JP4496939B2 - Exhaust purification device - Google Patents

Description

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

In order to process the particulates discharged from the diesel engine, a filter that collects particulates is arranged 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. Some apparatuses that perform so-called filter regeneration processing that burns and removes particulates that increase the oxygen concentration in the exhaust when the regeneration time comes (see Patent Document 1).
JP 2002-168112 A

  Incidentally, FIG. 16 shows how the maximum temperature of the filter (hereinafter referred to as “maximum bed temperature”) changes when the state suddenly shifts to the idle state during the regeneration process in a state where the vehicle is traveling at a high speed, for example. As a result of an experiment in which the amount of particulate collection in the filter is determined to be different, the increase in the maximum bed temperature increases as the amount of particulate collection in the filter increases. The filter has an allowable temperature due to heat resistance. If the maximum bed temperature of the filter rises above the allowable filter temperature, the heat resistance of the filter may be lowered. Therefore, in order to prevent the maximum bed temperature of the filter from exceeding the filter temperature allowable value, the particulate collection amount in the filter, strictly speaking, the particulate removal amount of the particulates in the filter during the regeneration process. It is necessary to control the temperature of the filter in consideration of the amount of curate regeneration. The filter bed temperature is equivalent to the burning rate of the particulates in the filter, and the burning rate depends on the oxygen concentration in the exhaust.

  Accordingly, an object of the present invention is to provide an apparatus that maintains the maximum bed temperature of a filter high regardless of the amount of particulate regeneration during the regeneration process of the filter.

  On the other hand, in the technique of Patent Document 1, when the differential pressure dP before and after the filter becomes larger than the allowable differential pressure dPc, the filter regeneration process is started. In this case, the number of times the engine control routine has been performed since the start of the regeneration process. Is detected by the counter n. While the counter n has not reached the first threshold number th1, the EGR valve is fully closed to increase the oxygen concentration in the exhaust to promote particulate combustion, and the counter n has the first threshold number th1. If the differential pressure across the filter does not decrease sufficiently even when the pressure reaches the value, the supercharging pressure is increased in addition to the EGR control to further increase the oxygen concentration in the exhaust gas and further promote the combustion of particulates. ing.

  As described above, the technique of Patent Document 1 only controls the oxygen concentration in the exhaust gas in accordance with the differential pressure across the filter and the elapsed time since the start of the filter regeneration process. The technical idea is different from the present invention in which the oxygen concentration in the exhaust gas is controlled based on the particulate regeneration amount.

The present invention provides a filter that collects particulates in exhaust gas, and in the exhaust gas purification apparatus for an engine that performs filter regeneration processing at the time of regeneration of the filter, the particulates accumulated in the filter during the regeneration processing. The oxygen concentration in the exhaust gas is increased as the particulate regeneration amount (PMr) that is the combustion removal amount of the curate increases. Further, the oxygen concentration increasing means is an intake fresh air amount control means, and calculates a new air amount increase time ratio, which is a ratio of time for increasing the fresh air amount to a certain time according to the particulate regeneration amount PMr during the regeneration process. Then, the intake fresh air amount control means is controlled in accordance with the new air amount increase time ratio.

  Even when the maximum bed temperature of the filter does not exceed the filter temperature allowable value as shown in FIG. 10, the particulate regeneration amount that is the combustion removal amount of the particulates deposited on the filter immediately after the regeneration processing is started. Since the oxygen concentration in the exhaust gas can be increased when the particulate regeneration amount has increased for a while after the start of the regeneration process than when the regeneration amount is small, according to the present invention, the particulate regeneration amount during the regeneration process can be increased. As (PMr) increases, the oxygen concentration in the exhaust gas is increased so that the combustion speed of the particulates in the filter does not decrease (that is, the bed temperature is kept high), and this affects the heat resistance of the filter. Reproduction processing time can be shortened without affecting. In general, the regeneration process is accompanied by a deterioration in fuel consumption, but the deterioration in fuel consumption can be suppressed by shortening the regeneration processing time in this way.

