JP5125634B2 - Exhaust gas purification device for idle stop vehicle - Google Patents

Description

  The present invention relates to an exhaust emission control device for an idle stop vehicle.

  2. Description of the Related Art Conventionally, a vehicle including an idle stop mechanism that automatically stops an engine when the vehicle is stopped, such as a signal wait, and then automatically restarts the engine without performing a start operation such as a key operation, is known.

  In a vehicle equipped with such an idle stop mechanism, if the state of the catalyst that purifies the exhaust gas is not known at the time of automatic engine restart, combustion cannot be performed at an air-fuel ratio that provides an optimal purification rate of the catalyst, As a result, emissions will deteriorate when the engine is automatically restarted.

Therefore, in order to ensure good emission by air-fuel ratio control in consideration of the state of the catalyst at the time of automatic restart after the engine is automatically stopped, in Patent Document 1, before the engine is automatically stopped, the oxygen adsorption of the catalyst. The fuel is injected so that the air-fuel ratio becomes rich when the amount is saturated and at the time of automatic restart after automatic stop. Thereby, in this patent document 1, since the oxygen adsorption amount of the catalyst at the time of automatic restart of the engine quickly returns to the neutral state, good emission can be ensured.
JP 2003-148200 A

  However, in Patent Document 1, it is necessary to perform fuel injection so that the air-fuel ratio becomes richer during automatic restart after automatic stop. That is, at the time of automatic restart, there is a problem that fuel consumption deteriorates because extra fuel needs to be injected only to quickly return the oxygen adsorption amount of the catalyst to the neutral state.

  In view of this, the present invention provides a bypass passage in which a bypass catalyst is interposed in parallel upstream of a main passage in which a main catalyst is interposed, and the main passage is connected to a portion of the main passage that is bypassed by the bypass passage. In the exhaust gas purifying apparatus for an idle stop vehicle, in which an automatic stop of the engine is carried out after scavenging for a predetermined time after the fuel cut, the catalyst temperature of the bypass catalyst is increased during the scavenging. Control is performed within a predetermined temperature range, and the main passage is closed by the flow path switching means during the scavenging. As a result, oxygen in the scavenging gas flowing in the exhaust system during scavenging is adsorbed to the activated bypass catalyst, and the main catalyst can be used in a state with a small amount of oxygen adsorbed when the engine is automatically restarted.

  According to the present invention, since the main catalyst can be used in a stoichiometric atmosphere at the time of automatic engine restart, the fuel injection amount can be relatively reduced, and fuel consumption can be improved.

  Hereinafter, an embodiment in which the present invention is applied to an exhaust purification device for an in-line four-cylinder engine will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram schematically showing the overall configuration of the exhaust emission control device.

  In the vehicle according to the first embodiment, a motor 3 having both a driving force assist function and a power generation function is sandwiched between an engine 1 and a transmission 2, and the driving force of the engine 1 and the motor 3 is interposed between driving wheels 4. Can be transmitted.

  A main passage 7 in which a main catalyst 6 is interposed is connected to the engine 1 via an exhaust manifold 5.

  A bypass passage 9 in which a bypass catalyst 8 is interposed is connected to the main passage 7. The bypass passage 9 is configured such that one end branches from the main passage 7 on the upstream side of the main catalyst 6, and the other end joins the main passage 7 again on the upstream side of the main catalyst 6.

  The portion of the main passage 7 that is bypassed by the bypass passage 9, in other words, downstream of the connection portion between the main passage 7 and one end of the bypass passage 9, the main passage 7 and the other end of the bypass passage 9 are connected. A switching valve 10 as a flow path switching means capable of closing the main passage 7 is disposed at a position upstream of the connection portion. The switching valve 10 is controlled to be opened and closed by an engine control unit (ECU) 11. When the main passage 7 is closed by the switching valve 10 (the switching valve is closed), the exhaust gas passes through the bypass catalyst 8 disposed in the bypass passage 9 and then passes through the main catalyst 6 disposed in the main passage 7. When the main passage 7 is not closed by the switching valve 10 (opening the switching valve), the exhaust mainly flows only through the main passage 7, but actually the exhaust gas slightly flows through the bypass passage 9.

