JP2004293491A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for improving the starting operability of an internal combustion engine after refueling. <P>SOLUTION: The controller for an internal combustion engine compensates the fuel injection quantity according to an alcohol concentration value temporarily fixed at a value adjacent to a substantial average of highest and lowest alcohol concentrations of fuels, which can be supplied to the engine until the air fuel ratio can be detected when the engine is judged to be actuated at least once in the case where the engine is newly refueled and an air fuel ratio detecting means cannot detect the air fuel ratio. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an internal combustion engine.
[0002]
[Prior art]
In a so-called flexible fuel vehicle (FFV), which is capable of running on a mixed fuel of various compositions of alcohol and gasoline in addition to gasoline, in order to obtain the same equivalence ratio, it is necessary to adjust the concentration of alcohol in the fuel in order to obtain the same equivalence ratio. It is necessary to correct the fuel injection amount.
[0003]
Accordingly, the alcohol concentration in the fuel is detected by the alcohol sensor, and when an abnormality occurs in the alcohol sensor, the alcohol concentration in the fuel is estimated using an air-fuel ratio feedback correction coefficient set based on a signal from the air-fuel ratio sensor. Such a configuration is conventionally known (see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-5-163992 (page 3-4, FIG. 5).
[0005]
[Problems to be solved by the invention]
However, when an alcohol sensor is provided to detect the alcohol concentration, there is a problem that providing an alcohol sensor increases the cost.
[0006]
When refueling / restarting is performed in the cold state where the air-fuel ratio sensor is not activated when the alcohol sensor is abnormal and the alcohol concentration in the fuel tank changes significantly before and after refueling, the fuel concentration is estimated. Cannot be performed, and depending on the fuel concentration value set at that time, the engine may be over-lean or over-rich, and the engine may not be able to be started.
[0007]
[Means for Solving the Problems]
The control device for an internal combustion engine according to the present invention, when it is determined that the internal combustion engine has been started at least once or more when the air-fuel ratio cannot be detected by the air-fuel ratio detection unit when fuel is newly supplied. Until the air-fuel ratio can be detected, the concentration is approximately the middle between the alcohol concentration of the fuel with the highest alcohol concentration and the alcohol concentration of the fuel with the lowest alcohol concentration among the fuels that may be refueled. The fuel injection amount is corrected in accordance with the provisional alcohol concentration fixed value fixed to a value in the vicinity.
[0008]
【The invention's effect】
According to the present invention, when the air-fuel ratio cannot be detected and the fuel is supplied, the fuel supply amount to the internal combustion engine is corrected by using the preset provisional ethanol concentration estimated value, whereby It is possible to prevent the internal combustion engine from being unable to start due to lean or over-rich.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 shows a schematic configuration of a control device for an internal combustion engine according to one embodiment of the present invention. The internal combustion engine according to the present embodiment is mounted on a vehicle called a so-called flexible fuel vehicle (FFV) that can run on a mixed fuel having various compositions of alcohol and gasoline in addition to gasoline. It is assumed that ethanol is used as alcohol.
[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 to the combustion chamber 2 via an exhaust valve 5.
[0012]
The intake passage 4 is provided with an air cleaner 7, an air flow meter 8 for detecting an intake air amount, a throttle valve 9 for controlling the intake air amount, and a fuel injection valve 10 for injecting fuel during intake.
[0013]
The fuel injection valve 10 injects and supplies fuel during intake so as to attain a predetermined air-fuel ratio in accordance with an operating condition by an injection command signal from an engine control unit 11 (hereinafter, referred to as ECU).
[0014]
The exhaust passage 6 is provided with an air-fuel ratio sensor 13 for detecting an exhaust air-fuel ratio in exhaust gas and a three-way catalyst 14.
[0015]
The three-way catalyst 14 can simultaneously purify NOx, HC, and CO in the exhaust gas with the maximum conversion efficiency when the air-fuel ratio is in a so-called window centered on the stoichiometric air-fuel ratio. The feedback control of the air-fuel ratio is performed based on the output from the air-fuel ratio sensor 13 provided so that the exhaust air-fuel ratio fluctuates at a constant cycle within the window.
