JP2013002366A - Failure diagnosing device for differential pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure diagnosing device for a pressure difference sensor capable of diagnosing presence/absence of a failure in a pressure introducing hose of the sensor.SOLUTION: An exhaust emission control device is equipped with a DPF installed in the exhaust passage of an internal combustion engine and a pressure difference sensor for sensing the pressure difference between in front of and behind the DPF. The failure diagnosing device for pressure difference sensor is to diagnose if the pressure difference sensor in the exhaust emission control device has a failure or not. The configuration includes a first judging means to make failure judgement on the DPF on the basis of the temperatures in front of and behind the DPF and a second judging means to make failure judgement on the pressure difference sensor on the basis of the judging result of the first means and the pressure difference value sensed by the sensor.

Description

  The present invention relates to a differential pressure sensor abnormality diagnosis device for diagnosing the presence or absence of abnormality of a differential pressure sensor for detecting a differential pressure before and after a particulate filter provided in an exhaust system of an internal combustion engine.

  Conventionally, in an exhaust system of an internal combustion engine mounted on a vehicle or the like, a particulate filter (hereinafter referred to as “PM (Particulate Material)”) such as soot contained in exhaust gas is collected. Hereinafter, it is referred to as “DPF (Diesel Particulate Filter)”. If the PM trapped in the DPF continues to increase, the DPF may become clogged, which may cause a deterioration in fuel consumption due to a decrease in output, a melting loss of the DPF, and the like. Therefore, control for regenerating DPF by burning PM collected in DPF is executed at predetermined time intervals.

  As an index for measuring the amount of DPF collected, there is a method of viewing the differential pressure before and after the DPF that can be detected using a differential pressure sensor. In this method, when the differential pressure reaches a predetermined threshold value, it is determined that the amount of PM trapped in the DPF has reached a predetermined level, and execution of regeneration control is started.

  If this differential pressure sensor is faulty, the DPF regeneration control cannot be executed at an appropriate time. Therefore, a differential pressure sensor fault detection system that can accurately detect the differential pressure sensor fault is proposed. ing. Specifically, the differential pressure between the pressure upstream of the DPF and the atmospheric pressure and / or the differential pressure between the pressure downstream of the DPF and the atmospheric pressure can be measured, and the exhaust flow rate flowing into the DPF with the exhaust flow rate changing means fully opened. And the failure of the differential pressure sensor is detected based on the change amount of the differential pressure between the pressure upstream of the DPF and the atmospheric pressure or the change amount of the differential pressure between the pressure downstream of the DPF and the atmospheric pressure at this time. A failure detection system for a differential pressure sensor is disclosed (see Patent Document 1).

JP 2008-111409 A

  By the way, the differential pressure sensor used to see the differential pressure before and after the DPF is attached by connecting a pressure introduction hose to each of the exhaust passage upstream of the DPF and the exhaust passage downstream. If this pressure introduction hose is disconnected from the connection with the exhaust passage, or if the pressure introduction hose is broken and opened to the atmosphere, the differential pressure cannot be detected accurately.

  A failure detection system for a differential pressure sensor described in Patent Document 1 introduces an atmospheric pressure into a pressure introduction hose upstream or downstream of a DPF, and changes an exhaust flow rate to change the differential pressure sensor. However, if each pressure introduction hose is disconnected or damaged from the connection point with the exhaust passage, there is a problem that such an abnormality cannot be detected. there were.

  In view of such problems, the inventors of the present invention diagnose the presence or absence of an abnormality in the differential pressure sensor using the DPF abnormality determination result based on the temperature before and after the DPF and the detection value of the differential pressure sensor. The present invention has been completed by finding that such problems can be solved. That is, an object of the present invention is to provide a differential pressure sensor abnormality diagnosis device capable of diagnosing the presence or absence of an abnormality in a pressure introduction hose of a differential pressure sensor.

  According to the present invention, whether or not there is an abnormality in the differential pressure sensor in an exhaust gas purification apparatus that includes a DPF provided in an exhaust passage of an internal combustion engine and a differential pressure sensor for detecting a differential pressure before and after the DPF. In the abnormality diagnosis device for the differential pressure sensor for diagnosing the abnormality, a first determination unit that determines abnormality of the DPF based on temperatures before and after the DPF, a determination result by the first determination unit, and the A differential pressure sensor abnormality diagnosis device comprising: a second determination unit configured to determine abnormality of the differential pressure sensor based on a differential pressure detection value detected by the differential pressure sensor; The problem can be solved.

