JP4780102B2 - Exhaust control device - Google Patents

Description

  The present invention relates to an exhaust control device that controls an exhaust system of exhaust gas discharged from an internal combustion engine.

  As a conventional exhaust system, an exhaust passage through which exhaust gas discharged from the internal combustion engine flows, a start catalyst (S / C) interposed in the exhaust passage, and provided downstream of the S / C in the exhaust passage An underfloor catalytic converter (U / F) interposed in the exhaust passage, and a bypass passage that branches from the exhaust passage upstream of the S / C and is connected to the exhaust passage between the S / C and U / F In addition, there is known a control system for an internal combustion engine that includes a bypass valve that switches a flow path between an exhaust passage and a bypass passage (for example, see Patent Document 1). The internal combustion engine control system includes an acceleration operation determination unit that determines whether an acceleration operation for accelerating the vehicle is performed by a driver of the vehicle, and a bypass valve when it is determined that the acceleration operation is performed. Control means for controlling and switching the flow path to the bypass passage side. Thus, in this control system for an internal combustion engine, when an acceleration operation is performed by the driver of the vehicle, the flow path is switched to the bypass passage side by the bypass valve, and the exhaust gas discharged from the internal combustion engine passes through the bypass passage. Passes and flows into U / F.

JP 2005-315171 A

  At this time, in the conventional control system for an internal combustion engine, when the vehicle driver gradually accelerates the vehicle, the temperature of the exhaust gas gradually increases with the acceleration, and the bypass valve Thus, the flow path is switched to the bypass passage side, and the exhaust gas flows into the U / F. Thereby, since the gas temperature of exhaust gas can be made to reach the catalyst activation temperature of U / F, exhaust gas can be purified suitably.

  However, on the other hand, when the vehicle driver suddenly accelerates the vehicle, the exhaust gas temperature cannot rise sufficiently with the sudden acceleration, and in this state, the bypass valve flows to the bypass passage side. The path is switched and the exhaust gas flows into the U / F. Then, since the exhaust gas that has not reached the U / F catalytic activation temperature flows into the U / F, the catalytic activation temperature of the U / F decreases, and the exhaust gas can be sufficiently purified. May be difficult.

  Accordingly, an object of the present invention is to provide an exhaust control device capable of suitably purifying exhaust gas even during rapid acceleration operation of an internal combustion engine.

  An exhaust control device of the present invention includes an exhaust passage through which exhaust gas discharged from an internal combustion engine flows, a first purification catalyst device interposed in the exhaust passage for purifying exhaust gas, and a downstream side of the first purification catalyst device. A second purification catalyst device that is disposed in the exhaust passage and purifies exhaust gas, and connects an exhaust passage upstream of the first purification catalyst device and an exhaust passage between the first purification catalyst device and the second purification catalyst device. In an exhaust control device for controlling an exhaust system provided with a bypass passage and an on-off valve that is provided in the bypass passage and opens and closes the bypass passage, the on-off valve based on a preset on-off condition of the on-off valve And an opening / closing valve control means for controlling the opening / closing of the valve, and an opening delay means for delaying the opening / closing of the opening / closing valve by the opening / closing valve control means.

  In this case, the open / close condition is set based on the load of the internal combustion engine and the rotational speed of the internal combustion engine, and the valve opening delay means sets the delay time of the open / close valve based on the load change rate of the internal combustion engine. The opening / closing valve control means preferably opens the opening / closing valve by delaying by the delay time set by the valve opening delay means when the opening condition is met.

  In these cases, when the load change rate of the internal combustion engine increases from the first predetermined value to the second predetermined value larger than the first predetermined value, the valve opening delay means increases the delay time along with this increase. When the load change rate of the internal combustion engine increases from a third predetermined value that is larger than the second predetermined value to a fourth predetermined value that is larger than the third predetermined value, the delay time can be decreased along with this increase. preferable.

  In these cases, it is preferable that the load of the internal combustion engine and the load change rate of the internal combustion engine are obtained from the amount of intake air taken into the internal combustion engine.

  In this case, the opening / closing condition is set based on the estimated bed temperature of the second purification catalyst device, and the valve opening delay means calculates the estimated bed temperature by a smoothing process. When the opening condition is met, the on-off valve may be opened.

