JP2007071119A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine having an automatic stop and automatic restart function and an EGR mechanism for recirculating exhaust gas through an EGR passage and inhibiting blow-up in automatic restart as much as possible while preventing fuel mileage deterioration. <P>SOLUTION: The internal combustion engine is equipped with an exhaust passage throttle valve 20 in an exhaust passage 2 for narrowing a passage from a combustion chamber 14 to a connection part of the EGR passage 6. Fuel injection is stopped at the same time when a condition for engine automatic stop is satisfied. Further, an EGR valve 7 in the EGR passage 6 is driven for open and the exhaust passage restriction valve 20 and a throttle valve 4 are driven for close. EGR gas is introduced in an intake passage 1 through the EGR passage 6 by a pumping action owing to dieseling until a predetermined period elapses from when the fuel injection is stopped. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine that has an automatic stop / automatic restart function and recirculates exhaust gas through an EGR passage.

  In recent years, due to low pollution, when a vehicle stops at an intersection or the like, the internal combustion engine is automatically stopped, and the internal combustion engine is restarted based on the establishment of a restart condition such as a decrease in brake pedal depression. A so-called idling stop is performed.

  Here, when the internal combustion engine is automatically stopped, more air (fresh air) stays in the intake passage than during engine operation. For this reason, at the time of subsequent restart, this staying fresh air is introduced into the combustion chamber, so that a so-called blow-up in which the engine speed rapidly increases occurs. The occurrence of such a blow-up causes an increase in vibration when the engine is restarted.

  Therefore, conventionally, by introducing exhaust gas into the intake passage, that is, by performing exhaust gas recirculation (EGR), the ratio of fresh air introduced into the combustion chamber is reduced, and the amount of combustible air in the combustion chamber is reduced. It is known to suppress the rising.

For example, in the internal combustion engine described in Patent Document 1, when an automatic stop request for the internal combustion engine is detected, the EGR valve of the EGR passage is opened and the exhaust gas in the exhaust passage is introduced into the intake passage as EGR gas. When the total amount of exhaust introduced reaches the required amount, the fuel injection is stopped and the EGR valve is closed, and the throttle valve is closed until the internal combustion engine is restarted. It is held in the intake passage.
Japanese Patent Application Laid-Open No. 2004-1000049

  By the way, in the internal combustion engine described in Patent Document 1, the fuel injection is stopped when the total amount of the exhaust gas recirculated reaches the required amount after the automatic stop request of the internal combustion engine is detected. During that period, fuel will be consumed. Therefore, it is conceivable that when an automatic stop request is detected, fuel injection is stopped and exhaust gas is introduced into the intake passage by opening the EGR valve of the EGR passage. However, even if the fuel injection is stopped in this way, a phenomenon (dieseling) in which the output shaft rotates for a while due to inertia occurs in the internal combustion engine, and during that period, fresh air is discharged into the exhaust passage and the EGR passage May be introduced. As a result, fresh air is returned to the intake passage through the EGR passage, and the effect of suppressing the blow-up at the time of engine restart cannot be sufficiently exhibited.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress deterioration of fuel consumption in an internal combustion engine having an automatic stop / automatic restart function and recirculating exhaust gas through an EGR passage. On the other hand, it is intended to suppress ascending as much as possible during automatic restart.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention according to claim 1 includes an automatic stop / automatic restart function for automatically stopping the engine operation based on an engine automatic stop request while restarting the engine based on establishment of a restart condition, In an internal combustion engine in which an EGR valve in an EGR passage communicating with an intake passage is opened based on the determination that there is an automatic stop request for engine operation, and the EGR amount is increased until a predetermined period elapses. A throttle valve for restricting the passage to the connection portion of the EGR passage in the exhaust passage is provided, and fuel injection is stopped based on the determination that the engine automatic stop request is present, and the passage to the connection portion of the EGR passage is restricted. Thus, the gist is to drive the throttle valve.

