JP2011196199A - Degradation diagnosis system of hc adsorption material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a degradation diagnosis system of an HC adsorption material with only one air-fuel ratio detection sensor, the system being able to detect a degradation state of the HC adsorption material.SOLUTION: The degradation diagnosis system of the HC adsorption material (100) includes: the HC adsorption material (40) that adsorbs HC of exhaust and emits the adsorbed HC when a temperature rises to a range of an HC emission temperature; the air-fuel ratio detection sensor (84); exhaust flowing mode switching means (60, 74 and 90) that performs switch between a normal mode where exhaust passes through the HC adsorption material and a bypass mode where the exhaust bypasses the HC adsorption material and flow more downwardly than the HC adsorption material of an exhaust passage; and a degradation detection means (90) that detects the degradation state of the HC adsorption material after the HC is started to be emitted from the HC adsorption material by using sub-feedback correction amount in the normal mode and the sub-feedback correction amount in the bypass mode.

Description

  The present invention relates to an HC adsorbent deterioration diagnosis system.

  Conventionally, an internal combustion engine system in which a three-way catalyst for purifying exhaust gas of an internal combustion engine is arranged in an exhaust passage is known. The three-way catalyst has a property that it is not activated until its exhaust gas purification function can be fully exerted unless its temperature becomes a predetermined temperature or higher. Therefore, the HC adsorbent that adsorbs HC (hydrocarbon) in the exhaust gas and releases the HC adsorbed so far when the temperature is raised to the HC release temperature range or more is placed in the exhaust passage upstream of the three-way catalyst. Arranged internal combustion engine systems have been proposed.

  In the exhaust purification system as described above, when the adsorption performance of the HC adsorbent deteriorates, for example, when the activity of the exhaust purification catalyst is insufficient, HC that was not adsorbed by the HC adsorbent is purified by the exhaust purification catalyst. Otherwise, there is a risk of exhaust from the internal combustion engine system. Therefore, in Patent Document 1, the deterioration of the HC adsorbent is based on the detection results of the upstream air-fuel ratio sensor arranged in the exhaust passage upstream of the HC adsorbent and the downstream air-fuel ratio sensor arranged in the downstream exhaust passage. An HC adsorbent deterioration diagnosis system for detecting a state is disclosed.

JP 2001-241319 A

  However, the technique according to Patent Document 1 requires two air-fuel ratio detection sensors. In this case, the manufacturing cost may increase.

  An object of the present invention is to provide an HC adsorbent deterioration diagnosis system that includes only one air-fuel ratio detection sensor and can detect the deterioration state of the HC adsorbent.

  The degradation diagnosis system for an HC adsorbent according to the present invention is arranged in an exhaust passage, adsorbs HC of exhaust gas, and releases the HC adsorbed so far when the temperature is raised to an HC release temperature region. An adsorbent, an air-fuel ratio detection sensor disposed downstream of the HC adsorbent in the exhaust passage, a normal mode in which the exhaust gas passes through the HC adsorbent, and the exhaust gas bypasses the HC adsorbent. And an exhaust gas flow mode switching means for switching between a bypass mode that flows downstream from the HC adsorbent in the exhaust passage, and in the case of the normal mode after the release of the HC from the HC adsorbent is started. A sub-feedback correction amount for controlling the output value of the air-fuel ratio detection sensor to a target value; and the sub-feedback correction amount in the bypass mode; With, a, and deterioration detecting means for detecting a deteriorated state of the HC adsorbent.

  The sub feedback correction amount in the normal mode and the sub feedback correction amount in the bypass mode have a correlation with the deterioration state of the HC adsorbent. Therefore, according to the HC adsorbent deterioration diagnosis system according to the present invention, it is possible to detect the deterioration state of the HC adsorbent by providing only one air-fuel ratio detection sensor.

  In the above configuration, the deterioration detection means uses the sub feedback correction amount in the normal mode and the average value of the sub feedback correction amounts in the bypass mode to determine the deterioration state of the HC adsorbent. May be detected.

  In the above configuration, the average value of the sub feedback correction amount in the bypass mode may be a value obtained by performing at least integral correction. In the above configuration, the deterioration detection means further uses the output value of the air-fuel ratio detection sensor in the normal mode and the output value of the air-fuel ratio detection sensor in the bypass mode, The deterioration state of the HC adsorbent may be detected.

