JP2010121588A - Exhaust device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the cracks and embrittlement of sensors and catalyst carriers due to the scattering of condensed water in an exhaust passage including an exhaust shutter valve when opening the exhaust shutter valve. <P>SOLUTION: The exhaust device for an internal combustion engine includes a first catalyst 2 mounted in a main exhaust passage 8, an opening/closing means 10 for opening/closing the main exhaust passage 8 on the upstream side beyond the first catalyst 2, a control means 6 for controlling the opening/closing operation of the opening/closing means 10, a bypass exhaust passage 9 for bypassing the opening/closing means 10 between the upstream and downstream sides, a second catalyst 1 having a smaller capacity than the first catalyst 2 and mounted in the bypass exhaust passage 9, and an exhaust gas temperature detecting means 15 for detecting the temperature of exhaust gas flowing into the first catalyst 2. The control means 6 actualizes the fully-closing operation of the opening/closing means 10 at cool-down start, holds the opening thereof smaller at the temperature rise of the first catalyst 2 up to a predetermined temperature, and actualizes the fully-opening operation thereof after holding the opening thereof smaller for a predetermined period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust device for an internal combustion engine, and more particularly, to an exhaust device configured so that exhaust passes through an exhaust purification catalyst provided in a bypass passage when starting a cold machine.

  An exhaust gas purification catalyst is provided in the exhaust passage of the internal combustion engine as a countermeasure for exhaust emission. However, since the exhaust purification catalyst needs to reach the activation temperature in order to exert its catalytic action, a sufficient exhaust purification action can be expected from the start of cooling until the temperature is raised to the activation temperature. There wasn't.

  Therefore, as a configuration for performing sufficient exhaust gas purification from the start of the cold engine, a shutter valve that opens and closes a main exhaust passage directly connected from the internal combustion engine to the main catalyst on the upstream side of the main catalyst for normal operation, and a main catalyst There is known a configuration in which a bypass passage having a smaller bypass catalyst and bypassing the shutter valve is provided. In such a configuration, the main exhaust passage is closed at the time of cold start so that the exhaust flows into the main catalyst via the bypass catalyst, and the main exhaust passage is opened when the temperature of the main catalyst rises to the activation temperature. In addition, the shutter valve is controlled. Since the bypass catalyst is smaller than the main catalyst, the temperature is quickly raised to the activation temperature. For this reason, the exhaust emission can be reduced from the time of cold start by the control as described above.

In such a configuration, when the main catalyst is heated up to the activation temperature, the torque fluctuation associated with the flow path switching is controlled by controlling the opening speed of the shutter valve so as to suppress a rapid change in the back pressure. A technique for suppressing this is disclosed in Patent Document 1.
JP 2007-154811 A

  By the way, in the above configuration, when the shutter valve is fully closed at the time of cold start, the exhaust flow rate of the main exhaust passage becomes zero, so the peripheral parts including the shutter valve and the main exhaust passage are not heated by the exhaust. Therefore, condensed water generated by cooling the water vapor in the exhaust gas is accumulated in the exhaust passage from the branch point to the bypass passage to the shutter valve. When the shutter valve is opened, the accumulated condensed water is scattered by the exhaust.

  When the scattered condensed water hits the main catalyst that has already been heated at that time or a sensor (exhaust temperature sensor or air-fuel ratio sensor, etc.) disposed at the main catalyst inlet, As a result, thermal stress is generated, which may cause cracking of the sensor element or the catalyst carrier. Further, even if cracks do not occur, there is a risk of causing so-called erosion that is eroded by exhaust due to embrittlement.

  In the configuration disclosed in Patent Document 1, the valve opening speed of the shutter valve is set according to the operating state, but the set valve opening speed is constant from the fully closed state to the fully open state. Therefore, when the predetermined opening degree is exceeded, there is a possibility that the accumulated condensed water is scattered and the sensor element and the catalyst are cracked as described above.

  Therefore, an object of the present invention is to provide an exhaust device that does not cause element cracking or catalyst cracking due to moisture when the shutter valve is opened.

  An exhaust system for an internal combustion engine according to the present invention includes a first catalyst interposed in a main exhaust passage of the internal combustion engine, an opening / closing means for opening / closing the main exhaust passage upstream of the first catalyst, and an opening / closing operation of the opening / closing means. A control means for controlling, a bypass exhaust passage branched from the main exhaust passage upstream of the opening / closing means and joined to the main exhaust passage downstream of the opening / closing means and upstream of the first catalyst, and a capacity smaller than that of the first catalyst And a second catalyst interposed in the bypass exhaust passage, and an exhaust temperature detecting means for detecting the temperature of the exhaust gas flowing into the first catalyst. Then, the control means fully closes the opening / closing means at the time of cold start, maintains a small opening when the first catalyst is heated to a predetermined temperature, and fully opens after a predetermined period has elapsed after maintaining the minute opening.

