JP4780100B2 - Exhaust purification control device - Google Patents

Description

  The present invention relates to an exhaust purification control device, and in particular, a catalyst provided on each of an upstream side and a downstream side of an exhaust path of an internal combustion engine, and a bypass passage that bypasses the upstream catalyst and guides exhaust gas to a downstream catalyst. The present invention relates to an exhaust gas purification control device that controls an exhaust gas purification device that includes a flow rate control unit that controls a flow rate of exhaust gas flowing through a bypass passage.

  For example, as in the control system for an internal combustion engine disclosed in Patent Document 1, the catalyst provided on the upstream side and the downstream side of the exhaust path of the internal combustion engine, respectively, and the upstream catalyst is bypassed and exhausted to the downstream catalyst. 2. Description of the Related Art An exhaust emission control device is known that includes a bypass passage that guides gas and a flow rate control unit that controls the flow rate of exhaust gas flowing through the bypass passage.

  By bypassing the upstream catalyst through the bypass passage and flowing the exhaust gas, it is possible to protect the upstream catalyst by preventing the temperature of the upstream catalyst from rising excessively, or to reduce the back pressure. It becomes possible to improve performance.

  When control is performed to flow exhaust gas through the bypass passage, whether or not to return from the control is determined based on, for example, operating conditions (operation information) of the internal combustion engine. The operating conditions of the internal combustion engine are, for example, the load and rotation speed of the internal combustion engine.

JP 2005-315171 A

  When it is determined whether to return from the control of flowing the exhaust gas to the bypass passage based on the operating condition of the internal combustion engine, the flow control means (for example, the flow control valve) is frequently opened and closed depending on the traveling environment. There is. For example, it is a case where the vehicle travels on an uphill road (a case where a high load area is frequently used). When traveling on an uphill road, it becomes easy to execute control that causes exhaust gas to flow through the bypass passage under high-speed and high-load operating conditions. However, even when traveling on an uphill road, the high rotation and high load operation conditions do not always continue. For example, during cornering, the operating condition is temporarily lightly loaded by returning the accelerator in front of the corner. However, after exiting the corner, the driving condition is again high. In such a case, if the control is made to return from the control of flowing the exhaust gas to the bypass passage due to a temporary change in the operating condition, the flow control means is frequently opened and closed, which is not preferable.

  The catalyst provided on the upstream side and the downstream side of the exhaust path of the internal combustion engine, the bypass passage for bypassing the upstream catalyst and introducing the exhaust gas to the downstream catalyst, and the flow rate of the exhaust gas flowing through the bypass passage are controlled. In an exhaust emission control device including a flow rate control unit, it is desired that the number of operations of the flow rate control unit can be reduced.

  An object of the present invention is to provide a catalyst provided upstream and downstream of an exhaust path of an internal combustion engine, a bypass passage that bypasses the upstream catalyst and guides exhaust gas to the downstream catalyst, and exhaust that flows through the bypass passage. An exhaust emission control device comprising a flow rate control means for controlling the flow rate of gas is to provide an exhaust emission control device capable of reducing the number of operations of the flow rate control means.

An exhaust purification control apparatus according to the present invention is provided in an upstream side catalyst that purifies exhaust gas flowing through an exhaust path of an internal combustion engine, and in the exhaust path that is downstream of the installation position of the upstream catalyst, and flows through the exhaust path. A downstream catalyst that purifies exhaust gas, a bypass passage that leads exhaust gas upstream of the upstream catalyst installation position in the exhaust path to the downstream catalyst by bypassing the upstream catalyst, and the exhaust The flow control means for controlling the flow rate of the exhaust gas flowing through the bypass passage by opening and closing at least one of the path and the bypass passage, and the bypass control for causing the exhaust gas to flow through the bypass passage by the flow control means are started. If the operation is performed, the control is returned from the bypass control based on the operation information of the internal combustion engine that affects the temperature of the upstream catalyst. A exhaust gas purification controller and a determining recovery judgment means and that comprises a gradient detection means for detecting the slope and magnitude of the upward gradient of the road on which the vehicle in which the internal combustion engine is mounted is traveling, the return When it is determined that an ascending slope has been detected based on the detection result of the gradient detecting means, the determining means has the operation information of the internal combustion engine as compared with a case where it is not determined that the ascending slope has been detected. Until the temperature of the upstream catalyst reaches a value that is predicted to be lower, it is not determined to return from the bypass control , and the return determination means has a large gradient of the upward gradient detected by the gradient detection means. In this case, the operation information of the internal combustion engine has a value predicted that the temperature of the upstream catalyst is lower than that in the case where the upward gradient is a small gradient. In, characterized in that it does not determined to return from the bypass control.

  In the exhaust purification control apparatus of the present invention, the exhaust purification control apparatus includes an estimation unit that estimates a current temperature of the upstream catalyst based on a transition of operation information of the internal combustion engine, and whether or not to start the bypass control is determined by the estimation unit It is determined based on the current temperature of the upstream catalyst estimated by the above.

  In the exhaust purification control apparatus of the present invention, the operation information of the internal combustion engine includes at least one of a load of the internal combustion engine and a rotational speed of the internal combustion engine.