  In the above configuration, the exhaust gas flow mode switching means may further switch between the normal mode and the bypass mode based on the activity level of an exhaust purification catalyst disposed downstream of the HC adsorbent in the exhaust passage. Good. In the above configuration, the air-fuel ratio detection sensor may be an oxygen sensor including a catalyst that promotes HC oxidation.

  According to the present invention, it is possible to provide a deterioration diagnosis system for an HC adsorbent that includes only one air-fuel ratio detection sensor and can detect the deterioration state of the HC adsorbent.

FIG. 1 is a schematic diagram illustrating a configuration of an internal combustion engine system in which a deterioration diagnosis system according to a first embodiment is incorporated. FIG. 2A and FIG. 2B are diagrams for specifically explaining the sub-feedback correction process. FIG. 3 is a diagram showing an example of a flowchart of ECU deterioration state detection processing. FIG. 4 is a schematic diagram illustrating an output of the oxygen sensor in the deterioration state detection process performed after the ECU according to the second embodiment stops the execution of the sub-feedback correction process. FIG. 5 is a diagram illustrating an example of a flowchart of a deterioration state detection process performed after the ECU according to the second embodiment stops the execution of the sub-feedback correction process.

  Hereinafter, modes for carrying out the present invention will be described.

  A deterioration diagnosis system 100 according to Embodiment 1 of the present invention will be described. FIG. 1 is a schematic diagram showing a configuration of an internal combustion engine system 200 in which a deterioration diagnosis system 100 is incorporated. The internal combustion engine system 200 includes an internal combustion engine 10, a fuel injection valve 20, a throttle 30, an HC adsorbent 40, an exhaust purification catalyst 50, a passage switching valve 60, various passages (an intake passage 70, an exhaust passage 72, and a bypass passage 74), various types. Sensors (air flow meter 80, throttle position sensor 81, accelerator position sensor 82, crank position sensor 83, oxygen sensor 84 and temperature sensor 85) and ECU 90 are provided. The deterioration diagnosis system 100 includes an HC adsorbent 40, an oxygen sensor 84, a passage switching valve 60, a bypass passage 74, and an ECU 90.

  The internal combustion engine 10 includes a cylinder 12, a piston 14 disposed in the cylinder 12, and a connecting rod 16 for connecting the piston 14 and the crankshaft. A crank position sensor 83 is disposed in the vicinity of the crankshaft. The output of the crank position sensor 83 is transmitted to the ECU 90. The ECU 90 calculates the crank angle and the rotation speed of the internal combustion engine 10 based on the output of the crank position sensor 83.

  An intake passage 70 is connected to the intake port of the internal combustion engine 10. The fuel injection valve 20 is disposed in the intake passage 70. The fuel injection valve 20 is controlled by the ECU 90 to inject fuel. A throttle 30 is disposed upstream of the fuel injection valve 20 in the intake passage 70. A throttle position sensor 81 is disposed in the vicinity of the throttle 30. The output of the throttle position sensor 81 is transmitted to the ECU 90. The ECU 90 is informed of the output of the accelerator position sensor 82 for detecting the opening of the accelerator 300. The ECU 90 receives the output of the throttle position sensor 81 and the output of the accelerator position sensor 82, and controls the throttle 30 according to the accelerator operation amount.

  An exhaust passage 72 is connected to the exhaust port of the internal combustion engine 10. In the exhaust passage 72, the HC adsorbent 40 is disposed. The HC adsorbent 40 adsorbs HC (hydrocarbon) of exhaust gas when the temperature is lower than the HC release temperature region, and releases HC adsorbed so far when the temperature is raised to the HC release temperature region. It is a material. If it is such an adsorbent, the HC adsorbent 40 is not particularly limited. As the HC adsorbent 40, for example, a material having an HC adsorbing component such as zeolite can be used.

An exhaust purification catalyst 50 is disposed downstream of the HC adsorbent 40 in the exhaust passage 72. The exhaust purification catalyst 50 is not particularly limited, but in the present embodiment, as an example, a three-way catalyst for promoting a chemical reaction of HC, carbon monoxide (CO), and nitrogen oxide (NO _x ) is used. Although it does not specifically limit as a three-way catalyst, For example, platinum, rhodium, palladium etc. can be used.

