JP6582908B2 - Exhaust gas recirculation control method and exhaust gas recirculation control device - Google Patents

Description

  The present invention relates to exhaust gas recirculation control for an internal combustion engine including a turbocharger and an exhaust gas recirculation system.

  An exhaust gas recirculation (EGR) device that recirculates a part of exhaust gas to an intake passage is known to prevent knocking and improve fuel efficiency by reducing pumping loss. In Patent Document 1, as an EGR device applied to an internal combustion engine with a turbocharger, a part of exhaust gas (hereinafter also referred to as EGR gas) is introduced into an intake passage upstream of a compressor of the turbocharger. A low pressure loop EGR device for recirculation is disclosed.

  This low-pressure loop EGR device includes a differential pressure generating valve for ensuring a differential pressure between the intake passage and the exhaust passage even in an operation region where the intake air amount is small. In the operation region where the intake air amount is small, control is performed to open and close the EGR valve that adjusts the EGR gas amount while the differential pressure generating valve is controlled to the closed side. That is, the differential pressure is generated by the differential pressure generating valve, and the EGR gas amount is adjusted by the EGR valve. Further, in the above document, when the EGR rate is changed to a predetermined change amount or more, the operation start order of the differential pressure generating valve and the EGR valve is determined and controlled.

JP 2012-7547 A

  By the way, when the EGR rate changes, the ignition timing is also changed according to the EGR rate. At this time, the ignition timing is generally changed at a constant change rate assuming that the EGR rate changes from the current EGR rate to a new target EGR rate at a constant change rate.

  However, when the differential pressure generating valve and the EGR valve are opened and closed as in the above document, there may be a sudden change in the EGR rate. For example, this is a case where the differential pressure generating valve starts closing when the EGR valve is opening. When the rate of change of the EGR rate becomes steep compared to the rate of change of the ignition timing, the ignition timing is not appropriate for the actual EGR rate, and the combustion stability deteriorates, leading to deterioration of drivability. Will do.

  Therefore, an object of the present invention is to change the EGR rate without deteriorating combustion stability.

According to an aspect of the present invention, the turbocharger, the exhaust gas recirculation passage that communicates the exhaust passage and the intake passage upstream of the compressor of the turbocharger, and the exhaust gas recirculation passage disposed in the exhaust gas recirculation passage. An exhaust gas recirculation control method for an internal combustion engine is provided that includes a circulation amount control valve and a differential pressure generating valve disposed upstream of a junction of fresh air gas and exhaust gas in an intake passage. In this exhaust gas recirculation control method, when exhaust gas recirculation is stopped or exhaust gas recirculation is started, that is, when the exhaust gas recirculation rate is changed, either the exhaust gas recirculation amount control valve or the differential pressure generating valve is selected. When the exhaust gas recirculation control valve is started, the exhaust gas recirculation amount control valve is started first. characterized by Rukoto to initiate the opening operation of the differential pressure generating valve after the closing of the exhaust gas recirculation quantity control valve is completed.

  According to the above aspect, either one of the exhaust gas recirculation amount control valve or the differential pressure generating valve is actuated first, and either one is actuated after the operation of either one is completed. The valves are not activated at the same time. For example, the exhaust gas recirculation amount control valve does not start during operation of the differential pressure generating valve, and only the differential pressure generating valve does not stop when both valves are operating.

  Therefore, there is no period during which the EGR rate changes sharply from the current EGR rate to the target EGR rate. As a result, the EGR rate can be changed without deteriorating the combustion stability.

FIG. 1 is a schematic configuration diagram of an internal combustion engine system. FIG. 2 is an EGR map showing the EGR rate for each operation region. FIG. 3 is a diagram for explaining a history of changes in the EGR rate. FIG. 4 is a flowchart showing the EGR control routine of the first embodiment. FIG. 5 is a timing chart when the EGR control routine of the first embodiment is executed. FIG. 6 is a flowchart showing an EGR control routine of the second embodiment. FIG. 7 is a timing chart when the EGR control routine of the second embodiment is executed. FIG. 8 is a flowchart showing an EGR control routine of the third embodiment. FIG. 9 is a timing chart when the EGR control routine of the third embodiment is executed. FIG. 10 is a flowchart showing an EGR control routine of the fourth embodiment. FIG. 11 is a timing chart when the EGR control routine of the fourth embodiment is executed.

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

[First embodiment]
FIG. 1 is a schematic configuration diagram of a system to which this embodiment is applied.

