JP2010275877A - Failure detection system for filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for enhancing the failure detection accuracy of a filter in a system for detecting a failure of a filter on the basis of a measurement value by a plurality of sensors arranged in an exhaust passage on the downstream side of the filter. <P>SOLUTION: The system includes a filter which is provided to the exhaust passage of an internal combustion engine to collect particulate matters in exhaust, a plurality of temperature sensors which measure the temperatures of exhaust in a plurality of positions substantially at equal distances from the downstream end of the filter, an exhaust temperature change means which changes the temperature of exhaust flowing into the filter, and a detection means which detects a failure of the filter based on the variations of a change amount of a measurement value by each temperature sensor before/after changing the temperature of exhaust flowing into the filter by the exhaust temperature change means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a failure detection system for a filter that collects particulate matter in exhaust gas from an internal combustion engine.

  In an internal combustion engine provided with a filter for collecting particulate matter in exhaust gas in an exhaust passage, a plurality of temperature sensors are arranged in the radial direction of the exhaust passage downstream of the filter, and the exhaust gas downstream of the filter is based on the measured value by the temperature sensor. There has been proposed a system that estimates an exhaust temperature distribution in a passage radial direction and detects a filter failure based on the exhaust temperature distribution (see Patent Document 1).

JP 2007-332911 A JP 2003-287526 A JP 2008-261302 A JP 2006-002736 A JP 2003-106140 A JP 2007-16619 A

  In the system that detects a filter failure based on the measurement values of a plurality of temperature sensors as in Patent Document 1, there is a possibility that the filter failure cannot be detected accurately when there is a variation in characteristics among the temperature sensors. .

  The present invention has been made in view of such circumstances, and in a system for detecting a filter failure based on measured values by a plurality of temperature sensors arranged in an exhaust passage downstream of the filter, the detection accuracy of the filter failure is improved. It aims at providing the technology to improve.

In order to solve the above problems, a filter failure detection system according to the present invention includes:
A filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A plurality of temperature sensors that measure the temperature of the exhaust at a plurality of positions that are substantially equal in distance from the downstream end of the filter;
Exhaust temperature changing means for changing the temperature of the exhaust gas flowing into the filter;
Detecting means for detecting a failure of the filter based on variation in the amount of change in the measured value by each temperature sensor before and after changing the temperature of the exhaust gas flowing into the filter by the exhaust temperature changing means;
It is characterized by providing.

  When the temperature of the exhaust gas flowing into the filter (hereinafter referred to as “incoming gas”) is changed, the temperature of the exhaust gas flowing out from the filter (hereinafter referred to as “outgoing gas”) changes accordingly. Depending on the presence or absence of a failure such as breakage at the passage location, the manner in which the temperature of the outgas changes varies. Specifically, the exhaust gas passing through the failure location and the vicinity thereof has a larger change amount of the output gas temperature when the input gas temperature is changed than the exhaust gas passing through the non-failure location. This is because the heat exchange between the exhaust and the filter is less at the failure location and in the vicinity thereof than at the non-failure location.

  Therefore, when there is a failure location in the filter, the amount of change in the output gas temperature when the inlet gas temperature is changed varies depending on the positional relationship between the location where the exhaust gas has passed in the filter and the failure location. . When there is no failure location in the filter, the amount of change in the output gas temperature when the inlet gas temperature is changed is substantially the same regardless of the position where the exhaust gas passes through the filter. The variation is small.

  From this, the presence or absence of a filter failure can be determined based on the variation in the amount of change in the output gas temperature when the input gas temperature is changed.

  In the present invention, variation in the amount of change in the output gas temperature when the input gas temperature is changed is acquired based on the amount of change in the measurement values by a plurality of temperature sensors arranged at equal distances from the downstream end of the filter. . By providing a plurality of temperature sensors at positions equidistant from the downstream end of the filter, it is possible to acquire a temperature change of the exhaust gas that has flowed out through different positions in the filter.

  When using a plurality of temperature sensors in this way, there may be a problem of variations in measured values for each temperature sensor due to individual differences in manufacturing for each temperature sensor or differences with time, but in the present invention, Since the change amount of the measurement value is acquired instead of the measurement value itself by the temperature sensor, the variation in the measurement value for each temperature sensor is offset. And since the variation in the variation in the output gas temperature is acquired based on the variation in the measured value by this temperature sensor, the case where the inlet gas temperature is changed regardless of the variation in the measured value for each temperature sensor. It is possible to acquire the variation in the change amount of the output gas temperature with high accuracy.

  As described above, according to the present invention, it is possible to accurately acquire the variation in the amount of change in the output gas temperature when the input gas temperature is changed. Therefore, it is possible to accurately detect a filter failure based on the variation. It becomes possible.

  As described above, when there is a failure location in the filter, the amount of change in the output gas temperature when the input gas temperature is changed depends on the positional relationship between the location where the exhaust gas passes in the filter and the failure location. On the other hand, variation occurs, but when there is no failure location in the filter, variation in the amount of change in the outgas temperature is small.

  Therefore, in the present invention, the detection means can determine that the filter is malfunctioning when the degree of variation in the amount of change in the measured value by each temperature sensor is greater than a predetermined threshold. .

  Here, the “predetermined threshold value” is a reference value for the degree of variation in the amount of change in the measured value by the temperature sensor, for determining whether or not a failure location exists in the filter. This threshold is based on, for example, the maximum value that can appear as a variation in the amount of change in the measurement value by the temperature sensor or the maximum value that can appear as a variation in the amount of change in the outgas temperature when there is no failure location in the filter. Can be determined. This threshold value may be set according to the amount of change given to the inlet gas temperature by the temperature changing means, the operating condition of the internal combustion engine when the inlet gas temperature is changed by the temperature changing means, and the like.

  The exhaust gas passing through the exhaust passage exchanges heat with the outside air through the wall surface of the exhaust passage. The characteristics of heat transfer between the outside air and the exhaust differ depending on the position where the exhaust in the exhaust passage circulates. Specifically, heat transfer between the outside air and the exhaust becomes easier as the position where the exhaust flows is closer to the wall surface of the exhaust passage in contact with the outside air. The greater the amount of heat exchange between the outside air and the exhaust, the smaller the amount of change in the output gas temperature that accompanies the change in the input gas temperature.