  A bypass passage 74 communicates upstream and downstream of the HC adsorbent 40 in the exhaust passage 72. The bypass passage 74 is a passage for allowing the exhaust gas in the exhaust passage to flow downstream from the HC adsorbent 40 in the exhaust passage 72 by bypassing the HC adsorbent 40. A passage switching valve 60 is disposed at a connection portion between the upstream end of the bypass passage 74 and the exhaust passage 72. The passage switching valve 60 is controlled by the ECU 90 to switch the destination of the exhaust gas.

  Specifically, when the passage switching valve 60 is controlled so that the bypass passage 74 is closed, the exhaust gas passes through the HC adsorbent 40 and the exhaust purification catalyst 50 in this order (hereinafter referred to as exhaust gas in this way). The mode in which the fluid flows so as to pass through the HC adsorbent 40 is referred to as “normal mode”). When the passage switching valve 60 is controlled such that the upstream portion of the HC adsorbent 40 in the exhaust passage 72 is closed, the exhaust gas passes through the exhaust purification catalyst 50 after passing through the bypass passage 74 (hereinafter, referred to as “the exhaust gas purification catalyst 50”). A mode in which the exhaust gas flows in such a manner as to bypass the HC adsorbent 40 is referred to as a “bypass mode”. That is, in this embodiment, the bypass passage 74, the passage switching valve 60, and the ECU 90 have a function as exhaust gas flow mode switching means for switching between the normal mode and the bypass mode.

  When the normal mode is entered when the HC adsorbent 40 is heated to the HC release temperature region, the HC adsorbent 40 releases the HC adsorbed so far. On the other hand, since the exhaust gas does not flow into the HC adsorbent 40 even when the HC adsorbent 40 is heated to the HC release temperature region when the bypass mode is set, the HC from the HC adsorbent 40 Release is suppressed.

  An oxygen sensor 84 is disposed downstream of the HC adsorbent 40 in the exhaust passage 72. The location of the oxygen sensor 84 is not particularly limited as long as it is downstream of the HC adsorbent 40 in the exhaust passage 72 and upstream of the exhaust purification catalyst 50. In the present embodiment, the oxygen sensor 84 is disposed downstream of the HC adsorbent 40 in the exhaust passage 72 and upstream of the connection point of the bypass passage 74 of the exhaust passage 72. The oxygen sensor 84 has a property of outputting a voltage corresponding to rich / lean of the air-fuel ratio of the exhaust gas. The output of the oxygen sensor 84 is transmitted to the ECU 90. The ECU 90 acquires the air-fuel ratio of the exhaust gas based on the output of the oxygen sensor 84. That is, in this embodiment, the oxygen sensor 84 has a function as an air-fuel ratio detection sensor for detecting the air-fuel ratio of the exhaust gas.

  The type of the oxygen sensor 84 is not particularly limited. As the oxygen sensor 84, various oxygen sensors such as a zirconia type and a titania type can be used. In the present embodiment, the oxygen sensor 84 includes a catalyst for promoting the oxidation of HC. That is, in this embodiment, a catalyst-attached oxygen sensor is used as the oxygen sensor 84.

  The exhaust purification catalyst 50 is provided with a temperature sensor 85 for detecting the catalyst bed temperature of the exhaust purification catalyst 50. The output of the temperature sensor 85 is transmitted to the ECU 90. The catalyst bed temperature of the exhaust purification catalyst 50 has a correlation with the degree of catalyst activity of the exhaust purification catalyst 50. In the present embodiment, the ECU 90 acquires the degree of catalyst activity of the exhaust purification catalyst 50 based on the output of the temperature sensor 85.

  The ECU 90 is a microcomputer having a CPU 92 as a calculation unit and a ROM 94 and a RAM 96 as storage units. The ECU 90 controls controlled parts such as the throttle 30, the fuel injection valve 20, and the passage switching valve 60 by the CPU 92 operating while using the RAM 96 as a temporary storage memory based on a program stored in the ROM 94. Further, in the present embodiment, the ECU 90 operates based on the program stored in the ROM 94 while the CPU 92 operates while using the RAM 96 as a temporary storage memory, whereby feedback correction processing, sub-feedback correction processing, and deterioration described below are performed. Perform state detection processing.

  The feedback correction process will be described. First, the ECU 90 stores a target air-fuel ratio that is a target value of the air-fuel ratio of the exhaust gas. In this embodiment, the stoichiometric air-fuel ratio is used as the target air-fuel ratio. Based on the output of the oxygen sensor 84, the ECU 90 controls the fuel injection amount from the fuel injection valve 20 so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio. In the feedback correction process, a fuel injection amount correction amount (hereinafter referred to as a feedback correction amount) for controlling the air-fuel ratio of the exhaust gas to the target air-fuel ratio is calculated, and fuel injection is performed based on the calculated feedback correction amount. This is a process of correcting the amount. The ECU 90 calculates a feedback correction amount based on the output of the oxygen sensor 84.