  According to the present invention, the catalyst provided on the upstream side and the downstream side of the exhaust path of the internal combustion engine, the bypass passage that bypasses the upstream catalyst and guides the exhaust gas to the downstream catalyst, and the exhaust that flows through the bypass passage In an exhaust gas purification apparatus that includes a flow rate control unit that controls the flow rate of gas, the number of operations of the flow rate control unit can be reduced.

  Hereinafter, an embodiment of an exhaust purification control apparatus of the present invention will be described in detail with reference to the drawings.

(First embodiment)
The first embodiment will be described with reference to FIGS. 1 to 3. The present embodiment includes a catalyst provided on the upstream side and the downstream side of the exhaust path of the internal combustion engine, a bypass passage that bypasses the upstream catalyst and guides the exhaust gas to the downstream catalyst, and an exhaust gas that flows through the bypass passage The present invention relates to an exhaust purification control device that controls an exhaust purification device that includes a flow rate control means for controlling the flow rate of the exhaust gas.

  In the present embodiment, an upstream catalyst (see reference numeral 5 in FIG. 1) and a downstream catalyst (reference numeral 8 in FIG. 1) are connected to an exhaust path (see reference numerals 2 and 7 in FIG. 1) of an engine (see reference numeral 1 in FIG. 1). Reference) is provided. The exhaust path 2 is provided with a bypass passage (see reference numeral 4 in FIG. 1) that bypasses the upstream catalyst 5. The bypass passage 4 is provided with an exhaust passage control valve (see reference numeral 6 in FIG. 1) that opens and closes the bypass passage 4, and the bypass passage 4 is opened by the exhaust passage control valve 6 based on the load and the rotational speed of the engine 1. Opened and closed. Here, the load and the rotational speed of the engine 1 are operating information that affects the temperature of the upstream catalyst 5. When the operating condition (operating information) of the engine 1 becomes a high load or a high rotational speed (a value at which the temperature of the upstream catalyst 5 is expected to rise), the exhaust passage control valve 6 is opened and exhausted to the bypass passage 4. Control (bypass control) for flowing gas is started.

  When the bypass control is started, when the load and the rotational speed of the engine 1 are predicted to be low in the temperature of the upstream catalyst 5, it is determined to return from the bypass control, and the exhaust passage control valve 6 Is closed.

  Here, when the opening / closing control of the bypass passage 4 is performed based on the load and the rotational speed, when traveling on an uphill road (when a high load region is frequently used), as described above, the exhaust passage control valve 6 There is a problem that the number of times of opening and closing tends to increase. In the present embodiment, when traveling on an uphill road, the exhaust passage control valve 6 is operated until a lighter load or lower rotation operating condition is obtained than when traveling on a road other than the uphill road (for example, a flat road). Is left open. In other words, it is not determined that the operation information of the engine 1 is returned from the bypass control until the temperature of the upstream catalyst 5 becomes a value predicted to become lower. Thereby, the complicated operation | movement of the exhaust passage control valve 6 at the time of climbing is suppressed, and reliability is ensured by the frequency | count of opening and closing of the exhaust passage control valve 6 being reduced.

  FIG. 1 is a schematic configuration diagram of an apparatus according to the present embodiment.

  In FIG. 1, reference numeral 1 denotes an engine (internal combustion engine). An exhaust manifold (exhaust path) 2 is connected to the internal combustion engine 1. Exhaust gas generated in each cylinder (not shown) of the internal combustion engine 1 is discharged to the exhaust manifold 2. The exhaust manifold 2 is provided with a first path (exhaust path) 3 and a bypass path 4 that bypasses the first path 3. The first path 3 is provided with an upstream catalyst (S / C catalyst) 5 for purifying exhaust gas. The exhaust gas flowing through the first path 3 is purified by the upstream catalyst 5.

  The bypass passage 4 is provided with an exhaust passage control valve (flow rate control means) 6 that opens and closes the bypass passage 4. The exhaust passage control valve 6 can block or open the bypass passage 4. By opening and closing the exhaust passage control valve 6, the flow rate of the exhaust gas flowing through the bypass passage 4 is controlled. When the exhaust passage control valve 6 is fully closed and the bypass passage 4 is shut off, the entire amount of exhaust gas discharged from the engine 1 flows through the first passage 3 and no exhaust gas flows through the bypass passage 4. . On the other hand, when the exhaust passage control valve 6 is opened and the bypass passage 4 is opened, the exhaust gas discharged from the engine 1 mainly flows through the bypass passage 4 and the amount of exhaust gas flowing into the first passage 3 is small. Alternatively, the exhaust gas does not substantially flow through the first path 3.

  The downstream end of the exhaust manifold 2 is connected to an exhaust pipe (exhaust path) 7. The exhaust gas that has passed through the exhaust manifold 2 flows to the exhaust pipe 7. The exhaust pipe 7 is provided with a downstream catalyst 8 that purifies the exhaust gas. The exhaust gas purified by the downstream catalyst 8 is discharged to the atmosphere through the main muffler.

