JP2019085930A - Control device for internal combustion engine - Google Patents

Abstract

To provide a control device for an internal combustion engine capable of, even when exhaust pressure upstream of a filter becomes abnormally high pressure exceeding a measurable range of a pressure sensor, determining whether or not the exhaust pressure is abnormal.SOLUTION: An internal combustion engine 10 includes: a filter 18 provided in the middle of an exhaust pipe 16 and collecting particulates in exhaust gas; and a pressure sensor 50 for measuring exhaust pressure upstream of the filter 18. A control device 200 performs first estimation processing for estimating particulate accumulation amount of the filter 18 on the basis of a detection value obtained by the pressure sensor 50 and second estimation processing for estimating particulate accumulation amount of the filter 18 on the basis of an engine operating state. When the detection value obtained by the pressure sensor 50 reaches an upper limit value in a measurable range of the pressure sensor 50, the control device 200 performs processing for comparing the particulate accumulation amount estimated in the second estimation processing with a predetermined threshold value to determine whether or not the exhaust pressure is abnormal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device of an internal combustion engine.

  An internal combustion engine provided with a filter for collecting particles in exhaust gas in an exhaust passage is known (for example, Patent Document 1). In the exhaust passage of such an internal combustion engine, a pressure sensor for measuring the pressure in the exhaust passage is provided upstream of the filter. Then, the particle deposition amount of the filter is calculated based on the detection value of the pressure sensor, and when the calculated particle deposition amount reaches a threshold value, a regeneration process of burning and removing particles deposited on the filter is performed.

Unexamined-Japanese-Patent No. 2015-21455

  By the way, for example, when the particle deposition amount of the filter is increased beyond the above-mentioned threshold due to a state where the regeneration process can not be sufficiently performed, the exhaust pressure upstream of the filter becomes the above-mentioned threshold The pressure will rise above the pressure at which it is reached, and in some cases it may reach the pressure limit of exhaust system components.

  Therefore, exhaust system parts can be protected if the exhaust pressure upstream of the filter is subjected to a limiting process to limit the increase in the exhaust pressure before reaching the pressure limit. Here, in order to start the restriction process before the exhaust pressure reaches the pressure limit, it is desirable to start the restriction process when the exhaust pressure reaches a restriction start pressure set to a value lower than the pressure limit.

  However, if such a limit start pressure is higher than the measurable range of the pressure sensor, it can not be determined whether the exhaust pressure has reached the limit start pressure, so that exhaust system components can not be protected. Therefore, it is necessary to extend the measurable range of the pressure sensor to at least such a detectable range of the limiting start pressure.

  However, if the measurable range of the pressure sensor is expanded, the following disadvantages occur. That is, the change width of the output value of the pressure sensor according to the pressure change is limited. Therefore, if the measurable range of the pressure sensor is expanded, the change in the output value of the pressure sensor with respect to the pressure change becomes small, and it becomes difficult to capture a minute pressure change, so calculation is performed based on the detection value of the pressure sensor The accuracy of the particle deposition amount is reduced. Therefore, there is a limit to expanding the measurable range of the pressure sensor.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust pressure upstream of the filter that is abnormally high even if it exceeds the measurable range of the pressure sensor. An object of the present invention is to provide a control device of an internal combustion engine capable of determining the presence or absence of an abnormality.

  A control device for an internal combustion engine that solves the above problems includes an internal combustion engine provided with a filter that is provided in the exhaust passage and that collects particles in the exhaust, and a pressure sensor that measures the exhaust pressure upstream of the filter. A first estimation process is applied that estimates the particle deposition amount of the filter based on the detection value of the pressure sensor, and a second estimation process that estimates the particle deposition amount of the filter based on the engine operating state . Then, when the detected value of the pressure sensor reaches the upper limit value of the measurable range of the pressure sensor, the control device determines the particle deposition amount estimated by the second estimation process and a predetermined threshold value. A process of determining the presence or absence of an abnormality in the exhaust pressure is executed by comparison.

  The exhaust pressure upstream of the filter is higher as the amount of particle deposition on the filter is larger. Therefore, in the same configuration, it is determined whether the exhaust pressure is abnormally high by comparing the particle deposition amount of the filter with a predetermined threshold value. Here, since the particle deposition amount to be compared with the threshold value in the determination is a value estimated by the second estimation processing that can estimate the particle deposition amount without using the detection value of the pressure sensor, it is upstream of the filter It is possible to determine the presence or absence of an abnormality in the exhaust pressure, even if the exhaust pressure is abnormally high pressure beyond the measurable range of the pressure sensor. Therefore, according to the same configuration, it is possible to determine whether the exhaust pressure upstream of the filter is in an abnormally high pressure state beyond the measurable range of the pressure sensor.