  In the intake passage 2 of the internal combustion engine 1, a differential pressure generation valve 12, a compressor 4 </ b> A of the turbocharger 4, and a throttle valve 5 for adjusting the engine load are arranged in order from the upstream side of the intake flow. ing. The differential pressure generating valve 12 and the throttle valve 5 are valves that are driven to open and close by an electric motor, and are controlled by a controller 100 described later. Although FIG. 1 shows a butterfly valve as the differential pressure generating valve 12 and the throttle valve 5, other types of valves may be used.

  In the exhaust passage 3 of the internal combustion engine 1, a turbine 4B of the turbocharger 4 and an exhaust purification catalyst 6 are arranged in this order from the upstream side of the exhaust flow. The exhaust purification catalyst 6 is, for example, a three-way catalyst.

  The internal combustion engine 1 includes a bypass passage 7 that communicates the upstream and downstream of the turbine 4 </ b> B of the exhaust passage 3. A waste gate valve 8 that opens and closes the bypass passage 7 is disposed in the bypass passage 7. The waste gate valve 8 is a valve that is opened and closed by an electric motor, and is controlled by a controller 100 described later. When the waste gate valve 8 opens, a part of the exhaust flows around the turbine 4B. Therefore, the supercharging pressure can be adjusted by controlling the opening degree of the waste gate valve 8. That is, the engine load is controlled by the waste gate valve 8 in the operation region where the supercharging pressure exceeds the atmospheric pressure and the throttle valve 5 cannot control the intake amount.

  FIG. 1 shows a swing valve as the waste gate valve 8, but other types of valves may be used.

  The system also includes an EGR device for recirculating a part of the exhaust gas to the intake passage 2. Hereinafter, the exhaust gas to be recirculated is referred to as EGR gas.

  The EGR device passes through an EGR passage 9 communicating with the exhaust passage 3A downstream from the exhaust purification catalyst 6 and the intake passage 2 upstream from the compressor 4A, an EGR valve 10 for opening and closing the EGR passage 9, and the EGR passage 9. And an EGR cooler 11 for cooling the exhaust gas. That is, a so-called low-pressure loop EGR device. The EGR valve 10 is a valve that is driven to open and close by an electric motor, and is controlled by a controller 100 described later. Although FIG. 1 shows a case where the EGR valve 10 is a butterfly valve, other types of valves may be used. The EGR cooler 11 may be either air-cooled or liquid-cooled.

  The internal combustion engine 1 includes a variable valve mechanism 13 for changing the valve timing of the intake valve and the exhaust valve. As the variable valve mechanism 13, a known mechanism may be applied. For example, a mechanism that changes the rotational phase of the intake camshaft with respect to the crankshaft is used.

  The controller 100 sets a fuel injection amount, a fuel injection timing, an ignition timing, an EGR rate, and the like based on detection values of a crank angle sensor, an accelerator opening sensor, an intake pressure sensor, an air flow meter, and the like (not shown). Based on these, the controller 100 controls the opening and closing of the differential pressure generating valve 12, the throttle valve 5, the EGR valve 10, and the waste gate valve 8, and controls the valve timing by causing the variable valve mechanism 13 to operate.

  The controller 100 includes a microcomputer that includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller 100 with a plurality of microcomputers.

  Next, exhaust gas recirculation control (hereinafter also referred to as EGR control) will be described.

  FIG. 2 is an EGR map showing an operation region in which EGR control is executed and an EGR rate. The horizontal axis in FIG. 2 is the engine rotation speed, and the vertical axis is the engine load. The EGR rate is the ratio of EGR gas to fresh air gas.

  The EGR area in the figure is an area for executing EGR control. The EGR region is divided into three regions E1, E2, and E3 according to the EGR rate. The EGR rate is set higher as the rotational speed becomes lower and the load becomes lower. For example, the region E1 is 10%, the region E2 is 15%, and the region E3 is 20%.

  A solid line A <b> 1-A <b> 3 in the region E <b> 3 is an equal opening degree line of the differential pressure generating valve 12. The opening of the solid line A1 is SA1, the opening of the solid line A2 is SA2, and the opening of the solid line A3 is SA3. The magnitude of the opening degree is SA1> SA2> SA3. In the low-pressure loop EGR device, the portion of the intake passage 2 where the EGR gas is introduced is almost atmospheric pressure, so the differential pressure between the intake side and the exhaust side of the EGR valve 10 (hereinafter also referred to as the front-rear differential pressure) is It is smaller than a conventional EGR device (high-pressure loop EGR device) that introduces EGR gas into the negative pressure portion downstream. Particularly, in the low rotation speed and low load region, the exhaust flow rate is small and the pressure in the exhaust passage does not increase, so the differential pressure across the EGR valve 10 decreases. Therefore, the pressure downstream of the differential pressure generating valve 12 is reduced by controlling the differential pressure generating valve 12 in the closing direction as the intake air amount decreases, thereby ensuring the differential pressure across the EGR valve 10.

