JP4774871B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine including a supercharger, and more particularly to a technique for suppressing an increase in exhaust temperature due to supercharging.

Patent Document 1 discloses an internal combustion engine including a supercharger that supercharges intake air. In addition, an exhaust gas recirculation device that recirculates a part of the exhaust gas to the intake system is provided, and swirl flow or tumble flow is imparted to the intake air flowing into the combustion chamber mainly in order to increase the exhaust gas recirculation rate in a low rotation and low load region An intake flow control valve is provided.
Japanese Patent Laid-Open No. 5-86913

  In an internal combustion engine equipped with a supercharger, as is well known, an excessive increase in exhaust temperature and occurrence of knocking in a supercharging region where the supercharging pressure is equal to or higher than atmospheric pressure are major issues. Conventionally, in order to suppress an excessive increase in the exhaust gas temperature, the fuel injection amount has been increased in the supercharging region, which has led to a decrease in fuel efficiency. In particular, when a turbocharger is used to improve fuel efficiency by reducing the amount of exhaust and reducing the size of an internal combustion engine, the desired fuel efficiency performance is impaired, and countermeasures have been desired. The present invention has been made in view of such problems.

The control apparatus for an internal combustion engine according to the present invention includes a supercharger that supercharges intake air of the internal combustion engine, an intake flow control valve that is provided in the intake passage and imparts a flow component to the intake air flowing into the combustion chamber, and the combustion and exhaust temperature detection means for detecting an actual exhaust temperature of the discharged exhaust from the chamber, based on the actual exhaust temperature, the exhaust temperature lowering means for opening and closing the intake flow control valve, have a, the exhaust temperature drop means When the actual exhaust temperature is equal to or higher than a predetermined determination temperature at which an increase in fuel is required to lower the exhaust temperature, the intake flow control valve is closed to flow into the combustion chamber so as to lower the exhaust temperature. It is characterized by strengthening the fluid component .

  According to the present invention, the exhaust gas temperature can be reduced using the intake flow control valve, and the amount of increase in the fuel injection amount for lowering the exhaust temperature can be reduced. Therefore, it is possible to satisfactorily achieve both a decrease in exhaust temperature in the supercharging region and an improvement in fuel efficiency.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a system configuration of an internal combustion engine according to the present invention. The internal combustion engine 10 is a spark ignition type gasoline engine having an ignition plug 19 and generates rotational power by burning fuel by spark ignition. The internal combustion engine 10 is provided with a turbocharger 13 that supercharges intake air using exhaust energy, and an exhaust gas recirculation (EGR) device 31 that recirculates part of the exhaust gas to the intake system. . The exhaust gas recirculation device 31 includes an exhaust gas recirculation passage 12 that connects the exhaust passage 14 and the intake air passage 16, and an electrically controlled exhaust gas recirculation control valve 11 provided in the exhaust gas recirculation passage 12. 11, the exhaust gas recirculation rate (exhaust gas recirculation amount) of the exhaust gas recirculated from the exhaust passage 14 to the intake passage 16 is adjusted. As is well known, the supercharger 13 includes a turbine 15 provided in the exhaust passage 14, a compressor 17 provided in the intake passage 16, and a rotating shaft 18 that couples both 15 and 17 so as to rotate together. When the turbine 15 rotates according to the exhaust amount (exhaust energy), the compressor 17 is rotationally driven via the rotary shaft 18 to supercharge the intake air amount.

  In the intake passage 16, an electronically controlled throttle valve 20 that opens and closes the intake passage 16 is provided on the upstream side of the compressor 17, and a plurality of intake branch passages 16 </ b> A connected to each cylinder of the internal combustion engine 10 are provided. A tumble control valve 21 is provided as an intake flow control valve for controlling the tumble flow of the intake air flowing into the combustion chamber of each cylinder. The exhaust passage 14 is provided with a bypass passage 22 that bypasses the turbine 15 and an electronically controlled waste gate valve 23 that opens and closes the bypass passage 22.

