JP6036533B2 - PM accumulation amount estimation device and exhaust purification system for internal combustion engine - Google Patents

Description

  The present invention relates to a PM accumulation amount estimation device and an exhaust gas purification system for an internal combustion engine, and more particularly to a PM accumulation amount estimation device for estimating a PM accumulation amount in a filter unit and an exhaust gas purification system for an internal combustion engine including the PM accumulation amount estimation device.

  In an exhaust gas purification system for an internal combustion engine for a vehicle, a differential pressure sensor, an absolute pressure sensor, or the like detects a differential pressure across the filter unit that collects PM (particulate matter) in exhaust gas, and the filter unit uses the differential pressure. It is known that the filter unit is regenerated when the exhaust gas pressure loss increases by estimating the amount of accumulated PM.

  As a PM accumulation amount estimation device equipped in such a system, a first estimation means for calculating the PM accumulation amount based on the differential pressure across the filter unit, and a fixed period of the PM accumulation amount from the engine operating state detection information There is a method for calculating the PM accumulation amount by selecting the second estimation means for calculating and accumulating the increase amount (PM generation amount) for each exhaust gas flow rate. In this apparatus, the second estimation means is used in the exhaust gas flow region where the detection error of the differential pressure sensor becomes large, and at that time, the PM estimation accuracy is increased by using the estimated PM accumulation amount by the first estimation means as the initial value of the cumulative start. (For example, refer to Patent Document 1).

JP 2006-77761 A

  However, in the conventional PM accumulation amount estimation device and the exhaust gas purification system for an internal combustion engine as described above, the accuracy of the PM accumulation amount estimation process based on the engine operating condition is estimated based on the detection value of the differential pressure sensor. Compared to the accuracy of processing, the accuracy is exclusively low. For this reason, there has been a problem in that the difference between the actual PM deposition amount and the estimated PM deposition amount becomes large if the operation state continues with few opportunities to adopt the PM deposition amount estimation processing from the differential pressure sensor.

  That is, when a running pattern in which the differential pressure across the DPF (diesel particulate filter) unit cannot be obtained with high accuracy continues, the estimated PM generation amount from the engine operating state with low estimation accuracy is being used continuously. Since the amount of increase in the PM deposition amount in the DPF unit at a certain time is calculated and accumulated, the estimation error of the PM deposition amount is integrated, and a divergence occurs between the actual PM deposition amount and the estimated PM deposition amount. End up. For example, if the estimated value of the PM accumulation amount deviates to the minus side with respect to the actual PM accumulation amount, there is a concern that the DPF unit may be overheated or overheated.

  In particular, in environments where there is a strong tendency for actual PM emissions to increase due to the use of poor fuel, the PM accumulation amount was interpolated from the engine operating conditions only when the detection accuracy of the differential pressure across the DPF decreased. However, when the traveling pattern in which the differential pressure across the DPF cannot be accurately obtained continues, there is a possibility that the DPF unit may be damaged due to overheating or overheating.

  Therefore, the present invention prevents the PM unit from being over-deposited when the operation state in which the PM accumulation amount cannot be estimated from the differential pressure across the filter continues for a long time, and prevents the filter unit from being overheated or overheated. An object of the present invention is to provide a PM accumulation amount estimation device and an exhaust purification system for an internal combustion engine that can be reliably prevented.

PM accumulation amount estimating apparatus according to the present invention, for this purpose achieved, a PM accumulation amount estimation device for estimating the PM deposition amount in (1) in the filter unit for exhaust gas purification of an internal combustion engine, detected by the sensor first a first estimation processing of calculating the estimated value, given the PM accumulation amount based on the operating conditions within the combustion engine corresponding to the PM accumulation amount based on the differential pressure of the filter unit which is A second estimation process for calculating an increase amount for each time and adding the change amount to the calculated first estimated value to calculate a second estimated value corresponding to the PM deposition amount ; The PM accumulation amount is repeatedly calculated while switching depending on whether or not a specific condition for adopting the first estimation process is established , and the establishment frequency of the specific condition for the first estimation process is preset. Correction request frequency or less Whether there is determined in a predetermined determination period, increasing the second estimate as compared to when the established frequency exceeds the correction request frequency when said established frequency is lowered below the correction request frequency correction It is characterized by doing.

With this configuration, the establishment of the specific condition is periodically checked, the first estimation value is calculated by the first estimation process when the specific condition is established, and the second estimation process is performed when the specific condition is not established. A second estimated value is calculated. When the second estimated value is calculated, it is determined whether or not the adoption frequency of the first estimation process, which is the frequency of establishment of the specific condition , is equal to or less than a preset correction request frequency. Is decreased below the correction request frequency, the second estimated value is corrected to increase. Therefore, it is effectively suppressed that the estimated value of the PM accumulation amount deviates to the minus side with respect to the actual PM accumulation amount, and damage due to overheating or overheating of the filter unit due to over-deposition of PM is prevented in advance. It will be.

In the PM accumulation amount estimation apparatus according to the present invention, (2) when the establishment frequency is reduced to be equal to or less than the correction request frequency , the second frequency is determined according to a reduction amount of the establishment frequency from the correction request frequency. You may make it carry out increase correction | amendment of the increase amount for every predetermined time of the said PM accumulation amount in an estimated value .

In this case, even if the estimated value of P M deposit amount deviates to the positive side with respect to the actual PM accumulated amount, by increasing the estimate of the filter unit before the estimation error becomes excessively large It becomes possible to prompt the reproduction processing and the like.

In the PM accumulation amount estimation apparatus according to the present invention, (3) when the second estimated value is increased and corrected, the increase amount of the PM accumulation amount per predetermined time is increased and corrected using a correction coefficient, and the correction coefficient May be set to a larger value as the establishment frequency of the first estimation process equal to or less than the correction request frequency decreases.

  In this case, it is possible to more accurately prevent the estimated value of the PM accumulation amount from greatly deviating to the minus side with respect to the actual PM accumulation amount, and the estimated value of the PM accumulation amount to be on the plus side with respect to the actual PM accumulation amount. Even when there is a divergence, the filter unit regeneration process or the like can be accurately promoted before the estimation error becomes large.

  In the PM accumulation amount estimation apparatus of the present invention, (4) the specific condition may include a condition that a flow rate of exhaust gas passing through the filter unit is equal to or higher than a preset threshold flow rate.

  In this case, the estimation accuracy of the PM accumulation amount in the filter unit based on the detected differential pressure of the differential pressure sensor is increased.