  A vehicle (not shown) on which the engine 1 is mounted is provided with a control unit 20 having an ECU (Electronic Control Unit) that controls each part of the vehicle. The engine 1 is connected to the control unit 20, and a command signal for controlling the operation of the engine 1 is output from the control unit 20 to the engine 1. Further, a signal indicating the operating conditions of the engine 1 such as the load and the rotation speed of the engine 1 is output from the engine 1 to the control unit 20. The control part 20 of this embodiment has a function as a return determination means.

  Reference numeral 10 denotes a gradient detecting means for detecting the gradient of the travel path on which the vehicle travels. The gradient detection means 10 can detect a gradient by a conventionally known method. The gradient detection means 10 can detect the gradient based on, for example, the correspondence between the load and acceleration of the engine 1. The gradient can be calculated based on the difference between the acceleration value obtained from the driving force of the engine 1, the vehicle speed, etc., and the acceleration value obtained from the amount of change in the output shaft rotation speed. A signal indicating the detection result of the gradient detection means 10 is output to the control unit 20.

  In the present embodiment, the opening / closing control of the exhaust passage control valve 6 is performed with reference to the catalyst bed temperature map shown in FIG. In the catalyst bed temperature map, the vertical axis represents the load of the engine 1 and the horizontal axis represents the rotational speed of the engine 1 (hereinafter simply referred to as engine rotational speed). In the catalyst bed temperature map, the catalyst bed temperature of the upstream catalyst 5 corresponding to the operating condition of the engine 1 is stored. Here, the value of the catalyst bed temperature in the catalyst bed temperature map is a value calculated as the catalyst bed temperature when the operation of the engine 1 is in a steady state. That is, the catalyst bed temperature in the catalyst bed temperature map is an estimated value of the catalyst bed temperature of the upstream catalyst 5 when the engine 1 is continuously operated in a steady state where the load and the engine speed do not vary. The catalyst bed temperature map is set based on the result of the experiment, for example. In this case, for example, the value of the catalyst bed temperature map can be set based on the value at which the catalyst bed temperature converges (stabilizes) when the steady state is continued. Alternatively, the value of the catalyst bed temperature map may be set based on the transition of the catalyst bed temperature when the steady state is continued for a predetermined time.

  As shown in FIG. 2, the catalyst bed temperature increases as the load increases and the engine speed increases. Reference numerals Ta, Tb, and Tc indicate catalyst bed temperature isotherms. Reference symbol Ta indicates a catalyst bed temperature threshold value (hereinafter referred to as a valve opening determination threshold value) for determining whether or not to open the exhaust passage control valve 6. When the catalyst bed temperature calculated based on the catalyst bed temperature map from the combination of the load and the engine speed under the current operating conditions of the engine 1 exceeds the valve opening determination threshold Ta as shown by the arrow A, the exhaust gas The passage control valve 6 is opened. The valve opening determination threshold Ta is set, for example, from the viewpoint of protecting the upstream catalyst 5. In this case, the valve opening determination threshold value Ta is set as a value that can suppress an excessive increase in the catalyst bed temperature of the upstream catalyst 5. Alternatively, the valve opening determination threshold Ta can be set based on a temperature range (for example, a value on the upper limit side of the temperature range) in which the exhaust gas can be efficiently purified in the upstream catalyst 5.

  By determining whether the exhaust passage control valve 6 is open based on the current operating conditions (load, engine speed) of the engine 1, the actual catalyst bed temperature of the upstream catalyst 5 reaches the temperature of the catalyst bed temperature map. Before rising, the exhaust passage control valve 6 can be opened. In other words, the exhaust path control valve 6 is opened based on the temperature estimated that the catalyst bed temperature of the upstream catalyst 5 will reach when the current operating conditions will continue in the future. Thereby, the upstream catalyst 5 is more reliably protected.

  By controlling the opening of the exhaust passage control valve 6 based on the load and the engine speed, not only can the upstream catalyst 5 be protected, but the output performance of the engine 1 can be improved. When the exhaust passage control valve 6 is opened, the exhaust gas mainly flows through the bypass passage 4, so that the exhaust pressure loss is reduced as compared with the case where the exhaust gas mainly passes through the upstream catalyst 5. By opening the exhaust passage control valve 6 under the high rotation and high load operating conditions, the back pressure of the engine 1 can be reduced and the performance of the engine 1 can be improved.

  Symbol Tb indicates a catalyst bed temperature threshold value (hereinafter referred to as a valve closing determination threshold value) for determining whether or not to close the opened exhaust passage control valve 6. The valve closing determination threshold value Tb is set as a value on a lower temperature side than the valve opening determination threshold value Ta. When the exhaust passage control valve 6 is controlled to be opened, the catalyst bed temperature calculated based on the catalyst bed temperature map from the combination of the load and the engine speed is based on the valve closing determination threshold Tb as shown by the arrow B. If the pressure also decreases, the exhaust passage control valve 6 is closed. The valve closing determination threshold value Tb is set based on, for example, the temperature at which the upstream side catalyst 5 can efficiently purify the exhaust gas. In this case, the valve closing determination threshold value Tb can be set based on the lower limit value of the temperature range in which the exhaust gas can be efficiently purified in the upstream catalyst 5.

