JP2008111409A - Failure detection system for differential pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology capable of accurately detecting a failure of a differential pressure sensor. <P>SOLUTION: This system is provided with a PM filter 10 and the differential pressure sensor 19 measuring difference of pressure in an upstream and a downstream of the PM filter 10. The differential pressure sensor 19 includes an atmospheric pressure introduction means 22 introducing atmospheric pressure, is capable of measuring difference of atmospheric pressure and pressure in the upstream of the PM filter and/or difference of atmospheric pressure and pressure in the downstream of the PM filter, and is provided with an exhaust gas flow rate change means 6 changing flow rate of exhaust gas flowing in the PM filter 10 and a failure detection means 20 changing flow rate of exhaust gas flowing into the PM filter by fully opening the exhaust gas flow rate change means 6 and detecting a failure of the differential pressure sensor 19 based on change quantity of difference of atmospheric pressure and pressure in the upstream of the PM filter or difference of atmospheric pressure and pressure in the downstream of the PM filter. The failure of the differential pressure sensor 19 can be accurately detected without being influenced by uncertain factor such as PM accumulation quantity in the PM filter 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a failure detection system for a differential pressure sensor.

  In an exhaust gas purification system using a filter that collects particulate matter (hereinafter referred to as “PM”) contained in exhaust gas from an internal combustion engine, the amount of PM collected in the filter is estimated based on the differential pressure across the filter. Failure detection such as filter erosion may be performed. The differential pressure before and after the filter is generally acquired by a differential pressure sensor that measures the difference between the pressures of the exhaust upstream and downstream of the filter.

  In such an exhaust purification system, if the differential pressure sensor fails, the estimation accuracy of the amount of PM trapped decreases, and the filter regeneration process cannot be executed at a suitable timing, or the filter failure cannot be detected or erroneously detected. There are cases where

On the other hand, as a method for detecting a failure of the differential pressure sensor, the amount of change in the measured value of the differential pressure across the filter by the differential pressure sensor when the flow rate of the exhaust gas flowing into the filter is changed is expected from the amount of change in the exhaust flow rate. There has been proposed a method for determining that a differential pressure sensor has failed when a certain amount of difference is generated with respect to the amount of change in the differential pressure across the filter (see Patent Document 1).
JP 2004-340138 A JP 2005-307880 A JP 2004-308492 A JP 2003-254041 A

  However, since the differential pressure before and after the filter depends on the PM accumulation state in the filter, the deterioration state of the filter, etc. In the failure determination method, the influence of the filter state cannot be avoided, and there is a possibility that accurate determination cannot be performed.

  The present invention has been made in view of such problems, and an object thereof is to provide a technique for detecting a failure of a differential pressure sensor with higher accuracy.

  In order to achieve the above object, a differential pressure sensor failure detection system according to the present invention includes a PM filter provided in the middle of an exhaust passage of an internal combustion engine for collecting particulate matter in exhaust gas, and a differential pressure across the PM filter. And an external pressure introducing means for introducing a constant pressure outside the exhaust system of the internal combustion engine (hereinafter referred to as “external pressure”), and a differential pressure between the pressure upstream of the PM filter and the external pressure A differential pressure sensor capable of measuring a differential pressure between a pressure downstream of the PM filter and the external pressure (hereinafter referred to as a “filter downstream external differential pressure”); Exhaust flow rate changing means for changing the exhaust flow rate flowing into the PM filter, and changing the exhaust flow rate flowing into the PM filter by the exhaust flow rate changing means, A failure detection means for detecting a failure of the differential pressure sensor based on a change amount of the differential pressure between the upstream and external sides of the filter or a change amount of the differential pressure between the downstream side and the downstream side of the filter in accordance with the change in the exhaust flow rate flowing into the filter; It is characterized by providing.

Here, the external pressure is a substantially constant pressure independent of the operating state of the PM filter or the internal combustion engine, and for example, atmospheric pressure can be selected.

  In the above configuration, when the exhaust flow rate flowing into the PM filter is changed by the exhaust flow rate changing means, the pressure upstream of the PM filter and the pressure downstream of the PM filter change. Accordingly, the differential pressure between the filter upstream and the exterior and the differential pressure between the filter downstream and the exterior also change. Here, the change amount of the differential pressure between the filter upstream and the exterior is substantially equal to the change amount of the pressure upstream of the PM filter because the external pressure is a substantially constant value. For the same reason, the amount of change in the differential pressure between the downstream and downstream sides of the filter is also approximately equal to the amount of change in the pressure downstream of the PM filter.