  Therefore, the amount of change in the measured value obtained by the temperature sensor obtained when the inlet gas temperature is changed is due to the difference in heat exchange between the filter and the outside air depending on the position where the exhaust gas passes through the exhaust passage. There is a possibility that variations unrelated to the presence / absence of a failure at a location where the filter has passed through the filter may occur. In that case, there is a possibility that the failure detection of the filter based on the variation of the change amount of the measured value by the temperature sensor cannot be performed with high accuracy.

  Therefore, in the present invention, the detection means further includes a correction means for correcting the amount of change in the measured value by the temperature sensor according to the distance between the temperature sensor and the wall surface of the exhaust passage. A failure of the filter may be determined based on the corrected amount of change.

  By performing such correction, the influence of the variation due to the difference in heat transfer between the outside air and the exhaust according to the position where the exhaust has passed is eliminated from the variation that appears in the change amount of the measured value by the temperature sensor. be able to. As a result, it is possible to detect a filter failure with higher accuracy.

  Here, as the exhaust flow position is closer to the wall surface of the exhaust passage as described above, the amount of change in the measured value by the temperature sensor when the inlet gas temperature is changed tends to be smaller. The closer the distance between the wall surface of the exhaust passage and the temperature sensor is, the better it is to correct so as to increase the amount of change in the measured value by the acquired temperature sensor.

  The variation due to the heat exchange between the exhaust gas and the outside air in the amount of change in the measured value by the temperature sensor becomes more significant as the difference between the exhaust gas temperature and the outside air temperature increases.

  Therefore, in the present invention, the correction means may determine a correction amount for the change amount of the measured value by the temperature sensor according to the difference between the outside air temperature and the exhaust temperature.

  For example, as the distance between the wall surface of the exhaust passage that is in contact with the outside air and the temperature sensor is closer, the correction amount in the case of correcting to increase the amount of change in the measured value by the acquired temperature sensor is the outside air temperature and the exhaust temperature. The larger the difference, the better.

  In the present invention, when performing filter failure determination, the temperature change means changes the input gas temperature and measures the amount of change in the output gas temperature that accompanies it. Therefore, the temperature sensor measures the outside air temperature and the exhaust gas temperature. It will be performed under the condition that the difference of fluctuates. Therefore, it is possible to correct the amount of change in the measured value by the temperature sensor in consideration of the difference between the outside air temperature and the exhaust temperature when the measurement by the temperature sensor is performed. Is particularly suitable for detecting.

  ADVANTAGE OF THE INVENTION According to this invention, in the technique which detects the failure of a filter based on the measured value by the several temperature sensor which has arrange | positioned the exhaust passage downstream of a filter, it becomes possible to improve the detection accuracy of the failure of a filter.

It is a figure which shows schematic structure of the engine which applies the filter failure determination system which concerns on Example 1 and 2, and its intake system and exhaust system. It is a figure which shows the installation aspect of the temperature sensor which concerns on Example 1. FIG. It is a figure which shows the time transition of the input gas temperature accompanying exhaust gas temperature rising control, and the time transition of the measured value by each temperature sensor. It is a figure which shows the time transition of the increase amount of the inlet gas temperature accompanying exhaust gas temperature rising control, and the time transition of the increase amount of the measured value by each temperature sensor. 6 is a flowchart illustrating a part of a filter failure determination process according to Embodiments 1 and 2. 6 is a flowchart illustrating a part of filter failure determination processing according to the first embodiment. It is a figure which shows the installation aspect of the temperature sensor which concerns on Example 2. FIG. It is a figure which shows the relationship between the distance from the stop axis line of an exhaust passage to the temperature measurement part of a temperature sensor, and the increase amount of the measured value by the temperature sensor accompanying exhaust gas temperature rising control. It is a figure for demonstrating the difference of the time transition of the increase amount of the measured value by a temperature sensor by the difference of the distance of the temperature measurement part of a temperature sensor, and the wall surface of an exhaust passage. It is a figure which shows the relationship between the temperature difference of exhaust gas and external air, and the difference of the raise amount of the measured value by two temperature sensors from which the distance from the wall surface of an exhaust passage differs from a temperature measurement part. 12 is a flowchart illustrating a part of filter failure determination processing according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail. The dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment are not intended to limit the technical scope of the invention only to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of an intake system and an exhaust system of an internal combustion engine to which a filter failure detection system of the present invention is applied. The engine 1 is a diesel engine having four cylinders 17. Each cylinder 17 communicates with the intake passage 8 via the intake manifold 2. Further, it communicates with the exhaust passage 9 via the exhaust manifold 3. The engine 1 includes a compressor 6 provided in an intake passage 8 and a turbine 7 provided in an exhaust passage 9, and includes a turbocharger 5 that performs supercharging using the energy of exhaust. An intake air passage 8 downstream of the compressor 6 is provided with an intercooler 4 for cooling the supercharged intake air. An intake air temperature sensor 19 for measuring the intake air temperature is provided in the intake passage 8 upstream of the compressor 6. The exhaust manifold 3 is provided with a fuel addition valve 14 for adding fuel to the exhaust. The exhaust manifold 3 and the intake manifold 2 communicate with each other through an EGR passage 15. A part of the exhaust gas is recirculated to the intake system via the EGR passage 15. The EGR passage 15 is provided with an EGR valve 18 that adjusts the amount of exhaust gas flowing into the intake manifold 2 via the EGR passage 15.

  In the exhaust passage 9 downstream of the turbine 7, a NOx storage reduction catalyst 12 that stores NOx in the exhaust and reduces and purifies it, and a wall flow type particulate filter (hereinafter simply referred to as a particulate flow filter that collects particulate matter in the exhaust). (Referred to as “filter”) 13. When it is determined that a predetermined amount of NOx has been stored in the NOx catalyst 12, the NOx reduction process is performed to reduce and purify the NOx stored in the NOx catalyst 12 by enriching the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 12. I do. If it is determined that a predetermined amount of particulate matter has been collected by the filter 13, a filter regeneration process is performed in which the temperature of the filter 13 is raised and the particulate matter collected by the filter 13 is oxidized and removed. The NOx reduction process and the filter regeneration process are performed by executing known controls such as fuel addition to the exhaust gas by the fuel addition valve 14, combustion by a rich air-fuel ratio, and post injection.