  In the catalyst bed temperature map, the valve closing determination threshold value Tb is smaller than the valve opening determination threshold value Ta, and so-called hysteresis is provided. However, depending on the traveling environment of the vehicle, the exhaust passage control valve 6 may be opened and closed. It may be done frequently. For example, as described above, the vehicle travels on an uphill road (uphill road). For example, when driving on a corner on an uphill road, the driving conditions may temporarily be light and low, and then immediately return to high and high operating conditions. In such a case, if the exhaust passage control valve 6 is closed just because a light load or low rotation operation condition is detected temporarily, the operation immediately shifts to a high rotation and high load operation condition. The exhaust passage control valve 6 is opened. It is not desirable to frequently open and close the exhaust passage control valve 6 from the viewpoint of ensuring the reliability of the exhaust passage control valve 6. Further, if the exhaust passage control valve 6 is frequently opened and closed during traveling, the output torque of the engine 1 may increase or decrease every time the opening and closing operation is performed, and drivability may deteriorate.

  In the present embodiment, when it is determined that an upward gradient is detected based on the detection result of the gradient detection means 10, the valve closing determination threshold is a lower temperature value than when it is not determined that an upward gradient is detected. (Refer to the reference symbol Tc in FIG. 2, hereinafter referred to as a valve closing determination threshold value when climbing). That is, when traveling on an uphill road, the driving conditions are lighter or lower than that on a road other than the uphill road (for example, a flat road or a downhill road). Until the exhaust passage control valve 6 is not closed. Thereby, the reliability of the exhaust passage control valve 6 can be ensured by reducing the number of times the exhaust passage control valve 6 is opened and closed when traveling on an uphill road. Further, drivability can be improved by reducing the number of times the exhaust passage control valve 6 is opened and closed.

  Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

  First, in step S10, the control unit 20 determines whether or not the engine 1 is in operation. As a result of the determination, if it is determined that the engine 1 is in operation (step S10-Y), the process proceeds to step S20, and if not (step S10-N), this control flow ends.

  In step S20, the control unit 20 determines whether or not the exhaust passage control valve 6 is currently open. In step S20, it is determined whether or not control (bypass control) for opening the exhaust passage control valve 6 has already been performed. As a result of the determination, if it is determined that the exhaust passage control valve 6 is currently open (step S20-Y), the process proceeds to step S30. If not (step S20-N), the control flow is repeated again. Executed from step S10.

  In step S30, the control unit 20 determines whether or not the vehicle is in an uphill state. In step S30, it is determined whether or not the vehicle is currently traveling on an uphill road. The control unit 20 performs the determination in step S30 based on the detection result of the gradient detection unit 10. As a result of the determination, if it is determined that the vehicle is in an uphill state (step S30-Y), the process proceeds to step S40, and if not (step S30-N), the process proceeds to step S50.

  In step S40, the closing condition of the exhaust passage control valve 6 is changed by the control unit 20. The control unit 20 changes the threshold value of the catalyst bed temperature for determining whether or not to close the exhaust passage control valve 6 in the opened state to the valve closing determination threshold value Tc at the time of climbing. This prevents the exhaust passage control valve 6 from being closed until a light load operating condition or a low rotation operating condition is achieved, as compared to a case where the vehicle travels on a road other than an uphill road (such as a flat road). Become. Therefore, the opening / closing frequency of the exhaust passage control valve 6 when traveling on an uphill road can be reduced. When step S40 is executed, the process proceeds to step S60.

  When a negative determination is made in step S30 and the process proceeds to step S50, in step S50, the control unit 20 returns the closing condition of the exhaust passage control valve 6 to the standard condition. The control unit 20 uses the threshold of the catalyst bed temperature for determining whether or not to close the opened exhaust passage control valve 6 as a threshold (standard condition) when traveling on a road other than an uphill road. The valve closing determination threshold value Tb is changed.

  In step S60, the control unit 20 determines whether or not the closing condition of the exhaust passage control valve 6 is satisfied. The control unit 20 calculates the catalyst bed temperature based on the detected values of the load and the engine speed with reference to the catalyst bed temperature map shown in FIG. The determination in step S60 is made based on the comparison result between the calculated catalyst bed temperature and the current valve closing determination threshold (the valve closing determination threshold Tb or the valve closing determination threshold Tc when climbing). When the calculated catalyst bed temperature is lower than the current valve closing determination threshold (the valve closing determination threshold Tb or the valve closing determination threshold Tc when climbing), an affirmative determination is made. As a result of the determination, if it is determined that the closing condition of the exhaust passage control valve 6 is satisfied (step S60-Y), the process proceeds to step S70; otherwise (step S60-N) The control flow is executed again from step S10.

  In step S <b> 70, the control unit 20 performs control to close the exhaust passage control valve 6. When step S70 is executed, this control flow is executed again from step S10.

(Modification of the first embodiment)
A modification of the first embodiment will be described.