  As various sensors for detecting the engine operating state, a boost pressure sensor 24 for detecting a pressure in the intake passage 16 downstream of the throttle valve 20, that is, a boost pressure, an accelerator corresponding to the driver's acceleration request / acceleration intention An accelerator opening sensor 25 that detects the opening of the pedal, a knock sensor 26 that detects the occurrence of knocking in the combustion chamber of the internal combustion engine 10, an exhaust temperature sensor 27 that detects the temperature of the exhaust gas in the exhaust passage 14, and the like are provided. It has been. The engine control unit (control unit: C / U) 30 is mainly composed of a microcomputer, and performs fuel injection control, ignition timing control by the spark plug 19 and the like based on detection signals from the various sensors. In addition to engine control processing, opening control of the throttle valve 20, waste gate valve 23 and exhaust gas recirculation control valve 11, control processing such as opening / closing switching control of the tumble control valve 21 is stored and executed.

  For example, based on the detection signals from the exhaust temperature sensor 27 and the knock sensor 26, the actual boost pressure is detected based on the output signal of the boost pressure sensor 24 while monitoring the excessive rise of the exhaust temperature and the occurrence of knocking. The supercharging pressure, specifically, the opening degree of the throttle valve 20 and the opening degree of the waste gate valve 23 are feedback-controlled so as to be maintained in the vicinity of the target supercharging pressure. For this reason, it is not necessary to provide an excessive margin in anticipation of component variations and dimensional tolerances for the setting of the supercharging pressure, the set supercharging pressure can be sufficiently increased, and the engine output can be improved.

  FIG. 2 is a flowchart showing a control flow that is a main part of the present embodiment, and this routine is repeatedly executed by the engine control unit 30 every extremely short time period (for example, 10 ms or a predetermined crank angle). FIG. 3 is a time chart according to the present embodiment. The broken line in FIG. 3 shows the characteristics according to the comparative example, and in this comparative example, the closing operation of the tumble control valve 21 for lowering the exhaust temperature is not performed. 4 and 5 are characteristic diagrams of engine speed-engine required torque, FIG. 4 corresponds to a comparative example, and FIG. 5 corresponds to the present embodiment.

  In step S11, based on the detection signal of the knock sensor 26, it is determined whether a predetermined level of knocking has occurred. When the occurrence of knocking is detected, the routine proceeds to step S12, where the ignition timing ADV is retarded in order to quickly avoid knocking, and this routine is terminated.

  In step S13, based on the engine speed and the engine required torque (load), it is determined whether or not a predetermined EGR region Regr. The engine speed is calculated from, for example, a detection signal of a known crank angle sensor or cam angle sensor. The engine required torque is calculated based on the accelerator opening detected by the accelerator opening sensor 25 described above. As shown in FIGS. 4 and 5, the EGR region Regr is a region on the low rotation / low load side, particularly in the negative pressure region Rlow where the supercharging pressure is lower than 0 kPa corresponding to atmospheric pressure.

  If it is the EGR region Regr, the process proceeds to step S14, the tumble control valve (TCV) 21 is closed, and this routine is terminated. In this way, by closing the tumble control valve 21 in the EGR region Regr that is a low rotation / low load region, the mixture is made uniform by the action of the tumble flow (vertical swirl flow) generated in the combustion chamber. Thus, since the combustion is stabilized, the exhaust gas recirculation rate (amount) can be greatly increased, and as a result, the fuel efficiency can be improved.

  In step S15, based on the current value of the supercharging pressure detected by the supercharging pressure sensor 24, that is, the actual supercharging pressure, it is determined whether the supercharging pressure is a supercharging region Rhigh higher than 0 kPa corresponding to atmospheric pressure. . If it is not the supercharging region Rhigh, that is, if it is the negative pressure region Rlow, the process proceeds to step S16, the tumble control valve 21 is opened, and this routine is terminated.