  An exhaust gas purification system for an internal combustion engine according to the present invention is (5) an exhaust gas purification system for an internal combustion engine provided with a PM accumulation amount estimation device having any one of the above configurations (1) to (4), A filter unit, the differential pressure sensor or the pressure sensor, and a regeneration processing mechanism that regenerates the filter unit based on an estimation result of the PM accumulation amount estimation device.

  With this configuration, when the second estimated value is calculated in the second estimation process, it is determined whether or not the adoption frequency of the first estimation process is equal to or less than the correction request frequency, and the adoption frequency is the correction request frequency. When it decreases below, the second estimated value is corrected to increase. Therefore, when the estimated value of the PM accumulation amount causes a minus side error with respect to the actual PM accumulation amount, the filter unit is prevented from being overheated or damaged due to overheating, and the estimated value of the PM accumulation amount. However, when an error on the positive side with respect to the actual PM accumulation amount occurs, the regeneration processing of the filter unit by the regeneration processing mechanism can be executed without excessively increasing the error.

  In the exhaust gas purification system for an internal combustion engine of the present invention, (6) the filter unit includes a diesel particulate filter, and the regeneration processing mechanism oxidizes the PM deposited in the filter unit. May be executed.

  In this case, even if bad fuel is used in the diesel engine, it is possible to effectively prevent the filter unit from being overheated or overheated due to excessive PM deposition.

  According to the present invention, when the frequency of adopting the first estimation process is equal to or less than the correction request frequency, the second estimated value is increased and corrected. Therefore, the estimated value of the PM accumulation amount is smaller than the actual PM accumulation amount. It is possible to provide a PM accumulation amount estimation device and an internal combustion engine exhaust purification system that can suppress the occurrence of excessive PM accumulation due to the deviation and prevent the filter unit from being damaged due to excessive temperature rise or overheating. .

1 is a schematic configuration diagram of an exhaust purification system for an internal combustion engine including a PM accumulation amount estimation device according to an embodiment of the present invention. It is explanatory drawing of the one-dimensional correction coefficient map for the increase correction used with PM deposition amount estimation apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the general | schematic procedure of the calculation process of the DPF front-back differential pressure value performed with PM deposition amount estimation apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the schematic procedure of the calculation process of the DPF front-back differential pressure utilization permission frequency performed with PM deposition amount estimation apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the schematic procedure of the 1st and 2nd estimation process performed with PM deposition amount estimation apparatus which concerns on one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(One embodiment)
1 to 5 are views showing a PM accumulation amount estimation device and an exhaust purification system for an internal combustion engine equipped with the same device according to an embodiment of the present invention. In the present embodiment, the present invention is applied to a diesel engine (hereinafter simply referred to as an engine) as a multi-cylinder internal combustion engine including a filter unit with a differential pressure sensor.

  First, the configuration will be described.

  The engine 10 of this embodiment shown in FIG. 1 has a plurality of, for example, four cylinders 11. The engine 10 includes a common rail type fuel having an intake device 14 that draws air into a combustion chamber (not shown) in each cylinder 11 through an intake passage 13 and a fuel injection nozzle 15a that injects fuel (for example, light oil) into the combustion chamber. An injection device 15 and an exhaust device 17 for exhausting exhaust gas from the combustion chamber to the outside are provided. Although not shown, the engine 10 includes an EGR device (exhaust gas recirculation mechanism) that recirculates and recirculates a part of the exhaust gas to the intake side, and the exhaust energy in the exhaust device 17 in the intake device 14. And an exhaust turbo supercharger that supercharges the air into the combustion chambers in the cylinders 11 of the engine 10. Further, the engine 10 includes an intake valve that opens when air is sucked into the combustion chamber through the intake passage 13, an exhaust valve that opens when exhaust gas from the combustion chamber is discharged to the exhaust device 17 side, A valve operating mechanism that opens and closes the intake valve and the exhaust valve according to the rotation angle of the crankshaft is provided.

  The intake device 14 has an intake manifold 14a and an intake pipe 14b on the upstream side thereof. Although not shown in detail, the intake device 14 further rises by supercharging in an air cleaner that cleans intake air by a filter upstream of the intake pipe 14b and an intake passage downstream of the compressor of the exhaust turbocharger. An intercooler that cools the warm intake air and a diesel throttle opening control actuator that can adjust the intake flow rate into the engine 10 are provided. These configurations are the same as those known.

  The fuel injection device 15 includes a low-pressure fuel pump that pumps fuel from a fuel tank (not shown), a high-pressure fuel pump 46 that pressurizes and discharges fuel from the low-pressure pump to a high-pressure fuel pressure (fuel pressure), and the high-pressure fuel pump. 46 and a common rail 45 into which fuel from 46 is introduced.

  The fuel injection nozzle 15a of the fuel injection device 15 is composed of, for example, an electromagnetically driven needle valve. Fuel (for example, light oil) supplied through the common rail 45 is supplied from an electronic control unit (hereinafter referred to as ECU) 50 described later. The fuel is injected into the combustion chamber at a timing and an injection period corresponding to the injection command signal.

  An air flow meter 48 (flow rate sensor) that detects the amount of fresh intake air is provided upstream of the intake device 14, and a fuel pressure sensor 49 that detects the fuel pressure inside the common rail 45 is mounted. ing.

  Each combustion chamber is formed inside each cylinder 11 above the piston, and the volume of the combustion chamber changes as the piston reciprocates, and the crankshaft rotates. The rotation angle position of the crankshaft is detected by a crank angle sensor 23, and the accelerator opening, which is a depression rate of an accelerator pedal (not shown), is detected by an accelerator opening sensor 24.

  The exhaust device 17 includes an exhaust manifold 38, an exhaust pipe 31 that forms an exhaust passage 31a on the downstream side, a catalyst 32 and a DPF unit 33 (filter unit) mounted on the exhaust pipe 31. And a purification unit 40.

  In FIG. 1, the detailed cross-sectional structure is not shown, and only the arrangement relationship in the exhaust passage direction is schematically shown. However, the DPF unit 33 is formed by alternately plugging the entrances and exits of the porous ceramic substrate, for example. The exhaust gas of the engine 10 is configured to flow through the wall of the base material that forms each passage to the downstream side that exits from the adjacent passage, and is included in the exhaust of the engine 10, For example, it has a function of collecting soot (SOOT) or the like in the substrate.

The catalyst 32 generates, for example, nitrogen dioxide (NO ₂ ) that oxidizes nitrogen monoxide (NO) in the exhaust gas of the engine 10 to burn PM at low temperature, or unburned hydrocarbon (HC) in the exhaust gas, It is an oxidation catalyst comprising a noble metal catalyst capable of oxidizing and purifying carbon monoxide (CO). The catalyst 32 raises the exhaust gas temperature by an oxidation reaction when the amount of HC in the exhaust gas is increased by fuel addition, which will be described later, and raises the temperature of the DPF unit 33 to a temperature higher than the self-combustion temperature of PM. Can be done.

