JP2017020405A - Control device of exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine pressure loss of a filter with high accuracy by using a pressure difference sensor detecting pressure difference between an exhaust pressure at an upstream side with respect to the filter and an atmospheric pressure, in a case when a pressure loss portion is disposed at a downstream side with respect to the filter.SOLUTION: A plurality of pieces of correlation information of a flow rate of an exhaust gas and pressure loss in a pressure loss portion are held, difference in pressure loss ratio as the difference between a ratio of pressure loss in the pressure loss portion obtained from the correlation information to a detection value of the differential pressure sensor in a first exhaust flow rate, and a ratio of pressure loss in the pressure loss portion obtained from the correlation information to a detection value of the differential pressure sensor in a second exhaust flow rate, is calculated on each correlation information, and the correlation information in which the difference in pressure loss ratio satisfies prescribed conditions, is selected as the correlation information to calculate the pressure loss of the pressure loss portion.SELECTED DRAWING: Figure 4

Description

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

  In a configuration in which a filter for collecting particulate matter (hereinafter also referred to as “PM”) in exhaust gas is disposed in an exhaust passage of an internal combustion engine, an exhaust pressure upstream of the filter and an exhaust pressure downstream of the filter There is known a technique for providing a differential pressure sensor for detecting the differential pressure of the filter and determining the amount of PM collected by the filter, abnormality, and the like based on the detected value of the differential pressure sensor (see, for example, Patent Document 1).

JP 2008-111409 A JP 2003-314248 A

  By the way, by using a differential pressure sensor that detects the differential pressure between the exhaust pressure upstream of the filter and the atmospheric pressure (hereinafter also referred to as the total differential pressure), the amount of PM trapped by the filter is calculated, the abnormality of the filter, etc. It is also possible to judge the above. Here, the difference between the pressure upstream of the filter and the pressure downstream of the filter can be calculated by subtracting the pressure loss in the exhaust system member provided downstream of the filter from the overall differential pressure. Hereinafter, the exhaust system member downstream from the filter is also referred to as a pressure loss part, the pressure loss in the pressure loss part is also referred to as pressure loss part pressure loss, and the pressure loss in the filter is also referred to as filter pressure loss. The pressure loss part is, for example, a catalyst, a muffler, or an exhaust pipe. The pressure loss pressure loss changes according to the exhaust gas flow rate. The relationship between the pressure loss pressure loss and the exhaust flow rate can be obtained and stored in advance by experiments, simulations, calculation formulas, or the like. Therefore, the filter pressure loss can be calculated by subtracting the stored pressure loss part pressure loss from the total differential pressure detected by the differential pressure sensor.

  However, since the pressure loss part has a tolerance, the actual pressure loss part pressure loss may deviate from the stored pressure loss part pressure loss. When calculating the filter pressure loss by subtracting the pressure loss pressure loss from the total pressure loss, if the pressure loss pressure loss accuracy is low, the filter pressure loss calculation accuracy is also low. If the calculation accuracy of the filter pressure loss is low, the accuracy of the filter abnormality determination based on the amount of collected PM and the filter pressure loss may be lowered.

  The present invention has been made in view of the above circumstances, and its purpose is to accurately measure the pressure loss of the filter by using a differential pressure sensor that detects the differential pressure between the exhaust pressure upstream of the filter and the atmospheric pressure. There is to ask well.

In order to solve the above problems, a filter that is provided in an exhaust passage of an internal combustion engine and collects particulate matter in the exhaust, a pressure loss portion that causes an exhaust pressure loss in the exhaust passage downstream of the filter, A control device for controlling an exhaust gas purification device of an internal combustion engine comprising: a differential pressure sensor that detects an actual differential pressure that is an actual difference between an exhaust pressure upstream of the filter and an atmospheric pressure; A flow rate acquisition unit for acquiring a flow rate of exhaust gas that passes through the filter in a control device of an exhaust gas purification device for an internal combustion engine that calculates pressure loss of the pressure loss unit using correlation information that is information relating to correlation with pressure loss in the pressure loss unit The flow rate of the exhaust gas acquired by the flow rate acquisition unit for each of the correlation information holding unit for holding a plurality of correlation information and the correlation information held by the correlation information holding unit. The ratio of the pressure loss in the pressure loss portion calculated using the correlation information to the differential pressure detected by the differential pressure sensor at the exhaust flow rate and the exhaust flow rate acquired by the flow rate acquisition portion are The difference between the pressure loss ratio in the pressure loss portion calculated using the correlation information with respect to the differential pressure detected by the differential pressure sensor when the second exhaust flow rate is a flow rate different from the one exhaust flow rate. A pressure loss ratio difference calculating unit that calculates a certain pressure loss ratio difference; and a selection unit that selects the correlation information in which the pressure loss ratio difference satisfies a predetermined condition as the correlation information for calculating the pressure loss of the pressure loss part; , Was prepared.

  The actual differential pressure detected by the differential pressure sensor includes pressure loss in the filter (hereinafter also referred to as filter pressure loss) and pressure loss in the pressure loss portion (hereinafter also referred to as pressure loss portion pressure loss). Therefore, in order to obtain the filter pressure loss, the pressure loss pressure loss may be subtracted from the actual differential pressure. The “pressure loss part” referred to here is an exhaust system member disposed downstream of the filter, such as an exhaust pipe, a muffler, or an exhaust purification catalyst. There are a plurality of pieces of correlation information held in the correlation information holding unit within a range in which the correlation between the flow rate of the exhaust gas and the pressure loss part pressure loss can be changed due to the tolerance of the pressure loss part. The correlation corresponding to each correlation information shows a different tendency. Unless otherwise specified, the correlation refers to the correlation between the exhaust gas flow rate and the pressure loss pressure loss.