  A temperature sensor 11 that measures the temperature of the exhaust gas flowing into the filter 13 is provided in the exhaust passage 9 near the inlet of the filter 13. A plurality of temperature sensors 10 for measuring the temperature of the exhaust gas flowing out from the filter 13 are provided in the exhaust passage 9 near the outlet of the filter 13. Detailed installation modes of the plurality of temperature sensors 10 will be described later.

  Furthermore, ECU16 which controls the driving | running state of the engine 1 is provided. The ECU 16 receives inputs from the temperature sensor 10, the temperature sensor 11 and other various sensors, acquires the operating state of the engine 1 and the driver's request based on the input data, and performs fuel injection control, filter regeneration processing, NOx reduction. It is a computer unit that executes various other engine controls.

  Since a failure such as breakage may occur inside the filter 13 due to an excessive temperature rise during the filter regeneration process, it is necessary to detect such a failure at an early stage.

  In the present embodiment, the temperature change of the exhaust gas flowing out from the filter 13 (hereinafter referred to as “outgas”) when the temperature of the exhaust gas flowing into the filter 13 (hereinafter referred to as “inlet gas”) is changed. Thus, the failure of the filter 13 is detected. Hereinafter, filter failure detection according to the present embodiment will be described.

  When the inlet gas temperature is changed, the outlet gas temperature also changes accordingly, but the manner in which the outlet gas temperature changes varies depending on the presence or absence of a failure at the location where the exhaust gas has passed through the filter 13. Specifically, the exhaust gas passing through the failure location and the vicinity thereof has a larger change amount of the output gas temperature when the input gas temperature is changed than the exhaust gas passing through the non-failure location.

  This is because, at the failure location of the filter 13, the contact area between the filter 13 and the exhaust gas is reduced and the pressure loss is reduced to increase the flow velocity of the exhaust gas. This is because less heat is exchanged between the exhaust gas and the filter 13 than the exhaust gas passing through the failure location.

  Therefore, when there is a failure location in the filter 13, the amount of change in the output gas temperature when the input gas temperature is changed depends on the positional relationship between the location where the exhaust gas passes in the filter 13 and the failure location. Variation occurs. On the other hand, when there is no failure location in the filter 13, the amount of change in the output gas temperature when the input gas temperature is changed is substantially the same regardless of the position where the exhaust gas passes in the filter 13. Variation in temperature change is small.

  Focusing on this point, in this embodiment, the presence or absence of a failure of the filter 13 is determined based on the variation in the amount of change in the output gas temperature accompanying the change in the input gas temperature, depending on the position where the exhaust gas passes through the filter 13.

  The “variation in the amount of change in the outgas temperature due to the position where the exhaust gas passes through the filter 13” is acquired based on the measurement values obtained by the plurality of temperature sensors 10 provided near the outlet of the filter 13.

  Here, the installation mode of the temperature sensor 10 is demonstrated based on FIG. FIG. 2 is a cross-sectional view of the exhaust passage 9 taken along a cross section (X-X ′ cross section in FIG. 1) perpendicular to the central axis of the exhaust passage 9. The plurality of temperature sensors 10 are arranged so as to measure the outgas temperature on a plane equidistant from the downstream end of the filter 13. In this embodiment, it is assumed that the downstream end of the filter 13 is perpendicular to the central axis of the exhaust passage 9. Therefore, a plane perpendicular to the central axis of the exhaust passage 9 is a plane equidistant from the downstream end of the filter 13.

  As shown in FIG. 2, a total of five temperature sensors 10 are provided (temperature sensors 10a, 10b, 10c, 10d, and 10e), and the temperature measuring units 11a of the temperature sensors 10a, 10b, 10c, 10d, and 10e, 11b, 11c, 11d, and 11e are located on the cross section XX ′. Therefore, each temperature measuring unit 11a, 11b, 11c, 11d, and 11e measures the temperature of the exhaust gas flowing out from the filter 13 at a position equidistant from the downstream end of the filter 13.

In FIG. 2, broken lines A1, A2, and A3 represent equidistant lines at distances R1, R2, and R3 from the central axis of the exhaust passage 9 on the cross section XX ′. As shown in FIG. 2, the temperature measurement unit 11a is disposed on the central axis of the exhaust passage 9, and the other temperature measurement units 11b, 11c, 11d, and 11e are disposed on the equidistant line A3 at equal intervals.

  In FIG. 2, a region 20 indicates a region corresponding to a failure location in the filter 13 on the cross section X-X ′. In this case, the temperature measurement unit 11b is closest to the region 20 corresponding to the failure location. Therefore, among the measured values of the outgas temperature by the temperature sensors 10 a, 10 b, 10 c, 10 d, 10 e, the measured value by the temperature sensor 10 b is most strongly affected by the failure in the filter 13. For example, when the inlet gas temperature is increased, the measured value of the outlet gas temperature by the temperature sensor 10b is considered to be higher than the measured value of the outlet gas temperature by the temperature sensors 10a, 10c, 10d, and 10e.

  However, when using a plurality of temperature sensors in this way, there may be variations in measurement characteristics such as offset error for each temperature sensor due to individual differences in manufacturing for each temperature sensor and differences with time. For this reason, depending on the comparison of the measurement values themselves by the temperature sensors 10a, 10b, 10c, 10d, and 10e, the presence or absence of a failure in the filter 13 may not be accurately determined. This problem will be described with reference to FIG.

FIG. 3 is a diagram illustrating an example of a time transition of the measured value of the outgas temperature by the temperature sensors 10a, 10b, 10c, 10d, and 10e when the input gas temperature is increased. The vertical axis in FIG. 3 represents temperature, and the horizontal axis represents time. As shown in FIG. 3, when increasing the inflow gas temperature Tin at time t _0, it with the gas temperature leaving behind a fixed time from the time t ₀ and begins to rise, the temperature sensor 10a before and after the time t _{0 ',} The measured values Ta, Tb, Tc, Td, Te of the outgas temperature by 10b, 10c, 10d, 10e start to rise.

  A measured value by the temperature sensor 10b close to the region 20 corresponding to the failure location is represented by a thick broken line Tb '. A measured value acquired by the temperature sensor 10b when there is no failure location in the filter 13 is represented by a thick solid line Tb. As can be seen from a comparison between the two, the measured value Tb 'when the failure location exists is higher than the measurement value Tb when the failure location does not exist.

