JP2018071402A - Control device for internal combustion engine - Google Patents

Abstract

An internal combustion engine having a structure in which gas can flow backward from an intake passage to an EGR passage provides a control device capable of suppressing a blow-by gas or a purge gas as a gas to be processed from flowing into an exhaust passage without being processed. A control device according to the present invention detects or predicts that a pressure acting on an intake passage side of an EGR valve is higher or higher than a pressure acting on an exhaust passage side of an EGR valve. Then, the introduction of the gas to be treated into the intake passage is stopped, or the gas introduction system is operated so as to reduce the introduction amount of the gas to be treated into the intake passage. [Selection diagram] FIG.

Description

  The present invention relates to a control device for an internal combustion engine including an EGR device that recirculates EGR gas into an intake passage and a system that introduces blow-by gas or purge gas into the intake passage, and in particular, gas flows backward from the intake passage to the EGR passage. The present invention relates to a control device for an internal combustion engine having a possible structure.

  Japanese Unexamined Patent Application Publication No. 2010-112497 discloses that, in an internal combustion engine equipped with an EGR device, when an acceleration request is made during EGR, the throttle opening is limited until the EGR valve is closed. Thus, a technique for suppressing the air in the intake passage from flowing backward into the EGR passage and flowing into the exhaust passage is disclosed.

JP 2010-121497 A JP-A-2015-0405543

  However, under the condition that the differential pressure between the inlet side and the outlet side of the EGR valve is large, even when the EGR valve is fully closed, minute gas leakage may occur. In addition, the EGR valve may not be fully closed due to a failure, a foreign object, etc., and gas leakage may occur. When such gas leakage occurs in the EGR valve, blow-by gas or purge gas introduced into the intake passage may flow back through the EGR passage and flow into the exhaust passage without being processed.

  The present invention has been made to solve the above-described problems. In an internal combustion engine having a structure in which gas can flow back from an intake passage to an EGR passage, blow-by gas to be processed in a cylinder is blow-by. It is an object of the present invention to provide a control device capable of suppressing the flow of gas and purge gas into an exhaust passage without being processed.

In order to achieve the above object, the present invention introduces an EGR passage connecting an exhaust passage and an intake passage, an EGR valve installed in the EGR passage, and a gas to be treated containing fuel components into the intake passage. In a control device for an internal combustion engine comprising a gas to be treated introduction system,
When it is detected or predicted that the pressure acting on the intake passage side of the EGR valve is higher or higher than the pressure acting on the exhaust passage side of the EGR valve, the intake air of the gas to be processed is detected. The introduction into the passage is stopped or the treatment gas introduction system is operated so as to reduce the introduction amount of the treatment gas into the intake passage.

  According to the present invention, in a situation where the gas may flow backward from the intake passage to the EGR passage, the introduction of the gas to be processed into the intake passage is stopped or the amount of the gas to be processed introduced into the intake passage is small. Since the amount is reduced, it is possible to prevent the gas to be processed from flowing into the exhaust passage without being processed.

It is a figure which shows the system configuration | structure of the internal combustion engine to which the control apparatus of Embodiment 1 of this invention is applied. It is a figure which shows the area | region where the differential pressure | voltage before and behind an EGR valve is large among the operating areas of an internal combustion engine. It is a figure which shows the relationship between the rotational speed of an internal combustion engine, a load, and an EGR valve downstream pressure. It is a figure which shows the relationship between intake air amount and EGR valve upstream pressure. It is a figure which shows the flowchart of valve control of Embodiment 1 of this invention. It is a figure which shows the flowchart of the modification of the valve control of Embodiment 1 of this invention. It is a figure which shows the flowchart of valve control of Embodiment 2 of this invention. It is a figure which shows the flowchart of the modification of the valve control of Embodiment 2 of this invention. It is a figure which shows the system configuration | structure of the internal combustion engine to which the control apparatus of Embodiment 3 of this invention is applied. It is a figure which shows the area | region where the operating point of an internal combustion engine may enter into the area | region where the differential pressure before and behind an EGR valve reverses before an EGR valve closes at the time of full open acceleration. It is a figure which shows the flowchart of valve control of Embodiment 3 of this invention. It is a figure which shows the flowchart of the modification 1 of the valve control of Embodiment 3 of this invention. It is a figure which shows the flowchart of the modification 2 of valve control of Embodiment 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. However, in the embodiment shown below, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the reference However, the present invention is not limited to these numbers. Further, the structures described in the embodiments described below are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

1. Embodiment 1
1-1. Configuration of Internal Combustion Engine FIG. 1 is a diagram showing a system configuration of an internal combustion engine to which the control device of Embodiment 1 of the present invention is applied. The internal combustion engine 2 includes an engine body 4 configured as a spark ignition engine. The engine body 4 is attached with a number of devices and actuators, such as a fuel injection valve, an intake valve and a valve mechanism for driving the intake valve, an exhaust valve and a valve mechanism for driving the exhaust valve, and a spark plug, all not shown. Yes.