  The main catalyst 6 and the bypass catalyst 9 are composed of, for example, a three-way catalyst that simultaneously reduces CO, HC, and NOx, and purifies the exhaust gas that passes through. The purifying ability of the exhaust gas is based on the amount of oxygen stored in the catalyst. The lower it is, the higher it is.

  The ECU 11 includes a vehicle speed sensor 12 that detects the vehicle speed VSP of the vehicle, an accelerator opening sensor 13 that detects the accelerator opening APO from the depression amount of the accelerator pedal, a first temperature sensor 14 that detects the temperature of the main catalyst 6, and a bypass catalyst. The output signals from the second temperature sensor 15 for detecting the catalyst temperature 8, the brake pedal sensor 16 for detecting ON / OFF of the brake pedal, and the like are input.

  Then, the ECU 11 automatically stops the engine 1 when a predetermined engine automatic stop condition is satisfied, and automatically restarts the engine 1 when a predetermined engine automatic restart condition is satisfied during the automatic stop.

  Here, the engine automatic stop condition is, for example, that the operation amount of the accelerator pedal is zero, the break pedal is on, the vehicle speed VSP is a predetermined value or less, and the engine 1 automatically stops when all of these conditions are satisfied. . Note that the case where the vehicle travels only by the motor 3 is also included in the state where the engine 1 is automatically stopped. The engine automatic restart condition is, for example, that the operation amount of the accelerator pedal is not zero, the brake pedal is in an off state, and the like, and the engine 1 is automatically restarted when at least one of these conditions is satisfied.

  And in this 1st Embodiment, when there exists possibility that a vehicle will perform an idle stop, ECU11 implements the following controls.

FIG. 2 is a flowchart showing a flow of control that is performed when the vehicle may perform idle stop.

  In step (hereinafter simply referred to as S) 1, it is determined whether or not the engine 1 can be automatically stopped, that is, whether or not an engine stop prediction condition is satisfied, and the engine stop prediction condition is satisfied. In this case, the process proceeds to S2, and if the engine stop prediction condition is not satisfied, the current routine is ended. Whether or not the engine stop prediction condition is satisfied will be described later.

  In S2, it is determined whether or not the current temperature of the bypass catalyst 8 is equal to or higher than a predetermined temperature T0. If the current temperature of the bypass catalyst 8 is equal to or higher than the predetermined temperature T0, the process proceeds to S3. Otherwise, the process proceeds to S8. . Here, the predetermined temperature T0 is set so that the temperature of the bypass catalyst 8 is within a predetermined temperature range when scavenging after fuel cut, which will be described later, and more specifically, the bypass catalyst 8 is used during scavenging. Is set to be activated. Accordingly, the predetermined temperature T0 is set to, for example, a catalyst activation temperature of the bypass catalyst 8 or a temperature higher than the catalyst activation temperature of the bypass catalyst 8.

  In S3, it is determined whether or not an automatic engine stop condition is satisfied. If satisfied, the process proceeds to S4. If not satisfied, the current routine is terminated.

  In S <b> 4, the switching valve 10 is closed, the main passage 7 is closed, and the exhaust gas flows into the bypass passage 9.

  In S5, a fuel cut for stopping fuel injection from a fuel injection valve (not shown) is performed, and the process proceeds to S6. In this embodiment, the fuel cut is performed after the switching valve 10 is closed. However, the switching valve 10 is closed simultaneously with the fuel cut or the fuel cut is performed prior to the switching valve 10 being closed. The switching valve 10 may be closed by the timing when the air entering the cylinder after the fuel cut reaches the upstream branching portion of the switching valve 10.

  Then, after scavenging for a predetermined time (S6), the engine 1 is stopped (S7). That is, the engine 1 is stopped (automatically stopped) after fresh air (scavenging gas) not containing fuel flows through the exhaust system until the engine rotation is completely stopped after the fuel cut. When the engine 1 automatically stops, the process proceeds to S14.

  In S8, the switching valve 10 is closed, the main passage 7 is closed, the exhaust gas flows to the bypass passage 9, and the process proceeds to S9.