  Here, the pressure upstream of the PM filter is less susceptible to the influence of uncertain factors such as the PM accumulation state and the failure state such as melting damage in the PM filter as compared to the differential pressure across the PM filter. The amount of change almost depends only on the amount of change in the exhaust flow rate flowing into the PM filter. Further, since the pressure downstream of the PM filter is the pressure of the exhaust gas after passing through the PM filter, its absolute value is affected by the state of the PM filter, but the amount of change is uncertain affected by the state of the PM filter. The components are offset and the influence of the state of the PM filter is less susceptible to the differential pressure across the PM filter. Accordingly, it is considered that the amount of change in pressure downstream of the PM filter also depends only on the amount of change in the exhaust flow rate flowing into the PM filter.

  Therefore, according to the above configuration, the amount of change in the differential pressure between the filter upstream and the exterior, which is a physical quantity that is hardly affected by the uncertain factor depending on the state of the PM filter compared with the differential pressure across the PM filter, or the filter downstream external Since the failure detection of the differential pressure sensor is performed based on the change amount of the differential pressure difference, it is possible to detect the failure with very high accuracy.

  For example, when the amount of change in the measured value by the differential pressure sensor of the differential pressure between the upstream and the downstream of the filter (or the differential pressure between the downstream and the downstream of the filter) is less than a predetermined lower limit (for example, approximately zero), the pressure upstream of the PM filter ( (Or the pressure downstream of the PM filter) is changed, but the measured value of the differential pressure sensor hardly changes, and it can be determined that a stack failure has occurred in the differential pressure sensor. Here, the “predetermined lower limit value” is the amount of change in the differential pressure between the filter upstream and the exterior (or the differential pressure between the filter downstream and the exterior) when the pressure upstream of the PM filter (or the pressure downstream of the PM filter) is changed. The allowable lower limit value of the measurement result when measured by a normal differential pressure sensor, which is determined in advance.

  Further, the PM filter of the amount of change in the measured value by the differential pressure sensor of the differential pressure between the upstream and external sides of the filter (or the differential pressure between the downstream side and the downstream side of the filter) If the difference from the estimated value based on the change amount of the exhaust flow rate flowing into the exhaust gas is larger than a predetermined first upper limit value (or second upper limit value), it is considered that some abnormality has occurred in the characteristics of the differential pressure sensor. It can be determined that a failure has occurred in the differential pressure sensor. Here, the “predetermined first upper limit value (or second upper limit value)” is the differential pressure between the filter upstream and the exterior (or the differential pressure between the filter downstream and the exterior) when the exhaust flow rate flowing into the PM filter is changed. The allowable upper limit value of the deviation between the estimated value when the change amount is estimated according to a known calculation model and the measured value when measured by the differential pressure sensor, is predetermined.

  The present invention further includes an intake throttle valve that changes the flow passage cross-sectional area of the intake passage of the internal combustion engine, and the exhaust flow rate changing means changes the exhaust flow rate flowing into the PM filter by changing the opening of the intake throttle valve. It may be changed. For example, since the intake air amount of the internal combustion engine increases by greatly increasing the opening of the intake throttle valve (opening side opening), the exhaust flow rate from the internal combustion engine increases accordingly, and PM The exhaust flow rate flowing into the filter can be increased.

Here, if the opening degree of the intake throttle valve is changed, the intake air amount of the internal combustion engine will fluctuate. Therefore, depending on the operating state of the internal combustion engine, there is a possibility that torque fluctuation will be caused and drivability will be deteriorated. Therefore, it is preferable to change the flow rate of the exhaust gas flowing into the PM filter during the deceleration operation of the internal combustion engine (when the fuel is cut). As a result, it is possible to prevent drivability from deteriorating when the exhaust flow rate flowing into the PM filter is changed to detect a failure of the differential pressure sensor.

  In the above configuration, as the external pressure, it is possible to select a pressure whose true value is known in advance or a pressure capable of estimating the true value with high accuracy by a predetermined method, even if it is not a constant pressure.

  According to the present invention, it is possible to accurately detect a failure of a differential pressure sensor.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram schematically showing a schematic configuration of an intake system and an exhaust system of an internal combustion engine according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.