In step S17, it is determined whether the actual exhaust temperature corresponding to the detected value of the exhaust temperature detected by the exhaust temperature sensor 27 is equal to or higher than a predetermined determination temperature Th (see FIG. 3 ). This determination temperature Th corresponds to the upper limit value of the allowable exhaust temperature. If the actual exhaust temperature is lower than the determination temperature Th, the process proceeds to step S18, the tumble control valve 21 is opened, and this routine is terminated.

  When the actual exhaust temperature is equal to or higher than the determination temperature Th, the process proceeds from step S17 to step S19, and it is determined whether or not the predetermined TCV closed operation region Rtcv is based on the engine speed and the engine required torque. As shown in FIG. 5, the TCV closing operation region Rtcv is a lower limit value where the engine speed Ne is in the range between the lower limit value NeA and the upper limit value NeB, and the engine required torque is equivalent to atmospheric pressure (0 kPa). The range is from TqA to the upper limit value TqB. If it is not the TCV closed operation region Rtcv, the process proceeds to step S20, the tumble control valve 21 is opened, and the process proceeds to step S24 and later described. That is, in the supercharging region Rhigh, a region outside the TCV closing operation region Rtcv, for example, a region Ra where the engine speed is lower than the lower limit value NeA and a region Rb where the engine required torque is higher than the upper limit value TqB, etc. The closing operation of the control valve 21 is prohibited.

  If it is the TCV closing operation region Rtcv, the process proceeds from step S19 to step S21 to determine whether the tumble control valve 21 is already closed. If the tumble control valve 21 is open, the process proceeds to step S22, and the tumble control valve 21 is switched to the closed state. Exit.

  By closing the tumble control valve 21 as described above and strengthening the flow component of the intake air flowing into the combustion chamber, specifically, the tumble flow component, combustion efficiency is improved, exhaust loss is reduced, and exhaust temperature is lowered. can do. Thus, by using the tumble control valve 21 mainly used for increasing the exhaust gas recirculation rate in the EGR region Regr, the exhaust temperature in the supercharging region Rhigh is effectively reduced, and the exhaust temperature is lowered. The increase in fuel can be suppressed, and the suppression of the exhaust temperature and the improvement of fuel consumption can be satisfactorily achieved while having a simple configuration using the existing tumble control valve 21.

  If the tumble control valve 21 is already closed in the determination process of step 21, the process proceeds to step S24. In this step S24, it is determined whether the fuel increase in step S25 has already been performed. For example, it is possible to detect the presence or absence of fuel increase by setting a flag after the fuel increase in step S25, or whether the air-fuel ratio detected by the air-fuel ratio sensor 28 provided in the exhaust passage 14 exceeds a predetermined value. It is also possible to accurately detect the presence or absence of fuel increase by determining the above. If the fuel increase has not been performed yet, the process proceeds to step S25, the fuel is increased, and this routine is terminated. That is, the target fuel injection amount set according to the engine required torque, the engine speed, etc. is corrected to the increasing side.

  If the fuel increase has already been performed, the process proceeds from step S24 to step S26, and the set boost pressure is corrected to the lower side. The set supercharging pressure is changed by adjusting the opening of the throttle valve 20 or the waste gate valve 23, for example. In subsequent step S27, the ignition timing ADV is corrected to the advance side in accordance with the decrease in the set supercharging pressure, and this routine is terminated.

  Next, the characteristic technical idea of this embodiment and the effects thereof will be listed. However, the present invention is not limited to the above embodiments, and includes various modifications and changes. For example, instead of the tumble control valve 21 as in the above embodiment, a swirl control valve that imparts a swirl (swirl) flow into the combustion chamber may be used as the intake flow control valve. In the above embodiment, the tumble control valve 21 is simply a two-position switching type of “open” and “closed”, but an intake flow control valve whose opening degree can be changed in multiple steps or continuously is used. May be.

  (1) A supercharger 13 that supercharges the intake air of the internal combustion engine 10, an intake air flow control valve 21 that is provided in the intake passage 16 and applies a flow component to the intake air that flows into the combustion chamber, and an actual exhaust temperature is detected. Exhaust temperature detection means (exhaust temperature sensor 27) and exhaust temperature lowering means (step S23) for opening and closing the intake flow control valve 21 based on the actual exhaust temperature.