  The porous ceramic substrate of the DPF unit 33 carries a noble metal catalyst dispersed on at least the inner wall surface of the exhaust passage, and the DPF unit 33 is porous in the vicinity of the noble metal catalyst. PM deposited on the inner wall surface of the ceramic substrate can be continuously oxidized and removed even at a low temperature lower than the self-combustion temperature.

Of course, the exhaust purification unit 40 may have any other configuration including a particulate (particulate) filter such as the DPF unit 33. For example, a NOx occlusion / reduction type catalyst including a noble metal catalyst and a NOx occlusion material is supported on the porous ceramic base material of the DPF unit 33 so that the air-fuel ratio of the exhaust gas introduced into the exhaust purification unit 40 is lean. During normal operation in an (oxidizing atmosphere), NOx (NO ₂ or NO) is occluded, while the air-fuel ratio of the exhaust gas introduced into the exhaust purification unit 40 becomes richer than the stoichiometric air-fuel ratio (reducing atmosphere). Sometimes, NOx stored in the NOx storage material can be reduced and released.

  The exhaust device 17 further opens and closes in response to a fuel addition command signal from the ECU 50, and a fuel addition valve 39 that can inject a part of the fuel pumped up by the low-pressure fuel pump into the exhaust manifold 38 or the exhaust pipe 31. Is attached.

  This fuel addition valve 39 has a built-in electromagnetic valve that opens and closes in response to a fuel addition command signal from the ECU 50, and the fuel supplied from the low-pressure fuel pump is fixed at an injection timing corresponding to the command signal from the ECU 50. It can be injected at an injection rate. Further, the fuel addition valve 39 is configured to inject the added fuel in the exhaust stroke of a specific cylinder 11 of the engine 10, for example, the fourth cylinder.

  When fuel addition by the fuel addition valve 39 is selectively executed and unburned fuel is introduced into the exhaust gas of the engine 10, the unburned fuel in the exhaust gas is oxidized by the catalyst 32 according to the amount of the fuel added. As a result of the reaction, the exhaust temperature rises to, for example, the self-combustion temperature of PM, and the regeneration process is performed in which the temperature inside the DPF unit 33 enters the ceramic base material of the DPF unit 33 and removes the collected PM, for example. It is like that.

  That is, the fuel addition valve 39 and the ECU 50 function as a regeneration processing mechanism that removes PM by raising the internal temperature of the DPF unit 33 to a regeneration processing temperature higher than the self-combustion temperature of PM (for example, about 600 degrees Celsius). It is like that. Further, the ECU 50 can switch the regeneration processing temperature between the low temperature regeneration processing temperature and the high temperature regeneration processing temperature by controlling the amount of fuel at the time of fuel addition by the fuel addition valve 39.

  The regeneration process of the DPF unit 33 can also be executed by switching control of the fuel injection condition of the engine 10 by the ECU 50. The switching control of the fuel injection condition means that the fuel injection device is provided on the condition that the amount of accumulated PM collected in the DPF unit 33 becomes a predetermined amount or more, in addition to executing the fuel addition by the fuel addition valve 39. 15 is to perform post injection into the combustion chamber, or to perform after injection or rich fuel injection, and at least one of these fuel injections is executed, whereby the exhaust temperature of the engine 10 is raised. . Therefore, at least one of the fuel addition valve 39 and the fuel injection device 15 and the ECU 50 may constitute a regeneration processing mechanism.

  The exhaust purification unit 40 is equipped with a differential pressure sensor 34 that detects a differential pressure between the upstream side and the downstream side of the catalyst 32 and the DPF unit 33, that is, a differential pressure across the gas passing through the catalyst 32 and the DPF unit 33. In addition, a temperature sensor 42 for detecting the temperature inside the DPF unit 33 is mounted. In the following description, the catalyst 32 and the DPF unit 33 of the exhaust purification unit 40 are simply referred to as the DPF unit 33.

  The differential pressure sensor 34 introduces a gas pressure on the inlet side (upstream side) of the DPF unit 33 and a gas pressure on the outlet side (downstream side) of the DPF unit 33. The upstream and downstream gas pressures from the second gas pressure introduction pipe part 34b and the first and second gas pressure introduction pipe parts 34a and 34b are received, and a front-rear differential pressure that is the difference between these pressures is detected. And a sensor main body 34c.

  Instead of the differential pressure sensor 34, upstream and downstream absolute pressure sensors (pressure sensors) for detecting gas pressure are provided on the upstream side and downstream side of the DPF unit 33, respectively, and the ECU 50 detects both absolute pressure sensors. You may make it grasp | ascertain the differential pressure | voltage calculated as a difference of a value. Also, an absolute pressure sensor that detects the gas pressure at the installation position is installed only on the upstream side of the DPF unit 33, and the ECU 50 estimates the gas pressure downstream of the DPF unit 33 using the atmospheric pressure as a parameter. The differential pressure calculated by the ECU 50 as the difference between the detected value of the upstream gas pressure and the estimated value of the downstream gas pressure may be grasped.

  The fuel addition by the fuel addition valve 39, the fuel injection condition switching control of the engine 10, the energization control of the low-pressure fuel pump, the fuel injection control by the fuel injection nozzle 15a, the diesel throttle opening control, the EGR valve opening control, etc. , Executed by the ECU 50.

  Although the specific hardware configuration is not illustrated, the ECU 50 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a backup RAM (may be a non-volatile memory). An input interface circuit including an A / D converter, a buffer, and the like, and an output interface circuit including a drive circuit for actuators and the like are included.

  In addition to the crank angle sensor 23, the accelerator opening sensor 24, the differential pressure sensor 34, the temperature sensor 42, the air flow meter 48, and the fuel pressure sensor 49, the input interface circuit of the ECU 50 includes lubricating oil in the engine 10 inside. An oil temperature sensor 26 that detects the temperature, a water temperature sensor 27 that detects the temperature of the cooling water of the engine 10, and the like are connected. The output interface circuit of the ECU 50 is connected to actuators such as a fuel addition valve 39, a low pressure fuel pump, a fuel injection nozzle 15a, a diesel throttle valve, and an EGR valve.

  The ECU 50 executes a control program stored in advance in the ROM, and based on various sensor information, setting information stored in the backup memory, etc. The processing function can be demonstrated.

  The ECU 50 is functionally configured to include a first estimation processing unit 51, a second estimation processing unit 52, and a regeneration time determination processing unit 53.

