JP5553690B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine accompanied by an exhaust gas recirculation device.

  In an internal combustion engine mounted on an automobile or the like, exhaust gas recirculation is performed in which an intake system and an exhaust system are connected via an external EGR passage and a part of the exhaust gas is recirculated to the intake system through the EGR passage. An EGR valve is provided on the EGR passage, and the recirculation amount and recirculation timing of the EGR gas can be adjusted by operating the opening degree of the EGR valve in accordance with the operation region of the internal combustion engine.

  The EGR gas flowing through the EGR passage contains particulate matter, lubricating oil, and the like, which adhere to the inner periphery of the EGR passage and the EGR valve, and accumulate as deposits. The deposit can reduce the effective flow path area of the EGR passage and hinder the operation of the EGR valve. For the purpose of removing this deposit, it is known to execute a cleaning process for forcibly opening and closing the EGR valve during a fuel cut period in which the fuel supply to the cylinder is temporarily stopped (see, for example, the following patent document). reference).

  During the fuel cut, the cylinder is filled with air that does not contain fuel, and the air that does not contain combustion gas is discharged from the cylinder. Therefore, the air containing no combustion gas is also filled in the EGR passage. In the operation control of the internal combustion engine at the time of return from fuel cut (resumption of fuel supply), it is assumed that the EGR rate, which is the ratio of EGR gas in the intake air, is 0, and the required fuel injection amount, ignition timing, etc. Perform the operation.

  However, when the fuel cut is completed in an extremely short period of time, such as when the brake pedal is depressed immediately after the start of the fuel cut, the EGR gas still remains in the EGR passage. If the EGR valve is opened at the time of return from the fuel cut, the residual EGR gas is mixed with the intake air, and the actual intake EGR rate becomes higher than expected, that is, 0. For this reason, the fuel injection amount, the ignition timing, and the like become inappropriate, which may cause misfire and other unstable combustion conditions.

JP 2000-064910 A JP 2008-038636 A

  The present invention is intended to prevent misfires and other unstable combustion conditions when returning from a fuel cut when performing a cleaning process of an EGR device during a fuel cut.

In the present invention, fuel is temporarily supplied to an internal combustion engine attached with an EGR device having an EGR valve on an external EGR passage connecting an exhaust system and an intake system, provided that a predetermined fuel cut condition is satisfied. Performing a fuel cut that stops automatically, and performing a cleaning process for forcibly opening and closing the EGR valve between a set maximum opening and a minimum opening during the fuel cut, The maximum opening when the elapsed time from the start of execution of the cleaning process is relatively short is set smaller than the maximum opening when the elapsed time is relatively long, and the fuel cut is performed in a very short time. constitutes a control device, characterized in that resumes fuel injection after the closed or full the EGR valve which was open for cleaning process closed until opening close to it when finished .

  That is, at the beginning of the execution of the cleaning process, the amplitude of the opening / closing operation of the EGR valve is reduced so that the EGR valve can be quickly closed when the fuel cut ends in a very short time. This effectively avoids the problem that the residual EGR gas is mixed with the intake air and the EGR rate increases when returning from the fuel cut, and the possibility of causing misfire and other unstable combustion conditions is reduced.

  In addition, when time has elapsed since the start of execution of the cleaning process and there seems to be almost no residual EGR gas, the amplitude of the opening / closing operation of the EGR valve is increased to increase the deposit peeling effect. In addition, the deposit and oil in the EGR passage are sufficiently scavenged.

  According to the present invention, when performing the cleaning process of the EGR device during the fuel cut, it is possible to prevent a misfire or other unstable combustion state from occurring when returning from the fuel cut.

The figure which shows the structure of the internal combustion engine in one Embodiment of this invention. The figure which shows the structure of the automatic transmission in the embodiment. 7 is a flowchart showing a procedure of a cleaning process executed by the control device according to the program according to the embodiment. 6 is a timing chart showing a state of a cleaning process in the embodiment.