  According to this configuration, since the fuel injection is stopped based on the determination that the engine automatic stop request is present, the operation of the internal combustion engine can be stopped quickly, and deterioration of fuel consumption can be suppressed. Further, when the fuel injection is stopped, the throttle valve is driven to throttle the exhaust passage from the combustion chamber to the connection portion of the EGR passage. Therefore, even if dieseling occurs after the fuel injection is stopped, it is possible to prevent fresh air from flowing into the EGR passage from the engine combustion chamber. Accordingly, it is possible to suppress the fresh air from being mixed into the exhaust gas remaining in the exhaust passage, and to return the exhaust gas, that is, EGR gas, from the EGR passage to the combustion chamber through the intake passage. As a result, it becomes possible to recirculate the amount of EGR gas necessary to suppress the rising at the time of restart to the combustion chamber. As described above, according to the above-described configuration, it is possible to suppress the rising at the time of automatic restart as much as possible while suppressing the deterioration of fuel consumption.

  According to a second aspect of the present invention, in the internal combustion engine of the first aspect, the throttle valve is located downstream of an exhaust valve that opens and closes an exhaust port that opens to the engine combustion chamber, and is provided separately from the exhaust valve. The gist is that

According to this configuration, by restricting the throttle valve provided downstream of the exhaust valve, it is possible to suppress fresh air from flowing into the EGR passage when the internal combustion engine stops.
According to a third aspect of the present invention, in the internal combustion engine according to the first aspect, the throttle valve is an exhaust valve that opens and closes an exhaust port opened in the engine combustion chamber. Its gist is that it can be driven independently.

  According to this configuration, the exhaust valve that opens and closes the exhaust port of the engine combustion chamber in synchronism with the engine rotation is also used as the throttle valve. Therefore, it is not necessary to separately provide such a throttle valve, and the configuration is simplified. Will be able to.

  A fourth aspect of the present invention is the internal combustion engine according to any one of the first to third aspects, wherein the EGR passage is connected to a downstream portion of a catalyst device provided in the exhaust passage. It is said.

  According to this configuration, since the EGR passage is connected to the downstream portion of the catalyst device in the exhaust passage, the distance from the engine combustion chamber to the connection portion of the EGR passage can be increased as much as possible, and recirculation is performed. The amount of EGR gas to be appropriately secured can be suitably secured, and the fresh air can be further prevented from flowing into the EGR passage.

  According to a fifth aspect of the present invention, in the internal combustion engine according to any one of the first to fourth aspects, the throttle valve of the intake passage is throttled based on the determination that the engine automatic stop request is present. The gist is to drive.

  According to this configuration, since the throttle valve is throttled based on the determination that there is an automatic engine stop request, the intake pressure can be reduced and the amount of EGR gas introduced into the intake passage through the EGR passage can be increased. A shortage of the amount of EGR gas introduced can be avoided.

  According to a sixth aspect of the present invention, in the internal combustion engine according to any one of the first to fifth aspects, the engine is automatically recirculated to the intake passage through the EGR passage after it is determined that there is a request for automatic engine stop. The gist of the present invention is to provide an integrating means for integrating the exhaust amount, and to close the EGR valve when the predetermined period has elapsed when the exhaust integrated amount integrated by the integrating means reaches a predetermined amount.

  According to this configuration, since the predetermined period is set based on the integrated flow rate, an amount of EGR gas necessary for suppressing the blow-up during restart can be introduced from the EGR passage to the intake passage. Further, instability of combustion at the time of starting the engine due to excessive introduction of EGR gas into the intake passage 1 can be suppressed.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a schematic configuration of an internal combustion engine according to the present embodiment. This internal combustion engine has an automatic stop / automatic restart function and an EGR mechanism that recirculates exhaust gas through an EGR passage.

  As shown in FIG. 1, the internal combustion engine includes a cylinder block 10 having a plurality of cylinders 11 and a cylinder head 12. An intake passage 1 and an exhaust passage 2 are connected to each cylinder 11. Each cylinder 11 is provided with a piston 13 that can reciprocate. A combustion chamber 14 is defined by the piston 13, the cylinder 11, and the cylinder head 12. The cylinder head 12 is provided with an intake valve 15 and an exhaust valve 16 that open and close the intake port 1a and the exhaust port 2a, respectively. The cylinder head 12 is provided with an injector 18 for injecting fuel into the intake port 1a.