  In S9, the warm-up control of the bypass catalyst 8 is started, and the process proceeds to S10. In other words, the main passage 7 is closed by the switching valve 10 so that the exhaust flows through the bypass passage 9.

  In S10, it is determined whether or not the temperature of the bypass catalyst 8 is equal to or higher than a predetermined temperature T0. When the temperature of the bypass catalyst 8 becomes equal to or higher than the predetermined temperature T0, the process proceeds to S11.

  In S11, it is determined whether the engine automatic stop condition is satisfied. If satisfied, the process proceeds to S12. If not satisfied, the current routine is terminated.

  That is, when the warm-up control of the bypass catalyst 8 is started in S9, the fuel cut is not performed even if the engine automatic stop condition is satisfied until the temperature of the bypass catalyst 8 becomes equal to or higher than the predetermined temperature T0. The temperature of the bypass catalyst 8 is surely equal to or higher than the predetermined temperature T0.

  In S12, a fuel cut for stopping fuel injection from a fuel injection valve (not shown) is performed, and after scavenging for a predetermined time, the engine 1 is stopped and the process proceeds to S14.

  In S14, it is determined whether or not the automatic restart condition of the engine 1 is satisfied, and if it is satisfied, the process proceeds to S15.

  In S15, the switching valve 10 is opened, the main passage 7 is opened, exhaust gas does not flow into the bypass passage 9, and the engine 1 is automatically restarted.

  In the first embodiment, the main passage 7 is closed by the switching valve 10 only at the time of cold start and the scavenging after the fuel cut.

  Next, determination of whether or not the above-described engine stop prediction condition is satisfied will be described with reference to the flowchart of FIG. Note that the ECU 11 determines whether the engine stop prediction condition is satisfied or not.

  In S21, it is determined whether or not the accelerator opening APO is larger than a preset predetermined value A1, and if it is larger, the process proceeds to S22, and if not, the process proceeds to S29.

  In S22, it is determined whether or not the vehicle speed VSP is greater than a predetermined value V1, and if it is greater, the process proceeds to S23, and if not, the process proceeds to S26.

In S23, when the change degree ΔAPO of the accelerator opening APO is smaller than the threshold value A2 determined according to the accelerator opening APO, and the change degree ΔVSP of the vehicle speed VSP is smaller than the threshold value V2 determined according to the vehicle speed VSP. If the change degree ΔAPO of the accelerator opening APO is smaller than the threshold value A2 and the change degree ΔVSP of the vehicle speed VSP is smaller than the threshold value V2, the process proceeds to S24 and the engine stop prediction condition is satisfied. If not, the process proceeds to S25, and it is determined that the engine stop prediction condition is not satisfied (not satisfied).

  Here, the threshold value A2 is calculated with reference to a map stored in the ECU 11. As shown in FIG. 4, the threshold value A2 is set to become larger as the accelerator opening APO becomes larger. The characteristic line itself of the threshold A2 is set to be a curve that is convex upward. The threshold value V2 is calculated with reference to a map stored in the ECU 11. As shown in FIG. 5, the threshold value V2 is set so as to increase as the vehicle speed VSP increases. The characteristic line itself is set to be a curve that is convex upward.

In S26, it is determined whether or not the change degree ΔAPO of the accelerator opening APO is smaller than a threshold value A2 determined according to the accelerator opening APO, and when the change degree ΔAPO of the accelerator opening APO is smaller than the threshold value A2. Advances to S27, determines that the engine stop prediction condition is satisfied, and if not, advances to S28 and determines that the engine stop prediction condition is not satisfied (not established).

  In S29, it is determined whether or not the vehicle speed VSP is larger than a predetermined value V1 set in advance. If it is larger, the process proceeds to S30, and if not, the process proceeds to S31 and it is determined that the engine stop prediction condition is satisfied. .

In S30, it is determined whether or not the change rate ΔVSP of the vehicle speed VSP is smaller than a threshold value V2 determined according to the vehicle speed VSP. If the change rate ΔVSP of the vehicle speed VSP is smaller than the threshold value V2, the process proceeds to S31 and the engine is stopped. It is determined that the prediction condition is satisfied. If not, the process proceeds to S32 and it is determined that the engine stop prediction condition is not satisfied (not satisfied).