  Note that the solid line A3 coincides with the upper limit fresh air volume equal fresh air volume line that is not affected even when the differential pressure generating valve 12 is controlled to the closed side. In a region where the intake air amount is small, such as a low rotational speed low load region, controlling the differential pressure generating valve 12 to the closed side does not affect the fresh air amount, but if the intake air amount increases, the differential pressure generating valve 12 Pumping loss occurs and the amount of fresh air is reduced. Therefore, the differential pressure generating valve 12 is fully opened in the regions E2 and E1 that exceed the upper limit fresh air amount that is not affected even if the differential pressure generating valve 12 is controlled to the closed side. That is, the differential pressure generating valve 12 has only a function of generating a differential pressure, and the load is not changed by opening / closing the differential pressure generating valve 12.

  In the regions E1 and E2, the differential pressure generating valve 12 is controlled to be fully opened. This is because the pressure difference across the EGR valve 10 is sufficiently developed even when the pressure in the exhaust passage increases and the differential pressure generating valve 12 is fully open.

  The controller 100 reads the engine rotation speed and the engine load as the operation state, and sets the target EGR rate and the target opening of the differential pressure generating valve 12 by referring to the map of FIG. Then, the controller 100 sets a target opening area of the EGR valve 10 based on the target EGR rate, and controls the opening degree so as to be the opening area. The engine rotation speed is calculated from the detection value of a crank angle sensor (not shown). The engine load may be calculated from a detected value of an air flow meter (not shown) or may be calculated from a detected value of an accelerator opening sensor (not shown).

  Note that the EGR rate is controlled by the opening degree of the EGR valve 10 except in a transient state in which the EGR rate changes, which will be described later. The differential pressure generating valve 12 creates an environment in which the EGR rate changes according to the opening degree of the EGR valve 10, and does not directly control the EGR rate.

  FIG. 3 is a diagram for explaining how the EGR rate changes when the operating point moves from the point on the solid line A1 in the region E3 to the outside of the EGR region, that is, when the EGR control is stopped. The horizontal axis of FIG. 3 indicates the opening area of the EGR valve (EGR / V) 10, and the vertical axis indicates the EGR rate. Moreover, the broken line of FIG. 3 has shown the opening degree of the differential pressure | voltage production valve (ADM / V) 12, respectively.

  When the operating point moves from the region E3 to outside the EGR region, the EGR rate changes from Regr3 to 0%, the EGR / V opening area changes from Segr3 to 0, and the opening of the differential pressure generating valve 12 changes from SA1 to fully open. Change.

  At this time, if the differential pressure generating valve 12 and the EGR valve 10 are operated toward their respective target openings without coordinating, there is a possibility that the EGR rate is sharply reduced. The history L2 in FIG. 3 indicates that the time until the differential pressure generating valve 12 is fully opened is shorter than the time until the EGR valve 10 is fully closed, and the differential pressure generating valve 12 and the EGR valve 10 start operating simultaneously. It is a history of the EGR rate when In this case, the EGR rate sharply decreases while both the differential pressure generating valve 12 and the EGR valve 10 are operating. When the operating state changes, the ignition timing is also changed, but the ignition timing in the transition transition generally changes at a constant rate from point E3 to 0 in FIG. 3 (history in FIG. 3). L1) is set. Therefore, if the history changes such that the EGR rate includes a portion where the EGR rate changes sharply as in the history L2, the combustion stability may deteriorate, leading to deterioration of the drivability. For example, in the history L2, a situation occurs where the actual EGR rate is lower than the assumed EGR rate. In this situation, if ignition is performed based on the history L1, that is, on the assumption that more EGR gas is introduced, knocking may occur.

  Therefore, in the present embodiment, the EGR rate is changed like the history L1 by the following control.

  FIG. 4 is a flowchart showing an EGR control routine executed by the controller 100 when the operating point moves from the EGR region to the outside of the EGR region. This control routine is repeatedly executed at a short interval of about 10 milliseconds, for example.

  This control routine controls the differential pressure generating valve 12 and the EGR valve 10 so that the EGR rate changes with the history L1 described above. Hereinafter, it demonstrates according to the step of a flowchart.

  In step S100, the controller 100 calculates the target EGR rate by searching the map shown in FIG. 2 using the engine speed and the engine load. The engine load is acquired based on the intake air amount or the accelerator opening.

