JP2011117410A - Method for controlling suction air amount in internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling suction air amount in an internal combustion engine in which a problem is solved as follows: as refluxed exhaust is left in an intake manifold, new intake amount to the exhaust left is short and is highly likely to cause fire when a gas pedal is returned when EGC control is executed. <P>SOLUTION: The internal combustion engine with an exhaust recirculation device for mixing part of the exhaust with intake air while a slot valve is controlled by the gas pedal means. When the exhaust recirculation device is being controlled and the gas pedal means is controlled in a direction in which the slot valve is closed, the internal combustion engine predicts a load factor of the internal combustion engine that finally converges to set a target value and controls the suction air amount so that the load factor of the internal combustion engine becomes below the target value until the load factor reaches the target value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an intake air amount control method in an internal combustion engine including an exhaust gas recirculation device for mixing a part of exhaust gas with intake air.

  2. Description of the Related Art Conventionally, for example, an internal combustion engine mounted on an automobile is provided with an exhaust gas recirculation device to improve fuel efficiency, and a part of the exhaust gas is recirculated downstream of a throttle valve and mixed with intake air. ing. In such an internal combustion engine, when operating in a high load range, if the vehicle is decelerated rapidly by returning the accelerator pedal, the exhaust gas recirculated inside the intake manifold remains, and the recirculation with respect to the total amount of intake air The exhaust gas recirculation rate (hereinafter referred to as the EGR rate), which is the ratio of the amount of exhaust gas generated, may be high, and the possibility of misfire may increase.

  In order to deal with such a problem, for example, in Patent Document 1, when rapid deceleration is detected while a part of the exhaust gas is recirculated, the auxiliary air is bypassed to the internal combustion engine by bypassing the throttle valve. The time is supplied and the EGR rate is corrected.

Japanese Patent Laid-Open No. 9-209798

  However, with such a configuration, as described above, when the rapid deceleration is performed, the exhaust gas that has been recirculated remains inside the intake manifold, so the possibility of misfire is maintained. Sometimes. That is, when supplying auxiliary air, a response delay occurs, so that the auxiliary air is insufficient immediately after detection of rapid deceleration. As a result, a high EGR rate was maintained, and the intake amount of fresh air that was not exhaust gas was small, which left a high possibility of misfire.

  Therefore, the present invention aims to eliminate such problems.

  That is, an intake air amount control method for an internal combustion engine according to the present invention includes an exhaust gas recirculation device for controlling a throttle valve with an accelerator means and mixing a part of the exhaust gas with the intake air. When the gas recirculation device is being controlled and the accelerator means is controlled to close the throttle valve, the load factor of the internal combustion engine that finally converges is predicted and set to the target value, and the load on the internal combustion engine is set. The intake air amount is controlled so that the rate does not fall below the target value until the rate reaches the target value.

  According to such a configuration, in the execution of the control in the closing direction of the throttle valve, the target value until the load factor reaches the target value that is set by predicting the load factor of the internal combustion engine that finally converges. Since the intake air amount is controlled so as not to fall below, it is possible to secure an appropriate amount of intake air for the remaining exhaust gas. Therefore, the occurrence of misfire can be suppressed.

  In such a configuration, it is preferable to control the intake air amount so that the difference between the load factor of the internal combustion engine and the exhaust gas recirculation rate by the exhaust gas recirculation device is equal to or greater than a predetermined value.

  The present invention is configured as described above, and in an operating state in which exhaust gas recirculation is performed by an exhaust gas recirculation device, the exhaust gas remaining after being recirculated even if the throttle valve is controlled to close. In contrast, sufficient fresh intake air (fresh air) can be secured, and the occurrence of misfire can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows schematic structure of embodiment of this invention. The flowchart which shows the outline of the control procedure of the embodiment. Action | operation explanatory drawing of the same embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

