JP4748396B2 - Exhaust throttle valve failure diagnosis device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust throttle valve failure diagnosis device for an internal combustion engine, and more particularly to an exhaust throttle valve failure diagnosis device for an internal combustion engine that includes an exhaust purification filter in an exhaust passage and an exhaust throttle valve disposed upstream thereof.

  In general, in internal combustion engines, particularly diesel engines, removal of particulate matter (particulate matter, hereinafter also referred to as PM) contained in exhaust gas is an important issue. For this reason, there is a technique for providing an exhaust purification filter (for example, diesel particulate filter, hereinafter also referred to as DPF) for collecting particulate matter in the exhaust system of the internal combustion engine so that particulate matter is not released into the atmosphere. .

  Further, a technique is known in which an exhaust throttle valve is provided in an exhaust passage of an internal combustion engine so that the flow rate of exhaust flowing through the exhaust passage is reduced as necessary. This is used to raise the exhaust gas temperature by reducing the flow rate of the exhaust gas and raising the back pressure. That is, for the purpose of early warming up of the exhaust gas purification catalyst provided in the exhaust system, regeneration of the DPF that collects PM, and the like.

  In this DPF, if the amount of accumulated PM is excessive, the filter is clogged, and there is a possibility that the fuel consumption is deteriorated due to the output reduction resulting from this, or the filter is damaged. Therefore, as a technique for determining such clogging, a technique for determining the presence or absence of clogging by detecting a pressure difference between upstream and downstream of the DPF with a differential pressure sensor is known.

  By the way, since the exhaust throttle valve is always exposed to the exhaust, oil components in the exhaust, unburned fuel components, and the like are likely to adhere to the exhaust throttle valve. If the exhaust throttle valve sticks to the open position, the exhaust temperature rise action cannot be achieved, and if the exhaust throttle valve sticks to the closed position, the engine is operated with a high exhaust back pressure. The engine output decreases and the acceleration performance deteriorates continuously. For this reason, it is important to reliably diagnose whether or not the exhaust throttle valve is abnormal (fixed).

  In such an internal combustion engine provided with an exhaust throttle valve in the exhaust passage, a temperature sensor or a pressure sensor is installed on the upstream side of the exhaust throttle valve, and the exhaust throttle valve is based on the temperature difference or pressure difference that occurs between normal and abnormal conditions. An apparatus for detecting a fault in the system is known.

  Further, for example, in the technique described in Patent Document 1, a differential pressure sensor that detects a differential pressure upstream and downstream of the exhaust throttle valve is provided, and the exhaust throttle valve is opened or closed. It may be possible to detect the presence or absence of an abnormality in the exhaust throttle valve based on the amount of change in the pressure difference between the front and rear.

JP 2003-269147 A

  However, in the case where a temperature sensor or pressure sensor is installed upstream of the exhaust throttle valve, a sensor dedicated to the exhaust throttle valve must be provided for failure detection. In this case, since the temperature difference between the upstream and downstream sides is small, there is a problem that it is difficult to reliably diagnose the failure.

  Further, the technique described in Patent Document 1 is also a dedicated sensor for the exhaust throttle valve, which causes a problem of cost increase.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an exhaust throttle valve failure diagnosis device for an internal combustion engine that can diagnose a failure of the exhaust throttle valve without increasing the cost.