  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 particulate accumulation amount of the filter 41 reaches a predetermined value (threshold value), the regeneration process of the filter is started, and the particulate accumulated on the filter 41 is 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.

  This control executed by the engine controller 31 will be described in detail with reference to a flowchart.

  FIG. 2 is for performing the regeneration process for one time of the filter 41. This flow is not repeatedly executed at a fixed period, but shows operations in time series.

  In step 1, the particulate collection amount PMi to the filter 41 is calculated based on the pressure loss ΔP detected by the differential pressure sensor 36.

  In step 2, the particulate collection amount PMi is compared with the target collection amount PMα. Here, the target collection amount PMα is determined in advance by experiments or the like according to the regeneration characteristics of the filter 41. If the particulate collection amount PMi does not reach the target collection amount PMα, the process returns to step 1 to repeat the calculation of PMi. By repeating this PMi calculation, PMi increases. When the target collection amount PMα is eventually exceeded, the process proceeds to step 3 to proceed to the regeneration phase, so that the regeneration phase flag (initially set to zero) = 1, the regeneration end flag (initially set to zero) ) = 0. Further, 1 is set to the value of the counter N.

  In step 4, it is checked whether or not it is immediately after the reproduction phase flag = 1 (first time). Specifically, it is checked whether or not the value of the counter N is 1. If it is immediately after the regeneration phase flag = 1 (N = 1), the process proceeds to step 5, and the target inlet temperature Td of the filter 41 is calculated by searching a map having the contents shown in FIG. 3 from the particulate collection amount PMi. To do.

  As shown in FIG. 3, the target inlet temperature Td decreases as the particulate collection amount PMi increases. This is because when the particulate collection amount PMi increases, the amount of particulates burned during the regeneration process of the filter 41 increases, and the temperature of the filter 41 rises excessively due to the temperature rise due to combustion. It is. The reason why the particulate collection amount PMi at the start of the regeneration process is used as a parameter is to cope with the difference in the specifications of the engine and the filter 41.

  In Step 6, the process proceeds to a phase (exhaust temperature raising phase) in which the exhaust temperature is increased so that the target inlet temperature Td calculated in Step 5 is reached, and the exhaust temperature is raised using the exhaust temperature raising means. As the exhaust temperature raising means, conventionally used means such as post-injection for performing fuel injection again after normal fuel injection, injection timing retarding means for delaying fuel injection timing, and the like are used.

  When the execution of the exhaust temperature raising phase in step 6 is completed, the process proceeds to step 7 and the bed of the filter 41 is based on the inlet temperature T1 detected by the inlet temperature sensor 37 and the inlet temperature T2 detected by the outlet temperature sensor 38. The temperature Tbed is estimated. For this purpose, the average value of the inlet temperature T1 and the outlet temperature T2 may be used as the bed temperature Tbed.

  In step 8, the time when the bed temperature Tbed of the filter 41 calculated in step 7 exceeds the target bed temperature Tx is integrated, and the integrated value is calculated as the effective regeneration time te. The target bed temperature tx is a temperature at which all the particulates in the filter 41 can be burned without being burned if the temperature is maintained for a certain period. The target bed temperature tx is determined from the target inlet temperature Td and further captures the particulates at the start of the regeneration process. The value also changes depending on the amount of collection PMi.

  As shown in FIG. 4, the bed temperature Tbed changes in response to changes in traveling conditions. Therefore, when the bed temperature Tbed is lower than the target bed temperature Tx, the particulates in the filter 41 cannot burn completely and remain burned. It is possible. Therefore, a period actually contributing to the complete combustion of the particulate is defined as an effective regeneration period te. Specifically, an integrated value during a period in which the bed temperature Tbed is equal to or higher than the target bed temperature Tx is defined as an effective regeneration period te. Therefore, in the case of FIG. 4, the effective reproduction period te is calculated by the following equation (1).

te = tx1 + tx2 + tx3 + tx4 (1)
By using the effective regeneration period te in which the bed temperature is equal to or higher than the target bed temperature in this way, the period during which the particulates in the filter 41 perform incomplete combustion can be excluded, so the filter 41 can be accurately obtained. It is possible to estimate the complete combustion amount (regeneration amount) of the particulates.