  According to the present invention, when the condensed water passes through the opening / closing means maintained at a minute opening, it is atomized by the spraying phenomenon and flows downstream. Further, by maintaining the minute opening, the exhaust flows into the main exhaust passage, the temperature of the vicinity of the opening / closing means is raised, and the evaporation of the condensed water is promoted.

  As a result, it is possible to prevent sensor element cracking, cracking of the catalyst carrier, and embrittlement due to scattering of condensed water.

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

  FIG. 1 is a system configuration diagram of the first embodiment.

  1 is a starting manifold catalyst as a second catalyst, 2 is a main catalyst as a first catalyst, 3 is a main A / F sensor, 4 is a water temperature sensor, 5 is an air flow meter, and 6 is an engine control unit as control means. (ECU), 7 is an intake passage, 8 is a main exhaust passage, 9 is a bypass exhaust passage, 10 is an exhaust shutter valve as an opening / closing means, 11 is a valve driving motor, 12 is an engine body, 13 is a throttle valve, and 14 is A sub A / F sensor 15 is an exhaust temperature sensor as exhaust temperature detecting means.

  The intake passage 7 is provided with an air flow meter for measuring the intake air amount and a throttle valve 13 for adjusting the intake air amount flowing into the engine body 12 in order from the upstream side of the intake air flow. Further, the engine body 12 is provided with a water temperature sensor 4 for detecting the cooling water temperature.

  The main exhaust passage 8 is provided with an exhaust shutter valve 10 that can open and close the flow path. The exhaust shutter valve 10 is driven to open and close by a valve driving motor 11. An exhaust purification main catalyst 2 is provided downstream of the exhaust shutter valve 10. A main A / F sensor 3 and an exhaust temperature sensor 15 for detecting the air-fuel ratio of the exhaust gas flowing into the main catalyst 2 are arranged near the inlet of the main catalyst 2.

  Further, a bypass exhaust passage 9 that bypasses the exhaust shutter valve 10 and communicates the upstream side and the downstream side of the exhaust shutter valve 10 is provided. The bypass exhaust passage 9 has a smaller start-up manifold than the main catalyst 2. A sub A / F sensor 14 for detecting the air-fuel ratio of the exhaust gas flowing into the catalyst 1 and the starting manifold catalyst 1 is provided. It is desirable to provide the starting manifold catalyst 1 at a position as close to the engine body 12 as possible, that is, at a position where high-temperature exhaust flows. In FIG. 1, the two start-up manifold catalysts 1 are arranged in series with respect to the exhaust flow, but may be one.

  The ECU 6 is a general engine based on detection signals from an air flow meter 5, a water temperature sensor 4, a main A / F sensor 3, a sub A / F sensor 14, and an accelerator opening sensor and a crank angle sensor (not shown). In addition to the throttle valve opening control, air-fuel ratio feedback control, and ignition timing control similar to the above, the opening / closing control of the exhaust shutter valve 10 described later is performed.

  Note that the air-fuel ratio feedback control is performed when the exhaust shutter valve 10 is fully closed and the opening degree is small, and the detected value of the sub A / F sensor 14 is detected. Based on.

  Next, opening / closing control of the exhaust shutter valve 10 will be described.

  Since the startup manifold catalyst 1 is smaller than the main catalyst 2 and is on the upstream side, higher temperature exhaust gas flows in, so that the temperature is raised to the activation temperature earlier than the main catalyst 2. On the other hand, thermal degradation is more likely to proceed than the main catalyst 2 by exposure to higher temperature exhaust.

  Therefore, at the time of cold start, the exhaust shutter valve 10 is closed until the main catalyst 2 is activated, and the exhaust performance is ensured by the starting manifold catalyst 1 that is activated earlier. When the main catalyst 2 is activated, the exhaust shutter valve 10 is opened, and exhaust gas is allowed to flow into the main catalyst 2 without passing through the start-time manifold catalyst 1, thereby suppressing thermal deterioration of the start-time manifold catalyst 1.

  Specific control will be described with reference to the flowchart of FIG. FIG. 2 is a flowchart of the opening / closing control of the exhaust shutter valve 10 started by the ECU 6 immediately after the engine is started.

  When the engine is started, the exhaust shutter valve 10 is fully closed.

