JP2014034959A - Exhaust gas recirculation device of engine with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To scavenge an air intake passage by exhausting an ERG gas remaining in the air intake passage a little early, causing neither deceleration misfire nor an increase in output of an engine during engine speed reduction.SOLUTION: An engine 1 includes a supercharger 7, an electronic throttle device 14, an EGR passage 17, and an EGR valve 18. The supercharger 7 includes a compressor 8 and a turbine 9 which can rotate in one body. An inlet 17b of the EGR passage 17 is connected to an exhaust passage 5 downstream from the turbine 9, and an outlet 17a is connected to an air intake passage 3 upstream from the compressor 8. In the air intake passage 3 upstream from the electronic throttle device 14 and downstream from the compressor 8, an air bypass passage 41 for flowing an ERG gas remaining there to the exhaust passage 5 is provided. The passage 41 is provided with an air bypass valve (ABV) 42. An electronic control unit (ECU) 50 opens the ABV 42 and closes the EGR valve 18 only for a period in which boost pressure exceeds back pressure during speed reduction of the engine 1.

Description

  The present invention relates to an engine having a supercharger that boosts the intake air of the engine, and an engine with a supercharger that causes a part of exhaust discharged from the engine to an exhaust passage to flow into the intake passage as EGR gas and return to the engine This relates to an exhaust gas recirculation apparatus.

  Conventionally, this type of technology has been employed in, for example, automobile engines. An exhaust gas recirculation (EGR) device guides part of the exhaust after combustion discharged from the combustion chamber of the engine to the exhaust passage to the intake passage via the EGR passage, and mixes it with the intake air flowing through the intake passage It is made to return to a combustion chamber. EGR gas flowing through the EGR passage is adjusted by an EGR valve provided in the EGR passage. By this EGR, nitrogen oxide (NOx) in the exhaust gas can be mainly reduced, and fuel efficiency can be improved at the time of partial load of the engine.

  The engine exhaust is either free of oxygen or lean. Therefore, by mixing a part of the exhaust gas with the intake air by EGR, the oxygen concentration in the intake air decreases. For this reason, in the combustion chamber, fuel burns in a state where the oxygen concentration is low, so that the peak temperature at the time of combustion is lowered and the generation of NOx can be suppressed. In a gasoline engine, the pumping loss of the engine can be reduced even when the throttle valve is closed to some extent without increasing the oxygen content in the intake air by EGR.

  Here, recently, in order to further improve the fuel efficiency of the engine, it is conceivable to perform EGR in the entire operation region of the engine, and it is required to realize a large amount of EGR. In order to realize a large amount of EGR, it is necessary to enlarge the inner diameter of the EGR passage or increase the flow passage opening area of the valve body or the valve seat of the EGR valve as compared with the conventional technology.

  By the way, it is well known that an EGR device is also provided in an engine including a supercharger that boosts intake air of the engine by a supercharging pressure. Patent Document 1 below describes this type of engine. The engine includes a turbocharger that includes a turbine provided in an exhaust passage and a compressor provided in an intake passage and driven by the turbine. Further, an EGR passage is disposed between the exhaust passage downstream of the turbine and the intake passage upstream of the compressor, and an EGR valve is provided in the EGR passage (low pressure loop EGR device).

  In this type of engine, the path of the intake passage from the outlet of the EGR passage to the throttle valve is relatively long. Therefore, as shown in FIG. 10 (a), the throttle opening is fully closed (time t1) and the EGR valve is immediately closed in accordance with the sudden decrease in the required EGR rate, as shown in FIG. Even so, a large amount of EGR gas remains in the intake passage from the outlet of the EGR passage to the throttle valve. Therefore, residual EGR gas is mixed in the intake air, and as shown in FIG. 10B, the decrease in the EGR rate from the time of engine deceleration is delayed (EGR attenuation delay). As a result, the EGR rate in the intake air taken into the combustion chamber becomes excessive, and there has been a risk that the engine will undergo deceleration misfire. This tends to prolong the EGR decay delay time as the engine is decelerated from the high boost pressure or the engine speed is decreased. FIG. 10 is a time chart showing the behavior of the throttle opening and the EGR rate before and after engine deceleration.

  Therefore, the engine described in Patent Document 1 includes a fresh air bypass passage that introduces fresh air into the intake passage downstream of the throttle valve, and a bypass valve that is disposed in the fresh air bypass passage, and the required EGR rate of the engine is reduced. When suddenly decreasing, the bypass valve is controlled to open and the throttle valve is controlled to close. As a result, when the required EGR rate rapidly decreases when the engine is decelerated, the fresh air is introduced from the fresh air bypass passage to the intake passage, thereby scavenging EGR gas remaining in the intake passage and the intake passage downstream of the throttle valve. The EGR rate is attenuated at an early stage by combining the EGR gas that has flowed into and the fresh air.

JP 2012-7547 A

  However, in the engine described in Patent Document 1, although the EGR rate can be attenuated early when the engine is decelerated, only fresh air is introduced into the intake passage. There was a risk that the combustion pressure in the engine would increase, the engine output would increase, and the engine deceleration could deteriorate. Therefore, during engine deceleration, it is desirable to process the EGR gas remaining in the intake passage upstream of the throttle valve early and scavenge the intake passage without causing engine deceleration misfire or increased output. In particular, when a large amount of EGR is assumed, the EGR gas remaining in the intake passage at the time of engine deceleration increases, so the necessity thereof increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to process EGR gas remaining in the intake passage at an early stage without decelerating misfire or increasing the output of the engine when the engine is decelerating. An object of the present invention is to provide an exhaust gas recirculation device for a supercharged engine capable of scavenging.

