JP2008128004A - Failure diagnostic device for exhaust emission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately diagnose the failure of an exhaust gas flow passage selection means in an exhaust emission control system. <P>SOLUTION: This failure diagnostic device for the exhaust emission control system comprises a first exhaust gas passage 360 allowing the exhaust gas from an engine to flow to a catalyst, a second exhaust gas passage 350 which is formed by bypassing the first exhaust gas passage and in which a HC adsorbent 340 is installed, and a selection control valve 370 for selecting one of these flow passages. The failure diagnostic device further comprises temperature sensors 380, 390 capable of detecting the temperatures in the first and second exhaust gas passages, respectively, an operating state detection means for detecting the operating state of the selection control valve 370 according to the detected temperatures, and a diagnostic means for diagnosing the failure of the selection control valve 370 according to the detected operating state and the state of instruction to the selection control valve 370. The operating state detection means detects the operating state of the selection control valve 370 according to the temperatures detected during the fuel cut operation of the engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification system in an internal combustion engine, and more particularly to a failure of an exhaust gas purification system capable of switching a flow path at a predetermined time to a bypass passage formed by bypassing an exhaust gas passage and provided with an HC adsorbent. The present invention relates to a failure diagnosis device for an exhaust gas purification system for diagnosis.

  As this type of exhaust gas purification system failure diagnosis apparatus, one that uses first and second temperature detection means installed upstream and downstream of the HC adsorbent has been proposed (see, for example, Patent Document 1). ). According to the failure diagnosis device disclosed in Patent Document 1, the detection value by the first temperature detection means is set to a predetermined value or the second temperature detection means in a predetermined detection period set in accordance with opening / closing of the exhaust gas switching valve. It is said that a failure of the exhaust gas switching valve can be detected by comparing with the detection value obtained by.

  By the way, when detecting the failure of the exhaust gas switching valve based on the exhaust temperature, the engine is in a stable combustion state, there is an exhaust gas amount suitable for detection, and the exhaust gas switching valve is driven. It is necessary to ensure a sufficient negative pressure. For this purpose, the device of Patent Document 2 detects a failure of the exhaust gas switching valve only when the exhaust temperature, the intake air amount, the engine speed and the intake pipe pressure are all equal to or higher than a predetermined value. ing.

  Further, the device of Patent Document 3 integrates the time during which the exhaust gas temperature exceeds a predetermined oxidation start temperature, and periodically switches the exhaust gas switching valve when the integrated value exceeds the reference value. Prevents sticking.

JP 2000-230416 A JP 2005-248736 A Japanese Patent No. 3303604

  Patent Documents 1 and 2 both perform failure detection during traveling after engine warm-up. However, since the operating state of the engine during traveling is not constant, it is not always easy to make the initial detection state constant.

  Patent Document 3 predicts a failure of the exhaust gas switching valve, but cannot detect an actual failure of the exhaust gas switching valve.

  Therefore, in view of the above-described circumstances, the present invention provides a failure diagnosis device for an exhaust gas purification system capable of accurately diagnosing a failure of an exhaust gas flow path switching unit in an exhaust gas purification system. And

  In order to solve the above problems, an exhaust gas purification system failure diagnosis apparatus according to the present invention bypasses the first exhaust gas passage for passing the exhaust gas from the engine, and the first exhaust gas passage. In an exhaust gas purification system comprising a second exhaust gas passage formed with HC adsorbent and an exhaust gas passage switching means for switching the passage to one of the first and second exhaust gas passages, Based on the temperature detection means for detecting the temperature of at least one of the first and second exhaust gas passages and the temperature detected by the temperature detection means, the operating state of the exhaust gas flow path switching means is determined. Based on the detected operation state detection means, the detected operation state, and the instruction state to the exhaust gas flow path switching means, failure of the exhaust gas flow path switching means is detected. And the operation state detection unit detects an operation state of the exhaust gas flow path switching unit based on the temperature detected during the fuel cut operation of the engine. To do.