  An exhaust throttle valve failure diagnosis device for an internal combustion engine according to an aspect of the present invention that achieves the above object, an exhaust purification filter installed in an exhaust passage of the internal combustion engine, an exhaust throttle valve upstream of the exhaust purification filter, Differential pressure disposed in communication with an upstream pressure guiding path communicating with the downstream side of the exhaust throttle valve and a downstream pressure guiding path communicated with the downstream side of the exhaust purification filter on the upstream side of the exhaust purification filter An exhaust purification device for an internal combustion engine comprising a differential pressure detecting means including a sensor, wherein the upstream side pressure guiding path communicated with the differential pressure sensor is communicated with the upstream side of the exhaust purification filter at a first position. First communication switching means capable of switching to the upstream side of the exhaust throttle valve at the downstream side or the second position of the exhaust throttle valve, and the communication of the downstream side pressure guiding path communicated with the differential pressure sensor, 1's And a second communication switching means capable of switching to the atmosphere downstream of the exhaust purification filter or at a second position, and a reference for obtaining a reference pressure corresponding to an indicated opening to the exhaust throttle valve and an intake air amount The pressure acquisition means, and at a predetermined time, the first and second communication switching means are respectively switched to the second position, the detected pressure obtained by the differential pressure detection means, and the reference obtained by the reference pressure acquisition means Diagnostic means for diagnosing whether the exhaust throttle valve is abnormal or normal based on a difference with pressure.

  Here, the diagnostic means diagnoses that the exhaust throttle valve is normal when the difference between the reference pressure and the detected pressure is less than an absolute value of a predetermined value.

  When the difference between the reference pressure and the detected pressure is positive and exceeds an absolute value of a predetermined value, the diagnostic means issues an instruction to close the exhaust throttle valve by a predetermined angle, and further, the differential pressure Whether the exhaust throttle valve is stuck open is diagnosed based on a difference between a detection pressure obtained by the detection means and a reference pressure obtained by the reference pressure acquisition means.

  Further, when the difference between the detected pressure and the reference pressure is negative and exceeds an absolute value of a predetermined value, the diagnostic means issues an instruction to open the exhaust throttle valve at a predetermined angle, and further, the differential pressure Whether or not the exhaust throttle valve is closed and stuck is diagnosed based on a difference between a detection pressure obtained by the detection means and a reference pressure obtained by the reference pressure acquisition means.

  Furthermore, it is preferable that the predetermined time is a deceleration state of the vehicle.

  According to the exhaust throttle valve failure diagnosis device for an internal combustion engine according to one aspect of the present invention, the first communication switching unit and the second communication switching unit are respectively set to the second position by the diagnostic unit at a predetermined time. The communication of the upstream pressure guiding path communicated with the differential pressure sensor is switched to the upstream side of the exhaust throttle valve, and the communication of the downstream pressure guiding path communicated to the differential pressure sensor is switched to the atmosphere. Then, the pressure between the upstream side of the exhaust throttle valve and the atmosphere is detected by a differential pressure detecting means including a differential pressure sensor arranged in communication with the upstream side pressure guiding path and the downstream side pressure guiding path. At the same time, the reference pressure obtaining means obtains a reference pressure corresponding to the indicated opening of the exhaust throttle valve and the intake air amount, and based on the difference between the detected pressure and the reference pressure, whether the exhaust throttle valve is abnormal or normal. Diagnosed. That is, when the difference between the two exceeds a predetermined value, it is diagnosed as abnormal when the difference is present, and normal otherwise. Thus, by using the differential pressure sensor for the exhaust purification filter, failure diagnosis of the exhaust throttle valve can be performed without increasing the cost.

  Here, when the difference between the reference pressure and the detected pressure is less than an absolute value of the predetermined value, the diagnosis means diagnoses that the exhaust throttle valve is normal, and the exhaust throttle is more reliably performed. Valve failure diagnosis is possible.

  When the difference between the reference pressure and the detected pressure is positive and exceeds a predetermined absolute value, the diagnostic means issues an instruction to close the exhaust throttle valve by a predetermined angle, and further, the differential pressure According to the form of diagnosing whether or not the exhaust throttle valve is stuck open based on the difference between the detection pressure obtained by the detection means and the reference pressure obtained by the reference pressure acquisition means, the exhaust throttle valve is in any state. It is also possible to diagnose whether a failure has occurred due to sticking.