However, as can be seen from the graph before (time _{t 0} ~t 0 ') the measured value by the temperature sensor 10 starts to rise, out in the context of the expected gas temperature is equal, the temperature sensor 10a, 10b, 10c, 10d, 10e There are variations in measured values due to In the example of FIG. 3, as a tendency, the measured values by the temperature sensors 10a, 10c, 10d, and 10e are higher than the measured values by the temperature sensor 10b.

  Among these, the tendency that the measured values by the temperature sensors 10c, 10d, and 10e are higher than the measured values by the temperature sensor 10b is that the offset error related to the measured values by the temperature sensors 10c, 10d, and 10e is the offset error related to the measured value by the temperature sensor 10b. This is a variation in measured value due to a variation in measurement characteristics between these temperature sensors, which is larger than the above.

  Due to such variation in the measured value for each temperature sensor 10, as shown in FIG. 3, the measured value Tb ′ by the temperature sensor 10b, which is high because it has passed through the failure location in the filter 13, and the temperature Since the offset error is larger than that of the sensor 10b, it is difficult to distinguish the measured values Tc, Td, Te by the temperature sensors 10c, 10d, 10e, which are generally higher than the measured values by the temperature sensor 10b. It has become. Variations in measurement characteristics for each temperature sensor 10 are random variations due to individual differences in manufacturing and differences in changes over time, and are difficult to predict and correct.

  In addition, the tendency that the measured value by the temperature sensor 10a is higher than the measured values by the temperature sensors 10b, 10c, 10d, and 10e is the position of the temperature measuring unit 11a, 11b, 11c, 11d, and 11e on the cross section XX ′. It is the variation of the measured value due to the difference. This variation is caused by the difference in the flow velocity of the exhaust gas passing through the central portion and the peripheral portion of the filter 13 and the difference in the amount of heat exchanged with the outside air depending on the distance from the wall surface of the exhaust passage 9. Yes, unlike the variation in measurement characteristics for each temperature sensor 10, it can be predicted, and correction can be performed based on the prediction. The failure determination of the filter 13 in consideration of the variation in the measurement value due to the difference in the position of the temperature measurement unit 11 will be described in the second embodiment.

  As described above, when a plurality of temperature sensors are used, it may be impossible to accurately determine the presence or absence of a failure in the filter 13 by comparing the measured values themselves by the temperature sensors 10a, 10b, 10c, 10d, and 10e.

  Therefore, in the filter failure detection system according to the present embodiment, the input gas temperature is changed, and the change amount of the output gas temperature associated therewith is acquired as the change amount of the measured value by each temperature sensor 10. As described above, when a failure location exists in the filter 13, the amount of change in the output gas temperature when the input gas temperature is changed includes the position where the exhaust gas passes in the filter 13 and the location where the failure location exists. Therefore, the presence or absence of a failure of the filter 13 can be determined based on the variation in the change amount of the outgas temperature obtained as described above.

  And since the variation | change_quantity of outgas temperature is acquired as a variation | change_quantity of the measured value by each temperature sensor 10, the part which is dependent on the measurement characteristic contained in the measured value of the temperature sensor 10 is a step which calculates the variation | change_quantity of a measured value. Is offset by Therefore, even if there is a variation in the measurement characteristics for each temperature sensor 10, the amount of change in the measured value by the temperature sensor 10 is not easily affected by the variation. Therefore, the variation in the change amount of the measurement value of the temperature sensor 10 accurately reflects the presence or absence of a failure in the filter 13.

  FIG. 4 shows the time of increase in the measured value of the output gas temperature by the temperature sensors 10a, 10b, 10c, 10d, and 10e having the same variation in measurement characteristics as the example of FIG. 3 when the input gas temperature is increased. It is a figure which shows an example of transition. The vertical axis in FIG. 4 represents the temperature rise, and the horizontal axis represents time. The temperature increase amount on the vertical axis represents the temperature increase amount with respect to the input gas temperature Tin, the initial value being the temperature immediately before the start of the process of increasing the input gas temperature, and is based on the temperature sensors 10a, 10b, 10c, 10d, and 10e. Regarding the measured value, it represents the amount of change in the measured value with the measured values obtained by the temperature sensors 10a, 10b, 10c, 10d, and 10e immediately before the outgas temperature starts rising as initial values.

As shown in FIG. 4, when the amount of increase of the inflow gas temperature starts to increase at time t _0, and begins at time t _{0 'of} the increase in the amount of increase in the gas temperature leaving behind a fixed time from the time t ₀ with it Before and after, the increase amounts ΔTa, ΔTb, ΔTc, ΔTd, ΔTe of measured values by the temperature sensors 10a, 10b, 10c, 10d, 10e start to increase.

  The amount of increase in the measured value by the temperature sensor 10b close to the region 20 corresponding to the failure location is represented by a thick broken line ΔTb '. In the same situation, the amount of increase in the measured value obtained by the temperature sensor 10b obtained when there is no fault location in the filter 13 is represented by a thick solid line ΔTb. As can be seen from a comparison between the two, the increase amount ΔTb ′ of the measured value when there is a failure location is larger than the increase amount ΔTb of the measurement value when there is no failure location.

  As shown in FIG. 4, when there is no failure location in the filter 13, the increase amount ΔTa of the measurement value by each temperature sensor 10 during a certain period from when the rise in the outgas temperature starts until it converges. , .DELTA.Tb, .DELTA.Tc, .DELTA.Td, .DELTA.Te are substantially the same values even though each temperature sensor 10 has the same variation in measurement characteristics as the example of FIG.

  On the other hand, when a failure location exists in the filter 13, the measured value of the temperature sensor 10 b close to the region 20 corresponding to the failure location is obtained during a certain period from when the rise in the outgas temperature starts until it converges. Except for the increase amount ΔTb ′, the increase amounts ΔTa, ΔTc, ΔTd, ΔTe of the measured values by the temperature sensors 10 are substantially equal. The amount of increase ΔTb ′ measured by the temperature sensor 10b close to the region 20 corresponding to the failure location is a value that is significantly larger than the amounts of increase ΔTa, ΔTc, ΔTd, ΔTe of the values measured by the other temperature sensors 10. Is obtained.