  The method for calculating the effective reproduction time te is not limited to this. That is, when the bed temperature Tbed is lower than the target bed temperature Tx, it has been described above that a part of the particulates remains unburned. Conversely, in other words, the remaining portions other than the unburned portion are completely burned and the particulates corresponding to that portion. Has disappeared. Therefore, when the bed temperature Tbed is lower than the target bed temperature Tx, the portion that disappears after complete combustion should be included in the effective regeneration period.

This will be described in detail with reference to FIG. 5. FIG. 5 shows the temporal change of the bed temperature Tbed as in FIG. The lowest temperature at which the particulates start combustion in the temperature range lower than the target bed temperature Tx is defined as the first temperature Ta, and the first temperature Ta and the target bed temperature Tx are divided into several parts. In the example shown in the figure, the temperature of the section is the second temperature Tb, the third temperature Tc, and the fourth temperature Td, and the periods in which the bed temperature Tbed is in the temperature range of Ta to Tb are ta1, ta2,
The periods in the temperature range of Tb to Tc are tb1, tb2, tb3,
A period in the temperature range of Tc to Td is defined as tc1, tc2, tc3,
The period in the temperature range from Td to Tx is td1, td2.
The period in the temperature range above Tx is tx1
And set. The number of divisions is not limited to four.

  At this time, the effective reproduction period te is calculated by the following equation.

te = Ka × (ta1 + ta2) + Kb × (tb1 + tb2 + tb3)
+ Kc × (tc1 + tc2 + tc3) + Kd × (td1 + td2)
+ Kx × (tx1) (2)
Where Ka, Kb, Kc, Kd, Kx; temperature coefficient of effective regeneration period,
Here, the temperature coefficient of the effective regeneration period is a value for weighting the part where the particulates in the filter 41 completely burn as an effective regeneration period. When the bed temperature Tbed is equal to or higher than the target bed temperature Tx, Since all of the particulates are completely burned and disappear, the temperature coefficient Kx is 1.0. When the bed temperature Tbed is lower than the target bed temperature Tx, for example, if 10% of the particulates in the filter 41 are burned and the remaining 90% are completely burned and lost, the temperature coefficient is 0.9. Similarly, if 50% of the particulates in the filter 41 are left unburned and the remaining 50% are completely burnt and disappear, the temperature coefficient is 0.5. When the bed temperature Tbed is lower than the target bed temperature Tx, the lower the bed temperature, the smaller the proportion of particulates that disappear due to complete combustion, so the magnitude relationship for the five temperature coefficients Ka, Kb, Kc, Kd, and Kx Is Ka <Kb <Kc <Kd <Kx (see FIG. 6).

  In this way, the amount of the particulate that is partially burnt and disappears in the temperature range where the bed temperature Tbed is lower than the target bed temperature Tx can be factored in as the effective regeneration time te. The amount of curated regeneration can be estimated with higher accuracy.

  In step 9, by searching a map having the contents shown in FIG. 7 from the effective regeneration time te and the particulate collection amount PMi at the start of the regeneration process, the particulates accumulated in the filter 41 are completely burned and lost. The particulate regeneration amount PMr, which is the amount, is calculated. As shown in FIG. 7, the particulate regeneration amount PMr increases as the effective regeneration time te is longer if the particulate collection amount PMi is the same, and if the effective regeneration time te is the same, the particulate collection amount PMi is greater. The larger the value, the larger the value.

  In step 10, the particulate collection amount PMi at the start of the regeneration process and the particulate regeneration amount PMr in the filter 41 obtained in step 9 are calculated as follows: A certain particulate residual amount PMx is calculated.