  An intake passage 6 for sucking air from the outside is connected to the intake port of the engine body 4. In the intake passage 6, an air cleaner 12, a compressor 20 a, an intercooler 14, and a throttle 16 are arranged in this order from the upstream toward the engine body 4.

  An exhaust passage 8 for discharging exhaust gas to the outside is connected to the exhaust port of the engine body 4. A turbine 20b, a first three-way catalyst 24, and a second three-way catalyst 26 constituting the turbocharger 20 together with the compressor 20a are arranged in this order in the exhaust passage 8 from the engine body 4 to the downstream. Has been. The first three-way catalyst 24 is provided in the vicinity of the outlet of the turbine 20b, and the second three-way catalyst 26 is provided under the floor of the vehicle.

  The internal combustion engine 2 includes an EGR device 30 that recirculates part of the exhaust gas from the exhaust passage 8 to the intake passage 6. The EGR device 30 includes an EGR passage 32, an EGR cooler 36, and an EGR valve 34. The EGR passage 32 connects the exhaust passage 8 downstream of the first three-way catalyst 24 and upstream of the second three-way catalyst 26 and the intake passage 6 downstream of the throttle 16. Specifically, the tip of the EGR passage 32 is branched for each cylinder, and each of the branched EGR passages 32 is connected to an intake manifold constituting the intake passage 6. The EGR cooler 36 is provided in the EGR passage 32. The EGR valve 34 is provided in the EGR passage 32 downstream of the EGR cooler 36 in the direction of EGR gas flow (forward flow direction).

  The internal combustion engine 2 includes a purge gas introduction system 40 that introduces evaporated fuel generated in the fuel tank 10 into the intake passage 6 as a purge gas. The purge gas is a gas to be processed containing a fuel component, and the purge gas introduction system 40 is a gas to be processed introduction system that introduces the gas to be processed into the intake passage 6. The purge gas introduction system 40 includes a canister 42, a purge gas passage 44, an ejector 46, and a purge gas valve 48. The canister 42 temporarily adsorbs and stores the evaporated fuel generated in the fuel tank 10. The purge gas passage 44 connects the canister 42 to the upstream side of the compressor 20 a in the intake passage 6. The ejector 46 is a device that uses the differential pressure between the upstream side and the downstream side of the compressor 20 a to suck purge gas from the canister 42. The ejector 46 is provided in the purge gas passage 44. The purge gas valve 48 is provided in the purge gas passage 44 downstream of the ejector 46 in the direction of the purge gas flow, and is used to adjust the flow rate of the purge gas introduced from the purge gas passage 44 into the intake passage 6. In the supercharging region where the supercharging by the compressor 20a is performed, the purge gas is sucked from the canister 42 into the purge gas passage 44 by the action of the ejector 46, and the purge gas having a flow rate corresponding to the opening of the purge gas valve 48 is passed from the purge gas passage 44 to the intake passage 6. To be introduced.

  The internal combustion engine 2 includes a blow-by gas introduction system 50 that introduces blow-by gas generated in the engine body 4 into the intake passage 6. The blow-by gas is also a gas to be processed containing a fuel component, and the blow-by gas introduction system 50 is also a gas to be processed to be introduced into the intake passage 6. The blow-by gas introduction system 50 includes a blow-by gas passage 54, an ejector 56, and a blow-by gas valve 58. The blow-by gas passage 54 connects the interior of the engine body 4 to the upstream side of the compressor 20 a in the intake passage 6. The ejector 56 is a device that uses the differential pressure between the upstream side and the downstream side of the compressor 20 a to suck blow-by gas from the inside of the engine body 4. The ejector 56 is provided in the blow-by gas passage 54. The blow-by gas valve 58 is provided in the blow-by gas passage 54 downstream of the ejector 56 in the blow-by gas flow direction, and is used to adjust the flow rate of the blow-by gas introduced from the blow-by gas passage 54 into the intake passage 6. In the supercharging region where supercharging by the compressor 20a is performed, blow-by gas is sucked into the blow-by gas passage 54 from the inside of the engine body 4 by the action of the ejector 56, and blow-by gas having a flow rate according to the opening degree of the blow-by gas valve 58 is blow-by. It is introduced from the gas passage 54 into the intake passage 6.

  The internal combustion engine 2 includes a control device 100. The control device 100 measures the state quantity of the internal combustion engine 2 such as the accelerator opening, the amount of air taken into the intake passage 6, the pressure at the inlet of the EGR passage 32, the pressure at the outlet of the EGR passage 32, and the engine speed. A plurality of sensors are connected. The control device 100 controls the operation of the internal combustion engine 2 by operating various devices and actuators included in the internal combustion engine 2 based on information obtained by these sensors. The control device 100 is an ECU (Electronic Control Unit) having at least one CPU, at least one ROM, and at least one RAM. However, the control apparatus 100 may be comprised from several ECU. In the control device 100, various functions relating to engine control are realized by loading a program stored in the ROM into the RAM and executing the program by the CPU.