  In order to achieve the above object, an invention according to claim 1 is provided between an intake passage and an exhaust passage of an engine, and a supercharger for boosting intake air in the intake passage by a supercharging pressure, The feeder includes a compressor disposed in the intake passage, a turbine disposed in the exhaust passage, a rotating shaft that connects the compressor and the turbine so as to be integrally rotatable, and adjusts an amount of intake air flowing through the intake passage. An intake air amount adjustment valve, an exhaust gas recirculation passage for flowing a part of the exhaust gas discharged from the combustion chamber of the engine into the exhaust passage to the intake passage as an exhaust recirculation gas, and a return to the combustion chamber; An exhaust passage connected to an exhaust passage downstream of the turbine, an outlet thereof connected to an intake passage upstream of the compressor, and an exhaust gas recirculation valve for adjusting the flow of exhaust gas recirculation in the exhaust gas recirculation passage; In the exhaust gas recirculation system for an engine with a supercharger provided, only when the supercharging pressure in the intake passage upstream of the intake air amount adjustment valve exceeds the back pressure in the exhaust passage when the engine in which the intake air amount adjustment valve is closed is decelerated The present invention is intended to include exhaust recirculation gas returning means for returning exhaust recirculation gas flowing from the exhaust recirculation passage to the intake passage and remaining in the intake passage upstream of the intake air amount adjusting valve to the exhaust passage.

According to the configuration of the above invention, in the engine with a supercharger, the inlet of the exhaust gas recirculation passage is connected to the exhaust passage downstream of the turbine, and the outlet of the exhaust gas recirculation passage is connected to the intake passage upstream of the compressor. At the time of engine deceleration when the intake air amount adjustment valve provided in the intake passage is closed, the exhaust gas recirculation gas flowing from the exhaust gas recirculation passage to the intake passage remains in the intake air passage upstream of the intake air amount adjustment valve. Further, when the engine is decelerated, the boost pressure in the intake passage upstream from the intake air amount adjustment valve increases until the rotation of the compressor decreases. Here, when the engine is decelerating, the exhaust gas recirculation gas return means remains in the intake passage upstream of the intake air amount adjustment valve only during a period in which the boost pressure in the intake passage upstream of the intake air amount adjustment valve exceeds the back pressure in the exhaust passage. By returning the exhaust gas recirculation gas to the exhaust passage, the exhaust gas recirculation gas remaining from the intake passage is removed, and instead, the intake air flows into the intake passage and is scavenged. Further, the exhaust gas recirculation gas or fresh air remaining in the intake passage does not flow to the combustion chamber.

  To achieve the above object, according to a second aspect of the present invention, in the first aspect of the present invention, the exhaust gas recirculation gas return means remains in the intake passage upstream of the intake air amount adjusting valve and downstream of the compressor. Including a return passage for flowing exhaust recirculation gas to the exhaust passage, a return on-off valve for opening and closing the return passage, and a control means. The control means returns and opens only during a period when the supercharging pressure exceeds the back pressure during engine deceleration. The purpose is to open the valve and close the exhaust gas recirculation valve.

  According to the configuration of the above invention, the control means opens the return on-off valve and closes the exhaust gas recirculation valve only during a period in which the supercharging pressure exceeds the back pressure when the engine is decelerated, thereby The exhaust gas recirculation gas remaining in the intake passage flows from the passage to the exhaust passage and is removed through the return passage. Instead, the intake air flows into the intake passage and is scavenged. Further, the exhaust gas recirculation gas or fresh air remaining in the intake passage does not flow to the combustion chamber.

  In order to achieve the above object, according to a third aspect of the present invention, in the first aspect of the present invention, the exhaust gas recirculation gas returning means is provided with an intake passage upstream of the intake air amount adjusting valve and downstream of the compressor. A bypass passage that bypasses the intake passage upstream, a bypass on-off valve that opens and closes the bypass passage, an intake on-off valve that opens and closes the intake passage upstream from the outlet of the exhaust recirculation passage, and control means, The purpose is to open the bypass on-off valve and the exhaust recirculation valve and close the intake on-off valve only during a period when the supercharging pressure exceeds the back pressure during engine deceleration.

  According to the configuration of the invention, the control means opens the bypass on-off valve and the exhaust recirculation valve and closes the intake on-off valve only during a period in which the supercharging pressure exceeds the back pressure at the time of engine deceleration. The exhaust gas recirculation gas remaining in the intake air passage is removed from the intake air passage downstream of the compressor through the bypass passage, the intake air passage upstream of the compressor and the exhaust gas recirculation passage, and the intake air flows into the intake air passage instead. Scavenged. Further, the exhaust gas recirculation gas or fresh air remaining in the intake passage does not flow to the combustion chamber.

  In order to achieve the above object, the invention according to claim 4 is the invention according to claim 2 or 3, further comprising operating state detecting means for detecting the operating state of the engine, wherein the control means The period during which the boost pressure exceeds the back pressure when the engine is decelerated based on the intake pressure and engine speed before the engine is decelerated and the opening of the intake air amount adjustment valve when the engine is decelerated, detected by the state detection means The purpose is to seek.