FIG. 1 is a schematic view of an internal combustion engine to which a first embodiment of a control device is applied. The graph which shows the relation between the exhaust pressure on the upstream of a filter, the amount of intake air, and the amount of PM deposition. The graph which shows the relation between the threshold for judging the abnormalities of exhaust pressure in the embodiment, and the amount of intake air. The flowchart which shows a series of processing procedures for determining abnormality of exhaust pressure in the embodiment. The flowchart which shows a series of processing procedures for determining abnormality of exhaust pressure in 2nd Embodiment.

First Embodiment
Hereinafter, a first embodiment of a control device for an internal combustion engine will be described with reference to FIGS. 1 to 4.
As shown in FIG. 1, the internal combustion engine 10 is mounted on a vehicle, and includes a plurality of cylinders 10 a. An intake passage 13 is connected to an intake port of each cylinder 10a. The intake passage 13 is provided with a throttle valve 14 for adjusting the amount of intake air.

  A fuel injection valve 11 is disposed in the combustion chamber of each cylinder 10a. Then, in the combustion chamber of each cylinder 10a, the mixture of the air taken in through the intake passage 13 and the fuel injected from the fuel injection valve 11 is burned by being ignited by the spark discharge. Exhaust gas produced by the combustion of the air-fuel mixture in the combustion chamber is discharged to an exhaust manifold 15 connected to an exhaust port of the internal combustion engine 10.

  A three-way catalyst 17 is connected downstream of the exhaust manifold 15. The three-way catalyst 17 oxidizes hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust to generate water and carbon dioxide. Further, the three-way catalyst 17 reduces nitrogen oxides (NOx) contained in the exhaust to generate nitrogen.

  An exhaust pipe 16 is connected downstream of the three-way catalyst 17. A filter 18 for collecting particulate matter (PM) in the exhaust is provided in the middle of the exhaust pipe 16. The PM deposited on the filter 18 includes soot generated by combustion of fuel in the engine body of the internal combustion engine 10, ash generated by combustion of lubricating oil and the like, and the like.

  The control device 200 of the internal combustion engine 10 includes a central processing unit (CPU), a memory, and the like, and the CPU executes programs stored in the memory to implement various controls of the internal combustion engine 10.

  Detection signals of various sensors are input to the control device 200. For example, the pressure sensor 50 attached to the upper portion of the internal combustion engine 10 is connected to the communication pipe 51 communicating with a portion of the exhaust pipe 16 downstream of the three-way catalyst 17 and upstream of the filter 18 The pressure sensor 50 detects the exhaust pressure EP which is the pressure in the exhaust passage upstream of the filter 18. The exhaust pressure EP detected by the pressure sensor 50 is a differential pressure between the pressure in the communication pipe 51 and the atmospheric pressure, and this differential pressure is the exhaust pressure on the upstream side of the filter 18 in the exhaust pipe 16. And the exhaust pressure on the downstream side of the filter 18. An exhaust temperature sensor 52 is provided at a portion downstream of the three-way catalyst 17 and upstream of the filter 18 in the exhaust pipe 16. The exhaust temperature sensor 52 passes through the three-way catalyst 17. Exhaust temperature THE, which is the temperature of the exhaust, is detected. A crank angle sensor 53 provided in the vicinity of the crankshaft of the internal combustion engine 10 detects an engine rotational speed NE of the internal combustion engine 10. An air flow meter 54 provided upstream of an intake passage of the internal combustion engine 10 detects an intake air amount GA of the internal combustion engine 10.

In the present embodiment, the exhaust manifold 15, the three-way catalyst 17, the exhaust pipe 16, the filter 18, the pressure sensor 50, the communication pipe 51, the exhaust temperature sensor 52 and the like correspond to exhaust system components.
The control device 200 controls the fuel injection of the fuel injection valve 11 and the opening degree of the throttle valve 14.

  Further, the control device 200 performs a first estimation process of estimating a first deposition amount DsP which is a PM deposition amount of the filter 18 based on the exhaust pressure EP which is a detection value of the pressure sensor 50, and a filter based on an engine operating state. A second estimation process of estimating a second deposition amount DsQ, which is a PM deposition amount of 18, is performed during engine operation.