1-2. Valve Control in Embodiment 1 In the internal combustion engine 2 having the above-described configuration, the pressure on the intake passage 6 side of the EGR valve 34 (hereinafter also referred to as the EGR valve downstream pressure) is the pressure on the exhaust passage 8 side of the EGR valve 34 (hereinafter referred to as the pressure). , Sometimes referred to as EGR valve upstream pressure). If the differential pressure between the EGR valve downstream pressure and the EGR valve upstream pressure becomes large, a minute gas may leak from the downstream side of the EGR valve 34 to the upstream side even though the EGR valve 34 is closed. There is. When the purge gas or blow-by gas introduced into the intake passage 6 is included in this gas, they are discharged from the exhaust passage without being subjected to the combustion treatment, so that the emission performance of the internal combustion engine 2 is deteriorated.

  Such a problem occurs in a low-rotation / high-load region indicated as “region A” on the plane having the engine load and the engine speed as axes shown in FIG. This is because the EGR valve downstream pressure depends on the engine load and the EGR valve upstream pressure depends on the intake air amount, so that the differential pressure before and after the EGR valve 34 becomes particularly large at low rotation and high load. . FIG. 3 is a diagram showing a relationship among the engine speed, the engine load, and the EGR valve downstream pressure. From this figure, it can be seen that the EGR valve downstream pressure increases as the load increases. FIG. 4 is a graph showing the relationship between the intake air amount and the EGR valve upstream pressure. From this figure, it can be seen that the EGR valve upstream pressure decreases as the intake air amount decreases, that is, as the engine rotation speed decreases and the engine load decreases.

  A region A shown in FIG. 2 is a region used only during acceleration that is not used in steady running. However, unless any countermeasure is taken, at least during acceleration, the fuel component contained in the purge gas or blow-by gas is released into the atmosphere as it is due to the backflow of the EGR gas. Therefore, the control device 100 executes control of the purge gas valve 48 and the blow-by gas valve 58 (hereinafter simply referred to as valve control) described below in order to suppress the influence of the backflow of EGR gas on the emission performance.

  FIG. 5 is a diagram illustrating a flowchart of valve control executed by the control device 100. Hereinafter, details of the valve control will be described with reference to this flowchart.

  In step S1, the current engine speed, engine load, and accelerator opening are read. The engine rotation speed is calculated from a signal from a crank angle sensor that outputs a signal corresponding to the rotation angle of the crankshaft. The engine load is calculated from, for example, the intake air amount measured by an air flow sensor installed at the inlet of the intake passage 6 and the engine speed. The accelerator opening is calculated from a signal of an accelerator opening sensor that outputs a signal corresponding to the depression amount of the accelerator pedal.

  In step S2, it is determined whether or not an acceleration in which the operating point of the internal combustion engine 2 defined by the engine speed and the engine load enters the region A is required. Specifically, a required torque for the internal combustion engine 2 and a required speed ratio for a transmission (not shown) are calculated from the accelerator opening acquired in step S1. Then, the locus of the operating point of the internal combustion engine 2 when the required torque and the required gear ratio are achieved based on the current engine speed and engine load is predicted, and the operating point enters the region A based on the predicted locus. It is determined whether or not. 2 is a region where the operating point of the internal combustion engine 2 may enter the region A due to acceleration.

  If acceleration is not required so that the operating point of the internal combustion engine 2 enters the region A, the subsequent steps are skipped and the process returns to step S1 again. However, if acceleration is requested such that the operating point of the internal combustion engine 2 enters the region A, steps S3 to S5 are executed.

  In step S3, the purge gas valve 48 and the blow-by gas valve 58 are fully closed. Thereby, introduction of purge gas and blow-by gas into the intake passage 6 is cut off.

  In step S4, it is determined whether or not a predetermined time has elapsed since the purge gas valve 48 and the blow-by gas valve 58 are fully closed. This fixed time is a time during which the operating point of the internal combustion engine 2 is predicted to stay in the region A. Since the region A is a region that is used only during acceleration that is not used in steady running, the operating point of the internal combustion engine 2 does not continue to remain in the region A. The time during which the operating point of the internal combustion engine 2 stays in the region A depends on the degree of acceleration, but the assumed maximum time may be the fixed time used for determination in step S4.

  The purge gas valve 48 and the blow-by gas valve 58 are kept fully closed until a certain time has elapsed. And step S5 is performed when the fixed time passes. In step S5, the control of the purge gas valve 48 and the blow-by gas valve 58 is returned to the normal control. The normal control here means that the purge gas valve 48 is controlled to an opening required from the amount of evaporated fuel in the fuel tank 10, and the blow-by is adjusted to the opening required from the amount of blow-by gas generated in the engine body 4. This means that the gas valve 58 is controlled. However, the specific content of normal control is not limited.

