and the regeneration speed of the filter is increased.
[0102]
The basic post injection amount 2 is the same as the post-stage injection amount 2, and gives a value proportional to the difference between the filter inlet temperature T1 and the second target bed temperature tTbed2. That is, the larger the difference from the second target bed temperature tTbed2 is, the larger the value of the basic post injection amount 2 is given. Here, since the filter inlet temperature T1 is lower on the low-load low-rotational-speed side, the basic rear injection amount 2 is correspondingly increased toward the low-load low-rotational-speed side (see FIG. 24).
[0103]
Steps 77 to 81 are for calculating the feedback amount FB22 of the post-injection amount 2 so that the actual bed temperature rTbed of the filter 41 matches the second target bed temperature tTbed2. That is, in step 77, the actual bed temperature rTbed of the filter 41 and the second target bed temperature upper limit (tTbed2 + ε), and in step 78, the actual bed temperature rTbed of the filter 41 and the second target bed temperature lower limit (tTbed2-ε). Compare with
[0104]
Here, the second target bed temperature tTbed2 used in the second half is higher than the first target bed temperature tTbed1 used in the first half and the middle half. This is because the particulates hardly burn in the later stage of the regeneration process (because they are cooled by the wall temperature), and it is necessary to raise the target bed temperature in order to maintain the regeneration speed of the filter 41 at the same level as in the middle stage. is there.
[0105]
When the actual bed temperature rTbed exceeds the second target bed temperature upper limit value (tTbed2 + ε), the routine proceeds to step 79, where the feedback amount (initial value is zero) FB22 is reduced by a predetermined value Δ22. Is lower than the second target bed temperature lower limit value (tTbed2-ε), the routine proceeds to step 80, where the feedback amount FB22 is increased by a predetermined value Δ22. On the other hand, when the actual bed temperature rTbed falls between the second target bed temperature upper limit value and the second target bed temperature lower limit value, the routine proceeds to step 81, where the feedback amount FB22 is maintained as it is.
[0106]
The predetermined value Δ22 may be a constant value, or may be given in proportion to the difference between the actual bed temperature rTbed and the second target bed temperature tTbed2.
[0107]
In step 82, a value obtained by adding the feedback amount FB22 thus obtained to the basic post injection amount 2 is calculated as the post injection amount 2.
[0108]
In a fuel injection control flow (not shown), post-injection (two post-injections per cycle) is performed using the post-injection amount 1, the post-injection timing 1, the post-injection amount 2, and the post-injection timing 2 obtained in this manner. Is
[0109]
[2] Oxygen concentration control:
[2] -1. Mid-term oxygen concentration control (first oxygen concentration control):
FIG. 26 shows the relationship between the filter inlet temperature, the oxygen concentration in the exhaust gas, and the maximum temperature of the bed temperature of the filter 41 when the regeneration process is performed in a state where the particulate accumulation amount (PM accumulation amount) is large (that is, in the middle stage). Since the amount of particulates deposited is large, the interval between the curves is short, which indicates that the temperature gradient is steep.
[0110]
In the state where the amount of accumulated particulates is large as described above, by providing the control range of the target oxygen concentration on the low oxygen concentration side, the regeneration process of the filter 41 can be performed within the allowable maximum temperature of the bed temperature of the filter 41.
[0111]
Here, when the target oxygen concentration in the exhaust gas is converted into an air-fuel ratio, the target oxygen concentration is leaner than the stoichiometric air-fuel ratio (for example, about 1.5 in excess air ratio). If there is a high concentration of oxygen in a state where the amount of accumulated particulates is large, the particulates deposited on the filter 41 burn rapidly due to the high burning speed of the particulates. Is set to a low oxygen concentration.
[0112]
Further, the reason why the width of the control range of the target oxygen concentration is set is to take into account the variation and the control delay in the transient state.
[0113]
[2] -2. Late oxygen concentration control (second oxygen concentration control):
FIG. 27 shows the relationship between the filter inlet temperature, the oxygen concentration in the exhaust gas, and the maximum temperature of the bed temperature of the filter 41 when the regenerating process is performed in a state where the amount of accumulated particulates is small (that is, the latter stage). In the state where the amount of curated deposition is small, the interval between the curves is widened (the temperature gradient becomes gentle), and the position of the maximum allowable bed temperature is also moving to the right as compared with the case of FIG.