  Here, the total differential pressure and the pressure loss pressure loss change according to the exhaust flow rate, but the ratio of the actual pressure loss pressure loss to the total differential pressure is constant regardless of the exhaust flow rate. Therefore, if the pressure loss pressure loss is accurate, the ratio of the pressure loss pressure loss to the actual differential pressure at the first exhaust flow rate and the ratio of the pressure loss pressure loss to the actual differential pressure at the second exhaust flow rate are substantially equal. Become. For this reason, the difference (that is, the pressure loss ratio difference) between the ratio of the pressure loss part pressure loss to the actual differential pressure at the first exhaust flow rate and the ratio of the pressure loss part pressure loss to the actual differential pressure at the second exhaust flow rate is A correlation that becomes smaller is considered to be close to the actual correlation. When the pressure loss ratio difference satisfies a predetermined condition, the correlation obtained from the correlation information is close to the actual correlation, so the correlation information at this time is selected. The predetermined condition here is set as a condition for determining that the correlation obtained from the correlation information indicates an actual correlation. Instead of this, the predetermined condition may be set as a condition for determining that the correlation obtained from the correlation information is closest to the actual correlation. That is, the selection unit selects correlation information that can obtain a correlation close to the actual correlation between the exhaust gas flow rate and the pressure loss pressure loss from among the plurality of correlation information held. By selecting the correlation information in this way, the filter pressure loss can be calculated more accurately using the correlation information. As a result, it is only necessary to select correlation information that reduces the pressure loss ratio difference. Therefore, when comparing the pressure loss ratio at the first exhaust flow rate with the pressure loss ratio at the second exhaust flow rate, the difference It is also possible to make a comparison using a ratio.

  In addition, the selection unit can select the correlation information in which the pressure loss ratio difference is the smallest as the correlation information in which the pressure loss ratio difference satisfies the predetermined condition. Of the correlations obtained from the correlation information, the correlation that minimizes the pressure loss ratio difference is considered to be the closest to the actual correlation. Therefore, the selection unit selects the correlation information that can obtain the correlation closest to the actual correlation between the flow rate of the exhaust gas and the pressure loss part pressure loss from the plurality of correlation information that is held, thereby the correlation information Can be used to calculate the filter pressure loss more accurately.

Further, the selection unit can select the correlation information in which the pressure loss ratio difference is not more than a predetermined value as the correlation information in which the pressure loss ratio difference satisfies the predetermined condition. Here, the predetermined value is a value that is sufficiently small and that can be determined that the pressure loss obtained from the corresponding correlation information substantially matches the actual pressure loss of the pressure loss portion. In this case, when correlation information is obtained in which the pressure loss ratio difference is equal to or less than a predetermined value, the pressure loss ratio difference can be immediately selected as correlation information that satisfies a predetermined condition. Therefore, it is not necessary to evaluate all correlation information. Thereby, it is possible to shorten the time until the correlation information is selected. In addition, when there is no correlation information in which the pressure loss ratio difference is equal to or less than a predetermined value, correlation information in which the pressure loss ratio difference is the smallest may be selected.

  The correlation information holding unit can store, as the correlation information, a plurality of maps representing the correlation between the exhaust flow rate and the pressure loss in the pressure loss unit. That is, among the maps showing the correlation between the exhaust flow rate and the pressure loss pressure loss, the map in which the pressure loss ratio difference satisfies the predetermined condition can be said to be a map representing an appropriate correlation. Select. Thereby, filter pressure loss can be calculated | required more correctly.

  The correlation information holding unit can store, as the correlation information, a plurality of functions representing the correlation between the exhaust flow rate and the pressure loss in the pressure loss unit. That is, among a plurality of functions showing the correlation between the exhaust flow rate and the pressure loss pressure loss, a function in which the pressure loss ratio difference satisfies a predetermined condition is a function that can calculate an appropriate correlation. Therefore, the function is selected. Thereby, filter pressure loss can be calculated | required more correctly.

  Further, the selection unit can store the selected correlation information as the correlation information for calculating the pressure loss of the pressure loss unit. By storing the correlation information, the pressure loss pressure loss can be obtained from the exhaust gas flow rate and the stored correlation information without calculating the pressure loss ratio difference by the pressure loss ratio difference calculation unit thereafter. For this reason, when subtracting the pressure loss portion pressure loss from the actual differential pressure to obtain the filter pressure loss, the filter pressure loss can be obtained more accurately and more quickly.

  In addition, the pressure loss ratio difference calculation unit can calculate the pressure loss ratio difference when the filter and the pressure loss part are new. Here, when PM accumulates on the filter, the filter pressure loss changes, so that the relationship that the ratio of the pressure loss portion pressure loss to the actual differential pressure is constant regardless of the flow rate of the exhaust gas does not hold. For this reason, there is a possibility that appropriate correlation information cannot be selected after PM is deposited on the filter. On the other hand, since the correlation information can be obtained before PM is deposited on the filter by obtaining the correlation information when it is new, the subsequent calculation accuracy of the filter pressure loss can be improved. In addition, a new article includes not only a state where it is not used at all, but also a state where a change in pressure loss of each member from a state where it is not used is within an allowable range.

  Further, the pressure loss ratio difference calculation unit can calculate the pressure loss ratio difference after regeneration of the filter. In other words, after the filter is regenerated, it is difficult to be affected by the PM accumulated on the filter, so that more appropriate correlation information can be selected.

  According to the present invention, the pressure loss of the filter can be accurately obtained using the differential pressure sensor that detects the differential pressure between the exhaust pressure upstream of the filter and the atmospheric pressure.