  In the first estimation process, the first deposition amount DsP is estimated such that the value of the first deposition amount DsP increases as the exhaust pressure EP increases. In the second estimation process, for example, the amount of ash and the ash discharged from the combustion chamber is determined based on engine operating conditions such as the fuel injection amount Q of the fuel injection valve 11, intake air amount GA and engine rotational speed NE and vehicle travel distance. The second deposition amount DsQ is estimated by estimation. The estimation of the PM deposition amount based on the exhaust pressure and the estimation of the PM deposition amount based on the engine operating state are well known, and the first deposition amount DsP and the second deposition amount DsQ are calculated in other modes. It is also good.

  Then, the control device 200 selects the larger one of the first deposition amount DsP and the second deposition amount DsQ as the final PM deposition amount. Then, when the selected PM deposition amount becomes equal to or more than a predetermined threshold value, the temperature rise of the exhaust flowing into the filter 18 is raised to burn off the PM deposited on the filter 18 and regenerate the filter 18. Execute the process

  In the present embodiment, in the temperature raising process, the air-fuel ratio of part of the cylinders 10a of the internal combustion engine 10 is made richer than the stoichiometric air-fuel ratio, and the air-fuel ratio of the remaining cylinders 10a is made greater than the stoichiometric air-fuel ratio. Implements dither control to make the lean combustion cylinder lean. When this dither control is executed, the three-way catalyst 17 reacts the unburned fuel component and the incomplete combustion component in the exhaust discharged from the rich combustion cylinder with the oxygen in the exhaust discharged from the lean combustion cylinder. Promoted, the three-way catalyst 17 is heated. Thus, when the temperature of the three-way catalyst 17 is increased, the temperature of the exhaust passing through the three-way catalyst 17 is increased, and the filter 18 is provided with the raised exhaust gas downstream of the three-way catalyst 17. The filter 18 is heated by flowing into the Then, by setting the atmosphere of the filter 18 that has been heated to an oxidizing atmosphere, the PM collected by the filter 18 is burned (oxidized) and removed.

  Further, the control device 200 calculates the PM removal amount, which is the amount of PM decreasing from the filter 18 during regeneration of the filter 18, based on the exhaust temperature THE and the like. Then, the control device 200 subtracts the PM removal amount from the PM deposition amount at the start of regeneration of the filter 18 to remove the PM remaining amount, which is the amount of PM remaining in the filter 18 during regeneration of the filter 18. calculate. Then, when the PM remaining amount becomes equal to or less than a predetermined threshold value, it is determined that the regeneration of the filter 18 is completed, and the temperature raising process is ended.

  By the way, for example, when the PM deposition amount of the filter 18 is increased beyond the above-mentioned threshold due to a state where the regeneration of the filter 18 described above can not be sufficiently continued, the exhaust pressure EP upstream of the filter 18 is The 18 PM deposition amount rises above the pressure at which the above threshold is reached. In some cases, the increased exhaust pressure EP may reach the pressure limit of the exhaust system components described above.

  Therefore, the control device 200 protects exhaust system components by performing a limiting process that limits the increase in the exhaust pressure before the exhaust pressure EP upstream of the filter 18 reaches such a pressure limit. In the present embodiment, as such limitation processing, processing for suppressing an increase in the exhaust pressure by reducing the opening amount of the throttle valve 14 to reduce the intake air amount is performed.

  Here, in the present embodiment, when the exhaust pressure upstream of the filter 18 reaches the restriction start pressure set to a value lower than the pressure limit in order to start the restriction process before the exhaust pressure EP reaches the pressure limit. It is determined that the exhaust pressure is in an abnormally high state. Then, when it is determined that the exhaust pressure is abnormal as described above, the above-described restriction processing is executed.

  As shown in FIG. 2, in the present embodiment, the pressure limit Pmax described above is a pressure higher than the upper limit value SRmax of the measurable range of the pressure sensor 50. The limit start pressure Ps is set to a pressure higher than the upper limit value SRmax of the measurable range of the pressure sensor 50 and to a value lower than the withstand pressure limit Pmax.

  As described above, the restriction start pressure Ps is higher than the upper limit value SRmax of the measurable range of the pressure sensor 50. Therefore, the exhaust pressure EP becomes abnormally high as it reaches the restriction start pressure Ps. It can not be judged whether or not Therefore, in the present embodiment, the presence or absence of abnormality of the exhaust pressure EP is determined as follows.

  In FIG. 2, the relationship between the intake air amount GA and the exhaust pressure EP when the PM deposition amount of the filter 18 is large is shown by a two-dot chain line L1, and the intake air amount GA when the PM deposition amount of the filter 18 is small The relationship with the exhaust pressure EP is shown by a two-dot chain line L2.