  FIG. 6 schematically shows whether the engine stop prediction condition is satisfied or not. Region 1 in FIG. 6 shows when the accelerator opening APO is A1 or less, the vehicle speed VSP is V1 or less, and when the engine 1 is It is an area that is not strange even if it stops automatically. In the first embodiment, the warming-up of the bypass catalyst 8 is performed in advance before the operating state shifts to this region 1, that is, when there is a possibility that the operating state shifts to this region 1. It is. Region 2 is a region where the accelerator opening APO is greater than or equal to A1 and the vehicle speed VSP is less than or equal to V1, and the above-described S26 in FIG. It is.

  Region 3 is a region where the accelerator opening APO is equal to or less than A1 and the vehicle speed VSP is equal to or greater than V1, and S30 in FIG. 3 described above determines whether or not an engine stop prediction condition is satisfied when the driving state is in this region 3. It is.

  Region 4 is a region where the accelerator opening APO is greater than or equal to A1 and the vehicle speed VSP is greater than or equal to V1, and the above-described S23 in FIG. 3 determines whether or not the engine stop prediction condition is satisfied when the operation state is in this region 4. It is.

  In region 4, even if only one of accelerator opening APO and vehicle speed VSP decreases, the driving state does not shift to region 1. That is, in the region 4, when only the accelerator opening becomes small, the region shifts to the region 3, and when only the vehicle speed VSP decreases, the region shifts to the region 2. Therefore, the change degree ΔAPO of the accelerator opening APO and the change degree of the vehicle speed VSP Both ΔVSP is used to determine whether the engine stop prediction condition is satisfied or not.

  In such a first embodiment, when the engine 1 automatically stops, the bypass catalyst 8 is activated, and the upstream side of the main passage 7 is blocked by the switching valve 10 prior to scavenging after the fuel cut. Therefore, oxygen in the scavenging gas flowing in the exhaust system during scavenging is adsorbed to the activated bypass catalyst 8, and the main catalyst 6 is used in a state where the oxygen adsorption amount is small when the engine 1 is automatically restarted. be able to.

  Therefore, when the engine is automatically restarted, the fuel injection amount can be reduced and the fuel efficiency can be improved as compared with the case where the oxygen adsorption amount of the main catalyst 6 is large. In other words, since the main catalyst 6 can be used in a stoichiometric atmosphere when the engine is automatically restarted, the fuel injection amount can be relatively reduced, and the fuel efficiency can be improved. In addition, it is possible to achieve both of ensuring exhaust performance during automatic engine restart and improving engine restartability.

  By limiting the warming up of the bypass catalyst 8 when the automatic stop of the engine 1 is expected, that is, before the automatic stop of the engine 1, the deterioration of the bypass catalyst 8 can be suppressed.

  Further, by using the change degree ΔAPO of the accelerator opening APO and the change degree of the vehicle speed VSP, the automatic stop of the engine 1 can be accurately predicted in advance, and the exhaust heat is efficiently used when the bypass catalyst 8 is warmed up. In addition, the temperature drop of the main catalyst 6 can be suppressed.

  Then, the engine stop prediction condition is satisfied with the degree of change ΔAPO of the accelerator opening APO that is smaller as the accelerator opening APO is smaller. In other words, the warm-up of the bypass catalyst 8 is started at a change degree ΔAPO of the accelerator opening APO that is smaller as the accelerator opening APO is smaller. Therefore, the automatic stop of the engine 1 can be accurately predicted according to the operating state at that time, and the bypass catalyst 8 can be warmed up only when necessary.

  Further, the engine stop prediction condition is satisfied with the change rate ΔVSP of the vehicle speed VSP that is smaller as the vehicle speed VSP is smaller. In other words, the warm-up of the bypass catalyst 8 is started with a change rate ΔVSP of the vehicle speed VSP that is smaller as the vehicle speed VSP is smaller. Therefore, also in this respect, the automatic stop of the engine 1 can be accurately predicted according to the operation state at that time, and the bypass catalyst 8 can be warmed up only when necessary.