  In the first aspect of the present invention, the operating state detecting means detects the operating state of the exhaust gas flow path switching means based on the temperature of at least one of the first and second exhaust gas passages. The diagnosis means diagnoses a failure of the exhaust gas flow path switching means based on the detected operation state and an instruction state to the exhaust gas flow path switching means. Here, since the operation state detection means detects the operation state of the exhaust gas flow path switching means based on the temperature detected during the fuel cut operation of the engine, the operation state detection means is based on the temperature of the exhaust gas during normal operation. Compared to, there is less influence from the operating state of the engine. Therefore, in the first aspect of the present invention, it is possible to accurately detect the operating state, and to accurately diagnose the failure of the exhaust gas flow path switching means.

  For the detection of the operating state, it is possible to use the temperature decrease rate from the start of detection during the fuel cut operation, that is, the amount of temperature decrease after the elapse of a predetermined time, and when this is larger than a predetermined threshold value, It is particularly preferable to determine that the exhaust gas passage including the temperature detection point is selected by the flow path switching means. However, another configuration, for example, a configuration in which the operating state is detected by repeatedly detecting the temperature during the fuel cut operation and comparing the degree of temperature decrease or inclination with a predetermined reference value.

  In one aspect of the present invention, the temperature detecting means detects the temperatures of both the first and second exhaust gas passages, and the operating state detecting means is the difference between the temperature decrease rates of the first and second exhaust gas passages. Based on the above, it is determined which exhaust gas passage is selected by the exhaust gas flow path switching means. In this case, since the determination is performed based on the difference between the temperatures of the first and second exhaust gas passages, the accuracy of the detection of the operation state is improved by suppressing the influence of the operation state (for example, the temperature at the start of temperature detection). Thus, it is possible to diagnose a failure with higher accuracy.

  In the present invention, “diagnosis” means that the degree of failure is specified in multiple stages according to a predetermined standard or some algorithm in addition to binary detection of the presence or absence of failure of the exhaust gas flow path switching means. It is a concept that includes what is done.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, a configuration of an exhaust gas purification system for a vehicle engine according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a partial cross-sectional view showing a system configuration of an engine exhaust gas purification system.

  In FIG. 1, the engine exhaust gas purification system includes an electronic control unit (ECU) 100, an engine 200, and a main exhaust gas purification device 300. The ECU 100 includes a digital computer and includes a ROM (Read Only Memory), a RAM (Random Access Memory), a CPU (Central Processor Unit), an input port, an output port, and the like that are connected to each other via a bidirectional bus. It is possible to control the operation. Further, the ECU 100 is configured to be able to execute a failure diagnosis process, which will be described later, by executing a program stored in the ROM, and together with the main exhaust gas purification device 300, the ECU 100 of the exhaust gas purification system according to the present invention. It is also configured to function as an example of a failure diagnosis apparatus.

  The engine 200 can cause the air-fuel mixture to explode in the cylinder 201 by the spark plug 202, and can convert the reciprocating motion of the piston 203 generated according to the explosive force into the rotational motion of the crankshaft 205 via the connecting rod 204. It is an example of the internal combustion engine which concerns on this invention comprised. Below, the principal part structure of the engine 200 is demonstrated.

  When the fuel is burned in the cylinder 201, the air sucked from the outside passes through the intake pipe 206 and is mixed with the fuel injected from the injector 207 to become the above-mentioned air-fuel mixture. Fuel (gasoline) is supplied to the injector 207 from a fuel tank (not shown), and the injector 207 is able to spray the supplied fuel into the intake pipe 206 under the control of the ECU 100. Has been.

  The communication state between the inside of the cylinder 201 and the intake pipe 206 is controlled by opening and closing of the intake port by the intake valve 208. The air-fuel mixture combusted inside the cylinder 201 becomes exhaust gas, passes through the exhaust valve 209 that opens and closes the exhaust port in conjunction with opening and closing of the intake valve 208, and is exhausted to the exhaust pipe 210.

  An air cleaner 211 is disposed upstream of the intake pipe 206 to purify air sucked from the outside. An air flow meter 212 is disposed on the cylinder side of the air cleaner 211. The air flow meter 212 is, for example, a hot wire type, and is configured to be able to directly measure the mass flow rate of inhaled air. The intake pipe 206 is further provided with an intake air temperature sensor 213 for detecting the temperature of the intake air.