  As shown by the two-dot chain line L1 and the two-dot chain line L2, the exhaust pressure EP upstream of the filter 18 becomes higher as the exhaust flow rate increases with the increase of the intake air amount GA. Further, even if the intake air amount GA is the same, the exhaust pressure EP becomes higher as the PM deposition amount of the filter 18 is larger. As described above, the exhaust pressure EP upstream of the filter 18 changes in accordance with the current PM deposition amount and the intake air amount GA of the filter 18, and the exhaust pressure EP becomes the restriction start pressure Ps as the intake air amount increases. The amount of PM deposition required to reach Therefore, the relationship between the amount of PM deposition required for the exhaust pressure EP to reach the restriction start pressure Ps and the amount of intake air GA is previously obtained. Then, assuming that the PM deposition amount corresponding to the present intake air amount GA is a value obtained from this relationship as the threshold A, the threshold A decreases as the intake air amount GA increases, as shown in FIG. Set to a value.

  Then, if the detected value of the pressure sensor 50 has reached the above upper limit value SRmax, that is, if there is a possibility that the actual exhaust pressure EP is higher than the measurable range of the pressure sensor 50, The second deposition amount DsQ calculated in the second estimation process, which can estimate the present PM deposition amount without using the detection value of the pressure sensor 50, is compared with the threshold A. Then, when the second deposition amount DsQ is less than the threshold A, it is determined that the exhaust pressure EP is normal. On the other hand, when the second deposition amount DsQ is equal to or more than the threshold value A, it is determined that the exhaust pressure EP is abnormal.

  Also, if the detected value of the pressure sensor 50 is less than the above upper limit value SRmax, that is, if the actual exhaust pressure EP is a pressure within the measurable range of the pressure sensor 50, discharge is performed as follows. It is determined whether there is a possibility that an abnormality occurs in the pressure EP.

  That is, when the maximum value of the intake air amount that can be realized in the internal combustion engine 10 is the maximum intake air amount GAmax, the PM deposition amount when the exhaust pressure EP reaches the restriction start pressure Ps at the maximum intake air amount GAmax It is the amount of deposition. Then, the relationship between the intake air amount GA and the exhaust pressure EP at this reference accumulation amount is obtained in advance (solid line Lbase shown in FIG. 2). Then, from the relationship between the intake air amount GA and the exhaust pressure EP at the reference accumulation amount, the exhaust pressure EP corresponding to the current intake air amount GA (for example, GAa shown in FIG. 2) is determined, and the determined exhaust pressure EP is determined. Set as a value α. As indicated by the solid line Lbase in FIG. 2, the determination value α is variably set so that the pressure value becomes higher as the intake air amount GA is larger.

  Next, the exhaust pressure EP (EPa shown in FIG. 2) measured by the pressure sensor 50 when the current intake air amount GA is acquired is compared with the judgment value α. Then, if the current exhaust pressure EP is lower than the determination value α, the current PM deposition amount is smaller than the reference deposition amount, so even if the intake air amount GA reaches the maximum intake air amount GAmax, the exhaust pressure EP Does not reach the limit start pressure Ps. Therefore, when the current exhaust pressure EP is less than the determination value α, it is determined that the exhaust pressure EP is normal.

  On the other hand, when the current exhaust pressure EP is equal to or higher than the determination value α, the current PM deposition amount is equal to or higher than the reference deposition amount. Therefore, at present, the exhaust pressure EP has not reached the restriction start pressure Ps, but if the intake air amount GA increases from now on, the exhaust pressure EP may reach the restriction start pressure Ps before reaching the maximum intake air amount GAmax. is there. Therefore, when the current exhaust pressure EP is equal to or higher than the determination value α, it is determined that the exhaust pressure EP is high to some extent from now on, and the exhaust pressure EP is abnormal in this case as well. Determine that there is.

FIG. 4 shows a series of processing procedures for determining the abnormality of the exhaust pressure EP described above. This process is executed by the control device 200 at predetermined intervals.
When the present process is started, the control device 200 reads the present intake air amount GA, the present exhaust pressure EP detected by the pressure sensor 50, and the present value of the second accumulation amount DsQ (S100). Next, the control device 200 determines whether the detected value (output value) of the pressure sensor 50 is less than the upper limit value SRmax (S110).

  Then, when the detection value of pressure sensor 50 is less than upper limit value SRmax (S110: YES), determination of exhaust pressure EP using the detection value of pressure sensor 50 is possible, so control device 200 performs the following steps S120 to The process of step S160 is performed.

  At step S120, control device 200 determines whether or not a predetermined pressure determination condition is satisfied. The pressure determination condition is a condition for determining whether or not the exhaust pressure EP read in the step S100 has such an accuracy that it can be used for the pressure determination in step S140 described later. When the condition A and the condition B, etc. are both satisfied, it is determined that the pressure determination condition is satisfied.