  According to the configuration of the invention described above, in addition to the operation of the invention according to claim 2 or 3, the control means controls the intake pressure before the engine is decelerated and the rotational speed of the engine, and the intake air amount adjusting valve when the engine is decelerated. Based on the opening, a period in which the boost pressure exceeds the back pressure during engine deceleration is obtained. Here, the intake pressure and the rotational speed of the engine before deceleration of the engine have a correlation with the magnitude of the supercharging pressure before deceleration of the engine. Further, the opening degree of the intake air amount adjustment valve when the engine is decelerated has a correlation with the degree of attenuation of the supercharging pressure after the engine is decelerated. Therefore, it is possible to estimate the period in which the supercharging pressure exceeds the back pressure by using these parameters.

  According to the first aspect of the present invention, the exhaust gas recirculation gas remaining in the intake passage can be processed early and the intake passage can be scavenged without decelerating misfire or increasing the output of the engine during engine deceleration.

  According to the second aspect of the present invention, the exhaust gas recirculation gas remaining in the intake passage can be processed early and the intake passage can be scavenged without decelerating misfire or increasing the output of the engine during engine deceleration.

  According to the third aspect of the present invention, the exhaust gas recirculation gas remaining in the intake passage can be processed early and the intake passage can be scavenged without decelerating misfire or increasing the output of the engine during engine deceleration.

  According to the invention described in claim 4, in addition to the effect of the invention described in claim 2 or 3, compared to the case where the exhaust gas recirculation gas remaining in the intake passage is uniformly discharged for a predetermined time, the engine before deceleration is reduced. Depending on the operating state, the exhaust gas recirculation gas remaining in the intake passage can be appropriately processed.

1 is a schematic configuration diagram showing an engine system according to a first embodiment and including an exhaust gas recirculation device (EGR device) for a supercharged engine. FIG. 4 is an enlarged cross-sectional view showing a part of the EGR passage where an EGR valve is provided according to the embodiment. The flowchart which shows an example of the processing content of "residual EGR gas scavenging control at the time of deceleration" according to the embodiment. The graph which shows the relationship between throttle opening and a back pressure according to the embodiment. The three-dimensional scavenging time map which shows the relationship between the throttle valve upstream intake pressure before sudden deceleration, the throttle opening at the time of deceleration, and scavenging time concerning the embodiment. The time chart which shows the behavior of the various parameters regarding control according to the embodiment. The schematic block diagram which shows the engine system which concerns on 2nd Embodiment and contains the exhaust gas recirculation apparatus (EGR apparatus) of the engine with a supercharger. The flowchart which shows an example of the processing content of "residual EGR gas scavenging control at the time of deceleration" according to the embodiment. The time chart which shows the behavior of the various parameters regarding control according to the embodiment. The time chart which shows the behavior of the throttle opening degree and EGR rate before and behind engine deceleration according to a conventional example.

<First Embodiment>
Hereinafter, a first embodiment of an exhaust gas recirculation device for an engine with a supercharger according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an engine system including an exhaust gas recirculation device (EGR device) for an engine with a supercharger in this embodiment. This engine system includes a reciprocating engine 1. An intake passage 3 is connected to the intake port 2 of the engine 1, and an exhaust passage 5 is connected to the exhaust port 4. An air cleaner 6 is provided at the inlet of the intake passage 3. A supercharger 7 for boosting the intake air in the intake passage 3 is provided in the intake passage 3 downstream of the air cleaner 6 between the exhaust passage 5 and the intake passage 3.

  The supercharger 7 includes a compressor 8 disposed in the intake passage 3, a turbine 9 disposed in the exhaust passage 5, and a rotating shaft 10 that connects the compressor 8 and the turbine 9 so as to be integrally rotatable. The supercharger 7 rotates the turbine 9 by the exhaust gas flowing through the exhaust passage 5 and integrally rotates the compressor 8 via the rotating shaft 10 to increase the intake air in the intake passage 3 by the supercharging pressure. Supercharge is to be done.

  An exhaust bypass passage 11 that bypasses the turbine 9 is provided in the exhaust passage 5 adjacent to the supercharger 7. A waste gate valve 12 is provided in the exhaust bypass passage 11. By adjusting the exhaust gas flowing through the exhaust bypass passage 11 by the waste gate valve 12, the exhaust gas flow rate supplied to the turbine 9 is adjusted, the rotational speeds of the turbine 9 and the compressor 8 are adjusted, and supercharging by the supercharger 7 is performed. The pressure is adjusted.

  In the intake passage 3, an intercooler 13 is provided between the compressor 8 of the supercharger 7 and the engine 1. The intercooler 13 is for cooling the intake air that has been pressurized by the compressor 8 to a high temperature. A surge tank 3 a is provided in the intake passage 3 between the intercooler 13 and the engine 1. An electronic throttle device 14 that is an electric throttle valve is provided in the intake passage 3 downstream from the intercooler 13 and upstream from the surge tank 3a. The electronic throttle device 14 corresponding to the intake air amount adjusting valve of the present invention includes a butterfly-type throttle valve 21 disposed in the intake passage 3, a step motor 22 for opening and closing the throttle valve 21, And a throttle sensor 23 for detecting an opening (throttle opening) TA. The electronic throttle device 14 is configured such that the throttle valve 21 is opened and closed by a step motor 22 in accordance with the operation of an accelerator pedal 26 by a driver, and the opening degree thereof is adjusted. As the configuration of the electronic throttle device 14, for example, the basic configuration of the “throttle device” described in FIGS. 1 and 2 of JP 2011-252482 A can be employed. The exhaust passage 5 downstream from the turbine 9 is provided with a catalytic converter 15 as an exhaust catalyst for purifying exhaust.

