JP3966202B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine.
[Prior art]
In addition to gasoline, there is an automobile called a so-called flexible fuel vehicle (FFV) that can run with a mixed fuel of various compositions of alcohol and gasoline.
[0003]
Alcohol has a C (carbon) atom content different from that of ordinary gasoline (mixed fuel). Therefore, when supplying a mixed fuel of alcohol and gasoline to an internal combustion engine used in a flexible fuel vehicle, alcohol in the fuel is used. It is necessary to adjust the fuel injection amount according to the concentration.
[0004]
In such a flexible fuel vehicle, the alcohol concentration in the fuel is detected by an alcohol concentration sensor disposed in the fuel tank, and when the alcohol concentration sensor fails, the air concentration calculated based on the exhaust air / fuel ratio is calculated. An apparatus that estimates an alcohol concentration based on a correlation between an average value of a fuel ratio feedback correction coefficient and an alcohol concentration is conventionally known (see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-5-163992 (page 1-4, FIG. 5).
[0006]
By the way, when the alcohol concentration in the fuel is estimated using the exhaust air-fuel ratio as in the above prior art, the exhaust air-fuel ratio is greatly influenced by various disturbance factors (for example, blow-by gas). Therefore, when a disturbance factor affecting the exhaust air / fuel ratio is generated, it is considered that the estimation of the alcohol concentration in the fuel using the exhaust air / fuel ratio is prohibited.
[0007]
[Problems to be solved by the invention]
However, when the alcohol concentration in the fuel changes greatly, such as immediately after fuel with different alcohol concentrations, if the estimation of the alcohol concentration is not performed due to the generation of a disturbance factor, the fuel injection is corrected according to the alcohol concentration in the fuel. Since it cannot be performed with respect to the amount, the combustion chamber may fall into an over-lean or over-rich state, and there is a risk that the operating performance and exhaust performance will deteriorate.
[Means for Solving the Problems]
The control apparatus for an internal combustion engine according to the present invention includes: a first permission determination unit that determines permission / prohibition of single component concentration estimation in fuel based on an operating state; and whether the air-fuel ratio correction amount is outside a predetermined range. It is determined whether the single component concentration estimation in the fuel is permitted or prohibited depending on whether or not, and when the air-fuel ratio correction amount for correcting the fuel injection amount is outside the predetermined range, the single component concentration estimation in the fuel is estimated. And a second permission judging means for authorizing.
[0009]
【The invention's effect】
According to the present invention, when the air-fuel ratio correction amount is outside the predetermined range, the single permission component concentration estimation in the fuel is permitted by the second permission determination means. By using the estimated value, it is possible to prevent the operating performance and the exhaust performance from deteriorating due to an insufficient air-fuel ratio correction amount.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration of a control device for an internal combustion engine according to an embodiment of the present invention. The internal combustion engine shown in FIG. 1 is an internal combustion engine that uses a fuel containing alcohol, and is mounted on a vehicle.
[0011]
An intake passage 4 is connected to the combustion chamber 2 of the engine body 1 via an intake valve 3, and an exhaust passage 6 is connected via an exhaust valve 5.
[0012]
In the intake passage 4, an air cleaner 7, an air flow meter 8 for detecting the intake air amount, a throttle valve 9 for controlling the intake air amount, and a fuel injection valve 11 for injecting and supplying fuel during intake are disposed.
[0013]
The fuel injection valve 11 injects and supplies fuel during intake air so as to achieve a predetermined air-fuel ratio in accordance with operating conditions by an injection command signal from an engine control unit 12 (hereinafter referred to as ECU).
[0014]
The exhaust passage 6 is provided with an oxygen concentration sensor 13 as an air-fuel ratio detection means and a three-way catalyst 14 that can calculate the air-fuel ratio in the exhaust gas by detecting the oxygen concentration in the exhaust gas.
[0015]
Since the three-way catalyst 14 can simultaneously purify NOx, HC, and CO in the exhaust gas with maximum conversion efficiency when the so-called window centered on the stoichiometric air-fuel ratio has an air-fuel ratio, the ECU 12 has an upstream side of the three-way catalyst 14. The exhaust air / fuel ratio is feedback-controlled so that the exhaust air / fuel ratio fluctuates within the range of the above window based on the output from the oxygen concentration sensor 13 provided in FIG.