  In step S110, the controller 100 determines whether or not the target EGR rate is 0%. If the target EGR rate is 0%, the process of step S120 is executed, and if not, the current routine is terminated.

  Since this control routine is specialized when the operating point moves from the EGR area to the outside of the EGR area, another control routine is executed when the target EGR rate is not 0%. For example, the EGR valve 10 and the differential pressure generating valve 12 are cooperatively controlled so as to suppress a steep change in the actual EGR rate.

  In step S120, the controller 100 sets a target opening degree (target EGR / V opening degree) of the EGR valve 10 according to the target EGR rate, and an opening degree instruction (EGR / V opening degree) according to the target EGR / V opening degree. ) Is sent to the EGR valve 10 to operate the EGR valve 10.

  In step S130, the controller 100 determines whether or not the actual opening degree of the EGR valve 10 (actual EGR / V opening degree) matches the target EGR / V opening degree. If they match, the process of step S140 is executed. If they do not match, the current routine is terminated.

  In step S140, the controller 100 sets the opening degree (target ADM / V opening degree) of the differential pressure generating valve 12 at the operating point after movement. Note that step S140 is executed in this routine when the target EGR rate is 0%, so that the target ADM / V opening is fully opened.

  In step S150, the controller 100 sends an operation speed instruction (ADM / V opening instruction) according to the target ADM / V opening to the differential pressure generating valve 12 to operate the differential pressure generating valve 12. Here, since the EGR valve 10 is already fully closed and the change in the opening degree of the differential pressure generating valve 12 does not affect the EGR rate, what value is the operating speed of the differential pressure generating valve 12? It doesn't matter.

  As described above, in this control routine, first, the EGR valve 10 is operated, and when the EGR valve 10 is fully closed, the differential pressure generating valve 12 is operated to be fully opened.

  FIG. 5 is a timing chart when the control routine of FIG. 4 is executed when the operating point moves from the region E3 in FIG. 2 to the outside of the EGR region. The solid line in the figure shows the case where the control routine of this embodiment is executed. Further, in the drawing, as a comparative example, a case where the differential pressure generating valve 12 and the EGR valve 10 are started to operate independently and simultaneously is indicated by a broken line.

  In the case of the comparative example, the differential pressure generating valve 12 and the EGR valve 10 start to operate simultaneously at timing T1, the differential pressure generating valve 12 is fully opened at timing T2, and the EGR valve 10 is fully closed at timing T3. ing. As a result, the change in the EGR rate is more steep from timing T1 to timing T2 than from timing T2 to timing T3.

  On the other hand, when the control routine of the present embodiment is executed, the EGR valve 10 first starts the closing operation at the timing T1. Then, after the EGR valve 10 is fully closed at timing T3, the differential pressure generating valve 12 starts to open and is fully opened. If the EGR valve 10 is opened while the opening of the differential pressure generating valve 12 remains constant, the EGR rate changes along the broken line of the opening SA1 in FIG. Since the EGR rate becomes 0% when the EGR valve 10 is fully closed, the EGR rate does not change even if the differential pressure generating valve 12 is subsequently closed. As a result, the EGR rate decreases at a constant change rate as shown in FIG. 5, and the history of the EGR rate becomes the history L1 in FIG.

  As described above, in the present embodiment, when EGR control (exhaust gas recirculation) is stopped, either one of the EGR control valve 10 and the differential pressure generating valve 12 is operated first, After the operation is completed, either one is operated. More specifically, the closing operation of the EGR valve 10 is started first, and the opening operation of the differential pressure generating valve 12 is started after the closing operation of the EGR valve 10 is completed. Thereby, the opening operation of the differential pressure generating valve 12 does not affect the decrease in the EGR rate. Therefore, the controllability of the EGR rate can be improved, and a sharp decrease in the EGR rate can be suppressed.

[Second Embodiment]
The present embodiment is different from the first embodiment in that the operating point moves from outside the EGR region into the EGR region, that is, when starting the EGR control.

  In contrast to the first embodiment, consider a case where the operating point moves from outside the EGR region (EGR rate = 0%) to the region E3 within the EGR region. In this case, if the differential pressure generating valve 12 and the EGR valve 10 are operated toward their respective target openings without cooperation, the EGR rate is maintained while both the differential pressure generating valve 12 and the EGR valve 10 are operating. May rise sharply and combustion stability may decrease. Therefore, in the present embodiment, a sudden change in the EGR rate is suppressed by executing a control routine described below.