  The specific calculation procedure of the feedback correction amount by the ECU 90 is not particularly limited. As an example, the ECU 90 according to the present embodiment calculates the feedback correction amount by performing proportional correction and integral correction based on the output of the oxygen sensor 84. Specifically, when it is detected that the output of the oxygen sensor 84 has become a voltage corresponding to rich or lean, the ECU 90 increases or decreases a correction coefficient for calculating a feedback correction amount by a predetermined amount at a time (that is, Proportional correction for skipping). Thereafter, the ECU 90 performs integral correction for gradually increasing or decreasing the correction coefficient. The procedure for calculating the feedback correction amount by performing the proportional correction and the integral correction is the feedback correction amount used in a known internal combustion engine system that controls the air-fuel ratio using the oxygen sensor of the technique according to Patent Document 1. Since this calculation procedure can be applied, further detailed description is omitted.

  Next, the sub feedback correction process will be described. First, the ECU 90 stores a target value for the output value of the oxygen sensor 84. In this embodiment, the ECU 90 stores a voltage value corresponding to the theoretical air-fuel ratio of the oxygen sensor 84 in the bypass mode (that is, when HC release from the HC adsorbent 40 is suppressed) as a target value. ing. The sub-feedback correction process calculates a target air-fuel ratio correction amount (hereinafter referred to as a sub-feedback correction amount) for controlling the output value of the oxygen sensor 84 to a target value, and based on the calculated sub-feedback correction amount. This is a process for correcting the target air-fuel ratio.

FIG. 2A and FIG. 2B are diagrams for specifically explaining the sub-feedback correction process. In FIG. 2A, the vertical axis indicates the output (output voltage value) of the oxygen sensor 84, and the horizontal axis indicates time. In FIG. 2B, the vertical axis represents the sub feedback correction amount (sub FB correction amount), and the horizontal axis represents time. Time t _1, in a state in which the HC adsorbent 40 by being heated by the heat or the like of the exhaust gas is raised to HC release temperature region, shows a case that has been switched to the normal mode from the bypass mode. That is, time t ₁ is the time when the HC adsorbent 40 starts to release HC, and also the time when the oxygen sensor 84 starts detecting HC release from the HC adsorbent 40.

  As shown in FIG. 2A, before the HC adsorbent 40 starts to release HC, the output of the oxygen sensor 84 matches the target value. Here, after the start of HC release, the air-fuel ratio of the exhaust passage 72 downstream from the HC adsorbent 40 becomes rich by the amount of HC released from the HC adsorbent 40 (that is, reacts with the released HC). Will be lacking oxygen). Therefore, when HC release is started, the output of the oxygen sensor 84 becomes a voltage corresponding to rich. In order to control the output value of the oxygen sensor 84 to a target value, a sub feedback correction process is performed.

  Specifically, in the sub-feedback correction process, the ECU 90 calculates a sub-feedback correction amount of the target air-fuel ratio for controlling the output value of the oxygen sensor 84 accompanying HC release to the target value. For example, as shown in FIG. 2A, when the output of the oxygen sensor 84 becomes a voltage corresponding to rich as the HC is released, the ECU 90 causes the oxygen sensor 84 to turn off as shown in FIG. A sub-feedback correction amount of the target air-fuel ratio for setting the output to a voltage corresponding to lean is calculated.

  Based on the sub feedback correction amount, the ECU 90 corrects the target air-fuel ratio so that the output value of the oxygen sensor 84 becomes a voltage corresponding to lean. As a result, in the feedback correction process, the fuel injection amount is corrected based on the corrected target air-fuel ratio, so that the output of the oxygen sensor 84 becomes a voltage corresponding to lean as shown in FIG. Become. As a result, the output of the oxygen sensor 84 converges to the target value.