  The exhaust control device according to the present invention causes the exhaust gas to flow into the second purification catalyst device in a state where the gas temperature of the exhaust gas has sufficiently increased by delaying the opening of the on-off valve during rapid acceleration. Therefore, the exhaust gas can be suitably purified.

  Hereinafter, an exhaust control device according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments.

  Here, FIG. 1 is a schematic configuration diagram of an exhaust system controlled by the exhaust control device according to the embodiment, and FIG. 2 is an explanatory diagram of an open / close control map for performing open / close control of the open / close valve. FIG. 3 is an explanatory diagram of a delay time setting map for setting the delay time, and FIG. 4 is a flowchart regarding valve opening delay control.

  First, an exhaust system 1 controlled by an exhaust control device will be described with reference to FIG. The exhaust system 1 includes an exhaust passage 11 through which exhaust gas discharged from an engine 10 (internal combustion engine) serving as a drive source flows, and a start catalytic converter 12 (first purification catalyst device: S / C) and an under-floor catalytic converter 13 (second purification catalyst device: hereinafter referred to as U / F catalyst) interposed in the exhaust passage 11 downstream of the S / C 12. The exhaust system 1 further includes a bypass passage 14 that branches from the exhaust passage 11 between the engine 10 and the S / C 12 and merges with the exhaust passage 11 between the S / C 12 and the U / F catalyst 13. The bypass passage 14 is provided with an opening / closing valve 15 that opens and closes the bypass passage 14. The exhaust system 1 is controlled by an ECU 2 as an exhaust control device.

  The exhaust passage 11 discharges exhaust gas sent from the engine 10 to the outside air, and its upstream side is connected to the engine 10 via an exhaust manifold 18 and its downstream side is exhausted via a muffler (not shown). It reaches to the mouth.

Since the S / C 12 is a relatively small catalyst and is disposed in the vicinity of the engine 10, the S / C 12 can be heated to the catalyst activation temperature in a short time after the engine 10 is cold-started. It is used for exhaust gas purification at start-up and when the engine 10 is under low load and low rotation. The U / F catalyst 13 is a large-capacity catalyst compared to the S / C 12, and is disposed at a position away from the engine 10, so that the temperature is raised to the catalyst activation temperature compared to the S / C 12. It has a difficult structure. Then, S / C12 and U / F catalyst 13 is composed of a three-way catalyst to purify HC, CO, by the oxidation-reduction reaction NO _X.

  The bypass passage 14 allows the exhaust gas discharged from the engine 10 to bypass the S / C 12 and flow into the U / F catalyst 13. The on-off valve 15 is configured to be controlled to be opened and closed by an ECU 2 to be described later. By opening the on-off valve 15, the bypass passage 14 is opened, and by closing the on-off valve 15, the bypass passage 14 is closed. Yes. Thereby, the flow of the exhaust gas to the bypass passage 14 can be regulated.

  When the on-off valve 15 is opened to open the bypass passage 14, the exhaust gas discharged from the engine 10 bypasses the S / C 12, passes through the bypass passage 14, and the exhaust gas flows to the U / F catalyst 13. On the other hand, when the on-off valve 15 is closed and the bypass passage 14 is closed, the exhaust gas discharged from the engine 10 passes through the S / C 12 and then passes through the U / F catalyst 13. The opening / closing valve 15 is controlled to be opened / closed by the ECU 2 based on an opening / closing control map M1, which will be described later.

  Next, the ECU 2 that controls the exhaust system 1 will be described. The ECU 2 has an opening / closing valve control unit 20 that controls opening / closing of the opening / closing valve 15, and the opening / closing valve control unit 20 (opening / closing valve control means) uses an opening / closing control map M 1 shown in FIG. 2 stored in the ECU 2. As an open / close condition, the open / close valve 15 is controlled to open and close. Specifically, the ECU 2 is connected to various sensors such as an air flow sensor 22 that detects the amount of intake air taken into the engine 10 and a crank angle sensor 23 that detects the engine speed, and based on the detection results. Thus, the open / close valve 15 is controlled to open and close.