A multi-cylinder engine 100 schematically showing the configuration of one cylinder in FIG. 1 is mounted on an automobile, for example. The engine 100 includes an intake system 1, a cylinder 2, and an exhaust system 5. The intake system 1 is provided with a throttle valve 11 that opens and closes in response to an accelerator pedal (not shown), and an intake manifold 12 that integrally has a surge tank 13 is attached downstream of the throttle valve 11. A spark plug 8 is attached to the ceiling of the combustion chamber 23 formed in the upper part of the cylinder 2. A fuel injection valve 3 is attached to an intake port side end of the intake manifold 12. The fuel injection valve 3 is controlled by an electronic control device 4 described later. Further, an exhaust gas recirculation device (hereinafter referred to as an EGR device) 6 is connected between the surge tank 13 and the exhaust system 5 including the O ₂ sensor 51, the three-way catalyst 52 and the exhaust manifold 53.

  In this embodiment, the throttle valve 11 is opened and closed according to the amount of operation of the accelerator pedal, and is electronically controlled that is opened and closed by the electronic control unit 4 during idle operation when the accelerator pedal is not depressed. A so-called electronic throttle 9 is configured. The electronic throttle 9 includes an accelerator sensor 91 that is an accelerator operation amount detector that detects an operation amount of the accelerator pedal, an electronic control device 4 that processes an operation amount signal output from the accelerator sensor 91, and an operation amount of the accelerator pedal. Correspondingly, a motor 92 for controlling the opening degree of the throttle valve 11 by a drive signal output from the electronic control unit 4 is provided. The accelerator sensor 91 is interlocked with the operation of the accelerator pedal so that when the accelerator pedal is depressed, an accelerator signal e corresponding to the depression amount, that is, the operation amount is output.

  The EGR device 6 includes an exhaust gas recirculation pipe (hereinafter referred to as an EGR pipe) 61 connected at one end so as to communicate with the surge tank 13, and an EGR pipe provided in the EGR pipe 61. An exhaust gas recirculation control valve (hereinafter referred to as an EGR valve) 62 that controls the flow rate of the exhaust gas passing through 61 is configured. The other end of the EGR pipe 61 is connected to the exhaust manifold 53 so as to communicate with the exhaust system 5 upstream of the three-way catalyst 52 provided in the exhaust 5 system. When the EGR valve 62 is controlled, that is, opened, the EGR device 6 passes the EGR pipe 61 at a flow rate corresponding to the opening degree of the EGR valve 62 and is located downstream of the throttle valve 11, that is, a surge tank. 13 is refluxed. The flow rate of the exhaust gas to be recirculated (hereinafter referred to as EGR gas) depends on the opening degree of the EGR valve 62, and the opening degree of the EGR valve 62 is controlled by the electronic control unit 4.

  The EGR valve 62 in this embodiment is connected to a through hole having a frustoconical inner surface, a frustoconical valve body having the same shape as the through hole disposed inside the through hole and opening and closing the through hole, and the valve body. The shaft includes a shaft and a stepper motor connected to the shaft and reciprocatingly moves the valve body in the direction of the central axis of the through hole. In such an EGR valve 62, a stepper motor, a DC motor, or the like can be used as a motor. When using a stepper motor, the valve opening degree of the EGR valve 62 is controlled by the number of steps of a signal supplied to the stepper motor. In the case of a DC motor, the opening degree is controlled by controlling energization by, for example, PMW (pulse width modulation) control.

  The electronic control unit 4 includes a microcomputer 41, a memory 42, an input interface 43, and an output interface 44. The microcomputer 41 controls the operation of the engine 100 by executing various programs described below stored in the memory 42. Information necessary for operation control of the engine 100 is input to the microcomputer 41 via the input interface 43, and the microcomputer 41 controls the fuel control valve 3, the EGR valve 62, the oil control valve 92, and the like. The signal is output via the output interface 44.

Specifically, the input interface 43 outputs an air flow rate signal a output from the air flow meter 71 for detecting the air flow rate flowing into the intake manifold 12, and an output from the rotation speed sensor 72 for detecting the engine speed. A rotation speed signal b, a vehicle speed signal c output from the vehicle speed sensor 73 for detecting the vehicle speed, an accelerator signal e output from the accelerator sensor 91, and a water temperature sensor 76 for detecting the cooling water temperature of the engine 100. An output water temperature signal f, a voltage signal h output from the O ₂ sensor 51, and the like are input. On the other hand, from the output interface 44, an ignition signal m for the spark plug 8, a fuel injection signal n for the fuel control valve 3, an open / close signal p for the motor 92, an open / close signal o for the EGR valve 62, and the like. Is output.