1 is a diagram illustrating a schematic configuration of an exhaust system of an internal combustion engine according to a first embodiment. It is the figure which showed the relationship between exhaust flow volume and differential pressure | voltage. It is the figure which showed the several map which showed the correlation with the exhaust_gas | exhaustion flow rate memorize | stored in ECU, and a muffler pressure loss. 3 is a flowchart illustrating a flow for changing memory pressure loss according to the first embodiment. 6 is another flowchart illustrating a flow for changing the memory pressure loss according to the first embodiment. 3 is a flowchart illustrating a flow of a filter abnormality determination process according to the first embodiment. 12 is a flowchart illustrating a flow for changing memory pressure loss according to the second embodiment. 10 is another flowchart showing a flow for changing the memory pressure loss according to the second embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an exhaust system of an internal combustion engine according to the present embodiment. The internal combustion engine 1 shown in FIG. 1 is a gasoline engine mounted on a vehicle, but may be a diesel engine. Connected to the internal combustion engine 1 is an exhaust pipe 2 for circulating burned gas burned in the cylinder of the internal combustion engine 1. A catalyst 3 is disposed in the middle of the exhaust pipe 2. The catalyst 3 is an exhaust purification catalyst such as an oxidation catalyst. A filter 4 is disposed in the exhaust pipe 2 downstream from the catalyst 3. The filter 4 collects particulate matter (PM) such as soot contained in the exhaust gas. A muffler 5 that reduces exhaust noise is disposed in the exhaust pipe 2 downstream of the filter 4. In this embodiment, the exhaust system member provided downstream of the filter 4 corresponds to the pressure loss part in the present invention. The pressure loss part includes a muffler 5. Examples of the exhaust system member provided downstream of the filter 4 include, in addition to the muffler 5, a catalyst provided downstream of the filter 4, an exhaust pipe 2 downstream of the filter 4, and the like. The pressure loss of the exhaust system member provided downstream of the filter 4 is hereinafter referred to as muffler pressure loss.

  A differential pressure sensor 6 is attached to the exhaust pipe 2 downstream of the catalyst 3 and upstream of the filter 4. The differential pressure sensor 6 is a sensor that detects an actual differential pressure between the pressure of the exhaust gas flowing into the filter 4 and the atmospheric pressure. The differential pressure sensor 6 may detect the pressure difference of the exhaust gas flowing into the filter 4 and the atmospheric pressure, and calculate the difference between the two pressures. Hereinafter, the differential pressure between the pressure of the exhaust gas flowing into the filter 4 and the atmospheric pressure is also referred to as “total differential pressure”. This total differential pressure changes according to the exhaust gas flow rate. The detection value of the differential pressure sensor 6 is input to the ECU 10. The ECU 10 is an electronic control unit that includes a CPU, a ROM, a RAM, a backup RAM, and the like. The ECU 10 is electrically connected to various sensors such as an air flow meter 11 in addition to the differential pressure sensor 6.

  The air flow meter 11 is a sensor that outputs an electrical signal correlated with the intake air amount of the internal combustion engine 1. Since the intake air amount has a correlation with the exhaust gas flow rate, the air flow meter 11 can be used to obtain the exhaust gas flow rate.

The ECU 10 controls the internal combustion engine 1 based on the detection values of the various sensors described above. Further, the ECU 10 stores the correlation between the exhaust flow rate and the muffler pressure loss as a map in order to calculate the filter pressure loss. The muffler pressure loss corresponding to the exhaust gas flow rate stored in the ECU 10 in this manner is also referred to as memory pressure loss below. The memory pressure loss can be said to be correlation information that is information relating to the correlation between the flow rate of the exhaust gas and the pressure loss in the pressure loss part. The initial value of the memory pressure loss corresponding to the exhaust flow rate is a value set at the time of design, for example, a value obtained in advance by experiments, simulations, calculation formulas, or the like. Further, the ECU 10 executes an abnormality determination process for the filter 4 using the stored pressure loss and the detected value of the differential pressure sensor 6. This abnormality determination process is a process for determining whether or not an abnormality has occurred in the filter 4. The abnormality of the filter 4 may include a case where the filter 4 is clogged even when the filter 4 is regenerated, when the filter 4 is removed, when the filter 4 is cracked, or when the filter 4 is regenerated. In the abnormality determination process, the ECU 10 determines whether or not the filter 4 is abnormal by comparing the filter pressure loss with a predetermined pressure loss range in which the filter 4 is normal. For example, when the filter 4 is removed or when a large crack is generated, the filter pressure loss is reduced to be lower than a predetermined pressure loss range, so that the filter pressure loss is smaller than the predetermined pressure loss range. In this case, it can be determined that the filter 4 is abnormal. On the other hand, when the filter 4 is clogged even when the filter 4 is regenerated, the filter pressure loss increases and becomes higher than the predetermined pressure loss range, and therefore the filter pressure loss becomes larger than the predetermined pressure loss range. In addition, it can be determined that the filter 4 is abnormal. The predetermined pressure loss range is obtained in advance by experiments or simulations as a filter pressure loss range when the filter 4 is normal. Further, since the filter pressure loss varies depending on the exhaust flow rate, a predetermined pressure loss range is also obtained in association with the exhaust flow rate.

  By the way, when the abnormality determination process is executed using the filter pressure loss calculated from the detection value of the differential pressure sensor 6, the calculated filter pressure loss needs to accurately reflect the state of the filter 4. Here, due to the tolerance of the muffler 5 and the like, even when the muffler 5 is new, the actual muffler pressure loss may be different from the memory pressure loss. When the filter pressure loss is obtained by subtracting the stored pressure loss from the detection value of the differential pressure sensor 6, the filter pressure loss cannot be determined accurately unless the stored pressure loss is accurate. For this reason, if the abnormality determination process of the filter 4 is performed based on the detected value of the differential pressure sensor 6 and the memory pressure loss without considering the difference between the actual muffler pressure loss and the memory pressure loss, the accuracy of the abnormality determination decreases. obtain.

  Therefore, in this embodiment, the stored pressure loss is changed so that the difference between the actual muffler pressure loss and the stored pressure loss is reduced, and the changed stored pressure loss is stored in the ECU 10. It can be said that this is learning memory pressure loss. FIG. 2 is a diagram showing the relationship between the exhaust flow rate and the differential pressure. A two-dot chain line is a memory pressure loss before the change, and is a muffler pressure loss actually stored in the ECU 10. The memory pressure loss at the first exhaust flow rate is defined as the first memory pressure loss, and the memory pressure loss at the second exhaust flow rate is defined as the second memory pressure loss. The second exhaust flow rate is larger than the first exhaust flow rate. The solid line is the differential pressure between the exhaust pressure upstream of the filter 4 and the atmospheric pressure (that is, the total differential pressure), and the detected value of the differential pressure sensor 6 at the first exhaust flow rate (hereinafter referred to as the first actual differential pressure). And the detected value of the differential pressure sensor 6 at the second exhaust flow rate (hereinafter also referred to as second actual differential pressure). A broken line is a filter pressure loss calculated based on the memory pressure loss. The filter pressure loss is obtained by subtracting the memory pressure loss from the total differential pressure at each exhaust flow rate. A one-dot chain line is a memory pressure loss after the change.