  Here, the opening / closing control of the opening / closing valve 15 is performed mainly for protection of the S / C 12. This is because, when the temperature of the exhaust gas discharged from the engine 10 becomes high, the floor temperature of the S / C 12 may be overheated, which may cause thermal degradation. The case where the exhaust gas becomes high temperature is, for example, when the engine 10 is in steady operation in an operation region where the engine speed is high and the load is high. The inflow of exhaust gas is regulated. On the other hand, the case where the exhaust gas has a low temperature is, for example, when the engine 10 is operating steadily in an operating region where the engine speed is low and the load is low. Exhaust gas is flowing in.

  Specifically, referring to the opening / closing control map M1 in FIG. 2, the opening / closing control map M1 has an engine speed on the horizontal axis and an engine load on the vertical axis. Based on the engine speed and the engine load, A valve opening region E1 and a valve closing region E2 of the on-off valve 15 are divided. The valve opening region E1 is set so as to open the on-off valve 15 in the operation region where the rotation is high and the load is high as described above, and the valve closing region E2 is the low rotation and the low load as described above. Is set to close the on-off valve 15. That is, the open / close control map M1 is created based on the gas temperature of the exhaust gas that is discharged when the engine 10 is in steady operation at a predetermined engine speed and engine load. The engine load is obtained from the detection result by the air flow sensor 22, and the engine speed is obtained from the detection result by the crank angle sensor 23.

  Thereby, for example, when the engine 10 is cold-started (warm-up) or when the engine 10 is operating at a low rotation / low load, the on-off valve 15 is closed and the exhaust gas is switched to S / C12. By flowing in, the exhaust gas that has passed through the S / C 12 is purified. The exhaust gas that has passed through the S / C 12 is purified by passing through the U / F catalyst 13 on the downstream side.

  On the other hand, when the engine 10 is warmed up or when the engine 10 is operating at a high speed and a high load, the on-off valve 15 is opened and the exhaust gas flows into the bypass passage 14 so that the exhaust gas is It is purified by bypassing the S / C 12 and passing through the U / F catalyst 13, and overheating of the S / C 12 is suppressed.

  By the way, for example, when the operation region of the engine 10 is shifted from the low rotation / low load operation region to the high rotation / high load operation region, that is, when the engine 10 is accelerated, the engine is The gas temperature of the exhaust gas discharged from 10 rises. At this time, when the engine 10 is gradually accelerated, the transition time for shifting from the low rotation / low load operation region to the high rotation / high load operation region can be increased. Can be sufficiently raised to the catalyst activation temperature of the U / F catalyst 13. For this reason, even if the on-off valve 15 is opened and the exhaust gas is allowed to flow into the U / F catalyst 13, the U / F catalyst 13 can appropriately purify the exhaust gas.

  On the other hand, when the engine 10 is operated at a rapid acceleration, the above-described transition time cannot be made longer but becomes shorter, so that the gas temperature of the exhaust gas can be raised to the catalytic activation temperature of the U / F catalyst 13. Can not. Thus, even if the on-off valve 15 is opened and exhaust gas flows into the U / F catalyst 13, the catalyst activation temperature of the U / F catalyst 13 cannot be increased, or the catalyst of the U / F catalyst 13 can be increased. Since the activation temperature is lowered, it may be difficult to sufficiently purify the exhaust gas in the U / F catalyst 13.

  For this reason, in the present embodiment, when the engine 10 performs a rapid acceleration operation, the opening of the on-off valve 15 is delayed and the time for increasing the temperature of the exhaust gas is increased so that the gas temperature of the exhaust gas is increased. Can be raised to the catalyst activation temperature of the U / F catalyst 13, whereby the exhaust gas can be appropriately purified in the U / F catalyst 13. Hereinafter, the valve opening delay control for delaying the opening of the on-off valve 15 during the acceleration operation of the engine 10 will be specifically described.

  The ECU 2 includes a load change rate deriving unit 25 for deriving a load change rate of the engine 10 based on the intake air amount detected by the air flow sensor 22, and an opening / closing valve 15 based on the derived load change rate. It further includes a valve opening delay time setting unit 26 (valve opening delay means) for setting a delay time (delay time).

