JPH10184428A - Number of idle revolution control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably prevent the number of revolutions of an engine during idle operation from being unstable by a method wherein idle operation sets a control amount of a control valve, located in a bypass passage, according to a lean operation state or a stoichiometric operation state. SOLUTION: In an internal combustion engine which is controllable by shifting stoichiometric operation in a theoretical air-fuel ratio and lean combustion operation in a high air-fuel ratio, a control valve is arranged in a bypass passage 13 detouring a throttle valve 12 arranged at an intake system 11, and the number of evolutions is controlled so that the number of revolutions is adjusted to a preset target value. During an idle operation state under a stoichiometric operation state, the control valve is controlled such that an intake air amount is adjusted to a value corresponding to the theoretical air-fuel ratio, and during idle operation state under lean combustion operation state, the control valve is controlled such that the intake air amount is adjusted to a value corresponding to lean combustion operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idling speed control method for switching between lean burn (hereinafter referred to as "lean burn") operation and operation based on a stoichiometric air-fuel ratio, mainly in an internal combustion engine for an automobile.

[0002]

2. Description of the Related Art Conventionally, in this type of engine idle speed control method, as described in Japanese Patent Application Laid-Open No. 64-336, for example, a rapid and stable idle speed control is performed. In order to perform this, there is known one that performs learning control correction of the idle speed. That is, when a control valve is provided in a bypass passage provided to bypass the throttle valve in the intake system, and the opening degree of the control valve is feedback-controlled to control the air flow passing through the bypass passage, the air flow is reduced. It learns and corrects the air flow rate based on the learned value.

[0003]

By the way, in an engine that performs lean burn operation in which the air-fuel ratio is made higher than the stoichiometric air-fuel ratio, the operation at the stoichiometric air-fuel ratio, that is, the stoichiometric operation and the lean burn operation are performed under load. The switching is performed according to the state of the engine or the engine temperature. In such an engine, the idle operation is generally performed at an air-fuel ratio corresponding to the stoichiometric operation so that the rotation does not become unstable.

However, in such a case, since the stoichiometric operation is always performed in the idling operation, it is not the best in terms of fuel efficiency and emission. In addition, in order to improve fuel efficiency and emissions, it is necessary to make the idle operation lean-burn, but when the engine temperature becomes low or the electric load of an air conditioner or the like is applied, stoichiometric operation is inevitable. There are areas where you have to drive. Therefore, also in the idling operation, the two operating states of the lean burn operation and the stoichiometric operation are mixed.

[0005] In such a configuration, for example, when the lean burn operation is switched to the stoichiometric operation during the idle operation, the learning value in the idle operation is learned based on the air-fuel ratio based on the lean burn operation. If an attempt is made to control the idle speed based on the air-fuel ratio in the burn operation, a larger amount of intake air is required, so that the correction of the intake air amount by the learning value in the stoichiometric operation has a small amount of correction of the intake air amount. There are cases. For this reason, the absolute amount of intake air is small and sufficient output cannot be obtained, so that the engine speed may decrease and the idle speed may become unstable.

An object of the present invention is to solve such a problem.

[0007]

In order to achieve the above object, the present invention takes the following measures. That is, the idle speed control method for the internal combustion engine of the present invention controls the control valve provided in the bypass passage so that the speed becomes the target speed in the idle operation corresponding to both the stoichiometric operation and the lean burn operation. This is a configuration of Therefore, in each of the transition to the idle operation during the stoichiometric operation and the transition to the idle operation during the lean burn operation, the control amount of the control valve, in other words, the amount of intake air passing through the bypass passage becomes appropriate. In addition, the rotation speed of the internal combustion engine can be stably maintained. Also, since the idle operation is controlled in accordance with the lean burn operation, NOx, HC, and CO ₂
Emissions can be reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present application is provided in an intake system in an internal combustion engine capable of switching and controlling stoichiometric operation based on a stoichiometric air-fuel ratio and lean-burn operation based on an air-fuel ratio higher than the stoichiometric air-fuel ratio. A control valve is provided in a bypass passage that bypasses the throttle valve provided, and the control valve is controlled in an idle operation state to control the rotation speed so as to reach a preset target rotation speed. Thus, the control valve is controlled so that the intake air amount corresponds to the stoichiometric air-fuel ratio during the idle operation state during the stoichiometric operation state, and corresponds to the lean combustion operation during the idle operation state during the lean combustion operation state. An idle speed control method for an internal combustion engine, characterized in that a control valve is controlled to obtain an intake air amount.