  Here, the ratio of the actual muffler pressure loss to the total differential pressure is considered to be constant regardless of the exhaust flow rate. Therefore, if the difference between the memory pressure loss and the actual muffler pressure loss is sufficiently small, the difference between the ratio of the first memory pressure loss to the first actual differential pressure and the ratio of the second memory pressure loss to the second actual differential pressure is sufficient. Becomes smaller. On the other hand, if the ratio of the first memory pressure loss to the first actual differential pressure and the ratio of the second memory pressure loss to the second actual differential pressure are greater than the determination threshold, the memory pressure loss and the actual muffler pressure loss are There seems to be a difference. The determination threshold here is obtained in advance by experiment or simulation as a value when there is a larger difference between the actual muffler pressure loss and the memory pressure loss than the allowable range. In the present embodiment, when it is determined that there is a difference between the memory pressure loss and the actual muffler pressure loss, the ratio of the actual muffler pressure loss to the total differential pressure is constant regardless of the exhaust flow rate. To change memory pressure loss. When changing the memory pressure loss, it is confirmed in advance by a well-known technique that there is no abnormality in the differential pressure sensor 6.

This will be described more specifically. First, the detected value (first actual differential pressure) of the differential pressure sensor 6 is read, and the exhaust flow rate (first exhaust flow rate) at the time when the first actual differential pressure is detected is detected. At this time, the first memory pressure loss can also be obtained from the memory pressure loss stored in the ECU 10. The first exhaust flow rate may be a predetermined exhaust flow rate. In this case, the first actual differential pressure may be read when the first exhaust flow rate is reached, and the first stored pressure loss corresponding to the first exhaust flow rate may be used. The exhaust flow rate may be detected directly by attaching a flow sensor to the exhaust pipe 2 or may be obtained based on the intake air amount obtained from the air flow meter 11. In the present embodiment, the air flow meter 11 corresponds to the flow rate acquisition unit in the present invention. When the exhaust flow rate is directly detected by a sensor, the sensor corresponds to the flow rate acquisition unit in the present invention.

  Next, the detected value (second actual differential pressure) of the differential pressure sensor 6 is read when the exhaust flow rate is different from the first exhaust flow rate, and the exhaust flow rate (secondary pressure) at the time when the second actual differential pressure is detected. Exhaust flow rate) is detected. At this time, the second memory pressure loss can also be obtained from the memory pressure loss stored in the ECU 10. The second exhaust flow rate may be a predetermined exhaust flow rate. In this case, the second actual differential pressure may be read when the second exhaust flow rate is reached, and the second stored pressure loss corresponding to the second exhaust flow rate may be used. If the absolute value of the difference between the ratio of the first memory pressure loss to the first actual differential pressure and the ratio of the second memory pressure loss to the second actual differential pressure is equal to or greater than the determination threshold, the memory pressure loss and the actual muffler pressure loss Therefore, the memory pressure loss is changed.

  The memory pressure loss is changed by selecting a map showing a correlation close to the actual correlation from among a plurality of maps showing the correlation between the exhaust flow rate stored in the ECU 10 and the muffler pressure loss. At this time, a map showing the correlation closest to the actual correlation may be selected. Here, FIG. 3 is a diagram showing a plurality of maps showing the correlation between the exhaust flow rate stored in the ECU 10 and the muffler pressure loss. The plurality of maps show the correlation between the exhaust flow rate and the muffler pressure loss in a range in which a deviation may occur due to the tolerance of the muffler 5. In the following, unless otherwise specified, the map refers to a map showing the correlation between the exhaust flow rate stored in the ECU 10 and the muffler pressure loss. The map according to the present embodiment is obtained in advance by experiments, simulations, calculation formulas, and the like and stored in the ECU 10. In the present embodiment, a map showing the correlation between the exhaust flow rate and the muffler pressure loss corresponds to the correlation information in the present invention.

  For each of the maps shown in FIG. 3, the ECU 10 calculates the difference between the ratio of the muffler pressure loss to the actual differential pressure at the first exhaust flow rate and the ratio of the muffler pressure loss to the actual differential pressure at the second exhaust flow rate. An absolute value (hereinafter also referred to as a pressure loss ratio difference) is calculated. The closer the correlation shown in the map is to the correlation between the actual exhaust flow rate and the muffler pressure loss, the smaller the pressure loss ratio difference. Therefore, since the map where the pressure loss ratio difference is small is considered to be a map representing a correlation close to the correlation between the actual exhaust flow rate and the muffler pressure loss, it is selected as the memory pressure loss after change and stored as the memory pressure loss used thereafter. (It may be updated.) At this time, a map in which the pressure loss ratio difference is the smallest or a map in which the pressure loss ratio difference is a predetermined value or less may be selected and stored. The updated memory pressure loss also includes the correlation between the exhaust flow rate other than the first exhaust flow rate and the second exhaust flow rate and the muffler pressure loss, and therefore, in the case of any exhaust flow rate other than the first exhaust flow rate and the second exhaust flow rate. Even so, the filter pressure loss can be calculated by subtracting the stored pressure loss from the total differential pressure.

  On the other hand, in this embodiment, the optimum memory pressure loss may be selected from the map without determining whether or not there is a difference between the memory pressure loss and the actual muffler pressure loss. For example, an appropriate one may be selected from the map during the first run and stored as the stored pressure loss without determining whether or not there is a difference between the stored pressure loss in the initial state and the actual muffler pressure loss. Also, the memory pressure loss may not be set in the initial state, and an appropriate one may be selected from the map during the first run and stored as the memory pressure loss.