  In step S100, the cooling water temperature detected by the water temperature sensor 4 is read.

  In step S101, it is determined whether or not the cooling water temperature is 50 ° C. or lower. If it is 50 ° C. or lower, the process proceeds to step S102, and if it is higher than 50 ° C., the process proceeds to step S108. In addition, determination here is determination of whether it is cold start, and 50 degreeC which is a reference value of determination is an example to the last.

  In step S102, it is determined whether or not the maximum water temperature during the previous travel period (one trip from engine start to stop) was 50 ° C. or less. If it is 50 ° C. or lower, the process proceeds to step S103, and if it is 50 ° C. or higher, the process proceeds to step S104.

  In step S103, the additional time tc1 based on the low temperature history is calculated. If the previous trip is not warmed up after the cold start, that is, if it is finished in the cold state, it is expected that condensed water has already accumulated in the exhaust passage at the time of this engine start. The In this case, all the condensed water accumulated in the exhaust passage cannot be atomized at the shutter opening time t1 on the assumption that the condensed water is not accumulated at the time of starting the engine. Further, when the previous trip is finished in the cold state, and the previous trip is also finished in the cold state, it is expected that the previous trip has already accumulated.

  Therefore, the additional time tc1 for atomizing the condensed water already accumulated at the time of starting the engine is set based on the operation history up to the previous trip.

  FIG. 3 is a map for setting the additional time tc1, where the vertical axis indicates the additional time tc1 and the horizontal axis indicates the number of times of low-temperature traveling. The additional time tc1 increases stepwise as the number of low temperature runs increases. The number of times of low-temperature traveling is the number of times when the cooling water temperature is read at the end of the trip to determine whether or not it is in the cold state, and in the cold state. If trips that have finished in the cold state continue, the number of low-temperature driving increases. On the other hand, if there is a trip that has ended in the warm-up state, the condensed water disappears by the control of this flowchart during the trip, so the number of times of low-temperature traveling is reset.

  In step S104, low-temperature valve opening control which will be described later is started, and the process proceeds to step S105. This low-temperature valve opening control is performed in parallel with this flowchart.

  In step S105, the cooling water temperature is read again, and in step S106, it is determined whether or not the cooling water temperature is 80 ° C. or higher. The determination in step S106 determines whether or not the main catalyst 2 has been heated to the activation temperature. If the cooling water temperature is 80 ° C., that is, if the engine body 12 is warmed up, the main catalyst 2 is activated. It is considered to have become. The determination reference value of 80 ° C. is merely an example.

  If the cooling water temperature is 80 ° C. or higher, the exhaust shutter valve 10 is fully opened in step S107 to end the process, and if the temperature is lower than 80 ° C., steps S105 and S106 are repeated until the temperature becomes 80 ° C. or higher. That is, when the cooling water temperature becomes 80 ° C. or higher during the low temperature valve opening control or the normal temperature valve opening control, for example, the exhaust shutter valve 10 is being held at the minute opening T1. In this case, the process is terminated with the valve fully open.

  On the other hand, if the cooling water temperature is higher than 50 ° C. in step S101, it is determined in step S108 whether or not the maximum water temperature during the previous trip is 50 ° C. or lower, as in step S102. When it is 50 ° C. or lower, the process proceeds to step S109, and when it is higher than 50 ° C., the process proceeds to step S110.

  In step S109, the additional time tc1 based on the low temperature history is calculated by the same method as in step S103.

  In step S110, the valve opening control at normal temperature described later is executed.

  In steps S111 and S112, processing similar to that in steps S105 and S106 is performed, and the process proceeds to step S107.

  Next, the low temperature valve opening control executed in step S104 of FIG. 2 will be described. FIG. 4 is a flowchart of the low-temperature valve opening control executed by the ECU 6.

  In step S1001, a holding time tk1 for holding the exhaust shutter valve 10 at the minute opening T1 is calculated. Specifically, it is calculated using a valve opening time map shown in FIG. In FIG. 5, the vertical axis represents the valve opening time, and the horizontal axis represents the cooling water temperature. The lower the cooling water temperature, the longer the valve opening time, and the higher the cooling water temperature, the shorter the valve opening time. This is because when the cooling water temperature is high, the wall temperature of the main exhaust passage 8 is also high, and evaporation of condensed water is promoted.

  Then, the additional time tc calculated in step S103 is added to the valve opening time t1, and this is set as the holding time tk1. That is, if the previous trip ends in the warm-up state, the valve opening time t1 remains as the holding time tk1, and if the previous trip ends in the cold state, the sum of the valve opening time t1 and the additional time tc is maintained. Time tk1 is reached.