  Specifically, the load change rate deriving unit 25 derives the load change rate of the engine 10 by calculating the change rate ΔGa of the detected intake air amount. That is, the load change rate of the engine 10 is the change rate ΔGa of the intake air amount, and the change rate ΔGa of the intake air amount is the change amount of the intake air amount per unit time (for example, the sampling time of the air flow sensor 22). . In this embodiment, the load change rate of the engine 10 is derived based on the intake air amount. However, the load change of the engine 10 is determined based on the throttle opening detected by a throttle position sensor (not shown) connected to the ECU 2. The rate may be derived.

  The valve opening delay time setting unit 26 sets a delay time from the delay time setting map M2 shown in FIG. 3 stored in the ECU 2 based on the derived change rate ΔGa of the intake air amount. Here, the delay time setting map M2 will be described. The delay time setting map M2 is a delay time setting map that changes based on the change rate ΔGa of the intake air amount. The horizontal axis is the change rate ΔGa of the intake air amount, and the delay time for which the vertical axis is set. It has become.

  As shown in the delay time setting map M2, when the change rate ΔGa of the intake air amount increases from ΔGa1 (first predetermined value) to ΔGa2 (second predetermined value), the delay time increases with this increase. It will become. In other words, the increase in the intake air amount change rate ΔGa means that the transition time for shifting from the low rotation / low load operation region to the high rotation / high load operation region is shortened, and the delay time By taking a long period of time, it is possible to secure time for increasing the gas temperature of the exhaust gas. As a result, the gas temperature of the exhaust gas can be raised to the catalyst activation temperature of the U / F catalyst 13.

  When the change rate ΔGa of the intake air amount increases from ΔGa2 to ΔGa3, the delay time during this period becomes a predetermined value. That is, the delay time in ΔGa2 and the delay time in ΔGa3 have the same length.

  Furthermore, when the change rate ΔGa of the intake air amount increases from ΔGa3 (third predetermined value) to ΔGa4 (fourth predetermined value), the delay time decreases with this increase. That is, when the rate of change ΔGa in the intake air amount is large, the exhaust gas temperature also rises rapidly. Therefore, if the delay time is increased, the S / C 12 may be overheated. For this reason, it is possible to protect the S / C 12 by shortening the delay time.

  Next, a series of control flow of the valve opening delay control when the on-off valve 15 is opened will be described with reference to the flowchart of FIG. First, when the ECU 2 is activated, the ECU 2 determines whether or not the engine 10 is operating (S1). In order to determine whether or not the engine 10 is operating, for example, a discharge of a spark plug (not shown) in the engine 10 may be detected.

  When it is determined that the engine 10 is operating, the ECU 2 determines whether the on-off valve 15 is closed by the on-off valve control unit 20 (S2). When the ECU 2 determines that the on-off valve 15 is closed, the process proceeds to S3 described later. On the other hand, if it is determined that the on-off valve 15 is open, the process proceeds to S8 described later.

  When the ECU 2 determines that the on-off valve 15 is closed, the ECU 2 determines that the on-off valve 15 is in the open condition (opening region E1) from the on-off control map M1 based on the engine speed and the engine load. It is determined whether or not (S3). When the ECU 2 determines that the opening / closing valve 15 is in the open condition, the process proceeds to S4 described later. On the other hand, if it is determined that the on-off valve 15 is not in the open condition, the process proceeds to S9 described later.

  When the ECU 2 determines that the opening / closing valve 15 is in the open condition, the ECU 2 derives the intake air amount change rate ΔGa based on the intake air amount detected by the air flow sensor 22 and derives the derived intake air amount. The delay time is set from the delay time setting map M2 based on the change rate ΔGa of (S4).

  Subsequently, the ECU 2 determines whether or not the set delay time has elapsed (S5). If the ECU 2 determines that the delay time has elapsed, the ECU 2 opens the on-off valve 15 (S7). On the other hand, if it is determined that the delay time has not elapsed, the process waits for the delay time to elapse (S6) and returns to S5 again. That is, a loop is made between S5 and S6 until the delay time elapses. In S7, when the on-off valve 15 is opened, the process returns to S1 and valve opening delay control is performed.