PMx = PMi-PMr (3)
In step 11, the particulate regeneration amount PMr is compared with the target regeneration amount ΔPM. Here, as the target regeneration amount ΔPM, for example, as shown in FIG. 8, when the target collection amount PMα is set to 4 g / L, 1/4 of that is set. Of course, the target regeneration amount ΔPM is not limited to ¼ of the target collection amount PMα, and is adapted according to the specifications of the engine and the filter 41. When the particulate regeneration amount PMr in the filter 41 is less than the target regeneration amount ΔPM, the process returns to step 8 and the operations of steps 8 to 11 are repeated. By repeating this, the particulate regeneration amount PMr increases, and the particulate residual amount PMx decreases.

  Eventually, when the particulate regeneration amount PMr reaches the target regeneration amount ΔPM, the routine proceeds from step 11 to step 12. At the time when the particulate regeneration amount PMr coincides with the target regeneration amount ΔPM, the particulate residual amount PMx is PMi−PMr = PMα−ΔPM = 4-1 = 3 [g / L] in FIG.

  In step 12, the particulate residual amount PMx is compared with the target residual amount PMd. Here, the target remaining amount PMd is a particulate amount that is allowed to remain in the filter 41 at the end of the regeneration phase in accordance with each traveling condition such as when traveling in a traffic jam or when traveling at high speed. As long as the target remaining amount PMd is 0 g / L under a driving condition in which complete regeneration (combustion removal of all particulates accumulated on the filter 41) can be performed as in continuous high-speed driving, the vehicle runs in a traffic jam. As shown in FIG. 8, the target remaining amount PMd under a traveling condition in which regeneration can be performed only partially, such as the time, is half that when the particulate collection amount at the start of regeneration processing is 4 g / L. 2 g / L is set. That is, not all the particulates accumulated in the filter 41 are burned and lost when traveling in a traffic jam, but the regeneration process is temporarily terminated when half of the particulates during high speed driving are burned and lost. It is determined what kind of driving conditions are present. As a result, the traveling condition has shifted to high speed traveling, and when the state shifts to the regeneration phase, the target remaining amount PMd is switched to 0 g / L and the regeneration process is executed.

  However, in the following, it is described that the traffic jam continues even after it is determined in step 12 that the particulate residual amount PMx exceeds the target residual amount PMd (= 2 g / L). Return to step 4 to continue. At this time, the value of the counter N is incremented by 1 in step 21 (N = 2). In step 4, since it is determined that it is not the first time (N ≠ 1), the process proceeds from step 4 to step 13, and the particulate remaining amount PMx calculated in step 10 is used instead of the particulate collection amount PMi at the start of the regeneration process. 3 is searched again from this remaining amount PMx to calculate the target inlet temperature Td, and the exhaust temperature is raised at step 14 using the exhaust temperature raising means so as to reach the target inlet temperature Td. Let Since the particulate residual amount PMx calculated in step 10 is smaller than the particulate collection amount PMi at the start of the regeneration process, the target inlet temperature Td obtained from the particulate residual amount PMx is calculated according to FIG. It becomes higher than the target inlet temperature Td obtained from the particulate collection amount PMi at the time. That is, instead of burning the particulates in the filter 41 to the target residual amount PMd without changing the target inlet temperature at the start of the regeneration process, the target regeneration amount PMr becomes the target regeneration amount ΔPM every time the particulate regeneration amount PMr becomes the target regeneration amount ΔPM. By increasing the inlet temperature Td, the bed temperature of the filter 41 is raised and the particulate combustion of the filter 41 is promoted.

  And operation of step 15-18 is performed similarly to above-mentioned step 7-10.

  In step 19, the particulate regeneration amount PMr is compared with the target regeneration amount ΔPM multiplied by N. While the particulate regeneration amount PMr is less than the target regeneration amount ΔPM × N, the operations in steps 16 to 19 are repeated, When the curated regeneration amount PMr becomes equal to or greater than the target regeneration amount ΔPM × N, the routine proceeds to step 12. That is, when the increase amount of the particulate regeneration amount PMr after the resetting of the target inlet temperature Td (step 13) reaches the target regeneration amount ΔPM, the process proceeds to step 12. At the time when the particulate regeneration amount PMr coincides with the target regeneration amount ΔPM × N in step 19, the particulate residual amount PMx in FIG. 8 is PMi−PMr = PMi−ΔPM × 2 = 4-2 = 2 [g / L]. It has become.

