JP2005194974A - Exhaust emission control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique by which residual quantity of particulates deposited in a filter can be surely detected during regeneration of a filter. <P>SOLUTION: When an operating condition of an internal combustion engine is brought into a deceleration operating state under which fuel supply to an internal combustion engine is stopped to be decelerated during regeneration of a filter (S102), the deposition quantity of particulates in the filter is estimated from changes in the intake air quantity and the filter temperature before and after the operating condition of an internal combustion engine is brought into the deceleration operating state (106). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine.

  The exhaust gas from an internal combustion engine contains particulate matter mainly composed of carbon. A technique for providing a particulate filter (hereinafter referred to as “filter”) for collecting particulate matter in an exhaust system of an internal combustion engine is known in order to prevent the emission of these particulate matter to the atmosphere.

  In such a filter, when the amount of collected particulate matter increases, the exhaust pressure increases due to clogging of the filter, and the engine performance decreases. Therefore, the amount of collected particulate matter deposited on the filter is estimated, and when the estimated amount of particulate matter deposited exceeds a predetermined amount, the accumulated particulate matter is oxidized and removed to evacuate the filter. The purification performance is regenerated (hereinafter referred to as “filter regeneration process”).

  Further, as a method for estimating the amount of particulate matter accumulated in the filter, there are a method for estimating the accumulated amount of intake air taken into the internal combustion engine, and exhaust pressure sensors on the exhaust upstream side and exhaust downstream side of the filter. A method of detecting the pressure loss of the filter from the differential pressure of the exhaust pressure detected by both sensors, a method of estimating by the deviation between the target filter temperature and the actual filter temperature can be exemplified.

  However, in the method of estimating based on the integrated value of the intake air amount described above, it is influenced by the performance of the air flow meter, which is a sensor for the intake air amount, and the state of the internal combustion engine such as an EGR cooler. In the method for detecting the pressure loss of the filter, the value of the differential pressure is affected by the temperature of the filter. Furthermore, the method for estimating the deviation between the target filter temperature and the actual filter temperature is affected by the combustion state of the internal combustion engine.

In addition, a technique has been proposed in which the amount of particulate matter deposited is estimated from the rate of temperature increase around 700 ° C. during the filter regeneration process (see, for example, Patent Document 1). However, this prior art is also affected by the engine operating state and the intake air amount during the regeneration process.
Japanese Patent Laid-Open No. 08-61044 JP 2002-89234 A

  In the above prior art, it may be difficult to detect the amount of particulate matter deposited on the filter with sufficient accuracy. As a result, it may be difficult to accurately determine the reproduction time in the filter reproduction process. Here, if the remaining amount of the particulate matter in the filter can be accurately detected during the filter regeneration process, the subsequent regeneration time of the filter can be accurately determined.

  In view of the above, an object of the present invention is to provide a technique capable of accurately detecting the remaining amount of particulate matter deposited in the filter during the regeneration process of the filter.

  In order to achieve the above object, according to the present invention, during the regeneration process of the filter, the operating state of the internal combustion engine is a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and the intake air amount is throttled (hereinafter referred to as the deceleration operation state). , Simply referred to as “decelerated operation state”), the particulate matter in the filter based on the change in the intake air amount and the change in the filter temperature before and after the operation state of the internal combustion engine becomes the deceleration operation state. The greatest feature is to estimate the amount of sediment.

More specifically, a filter that is provided in the exhaust passage of the internal combustion engine and collects particulate matter in the exhaust of the internal combustion engine;
A filter regeneration means for increasing the temperature of the exhaust gas of the internal combustion engine and oxidizing the particulate matter collected by the filter to regenerate the collection ability of the filter;
An intake air amount detecting means for detecting an intake air amount sucked into the internal combustion engine;
Filter temperature detecting means for detecting the temperature of the filter;
During the regeneration process by the filter regeneration means, when the operating state of the internal combustion engine is in a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and the intake air amount is reduced to decelerate, the internal combustion engine From the change in the intake air amount detected by the intake air amount detection means and the change in the filter temperature detected by the filter temperature detection means before and after the operating state of the engine becomes the deceleration operation state, PM deposition amount estimation means for estimating the amount of particulate matter deposited on the filter;
It is characterized by providing.

  Here, during the regeneration process of the filter, the temperature of the filter mainly depends on the balance between the amount of heat generated by oxidizing the particulate matter deposited on the filter and the amount of heat that the exhaust passing through the filter takes away from the filter. It depends. When the operation state of the internal combustion engine becomes a decelerating operation state during the regeneration process of the filter, the intake air amount rapidly decreases, and the amount of heat taken away from the filter by the exhaust gas passing through the filter decreases. The temperature rises temporarily.

  The temperature rise of the filter at this time increases as the amount of particulate matter deposited on the filter increases, and increases as the amount of reduction in the intake air amount increases. In other words, if the temperature rise of the filter and the amount of decrease in the intake air amount are detected at this time, the amount of particulate matter accumulated on the filter can be estimated.

  The present invention utilizes this principle, and accumulates on the filter from the amount of change in temperature and the amount of intake air when the operating state of the internal combustion engine becomes a decelerating operation state during the regeneration process of the filter. The amount of particulate matter produced is estimated.

  According to this, since the amount of particulate matter deposited on the filter is estimated not by the detection value itself of the filter temperature and the intake air amount but by the change amount of the filter temperature and the intake air amount, the internal combustion engine The amount of particulate matter deposited on the filter can be estimated more accurately because it can be made less susceptible to the influence of engine conditions and sensor performance.