  That is, the abnormality diagnosis device for the differential pressure sensor according to the present invention diagnoses the presence or absence of abnormality of the differential pressure sensor based on the abnormality determination result of the DPF and the differential pressure detection value by the differential pressure sensor. When an abnormality occurs, an appropriate differential pressure detection value corresponding to the DPF abnormality determination result is not output, so it is possible to appropriately determine whether there is an abnormality in the pressure introduction hose of the differential pressure sensor. can do.

  Moreover, in the abnormality diagnosis device for a differential pressure sensor according to the present invention, the second determination unit is configured such that the determination result of the first determination unit is normal and the differential pressure detection value is equal to or greater than a predetermined upper limit threshold value. In addition, it is preferable to determine that there is an abnormality in the pressure introduction hose of the differential pressure sensor connected to the exhaust passage downstream of the DPF.

  By making such a determination, it is possible to detect disconnection or breakage of the pressure introduction hose connected to the exhaust passage downstream of the DPF.

  Moreover, in the abnormality diagnosis device for a differential pressure sensor according to the present invention, the second determination unit is configured such that the determination result of the first determination unit is normal and the differential pressure detection value is equal to or less than a predetermined lower limit threshold value. In addition, it is preferable to determine that there is an abnormality in the pressure introduction hose of the differential pressure sensor connected to the exhaust passage upstream of the DPF.

  By making such a determination, it is possible to detect disconnection or breakage of the pressure introduction hose connected to the exhaust passage upstream of the DPF.

  Moreover, in the abnormality diagnosis device for a differential pressure sensor according to the present invention, the second determination unit is configured such that when the determination result of the first determination unit is abnormal and the differential pressure detection value is in a normal range, It is preferable to determine that the pressure introduction hose of the differential pressure sensor connected to the exhaust passage upstream or downstream of the DPF is abnormal.

  By making such a determination, it is possible to detect the disconnection or breakage of the pressure introduction hose on either the upstream side or the downstream side of the DPF even if there is an abnormality in the DPF.

  Further, in the abnormality diagnosis device for a differential pressure sensor according to the present invention, the upper limit threshold, the lower limit threshold, or the normal range is set according to an exhaust flow rate assuming an abnormality in which the pressure introduction hose is open to the atmosphere. It is preferable to do.

  By setting the upper limit threshold, the lower limit threshold, or the normal range as described above, it is possible to appropriately determine whether there is an abnormality in the differential pressure sensor according to the operating state of the internal combustion engine at the time of diagnosis.

  Further, in the abnormality diagnosis device for a differential pressure sensor according to the present invention, when the exhaust gas temperature upstream of the DPF changes, the first determination means detects the exhaust gas temperature upstream of the DPF and the downstream gas temperature. It is preferable to determine that the DPF is abnormal when the difference from the exhaust temperature is less than a predetermined temperature difference threshold.

  By determining the abnormality of the DPF in this way, it is possible to determine the abnormality of the DPF without depending on the reliability of the differential pressure sensor. As a result, the reliability of the abnormality determination of the differential pressure sensor can be improved. it can.

  In the abnormality diagnosis device for a differential pressure sensor according to the present invention, when the exhaust temperature on the upstream side of the DPF changes, the first determination means determines that the exhaust temperature on the downstream side of the DPF is the upstream side. It is preferable to determine that the DPF is abnormal when the time until the degree of change in the exhaust gas temperature is less than a predetermined time threshold.

  By performing DPF abnormality determination in this way, DPF abnormality determination can be performed without depending on the reliability of the differential pressure sensor, and as a result, the reliability of abnormality determination of the differential pressure sensor can be improved. Can do.

It is a figure shown in order to demonstrate the structure of the exhaust system of the internal combustion engine with which the abnormality diagnosis apparatus of the differential pressure sensor concerning this Embodiment is provided. It is a block diagram which shows functionally the structure of the electronic controller as an abnormality diagnosis apparatus of the differential pressure sensor concerning this Embodiment. It is a flowchart figure for demonstrating an example of the abnormality diagnosis method performed by the abnormality diagnosis apparatus of the differential pressure sensor concerning this Embodiment. It is a flowchart for demonstrating an example of the abnormality determination method of DPF. It is a flowchart for demonstrating an example of the determination method of the presence or absence of abnormality of a downstream hose. It is a flowchart figure for demonstrating an example of the determination method of the presence or absence of abnormality of an upstream hose. It is a figure shown in order to demonstrate the outline of the abnormality determination method of DPF. It is a flowchart for demonstrating another example of the abnormality determination method of DPF.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to an abnormality diagnosis device for a differential pressure sensor according to the present invention will be specifically described below with reference to the drawings.
In addition, what is attached | subjected with the same code | symbol in each figure has shown the same component unless there is particular description, and description is abbreviate | omitted suitably.