  For this reason, the process proceeds from step 19 to step 12 where the particulate residual amount PMx (= 2 g / L) is compared with the target residual amount PMd (= 2 g / L) at the time of traffic jam. In order to prepare for the next reproduction process, the process proceeds to step 20 where the reproduction phase flag = 0 and the reproduction end flag (initially set to zero) = 1.

  This completes one reproduction process, and the operation from step 1 is repeated again.

  FIG. 9 is for controlling the intake fresh air amount using the intake fresh air amount control means during the filter regeneration process. In relation to FIG. 2, FIG. 9 collectively shows the control performed in the exhaust temperature raising phase in steps 6 and 14 of FIG. 2. The flow in FIG. 9 is executed at regular intervals (for example, every 10 ms) unlike FIG.

  In step 31, the reproduction phase flag (set in step 3 in FIG. 2) is checked. When the reproduction phase flag = 1, that is, during the reproduction process, the routine proceeds to step 32 where the particulate regeneration amount PMr is read. This particulate regeneration amount PMr is a value calculated in steps 9 and 17 in FIG.

  In step 32, a fresh air amount increase time ratio corresponding to the particulate regeneration amount PMr is calculated by searching a table having the contents shown in FIG. 10 from the particulate regeneration amount PMr.

  Here, the new air volume increase time ratio is the ratio of the time during which the intake fresh air volume is increased with respect to a certain time. The minimum value of the new air volume increase time ratio is 0% and the maximum value is 100%. For example, FIG. 11 shows the difference between the case where the fresh air amount increase time ratio is small and the case where the fresh air amount increase time ratio is large.

  The maximum bed temperature of the filter 41 changes as shown in FIG. 10 in accordance with the new air amount increase time ratio and the particulate regeneration amount. That is, if the particulate regeneration amount is the same, the maximum bed temperature of the filter 41 increases in proportion to the fresh air amount increase time ratio. If the fresh air volume increase time ratio is the same, the maximum bed temperature of the filter 41 becomes higher when the particulate regeneration amount is small.

  In this case, the higher the maximum bed temperature of the filter 41, the faster the burning speed of the particulates in the filter 41 and the more the burning of the particulates in the filter 41 is promoted. The larger the amount increase time ratio, the better. On the other hand, if the maximum bed temperature of the filter 41 exceeds the allowable filter temperature (for example, about 900 ° C. as shown in FIG. 16), the durability of the filter 41 is increased. Since it gets worse, the maximum bed temperature of the filter 41 needs to be limited to the allowable filter temperature. Therefore, the new air volume increase time ratio at the point where the straight line with respect to the particulate regeneration amount at that time and the parallel line representing the filter temperature allowable value intersect is set as the new air volume increase time ratio according to the particulate regeneration amount at that time. Set as.

  For example, FIG. 10 exemplifies two cases where the particulate regeneration amount is small and large, and the fresh air volume increase time ratio when the particulate regeneration amount is small is the predetermined value A, and the particulate regeneration amount is Assuming that the ratio of the fresh air volume increase time when there is a large amount is the predetermined value B, the new air volume increase time ratio is increased as the particulate regeneration amount increases with the progress of regeneration. As the fresh air amount increase time ratio increases, the regeneration speed (particulate combustion speed) increases as shown in FIGS. 12 and 13, and the particulate regeneration amount increases. That is, if the fresh air amount increase time ratio is kept at the predetermined value A from the start to the end of the regeneration process, the maximum bed temperature (regeneration temperature) of the filter 41 is lower than the filter temperature allowable value as the particulate regeneration amount increases. Move away to the side. When the regeneration temperature decreases, as shown in FIGS. 14 and 15, the time until the end of regeneration (reproduction processing time) is prolonged. On the other hand, when the particulate regeneration amount increases, the fresh air volume increase time ratio is increased in accordance with the particulate regeneration amount so that the maximum bed temperature of the filter 41 maintains the filter temperature allowable value. Thus, even when the amount of particulate regeneration increases, the regeneration temperature can be kept high, which makes it possible to maintain the fresh air volume increase time ratio at a predetermined value A from the start to the end of the regeneration process. Playback processing time can be shortened.