  The engine 1 is provided with an injector 25 for injecting and supplying fuel to the combustion chamber 16. Fuel is supplied to the injector 25 from a fuel tank (not shown). The engine 1 is provided with a spark plug 29 corresponding to each cylinder. Each spark plug 29 is ignited by receiving a high voltage output from the igniter 30. The ignition timing of each spark plug 29 is determined by the high voltage output timing from the igniter 30.

  In this embodiment, the EGR device for realizing a large amount of EGR causes a part of the exhaust discharged from the combustion chamber 16 of the engine 1 to the exhaust passage 5 to flow into the intake passage 3 as EGR gas and to be returned to the combustion chamber 16. An exhaust gas recirculation passage (EGR passage) 17 and an exhaust gas recirculation valve (EGR valve) 18 provided in the EGR passage 17 for adjusting the flow of EGR gas in the EGR passage 17 are provided. The EGR passage 17 is provided between the exhaust passage 5 downstream from the catalytic converter 15 and the intake passage 3 upstream from the compressor 8. That is, in order to flow part of the exhaust gas flowing through the exhaust passage 5 as EGR gas to the intake passage 3 through the EGR passage 17 and return to the combustion chamber 16, the outlet 17 a of the EGR passage 17 is connected to the intake passage 3 upstream of the compressor 8. Connected to. Further, the inlet 17 b of the EGR passage 17 is connected to the exhaust passage 5 downstream from the catalytic converter 15.

  The EGR passage 17 is provided with an EGR cooler 20 for cooling the EGR gas flowing through the passage 17. In this embodiment, the EGR valve 18 is disposed in the EGR passage 17 downstream of the EGR cooler 20.

FIG. 2 is an enlarged sectional view showing a part of the EGR passage 17 where the EGR valve 18 is provided. As shown in FIGS. 1 and 2, the EGR valve 18 is constituted by a poppet valve and an electric valve. That is, the EGR valve 18 includes a valve body 32 that is driven by the step motor 31. The valve body 32 has a substantially conical shape, and is provided so as to be seated on a valve seat 33 provided in the EGR passage 17. The step motor 31 includes an output shaft 34 that is configured to be capable of linearly reciprocating (stroke), and a valve body 32 is fixed to the tip of the output shaft 34. The output shaft 34 is supported by a housing constituting the EGR passage 17 via a bearing 35.
The opening degree of the valve body 32 relative to the valve seat 33 is adjusted by moving the output shaft 34 of the step motor 31 by a stroke. The output shaft 34 of the EGR valve 18 is provided so as to be able to perform a stroke movement by a predetermined stroke L1 from a fully closed state in which the valve body 32 is seated on the valve seat 33 to a fully open state in which the valve body 32 contacts the bearing 35. . In this embodiment, in order to realize a large amount of EGR, the opening area of the valve seat 33 is enlarged as compared with the conventional technique. Accordingly, the valve body 32 is enlarged. As a configuration of the EGR valve 18, for example, a basic configuration of “EGR valve” described in FIG. 1 of JP 2010-275941 A can be adopted.

As shown in FIG. 1, in this embodiment, the intake passage 3 upstream of the electronic throttle device 14 and downstream of the compressor 8 of the supercharger 7 (the intake passage 3 between the electronic throttle device 14 and the compressor 8). An air bypass passage 41 is provided for returning the EGR gas remaining in the exhaust gas to the exhaust passage 5 and scavenging the portion of the intake passage 3. The air bypass passage 41 corresponding to the return passage of the present invention has an inlet 41 a connected to the intake passage 3 upstream of the intercooler 13 and downstream of the compressor 8, and an outlet 41 b of EGR upstream of the EGR cooler 20. Connected to the passage 17. In the middle of the air bypass passage 41, an electric air bypass valve (ABV) 42 corresponding to the return on-off valve of the present invention is provided. ABV42 is comprised so that a valve body may be opened and closed by a solenoid.

  In this embodiment, in order to execute fuel injection control, ignition timing control, intake air amount control, EGR control, “deceleration residual EGR gas scavenging control”, and the like according to the operating state of the engine 1, the injector 25 and igniter 30 The step motor 22 of the electronic throttle device 14, the step motor 31 of the EGR valve 18, and the ABV 42 are controlled by an electronic control unit (ECU) 50 according to the operating state of the engine 1. The ECU 50 stores in advance a central processing unit (CPU), a predetermined control program and the like, various memories for temporarily storing a calculation result of the CPU, and the like, an external input circuit connected to these parts, and an external And an output circuit. The ECU 50 corresponds to the control means of the present invention. An igniter 30, an injector 25, step motors 22 and 31, and an ABV 42 are connected to the external output circuit. Various sensors 27 and 51 to 55 corresponding to the operating state detecting means of the present invention for detecting the operating state of the engine 1 including the throttle sensor 23 are connected to the external input circuit so that various engine signals are input. It has become.

  Here, in addition to the throttle sensor 23, an accelerator sensor 27, an intake pressure sensor 51, a rotation speed sensor 52, a water temperature sensor 53, an air flow meter 54, and an air-fuel ratio sensor 55 are provided as various sensors. The accelerator sensor 27 detects an accelerator opening ACCP that is an operation amount of the accelerator pedal 26. The accelerator pedal 26 corresponds to an operating means for operating the operation of the engine 1. The intake pressure sensor 51 detects the intake pressure PM in the surge tank 3a. That is, the intake pressure sensor 51 detects the intake pressure PM in the intake passage 3 (surge tank 3a) downstream from the position where EGR gas flows from the EGR passage 17 into the intake passage 3. The rotational speed sensor 52 detects the rotational angle (crank angle) of the crankshaft 1a of the engine 1 and detects the change in the crank angle as the rotational speed (engine rotational speed) NE of the engine 1. The water temperature sensor 53 detects the cooling water temperature THW of the engine 1. That is, the water temperature sensor 53 corresponds to a temperature state detecting means and detects the cooling water temperature THW indicating the temperature state of the engine 1. The air flow meter 54 detects the intake air amount Ga flowing through the intake passage 3 immediately downstream of the air cleaner 6. The air-fuel ratio sensor 55 is provided in the exhaust passage 5 immediately upstream of the catalytic converter 15, and detects the air-fuel ratio A / F in the exhaust.