  By performing the valve control described above, even if a back flow of gas occurs in the EGR valve 34 during acceleration, the introduction of purge gas and blow-by gas into the intake passage 6 is cut off, so that combustion processing is performed in the cylinder. It is possible to suppress the blow-by gas and the purge gas, which are to-be-processed gases, from flowing into the exhaust passage 8 without being processed.

  In step S3 of the above-described flowchart, the purge gas valve 48 and the blow-by gas valve 58 are fully closed, but may be closed by a certain amount without being fully closed. Alternatively, only one of the purge gas valve 48 and the blow-by gas valve 58 may be fully closed and the other may be closed by a certain amount. Alternatively, only one of the purge gas valve 48 and the blow-by gas valve 58 may be fully closed or closed by a certain amount, and the other may be kept under normal control. In any embodiment, since the amount of fuel component contained in the gas flowing back through the EGR valve 34 can be reduced, the EGR valve 34 is compared with the case where the purge gas valve 48 and the blow-by gas valve 58 are controlled depending on the situation. The influence of the backflow of gas on the emission performance can be suppressed. Note that the modified example related to step S3 also applies to a modified example of valve control of the first embodiment described below.

  Further, in step S4 of the above-described flowchart, it is a condition that the process proceeds to step S5 when a certain time elapses. However, the current engine rotation speed and the engine load are calculated each time, and the operating point of the internal combustion engine 2 is a region. You may determine whether it went out of A each time. Note that the modification regarding step S4 also applies to the modification of valve control according to the first embodiment described below.

1-3. By the way, according to the configuration shown in FIG. 1, the EGR passage 32 branches from the upstream of the second three-way catalyst 26 in the exhaust passage 8. For this reason, the gas flowing backward through the EGR passage 32 always passes through the second three-way catalyst 26 when flowing through the exhaust passage 8. If the second three-way catalyst 26 is sufficiently warmed up so that its purification ability can be exhibited, even if the fuel component is mixed in the gas flowing backward through the EGR passage 32, Since it is purified by the three-way catalyst 26, release into the atmosphere is suppressed. Conversely, if the second three-way catalyst 26 is sufficiently warm, the purge gas valve 48 and the blow-by gas valve 58 need not be closed. On the contrary, by continuing to release evaporated fuel and blow-by gas without closing them, it is possible to prevent the internal pressure of the fuel tank 10 from rising, and to prevent deterioration of oil due to the stay of blow-by gas in the engine body 4. Can be prevented.

  FIG. 6 is a flowchart illustrating a modification of the valve control according to the first embodiment. In this flowchart, the same step number is assigned to the same process as that performed in the valve control of the first embodiment. In the following description, the contents already described in the description of the valve control of the first embodiment are omitted, and the contents specific to this modification will be described.

  In the variation of the valve control according to the first embodiment, when it is determined in step S2 that acceleration is required such that the operating point of the internal combustion engine 2 enters the region A, the determination in step S6 is subsequently performed. In step S6, it is determined whether the temperature of the second three-way catalyst (shown as U / F catalyst in the figure) 26 is lower than a predetermined temperature. This predetermined temperature is a temperature at which the second three-way catalyst 26 is activated. The temperature of the second three-way catalyst 26 may be measured, for example, by measuring the bed temperature of the second three-way catalyst 26 using a sensor, or may be estimated from the exhaust temperature measured by the sensor.

  When the temperature of the second three-way catalyst 26 is equal to or higher than a predetermined temperature, the second three-way catalyst 26 is activated. Even if a part of the purge gas or blow-by gas flows into the exhaust passage 8, the fuel component contained therein is purified by the second three-way catalyst 26. Therefore, since it is not necessary to cut off the introduction of purge gas or blow-by gas into the intake passage 6, control of the purge gas valve 48 and blow-by gas valve 58 is maintained at normal control. The subsequent steps are skipped and the process returns to step S1 again.

  When the temperature of the second three-way catalyst 26 is lower than the predetermined temperature, the second three-way catalyst 26 is not activated. In this case, step S3 is selected, and the purge gas valve 48 and the blow-by gas valve 58 are fully closed. As a result, the introduction of the purge gas and blow-by gas into the intake passage 6 is cut off, so that the fuel component is prevented from flowing into the exhaust passage 8 together with the gas flowing backward through the EGR valve 34.

2. Embodiment 2
2-1. Configuration of Internal Combustion Engine A system configuration of the internal combustion engine to which the control device of Embodiment 2 of the present invention is applied is shown in FIG. That is, since the system configuration is the same as that of the internal combustion engine to which the control device of the first embodiment is applied, the description thereof is omitted.

2-2. Valve Control of Embodiment 2 If the flow of the fuel component to the exhaust passage 8 due to the backflow of gas through the EGR valve 34 is more reliably suppressed, the purge gas must be purged when the EGR valve downstream pressure is larger than the EGR valve upstream pressure. The valve 48 and the blow-by gas valve 58 may be closed. However, if the purge gas valve 48 remains closed, the internal pressure of the fuel tank 10 becomes excessive. Further, when the blow-by gas valve 58 remains closed, the deterioration of the oil by the staying blow-by gas proceeds. Therefore, the purge gas valve 48 and the blow-by gas valve 58 cannot simply be closed just because the gas is flowing back through the EGR valve 34. Therefore, the control device 100 performs valve control on the purge gas valve 48 and the blow-by gas valve 58 according to the flowchart shown in FIG.