  Further, when the difference between the detected pressure and the reference pressure is negative and exceeds an absolute value of a predetermined value, the diagnostic means issues an instruction to open the exhaust throttle valve at a predetermined angle, and further, the differential pressure According to the embodiment for diagnosing whether or not the exhaust throttle valve is closed and closed based on the difference between the detection pressure obtained by the detection means and the reference pressure obtained by the reference pressure acquisition means, the exhaust throttle It is also possible to diagnose what state the valve has failed due to sticking.

  Furthermore, according to the mode in which the predetermined time is the deceleration state of the vehicle, it is possible to prevent the deterioration of the emission due to the failure diagnosis of the exhaust throttle valve.

  In the description of the present specification, “closed sticking” and “open sticking” of the exhaust throttle valve means that the exhaust throttle valve is in a state where the exhaust throttle valve cannot move in the fully closed state and the fully opened state, and the closed side from the half-open position. In addition to the state incapable of moving on the open side, the term also includes a state in which the movement or rotation from the closed side and the open side to the opposite sides is not performed in accordance with the operation instruction.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram illustrating a schematic configuration of an embodiment in which the present invention is applied to an automobile diesel engine.

  In FIG. 1, 100 is a diesel engine body, 102 is an intake passage of the engine 100, 104 is a surge tank provided in the intake passage 102, and 106 is an intake branch pipe connecting the surge tank 104 and the intake port of each cylinder. . In the present embodiment, the intake passage 102 is provided with an intake throttle valve 108 that restricts the flow rate of intake air flowing through the intake passage 102 and an intercooler 110 that cools intake air. The intake throttle valve 108 includes an actuator 108A of an appropriate type such as a solenoid or a vacuum actuator, and takes an opening degree according to a control signal from an electronic control unit (ECU) 200 described later. In the present embodiment, the intake throttle valve 108 reduces the intake pressure, for example, at the time of low engine rotation, and increases the amount of exhaust gas (EGR gas) that returns to the surge tank 104 through the EGR passage 152 described later. Used.

  In FIG. 1, an air flow meter 112 is provided near the intake inlet of the intake passage 102. In the present embodiment, the air flow meter 112 is of a type that can measure the mass flow rate of the intake air flowing through the intake passage 102, such as a hot-wire flow meter. After the air flowing into the intake passage 102 passes through the air flow meter 112, the air is pressurized by the compressor 130 </ b> C driven by the turbine 130 </ b> T of the turbocharger 130, cooled by the intercooler 110 provided in the intake passage 102, and then the surge tank 104. Then, it is sucked into each cylinder through the branch pipe 106.

  Reference numeral 114 in FIG. 1 denotes a fuel injection valve that directly injects fuel into each cylinder. The fuel injection valve 114 is connected to a common pressure accumulation chamber (common rail) 116 that stores high-pressure fuel. The fuel of the engine 100 is boosted by a high-pressure fuel pump 118, supplied to the common rail 116, and injected directly into each cylinder from the common rail 116 via each fuel injection valve 114.

  Further, reference numeral 120 in FIG. 1 is an exhaust manifold that connects the exhaust port of each cylinder and the exhaust passage 122, and the turbocharger 130 described above is disposed downstream thereof. As described above, the turbocharger 130 includes the exhaust turbine 130T driven by the exhaust gas in the exhaust passage 122 and the intake compressor 130C driven by the exhaust turbine 130T.

  Further, in the present embodiment, a catalyst device (for example, an oxidation catalyst or a three-way catalyst) 132 is disposed in the exhaust passage 122 on the downstream side of the turbocharger 130 and the exhaust flow rate flowing through the exhaust passage 122 is controlled downstream thereof. An exhaust throttle valve 134 is provided for this purpose. The exhaust throttle valve 134 includes an actuator 134A similar to the intake throttle valve 108, and takes a fully open position, a closed position with a predetermined opening degree, and a fully closed position in accordance with a control signal from the ECU 200. In the present embodiment, the exhaust throttle valve 134 is used when raising the exhaust temperature for early activation of the catalyst device 132 and regeneration of the DPF described later. In the present embodiment, the above-described DPF 136 is disposed downstream of the exhaust throttle valve 134.