  Specifically, the relationship between the change in the temperature of the filter, the change in the intake air amount, and the amount of particulate matter deposited on the filter is experimentally investigated in advance and is mapped to be detected from the map. It is preferable to read out the value of the accumulated amount of particulate matter corresponding to the temperature change of the filter and the change of the intake air amount. This makes it possible to estimate the amount of particulate matter deposited on the filter more easily.

  Further, in the present invention, when the operation state of the internal combustion engine immediately before entering the deceleration operation state belongs to a predetermined low load low rotation speed range, the particulate matter accumulation by the PM accumulation amount estimation means is performed. It is advisable to prohibit the estimation of quantity.

  That is, when the operation state of the internal combustion engine is a so-called low-load low-revolution state, the change in the intake air amount when the internal combustion engine is in a decelerating operation state is not significant. The temperature rise of the filter due to the decrease in heat quantity does not appear clearly. Therefore, in this case, it is relatively difficult to accurately estimate the amount of particulate matter deposited on the filter.

  Therefore, the filter according to the present invention is limited to the case where the operating state of the internal combustion engine immediately before entering the deceleration operating state belongs to the state of the medium-load medium rotational speed and the range on the higher load and / or higher rotational speed side than that state. By estimating the amount of particulate matter deposited on the filter, the amount of particulate matter deposited on the filter can be estimated more accurately.

  In the present invention, the subsequent regeneration processing time by the filter regeneration means may be determined based on the particulate matter accumulation amount in the filter estimated by the PM deposition amount estimation means.

  In other words, the present invention is applied when the operating state of the internal combustion engine becomes a deceleration operating state during the filter regeneration process. In this case, normally, the filter regeneration process is interrupted while the operating state of the internal combustion engine is in the deceleration operating state. When the operation state of the internal combustion engine shifts from the deceleration operation state to another state, it is necessary to restart the filter regeneration process.

  Therefore, when the operation state of the internal combustion engine becomes a decelerating operation state during the regeneration process of the filter, the amount of particulate matter accumulated in the filter is newly estimated according to the present invention, and the operation state of the internal combustion engine becomes the decelerating operation state. Therefore, the regeneration processing time of the filter after shifting to other states is determined based on the amount of particulate matter deposited estimated by the present invention. In this way, the filter regeneration processing time can be determined more accurately, the filter regeneration processing time becomes uselessly long, causing deterioration of the fuel consumption of the internal combustion engine, and the filter regeneration processing time is short. Such as incomplete reproduction processing can be suppressed.

In the present invention, a part of the exhaust gas of the internal combustion engine is recirculated to the intake system of the internal combustion engine, and the amount of exhaust gas to be recirculated is increased or decreased by increasing or decreasing the opening of the EGR valve. Further comprising a device,
Prior to the estimation of the particulate matter deposition amount by the PM deposition amount estimation means, it is preferable to perform EGR full-opening control in which the amount of exhaust gas to be recirculated is increased with the opening of the EGR valve fully opened.

  Here, when the operation state of the internal combustion engine becomes a deceleration operation state, the change in the intake air amount when the operation state of the internal combustion engine becomes the deceleration operation state is increased by fully opening the EGR valve. Furthermore, the temperature drop of the exhaust gas passing through the filter can be suppressed. And the width | variety of the temperature change of the filter accompanying it can be enlarged. As a result, the accuracy of estimation in the present invention can be improved.

Further, in this case, the EGR full-open control is permitted only when the operation state of the internal combustion engine immediately before entering the deceleration operation state belongs to a range equal to or less than a predetermined medium load medium rotation speed range. It is good. That is, when the operation state of the internal combustion engine immediately before entering the deceleration operation state is a high load or high speed range, the original exhaust temperature is high, and the oxidation reaction of the particulate matter in the filter 20 is active. In addition, the intake air amount changes greatly when the operating state of the internal combustion engine becomes a decelerating operation state, and the reduction of the amount of heat taken away tends to be excessive. Therefore, if EGR fully open control is executed in such a case, the filter may be overheated. Therefore, if the EGR full-opening control is permitted only when the operation state of the internal combustion engine immediately before the deceleration operation state belongs to a range equal to or less than a predetermined medium-load medium rotation speed range, Can be prevented from overheating. Note that an operating state range equal to or lower than the medium-load rotation speed range in which EGR fully open control is permitted is obtained experimentally in advance.

  Further, in the present invention, a PM accumulation amount temporary estimation unit that temporarily estimates the amount of particulate matter deposited on the filter before the EGR full-opening control is executed is provided. If the estimated accumulation amount of the particulate matter is equal to or less than a predetermined amount, it is preferable to expand the range below the predetermined medium-load medium rotation speed range to a higher load / high rotation speed side.

  Here, when the amount of particulate matter deposited on the filter is small, even if the amount of heat taken away from the filter is reduced by reducing the amount of intake air, the amount of heat generated by oxidation of the particulate matter itself Therefore, there is little possibility that the filter will overheat. Therefore, when the amount of particulate matter deposited on the filter is small, compared to when the amount of particulate matter deposited on the filter is large, it is within the operating state range of the internal combustion engine immediately before entering the deceleration operation state. Thus, the range in which the excessive temperature rise of the filter is not caused even when the EGR full-opening control is performed is expanded to a range on the higher load high rotation speed side.

