JP2008082255A - Suction air quantity control method for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that rotation speed varies if suction air quantity is corrected by correction quantity based on learned correction quantity when load is removed in an engine learning correction quantity of suction air quantity controlling idling speed when load is applied on an internal combustion engine. <P>SOLUTION: In this idling speed control method for an internal combustion engine feedback-controlling suction air quantity to keep engine speed at idling target speed in idling operation of an internal combustion engine, feedback correction quantity for correcting intake air quantity is learned when load is applied on the internal combustion engine and is stored as learning value (S2), and feedback correction quantity is calculated by adding predetermined quantity to the stored learning value when load applied on the internal combustion engine is removed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an intake air amount control method for an internal combustion engine in which the intake air amount is feedback controlled at least during idling.

  2. Description of the Related Art Conventionally, for example, an internal combustion engine, that is, an engine mounted on an automobile, is provided with an idle rotation control valve in a bypass passage that bypasses a throttle valve of an intake system in order to control the idle rotation speed. Then, in an idle operation state in which the throttle valve is almost fully closed, feedback control of the intake air amount is performed by controlling the opening of the idle rotation control valve so that the engine rotation speed during idle operation becomes the idle target rotation speed. Is.

  In such idle speed control, for example, in the one described in Patent Document 1, the valve opening control amount of the idle rotation control valve corresponds to the presence / absence of a load so that the rotation fluctuation does not occur due to switching of the engine load. And is configured to learn. That is, during idle operation, the valve opening of the idle rotation control valve is controlled by increasing or decreasing the feedback correction value by feedback control to control the intake air amount, and the idle rotation speed is set so that the engine rotation speed at that time becomes the idle target rotation speed. Control. And when feedback control is carried out in this way, if an external load on the engine is used, the feedback correction value at that time is learned and stored, and similarly when the use of the external load is stopped The feedback correction value is learned and stored.

In this way, the learning values of the two feedback correction values are stored corresponding to the usage state of the external load, and when the usage state of the external load changes, that is, from use to non-use or from non-use to use. In this case, the basic control value of the idle rotation control valve is corrected using the learning value corresponding to the state after switching. Then, the opening degree of the idle rotation control valve is feedback-controlled using the corrected basic control value as an initial value.
Japanese Patent Laid-Open No. 4-187849

  However, with such a configuration, when the external load is not used, the idle speed control is performed with the basic control value corrected by the feedback correction value at the time of idle operation not using the previous load as the initial value. When the valve opening degree is controlled, in other words, when the intake air amount is controlled, there may be a case where there is no margin in the amount of air supplied to the engine. For this reason, if there is a factor that reduces the engine speed other than the external load, the intake air amount will be insufficient, and it will be very difficult to maintain the idle speed, resulting in rotational fluctuations. Or even idle operation could not be continued.

  Therefore, the present invention aims to eliminate such problems.

  That is, the intake air amount control method for an internal combustion engine according to the present invention is an idle speed control for an internal combustion engine that feedback-controls the intake air amount so that the engine speed is equal to the target idle speed at the time when the internal combustion engine is idling. A feedback correction amount for correcting the intake air amount is learned when a load is applied to the internal combustion engine and stored as a learned value, and when the load applied from the internal combustion engine is released, the stored learned value is a predetermined amount. Is added to obtain a feedback correction amount.

  According to such a configuration, the intake air amount when the load is removed is controlled by the feedback correction value that is larger by a predetermined value than the learned value of the feedback correction value learned and stored when the internal combustion engine is loaded. The As a result, even if there is a factor that causes the engine speed to fluctuate in addition to the load when the load is removed, the intake air amount will not be insufficient, and the engine speed during idling can be quickly set to the target idling speed. It becomes possible to approach.

  In order to suppress the rotational fluctuation due to the predetermined value, it is preferable to prohibit the learning of the feedback correction amount when a fluctuation is expected in the engine speed due to the addition of the predetermined amount when a load is applied to the internal combustion engine. With such a configuration, even when the load is intermittently applied, it is possible to prevent learning of the feedback correction amount increased by a predetermined value added each time the load is removed. For this reason, the feedback correction value can be maintained at an appropriate value, and the engine speed can be quickly brought close to the idle target speed. The condition for prohibiting learning of the feedback correction amount in such a configuration is that the difference between the engine speed and the idle target speed at that time exceeds a predetermined speed.

  The present invention is configured as described above, and the learning value of the feedback correction value is learned and stored when a load is applied to the internal combustion engine, and the feedback obtained by adding a predetermined value to the learning value Since the intake air amount when the load is removed is controlled by the correction value, even if there is a factor that causes the engine speed to fluctuate in addition to the load when the load is removed, the intake air amount will not be insufficient and idle The engine speed during operation can be quickly brought close to the idle target speed.