  Thus, when there is a failure location in the filter 13, the variation in the amount of increase in the measured value due to each temperature sensor 10a, 10b, 10c, 10d, 10e accompanying the increase in the inlet gas temperature does not exist. It becomes larger than the case. The variation in the amount of increase in the measured value by each temperature sensor 10a, 10b, 10c, 10d, 10e is not easily affected by the variation in the measurement characteristics of each temperature sensor 10. Therefore, the variation in the amount of increase in the measured value by each of the temperature sensors 10a, 10b, 10c, 10d, and 10e can be used for determining the failure of the filter 13 as an amount that accurately reflects the presence or absence of the failure in the filter 13.

  The filter failure detection process in the present embodiment will be described with reference to FIGS. 5 and 6 are flowcharts of filter failure detection processing according to the present embodiment. This flowchart is repeatedly executed by the ECU 16 during operation of the engine 1.

  In step S <b> 101, the ECU 16 determines whether a condition for executing the failure detection process for the filter 13 is satisfied. Specifically, the temperature of the filter 13 is stable at a predetermined temperature or higher, the inlet gas temperature sensor 11 and the temperature sensors 10a, 10b, 10c, 10d, and 10e are all normal, and the flow rate of the exhaust gas flowing into the filter 13 Is equal to or greater than the predetermined flow rate, and it is determined that the condition for executing the failure detection process is satisfied when no abnormality of the filter 13 has been detected so far. Whether or not the inlet gas temperature sensor 11 and the temperature sensors 10a, 10b, 10c, 10d, and 10e are normal is determined by a separately executed process. However, since a known sensor abnormality detection routine can be used, details are described here. I will omit the explanation. The system can also be configured so that the failure detection process for the filter 13 is executed simultaneously with the regeneration process for the filter 13. In that case, it may be added to the condition that the amount of particulate matter collected in the filter 13 is a predetermined amount or more. If an affirmative determination is made in step S101, the ECU 16 proceeds to the process of step S102. In other cases, the process of this flowchart is temporarily terminated.

  In step S102, the ECU 16 determines whether the exhaust gas temperature raising control is being performed. Since the exhaust gas temperature raising control is not performed during the first processing of this step, a negative determination is made, and in that case, the ECU 16 proceeds to the processing of step S103. If a positive determination is made, the ECU 16 proceeds to the process of step S105 in FIG.

  In step S103, the ECU 16 starts the exhaust gas temperature raising control. Specifically, fuel addition into the exhaust gas by the fuel addition valve 14, post injection, EGR cut by closing the EGR valve 18 and the like are executed. Since the known control can be used as the exhaust gas temperature raising control, a detailed description is omitted here. ECU16 which performs the process of step S103 is equivalent to the temperature change means in this invention.

In step S104, the ECU 16 obtains the initial value Tin (t ₀ ) of the inlet gas temperature and the initial value T _i (t ₀ ) (i = a, b, c, d, e) of the measured value by each temperature sensor 10. get. The initial value Tin (t ₀ ) of the inlet gas temperature is acquired from the measured value by the inlet gas temperature sensor 11.

  By executing the process of the flowchart described above, the control for increasing the input gas temperature is being performed. Therefore, an affirmative determination is made in step S102 at the next execution of this flowchart, and the ECU 16 proceeds to the process of step S105.

In step S105 of FIG. 6, ECU 16, the time to get the inflow gas temperature Tin _{(t M)} at _{t M,} continues in step S106, time _t measured by the temperature sensor 10 in _{M T i (t M) (} i = A, b, c, d, e). Here, as shown in FIG. 4, the time t _M is within a period from the time t ₀ ′ when the rise of the measured value by the temperature sensor 10 accompanying the rise of the inlet gas temperature starts until the time t ₀ ″ where the convergence is substantially achieved. It is a predetermined time. As can be seen from FIG. 4, during this period, the exhaust gas that has passed through the failure point of the filter 13 and the exhaust gas that has passed through the non-failure point have greatly different behaviors over time in the amount of increase in the outgas temperature. Since the behavior of the time transition of the temperature rise amount of the exhaust gas that has passed through the failure location is substantially the same, if there is a failure location in the filter 13, the variation between the increase amounts of the measured values of the temperature sensors 10 varies. Appears prominently. Therefore, the failure of the filter 13 can be detected with high accuracy.

In step S107, the ECU 16 obtains the amount of increase ΔT _i (i = a, b, c, d, e) from the initial value of the measured value by each temperature sensor 10. Specifically, the measured values T _i (t _M ) (i = a, b, c, d, e) at the time t _M acquired at step S106 and the temperature sensors acquired at step S104. The difference between the measured value and the initial value T _i (t ₀ ) (i = a, b, c, d, e) is calculated.

In subsequent steps S108 and S109, the ECU 16 acquires the variation in the amount of increase in the measured value by each temperature sensor 10. In the present embodiment, the difference between the maximum and minimum of the increase amounts ΔT _i (i = a, b, c, d, e) of the measured values by each temperature sensor 10 is determined by each temperature sensor 10. Calculated as variation in the rise in measured value.

  First, in step S108, the ECU 16 acquires the maximum value ΔTmax and the minimum value ΔTmin among the increase amounts of the measured values obtained by the temperature sensors 10 acquired in step S107.

  In step S109, the ECU 16 determines the difference | ΔTmax−ΔTmin | between the maximum value ΔTmax and the minimum value ΔTmin of the increase in the measurement value obtained by each temperature sensor 10 acquired in step S108 as the measurement value obtained by each temperature sensor 10. The increase amount variation ΔTfin.

  In step S110, the ECU 16 determines whether or not the variation ΔTfin of the amount of increase in the measurement value obtained by each temperature sensor 10 acquired in step S109 is greater than a predetermined threshold value. Here, the predetermined threshold value is a reference value for the variation in the amount of increase in the measured value by each temperature sensor 10 for determining whether or not a failure location exists in the filter 13. This threshold value is determined based on a value obtained by examining in advance an experiment or the like the maximum value that may appear as a variation in the amount of increase in the measured value by each temperature sensor 10 when there is no failure location in the filter 13. This threshold value may be set to a value corresponding to the target exhaust temperature of the exhaust gas temperature raising control in step S103, or the operating state such as the load or the rotational speed of the engine 1.

  When the variation ΔTfin is larger than the threshold value in step S110, the ECU 16 proceeds to step S111 and determines that a failure location exists in the filter 13. At this time, it is possible to perform processing such as turning on the MIL for notifying the driver of the failure of the filter 13. On the other hand, when the variation ΔTfin is equal to or smaller than the threshold value in step S110, the ECU 16 proceeds to step S112 and determines that there is no failure location in the filter 13.