  FIG. 7 is a diagram illustrating a flowchart of valve control executed by the control device 100 in the second embodiment. Hereinafter, the details of the valve control according to the second embodiment will be described with reference to this flowchart.

  In step S11, the amount of blow-by gas staying in the engine body 4 is estimated. Further, the amount of evaporated fuel in the fuel tank 10 is estimated. These estimation methods are not limited. Since various methods have been proposed for both, these conventional methods can be used. For example, Japanese Patent Application Laid-Open No. 2004-204829 describes an example of a method for estimating the amount of evaporated fuel.

  In step S12, it is determined whether or not the blow-by gas discharge can be stopped based on the blow-by gas amount estimated in step S11. Further, it is determined whether or not the purge gas discharge can be stopped based on the evaporated fuel amount estimated in step S11. If the amount of blow-by gas exceeds a predetermined allowable value, the blow-by gas cannot be stopped. Further, when the amount of evaporated fuel exceeds a predetermined allowable value, the purge gas discharge cannot be stopped. In these cases, step S15 is selected. In step S15, the valve corresponding to the negative determination result in step S12 is controlled as usual. For example, if the blow-by gas cannot be stopped, the blow-by gas valve 58 is controlled as usual.

  When the amount of blow-by gas is less than the allowable value, the blow-by gas discharge can be stopped if it is temporary. Further, when the amount of evaporated fuel is less than the allowable value, the purge gas can be stopped if it is temporary. In these cases, step S13 is selected. In step S13, it is determined whether or not the difference between the EGR valve downstream pressure and the EGR valve upstream pressure is greater than zero, that is, whether or not the gas can flow back through the EGR valve 34. If the EGR valve downstream pressure is equal to or lower than the EGR valve upstream pressure, the gas does not flow back through the EGR valve 34, and the purge gas or blow-by gas does not flow through the EGR passage 32 into the exhaust passage 8. Therefore, in this case, step S15 is selected. In step S15, both the purge gas valve 48 and the blow-by gas valve 58 are controlled as usual.

  When the EGR valve downstream pressure is larger than the EGR valve upstream pressure, the gas flows backward through the EGR valve 34 when the EGR valve 34 is open or when there is a leak in the EGR valve 34. In this case, step S14 is selected. In step S14, the valve corresponding to the positive determination result in step S12 is fully closed. For example, if only the purge gas can be stopped, only the purge gas valve 48 is fully closed. If both the purge gas and the blowby gas can be stopped, both the purge gas valve 48 and the blowby gas valve 58 are fully closed. Closing is done.

  By performing the valve control described above, the amount of blow-by gas that stays in the engine body 4 and the amount of evaporated fuel in the fuel tank 10 do not exceed an allowable value under the condition that the gas can flow back through the EGR valve 34. In the limit, the introduction of purge gas or blow-by gas into the intake passage 6 is cut off. As a result, blow-by gas and purge gas, which are gas to be processed in the cylinder, are prevented from flowing into the exhaust passage 8 without being processed.

  In step S12 of the above-described flowchart, it is determined whether or not the purge gas or blow-by gas release can be stopped, but it may be determined whether or not the purge gas or blow-by gas discharge amount can be reduced. As the determination method, for example, it may be determined whether or not the discharge amount of the purge gas can be reduced depending on whether or not the amount of evaporated fuel in the fuel tank 10 is less than a predetermined allowable value. Whether the blow-by gas discharge amount can be reduced may be determined based on whether or not the blow-by gas amount is less than a predetermined allowable value. If the purge gas release amount can be reduced, the purge gas valve 48 is closed by a predetermined amount in step S14, and if the blow-by gas release amount can be reduced, the blow-by gas valve 58 is closed by a predetermined amount in step S14. May be. It should be noted that the modification regarding steps S12 and S14 also applies to the modification of valve control of the second embodiment described below.

2-3. Modified Example of Valve Control of Second Embodiment The active state of the second three-way catalyst 26 may be reflected in the valve control of the second embodiment. FIG. 8 is a diagram illustrating a flowchart of a modification of the valve control according to the second embodiment. In this flowchart, the same step number is assigned to the same process as that performed in the valve control of the second embodiment. In the following description, the contents already described in the description of the valve control of the second embodiment are omitted, and the contents specific to this modification will be described.

  In the modification of the valve control according to the second embodiment, when it is determined in step S13 that the differential pressure between the EGR valve downstream pressure and the EGR valve upstream pressure is greater than zero, the determination in step S16 is subsequently performed. In step S16, it is determined whether or not the temperature of the second three-way catalyst (shown as U / F catalyst in the figure) 26 is lower than a predetermined temperature. This predetermined temperature is a temperature at which the second three-way catalyst 26 is activated.