  The specific calculation procedure of the sub feedback correction amount by the ECU 90 is not particularly limited, but the ECU 90 according to the present embodiment, for example, performs sub-proportional correction and integral correction based on the output of the oxygen sensor 84. Calculate the feedback correction amount. Specifically, when detecting that the output of the oxygen sensor 84 has become a voltage corresponding to rich or a voltage corresponding to lean, the ECU 90 sets a correction coefficient for calculating the sub feedback correction amount at a predetermined amount at a time. Proportional correction for increasing / decreasing (ie skipping) is performed. Thereafter, the ECU 90 performs integral correction for gradually increasing or decreasing the correction coefficient. The calculation procedure of the sub feedback correction amount by performing the proportional correction and the integral correction is the sub feedback used in the known internal combustion engine system that controls the air-fuel ratio using the technique according to Patent Document 1 and other oxygen sensors. Since a correction amount calculation procedure can be applied, further detailed description is omitted.

  Subsequently, the deterioration state detection process will be described. In the deterioration state detection process, first, the ECU 90 determines whether or not the operating state of the internal combustion engine 10 is a state suitable for detection of the deterioration state. Specifically, the ECU 90 operates the internal combustion engine 10 in at least one of the case where the rotational speed of the internal combustion engine 10 is within a predetermined range and the case where the load of the internal combustion engine 10 is within the predetermined range. It is determined that the state is a state suitable for the deterioration state detection. The ECU 90 acquires the load of the internal combustion engine 10 based on, for example, the accelerator opening, the fuel injection amount, and the like.

  Further, the ECU 90 determines whether or not the temperature of the HC adsorbent 40 is equal to or higher than the HC release temperature. The temperature detection method of the HC adsorbent 40 of the ECU 90 is not particularly limited. For example, the ECU 90 can detect the temperature of the HC adsorbent 40 by estimating the temperature of the HC adsorbent 40 based on an index having a correlation with the temperature of the HC adsorbent 40. As such an index, for example, an integrated value of the intake air amount of the internal combustion engine 10, a load of the internal combustion engine 10, or the like can be used. Alternatively, the internal combustion engine system 200 may include a temperature sensor for detecting the temperature of the HC adsorbent 40, and the ECU 90 may detect the temperature of the HC adsorbent 40 using the detection result of the temperature sensor.

  Further, the ECU 90 determines whether or not the oxygen sensor 84 is activated to the extent that the oxygen sensor 84 can sufficiently perform its function. For example, the ECU 90 determines whether the oxygen sensor 84 is activated based on the detection result of the temperature sensor 85, the load of the internal combustion engine 10, and the like.

  When it is determined that the operating state of the internal combustion engine 10 is suitable for detecting the deterioration state, the temperature of the HC adsorbent 40 is equal to or higher than the HC release temperature, and the oxygen sensor 84 is activated, the ECU 90 The passage switching valve 60 is controlled so as to be in the mode. Then, the ECU 90 acquires an average value of the sub feedback correction amounts in the bypass mode. Specifically, the ECU 90 acquires an average value of the sub feedback correction amount from when the mode is switched to the bypass mode until a predetermined period elapses. The acquired average value is stored in the RAM 96, for example.

  Next, the ECU 90 controls the passage switching valve 60 so as to enter the normal mode. Then, the ECU 90 acquires the sub feedback correction amount in the normal mode.

  Next, the ECU 90 detects the deterioration state of the HC adsorbent 40 by comparing the sub feedback correction amount in the normal mode with the average value of the sub feedback correction amounts in the bypass mode. For example, when there is no difference between the sub feedback correction amount in the normal mode and the average value of the sub feedback correction amount in the bypass mode, it means that the HC is not released from the HC adsorbent 40. This means that the HC adsorbent 40 did not adsorb HC. That is, in this case, it can be seen that the HC adsorbent 40 has deteriorated and has lost its HC adsorbability.

  On the other hand, if there is a difference between the average value of the sub feedback correction amount in the normal mode and the sub feedback correction amount in the bypass mode, it is understood that the HC adsorbent 40 has released HC after switching to the normal mode. The That is, in this case, it can be seen that the HC adsorbent 40 has not lost its HC adsorptivity.

  Further, the degree of deterioration of the HC adsorbent 40 can be determined based on the magnitude of the difference between the sub feedback correction amount in the normal mode and the average value of the sub feedback correction amounts in the bypass mode. For example, as the difference between the sub feedback correction amount in the normal mode and the average value of the sub feedback correction amounts in the bypass mode is smaller, the degree of deterioration of the HC adsorbent 40 is higher (that is, the deterioration is more advanced). )

  FIG. 3 is a diagram illustrating an example of a flowchart of the deterioration state detection process of the ECU 90. The ECU 90 repeatedly executes the flowchart of FIG. 3 at a predetermined cycle. First, the ECU 90 determines whether or not the operating state of the internal combustion engine 10 is a state suitable for detecting the deterioration state (step S10). The ECU 90 repeatedly executes step S10 until it is determined that the operating state of the internal combustion engine 10 is suitable for detecting the deterioration state.