  In this embodiment, the ECU 50 controls the EGR valve 18 in order to control the EGR in accordance with the operation state of the engine 1 in the entire operation region of the engine 1. Further, the ECU 50 is configured to execute control described later when the engine is decelerated.

  Here, in this embodiment, since the path of the intake passage 3 from the outlet 17a of the EGR passage 17 to the electronic throttle device 14 is relatively long, the electronic throttle device 14 is controlled to be closed when the engine 1 is decelerated. EGR gas stays or remains in the path. For this reason, the residual EGR gas flows into the combustion chamber 16 and may cause a deceleration misfire of the engine 1. Therefore, in this embodiment, when the engine 1 is decelerated, the EGR gas remaining in the intake passage 3 between the electronic throttle device 14 and the compressor 8 is quickly returned to the exhaust passage 5 to scavenge the portion of the intake passage 3. Further, the ECU 50 is configured to execute “residual EGR gas scavenging control during deceleration”. In this embodiment, the above-described air bypass passage 41, ABV 41 and ECU 50 constitute the exhaust gas recirculation gas returning means of the present invention.

  FIG. 3 is a flowchart showing an example of the processing content of “residual EGR gas scavenging control during deceleration”.

  When the processing shifts to this routine, first, at step 100, the ECU 50 captures various engine signals based on the detection values of the various sensors 51-55.

  Next, at step 101, the ECU 50 determines whether or not EGR is on, that is, whether or not EGR is being executed. When this determination result is negative, the ECU 50 returns the process to step 100, and when this determination result is affirmative, the process proceeds to step 102.

  In step 102, the ECU 50 obtains the accelerator opening change ΔACCP based on the detection value of the accelerator sensor 27. The ECU 50 obtains the accelerator opening change ΔACCP from the difference between the accelerator opening ACCP detected this time and the accelerator opening ACCP detected last time in a predetermined processing cycle.

  Next, in step 103, the ECU 50 determines whether or not there is a request for rapid deceleration of the engine 1 since EGR is on. The ECU 50 determines whether or not there is a sudden deceleration request based on the accelerator opening change ΔACCP. For example, it can be determined that there has been a sudden deceleration request when the accelerator opening change ΔACCP is greater than a predetermined value. When this determination result is negative, the ECU 50 returns the process to step 100, and when this determination result is affirmative, the process proceeds to step 104.

  In step 104, the ECU 50 closes the EGR valve 18. Thereby, the EGR passage 17 is shut off.

  Next, at step 105, the ECU 50 takes in the engine rotation speed NE based on the detection value of the rotation speed sensor 52.

  Next, in step 106, the ECU 50 takes in the intake pressure PMin before the deceleration or the engine load KL. Here, the ECU 50 takes in the intake pressure PM before the engine 1 is decelerated as the intake pressure PMin before the deceleration. Further, the ECU 50 can determine the engine load KL from the relationship between the engine rotational speed NE and the intake air amount Ga or the intake pressure PM.

  Next, in step 107, the ECU 50 takes in the accelerator opening ACCP, and in step 108, obtains a target throttle opening TTAd during engine deceleration based on the accelerator opening ACCP. The ECU 50 can perform this process by referring to a preset target opening degree map (not shown).

  Next, in step 109, the ECU 50 controls the electronic throttle device 14 based on the target throttle opening degree TTAd at the time of deceleration. As a result, the throttle valve 21 is closed to the target throttle opening degree TTAd, the amount of intake air taken into the combustion chamber 16 from the intake passage 3 is reduced, and the engine 1 is decelerated.

  Next, at step 110, the ECU 50 takes in the throttle opening degree TAd during deceleration based on the detection value of the throttle sensor 23.

  Next, in step 111, the ECU 50 obtains the scavenging time Tpmta during engine deceleration based on the intake pressure PMin before deceleration, the engine speed NE, and the throttle opening degree TAd during deceleration. Here, the scavenging time Tpmta means a time during which the throttle valve upstream intake pressure PMta exceeds the value “PMex + α” obtained by adding a predetermined value α to the back pressure PMex during engine deceleration. The throttle valve upstream intake pressure PMta means a supercharging pressure associated with the operation of the supercharger 7. The ECU 50 can obtain the scavenging time Tpmta by referring to a scavenging time map shown in FIG.

  FIG. 4 is a graph showing the relationship between the throttle opening degree TA and the back pressure PMex. FIG. 5 shows a relationship among the throttle valve upstream intake pressure PMta before sudden deceleration, the throttle opening degree TAd during deceleration, and the scavenging time Tpmta by a three-dimensional scavenging time map. The back pressure PMex means the pressure of the exhaust gas discharged from the engine 1, and as shown in FIG. 4, the back pressure PMex increases in a curve as the throttle opening degree TA increases. As shown in FIG. 5, the scavenging time Tpmta increases as the throttle valve upstream intake pressure PMta before sudden deceleration increases from the atmospheric pressure, and decreases as the throttle opening degree TAd during deceleration increases. Set to do.