[0016]
The ECU 12 receives a signal from a water temperature sensor 15 for detecting the coolant temperature of the engine body 1 and an alcohol concentration input device 16 (details will be described later) serving as a first fuel property representative value providing unit. This signal can be input.
[0017]
Alcohol-containing fuel has a different C (carbon) atom content than ordinary gasoline, so a large injection amount is required to obtain the same equivalent ratio. When supplying the engine, it is necessary to adjust the fuel injection amount in accordance with the alcohol concentration in the fuel.
[0018]
Therefore, in the present embodiment, the alcohol concentration in the fuel is estimated by the following procedure as the single component concentration in the fuel. FIG. 2 shows a control flow for estimating the alcohol concentration in the fuel.
[0019]
First, in step (hereinafter simply referred to as S) 1, an air-fuel ratio feedback correction coefficient α calculated based on the output signal of the oxygen concentration sensor 13 is calculated.
[0020]
In S2, it is determined whether or not the air-fuel ratio learning condition is satisfied. If the air-fuel ratio learning condition is satisfied, the process proceeds to S3, and the map value of the αm calculation map for each operating region is rewritten. . If the air-fuel ratio learning condition is not satisfied, the process proceeds to S4 without rewriting the map value of each αm calculation map. Here, αm is an air-fuel ratio learning correction coefficient calculated based on α. The air-fuel ratio feedback correction coefficient α and the air-fuel ratio learning correction coefficient αm are air-fuel ratio correction amounts used for the above-described exhaust air-fuel ratio feedback control, and the fuel injection amount from the fuel injection valve 11 depends on α and αm. Corrected. The calculation method of the air-fuel ratio feedback correction coefficient α and the air-fuel ratio learning correction coefficient αm can be any known calculation method, and thus detailed description of these calculation methods is omitted.
[0021]
In S4, the current αm map for each operation region is referred to, and an air-fuel ratio learning correction coefficient αm as an air-fuel ratio correction amount is obtained for each operation region.
[0022]
Here, S1 to S4 correspond to air-fuel ratio correction amount calculation means.
[0023]
In S5 corresponding to the first permission determining means, it is determined whether or not a disturbance affecting the exhaust air / fuel ratio has occurred, that is, whether or not a normal permission condition for estimating the alcohol concentration is satisfied. Specifically, in S5, conditions such as the water temperature, the time after engine startup, the progress of air-fuel ratio learning control, the refueling history, and the amount of blow-by gas that affects the exhaust air-fuel ratio are below a predetermined value (operating state). If the condition is satisfied, the process proceeds to S6. If the condition is not satisfied, the process proceeds to S9.
[0024]
In S6, an air-fuel ratio sensitivity correction total amount αt expressed as the following equation (1) is calculated.
[0025]
[Expression 1]
αt = α × αm ′ × ETAHOS (1)
Here, ETAHOS is the previous first alcohol concentration estimated value ALC1 (described later), that is, the fuel property correction amount calculated from the currently stored first alcohol concentration estimated value ALC1, and will be described later with reference to FIG. The previous value of αt calculated by reverse lookup from the previous first alcohol concentration estimated value ALC1.
[0026]
In addition, αm ′ in S6 is an average value of αm in a representative rotational load region among αm for each operation region obtained in S4, in other words, αm in about four regions frequently used as an engine. Average value.
[0027]
In S7, using the map shown in FIG. 3, the first alcohol concentration estimated value ALC1 as the first single component concentration estimated value is calculated and updated from the air-fuel ratio sensitivity correction total amount αt calculated in S6.