  Further, once the engine stop prediction condition is satisfied and the warming-up of the bypass catalyst 8 is started, the engine 1 is not automatically stopped until the catalyst temperature of the bypass catalyst 8 becomes equal to or higher than the predetermined temperature T0. The bypass catalyst 8 can be activated reliably, and this is also advantageous in achieving both of ensuring exhaust performance and improving restartability at the time of automatic engine restart.

  Next, a second embodiment of the present invention will be described. The second embodiment has substantially the same configuration as the first embodiment described above, but compares the temperature of the main catalyst 6 and the temperature of the bypass catalyst 8 at the time of automatic engine restart. If it is higher, the switching valve 10 is opened and the main passage 7 is opened. If the temperature of the bypass catalyst 8 is higher, the switching valve 10 is closed and the main passage 7 is closed.

  That is, when the temperature of the main catalyst 6 has greatly decreased during the automatic stop of the engine 1, the exhaust gas at the time of automatic engine restart is passed through the activated bypass catalyst 8 and then passed to the main catalyst 6. By introducing, the deterioration of the exhaust performance until the temperature of the main catalyst 6 rises (until activation) is minimized.

FIG. 7 is a flowchart illustrating a flow of control that is performed when there is a possibility that the vehicle may perform idle stop in the second embodiment. Note that the flow of control from S41 to S54 in FIG. 7 and the contents of each step, that is, the flow of control from the determination of satisfaction of the engine stop prediction condition to the determination of satisfaction of the engine automatic restart condition are the same as S1 in FIG. Since it is the same as the control flow of S14 and the contents of each step, the description of S41 to S54 is omitted as it uses the description of S1 to S14 of FIG. 2 described above, and here, S55 to S58 of FIG. Only will be described.

  In S55, the temperature of the bypass catalyst 8 and the temperature of the main catalyst 6 are compared. If the temperature of the bypass catalyst 8 is higher, the process proceeds to S56, and if the temperature of the bypass catalyst 8 is lower, the process proceeds to S57. .

  In S56, the switching valve 10 is closed, the main passage 7 is closed, and the exhaust gas flows to the bypass passage 9, and the process proceeds to S58. That is, the switching valve 10 is kept closed and the process proceeds to S58.

  In S57, the switching valve 10 is opened, the main passage 7 is opened, the exhaust gas does not flow into the bypass passage 9, and the process proceeds to S58.

  In S58, the engine 1 is automatically restarted.

  In such a second embodiment, in addition to the effects of the first embodiment described above, a catalyst that is in an active state can be used when the engine is automatically restarted, and the exhaust purification capability is ensured when the engine is automatically restarted. And higher startability can be achieved at a higher level.

  In the second embodiment, the switching valve 10 is closed when the engine is automatically restarted. However, when the temperature of the main catalyst 6 rises and reaches the activation temperature or the like after that, the switching valve 10 is closed. 10 may be opened.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

(1) An exhaust emission control device for an idle stop vehicle that automatically stops and restarts an engine, the main passage having a main catalyst for purifying exhaust gas on the downstream side, and one end on the upstream side of the main catalyst A bypass passage that branches off from the main passage and whose other end joins the main passage again on the upstream side of the main catalyst, a bypass catalyst that purifies exhaust gas disposed in the bypass passage, and the bypass among the main passages A passage switching means that is located in a portion bypassed by the passage, and that can close the main passage, and the engine is automatically stopped after scavenging for a predetermined time after the fuel cut. In the exhaust purification apparatus, the catalyst temperature of the bypass catalyst falls within a predetermined temperature range during the scavenging by switching the flow path by the flow path switching means. And the main passage is closed by the flow path switching means during the scavenging. As a result, oxygen in the scavenging gas flowing in the exhaust system during scavenging is adsorbed to the activated bypass catalyst, and the main catalyst can be used in a state with a small amount of oxygen adsorbed when the engine is automatically restarted. Therefore, when the engine is automatically restarted, the fuel injection amount can be reduced and the fuel consumption can be improved as compared with the case where the oxygen adsorption amount of the main catalyst is large. In addition, it is possible to ensure both exhaust performance at the time of automatic engine restart and improvement of engine restartability. And by limiting the warm-up of the bypass catalyst before the engine is automatically stopped, the deterioration of the bypass catalyst can be suppressed .
(2) In the exhaust emission control device for an idle stop vehicle according to (1) above, when the temperature of the bypass catalyst is equal to or lower than a predetermined temperature, the vehicle is operating at a predetermined vehicle speed or lower and the accelerator opening is equal to or higher than the predetermined accelerator opening. Sometimes, by starting the warming-up of the bypass catalyst according to the degree of change in the accelerator opening, the catalyst temperature of the bypass catalyst is controlled to be within a predetermined temperature range during the scavenging. As a result, the automatic stop of the engine is predicted in advance and the bypass catalyst is warmed up, so that exhaust heat can be used efficiently and deterioration of the catalyst can be suppressed.