  Here, if it is determined in S2 that the on-off valve 15 is open, in S8, the ECU 2 determines from the on-off control map M1 that the on-off valve 15 is closed based on the engine speed and the engine load. It is determined whether or not the valve closing region E2). When the ECU 2 determines that the on-off valve 15 is in the closing condition, the process proceeds to S9 described later. On the other hand, if it is determined that the on-off valve 15 is not in the closing condition, the process returns to S1 again to perform the valve opening delay control.

  If it is determined in S8 that the on-off valve 15 is in a closed condition, or if it is determined in S3 that the on-off valve 15 is not in an open condition, the process proceeds to S9, and in S9, The ECU 2 closes the on-off valve 15. Thereafter, the process returns to S1 again to perform valve opening delay control.

  According to the above configuration, when the opening / closing valve 15 is in the opening condition, the delay time can be set based on the rate of change ΔGa in the intake air amount, and therefore the opening of the opening / closing valve 15 is delayed by the set delay time. As a result, it is possible to secure time for increasing the gas temperature of the exhaust gas. Thus, after raising the gas temperature of the exhaust gas to the catalyst activation temperature of the U / F catalyst 13, the on-off valve 15 can be opened to open the bypass passage 14, so that the catalyst activation temperature of the U / F catalyst 13 is increased. The exhaust gas can be appropriately purified in the U / F catalyst 13 without lowering.

  Further, in the delay time setting map M2, exhaust gas whose temperature rises suddenly flows into the S / C 12 by decreasing the delay time as the change rate ΔGa of the intake air amount from ΔGa3 to ΔGa4 increases. Thus, since the S / C 12 is not overheated, the overheating of the S / C 12 can be suppressed and the S / C 12 can be protected.

  Furthermore, based on the intake air amount detected by the air flow sensor 22, the engine load in the open / close control map M1 and the intake air amount change rate ΔGa (engine load change rate) in the delay time setting map M2 can be derived. Therefore, the valve opening delay control can be performed with a simple configuration.

  Next, an exhaust control apparatus according to the second embodiment will be described with reference to FIGS. 1, 5, and 6. Only different parts will be described in order to avoid duplicate descriptions. The exhaust system controlled by the ECU 30 as the exhaust control device has the same configuration as the exhaust system 1 according to the first embodiment. Here, as shown in FIG. 1, the ECU 30 in the second embodiment includes an on-off valve control unit 31 that opens and closes the on-off valve 15, and the on-off valve control unit 31 is based on the engine speed and the engine load. The opening / closing valve 15 is controlled to open / close using the estimated bed temperature of the estimated U / F catalyst 13 as an opening / closing condition.

  Specifically, the on-off valve control unit 31 opens the on-off valve 15 when the estimated bed temperature of the U / F catalyst 13 is equal to or higher than a preset valve opening estimated bed temperature, and also sets a preset valve closing estimate. When the temperature is lower than the bed temperature, the on-off valve 15 is closed. At this time, the estimated bed temperature of the U / F catalyst 13 is calculated by the annealing process, thereby delaying the opening of the on-off valve 15. Hereinafter, the valve opening delay control for delaying the opening of the on-off valve 15 during the acceleration operation of the engine 10 will be specifically described.

  The ECU 2 includes a U / F simulated bed temperature deriving unit 32 for deriving the simulated bed temperature of the U / F catalyst 13, the derived simulated bed temperature of the U / F catalyst 13, and the estimated bed of the U / F catalyst 13 calculated previously. And an estimated bed temperature calculation unit 33 (valve opening delay means) that calculates an estimated bed temperature of the new U / F catalyst 13 based on the temperature by a smoothing process.