  Therefore, before the execution of the EGR full-opening control, there is provided PM deposition amount temporary estimation means for temporarily estimating the amount of particulate matter deposited on the filter, and the particles temporarily estimated by the PM deposition amount temporary estimation means When the amount of deposits of the particulate matter is less than or equal to a predetermined amount, the range below the predetermined medium-load medium rotation speed range is expanded to a higher load side and / or a higher rotation speed side. Thereby, the range of the operation state in which the EGR full-open control is performed can be expanded according to the amount of the particulate matter deposited on the filter. As a result, the estimation accuracy of the particulate matter deposition amount by the PM deposition amount estimation means in the present invention can be improved as a whole.

  Here, the PM accumulated amount temporary estimation means may be based on a conventional technique for estimating the accumulated amount of particulate matter in the filter from the differential pressure between the exhaust pressure upstream and downstream of the filter, The particulate matter deposition amount in the filter previously estimated by the PM deposition amount estimation means in the present invention may be used as it is. Or you may perform the subtraction according to the filter regeneration process time after that with respect to the accumulation amount of the particulate matter in the filter estimated previously by the PM accumulation amount estimation means in this invention.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, the remaining amount of particulate matter deposited in the filter can be accurately detected during the regeneration process of the filter.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its exhaust purification system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a multi-cylinder diesel engine having four cylinders 2.

The internal combustion engine 1 includes a fuel injection valve 3 that injects fuel directly into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 that accumulates fuel to a predetermined pressure. The common rail 4 communicates with the fuel pump 6 through the fuel supply pipe 5.

  An intake branch pipe 8 is connected to the internal combustion engine 1, and an upstream side of the intake branch pipe 8 is further connected to an intake passage 9. The intake passage 9 is provided with an intake throttle valve 10 that controls the amount of intake air that passes through the intake passage 9 and flows into the internal combustion engine 1. The intake throttle valve 10 is provided with an intake throttle actuator 14 that is configured by a stepper motor or the like and that drives the intake throttle valve 10 to open and close.

  Further, on the further upstream side of the intake passage 9, a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 and an intercooler 16 for cooling the intake air that has been compressed in the compressor housing 15a and heated to a high temperature. Is attached. Further, an air flow meter 37 that outputs an electrical signal corresponding to the mass of the intake air flowing through the intake passage 9 is provided further upstream of the intake passage 9.

  On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and the exhaust branch pipe 18 is connected to a turbine housing 15 b of the centrifugal supercharger 15. The turbine housing 15 b is connected to the exhaust passage 19. The exhaust passage 19 is connected to a muffler (not shown) downstream.

  A filter 20 that collects particulate matter (for example, soot) in the exhaust gas is disposed in the middle of the exhaust passage 19.

  Examples of the filter 20 include a wall flow type filter made of a porous base material that collects fine particles contained in exhaust gas, a filter carrying an oxidation catalyst typified by platinum (Pt), an oxidation catalyst and potassium. Examples thereof include a filter in which a NOx storage agent typified by (K) or cesium (Cs) is supported.

  An upstream exhaust pressure sensor 28 that outputs an electrical signal corresponding to the pressure of the exhaust gas flowing upstream with respect to the filter 20 is attached to the exhaust pipe 19 upstream of the filter 20. The exhaust pipe 19 downstream of the filter 20 corresponds to the exhaust temperature sensor 23 that outputs an electrical signal corresponding to the temperature of the exhaust gas flowing through the exhaust pipe 19 and the pressure of the exhaust gas flowing downstream from the filter 20. A downstream exhaust pressure sensor 29 that outputs an electrical signal is attached.

  Further, the internal combustion engine 1 is provided with an exhaust gas recirculation device 40 that recirculates a part of the exhaust gas flowing through the exhaust system of the internal combustion engine 1 to the intake system. The exhaust gas recirculation device 40 includes an EGR passage 25 formed from the exhaust branch pipe 18 to the gathering portion of the intake branch pipe 8, an electromagnetic valve, etc., and an EGR that flows in the EGR passage 25 according to the magnitude of the applied voltage. An EGR valve 26 that adjusts the gas flow rate and an EGR cooler 27 that is provided in the EGR passage 25 upstream of the EGR valve 26 and cools the EGR gas flowing through the EGR passage 25 are provided.

  In the exhaust gas recirculation device 40 configured as described above, when the EGR valve 26 is opened, a part of the exhaust gas flowing in the exhaust branch pipe 18 passes through the EGR passage 25 and is cooled by the EGR cooler 27. Then, it flows into the collecting portion of the intake branch pipe 8. The EGR gas flowing into the intake branch pipe 8 is distributed to the combustion chamber of each cylinder 2 while being mixed with fresh air flowing from the upstream side of the intake branch pipe 8.

  The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operating state of the internal combustion engine 1 in accordance with the operating conditions of the internal combustion engine 1 and the request of the driver.

  In addition to the above-described upstream exhaust pressure sensor 28, downstream exhaust pressure sensor 29, exhaust temperature sensor 23, air flow meter 37, and the like, an accelerator position sensor 33 is connected to the ECU 35 via electric wiring, and an output signal is input to the ECU 35. It has come to be. The accelerator position sensor 33 outputs a signal corresponding to the accelerator opening that is linked to the movement of the accelerator pedal 32 operated by the driver. On the other hand, in addition to the fuel injection valve 3, the intake throttle valve 10, the EGR valve 26, and the like are connected to the ECU 35 via electric wiring and are controlled by the ECU 35.

  The ECU 35 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. The particulate matter accumulation amount estimation routine in the present invention, which will be described later, is also one of the programs stored in the ROM of the ECU 35.