  In step S1002, it is determined whether or not the main catalyst 2 is activated based on the detection value of the exhaust temperature sensor 15. If activated, the process proceeds to step S1003. If not activated, the process proceeds to activation. Repeat S1002. Here, for example, if the exhaust temperature is 350 ° C. or higher, it is determined that the air is activated.

  In step S1003, the exhaust shutter valve 10 is opened to the minute opening T1. The minute opening T <b> 1 is an angle such that condensed water accumulated on the upstream side of the exhaust shutter valve 10 is atomized when passing through the exhaust shutter valve 10. The condition for condensing condensed water is determined by the exhaust gas pressure difference between the upstream and downstream of the exhaust shutter valve 10 and the flow velocity of the opening, so the minute opening T1 is based on the specifications of the engine body 12 and the main exhaust passage 8. And set in advance by experiments or the like.

  Although the exhaust gas flow rate can be calculated based on the opening of the throttle valve 13, the intake air amount detected by the air flow meter 5 is regarded as the exhaust gas flow rate here.

  The minute opening T1 set in this way is about 0.1 to 10 degrees with reference to the state where the exhaust shutter valve 10 is fully closed. When the exhaust gas flow rate is extremely low, it is fully closed to prevent backflow.

  In step S1004, it is determined whether or not the holding time tk1 has elapsed from the start of opening of the valve. If it has elapsed, the exhaust shutter valve 10 is fully opened in step S1005, and the low-temperature valve opening control is terminated. Note that when the low-temperature valve opening control is finished, the control shown in FIG. 2 is also finished.

  The valve opening control at room temperature executed in step S110 in FIG. 2 is the same as the valve opening control at low temperature in FIG. 4 except that the valve opening time t1 and the additional time tc1 are shorter than the valve opening control at low temperature. The reason why the valve opening time t1 and the additional time tc are shorter than in the low temperature valve opening control is that evaporation of condensed water is promoted because the wall temperature of the main exhaust passage 8 is high.

  FIG. 6 is a time chart of the exhaust shutter valve opening when the above control is executed at the time of cold start. The solid line indicates the case where the previous trip has ended in the warm-up state, and the broken line indicates the case where the previous trip has ended before the warm-up state, and the time when the main catalyst 2 is activated is set to zero.

  When the previous trip has been completed in the warm-up state, the holding time tk1 is the shutter valve opening time t1, so when the exhaust shutter valve 10 is opened to the minute opening T1, this opening is held for the time t1. . If the opening degree is small, the condensed water accumulated on the upstream side of the exhaust shutter valve 10 is atomized and passes through the exhaust shutter valve 10. Further, when the temperature of the main exhaust passage 8 is increased by the exhaust, the wall temperature of the main exhaust passage 8 is increased and the evaporation of condensed water is promoted. If the water is atomized or steamed, even if it adheres to the main A / F sensor 3 or the main catalyst 2, there is no risk of element cracking, catalyst carrier cracking or embrittlement.

  The holding time tk1 is set to a time sufficient for all of the accumulated condensed water to be atomized or steamed and pass through the exhaust shutter valve 10, so that the exhaust shutter valve 10 is fully opened after t1. However, the condensed water will not scatter.

  On the other hand, if the previous trip is finished before the warm-up state is reached, the minute opening T1 is maintained for an additional time tc1 so that the condensed water accumulated during the previous trip is atomized or steamed. Can do.

  As described above, in the present embodiment, the following effects can be obtained.

  (1) The exhaust shutter valve 10 is fully closed at the time of cold start, and when the main catalyst 2 is activated, the minute opening T1 is held for a predetermined period and then fully opened, so that the condensed water is opened and closed with the minute opening. When passing through the means, it is atomized by the spraying phenomenon and flows downstream. Further, by maintaining the minute opening, the exhaust flows into the main exhaust passage, the temperature of the vicinity of the opening / closing means is raised, and the evaporation of the condensed water is promoted. As a result, it is possible to prevent sensor element cracking, cracking of the catalyst carrier, and embrittlement due to scattering of condensed water.

  (2) The minute opening T1 is an opening at which condensed water is atomized when passing through the exhaust shutter valve 10 and is set according to the exhaust flow rate passing through the main exhaust passage 8. Since the conditions under which the condensed water is atomized are determined by the exhaust gas pressure difference before and after the exhaust shutter valve 10 and the flow velocity of the opening, an appropriate opening is set by setting the minute opening T1 according to the exhaust gas flow rate. be able to.