Condition A: The pressure sensor 50 is at a temperature within the operation guarantee temperature where the output accuracy can be guaranteed.
Condition B: The intake air amount GA is a predetermined amount or more, and the intake air amount is such that the difference in the exhaust pressure EP due to the difference in the PM deposition amount clearly appears.

  When it is determined in step S120 that the pressure determination condition is satisfied (S120: YES), the controller 200 sets the above-described determination value α based on the read intake air amount GA (S130). ), It is determined whether the read exhaust pressure EP is less than the determination value α (S140). Then, when the exhaust pressure EP is less than the determination value α (S140: YES), the control device 200 determines that the exhaust pressure EP is normal (S150), and temporarily ends this processing.

  On the other hand, when it is determined in step S140 that the exhaust pressure EP is greater than or equal to the determination value α (S140: NO), the control device 200 determines that the exhaust pressure EP is abnormal (S160), It will end once. Thus, when it is determined that the exhaust pressure EP is abnormal, the above-described limitation process is performed.

  When it is determined in step S160 that the exhaust pressure EP is abnormal, that is, when the detected value of the pressure sensor 50 is less than the upper limit SRmax, the exhaust pressure EP is equal to or greater than the determination value α. As described above, when the intake air amount GA increases from now on, the exhaust pressure EP may reach the restriction start pressure Ps before reaching the maximum intake air amount GAmax, but at present the exhaust pressure EP is the restriction start pressure Ps Has not reached. Therefore, the execution of the restriction process may be delayed instead of immediately executing the restriction process when it is determined in step S160 that the exhaust pressure EP is abnormal. For example, the limiting process may be performed when the detected value of the pressure sensor 50 reaches the upper limit value SRmax.

  When it is determined in step S110 that the detection value of the pressure sensor 50 is equal to or greater than the upper limit SRmax (S110: NO), that is, when determination of the exhaust pressure EP using the detection value of the pressure sensor 50 is impossible, control is performed. The apparatus 200 performs the process of the following step S170-step S200.

  When it is determined in step S120 that the pressure determination condition is not satisfied (S120: NO), that is, the accuracy with which the exhaust pressure EP detected by the pressure sensor 50 can be used for the pressure determination in step S140. Even when not possessed, the control device 200 performs the processing of the following steps S170 to S200.

  In step S170, the control device 200 sets the above-described threshold A based on the read intake air amount GA. Then, the control device 200 determines whether the second deposition amount DsQ read in step S100 is less than the threshold A (S180), and if the second deposition amount DsQ is less than the threshold A (S180: YES) And the control device 200 determines that the exhaust pressure EP is normal (S190), and temporarily ends this processing.

  On the other hand, when it is determined in step S180 that the second deposition amount DsQ is greater than or equal to the threshold A (S180: NO), it is determined that the current exhaust pressure EP is high enough to reach the above limit start pressure Ps. Therefore, the control device 200 determines that the exhaust pressure EP is abnormal (S200), and once ends the present process. Thus, when it is determined that the exhaust pressure EP is abnormal, the above-described limitation process is performed.

The effects of the present embodiment will be described.
(1) As described above, the exhaust pressure EP upstream of the filter 18 increases as the amount of PM deposition on the filter 18 increases. Therefore, in the present embodiment, it is determined whether the exhaust pressure EP is abnormally high by comparing the PM deposition amount with the predetermined threshold value A. Here, the PM deposition amount to be compared with the threshold A at the time of the determination is a value estimated by the second estimation process that can estimate the PM deposition amount without using the detection value of the pressure sensor 50 (second deposition amount DsQ ). Therefore, even if the exhaust pressure EP upstream of the filter 18 is an abnormally high pressure beyond the measurable range of the pressure sensor 50, it is possible to determine whether or not there is an abnormality in the exhaust pressure EP. .

  (2) If the measurable range of the pressure sensor 50 is expanded in order to detect that the exhaust pressure EP has reached the restriction start pressure Ps, the change in the output value of the pressure sensor 50 with respect to the pressure change becomes small, It becomes difficult to capture pressure changes. Therefore, the accuracy of the first deposition amount DsP calculated based on the detection value of the pressure sensor 50 is lowered. In this respect, in the present embodiment, it is possible to grasp that the exhaust pressure EP has reached the restriction start pressure Ps without extending the measurable range of the pressure sensor 50, so that the calculation accuracy of the first deposition amount DsP Can be reduced.