  Next, the principle of estimating the amount of particulate matter deposited in this embodiment will be described with reference to FIG. FIG. 2 shows the amount of change in the intake air amount and the amount of change in the filter temperature when the amount of particulate matter accumulated in the filter 20 is large and small when the internal combustion engine 1 is in a decelerating operation state. It is the figure which showed the relationship.

  In FIG. 2, (a) and (b) show the change in the intake air amount and the accompanying change in the temperature of the filter 20 when the accumulation amount of the particulate matter is a relatively large accumulation amount Pa. On the other hand, (c) and (d) show the change in the intake air amount and the accompanying change in the temperature of the filter 20 when the accumulation amount Pb of the particulate matter is relatively small.

  Here, when the operation state of the internal combustion engine 1 is in a decelerating operation state during the regeneration process of the filter 20, for example, as shown in FIG. As a result, the amount of heat taken away from the filter 20 by the exhaust gas passing through the filter 20, that is, the amount of heat that is taken away decreases, so that the temperature of the filter 20 once rises as shown in FIG. Here, when the operation state of the internal combustion engine 1 becomes a deceleration operation state during the regeneration process of the filter 20, the regeneration process is interrupted while the deceleration operation state is continued. For this reason, the temperature of the filter 20 once increased then decreases.

  Generally, when the amount of particulate matter deposited on the filter 20 is relatively large, the amount of heat generated by the oxidation of the particulate matter in the filter 20 is also large. Even when the amount of heat taken away from the filter 20 does not decrease so much, the temperature rise of the filter 20 should increase. Conversely, when the amount of particulate matter accumulated in the filter 20 is small, the amount of heat generated by the oxidation of the particulate matter in the filter 20 is also small, so the temperature rise of the filter 20 should be small.

  Therefore, in the present invention, attention is paid to the change in the intake air amount and the change in the filter temperature when the operation state of the internal combustion engine 1 is in the deceleration operation state. For example, when the change in the intake air amount and the change in the filter temperature when the operation state of the internal combustion engine 1 is in the decelerating operation state become as shown in (a) and (b) in FIG. When the c) and (d) are compared with each other, the amount of change in the filter temperature is the same in both cases, but when comparing (a) and (c) in FIG. The change in the intake air amount shown in (a) is smaller than the change in the intake air amount shown in (c). In such a case, it can be estimated that the particulate matter deposition amount Pa in the former is larger than the particulate matter deposition amount Pb in the latter.

Similarly, when attention is paid to the change in the intake air amount and the change in the filter temperature when the operation state of the internal combustion engine 1 is in the decelerating operation state, the change in the intake air amount is also equivalent. If the temperature rise of the filter 20 is large in some cases and the temperature rise of the filter 20 is small in other cases, the amount of particulate matter deposited in the former case is naturally the amount of particulate matter deposited in the latter case. It can be estimated that there is more than quantity.

  FIG. 3 shows a flowchart of a particulate matter accumulation amount estimation routine in the present embodiment using the above principle. This routine is a routine stored in the ROM of the ECU 35 and is executed every predetermined period during the regeneration process of the filter 20 in the internal combustion engine 1.

  When this routine is executed, first, in S101, it is determined whether or not the temperature of the filter 20 is higher than 400 ° C. Specifically, the temperature of the filter 20 is estimated by taking the output signal from the exhaust temperature sensor 23 into the ECU 35, and the estimated temperature is compared with 400 ° C. Here, if the temperature of the filter 20 is 400 ° C. or lower, it is difficult for the particulate matter to cause an oxidation reaction in the filter 20, so that it is difficult to estimate the amount of particulate matter deposited in the present invention. Accordingly, when it is determined in S101 that the temperature of the filter 20 is 400 ° C. or lower, this routine is terminated. On the other hand, if it is determined that the temperature is higher than 400 ° C., the process proceeds to S102.

  In S102, it is determined whether or not the operation state of the internal combustion engine 1 is a deceleration operation state. Specifically, the output signal of the accelerator position sensor 33 is read into the ECU 35, and it is determined whether or not the output value is smaller than a predetermined value. Further, for this determination, an engine speed obtained from a signal from a crank position sensor (not shown) may be supplementarily used. If it is determined that the vehicle is not in the deceleration operation state, the particulate matter accumulation amount estimation in this embodiment cannot be performed, and thus this routine is temporarily terminated.

  On the other hand, if it is determined in S102 that the internal combustion engine 1 is in the decelerating operation state, the process proceeds to S103. In S103, it is determined whether or not the operation state immediately before the internal combustion engine 1 enters the decelerating operation state belongs to a predetermined low load and low speed range.

  Here, the predetermined low-load low-speed range described above will be described with reference to FIG. FIG. 4 is a graph in which the horizontal axis represents the engine speed and the vertical axis represents torque, and shows the operating state of the internal combustion engine 1. In the range on the low load and low rotation speed side in the range, as described above, since the change in the intake air amount when entering the deceleration operation state is small, the temperature of the filter 20 does not rise significantly. Therefore, when the operating state of the internal combustion engine 1 falls within this range immediately before the deceleration operating state, it becomes difficult to ensure the detection accuracy of the particulate matter accumulation amount in the present embodiment.

  On the other hand, in the range on the high load or high speed side in FIG. 4, the change in the intake air amount when the operation state of the internal combustion engine 1 becomes the deceleration operation state is excessively large, and the amount of heat taken away by the filter 20 is reduced at a stretch. As a result, the filter 20 may overheat. Therefore, when the operating state of the internal combustion engine 1 falls within this range immediately before the deceleration operation state is entered, the transition to the deceleration operation state itself is prohibited. In this case, for example, when there is a deceleration request from the driver, the control does not suddenly shift to the deceleration operation state, but instead the fuel supply to the internal combustion engine is stopped but the intake air amount is not reduced. Etc. are performed. As a result, the amount of particulate matter deposited in this embodiment is estimated because the operating state of the internal combustion engine 1 belongs to the hatched range in FIG. Is the case.