[0114]
For this reason, in the state where the amount of accumulated particulates is small, even if the oxygen concentration in the exhaust gas is increased compared to the medium period, the maximum bed temperature during the regeneration treatment of the filter 41 can be kept at or below the allowable maximum temperature. In the latter period, the target oxygen concentration is made larger than in the middle period as shown in 1) in the figure. This makes it possible to supply sufficient oxygen to increase the burning speed of the particulates, and to completely burn out all the particulates remaining in the filter 41 in a short period of time. Further, by increasing the target value tT1 of the filter inlet temperature as shown in 2) in the figure, it is possible to further shorten the regeneration processing time and improve the particulate regeneration efficiency.
[0115]
[2] -3. Control result of oxygen concentration control:
FIG. 28 shows a control target (target oxygen concentration) of the oxygen concentration in the exhaust gas according to the present embodiment and a change in the actual oxygen concentration in the exhaust gas as a result of the control. As shown in the figure, the oxygen concentration is controlled to a low oxygen concentration in the middle stage, but is switched to a higher oxygen concentration in the later stage. Note that the oxygen concentration in the exhaust gas changes drastically in other periods (including the former period) except the middle period and the latter period. This is because the control of the oxygen concentration in the exhaust gas is not originally performed in other periods, and also because of the transient state in which acceleration and deceleration are repeated.
[0116]
FIG. 28 simply switches the target oxygen concentration in the exhaust gas from a low concentration to a high concentration in two stages. As shown in FIG. 29, the target oxygen concentration is gradually increased in the latter half of the middle period, and By smoothly connecting to the target oxygen concentration, it is possible to shorten the regeneration processing period as compared with the case of FIG.
[0117]
[2] -4. Oxygen concentration control means:
Assuming that a target oxygen concentration in the exhaust gas is tRO2 [%] and an excess air ratio at which the target oxygen concentration tRO2 is obtained is a target excess air ratio tλ, the following equation is established.
[0118]
tλ = 21 / (21−tRO2) (3)
However, 21: oxygen concentration in fresh air [%],
Although equation (3) does not take into account the increase in the working gas mole due to combustion, this effect can be included in equation (3) in order to further improve the control accuracy.
[0119]
The control for obtaining the target excess air ratio tλ in the equation (3) includes control of the intake fresh air amount and control of the fuel injection.
[0120]
[2] -4-1. Control of intake fresh air volume:
Assuming that the intake fresh air amount for obtaining the target excess air ratio tλ in the expression (3) is tQa, the following expression is established between the intake air amount and the fuel injection amount Qf.
[0121]
tQa = Qf × theoretical air-fuel ratio × tλ (4)
By substituting equation (3) into equation (4), the following equation is obtained.
[0122]
tQa = Qa × theoretical air-fuel ratio × 21 / (21−tRO2) (5)
Therefore, the intake fresh air amount is controlled so that the target intake fresh air amount tQa of the equation (5) is obtained.
[0123]
In this case, the operating range that can be covered by the intake fresh air amount control means is different as shown in FIG. 30, so the oxygen concentration control is performed as follows according to the intake fresh air amount control means.
[0124]
{Circle around (1)} When the intake fresh air control means is the variable capacity turbocharger 21:
In the regions R6, R7, and R8, the intake fresh air amount is controlled by the variable capacity turbocharger 21. For example, when the opening of the variable nozzle 24 is reduced, the rotation speed of the turbine 22 increases, and the intake fresh air amount can be increased (oxygen concentration can be increased). Conversely, when the opening degree of the variable nozzle 24 is increased, the rotation speed of the turbine 22 decreases, and the intake fresh air amount can be reduced.
[0125]
(2) When the intake fresh air amount control means is an EGR device:
In the regions R7 and R8, the intake fresh air amount is controlled by the EGR valve 6 (EGR device). For example, if the EGR rate or the EGR amount is increased, the intake fresh air amount can be reduced. Conversely, if the EGR rate or the EGR amount is reduced, the intake fresh air amount can be increased.
[0126]
(3) When the intake fresh air amount control means is the intake throttle valve 42 (intake throttle device):
In the region R8, the intake throttle valve 42 controls the intake fresh air amount. For example, by closing the intake throttle valve 42, the intake fresh air amount can be reduced, and conversely, by returning the intake throttle valve 42, the intake fresh air amount can be increased.
[0127]
[2] -4-2. Control of fuel injection:
Assuming that the target fuel injection amount for obtaining the target excess air ratio tλ in the above expression (5) is tQf, the following expression is established between the target fuel injection amount and the intake fresh air amount Qa.
[0128]
Qa = tQf × theoretical air-fuel ratio × tλ (6)
By solving the equations (3) and (6) for the target fuel injection amount tQf, the following equation is obtained.