  (3) Since the predetermined period during which the minute opening T1 is maintained is a period until the condensed water runs out, scattering of the condensed water when the exhaust shutter valve 10 is fully opened can be prevented.

  (4) When the predetermined time elapses after the minute opening T1 is maintained, the valve is fully opened, and the predetermined time is increased as the cooling water temperature is lower. Therefore, the retention time can be set according to the amount of condensed water.

  A second embodiment will be described.

  In this embodiment, the system configuration is the same as that in FIG. 1, and the opening / closing control of the exhaust shutter valve 10 is different. In the present embodiment, the exhaust shutter valve 10 is held at a minute opening degree until the cumulative value of the intake air amount of the engine body 12 exceeds a predetermined value. The predetermined value is set based on the exhaust temperature at the inlet of the main catalyst 2. Hereinafter, description will be given with reference to a flowchart.

  FIG. 7 is a flowchart of the opening / closing control of the exhaust shutter valve 10 started by the ECU 6 immediately after the engine is started. Steps S200 to S202, S205 to S208, and S211 to S212 are the same as steps S100 to S102, S105 to S108, and S111 to S112 in FIG. To do.

  In step S203, an additional intake air amount qinc1 based on the low temperature history is calculated. FIG. 9 is a map for calculating the load intake air amount qinc1. The vertical axis represents the additional intake air amount qinc1, the horizontal axis represents the number of times of low-temperature traveling, and the amount of additional intake air qinc1 increases stepwise as the number of times of low-temperature traveling increases.

  In step S204, low temperature valve opening control, which will be described later, is started.

  In step S209, the additional intake air amount qinc1 based on the low temperature history is calculated by the same method as in step S103.

  In step S210, normal temperature valve opening control, which will be described later, is executed.

  FIG. 8 is a flowchart of low temperature valve opening control executed by the ECU 6.

  In step S2001, the cumulative intake air amount qink1 until the exhaust shutter valve 10 is fully opened from the minute opening is calculated. The cumulative intake air amount qink1 is set to a value sufficient to atomize or steam all the condensed water accumulated on the upstream side of the exhaust shutter valve 10 with the exhaust shutter valve 10 held at a small opening. . Specifically, the valve opening intake air amount qin is calculated from the map of FIG. 10 based on the inlet temperature of the main catalyst 2 detected by the exhaust temperature sensor 15, and the additional intake air amount qinc1 based on the low temperature history is added to this. Thus, the cumulative intake air amount is qink1.

  Steps S2002 and S2003 are the same as steps S1002 and S1003 in FIG.

  In step S2004, it is determined whether or not the cumulative value of the intake air amount detected by the air flow meter 5 has reached the cumulative intake air amount qink1, and if so, the process proceeds to step S2005 to fully open the exhaust shutter valve 10.

  The valve opening control at normal temperature is basically the same control as the valve opening control at low temperature, but the cumulative intake air amount qink1 is smaller than that in the valve opening control at low temperature.

  FIG. 11 is a time chart of the exhaust shutter valve opening when the above control is executed at the time of cold start. The solid line indicates the case where the previous trip has ended in the warm-up state, and the broken line indicates the case where the previous trip has ended before the warm-up state, and the time when the main catalyst 2 is activated is set to zero.

  When the previous trip is finished in the warm-up state, the cumulative intake air amount qink1 becomes the valve opening intake air amount qin. Therefore, when the exhaust shutter valve 10 is opened to the minute opening T1, this opening is opened. This is held until the cumulative value of the intake air amount after the valve reaches the valve opening intake air amount qin.

  On the other hand, if the previous trip is completed before the warm-up state is reached, the minute opening T1 is maintained until the cumulative value of the intake air amount after the valve opening becomes larger by the additional intake air amount qinc.

  Thereby, the element crack of the main A / F sensor 3 by the adhesion of condensed water, the crack generation of the catalyst support | carrier of the main catalyst 2, and embrittlement can be prevented.

  As described above, according to the present embodiment, the following effects can be obtained in addition to the same effects as those of the first embodiment.

  (1) When the cumulative intake air amount after the minute opening T is maintained exceeds a predetermined amount, it is fully opened, and the predetermined amount is set to a larger value as the inlet temperature of the main catalyst 2 is lower. It can be a holding time.

  A third embodiment will be described.

  In the present embodiment, the system configuration is the same as that in FIG. 1, and the opening / closing control of the exhaust shutter valve 10 is different. In the present embodiment, the exhaust shutter valve 10 is held at a minute opening until the accumulated value of the exhaust gas amount of the engine body 12 exceeds a predetermined value. The predetermined value is set based on the cooling water temperature. Hereinafter, description will be given with reference to a flowchart.