  When it is determined in step S10 that the operating state of the internal combustion engine 10 is suitable for detecting the deterioration state, the ECU 90 determines whether or not the temperature of the HC adsorbent 40 is equal to or higher than the HC release temperature (step S20). The ECU 90 repeatedly executes step S20 until it is determined that the temperature of the HC adsorbent 40 is equal to or higher than the HC release temperature.

  When it is determined in step S20 that the temperature of the HC adsorbent 40 is equal to or higher than the HC release temperature, the ECU 90 determines whether or not the oxygen sensor 84 is sufficiently activated to perform its function (step S30). ). The ECU 90 repeatedly executes step S30 until it is determined that the oxygen sensor 84 is sufficiently activated to exhibit its function.

  If it is determined in step S30 that the oxygen sensor 84 is sufficiently activated to exhibit its function, the ECU 90 acquires an average value (A) of the feedback correction amount in the bypass mode (step S40). . Specifically, the ECU 90 controls the passage switching valve 60 so as to switch to the bypass mode, and then acquires an average value (A) of the feedback correction amount from when the mode is switched to the bypass mode until a predetermined period elapses.

  Next, the ECU 90 acquires the feedback correction amount (B) in the normal mode (step S50). Specifically, the ECU 90 acquires the feedback correction amount after controlling the passage switching valve 60 to switch to the normal mode.

  Next, the ECU 90 detects a deterioration state by comparing the average value (A) of the feedback correction amount acquired in step S40 with the feedback correction amount (B) acquired in step S50 (step S60). Next, the ECU 90 ends the execution of the flowchart.

  As described above, according to the deterioration diagnosis system 100 according to the present embodiment, after the release of HC from the HC adsorbent 40 is started, the feedback correction amount in the normal mode and the feedback correction amount in the bypass mode. And the deterioration state of the HC adsorbent 40 is detected. Thereby, the deterioration state of the HC adsorbent 40 can be detected only by providing the air-fuel ratio detection sensor (oxygen sensor 84) disposed downstream of the HC adsorbent 40 in the exhaust passage 72. Therefore, the manufacturing cost of the deterioration diagnosis system 100 can be reduced as compared with the case where the deterioration state of the HC adsorbent 40 is detected using two or more air-fuel ratio detection sensors.

  Further, as the oxygen sensor 84, an oxygen sensor provided with a catalyst for promoting HC oxidation is used. In this case, the reaction of HC and oxygen is promoted by the catalyst of the oxygen sensor 84. This makes it easier to detect changes in the air-fuel ratio. However, even when an oxygen sensor without a catalyst is used as the oxygen sensor 84, it is possible to detect the deterioration of the HC adsorbent 40.

  The average value of the sub feedback correction amount is a value obtained by performing at least integral correction. In this case, the detection accuracy of the deterioration state of the HC adsorbent 40 is improved as compared with the case where the average value of the sub feedback correction amount is obtained by performing only the proportional correction without performing the integral correction, for example. Can do.

  In order to detect the deterioration of the HC adsorbent 40, it is necessary to release the HC from the HC adsorbent 40 for a predetermined time. Therefore, the ECU 90 may switch between the normal mode and the bypass mode based on the degree of activity of the exhaust purification catalyst 50. Specifically, the ECU 90 sets the normal mode so that the HC release time by the HC adsorbent 40 becomes an appropriate time based on the activity level of the exhaust purification catalyst 50 acquired based on the output of the temperature sensor 85, for example. You may switch to bypass mode. In this case, for example, when the degree of activity of the exhaust purification catalyst 50 is low, the release time of the HC adsorbent 40 is shortened as much as possible while securing the time required for detecting the deterioration of the HC adsorbent 40, thereby making the HC adsorbent 40 It is possible to prevent HC released from 40 from being exhausted without being purified by the exhaust purification catalyst 50. Further, the ECU 90 may switch from the bypass mode to the normal mode when the activation degree of the exhaust purification catalyst 50 is activated to such an extent that the HC emission amount necessary for detecting the deterioration state can be purified. In this case, it is possible to suppress exhaust of the HC released from the HC adsorbent 40 without being purified by the exhaust purification catalyst 50.