  In step 112, the ECU 50 determines whether or not the obtained scavenging time Tpmta is greater than “0”. When this determination result is negative, the ECU 50 returns the process to step 100, and when this determination result is affirmative, the process proceeds to step 113.

  In step 113, the ECU 50 opens the ABV 42. By opening the valve ABV 42, the intake passage 3 downstream from the compressor 8 leads to the exhaust passage 5 via the air bypass passage 41 and the like, and remains in the intake passage 3 between the electronic throttle device 14 and the compressor 8. The EGR gas that has been discharged is discharged to the exhaust passage 5 through the air bypass passage 41.

  Next, in step 114, the ECU 50 determines whether or not an elapsed time (deceleration time) after the engine 1 starts decelerating exceeds the scavenging time Tpmta. If this determination result is negative, the ECU 50 returns the process to step 113, and if this determination result is affirmative, the ECU 50 proceeds to step 115.

  In step 115, the ECU 50 closes the ABV 42 and then returns the process to step 100. By closing the ABV 42, the air bypass passage 41 is blocked.

  According to the control in this embodiment, the ECU 50 opens the ABV 42 and opens the EGR valve 18 only during a period when the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex when the engine 1 is decelerated. The valve opens.

  Here, the behavior of various parameters related to the above control is shown in FIG. In FIG. 6, during steady operation of the engine 1 before time t1, the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex (FIG. 6B). At time t1, when the accelerator opening ACCP is fully closed, the throttle opening TA is closed toward the fully closed position (FIG. 5A), and the EGR valve 18 is fully closed (same as above). (D).

  Thereafter, when the throttle opening degree TA is fully closed at time t2 (FIG. 5A), the ABV 42 is opened toward the fully open position (FIG. 5C). Thereafter, between times t2 and t3, the throttle valve upstream intake pressure PMta (supercharging pressure) once increases and then gradually decreases (thick line in FIG. 4B). Further, the back pressure PMex gradually decreases from time t2, and eventually becomes a constant value ((b) in the figure). At this time, the EGR gas staying or remaining in the intake passage 3 between the electronic throttle device 14 and the compressor 8 is discharged to the exhaust passage 3 through the air bypass passage 41, and the portion of the intake passage 3 is scavenged. . On the other hand, when the ABV 42 does not open at time t2, the throttle valve upstream side intake pressure PMta (supercharging pressure) rapidly increases and then gradually decreases (two-dot chain line in FIG. 2B). At this time, the EGR gas remains in the intake passage 3 between the electronic throttle device 14 and the compressor 8.

  At time t3, when the deceleration time from time t2 exceeds the scavenging time Tpmta, the ABV 42 closes toward full closure ((c) in the figure).

  According to the exhaust gas recirculation device for a turbocharged engine in the present embodiment described above, in the engine 1 provided with the supercharger 7, the inlet 17b of the EGR passage 17 is connected to the exhaust passage 5 downstream from the turbine 9, An outlet 17 a of the EGR passage 17 is connected to the intake passage 3 upstream from the compressor 8. Therefore, when the engine 1 in which the electronic throttle device 14 is closed is decelerated, the EGR gas flowing from the EGR passage 17 to the intake passage 3 remains in the intake passage 3 between the electronic throttle device 14 and the compressor 8. Become. Further, when the engine 1 is decelerated, the boost pressure in the intake passage 3 between the electronic throttle device 14 and the compressor 8 increases until the rotation of the compressor 8 decreases. Here, the exhaust gas recirculation gas returning means is configured such that the throttle valve upstream intake pressure PMta (supercharging pressure) in the intake passage 3 between the electronic throttle device 14 and the compressor 8 is the back pressure in the exhaust passage 5 when the engine 1 is decelerated. The EGR gas remaining in the intake passage 3 is returned to the exhaust passage 5 only during a period exceeding PMex. More specifically, when the engine 1 is decelerated, the ECU 50 opens the ABV 42 and closes the EGR valve 18 only during a period in which the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex. As a result, the residual EGR gas flows from the intake passage 3 between the electronic throttle device 14 to the compressor 8 through the air bypass passage 41 to the exhaust passage 5 and is removed, and instead, the intake air flows into the intake passage 3 portion. It is scavenged at. Further, EGR gas or fresh air remaining in the intake passage 3 does not flow to the combustion chamber 16. For this reason, when the engine 1 is decelerated, the EGR gas remaining in the intake passage 3 can be processed early and the intake passage 3 can be scavenged without decelerating misfire or increasing the output of the engine 1.

  In this embodiment, the ECU 50 detects the intake pressure PMin and the engine rotational speed NE before the engine 1 is decelerated and the throttle opening when the engine 1 is decelerated, which are detected by the intake pressure sensor 51, the rotational speed sensor 52 and the throttle sensor 23. Based on the degree TA, a period during which the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex when the engine 1 is decelerated is obtained. Here, the intake pressure PMin and the engine rotational speed NE before the deceleration of the engine 1 have a correlation with the magnitude of the throttle valve upstream intake pressure PMta (supercharging pressure) before the deceleration. The throttle opening degree TA when the engine 1 is decelerated has a correlation with the degree of attenuation of the throttle valve upstream side intake pressure PMta (supercharging pressure) from when the engine 1 is decelerated. Therefore, it is possible to estimate the period during which the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex, that is, the scavenging time Tpmta, using these parameters. For this reason, compared with the case where residual EGR gas is uniformly discharged only for a predetermined time, the residual EGR gas can be appropriately processed according to the operating state of the engine 1 before deceleration.