  In such a configuration, the electronic control unit 4 is set according to the operating state using the air flow rate signal a output from the air flow meter 71 and the rotation speed signal b output from the rotation speed sensor 72 as main information. The fuel injection amount is calculated using the coefficient to determine the fuel injection time corresponding to the fuel injection amount, that is, the energization time for the fuel injection valve 3, and the fuel injection valve 3 is controlled by the determined energization time. Is injected into the intake system 1. Such fuel injection control itself may apply what is known in this field.

  Further, an EGR control program for controlling the opening degree of the EGR valve 62 in accordance with the operating state of the engine 100 and performing EGR control is stored in the electronic control unit 4. This EGR control program may be widely known in this field.

  Further, the electronic control device 4 predicts the load factor of the internal combustion engine that finally converges when the EGR device 6 is being controlled and the accelerator pedal is controlled in the direction in which the throttle valve 11 is closed. An intake air amount control program that controls the intake air amount so that the load rate of the engine 100 does not fall below a predetermined change rate before reaching the target value is stored.

  This intake air amount control program is executed when the EGR device 6 is being controlled, in other words, when a part of the exhaust gas is recirculated to the surge tank 13 via the EGR conduit 61 by the EGR control. Therefore, when the EGR control is not performed, the intake air amount control program is not executed.

  In FIG. 2, first, in step S1, it is determined whether or not the engine 100 is operated in the driving state in the EGR use range and the vehicle is rapidly decelerated from the traveling state. That is, the EGR usage range, that is, the operating state in which the EGR device 6 is controlled is detected by controlling the EGR valve 62 in the opening direction. This is detected based on a signal (number of steps) applied to the stepper motor of the EGR valve 62. The accelerator signal output from the accelerator sensor 91 indicates whether or not the operation of the accelerator pedal has been operated in a direction to close the throttle valve 11, that is, whether or not the accelerator pedal has been switched from being depressed to not being depressed. Judgment based on. When such an operation of the accelerator pedal is executed, the intake amount of fresh air rapidly decreases.

  In this embodiment, as shown in FIG. 3, when the accelerator pedal is no longer depressed, the throttle valve 11 is set almost instantly in accordance with this, and is set by this intake air amount control program. Closed gradually at a predetermined closing speed to prevent a sudden decrease in intake air. Thus, the period T for closing the throttle valve 11 at a predetermined closing speed is set corresponding to a period in which the EGR rate does not change due to a mechanical operation delay of the EGR valve 62. During this time, it is determined whether or not the opening of the throttle valve 11 has become an idle opening. A predetermined opening for that is set, and the opening of the throttle valve 11 is set to the predetermined opening. It is determined that the vehicle is in an idling operation state when the temperature becomes less than or equal to the degree. Further, when the mechanical operation delay of the EGR valve 62 ends and the EGR rate starts to drop, the intake air that is larger than the opening amount in the idle operation, that is, the intake air amount that is larger than the intake air amount in the idle rotation control. The opening of the throttle valve 11 is held so that the amount becomes equal. The intake air amount at this time is an amount that satisfies the relationship between the load factor of the engine 100 and the EGR rate described below.

  As described above, when the accelerator pedal is not depressed at all, the operation state of the engine 100 deviates from the operation region in which EGR control is performed, that is, the EGR use region, so that the EGR valve 62 is controlled to be closed. In this case, the open / close signal for the stepper motor that drives the EGR valve 62 is an instruction to instantly close (indicated by a two-dot chain line in FIG. 3). However, the EGR valve 62 gradually increases due to a mechanical delay. Will be closed. Therefore, the EGR rate gradually decreases in accordance with the EGR gas remaining in the intake system 1 and the operation delay of the EGR valve 62. Since the flow rate of EGR gas can be calculated based on the opening degree of the EGR valve 62, the EGR rate can be obtained from the calculated flow rate.

