JP2006183514A - Idle rotation control method of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an idle rotation control method of an internal combustion engine, capable of expanding a controllable range to a control quantity in controlling an idle rotation control device by making a feedback process, even if the ignition timing is controlled to the ignition timing delay side more than the ordinary ignition timing for early raising the temperature of a catalyst. <P>SOLUTION: This internal combustion engine has the idle rotation control device for controlling an engine speed in a target engine speed by making a feedback process in idling operation by adjusting the suction air volume, and the catalyst for purifying exhaust gas; and is constituted for controlling the ignition timing to the ignition timing delay side more than the ordinary ignition timing for early raising the temperature of the catalyst; and is provided with an upper limit quantity and a lower limit quantity for limiting an upper limit and a lower limit of the control quantity when controlling the idle rotation control device by making the feedback process; and respectively changes the upper limit quantity to the increasing side and the lower limit quantity to the reducing side so that a difference between the upper limit quantity and the lower limit quantity increases for increasing an ignition timing delay quantity of the ignition timing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an idle rotation control method in a case where an ignition timing is greatly retarded in order to raise the temperature of a catalyst early in an internal combustion engine mounted on a vehicle such as an automobile.

  Conventionally, in an engine that is an internal combustion engine mounted on an automobile, for example, a flow control valve is provided in a bypass route that bypasses the throttle valve, and the intake air amount is corrected to increase or decrease by feedback control of the opening degree of the flow control valve. Thus, the engine speed is controlled so that the idling speed during idling is converged to the target speed. In such engine rotation control during idling operation, that is, idling rotation control, for example, as shown in Japanese Patent Application Laid-Open No. 2003-133, an upper and lower limit amount is substantially provided for the control amount of the flow rate control valve, so It is known that the control range of feedback control is expanded as the resistance increases. I teach that.

  In addition to the above, there is also known idle rotation control in which upper and lower limit amounts with respect to the control amount of the flow control valve are set based on the ignition timing. This is because the output torque changes when the ignition timing is retarded or advanced, but when the opening of the flow control valve is controlled to absorb the change in the output torque, excessive output torque This is to suppress the change of.

In addition, this type of engine is generally provided with a catalyst for purifying exhaust gas. However, since the catalyst is activated at a temperature higher than a certain temperature, for example, the engine is operated at a cold start. If it is cold, it may not be activated. For this reason, in order to accelerate the activation of the catalyst, the ignition timing is retarded in large quantities at the time of cold start and the combustion timing is sent to promote the increase in the temperature of the catalyst (for example, Patent Documents). 2).
JP-A-5-106482 JP-A-6-146955

  By the way, as in Patent Document 2, if the ignition timing is retarded in large quantities for early activation of the catalyst, the engine output torque decreases due to the retard, and the output torque is sensitive due to the influence of friction in the engine. The engine speed may become unstable due to fluctuations in the output torque. In such a case, the control amount of the flow rate control valve is corrected by idle rotation control so that the intake air increases, but the control amount is set to an upper limit value based on the running resistance as in the above-mentioned Patent Document 1. A catalyst that is retarded by more than the retard amount of the ignition timing that is controlled in the normal operating state because the control range is set based on the lower limit value or because the control range is set based on the ignition timing In the operating state for activation, if the control amount corresponding to the retard amount at that time is greater than the upper limit value, in actual idle rotation control, the control valve is controlled in a state that is fixed at the upper limit amount. It became virtually uncontrollable.

  In this state where the flow control valve is controlled by the upper limit value, the control amount of the flow control valve is large. That is, the sensitivity of rotational speed correction is reduced. In addition, since the flow rate control valve reaches the upper limit value in this way, the range of the idle speed that can be corrected in the feedback control becomes narrow, and it may be difficult to converge to the target speed.

  The object of the present invention is to eliminate such problems.

  That is, the idle rotation control method for an internal combustion engine of the present invention includes an idle rotation control device that adjusts the intake air amount and feedback-controls the engine rotation speed during idling operation to a target rotation speed, and a catalyst that purifies exhaust gas. In an internal combustion engine, the ignition timing is controlled to be retarded from the normal ignition timing in order to raise the catalyst temperature early, and the upper and lower limits of the control amount for feedback control of the idle rotation control device are limited. An upper limit and a lower limit are provided, and the upper limit is increased and the lower limit is decreased so that the difference between the upper limit and the lower limit increases as the ignition timing retard amount increases. It is characterized by.