  Next, the description returns to FIG. When it is determined in S103 in FIG. 3 that the operation state immediately before the operation state of the internal combustion engine 1 is in the deceleration operation state belongs to the low-load and low-speed range described in FIG. In addition, since it is determined that it is difficult to estimate the particulate matter deposition amount in the present embodiment, this routine is temporarily terminated. On the other hand, when it is determined that the operation state immediately before the operation state of the internal combustion engine 1 is in the decelerating operation state does not belong to the low load low rotation speed range, the amount of particulate matter deposited in the present embodiment The process proceeds to S104 in order to estimate.

  In S104, EGR full-opening control is performed to increase the amount of exhaust gas to be recirculated by opening the EGR valve 26 in a fully open state. By this control, the exhaust gas passing through the filter 20 can be reduced and a decrease in the exhaust gas temperature can be suppressed, so that the temperature change of the filter 20 can be made more remarkable.

  Next, the process proceeds to S105, where the change ΔGa in the intake air amount and the temperature change ΔT of the filter 20 are acquired. Specifically, the output signal from the air flow meter 37 and the output signal from the exhaust temperature sensor 23 are acquired by the ECU 35. In particular, in this embodiment, the output signal of the air flow meter 37 and the output signal of the exhaust temperature sensor 23 are acquired at every minute sampling time, and the change of both signals becomes substantially 0 (differential value is 0). When the routine is executed before the current execution of the current routine, and finally when the operation state of the internal combustion engine 1 is determined not to be the deceleration operation state in S102 ΔGa and ΔT are obtained from the difference from each output signal value.

  In other words, in S105, it waits until the change in the intake air amount and the change in the temperature of the filter 20 converge, and by detecting the difference from the value before the operation state of the internal combustion engine 1 becomes the deceleration operation state, ΔGa and ΔT are obtained.

  Next, proceeding to S106, the amount of particulate matter deposited on the filter 20 is estimated. Here, the relationship between the change ΔGa in the intake air amount and the value of the temperature change ΔT of the filter 20 and the amount of particulate matter deposited on the filter 20 is experimentally investigated and mapped in advance. In S106, the value of the accumulation amount of the particulate matter in the filter 20 corresponding to the change ΔGa in the intake air amount acquired in S105 and the temperature change ΔT of the filter 20 is read from the map.

  Further, in this routine, the process proceeds to S107, and the filter regeneration time when the regeneration process of the filter 20 is performed after the end of this routine is determined. That is, this routine is executed when the operation state of the internal combustion engine 1 is in a decelerating operation state during the regeneration process of the filter 20, and the regeneration of the filter 20 is performed while this routine is being executed. Processing is suspended. Therefore, after that, when the operation state of the internal combustion engine 1 is not the deceleration operation state, the regeneration process of the filter 20 is resumed.

  Therefore, in S106, the remaining filter regeneration time when the regeneration process of the filter 20 is resumed is determined based on the estimated amount of accumulated particulate matter. Specifically, it is determined by reading the value of the filter regeneration time from a map that stores the relationship between the value of the amount of particulate matter accumulated in the filter 20 and the filter regeneration time. When the process of S106 is completed, this routine is once ended.

  As described above, in the present embodiment, when the operating state of the internal combustion engine 1 becomes a decelerating operation state during the regeneration process of the filter 20, a change in the intake air amount and a change in the temperature of the filter 20 due to this change. And the amount of particulate matter deposited on the filter 20 is estimated based on these values. According to this, the amount of particulate matter deposited on the filter 20 is estimated not by the temperature of the filter 20 or the detected value of the intake air amount but by the temperature of the filter 20 and the amount of change in the intake air amount. The influence of the state of the internal combustion engine 1 and the performance of sensors can be suppressed, and the amount of particulate matter deposited on the filter 20 can be estimated more accurately.

Further, in this embodiment, when the operation state of the internal combustion engine 1 immediately before entering the deceleration operation state belongs to a predetermined low load low rotation speed range, the estimation of the amount of particulate matter accumulated in the filter 20 is prohibited. ing. Therefore, since the above estimation is performed only when the amount of particulate matter deposited can be estimated with high accuracy, the estimation accuracy can be improved.

  Further, in this embodiment, the remaining regeneration time in the regeneration process of the filter 20 is determined using the value of the accumulated amount of the particulate matter estimated in S106. Therefore, the regeneration processing time of the filter 20 can be determined more accurately. As a result, the regeneration processing time of the filter 20 is unnecessarily long, resulting in deterioration of fuel consumption, and the regeneration processing time of the filter 20 is too short, so that the regeneration processing of the filter 20 is not performed completely. Can be suppressed.

  Further, in this embodiment, before detecting the change ΔGa in the intake air amount and the temperature change ΔT of the filter 20, the EGR full-open control for increasing the amount of EGR gas by fully opening the opening of the EGR valve is performed. Is going.

  By this control, the amount of intake air introduced into the filter 20 can be significantly reduced, and further, the temperature drop of the exhaust gas introduced into the filter 20 can be suppressed. Thereby, the width of the temperature change of the filter when the operation state of the internal combustion engine becomes the deceleration operation state can be increased. As a result, the accuracy of estimation in the present invention can be improved.