  ECU16 which performs the process of step S106-step S112 is equivalent to the detection means in this invention.

  By executing the processing of the flowchart described above, even when the measurement characteristics of the temperature sensors 10a, 10b, 10c, 10d, and 10e vary, the measurement values of the temperature sensors 10a, 10b, 10c, 10d, and 10e are measured. A failure of the filter 13 can be accurately detected based on the amount of increase.

  Next, Example 2 will be described. In the present embodiment, the installation mode of the temperature sensor 10 is different from that of the first embodiment. FIG. 7 is a diagram showing an installation mode of the temperature sensor 10 in the present embodiment. The difference from the installation mode of the temperature sensor 10 of the first embodiment is that in the first embodiment, the temperature measuring units 11b, 11c, 11d, and 11e of the peripheral temperature sensors 10b, 10c, 10d, and 10e are all from the central axis. Is arranged on the equidistant line A3 of R3, in the present embodiment, among the temperature sensors 10b, 10c, 10d, and 10e in the peripheral part, the temperature measuring part 11b of the temperature sensor 10b is the central axis. The temperature measurement units 11c, 11d, and 11e of the temperature sensors 10c, 10d, and 10e are disposed on the equidistant line A2 with the distance from the central axis line, while being disposed on the equidistant line A3 with the distance from R3. It is a point.

  Thus, when the position of the temperature measuring unit 11 on the cross section XX ′ is different, the amount of change in the measured value by the temperature sensor 10 when the inlet gas temperature is increased is different from the position of the temperature measuring unit 11. There may be variations caused by it.

  For example, the exhaust gas flowing through the exhaust passage 9 exchanges heat with the outside air through the wall surface of the exhaust passage 9, but the closer the position where the exhaust gas flows in the exhaust passage 9 to the wall surface of the exhaust passage 9, There is a tendency for the amount of heat exchange to take place between. When increasing the inlet gas temperature, the closer the position where the exhaust gas flows in the exhaust passage 9 to the wall surface of the exhaust passage 9 (in other words, the longer the distance from the central axis of the exhaust passage 9), the more heat radiation to the outside air. Increases and the amount of increase in the outgas temperature decreases.

  Therefore, as shown in FIG. 8, when the inlet gas temperature is increased, the amount of increase in the measured value by the temperature sensor 10 is such that the position of the temperature measuring unit 11 of the temperature sensor 10 moves from the central axis of the exhaust passage 9 to the outer peripheral side. There is a tendency to decrease.

  Therefore, in the configuration in which the positions of the temperature measuring units 11b, 11c, 11d, and 11e of the peripheral temperature sensors 10b, 10c, 10d, and 10e are not equidistant from the central axis as in the present embodiment, the temperature sensors 10b and 10c are used. The variation in the amount of increase in the measured value due to 10d, 10e includes a variation due to a factor different from the presence or absence of a failure in the filter 13. Therefore, the filter based on the variation in the amount of increase in the measured value by the temperature sensor 10 13 failure detection may not be performed with high accuracy.

  For example, as shown in FIG. 7, when the temperature measurement unit 11 b of the temperature sensor 10 b is located closest to the region 20 corresponding to the failure location in the filter 13 on the cross section XX ′, the incoming gas temperature increases. The amount of increase in the measured value obtained by each temperature sensor 10 is increased in comparison with the amount of increase in the measured value by the other temperature sensors 10a, 10c, 10d, and 10e. Variation occurs. A failure of the filter 13 can be detected based on the degree of variation (in the case of the first embodiment, the difference between the maximum value and the minimum value of the increase amount of the measured value) being larger than the threshold value.

  However, the temperature measurement unit 11b of the temperature sensor 10b is closer to the outer wall of the exhaust passage 9 than the temperature measurement units 11a, 11c, 11d, and 11e of the other temperature sensors 10a, 10c, 10d, and 10e. The increase in value decreases due to the effect of heat dissipation to the outside air. Therefore, as shown in FIG. 9, the amount of increase ΔTb ′ measured by the temperature sensor 10b (indicated by the alternate long and short dash line) is the amount of increase ΔTc, ΔTd of the values measured by the other temperature sensors 10c, 10d, 10e in the periphery. It is not much different from ΔTe (indicated by a thick solid line), and variation in the amount of increase in the measured value by each temperature sensor 10 (in the example of Example 1, the difference ΔTmax between the maximum value and the minimum value of the measured value) ) Does not become larger than the threshold value, and as a result, there is a possibility of causing an erroneous determination that there is no failure location in the filter 13.

  Therefore, in this embodiment, based on the difference in position on the cross section XX ′ between the peripheral temperature sensor 10b and the other peripheral temperature sensors 10c, 10d, and 10e, the measured value of the temperature sensor 10b is measured. The amount of increase was corrected. Specifically, an increase correction is performed for the amount of increase in the measured value by the temperature sensor 10b. The correction amount is determined so that the amount of increase in the measured value by the temperature sensors 10b, 10c, 10d, and 10e when there is no failure in the filter 13 is substantially equal.

  By performing such correction, as shown in FIG. 9, the amount of increase ΔTb ″ (indicated by a thick broken line) after the correction of the measurement value by the temperature sensor 10b becomes the other temperature sensors 10c, 10d, As a result, the measured value increase amounts ΔTc, ΔTd, and ΔTe (represented by thick solid lines) by 10e are significantly larger, and the variation ΔTmax ′ in the increase amount of the measured value by each temperature sensor 10 becomes larger than the threshold value. It is possible to appropriately determine that there is a fault location.

  As described above, when the input gas temperature is increased by correcting the amount of increase in the measured value by each temperature sensor 10 according to the difference in the position of each temperature measurement unit 11 on the cross section XX ′. Eliminating the influence of variation caused by heat exchange between the outside air and the exhaust due to the difference in the position of the temperature measurement unit 11 of each temperature sensor 10 from the variation in the amount of increase in the measured value by each temperature sensor 10 acquired. Can do. Thus, even when the temperature sensors 10b, 10c, 10d, and 10e in the peripheral portion are not arranged at the same distance from the central axis as in the present embodiment, the failure of the filter 13 can be detected with high accuracy. Can do.

