JP2008128114A - Exhaust throttle valve failure diagnosis device for internal combustion engine - Google Patents

Abstract

An exhaust throttle valve failure diagnosis device for an internal combustion engine capable of reliably diagnosing an exhaust throttle valve failure without increasing the cost.
An exhaust gas recirculation device having an EGR control valve for controlling an exhaust gas recirculation amount in an exhaust gas recirculation passage that communicates the intake passage and the exhaust passage, and an exhaust throttle disposed in the exhaust passage. In an internal combustion engine having a valve 134, an exhaust throttle valve opening / closing operation means for temporarily closing the exhaust throttle valve 134 in a predetermined operation state, and an opening / closing operation of the exhaust throttle valve 134 by the exhaust throttle valve opening / closing operation means. Correspondingly detecting intake air amount change detecting means for detecting a change in intake air amount, and diagnosing whether the exhaust throttle valve is abnormal or normal based on the change in intake air amount detected by the intake air amount change detecting means Diagnostic means.
[Selection] Figure 1

Description

  The present invention relates to an exhaust throttle valve failure diagnosis device for an internal combustion engine, in particular, an exhaust gas recirculation device having an exhaust gas recirculation control valve for controlling an exhaust gas recirculation amount in an exhaust gas recirculation passage communicating the intake passage and the exhaust passage, The present invention relates to an exhaust throttle valve failure diagnosis device for an internal combustion engine including an exhaust throttle valve disposed in an exhaust passage.

  In general, a technique is known in which an exhaust throttle valve is provided in an exhaust passage of an internal combustion engine, and 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 early warm-up of an exhaust purification catalyst provided in an exhaust system, regeneration of a DPF (diesel particulate filter) that collects particulates (particulate matter, hereinafter referred to as PM) in exhaust, and the like. .

  By the way, since such an exhaust throttle valve is always exposed to exhaust gas, oil components, unburned fuel components, and the like in the exhaust gas 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 there is a failure of the exhaust throttle valve, that is, whether there is an abnormality (adherence).

  In an internal combustion engine having an exhaust throttle valve in the exhaust passage as described above, a temperature sensor or a pressure sensor is installed upstream of the exhaust throttle valve, and the exhaust throttle valve is based on a temperature difference or a pressure difference generated between a normal time and an abnormal time. An apparatus for detecting a fault in the system is known.

  For example, a technique described in Patent Document 1 has been proposed as an abnormality detection device that simply and reliably detects the presence or absence of such an exhaust throttle valve abnormality. In this device, the opening degree of the exhaust gas recirculation control valve is feedback-controlled so that the intake air amount detected by the air flow meter becomes the target intake air amount determined according to the engine operating state. Then, when the opening degree of the exhaust gas recirculation control valve is feedback-controlled, the exhaust throttle valve is opened or closed, and the exhaust gas recirculation control valve opening degree before and after this operation is controlled based on the amount of change in the exhaust gas recirculation control valve opening degree. Whether there is an abnormality in the throttle valve is detected.

Japanese Patent Laid-Open No. 2001-207917

  However, in the case where a temperature sensor or a pressure sensor is installed on the upstream side of the exhaust throttle valve described above, it is necessary to provide a dedicated sensor for detecting a failure. 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 technology described in Patent Document 1 feedback-controls the opening degree of the exhaust gas recirculation control valve so that the intake air amount becomes a target intake air amount determined according to the engine operating state, and the exhaust gas recirculation control valve When the opening degree of the exhaust gas is being feedback-controlled, the presence or absence of an abnormality of the exhaust throttle valve is detected, and when the abnormality is detected, the change in the opening degree of the exhaust gas recirculation control valve is caused by the feedback control. Therefore, complicated control is required to distinguish whether it is caused by abnormality of the exhaust throttle valve. Furthermore, it is not easy to accurately detect the amount of change in the exhaust gas recirculation control valve opening, and in this case as well, there is a problem that it is difficult to reliably diagnose a failure.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust throttle valve failure diagnosis device for an internal combustion engine that can reliably diagnose an exhaust throttle valve failure 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 includes an exhaust gas recirculation control valve that controls an exhaust gas recirculation amount in an exhaust gas recirculation passage that connects the intake passage and the exhaust passage. In an internal combustion engine having an exhaust gas recirculation device and an exhaust throttle valve disposed in an exhaust passage, exhaust throttle valve opening / closing operation means for temporarily closing the exhaust throttle valve in a predetermined operation state, and the exhaust Intake air amount change detecting means for detecting a change in the intake air amount in response to the opening / closing operation of the exhaust throttle valve by the throttle valve opening / closing operation means, and a change in the intake air amount detected by the intake air amount change detecting means. And a diagnostic means for diagnosing whether the exhaust throttle valve is abnormal or normal.