  An embodiment of the present invention will be described with reference to the drawings. The internal combustion engine 0 schematically showing the configuration of one cylinder in FIG. 1 is mounted on, for example, an automobile. The intake system 1 of the internal combustion engine 0 is provided with a throttle valve 11 that opens and closes according to the amount of depression of the accelerator pedal, and an intake manifold 12 that integrally has a surge tank 13 is attached downstream of the throttle valve 11. The surge tank 13 is provided with a pressure sensor 71 for detecting the intake pipe pressure (or intake negative pressure).

An exhaust manifold 51 is attached to the exhaust system 5 and a three-way catalyst 52 for exhaust gas purification is attached. A front O ₂ sensor 53 is disposed upstream of the catalyst 52, and a rear O ₂ sensor 54 is disposed downstream. The O ₂ sensors 53 and 54 output a voltage signal corresponding to the oxygen concentration in the exhaust gas by reacting in contact with the exhaust gas.

  An EGR device 6 is interposed between the intake system 1 and the exhaust system 5. The EGR device 6 includes an external EGR passage 61 having a start end communicating with the exhaust manifold 51 and a terminal end communicating with the surge tank 13, and an external EGR valve 62 provided on the EGR passage 61. If the EGR valve 62 is opened, an external EGR that recirculates the exhaust gas from the exhaust system 5 to the intake system 1 and mixes it with the intake air can be realized.

  An intake valve 21, an exhaust valve 22, an injector 3, and a spark plug 23 are provided on the ceiling portion (cylinder head) of the combustion chamber formed in the upper part of the cylinder 2.

  Recent automobiles are often AT cars equipped with automatic transmissions. FIG. 2 shows an example of an automatic transmission. The automatic transmission shown in FIG. 2 is a continuously variable transmission provided with a torque converter 7 and a belt-type continuously variable transmission mechanism (Continuously Variable Transmission) 9. The driving force output from the internal combustion engine 0 is input to the input shaft 71 of the torque converter 7 and transmitted to the output shaft 72. The rotation of the output shaft 72 of the torque converter 7 is transmitted to the drive shaft 94 of the CVT 9 via the forward / reverse switching device 8 using a planetary gear mechanism, and the driven shaft 95 is rotated through a shift in the CVT 9. An output gear 101 is fixed to the driven shaft 95, and this output gear 101 meshes with the ring gear 102 of the differential device to rotate the axle 103 and thus the drive wheel (not shown).

  The torque converter 7 includes a lockup mechanism (not shown). The lock-up mechanism is known in this field, and includes a lock-up clutch that locks up the input shaft 71 and the output shaft 72 of the torque converter 7, and a lock that controls hydraulic pressure for driving the connection and disconnection of the lock-up clutch. The element is an up solenoid valve. The lockup mechanism connects the lockup clutch and fastens the input shaft 71 and the output shaft 72 in a situation where the gear ratio is not changed by the automatic transmission.

  The CVT 9 includes a driving pulley 91 and a driven pulley 92, and a belt 93 wound around the pulleys 91 and 92 as elements. The drive pulley 91 is disposed behind the movable sheave 912, a fixed sheave 911 fixed to the drive shaft 94, a movable sheave 912 supported on the drive shaft 91 via a roller spline so as to be displaceable in the axial direction. A hydraulic servo 913 is provided, and the gear ratio can be changed steplessly by operating the hydraulic servo 913 and displacing the movable sheave 912. The driven pulley 92 is disposed on the back of the movable sheave 922, a fixed sheave 921 fixed to the driven shaft 95, a movable sheave 922 supported on the driven shaft 95 via a roller spline so as to be axially displaceable. A hydraulic servo 923 is provided, and a belt thrust necessary for torque transmission is applied by operating the hydraulic servo 923 and displacing the movable sheave 922.

  An electronic control unit 4 that controls the operation of the internal combustion engine 0 is a microcomputer system having a central processing unit 41, a storage device 42, an input interface 43, an output interface 44, and the like.