  A throttle valve 4 for controlling the amount of air flowing into the combustion chamber 14 is provided in the intake passage 1. The opening degree of the throttle valve 4 is adjusted by a motor 5. On the other hand, the exhaust passage 2 is provided with a catalyst device 3 for purifying exhaust gas. In the exhaust passage 2, an exhaust passage throttle valve 20 is provided between the exhaust valve 16 and the catalyst device 3. The opening degree of the exhaust passage throttle valve 20 is adjusted by a motor 21.

  A downstream portion of the throttle valve 4 in the intake passage 1 and a downstream portion of the catalyst device 3 in the exhaust passage 2 are connected by an EGR passage 6. Exhaust gas (EGR gas) in the exhaust passage 2 is taken into the intake passage 1 through the EGR passage 6. The EGR passage 6 is provided with an EGR valve 7 for metering the EGR gas. The opening degree of the EGR valve 7 is adjusted by a motor 8.

  In addition, the electronic control device 30 that executes various controls related to the internal combustion engine, such as control related to engine automatic stop / automatic restart, fuel injection control, EGR amount control, and the like, includes various sensors for detecting the engine operating state. Is connected. Specifically, the electronic control unit 30 includes an accelerator sensor 31 that detects the amount of depression of the accelerator pedal, an engine rotation speed sensor 32 that detects the engine rotation speed, and a brake switch 33 that detects that the brake pedal is depressed. A vehicle speed sensor 34, a coolant temperature sensor 35, and the like are connected. Based on the detection results of these various sensors 31 to 35, the electronic control unit 30 executes various controls related to the internal combustion engine, such as control related to automatic engine stop / automatic restart, fuel injection control, and control of EGR amount.

Next, referring to FIGS. 2 and 3 together, processing procedures such as fuel injection control at the time of automatic engine stop, opening control of the exhaust passage throttle valve 20, and EGR amount control will be described.
In this series of processes, first, it is determined whether or not there is an engine automatic stop request, that is, whether or not an engine automatic stop condition is satisfied (step S100). Incidentally, the conditions such as the accelerator pedal not being depressed, a predetermined period of time has elapsed since the vehicle stopped, the brake pedal being depressed, warm-up operation has been completed, etc. are all satisfied. Sometimes, it is determined that the engine automatic stop condition is satisfied.

  Here, when it is determined that the engine automatic stop condition is not satisfied (step S100: NO), this process is temporarily ended. On the other hand, when it is determined that the engine automatic stop condition is satisfied (step S100: YES), as shown in FIG. 3 (timing t1), the electronic control unit 30 executes the following processes (step S110). ).

-Fuel injection by the injector 18 is stopped.
-Open the EGR valve 7.
-Close the throttle valve 4 to the opening when the engine is idle.
-The exhaust passage throttle valve 20 is closed.

That is, in this process, the fuel injection is stopped at the same time as the automatic engine stop condition is satisfied. Accordingly, the internal combustion engine is quickly stopped. However, as shown in FIG. 3, even if the fuel injection is stopped, the engine rotation speed only decreases gradually, so that the pumping action by the piston 13 continues for a period of time (timing t1 to t3). .

  Accordingly, by opening the EGR valve 7 during this period (timing t1 to t3), EGR gas is introduced from the exhaust passage 2 into the intake passage 1 through the EGR passage 6. Further, by closing the throttle valve 4, the intake pressure is reduced and the introduction of EGR gas is promoted. Further, by closing the exhaust passage throttle valve 20, fresh air is prevented from flowing into the EGR passage 6. FIG. 3 shows an example in which the exhaust passage throttle valve 20 is changed from the fully open state to the fully closed state.

  In addition, after the fuel injection stop process, the EGR valve opening process, and the throttle valve closing process are performed in this way, the EGR gas flow rate integrated counter value is incremented every predetermined time. Therefore, as shown in FIG. 3, the EGR gas flow rate integrated value counter value gradually increases after timing t1. The EGR gas flow rate integrated counter value indicates the total amount of EGR gas introduced into the intake passage after the fuel injection is stopped.