FIG. 4 is a flowchart showing a flow for changing the memory pressure loss according to the present embodiment. This flowchart is executed only once by the ECU 10 when the filter 4 and the muffler 5 are new. Here, when PM is deposited on the filter 4, an increase in pressure loss due to PM is included in the first actual differential pressure and the second actual differential pressure. In this way, when PM is deposited on the filter 4, the relationship that the ratio of the muffler pressure loss to the actual differential pressure is constant regardless of the flow rate of the exhaust gas does not hold. For this reason, in this embodiment, the memory pressure loss is changed when the filter 4 and the muffler 5 are new. In addition, new is not only the state that is not used at all,
It also includes a state in which the change in pressure loss of each member from a state where it is not used at all is within an allowable range. For example, when the accumulated operation time of the internal combustion engine 1 is within a predetermined time, or when the accumulated travel distance of the vehicle on which the internal combustion engine 1 is mounted is within a predetermined distance, a new product may be used. The predetermined time or the predetermined distance is obtained in advance by experiment or simulation as a value at which the change in pressure loss of each member falls within the allowable range. On the other hand, it may be considered as a new product before PM is deposited on the filter 4 by a predetermined amount or more. The predetermined amount here can be obtained in advance by experiments, simulations, or the like as the PM accumulation amount when the error of the memory pressure loss after the change exceeds the allowable range. Further, when the vehicle equipped with the internal combustion engine 1 travels for the first time, the memory pressure loss may be changed assuming that the filter 4 and the muffler 5 are new.

  In step S101, an unevaluated map is set. An unevaluated map is a map that has not been evaluated by this flowchart among a plurality of maps. In this flowchart, the following processing from step S102 to step S108 is executed for each of all maps stored in the ECU 10. In this step S101, one map is set from among the unevaluated maps as a map to be evaluated by the following processing. When the process of step S101 ends, the process proceeds to step S102.

  In step S102, it is determined whether the exhaust flow rate is the first exhaust flow rate. The first exhaust flow rate may be a fixed value or an arbitrary value. When the first exhaust flow rate is an arbitrary value, the current exhaust flow rate is set as the first exhaust flow rate. If an affirmative determination is made in step S102, the process proceeds to step S103, whereas if a negative determination is made, the process returns to step S102.

  In step S103, for the map set in step S101, the detected value of the differential pressure sensor 6 at the first exhaust flow rate, that is, the first actual differential pressure, and the first exhaust flow rate obtained from the map set in step S101. The muffler pressure loss (hereinafter also referred to as first map pressure loss) is read, and based on these values, the ratio of the muffler pressure loss to the actual differential pressure at the first exhaust flow rate (hereinafter also referred to as the first pressure loss ratio). .) Is calculated. In this step S103, the ratio of the first map pressure loss to the first actual differential pressure becomes the first pressure loss ratio. When the process of step S103 ends, the process proceeds to step S104.

  In step S104, it is determined whether the exhaust flow rate is the second exhaust flow rate. The second exhaust flow rate may be a fixed value or an arbitrary value. When the second exhaust flow rate is an arbitrary value, it is determined whether or not the difference between the current exhaust flow rate and the first exhaust flow rate is greater than or equal to a predetermined flow rate. The predetermined flow rate is a value used to determine the second exhaust flow rate, and is set to accurately change the memory pressure loss. That is, if the difference between the first exhaust flow rate and the second exhaust flow rate is small, even if the muffler pressure loss is not accurate, a pressure loss ratio difference is unlikely to occur, and it may be difficult to select an appropriate map. Therefore, since it is better that there is a certain difference between the first exhaust flow rate and the second exhaust flow rate, if the difference between the current exhaust flow rate and the first exhaust flow rate is greater than or equal to a predetermined flow rate, The flow rate is the second exhaust flow rate. The predetermined flow rate is obtained in advance by experiment or simulation so that the error of the memory pressure loss after changing the memory pressure loss is within the allowable range. If an affirmative determination is made in step S104, the process proceeds to step S105. On the other hand, if a negative determination is made, the process returns to step S104.

In step S105, for the map set in step S101, the detected value of the differential pressure sensor 6 at the second exhaust flow rate, that is, the second actual differential pressure, and the second exhaust flow rate obtained from the map set in step S101. The muffler pressure loss (hereinafter also referred to as second map pressure loss) is read, and based on these values, the ratio of the muffler pressure loss to the actual differential pressure at the second exhaust flow rate (hereinafter also referred to as the second pressure loss ratio). .) Is calculated. In step S105, the ratio of the second map pressure loss to the second actual differential pressure becomes the second pressure loss ratio. Step S
When the process of 105 ends, the process proceeds to step S106.

  In step S106, it is determined whether or not the absolute value of the difference between the first pressure loss ratio and the second pressure loss ratio, that is, the pressure loss ratio difference is smaller than the already obtained value. The acquired value is the smallest value among the pressure loss ratio differences calculated while the processing from step S101 to step S109 is repeated. The initial value of the acquired value is set to a sufficiently large value. In this step S106, it is determined whether or not the current pressure loss ratio difference is smaller than the previously calculated minimum value of the pressure loss ratio difference. If an affirmative determination is made in step S106, the process proceeds to step S107. On the other hand, if a negative determination is made, the process proceeds to step S109.

  In step S107, the current pressure loss ratio difference is set as an already obtained value. Then, the process proceeds to step S108, and the map set at the present time is stored as a map corresponding to the acquired value. That is, in this step S108, a map having the smallest pressure loss ratio difference at the present time is stored. When the process of step S108 ends, the process proceeds to step S109.

  In step S109, it is determined whether or not an unevaluated map exists. That is, in this step S109, it is determined whether or not the processing prior to step S109 has been completed for all the maps stored in the ECU 10. If an affirmative determination is made in step S109, the process proceeds to step S110. On the other hand, if a negative determination is made, the process returns to step S101. Thus, steps S101 to S109 are repeatedly performed until there is no unevaluated map.

  In step S110, the memory pressure loss is changed. That is, the map stored in step S108 is selected as a new stored pressure loss and stored in the ECU 10. In this way, the map having the smallest pressure loss ratio difference is selected from the plurality of maps and used for subsequent processing.