The input interface 43 includes an intake pressure signal a output from the pressure sensor 71 that detects the pressure in the intake pipe, a rotation speed signal b output from the rotation speed sensor 72 that detects the engine speed, and a vehicle speed sensor 73 that detects the vehicle speed. Is output from the throttle position sensor 74 for detecting the opening degree of the throttle valve 11 (or the depression amount of the accelerator pedal), and the water temperature sensor 76 for detecting the cooling water temperature. Water temperature signal f, knocking signal e output from a knocking sensor 75 for detecting a knocking state by a change in combustion pressure, a crank angle signal output from a timing sensor 96 at the end of the intake camshaft 91, and cylinder discrimination Signal g, 2 from the timing sensor 97 at the end of the exhaust camshaft 92 0 ° CA (crank angle) exhaust cam signal h which is output every rotation, the upstream air-fuel ratio signal output from the front O ₂ sensor 53 i, the downstream air-fuel ratio signal j or the like to be output from the rear O ₂ sensor 54 Is entered.

  From the output interface 44, the fuel injection signal n for the injector 3, the ignition signal m for the spark plug 8, the EGR valve opening signal o for the EGR valve 62, the transmission ratio signal p for CVT 9, and the torque converter An open / close signal q or the like is output to the lockup solenoid valve 7.

  The central processing unit 41 interprets and executes a program stored in the storage device 42 in advance, such as the fuel injection amount and ignition timing of the internal combustion engine 0, the EGR gas recirculation amount (intake EGR rate), the gear ratio, and the like. Carry out control.

  In the operation control of the internal combustion engine 0, the ECU 4 acquires various information a, b, c, d, e, f, g, h, i, j necessary for the operation control of the internal combustion engine 0 via the input interface 43. Further, the current intake air amount and the EGR rate of the intake air are estimated, and based on these, the fuel injection amount, the fuel injection timing, the ignition timing, the opening degree of the EGR valve 62 (number of EGR steps), and the shift of the CVT 9 are input. Ratio, whether or not the torque converter 7 can be locked up, and the like are calculated. Then, control signals m, n, o, p, q corresponding to the calculated control input are applied via the output interface 44. Since the calculation method of the control input can be the same as the known operation control of the internal combustion engine 0, the description is omitted here.

  Therefore, the ECU 4 as the control device in the present embodiment executes a cleaning process for forcibly opening and closing the EGR valve 62 during the fuel cut for temporarily stopping the fuel supply.

  FIG. 3 shows a procedure of processes executed by the ECU 4 in the cleaning process. The ECU 4 stops fuel injection from the injector 3 (step S2) when a predetermined fuel cut condition is satisfied (step S1). For example, the fuel cut is started on the condition that the opening degree of the throttle valve 11 (or the amount of depression of the accelerator pedal) is 0 or less than a predetermined threshold value near 0 and the engine speed is more than a certain value.

  The cleaning process of the EGR device 6 is started during the fuel cut and when the intake pipe pressure becomes equal to or lower than the predetermined pressure PMa (step S3).

  In the cleaning process, the maximum opening of the EGR valve 62 is set (step S5), and the process of opening and closing the EGR valve 62 between the maximum opening and the minimum opening (step S6) is repeated. FIG. 4 illustrates the pattern of the cleaning process. The maximum opening of the EGR valve 62 in the cleaning process is set to an opening that can sufficiently suppress the EGR rate when returning from the fuel cut. As indicated by the one-dot chain line in FIG. 4, the maximum opening degree of the EGR valve 62 in the cleaning process is the smallest at the beginning of the cleaning process, and is increased as time elapses from the start of the cleaning process. The minimum opening of the EGR valve 62 is fully closed.

  The cleaning process ends when the intake pipe pressure becomes equal to or higher than the predetermined pressure PMb (step S7) or when a predetermined fuel cut end condition is satisfied (step S9). Here, PMb is set to a larger value than PMa.

  When the fuel cut end condition is satisfied during the fuel cut (step S4, S8 or S9), the EGR valve 62 is closed toward the fully closed position (step S10), and the fuel injection from the injector 3 is resumed. (Step S11). For example, the fuel cut is ended on the condition that the opening degree of the throttle valve 11 (or the accelerator pedal depression amount) exceeds a threshold value or the engine speed has decreased to a predetermined return speed IDL. Immediately after returning from the fuel cut, it is assumed that the EGR rate of the intake air is 0, and the required fuel injection amount and other control inputs are calculated.

  In the AT vehicle, the input shaft 71 and the output shaft 72 of the torque converter 7 are locked up during the fuel cut, and the lockup is released when returning from the fuel cut. In particular, in situations where a sudden brake is applied, the lockup must be released before the wheels are locked. However, if the resumption of fuel supply is not in time for the release of the lockup, an engine stall occurs.