  Step S15 is selected when the temperature of the second three-way catalyst 26 is equal to or higher than the predetermined temperature. If the second three-way catalyst 26 is activated, even if a part of the purge gas or blow-by gas flows into the exhaust passage 8, the fuel component contained therein is purified by the second three-way catalyst 26. . Therefore, in step S15, both the purge gas valve 48 and the blow-by gas valve 58 are controlled as usual.

  When the temperature of the second three-way catalyst 26 is lower than the predetermined temperature, the second three-way catalyst 26 is not activated. In this case, step S14 is selected. In step S14, the valve corresponding to the positive determination result in step S12 is fully closed. As a result, the introduction of purge gas or blow-by gas into the intake passage 6 is cut, so that the fuel component is prevented from flowing into the exhaust passage 8 together with the gas flowing backward through the EGR valve 34.

3. Embodiment 3
3-1. Configuration of Internal Combustion Engine FIG. 9 is a diagram showing a system configuration of an internal combustion engine to which the control device of Embodiment 3 of the present invention is applied. In the system configuration of the internal combustion engine shown in FIG. 9, the same components as those in the system configuration of the internal combustion engine shown in FIG. In the following description, the contents already described in the description of the system configuration of the internal combustion engine shown in FIG. 1 are omitted, and elements unique to the system configuration of the internal combustion engine shown in FIG. 9 will be described.

  The internal combustion engine 3 according to Embodiment 3 includes two systems of purge gas introduction systems 40 and 60. The first purge gas introduction system 40 is a system that draws purge gas from the canister 42 using the ejector 46, and functions in a supercharging region where a differential pressure is generated before and after the compressor 20a. In the NA region (natural intake region) where the differential pressure does not occur before and after the compressor 20a, the ejector 46 does not function, so the introduction of purge gas from the purge gas passage 44 to the intake passage 6 stops. Since the configuration of the first purge gas introduction system 40 has already been described, the description thereof is omitted here.

  The second purge gas introduction system 60 includes a purge gas passage 62 that connects the canister 42 to the intake passage 6 downstream of the throttle 16, and a purge gas valve 64 provided in the purge gas passage 62. When the pressure on the downstream side of the throttle 16 in the intake passage 6 is negative, purge gas is sucked into the purge gas passage 62 from the canister 42 by the action of the negative pressure, and the purge gas having a flow rate corresponding to the opening of the purge gas valve 64 is purged. 62 is introduced into the intake passage 6. In the supercharging region where the supercharging by the compressor 20a is performed, the pressure on the downstream side of the throttle 16 in the intake passage 6 becomes a positive pressure, so the introduction of the purge gas from the purge gas passage 62 to the intake passage 6 stops. In the following description, the purge gas valve 64 of the second purge gas introduction system 60 is referred to as a second purge gas valve, and the purge gas valve 48 of the first purge gas introduction system 40 is referred to as a first purge gas valve.

  The internal combustion engine 3 according to Embodiment 3 includes two systems of blow-by gas introduction systems 50 and 70. The first blow-by gas introduction system 50 is a system that sucks blow-by gas from the inside of the engine body 4 using the ejector 56, and functions in a supercharging region where differential pressure is generated before and after the compressor 20a. Since the ejector 56 does not function in the NA region where no differential pressure occurs before and after the compressor 20a, the introduction of the purge gas from the blow-by gas passage 54 to the intake passage 6 is stopped. Since the configuration of the first blow-by gas introduction system 50 has already been described, the description thereof is omitted here.

  The second blow-by gas introduction system 70 includes a blow-by gas passage 72 that connects the interior of the engine body 4 to the intake passage 6 downstream of the throttle 16, and a blow-by gas valve 74 provided in the blow-by gas passage 72. When the pressure on the downstream side of the throttle 16 in the intake passage 6 is negative, blow-by gas is sucked into the blow-by gas passage 72 from the inside of the engine body 4 by the action of the negative pressure, and the flow rate according to the opening degree of the blow-by gas valve 74. The blow-by gas is introduced into the intake passage 6 from the blow-by gas passage 72. In the supercharging region where the supercharging by the compressor 20a is performed, the pressure on the downstream side of the throttle 16 in the intake passage 6 becomes a positive pressure, so the introduction of blowby gas from the blowby gas passage 72 to the intake passage 6 stops. In the following description, the blow-by gas valve 74 of the second blow-by gas introduction system 70 is referred to as a second blow-by gas valve, and the blow-by gas valve 58 of the first blow-by gas introduction system 50 is referred to as a first blow-by gas valve.

  The internal combustion engine 3 includes a control device 102. The first purge gas valve 48, the second purge gas valve 64, the first blow-by gas valve 58, and the second blow-by gas valve 74 are operated by the control device 102. In the third embodiment, these valves 48, 64, 58, 74 are controlled by valve control executed by the control device 102.