  In such a configuration, when the ignition timing is controlled to be retarded from the normal ignition timing in order to raise the catalyst temperature early, when the idle rotation control device is feedback controlled based on the retard amount of the ignition timing. The upper limit amount and lower limit amount of the control amount are changed so that the upper limit value of the control amount becomes larger and the lower limit amount becomes smaller as the retard amount of the ignition timing becomes larger. Therefore, the controllable range for the control amount in the feedback control of the idle rotation control device is expanded, so that the engine speed during idling operation can be kept at the target speed when the ignition timing is delayed by a large amount. It becomes possible.

  In the above configuration, in order to prevent the responsiveness of the feedback control of the idle rotation control device from being deteriorated, the control speed of the feedback control of the idle rotation control device increases as the retard amount of the ignition timing increases. preferable.

  Since the present invention is configured as described above, even if the ignition timing is controlled to be retarded from the normal ignition timing in order to raise the temperature of the catalyst early, it is based on the retard amount of the ignition timing. The upper limit and the lower limit of the control amount for feedback control of the idle rotation control device are changed to the side where the upper limit amount becomes larger and the lower limit amount becomes smaller as the retard amount of the ignition timing becomes larger. Thus, the controllable range for the control amount in the feedback control of the idle rotation control device can be expanded. Therefore, when the ignition timing is retarded in a large amount in order to promote the activation of the catalyst, the range in which the engine speed can be corrected during idling operation is prevented from being narrowed. The target rotation speed can be maintained.

  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 shows a one-cylinder configuration of a multi-cylinder engine, for example, a three-cylinder engine. The intake system 1 is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown), and a vise passage 3 that bypasses the throttle valve 2 is provided. A flow rate control valve (hereinafter referred to as ISC valve) 4 constituting the device ISC is interposed. The ISC valve 4 is an electronic switching type abbreviated as a large flow rate VSV, and controls an operation duty ratio DISC which is a control value of a control signal g applied to an input terminal 4a thereof, so that per unit time. The opening can be changed. That is, the calculated duty ratio DISC determines the control amount of the idle rotation control device ISC. By controlling the calculated duty ratio DISC, the opening degree of the ISC valve 4 is controlled, and the air flow rate of the bypass passage 3 is reduced. It can be adjusted. By a set of the bypass passage 3 and the ISC valve 4, normally, a bypass system provided for each correction item such as start-up correction, water temperature correction, rotation feedback correction, and load correction in feedback control at idling. The road is unified.

  The calculation duty ratio DISC described above corresponds to each correction item described above, for example, so that the correction amount at start, the water temperature correction amount, the rotation feedback correction amount, the load correction amount, and the like are not combined to become extremely large or small. The variable range is limited by the upper limit value and the lower limit value. The upper limit value and the lower limit value are stored in the storage device 8 of the electronic control unit 6 to be described later. Ignition during normal operation is different from the retard of the ignition timing for raising the temperature of the catalyst 22. The basic value is set based on the maximum retard value of the timing, and similarly, the lower limit value is set based on the maximum advance value of the ignition timing during normal operation. It is.

The intake system 1 is further provided with a fuel injection valve 5, and the fuel injection valve 5 and the ISC valve 4 are controlled by an electronic control device 6. On the other hand, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas is attached to the exhaust system 20 at a position upstream of the catalyst 22 disposed in a pipe line leading to a muffler (not shown). . A spark plug 18 is attached at a position corresponding to the ceiling portion of the combustion chamber 10.

  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 has an intake pressure signal a output from an intake pressure sensor 13 for detecting the pressure in the surge tank 12, a rotation speed signal b output from a rotation speed sensor 14 for detecting the engine speed, An N signal c as a cylinder discrimination signal output from the rotation angle sensor 15 for detecting the cylinder, an idle signal d output from the idle switch 16 for detecting the open / closed state of the throttle valve 2, and the engine as the engine temperature A water temperature signal e or the like output from the water temperature sensor 17 for detecting the cooling water temperature is input. From the output interface 11, a drive signal f corresponding to the calculated fuel injection time is supplied to the fuel injection valve 5, and a control signal g based on the calculated duty ratio DISC is supplied to the ISC valve 4. Each is output. Therefore, the electronic control unit 6 constitutes the idle rotation control unit ISC. Although not shown, the electronic control unit 6 includes an A / D converter for converting an input analog signal into digital data, and converts the water temperature signal e and the like into digital data at regular intervals. Are output to the central processing unit 7. Further, instead of the coolant temperature, an engine lubricating oil temperature, an intake air temperature, or the like may be used.