Second Embodiment
Next, a second embodiment in which the exhaust gas recirculation device for a supercharged engine according to the present invention is embodied will be described in detail with reference to the drawings.

  In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and different points are mainly described.

  This embodiment differs from the first embodiment in the configuration of the exhaust gas recirculation gas returning means of the present invention and the processing content of “deceleration residual EGR gas scavenging control”. FIG. 7 is a schematic configuration diagram showing the engine system in this embodiment. As shown in FIG. 7, in this embodiment, the outlet 41 b of the air bypass passage 41 is connected to the intake passage 3 upstream of the compressor 8. That is, the air bypass passage 41 of this embodiment is configured to bypass the intake passage 3 between the electronic throttle device 14 and the compressor 8 to the intake passage 3 upstream of the compressor 8. The air bypass passage 41 corresponds to the bypass passage of the present invention, and the ABV 42 corresponds to the bypass on-off valve of the present invention. The intake passage 3 downstream of the air cleaner 6 and upstream of the outlet 17a of the EGR passage 17 is provided with a check valve 43 as an intake opening / closing valve of the present invention that opens and closes the intake passage 3. The check valve 43 includes a butterfly throttle valve 44 disposed in the intake passage 3 and a step motor 45 for opening and closing the throttle valve 44. The step motor 45 is configured to be controlled by the ECU 50.

  FIG. 8 is a flowchart showing an example of the processing content of the “deceleration residual EGR gas scavenging control” according to this embodiment.

  In the flowchart of FIG. 8, the processing of step 104 in the flowchart of FIG. 3 is omitted, the processing of step 201 and step 202 is added between step 113 and step 114, and the step between step 114 and step 115 is performed. The processing content of the flowchart of FIG. 3 in the first embodiment is different in that the processing of step 203 and step 204 is added.

  That is, if the determination result in step 103 is affirmative, the ECU 50 proceeds to step 105 without closing the EGR valve 18 and takes in the engine rotational speed NE.

  If the determination result in step 112 is affirmative, the ECU 50 opens the ABV 42 in step 113, closes the check valve 43 in step 201, and opens the EGR valve 18 in step 202. To do. That is, in step 201, the ECU 50 controls the drive of the step motor 45 in order to close the check valve 43. In step 202, since the process starts from the EGR on state, the valve opening of the EGR valve 18 that has already been opened is continued. By controlling the ABV 42, the check valve 43 and the EGR valve 18, the intake passage 3 downstream from the compressor 8 leads to the exhaust passage 5 via the air bypass passage 41, the intake passage 3 and the EGR passage 17. The EGR gas remaining in the intake passage 3 between the throttle device 14 and the compressor 8 is discharged to the exhaust passage 5 through these passages 41, 3, and 17. At this time, since the check valve 43 is closed, the residual EGR gas does not flow back to the air cleaner 6 and the air flow meter 54 can be protected from the EGR gas.

On the other hand, if the determination result in step 114 is affirmative, the ECU 50 closes the EGR valve 18 in step 203, opens the check valve 43 in step 204, and closes the ABV 42 in step 115. . That is, in step 203, the ECU 50 causes the EGR valve 18 that has been opened at the time of deceleration of the engine 1 to be fully closed. In step 204, the ECU 50 controls the drive of the step motor 45 in order to open the check valve 43. By controlling the ABV 42, the check valve 43, and the EGR valve 18, the air bypass passage 41 and the EGR passage 17 are shut off. Further, since the check valve 43 is opened, air can be taken into the intake passage 3 from the air cleaner 6.

  According to the control of this embodiment, the ECU 50 opens the ABV 42 and the EGR valve 18 only during a period in which the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex when the engine 1 is decelerated. The check valve 43 is closed.

  Here, the behavior of various parameters relating to the above control is shown in FIG. In FIG. 9, at the time of steady operation of the engine 1 before time t1, the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex (FIG. 9B). At time t1, when the accelerator opening ACCP is fully closed, the throttle opening TA is closed toward the fully closed position (FIG. 5A). At this time, the EGR valve 18 is in an open state ((d) in the figure).

  Thereafter, when the throttle opening degree TA is fully closed at time t2 (FIG. 1A), the ABV 42 is opened toward the fully open state (FIG. 3C), and the EGR valve 18 is kept open. ((D) in the figure). Further, the check valve 43 is closed from the fully open state toward the fully closed state ((e) in the figure). Thereafter, between times t2 and t3, the throttle valve upstream intake pressure PMta (supercharging pressure) once increases and then gradually decreases (thick line in FIG. 4B). Further, the back pressure PMex gradually decreases from time t2, and eventually becomes a constant value ((b) in the figure). At this time, the EGR gas staying or remaining in the intake passage 3 between the electronic throttle device 14 and the compressor 8 is discharged to the exhaust passage 3 through the air bypass passage 41, the intake passage 3 and the EGR passage 17, and the intake air The portion of the passage 3 is scavenged. On the other hand, when the ABV 42 does not open at time t2, the throttle valve upstream side intake pressure PMta (supercharging pressure) rapidly increases and then gradually decreases (two-dot chain line in FIG. 2B). At this time, the EGR gas remains in the intake passage 3 between the electronic throttle device 14 and the compressor 8.

  At time t3, when the deceleration time from time t2 exceeds the scavenging time Tpmta, the ABV 42 is closed toward the fully closed state ((c) in the figure), and the EGR valve 18 is closed toward the fully closed state. ((D) in the figure). Further, the check valve 43 is opened toward the fully open position ((e) in the figure).