  In the present embodiment, the intake air amount detecting means includes an air flow meter 37 and an ECU 35 into which the signal is taken. The filter temperature detection means includes an exhaust temperature sensor 23 and an ECU 35. The PM accumulation amount estimation means includes an ECU 35 that executes the particulate matter accumulation amount estimation routine described above.

  Next, Example 2 will be described. Since the hardware configuration of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment, the description thereof is omitted.

  In the present embodiment, during the regeneration process of the filter 20, when the operation state of the internal combustion engine 1 is in a decelerating operation state, the amount of particulate matter accumulated in the filter 20 is simply changed to the intake air amount change ΔGa and Instead of estimating from the temperature change ΔT of the filter 20, attention is also paid to the intake air amount and the middle of the period during which the temperature of the filter 20 is changing, and an integrated ΔGa that is a value obtained by integrating the change of the intake air amount. The case where the accumulated amount of the particulate matter in the filter 20 is estimated from the temperature change ΔT of the filter 20 will be described.

  The principle of estimating the amount of particulate matter deposited in this embodiment will be described with reference to FIG. FIG. 5 shows the amount of change in the intake air amount and the amount of change in the filter temperature for each of the cases where the accumulation amount of particulate matter in the filter 20 is large and small when the internal combustion engine 1 is in a decelerating operation state. It is the figure which showed the relationship. This figure is a more detailed view of the change in the intake air amount at the time when the intake air amount changes in FIG.

  In FIG. 5, (a) and (b) show the change in the intake air amount when the deposition amount Pa of the particulate matter is a relatively large deposition amount, and the accompanying temperature change of the filter 20. On the other hand, (c) and (d) show the change in the intake air amount and the accompanying change in the temperature of the filter 20 when the accumulation amount Pb of the particulate matter is relatively small.

Here, when the operation state of the internal combustion engine 1 is in a decelerating operation state during the regeneration process of the filter 20, for example, as shown in FIG. Specifically, the intake air amount does not decrease instantaneously, but continuously decreases during a predetermined period. Then, during the period in which the intake air amount is decreasing, the temperature of the filter 20 increases by a temperature corresponding to the amount of decrease in the intake air amount. After the intake air amount change period ends, the temperature of the filter 20 once increased for the same reason as described in the first embodiment is then decreased.

  That is, strictly speaking, the range of the temperature rise of the filter 20 is closely related to the integrated value of the change in the intake air amount during the change period of the intake air amount, rather than the change amount ΔGa of the intake air amount. . In FIG. 5, the integrated value of the change in the intake air amount is indicated by a hatched area.

  Therefore, as in this embodiment, by detecting the integrated ΔGa that is the integrated value of the change in the intake air amount during the change period of the intake air amount, the estimation accuracy of the accumulation amount of the particulate matter in the filter 20 is improved. Can do.

  FIG. 6 shows a particulate matter accumulation amount estimation routine in the present embodiment. The difference from FIG. 3 in this routine is that the process of S201 for obtaining the integrated ΔGa and ΔT is executed instead of the process of S105. Other processing is the same as that of the first embodiment shown in FIG.

  In S201, as in S105 in the first embodiment, the change in the output signal of the air flow meter 37 is acquired at every minute sampling time, the value of the output signal from the air flow meter 37 at each minute sampling time, and the current book. When this routine is executed before the execution of the routine, a difference from the value of the output signal of the air flow meter 37 when it is finally determined in S102 that the operation state of the internal combustion engine 1 is not the deceleration operation state is detected. .

  Further, in this embodiment, each time this routine is executed, the detected value is added up to the same detected value detected at the previous execution of this routine. Then, the integrated value when the change in the output signal of the air flow meter 37 becomes substantially 0 (differential value is 0) is defined as integrated ΔGa. Note that ΔT is acquired in the same manner as in S105. When the accumulated ΔGa and ΔT values are determined, the process of S201 is terminated, and the process proceeds to S202.

  In S202, the amount of particulate matter deposited on the filter 20 is estimated. Here, the relationship between the integrated value ΔGa, which is the integrated value of the intake air amount change, the value of the temperature change ΔT of the filter 20, and the amount of particulate matter deposited on the filter 20 is experimentally investigated and mapped in advance. Yes. In S202, the integrated value ΔGa, which is the integrated value of the intake air amount change acquired in S201, and the value of the particulate matter accumulation amount in the filter 20 corresponding to the temperature change ΔT of the filter 20 are read from the map. It is.

  As described above, in the present embodiment, since the integrated ΔGa that is the integrated value of the change in the intake air amount during the intake air amount change period is acquired, the width of the temperature rise of the filter 20 is more closely related. Can be used to estimate the amount of particulate matter accumulated. As a result, it is possible to improve the accuracy of the map that reads the value of the amount of particulate matter deposited in S202, and to improve the accuracy of estimating the amount of particulate matter deposited.

  Next, Example 3 will be described. Since the hardware configuration of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment, the description thereof is omitted.

  In the present embodiment, the opening degree of the EGR valve 26 is set to the fully open state only when the operating state of the internal combustion engine 1 belongs to a range equal to or lower than the predetermined medium load rotation speed range immediately before the operating state of the internal combustion engine 1 is reduced. An example in which the EGR fully open control for increasing the amount of EGR gas is permitted will be described.

  FIG. 7 shows a particulate matter accumulation amount estimation routine in the present embodiment. The difference between this routine and the first embodiment shown in FIG. 3 is that in S301, immediately before the operating state of the internal combustion engine 1 becomes a decelerating operation state, it belongs to a range equal to or less than a predetermined medium-load medium speed range. EGR full open control by skipping S104 when it does not belong to the range below the predetermined medium load medium rotation speed range, in other words, when it belongs to the high load high rotation speed range The process proceeds to the process of obtaining ΔGa and ΔT without performing the above.