When the differential pressure utilization condition described later is satisfied, the first estimation processing unit 51 determines the DPF based on the detected differential pressure of the differential pressure sensor 34, the detected temperature of the temperature sensor 42, and the detected intake air amount of the air flow meter 48. A first accumulation amount estimation process for calculating a DPF differential pressure value dp corresponding to the estimated value of the PM accumulation amount in the unit 33 is executed. Here, DPF differential pressure dp in the but it may also be estimated value of the PM accumulation amount in the DPF unit 33. Estimates or DPF differential pressure dp corresponding to that of the PM accumulation amount calculated by the first estimation processor 51 This refers to the first estimate.

The second estimation processing unit 52 performs a second accumulation amount estimation process for estimating the PM accumulation amount in the DPF unit 33 based on at least the operating condition of the engine 10 when the differential pressure utilization condition described later is not satisfied. It has become. Further, the second estimation processing unit 52 integrates the estimated value of the PM discharge amount during a period when the differential pressure utilization condition is not satisfied, and adds the estimated value of the PM deposition amount pmdp before that period to thereby add the current PM deposition amount pmdp. Estimated. Further, the second estimation processing unit 52 performs a reverse calculation of the DPF differential pressure value dp2 based on the estimated PM deposition amount pmdp, and the first estimation processing unit 51 calculates the DPF differential pressure value dp1. It is determined whether or not the adoption frequency (the establishment frequency of the specific condition) is equal to or less than a preset correction request frequency thf. When the frequency of adoption of the first estimation process is reduced below the correction request frequency thf, the current PM accumulation amount pmdp is increased and corrected by a correction process described later. Note that the PM accumulation amount is calculated by the second estimation processor 52 Pmdp or DPF differential pressure dp, referred to as a second estimate.

  The regeneration time determination processing unit 53 selects either the first estimation processing unit 51 or the second estimation processing unit 52 depending on whether or not the differential pressure utilization condition is satisfied, and estimates the PM accumulation amount in the DPF unit 33, respectively. The possible first estimation process and second estimation process are selectively executed to calculate the DPF differential pressure value dp corresponding to the estimated value of the PM accumulation amount in the DPF unit 33. Then, the regeneration timing determination processing unit 53 determines whether or not the regeneration process in the DPF unit 33 is necessary by determining whether or not the DPF differential pressure value dp reaches a preset regeneration request accumulation amount every predetermined time. It is supposed to be.

  More specifically, the ECU 50 determines the operating state of the engine 10 by repeatedly determining whether or not a preset differential pressure utilization condition is satisfied by a function of the regeneration timing determination processing unit 53 at a predetermined calculation cycle. It is determined whether or not the detected differential pressure dpsen of the differential pressure sensor 34 can be acquired with the required detection accuracy.

  The differential pressure utilization condition here is a specific condition for adopting the detected differential pressure dpsen of the differential pressure sensor 34 as the differential pressure across the DPF, and allows the first estimation process with the required estimation accuracy and reliability. The following conditions are satisfied, including the following plurality of employment conditions C1-C7. Further, the ECU 50 grasps the differential pressure utilization permission condition as dpuse, and determines that dpuse = ON when all of the employment conditions C1-C7 are satisfied, and determines dpuse = OFF when other conditions are not satisfied. .

C1: When the intake air amount is greater than or equal to a predetermined value (when the flow rate of exhaust gas passing through the DPF unit 33 is greater than or equal to a preset threshold flow rate)
C2: When the amount of change in the DPF differential pressure is less than or equal to a predetermined value C3: When the exhaust gas temperature is greater than or equal to a predetermined value C4: When there is no effect of increasing the differential pressure due to entering catalyst water C5: When the related parts are not abnormal i) DPF When the differential pressure is not abnormal
ii) When PM combustion control is not impossible
iii) When the differential pressure sensor or absolute pressure sensor (differential pressure detector) is not abnormal
iv) When the air flow meter (intake flow rate detector) is not abnormal v) When the exhaust temperature sensor is not abnormal
vi) When the fuel addition valve is not abnormal C6: When fuel addition control is not performed, or when post injection control is not performed C7: When zero-point learning of the differential pressure sensor is completed The ECU 50 uses the differential pressure When the condition dpuse is satisfied (when dpuse = ON), the detection difference of the differential pressure sensor 34 is used as a DPF differential pressure value for determining the necessity of regeneration processing in the DPF unit 33 by the function of the first estimation processing unit 51. The first estimation process described below is executed using the pressure.

  In the first estimation process, the ECU 50 determines the regeneration request corresponding to the regeneration processing request time when the PM accumulation amount pmdp in the DPF unit 33 removes the PM based on the detected differential pressure dpsen of the differential pressure sensor 34. Whether or not the deposition amount is reached is determined every predetermined time.

  The ECU 50 first converts, for example, the detected differential pressure dpsen of the differential pressure sensor 34 into the DPF differential pressure value dp1 in the reference state using the following equation [1].

dp1 = dpsen / (Ga × (T / 573)) (1)
Here, T [K] is a temperature value representing the temperature detected by the temperature sensor 42 in Kelvin, and Ga is an intake air flow rate [g / s].

  In this case, the detected differential pressure dpsen of the differential pressure sensor 34 is obtained by replacing the current intake air amount Ga with a flow rate when the internal temperature of the filter, which is a typical state during normal operation of the engine 10, is 300 degrees Celsius. Is replaced with a regeneration request determination DPF differential pressure value dp1 corresponding to the detected differential pressure per unit flow rate. Thus, the DPF differential pressure value dp accurately reflects the influence of the PM accumulation amount in the DPF unit 33 from which the fluctuation component of the detected differential pressure of the differential pressure sensor 34 due to the change in the operating state of the engine 10 is removed.

  In this way, the ECU 50 detects the detected differential pressure dpsen, which fluctuates due to the intake air amount Ga (corresponding exhaust gas flow rate) and the filter internal temperature T, which change every moment during the operation of the engine 10, in the reference state. The current PM accumulation amount that can be compared with the regeneration required differential pressure value dpth (determination differential pressure at the start time of regeneration processing) corresponding to the regeneration required accumulation amount in the reference state by converting to the DPF differential pressure value dp1 of The differential pressure value dp corresponding to is calculated.

  Further, when the calculated DPF differential pressure value dp1 reaches the regeneration required differential pressure value dpth, the ECU 50 determines that the PM accumulation amount in the DPF unit 33 has reached the regeneration required accumulation amount, and uses the fuel addition valve 39. The execution timing of fuel addition and the injection amount are calculated, and a fuel addition command signal corresponding to the calculation result is output to the solenoid valve portion of the fuel injection nozzle 15a to execute the regeneration process of the DPF unit 33. ing.