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

  An engine 100 schematically shown in FIG. 1 is for an automobile, and an automobile equipped with the engine 100 is an air conditioner (not shown; hereinafter referred to as an air conditioner) that operates using the output of the engine 100 as a driving force. ) Is installed. The air conditioner itself may be well known in the art, and includes a compressor that compresses the cooling medium, and the compressor operates by receiving a driving force from the engine when an electromagnetic clutch is connected, for example. Configured as follows.

  The engine 100 is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown) in the intake system 1 and a bypass passage 3 that bypasses the throttle valve 2. The bypass passage 3 is provided with a flow rate control valve 4 for controlling the idle speed. The flow rate control valve 4 is an electromagnetic open / close type abbreviated as a large flow rate VSV that can collectively realize various correction items such as start-up correction and water temperature correction. It constitutes a control device. In addition to this, a fuel injection valve 5 is further provided in the vicinity of the intake port 10 constituting the intake system 1. The fuel injection valve 5 and the flow rate control valve 4 are controlled by an electronic control unit 6.

  The flow rate control valve 4 can change the opening degree per unit time by controlling the calculation duty ratio DISC of the applied drive voltage, and thereby the flow rate of air flowing through the bypass passage 3 can be adjusted. ing. That is, a set of the bypass passage 3 and the flow control valve 4 unifies the bypass system path provided for each correction item in the feedback control at the time of idling. The calculation duty ratio DISC includes these items and corresponds to each correction amount. For example, the correction items such as the start time correction coefficient DSTA, the water temperature correction coefficient DAAV, the air conditioner correction coefficient ACC, and the feedback correction coefficient DFB are added together. The variable range is limited so as not to become extremely large or small. In addition, as will be described later, the feedback correction coefficient DFB corresponding to the feedback correction amount is stored as a learning value DFBRAC when a predetermined condition is satisfied.

  The electronic control device 6 is mainly configured by a microcomputer system including a central processing unit 7, a storage device 8, an input interface 9, and an output interface 11. The input interface 9 detects the engine speed NE including the intake pressure signal a output from the intake pressure sensor 13 for detecting the pressure in the surge tank 12 constituting the intake system 1 and the idle speed. A rotation speed signal b output from the rotation speed sensor 14, a vehicle speed signal c output from the vehicle speed sensor 15 for detecting the vehicle speed, and an opening degree output from the throttle sensor 16 for detecting the open / closed state of the throttle valve 2. The signal d, the water temperature signal e output from the water temperature sensor 17 for detecting the engine coolant temperature as the engine temperature, and the like are input. Further, a drive signal f corresponding to the calculated fuel injection time is output from the output interface 11 to the fuel injection valve 5, and a control signal having a calculated duty ratio DISC described later is supplied to the flow rate control valve 4. An ignition signal g is output to the spark plug 18 and a control signal is output to the electromagnetic clutch of the air conditioner. Although not shown, the electronic control unit 6 includes an A / D converter for converting an input analog signal into digital data, and the analog temperature signal e.g., a water temperature signal e is digitally distributed at regular intervals. The data is converted into data and output to the central processing unit 7.

  The electronic control unit 6 determines the fuel injection valve opening time (fuel injection amount) using the intake pressure signal a and the rotation speed signal b from the intake pressure sensor 13 and the rotation speed sensor 14 as main information, and the fuel is determined by the determination. A program for controlling the injection valve 5 and injecting fuel corresponding to the load from the fuel injection valve 5 to the intake system 1 is incorporated. Further, the opening degree of the flow rate control valve 4 provided in the bypass passage 3 that bypasses the throttle valve 2 corresponds to the calculated duty ratio DISC calculated based on various correction coefficients that are appropriately set according to the operating state. Control is performed by the control signal g, and the air flow rate to the intake system 1 is adjusted so that the engine speed during idling, that is, the idle speed NE is set to the target speed.

  In this idle speed control, i.e., idle speed control, a feedback correction coefficient DFB corresponding to a feedback correction amount for correcting the intake air amount is learned when the air conditioner as a load is applied to the engine 100 and stored as a learning value DFBRAC. A control program for the feedback correction coefficient DFB is configured so that when the load is removed, a predetermined value is added to the stored learned value DFBRAC to obtain the feedback correction coefficient DFB. As correction coefficients other than the feedback correction coefficient DFB such as the start-time correction coefficient DSTA and the water temperature correction coefficient DAAV, those known in this field can be applied, and the description thereof will be omitted.