  According to the exhaust gas recirculation apparatus for an engine with a supercharger in the present embodiment described above, the ECU 50 performs only the period when the throttle valve upstream intake pressure PMta (supercharging pressure) exceeds the back pressure PMex when the engine 1 is decelerated. The ABV 42 and the EGR valve 18 are opened, and the check valve 43 is closed. As a result, the residual EGR gas flows to the exhaust passage 5 through the intake passage 3 between the electronic throttle device 14 and the compressor 8 via the air bypass passage 41, the intake passage 3 upstream of the compressor 8 and the EGR passage 17, and is removed. Instead, the intake air flows into the portion of the intake passage 3 and is scavenged. Further, EGR gas or fresh air remaining in the intake passage 3 does not flow to the combustion chamber 16. For this reason, when the engine 1 is decelerated, the EGR gas remaining in the intake passage 3 can be processed early into the exhaust passage 5 and the intake passage 3 can be scavenged without causing a deceleration misfire or an increase in output of the engine 1.

  Note that the present invention is not limited to the above-described embodiments, and a part of the configuration can be changed as appropriate without departing from the spirit of the invention.

  For example, in the first embodiment, the outlet 41b of the air bypass passage 41 is connected to the EGR passage 17, but the outlet of the air bypass passage can be directly connected to the exhaust passage.

  The present invention can be used for an automobile engine regardless of, for example, a gasoline engine or a diesel engine.

1 Engine 3 Intake passage 3a Surge tank (Intake passage)
5 Exhaust passage 7 Supercharger 8 Compressor 9 Turbine 10 Rotating shaft 14 Electronic throttle device (intake air amount adjustment valve)
16 Combustion chamber 17 EGR passage (exhaust gas recirculation passage)
17a outlet 17b inlet 18 EGR valve (exhaust gas recirculation valve)
23 Throttle sensor (operating state detection means)
27 Accelerator sensor (operating state detection means)
41 Air bypass passage (return passage, bypass passage)
41a Inlet 41b Outlet 42 ABV (return on-off valve, bypass on-off valve)
43 Check valve (intake on / off valve)
50 ECU (control means)
51 Intake pressure sensor (operating state detection means)
52 Rotational speed sensor (Operating state detection means)
53 Water temperature sensor (Operating state detection means)
54 Air flow meter (Operating state detection means)
55 Air-fuel ratio sensor (operating state detection means)
TA throttle opening NE engine speed PMin intake pressure before deceleration Tpmta scavenging time

Claims (4)

A turbocharger that is provided between an intake passage and an exhaust passage of the engine and boosts intake air in the intake passage by a supercharging pressure;
The supercharger includes a compressor disposed in the intake passage, a turbine disposed in the exhaust passage, and a rotation shaft that connects the compressor and the turbine so as to be integrally rotatable.
An intake air amount adjusting valve for adjusting an intake air amount flowing through the intake passage;
An exhaust gas recirculation passage that causes a part of the exhaust gas discharged from the combustion chamber of the engine to flow into the intake passage as exhaust gas recirculation gas and recirculates to the combustion chamber;
The exhaust gas recirculation passage has an inlet connected to the exhaust passage downstream of the turbine and an outlet connected to the intake passage upstream of the compressor;
In an exhaust gas recirculation device for a supercharged engine, comprising an exhaust gas recirculation valve for adjusting the flow of the exhaust gas recirculation gas in the exhaust gas recirculation passage,
At the time of deceleration of the engine in which the intake air amount adjustment valve is closed, the supercharging pressure in the intake passage upstream from the intake air amount adjustment valve is from the exhaust gas recirculation passage only during a period in which the boost pressure exceeds the back pressure in the exhaust passage. An engine with a supercharger comprising exhaust recirculation gas return means for returning the exhaust gas recirculation gas flowing into the intake passage and remaining in the intake passage upstream of the intake air amount adjustment valve to the exhaust passage. Exhaust gas recirculation device. The exhaust recirculation gas return means includes a return passage for flowing exhaust recirculation gas remaining in the intake passage upstream of the intake air amount adjustment valve and downstream of the compressor to the exhaust passage, and a return opening and closing for opening and closing the return passage. Including a valve and control means,
The said control means opens the said return on-off valve and closes the said exhaust gas recirculation valve only for the period when the said supercharging pressure exceeds the said back pressure at the time of the deceleration of the said engine. Exhaust gas recirculation device for supercharged engines. The exhaust gas recirculation gas return means includes a bypass passage that bypasses the intake passage upstream of the intake air amount adjustment valve and downstream of the compressor to the intake passage upstream of the compressor, and bypass opening and closing that opens and closes the bypass passage A valve, an intake on-off valve that opens and closes the intake passage upstream from the outlet of the exhaust gas recirculation passage, and a control means,
The control means opens the bypass on-off valve and the exhaust gas recirculation valve and closes the intake on-off valve for a period in which the supercharging pressure exceeds the back pressure when the engine is decelerated. The exhaust gas recirculation device for a supercharged engine according to claim 1. And further comprising an operating state detecting means for detecting the operating state of the engine,
The control means is based on the intake pressure before the engine is decelerated and the rotational speed of the engine, and the opening of the intake air amount adjusting valve when the engine is decelerated, which is detected by the operating state detecting means. The exhaust gas recirculation apparatus for an engine with a supercharger according to claim 2 or 3, wherein a period during which the supercharging pressure exceeds the back pressure is determined during deceleration of the engine.

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