Further, the ECU 50 estimates the remaining amount of ash in the DPF unit 33 based on at least the detected differential pressure dpsen of the differential pressure sensor 34 when the high temperature regeneration process ends (based on the ash amount in the multiple times of high temperature regeneration processes). The above-mentioned regeneration required differential pressure value dpth can be corrected based on the estimated ash amount that is the estimated value. The ash here is a powdery substance that does not burn at the regeneration processing temperature of the DPF unit 33 and tends to remain in the DPF unit 33, and is mainly calcium (Ca) contained in the lubricating oil in the exhaust gas. The component is composed of calcium sulfate (CaSO ₄ ) or the like produced by combining the component and the sulfur (S) component in the fuel adsorbed together with PM on the DPF filter. For calculating the estimated ash amount, any conventional ash amount estimation method can be used.

  On the other hand, when the differential pressure utilization condition dpuse is not satisfied (when dpuse = OFF), the ECU 50 detects the differential pressure detected by the differential pressure sensor 34 as a DPF differential pressure value for determining whether or not the regeneration process in the DPF unit 33 is necessary. The second estimation processing by the second estimation processing unit 52 is executed without directly using.

  In this case, the second estimation processing unit 52 of the ECU 50, for example, based on the required load of the engine 10 or the engine rotation speed, increases the PM discharge amount per predetermined time that increases as the load on the engine 10 increases and the engine rotation speed increases. Is estimated with reference to the PM emission amount map M1. Further, the second estimation processing unit 52 subtracts the amount of PM in the DPF unit 33 that is continuously oxidized and removed by the aforementioned catalyst from the estimated PM emission amount, and calculates the added value of the PM accumulation amount, This calculated value is added to the previously calculated PM deposition amount to calculate the current PM deposition amount pmdp. As a result, the second estimation processing unit 52 accumulates the PM discharge amount during a period in which the differential pressure utilization condition dpuse is not established, and immediately before this differential pressure utilization condition unsatisfied period (differential pressure utilization non-permission period). The current PM accumulation amount pmdp can be estimated by adding the integrated value of the PM discharge amount to the PM accumulation amount.

  Further, the ECU 50 refers to the calculated current PM accumulation amount pmdp and the two-dimensional map M2 that associates the relationship between the estimated Ash amount and the DPF differential pressure value, and corresponds to the estimated value of the current PM accumulation amount pmdp. The differential pressure value dpmap to be calculated is calculated as the DPF differential pressure value dp2. That is, the ECU 50 integrates the PM emission amount per predetermined time based on the operating condition of the engine 10 under the operating condition in which the differential pressure utilization permission condition dpuse is not established, and calculates the latest DPF calculated in the differential pressure utilization permission period. By adding to the differential pressure value dp1 (first estimated value), a DPF differential pressure value dp2 (second estimated value) that interpolates the DPF differential pressure value dp1 in the preceding and following periods is calculated.

  Note that the two-dimensional map Mp for calculating the differential pressure is based on the previous experimental results in the engine 10, and the PM accumulation amount pmdp and the estimated Ash amount in each operation state and before and after the DPF detected by the differential pressure sensor 34 in that state The relationship with the differential pressure is associated, and the current DPF differential pressure value can be calculated backward based on the current PM deposition amount pmdp and the estimated Ash amount.

  By the way, if the operation condition with low detection accuracy of the detected differential pressure dpsen of the differential pressure sensor 34 continues for a long time, the second estimation processing unit 52 repeatedly calculates the DPF differential pressure value dp2 as the second estimated value. Therefore, the PM accumulated amount estimation error is accumulated until the DPF differential pressure value dp1 based on the detected differential pressure dpsen of the differential pressure sensor 34 becomes reliable again, and the PM accumulated amount pmdp deviates from the actual PM accumulated amount. there's a possibility that.

  Therefore, in the present embodiment, it is determined whether or not the differential pressure utilization condition dpuse is established so low that the ECU 50 can determine that the PM accumulation amount calculated based on the DPF differential pressure value dp2 can no longer reflect the actual PM accumulation amount. In the second accumulation amount estimation process for calculating the DPF differential pressure value dp2 based on the operating state of the engine 10, when the establishment frequency is equal to or less than the predetermined value, the addition value dlpm of the PM accumulation amount per predetermined time is calculated. The amount of increase is corrected.

  The increase correction here is a process of multiplying the added value dlpm of the PM accumulation amount every predetermined time by a correction coefficient mpm corresponding to the variation of the PM emission amount considered from the configuration of the engine 10. Further, the correction coefficient mpm is calculated with reference to a one-dimensional correction coefficient map M3 as shown in FIG. 2 based on a calculated value dpfrq (adopting frequency of the first estimation process) of the establishment frequency of the differential pressure utilization condition dpuse. -One or more coefficients set.

  As shown in FIG. 2, the correction coefficient mpm is set to a larger coefficient value as the adoption frequency dpfrq of the first estimation process becomes smaller within the range of the correction request frequency thf or less, and within the range exceeding the correction request frequency thf. Is set to a fixed value.

  In this way, the ECU 50 multiplies the PM accumulation amount addition value dlpm for each predetermined time by the correction coefficient mpm to estimate the PM accumulation amount addition value dlpm, which is the estimated PM discharge amount for each predetermined time, to be large. When the operation state in which the PM accumulation amount cannot be accurately estimated from the differential pressure detected by the differential pressure sensor 34 continues for a long time, the PM over-deposition state is prevented in advance. That is, the state in which the actual PM deposition amount in the DPF unit 33 becomes larger than the estimated PM deposition amount pmdp (pmdp (i) = pmdp (i−1) + dlpm × mpm) continues, It is possible to prevent the deposition state. Here, i is an integer indicating the number of executions of the process.

  Next, a differential pressure calculation process executed by the ECU 50, a differential pressure utilization permission frequency calculation process, an estimated PM emission amount calculation based on the operating conditions of the engine 10, and an estimated PM accumulation amount interpolation process will be described. To do.

  The differential pressure calculation process executed by the ECU 50 is repeatedly executed every predetermined time in the procedure as shown in FIG.

  As shown in FIG. 3, in this differential pressure calculation process, first, it is determined whether or not the differential pressure utilization permission condition dpuse is ON (step S11). If the differential pressure utilization condition dpuse is satisfied (YES in step S11). ), The detected differential pressure dpsen of the differential pressure sensor 34 is adopted as the DPF differential pressure value dp1 (step S12).