  A schematic configuration of a control program for the feedback correction coefficient DFB of this embodiment is shown in FIGS. The feedback correction coefficient DFB is set to an initial value, for example, and after the engine 100 is started, a predetermined operation state, for example, the engine temperature (cooling water temperature) is equal to or higher than the predetermined temperature, and the engine speed is equal to or higher than the predetermined speed. When the operation state where the feedback control condition such as is satisfied is established, control is performed so that the idling engine speed becomes the target idling engine speed starting from the set initial value.

  In FIG. 2, in step S <b> 1, whether or not the feedback control condition is satisfied and the air conditioner operates (air conditioner ON), that is, whether the compressor of the air conditioner has become a load on the engine 100 due to the operation of the electromagnetic clutch. judge. This determination assumes that the air conditioner is activated when a control signal for the electromagnetic clutch is output. In step S2, the feedback correction coefficient DFB at the time when it is determined that the air conditioner has been operated is learned and stored in the storage device 8 of the electronic control unit 6 as the learned value DFBLAC. In this case, if the feedback correction coefficient DFB is already stored in the storage device 8, the latest one is stored and the learning value DFBRAC is updated.

  Next, in FIG. 3, in step S3, it is determined whether or not the air conditioner has been stopped (air conditioner OFF). In other words, it is determined whether or not the electromagnetic clutch of the compressor of the air conditioner that has been operating until then is disengaged (stopped) and is no longer a load on the engine 100, that is, whether or not the load is removed from the engine 100. Contrary to the case where the air conditioner is ON, it is determined that the air conditioner is OFF when the control signal for the electromagnetic clutch is disconnected.

  After determining that the air conditioner is OFF, in step S4, a predetermined value is added to the learning value DFBLAC to obtain a new feedback correction coefficient DFB. The feedback correction coefficient DFB that is larger than the learning value DFBLAC by a predetermined value is an initial value of the feedback correction coefficient DFB used for calculation of the calculation duty ratio DISC in the subsequent idle rotation control.

  In such a configuration, when the engine 100 is operated and the intake air amount feedback control condition is satisfied, as shown in FIG. Are stored as learning values DFBRAC. Thereafter, the feedback correction coefficient DFB is controlled (increased or decreased) based on the difference between the engine 100 so that the idle speed of the engine 100 becomes the target idle speed, that is, the difference between the two. Thereby, the calculation duty ratio DISC of the drive signal of the flow control valve 4 is adjusted, the opening degree of the flow control valve 4 is adjusted corresponding to the adjustment, and the amount of intake air passing through the bypass passage 3 is controlled (increase / decrease). Thus, the idle rotation speed approaches the target idle rotation speed.

  Thus, since the initial value of the feedback correction coefficient DFB when the air conditioner is OFF is larger than the learning value DFBRAC, for example, the alternator is a load on the engine 100 when the air conditioner is OFF, and the idling speed is set. Even if a factor causing the reduction occurs, it is possible to prevent the idle rotation speed from decreasing. That is, in the conventional apparatus, the increase in the intake air amount corresponding to the air conditioner correction coefficient ACC disappears simultaneously with the air conditioner OFF. In such a situation, when a relatively large auxiliary machine that is not as operated as an air conditioner is operating and becomes a load on the engine 100, the intake air amount is reduced by the increased amount that has disappeared. However, in this embodiment, since the intake air amount is controlled by the feedback correction coefficient DFB obtained by adding a predetermined value, the idling speed can be maintained. Therefore, even in such an operating state, the rotational fluctuation of engine 100 can be reliably suppressed.

  In contrast to the above-described configuration, a configuration in which learning of the feedback correction coefficient DFB is limited with respect to an operation state in which the air conditioner is continuously turned on / off will be described with reference to FIGS. 5 and 6. The program configuration described below adds a predetermined condition, that is, a condition for prohibiting learning of the feedback correction coefficient DFB to the above-described steps S1 and S2.

  In FIG. 5, in step S21, it is determined whether or not the air conditioner has been operated, that is, whether or not the air conditioner has been changed from the stopped state to the activated state. In step S22, it is determined whether or not a predetermined time has elapsed since the feedback control was started. The predetermined time is set based on the time required for the idle speed to become substantially equal to the target idle speed after the feedback control is started. In step S23, it is determined whether the rotational speed difference ΔNE between the idle rotational speed at this time and the target idle rotational speed is equal to or smaller than the determination rotational speed KNE. In step S24, the learning value DFBRAC is updated assuming that a predetermined condition is satisfied.

  In such a configuration, as shown in FIG. 6, when the air conditioner repeats ON / OFF after a short time, the air conditioner OFF is performed in the above-described control of steps S1 and S2, and steps S3 and S4. When step S3 and step S4 are executed at the timing, the feedback correction coefficient DFB becomes a situation where a multiple of a predetermined value is added to the learned value DFBRAC when the number of times the air conditioner is turned off increases. In this case, if the feedback correction coefficient DFB is a large value, the calculation duty ratio DISC increases due to the influence, and the opening degree of the flow control valve 4 increases. As a result, the amount of intake air increases and the idling speed increases.