  (2) More specifically, the exhaust temperature lowering means closes the intake flow control valve 21 so as to lower the exhaust temperature when the actual exhaust temperature is equal to or higher than a predetermined determination temperature Th, and performs combustion. The fluid component is strengthened in the intake air flowing into the room.

  Thus, since the exhaust gas temperature can be lowered using the intake flow control valve 21, the increase range of the fuel injection amount for lowering the exhaust gas temperature can be reduced, and the fuel efficiency can be improved. . Further, since the control is performed based on the actual exhaust temperature detected by the exhaust temperature detecting means such as the exhaust temperature sensor 27, the intake flow control valve 21 can be switched with high accuracy according to the actual exhaust temperature. it can. If the intake flow control valve 21 is switched based on, for example, a control map based on the engine load and the engine speed without using the exhaust temperature detecting means such as the exhaust temperature sensor 27, it is not necessary to lower the exhaust temperature, for example. There is a possibility that the intake flow control valve 21 may be closed accidentally under certain circumstances, or the intake flow control valve 21 may remain open in situations where the exhaust temperature needs to be lowered. Thus, fuel consumption performance can be improved while reliably suppressing an excessive increase in the exhaust gas temperature.

  (3) An exhaust gas recirculation device 31 that recirculates part of the exhaust gas to the intake air is provided, and the intake flow control valve 21 has a flow component in the intake air flowing into the combustion chamber in a predetermined EGR region Regr on the low rotation / low load side. Is closed to enhance the exhaust gas recirculation rate. That is, with the simple structure using the intake air flow control valve 21 for increasing the exhaust gas recirculation rate, the above-described operational effects can be obtained. Therefore, if the internal combustion engine is provided with the intake flow control valve 21 in advance, the present invention can be applied simply and easily without additional components.

  (4) Excessive rise in the exhaust temperature becomes a problem at least in the supercharging region Rhigh where the supercharging pressure exceeds atmospheric pressure. Accordingly, a supercharging pressure detecting means (supercharging pressure sensor 24) for detecting the actual supercharging pressure and means for determining whether the actual supercharging pressure is in the supercharging region Rhigh exceeding the atmospheric pressure (step S15) are provided. In the supercharging region Rhigh, the exhaust temperature lowering means is operated (step S22). As a result, it is possible to prevent the intake flow control valve 21 from being erroneously closed by the exhaust temperature lowering means in the negative pressure region Rlow where an excessive increase in the exhaust temperature does not cause a problem.

  (5) Referring to FIG. 5, in the region Ra where the engine speed is lower than the predetermined lower limit value NeA in the supercharging region Rhigh, it is difficult to secure the intake amount when the intake flow control valve 21 is closed, so that the combustion is stable. There is a risk of damage. Therefore, in the region Ra, the closing operation of the intake flow control valve 21 by the exhaust temperature lowering means is prohibited (step S19). Thereby, the exhaust temperature reduction effect by the intake flow control valve 21 can be effectively obtained without impairing the combustion stability.

  (6) In the region Rb in the vicinity of the fully open torque where the engine required torque (load) exceeds the predetermined upper limit value TqB, if the intake flow control valve 21 is closed, the ventilation resistance increases and the desired intake air amount cannot be obtained. There is a risk of lowering. Accordingly, in the above-described region Rb, the closing operation of the intake flow control valve 21 by the exhaust temperature reducing means is prohibited. Thereby, the exhaust temperature reduction effect by the intake flow control valve 21 can be effectively obtained without causing a decrease in the fully open output.

  (7) Referring to FIG. 2, even if the tumble control valve 21 is already closed in step S22, if the actual exhaust temperature is equal to or higher than the predetermined determination temperature Th, the process proceeds from step S21 to step S24, and the fuel An increase is made. That is, when the intake flow control valve is closed by the exhaust temperature lowering means and the actual exhaust temperature is equal to or higher than the predetermined determination temperature Th, the fuel increase is performed. As described above, when the exhaust gas temperature is lowered, the intake flow control valve 21 is first closed, and the fuel increase is performed only when the exhaust gas temperature is not sufficiently lowered. Therefore, it is possible to reliably reduce the exhaust temperature while suppressing the frequency of fuel increase.