  On the other hand, if the differential pressure utilization condition dpuse is not satisfied (NO in step S11), the DPF differential pressure value dpmap calculated from the two-dimensional map M2 based on the current PM deposition amount pmdp and the estimated Ash amount is the DPF differential pressure value. Adopted as dp2 (step S13).

  The calculation process of the differential pressure utilization permission frequency executed by the ECU 50 is repeatedly executed at predetermined time intervals in a procedure as shown in FIG.

  As shown in FIG. 4, in the calculation process of the differential pressure utilization permission frequency, first, a known engine stall determination process (for example, a process for determining that the rotation of the engine 10 has stopped while the engine switch is in the ON position). ) Is outside the period of execution.

  At this time, if it is outside the period of the engine stall determination process (in a state where the engine 10 is not stopped) (YES in step S21), then the count value tim (i) of the counter for calculating the differential pressure utilization permission frequency Is incremented to a value obtained by adding a calculation cycle that is a cycle of the differential pressure utilization permission frequency calculation process to the immediately preceding count value tim (i−1), for example (step S22).

  Next, it is determined whether or not the differential pressure utilization permission condition dpuse is ON (step S23). At this time, the count value dptim (i) of the differential pressure utilization permission time counter that counts the differential pressure utilization permission time is, for example, changed to the immediately preceding count value dptim (i-1) in the period of the differential pressure utilization permission frequency calculation process. The value is incremented to a value obtained by adding a certain calculation cycle (step S24).

  Next, in order to calculate the differential pressure utilization permission frequency for each predetermined time, first, the count value dptim (i) (hereinafter referred to as dpim) of the differential pressure utilization permission time counter exceeds a predetermined value corresponding to the predetermined time. Is determined (step S25).

  This determination step S25 is also performed in each determination step when the differential pressure utilization condition dpuse is not satisfied in step S22 (in the case of NO) or in the period of the engine stall determination process in step S21 (in the case of NO). It is then executed.

  If the count value dptim of the differential pressure utilization permission time counter exceeds a predetermined value, the differential pressure utilization permission time counter has reached the count value tim corresponding to the predetermined time. In this case, the differential pressure utilization permission frequency dpfrq is then calculated by dividing the count value dptim of the differential pressure utilization permission time counter by the count value tim for a predetermined time (step S26).

  Next, the count values dptim and tim of each counter are cleared for calculation of the next differential pressure utilization permission frequency dpfrq (step S26).

  The calculation process of the estimated PM emission amount and the interpolation process of the estimated PM accumulation amount based on the operating condition of the engine 10 executed by the ECU 50 are repeatedly executed at predetermined time intervals in the procedure as shown in FIG.

  As shown in FIG. 5, in the calculation of the PM emission amount and the interpolation process of the PM accumulation amount, first, as the load on the engine 10 increases and the engine rotation speed increases based on the required load of the engine 10 and the engine rotation speed. An increasing PM emission amount engpm (an amount corresponding to an increase amount of the PM accumulation amount per predetermined time) is calculated with reference to the PM emission amount map M1. Further, an addition value dlpm of the PM deposition amount is calculated by subtracting the oxidation removal amount pmburn from which the PM in the DPF unit 33 is continuously oxidized and removed by the catalyst 32 from the estimated PM discharge amount engpm (step S31). .

  Next, the DPF differential pressure reference permission flag dpflg for switching the calculation processing of the two types of PM accumulation amount pmdp, which is the first and second accumulation amount estimation processing, depending on whether or not the differential pressure utilization condition dpuse is satisfied, 1 ", that is, whether or not it is ON is determined (step S32).

  At this time, if the DPF differential pressure reference permission flag dpflg is “1” (in the case of YES in step S32), then it is determined whether it is not when PM regeneration processing is requested (it is outside PM regeneration processing request time). (Step S33).

  If the PM regeneration process is not requested (YES in step S33), then, based on the calculated value dpfrq of the establishment frequency of the differential pressure utilization condition dpuse, from the differential pressure utilization permission frequency one-dimensional correction coefficient map M3 The correction coefficient mpm is calculated and set (step S34).

  If the DPF differential pressure reference permission flag dpflg is “0” in determination step S32, that is, if it is OFF, the differential pressure utilization condition dpuse is not satisfied, and the DPF difference as a result of the first accumulation amount estimation process The pressure value dp1 is not input as the DPF differential pressure value dp. That is, it becomes a differential pressure utilization non-permission state.

  When the differential pressure utilization disapproval state is entered in the determination step S32 (in the case of NO), the correction coefficient mpm is set to a predetermined fixed value, for example 1, without considering the calculated value dpfrq of the establishment frequency of the differential pressure utilization condition dpuse. It is set (step S35). Further, when it is determined in step S33 that the PM regeneration process is not requested (NO), that is, when the PM regeneration process is requested, the calculated value of the establishment frequency of the differential pressure utilization condition dpuse is also obtained. The correction coefficient mpm is set to a predetermined fixed value, for example, 1 without considering dpfrq (step S35).

  When the correction coefficient mpm is calculated, it is then determined whether or not the differential pressure utilization permission condition dpuse is ON (step S36).

  At this time, if the differential pressure utilization permission condition dpuse = ON (YES in step S36), then, whether or not the differential pressure utilization permission frequency dpfrq exceeds the correction request frequency thf, or the differential pressure utilization permission frequency dpfrq. Is determined to be less than or equal to the correction request frequency thf (step S37).

  If the differential pressure utilization permission frequency dpfrq exceeds the correction request frequency thf (in the case of YES in step S37), the DPF differential pressure value dp1 corresponding to the detected differential pressure dpsen of the differential pressure sensor 34 and the above-described estimated Ash amount Based on the above, the current PM deposition amount pmdp (i) is calculated with reference to the two-dimensional map M2 or an equivalent deposition amount estimation map (step S38; first estimation process).

  On the other hand, when the differential pressure utilization permission condition dpuse = OFF in step S36 (in the case of NO), and in the case where the differential pressure utilization permission frequency dpfrq is equal to or less than the correction request frequency thf in step S37 (in the case of NO). The increase correction using the correction coefficient mpm is performed.

  That is, the PM accumulated amount addition value dlpm for each predetermined time is added to the previously calculated estimated PM accumulated amount value pmdp (i-1) to calculate the current estimated PM accumulated amount pmdp (i). At this time, a process of multiplying the addition value dlpm of the PM deposition amount per predetermined time by the correction coefficient mpm (a process of pmdp (i) = pmdp (i−1) + (dlpm × mpm)) is performed (step S39; Second estimation process).