[0028]
In FIG. 3, the first alcohol concentration estimated value ALC1 has a continuous characteristic with respect to the air-fuel ratio sensitivity correction total amount αt. This is because fuel injection is performed in order to maintain the air-fuel ratio at the stoichiometric air-fuel ratio. This is a characteristic reserved for realizing a correction with respect to the air-fuel ratio deviation, that is, the deviation of the air-fuel ratio calculated based on the detected value of the oxygen concentration sensor 13 with respect to the target air-fuel ratio. 3 in detail, in a state where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio (a region where αt is 100% or more), the air-fuel ratio sensitivity correction total amount αt is the first alcohol concentration estimated value ALC1. When the air-fuel ratio is on the rich side with respect to the stoichiometric air-fuel ratio (a region where αt is 100% or less), the alcohol concentration in the fuel is determined to be 0%. More specifically, when the air-fuel ratio sensitivity correction total amount αt = 100%, the alcohol concentration in the fuel is estimated to be 0%, and when the air-fuel ratio sensitivity correction total amount αt = 140%, The alcohol concentration is estimated to be 85%.
[0029]
In S8, using the ALC2 calculation map shown in FIG. 4, the second alcohol concentration estimated value ALC2 as the second single composition concentration estimated value is calculated from the first alcohol concentration estimated value ALC1 calculated in S7, Update.
[0030]
This ALC2 calculation map has a characteristic that the second alcohol concentration estimated value ALC2 has a dead zone with respect to the first alcohol concentration estimated value ALC1. In other words, the ALC2 calculation map shows the increase / decrease of the air-fuel ratio sensitivity correction total amount, that is, the first alcohol concentration estimated value ALC1 in a specific region of the air-fuel ratio sensitivity correction total amount where the exhaust air-fuel ratio is leaner than the stoichiometric air-fuel ratio. There is a dead zone in which the second alcohol concentration estimated value ALC2 becomes substantially constant regardless of the increase or decrease. In the present embodiment, in the region where the first alcohol concentration estimated value ALC1 is 0% to 30%, the second alcohol concentration estimated value ALC2 In the region where the estimated value ALC2 is uniformly 0% and the first alcohol concentration estimated value ALC1 is 65% to 85%, the second alcohol concentration estimated value ALC2 is set to be uniformly 85%.
[0031]
This is because when gasoline (that is, E0 fuel with an ethanol concentration of 0%) is put in, or a standard blend fuel (gasoline-alcohol fuel), for example, the so-called E85 fuel with an ethanol concentration of 85% is used. If it is entered, the characteristic is set to use a stable control value (control constant). Here, the control value includes ignition timing-related, fuel wall flow correction-related, cooler increase-related, so-called λ control ternary point adjustment constants, in other words, target air-fuel ratio in air-fuel ratio control, and the like. If these fluctuate, the reproducibility of emissions deteriorates.
[0032]
Note that the first alcohol concentration estimated value ALC1 calculated in S7 is a combustion parameter that guarantees performance according to the alcohol concentration in the fuel among the combustion parameters that require correction based on the alcohol concentration in the fuel, specifically, Is used when correcting the basic fuel injection amount (calculated from the engine speed and the intake air intake amount) calculated according to the operating conditions.
[0033]
In addition, the second alcohol concentration estimated value ALC2 calculated in S8 is an estimated concentration with respect to an actual concentration or a stable performance guarantee with respect to a marketed fuel among combustion parameters that require correction based on the alcohol concentration in the fuel. This is used when correcting parameters such as a wall flow correction amount, a cold-time increase amount, a target air-fuel ratio, and an ignition timing.
[0034]
On the other hand, if it is determined in S5 that the condition is not satisfied, the process proceeds to S9 corresponding to the second permission determination means, and it is determined whether or not the air-fuel ratio feedback correction coefficient α calculated in S1 is within a predetermined range. . That is, it is determined whether or not the air-fuel ratio feedback correction coefficient α is within the range of 85% (0.85) or more and 125% (1.25) or less, and when the air-fuel ratio feedback correction coefficient α is outside this range. Advances to S10, and if the air-fuel ratio feedback correction coefficient α is within this range, the process is terminated without estimating the alcohol concentration.
[0035]
Here, when the air-fuel ratio feedback correction coefficient α is outside the range of 85% (0.85) to 125% (1.25), it is assumed that the normal permission condition is not satisfied in S5 described above.