  Furthermore, in the present embodiment, the first upstream pressure guiding path 137 communicated with the downstream side of the DPF 136 and the downstream side of the first upstream pressure guiding path 137 communicated with the upstream side of the DPF 136 downstream of the exhaust throttle valve 134 installed in the exhaust passage 122. A differential pressure sensor 138 is provided in communication with the pressure guiding path 139. Then, the second upstream pressure guiding path 140 connected to the upstream side of the exhaust throttle valve 134 is joined to the first upstream pressure guiding path 137 in the middle thereof, and the differential pressure sensor 138 is connected to this joining portion. And a second position where the differential pressure sensor 138 and the upstream side of the exhaust throttle valve 134 are communicated with each other, and a first position where the downstream side of the exhaust throttle valve 134 and the upstream side of the DPF 136 are in communication with each other. The 1st switching valve 142 which can be switched by is provided. Further, the downstream-side pressure guiding path 139 communicates with the atmospheric communication path 141 branched in the middle thereof, and a first position for maintaining the differential pressure sensor 138 and the downstream side of the DPF 136 in a communicating state is connected to the branched portion. A second switching valve 143 that can be switched by an actuator (not shown) is provided at a second position where the differential pressure sensor 138 communicates with the atmospheric communication path 141.

  Further, in the present embodiment, an EGR device 150 that recirculates part of the engine exhaust to the intake system is provided. The EGR device 150 includes the EGR passage 152 that connects the exhaust manifold 120 and the intake surge tank 104, an EGR control valve (hereinafter referred to as an EGR valve) 154 disposed in the EGR passage 152, and an upstream side of the EGR valve 154. The EGR cooler 156 provided in the EGR passage 152 is provided. The EGR valve 154 includes actuators such as stepper motors and solenoid actuators (not shown), takes an opening degree according to a control signal from the ECU 200, and controls an EGR gas flow rate recirculated to the intake surge tank 104 through the EGR passage 152. . Since the EGR gas is a high-temperature exhaust gas discharged from the cylinder, when a large amount of EGR gas is recirculated to the intake air, the intake air temperature rises, and the intake volume efficiency of the engine decreases. In the present embodiment, in order to prevent this, a water-cooled or air-cooled EGR cooler 156 is provided in the EGR passage 152 upstream of the EGR valve 154. In the present embodiment, by using the EGR cooler 156 to reduce the temperature of the EGR gas recirculated to the intake system, it is possible to recirculate a relatively large amount of EGR gas while suppressing a decrease in the intake volume efficiency of the engine. ing.

  Further, an electronic control unit (ECU) of the engine 100 is indicated by 200 in FIG. The ECU 200 according to the present embodiment is configured as a microcomputer having a known configuration, and is configured such that a CPU, a RAM, a ROM, an input port, and an output port are connected to each other via a bidirectional bus. The ECU 200 performs basic control such as fuel injection control and rotation speed control of the engine 100, and in this embodiment, performs failure diagnosis of the exhaust throttle valve 134 as described later.

  In order to perform these controls, a signal corresponding to the engine rotational speed NE is input to the input port of the ECU 200 from the rotational speed sensor 160 disposed in the vicinity of the crankshaft of the engine 100, and the engine flow from the air flow meter 112 is A signal corresponding to the intake air amount Gn per rotation, a signal corresponding to the accelerator pedal depression amount (accelerator opening) of the driver from an accelerator opening sensor 162 arranged in the vicinity of an unillustrated accelerator pedal, and an EGR valve A signal indicating the EGR valve opening degree is input from an EGR valve opening degree sensor 164 arranged at 154.