Further, the invention according to claim 2 of the present application is provided in an intake system in an internal combustion engine capable of switching and controlling between stoichiometric operation at a stoichiometric air-fuel ratio and lean burn operation at an air-fuel ratio higher than the stoichiometric air-fuel ratio. An idle rotation control method for an internal combustion engine, wherein a control valve is provided in a bypass passage that bypasses a throttle valve, and the control valve is controlled in an idle operation state to control a rotation speed so as to reach a preset target rotation speed, Two different control amounts are set corresponding to the respective operating states based on a learning value learned according to a difference between the control amount of the control valve and the control center, and the control set according to the operating state in the idle operation. An idle speed control method for an internal combustion engine, characterized by switching to an amount.

[0010] The control amounts set in accordance with the stoichiometric operation state and the lean burn operation state based on the learning value may include the following ones. 1. A learning value corresponding to the stoichiometric operation and a learning value corresponding to the lean burn operation are set, and the control amount is set based on each of the learning values. 2. A learning value corresponding to the stoichiometric operation is set, a control amount is set based on the learning value in the case of the idling operation of the stoichiometric operation, and the learning value is set to the learning value in the case of the idling operation of the lean combustion operation. A learning value is calculated by multiplying the correction coefficient, and a control amount is set based on the calculated learning value. 3. Set the learning value corresponding to stoichiometric operation,
In the case of the idling operation of the stoichiometric operation, the control amount is set based on the learning value. In the case of the idling operation of the lean burn operation, the control amount is set by multiplying the control amount by a correction coefficient in the lean burn operation.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. The engine 100 schematically shown in FIG. 1 is for a water-cooled automobile, and is a stoichiometric operation in which the air-fuel ratio is substantially equal to the stoichiometric air-fuel ratio, and a lean operation in which the air-fuel ratio is higher than the stoichiometric air-fuel ratio. The combustion operation, that is, the lean burn operation (hereinafter, abbreviated as "lean operation") is defined as a cooling water temperature,
The control is performed by switching according to the engine speed, load, and the like. Correspondingly, in the idling operation, the required intake air amount is separately set for the stoichiometric operation and the lean operation, and the idling speed control is performed.

In the intake system 11 of the engine 100, a throttle valve 12 that opens and closes in response to an accelerator pedal (not shown) is provided, and a bypass passage 13 that bypasses the throttle valve 12 is provided. A flow control valve 14 for controlling the idle speed is provided. The flow control valve 14 is of an electronic opening and closing type, abbreviated as a large flow rate VSV, and calculates a duty ratio of a drive voltage, which is a control value applied to a terminal 14a, based on various correction amounts. Calculation duty ratio DIS
By controlling with C, the opening degree per unit time can be changed, whereby the air flow rate in the bypass passage 13 can be adjusted and the engine speed can be maintained at the target speed.

The calculated duty ratio DISC therefore indicates the amount of air correction during idle operation. As described above, the pair of the bypass passage 13 and the flow control valve 14 unifies a bypass path normally provided for each correction item in the feedback control during the idling operation. And the calculation duty ratio DI
SC includes these items, and includes, for example, correction items such as a start-time correction amount DSTA, a water temperature correction amount DAAV, a feedback correction amount DFB, an electric load correction amount DSET, and a stoichiometric learning value DRNL and a lean learning value. DRLNL
The variable range is limited so that either one of N and N does not become extremely large or small. The calculation duty ratio DISC is calculated by the following equation. DISC (%) = DSTA + DAAV + DSET + DFB + DRLN (+
DRLNLN)

The intake system 11 is further provided with a fuel injection valve 15.
Is controlled by an electronic control unit (ECU) 4.

The electronic control unit 4 includes a central processing unit 4a
, A storage device 4b, an input interface 4c, and an output interface 4d. The input interface 4c has an intake pressure signal a output from an intake pressure sensor 17 for detecting the pressure in the surge tank 16 and a rotational speed output from a rotational speed sensor 18 for detecting the engine rotational speed NE. A signal b, a vehicle speed signal c output from a vehicle speed sensor 19 for detecting the vehicle speed, an idle switch 20 for detecting the open / closed state of the throttle valve 12 or a water temperature signal e, a distributor 22
, A reference position signal f output from a crank angle reference position sensor 23 incorporated therein, and an output signal h varying according to the air-fuel ratio from an O ₂ sensor 24 provided in the exhaust system 23 are input.

The electronic control unit 4 determines whether the current operating condition satisfies the stoichiometric operation or the lean operation based on signals from the respective sensors, and based on the determination result, The fuel injection valve opening time is determined using the intake pressure sensor 17 and the signal from the rotation speed sensor 18 as main information, and the fuel injection valve 15
And a program for injecting fuel corresponding to the stoichiometric operation and the lean operation from the fuel injection valve 15 to the intake system 11 is built in. Further, the electronic control unit 4 controls the control valve so that the intake air amount corresponds to the stoichiometric air-fuel ratio during the idle operation state during the stoichiometric operation state, and performs the idle operation during the lean combustion operation, that is, the lean operation state. A program for controlling the control valve so that the intake air amount corresponds to the lean burn operation in the state is stored.