  It should be noted that, depending on the position difference between the central temperature sensor 10a and the peripheral temperature sensors 10b, 10c, 10d, and 10e on the cross section XX ′, the amount of increase in the measured value by the temperature sensor 10a and the temperature sensor You may make it correct | amend the increase amount of the measured value by 10b, 10c, 10d, 10e. In that case, for example, the amount of increase in the measured value by the temperature sensor 10a is corrected to be decreased, and the amount of increase in the measured value by the temperature sensor 10b is increased and corrected as described above, so that all of the filters 13 can be operated normally. It is preferable that the amount of increase in the measured value by the temperature sensor 10 is substantially equal. Alternatively, the increase amount of the measurement value by the temperature sensor 10b is corrected as described above, and the increase amount of the measurement value by the temperature sensors 10c, 10d, and 10e is smaller than the correction amount of the increase amount of the measurement value of the temperature sensor 10b. The amount of increase in the measured values by all the temperature sensors 10 may be made substantially equal when the filter 13 is in a normal state by correcting the increase by the amount.

Further, the decrease in the temperature rise of the outgas due to the effect of heat exchange between the outside air and the exhaust is also affected by the difference between the outside air temperature and the exhaust temperature. FIG. 10 is a diagram showing the relationship between the temperature difference between the exhaust gas and the outside air and the difference in the amount of increase in the measured value by the two temperature sensors 10 having different distances from the wall surface of the exhaust passage 9 to the temperature measurement unit 11. . As shown in FIG. 10, as the temperature difference between the exhaust gas and the outside air increases, the difference in the amount of increase in the measured value due to the difference in the position of the temperature measurement unit 11 increases. For example, in FIG. 10, the temperature of the exhaust after Δt _{2 has} elapsed since the start of the exhaust gas temperature raising control is Δt ₁ (<Δt ₂
) Since the temperature of the exhaust after the passage is higher, and the temperature difference between the exhaust and the outside air is also larger, for example, the amount of increase in the measured value by the temperature sensor 10b and the measurement by the temperature sensors 10c, 10d, and 10e The difference between the value increase amount and the value increase amount is larger at the time when Δt _{2 has} elapsed than when Δt _{1 has} elapsed since the start of the exhaust gas temperature raising control.

  Therefore, when the amount of increase in the measured value by the temperature sensor 10 is corrected according to the difference in the position of the temperature measuring unit 11 on the cross section XX ′, the correction amount is influenced by the temperature difference between the exhaust and the outside air. It may be determined in consideration of the above. By doing so, the failure of the filter 13 can be detected with higher accuracy.

  In this embodiment, the measurement by the temperature sensor 10 is performed a plurality of times over a predetermined period after the start of the exhaust gas temperature raising control. Then, in each measurement, the difference between the measurement value obtained by the previous measurement and the measurement value obtained by the current measurement is calculated, and the difference between the measurement value obtained by each temperature sensor 10 in the measurement measurement and To do. The difference between the maximum value and the minimum value among the change amounts of the measured values obtained by the respective temperature sensors 10 is calculated. Then, this difference is integrated over all measurements, and this is taken as the degree of variation in the amount of change in the measured value by each temperature sensor 10. Based on the comparison between the degree of variation calculated in this way and the threshold value, a failure of the filter 13 is determined.

Here, the predetermined period is the time t ₀ ″ (temperature) from the time t ₀ ′ (time when the rise of the measured value by the temperature sensor 10 accompanying the rise in the incoming gas temperature) described in FIG. The time until the rise in the measured value by the sensor 10 substantially converges), and the behavior of the amount of increase in the output gas temperature over time between the exhaust gas that has passed through the failure point of the filter 13 and the exhaust gas that has passed through the non-failure point. Is a period in which the behavior of the time transition of the temperature rise amount of the exhaust gas that has passed through the non-failure point substantially matches. Since the variation due to the fault location existing in the filter 13 appears significantly in the amount of increase in the output gas temperature acquired within this period, the fault of the filter 13 can be detected with high accuracy.

The measurement number N is determined in advance, and the measurement by the temperature sensor 10 is executed at every time interval (t ₀ ″ −t ₀ ′) / N obtained by dividing a predetermined period by the number N.

  The filter failure detection process according to the present embodiment will be described based on the flowchart of FIG. In this flowchart, when an affirmative determination is made in step S102 of the flowchart of FIG. 5 described in the first embodiment, that is, it is determined that the failure detection execution condition for the filter 13 is satisfied and the exhaust gas temperature raising control is being performed. In this case, the processing content to be executed is shown.

In step S205, ECU 16, the time _t acquires the inflow gas temperature Tin _{(t j)} at the _j, continues in step S206, the value measured by the temperature sensor 10 at time _{t j T i (t j)} (i = a, b, c, d, e) are obtained. Here, the time t _j represents the time when the j-th measurement is performed among the plurality of measurements performed within the predetermined period.

In step S207, the ECU 16 increases the amount ΔT from the measurement value T _i (t _j−1 ) (i = a, b, c, d, e) obtained by each temperature sensor 10 acquired at the previous time (time t _j−1 ). _{Get i} (t _j ). Here, the measured value _T i _{(t j)} by the temperature sensor 10 in the obtained time _{t j} in step S205, the previous (time _{t j-1)} at time _t obtained in step S205 during this flowchart processing _j- a measured value _T i by each temperature sensor 10 in _{1 (t j-1),} calculates the difference.

In step S208, the ECU 16 calculates a correction amount Tcor _i (t _j ) (i = a, b, c, d, e) for correcting the amount of increase in the measurement value obtained by each temperature sensor 10 acquired in step S207. To do. Here, as the temperature measuring unit 11 of each temperature sensor 10 is closer to the wall surface of the exhaust passage 9, the increase amount ΔT _i (t _j ) is increased and corrected, and as the temperature difference between the exhaust and the outside air is larger, the increase correction is corrected. The amount of correction Tcor _i (in accordance with a predetermined relationship according to the distance between the temperature measuring unit 11 of each temperature sensor 10 and the wall surface of the exhaust passage 9 and the temperature difference between the exhaust and the outside air so that the amount increases. t _j ) is calculated. The temperature difference between the exhaust gas and the outside air is calculated as the difference between the inlet gas temperature Tin (t _j ) at time t _j acquired in step S205 and the intake air temperature measured by the intake air temperature sensor 19.