  As described above, in the exhaust gas purification system for an internal combustion engine according to the present embodiment, when the error of the detected differential pressure dpsen of the differential pressure sensor 34 becomes large by the ECU 50 because the exhaust gas flow rate is small, the operating condition of the engine 10 is satisfied. Based on the differential pressure utilization non-permission period in which the normal first deposition amount estimation process cannot be executed because the increase amount dlpm of the PM deposition amount per predetermined time is calculated and the detected differential pressure dpsen of the differential pressure sensor 34 cannot be used. The amount of change in the PM accumulation amount is calculated and interpolated using the second accumulation amount estimation process. Based on this assumption, the control for periodically calculating the differential pressure utilization permission frequency dpfrq, which is the frequency at which the DPF differential pressure dpsen detected by the differential pressure sensor 34 can be trusted, and the differential pressure utilization permission frequency dpfrq are Control for multiplying the PM discharge amount (current value) per predetermined time by a correction coefficient mpm when the correction request frequency is equal to or less than a predetermined value, and control for variably setting the correction coefficient mpm according to the differential pressure utilization permission frequency dpfrq And is supposed to run.

In the case where an upstream and downstream absolute pressure sensor (pressure sensor) for detecting the gas pressure is provided in place of the differential pressure sensor 34 on the upstream side and downstream side of the DPF unit 33, the ECU 50 is provided with both absolute pressure sensors. A differential pressure detection unit having a function of calculating a detected differential pressure as a difference between the detected values is also provided. Further, a pressure sensor for detecting the gas pressure at the upstream position is provided only on the upstream side of the DPF unit 33, and the pressure of the gas on the downstream side of the DPF unit 33 is obtained by the ECU 50 by an estimation process using atmospheric pressure or the like as a parameter. In this case, the ECU 50 has a differential pressure detector that calculates a detected differential pressure as a difference between the detected value of the upstream gas pressure and the estimated value of the downstream gas pressure. Furthermore, the differential pressure sensor and pressure sensor referred to in the present invention are not limited to those having a pressure detection element that can directly detect the gas pressure, but indirectly determine the gas pressure from other detection values or estimated values. The ECU 50 and various sensors connected to the ECU 50 only need to be configured as such a differential pressure sensor or a differential pressure detection mechanism having a pressure sensor function. Therefore, in the first estimation processing unit 51, the differential pressure across the DPF detected indirectly by a pressure sensor or the like (differential pressure detection mechanism) instead of the differential pressure sensor 34, the detected temperature of the temperature sensor 42, and the detection of the air flow meter 48 Based on the intake air amount, the DPF differential pressure value dp corresponding to the PM accumulation amount in the DPF unit 33 may be calculated as the first estimated value.

  Next, the operation of this embodiment will be described.

  In the PM accumulation amount estimation device and the exhaust gas purification system for the internal combustion engine of the present embodiment configured as described above, the ECU 50 can estimate the PM accumulation amount in the DPF unit 33 in accordance with the operating conditions of the engine 10. This estimation process and the second estimation process are selectively employed to estimate the PM deposition amount.

  In the first estimation process, the DPF differential pressure value dp1 and the estimated PM deposition amount pmdp corresponding to the PM deposition amount in the DPF unit 33 based on the detected differential pressure dpsen of the differential pressure sensor 34 are used as the first estimation value. Calculated. In the second estimation process, the estimated PM accumulation amount pmdp and the DPF differential pressure value dp2 are calculated as the second estimated value based on the operating conditions of the engine 10, and the differential pressure utilization permission frequency dpfrq is set in advance. It is determined whether or not the correction request frequency thf is equal to or less than the correction request frequency thf. When the adoption frequency is reduced to the correction request frequency thf or less, the second estimated value dp2 is increased and corrected.

  Therefore, the operation state in which the differential pressure utilization permission condition C1-C7 is not satisfied continues, the error of the estimated PM accumulation amount pmdp calculated by interpolation based on the operation condition of the engine 10 is integrated, and the estimated PM accumulation amount pmdp becomes the actual PM. Deviation to the minus side with respect to the accumulation amount is effectively suppressed. As a result, it is possible to prevent the DPF unit 33 from being overheated or damaged due to overheating due to PM overdeposition.

  Further, in the present embodiment, it is determined whether or not the differential pressure utilization permission condition C1-C7 in which the first estimation process is adopted among the first and second estimation processes is satisfied, and based on the determination result. Thus, it is determined whether or not the differential pressure utilization permission frequency dpfrq is equal to or less than the correction request frequency thf. Therefore, whether or not the differential pressure utilization permission frequency dpfrq is equal to or less than the correction request frequency thf is periodically checked according to the establishment determination period of the differential pressure utilization permission frequency dpfrq, and the estimated PM accumulation amount pmdp Is reliably prevented from deviating greatly from the actual PM accumulation amount to the minus side.

  Further, even when the estimated PM accumulation amount pmdp deviates to the positive side with respect to the actual PM accumulation amount, the regeneration value of the DPF unit 33 is executed before the estimation error becomes excessive by increasing the estimated value. This makes it possible to shorten the operation period with a large estimation error.

  In addition, in the present embodiment, the correction coefficient mpm for increasing the second estimated value dp2 is set to a larger coefficient value as the differential pressure utilization permission frequency dpfrq becomes smaller within the range of the correction request frequency thf or less. Is done. Therefore, the estimated PM deposition amount pmdp is more accurately prevented from deviating greatly from the actual PM deposition amount to the minus side, and the estimated PM deposition amount pmdp is deviating from the actual PM deposition amount to the plus side. Even so, the regeneration processing of the DPF unit 33 and the like can be executed accurately at an early stage before the estimation error becomes large.

  In the present embodiment, the differential pressure utilization permission condition dpfrq includes the condition C1 that the flow rate of the exhaust gas passing through the DPF unit 33 is equal to or higher than a preset threshold flow rate. The estimation accuracy of the PM accumulation amount in the DPF unit 33 based on the above is sufficiently increased.

  As described above, in the exhaust gas purification system of the internal combustion engine of the present embodiment, when the estimated PM accumulation amount pmdp causes a minus side error with respect to the actual PM accumulation amount, the DPF unit 33 is overheated or overheated due to PM overdeposition. When the estimated PM accumulation amount pmdp causes an error on the plus side with respect to the actual PM accumulation amount, the regeneration process of the DPF unit 33 can be executed without excessively increasing the error.

  Further, in the exhaust purification system of the present embodiment, the DPF unit 33 includes a DPF filter, and the regeneration processing mechanism configured by the fuel addition valve 39 and the ECU 50 removes the PM accumulated in the DPF unit 33. Execute high temperature regeneration process to oxidize. Therefore, even if bad fuel is continuously used in the diesel engine, it is possible to effectively prevent the DPF unit 33 from being overheated or damaged due to overheating due to PM overdeposition.