  FIG. 12 is a flowchart of the opening / closing control of the exhaust shutter valve 10 started by the ECU 6 immediately after the engine is started. Steps S300 to S302, S305 to S308, and S311 to S312 are the same as steps S100 to S102, S105 to S108, and S111 to S112 in FIG. To do.

  In step S303, an additional exhaust gas amount qexc1 based on the low temperature history is calculated. FIG. 14 is a map for calculating the load exhaust gas amount qexc1. The vertical axis represents the amount of additional exhaust gas qexc1, the horizontal axis represents the number of times of low temperature travel, and the amount of additional exhaust gas qinc1 increases stepwise as the number of times of low temperature travel increases.

  In step S304, low-temperature valve opening control, which will be described later, is started.

  In step S309, the additional exhaust gas amount qexc1 based on the low temperature history is calculated by the same method as in step S103.

  In step S310, the valve opening control at normal temperature described later is executed.

  FIG. 13 is a flowchart of the low-temperature valve opening control executed by the ECU 6.

  In step S3001, an accumulated exhaust gas amount qexk1 is calculated from when the exhaust shutter valve 10 is fully opened to when the exhaust shutter valve 10 is fully opened. The accumulated exhaust gas amount qexk1 is set to a value sufficient to atomize or steam all the condensed water accumulated on the upstream side of the exhaust shutter valve 10 in a state where the exhaust shutter valve 10 is held at a minute opening. Specifically, the valve opening exhaust gas amount qex is calculated from the map of FIG. 15 based on the cooling water temperature, and the additional exhaust gas amount qexc1 based on the low temperature history is added to this to obtain the cumulative exhaust gas amount qexk1.

  Steps S3002 and S3003 are the same as steps S1002 and S1003 in FIG.

  In step S3004, it is determined whether or not the cumulative value of the intake air amount detected by the air flow meter 5 has reached the cumulative intake air amount qexk1, and if it reaches, the process proceeds to step S3005 and the exhaust shutter valve 10 is fully opened.

  The valve opening control at normal temperature is basically the same control as the valve opening control at low temperature, but the accumulated exhaust gas amount qexk1 is smaller than that in the valve opening control at low temperature.

  FIG. 16 is a time chart of the exhaust shutter valve opening when the above control is executed at the time of cold start. The solid line indicates the case where the previous trip has ended in the warm-up state, and the broken line indicates the case where the previous trip has ended before the warm-up state, and the time when the main catalyst 2 is activated is set to zero.

  When the previous trip is finished in the warm-up state, the accumulated exhaust gas amount qexk1 becomes the valve opening exhaust gas amount qex. Therefore, when the exhaust shutter valve 10 is opened to the minute opening T1, this opening is changed to the value after opening the valve. Until the accumulated value of the exhaust gas amount reaches the valve opening exhaust gas amount qex.

  On the other hand, if the previous trip has ended before the warm-up state is reached, the minute opening T1 is maintained until the accumulated value of the exhaust gas amount after the valve opening becomes larger by the additional exhaust gas amount qexc.

  Thereby, the element crack of the main A / F sensor 3 by the adhesion of condensed water, the crack generation of the catalyst support | carrier of the main catalyst 2, and embrittlement can be prevented.

  As described above, according to the present embodiment, the following effects can be obtained in addition to the same effects as those of the first embodiment.

  (1) When the accumulated exhaust gas flow rate after being held at the minute opening T1 exceeds a predetermined amount, it is fully opened, and the predetermined amount is set to a larger value as the cooling water temperature is lower. can do.

  A fourth embodiment will be described.

  FIG. 17 is a system configuration diagram of this embodiment. The configuration is basically the same as that in FIG. 1, but the configuration of the merging portion 20 between the main exhaust passage 8 and the bypass exhaust passage 9 is different. Note that the opening / closing control of the exhaust shutter valve 10 is performed in the same manner as in any of the first to third embodiments.

  An exhaust shutter valve 10 is arranged near the junction 20 between the main exhaust passage 8 and the bypass exhaust passage 9. The bypass exhaust passage 9 joins the main exhaust passage 8 in such a direction that the exhaust directly hits the exhaust shutter valve 10.

  With this configuration, the exhaust shutter valve 10 is heated by the exhaust gas flowing from the bypass exhaust passage 9 into the main exhaust passage 8 in a fully closed state. The condensed water generated upstream from the exhaust shutter valve 10 evaporates by contacting the heated exhaust shutter valve 10.