  The output port of the ECU 200 is connected to the fuel injection valve 114 of the engine 100 via a fuel injection circuit (not shown), and controls the fuel injection amount from the fuel injection valve 114 and the fuel injection timing. Further, the output port of the ECU 200 is connected to the actuators 108A and 134A of the EGR valve 154, the intake throttle valve 108 and the exhaust throttle valve 134 and the actuators of the first and second switching valves 142 and 143 through a drive circuit (not shown). Each valve opening is controlled or switched.

  As described above, PM in the exhaust gas during engine operation is collected in the DPF 136, and the amount of PM collected by the DPF 136 gradually increases. In this embodiment, when the PM collection amount of the DPF 136 increases, the regeneration operation of the DPF 136 is performed by closing the exhaust throttle valve 134 to decrease the engine intake amount and increasing the exhaust temperature.

  Hereinafter, a control procedure for failure diagnosis of the exhaust throttle valve of the present embodiment configured as described above will be described with reference to the flowchart of FIG. This failure diagnosis routine is executed at a predetermined cycle.

  Therefore, when the failure diagnosis routine starts, it is determined in step S201 whether or not the vehicle is in a decelerating state. In this embodiment, it is determined whether or not the vehicle is in a deceleration state. In this embodiment, the accelerator opening detected by the accelerator opening sensor 162 is 0%, and the amount of fuel injected from the fuel injection valve 114 is determined. The process proceeds to the next step S202 only when the vehicle is in a deceleration state where these conditions are satisfied. In other words, step S202 is executed when the vehicle is decelerated. This is because the fuel injection from the fuel injection valve 114 is normally stopped when the vehicle is in a deceleration state, so that it is possible to prevent the emission from deteriorating due to the failure diagnosis of the exhaust throttle valve 134.

  When the vehicle is decelerated, in the next step S202, the second switching valve 143 communicates between the differential pressure sensor 138 and the downstream side of the DPF 136 while maintaining the first switching valve 142 at the first position. Is switched to the second position where the differential pressure sensor 138 and the atmospheric communication path 141 are communicated, and the downstream pressure guiding path 139 of the differential pressure sensor 138 is communicated with the atmosphere. In the next step S203, the differential pressure sensor 138 is moved from the first position where the first switching valve 142 maintains the downstream side of the differential pressure sensor 138 and the exhaust throttle valve 134 and the upstream side of the DPF 136 in communication. And the second position where the upstream side of the exhaust throttle valve 134 communicates. Then, in the next step S204, the differential pressure sensor 138 communicating with the upstream side of the exhaust throttle valve 134 and the atmosphere causes the differential pressure between the upstream side of the exhaust throttle valve 134 and the atmosphere at a predetermined opening degree θ. It is calculated | required and memorize | stored as the present detected pressure value P (theta).

  Further, in the next step S205, the differential pressure that is inherently generated when the exhaust throttle valve 134 is at the predetermined opening degree θ is obtained as the reference pressure value Pθref. In the present embodiment, the reference pressure value Pθref is obtained as follows. That is, the predetermined opening degree θ of the exhaust throttle valve 134 is obtained based on the command signal Sθ sent from the ECU 200 to the actuator 134A of the exhaust throttle valve 134, and the intake air amount Gn is used as a detection signal of the air flow meter 112. Based on. Then, using these command signal Sθ and intake air amount Gn as parameters, a reference pressure value Pθref at the opening θ is obtained from a map that has been obtained and stored in advance in the ROM of ECU 200 through experiments or the like.

  Then, the process proceeds to step S206, and the difference between the reference pressure value Pθref obtained in step S205 above and the detected pressure value Pθ obtained in step S204, in other words, the deviation from the reference pressure value to the positive side or the negative side. The quantity ± ΔPθ (= Pθref−Pθ) is calculated. In the next step S207, whether or not the deviation ± ΔPθ from the reference pressure to the positive side or the negative side exceeds a predetermined absolute value | α | It is determined which is the negative side, and when the deviation amount ± ΔPθ does not exceed the predetermined absolute value | α |, ie, “1”, the process proceeds to step S214 and step S215 in order, and the exhaust throttle valve Assuming that 134 is functioning normally, the “open sticking detection flag” and the “close sticking detection flag” are set to “OFF”, and this diagnosis routine is ended.