  In the first embodiment (FIG. 3), when it is determined that the vehicle is in an uphill state (step S30-Y) and the closing condition of the exhaust passage control valve 6 is changed (step S40), the valve opening determination threshold value Ta ( The difference in the catalyst bed temperature threshold value (the magnitude of hysteresis) ΔT between the valve closing judgment threshold value Tc (see FIG. 2) during climbing is set based on the magnitude of the upward gradient. Can do. In this case, for example, the temperature difference ΔT of the threshold value of the catalyst bed temperature is set to a larger value as the magnitude of the upward gradient detected by the gradient detection means 10 increases (steep gradient). That is, as the magnitude of the detected upward gradient becomes larger (steep slope), the threshold of the operating condition for determining that the exhaust passage control valve 6 in the opened state is closed (the valve closing determination threshold Tc when climbing) ) Is changed to lighter load or lower rotation operating conditions. Thereby, the closing conditions of the exhaust passage control valve 6 can be changed more appropriately according to the uphill slope.

(Second Embodiment)
A second embodiment will be described with reference to FIGS. 4 and 5. In the second embodiment, only differences from the first embodiment will be described.

  In the first embodiment (FIG. 2), whether to open the exhaust passage control valve 6 is determined based on the current operating conditions (load and engine speed) of the engine 1. In this case, depending on the operating conditions of the engine 1, a quick opening may occur in which the exhaust passage control valve 6 is opened before the temperature of the upstream catalyst 5 actually increases. For example, when accelerating (transient). As will be described below with reference to FIG. 4, when the operating condition changes, the temperature corresponding to the operating condition after the temperature of the upstream catalyst 5 actually changes after the change of the operating condition occurs. This is because there is a time difference until

  In the present embodiment, it is determined whether or not to open the exhaust passage control valve 6 based on the estimated bed temperature, which is the estimated value of the current catalyst bed temperature, instead of the current operating conditions of the engine 1. The estimated bed temperature is an estimated value of the current catalyst bed temperature calculated based on the transition (history) of the operating conditions of the engine 1. Therefore, the above determination can be made based on a value closer to the actual catalyst bed temperature, compared to a case where it is determined whether or not to open the exhaust passage control valve 6 based on the current operating conditions. . Thereby, generation | occurrence | production of the quick opening at the time of acceleration etc. can be suppressed. The control part 20 of this embodiment has a function as an estimation means.

  FIG. 4 is a time chart showing a temporal transition when control for opening the exhaust passage control valve 6 is performed.

  4, (a) shows the open / close state of the exhaust passage control valve 6, (b) shows the accelerator opening, and (c) shows the estimated bed temperature of the upstream catalyst (S / C catalyst). Reference numerals 101 and 102 indicate command values for the open / close state of the exhaust passage control valve 6. Reference numeral 101 indicates a command value for an open / close state when it is determined whether or not the exhaust passage control valve 6 is to be opened based on the load of the engine 1 (current operating conditions). Reference numeral 102 indicates a command value for an open / close state when it is determined whether or not the exhaust passage control valve 6 is to be opened based on the estimated floor temperature in the present embodiment.

  Reference numeral 103 indicates an accelerator opening. The accelerator opening 103 corresponds to the load of the engine 1. Reference numeral 104 indicates an estimated bed temperature of the upstream catalyst 5 (hereinafter simply referred to as an estimated bed temperature). The estimated bed temperature 104 can be calculated by a conventionally known method. The estimated bed temperature 104 can be calculated based on the transition of the operating conditions of the engine 1. In this case, for example, the amount of heat given from the exhaust gas to the upstream catalyst 5 is calculated based on the operating conditions (load, engine speed, etc.) of the engine 1, and the current upstream side is calculated based on the integrated value of the calculated amount of heat. An estimated bed temperature 104 that is an estimated value of the catalyst bed temperature of the catalyst 5 is calculated.

  As shown in FIG. 4, when it is determined whether or not to open the exhaust passage control valve 6 based on the current operating conditions of the engine 1, the exhaust passage control is performed in conjunction with the depression of the accelerator at time t1. The command value 101 of the open / close state of the valve 6 is changed from the closed valve to the opened valve. However, from the time when the accelerator is depressed (accelerator opening 103 is increased) and acceleration is started until the temperature of the exhaust gas actually flowing into the upstream catalyst 5 becomes high, as indicated by reference numeral 104a. A certain amount of time is required. Therefore, if the exhaust passage control valve 6 is opened immediately after the accelerator is depressed, the low temperature exhaust gas flows into the downstream side catalyst 8 and the emission deteriorates (the emission amount of harmful substances increases). There is a possibility that.

  In the present embodiment, it is determined whether to open the exhaust passage control valve 6 based on the estimated bed temperature 104 instead of the current operating condition of the engine 1. When the estimated bed temperature 104 exceeds a predetermined temperature T0, the exhaust passage control valve 6 is opened. Since the estimated bed temperature 104 is calculated based on the transition of the operating condition of the engine 1, it is compared with the case where it is determined whether or not the exhaust passage control valve 6 is to be opened based on the current operating condition. Thus, the above determination can be made based on a value closer to the actual catalyst bed temperature.

  The operation of this embodiment will be described based on the flowchart shown in FIG.

  First, in step S110, the control unit 20 determines whether or not the engine 1 is in operation. As a result of the determination, if it is determined that the engine 1 is in operation (step S110-Y), the process proceeds to step S120. If not (step S110-N), the control flow ends.

  Next, in step S120, the estimated bed temperature 104 of the upstream catalyst 5 is calculated by the control unit 20. The control unit 20 calculates the estimated bed temperature 104 based on the transition of the operating conditions of the engine 1.