  In the above-described embodiment, the differential pressure utilization permission frequency dpfrq is used as a frequency value within a predetermined time (all time) for each predetermined time corresponding to the repetition cycle of the operation using the differential pressure utilization permission time count dptim. Although calculated, the differential pressure utilization permission frequency dpfrq may be a frequency value within a part of the predetermined time corresponding to the calculation repetition cycle.

  In other words, the differential pressure utilization permission frequency dpfrq is not a frequency value for every predetermined time, but a specific time (for example, m seconds) immediately before the execution of the predetermined time corresponding to the repetition cycle (for example, N seconds) of the calculation; , M <N) may be obtained as a differential pressure utilization permission frequency (differential pressure utilization permission time within a specific time / specific time). For example, if the repetition cycle of the calculation is N seconds of about several seconds and the specific time immediately before the execution of the calculation is m seconds shorter than N seconds, the differential pressure utilization permission frequency (m You may obtain | require as differential pressure utilization permission time / m second) among seconds.

  In this case, the calculation period of the differential pressure utilization permission frequency dpfrq and the calculation cycle of the process using the same can be easily optimized, and the frequency value can be set to a value with high correction accuracy.

  In the above-described embodiment, the internal combustion engine is a diesel engine, and the filter unit includes a DPF filter. However, the PM accumulation amount estimation apparatus of the present invention is also applicable to an exhaust gas purification system for an internal combustion engine that uses another filter unit that collects PM (particulate matter, fine particles) and regenerates and removes it.

  Further, a process for calculating the PM emission amount engpm per predetermined time from the operating state of the engine 10, a process for calculating the increase amount dlpm of the PM deposition amount per predetermined time using the PM discharge amount dlpm per predetermined time, and the like. Needless to say, it can be replaced with a conventional processing method other than the above-described processing.

  As described above, according to the present invention, the PM accumulation due to the estimated PM accumulation amount pmdp deviating from the actual PM accumulation amount can be suppressed, and the DPF unit 33 is overheated or overheated. Damage can be prevented in advance. The present invention is useful for the PM accumulation amount estimation device for estimating the PM accumulation amount in the filter unit and the exhaust gas purification system for an internal combustion engine including the PM accumulation amount estimation device.

DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 11 ... Cylinder, 13 ... Intake passage, 15 ... Fuel injection device, 15a ... Fuel injection nozzle, 17 ... Exhaust device, 23 ... Crank angle sensor (engine speed sensor), 24 ... Accelerator opening Degree sensor, 26 ... Oil temperature sensor, 27 ... Water temperature sensor, 31 ... Exhaust pipe, 31a ... Exhaust passage, 32 ... Catalyst, 33 ... DPF unit (filter unit), 34 ... Differential pressure sensor (pressure sensor, differential pressure detection mechanism) ), 34a ... first gas pressure introduction pipe part, 34b ... second gas pressure introduction pipe part, 34c ... sensor body part, 38 ... exhaust manifold, 39 ... fuel addition valve (regeneration processing mechanism), 40 ... exhaust purification unit, 42 ... temperature sensor, 45 ... common rail, 46 ... high pressure fuel pump, 48 ... air flow meter, 49 ... fuel pressure sensor, 50 ... ECU (PM accumulation amount estimation device, re- Processing mechanism), 51 ... first estimation processing unit, 52 ... second estimation processing unit, 53 ... regeneration time determination processing unit, C1-C7 ... adopting condition (specific condition), dp1 ... DPF differential pressure value (first estimation) Value), dp2 ... DPF differential pressure value (second estimated value), dpflg ... differential pressure reference permission flag, dpfrq ... differential pressure utilization permission frequency (adopting frequency of the first estimation process), dptim ... differential pressure utilization permission time Counter, dpuse ... Differential pressure utilization permission condition (specific condition), engpm ... PM emission amount (amount corresponding to the increase amount of PM deposition amount per predetermined time), M1 ... PM emission amount map, M2 ... two-dimensional map, M3 ... one-dimensional correction coefficient map, mpm ... correction coefficient, pmburn ... oxidation removal amount, pmdp ... estimated value (estimated value of PM deposition amount), thf ... correction request frequency (predetermined value), tim ... differential pressure utilization permission frequency counter

Claims (6)

A PM deposition amount estimation device for estimating a PM deposition amount in a filter unit for exhaust gas purification of an internal combustion engine,
First and estimation processing of calculating a first estimation value corresponding to the PM accumulation amount based on the differential pressure of the filter unit which is detected by the sensor, on the basis of the operating condition of the internal combustion engine PM Second estimation processing for calculating an increase amount of the accumulation amount per predetermined time and adding the change amount to the calculated first estimation value to calculate a second estimation value corresponding to the PM accumulation amount And repeatedly calculating the PM deposition amount while switching depending on whether or not the specific condition for adopting the first estimation process is satisfied,
It is determined in a predetermined determination cycle whether the establishment frequency of the specific condition of the first estimation process is equal to or less than a preset correction request frequency,
The PM accumulation amount estimation apparatus characterized in that when the establishment frequency decreases below the correction request frequency, the second estimated value is increased and corrected as compared to when the establishment frequency exceeds the correction request frequency . When the establishment frequency decreases below the correction request frequency, an increase amount of the PM accumulation amount per predetermined time in the second estimated value according to a decrease amount of the establishment frequency from the correction request frequency The PM accumulation amount estimation apparatus according to claim 1, wherein the PM is increased and corrected . When the second estimated value is increased and corrected, the increase amount of the PM deposition amount per predetermined time is increased and corrected using a correction coefficient,
The PM accumulation amount estimation apparatus according to claim 2, wherein the correction coefficient is set to a larger value as the frequency of establishment of the first estimation process equal to or less than the correction request frequency decreases. The claim according to any one of claims 1 to 3 , wherein the specific condition includes a condition that a flow rate of exhaust gas passing through the filter unit is equal to or greater than a preset threshold flow rate. The PM accumulation amount estimation apparatus described. An exhaust gas purification system for an internal combustion engine comprising the PM accumulation amount estimation device according to any one of claims 1 to 4,
The filter unit;
The differential pressure sensor or pressure sensor;
An exhaust gas purification system for an internal combustion engine, comprising: a regeneration processing mechanism that regenerates the filter unit based on an estimation result of the PM accumulation amount estimation device. The filter unit includes a diesel particulate filter;
6. The exhaust gas purification system for an internal combustion engine according to claim 5, wherein the regeneration processing mechanism executes a regeneration process for oxidizing the PM accumulated in the filter unit.

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