  In other words, immediately before the operating state of the internal combustion engine 1 becomes the decelerating operating state, if the operating state does not belong to a range equal to or lower than the predetermined medium-load medium rotational speed range, the operating state is, for example, the particulate matter accumulation amount in FIG. Even if it belongs to the estimable range, if EGR fully open control is performed, the filter 20 may overheat. This is because in the range of such high load and high rotation speed, the original exhaust temperature is high, the particulate matter oxidation reaction in the filter 20 is active, and the amount of reduction in the intake air amount is large.

  Therefore, in this embodiment, if it is determined in S301 that the internal combustion engine 1 does not belong to a range equal to or lower than the predetermined medium load rotation speed range immediately before the operation state of the internal combustion engine 1 is changed to the deceleration operation state, the process proceeds to S104. The process is skipped and the process of S105 is executed. By carrying out like this, the excessive temperature rise of the filter 20 at the time of implementing the said EGR full open control can be suppressed.

  Here, the range equal to or lower than the predetermined middle load mid-speed range means a range including the EGR full-open control permission range 1 in FIG. 8 and the low-load low-speed range in FIG. However, in the particulate matter accumulation amount estimation routine shown in FIG. 7, immediately before the operating state of the internal combustion engine 1 becomes the decelerating operation state, if it belongs to the low load low speed range in FIG. After the processing, this routine is terminated without executing S301. Therefore, it is considered that the range below the predetermined medium-load medium rotation speed range means the EGR full-open control permission range 1 in FIG.

  Next, Example 4 will be described. Since the hardware configuration of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment, the description thereof is omitted.

  In the present embodiment, the opening degree of the EGR valve 26 is set to the fully open state only when the operating state of the internal combustion engine 1 belongs to a range equal to or lower than the predetermined medium-load rotation speed range immediately before the operating state becomes the deceleration operating state. This is an example in which the EGR full-opening control for increasing the amount of EGR gas is performed, and the range below the predetermined medium-load rotation speed range is changed according to the amount of particulate matter accumulated in the filter 20. explain.

  FIG. 9 shows a particulate matter accumulation amount estimation routine in the present embodiment. The difference of this routine from the third embodiment is that the processing of S401 to S403 is performed instead of the processing of S301.

  In S401 in this routine, a temporary estimation of the particulate matter accumulation amount is performed. Specifically, provisional estimation is performed by reading the accumulated amount of the particulate matter in the filter 20 estimated in the processing of S106 of this routine from the RAM in the ECU 35 at the previous execution of this routine. Here, the ECU 35 that performs this processing constitutes the PM accumulation amount temporary estimation means in the present embodiment.

Then, the process proceeds to S402, where an EGR fully open control permission range is determined. Specifically, if the amount of particulate matter accumulated in the filter 20 temporarily estimated in S401 is larger than a predetermined amount, the EGR full-open control permission range is set to the EGR full-open control permission region 1 in FIG. If the amount of particulate matter accumulated in the temporarily estimated filter 20 is equal to or less than a predetermined amount, the EGR full-open control permission range is set to the EGR full-open control permission range 2 in FIG.

  Here, the predetermined amount to be compared with the temporarily estimated amount of particulate matter accumulated in the filter 20 is immediately before the internal combustion engine 1 enters the decelerating operation state when the amount of particulate matter deposited is less than that. If it belongs to the EGR full-open control permission range 2, even if it does not belong to the EGR full-open control permission range 1, it is determined that the filter 20 does not overheat when the EGR full-open control is performed in S104. It is.

  In S402, after the EGR fully open control permission range is determined, the process proceeds to S403, and immediately before the operating state of the internal combustion engine 1 enters the decelerating operation state, it is determined whether it belongs to the EGR fully open control permission range determined in S402. Is done. Here, if it is determined that the EGR fully open control permission range is not included, the filter 20 can be determined to overheat if the EGR fully open control is performed, so the process of S104 is skipped and the process proceeds to S105. On the other hand, if it is determined in S403 that it belongs to the EGR full-open control permission region, it is determined that the filter 20 does not overheat even if the EGR full-open control is performed, so the EGR full-open control is performed in S104. Then, the process proceeds to S105.

  As described above, according to the present embodiment, the amount of particulate matter accumulated in the filter 20 is temporarily estimated, and based on the result, EGR full-open control permission serving as a reference for determining whether or not to implement EGR full-open control is given. Change the range. Therefore, it is possible to improve the accuracy of the determination as to whether or not the EGR fully open control is performed. As a result, the EGR full-opening control can be performed to improve the estimation accuracy of the accumulated amount of the particulate matter in the filter 20 by performing the EGR full-opening control and the EGR full-opening control. It is possible to suppress problems and the like that deteriorate the estimation accuracy unnecessarily.

  In this embodiment, as a method for temporarily estimating the accumulation amount of the particulate matter in the filter 20 in S401, the particulate matter in the filter 20 estimated in the processing of S106 of this routine at the previous execution of this routine. Although the method of reading the amount of deposited material from the RAM in the ECU 35 is used, the method is not limited to this method. For example, a method of detecting a change in the exhaust pressure in the filter 20 from the difference between the output signals of the upstream side exhaust pressure sensor 28 and the downstream side exhaust pressure sensor 29, or the processing of S106 of this routine at the previous execution of this routine A method may be used in which the accuracy of the temporary estimation is increased by performing subtraction corresponding to the subsequent filter regeneration processing time with respect to the accumulated amount of the particulate matter in the filter 20 estimated in step (1).