  In FIGS. 10, 12, and 14, “PM trapping amount” refers to the remaining particulate amount.

  Returning to FIG. 9, in step 34, the intake fresh air amount control means is controlled using the fresh air amount increase time ratio obtained in step 33. As the intake fresh air amount control means, there are a variable capacity turbocharger 21, an EGR valve 6, and an intake throttle valve. For example, when the opening degree of the variable nozzle 24 is reduced, the rotational speed of the turbine 22 is increased and the amount of fresh intake air is increased (the oxygen concentration in the exhaust gas is increased). When the opening degree of the EGR valve 6 is reduced, the amount of fresh intake air increases. If the opening of the intake throttle valve 42 is opened from the closed state, the amount of fresh intake air increases.

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

As shown in FIG. 10, even if the maximum bed temperature of the filter 41 does not exceed the allowable filter temperature value, the particulates that are the combustion removal amount of the particulates accumulated on the filter 41 immediately after the start of the regeneration process. Since the oxygen concentration in the exhaust gas can be increased when the particulate regeneration amount increases after a while from the start of the regeneration process, compared with the case where the regeneration amount is small, this embodiment (the invention according to claim 1) ), As the particulate regeneration amount PMr increases during the regeneration process, the oxygen concentration in the exhaust gas is increased so that the combustion speed of the particulates in the filter 41 does not decrease (that is, the bed temperature is kept high). Thus, the reproduction processing time can be shortened.
In general, the regeneration process is accompanied by a deterioration in fuel consumption. By thus shortening the regeneration processing time, it is possible to suppress the deterioration in fuel consumption.
Further, the oxygen concentration increasing means is an intake fresh air amount control means, and calculates a new air amount increase time ratio, which is a ratio of time for increasing the fresh air amount to a certain time according to the particulate regeneration amount PMr during the regeneration process. Then, since the intake fresh air amount control means is controlled in accordance with this new air amount increase time ratio (see steps 31 to 34 in FIG. 9), the maximum bed temperature of the filter 41 exceeds the filter temperature allowable value and rises too much. While preventing this, the burning rate of the particulates during the regeneration process can be controlled more appropriately.

  According to the present embodiment (the invention described in claim 2), the oxygen concentration in the exhaust gas is increased so that the maximum bed temperature of the filter 41 does not exceed the filter temperature allowable value, so the amount of particulate regeneration increases. Even at this stage, the maximum bed temperature can be maintained near the filter temperature allowable value, so that the regeneration processing time can be further shortened and fuel consumption deterioration can be further suppressed.

  According to the present embodiment (the invention described in claim 4), the value obtained by integrating the periods in which the bed temperature Tbed of the filter 41 is equal to or higher than the target bed temperature Tx, which is a temperature necessary for burning and removing the particulates. Is calculated as the effective regeneration period te, and the particulate regeneration amount PMr is estimated based on the effective regeneration period te. Therefore, the particulate regeneration amount using the differential pressure across the filter that varies due to uneven distribution of the particulates, etc. Compared to the estimation, the particulate regeneration amount can be estimated with high accuracy.

  In the embodiment, the case where the new air amount time ratio is calculated according to the particulate regeneration amount PMr has been described. However, the fresh air amount is determined according to the particulate remaining amount PMx calculated in steps 10 and 18 of FIG. The time ratio may be calculated.