  An intake manifold 17 and an exhaust manifold 18 are connected to the cylinder 2 of the internal combustion engine 1. An intake pipe 3 is connected to the intake manifold 17. Near the connecting portion between the intake manifold 17 and the intake pipe 3, a second intake throttle valve 9 for adjusting the flow rate of the intake air flowing through the intake pipe 3 is provided. The second intake throttle valve 9 is opened and closed by an electric actuator. The intake pipe 3 upstream of the second intake throttle valve 9 is provided with an intercooler 8 that cools the intake air by exchanging heat between the intake air and the outside air. The intake pipe 3 upstream of the intercooler 8 is provided with a compressor housing 11 of a turbocharger 5 that operates using exhaust energy as a drive source. The intake pipe 3 upstream of the compressor housing 11 is provided with a first intake throttle valve 6 that adjusts the flow rate of intake air flowing through the intake pipe 3. The first intake throttle valve 6 is opened and closed by an electric actuator.

  On the other hand, the exhaust manifold 4 is connected to the exhaust manifold 18. A turbine housing 12 of the turbocharger 5 is provided in the middle of the exhaust pipe 4. A particulate filter (hereinafter referred to as “filter”) 10 is provided in the exhaust pipe 4 downstream of the turbine housing 12. The filter 10 collects particulate matter (hereinafter referred to as “PM”) in the exhaust gas. Downstream of the filter 10, the exhaust pipe 4 is opened to the atmosphere through a muffler (not shown).

  The internal combustion engine 1 is provided with an EGR device 40 that guides a part of the exhaust gas flowing through the exhaust pipe 4 to the intake pipe 3 and recirculates it to the cylinder 2. The EGR device 40 includes an EGR passage 41, an EGR valve 42, and an EGR cooler 43. The EGR passage 41 connects the exhaust manifold 18 and the intake manifold 17. Exhaust gas is guided to the intake pipe 3 through the EGR passage 41. In the present embodiment, the exhaust gas recirculated to the cylinder 2 via the EGR passage 41 is referred to as EGR gas. The EGR valve 42 is a flow rate control valve that can change the amount of exhaust gas flowing through the EGR passage 41 by changing the flow passage cross-sectional area of the EGR passage 41. The EGR gas is adjusted by adjusting the opening degree of the EGR valve 42. The EGR cooler 43 cools the EGR gas by exchanging heat between the EGR gas and the cooling water that cools the internal combustion engine 1.

  The internal combustion engine 1 is provided with an electronic control unit (ECU) 20 that controls the engine. The ECU 20 connects a read-only memory (ROM), a random access memory (RAM), a central processing unit (CPU), an input / output port, a digital analog converter (DA converter), an analog digital converter (AD converter), etc. with a bidirectional bus. The microcomputer has a known configuration as described above.

  The ECU 20 performs various basic controls known in the diesel engine such as fuel injection control in accordance with the operation state of the internal combustion engine 1 or a request from the driver. For this purpose, the internal combustion engine 1 in this embodiment measures the crank position sensor 16 for measuring the rotational phase (crank angle) of the crankshaft of the internal combustion engine 1 and the amount of depression of the accelerator pedal 14 by the driver (accelerator opening). An accelerator opening sensor 15 for performing the measurement, an air flow meter 7 for measuring the flow rate of fresh air flowing into the intake pipe 3, a differential pressure sensor 19 for measuring a pressure difference between exhaust gas upstream and downstream of the filter 10, and other diesel engines are generally used. Provided sensors (not shown) are provided.

  Here, the differential pressure sensor 19 in the present embodiment will be described in detail. Connected to the differential pressure sensor 19 are a filter upstream pressure introduction pipe 13 for introducing the exhaust pressure upstream of the filter 10 and a filter downstream pressure introduction pipe 23 for introducing the exhaust pressure downstream of the filter 10. The differential pressure between the exhaust pressure upstream of the filter 10 (hereinafter referred to as “filter upstream pressure”) and the exhaust pressure downstream of the filter 10 (hereinafter referred to as “filter downstream pressure”) can be measured.

  In the case of the present embodiment, an atmospheric pressure introduction pipe 22 for introducing atmospheric pressure is further connected to the differential pressure sensor 19, and the filter downstream pressure introduction pipe 23 and the atmospheric pressure introduction pipe 22 can be switched by a switching valve 21. It has become. When the switching valve 21 is switched to the filter downstream pressure introducing pipe 23 side, the differential pressure sensor 19 measures the differential pressure between the filter upstream pressure and the filter downstream pressure, and the switching valve 21 is connected to the atmospheric pressure introducing pipe 22 side. Is switched, the differential pressure sensor 19 measures the differential pressure between the filter upstream pressure and the atmospheric pressure.