  FIG. 1 is a diagram for explaining the configuration of an exhaust system of an internal combustion engine provided with the differential pressure sensor abnormality diagnosis device according to the present embodiment. FIG. 2 is a block diagram functionally showing the configuration of the electronic control device as the abnormality diagnosis device for the differential pressure sensor according to the present embodiment. FIG. 3 is a flowchart for explaining an example of the abnormality diagnosis method executed by the abnormality diagnosis device for the differential pressure sensor according to the present embodiment. FIG. 4 is a flowchart for explaining an example of a DPF abnormality determination method. FIG. 5 is a flowchart for explaining an example of a method for determining whether there is an abnormality in the downstream hose. FIG. 6 is a flowchart for explaining an example of a method for determining whether there is an abnormality in the upstream hose. FIG. 7 is a diagram for explaining the outline of the DPF abnormality determination method.

1. 1. Overall Configuration of Exhaust System of Internal Combustion Engine In FIG. 1, an internal combustion engine 1 is typically a diesel engine, and includes a plurality of fuel injection valves 5 and an exhaust pipe 3 through which exhaust gas is circulated. . The fuel injection valve 5 is energized and controlled by the electronic control unit 30. The electronic control unit 30 calculates the fuel injection amount based on the engine speed, the accelerator operation amount, and other information, and calculates the calculated fuel. The energization timing and energization time of the fuel injection valve 5 are obtained based on the injection amount, and the energization control of the fuel injection valve 5 is executed.

An exhaust gas purification device 10 is provided in the exhaust pipe 3 connected to the internal combustion engine 1. The exhaust purification device 10 includes a DPF 12 and an NO _x purification catalyst 13 that are sequentially provided from the upstream side of the exhaust pipe 3. Further, the exhaust purification device 10 includes a differential pressure sensor 15 for detecting a differential pressure before and after the DPF 12. The sensor signal of the differential pressure sensor 15 is input to the electronic control device 30.

  The DPF 12 is a filter having a function of collecting PM such as soot contained in the exhaust gas. The DPF 12 is typically a filter having a honeycomb structure, but is not limited to such a filter. The DPF 12 is subjected to regeneration control for burning (oxidizing) PM at a predetermined time so that the amount of collected PM does not increase and clogging occurs.

The NO _x purification catalyst 13 is a catalyst having a function of reducing and purifying NO _x (nitrogen oxide) contained in the exhaust gas. Typically, NO _X is occluded when the air-fuel ratio of the exhaust is fuel lean, while NO _X is released when the air-fuel ratio becomes fuel rich, and NO _X and HC (unburned fuel) the reaction and the NO _X storing catalyst to promote, while adsorbing a reducing agent such as ammonia or HC, like selective reduction catalyst to be reacted with the selective reducing agent NO _X flowing into the. However, the type and position of the NO _x purification catalyst 13 are not particularly limited.

  The differential pressure sensor 15 is used to detect a differential pressure between the exhaust pressure upstream of the DPF 12 and the exhaust pressure downstream. An upstream exhaust pressure is introduced into the differential pressure sensor 15 via an upstream pressure introduction hose (hereinafter referred to as “upstream hose”) 17 connected to the exhaust passage 7 upstream of the DPF 12. Further, the downstream pressure is introduced into the differential pressure sensor 15 via a downstream pressure introduction hose (hereinafter referred to as “downstream hose”) 19 connected to the exhaust passage 9 downstream of the DPF 12. The

In the present embodiment, the NO _x purification catalyst 13 is provided on the downstream side of the DPF 12, and the exhaust pressure on the downstream side of the DPF 12 during operation of the internal combustion engine 1 is lower than the exhaust pressure on the upstream side of the DPF 12. The pressure is higher than the atmospheric pressure.

  In the differential pressure sensor abnormality diagnosis device according to the present embodiment, information on the differential pressure detected using the differential pressure sensor 15 is used for estimating the amount of PM trapped in the DPF 12, and an upstream hose and a downstream hose. It is also used for abnormal diagnosis.

2. Electronic control device (Differential pressure sensor abnormality diagnosis device)
(1) Device Configuration FIG. 2 is a functional block diagram of a portion of the configuration of the electronic control device 30 related to the abnormality diagnosis of the differential pressure sensor 15. This electronic control device 30 has a function as an abnormality diagnosis device for the differential pressure sensor 15.

  The electronic control unit 30 is configured around a known microcomputer, and includes a differential pressure detection unit 31, a first determination unit 33, and a second determination unit 35. Specifically, each of these means is realized by executing a program by a microcomputer.