  A throttle valve 214 that adjusts the amount of intake air into the cylinder 201 is disposed on the cylinder side of the air flow meter 212 in the intake pipe 206. The throttle valve 214 is provided with a throttle valve motor 217 and a throttle position sensor 215, and constitutes an electronically controlled throttle valve. In this embodiment, the electronically controlled throttle valve also serves as an idle control valve that adjusts the intake air amount during idling. On the other hand, the depression amount of the accelerator pedal 223 is input to the ECU 100 via the accelerator position sensor 216, and a signal indicating the throttle valve opening corresponding to the output of the accelerator position sensor 216 is output from the ECU 100 to the throttle valve motor 217. The intake air amount is controlled.

  A crank position sensor 218 that detects the rotational position of the crankshaft 205 is provided in the vicinity of the crankshaft 205. The crank position sensor 218 is a sensor configured to be able to detect the position of the crankshaft 205, and the ECU 100 determines the position of the piston 203 and the rotational speed of the engine 200 based on the output signal of the crank position sensor 218. It is configured to be able to obtain. The position of the piston 203 is used for controlling the ignition timing in the spark plug 202 described above. The ignition timing in the spark plug 202 is, for example, retarded or advanced with respect to a preset basic value associated with the position of the piston 203.

  Further, a knock sensor 219 capable of measuring the knock strength of the engine 200 is disposed in the cylinder block that accommodates the cylinder 201, and the cooling water of the engine 200 is placed in the water jacket in the cylinder block. A water temperature sensor 220 for detecting the temperature is provided.

  A relatively small-capacity start-up catalyst 222 is installed at the collecting portion of the exhaust pipe 210. The start-up catalyst 222 is a three-way catalyst that can purify CO (carbon monoxide), HC (hydrocarbon), and NOx (nitrogen oxide) discharged from the engine 200, for example. An air-fuel ratio sensor 221 is disposed upstream of the startup catalyst 222 in the exhaust pipe 210. The air-fuel ratio sensor 221 is configured to be able to detect the air-fuel ratio of the engine 200 from the exhaust gas discharged from the exhaust pipe 210.

  The main exhaust gas purification device 300 is a catalyst device installed in the exhaust pipe 210 on the downstream side of the start-up catalyst 222, and functions together with the ECU 100 as an example of a failure diagnosis device for the exhaust gas purification system according to the present invention. It is configured to be possible. The main exhaust gas purifying device 300 and the ECU 100 are electrically connected via a control bus line.

  The ECU 100 is configured to receive a signal representing the vehicle speed VS from a vehicle speed sensor capable of detecting a traveling speed of a vehicle (not shown) and a range signal RS selected from the shift position sensor.

  Next, a detailed configuration of the main exhaust gas purification apparatus 300 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of the main exhaust gas purification device 300. In the figure, the same reference numerals are assigned to the same parts as in FIG. 1, and the description thereof is omitted.

  Inside the outer cylinder 310 of the main exhaust gas purification apparatus 300, the inner cylinder 320 is concentric with the outer cylinder 310 and has a gap in the radial direction through a flange 322 formed integrally with the end thereof. Is provided. The inner cylinder 320 is installed in an open state in the main exhaust gas purification apparatus 300 with its upstream side extending to the vicinity of the corresponding end of the outer cylinder 310. Further, the downstream end of the inner cylinder 320 is installed in an open state while facing the end surface of the underfloor catalyst 330 disposed in the outer cylinder 310 via a predetermined space. A plurality of vent holes 324 are formed in the flange portion 322 of the inner cylinder 320. An annular HC adsorbent 340 is provided in an annular space formed between the outer cylinder 310 and the inner cylinder 320 of the main exhaust gas purification device 300, that is, a bypass passage 350 described later. An exhaust pipe 210 is connected to the upstream and downstream ends of the outer cylinder 310 of the main exhaust gas purification device 300.

  Further, in FIG. 2, the main exhaust gas purification apparatus 300 of the present embodiment includes a switching control valve 370, first and second temperature sensors 380 and 390, in addition to the above-described underfloor catalyst 330 and HC adsorbent 340. A heat insulating layer 395 is provided.

  The underfloor catalyst 330 is, for example, a three-way catalyst installed under the floor of the vehicle, and purifies the exhaust gas that passes through the upstream startup catalyst 222 (not shown in FIG. 2) and flows in the direction of arrow A.