In step S209, the ECU 16 corrects the amount of increase ΔT _i (t _j ) measured by each temperature sensor 10 acquired in step S207 by the correction amount Tcor _i (t _j ) calculated in step S208. The amount of increase ΔTfin _i (t _j ) (i = a, b, c, d, e) after correction of the measured value is calculated.

In step S210, the maximum value ΔTmax (t _j ) and the minimum of the amount of increase ΔTfin _i (t _j ) (i = a, b, c, d, e) of the measurement value calculated by each temperature sensor 10 calculated in step S209. The value ΔTmin (t _j ) is acquired.

In step S211, the ECU 16 calculates a difference between the maximum value ΔTmax (t _j ) and the minimum value ΔTmin (t _j ) of the amount of increase in the measurement value obtained by each temperature sensor 10 acquired in step S210. It is assumed that the variation ΔTfin (t _j ) in the amount of increase in the measured value by each temperature sensor 10 in the measurement.

In step S212, the ECU 16 adds each temperature sensor calculated in the current (j-th) measurement to the integrated value of the variation in the amount of increase in the measured value by each temperature sensor 10 calculated up to the previous (j-1) measurement. The variation ΔTfin (t _j ) of the increase in the measured value by 10 is added.

  In step S213, the ECU 16 determines whether or not the predetermined number of times (N times) of measurement has been completed. When the number of times of measurement j has not reached the predetermined number N, the process of this flowchart is temporarily exited, and the process of this flowchart is executed again after the measurement time interval described above has elapsed. If the number j of measurements reaches the predetermined number N, the process proceeds to step S214.

  In step S214, the ECU 16 determines whether or not the integrated value of the variation in the amount of increase in the measured value by each temperature sensor 10 for all N times is greater than a predetermined threshold value. This threshold value is a reference value of the integrated value for N times of variation in the amount of increase in the measured value by each temperature sensor 10 for determining whether or not there is a failure location in the filter 13. Is determined based on the maximum value of the integrated values that can be calculated in the absence of. This threshold value may be set to a value corresponding to the target exhaust temperature of the exhaust gas temperature raising control in step S103, or the operating state such as the load or the rotational speed of the engine 1.

  When the integrated value of variation is larger than the threshold value in step S214, the ECU 16 proceeds to step S215 and determines that there is a failure location in the filter 13. At this time, it is possible to perform processing such as turning on the MIL for notifying the driver of the failure of the filter 13. On the other hand, if the integrated value of variation is equal to or smaller than the threshold value in step S214, the ECU 16 proceeds to step S216, and determines that there is no failure location in the filter 13.

  ECU16 which performs the process of step S205-step S216 is equivalent to the detection means in this invention.

  By executing the processing of the flowchart described above, the influence of the variation in the amount of increase in the measurement value due to the difference in the positions of the temperature measuring units 11a, 11b, 11c, 11d, and 11e of the temperature sensors 10a, 10b, 10c, 10d, and 10e. And the failure of the filter 13 can be detected with high accuracy based on the amount of increase in the measured values by the temperature sensors 10a, 10b, 10c, 10d, and 10e.

  Each example described above is one embodiment of the present invention, and various combinations and modifications can be made without departing from the scope of the present invention. For example, although the above embodiment has been described with respect to an example in which one temperature sensor is arranged in the central portion and five temperature sensors are arranged in the peripheral portion, the arrangement and the number of temperature sensors are not limited thereto. In particular, any irregular sensor arrangement can be dealt with by performing the correction described in the second embodiment. Conversely, the filter failure detection process can be simplified by disposing the temperature sensor at a position where the distance from the wall surface of the exhaust passage and the distance from the central axis are the same distance and omitting the correction process. The inlet gas temperature sensor 11 is not necessarily an essential component for carrying out the present invention. It is sufficient that the amount of change in the output gas temperature of the filter 13 can be measured at a plurality of locations. In the second embodiment, the case where both the correction based on the position of the temperature sensor and the correction based on the temperature difference between the outside air and the exhaust gas are corrected has been described, but it is not always necessary to perform both corrections. In addition, each of the above embodiments has described an example in which a filter failure determination is made based on variation in the amount of increase in the measured value by the temperature sensor when the temperature of the filter inlet gas is raised by exhaust gas temperature raising control. It is possible to detect a failure based on variation in the amount of decrease in the measured value by the temperature sensor when the temperature of the exhaust gas is lowered. However, since the accuracy of filter failure detection becomes higher when the filter inlet gas temperature is changed more greatly, it is easier to improve the detection accuracy when the inlet gas temperature is raised at that point. The correction process described in the second embodiment can be applied not only to the failure detection based on the integrated value of the variation in the increase amount of the measurement value by the temperature sensor of the second embodiment but also to the failure detection of the first embodiment.

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake manifold 3 Exhaust manifold 4 Intercooler 5 Turbocharger 6 Compressor 7 Turbine 8 Intake passage 9 Exhaust passage 10, 10a, 10b, 10c, 10d, 10e Temperature sensor 11, 11a, 11b, 11c, 11d, 11e Temperature measurement Part 12 NOx catalyst 13 Filter 14 Fuel addition valve 15 EGR passage 16 ECU
17 Cylinder 18 EGR valve 19 Intake air temperature sensor 20 Region corresponding to the failure location in the filter on the XX ′ cross section

Claims (4)

A filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A plurality of temperature sensors that measure the temperature of the exhaust at a plurality of positions that are substantially equal in distance from the downstream end of the filter;
Exhaust temperature changing means for changing the temperature of the exhaust gas flowing into the filter;
Detecting means for detecting a failure of the filter based on variation in the amount of change in the measured value by each temperature sensor before and after changing the temperature of the exhaust gas flowing into the filter by the exhaust temperature changing means;
A failure detection system for a filter, comprising: In claim 1,
The failure detection system for a filter, wherein the detection means determines that the filter is broken when the degree of variation in the amount of change in the measured value by each temperature sensor is greater than a predetermined threshold value. In claim 1 or 2,
The detection means further includes correction means for correcting a change amount of a measured value by the temperature sensor according to a distance between the temperature sensor and the wall surface of the exhaust passage, and the change amount corrected by the correction means. A filter failure detection system, wherein the filter failure is determined based on In claim 3,
The filter failure detection system according to claim 1, wherein the correction unit determines a correction amount for a change amount of a measurement value by the temperature sensor according to a difference between an outside air temperature and an exhaust temperature.

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