[0016]
The ECU 11 includes a water temperature sensor 15 for detecting a coolant temperature of the engine body 1, a crank angle sensor 16 for detecting an engine speed, and a fuel level gauge sensor for detecting a fuel level in a fuel tank (not shown). The signal from 17 is input.
[0017]
The ECU 11 also monitors whether or not a starter motor (not shown) has been driven by a driver's operation of an engine key by using an ON-OFF signal of a starter motor switch 18 (starter motor drive when ON, starter motor stop when OFF). are doing.
[0018]
Next, a calculation process for estimating the ethanol concentration in fuel performed in the ECU 11 will be described with reference to a flowchart of FIG. This flowchart is executed every predetermined time (for example, every 10 ms). In this embodiment, the ethanol concentration is estimated as the alcohol concentration in the fuel.
[0019]
In step (hereinafter simply referred to as S) 1, it is determined whether the λ control by the air flow meter 8 or the air-fuel ratio sensor 13 is under closed loop (feedback) control or open loop control. If the closed loop control is being performed, the process proceeds to S2. If the open loop control is being performed, the process proceeds to S3. Here, when λ control is in closed loop control, it means that the air-fuel ratio sensor 13 is activated by warming up, and when λ control is in open loop control, the air-fuel ratio sensor 13 is not activated. It means cold state.
[0020]
In S2, the air-fuel ratio deviation amount, which is the deviation amount of the exhaust air-fuel ratio detected by the air-fuel ratio sensor 13 in the warm-up state from the target air-fuel ratio, is multiplied by a correction gain to calculate the ethanol concentration in the fuel. To end. Here, the correction gain uses the fact that there is a proportional relationship between the air-fuel ratio deviation amount and the ethanol concentration in the fuel, as shown in the METANL map shown in FIG. 3, and the slope in FIG. Set. Then, the fuel injection amount is corrected according to the estimated value of the ethanol concentration in the fuel calculated from the METANL map shown in FIG.
[0021]
On the other hand, when the λ control is under the open loop control, first, a refueling determination is performed. That is, in S3, the output value FGAGE of the fuel level gauge sensor 17 disposed in the fuel tank is read, and in S4, the output value FGAGE read in S3 is stored in the non-volatile ROM in the ECU 11. ΔFGAGE is calculated by subtracting the previous output value FGAGE ₀ of the put fuel level gauge sensor 17.
[0022]
The previous output value FGAGE ₀ is the output value of the fuel level gauge sensor 17 when the power supply of the ECU 11 was last turned off by the driver's operation of the engine key.
[0023]
Then, in S5, it is determined whether or not ΔFGAGE is equal to or greater than a predetermined value. If it is equal to or greater than the predetermined value, it is determined that fuel has been supplied, and the process proceeds to S6. That is, when the output value FGAGE of the fuel level gauge sensor 17 is increasing in the increasing direction by a predetermined value or more, it is determined that the fuel is supplied. If ΔFGAGE is less than the predetermined value, it is determined that refueling, which is a factor for changing the ethanol concentration in the fuel, has not been performed, and the flow ends without newly estimating the ethanol concentration in the fuel. . If the ethanol concentration in the fuel is not estimated, the previous value of the estimated ethanol concentration in the fuel stored in the ECU 11 (the previous value calculated in the map shown in FIG. 3) is used. The fuel injection amount is corrected, and when the λ control becomes the closed-loop control, an estimated value of the ethanol concentration in the fuel is newly calculated from the air-fuel ratio deviation amount described above, and according to the newly calculated ethanol concentration estimated value. Correct the fuel injection amount.
[0024]
In S6, the ON / OFF signal of the starter motor switch 18 and the engine speed from the crank angle sensor 16 are read.
[0025]
In S7, a start counter FSTART is calculated. That is, when the power supply of the ECU 11 changes from OFF to ON, then the starter motor switch 18 changes from OFF to ON (starter motor switch condition), and when the engine stall state changes to a non-engine stall state (engine stall state). Condition), the starting counter is incremented by one. That is, the start determination of the internal combustion engine is performed using both the starter motor switch condition and the engine stall condition.
[0026]
If the start of the internal combustion engine fails, the start counter FSTART is incremented by one. Here, the engine stall state is defined as a case where a predetermined time has elapsed after the starter motor was driven and the engine speed became 0 (rpm).