[0129]
tQf = Qa × (1 / theoretical air-fuel ratio) × (21−tRO2) / 21 (7)
Therefore, the fuel injection is controlled such that the target fuel injection amount tQf of the equation (7) is obtained.
[0130]
In this case, since the operating range that can be covered by the fuel injection control means differs as shown in FIG. 31, the oxygen concentration control is performed as follows according to the fuel injection control means.
[0131]
Region R9: The fuel injection is controlled such that the target fuel injection amount tQf of Expression (7) is obtained while retarding the main injection timing.
[0132]
Region R10: The fuel injection is controlled such that the target fuel injection amount tQf of Expression (7) is obtained while performing the main injection timing retard and post injection. Increasing the post-injection amount can increase the fuel injection amount (decrease the oxygen concentration). Since the post-injection is performed in the expansion stroke of the engine, the injection amount can be increased without much increase in the torque. The increase in torque is controlled by decreasing the main injection amount.
[0133]
Region R11: The fuel injection amount is controlled by the post injection, the intake throttle, and the main injection timing. For example, when the intake throttle is performed, the pumping loss increases. Therefore, the post-injection amount can be increased by an amount corresponding to the pumping loss. At this time, the main injection timing is controlled to be more advanced than when the injection amount is not controlled.
[0134]
[2] -4-3. Feedback control of oxygen concentration in exhaust gas:
The control in [2] -4-1 and [2] -4-2 is open loop control, but feedback control may be performed. For example, the actual intake new air amount detected from the output of the air flow meter 35 is equal to the target intake new air amount tQa in the above equation (5), or the actual fuel injection amount is the target fuel injection in the above equation (7). Feedback control is performed so as to coincide with the amount tQf.
[0135]
Further, a sensor (for example, a wide-range air-fuel ratio sensor) for detecting the actual oxygen concentration in the exhaust gas is provided in the exhaust passage 2 so that the actual oxygen concentration in the exhaust gas detected by this sensor matches the target oxygen concentration. Can also perform feedback control.
[0136]
Here, the operation of the present embodiment will be described with reference to FIG. 3. FIG. 3 shows, from the top, the regeneration speed, the filter bed temperature, the particulate accumulation amount, the period and timing of the post-injection, and the target oxygen concentration in the exhaust gas. The movement is modeled. In the second stage, the case of the present embodiment is indicated by a solid line, while the case of the conventional device is indicated by a broken line.
[0137]
(1) The first half of the regeneration process:
In the first half, only post-injection 1 for the purpose of increasing the exhaust gas temperature is performed in the former stage before the actual bed temperature rTbed reaches the catalyst activation temperature, and in the latter stage after the actual bed temperature rTbed reaches the catalyst activation temperature, HC is reduced. The post-injection 2 for the purpose of supply is added to supply HC to the catalyst in an active state, so that the catalyst generates heat due to an oxidation catalyst reaction, thereby causing the bed temperature to reach the first target bed temperature. It is rising rapidly.
[0138]
(2) Medium-term reproduction process:
(1) While the bed temperature of the filter is maintained at the first target bed temperature, which is the temperature at which the particulates self-ignite, the target oxygen concentration in the exhaust gas is set to the low concentration side as shown in the lowermost row, and the filter 41 Since the burning rate of the particulates deposited on the filter is suppressed, the maximum temperature of the filter bed does not exceed the maximum allowable temperature, and the durability of the filter 41 is not impaired.
[0139]
{Circle around (2)} There is a method of suppressing the burning speed of particulates by lowering the exhaust gas temperature. However, with this method of controlling the burning speed of the particulates based on the exhaust gas temperature, control of the control is affected by the thermal inertia of the exhaust gas and the filter 41. Responsiveness deteriorates. On the other hand, in the present embodiment, since the particulate combustion speed control method is not based on the exhaust gas temperature, the influence of the thermal inertia of the exhaust gas and the filter 41 can be eliminated, and the control response is good and the control reliability is high.
[0140]
(3) According to the particulate combustion speed control method based on the exhaust gas temperature, when the exhaust gas temperature is reduced in order to suppress the particulate combustion speed, the bed temperature of the filter 41 is reduced below the target bed temperature. If so, reproduction failure may occur. On the other hand, in the present embodiment, the suppression of the burning rate of particulates is performed by oxygen concentration control while maintaining the first target bed temperature. Therefore, even during the burning of particulates, the bed temperature of the filter 41 is maintained at the first target bed temperature. Never drop below bed temperature. That is, since the present embodiment is not a method for controlling the particulate combustion speed based on the exhaust gas temperature, it is not necessary to lower the bed temperature of the filter 41 below the first target bed temperature, thereby preventing regeneration failure due to a temperature drop around the filter. .