[0036]
If the alcohol concentration is not estimated as a result of the determination in S9 (if it does not proceed to S10), the first alcohol concentration estimated value ALC1 currently stored in the ECU 12 is used without being updated. And correcting the combustion parameter for guaranteeing performance according to the alcohol concentration in the fuel, and correcting the alcohol concentration in the fuel by using the second alcohol concentration estimated value ALC2 currently stored in the ECU 12 without updating. Among the necessary combustion parameters, the combustion parameters that require stable performance guarantee for marketed fuel and guarantee of deviation of estimated concentration from actual concentration are corrected.
[0037]
In S10, the air-fuel ratio sensitivity correction total amount αt is calculated by the same method as in S6 described above, and the process proceeds to S11.
[0038]
Then, in S11, the first alcohol concentration estimated value ALC1 is calculated and updated from the air-fuel ratio sensitivity correction total amount αt calculated in S10 using the map shown in FIG. That is, the second alcohol concentration estimated value ALC2 is not updated, and the second alcohol concentration estimated value ALC2 currently stored in the ECU 12 is continuously used.
[0039]
As described above, the first alcohol concentration estimated value ALC1 calculated in S11 is a combustion that guarantees performance according to the alcohol concentration in the fuel among the combustion parameters that need to be corrected by the alcohol concentration in the fuel. It is used when correcting a parameter, specifically, a basic fuel injection amount (calculated from the engine speed and the intake air intake amount) calculated according to operating conditions.
[0040]
Here, the first alcohol concentration estimated value ALC1 calculated in S7 is calculated until the first alcohol concentration estimated value ALC1 is calculated in the next S7 or the first alcohol concentration estimated value ALC1 is calculated in S11. It is stored in the ECU 12. The second alcohol concentration estimated value ALC2 calculated in S8 is stored in the ECU 12 until the second alcohol concentration estimated value ALC2 is calculated in the next S8.
[0041]
In such a control apparatus for an internal combustion engine, when the alcohol concentration estimation in the fuel is permitted in S5, the first alcohol concentration estimated value ALC1 and the second alcohol concentration estimated value ALC2 are calculated and updated, and the first alcohol is estimated. The basic fuel injection amount calculated according to the operating conditions is corrected using the concentration estimated value ALC1, and the wall flow correction amount, the cold-time increase amount, which is a combustion parameter of the internal combustion engine, and the target are corrected using the second alcohol concentration estimated value ALC2. When the air-fuel ratio and ignition timing are corrected and the alcohol concentration estimation in the fuel is permitted in S9, only the first alcohol concentration estimated value ALC1 is calculated and updated, and the second alcohol concentration estimated value ALC2 is calculated and updated. Not performed.
[0042]
That is, when there is a large deviation between the estimated alcohol concentration value stored in the ECU 12 and the actual alcohol concentration in the fuel tank, just after refueling, a disturbance factor for estimating the alcohol concentration. Even when the alcohol concentration estimation is not permitted due to the occurrence of (the normal permission condition of S5 is not satisfied), the first alcohol concentration estimated value ALC1 is calculated and updated, and the updated first alcohol concentration estimated value ALC1 is used. Because the basic fuel injection amount can be corrected, the lack of control amount for air-fuel ratio correction in exhaust air-fuel ratio feedback control can be solved, and the combustion chamber falls into an over-lean or over-rich state, resulting in operating performance and exhaust performance. Can be prevented from deteriorating.
[0043]
Further, the second alcohol concentration estimated value ALC2 is not updated when the process proceeds to S9 and thereafter (that is, updated only under a more reliable condition in which the normal permission condition of S5 is satisfied). This is appropriate for the intended use of the 2-alcohol concentration estimate ALC2.
[0044]
The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.
[0045]
(1) A control device for an internal combustion engine estimates a single component concentration in fuel, and includes an air-fuel ratio calculating means for detecting an exhaust air-fuel ratio, and an air-fuel ratio correction amount for correcting a fuel injection amount. An air-fuel ratio correction amount calculating means for calculating the air-fuel ratio based on the detected value of the air-fuel ratio calculating means, a first permission determining means for determining permission / prohibition of single component concentration estimation in the fuel based on the operating state, Permission / prohibition of single component concentration estimation in the fuel is determined depending on whether or not the fuel ratio correction amount is outside the predetermined range. When the air fuel ratio correction amount is outside the predetermined range, the single composition in the fuel is determined. Second permission determination means for permitting partial concentration estimation. As a result, it is possible to prevent the operating performance and the exhaust performance from deteriorating due to an insufficient air-fuel ratio correction amount.