  Here, it is preferable that the opening degree of the exhaust gas recirculation control valve is fixed when the exhaust throttle valve opening / closing operation means is operated.

  Moreover, it is preferable that the opening degree of the exhaust gas recirculation control valve is fixed to be fully open.

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

  In the exhaust throttle valve failure diagnosis device for an internal combustion engine according to one aspect of the present invention, when the exhaust throttle valve is temporarily closed by the exhaust throttle valve opening / closing operation means in a predetermined operation state, the intake air amount change The detection means detects a change in the intake air amount based on the intake air amount when the exhaust throttle valve is closed and the intake air amount when the exhaust throttle valve is opened. Based on the change in the intake air amount, the diagnostic means detects the exhaust throttle valve. Diagnose whether it is abnormal or normal. Specifically, when there is a large difference in the intake air amount before and after the valve opening / closing operation of the exhaust throttle valve, the back pressure increases due to the closing operation of the exhaust throttle valve, the reflux exhaust gas amount increases, and the intake air amount decreases. And the exhaust throttle valve is diagnosed as functioning normally.

  Conversely, when the difference in the intake air amount before and after that is small, it is the result that there was no change in the recirculated exhaust gas amount regardless of the valve opening / closing operation command of the exhaust throttle valve, and the intake air amount hardly changed. The throttle valve is diagnosed as malfunctioning. Therefore, according to the configuration of the above embodiment, the cost can be increased based on the change in the intake air amount corresponding to the valve opening / closing operation of the exhaust throttle valve without requiring additional parts such as a temperature sensor or a pressure sensor. A failure of the exhaust throttle valve can be diagnosed without fail.

  Here, during the operation of the exhaust throttle valve opening / closing operation means, according to the embodiment in which the opening degree of the exhaust gas recirculation control valve is fixed, the fluctuation factor of the recirculated exhaust gas amount is caused by the back pressure accompanying the valve opening / closing operation of the exhaust throttle valve. Since only the change in the intake air amount can be caused only by the change in the back pressure, a failure of the exhaust throttle valve can be diagnosed more reliably.

  In addition, according to the embodiment in which the opening degree of the exhaust gas recirculation control valve is fixed at the fully open position, the control and the holding are easy because the control is to the limit position.

  Further, according to the mode in which the predetermined operation state is a deceleration state of the vehicle, it is not necessary to perform normal combustion, and it is possible to prevent the deterioration of the emission due to the failure diagnosis of the exhaust throttle valve.

  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) recirculated to the surge tank 104 through the EGR passage 152 described later. Used for.

  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, it is pressurized by the compressor 130C driven by the turbine 130T 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.

  In the present embodiment, a first 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 that flows through the exhaust passage 122 downstream thereof. An exhaust throttle valve 134 for controlling the exhaust gas is arranged. The exhaust throttle valve 134 includes an actuator 134A similar to the intake throttle valve 108, and takes a fully open position and a closed position with a predetermined opening according to a control signal from the ECU 200. In this embodiment, the exhaust throttle valve 134 is used when raising the exhaust temperature for early activation of the first catalyst device 132 and regeneration of the particulate filter (DPF) in the second catalyst device 136 described later. . In the present embodiment, the above-described second catalytic device (storage reduction type NOx catalyst and DPF) 136 is disposed downstream of the exhaust throttle valve 134.

  In the second catalyst device 136 in the present embodiment, the NOx storage reduction catalyst is accommodated upstream thereof. With this NOx storage reduction catalyst, NOx is stored in the NOx storage reduction catalyst when the exhaust is in an oxidizing atmosphere (lean) during engine operation. In a reducing atmosphere (stoichiometric or rich), NOx stored in the NOx storage reduction catalyst is released as nitrogen oxide (NO) and is reduced by hydrocarbon (HC) or carbon monoxide (CO). As a result, purification of NOx is performed.

  Then, downstream of the second catalytic device 136, that is, downstream of the NOx storage reduction catalyst, DPF having a wall portion formed in a monolith structure is accommodated, and exhaust passes through the minute hole in the wall portion. Is configured to do. The DPF surface is coated with a NOx storage reduction catalyst. For this reason, NOx purification is performed as described above. Moreover, since particulate matter (PM) in the exhaust is trapped on the DPF surface, the oxidation of PM is started by active oxygen generated during NOx occlusion in an oxidizing atmosphere, and the entire PM is oxidized by excess oxygen in the surroundings. . In a reducing atmosphere (stoichiometric or rich), oxidation of PM is promoted by a large amount of active oxygen generated from the NOx storage reduction catalyst. As a result, the purification of PM is performed together with the purification of NOx.

  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 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. A signal corresponding to the air amount Gn is also disposed in the EGR valve 154 and a signal corresponding to the accelerator pedal depression amount (accelerator opening) of the driver from an accelerator opening sensor 162 disposed in the vicinity of an unillustrated accelerator pedal. A signal indicating the EGR valve opening degree is input from the EGR valve opening degree sensor 164, respectively.