  Each sensor described above is connected to the ECU 20 via electrical wiring, and an output signal from each sensor is input to the ECU 20. Further, the ECU 20 is connected to devices such as a driving device for driving the first intake throttle valve 6, the second intake throttle valve 9, the switching valve 21, and the EGR valve 42 via electric wiring, and is output from the ECU 20. These devices are controlled according to the control signal.

  ECU20 grasps | ascertains the driving | running state of the internal combustion engine 1, and a driver | operator's request | requirement based on the measured value by each sensor. For example, the ECU 20 calculates the engine speed from the crank angle input from the crank position sensor 16, calculates the engine load from the accelerator opening input from the accelerator opening sensor 15, and calculates the calculated engine speed and The operating state of the internal combustion engine 1 is acquired based on the engine load. Then, the first intake throttle valve 6, the second intake throttle valve 9, the switching valve 21, the pressure EGR valve 42, and the like are controlled based on the acquired engine operating state and the driver's request.

  In the present embodiment, the difference between the front and rear of the filter 10 measured by the differential pressure sensor 19 is used to determine the execution timing of the filter regeneration process for removing the PM accumulated on the filter 10 by oxidation and to detect a failure such as melting damage in the filter 10. Use pressure. However, when the differential pressure sensor 19 is deteriorated or malfunctioned, there is a possibility that the execution time of the filter regeneration process cannot be properly determined, or the malfunction of the filter 10 cannot be detected with high accuracy.

Therefore, in this embodiment, in order to detect the deterioration or failure of the differential pressure sensor 19, the differential pressure sensor failure detection control as shown in FIG. 2 is executed. FIG. 2 is a flowchart showing a routine for performing failure detection control of the differential pressure sensor 19. This routine is repeatedly executed at predetermined time intervals by the ECU 20 during operation of the internal combustion engine 1.

  In step S100, the ECU 20 acquires the operating state of the internal combustion engine 1. Specifically, the engine speed is calculated from the measured value of the crank angle by the crank position sensor 16, and the engine load is calculated from the measured value of the accelerator opening by the accelerator opening sensor 15.

  In step S101, ECU20 determines whether the internal combustion engine 1 is decelerating based on the driving | running state of the internal combustion engine 1 acquired in step S100. When an affirmative determination is made in step S101, the ECU 20 executes step S102. On the other hand, if a negative determination is made in step S101, the ECU 20 once ends the execution of this routine.

  In step S102, the ECU 20 switches the switching valve 21 to the atmospheric pressure introduction pipe 22 side. As a result, the differential pressure sensor 19 can measure a differential pressure ΔP between the filter upstream pressure Pin and the atmospheric pressure Pa (hereinafter referred to as “filter upstream atmospheric differential pressure”) ΔP.

  In step S103, the ECU 20 measures the filter upstream atmospheric pressure differential pressure ΔP1 during the deceleration operation. When the filter upstream pressure at this time is Pin1, ΔP1 = Pin1−Pa.

  In step S104, the ECU 20 fully opens the opening of the first intake throttle valve 6. As a result, the intake air amount increases, and the exhaust flow rate from the internal combustion engine 1 increases accordingly, so the filter upstream pressure increases.

  In step S105, the ECU 20 measures the filter upstream atmospheric pressure differential pressure ΔP2 when the intake air amount is increased. If the filter upstream pressure at this time is Pin2, ΔP2 = Pin2-Pa.

  In step S106, the ECU 20 determines the differential pressure upstream atmospheric pressure ΔP1 during the deceleration operation measured in step S103, and the differential upstream pressure differential air ΔP2 when the intake air amount is increased during the deceleration operation measured in step S105. Are equal to each other. In this embodiment, when the absolute value of the difference between ΔP1 and ΔP2 is less than a predetermined small value δ, it is determined that ΔP1 and ΔP2 are equal.