[0046]
(2) More specifically, in the control device for an internal combustion engine according to (1), the single component concentration in the fuel is estimated based on the air-fuel ratio correction amount, and the first permission determination means is the exhaust It is determined that the single component concentration estimation is prohibited when a disturbance affecting the air-fuel ratio occurs.
[0047]
(3) More specifically, in the control device for an internal combustion engine described in (2) above, when a disturbance that affects the exhaust air-fuel ratio occurs when the amount of blow-by gas generated is equal to or greater than a predetermined value. judge.
[0048]
(4) More specifically, the control device for an internal combustion engine according to any one of (1) to (3) is calculated based on the detection value of the air-fuel ratio detection means in the second permission determination means. When the air-fuel ratio feedback correction coefficient value deviates from 1.0 by a predetermined value or more, single component concentration estimation in the fuel is permitted.
[0049]
(5) The control apparatus for an internal combustion engine according to any one of (1) to (4), more specifically, estimates / updates the single component concentration in the fuel, and updates the single composition A control device for an internal combustion engine for storing a concentration, a fuel property correction amount calculating means for calculating a fuel property correction amount based on a currently stored single component concentration, an air-fuel ratio correction amount, and a fuel property The air-fuel ratio sensitivity correction total amount calculating means for calculating the air-fuel ratio sensitivity correction total amount from the minute correction amount, and the air-fuel ratio sensitivity correction in a state where the exhaust air-fuel ratio detected by the air-fuel ratio detection means is on the lean side with respect to the theoretical air-fuel ratio And a first single component concentration estimating means for calculating a first single component concentration in which the total amount and the single component concentration estimated value are approximately proportional to each other, and the first permission determining means includes Single component concentration estimation is prohibited, and the second permission judgment means When the single component concentration estimation is permitted, the first single component concentration estimation value is calculated from the first single component concentration estimation means, and the operation is performed using the first single component concentration estimation value. The basic fuel injection amount calculated according to the conditions is corrected.
[0050]
(6) The control apparatus for an internal combustion engine according to any one of (1) to (4), more specifically, estimates / updates the single component concentration in the fuel, and updates the single composition In a control device for an internal combustion engine that stores a concentration, a fuel property correction amount calculating means for calculating a fuel property correction amount based on a currently stored single component concentration, an air-fuel ratio correction amount, and a fuel property correction An air-fuel ratio sensitivity correction total amount calculating means for calculating an air-fuel ratio sensitivity correction total amount from the amount, and a first single component concentration for correcting a basic fuel injection amount calculated according to operating conditions, In the state where the exhaust air-fuel ratio detected by the air-fuel ratio detecting means is on the lean side with respect to the stoichiometric air-fuel ratio, the first single single component in which the total air-fuel ratio sensitivity correction amount and the first single component concentration estimated value are approximately proportional to each other Composition concentration estimating means and a wall which is a combustion parameter of an internal combustion engine A flow rate correction amount, a cold-time increase amount, a target air-fuel ratio, and a second single component concentration that corrects the ignition timing are calculated. A second unit having a dead zone in which the second single component concentration estimated value calculated regardless of the increase / decrease in the air / fuel ratio sensitivity correction amount is substantially constant in a specific region of the air / fuel ratio sensitivity correction amount on the lean side with respect to the fuel ratio. A single component concentration estimating means, and when the first permission determining means permits the single component concentration estimation within the fuel, the first single composition concentration estimating means The partial concentration estimated value is calculated and updated, and the second single composition concentration estimated value is calculated and updated from the second single composition concentration estimated means, and the single composition in the fuel is determined by the first permission determining means. Concentration estimation is prohibited, and the second permission judgment means will concentrate the single component in the fuel. If the estimation is permitted, the first single composition component concentration estimating means calculates a first single composition component concentration estimates update, updating the second single composition component concentration estimates is not performed.