  As a result, the amount of condensed water accumulated while the exhaust shutter valve 10 is closed can be reduced, so that the period during which the exhaust shutter valve 10 is held at the minute opening T1 during valve opening control can be shortened.

  As described above, in the present embodiment, in addition to the same effects as those in the first to third embodiments, the following effects can also be obtained.

  (1) The exhaust shutter valve 10 is disposed in the vicinity of the junction 20 between the main exhaust passage 8 and the bypass exhaust passage 9, and the bypass exhaust passage 9 is configured such that the exhaust flowing into the main exhaust passage 8 hits the exhaust shutter valve 10. Therefore, the exhaust shutter valve 10 is directly heated by the heat of the exhaust. Thereby, evaporation of condensed water is accelerated | stimulated.

  A fifth embodiment will be described.

  FIG. 18 is a system configuration diagram of this embodiment. The configuration is basically the same as in FIG. 1, but the arrangement of the exhaust shutter valve 10 is different. Note that the opening / closing control of the exhaust shutter valve 10 is performed in the same manner as in any of the first to third embodiments.

  The exhaust shutter valve 10 is disposed in the vicinity of the branch portion 21 between the main exhaust passage 8 and the bypass exhaust passage 9 and on the downstream side. With this configuration, when the exhaust shutter valve 10 is fully closed, the volume from the branch portion 21 to the exhaust shutter valve 10, that is, the volume of the portion where condensed water can be generated is the configuration of FIG. Smaller than that. Therefore, the amount of condensed water generated can be reduced, and the period during which the exhaust shutter valve 10 is held at the minute opening T1 can be shortened.

  As described above, in the present embodiment, in addition to the same effects as those in the first to third embodiments, the following effects can also be obtained.

  (1) Since the exhaust shutter valve 10 is disposed in the vicinity of the branch portion 21 of the main exhaust passage 8 and the bypass exhaust passage 9, it is difficult for condensed water to accumulate on the upstream side of the exhaust shutter valve 10.

  A sixth embodiment will be described.

  FIG. 19 is a system configuration diagram of the present embodiment. The configuration is basically the same as in FIG. 1 except that the exhaust shutter valve 10 includes a heater 16 as a heating means.

  In the system as described above, the heater 16 is operated at the start of the cold machine to heat the exhaust shutter valve 10 and evaporate the condensed water.

  As a result, the amount of condensed water accumulated while the exhaust shutter valve 10 is closed can be reduced, so that the period during which the exhaust shutter valve 10 is held at the minute opening T1 during valve opening control can be shortened.

  As described above, in the present embodiment, in addition to the same effects as those in the first to third embodiments, the following effects can also be obtained.

  (1) Since the heater 16 for heating the exhaust shutter valve 10 is provided and the exhaust shutter valve 10 is heated by the heater 16 at the time of cold start, evaporation of condensed water can be promoted.

  A seventh embodiment will be described.

  FIG. 20 is a system configuration diagram of this embodiment. Although the structure is basically the same as that in FIG. 1, in this embodiment, the upstream side surface of the exhaust shutter valve 10 and the peripheral wall surface are coated with a water absorbing material 17.

  As the water absorbing material 17, a material excellent in heat resistance, such as alumina, zeolite, silica, etc., which has high water absorption and hardly undergoes structural change even at high temperatures.

  In a state where the exhaust shutter valve 10 is fully closed when the cold machine is started, the water absorbing material 17 absorbs condensed water. For this reason, when the exhaust shutter valve 10 is opened, the condensed water is less likely to be scattered. When the exhaust shutter valve 10 is opened, the water absorbing material 17 is heated by the exhaust gas flowing through the main exhaust passage 8, and the absorbed moisture becomes water vapor and flows downstream.

  Thus, since the water absorbing material absorbs the condensed water, the condensed water is hardly scattered even when the exhaust shutter valve 10 is opened. Therefore, it is possible to shorten the period for maintaining the minute opening T1.

  As described above, in the present embodiment, in addition to the same effects as those in the first to third embodiments, the following effects can also be obtained.