  (8) Referring to FIG. 2, even if fuel increase has already been performed in step S25, if the actual exhaust temperature is equal to or higher than a predetermined determination temperature Th, the process proceeds from step S24 to step S26, where the set boost pressure is set. To lower the exhaust temperature. That is, there is a boost pressure lowering means (step S26) for lowering the boost pressure when the fuel is increased by the fuel increasing means (step S25) and the actual exhaust temperature is equal to or higher than the predetermined judgment temperature Th. ing. As described above, when the exhaust gas temperature is lowered, the intake flow control valve 21 is first closed and then the fuel is increased. Even when the exhaust gas temperature is not sufficiently lowered, the set boost pressure with the output reduction is reduced. I try to do a decline. Accordingly, it is possible to satisfactorily reduce the exhaust gas temperature while minimizing the decrease in output due to the decrease in the supercharging pressure.

1 is a system configuration diagram of an internal combustion engine according to an embodiment of the present invention. The flowchart which shows the flow of control of a present Example. The time chart which concerns on a present Example. The engine rotational speed which concerns on a comparative example-engine required torque characteristic figure. The engine speed-engine required torque characteristic diagram according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 13 ... Supercharger 14 ... Exhaust passage 16 ... Intake passage 21 ... Tumble control valve (intake flow control valve)
24 ... Supercharging pressure sensor (supercharging pressure detection means)
27. Exhaust temperature sensor (exhaust temperature detection means)
30 ... Engine control unit 31 ... Exhaust gas recirculation device

Claims (7)

A supercharger for supercharging the intake air of the internal combustion engine;
An intake flow control valve provided in the intake passage and imparting a flow component to the intake air flowing into the combustion chamber;
Exhaust temperature detecting means for detecting the actual exhaust temperature of the exhaust discharged from the combustion chamber;
Exhaust temperature lowering means for opening and closing the intake flow control valve based on the actual exhaust temperature;
I have a,
The exhaust temperature lowering means closes the intake air flow control valve so as to lower the exhaust temperature when the actual exhaust temperature is equal to or higher than a predetermined determination temperature that requires an increase in fuel for lowering the exhaust temperature. As a control device for an internal combustion engine, the flow component flowing into the combustion chamber is strengthened . An exhaust gas recirculation device that recirculates part of the exhaust gas to the intake air,
2. The control apparatus for an internal combustion engine according to claim 1 , wherein the intake flow control valve is closed in order to increase the exhaust gas recirculation rate in a predetermined EGR region on a low rotation / low load side. Supercharging pressure detecting means for detecting the actual supercharging pressure;
Means for determining whether the actual supercharging pressure is in a supercharging region exceeding atmospheric pressure,
The control apparatus for an internal combustion engine according to claim 1 or 2 , wherein the exhaust temperature lowering means is operated when the supercharging region is set. The internal combustion engine control device according to any one of claims 1 to 3 , wherein when the engine speed is lower than a predetermined lower limit value, closing operation of the intake flow control valve by the exhaust temperature reducing means is prohibited. . The internal combustion engine control device according to any one of claims 1 to 3 , wherein when the engine required torque is higher than a predetermined upper limit value, the exhaust flow control valve is prohibited from being closed by the exhaust temperature reducing means. . Intake flow control valve by the exhaust temperature lowering means is closed, and claims 1-5, characterized in that the actual exhaust temperature when more than a predetermined judgment temperature, with a fuel increase means for performing fuel increase The control apparatus for an internal combustion engine according to any one of the above. Is fuel increased by the fuel increase means, and, when the actual exhaust temperature is equal to or higher than the predetermined judgment temperature, according to claim 6, characterized in that it comprises a supercharging pressure lowering means for decreasing the boost pressure Control device for internal combustion engine.

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