  In the example of the above flowchart, all the maps are evaluated, and the map with the smallest pressure loss ratio difference is selected. In another example, when the map is evaluated, the pressure loss ratio difference may be compared with a predetermined value, and if the pressure loss ratio difference is equal to or less than the predetermined value, the stored pressure loss may be changed immediately and the process may be terminated. In this case, an unevaluated map may remain. Here, the predetermined value is a value that can be determined to have a sufficiently small value and that the pressure loss pressure loss determined by the corresponding map substantially matches the actual pressure loss of the pressure loss portion. Thereby, it is possible to shorten the time for evaluating the map and change the memory pressure loss at an earlier timing.

  FIG. 5 is another flowchart showing a flow for changing the memory pressure loss according to the present embodiment. This flowchart is executed by the ECU 10 in place of the flowchart shown in FIG. Steps that are the same as those in the flowchart shown in FIG.

  In the flowchart shown in FIG. 5, when the process of step S105 ends, the process proceeds to step S201. In step S201, it is determined whether the pressure loss ratio difference is equal to or less than a predetermined value. The predetermined value is a value that is sufficiently small so that it can be determined that the pressure loss part pressure loss obtained from the corresponding map substantially matches the actual pressure loss of the pressure loss part, and is obtained in advance by experiments or simulations. If an affirmative determination is made in step S201, the process proceeds to step S202. On the other hand, if a negative determination is made, the process proceeds to step S109.

In step S202, the memory pressure loss is changed. That is, the map set in step S101 is selected as a new memory pressure loss and stored in the ECU 10. In this way, a map having a pressure loss ratio difference equal to or less than a predetermined value is selected from a plurality of maps and used for subsequent processing. On the other hand, if an affirmative determination is made in step S109, this flowchart is terminated. If an affirmative determination is made in step S109, the memory pressure loss has not been changed. Therefore, the memory pressure loss may be changed by executing the flowchart shown in FIG. You may use for. On the other hand, in the flowchart shown in FIG. 4, if there is a map in which the pressure loss ratio difference is equal to or smaller than a predetermined value before the evaluation of all maps is completed, the map is changed as a memory pressure loss and the flowchart is ended. Can do.

  Next, the flow of the abnormality determination process will be described. FIG. 6 is a flowchart showing the flow of the abnormality determination process of the filter 4 according to the present embodiment. This flowchart is executed every predetermined time by the ECU 10. The flowchart of FIG. 6 is executed after the flowchart of FIG. 4 is executed.

  In step S301, the filter pressure loss is calculated. The filter pressure loss can be calculated by subtracting the muffler pressure loss corresponding to the current exhaust flow rate from the memory pressure loss changed in the flowchart shown in FIG. 4 from the actual differential pressure at the current time.

  In step S302, an upper limit threshold and a lower limit threshold are acquired. The upper limit threshold and the lower limit threshold are the upper limit value and the lower limit value of a predetermined pressure loss range of the filter pressure loss at which the filter 4 can be said to be normal at the exhaust flow rate when the filter pressure loss is calculated in step S301. The ECU 10 acquires an upper limit threshold and a lower limit threshold stored in advance in the ECU 10 based on the exhaust flow rate.

  In step S303, it is determined whether or not the filter pressure loss is not less than the lower limit threshold and not more than the upper limit threshold. In step S303, it is determined whether or not the filter 4 is normal. If an affirmative determination is made in step S303, the process proceeds to step S304, whereas if a negative determination is made, the process proceeds to step S305. In step S304, it is determined that the filter 4 is normal, and in step S305, it is determined that the filter 4 is abnormal.

  Thus, by performing the abnormality determination process of the filter 4 based on the memory pressure loss after the change, the accuracy of the abnormality determination process of the filter 4 can be improved.

  In the above description, the memory pressure loss is changed when the filter 4 and the muffler 5 are new. Instead, the regeneration of the filter 4 for removing the particulate matter (PM) deposited on the filter 4 is performed. After doing so, the memory pressure loss may be changed. At this time, it may be confirmed beforehand that there is no abnormality in the filter 4 by a known technique. Here, since the PM is not deposited on the filter 4 immediately after the regeneration of the filter 4, the first actual differential pressure and the second actual differential pressure are detected at this time, so that the filter The memory pressure loss can be changed without being affected by the PM accumulated in the layer 4. For this reason, memory pressure loss can be changed appropriately. At this time, it is possible to change the memory pressure loss including not only the tolerance of the muffler 5 but also the influence of the secular change.

  In the above description, the memory pressure loss is changed based on the pressure loss ratio difference. Alternatively, the memory pressure loss can be changed based on the ratio between the first pressure loss ratio and the second pressure loss ratio. For example, the ratio of the ratio of the muffler pressure loss to the actual differential pressure at the first exhaust flow rate and the ratio of the muffler pressure loss to the actual differential pressure at the second exhaust flow rate is calculated for each map, and this value is 1 You may select the map close | similar to as memory pressure loss after a change. Even in this case, it can be said that the correlation information that reduces the pressure loss ratio difference is selected.

Further, in this embodiment, the ratio of the muffler pressure loss to the total differential pressure is compared, but instead, the ratio of the muffler pressure loss to the filter pressure loss may be compared. Here, since the total differential pressure is the sum of the filter pressure loss and the muffler pressure loss, if the ratio of the muffler pressure loss to the total differential pressure is constant regardless of the exhaust flow rate, the ratio of the muffler pressure loss to the filter pressure loss is also the exhaust pressure. It becomes constant regardless of the flow rate of. Therefore, changing the memory pressure loss based on the ratio of the muffler pressure loss to the filter pressure loss is equivalent to changing the memory pressure loss based on the ratio of the muffler pressure loss to the total differential pressure. For example, the ECU 10 compares the ratio of the first memory pressure loss to the filter pressure loss at the first exhaust flow rate (hereinafter also referred to as the first filter pressure loss) and the filter pressure loss at the second exhaust flow rate (hereinafter also referred to as the second filter pressure loss). If the absolute value of the difference between the ratio of the second memory pressure loss and the second memory pressure loss is equal to or greater than the determination threshold, it is determined that there is a difference between the memory pressure loss and the actual muffler pressure loss, and the memory pressure loss is changed. Then, the ECU 10 selects a map in which the absolute value of the difference between the ratio of the first memory pressure loss to the first filter pressure loss and the ratio of the second memory pressure loss to the second filter pressure loss is small.