[0027]
In S8, it is determined whether or not the start counter FSTART becomes 2 or more. If the start counter FSTART becomes 2 or more, the process proceeds to S9, and the provisional ethanol concentration fixed value as the provisional alcohol concentration fixed value is set to 40%. The fuel injection amount is corrected by regarding the provisional ethanol concentration fixed value as the ethanol concentration in the fuel.
[0028]
On the other hand, if the start counter FSTART is less than 2 in S8, the fuel injection amount is calculated using the previous value of the ethanol concentration estimated value stored in the ECU 11 (the value calculated last time in the map shown in FIG. 3). The flow is terminated without estimating the ethanol concentration in the fuel as a correction to the above.
[0029]
Here, the value of the provisional ethanol concentration fixed value (40%) set in S9 is an abbreviation of the ethanol concentration of so-called E85 fuel having an ethanol concentration of 85% and the ethanol concentration of gasoline having an ethanol concentration of 0%. Even if the fuel in the fuel tank is a gasoline having an ethanol concentration of 0% or the above-mentioned E85 fuel, the starting time of the internal combustion engine is slightly longer, even if the fuel in the fuel tank is set to a value near the medium concentration. This is a value that does not make it impossible to start.
[0030]
Note that the start counter FSTART is cleared to 0 when the ethanol concentration is estimated in the flowchart, that is, when the ethanol concentration is updated in S2 or S9.
[0031]
FIG. 4 shows an example of a timing chart of the ethanol concentration estimation in the above-described embodiment. Note that FIG. 4 shows a case where gasoline fuel (ethanol concentration 0%) is used and E85 fuel is supplied when the remaining fuel amount is close to zero.
[0032]
Since the old and new fuels are easily mixed in the fuel tank, even if the old fuel (E0 fuel in the fuel tank) is refueled with the new fuel (E85 fuel), the alcohol concentration of the fuel in the fuel tank is uniform at the same time as the refueling. It can be considered that the alcohol concentration becomes approximately the new fuel (E85 fuel).
[0033]
However, since the fuel remaining in the fuel pipe connecting the fuel tank and the fuel injection valve 10 is not easily mixed with the new fuel, the alcohol concentration of the fuel injected from the fuel injection valve 10 when the internal combustion engine is started after refueling. Will gradually change. At the time of starting the internal combustion engine, the fuel injection amount is corrected using the previous value of the estimated ethanol concentration in the fuel stored in the ECU 11 (the value calculated last time in the map shown in FIG. 3). If the start of the internal combustion engine fails due to the change in the alcohol concentration of the fuel injected from the fuel injection valve 10 due to refueling and the start counter FSTART becomes 2 or more, the ethanol concentration estimated value is stored in the ECU 11 in the fuel. Is switched from the previous value of the estimated ethanol concentration to the provisional ethanol concentration fixed value of 40%.
[0034]
Then, after the estimated ethanol concentration is switched to the provisional ethanol concentration fixed value of 40%, when the λ control shifts to the closed loop (feedback) control, it is updated to the estimated ethanol concentration according to the operating conditions of the internal combustion engine.
[0035]
If the λ control can be shifted to the closed loop (feedback) control before the start counter FSTART becomes 2 or more, the switching to the provisional ethanol concentration fixed value of 40% is not performed, and the λ control is changed according to the operating conditions of the internal combustion engine. Update to the estimated ethanol concentration.
[0036]
In such a control device for an internal combustion engine, when the air-fuel ratio deviation amount cannot be detected and fuel is supplied, that is, for example, the E85 fuel is supplied while gasoline having an ethanol concentration of 0% is used. For example, when the ethanol concentration in the fuel in the fuel tank is remarkably changed and the air-fuel ratio sensor 13 is not activated and the ethanol concentration in the fuel cannot be estimated, the preset temporary ethanol concentration is fixed. By correcting the fuel supply amount to the internal combustion engine using the value, it is possible to reliably prevent the internal combustion engine from being unable to start due to over-lean or over-rich.
[0037]
Further, the alcohol concentration estimated value is not switched to the provisional alcohol concentration fixed value just by turning on / off the power supply of the ECU 11 continuously.