  FIG. 6 is a flowchart showing an EGR control routine executed by the controller 100 in the present embodiment. This control routine is repeatedly executed at a short interval of about 10 milliseconds, for example.

  In step S200, the controller 100 calculates the target EGR rate as in step S100 of FIG.

  In step S210, the controller 100 determines whether or not the actual EGR rate at the start of this routine is 0%. If the actual EGR rate is 0%, the controller 100 executes the process of step S220, and otherwise ends the current routine.

  In step S220, the controller 100 calculates the opening degree of the differential pressure generating valve 12 (target ADM / V opening degree) according to the target EGR rate, and sets the differential pressure generating valve 12 to ADM / V according to the target ADM / V opening degree. A V opening instruction is sent to activate the differential pressure generating valve 12. For the target ADM / V opening, for example, the relationship with the target EGR rate is mapped in advance and searched.

  In step S230, the controller 100 determines whether or not the actual opening of the differential pressure generating valve 12 (actual ADM / V opening) is equal to the target ADM / V opening, and if so, the process of step S240 is performed. If it is not equal, the current routine is terminated.

  In step S240, the controller 100 calculates the opening degree of the EGR valve 10 (target EGR / V opening degree) according to the target EGR rate.

  In step S250, the controller 100 sends an operation speed instruction (EGR / V opening instruction) according to the target EGR / V opening to the EGR valve 10 to operate the EGR valve 10. Here, the EGR / V opening instruction is set so that the EGR rate changes at a constant speed.

  As described above, in this control routine, first, the differential pressure generating valve 12 is closed, and when the differential pressure generating valve 12 reaches the target opening, the EGR valve 10 is opened.

  FIG. 7 is a timing chart when the control routine of FIG. 6 is executed when the operating point moves from outside the EGR region to the region E3 in FIG. The solid line in the figure shows the case where the control routine of this embodiment is executed. Further, in the drawing, as a comparative example, a case where the differential pressure generating valve 12 and the EGR valve 10 are started to operate independently and simultaneously is indicated by a broken line.

  In the case of the comparative example, the differential pressure generating valve 12 and the EGR valve 10 start to operate simultaneously at the timing T1, the differential pressure generating valve 12 becomes the opening degree SA1 at the timing T2, and the EGR valve 10 opens at the timing T3. B1. As a result, the change in the EGR rate is more steep from timing T1 to timing T2 than from timing T2 to timing T3.

  On the other hand, when the control routine of the present embodiment is executed, when the target operating point is switched from the outside of the EGR region to the EGR region E3 at the timing T1, first, the differential pressure generating valve 12 in the fully opened state is closed. Start. Then, after the differential pressure generating valve 12 reaches the opening degree SA1 at the timing T2, the EGR valve 10 operates from the fully closed state to the target EGR / V opening degree (B1). The control routine will be described with reference to FIG. 3. When the differential pressure generating valve 12 is closed while the EGR valve 10 is fully closed, the history of changes in the EGR rate when the EGR valve 10 is operated is fully opened. The broken line of the hour is switched to the broken line of the opening degree SA1. Next, by opening the EGR valve 10, the EGR rate increases along the broken line of the opening degree SA1. As a result, the EGR rate increases at a constant change rate as shown in FIG.

  As described above, in this embodiment, when EGR control (exhaust gas recirculation) is started, either one of the EGR control valve 10 and the differential pressure generating valve 12 is operated first, After the operation is completed, either one is operated. More specifically, the closing operation of the differential pressure generating valve 12 is started first, and the opening operation of the EGR valve 10 is started after the closing operation of the differential pressure generating valve 12 is completed. Thereby, the closing operation of the differential pressure generating valve 12 does not affect the increase in the EGR rate. Therefore, the controllability of the EGR rate can be improved, and a sharp increase in the EGR rate can be suppressed.

[Third embodiment]
This embodiment is the same as the first embodiment in that the operating point moves from the EGR region to the outside of the EGR region, but the order of operating the differential pressure generating valve 12 and the EGR valve 10 is the same as that of the first embodiment. Is the opposite.

  In FIG. 3, when the differential pressure generating valve 12 is operated from the opening degree SA1 to the fully open position while the EGR valve 10 is fixed from the point E3, the EGR rate decreases vertically in the figure. When the EGR valve 10 is operated from the opening degree Segr3 to the fully closed state after the differential pressure generating valve 12 is fully opened, the EGR rate decreases along the broken line when fully opened. That is, the history of the EGR rate in FIG. 3 decreases sharply with the opening operation of the differential pressure generating valve 12 and then gradually decreases with the closing operation of the EGR valve 10. However, by setting the operating speeds of the differential pressure generating valve 12 and the EGR valve 10 appropriately as described later, it is possible to make a history such that the EGR rate changes at a constant speed when viewed on the time axis.