3-2. Valve control according to Embodiment 3 The fact that the EGR valve downstream pressure becomes higher than the EGR valve upstream pressure is indicated as “region C” in the plane with the engine load and the engine speed shown in FIG. 10 as axes. This is a phenomenon that occurs in high-load areas. Since the EGR gas cannot be introduced into the intake passage 6 in the region C, the control device 102 fully closes the EGR valve 34 in the region C.

  However, a certain amount of time is required until the EGR valve 34 is completely closed. For this reason, immediately after the operating point of the internal combustion engine 3 enters the region C, the EGR valve 34 is not yet completely closed, and there is a possibility that the gas flows backward through the EGR valve 34. The operating point of the internal combustion engine 3 enters the region C at the time of acceleration. Whether the EGR valve 34 is closed before entering the region C depending on the distance from the operating point before the acceleration to the region C and the degree of acceleration. It will be decided. A “region B” surrounded by a broken line in FIG. 10 is a region where the operating point of the internal combustion engine 3 may enter the region C before the EGR valve 34 is closed during full open acceleration. Since the supercharging response is faster as the engine speed and the engine load are larger, the region B tends to spread to the high rotation / high load side. In order to prevent the fuel component from flowing into the exhaust passage 8 together with the gas flowing back through the EGR valve 34, when the operating point of the internal combustion engine 2 is predicted to enter the region C, the valves 48, 64, 58 and 74 are closed. What should I do?

  FIG. 11 is a diagram illustrating a flowchart of valve control executed by the control device 102. Hereinafter, the details of the valve control according to the third embodiment will be described with reference to this flowchart.

  In step S21, the current engine speed, engine load, and accelerator opening are read. In step S22, it is determined whether the opening degree of the EGR valve 34 is larger than zero, that is, whether the EGR valve 34 is not fully closed. The opening degree of the EGR valve 34 is measured by a sensor. If the EGR valve 34 is fully closed, the subsequent steps are skipped and the process returns to step S21 again. In this case, control of each valve 48, 64, 58, 74 is maintained at normal control.

  If the EGR valve 34 is open, step S23 is selected. In step S23, it is determined whether or not the operating point of the internal combustion engine 2 is in the region B. If the operating point is not in the region B, the EGR valve 34 can be closed before the operating point enters the region C even when the internal combustion engine 3 is fully opened. Therefore, the subsequent steps are skipped and returned to step S21 again, and the control of each valve 48, 64, 58, 74 is maintained at normal control.

  If the operating point of the internal combustion engine 2 is in the region B, step S24 is selected. In step S24, it is determined whether the acceleration request value is larger than a threshold value. Even if the operating point is in the region B, if the acceleration from there is slow, the EGR valve 34 can be closed before the operating point enters the region C. The acceleration request value is a parameter indicating the magnitude of the requested acceleration, and is calculated from the accelerator opening. The threshold value for the acceleration request value is a criterion for determining whether or not each valve 48, 64, 58, 74 is closed. Whether or not the operating point enters the region C due to acceleration also depends on the position of the current operating point. Therefore, the threshold value is not a fixed value but a variable depending on the engine speed and the engine load. If the acceleration request value is less than or equal to the threshold value, the subsequent steps are skipped and returned to step S21 again, and the control of each valve 48, 64, 58, 74 is maintained in the normal control. However, if the acceleration request value is larger than the threshold value, steps S25 to S28 are executed.

  In step S25, the second purge gas valve 64 and the second blow-by gas valve 74 are fully closed. Thereby, introduction of purge gas and blow-by gas into the intake passage 6 in the NA region is cut.

  In step S26, the first purge gas valve 48 and the first blow-by gas valve 58 are fully closed. Thereby, introduction of purge gas and blow-by gas into the intake passage 6 in the supercharging region is cut.

  In step S27, it is determined whether or not the EGR valve 34 is fully closed. Until the EGR valve 34 is fully closed, the valves 48, 64, 58, and 74 are kept fully closed. Then, step S28 is executed when the EGR valve 34 is fully closed. In step S28, the control of each valve 48, 64, 58, 74 is returned to normal control.

  If the EGR valve 34 is not fully closed before the operating point of the internal combustion engine 3 enters the region where the EGR valve downstream pressure is higher than the EGR valve upstream pressure by performing the valve control described above, the intake passage 6 The introduction of purge gas and blow-by gas into the air is cut in advance. As a result, blow-by gas and purge gas, which are gas to be processed in the cylinder, are prevented from flowing into the exhaust passage 8 without being processed.

  In step S26 of the above-described flowchart, the first purge gas valve 48 and the first blow-by gas valve 58 are fully closed, but they may be closed by a certain amount without being fully closed. Alternatively, only one of the first purge gas valve 48 and the first blow-by gas valve 58 may be fully closed and the other may be closed by a certain amount. Alternatively, only one of the first purge gas valve 48 and the first blow-by gas valve 58 may be fully closed or closed by a certain amount, and the other may be kept under normal control. A similar modification applies to the opening of the second purge gas valve 64 and the opening of the second blow-by gas valve 74 set in step S25. And the modification regarding these steps S25 and S26 is applicable also to the modification of valve control of Embodiment 3 explained below.