  Although not shown, the electronic control device 30 is provided with storage means such as a storage element such as a RAM or a ROM. In the storage means, a control program and various calculation maps are stored in advance, and calculation results and the like by the respective means described above are written.

  The differential pressure detection means 31 is configured to obtain a differential pressure detection value ΔP before and after the DPF 12 based on the sensor signal of the differential pressure sensor 15. In the electronic control unit 30 according to the present embodiment, the differential pressure detection means 31 is configured to be able to detect a pressure difference obtained by subtracting the downstream exhaust pressure from the upstream exhaust pressure, and not only a positive value. Negative values can also be detected.

  The first determination means 33 is configured to determine whether there is an abnormality in the DPF 12 based on the exhaust temperature Tu upstream of the DPF 12 and the exhaust temperature Td downstream. The abnormality of the DPF 12 indicates an abnormal state such as a melting loss due to overcombustion of the DPF 12, a penetration of the DPF 12 due to physical damage, or a DPF 12 not being attached. The upstream exhaust temperature Tu can be detected using an exhaust temperature sensor, or can be estimated by calculation based on the operating state of the internal combustion engine 1 or the like. The downstream exhaust temperature Td can be detected using an exhaust temperature sensor.

  The second determination unit 35 determines whether there is an abnormality in the upstream hose 17 and the downstream hose 19 of the differential pressure sensor 15 based on the differential pressure detection value ΔP and the determination result A1 of the first determination unit 33. It is configured.

(2) Flowchart Next, an abnormality diagnosis routine for the differential pressure sensor executed by the electronic control unit 30 will be described with reference to the flowcharts of FIGS. This routine may be executed at every predetermined time during the operation of the internal combustion engine 1, or is executed at a rate of once every time the internal combustion engine 1 is started once. It may be.

  First, in step S1 of the flowchart in FIG. 3, the electronic control unit 30 determines abnormality of the DPF 12. FIG. 4 is a flowchart specifically illustrating an example of the abnormality determination of the DPF 12.

  In step S11 of FIG. 4, the electronic control unit 30 determines whether or not the exhaust temperature Tu on the upstream side of the DPF 12 is changing. Whether the exhaust temperature Tu is changing is determined, for example, by continuously detecting the upstream exhaust temperature Tu and whether the temperature change rate per unit time is a predetermined value or more, It can be determined by determining whether or not the operating state of 1 is changing rapidly. It does not matter whether the temperature is rising or falling.

  This step S11 is a step for confirming that if the DPF 12 is normal, the temperature difference between the upstream exhaust temperature Tu and the downstream exhaust temperature Td is increased by a predetermined amount. Yes. The thresholds and conditions in the above-described specific determination method examples can be optimal values obtained in advance through experiments or the like. However, the specific determination method in step S11 is not limited to the above example.

  By such a determination method, the determination in step S11 is repeated until it is determined that the upstream exhaust temperature Tu is changing. If the determination in step S11 is Yes, the process proceeds to step S12. In step S12, the electronic control unit 30 determines whether or not the absolute value of the difference between the upstream exhaust temperature Tu and the downstream exhaust temperature Td is less than a predetermined temperature difference threshold value ΔT1.

  This step S12 is a step for determining whether or not the difference between the upstream exhaust temperature Tu and the downstream exhaust temperature Td is appropriately large according to the current exhaust situation. The temperature difference threshold value ΔT1 can be set to an optimum value in consideration of a temperature difference assumed from the immediately preceding exhaust gas temperatures Tu and Td and the current exhaust gas situation. Alternatively, the temperature difference threshold value ΔT1 can be set to a constant value if the change in the exhaust gas temperature Tu on the upstream side in step S11 is conditional on a temperature change that causes a certain difference.

  If it is determined Yes in step S12, the temperature difference between the upstream exhaust temperature Tu and the downstream exhaust temperature Td is large, but the temperature difference is not large. The electronic control unit 30 proceeds to step S13, sets a flag notifying the occurrence of abnormality of the DPF 12, and ends the abnormality determination of the DPF 12. On the other hand, when it is determined No in step S12, the temperature difference between the upstream exhaust temperature Tu and the downstream exhaust temperature Td is large depending on the current exhaust state. The apparatus 30 proceeds to step S14 and ends the determination of the abnormality of the DPF 12 with the flag informing that the abnormality of the DPF 12 is lowered.