  In this embodiment, since the ECU 10 stores a plurality of maps, it can be said that the ECU 10 includes the correlation information holding unit in the present invention. In the present embodiment, since the ECU 10 calculates the pressure loss ratio difference for each piece of correlation information, it can be said that the ECU 10 includes the pressure loss ratio difference calculation unit according to the present invention. Further, in the present embodiment, the ECU 10 includes a selection unit according to the present invention in order for the ECU 10 to select a map in which the pressure loss ratio difference satisfies a predetermined condition as correlation information for calculating the pressure loss of the pressure loss unit. It can be said that.

  As described above, according to the present embodiment, even if the actual muffler pressure loss deviates from the stored pressure loss stored in the ECU 10, an appropriate map is selected from a plurality of maps and stored according to this map. By changing the pressure loss, the muffler pressure loss can be calculated more accurately. By calculating the filter pressure loss based on the muffler pressure loss, the filter pressure loss can be obtained more accurately. Therefore, when calculating the amount of PM trapped based on the differential pressure detected by the differential pressure sensor 6 or determining whether or not there is an abnormality in the filter 4, using more accurate filter pressure loss, More accurate determination is possible.

<Example 2>
In the first embodiment, the ECU 10 stores a plurality of maps in advance as correlation information. On the other hand, in this embodiment, the ECU 10 stores a plurality of functions in advance as correlation information. Then, the ECU 10 obtains a function that reduces the pressure loss ratio difference and changes the memory pressure loss. Since other devices are the same as those in the first embodiment, the description thereof is omitted.

The ECU 10 stores the correlation between the exhaust flow rate and the muffler pressure loss as a function in order to calculate the filter pressure loss. Therefore, in this embodiment, the memory pressure loss is stored as a function. For example, since the relationship between the exhaust flow rate and the muffler pressure loss is close to a quadratic function, it is assumed in the present embodiment that the following relationship exists between the exhaust flow rate and the muffler pressure loss.
Y = A · X ² + B · X
However, Y is a muffler pressure loss, X is an exhaust flow rate, and A and B are coefficients determined within a tolerance range of exhaust system members. The initial value of A or B is a value at the time of designing the exhaust system member.

The memory pressure loss in the present embodiment is changed by selecting a function showing a correlation close to the actual correlation from among a plurality of functions showing the correlation between the exhaust flow rate and the muffler pressure loss stored in the ECU 10. . At this time, a function indicating a correlation closest to the actual correlation may be selected. In the following, unless otherwise specified, the function refers to a function indicating a correlation between the exhaust flow rate stored in the ECU 10 and the muffler pressure loss. In this embodiment, the ECU 10 stores a plurality of functions in which either one of the coefficients A or B is different. Note that A or B in each function may be a value that is different from each other by a preset size or a preset ratio, and is a value that is set according to a preset condition. Alternatively, it may be a predetermined value. Then, a pressure loss ratio difference is calculated for each function, and a function having a small pressure loss ratio difference is set as a new memory pressure loss. Thus, from the next time on, the muffler pressure loss can be calculated from the stored function and the exhaust flow rate.

  FIG. 7 is a flowchart showing a flow for changing the memory pressure loss according to the present embodiment. This flowchart is executed only once by the ECU 10 when the filter 4 and the muffler 5 are new, instead of the flowchart shown in FIG. Steps that are the same as those in the flowchart shown in FIG.

  In step S401, an unevaluated function is set. An unevaluated function is a function that has not been evaluated by this flowchart among a plurality of functions. In this flowchart, a plurality of functions are stored in advance in the ECU 10, and the plurality of functions are sequentially evaluated. In this flowchart, the following processing from step S102 to step S404 is executed for each of all functions stored in the ECU 10. In step S401, one function is set from unevaluated functions as a function to be evaluated in the following processing. When the process of step S401 ends, the process proceeds to step S102.

  If an affirmative determination is made in step S102, the process proceeds to step S402. In step S402, the first actual differential pressure at the first exhaust flow rate and the muffler pressure loss (hereinafter also referred to as first function pressure loss) obtained by the function set in step S401 are read, and these values are further read. Based on this, the first pressure loss ratio is calculated. In step S402, the ratio of the first function pressure loss to the first actual differential pressure is the first pressure loss ratio. When the process of step S402 ends, the process proceeds to step S104.

  If an affirmative determination is made in step S104, the process proceeds to step S403. In step S403, the second actual differential pressure at the second exhaust flow rate and the muffler pressure loss (hereinafter also referred to as the second muffler pressure loss) obtained by the function set in step S401 are read, and these values are further read. Based on this, the second pressure loss ratio is calculated. In step S403, the ratio of the second muffler pressure loss to the second actual differential pressure is the second pressure loss ratio. When the process of step S403 ends, the process proceeds to step S106.

  Then, an affirmative determination is made in step S106, and the current pressure loss ratio difference is set to an already obtained value in step S107. Then, the process proceeds to step S404, and the function set at the current time is stored as a function corresponding to the already obtained value. That is, in this step S404, a function having the smallest pressure loss ratio difference at the present time is stored. When the process of step S404 ends, the process proceeds to step S405.

  In step S405, it is determined whether there is no unevaluated function. That is, in this step S405, it is determined whether or not the evaluation has been completed for all the functions stored in the ECU 10. If an affirmative determination is made in step S405, the process proceeds to step S406. On the other hand, if a negative determination is made, the process returns to step S401. Thereby, steps S401 to S405 are repeatedly performed until there is no unevaluated function.