  The bypass flow path 350 is an example of the “second exhaust gas passage” according to the present invention, and the “first exhaust gas passage” according to the present invention formed inside the inner cylinder 320 (hereinafter referred to as bypassed flow). This is a flow path for guiding exhaust gas to the underfloor catalyst 330 by bypassing the road or the normal flow path 360).

  The HC adsorbent 340 is, for example, a filter formed of zeolite, and is a mesh-like filter that adsorbs (or traps) HC molecules at a low temperature (approximately less than 100 ° C.). At about 100 ° C. or higher), desorption starts spontaneously as the kinetic energy increases due to heat.

  The switching control valve 370 is configured to be able to selectively switch the flow path of the exhaust gas that has passed through the startup catalyst 222 between the bypass flow path 360 and the bypass flow path 350. The switching control valve 370 can switch the flow path of the exhaust gas by rotating the shaft portion 372 rotatably supported in the arrow B direction along with the linear motion of the rod 374 in the horizontal direction of the paper surface. It is configured. The operation of the rod 374 is controlled by an actuator 376, and the actuator 376 is electrically connected to the ECU 100 via the control bus line described above. That is, the main exhaust gas purification device 300 is configured such that the open / close bear of the switching control valve 370 changes in accordance with a control signal from the ECU 100.

  The first temperature sensor 380 of the present embodiment is composed of a thermistor element, and can detect the temperature T1 of the bypass flow path 360 on the upstream side of the underfloor catalyst 330 in the main exhaust gas purification device 300. Has been placed.

  The second temperature sensor 390 is also composed of a thermistor element, and is configured to be able to detect the temperature T2 upstream of the HC adsorbent 340 in the bypass flow path 350. The first and second temperature sensors 380 and 390 detect the temperature as a voltage value corresponding to the temperature and output it to the ECU 100, and the ECU 100 specifies the temperatures T1 and T2. The second temperature sensor 390 may be disposed on the downstream side of the HC adsorbent 340 in the bypass channel 350 so that the temperature in the bypass channel 350 can be detected.

  The heat insulating layer 395 is a heat insulator formed between the bypass flow channel 350 and the bypass flow channel 360, and heat exchange between the bypass flow channel 350 and the bypass flow channel 360 is suppressed.

  Next, with reference to FIGS. 3 and 4, an exhaust gas flow path formed in accordance with the operation of the switching control valve 370 will be described. FIG. 3 is a schematic diagram of the exhaust gas flow when the switching control valve 370 is closed in the main exhaust gas purification apparatus 300. FIG. 4 is a schematic diagram of the switching control valve 370 opened in the main exhaust gas purification apparatus 300. It is a schematic diagram of the exhaust gas flow in the case of. In these drawings, the same reference numerals are given to the same portions as those in FIG. 2 and the description thereof is omitted.

  In FIG. 3, the exhaust gas flowing in the direction of arrow A does not flow into the bypassed flow channel 360 but is guided to the bypass flow channel 350 because the switching control valve 370 is closed. Then, after HC is adsorbed by the HC adsorbent 340, the HC adsorbent 340 flows out from the vent 324 formed on the downstream side of the HC adsorbent 340 in the direction of arrow C and flows into the underfloor catalyst 330.

  In FIG. 4, the exhaust gas flowing in from the direction of arrow A is guided to the bypassed flow path 360 due to the difference in exhaust resistance because the switching control valve 370 is open. On the other hand, a part of the exhaust gas passing through the bypassed flow channel 360 changes its direction in the direction of the arrow D shown in the vicinity of the end of the bypassed flow channel 360 and is formed in the flange 322 at the end of the bypass flow channel 350. It flows into the bypass channel 350 from the downstream side through the vent hole 324 formed. Then, the direction of the exhaust gas is changed again in the exhaust gas flow direction (arrow A direction) at the upstream end of the bypass flow channel 350 and guided to the bypass flow channel 360. That is, part of the exhaust gas recirculates inside the main exhaust gas purification device 300. In the main exhaust gas purification apparatus 300, the cross-sectional area ratio between the bypass flow path 360 and the bypass flow path 350, the curvature of the flange 322 that defines the end portion of the bypass flow path 350, the shape and size of the vent hole 324, and the like However, it is determined in advance to cause such a reflux phenomenon. Note that it is not essential to cause such a reflux phenomenon in the context of the present invention.