  (3) In the exhaust emission control device for an idle stop vehicle according to (2), when the temperature of the bypass catalyst is equal to or lower than a predetermined temperature, the vehicle is operating at a predetermined vehicle speed or higher and an accelerator opening is equal to or lower than the predetermined accelerator opening. Sometimes, by starting the warm-up of the bypass catalyst according to the degree of change in vehicle speed, control is performed so that the catalyst temperature of the bypass catalyst falls within a predetermined temperature range during the scavenging. As a result, the automatic stop of the engine is predicted in advance and the bypass catalyst is warmed up, so that exhaust heat can be used efficiently and deterioration of the catalyst can be suppressed.

  (4) In the exhaust emission control device for an idle stop vehicle according to (3) above, when the temperature of the bypass catalyst is equal to or lower than a predetermined temperature, the vehicle is operating at a predetermined vehicle speed or higher and the accelerator opening is equal to or higher than the predetermined accelerator opening. Sometimes, the bypass catalyst is started to warm up in accordance with both the degree of change in accelerator opening and the degree of change in vehicle speed, so that the catalyst temperature of the bypass catalyst is controlled to be within a predetermined temperature range during the scavenging. As a result, the automatic stop of the engine is predicted in advance and the bypass catalyst is warmed up, so that exhaust heat can be used efficiently and deterioration of the catalyst can be suppressed.

  (5) In the exhaust emission control device for an idle stop vehicle according to any one of (2) to (4), the bypass catalyst is started to warm up with a smaller degree of change in the accelerator opening as the accelerator opening becomes smaller. . Thereby, it is possible to accurately predict the automatic stop of the engine according to the operation state at that time, and it is possible to warm up the bypass catalyst only when necessary.

  (6) In the exhaust emission control device for an idle stop vehicle according to any one of (3) and (4) above, the warm-up of the bypass catalyst is started with a smaller change rate of the vehicle speed as the vehicle speed decreases. Thereby, it is possible to accurately predict the automatic stop of the engine according to the operation state at that time, and it is possible to warm up the bypass catalyst only when necessary.

  (7) In the exhaust emission control device for an idle stop vehicle according to any one of (1) to (6), after the start of warming up of the bypass catalyst, the engine is operated until the temperature of the bypass catalyst becomes equal to or higher than a predetermined temperature. Prohibit automatic stop. As a result, the bypass catalyst can be reliably activated, and it is possible to more surely ensure the exhaust performance at the time of automatic engine restart and improve the restartability.