  On the other hand, when the deviation amount + ΔPθ to the positive side exceeds the absolute value | α | of the predetermined value, that is, “2”, the ECU 200 obtains the above-described predetermined opening degree θ of the exhaust throttle valve 134. Although the command signal Sθ is sent to the actuator 134A of the exhaust throttle valve 134, the exhaust throttle valve 134 may be opened larger than the predetermined opening θ, so the process proceeds to step S208. It is diagnosed whether it is stuck on the open side.

  On the other hand, when the deviation amount −ΔPθ to the negative side exceeds the absolute value | α | of the predetermined value, in other words, when the predetermined value −α exceeds the negative side, that is, “3”, Despite the command signal Sθ being sent from the ECU 200 to the actuator 134A of the exhaust throttle valve 134 in order to obtain the aforementioned predetermined opening degree θ of the exhaust throttle valve 134, the exhaust throttle valve 134 has its predetermined opening degree θ. Therefore, the process proceeds to step S216, which will be described later, and it is diagnosed whether it is not fixed on the closed side.

  Therefore, in step S208 that proceeds when the positive deviation + ΔPθ from the reference pressure exceeds the predetermined value α, in the present embodiment, the fully closed command signal Sc for fully closing the exhaust throttle valve 134 is the exhaust throttle valve. 134 is sent to the actuator 134A. Then, in the next step S209, the differential pressure sensor 138 communicating with the upstream side of the exhaust throttle valve 134 and the atmosphere is instructed to fully close and the upstream side of the exhaust throttle valve 134 at a predetermined opening degree and the atmosphere. The current differential pressure is obtained and stored as the fully closed detection pressure value Pθc.

  In the description of the present specification, “fully closed” of the exhaust throttle valve 134 means a minimum opening state in which the flow resistance of the exhaust gas flowing through the exhaust passage 122 is maximized, and “fully opened” of the exhaust throttle valve 134. "Means a maximum opening state in which the flow resistance of the exhaust gas flowing through the exhaust passage 122 is minimized.

  Then, in the next step S210, the differential pressure that is inherently generated when the exhaust throttle valve 134 is at the fully closed opening degree θc is obtained as the fully closed reference pressure value Pθcref. This fully closed reference pressure value Pθcref is the intake air amount based on the fully closed command signal Sc sent to the actuator 134A of the exhaust throttle valve 134 and the detection signal of the air flow meter 112, as in the case of the above-described reference pressure value Pθref. Using Gn as a parameter, the fully closed reference pressure value Pθcref at the fully closed opening θc is obtained from a map that is obtained and stored in advance in the ROM of the ECU 200 by experiments or the like.

  In step S211, the difference between the fully closed reference pressure value Pθcref obtained in step S210 above and the fully closed detected pressure value Pθc obtained in step S209, in other words, the deviation ΔPθc from the fully closed reference pressure. (= Pθcref−Pθc) is calculated. Then, in the next step S212, it is determined whether or not the deviation amount ΔPθc from the fully closed reference pressure exceeds a predetermined value β. If it exceeds, that is, if “Yes”, the process proceeds to step S213. When the deviation amount ΔPθc from the fully closed reference pressure exceeds a predetermined value β, the fully closed command signal Sc for fully closing the exhaust throttle valve 134 is sent to the actuator 134A of the exhaust throttle valve 134. Regardless, this means that the exhaust throttle valve 134 is not normally closed. Therefore, assuming that the exhaust throttle valve 134 is in the open stuck state, the “open stuck detection flag” is set to “ON”, and this diagnostic routine is executed. finish.