  FIG. 8 is a flowchart showing a control routine executed by the controller 100 in the present embodiment. Steps S300 and S310 are the same as steps S100 and S110 in FIG.

  In step S312, the controller 100 sets an EGR rate history. The EGR rate history is, for example, a history in which the EGR rate decreases at a constant speed. In this case, the rate of decrease in the EGR rate due to the opening operation of the differential pressure generating valve 12 is the same as the rate of decrease in the EGR rate due to the closing operation of the EGR valve 10.

  In step S314, the controller 100 calculates the target EGR rate in the current routine determined from the EGR rate history, and the EGR rate and the opening area of the differential pressure generating valve 12 (ADM / V opening area) as shown in the figure. From the table showing the relationship, the ADM / V opening area is calculated.

  In step S320, the controller 100 sends an ADM / V opening degree instruction according to the ADM / V opening area calculated in step S314 to the differential pressure generating valve 12, and operates the differential pressure generating valve 12.

  In step S330, the controller 100 determines that the current opening of the differential pressure generating valve 12 (actual ADM / V opening) is the opening of the differential pressure generating valve 12 (target ADM / V) according to the target EGR rate set in step S300. V opening degree) is determined. If so, the process of step S340 is executed, and if not, the current routine is terminated.

  In step S340, the controller 100 sends an EGR / V opening instruction to the EGR valve 10 to operate the EGR valve 10. Here, an EGR / V opening degree instruction is sent so that the EGR rate changes according to the EGR rate history set in step S312.

  As described above, in the present control routine, first, the differential pressure generating valve 12 is opened, and when the differential pressure generating valve 12 is fully opened, the EGR valve 10 is closed and fully closed. Then, the rate of decrease in the EGR rate due to the opening operation of the differential pressure generating valve 12 is controlled to be equal to the rate of decrease in the EGR rate due to the closing operation of the EGR valve 10.

  FIG. 9 is a timing chart when the control routine of FIG. 8 is executed when the operating point moves from the region E3 in FIG. 2 to the outside of the EGR region. The solid line in the figure shows the case where the control routine of this embodiment is executed. Further, in the drawing, as a comparative example, a case where the differential pressure generating valve 12 and the EGR valve 10 are started to operate independently and simultaneously is indicated by a broken line.

  The comparative example is the same as in FIG.

  In the present embodiment, first, the differential pressure generating valve 12 starts the opening operation at the timing T1. When the differential pressure generating valve 12 is fully opened at timing T3, the EGR valve 10 starts to close, and the EGR valve 10 is fully closed at timing T4. Since the EGR rate decreasing speed due to the opening operation of the differential pressure generating valve 12 and the EGR rate decreasing speed due to the closing operation of the EGR valve 10 are controlled to be equal to each other, as shown in FIG. Decreases at a constant rate until T4.

  In this embodiment, in order to decrease the EGR rate at a constant speed, the EGR rate decreasing rate due to the opening operation of the differential pressure generating valve 12 is equal to the EGR rate decreasing rate due to the closing operation of the EGR valve 10. However, the present invention is not limited to this. As long as the above-described deterioration in drivability does not occur, the rate of decrease in the EGR rate may change midway. That is, there may be a difference between the rate of decrease in the EGR rate due to the opening operation of the differential pressure generating valve 12 and the rate of decrease in the EGR rate due to the closing operation of the EGR valve 10. The extent to which the difference is allowed varies depending on the specifications of the internal combustion engine 1, the configuration of each pipe, and the like, and is determined by conformance.

  Further, while the operating range of the EGR valve 10 is 0 ° to 90 ° in terms of the rotation angle of the shaft, the operating range of the differential pressure generating valve 12 is a range that does not affect the load as described above, and the EGR valve Less than 10 working ranges. For this reason, the differential pressure generating valve 12 is shorter than the EGR valve 10 in the arrival time from the current opening to the target opening when operated at the same speed. That is, if the operating speeds of both valves are the same, the rate of decrease of the EGR rate due to the opening operation of the differential pressure generating valve 12 is faster than the rate of decrease of the EGR rate due to the closing operation of the EGR valve 10. Therefore, the control of the present embodiment is such that the differential pressure generating valve 12 is opened so that the EGR rate decreasing speed due to the opening operation of the differential pressure generating valve 12 does not exceed the decreasing speed of the EGR rate due to the closing operation of the EGR valve 10. It can also be expressed as limiting the speed.