  FIG. 7 is a diagram for explaining an outline of the abnormality determination of the DPF 12 according to the example of the flowchart of FIG. FIG. 7A shows a change in the exhaust temperature Td on the downstream side when the exhaust temperature Tu on the upstream side of the DPF 12 changes in the normal operation region and the DPF regeneration operation region when no abnormality is occurring in the DPF 12. They are shown separately. FIG. 7B shows the normal operation region and the DPF regeneration operation region with respect to the change in the exhaust temperature Td on the downstream side when the exhaust temperature Tu on the upstream side of the DPF 12 changes when the abnormality of the DPF 12 occurs. These are shown separately.

  As shown in FIG. 7 (a), when there is no abnormality in the DPF 12, the upstream side and the downstream side of the DPF 12 are not in the through state, and the upstream exhaust temperature Tu is not increased due to the heat transfer delay of the DPF 12. There is a delay after the change until the downstream exhaust temperature Td changes. Therefore, when the upstream exhaust temperature Tu is changing, comparing the upstream exhaust temperature Tu and the downstream exhaust temperature Td at a certain time reveals that there is a large temperature difference.

  On the other hand, as shown in FIG. 7B, when an abnormality occurs in the DPF 12, the downstream exhaust temperature Td changes almost simultaneously with the upstream exhaust temperature Tu. Therefore, it can be seen that a large temperature difference does not occur even when the upstream exhaust temperature Tu and the downstream exhaust temperature Td at a certain time are compared in a period in which the upstream exhaust temperature Tu is changing.

  Therefore, in the example of FIG. 4, it is determined whether or not the difference between the upstream exhaust temperature Tu and the downstream exhaust temperature Td when the upstream exhaust temperature Tu is changing is less than the temperature difference threshold value ΔT1. By doing so, it is determined whether or not an abnormality has occurred in the DPF 12.

  Returning to FIG. 3, when the abnormality determination of the DPF 12 is completed, the electronic control unit 30 obtains the differential pressure detection value ΔP based on the sensor value of the differential pressure sensor 15 in step S2, and then in step S3, the differential pressure sensor. 15 abnormality determinations are executed.

  5 and 6 are flowcharts specifically showing an example of the abnormality determination of the differential pressure sensor 15. FIG. 5 shows a flowchart for determining the presence or absence of an abnormality in the downstream hose 19, and FIG. The flowchart figure for determining the presence or absence of abnormality of the upstream hose 17 is shown.

  First, when determining whether or not the downstream hose 19 is abnormal, the electronic control unit 30 determines whether or not the DPF 12 is abnormal in step S21 of FIG. Specifically, the determination is made based on whether or not a flag for notifying the occurrence of an abnormality in the DPF 12 is set.

If it is judged No in step S21, the process proceeds to step S25, the electronic control unit 30, the differential pressure detection value [Delta] P is determined whether or not equal to or more than a predetermined upper limit threshold [Delta] P _H. The upper threshold [Delta] P _H, in a state where there is no abnormality of the DPF 12, a threshold set to determine whether the downstream hose 19 is atmospheric pressure not introduced. Upper threshold [Delta] P _H, such that is selected according to the upstream side of the impact exhaust flow rate Fg in exhaust pressure, is stored sought in advance by experiment or the like.

  If it is determined as Yes in step S25, since the differential pressure detection value ΔP is significantly large in a situation where the DPF 12 is not abnormal and a normal differential pressure should be detected, the downstream hose 19 is estimated to be open to the atmosphere due to omission or breakage. Therefore, the electronic control unit 30 proceeds to step S23, sets a flag notifying the occurrence of the abnormality in the downstream hose 19, and ends the determination of whether the downstream hose 19 is abnormal.

  On the other hand, when it is determined No in step S25, since the appropriate differential pressure detection value ΔP is indicated in accordance with the current situation, the electronic control unit 30 proceeds to step S24 and proceeds to the downstream hose 19. With the flag informing of the occurrence of abnormality being lowered, the determination of whether there is an abnormality in the downstream hose 19 is terminated.

  If it is determined Yes in step S21, the process proceeds to step S22, and the electronic control unit 30 determines whether the absolute value of the difference between the differential pressure detection value ΔP and the differential pressure reference value ΔP0 is equal to or less than the threshold value α. Determine whether or not. This differential pressure reference value ΔP0 is a differential pressure value that is assumed when it is assumed that there is no abnormality in the DPF 12, and is obtained in advance through experiments or the like so as to be selected according to the exhaust flow rate Fg. It is remembered. Further, the threshold value α can be set to an optimum value in consideration of an allowable error.