  If the determination in step S106 is affirmative, it means that the measured value of the differential pressure between the upstream of the filter has hardly changed even though the upstream pressure of the filter has been changed. Theoretically, when the filter upstream pressure changes from Pin1 to Pin2, the amount of change in the filter upstream atmospheric differential pressure becomes ΔP2−ΔP1 = (Pin2−Pa) − (Pin1−Pa) = Pin2−Pin1. Should be equal to the upstream pressure change. On the other hand, if the measured value of the change amount of the differential pressure between the upstream of the filter is substantially zero, a stack failure of the differential pressure sensor 19 is suspected. Therefore, in this case, the ECU 20 determines that the differential pressure sensor 19 has failed in step S107. In step S109, a warning is displayed to notify the driver that the differential pressure sensor 19 has failed. On the other hand, if a negative determination is made in step S106, the ECU 20 determines that the differential pressure sensor 19 is normal in step S108. After executing step S109 or step S108, the ECU 20 executes step S110.

  In step S110, the ECU 20 switches the switching valve 21 to the filter downstream pressure introduction pipe 23 side. As a result, the differential pressure sensor 19 returns to a normal state where the differential pressure across the filter 10 can be measured. After executing step S110, the ECU 20 once ends the execution of this routine.

  According to the differential pressure sensor failure detection routine described above, the failure detection of the differential pressure sensor 19 is based on the output change of the differential pressure sensor 19 caused only by the change in the upstream pressure of the filter accompanying the change in the flow rate of the exhaust gas flowing into the filter 10. Therefore, the failure of the differential pressure sensor 19 can be detected with high accuracy without being influenced by uncertain factors such as a failure state such as a PM accumulation state or melting damage in the filter 10.

  FIG. 3 shows time transitions of the vehicle speed, the filter upstream atmospheric differential pressure, and the intake air amount when the differential pressure sensor failure detection routine is executed. In FIG. 3A, the vertical axis represents vehicle speed, and the horizontal axis represents time. In FIG. 3B, the vertical axis represents the differential pressure between the air upstream of the filter, and the horizontal axis represents time. In FIG. 3C, the vertical axis represents the intake air amount, and the horizontal axis represents time.

  As shown in FIG. 3A, the internal combustion engine 1 enters a decelerating operation state at a time t1, and the vehicle speed starts to decrease accordingly. At this time, the switching valve 21 is switched from the filter downstream pressure introduction pipe 23 side to the atmospheric pressure introduction pipe 22 side, so that the differential pressure sensor 19 can measure the differential pressure between the filters upstream. As shown in FIG. 3B, at this time, the flow rate of the exhaust gas from the internal combustion engine 1 is rapidly decreasing, so the filter upstream atmospheric pressure difference ΔP1 is a small value. Here, when the first intake throttle valve 6 is fully opened at time t2, as shown in FIG. 3 (C), the intake air amount increases rapidly, and the filter upstream pressure increases accordingly. As shown in (B), the differential pressure between the air upstream of the filter also increases to ΔP2. In this way, it is possible to detect a failure of the differential pressure sensor 19 by changing the differential pressure between the upstream air of the filter and measuring the change amount by the differential pressure sensor 19.

  In the above embodiment, the stack failure of the differential pressure sensor 19 is detected based on whether or not the measured value of the differential pressure across the atmosphere upstream of the filter changes when the upstream pressure of the filter is changed. The theoretical value (or estimated value) of the amount of change in the differential pressure between the upstream of the filter that is expected when the pressure is changed is compared with the measured value of the differential pressure between the upstream of the filter actually measured by the differential pressure sensor 19 Then, a failure of the differential pressure sensor 19 may be detected based on the comparison result. According to this detection method, not only a stack failure of the differential pressure sensor 19 but also a subtle failure or abnormality such as a characteristic deviation of the differential pressure sensor 19 can be detected. When this detection method is employed, the measurement value allowed when the change amount of the filter upstream atmospheric differential pressure is measured by a normal differential pressure sensor 19 is used as a comparison target of the measured value of the filter upstream atmospheric differential pressure. It may be used.

  In the above embodiment, the atmospheric pressure is introduced into the differential pressure sensor 19, but it may not be atmospheric pressure as long as the pressure is constant. Further, if the true value is a clearly known pressure, a non-constant pressure may be introduced. That is, any pressure can be used as long as the value measured by the differential pressure sensor 19 and the value to be compared can be accurately calculated by theoretical calculation or estimation.