  The ECU 100 is configured to be able to diagnose a failure of the switching control valve 370 by executing a failure diagnosis process according to a program stored in the ROM during the operation of the exhaust gas purification system 10.

  In ECU 100, fuel cut control is executed separately from control of flow path control valve 370 for the purpose of reducing fuel consumption and improving emissions. This fuel cut control is a control for individually cutting the fuel supply to each cylinder. Specifically, for example, the throttle opening and the engine speed input from sensors 215, 218, 220 and a vehicle speed sensor (not shown), for example. By referring to a predetermined fuel cut area map according to the engine water temperature and the vehicle speed, it is determined that the execution condition of the fuel cut control is satisfied when the running state is in the fuel cut area (for example, at the time of deceleration or high rotation). Then, the fuel supply to a predetermined cylinder is cut. By the fuel cut control, the fuel supply is cut for all cylinders or a part of the cylinders.

  Next, an example of the operation state detection process executed by the ECU 100 will be described with reference to FIG. The routine of FIG. 5 is repeatedly executed every predetermined time after the engine 200 is started and when a predetermined warm-up end condition is satisfied. For example, it is possible to set such a warm-up end condition that the engine water temperature is equal to or higher than a predetermined value. Note that the present invention can also be applied to a case where the warm-up has not ended.

  In FIG. 5, the ECU 100 determines whether or not the fuel cut operation due to all cylinder deactivation is started (S10). This determination may be made according to whether or not the execution condition for all cylinder deactivation by the fuel cut control described above is satisfied, or a predetermined flag is set during execution of all cylinder deactivation and the flag is set every predetermined time. This may be done by referring to

  Next, ECU 100 obtains temperature T1 and temperature T2 from the output voltages of first temperature sensor 380 and second temperature sensor 390, respectively, and sets them as initial values Ta1 and Ta2 (S20).

  Next, the ECU 100 repeatedly determines whether the fuel cut operation continues (S30) and whether a predetermined time x [seconds] after the start of the fuel cut operation has elapsed (S40). If the fuel cut operation is terminated, the routine is exited.

  The ECU 100 acquires current values Tb1 and Tb2 of the first and second temperature sensors 380 and 390 (S50) and calculates temperature drop amounts Tc1 and Tc2 (S60) on the condition that the predetermined time has elapsed. The temperature drop amounts Tc1 and Tc2 are calculated by subtracting the initial values Ta1 and Ta2 from the current temperature values Tb1 and Tb2 for the first and second temperature sensors 380 and 390, respectively.

  Next, the ECU 100 determines whether a predetermined valve closing condition is satisfied (S70). This determination is made according to the following conditions (1) to (3).

(1) Absolute value of temperature drop amount of first temperature sensor | Tc1 | <reference value Td1

(2) Absolute value | Tc2 |> reference value Td2 of the temperature drop amount of the second temperature sensor

(3) | Tc1 | <| Tc2 |

  The valve closing condition referred to here is a condition for determining that the switching control valve 370 is closed. In step S70, when all of these (1) to (3) are positive, the valve is closed. If it is determined that the condition is satisfied and the result is negative in any of (1) to (3), it is determined that the condition is not satisfied.

  As shown in FIG. 6, the detected value of the first temperature sensor 380 has a larger temperature drop during the fuel cut operation when the switching control valve 370 is open than when it is closed. Further, as shown in FIG. 7, the detected value of the second temperature sensor 390 shows a smaller temperature drop during the fuel cut operation when the switching control valve 370 is open than when it is closed. . Further, as shown in FIG. 8, the deviation | Tc1 | − | Tc2 | of the temperature decrease amount is larger when the switching control valve 370 is open than when it is closed, and When the switching control valve 370 is open, it takes a positive value (ie, | Tc1 |> | Tc2 |), and when it is closed, it takes a negative value (ie, | Tc1 | <| Tc2 | ).