  The electronic control unit 6 determines the fuel injection valve opening time using the respective signals from the intake pressure sensor 13 and the rotation speed sensor 14 as main information, and controls the fuel injection valve 5 according to the determination to respond to the load. A program for injecting fuel from the fuel injection valve 5 to the intake system 1 is incorporated. Further, in order to control the idling engine speed after starting, an idling engine speed controller ISC that adjusts the intake air amount and feedback-controls the engine engine speed during idling operation to the target engine speed, and a catalyst 22 that purifies exhaust gas, In the engine 100 having the above, the ignition timing is controlled to be retarded from the normal ignition timing in order to raise the temperature of the catalyst 22 early, and the upper limit of the control amount when the idle rotation control device ISC is feedback controlled and An upper limit and a lower limit are provided to limit the lower limit, and the upper limit is increased and the lower limit is decreased so that the difference between the upper limit and the lower limit increases as the ignition timing retard amount increases. A program for changing each is built in the electronic control unit 6.

  A general procedure of the idle rotation control program will be described with reference to FIG. The idle rotation control program is repeatedly executed at a predetermined cycle when the engine 100 is in the idling operation state. Further, the feedback control of the engine speed (idle speed) in the idling operation state may be known in this field. The engine speed is detected, and the detected engine speed and the operation at that time are detected. By controlling the opening of the ISC valve 4 of the idle rotation control device ISC based on the rotational speed that is different from the target rotational speed set according to the state, and controlling the flow rate of air passing through the bypass passage 3, The engine speed is controlled so as to converge to the target speed.

  First, in step S1, an upper limit operation range and a lower limit operation range of the idle rotation control device ISC in the idle rotation feedback control, that is, an upper limit value and a lower limit value are obtained. That is, the upper limit value and the lower limit value of the correction amount when the intake air amount is corrected by the idle rotation control device ISC in the idle rotation feedback control are set based on the retard amount of the ignition timing. Specifically, an upper limit value that defines an upper limit operation range and a lower limit operation range that define the upper limit operation range when performing feedback control on the calculation duty ratio DISC of the control signal of the ISC valve 4 based on the retard amount of the ignition timing. Set the value.

  The upper limit and lower limit values are the values during normal idling operation that do not retard the ignition timing in large quantities as the upper basic value and lower basic value, and the ignition timing is retarded by a large amount compared to the normal operating state. The upper limit value is set larger than the upper basic value based on the amount of retardation, and the lower limit value is set smaller than the lower basic value. In this case, the upper limit value and the lower limit value are set by, for example, a two-dimensional map corresponding to the retard amount of the ignition timing, and the necessary two-dimensional map is searched by using the retard amount of the ignition timing during idling operation. In such a case, interpolation calculation is performed for setting. It should be noted that the absolute value of the change amount with respect to the same retardation amount of the upper limit value and the lower limit value is not necessarily the same, and the upper limit value may change more greatly than the change of the lower limit value. .

  Next, in step S2, the idle rotation control device ISC, specifically, the ISC valve 4 is feedback controlled within the operation range defined by the upper limit value and the lower limit value set in step S1. The feedback control of the ISC valve 4 is performed as follows.

  First, in FIG. 3, in step S11, the correction amount of the intake air amount to be increased in idle rotation feedback control is calculated based on the engine speed and the target speed during idling operation. The correction amount of the intake air amount corresponds to the air flow rate that passes through the bypass passage 3, and specifically does not calculate the air flow rate itself, but is an ISC valve required to obtain a necessary air flow rate. This is indicated by the operation duty ratio DISC of the control signal g of the ISC valve 4 that determines the opening degree of 4.

  Next, in step S12, a correction coefficient based on the retard amount of the ignition timing with respect to the correction amount in the idle rotation feedback control is obtained. For this correction coefficient, for example, a correction coefficient for the retard amount is set by a two-dimensional map, the two-dimensional map is searched, and if necessary, interpolation calculation is performed, and the retard of the ignition timing in the operating state at this time is performed. The correction coefficient is obtained from the quantity. For example, the correction coefficient is set to 1.0 when the retardation amount is zero, and is set to increase as the retardation amount increases.

  In step S13, the final correction amount in the final idle rotation feedback control is determined by multiplying the correction amount (calculation duty ratio DISC) calculated in step S11 by the correction coefficient obtained in step S12. This final correction amount is calculated by multiplying the calculation duty ratio DISC by the correction coefficient, and the ISC valve 4 is controlled by applying the control signal g of the calculation duty ratio DISC corrected by the correction coefficient to the ISC valve 4. Feedback control is performed so that the engine speed, which fluctuates by retarding the ignition timing from the bypass passage 3, converges to the target speed during idling operation.