  If the determination in Step S22 is Yes, the DPF 12 is abnormal, and the differential pressure detection value ΔP close to the assumed value is detected despite the fact that the differential pressure is unlikely to occur. It is estimated that the downstream hose 19 is open to the atmosphere due to disconnection or breakage. Therefore, the electronic control unit 30 proceeds to step S23, sets a flag notifying the occurrence of the abnormality in the downstream hose 19, and ends the determination of whether the downstream hose 19 is abnormal.

  On the other hand, when it is determined No in step S22, since the appropriate differential pressure detection value ΔP is indicated according to the current situation, the electronic control unit 30 proceeds to step S24 and determines the downstream hose 19. With the flag informing of the occurrence of abnormality being lowered, the determination of whether there is an abnormality in the downstream hose 19 is terminated.

  Next, when determining whether or not there is an abnormality in the upstream hose 17, the electronic control unit 30 determines whether or not there is an abnormality in the DPF 12 in step S31 of FIG. Specifically, the determination is made based on whether or not a flag for notifying the occurrence of an abnormality in the DPF 12 is set.

If it is judged No in step S31, the process proceeds to step S35, the electronic control unit 30, the differential pressure detection value [Delta] P is determined whether or not it is less than a predetermined lower limit threshold [Delta] P _L. This lower limit threshold value ΔP _L is a threshold value that is set to determine whether or not atmospheric pressure is introduced into the upstream hose 17 in a state where no abnormality has occurred in the DPF 12. The lower limit threshold value ΔP _L is obtained and stored in advance by experiments or the like so as to be selected according to the exhaust flow rate Fg that affects the exhaust pressure on the downstream side as well as the upstream side.

  If it is determined as Yes in step S35, the differential pressure detection value ΔP is extremely small in a situation where no abnormality of the DPF 12 has occurred and a normal differential pressure should be detected. 17 is estimated to be open to the atmosphere due to omission or damage. Therefore, the electronic control unit 30 proceeds to step S33, sets a flag notifying the occurrence of the abnormality in the upstream hose 17, and ends the determination of whether there is an abnormality in the upstream hose 17.

  On the other hand, when it is determined No in step S35, since the appropriate differential pressure detection value ΔP is indicated according to the current situation, the electronic control unit 30 proceeds to step S34 and determines the upstream hose 17. With the flag informing of the occurrence of abnormality being lowered, the determination of whether there is an abnormality in the upstream hose 17 is terminated.

If it is determined Yes in step S31, the process proceeds to step S32, and the electronic control unit 30 determines whether or not the differential pressure detection value ΔP is equal to or less than a predetermined abnormality threshold value ΔP _L ′. This abnormal time threshold value ΔP _L ′ is a threshold value set for determining whether or not atmospheric pressure is introduced into the upstream hose 17 on the assumption that an abnormality has occurred in the DPF 12. The abnormal time threshold value ΔP _L ′ is obtained and stored in advance by an experiment or the like so as to be selected according to the exhaust flow rate Fg that affects the exhaust pressure, assuming that the DPF 12 is abnormal.

  If it is determined Yes in step S32, the DPF 12 is abnormal, and the differential pressure detection value ΔP close to the assumed value is detected despite the fact that the differential pressure is unlikely to occur. It is estimated that the upstream hose 17 is open to the atmosphere due to disconnection or breakage. Therefore, the electronic control unit 30 proceeds to step S33, sets a flag notifying the occurrence of the abnormality in the upstream hose 17, and ends the determination of whether there is an abnormality in the upstream hose 17.

  On the other hand, when it is determined No in step S32, since the appropriate differential pressure detection value ΔP is indicated according to the current situation, the electronic control unit 30 proceeds to step S34 and proceeds to the upstream hose 17. With the flag informing of the occurrence of abnormality being lowered, the determination of whether there is an abnormality in the upstream hose 17 is terminated.

  Note that the order of determining the abnormality of the downstream hose 19 and the abnormality of the upstream hose 17 is not particularly limited. Moreover, you may make it perform only the abnormality determination of any one of the downstream hose 19 or the upstream hose 17. FIG.

3. Effects of the present embodiment The electronic control device 30 as the differential pressure sensor abnormality diagnosis device according to the present embodiment described above is based on the abnormality determination result of the DPF 12 and the differential pressure detection value ΔP by the differential pressure sensor 15. The presence or absence of abnormality in the downstream hose 19 and / or the upstream hose 17 of the differential pressure sensor 15 is diagnosed. For this reason, when an abnormality has occurred in the pressure introduction hose, the differential pressure detection value ΔP corresponding to the abnormality determination result of the DPF 12 is not appropriately output. Can be determined.