  The U / F simulated bed temperature deriving unit 32 derives the simulated bed temperature of the U / F catalyst 13 from the simulated bed temperature map M3 of the U / F catalyst 13 shown in FIG. 5 based on the engine load and the engine speed. . The engine load is obtained from the detection result by the air flow sensor 22, and the engine speed is obtained from the detection result by the crank angle sensor 23. Here, the simulated bed temperature map M3 of the U / F catalyst 13 will be described. In the simulated bed temperature map M3 of the U / F catalyst 13, the horizontal axis represents the engine speed and the vertical axis represents the engine load, and the simulated bed temperature of the U / F catalyst 13 is based on the engine speed and the engine load. Is set. That is, the simulated bed temperature map M3 of the U / F catalyst 13 indicates the bed temperature of the U / F catalyst 13 when the engine 10 is normally operated at a predetermined engine speed and engine load based on experiments or the like. It was created. Thereby, the ECU 2 can derive the simulated bed temperature of the U / F catalyst 13 based on the engine speed and the engine load.

  The estimated bed temperature calculation unit 33 includes the simulated bed temperature of the U / F catalyst 13 derived by the U / F simulated bed temperature deriving unit 32 and the previous U / F catalyst 13 estimated by the estimated bed temperature calculation unit 33. Based on the estimated bed temperature, for example, “the estimated bed temperature of the new U / F catalyst = the simulated bed temperature of the U / F catalyst × 1/16 + the estimated bed temperature of the U / F catalyst calculated the last time × 15/16” From this equation, the estimated bed temperature of the new U / F catalyst 13 is calculated. That is, the estimated bed temperature calculation unit 33 can calculate the estimated bed temperature of the U / F catalyst 13 by the annealing process by performing the calculation based on the above formula. Thereby, the ECU 2 delays and raises the estimated bed temperature of the U / F catalyst 13 as compared with the case where the simulated bed temperature of the U / F catalyst 13 is directly used as the estimated bed temperature of the U / F catalyst 13. Therefore, it is possible to take a long time for the exhaust gas temperature to rise. In the above formula, the distribution of the simulated bed temperature of the U / F catalyst 13 is 1/16, and the distribution of the estimated bed temperature of the U / F catalyst 13 calculated last time is 15/16. However, the present invention is not limited to this. The distribution may be arbitrarily changed according to the amount of annealing performed. In this case, the smaller the distribution of the simulated bed temperature of the U / F catalyst 13 is, the longer the delay time is. The larger the distribution of the simulated bed temperature of the U / F catalyst 13 is, the shorter the delay time is. Become.

  Next, a series of control flows of the valve opening delay control when the on-off valve 15 is opened will be described with reference to the flowchart of FIG. First, when the ECU 2 is activated, the ECU 2 determines whether or not the engine 10 is operating (S11). If it is determined that the engine 10 is operating, the ECU 2 calculates the estimated bed temperature of the U / F catalyst 13 by the estimated bed temperature calculation unit 33 (S12).

  Subsequently, the ECU 2 determines whether or not the calculated estimated bed temperature of the U / F catalyst 13 has reached a preset estimated valve opening temperature, that is, whether or not it is equal to or higher than the estimated valve opening temperature. (S13). When it is determined that the estimated bed temperature of the U / F catalyst 13 calculated by the ECU 2 has reached (or above) the estimated valve opening bed temperature, the process proceeds to S14 to be described later, while the calculated U / F catalyst 13 If it is determined that the estimated bed temperature has not reached (below) the valve opening estimated bed temperature, the process proceeds to S16 described later.

  If it is determined that the estimated bed temperature of the U / F catalyst 13 calculated by the ECU 2 has reached the estimated valve opening temperature, the ECU 2 determines whether the on-off valve 15 is closed (S14). If the ECU 2 determines that the on-off valve 15 is closed, the ECU 2 opens the on-off valve 15 (S15). On the other hand, if it is determined that the on-off valve 15 is open, the process returns to S11 again. Valve opening delay control.

  If it is determined in S13 that the estimated bed temperature of the U / F catalyst 13 calculated by the ECU 2 has not reached the estimated valve opening bed temperature, the ECU 2 calculates the estimated bed of the U / F catalyst 13 calculated by the ECU 2. It is determined whether or not the temperature has reached the estimated valve closing bed temperature, that is, whether or not it is greater than the estimated valve closing bed temperature (S16). When it is determined that the estimated bed temperature of the U / F catalyst 13 calculated by the ECU 2 has not reached the valve closing estimated bed temperature (below), the process proceeds to S17 described later, while the calculated U / F catalyst 13 When it is determined that the estimated bed temperature has reached the estimated valve closing bed temperature (greater than the estimated valve closing bed temperature), the process returns to S11 again to perform valve opening delay control.