Second Embodiment
Next, a second embodiment of a control device for an internal combustion engine will be described with reference to FIG. In the present embodiment, the pressure determination condition is not satisfied in the processing procedure at the time of abnormality of the pressure sensor 50 or the processing of step S120 with respect to the abnormality determination processing of the exhaust pressure EP described in FIG. In the case where the predetermined condition is satisfied, a processing procedure or the like for performing abnormality determination of the exhaust pressure EP using the first deposition amount DsP is further added. Hereinafter, the present embodiment will be described focusing on such changes.

  FIG. 5 shows a processing procedure of abnormality determination of the exhaust pressure EP in the present embodiment. This process is also executed by the control device 200 at predetermined intervals. Also, each processing of steps S300, S320, S330, S340, S350, S360, S370, S470, and S480 in FIG. 5 is the same as the processing in steps S100, S110, S120, S130, S140, S140, S150, S160, and S190 in FIG. It is the same processing as each processing of S200. Further, each process of steps S410 and S440 in FIG. 5 is the same process as the process of step S170 in FIG. 4 described above.

When the present process is started, the control device 200 reads the present intake air amount GA, the present exhaust pressure EP detected by the pressure sensor 50, and the present value of the second accumulation amount DsQ (S300).
Next, the control device 200 determines whether the pressure sensor 50 is normal (S310). Such normal determination of the pressure sensor 50 can be made as appropriate. For example, when the detection value of the pressure sensor 50 is not an abnormal value that should not be output originally, it can be determined that the pressure sensor 50 is not broken and is normal. Further, if the detection value of the pressure sensor 50 does not stick to a constant value for a long time, it can be determined that the pressure sensor 50 is not broken and is normal.

  When it is determined that the pressure sensor 50 is normal (S310: YES), the control device 200 determines whether the detected value (output value) of the pressure sensor 50 is less than the upper limit value SRmax. (S320).

  Then, when the detection value of the pressure sensor 50 is less than the upper limit value SRmax (S320: YES), the control device 200 determines whether the above-mentioned pressure determination condition is satisfied (S330).

  When it is determined that the pressure determination condition is satisfied (S330: YES), the control device 200 sets the above-described determination value α based on the read intake air amount GA (S340), and the read It is determined whether the exhaust pressure EP is less than the determination value α (S350). Then, when the exhaust pressure EP is less than the determination value α (S350: YES), the control device 200 determines that the exhaust pressure EP is normal (S360), and temporarily ends this processing.

  On the other hand, when it is determined in step S350 that the exhaust pressure EP is equal to or higher than the determination value α (S350: NO), the control device 200 determines that the exhaust pressure EP is abnormal (S370), It will end once. Thus, when it is determined that the exhaust pressure EP is abnormal, the above-described limitation process is performed.

  When it is determined in step S330 that the pressure determination condition is not established (S330: NO), the control device 200 determines whether a predetermined pressure-PM amount conversion condition is established (S380). The pressure-PM amount conversion condition is a condition for determining that the exhaust pressure EP detected by the pressure sensor 50 may be converted into the PM accumulation amount, that is, the first accumulation amount by the first estimation process. This is a condition for determining that the calculation of DsP may be performed, and an affirmative determination is made if there is a history in which the detection value of the pressure sensor 50 is normally measured.

  And in this embodiment, it is judged as follows that there is a history where the detection value of such pressure sensor 50 was measured normally. That is, when an affirmative determination is made in step S330 (that is, when the pressure determination condition is satisfied and it can be determined that the detection value of the pressure sensor 50 is normal), the second deposition amount DsQ read at that time is Is stored in the memory as a judgment value. Then, each time the positive determination is made in step S330, the determination value stored in the memory is overwritten with the value of the second deposition amount DsQ read at the time of the positive determination. Thus, the difference between the latest determination value stored in the memory and the second deposition amount DsQ read at the time of execution of the present process is compared with a predetermined value determined in advance. Then, if the difference is equal to or less than the predetermined value, the second deposition amount DsQ does not increase so much, so the exhaust pressure EP, which changes according to the PM deposition amount, is also positively determined in the process of step S330. It is determined that there is not a large change from the exhaust pressure of (1), and there is a history in which the detection value of the pressure sensor 50 has been normally measured most recently.

  Thus, when it is determined in step S380 that the pressure-PM amount conversion condition is satisfied (S380: YES), the exhaust pressure read in step S300 even if the pressure determination condition is not satisfied in step S330. It is determined that EP is a reliable value. Then, the control device 200 calculates the first deposition amount DsP based on the read exhaust pressure EP through execution of the first estimation process (S390). In step S390, the currently calculated first deposition amount DsP may be read.