  The ECU 90 of the deterioration diagnosis system 100 according to the present embodiment is different from the ECU 90 according to the first embodiment in that the execution of the sub feedback correction process is stopped when a predetermined sub feedback correction process stop condition is satisfied. Further, the ECU 90 according to the present embodiment executes the deterioration state detection process according to the first embodiment when the sub feedback correction process is executed, and the normal mode when the execution of the sub feedback correction process is stopped. The ECU 90 according to the first embodiment is different from the ECU 90 according to the first embodiment in that the deterioration value of the HC adsorbent 40 is detected using the output value of the oxygen sensor 84 in this case and the output value of the oxygen sensor 84 in the bypass mode. The sub feedback correction process stop condition is not particularly limited.

FIG. 4 is a schematic diagram illustrating an output of the oxygen sensor 84 in the deterioration state detection process performed after the ECU 90 according to the second embodiment stops the execution of the sub-feedback correction process. In FIG. 4, the vertical axis indicates the output (output voltage value) of the oxygen sensor 84, and the horizontal axis indicates time. Time t _1, in a state in which the HC adsorbent 40 by being heated by the heat or the like of the exhaust gas is raised to HC release temperature region, shows a case that has been switched to the normal mode from the bypass mode. That is, time t ₁ is the time when the HC adsorbent 40 starts to release HC, and also the time when the oxygen sensor 84 starts detecting HC release from the HC adsorbent 40.

  Before the start of HC release, the output of the oxygen sensor 84 matches the target value (in this embodiment, the voltage corresponding to the theoretical air-fuel ratio). However, when the HC adsorbent 40 starts releasing HC, the output of the oxygen sensor 84 becomes a voltage corresponding to rich. Unlike the case of the first embodiment, since the sub-feedback correction process is stopped, as long as the HC release from the HC adsorbent 40 continues, the state in which the output of the oxygen sensor 84 is a voltage corresponding to the rich state is as follows. Continue.

  The ECU 90 according to the present embodiment detects the deterioration state of the HC adsorbent 40 by paying attention to the change in the output of the oxygen sensor 84 when HC is released as shown in FIG. Specifically, the ECU 90 calculates and stores an average value of output values of the oxygen sensor 84 in the bypass mode. Specifically, the average value of the output value of the oxygen sensor 84 from the switching to the bypass mode until the elapse of a predetermined period is stored. Then, the ECU 90 detects the deterioration state of the HC adsorbent 40 by comparing the output value of the oxygen sensor 84 in the normal mode with the average value of the output values of the oxygen sensor 84 in the bypass mode.

  For example, if there is no difference between the output value of the oxygen sensor 84 in the normal mode and the average value of the output value of the oxygen sensor 84 in the bypass mode, HC is not released from the HC adsorbent 40. Become. That is, in this case, it can be seen that the HC adsorbent 40 has deteriorated and has lost its HC adsorbability.

  On the other hand, when there is a difference between the output value of the oxygen sensor 84 in the normal mode and the average value of the output value of the oxygen sensor 84 in the bypass mode, the HC adsorbent 40 releases HC after switching to the normal mode. I know what I did. That is, in this case, it can be seen that the HC adsorbent 40 has not lost its HC adsorptivity.

  Further, the degree of deterioration of the HC adsorbent 40 can be determined based on the magnitude of the difference between the output value of the oxygen sensor 84 in the normal mode and the average value of the output values of the oxygen sensor 84 in the bypass mode. For example, the smaller the difference between the output value of the oxygen sensor 84 in the normal mode and the average value of the output value of the oxygen sensor 84 in the bypass mode, the higher the degree of deterioration of the HC adsorbent 40 (that is, the deterioration is greater). I know that it is going on.

  FIG. 5 is a diagram illustrating an example of a flowchart of a deterioration state detection process performed after the ECU 90 according to the second embodiment stops the execution of the sub-feedback correction process. The ECU 90 repeatedly executes the flowchart of FIG. 5 at a predetermined cycle. FIG. 5 differs from the flowchart of FIG. 3 in that steps S40a, S50a, and S60a are provided instead of steps S40, S50, and S60, respectively. Other configurations are the same as those in the flowchart of FIG.