  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 of the EGR valve 154, the intake throttle valve 108, and the exhaust throttle valve 134 via a drive circuit (not shown), and controls the valve opening degree.

  In this embodiment, the EGR valve opening sensor 164 for detecting the EGR valve opening is provided. However, for example, when the stepper motor is used as the actuator of the EGR valve 154 without providing the opening sensor 164, the motor EGR valve opening based on the number of drive steps and, if a solenoid actuator is used as the actuator, the duty ratio of the solenoid drive pulse on / off (the ratio of the on time in the drive pulse on / off cycle) It is also possible to calculate.

  As described above, PM in exhaust gas is collected in the DPF during engine operation, and the amount of PM collected in the DPF gradually increases. In the present embodiment, when it is desired to activate the first catalyst device 132 at an early stage, and when the amount of PM collected by the DPF in the second catalyst device 136 increases, the exhaust throttle valve 134 is closed. By reducing the intake air amount of the engine and raising the exhaust gas temperature, early activation and regeneration of the DPF are performed.

  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 S201 is repeated until the vehicle is decelerated and the standby state is maintained.

  When the vehicle is decelerated, in the next step S202, the EGR valve 154 is fixed at a predetermined opening or is fully opened. In the next step S203, the intake air amount GnA before the exhaust throttle valve fully closing command, which will be described later, is output from the air flow meter 112 at a predetermined time after the EGR valve 154 is operated to a predetermined opening or fully opened position. It is measured and stored based on the value. Thereafter, in step S204, the exhaust throttle valve 134 fully closed command is sent to the actuator 134A of the exhaust throttle valve 134.

  In the normal running state of the vehicle, the exhaust throttle valve 134 is generally maintained in a fully open state. Therefore, there is no problem even if the full close command described above for failure diagnosis is issued immediately. When the valve 134 is in a position other than full open or is unknown, it is preferable to issue a full open command in advance to make the exhaust throttle valve 134 fully open before issuing the full close command.

  In the next step S205, the intake air amount GnB after the exhaust throttle valve full-close command is measured and stored by the air flow meter 112 at a predetermined time after the exhaust throttle valve 134 is fully closed. Then, the process proceeds to the next step S206, waits for a predetermined temporary period t0 to elapse, and then proceeds to step S207, where a full open command of the exhaust throttle valve 134 is sent to the actuator 134A of the exhaust throttle valve 134.

  Further, in the next step S208, the difference ΔGn (= | GnA−GnB) between the intake air amount GnA measured and stored in step S203 and the intake air amount GnB measured and stored in step S205. |) Is calculated. In step S209, the obtained difference in intake air amount ΔGn is compared with a predetermined threshold value α to diagnose whether or not the exhaust throttle valve 134 has failed. That is, when the difference ΔGn in the intake air amount is small without exceeding the predetermined threshold value α, it is a result that the exhaust throttle valve 134 is not closed despite the exhaust throttle valve 134 being fully closed, and the exhaust throttle Proceeding to step S210 on the assumption that the valve 134 is, for example, an open fixing failure, a diagnosis of abnormality is made. On the other hand, when the difference ΔGn in the intake air amount exceeds the predetermined threshold value α, it is a result of the exhaust throttle valve 134 being closed as commanded, and it is determined that the exhaust throttle valve 134 is operating normally and the process proceeds to step S211. Proceed and be diagnosed as normal.

  Here, FIG. 3 is a time chart showing a state of change of the related part in the above-described diagnosis procedure and a state of change of the intake air amount Gn measured by the air flow meter 112. 3 (A) is the accelerator opening, (B) is the vehicle speed, (C) is the opening of the EGR valve 154, (D) is the drive command signal for the exhaust throttle valve 134, and (E) is measured by the air flow meter 112. The intake air amount Gn to be performed is shown.

  As is apparent from FIG. 3, the diagnosis routine according to the present embodiment starts at time t1, is in a deceleration state of the vehicle in which the accelerator opening is 0% and the fuel injection amount from the fuel injection valve 104 is stopped, and The measurement is performed with the opening degree of the EGR valve 154 fully opened (100%), and the intake air amount Gn at a predetermined time t2 and time t4 before and after the fully closing command to the exhaust throttle valve 134 at time t3. Thus, failure diagnosis of the exhaust throttle valve 134 is performed. More specifically, the intake air amount GnA is measured by the air flow meter 112 at a predetermined time t2 when the opening of the EGR valve 154 is fully open and the exhaust throttle valve 134 is also fully open. Then, the exhaust throttle valve 134 is temporarily closed during time t0 until time t5 by a full-close command at a predetermined time t3 thereafter. Furthermore, the intake air amount GnB is measured by the air flow meter 112 at a predetermined time t4 during the temporary closing operation. Thereafter, although not shown in FIG. 3, a diagnosis is made as to whether or not the exhaust throttle valve 134 is functioning normally.