  Next, in step S130, the control unit 20 determines whether or not the opening condition of the exhaust passage control valve 6 is satisfied. The control unit 20 performs the determination in step S130 based on the estimated bed temperature 104 calculated in step S120. An affirmative determination is made when it is determined that the estimated bed temperature 104 is higher than a predetermined temperature T0 set as a threshold value of the estimated bed temperature 104 for determining that the exhaust passage control valve 6 is opened. As a result of the determination in step S130, if it is determined that the opening condition of the exhaust passage control valve 6 is satisfied (step S130-Y), the process proceeds to step S140. If not (step S130-N), Proceed to step S160.

  In step S140, the control unit 20 determines whether or not the exhaust passage control valve 6 is currently closed. As a result of the determination, if it is determined that the exhaust passage control valve 6 is currently closed (step S140-Y), the process proceeds to step S150. If not (step S140-N), the present control flow is re-stepped. Executed from S110.

  In step S150, the control unit 20 performs control to open the exhaust passage control valve 6 (bypass control). When step S150 is executed, the control flow is executed again from step S110.

  When a negative determination is made in step S130 and the process proceeds to step S160, in step S160, the control unit 20 determines whether or not the closing condition of the exhaust passage control valve 6 is satisfied. Similar to the first embodiment (step S60 in FIG. 3), the control unit 20 performs a step based on the load, the engine speed, and the valve closing determination threshold value (the valve closing determination threshold value Tb or the valve closing determination threshold value Tc at the time of climbing). The determination of S160 is performed. As a result of the determination, if it is determined that the closing condition of the exhaust passage control valve 6 is satisfied (step S160-Y), the process proceeds to step S170. If not (step S160-N), the present control is performed. The flow is executed again from step S110.

  In step S170, the control unit 20 determines whether or not the exhaust passage control valve 6 is currently closed. As a result of the determination, if it is not determined that the exhaust passage control valve 6 is currently closed (step S170-N), the process proceeds to step S180. If not (step S170-Y), the present control flow is stepped again. Executed from S110.

  In step S180, the control unit 20 performs control to close the exhaust passage control valve 6. When step S180 is executed, this control flow is executed again from step S110.

  According to the present embodiment, the estimated bed temperature 104 of the upstream catalyst 5 is calculated based on the transition of the operating condition of the engine 1 (step S120), and the exhaust passage control valve 6 is controlled based on the calculated estimated bed temperature 104. It is determined whether or not to open (step S130). Thereby, the timing for opening the exhaust passage control valve 6 is set to the timing after the temperature of the exhaust gas becomes sufficiently high and the upstream catalyst 5 needs to be bypassed. If it is not necessary to bypass the upstream catalyst 5, such as when acceleration is terminated before the actual exhaust gas temperature (catalyst bed temperature of the upstream catalyst 5) rises greatly although the accelerator is depressed, Since the exhaust passage control valve 6 does not open, the number of operations of the exhaust passage control valve 6 is reduced, and reliability is ensured.

(Modification of the second embodiment)
A modification of the second embodiment will be described.

  In the second embodiment, not only the determination of whether or not to open the exhaust passage control valve 6 (step S130) but also the determination of whether or not to close (step S160) may be made based on the estimated bed temperature 104. .

  In this case, in step S160, the control unit 20 determines whether or not the closing condition of the exhaust passage control valve 6 is satisfied based on the estimated bed temperature 104 calculated in step S120. The control unit 20 makes an affirmative determination when it is determined that the estimated bed temperature 104 is lower than a predetermined temperature T1 that is predetermined as a threshold value of the estimated bed temperature 104 for determining that the exhaust passage control valve 6 is closed. I do. Note that the predetermined temperature T1 that is determined to close the exhaust passage control valve 6 is set to a lower temperature (the operation hysteresis is provided) than the predetermined temperature T0 that is determined to open the exhaust passage control valve 6. Other operations can be the same as those in the second embodiment.

  Even if the operating condition of the engine 1 fluctuates, the estimated bed temperature 104 does not fluctuate greatly if the fluctuation is temporary. Accordingly, when the closing condition of the exhaust passage control valve 6 is determined on the basis of the estimated bed temperature 104, the accelerator is temporarily returned while traveling on the uphill road, resulting in a light load or low rotation operating condition. Even soon, it is difficult to return from the control of opening the exhaust passage control valve 6. That is, the number of times of opening and closing the exhaust passage control valve 6 traveling on the uphill road can be reduced as compared with the case where the closing condition of the exhaust passage control valve 6 is determined based on the current operating conditions of the engine 1. .

(Third embodiment)
A third embodiment will be described with reference to FIGS. 6 and 7. In the third embodiment, only differences from the above embodiments will be described.

  In the second embodiment, it is determined whether or not the exhaust passage control valve 6 is to be opened based on the estimated bed temperature 104, so that the early opening of the exhaust passage control valve 6 is suppressed. In this embodiment, a delay according to the load change is added to the calculation of the estimated bed temperature 104. As a result, the valve opening control of the exhaust passage control valve 6 can be performed more accurately, and the number of operations of the exhaust passage control valve 6 can be reduced.