The outline of the idle speed control (ISC) program is as shown in FIG. In executing this program, it is needless to say that it is detected that the idle operation condition is satisfied. The idle operation condition is set based on, for example, that the throttle valve 12 is closed, the vehicle speed is equal to or lower than a predetermined speed, and the like.

In this idle speed control, a lean learning value DRLNLN during lean operation and a stoichiometric learning value DRLN during stoichiometric operation are set. Each of the learning values DRLNLN and DRLN is calculated based on the operation duty ratio D
The average value of the ISC is set based on the degree of deviation of the operation duty ratio DISC from the control center, and is updated at predetermined intervals while the idle speed control is being performed.

First, in step S1, it is determined whether or not the operating state at that time is a lean operating state, in other words, whether or not the operation has shifted to the idling operation in the lean operating state. Otherwise, the process proceeds to step S3. The conditions for determining the lean operation state include, for example, the engine speed, the magnitude of the load,
And the cooling water temperature, etc., except when the engine is in a steady state except when the engine is being started, the warming-up operation is being performed during the warming-up operation, and the engine is in a transient state such as acceleration. Set to be able to determine that there is. In step S2, the lean learning value DRLNLN is calculated. In step S3, since the vehicle is not in the lean operation state, the stoichiometric learning value DRLN is calculated.

In such a configuration, when the operation shifts to the lean idling operation, it is determined that the engine is in the lean operation state. Therefore, the lean learning value DRLNLN of the calculated duty ratio DISC during the lean operation is calculated, and the lean learning value DRLNLN is calculated. Is calculated based on the calculation learning value DISC. Therefore, the amount of air passing through the bypass passage 13 that reflects the control amount of the flow control valve 14 becomes appropriate in the lean operation, and it is possible to prevent the engine speed NE from dropping or suddenly rising. it can. Conversely, during the idle operation of the lean operation, for example, when the cooling water temperature decreases and the lean operation condition is not satisfied,
Since the lean operation is not determined in step S1, the operation shifts to the stoichiometric operation, and the stoichiometric learning value DRLN is calculated to calculate the calculated duty ratio DISC. Similarly, to prevent the engine speed from becoming unstable. Can be. Further, since the control of the engine speed during the idling operation is performed based on each operation control, NOx in the exhaust gas is controlled.
And the emission of HC and the like can be reduced, and the fuel efficiency can be improved.

The present invention is not limited to the embodiment described above. In the second embodiment described below, as the learning value, only the stoichiometric learning value DRLN is set, and when the lean operation state in the idling operation is determined, the stoichiometric learning value DRLN is set to the lean coefficient. K
To calculate a lean learning value. That is, in this embodiment, unlike the above embodiment, the learning value is one stoichiometric learning value DRLN corresponding to the stoichiometric operation, and during the lean operation, the stoichiometric learning value DRLN is used.
The lean learning value DRLNLN is set on the basis of. In this example, the lean time coefficient K is set to take a larger value as the air-fuel ratio becomes higher, that is, leaner, as shown in FIG. 3, for example. Note that the lean time coefficient K may be set, for example, by using a map so that the leaned learning value DRLNLN of the calculation result becomes larger than the stoichiometric learning value DRLN in the lean operation, regardless of the air-fuel ratio. Alternatively, it may be set to a constant value larger than 1.

In this embodiment, in the stoichiometric operation and the lean operation, the idle speed is controlled by the control amount of the flow rate control valve 14 calculated based on the stoichiometric learning value DRLN, that is, the calculated duty ratio DISC. Thus, the stoichiometric learning value DR during stoichiometric operation
Only LN is set, and the stoichiometric learning value DRL is set.
Learning value DRLNL during lean operation based on N
If N is calculated, the number of times of learning can be reduced, and the configuration of the program can be simplified.

Next, in the third embodiment, only the stoichiometric learning value DRLN is set as the learning value, and when the lean operation state is determined, the stoichiometric learning value DRLN is set.
Is used to calculate the operation duty ratio DISC, and the obtained operation duty ratio DISC is multiplied by the correction coefficient in the lean operation to obtain the operation duty ratio DIS in the lean operation.
This is to calculate C. That is, in the stoichiometric operation and the lean operation, the control amount of the flow control valve 14 is basically set by the calculated duty ratio DISC calculated based on the stoichiometric learning value DRLN. The control amount of the flow control valve 14 during the lean operation is the control amount during the stoichiometric operation, that is, the calculated duty ratio DISC.
Is multiplied by a predetermined coefficient.