  In the present embodiment, | Tc1 | <| Tc2 |, that is, | Tc1 | − | Tc2 | <0 is one of the valve closing conditions, but | Tc1 | − | Tc2 | <Td is It is good also as conditions which replace the said conditions (3). In this case, Td is a threshold value and can be set to an arbitrary real number through experiments or simulations.

  If the valve closing condition is satisfied, the predetermined valve closing determination flag is set to “1” (S80). If the valve closing condition is not satisfied, the predetermined valve opening determination flag is set to “1”. (S90), this routine is exited. The valve closing determination flag and the valve opening determination flag are thereafter referred to in the valve diagnosis process of FIG.

  Next, an example of the valve diagnosis process executed by the ECU 100 will be described with reference to FIG. The routine of FIG. 9 is repeatedly executed every predetermined time after the engine 200 is started and when a predetermined warm-up termination condition is satisfied.

  First, the ECU 100 determines whether valve operation is detected by referring to the valve closing determination flag and the valve opening determination flag described above (S110). Here, affirmation is made when either of the flags is set. Next, the ECU 100 acquires the state of the operation instruction for the switching control valve 370 (S120).

  Next, ECU 100 determines whether or not the detected valve operation state matches the acquired operation instruction state (S130). That is, the ECU 100 determines whether or not the detected valve operation state and the acquired operation instruction state coincide with each other by “open” or “closed”. If the two match, a normal determination is made (S140), and if not, an abnormal determination is made (S150). The normality determination and abnormality determination may be executed by setting a flag referred to in another processing routine, or predetermined processing performed according to these results, for example, recording in a predetermined traveling log file, abnormality determination In this case, the alarm may be output to the user by a predetermined indicator or the like.

  As described above, in the present embodiment, the operation state of the switching control valve 370 is detected based on the temperatures of the first and second exhaust gas passages 360 and 350, and the detected operation state and the exhaust gas flow path are detected. The failure of the switching control valve 370 is diagnosed based on the instruction state to the switching means. Here, since the ECU 100 detects the operating state of the switching control valve 370 based on the amount of change in temperature detected during the fuel cut operation of the engine, the ECU 100 is compared with the case based on the temperature of the exhaust gas during normal operation. Therefore, the influence of the operating state of the engine is small, so that the detection of the operating state can be performed with high accuracy, and the failure of the exhaust gas flow path switching means can be diagnosed with high accuracy.

  In the present embodiment, when the operating state is detected, the temperature reduction rate from the start of detection, that is, the amount of temperature reduction after the elapse of a predetermined time is used during the fuel cut operation, and this is larger than a predetermined threshold value. In addition, since it is determined that the exhaust gas passage including the temperature detection point is selected by the switching control valve 370, the desired effect of the present invention can be obtained with a simple configuration.

  Further, in the present embodiment, the temperature of both the first and second exhaust gas passages 360 and 350 is detected, and switching is performed based on the difference in the temperature decrease rates of the first and second exhaust gas passages 360 and 350. Since it is determined which exhaust gas passage is selected by the control valve 370, it is possible to improve the accuracy of detection of the operating state by suppressing the influence of the operating state (for example, the temperature at the start of temperature detection), and to further improve the accuracy of the failure. Diagnosis is possible.

  It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and is accompanied by such changes. A system failure diagnosis apparatus is also included in the branching scope of the present invention. For example, in the above embodiment, the operation of the switching control valve 370 is set to the two states of fully closed or fully opened, but the switching control valve 370 may be stopped at any angle between the fully closed and fully opened, The operation state detection and the failure diagnosis based on the temperature decrease rate according to the present invention can be performed at any angle between the fully closed state and the fully opened state. That is, a map or function that defines the relationship between the temperature decrease amount or the temperature decrease rate during the fuel cut and the angle of the switching control valve 370 is held in the ECU 100 in advance, and the temperature decrease rate detected during the fuel cut operation is determined. The operation state is detected by referring to the map or calculating the function to obtain the corresponding angle of the switching control valve 370, and the detected angle and the angle command value for the switching control valve 370 match within a predetermined range. In this case, the switching control valve 370 may be determined to be normal.