  Here, a supplementary explanation will be given as to why the exhaust throttle valve 134 can be diagnosed depending on whether or not the difference ΔGn in the intake air amount exceeds the predetermined threshold value α. In the present embodiment, in the deceleration state of the vehicle, In addition, since the opening of the EGR valve 154 is executed in a fully opened state, the intake amount sucked into the cylinder 102 of the engine 100 at this time is determined by the flow resistance, back pressure, etc. of the exhaust gas recirculation passage 122. The maximum amount of EGR gas and the amount of fresh air passing through the air flow meter 112 are added. Accordingly, the amount of intake air drawn into the cylinder 102 of the engine 100 is constant per one rotation of the engine 100 in the deceleration state of the vehicle, so that the fresh air amount increases as the amount of EGR gas drawn into the cylinder 102 of the engine 100 increases. The amount of fresh air increases as the amount of EGR gas decreases.

  By the way, the difference ΔGn in the intake air amount before and after the opening / closing operation of the exhaust throttle valve 134 is large because the back pressure rises due to the closing operation of the exhaust throttle valve 134, the EGR gas amount increases, and the intake air amount Gn decreases. As a result, it is diagnosed that the exhaust throttle valve 134 is functioning normally (shown by a solid line in FIG. 3E). Conversely, the difference ΔGn between the intake air amount before and after that is small because the closing operation is not sufficient despite the close command of the exhaust throttle valve 134, there is no change in the EGR gas amount, and the intake air amount Gn almost changes. The result is that there is no failure, and the exhaust throttle valve 134 is diagnosed as having a failure (shown by the broken line (E) in FIG. 3).

  Therefore, according to the above-described present embodiment, the exhaust throttle valve 134 can be reliably and without an additional cost based on a change in the intake air amount Gn, without requiring additional components such as a temperature sensor or a pressure sensor. A failure can be diagnosed. Here, during the closing operation of the exhaust throttle valve 134, according to the embodiment in which the opening degree of the EGR control valve 154 is fixed, the fluctuation factor of the recirculated exhaust gas amount is determined only by the back pressure accompanying the closing operation of the exhaust throttle valve 134. Therefore, the failure of the exhaust throttle valve 134 can be diagnosed more reliably, and according to the embodiment in which the opening degree of the EGR control valve 154 is fixed fully open, its control and holding are easy. Furthermore, according to the mode in which the predetermined operation state is the vehicle deceleration state, it is possible to prevent the deterioration of the emission due to the failure diagnosis of the exhaust throttle valve 134.

1 is a schematic diagram showing an embodiment of an exhaust throttle valve failure diagnosis device for an internal combustion engine according to the present invention. It is a flowchart which shows an example of the failure diagnosis control procedure of embodiment of this invention. It is a time chart which shows the mode of the change of the related site | part in a failure diagnosis procedure, and the mode of change of the intake air amount Gn, The solid line in (E) shows a normal state and the broken line has shown the abnormal (failure) state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Diesel engine body 102 Intake passage 112 Air flow meter 122 Exhaust passage 134 Exhaust throttle valve 150 EGR device 152 EGR passage 154 EGR control valve (EGR valve)
160 Rotational speed sensor 162 Accelerator opening sensor 200 ECU

Claims (4)

In an internal combustion engine including an exhaust gas recirculation device having an exhaust gas recirculation control valve for controlling an exhaust gas recirculation amount in an exhaust gas recirculation passage communicating the intake passage and the exhaust passage, and an exhaust throttle valve disposed in the exhaust passage,
Exhaust throttle valve opening / closing operation means for temporarily closing the exhaust throttle valve in a predetermined operation state;
An intake air amount change detecting means for detecting a change in the intake air amount corresponding to the opening / closing operation of the exhaust throttle valve by the exhaust throttle valve opening / closing operation means;
Diagnostic means for diagnosing whether the exhaust throttle valve is abnormal or normal based on a change in the intake air amount detected by the intake air amount change detecting means;
An exhaust throttle valve failure diagnosis device for an internal combustion engine, comprising:   2. The exhaust throttle valve failure diagnosis device for an internal combustion engine according to claim 1, wherein an opening degree of the exhaust gas recirculation control valve is fixed when the exhaust throttle valve opening / closing operation means is operated.   3. The exhaust throttle valve failure diagnosis device for an internal combustion engine according to claim 2, wherein the opening degree of the exhaust gas recirculation control valve is fixed at full open.   The exhaust throttle valve failure diagnosis device for an internal combustion engine according to any one of claims 1 to 3, wherein the predetermined operation state is a deceleration state of a vehicle.

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