  In step S406, the memory pressure loss is changed. That is, the function stored in step S404 is selected as a new stored pressure loss and stored in the ECU 10. In this way, the function having the smallest pressure loss ratio difference is selected from the plurality of functions and used for the subsequent processing.

In the example of the above flowchart, all the functions are evaluated, and the function having the smallest pressure loss ratio difference is selected. In another example, when the function is evaluated, the pressure loss ratio difference may be compared with a predetermined value set in advance, and if the pressure loss ratio difference is less than or equal to the predetermined value, the stored pressure loss may be changed immediately and the process may be terminated. In this case, unevaluated functions may remain. Here, the predetermined value is a value that can be determined to have a sufficiently small value and that the pressure loss pressure loss determined by the corresponding function substantially matches the actual pressure loss of the pressure loss portion. Thereby, the time for performing the function evaluation can be shortened, and the pressure loss pressure loss can be changed to the changed value at an earlier timing.

  FIG. 8 is another flowchart showing a flow for changing the memory pressure loss according to the present embodiment. This flowchart is executed by the ECU 10 instead of the flowchart shown in FIG. Steps in which the same processing as in the flowchart is performed are denoted by the same reference numerals and description thereof is omitted.

  In the flowchart shown in FIG. 8, if an affirmative determination is made in step S201, the process proceeds to step S501. On the other hand, if a negative determination is made, the process proceeds to step S405.

  In step S501, the memory pressure loss is changed. That is, the function set in step S401 is selected as a new memory pressure loss and stored in the ECU 10. In this way, a function having a pressure loss ratio difference equal to or less than a predetermined value is selected from a plurality of functions and used for subsequent processing. On the other hand, if an affirmative determination is made in step S405, this flowchart is terminated. If an affirmative determination is made in step S405, the memory pressure loss has not been changed. Therefore, the memory pressure loss may be changed by executing the flowchart shown in FIG. You may use for. On the other hand, in the flowchart shown in FIG. 7, if there is a function whose pressure loss ratio difference is equal to or smaller than a predetermined value before the evaluation of all the functions is completed, the function is changed as a memory pressure loss and the flowchart is ended. Can do.

  In the present embodiment, the function indicating the correlation between the exhaust gas flow rate and the muffler pressure loss corresponds to the correlation information in the present invention. In this embodiment, since the ECU 10 stores a plurality of functions, it can be said that the ECU 10 includes the correlation information holding unit in the present invention. In the present embodiment, since the ECU 10 calculates the pressure loss ratio difference for each function, it can be said that the ECU 10 includes the pressure loss ratio difference calculation unit according to the present invention. Furthermore, in the present embodiment, the ECU 10 includes a selection unit according to the present invention in order for the ECU 10 to select a function whose pressure loss ratio difference satisfies a predetermined condition as correlation information for calculating the pressure loss of the pressure loss unit. It can be said that.

  As described above, according to this embodiment, the muffler pressure loss can be obtained more accurately by optimizing the function for calculating the muffler pressure loss from the exhaust flow rate. Thereby, the pressure loss of the filter can be obtained with high accuracy. In the present embodiment, a quadratic function has been described as an example. However, the present invention is not limited to this, and other functions can also be used. The function can also be obtained by experiment or simulation.

1 Internal combustion engine 2 Exhaust pipe 3 Catalyst 4 Filter 5 Muffler 6 Differential pressure sensor 10 ECU
11 Air flow meter

Claims (8)

A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A pressure loss portion that causes an exhaust pressure loss in the exhaust passage downstream of the filter;
A differential pressure sensor that detects an actual differential pressure that is an actual difference between the pressure of the exhaust gas upstream of the filter and the atmospheric pressure;
An exhaust gas for an internal combustion engine that calculates a pressure loss of the pressure loss portion using correlation information that is information relating to a correlation between the flow rate of exhaust gas and the pressure loss in the pressure loss portion. In the control device of the purification device,
A flow rate acquisition unit for acquiring a flow rate of exhaust gas passing through the filter;
A correlation information holding unit for holding a plurality of the correlation information;
For each of the correlation information held by the correlation information holding unit, the correlation information for the differential pressure detected by the differential pressure sensor when the flow rate of the exhaust gas acquired by the flow rate acquisition unit is the first exhaust gas flow rate. The differential pressure sensor when the ratio of the pressure loss in the pressure loss part calculated using the flow rate and the exhaust flow rate acquired by the flow rate acquisition unit is a second exhaust flow rate different from the first exhaust flow rate A pressure loss ratio difference calculating unit that calculates a pressure loss ratio difference that is a difference between the pressure loss ratio in the pressure loss part calculated using the correlation information with respect to the differential pressure detected by
As the correlation information for calculating the pressure loss of the pressure loss unit, a selection unit that selects the correlation information in which the pressure loss ratio difference satisfies a predetermined condition;
A control device for an exhaust gas purification device for an internal combustion engine.   2. The control device for an exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the selection unit selects the correlation information in which the pressure loss ratio difference is the smallest as the correlation information in which the pressure loss ratio difference satisfies the predetermined condition. .   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the selection unit selects the correlation information in which the pressure loss ratio difference is equal to or less than a predetermined value as the correlation information in which the pressure loss ratio difference satisfies the predetermined condition. Control device.   4. The internal combustion engine according to claim 1, wherein the correlation information holding unit stores, as the correlation information, a plurality of maps representing a correlation between an exhaust flow rate and a pressure loss in the pressure loss unit. 5. Control device for exhaust purification system.   The internal combustion engine according to any one of claims 1 to 3, wherein the correlation information holding unit stores, as the correlation information, a plurality of functions representing a correlation between an exhaust flow rate and a pressure loss in the pressure loss unit. Control device for exhaust purification system.   The control device for an exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the selection unit stores the selected correlation information as the correlation information for calculating a pressure loss of the pressure loss unit. .   The control device for an exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the pressure loss ratio difference calculation unit calculates the pressure loss ratio difference when the filter and the pressure loss part are new.   The control device for an exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the pressure loss ratio difference calculation unit calculates the pressure loss ratio difference after regeneration of the filter.

Images