  When the fuel cut is completed in an extremely short period of time, EGR gas still remains in the EGR passage 61. If the EGR valve is opened when returning from the fuel cut, the EGR rate of the intake air increases. As already described, the required fuel injection amount and the like are determined immediately after returning from the fuel cut, assuming that the intake EGR rate is 0. Therefore, combustion becomes unstable unless the actual EGR rate is close to 0. Therefore, the fuel supply cannot be resumed until the EGR valve 62 is closed.

  In the present embodiment, since the maximum opening of the EGR valve 62 is set to a relatively small value at the beginning of the cleaning process, the EGR valve 62 can be quickly fully closed or close to the opening in step S10. . In particular, in the first opening / closing operation of the EGR valve 62 in the cleaning process, it is desirable to set the maximum opening, that is, the stroke amount, to a value that allows the EGR valve 62 to be fully closed before the unlocking is completed. . This value can be determined (or calculated) from the operating speed at which the EGR valve 62 is closed and the time required to release the lockup. As a result, even if the fuel supply is resumed early in step S11, the actual intake EGR rate is close to 0 and combustion does not become unstable.

  In contrast, when the fuel cut has continued for a certain extent, the EGR passage 61 is already filled with fresh air. Since it is guaranteed that the EGR rate of the intake air will be almost zero regardless of the opening degree of the EGR valve 62, the fuel supply resumes in step S11 before the opening degree of the EGR valve 62 is sufficiently reduced in step S10. You can move on.

  According to the present embodiment, a predetermined fuel cut condition is established for the internal combustion engine 0 attached with the EGR device 6 in which the EGR valve 62 is provided on the external EGR passage 61 connecting the exhaust system 5 and the intake system 1. On the condition that the fuel supply is cut, the fuel cut is temporarily stopped, and the EGR valve 62 is forcibly opened and closed between the set maximum opening and minimum opening during the fuel cut. The maximum opening when the elapsed time from the start of execution of the cleaning process is relatively short is set to be smaller than the maximum opening when the elapsed time is relatively long. Since the control device 4 is configured, the amplitude of the opening / closing operation of the EGR valve 62 is small at the beginning of the execution of the cleaning process, and the fuel cut is finished in a very short time. It can be closed promptly EGR valve 62 as. Therefore, the problem that residual EGR gas mixes with intake air and the EGR rate increases when returning from the fuel cut is effectively avoided. Even when the fuel cut is completed in an extremely short time, the fuel supply can be restarted at an early stage. Therefore, in the AT vehicle, the restart of the fuel supply is not in time for the release of the lockup, and the engine stall does not occur.

  In addition, when time has elapsed since the start of execution of the cleaning process and there seems to be almost no residual EGR gas, the amplitude of the opening / closing operation of the EGR valve is increased to increase the deposit peeling effect. It can be increased, and the deposit and oil scavenging in the EGR passage 61 can be sufficiently performed.

  The present invention is not limited to the embodiment described in detail above. For example, although the internal combustion engine in the above embodiment is a spark ignition engine, the present invention can be applied even if it is a diesel engine.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to an internal combustion engine mounted on an automobile or the like.

DESCRIPTION OF SYMBOLS 100 ... Internal combustion engine 4 ... ECU (control apparatus)
6 ... EGR device 61 ... EGR passage 62 ... EGR valve

Claims (1)

Temporary fuel supply to an internal combustion engine with an exhaust gas recirculation device with an EGR valve on the external EGR passage connecting the exhaust system and the intake system, provided that a predetermined fuel cut condition is satisfied In addition to implementing a fuel cut that stops at
Performing a cleaning process for forcibly opening and closing the EGR valve between a set maximum opening and a minimum opening during fuel cut,
The maximum opening when the elapsed time from the start of execution of the cleaning process is relatively short is set smaller than the maximum opening when the elapsed time is relatively long, and the fuel cut is performed in a very short time. A control device characterized by restarting fuel injection after the EGR valve that has been opened for the cleaning process is fully closed or closed to an opening degree close thereto when the operation is to be ended .

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