[0141]
(3) Late stage of the regeneration process:
By keeping the target oxygen concentration in the exhaust gas higher than that in the middle stage as in the lowermost stage while maintaining the second target bed temperature higher than the first target bed temperature, it remains in the filter 41 near the end of the regeneration process. All of the particulates can be quickly and reliably burned out, whereby the regeneration processing time can be reduced and almost complete filter regeneration can be achieved.
[0142]
As a result, the following effects are obtained in the present embodiment.
[0143]
(1) Reduction of reproduction processing time:
An increase in fuel consumption required for the regeneration process can be minimized, and deterioration in fuel efficiency can be suppressed. The high-temperature maintenance time during the regenerating process is reduced, the thermal deterioration of the filter can be suppressed, the exhaust performance can be improved, and the life can be extended.
[0144]
(2) Realization of complete reproduction:
Since there is no longer any increase in pressure loss due to unburned particulates, deterioration of fuel efficiency can be prevented. In addition, non-uniform particulate deposition resulting from the deposition of new particulates on unburned particulates may cause local, rapid particulate combustion, which may reduce durability. This can be prevented.
[0145]
In the embodiment, the case where the first half, the middle half, and the second half of the reproduction process are separated by time has been described. However, the present invention is not limited to this, and the following method is used for determining the shift to the middle half and the second half.
[0146]
(A) Another method for determining the transition to the middle term in the previous term: comparing the actual bed temperature rTbed with the first target bed temperature tTbed1, and transitioning to the middle term when the actual bed temperature rTbed reaches the first target bed temperature tTbed1. .
[0147]
(B) Another method for determining the transition to the latter period in the middle period: When the burning of particulates progresses considerably and burns out, the filter outlet temperature T2 becomes lower than the filter inlet temperature T1. Therefore, when the filter outlet temperature T2 falls below a value obtained by subtracting a predetermined value (for example, several tens of degrees Celsius) from the filter inlet temperature T1 (that is, a threshold value), the process shifts to the latter period.
[0148]
Now, as can be seen from the fourth stage in FIG. 3, the post-stage injection amount 2 is large. For this reason, as shown by the broken line in the lower part of FIG. 32, when the large post-stage post-injection amount 2 is given in a stepwise manner at the timing when the actual bed temperature rTbed reaches the catalyst activation temperature (240 ° C.), the particulates are regenerated. The bed temperature during combustion rises abnormally (see the upper broken line in FIG. 32). This is because when the post-stage injection 2 is performed by giving a target value (map value) that changes stepwise when the actual bed temperature reaches the catalyst activation temperature, the injected fuel deprives the catalyst of latent heat of vaporization on the catalyst. The actual bed temperature is reduced, and the fuel that cannot be evaporated remains on the catalyst. Then, when the actual bed temperature rises again to the catalyst activation temperature, the particulates remaining on the catalyst burn rapidly.
[0149]
In order to cope with this, it is preferable to provide a value obtained by performing a response delay process on the target value as shown by the solid line in the lower part of FIG. As described above, when the actual bed temperature is near the catalyst activation temperature, the post-stage post-injection amount 2 is given by subjecting the target value to the response delay processing (the invention according to claim 8). The bed temperature can be prevented from lowering due to evaporation of the catalyst, and the bed temperature can be increased at the timing when the catalytic reaction starts.
[0150]
In the invention according to claim 2, the means for performing the temperature rise control in the first half is steps 4 and 11 in FIG. 5, and the means for performing the first target bed temperature maintenance control in the middle is the steps 6 and 18 in FIG. The means for performing the first oxygen concentration control is shown in step 5 of FIG. 5, the means for performing the second target bed temperature maintenance control in the latter stage is shown in steps 8 and 21 of FIG. Each of the steps 7 and 5 has been performed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a characteristic diagram showing three stages of a reproduction processing period.
FIG. 3 is a waveform chart for explaining the operation and effect of the embodiment.
FIG. 4 is a view for explaining the use of post-injection having different functions.
FIG. 5 is a flowchart for explaining the entire reproduction process.
FIG. 6 is a flowchart for explaining setting of a reproduction processing flag.
FIG. 7 is a flowchart for explaining setting of a reproduction phase.
FIG. 8 is a characteristic diagram of a set time t1.
FIG. 9 is a characteristic diagram of a set time t2.
FIG. 10 is a characteristic diagram of a filter pressure loss with respect to a particulate deposition amount.