  When the deviation amount ΔPθc from the fully closed reference pressure does not exceed the predetermined value β, a fully closed command signal Sc for fully closing the exhaust throttle valve 134 is sent to the actuator 134A of the exhaust throttle valve 134. Since the exhaust throttle valve 134 can be regarded as a result of the normal closing operation, it is assumed that the exhaust throttle valve 134 is functioning normally, and the process proceeds to the above-described steps S214 and S215 in order. The “detection flag” is set to “OFF”, and the diagnosis routine is terminated.

  On the other hand, in the determination in step S207 described above, when the deviation amount −ΔPθ to the negative side exceeds the absolute value | α | of the predetermined value, in other words, when the predetermined value −α exceeds the negative side, that is, In step S 216, which proceeds when “3”, in the present embodiment, a fully open command signal So for fully opening the exhaust throttle valve 134 is sent to the actuator 134 A of the exhaust throttle valve 134. In the next step S217, the upstream side of the exhaust throttle valve 134 that is instructed to be fully opened by the differential pressure sensor 138 communicating with the upstream side of the exhaust throttle valve 134 and the atmosphere, and the current state of the atmosphere. Is obtained and stored as a fully open detection pressure value Pθo.

  Then, in the next step S218, a differential pressure that is inherently generated when the exhaust throttle valve 134 is at the fully opened opening degree θo is obtained as the fully opened reference pressure value Pθoref. The full open reference pressure value Pθoref is the same as the reference pressure value Pθref described above, and is the intake air amount Gn based on the full open command signal So sent to the actuator 134A of the exhaust throttle valve 134 and the detection signal of the air flow meter 112. As a parameter, the fully open reference pressure value Pθoref at the fully open degree θo is acquired from a map that is obtained and stored in advance in the ROM of the ECU 200 by experiments or the like.

  Then, the process proceeds to step S219, and the difference between the fully open reference pressure value Pθoref obtained in step S218 above and the fully open detected pressure value Pθo obtained in step S217, in other words, the deviation amount ΔPθo (= Pθoref from the fully open reference pressure). -Pθo) is calculated. Then, in the next step S212, it is determined whether or not the absolute value of the deviation amount ΔPθo from the fully open reference pressure exceeds a predetermined value γ. If it exceeds, ie, “Yes”, the process proceeds to step S221. move on. When the amount of deviation ΔPθo from the fully open reference pressure exceeds a predetermined value γ, the fully open command signal So for fully opening the exhaust throttle valve 134 is sent to the actuator 134A of the exhaust throttle valve 134. This means that the exhaust throttle valve 134 is not normally opened. Therefore, assuming that the exhaust throttle valve 134 is in the closed fixed state, the “closed fixed detection flag” is set to “ON”, and this diagnosis routine is ended.

  When the deviation amount ΔPθo from the fully open reference pressure does not exceed the predetermined value γ, the fully open command signal So for fully opening the exhaust throttle valve 134 is sent to the actuator 134A of the exhaust throttle valve 134, and the exhaust throttle valve Since the exhaust throttle valve 134 is functioning normally, the process proceeds to the above-described steps S214 and S215 in order, and the “open sticking detection flag” and the “close sticking detection flag” are displayed. The diagnosis routine is terminated with “OFF” for each.

  As is clear from the above description, according to the present embodiment, the use of the differential pressure sensor 138 for the DPF 136 makes it possible to diagnose a failure of the exhaust throttle valve 134 without increasing the cost. Furthermore, it is possible to diagnose what state the exhaust throttle valve 134 is malfunctioning.

  In the above-described embodiment, when the deviation ± ΔPθ from the reference pressure to the positive side or the negative side exceeds the absolute value | α | of the predetermined value, the exhaust throttle valve 134 is fully closed or fully opened. Although the close or full open command signal Sc or So is generated, it is not always necessary to perform the full close or full open operation, and an instruction to operate the closed side or the open side by a predetermined angle may be issued. However, if the fully-closed or fully-open command signal Sc or So that causes the exhaust throttle valve 134 to be fully closed or fully opened is generated, the amount of reference pressure stored in the map can be reduced and the control is simplified.