  In step S2, the load factor of the engine 100 that finally converges when the throttle valve 11 is fully closed is determined from the opening of the throttle valve 11 before the throttle valve 11 is controlled to close (hereinafter referred to as the convergence target engine load factor). Is set to a target value, and the opening degree of the throttle valve 11 is controlled so that the engine load factor at the convergence destination and the value obtained by adding the predetermined value α to the EGR rate are substantially equal. That is, the opening degree of the throttle valve 11 is controlled, that is, the intake air amount is controlled such that the difference between the engine load factor at the convergence destination, that is, the difference between the target value and the EGR rate becomes the predetermined value α. Here, the engine load factor indicates the ratio of the load at a certain point in time to the operating state in which the maximum torque is output, that is, the entire load.

  In the control of the throttle valve 11 and hence the intake air amount, the engine load factor until the engine load factor at the convergence destination reaches the target value by controlling the intake air amount as described above. It will not be less.

  Thereafter, in step S3, it is determined whether or not the EGR rate is equal to or less than a predetermined rate β corresponding to the target value. If it is determined that the rate is equal to or lower, the throttle valve 11 is almost fully closed in step S4, that is, idle rotation. The opening is set so that the intake air amount in the control can be secured, and the control of the intake air amount is finished.

  As described above, when the engine 100 is suddenly changed to a state where the accelerator pedal is not depressed at all in the state where the EGR control is performed, in the conventional configuration, as shown by the dotted line in FIG. By delaying the increase correction of the amount, the EGR gas remaining in the intake system becomes excessive with respect to the intake air amount, and the load factor of the engine falls and the engine is likely to misfire. Is corrected so as to increase the intake air amount before the determination of the idling operation, so that the load factor of the engine 100 does not decrease, that is, the torque does not rapidly decrease.

  In addition, after the determination of the idle operation, the opening degree of the throttle valve 11 is controlled so that the difference between the engine load factor at the convergence destination and the EGR rate becomes a predetermined value α, and the intake air amount is increased. After that, since the increase of the intake air amount is stopped when the engine load factor at the convergence destination is reached, even when decelerating from the operating region where EGR gas is used to the maximum, the remaining EGR gas It is possible to reliably suppress a shortage of fresh intake air leading to misfire.

  In the above-described embodiment, the electronic throttle 9 has been described. However, a bypass route communicating with the upstream and downstream of the throttle valve is provided in the intake system, and the amount of air passing through the bypass route is adjusted in the bypass route. A control valve capable of correcting the intake air amount by controlling the open / close state of the control valve may be provided.

  Moreover, it may replace with step S3 and you may comprise so that it may be determined whether the elapsed time from the execution start of this intake air amount control program became more than predetermined time. In this case, when the elapsed time becomes equal to or longer than the predetermined time, the process proceeds to step S4 to end the control. In this case, the predetermined time may be set based on the time required to reach the target value according to the characteristics of the EGR valve when the target value is obtained.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, it can be used in an internal combustion engine that includes an exhaust gas recirculation device and can perform idle rotation control.

4 ... Electronic control device 6 ... Exhaust gas recirculation device 11 ... Throttle valve 41 ... Central processing control device 42 ... Storage device 43 ... Input interface 44 ... Output interface 91 ... Accelerator sensor

Claims (2)

In an internal combustion engine having an exhaust gas recirculation device for controlling a throttle valve by an accelerator means and mixing a part of exhaust gas with intake air, the exhaust gas recirculation device is being controlled, and the accelerator means is a throttle When the valve is controlled in the closing direction, the load factor of the internal combustion engine that finally converges is predicted and set to the target value,
An intake air amount control method for an internal combustion engine, wherein the intake air amount is controlled so that the load factor of the internal combustion engine does not fall below the target value until the load factor reaches the target value.   2. The intake air amount control method for an internal combustion engine according to claim 1, wherein the intake air amount is controlled so that a difference between a load factor of the internal combustion engine and an exhaust gas recirculation rate by the exhaust gas recirculation device is equal to or greater than a predetermined value.

Images