  Next, the control device 200 sets the calculated first deposition amount DsP as the determination deposition amount DH (S400). Then, the control device 200 sets the threshold A described above based on the read intake air amount GA (S410), and sets the threshold A as a final threshold H (S420).

  Next, the control device 200 determines whether the determination deposition amount DH (= first deposition amount DsP) set in step S400 is less than the threshold H (threshold H = threshold A) (S460). When the determination deposition amount DH is less than the threshold value H (S460: YES), the control device 200 determines that the exhaust pressure EP is normal (S470), and temporarily ends this processing.

  On the other hand, when it is determined in step S460 that the determination deposition amount DH (= first deposition amount DsP) is greater than or equal to the threshold H (threshold H = threshold A) (S460: NO), the current exhaust pressure EP is the above It can be determined that the pressure is high to reach the limit start pressure Ps. Therefore, the control device 200 determines that the exhaust pressure EP is abnormal (S480), and once ends the present process. Thus, when it is determined that the exhaust pressure EP is abnormal, the above-described limitation process is performed.

  When it is determined in step S310 that the pressure sensor 50 is malfunctioning and it is determined that an abnormality is occurring (S310: NO), that is, when the determination of the exhaust pressure EP using the detection value of the pressure sensor 50 is impossible Control device 200 performs the process of the following step S430-step S480.

  In addition, even when it is determined in step S320 that the detection value of the pressure sensor 50 is equal to or more than the upper limit value SRmax (S320: NO), the control device 200 performs the following steps S430 to S480.

  Then, even when it is determined in step S380 that the pressure-PM amount conversion condition is not satisfied (S380: NO), the control device 200 performs the processing of the following steps S430 to S480.

  In step S430, the control device 200 sets the read second deposition amount DsQ as the determination deposition amount DH (S430). Then, the control device 200 sets the above-mentioned threshold A based on the read intake air amount GA (S440), and sets a value obtained by subtracting the predetermined value C from the threshold A as the final threshold H (S450). ).

  Next, the control device 200 determines whether or not the determination deposition amount DH (= second deposition amount DsQ) set in step S430 is less than the threshold H (threshold H = threshold A-predetermined value C). (S460) When the determination deposition amount DH is less than the threshold H (S460: YES), the control device 200 determines that the exhaust pressure EP is normal (S470), and temporarily ends this processing.

  On the other hand, when it is determined in step S460 that the determination deposition amount DH (= the second deposition amount DsQ) is greater than or equal to the threshold H (threshold H = threshold A-predetermined value C) (S460: NO), the current emission The pressure EP can be determined to be a high pressure that reaches the above-mentioned limit start pressure Ps. Therefore, the control device 200 determines that the exhaust pressure EP is abnormal (S480), and once ends the present process. Thus, when it is determined that the exhaust pressure EP is abnormal, the above-described limitation process is performed.

The effects of the present embodiment will be described.
(1) As described above, the exhaust pressure EP upstream of the filter 18 increases as the amount of PM deposition on the filter 18 increases. Therefore, in the present embodiment, it is determined whether the exhaust pressure EP is abnormally high by comparing the PM deposition amount with the predetermined threshold value H. Here, the PM deposition amount to be compared with the threshold value H in the determination is a value estimated by the second estimation process that can estimate the PM deposition amount without using the detection value of the pressure sensor 50 (second deposition amount DsQ ). Therefore, even if the exhaust pressure EP upstream of the filter 18 is an abnormally high pressure beyond the measurable range of the pressure sensor 50, it is possible to determine whether or not there is an abnormality in the exhaust pressure EP. .

  (2) The pressure sensor 50 is not normal (S310: NO), the detected value of the pressure sensor 50 is the upper limit SRmax or more (S320: NO), the pressure-PM amount conversion condition is not satisfied (S380: NO), the detection value of the pressure sensor 50 is in an unreliable state. Therefore, in such a state, as described above, the second deposition amount DsQ estimated by the second estimation process capable of estimating the PM deposition amount without using the detection value of the pressure sensor 50 is compared with the threshold H. Thus, the abnormality determination of the exhaust pressure EP is performed.

  On the other hand, when the pressure-PM amount conversion condition is satisfied (S380: YES), the first deposition amount DsP calculated based on the exhaust pressure EP which is a detected value of the pressure sensor 50 is compared with the threshold value H. Thus, the abnormality determination of the exhaust pressure EP is performed. Since the first deposition amount DsP calculated based on the exhaust pressure EP is a value with high estimation accuracy with respect to the actual PM deposition amount as compared to the second deposition amount DsQ calculated based on the engine operating state, When comparing and determining the 1 accumulation amount DsP and the threshold value H, the accuracy of the abnormality determination of the exhaust pressure EP can be enhanced as compared with the case of comparing and determining the second accumulation amount DsQ and the threshold value H.