  In the embodiment, the case where the particulate residual amount PMx is obtained after obtaining the particulate regeneration amount MRr has been described. However, the present invention is not limited to this, and the particulate residual amount may be obtained directly.

  The function of the oxygen concentration increasing means described in claim 1 is performed by steps 32 and 33 in FIG.

The schematic block diagram which shows one Embodiment of this invention. The flowchart for demonstrating reproduction | regeneration processing. The characteristic figure of target inlet temperature. The bed temperature time change figure for explaining the effective regeneration period of a 1st embodiment. The bed temperature time change figure for demonstrating the effective regeneration period of 2nd Embodiment. The characteristic figure of the temperature coefficient of effective regeneration time. The characteristic view of the amount of particulate regeneration. The characteristic view which shows the relationship of the particulate remaining amount with the effective reproduction time. The flowchart for demonstrating control of the amount of intake fresh air. The characteristic diagram of the maximum bed temperature of the filter with respect to the air volume increase time ratio and the particulate regeneration amount. The wave form diagram for demonstrating the air quantity increase time ratio. The characteristic figure of the reproduction | regeneration speed with respect to the air volume increase time ratio and the particulate regeneration amount. The characteristic view of the air amount increase time ratio with respect to the particulate regeneration amount. The characteristic view which shows the relationship between the regeneration temperature in a regeneration process, and the amount of particulate collection. The characteristic view which shows the relationship between the reproduction | regeneration temperature in a reproduction | regeneration process, and a particulate regeneration amount. The characteristic figure of the maximum bed temperature with respect to the filter outlet exhaust temperature of the conventional apparatus.

Explanation of symbols

1 Engine 31 Engine controller 37, 38 Temperature sensor (bed temperature detection means)
41 Filter

Claims (6)

It has a filter that collects particulates in the exhaust,
In the exhaust emission control device of the engine that performs the regeneration process of the filter at the regeneration time of the filter,
Oxygen concentration increasing means for increasing the oxygen concentration in the exhaust gas as the particulate regeneration amount, which is the combustion removal amount of the particulate deposited on the filter during the regeneration process, increases;
Further, the oxygen concentration increasing means is an intake fresh air amount control means, and calculates a fresh air volume increase time ratio, which is a ratio of time for increasing the fresh air volume with respect to a predetermined time in accordance with the particulate regeneration amount. An exhaust emission control device that controls the intake fresh air amount control means in accordance with a new air amount increase time ratio . The exhaust gas purification apparatus according to claim 1, wherein the oxygen concentration in the exhaust gas is increased so that a bed temperature of the filter does not exceed a filter temperature allowable value. 2. The exhaust emission control device according to claim 1, further comprising means for estimating a particulate regeneration amount, wherein the oxygen concentration in the exhaust gas is increased as the estimated particulate regeneration amount increases. The means for estimating the particulate regeneration amount includes a bed temperature detection means for detecting the bed temperature of the filter and a value obtained by integrating a period during which the detected bed temperature is equal to or higher than the target bed temperature as an effective regeneration period. 2. The exhaust emission control device according to claim 1, further comprising: an effective regeneration period calculating means for calculating; and a particulate regeneration amount calculating means for calculating the particulate regeneration amount based on the effective regeneration period. When the filter is being regenerated, the residual amount of particulates remaining in the filter being regenerated is obtained, and the amount of particulate regeneration increases as the residual amount of particulates decreases. The exhaust emission control device according to claim 1, wherein the concentration is increased. The means for obtaining the particulate residual amount is a bed temperature detection means for detecting the bed temperature of the filter, and a value obtained by integrating a period during which the detected bed temperature is equal to or higher than the target bed temperature as an effective regeneration period. The effective regeneration period calculating means for calculating, the particulate regeneration amount calculating means for calculating the particulate regeneration amount based on the effective regeneration period, and the particulate regeneration from the particulate collection amount at the start of the regeneration processing of the filter 6. The exhaust emission control device according to claim 5, further comprising a particulate residual amount calculating means for calculating a value obtained by subtracting the amount as the particulate residual amount.

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