Further, according to the electronic control unit 30 according to this embodiment, the abnormality determination result is no abnormality of the DPF 12, and, when the difference between pressure detection value [Delta] P is equal to or higher than the upper limit threshold [Delta] P _H, the exhaust downstream of the DPF 12 Since it is determined that there is an abnormality in the downstream hose 19 connected to the passage 9, it is possible to reliably detect disconnection or breakage of the downstream hose 19.

Further, according to the electronic control unit 30 according to the present embodiment, when the result of the abnormality determination of the DPF 12 is not abnormal and the differential pressure detection value ΔP is equal to or lower than the lower limit threshold ΔP _L , the exhaust gas upstream of the DPF 12 is exhausted. Since it is determined that there is an abnormality in the upstream hose 17 connected to the passage 7, it is possible to reliably detect disconnection or breakage of the upstream hose 17.

  Further, according to the electronic control unit 30 according to the present embodiment, the result of the abnormality determination of the DPF 12 is abnormal, and the absolute value of the difference between the differential pressure detection value ΔP and the differential pressure reference value ΔP0 is equal to or less than the threshold value α. In some cases, it is determined that there is an abnormality in the upstream hose 17 or the downstream hose 19 relative to the DPF 12, so that even if there is an abnormality in the DPF 12, the upstream hose 17 or the downstream hose 19 is disconnected or damaged. Can be reliably detected.

Further, according to the electronic control unit 30 according to the present embodiment, it is determined whether or not the upper limit threshold value ΔP _H and the lower limit threshold value ΔP _L for performing the determination, and further, whether the differential pressure detection value ΔP indicates a normal range. Since the differential pressure reference value ΔP0, which is a reference to be set, is set according to the exhaust flow rate Fg on the assumption that the upstream hose 17 or the downstream hose 19 is open to the atmosphere, the internal combustion engine at the time of diagnosis The presence or absence of abnormality of the upstream hose 17 or the downstream hose 19 can be appropriately determined according to the operation state of 1.

  Further, according to the electronic control unit 30 according to the present embodiment, when the exhaust temperature Tu upstream of the DPF 12 changes, the difference between the exhaust temperature Tu upstream of the DPF 12 and the exhaust temperature Td downstream. When the absolute value of DPF 12 is less than the predetermined temperature difference threshold value ΔT 1, it is determined that the DPF 12 is abnormal. Therefore, the abnormality determination of the DPF 12 can be performed without depending on the reliability of the differential pressure sensor 15. In addition, the reliability of the abnormality determination of the differential pressure sensor 15 can be improved.

4). Modification The above-described abnormality diagnosis device for a differential pressure sensor according to the present embodiment shows one aspect of the present invention and does not limit the present invention. The embodiment is within the scope of the present invention. It is possible to change arbitrarily. The abnormality diagnosis device for the differential pressure sensor according to the present embodiment can be modified as follows, for example.

(1) Each component constituting the exhaust system of the internal combustion engine 1 described in the present embodiment, the set value and the set condition of the electronic control unit 30 are merely examples, and can be arbitrarily changed. .

(2) In the abnormality diagnosis device for the differential pressure sensor according to the present embodiment, the upstream exhaust temperature Tu and the downstream exhaust temperature Td at a certain point in time when the upstream exhaust temperature Tu changes. The abnormality of the DPF 12 is determined based on the temperature difference. However, the time difference from when the upstream exhaust temperature Tu reaches the temperature TuA at which the upstream exhaust temperature Tu changes to the downstream temperature TuA becomes the time difference. Based on this, abnormality determination of the DPF 12 can be performed. That is, as shown in FIGS. 7A to 7B, when there is an abnormality in the DPF 12, there is no delay in the change between the upstream exhaust temperature Tu and the downstream exhaust temperature Td. An abnormality determination of the DPF 12 can also be made based on this time difference.

  FIG. 8 is a flowchart specifically illustrating an example in which abnormality determination of the DPF 12 is performed based on a time difference. In this example, first, in step S41, the electronic control unit determines whether or not the exhaust temperature Tu upstream of the DPF is changing. A specific determination method can be the same as in step S11 of FIG. Step S41 is repeated until it is determined Yes, and if it is determined Yes in Step S41, the process proceeds to Step S42, and the electronic control unit reads the upstream exhaust temperature Tu0 at that time and the start time TIstart. Remember.

  Next, in step S43, the electronic control unit determines whether or not the exhaust temperature Td on the downstream side of the DPF has reached the stored exhaust temperature Tu0. When the downstream exhaust temperature Td reaches the stored exhaust temperature Tu0 (Yes determination), the process proceeds to step S44, and the electronic control unit reads and stores the end time TIend at that time. Next, in step S45, the electronic control unit determines whether or not the time difference between the start time TIstart and the end time TIend is less than a predetermined time difference threshold value ΔTIthre. The time difference threshold value ΔTIthre can be set to an optimum value in consideration of the heat transfer efficiency of the DPF 12, the level of the abnormal state, and the like.