  Although opening of the exhaust passage control valve 6 can be suppressed by opening control of the exhaust passage control valve 6 based on the estimated bed temperature 104, when the acceleration is sudden, the exhaust passage control valve 6 is opened early. The problem remains. This is because a temperature lag due to a thermal mass (heat capacity) of the exhaust manifold 2 or the like occurs. Since the heat of the exhaust gas is absorbed by the exhaust manifold 2 or the like, there is a delay time from the rise in the temperature of the exhaust gas (the engine 1 outgas) to the rise in the catalyst bed temperature of the upstream catalyst 5.

  The estimated bed temperature 104 is calculated based on the temperature of the exhaust gas in the steady operation condition of the engine 1. However, since the heat of the exhaust gas is absorbed by the exhaust manifold 2 between the engine 1 and the upstream side catalyst 5, Even when acceleration is started, the temperature of the exhaust gas flowing into the upstream catalyst 5 does not change suddenly. During acceleration (transition time), a temperature delay corresponding to the amount of heat mass of the exhaust manifold 2 and the amount of exhaust gas occurs.

  In this embodiment, the exhaust passage control valve is more reliably added by adding a delay (see reference numeral TD in FIG. 6 described later) corresponding to a load change to the calculation of the estimated bed temperature (see reference numeral 206 in FIG. 6 described later). Suppresses the early opening of 6. FIG. 6 is a time chart showing a temporal transition when control for opening the exhaust passage control valve 6 is performed. FIG. 6 shows respective operations when the delay according to the load change is not added and when the delay according to the load change is added in the present embodiment when acceleration is abrupt.

  In FIG. 6, (d) shows the open / close state of the exhaust passage control valve 6, (e) shows the accelerator opening, and (f) shows the catalyst bed temperature of the upstream catalyst 5. Reference numerals 201 and 202 indicate command values for the open / close state of the exhaust passage control valve 6. Reference numeral 201 indicates a command value for an open / close state when no delay according to a load change is added. Reference numeral 202 indicates a command value for the open / close state when adding a delay according to a load change in the present embodiment.

  Reference numeral 203 indicates an accelerator opening. Reference numeral 204 indicates the actual catalyst bed temperature of the upstream catalyst 5. Reference numeral 205 indicates an estimated bed temperature when no delay according to a load change is added. Reference numeral 206 indicates an estimated bed temperature of the present embodiment in which a delay according to a load change is added. When acceleration is abrupt, as indicated by symbol R in FIG. 6, even if the accelerator opening 203 increases at time t1, the actual catalyst bed temperature 204 does not rise immediately, but is delayed to some extent. Starts rising at t3. This is because the heat of the exhaust gas is absorbed in the exhaust manifold 2 from time t1 to time t3. The delay time TD from the time t1 to the time t3 varies according to the load change, the heat mass amount of the exhaust manifold 2, the gas amount of the exhaust gas, and the like.

  If the heat absorption by the exhaust manifold 2 is not taken into consideration and the delay time TD corresponding to the load is not added, the estimated bed temperature 205 is calculated as a temperature higher than the actual catalyst bed temperature 204.

  In the present embodiment, when the load changes to some extent, the calculation of the estimated bed temperature 206 is stopped until the delay time TD has elapsed at the initial stage after the load change. The estimated bed temperature 206 remains the value before the load change until the delay time TD elapses. Thereby, the estimated bed temperature 206 to which the delay according to the load change of the present embodiment is added can be a value close to the actual catalyst bed temperature 204. Therefore, the exhaust passage control valve 6 can be opened at substantially the same time t4 as when the actual catalyst bed temperature 204 exceeds a predetermined temperature T1 set in advance.

  Next, the operation of this embodiment will be described with reference to FIG.

  First, in step S210, the control unit 20 determines whether or not the engine 1 is in operation. As a result of the determination, if it is determined that the engine 1 is in operation (step S210-Y), the process proceeds to step S220. If not (step S210-N), the control flow ends.

  Next, in step S220, the controller 20 determines whether or not the difference between the current estimated bed temperature 206 and the stabilized catalyst bed temperature under the current operating conditions is equal to or greater than a predetermined value. The In step S220, it is determined whether a load change (acceleration) greater than a predetermined value has occurred. When the load change occurs, the control unit 20 calculates the estimated bed temperature 206 calculated based on the previous operation conditions (for example, the operation conditions until the load change occurs) and the operation after the load change occurs. A difference in value from the stabilized catalyst bed temperature when a steady state in which the operating conditions do not vary under the conditions continues is calculated. When the calculated difference is equal to or greater than the predetermined value, it can be determined that a load change equal to or greater than a predetermined value has occurred. As a result of the determination in step S220, when it is determined that the difference between the current estimated bed temperature 206 and the stabilized catalyst bed temperature under the current operating conditions is equal to or greater than a predetermined value (step S220-Y). In step S230, the process proceeds to step S230. Otherwise (step S220-N), the process proceeds to step S250.

  In step S230, the controller 20 stops the calculation of the estimated bed temperature 206 and calculates the delay time TD. The delay time TD can be calculated, for example, according to the exhaust specification of the engine 1 and the load change. The delay time TD is calculated, for example, by referring to a map set in advance based on the result of the experiment.