  In the configuration of the modified example shown in FIG. 5, the air conditioner is activated, and the learning value DFBRAC is updated at that time. Thereafter, the air conditioner is stopped and the feedback correction coefficient DFB is set to a predetermined value from the learning value DFBLAC. The premise is that it grows. In such an operating state, when the predetermined condition defined in steps S21 to S23 is satisfied, the learning value DFBRAC is updated in step S24. That is, during the air conditioner operation that is a learning condition, feedback control is being performed and a predetermined time has elapsed since the start of the feedback control, and after the predetermined time has elapsed, the rotational speed difference ΔNE is equal to or less than the determined rotational speed KNE. In some cases, it is determined that a predetermined condition is satisfied.

  Therefore, even when the air conditioner is activated, when the predetermined time has not elapsed since the start of the feedback control, and when the predetermined time has elapsed but the rotational speed difference ΔNE exceeds the determined rotational speed KNE This prohibits learning of the feedback correction coefficient DFB. That is, when the air conditioner is activated and the calculation duty ratio DISC is controlled to increase the intake air amount by the air conditioner correction coefficient ACC, the idle rotation speed is caused by the feedback correction coefficient DFB in addition to the increase. In the rising operating state, the feedback correction coefficient DFB is not learned.

  In this way, the rotational speed difference ΔNE exceeds the determined rotational speed KNE, that is, the feedback correction coefficient DFB becomes excessively large by adding a predetermined value to the learning value DFBRAC several times, and the idle rotational speed is set to the target. The learning value DFBRAC is not updated when the driving state is far from the idling speed. Therefore, in the operation state in which the operation and stop of the air conditioner are repeated, the learning value DFBLAC is suppressed from being updated at the operation timing of the air conditioner. As a result, the learning value DFBLAC can be maintained at an appropriate value that can maintain the idle rotation speed, and rotation fluctuation can be prevented.

  In addition, since the learning value DFBRAC is updated only in the operating state where the rotational speed difference ΔNE is equal to or less than the determination rotational speed KNE, it is possible to improve the accuracy of suppressing rotational fluctuation.

  In the above-described configuration, the learning condition for the feedback correction coefficient DFB to which a predetermined value is added is set with reference to the rotational speed difference ΔNE between the idle rotational speed and the target idle rotational speed. It may be configured to measure the elapsed time until the operation of, and prohibit the updating of the learning value DFBRAC when the measured elapsed time is less than or equal to the determination time set for determination. In this case, the determination time is set on the basis of the time required for the feedback correction coefficient DFB to substantially converge the idle speed to the target idle speed.

  Moreover, in the said embodiment, although the air conditioner was demonstrated as load, it is not limited to an air conditioner. It is a target that is mounted as an auxiliary machine of the engine 100 and is supplied with energy required for operation from the engine 100, and in particular, has a great influence on the output of the engine 100. Therefore, the present invention is particularly effective when applied to a small displacement engine having a large displacement of 660 cc or less, which is greatly affected by rotational fluctuations that are likely to occur when such an auxiliary machine becomes a load on the engine 100. It is.

  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.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic structure explanatory drawing of the engine of embodiment of this invention. The flowchart which shows the control procedure of the embodiment. The flowchart which shows the control procedure of the embodiment. Action | operation explanatory drawing of the same embodiment. The flowchart which shows the control procedure of the modification in the embodiment. Action explanatory drawing of the modification of the embodiment.

Explanation of symbols

6 ... Electronic control device 7 ... Central information processing device 8 ... Storage device 9 ... Input interface 11 ... Output interface

Claims (3)

An internal combustion engine idle speed control method that feedback-controls the intake air amount so that the engine speed is equal to the target idle speed at that time when the internal combustion engine is in idle operation,
A feedback correction amount for correcting the intake air amount is learned when a load is applied to the internal combustion engine and stored as a learned value.
A method for controlling an intake air amount of an internal combustion engine, wherein a predetermined amount is added to a stored learning value to obtain a feedback correction amount when a load applied from the internal combustion engine is released.   2. The intake air amount control method for an internal combustion engine according to claim 1, wherein when a load is applied to the internal combustion engine, learning of a feedback correction amount is prohibited when fluctuations in engine speed due to addition of a predetermined amount are expected.   3. The intake air amount control method for an internal combustion engine according to claim 2, wherein the condition for prohibiting learning of the feedback correction amount is set such that the difference between the engine speed and the idle target speed at that time exceeds a predetermined speed.

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