  In the above-described embodiment, the failure detection routine of the differential pressure sensor 19 is executed during the deceleration operation of the internal combustion engine 1. However, the failure detection control unit from step S102 to step S110 in the failure detection routine described above is an internal combustion engine. It can be executed even when the engine 1 is not decelerating. However, if it is executed in a limited manner during the deceleration operation, it is possible to avoid that the drivability is deteriorated due to the torque fluctuation caused by the increase in the intake air amount for detecting the failure of the differential pressure sensor 19. There is an advantage.

  In the above embodiment, the intake air amount is changed by fully opening the first intake throttle valve in order to change the filter upstream pressure. However, the method of changing the filter upstream pressure is not limited to this. For example, the EGR valve 42 may be fully closed, or when the turbocharger 5 is a variable capacity turbocharger provided with nozzle vanes, the nozzle vanes may be fully opened. Further, the first intake throttle valve opening may not be fully open, but may be any opening as long as the opening is closer to the opening than during the deceleration operation. However, since the comparison accuracy with the theoretical value increases as the amount of change in the filter upstream pressure increases, it is preferable to fully open the filter. The same applies to the opening degree of the EGR valve and the opening degree of the nozzle vane.

  In the above embodiment, the differential pressure between the filter upstream pressure and the atmospheric pressure is measured to detect a failure of the differential pressure sensor 19, but the differential pressure between the filter downstream pressure and the atmospheric pressure is measured. May be. In this case, a switching valve that switches between the filter upstream pressure introduction pipe 13 and the atmospheric pressure introduction pipe 22 is provided, and when the differential pressure sensor 19 is normally used, the switching valve is switched to the filter upstream pressure introduction pipe 13 side so that The differential pressure can be measured, and when the failure of the differential pressure sensor 19 is detected, the switching valve is switched to the atmospheric pressure introduction pipe 22 side so that the differential pressure between the atmospheric pressure downstream of the filter can be measured.

  Moreover, as shown in FIG. 4, it is good also as a structure which can measure both a filter upstream atmospheric differential pressure and a filter downstream atmospheric differential pressure. FIG. 4 is a diagram showing a schematic configuration around a differential pressure sensor and a filter for realizing such a configuration. In FIG. 4, the same reference numerals are given to the same components as in FIG. 1, and the internal combustion engine, intake system, and EGR system that are common to FIG. In FIG. 4, the arrows drawn on the exhaust pipe 4 indicate the flow of exhaust. In this configuration, the differential pressure sensor 19 is switched to the filter upstream pressure introduction pipe 13 that introduces the pressure of the exhaust gas upstream of the filter 10, and the second atmospheric pressure introduction that is switched to the filter upstream pressure introduction pipe 13 to introduce the atmospheric pressure. A pipe 24, a second switching valve 25 that switches between the filter upstream pressure introduction pipe 13 and the second atmospheric pressure introduction pipe 24, a filter downstream pressure introduction pipe 23 that introduces exhaust pressure downstream of the filter 10, and a filter downstream pressure An atmospheric pressure introduction pipe 22 that is switched to the introduction pipe 23 to introduce atmospheric pressure, and a switching valve 21 that switches between the filter downstream pressure introduction pipe 23 and the atmospheric pressure introduction pipe 22 are connected. The switching valve 21, the second switching valve 25, and the differential pressure sensor 19 are each connected to the ECU 20 via electric wiring.

  According to this configuration, the switching valve 21 is switched to the atmospheric pressure introduction pipe 22 side, and the second switching valve 25 is switched to the filter upstream pressure introduction pipe 13 side, so that the differential pressure sensor 19 changes the filter upstream atmospheric differential pressure. It becomes possible to measure. On the other hand, by switching the switching valve 21 to the filter downstream pressure introduction pipe 23 side and switching the second switching valve 25 to the second atmospheric pressure introduction pipe 24 side, the differential pressure sensor 19 can measure the filter downstream atmospheric pressure difference. It becomes. Further, the differential pressure sensor 19 can measure the differential pressure across the filter 10 by switching the switching valve 21 to the filter downstream pressure introduction pipe 23 side and switching the second switching valve 25 to the filter upstream pressure introduction pipe 13 side. Become. Furthermore, by switching the switching valve 21 to the atmospheric pressure introduction pipe 22 side and switching the second switching valve 25 to the second atmospheric pressure introduction pipe 24 side, equal pressure is introduced into the differential pressure sensor 19. Therefore, the zero point correction of the differential pressure sensor 19 can be performed. According to this configuration, there is an advantage that the zero point correction can be executed in an arbitrary operation state of the internal combustion engine 1.