  Here, in the above-described embodiment, an example in which the present invention is applied to a multi-cylinder diesel engine has been described, but it is needless to say that the present invention may be applied to a gasoline engine.

  Further, in the above embodiment, the description has been made on the assumption that the regeneration process of the filter 20 is interrupted when the operation state of the internal combustion engine 1 is in the deceleration operation state during the regeneration process of the filter 20. However, the present invention can also be applied to an exhaust purification system that does not interrupt the regeneration process of the filter 20 when the operation state of the internal combustion engine 1 is in a decelerating operation state.

  For example, when the operation state of the internal combustion engine 1 becomes a deceleration operation state, the system that lowers the temperature of the filter 20 in the regeneration process of the filter 20 or the operation state of the internal combustion engine 1 becomes the deceleration operation state. Even in this case, when applied to a system in which the same regeneration process of the filter 20 as before is applied, the change in the filter temperature described in FIGS. 2 and 5 is considered to change. The same effect as the above-described embodiment can be obtained.

1 is a diagram showing a schematic configuration of an internal combustion engine and an exhaust purification system thereof according to the present invention. FIG. 5 is a diagram showing the relationship between the amount of change in intake air amount and the amount of change in filter temperature for each of cases where the amount of particulate matter accumulated in the filter is large and small when the internal combustion engine enters a deceleration operation state. is there. It is a flowchart which shows the particulate matter deposition amount estimation routine in Example 1 of this invention. It is a figure explaining the low load low rotation speed range in Example 1 of this invention. A second example showing the relationship between the amount of change in the intake air amount and the amount of change in the filter temperature for each of the cases where the amount of particulate matter accumulated in the filter is large and small when the internal combustion engine enters a deceleration operation state. FIG. It is a flowchart which shows the particulate matter deposition amount estimation routine in Example 2 of this invention. It is a flowchart which shows the particulate matter deposition amount estimation routine in Example 3 of this invention. It is a figure explaining the EGR full open control permission range in Examples 3 and 4 of the present invention. It is a flowchart which shows the particulate matter deposition amount estimation routine in Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Common rail 5 ... Fuel supply pipe 6 ... Fuel pump 8 ... Intake branch pipe 9 ... Intake passage 10 ... Intake throttle valve 14 ... Intake throttle actuator 15 ... Centrifuge supercharger 15a ... Compressor housing 15b ... Turbine housing 16 ... Intercooler 18 ... Exhaust branch pipe 19 .... -Exhaust passage 20 ... Filter 23 ... Exhaust temperature sensor 25 ... EGR passage 26 ... EGR valve 27 ... EGR cooler 28 ... Upstream exhaust pressure sensor 29 ... Downstream exhaust pressure Sensor 32 ... Accelerator pedal 33 ... Accelerator position sensor 35 ... ECU
37 ... Air flow meter 40 ... Exhaust gas recirculation device

Claims (6)

A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust of the internal combustion engine;
A filter regeneration means for increasing the temperature of the exhaust gas of the internal combustion engine and oxidizing the particulate matter collected by the filter to regenerate the collection ability of the filter;
An intake air amount detecting means for detecting an intake air amount sucked into the internal combustion engine;
Filter temperature detecting means for detecting the temperature of the filter;
During the regeneration process by the filter regeneration means, when the operating state of the internal combustion engine is in a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and the intake air amount is reduced to decelerate, the internal combustion engine From the change in the intake air amount detected by the intake air amount detection means and the change in the filter temperature detected by the filter temperature detection means before and after the operating state of the engine becomes the deceleration operation state, PM deposition amount estimation means for estimating the amount of particulate matter deposited on the filter;
An exhaust gas purification system for an internal combustion engine, comprising:   When the operation state of the internal combustion engine immediately before entering the deceleration operation state belongs to a predetermined low load and low rotation speed range, prohibiting the estimation of the particulate matter accumulation amount by the PM accumulation amount estimation unit is prohibited. The exhaust gas purification system for an internal combustion engine according to claim 1.   The regeneration processing time by the filter regeneration unit is determined based on the accumulation amount of the particulate matter collected by the filter estimated by the PM deposition amount estimation unit. Exhaust gas purification system for internal combustion engines. An EGR device that recirculates part of the exhaust gas of the internal combustion engine to the intake system of the internal combustion engine and increases or decreases the amount of exhaust gas to be recirculated by increasing or decreasing the opening of an EGR valve;
Before the estimation of the particulate matter deposition amount by the PM deposition amount estimation means, EGR full-opening control for increasing the amount of exhaust gas to be recirculated is performed with the opening of the EGR valve being fully opened. The exhaust gas purification system for an internal combustion engine according to claim 1, 2, or 3.   The EGR full-open control is permitted only when the operation state of the internal combustion engine immediately before the deceleration operation state belongs to a range equal to or less than a predetermined medium-load medium rotation speed range. 5. An exhaust gas purification system for an internal combustion engine according to 4. PM accumulated amount temporary estimation means for temporarily estimating the amount of particulate matter deposited on the filter before the EGR fully open control is executed,
When the particulate matter deposition amount temporarily estimated by the PM deposition amount provisional estimation means is less than or equal to a predetermined amount, a range that is less than or equal to the predetermined medium load / medium rotation speed range is set to a higher load side and / or higher rotation speed. 6. The exhaust gas purification system for an internal combustion engine according to claim 5, wherein the exhaust gas purification system is expanded to several sides.

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