  As described above, in the present embodiment, when EGR control (exhaust gas recirculation) is stopped, either one of the EGR control valve 10 and the differential pressure generating valve 12 is operated first, After the operation is completed, either one is operated. More specifically, when the EGR control is stopped, the opening operation of the differential pressure generating valve 12 is started first, and the closing operation of the EGR valve 10 is started after the opening operation of the differential pressure generating valve 12 is completed. At the same time, the opening operation speed of the differential pressure generating valve 12 is limited so that the EGR rate decreasing speed due to the opening operation of the differential pressure generating valve 12 does not exceed the EGR rate decreasing speed due to the closing operation of the EGR valve 10. By limiting the opening operation speed of the differential pressure generating valve 12 as described above, it is possible to suppress a sharp decrease in the EGR rate.

[Fourth embodiment]
This embodiment is the same as the second embodiment in that the operating point moves from outside the EGR region into the EGR region, but the order in which the differential pressure generating valve 12 and the EGR valve 10 are operated is the same as in the second embodiment. Is the opposite.

  When the operating point moves from outside the EGR region (EGR rate = 0%) to the region E3 in the EGR region, if the differential pressure generating valve 12 is closed after the EGR valve 10 reaches the target opening, 3, the EGR rate rises vertically in the figure as the differential pressure generating valve 12 is closed. That is, the history of the EGR rate in FIG. 3 rises with the closing operation of the EGR valve 10 and then sharply rises with the opening operation of the EGR valve 10. However, by setting the operating speeds of the differential pressure generating valve 12 and the EGR valve 10 appropriately as described later, it is possible to make a history such that the EGR rate changes at a constant speed when viewed on the time axis.

  FIG. 10 is a flowchart showing a control routine executed by the controller 100 in the present embodiment. Steps S400 and S410 are the same as steps S200 and S210 in FIG.

  In step S412, the controller 100 sets an EGR rate history. The EGR rate history is, for example, a history in which the EGR rate increases at a constant speed. In this case, the increasing speed of the EGR rate due to the closing operation of the differential pressure generating valve 12 is the same as the increasing speed of the EGR rate due to the opening operation of the EGR valve 10.

  In step S414, the controller 100 shows the relationship between the target EGR rate in the current routine determined from the EGR rate history and the EGR rate and the opening area (EGR / V opening area) of the EGR valve 10 as shown in the figure. From the table, the EGR / V opening area is calculated.

  In step S420, the controller 100 sends an EGR / V opening instruction according to the EGR / V opening area calculated in step S414 to the EGR valve 10 to operate the EGR valve 10.

  In step S340, the controller 100 determines that the current opening degree of the EGR valve 10 (actual EGR / V opening degree) is the opening degree of the EGR valve 10 corresponding to the target EGR rate set in step S400 (target EGR / V opening degree). It is determined whether or not. If so, the process of step S440 is executed, and if not, the current routine is terminated.

  In step S440, the controller 100 sends an ADM / V opening instruction to the differential pressure generating valve 12 to operate the differential pressure generating valve 12. Here, an ADM / V opening instruction is sent so that the EGR rate changes according to the EGR rate history set in step S412.

  As described above, in this control routine, first, the EGR valve 10 is opened, and when the EGR valve 10 reaches the target EGR / V opening (B1), the differential pressure generating valve 12 is closed. Then, the EGR rate increasing speed due to the closing operation of the differential pressure generating valve 12 is controlled to be equal to the EGR rate increasing speed due to the opening operation of the EGR valve 10.

  FIG. 11 is a timing chart when the control routine of FIG. 10 is executed when the operating point moves from outside the EGR region to the region E3 in FIG. The solid line in the figure shows the case where the control routine of this embodiment is executed. Further, in the drawing, as a comparative example, a case where the differential pressure generating valve 12 and the EGR valve 10 are started to operate independently and simultaneously is indicated by a broken line.

  The comparative example is the same as in FIG.

  In the present embodiment, first, the EGR valve 10 starts to open at timing T1. When the EGR valve 10 reaches the target EGR / V opening (B1) at timing T2, the differential pressure generating valve 12 starts to close, and the differential pressure generating valve 12 reaches the opening SA1 at timing T3. Since the EGR rate increasing speed due to the closing operation of the differential pressure generating valve 12 and the EGR rate increasing speed due to the opening operation of the EGR valve 10 are controlled to be equal to each other, the EGR rate is changed from timing T1 to T3 as shown in the figure. It rises at a constant speed until.