1 is a schematic diagram showing a schematic configuration of an internal combustion engine and a control device to which an embodiment of the present invention is applied. It is a flowchart which shows the process sequence of the abnormality diagnosis process concerning the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Engine 102 Intake passage 112 Air flow meter 122 Exhaust passage 134 Exhaust throttle valve 134A Actuator 136 DPF
137 First upstream side pressure guiding path 138 Differential pressure sensor 139 Downstream side pressure guiding path 140 Second upstream side pressure guiding path 141 Atmospheric communication path 142 First switching valve 143 Second switching valve 200 ECU

Claims (5)

An exhaust purification filter installed in an exhaust passage of the internal combustion engine, an exhaust throttle valve upstream of the exhaust purification filter, and an upstream pressure guiding path communicated upstream of the exhaust purification filter and downstream of the exhaust throttle valve And an exhaust gas purification apparatus for an internal combustion engine, comprising differential pressure detection means including differential pressure sensors respectively arranged in communication with downstream pressure guiding paths communicated with the downstream side of the exhaust purification filter.
The upstream side pressure guiding path communicated with the differential pressure sensor is connected upstream of the exhaust purification filter at the first position downstream of the exhaust throttle valve or upstream of the exhaust throttle valve at the second position. First communication switching means capable of switching to
A second communication switching means capable of switching the communication of the downstream pressure guiding path communicated with the differential pressure sensor to the atmosphere at the first position downstream of the exhaust purification filter or at the second position;
A reference pressure obtaining means for obtaining a reference pressure corresponding to the indicated opening and the intake air amount to the exhaust throttle valve;
At a predetermined time, the first and second communication switching means are respectively switched to the second position, and a detected pressure value obtained by the differential pressure detecting means and a reference pressure value obtained by the reference pressure acquiring means Diagnosing means for diagnosing whether the exhaust throttle valve is abnormal or normal based on a deviation amount of the difference to the positive side or the negative side ;
An exhaust throttle valve failure diagnosis device for an internal combustion engine, comprising: The diagnostic means determines that the exhaust throttle valve is normal when the absolute value of the deviation amount to the positive side or the negative side of the difference between the reference pressure value and the detected pressure value is less than an absolute value of a predetermined value. The exhaust throttle valve failure diagnosis device for an internal combustion engine according to claim 1, wherein diagnosis is performed. When the difference between the reference pressure value and the detected pressure value is positive and exceeds a predetermined absolute value, the diagnostic means issues an instruction to close the exhaust throttle valve by a predetermined angle, and and the detected pressure value obtained by the differential pressure detection means, based on the difference between the reference pressure value of a predetermined angle closing of the exhaust throttle valve obtained by said reference pressure obtaining means, the exhaust throttle valve is whether open sticking or The exhaust throttle valve failure diagnosis device for an internal combustion engine according to claim 1 or 2, characterized in that The diagnostic means gives an instruction to open the exhaust throttle valve at a predetermined angle when the difference between the reference pressure value and the detected pressure value is negative and the absolute value exceeds a predetermined absolute value. issued, further comprising detecting the pressure value obtained by the differential pressure detection means, based on the difference between the reference pressure value at a predetermined angle to open the exhaust throttle valve obtained by said reference pressure obtaining means, the exhaust throttle valve is closed The exhaust throttle valve failure diagnosis device for an internal combustion engine according to any one of claims 1 to 3, characterized in that it is diagnosed whether or not it is stuck.   5. The exhaust throttle valve failure diagnosis apparatus for an internal combustion engine according to claim 1, wherein the predetermined time is a deceleration state of the vehicle.

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