FIG. 11 is a flowchart for explaining temperature rise control.
FIG. 12 is a characteristic diagram of a pre-stage post injection amount 1;
FIG. 13 is a characteristic diagram of pre-stage post injection timing 1.
FIG. 14 is a characteristic diagram of the post-stage post-injection amount 1;
FIG. 15 is a characteristic diagram of post-stage post injection timing 1.
FIG. 16 is a characteristic diagram of a basic post-stage post-injection amount 2;
FIG. 17 is a characteristic diagram of post-stage post-injection timing 2;
FIG. 18 is a flowchart illustrating first target bed temperature maintenance control.
FIG. 19 is a characteristic diagram of the post injection amount 1.
FIG. 20 is a characteristic diagram of post injection timing 1.
FIG. 21 is a flowchart illustrating a second target bed temperature maintaining control.
FIG. 22 is a characteristic diagram of the post injection amount 1.
FIG. 23 is a characteristic diagram of post injection timing 1.
FIG. 24 is a characteristic diagram of a basic post injection amount 2.
FIG. 25 is a characteristic diagram of post injection timing 2.
FIG. 26 is a characteristic diagram of the maximum bed temperature during the regeneration process when the amount of accumulated particulates is large.
FIG. 27 is a characteristic diagram of the maximum bed temperature during regeneration processing when the amount of accumulated particulates is small.
FIG. 28 is a waveform chart for explaining a method of setting a target oxygen concentration in exhaust gas.
FIG. 29 is a waveform chart for explaining a method of setting a target oxygen concentration in exhaust gas according to another embodiment.
FIG. 30 is a region diagram for describing intake fresh air amount control means.
FIG. 31 is a region diagram for explaining fuel injection control means.
FIG. 32 is a change waveform diagram of a post-stage post-injection amount 2;
[Explanation of symbols]
1 engine
2 Exhaust passage
3 Intake passage
6 EGR valve
10 Common rail fuel injection system
17 nozzle (fuel injection valve)
21 Variable capacity turbocharger
31 Engine Controller
33 Crank angle sensor
36 Differential pressure sensor
37, 38 Temperature sensor
41 Filter
42 Intake throttle valve

Claims (8)

Equipped with a filter to collect particulates in the exhaust passage,
In the exhaust gas purification device of the engine that performs the filter regeneration process when the filter regeneration time comes,
An exhaust gas purification apparatus comprising a regeneration processing means for performing two post-injections per cycle of an engine and controlling oxygen concentration of exhaust gas so that a constant target regeneration speed is obtained during regeneration processing of a filter. The filter regeneration processing period consists of the first half, the middle half, and the second half,
In the first half period, a temperature increase control is performed to control the temperature to the first target bed temperature so that the regeneration speed increases to the target regeneration speed,
Performing a first target bed temperature maintenance control for maintaining the first target bed temperature such that the regeneration speed decreases to the target regeneration speed in the middle period, and a first oxygen concentration control for setting the target oxygen concentration in the exhaust gas to a low concentration;
The second target bed temperature maintenance control for maintaining the second target bed temperature higher than the first target bed temperature so that the regeneration speed increases to the target regeneration speed in the later period, and the second process in which the target oxygen concentration in the exhaust gas is set to a high concentration 2. The exhaust gas purifying apparatus according to claim 1, wherein the oxygen concentration control is performed. The exhaust gas purification apparatus according to claim 2, wherein the first target bed maintenance control for maintaining the first target bed temperature in the middle period is performed by one post-injection for raising the exhaust gas temperature per cycle. 3. The exhaust system according to claim 2, wherein the second target bed maintenance control for maintaining the second target bed temperature in the latter period is performed by two post-injections for raising the exhaust temperature and supplying the HC per cycle. Purification device. When a catalyst is carried on the filter, the former period includes a former stage for performing a temperature rise control for controlling to a catalyst activation temperature and a latter stage for performing a temperature rise control for controlling to a first target bed temperature. The exhaust gas purification device according to claim 2, wherein 6. The exhaust gas purifying apparatus according to claim 5, wherein the temperature raising control for controlling to the catalyst activation temperature in the preceding stage is performed by one post-injection for raising the exhaust gas temperature per cycle. The exhaust gas purifying apparatus according to claim 5, wherein the temperature raising control for controlling to the first target bed temperature in the subsequent stage is performed by two post-injections for raising the exhaust gas temperature and supplying HC per cycle. . The exhaust gas purifying apparatus according to claim 7, wherein a response delay process is performed on a target value when the post-injection for supplying HC is performed.

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