  Next, it is determined whether or not a predetermined period has elapsed since the EGR valve 7 was opened, in other words, whether or not the EGR gas flow rate integrated counter value has reached a predetermined value (step S120). If the predetermined period has not elapsed (step S120: NO), the process waits without shifting to the next process (FIG. 3: timing t1 to timing t2). Here, the predetermined value is set so that the amount of EGR gas introduced from the exhaust passage 2 into the intake passage 1 is a necessary and sufficient amount for suppressing the rise at the time of engine restart.

  When the EGR gas flow rate integrated counter value reaches a predetermined value, that is, when it is determined that a necessary and sufficient amount of EGR gas has been introduced into the intake passage 1 (step S120: YES), the EGR valve 7 is fully closed. In addition, the exhaust passage throttle valve 20 is opened (step S130). Here, the throttle valve 4 is maintained in a closed state as it is so that EGR gas does not leak to the upstream side of the throttle valve 4 as much as possible.

Incidentally, the electronic control unit 30 restarts the engine when an engine restart condition such as a decrease in the amount of depression of the brake pedal or depression of the accelerator pedal is satisfied.
As described above, according to the embodiment described above, the following effects can be obtained.

  (1) Since the fuel injection is stopped at the same time as the engine automatic stop condition is satisfied, the operation of the internal combustion engine can be stopped quickly, and deterioration of fuel consumption can be suppressed. Then, by closing the exhaust passage throttle valve 20 in conjunction with the stop of fuel injection, after the fuel injection is stopped, fresh air is prevented from flowing into the EGR passage 6 from the combustion chamber 14. Accordingly, it is possible to prevent fresh air from being mixed into the exhaust gas remaining in the exhaust passage 2 and return the exhaust gas, that is, EGR gas, from the EGR passage 6 to the combustion chamber 14 via the intake passage 1. As a result, it is possible to recirculate the amount of EGR gas necessary to suppress the rising at the time of restart to the combustion chamber 14.

  (2) Since the EGR passage 6 is connected to the downstream portion of the catalyst device 3 in the exhaust passage 2, the distance from the combustion chamber 14 to the connection portion of the EGR passage can be made as long as possible, and recirculation is performed. The amount of EGR gas to be appropriately secured can be suitably secured, and the fresh air can be further prevented from flowing into the EGR passage 6.

  (3) Since the throttle valve 4 is throttled at the same time as the engine automatic stop condition is satisfied, the intake pressure can be reduced. Therefore, the amount of EGR gas introduced into the intake passage 1 through the EGR passage 6 can be increased, and a shortage of EGR gas introduction amount can be avoided.

  (4) The elapsed time after stopping the fuel injection and introducing the EGR gas is counted, and the EGR valve 7 is closed when a predetermined period has elapsed. Accordingly, an amount of EGR gas necessary for suppressing the engine blow-up during the automatic engine restart can be introduced from the EGR passage 6 into the intake passage 1 and excessively EGR gas is introduced into the intake passage 1. It is possible to suppress instability of combustion at the time of starting the engine due to the above.

Note that the configuration of the above embodiment can be changed as follows.
In the above embodiment, the throttle valve 4 is closed to the opening at the time of engine idling, but may be larger than the opening at idling if the intake pressure can be reduced. Similarly, the exhaust passage throttle valve 20 is changed from the fully open state to the fully closed state. However, the exhaust passage throttle valve 20 may not be fully closed as long as fresh air can be prevented from flowing into the EGR passage 6 from the combustion chamber 14.

In the above embodiment, the exhaust passage throttle valve 20 is opened in step S130, but the valve closing state may be maintained until the engine is automatically restarted.
In the above embodiment, the EGR passage 6 is connected to the downstream portion of the catalyst device 3 in the exhaust passage 2, but if the necessary and sufficient amount of EGR gas can be introduced, the EGR passage 6 May be connected to the upstream portion of the catalyst device 3.