(8) In the exhaust emission control device for an idle stop vehicle according to any one of (1) to (7), when the engine is automatically restarted after the engine is automatically stopped, the temperature of the main catalyst and the temperature of the bypass catalyst are set. In comparison, when the temperature of the main catalyst is higher, the flow path switching means is opened to open the main passage, and when the temperature of the bypass catalyst is higher, the flow path switching means is closed. The main passage is closed. This makes it possible to use a catalyst that is in a more active state when the engine is automatically restarted, which is further advantageous in ensuring both exhaust performance and improving restartability when the engine is automatically restarted.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which showed typically the whole structure of the exhaust gas purification apparatus which concerns on this invention. The flowchart which shows the flow of control when a vehicle performs idle stop in 1st Embodiment. The flowchart which shows the flow of control at the time of determining whether the engine stop prediction conditions are satisfied or not in the exhaust purification apparatus according to the present invention. Calculation map of threshold value A2. Calculation map of threshold value V2. Explanatory drawing which showed typically determination of establishment of engine stop prediction conditions, and failure. The flowchart which shows the flow of control when a vehicle performs idle stop in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Transmission 3 ... Motor 4 ... Drive wheel 5 ... Exhaust manifold 6 ... Main catalyst 7 ... Main passage 8 ... Bypass catalyst 9 ... Bypass passage 10 ... Switching valve 11 ... ECU

Claims (8)

An exhaust purification device for an idle stop vehicle that automatically stops and restarts an engine,
A main passage provided with a main catalyst on the downstream side for purifying exhaust gas;
A bypass passage having one end branched from the main passage on the upstream side of the main catalyst and the other end joined again to the main passage on the upstream side of the main catalyst;
A bypass catalyst for purifying exhaust gas disposed in the bypass passage;
A passage switching means that is located in a portion of the main passage that is bypassed by the bypass passage, and that can close the main passage, and after the engine has been automatically shut off for a predetermined time after the fuel cut In an exhaust emission control device for an idle stop vehicle to be implemented,
By switching the flow path by the flow path switching means, the catalyst temperature of the bypass catalyst is controlled to be within a predetermined temperature range during the scavenging, and the main passage is closed by the flow path switching means during the scavenging. An exhaust emission control device for an idle stop vehicle.   When the temperature of the bypass catalyst is equal to or lower than the predetermined temperature, when the vehicle is operating at a predetermined vehicle speed or lower and the accelerator opening is equal to or higher than the predetermined accelerator opening, the bypass catalyst is started to warm up according to the degree of change in the accelerator opening. Thus, the exhaust gas purifying apparatus for an idle stop vehicle according to claim 1, wherein the catalyst temperature of the bypass catalyst is controlled to be within a predetermined temperature range during the scavenging.   When the temperature of the bypass catalyst is equal to or lower than a predetermined temperature, when the vehicle is operating at a predetermined vehicle speed or higher and the accelerator opening is equal to or lower than the predetermined accelerator opening, the warm-up of the bypass catalyst is started according to the degree of change in the vehicle speed. The exhaust emission control device for an idle stop vehicle according to claim 2, wherein control is performed so that the catalyst temperature of the bypass catalyst falls within a predetermined temperature range during the scavenging.   When the temperature of the bypass catalyst is equal to or lower than a predetermined temperature, when the vehicle is operating at a predetermined vehicle speed or higher and the accelerator opening is equal to or higher than the predetermined accelerator opening, 4. The exhaust emission control device for an idle stop vehicle according to claim 3, wherein by starting warming up of the bypass catalyst, control is performed so that the catalyst temperature of the bypass catalyst falls within a predetermined temperature range during the scavenging.   The exhaust emission control device for an idle stop vehicle according to any one of claims 2 to 4, wherein warming-up of the bypass catalyst is started with a smaller degree of change in the accelerator opening as the accelerator opening becomes smaller.   The exhaust emission control device for an idle stop vehicle according to claim 3 or 4, wherein warming-up of the bypass catalyst is started with a degree of change in vehicle speed that decreases as the vehicle speed decreases.   The exhaust of the idling stop vehicle according to any one of claims 1 to 6, wherein after the start of warming-up of the bypass catalyst, the automatic stop of the engine is prohibited until the temperature of the bypass catalyst reaches a predetermined temperature or higher. Purification equipment. At the time of automatic engine restart after automatic engine stop, the temperature of the main catalyst is compared with the temperature of the bypass catalyst,
When the temperature of the main catalyst is higher, the flow path switching means is opened to open the main passage, and when the temperature of the bypass catalyst is higher, the flow path switching means is closed to close the main passage. The exhaust emission control device for an idle stop vehicle according to any one of claims 1 to 7, characterized in that

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