  If it is determined that the estimated bed temperature of the U / F catalyst 13 calculated by the ECU 2 has not reached the estimated valve closing bed temperature, the ECU 2 determines whether or not the on-off valve 15 is closed (S17). If the ECU 2 determines that the on-off valve 15 is open, the ECU 2 closes the on-off valve 15 (S18), while if it is determined that the on-off valve 15 is closed, the process returns to S11 again. Valve opening delay control.

  Also in the above configuration, the time for increasing the gas temperature of the exhaust gas can be secured by calculating the estimated bed temperature of the U / F catalyst 13 by the annealing process. Thereby, after raising the gas temperature of the exhaust gas to the catalyst activation temperature of the U / F catalyst 13, the on-off valve 15 can be opened to open the bypass passage 14. The exhaust gas can be appropriately purified in the U / F catalyst 13 without lowering the activation temperature.

  As described above, the present invention is useful for an exhaust control device that controls the flow of exhaust gas discharged from an engine, and is particularly suitable for the case where a purification catalyst device that purifies exhaust gas is provided.

1 is a schematic configuration diagram of an exhaust system controlled by an exhaust control device according to Embodiment 1. FIG. It is explanatory drawing of the opening / closing control map for performing opening / closing control of an on-off valve. It is explanatory drawing of the delay time setting map for setting delay time. It is a flowchart figure regarding valve opening delay control. It is explanatory drawing of the simulation bed temperature map for performing opening / closing control of the on-off valve by the exhaust control apparatus concerning Example 2. FIG. FIG. 9 is a flowchart regarding valve opening delay control by the exhaust control device according to the second embodiment.

Explanation of symbols

1 Exhaust system 2 ECU
10 Engine 11 Exhaust passage 12 S / C
13 U / F catalyst 14 Bypass passage 15 Open / close valve 18 Exhaust manifold 20 Open / close valve control unit 22 Air flow sensor 23 Crank angle sensor 25 Load change rate deriving unit 26 Valve open delay time setting unit M1 Open / close control map E1 Valve open region E2 Valve close Area M2 Delay time setting map 30 ECU (Example 2)
31 On-off valve controller (Example 2)
32 U / F simulated bed temperature deriving unit 33 Estimated bed temperature calculating unit M3 Simulated bed temperature map

Claims (2)

An exhaust passage through which exhaust gas discharged from the internal combustion engine flows;
A first purification catalyst device interposed in the exhaust passage and purifying the exhaust gas;
A second purification catalyst device that is interposed in the exhaust passage downstream of the first purification catalyst device and purifies the exhaust gas;
A bypass passage connecting the exhaust passage upstream of the first purification catalyst device and the exhaust passage between the first purification catalyst device and the second purification catalyst device;
In an exhaust control device for controlling an exhaust system provided with an on-off valve interposed in the bypass passage and opening and closing the bypass passage,
An on-off valve control means for controlling on-off of the on-off valve based on a preset on-off condition of the on-off valve;
Opening delay means for delaying the opening and closing of the on-off valve by the on-off valve control means ,
The opening / closing condition is set based on the load of the internal combustion engine and the rotational speed of the internal combustion engine,
The valve opening delay means sets the delay time of the on-off valve based on the load change rate of the internal combustion engine, and the load change rate of the internal combustion engine is greater than a first predetermined value to a first predetermined value. When increasing to the second predetermined value, the delay time is increased along with this increase, and the load change rate of the internal combustion engine is increased from the third predetermined value larger than the second predetermined value to the third predetermined value. Is increased to a fourth predetermined value that is also greater, the delay time is decreased with this increase,
The on-off valve control means opens the on-off valve by delaying the delay time set by the valve opening delay means when an open condition is met. The load change rate of the load and the internal combustion engine of the internal combustion engine, an exhaust control device according to claim 1, characterized in that it is determined by the amount of intake air taken into the internal combustion engine.

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