[0051]
(7) In the control device for an internal combustion engine according to any one of (1) to (6), the single component concentration is an alcohol concentration in the fuel.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel property estimation device for an internal combustion engine according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of control for calculating an estimated value of alcohol concentration in fuel.
FIG. 3 is an explanatory diagram showing a characteristic example of an ALC1 calculation map.
FIG. 4 is an explanatory diagram showing an example of characteristics of an ALC2 calculation map.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine main body 2 ... Combustion chamber 3 ... Intake valve 4 ... Intake passage 5 ... Exhaust valve 6 ... Exhaust passage 7 ... Air cleaner 8 ... Air flow meter 9 ... Throttle valve 11 ... Fuel injection valve 12 ... Engine control unit 13 ... Oxygen concentration sensor 14 ... Three-way catalyst 15 ... Water temperature sensor

Claims (5)

In a control device for an internal combustion engine that estimates a single component concentration in fuel,
Air-fuel ratio calculating means for detecting the exhaust air-fuel ratio;
An air-fuel ratio correction amount calculating means for calculating an air-fuel ratio correction amount for correcting the fuel injection amount based on a detection value of the air-fuel ratio calculating means;
First permission determination means for determining permission / prohibition of single component concentration estimation in the fuel based on the operating state;
Whether the single component concentration estimation in the fuel is permitted / prohibited is determined based on whether the air-fuel ratio correction amount is outside the predetermined range, and if the air-fuel ratio correction amount is outside the predetermined range, Second permission determination means for permitting composition concentration estimation;
A fuel property correction amount calculating means for calculating a fuel property correction amount based on the currently stored single component concentration;
An air-fuel ratio sensitivity correction total amount calculating means for calculating an air-fuel ratio sensitivity correction total amount from the air-fuel ratio correction amount and the fuel property correction amount;
The first single component concentration for correcting the basic fuel injection amount calculated according to the operating condition is calculated, and the exhaust air-fuel ratio detected by the air-fuel ratio detecting means is leaner than the stoichiometric air-fuel ratio. A first single component concentration estimating means in which the air-fuel ratio sensitivity correction total amount and the first single component concentration estimated value are approximately proportional to each other,
A second single component concentration for correcting a wall flow correction amount that is a combustion parameter of an internal combustion engine is calculated, and the air-fuel ratio calculated based on the detected value of the air-fuel ratio detecting means The second single composition component having a dead zone in which the second single component concentration estimated value calculated regardless of the increase / decrease in the air / fuel ratio sensitivity correction amount is substantially constant in a specific region of the air / fuel ratio sensitivity correction amount on the lean side. Concentration estimation means, and
If the first permission determination means permits the single component concentration estimation in the fuel, the first single composition concentration estimation value is calculated and updated from the first single composition concentration estimation means, and updated. Calculating and updating the second single component concentration estimated value from the second single component concentration estimating means;
When the first permission determination means prohibits the single component concentration estimation in the fuel and the second permission determination means permits the single composition concentration estimation in the fuel, the first single composition concentration estimation A control device for an internal combustion engine, characterized in that the first single component concentration estimated value is calculated and updated from the means, and the second single component concentration estimated value is not updated .   The single component concentration in the fuel is estimated based on the air-fuel ratio correction amount, and the first permission determining means prohibits the single component concentration estimation when a disturbance that affects the exhaust air-fuel ratio occurs. The control apparatus for an internal combustion engine according to claim 1, wherein the determination is made.   3. The control apparatus for an internal combustion engine according to claim 2, wherein when the amount of blow-by gas generated is equal to or greater than a predetermined value, it is determined that a disturbance affecting the exhaust air-fuel ratio has occurred.   The second permission determination unit is configured to detect a single value in the fuel when the value of the air-fuel ratio feedback correction coefficient calculated based on the detection value of the air-fuel ratio detection unit deviates from 1.0 by a predetermined value or more. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the composition concentration estimation is permitted. The control apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the single component concentration is an alcohol concentration in the fuel.

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