3-3. Modification Example 1 of Valve Control of Embodiment 3
The active state of the second three-way catalyst 26 may be reflected in the valve control of the third embodiment. FIG. 12 is a diagram illustrating a flowchart of the first modification of the valve control according to the third embodiment. In this flowchart, the same step number is assigned to the same process as that performed in the valve control of the third embodiment. In the following description, the contents already described in the description of the valve control of the third embodiment will be omitted, and the contents specific to the first modification will be described.

  In the first variation of the valve control according to the third embodiment, if it is determined in step S24 that the acceleration request value is greater than the threshold value, the determination in step S29 is subsequently performed. In step S29, it is determined whether or not the temperature of the second three-way catalyst (shown as U / F catalyst in the figure) 26 is lower than a predetermined temperature. This predetermined temperature is a temperature at which the second three-way catalyst 26 is activated.

  When the temperature of the second three-way catalyst 26 is equal to or higher than a predetermined temperature, even if a part of the purge gas or blow-by gas flows into the exhaust passage 8, the fuel component contained therein is purified by the second three-way catalyst 26. The Therefore, control of each valve 48, 64, 58, 74 is maintained at normal control, and the subsequent steps are skipped and returned to step S21 again.

  When the temperature of the second three-way catalyst 26 is lower than the predetermined temperature, steps S25 and S26 are selected, and the valves 48, 64, 58, and 74 are fully closed. As a result, the introduction of the purge gas and blow-by gas into the intake passage 6 is cut off, so that the fuel component is prevented from flowing into the exhaust passage 8 together with the gas flowing backward through the EGR valve 34.

3-4. Variation 2 of valve control of Embodiment 3
When the operating point of the internal combustion engine 3 is in the region B, the valves 48, 64, 58, and 74 may always be fully closed regardless of the magnitude of the acceleration request. FIG. 13 is a diagram illustrating a flowchart of a second modification of the valve control according to the third embodiment. In this flowchart, the same step number is assigned to the same process as that performed in the valve control of the third embodiment. In the following description, the contents already described in the description of the valve control according to the third embodiment will be omitted, and the contents specific to the second modification will be described.

  In the second variation of the valve control according to the third embodiment, when it is determined in step S23 that the operating point of the internal combustion engine 2 is in the region B, steps S25 and S26 are selected, and the valves 48, 64, 58 and 74 are fully closed. In step S30, it is determined whether or not the EGR valve 34 is fully closed, or whether or not the operating point of the internal combustion engine 2 is out of the regions B and C. Until the EGR valve 34 is fully closed or until the operating point of the internal combustion engine 2 is out of the regions B and C, the valves 48, 64, 58, and 74 are kept fully closed. Then, step S28 is executed when the EGR valve 34 is fully closed or when the operating point of the internal combustion engine 2 goes out of the regions B and C. In step S28, the control of each valve 48, 64, 58, 74 is returned to normal control.

4). Other embodiments.
In the configuration shown in FIG. 1 or FIG. 9, the EGR passage 32 may be connected to the exhaust passage 8 downstream of the second three-way catalyst 26. Further, the present invention can also be applied to an internal combustion engine that includes only one of a blow-by gas introduction system and a purge gas introduction system. Furthermore, the present invention can also be applied to an internal combustion engine having a so-called HPL-EGR in which an inlet of the EGR passage is connected to an exhaust passage upstream of the turbine.

2, 3 Internal combustion engine 4 Engine body 6 Intake passage 8 Exhaust passage 10 Fuel tank 16 Throttle 30 EGR device 32 EGR passage 34 EGR valve 40 Purge gas introduction system (first purge gas introduction system)
42 canister 44 purge gas passage 46 ejector 48 purge gas valve (first purge gas valve)
50 Blow-by gas introduction system (first blow-by gas introduction system)
54 Blow-by gas passage 56 Ejector 58 Blow-by gas valve (first blow-by gas valve)
60 second purge gas introduction system 62 purge gas passage 64 second purge gas valve 70 second blow-by gas introduction system 72 blow-by gas passage 74 second blow-by gas valves 100 and 102

Claims (1)

Control of an internal combustion engine comprising an EGR passage connecting an exhaust passage and an intake passage, an EGR valve installed in the EGR passage, and a treated gas introduction system for introducing a treated gas containing a fuel component into the intake passage In the device
When it is detected or predicted that the pressure acting on the intake passage side of the EGR valve is higher or higher than the pressure acting on the exhaust passage side of the EGR valve, the intake air of the gas to be processed is detected. An internal combustion engine configured to operate the gas to be treated introduction system so as to stop introduction into the passage or to reduce the amount of the gas to be treated introduced into the intake passage. Control device.

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