  In addition, it is the same as that of 3rd Embodiment that the raise speed | rate of an EGR rate may change in the range which does not produce deterioration of drivability. Further, the control of the present embodiment is such that the differential pressure generating valve 12 is closed so that the increasing speed of the EGR rate due to the closing operation of the differential pressure generating valve 12 does not exceed the increasing speed of the EGR rate due to the opening operation of the EGR valve 10. It can also be expressed as limiting the speed.

  As described above, in this embodiment, when EGR control (exhaust gas recirculation) is started, either one of the EGR control valve 10 and the differential pressure generating valve 12 is operated first, After the operation is completed, either one is operated. More specifically, when the EGR control is started, the opening operation of the EGR valve 10 is started first, and after the opening operation of the EGR valve 10 is completed, the closing operation of the differential pressure generating valve 12 is started. The closing operation speed of the differential pressure generating valve 12 is limited so that the increasing speed of the EGR rate due to the closing operation of the differential pressure generating valve 12 does not exceed the increasing speed of the EGR rate due to the opening operation of the EGR valve 10. By limiting the closing operation speed of the differential pressure generating valve 12 as described above, a sharp increase in the EGR rate can be suppressed.

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

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake passage 3 Exhaust passage 4 Turbo supercharger 5 Throttle valve 10 EGR valve (Exhaust gas recirculation amount control valve)
12 Differential pressure generating valve 100 Controller

Claims (4)

A turbocharger,
An exhaust gas recirculation passage that communicates an exhaust passage and an intake passage upstream of the compressor of the turbocharger;
An exhaust gas recirculation amount control valve disposed in the exhaust gas recirculation passage;
A differential pressure generating valve disposed upstream of the merged portion of fresh air gas and exhaust gas in the intake passage;
In an exhaust gas recirculation control method for an internal combustion engine comprising:
When changing the exhaust gas recirculation rate,
Either one of the exhaust gas recirculation amount control valve and the differential pressure generating valve is operated after the other valve is operated ,
When stopping the exhaust gas recirculation, first the closing operation of the exhaust gas recirculation amount control valve is started, and after the closing operation of the exhaust gas recirculation amount control valve is completed, the differential pressure generating valve is opened. exhaust gas recirculation control method comprising Rukoto is started. A turbocharger,
An exhaust gas recirculation passage that communicates an exhaust passage and an intake passage upstream of the compressor of the turbocharger;
An exhaust gas recirculation amount control valve disposed in the exhaust gas recirculation passage;
A differential pressure generating valve disposed upstream of the merged portion of fresh air gas and exhaust gas in the intake passage;
In an exhaust gas recirculation control method for an internal combustion engine comprising:
When changing the exhaust gas recirculation rate,
Either one of the exhaust gas recirculation amount control valve and the differential pressure generating valve is operated after the other valve is operated,
When the exhaust gas recirculation is started, the closing operation of the differential pressure generating valve is started first, and the opening operation of the exhaust gas recirculation amount control valve is started after the closing operation of the differential pressure generating valve is completed. An exhaust gas recirculation control method. A turbocharger,
An exhaust gas recirculation passage that communicates an exhaust passage and an intake passage upstream of the compressor of the turbocharger;
An exhaust gas recirculation amount control valve disposed in the exhaust gas recirculation passage;
A differential pressure generating valve disposed upstream of the merged portion of fresh air gas and exhaust gas in the intake passage;
In an exhaust gas recirculation control device for an internal combustion engine comprising:
When changing the exhaust gas recirculation rate, either the exhaust gas recirculation amount control valve or the differential pressure generating valve is operated, and then the other one is operated to stop the exhaust gas recirculation. If, before the to start the closing operation of the exhaust gas recirculation quantity control valve comprises a control unit which Ru to start opening operation of the differential pressure generating valve from closing operation is completed the exhaust gas recirculation control valve An exhaust gas recirculation control device. A turbocharger,
  An exhaust gas recirculation passage that communicates an exhaust passage and an intake passage upstream of the compressor of the turbocharger;
  An exhaust gas recirculation amount control valve disposed in the exhaust gas recirculation passage;
  A differential pressure generating valve disposed upstream of the merged portion of fresh air gas and exhaust gas in the intake passage;
In an exhaust gas recirculation control device for an internal combustion engine comprising:
  When changing the exhaust gas recirculation rate, either the exhaust gas recirculation amount control valve or the differential pressure generating valve is operated, and then the other one is operated to start the exhaust gas recirculation. A control unit that starts the closing operation of the differential pressure generating valve first and starts the opening operation of the exhaust gas recirculation amount control valve after the closing operation of the differential pressure generating valve is completed. Exhaust gas recirculation control device.

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