  (3) As described above, the first deposition amount DsP has a higher estimation accuracy than the second deposition amount DsQ. Conversely, the second deposition amount DsQ has a lower estimation accuracy than the first deposition amount DsP. Therefore, in the present embodiment, when the first deposition amount DsP is set as the determination deposition amount DH, the threshold A is set as the threshold value H for abnormality determination as it is, while the second deposition amount as the determination deposition amount DH. When the deposition amount DsQ is set, a value obtained by subtracting the predetermined value C from the threshold value A is set as the threshold value H. As described above, when the second deposition amount DsQ is set as the determination deposition amount DH, the threshold H is smaller than the case where the first deposition amount DsP is set as the determination deposition amount DH. Since it is set, it is possible to set an appropriate threshold H in accordance with the estimation accuracy of the first deposition amount DsP and the second deposition amount DsQ.

  (4) If the measurable range of the pressure sensor 50 is expanded in order to detect that the exhaust pressure EP has reached the restriction start pressure Ps, the change in the output value of the pressure sensor 50 with respect to the pressure change becomes small, It becomes difficult to capture pressure changes. Therefore, the accuracy of the first deposition amount DsP calculated based on the detection value of the pressure sensor 50 is lowered. In this respect, in the present embodiment, it is possible to grasp that the exhaust pressure EP has reached the restriction start pressure Ps without extending the measurable range of the pressure sensor 50, so that the calculation accuracy of the first deposition amount DsP Can be reduced.

The above-described embodiments can be modified as follows. Each embodiment and the following modifications can be implemented in combination with each other to the extent that there is no technical contradiction.
The threshold H calculated in step S450 of the second embodiment may be applied as the threshold A in step S180 of the first embodiment.

  In the second embodiment, when the second deposition amount DsQ is set as the determination deposition amount DH, a value obtained by subtracting the predetermined value C from the threshold A is set as the threshold H. In addition, even when the second deposition amount DsQ is set as the determination deposition amount DH, the threshold value A is directly set as the threshold value H as in the case where the first deposition amount DsP is set as the determination deposition amount DH. It may be set.

In the first embodiment, the process of step S120 for determining the establishment of the pressure determination condition may be omitted.
Although the dither control is performed as the temperature raising process for raising the temperatures of the three-way catalyst 17 and the filter 18, another temperature raising process may be performed.

  Further, the temperature of the exhaust gas discharged from the combustion chamber to the exhaust passage may be raised by performing retardation processing of the ignition timing as the temperature raising processing, and thereby the temperature of the three-way catalyst 17 or the filter 18 may be raised. .

  When the above-described estimation of the exhaust pressure EP is performed, the pressure sensor 50 may be used which has a narrower measurable range of pressure as compared to the case where the estimation is not performed. In this case, the output value change of the pressure sensor 50 with respect to the pressure change becomes large, and it becomes easy to capture a minute pressure change. Therefore, the first deposition amount DsP calculated based on the detection value of the pressure sensor 50 The calculation accuracy can be enhanced.

  The exhaust pressure EP upstream of the filter 18 is measured via the communication pipe 51. However, the exhaust pressure EP may be measured by another structure. For example, the detection element portion of the pressure sensor 50 may be directly disposed in the exhaust pipe 16 at a position upstream of the filter 18.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 10a ... Cylinder, 11 ... Fuel injection valve, 13 ... Intake passage, 14 ... Throttle valve, 15 ... Exhaust manifold, 16 ... Exhaust pipe, 17 ... Three-way catalyst, 18 ... Filter, 50 ... Pressure sensor, 51 ... communication pipe, 52 ... exhaust temperature sensor, 53 ... crank angle sensor, 54 ... air flow meter, 200 ... control device.

Claims (1)

The present invention is applied to an internal combustion engine provided with a filter provided in the middle of an exhaust passage to collect particles in the exhaust, and a pressure sensor for measuring the exhaust pressure upstream of the filter, based on the detection value of the pressure sensor A control device for performing a first estimation process of estimating a particle deposition amount of the filter and a second estimation process of estimating a particle deposition amount of the filter based on an engine operating state,
When the detected value of the pressure sensor reaches the upper limit value of the measurable range of the pressure sensor, the exhaust pressure is compared by comparing the particle deposition amount estimated by the second estimation process with a predetermined threshold value. A control device for an internal combustion engine that executes processing to determine the presence or absence of an abnormality.