  If it is determined Yes in step S45, the time difference between the upstream exhaust temperature Tu and the downstream exhaust temperature Td becomes large, but no time difference has occurred. The electronic control unit proceeds to step S46, sets a flag notifying the occurrence of the DPF abnormality, and ends the DPF abnormality determination. On the other hand, when it is determined No in step S45, the time difference of the temperature change between the upstream exhaust temperature Tu and the downstream exhaust temperature Td is generated according to the current exhaust state. The control device proceeds to step S47, ends the DPF abnormality determination with the flag informing that the DPF abnormality has occurred being lowered.

  By executing DPF abnormality determination in this way, DPF abnormality determination can be performed without depending on the reliability of the differential pressure sensor, and as a result, the reliability of the abnormality determination of the differential pressure sensor can be improved. Can do.

(3) The abnormality diagnosis routine by the differential pressure sensor abnormality diagnosis device according to the present embodiment is executed after the regeneration control of the DPF 12 is executed, that is, in a state where the amount of PM trapped in the DPF 12 is small. Is preferred. If the amount of PM collected is small, it can be determined whether or not the differential pressure detection value ΔP shows an appropriate value without considering the amount of PM collected. Or abnormality of the downstream hose 19 can be determined.

1: internal combustion engine, 3: exhaust pipe, 5: fuel injection valve, 7: upstream exhaust passage, 9: downstream exhaust passage, 10: exhaust purification device, 12: particulate filter (DPF), 13: NOx purification catalyst , 15: differential pressure sensor, 17: upstream pressure introduction hose (upstream hose), 19: downstream pressure introduction hose (downstream hose), 30: electronic control device (differential pressure sensor abnormality diagnosis device), 31: differential pressure Detection means, 33: first determination means, 35: second determination means

Claims (7)

Diagnosing the presence or absence of abnormality of the differential pressure sensor in an exhaust purification device comprising a particulate filter provided in an exhaust passage of an internal combustion engine and a differential pressure sensor for detecting a differential pressure before and after the particulate filter In the abnormality diagnosis device of the differential pressure sensor for
First determining means for determining abnormality of the particulate filter based on temperatures before and after the particulate filter;
Second determination means for performing abnormality determination of the differential pressure sensor based on a determination result by the first determination means and a differential pressure detection value detected by the differential pressure sensor;
An apparatus for diagnosing abnormality of a differential pressure sensor, comprising:   When the determination result of the first determination unit is normal and the differential pressure detection value is equal to or greater than a predetermined upper limit threshold, the second determination unit is disposed in the exhaust passage downstream of the particulate filter. The abnormality diagnosis device for a differential pressure sensor according to claim 1, wherein the pressure introduction hose of the connected differential pressure sensor is determined to be abnormal.   When the determination result of the first determination unit is normal and the differential pressure detection value is equal to or lower than a predetermined lower limit threshold, the second determination unit is disposed in the exhaust passage upstream of the particulate filter. The abnormality diagnosis device for a differential pressure sensor according to claim 1, wherein the pressure introduction hose of the differential pressure sensor connected is determined to be abnormal.   When the determination result of the first determination unit is abnormal and the differential pressure detection value is in a normal range, the second determination unit is disposed in an exhaust passage upstream or downstream of the particulate filter. The abnormality diagnosis device for a differential pressure sensor according to any one of claims 1 to 3, wherein the pressure introduction hose of the differential pressure sensor to be connected is determined to be abnormal.   The upper limit threshold value, the lower limit threshold value, or the normal range is set according to an exhaust flow rate, assuming an abnormality in which the pressure introduction hose is in an atmosphere open state. The abnormality diagnosis device for a differential pressure sensor according to one item.   When the exhaust temperature upstream of the particulate filter changes, the first determination means determines that a difference between the exhaust temperature upstream of the particulate filter and the downstream exhaust temperature is a predetermined temperature difference. The abnormality diagnosis device for a differential pressure sensor according to any one of claims 1 to 5, wherein when the particulate filter is less than a threshold value, it is determined that the particulate filter is abnormal.   When the exhaust temperature upstream of the particulate filter has changed, the first determination means until the exhaust temperature downstream of the particulate filter reaches the degree of change in the upstream exhaust temperature. 6. The apparatus for diagnosing an abnormality of a differential pressure sensor according to claim 1, wherein the particulate filter is determined to be abnormal when the time is less than a predetermined time threshold.

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