  In the above embodiment, it is determined that a necessary and sufficient amount of EGR gas has been introduced into the intake passage 1 when a predetermined period has elapsed since the fuel injection was stopped and the EGR valve 7 was opened. . Here, since the amount of EGR gas introduced from the EGR passage 6 into the intake passage 1 increases as the engine rotational speed increases, for example, the engine rotational speed when the fuel injection is stopped, or after the fuel injection is stopped. The predetermined period can be variably set based on the engine speed.

  In the above embodiment, the exhaust passage throttle valve 20 restricts the passage from the combustion chamber 14 to the connection portion of the EGR passage 6, but the exhaust valve 16 can be substituted for the exhaust passage throttle valve 20. In this case, the exhaust valve 16 is an open / closed type independent of the engine rotation phase, such as an electromagnetically driven valve. According to such a configuration, since the exhaust valve 16 has the function of a throttle valve, it is not necessary to separately provide the throttle valve, and the configuration can be simplified.

  Further, although the exhaust passage throttle valve 20 is opened when a predetermined period has elapsed from when fuel injection is stopped, the exhaust passage throttle valve 20 may be maintained in a closed state. . In this way, it is possible to prevent EGR gas from leaking from the combustion chamber 14 to the exhaust passage 2 while the engine is stopped.

1 is a schematic configuration diagram of an internal combustion engine. The flowchart which shows the control processing procedure of the internal combustion engine at the time of an engine automatic stop. The timing chart which shows the control aspect of the internal combustion engine at the time of an engine automatic stop.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Intake passage, 2 ... Exhaust passage, 3 ... Catalytic device, 4 ... Throttle valve, 5, 8, 21 ... Motor, 6 ... EGR passage, 7 ... EGR valve, 10 ... Cylinder block, 11 ... Cylinder, 12 ... Cylinder Head, 13 ... piston, 14 ... combustion chamber, 15 ... intake valve, 16 ... exhaust valve, 18 ... injector, 20 ... exhaust passage throttle valve, 30 ... electronic control device, 31 ... accelerator sensor, 32 ... engine speed sensor, 33 ... Brake switch, 34 ... Vehicle speed sensor, 35 ... Cooling water temperature sensor, 1a ... Intake port, 2a ... Exhaust port.

Claims (6)

The engine operation is automatically stopped on the basis of the engine automatic stop request, and the EGR passage is provided with an automatic stop / automatic restart function for restarting the engine on the basis of establishment of the restart condition, and communicating the exhaust passage and the intake passage. In an internal combustion engine that opens an EGR valve based on the determination that there is an automatic stop request for engine operation and increases the EGR amount until a predetermined period elapses.
A throttle valve that throttles a passage from the engine combustion chamber to the connection portion of the EGR passage in the exhaust passage, stops fuel injection based on the determination that the engine automatic stop request is present, and is connected to the connection portion of the EGR passage; An internal combustion engine, wherein the throttle valve is driven so that a passage to be reached is throttled. The internal combustion engine according to claim 1,
The internal combustion engine, wherein the throttle valve is located downstream of an exhaust valve that opens and closes an exhaust port that opens to an engine combustion chamber, and is provided separately from the exhaust valve. The internal combustion engine according to claim 1,
The throttle valve is an exhaust valve that opens and closes an exhaust port opened in the engine combustion chamber, and the exhaust valve can be driven independently of the engine rotation state. The internal combustion engine according to any one of claims 1 to 3,
The internal combustion engine, wherein the EGR passage is connected to a downstream portion of a catalyst device provided in the exhaust passage. The internal combustion engine according to any one of claims 1 to 4,
An internal combustion engine that drives the throttle valve of the intake passage so that the throttle valve is throttled based on the determination that the engine automatic stop request is present. The internal combustion engine according to any one of claims 1 to 5,
An integration means for integrating the amount of exhaust gas recirculated through the EGR passage to the intake passage after the determination that the engine automatic stop request is made is provided, and the integrated exhaust amount integrated by the integration means reaches a predetermined amount. An internal combustion engine characterized in that the EGR valve is closed when the predetermined period has elapsed.

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