In this embodiment, in FIG. 4, first, in step S21, a calculation duty ratio DISC is calculated. In this case, the calculation duty ratio DISC is calculated by adding the stoichiometric learning value DRLN to another correction amount. In step S22, it is determined whether or not the operation state at this time is a lean operation state. If the operation state is the lean operation state, the process proceeds to step S23. If the operation state is the stoichiometric operation state, the process returns to the main routine. Therefore, in the stoichiometric operation state,
The calculation duty ratio DISC is the one calculated in step S21.

On the other hand, in the lean operation state, step S2
In 3, the calculation duty ratio DISC during the lean operation is calculated by multiplying the calculation duty ratio DISC by the ratio correction coefficient KLEANISC during the lean operation. The ratio correction coefficient KLEANISC may be set by, for example, a map such that the calculated duty ratio DISC during the lean operation becomes larger than that during the stoichiometric operation, as in the second embodiment. May be set to a constant value greater than 1.

In the fourth embodiment shown in FIG. 5, the operation duty ratio DISC is different between the stoichiometric operation and the lean operation.
Each of the above-mentioned correction amounts for calculating is calculated separately, and the calculation duty ratio D is set in accordance with each operation state.
It calculates ISC. That is, in this embodiment, the operation duty ratio DISC, which is completely different between the stoichiometric operation and the lean operation, is calculated, and the flow control valve 14 is controlled by the operation duty ratio.

More specifically, first, in step S31, it is determined whether or not the operating state at this time is a lean operating state, that is, a lean operating state of an idling operation. If not, the process proceeds to step S33. In step S32, the calculation at the time of the lean operation is performed based on the correction items such as the start-time correction amount DSTA, the water temperature correction amount DAAV, the feedback correction amount DFB, and the electric load correction amount DSET, which are set corresponding to the air-fuel ratio in the lean operation state. Duty ratio D
Calculate ISC. In step S33, similarly,
According to the correction amounts set corresponding to the air-fuel ratio in the stoichiometric operation state, the calculation duty ratio DI during the stoichiometric operation is calculated.
Calculate SC.

In each of the other embodiments described above, as in the first embodiment, the effects of improving the stability of the engine speed and reducing the emission can be obtained. is there. In addition, the configuration of each unit is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0029]

As described above, according to the first and second aspects of the present invention, the control amount of the control valve provided in the bypass passage is controlled according to whether the idle operation is the lean operation state or the stoichiometric operation state. Since the setting is made, it is possible to reliably prevent the engine speed during idling from becoming unstable. Further, since the number of revolutions of the internal combustion engine in the idling operation is controlled by the lean burn operation, the fuel efficiency is improved and the exhaust amount of NOx, HC, etc. can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory view showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is a graph showing a change in a lean time coefficient with respect to an air-fuel ratio according to a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating a control procedure according to a third embodiment of the present invention.

FIG. 5 is a flowchart showing a control procedure according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 4 ... Electronic control device 4a ... Central processing unit 4b ... Storage device 4c ... Input interface 4d ... Output interface 11 ... Intake system 12 ... Throttle valve 13 ... Bypass passage 14 ... Flow control valve

Claims (2)

[Claims] In an internal combustion engine capable of switching and controlling between stoichiometric operation based on a stoichiometric air-fuel ratio and lean-burn operation based on an air-fuel ratio higher than the stoichiometric air-fuel ratio, a control valve is provided in a bypass passage bypassing a throttle valve provided in an intake system. An idle rotation control method for an internal combustion engine that controls a control valve in an idle operation state to control a rotation number to a preset target rotation number. The control valve is controlled so that the intake air amount corresponds to the stoichiometric air-fuel ratio, and the control valve is controlled so that the intake air amount corresponds to the lean burn operation during the idle operation state during the lean burn operation state. An idle speed control method for an internal combustion engine, comprising: 2. In an internal combustion engine capable of switching and controlling between stoichiometric operation based on a stoichiometric air-fuel ratio and lean burn operation based on an air-fuel ratio higher than the stoichiometric air-fuel ratio, a control valve is provided in a bypass passage bypassing a throttle valve provided in an intake system. An idle rotation control method for an internal combustion engine that controls a control valve in an idle operation state to control a rotation speed so as to reach a preset target rotation speed, wherein the control amount of the control valve is controlled from a control center. An internal combustion engine that sets two different control amounts corresponding to each of the operating states based on a learning value learned according to a difference, and switches to a control amount set according to the operating state in idle operation. Idle speed control method.