  (1) Since the exhaust shutter valve 10 includes the water absorbing material 17 in the upstream portion of the exhaust flow, the condensed water is absorbed by the water absorbing material 17 and is not easily scattered.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a system configuration figure of a 1st embodiment. 3 is a flowchart showing a control routine of an exhaust shutter valve at the time of engine start (first embodiment). It is a map for additional time setting. It is a flowchart which shows the control routine of valve opening control at the time of low temperature (1st Embodiment). It is a map for valve opening time setting. 3 is a time chart of an exhaust shutter valve opening degree (first embodiment). 7 is a flowchart showing a control routine of an exhaust shutter valve at the time of engine start (second embodiment). It is a flowchart which shows the control routine of valve opening control at the time of low temperature (2nd Embodiment). It is an additional intake air amount setting map. It is a map for valve opening intake air amount setting. It is a time chart of an exhaust shutter valve opening (2nd Embodiment). 12 is a flowchart showing a control routine of an exhaust shutter valve at the time of engine start (third embodiment). It is a flowchart which shows the control routine of valve opening control at the time of low temperature (3rd Embodiment). It is a map for additional exhaust gas amount setting. It is a map for valve opening exhaust gas amount setting. It is a time chart of an exhaust shutter valve opening degree (3rd Embodiment). It is a system configuration figure of a 4th embodiment. It is a system configuration figure of a 5th embodiment. It is a system configuration figure of a 6th embodiment. It is a system configuration figure of a 7th embodiment.

Explanation of symbols

1 Manifold catalyst for start-up 2 Main catalyst 3 Main A / F sensor 4 Water temperature sensor 5 Air flow meter 6 Engine control unit (ECU)
7 Intake passage 8 Main exhaust passage 9 Bypass exhaust passage 10 Exhaust shutter valve 11 Valve drive motor 12 Engine body 13 Throttle valve 14 Sub A / F sensor 15 Exhaust temperature sensor 16 Heating heater 17 Water absorbing material

Claims (11)

A first catalyst interposed in a main exhaust passage of the internal combustion engine;
Opening and closing means for opening and closing the main exhaust passage upstream of the first catalyst;
Control means for controlling the opening and closing operation of the opening and closing means;
A bypass exhaust passage branched from the main exhaust passage upstream of the opening / closing means and joined to the main exhaust passage downstream of the opening / closing means and upstream of the first catalyst;
A second catalyst interposed in the bypass exhaust passage with a smaller capacity than the first catalyst;
Exhaust gas temperature detecting means for detecting the temperature of the exhaust gas flowing into the first catalyst;
An exhaust device for an internal combustion engine comprising:
The control means fully closes the opening / closing means at the time of cold start, maintains a small opening when the first catalyst is heated to a predetermined temperature, and fully opens after a predetermined period of time since the first opening is maintained. An exhaust system for an internal combustion engine characterized by the above.   The minute opening is an opening at which condensed water generated upstream of the opening / closing means is atomized when passing through the opening / closing means, and the control means corresponds to an exhaust flow rate passing through the main exhaust passage. The exhaust system for an internal combustion engine according to claim 1, wherein the exhaust system is set.   The exhaust system for an internal combustion engine according to claim 2, wherein the predetermined period is a period until the condensed water runs out.   The control means determines that the predetermined period has elapsed when an elapsed time since the minute opening is maintained exceeds a threshold value, and sets a larger value as the threshold value as the cooling water temperature is lower. An exhaust system for an internal combustion engine according to any one of claims 1 to 3.   The control means determines that the predetermined period has elapsed when a cumulative intake air amount after being held at the minute opening exceeds a threshold value, and the threshold value increases as the inlet temperature of the main catalyst decreases. The exhaust system for an internal combustion engine according to any one of claims 1 to 3, wherein:   The control means determines that the predetermined period has elapsed when the accumulated exhaust gas flow rate after maintaining the minute opening exceeds a threshold value, and sets a larger value as the threshold value as the cooling water temperature is lower. The exhaust device for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust device is an internal combustion engine.   The internal combustion engine according to any one of claims 1 to 6, wherein the control means fully opens the opening / closing means when the coolant temperature rises to a predetermined temperature even before the predetermined period has elapsed. Exhaust system.   The opening / closing means is disposed in the vicinity of a junction between the main exhaust passage and the bypass exhaust passage, and the bypass exhaust passage is configured such that exhaust gas flowing into the main exhaust passage hits the opening / closing means. The exhaust system for an internal combustion engine according to any one of claims 1 to 7.   The exhaust device for an internal combustion engine according to any one of claims 1 to 7, wherein the opening / closing means is disposed in the vicinity of a branch portion between the main exhaust passage and the bypass exhaust passage.   The exhaust system for an internal combustion engine according to any one of claims 1 to 9, further comprising a heating unit that heats the opening / closing unit, wherein the opening / closing unit is heated by the heating unit when a cold machine is started.   The exhaust device for an internal combustion engine according to any one of claims 1 to 10, wherein the opening / closing means includes a water absorbing material in an upstream portion of the exhaust flow.

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