  Each embodiment described above is an example for explaining the present invention, and can be combined and modified as much as possible without departing from the spirit of the present invention.

1 is a diagram showing a schematic configuration of an intake system and an exhaust system of an internal combustion engine in Embodiment 1. FIG. 3 is a flowchart illustrating a failure detection control routine for a differential pressure sensor in the first embodiment. 6 is a time chart showing time transitions of the vehicle speed, the filter upstream atmospheric differential pressure, and the intake air amount when executing the differential pressure sensor failure detection control routine in the first embodiment. It is a figure which shows the modification of a structure of the differential pressure sensor in Example 1. FIG.

Explanation of symbols

1 Internal combustion engine 2 Cylinder 3 Intake pipe 4 Exhaust pipe 5 Turbocharger 6 First intake throttle valve 7 Air flow meter 8 Intercooler 9 Second intake throttle valve 10 Filter 11 Compressor housing 12 Turbine housing 13 Filter upstream pressure introduction pipe 14 Accelerator pedal 15 Accelerator opening sensor 16 Crank position sensor 17 Intake manifold 18 Exhaust manifold 19 Differential pressure sensor 20 ECU
21 switching valve 22 atmospheric pressure introduction pipe 23 filter downstream pressure introduction pipe 24 second atmospheric pressure introduction pipe 25 second switching valve 40 EGR device 41 EGR passage 42 EGR valve 43 EGR cooler

Claims (6)

A PM filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
An external pressure introducing means for introducing a constant pressure outside the exhaust system of the internal combustion engine, capable of measuring a differential pressure across the PM filter, and a pressure upstream of the PM filter and a constant pressure outside the exhaust system, And / or a differential pressure sensor capable of measuring a differential pressure between a pressure downstream of the PM filter and a constant pressure outside the exhaust system;
Exhaust flow rate changing means for changing the exhaust flow rate flowing into the PM filter;
The exhaust flow rate changing means changes the exhaust flow rate flowing into the PM filter, and the difference between the pressure upstream of the PM filter and a constant pressure outside the exhaust system due to the change in the exhaust flow rate flowing into the PM filter. A failure detecting means for detecting a failure of the differential pressure sensor based on an amount of change in pressure, or an amount of change in differential pressure between a pressure downstream of the PM filter and a constant pressure outside the exhaust system;
A fault detection system for a differential pressure sensor. In claim 1,
The failure detecting means is the differential pressure sensor for the differential pressure between the pressure upstream of the PM filter and a constant pressure outside the exhaust system when the exhaust flow rate flowing into the PM filter is changed by the exhaust flow rate changing means. Or when the change amount of the measured value by the differential pressure sensor of the differential pressure between the pressure downstream of the PM filter and the constant pressure outside the exhaust system is less than a predetermined lower limit value, A differential pressure sensor failure detection system that determines that a differential pressure sensor has failed. In claim 1,
The failure detection means, when the exhaust flow rate flowing into the PM filter is changed by the exhaust flow rate change means,
The amount of change in the measured value by the differential pressure sensor of the differential pressure between the pressure upstream of the PM filter and the constant pressure outside the exhaust system;
The difference between the change amount of the differential pressure between the pressure upstream of the PM filter and the constant pressure outside the exhaust system and the estimated value based on the change amount of the exhaust flow rate flowing into the PM filter is larger than a predetermined first upper limit value. If
Or
The amount of change in the measured value by the differential pressure sensor of the differential pressure between the pressure downstream of the PM filter and the constant pressure outside the exhaust system;
The difference between the change amount of the differential pressure between the pressure downstream of the PM filter and the constant pressure outside the exhaust system and the estimated value based on the change amount of the exhaust flow rate flowing into the PM filter is larger than a predetermined second upper limit value. In case,
A differential pressure sensor failure detection system for determining that the differential pressure sensor has failed. In any one of Claims 1-3,
The external pressure introduction means is a differential pressure sensor failure detection system for introducing atmospheric pressure to the differential pressure sensor. In any one of Claims 1-4,
An intake throttle valve for changing the cross-sectional area of the intake passage of the internal combustion engine,
The exhaust pressure change means is a differential pressure sensor failure detection system that changes an exhaust flow rate flowing into the PM filter by changing an opening of the intake throttle valve. In any one of Claims 1-5,
The failure detection means is a differential pressure sensor failure detection system that performs failure determination of the differential pressure sensor during deceleration operation of the internal combustion engine.

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