  Next, in step S240, the control unit 20 determines whether or not the delay time TD calculated in step S230 has elapsed. For example, the elapsed time (delay elapsed counter) is counted by the control unit 20 from the time when the delay time TD is calculated in step S230. As a result of the determination in step S240, if it is determined that the delay time TD has elapsed, the process proceeds to step S260, and if not, the process proceeds to step S220.

  If a negative determination is made in step S220 and the process proceeds to step S250, the delay time TD and the delay elapsed counter are reset by the control unit 20 in step S250. When step S250 is executed, the process proceeds to step S260.

  In step S260, the estimated bed temperature 206 is calculated by the control unit 20.

  The operation from step S270 to step S320 can be the same as that in the second embodiment (from step S130 to step S180 in FIG. 5).

  According to this embodiment, the estimated bed temperature 206 can be calculated as a temperature closer to the actual catalyst bed temperature 204 by adding the delay time TD corresponding to the load change in the calculation of the estimated bed temperature 206. . Thereby, the valve opening timing of the exhaust passage control valve 6 can be set to a more appropriate timing corresponding to the temperature of the upstream catalyst 5.

  Here, instead of adding the delay time TD to the calculation of the estimated bed temperature 206, the delay time (hereinafter referred to as the pre-valve delay time) is inserted before the exhaust passage control valve 6 is opened. It is conceivable to suppress early opening of the passage control valve 6. For example, the opening determination of the exhaust passage control valve 6 is performed based on the estimated bed temperature 205 when the delay time TD corresponding to the load change is not added, and the exhaust passage control valve 6 is actually turned on after the opening determination is made. It is conceivable to include a delay time before the valve opening according to the load change before opening. However, in this case, when the operation information (load or the like) of the engine 1 changes between when the valve opening determination is made and before the delay time before valve opening, the change cannot be dealt with. For example, there is a possibility that the exhaust passage control valve 6 is opened despite the change to operation information that does not require the exhaust passage control valve 6 to be opened. In the present embodiment, even if the operation information of the engine 1 changes during the delay time TD, the estimated bed temperature 206 is calculated corresponding to the change, so that a problem occurs when the delay time before valve opening is included. It is possible to prevent.

It is a schematic block diagram of 1st Embodiment of the exhaust gas purification control apparatus of this invention. It is a catalyst bed temperature map of 1st Embodiment of the exhaust gas purification control apparatus of this invention. It is a flowchart which shows operation | movement of 1st Embodiment of the exhaust gas purification control apparatus of this invention. It is a time chart in case control of 2nd Embodiment of the exhaust gas purification control apparatus of this invention is performed. It is a flowchart which shows operation | movement of 2nd Embodiment of the exhaust gas purification control apparatus of this invention. It is a time chart in case control of 3rd Embodiment of the exhaust gas purification control apparatus of this invention is performed. It is a flowchart which shows operation | movement of 3rd Embodiment of the exhaust gas purification control apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust manifold 3 First path 4 Bypass path 5 Upstream catalyst 6 Exhaust path control valve 7 Exhaust pipe 8 Downstream catalyst 10 Gradient detection means 20 Control part Ta Opening determination threshold Tb Closed valve determination threshold Tc Valve judgment threshold TD delay time

Claims (3)

An upstream catalyst for purifying exhaust gas flowing through the exhaust path of the internal combustion engine;
A downstream catalyst that is provided in the exhaust path downstream from the installation position of the upstream catalyst and purifies exhaust gas flowing through the exhaust path;
A bypass passage for guiding exhaust gas upstream of the upstream catalyst installation position in the exhaust path to the downstream catalyst by bypassing the upstream catalyst;
A flow rate control means for controlling the flow rate of the exhaust gas flowing through the bypass passage by opening and closing at least one of the exhaust passage and the bypass passage;
When bypass control for flowing exhaust gas into the bypass passage is started by the flow rate control means, when returning from the bypass control based on the operation information of the internal combustion engine that affects the temperature of the upstream catalyst. An exhaust purification control device having a return determination means for determining,
Gradient detecting means for detecting the gradient of the traveling path on which the vehicle equipped with the internal combustion engine travels and the magnitude of the ascending gradient are provided,
The return determination means, when it is determined that an upward gradient is detected based on the detection result of the gradient detection means, compared with the case where it is not determined that the upward gradient is detected, the operation information of the internal combustion engine However, it is not determined to return from the bypass control until the temperature of the upstream catalyst reaches a value predicted to be lower ,
The return determination means indicates that the operation information of the internal combustion engine indicates that the upstream engine detected when the upward slope detected by the slope detection means is a large slope, compared with a case where the upward slope is a small slope. The exhaust gas purification control apparatus according to claim 1, wherein it is not determined to return from the bypass control until the temperature of the side catalyst reaches a value predicted to be lower . The exhaust purification control apparatus according to claim 1,
An estimation means for estimating a current temperature of the upstream catalyst based on a transition of operation information of the internal combustion engine;
Whether or not to start the bypass control is determined based on a current temperature of the upstream catalyst estimated by the estimation means . The exhaust purification control apparatus according to claim 1 or 2,
The operation information of the internal combustion engine includes at least one of a load of the internal combustion engine and a rotation speed of the internal combustion engine .

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