  In such a configuration, for example, in idling operation started when the engine 100 is cold, if the ignition timing is retarded by a large amount in order to quickly increase the temperature of the catalyst 22, step S1 is executed, The upper limit value and the lower limit value for the correction amount (that is, the control amount) of the rotation control device ISC are changed so that the correction range of the correction amount is expanded. Further, in steps S11 to S13, the correction amount is corrected based on the retard amount of the ignition timing to determine the final correction amount, and the ISC valve 4 of the idle rotation control device ISC is feedback-controlled based on the final correction amount. In this case, the final correction amount is larger than that during normal operation because the correction coefficient is set by the retard amount of the ignition timing. As the time elapses, the retard amount of the ignition timing is changed, and the final correction amount is changed accordingly, whereby the flow rate of air passing through the bypass passage 3 is controlled, and the engine speed is converged to the target speed. It is something to be made.

  Therefore, since the ignition timing is retarded by a large amount of retardation, the temperature of the catalyst 22 can be raised. At substantially the same time, the upper limit value and the lower limit value for the correction amount of the idle rotation control device ISC are changed based on the retard amount of the ignition timing so as to expand the variable range of the correction amount. Therefore, even if the ignition timing is retarded by a large amount, the final correction amount does not reach the upper limit value, and even when the output torque decreases due to the retard of the ignition timing, the intake air amount is increased to compensate for the idle speed. Therefore, the engine speed can be prevented from becoming unstable. In addition, since the upper limit value is changed to the larger side and the lower limit value is changed to the smaller side, the variable range of the correction amount is expanded. Therefore, the engine speed range that can be adjusted in the idle speed feedback control is widened, and a sufficient variable range can be secured on the side where the engine speed is increased and decreased, so that the engine speed can be quickly converged to the target speed.

  Next, in addition to the above configuration, a description will be given of changing the control speed of the idle rotation control device ISC according to the retard amount of the ignition timing. As for the control speed of the idle rotation control device ISC, there are a control speed whose operation amount is changed according to the retard amount of the ignition timing, and an operation update cycle which is changed according to the retard amount of the ignition timing.

  First, what changes the operation amount of the idle rotation control device ISC will be described with reference to FIG.

  First, in step S21, in the idle rotation feedback control, the operation amount of the idle rotation control device ISC is determined based on the retard amount of the ignition timing. In this example, the operation amount of the idle rotation control device ISC refers to the size of the opening per unit time of the ISC valve 4 when the idle rotation control device ISC is feedback-controlled. In this example, The ignition timing is set to increase as the retard amount increases. Therefore, the ISC valve 4 has a different rate of change in opening within a predetermined period, and the control speed increases as the retard amount of the ignition timing increases. The operation amount is composed of an ascending operation amount when the ISC valve 4 is opened to increase the engine speed and a descending operation amount when the engine speed is decreased by closing the ISC valve 4. For the ascending operation amount and the descending operation amount, an amount corresponding to the retard amount of the ignition timing is set by, for example, a two-dimensional map, and the two-dimensional map is searched based on the retard amount at this time, and interpolated as necessary. It is obtained by calculation.

  Next, in step S22, the ISC valve 4 of the idle rotation control device ISC is operated on the basis of the determined ascending operation amount and descending operation amount. That is, when the engine speed at this time is lower than the target speed, the ISC valve 4 is opened by the ascending operation amount, and the intake air amount is increased so that the engine speed converges to the target speed. To do. Conversely, if the engine speed at this time exceeds the target speed, the ISC valve 4 is closed by the descending operation amount so that the intake air amount is reduced so that the engine speed converges to the target speed. To control.

  As described above, by changing the operation amount of the ISC valve 4 according to the retard amount of the ignition timing, when the ignition timing is retarded in a large amount, the intake air amount is increased and corrected by the air amount corresponding to the retard amount. The Since the operation amount is increased as the retard amount of the ignition timing is increased, the ISC valve 4 is retarded even if the engine speed may fluctuate greatly by retarding the ignition timing in a large amount. Depending on the amount, it can be established with a control speed that depends on the amount of movement. Therefore, it is possible to quickly increase or decrease the engine speed during idling operation, and to prevent the responsiveness of the idle rotation feedback control from being lowered.

  Next, instead of changing the operation amount of the idle rotation control device ISC according to the retard amount of the ignition timing, the operation update cycle of the idle rotation control device ISC is changed according to the retard amount of the ignition timing. Will be described with reference to FIG.