  In the above embodiment, the temperatures of both the first and second exhaust gas passages 360 and 350 are detected. In the present invention, either one of the first and second exhaust gas passages 360 and 350 is detected. As long as the temperature of the exhaust gas is detected, the operation state can be detected based on the temperature drop rate during the fuel cut in the exhaust gas passage including the temperature detection point, and the intended effect can be obtained in the present invention within that range. it can.

  In the above embodiment, the operation state is detected using the temperature detected after the elapse of a specific time from the start of the fuel cut operation. Instead of such a configuration, the temperature is changed during the fuel cut operation. The operation state may be detected by repeatedly detecting and comparing the degree of temperature decrease or inclination with a predetermined reference value.

  In the above embodiment, it is determined that the valve closing condition is satisfied when all of the above conditions (1) to (3) are satisfied. However, any of the above conditions (1) to (3) is the valve closing condition alone. The effect in this invention can be acquired in the range.

  The present invention can be applied not only to a vehicle that uses only an internal combustion engine as a drive source, but also to a hybrid vehicle that uses an internal combustion engine and an electric motor as drive sources, and such a configuration also belongs to the category of the present invention.

1 is a system configuration diagram of an exhaust gas purification system according to an embodiment of the present invention. It is a schematic cross section of the main exhaust gas purification apparatus in the exhaust gas purification system of FIG. FIG. 3 is a schematic diagram of an exhaust gas flow when a switching control valve is closed in the main exhaust gas purification device of FIG. 2. FIG. 3 is a schematic diagram of an exhaust gas flow when a switching control valve is open in the main exhaust gas purification device of FIG. 2. It is a flowchart which shows an example of the control routine of an operation state detection process. It is a graph which shows the relationship between the continuous time of a fuel cut driving | operation, and the temperature change of the 1st temperature sensor at the time of valve opening and valve closing. It is a graph which shows the relationship between the continuation time of a fuel cut driving | operation, and the temperature change of the 2nd temperature sensor at the time of valve opening and valve closing. It is a graph which shows the relationship between the continuation time of a fuel cut driving | operation, and the deviation of the temperature fall amount at the time of valve opening and valve closing. It is a flowchart which shows an example of the control routine of a failure diagnosis process.

Explanation of symbols

100 Electronic control unit (ECU)
200 Engine 212 Air Flow Meter 222 Start-up Three-way Catalyst 300 Main Exhaust Gas Purifier 330 Underfloor Catalyst 340 HC Adsorbent 350 Bypass Channel (Second Exhaust Gas Path)
360 Bypassed passage (first exhaust gas passage, normal passage)
370 Switching control valve 376 Actuator 380 First temperature sensor 390 Second temperature sensor

Claims (3)

A first exhaust gas passage through which exhaust gas from the engine flows, a second exhaust gas passage formed by bypassing the first exhaust gas passage and provided with an HC adsorbent, the first and second In an exhaust gas purification system comprising exhaust gas flow path switching means for switching the flow path to any of the exhaust gas passages of
Temperature detecting means for detecting the temperature of at least one of the first and second exhaust gas passages;
An operating state detecting means for detecting an operating state of the exhaust gas flow path switching means based on the temperature detected by the temperature detecting means;
Diagnostic means for diagnosing a failure of the exhaust gas flow path switching means based on the detected operating state and an instruction state to the exhaust gas flow path switching means,
The failure diagnosis device for an exhaust gas purification system, wherein the operation state detection means detects an operation state of the exhaust gas flow path switching means based on the temperature detected during a fuel cut operation of the engine. . A failure diagnosis device for an exhaust gas purification system according to claim 1,
The operating state detecting means is configured to detect the exhaust gas when a temperature decrease rate during fuel cut of the engine in one exhaust gas passage of the first and second exhaust gas passages is equal to or higher than a predetermined threshold value. A failure diagnosis device for an exhaust gas purification system, characterized in that it is determined that the one exhaust gas passage is selected by a flow path switching means. A failure diagnosis device for an exhaust gas purification system according to claim 1 or 2,
The temperature detecting means detects the temperature of both the first and second exhaust gas passages;
The operating state detecting means determines which exhaust gas passage is selected by the exhaust gas flow path switching means based on a difference in temperature drop rate between the first and second exhaust gas passages. A failure diagnosis device for a featured exhaust gas purification system.

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