  In step S40a of FIG. 5, the ECU 90 acquires the average value (C) of the output voltage of the oxygen sensor 84 in the bypass mode. Specifically, the ECU 90 controls the passage switching valve 60 so as to be switched to the bypass mode, and then the average value (C) of the output value of the oxygen sensor 84 from when the bypass mode is switched to when a predetermined period elapses. ) Is calculated. For example, the RAM 96 stores the average value (C) obtained as a result.

  In step S50a, the ECU 90 acquires the output value (D) of the oxygen sensor 84 in the normal mode. Specifically, the ECU 90 acquires the output value (D) of the oxygen sensor 84 after controlling the passage switching valve 60 to switch to the normal mode.

  In step S60a, the ECU 90 compares the average value (C) of the output value of the oxygen sensor 84 acquired in step S40a with the output value (D) of the oxygen sensor 84 acquired in step S50a. Detect the deterioration state.

  As described above, according to the deterioration diagnosis system 100 according to the present embodiment, when the execution of the sub-feedback correction process is stopped, the output value of the oxygen sensor 84 in the normal mode and the output value in the bypass mode The deterioration value of the HC adsorbent 40 is detected using the output value of the oxygen sensor 84. Thereby, even when the execution of the sub-feedback correction process is stopped, the HC adsorbent 40 is simply provided with the air-fuel ratio detection sensor (oxygen sensor 84) disposed downstream of the HC adsorbent 40 in the exhaust passage 72. It is possible to detect the deterioration state. Therefore, the manufacturing cost of the deterioration diagnosis system 100 can be reduced as compared with the case where the deterioration state of the HC adsorbent 40 is detected using two or more air-fuel ratio detection sensors.

  Also in the present embodiment, as in the case of the first embodiment, as the oxygen sensor 84, an oxygen sensor including a catalyst that promotes HC oxidation is used. In this case, the same effect as in the first embodiment can be obtained.

  Also in the present embodiment, as in the case of the first embodiment, the ECU 90 may switch between the normal mode and the bypass mode based on the activity level of the exhaust purification catalyst 50. In this case, the same effect as in the first embodiment can be obtained.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 20 Fuel injection valve 30 Throttle 40 HC adsorbent 50 Exhaust purification catalyst 60 Passage switching valve 70 Intake passage 72 Exhaust passage 74 Bypass passage 84 Oxygen sensor 85 Temperature sensor 90 ECU
100 Deterioration diagnosis system 200 Internal combustion engine system

Claims (6)

An HC adsorbent that is disposed in the exhaust passage, adsorbs HC of the exhaust gas, and releases the HC adsorbed so far when the temperature is raised to the HC release temperature region;
An air-fuel ratio detection sensor disposed downstream of the HC adsorbent in the exhaust passage;
An exhaust gas flow mode that switches between a normal mode in which the exhaust gas passes through the HC adsorbent and a bypass mode in which the exhaust gas bypasses the HC adsorbent and flows downstream from the HC adsorbent in the exhaust passage. Switching means;
After the release of the HC from the HC adsorbent, a sub feedback correction amount for controlling the output value of the air-fuel ratio detection sensor in the normal mode to a target value, and in the bypass mode A deterioration diagnosis system for an HC adsorbent, comprising: a deterioration detection unit that detects a deterioration state of the HC adsorbent using the sub feedback correction amount.   The deterioration detection means detects a deterioration state of the HC adsorbent using the sub feedback correction amount in the normal mode and an average value of the sub feedback correction amounts in the bypass mode. Item 6. The HC adsorbent deterioration diagnosis system according to Item 1.   3. The HC adsorbent deterioration diagnosis system according to claim 2, wherein an average value of the sub feedback correction amount in the bypass mode is a value obtained by performing at least integral correction.   The deterioration detection means further uses the output value of the air-fuel ratio detection sensor in the normal mode and the output value of the air-fuel ratio detection sensor in the bypass mode to detect the HC adsorbent. The deterioration diagnosis system for an HC adsorbent according to any one of claims 1 to 3, wherein a deterioration state is detected.   The exhaust gas flow mode switching means further switches between the normal mode and the bypass mode based on the degree of activity of an exhaust purification catalyst disposed downstream of the HC adsorbent in the exhaust passage. The deterioration diagnosis system for an HC adsorbent according to any one of the preceding claims.   The HC adsorbent deterioration diagnosis system according to any one of claims 1 to 5, wherein the air-fuel ratio detection sensor is an oxygen sensor including a catalyst that promotes HC oxidation.

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