  First, in step S31, in the idle rotation feedback control, the operation change period of the idle rotation control device ISC is determined based on the retard amount of the ignition timing. The operation change cycle of the idle rotation control device ISC differs from the cycle for changing the calculation duty ratio DISC of the control signal g applied to the ISC valve 4 when feedback control of the idle rotation control device ISC, that is, a certain calculation duty ratio DISC. This indicates a period until the value is changed to the value calculation duty ratio DISC. In this example, the value is set so as to become shorter as the retard amount of the ignition timing increases. The operation change cycle is composed of an ascending operation change cycle when the ISC valve 4 is opened to increase the engine speed and a descending operation change cycle when it is closed and the engine speed is decreased. The ascending motion change period and the descending motion change period are set by a two-dimensional map and obtained from the two-dimensional map, as in the case of the above-described motion amount.

  In step S32, the operation amount, that is, the operation duty ratio DISC is changed in the determined ascending operation changing cycle and descending operation changing cycle, and the ISC valve 4 of the idle rotation control device ISC is operated. That is, when the engine speed at this time is lower than the target speed, the calculation duty ratio DISC is changed at the rising operation change period to open the ISC valve 4, and the intake air amount is increased to increase the engine speed. Control to converge to the target rotational speed. On the other hand, if the engine speed at this point exceeds the target speed, the calculation duty ratio DISC is changed in the descending operation change period to close the ISC valve 4, and the intake air amount is reduced to reduce the engine speed. The number is controlled to converge to the target rotational speed.

  Thus, by changing the operation change cycle for changing the calculated duty ratio DISC of the ISC valve 4 according to the retard amount of the ignition timing, the cycle for changing the calculated duty ratio DISC when the ignition timing is delayed by a large amount is obtained. It becomes earlier than the operation change cycle when the normal ignition timing is retarded. As a result, the operation of the ISC valve 4 can be changed until the engine speed is greatly reduced. Therefore, even if the engine speed fluctuates, the intake air amount is corrected to be increased by the air amount corresponding to the retard amount at an early stage. The operation change cycle is shorter as the ignition timing retard amount is larger. Therefore, even if the engine speed may fluctuate greatly by retarding the ignition timing in large amounts, the retard amount The opening degree of the ISC valve 4 can be changed at a timing according to. In this way, it is possible to quickly increase or decrease the engine speed during idling operation, and to prevent the responsiveness of the idle rotation feedback control from being lowered.

  Note that a configuration in which the operation change period is changed based on the retard amount of the ignition timing and a configuration in which the operation amount is changed based on the retard amount of the ignition timing may be combined. That is, in the idle rotation feedback control, the operating range of the correction amount of the intake air amount by the idle rotation control device ISC is changed based on the retard amount of the ignition timing, and the control speed of the idle rotation control device ISC is changed. A configuration may be adopted in which the operation amount is increased as the retardation amount is increased so as to be faster, and the operation change period is shortened as the retardation amount is increased.

  With such a configuration, the amount of intake air can be corrected in large quantities by increasing the operation amount, and the cycle for switching the opening of the ISC valve 4 can be shortened by shortening the operation change cycle. it can. Therefore, when the ignition timing is retarded in a large amount, the intake air amount can be corrected sufficiently and quickly during the idle rotation feedback control, and the engine speed can be stabilized early.

  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 which shows schematic structure of the engine and electronic control apparatus in embodiment of this invention. The flowchart which shows the control procedure of the embodiment. The flowchart which shows the control procedure of the embodiment. The flowchart which shows the control procedure of other embodiment of this invention. The flowchart which shows the control procedure of other embodiment of this invention.

Explanation of symbols

6 ... Electronic control unit 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 11 ... Output interface 22 ... Catalyst ISC ... Idle rotation control unit

Claims (2)

In an internal combustion engine having an idle rotation control device that adjusts the intake air amount and feedback-controls the engine speed during idling to a target speed, and an internal combustion engine having a catalyst that purifies exhaust gas, an ignition timing is set to raise the temperature of the catalyst early. Is controlled to the retarded side from the normal ignition timing,
An upper limit amount and a lower limit amount for limiting an upper limit and a lower limit of a control amount when performing feedback control of the idle rotation control device are provided,
An idling rotation control method for an internal combustion engine, wherein the upper limit amount is increased and the lower limit amount is decreased so that the difference between the upper limit amount and the lower limit amount increases as the ignition timing retard amount increases. 2. The idle rotation control method for an internal combustion engine according to claim 1, wherein the control speed of the feedback control of the idle rotation control device is increased as the retard amount of the ignition timing is increased.

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