[0038]
In the above-described embodiment, the start determination of the internal combustion engine is performed by combining the starter motor switch condition (starter motor ON / OFF) and the engine stall condition (change from the engine stall state to the non-engine stall state). However, the start determination of the internal combustion engine may be performed using only one of the starter motor switch condition and the engine stall condition.
[0039]
Further, the start counter FSTART is determined by considering the frequency at which the alcohol concentration cannot be estimated, that is, the frequency at which the λ control does not become the closed droop control due to refueling, and the start time deterioration due to the provisional ethanol concentration fixed value. The number is not limited to two or more as in the present embodiment, but may be three or more, for example.
[0040]
In the above-described embodiment, the fuel having the highest alcohol concentration among the fuels that may be refueled is E85, and the fuel having the lowest alcohol concentration is E0. % Is a provisional ethanol concentration fixed value (provisional alcohol concentration fixed value), but the provisional ethanol concentration fixed value is not limited to only the ethanol (alcohol) concentration of 40%, and the friction and the like differ depending on the type of the internal combustion engine. Therefore, the provisional ethanol concentration fixed value (temporary alcohol concentration fixed value) may be adapted in an actual vehicle.
[0041]
The technical ideas of the present invention that can be grasped from the above embodiments will be listed together with their effects.
[0042]
(1) A control device for an internal combustion engine that corrects a fuel injection amount according to an alcohol concentration in fuel includes an air-fuel ratio detection unit that detects an air-fuel ratio, and an alcohol concentration of the fuel based on a value detected by the air-fuel ratio detection unit. Alcohol resumption determination means for determining whether or not fuel has been newly refueled, and start determination means for determining whether to start the internal combustion engine. In the state where the air-fuel ratio cannot be detected by the air-fuel ratio detection means, if the start determination means determines that the internal combustion engine has been started at least once, the air-fuel ratio can be detected by the air-fuel ratio detection means. Up to approximately the middle of the alcohol concentration of the fuel with the highest alcohol concentration and the alcohol concentration of the fuel with the lowest alcohol concentration among the fuels that may be refueled The fuel injection amount is corrected according to the provisional alcohol concentration fixed value fixed to the value. With this, when the air-fuel ratio cannot be detected and fuel is supplied, the fuel supply amount to the internal combustion engine is corrected by using a preset provisional ethanol concentration estimated value, so that over lean or over It is possible to reliably prevent the internal combustion engine from being unable to start due to the richness.
[0043]
(2) In the configuration according to the above (1), the start determination means may be a starter motor drive number detection means for detecting the number of drive times of the starter motor, or an engine for detecting a difference between an engine stalled state and a non-engine stalled state. At least one of the state detection means is provided, and the start determination of the internal combustion engine is performed using at least one of the starter motor drive frequency detection means and the engine state detection means. As a result, the estimated alcohol concentration is not switched to the provisional alcohol concentration fixed value only when the power of the control device of the internal combustion engine is continuously turned ON / OFF.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a control device for an internal combustion engine according to the present invention.
FIG. 2 is a flowchart showing a flow of control for estimating ethanol concentration in the control device for an internal combustion engine according to the present invention.
FIG. 3 is a characteristic diagram of an ethanol concentration calculation table for estimating ethanol concentration in fuel from an air-fuel ratio deviation amount.
FIG. 4 is a timing chart for estimating ethanol concentration in the control device for an internal combustion engine according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine 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 10 ... Fuel injection valve 11 ... Engine control unit 13 ... Oxygen concentration sensor 14 ... three-way catalyst 15 ... water temperature sensor 16 ... crank angle sensor 17 ... fuel level gauge sensor 18 ... starter motor switch

Claims (2)

In a control device for an internal combustion engine that corrects a fuel injection amount according to an alcohol concentration in fuel,
Air-fuel ratio detecting means for detecting an air-fuel ratio,
Alcohol concentration estimating means for estimating the alcohol concentration of the fuel based on the value detected by the air-fuel ratio detecting means,
Refueling determination means for determining whether or not fuel has been newly supplied;
Start determination means for determining the start of the internal combustion engine,
When the air-fuel ratio cannot be detected by the air-fuel ratio detection means when the fuel is newly supplied, and when the start determination means determines that the internal combustion engine has been started at least once or more, the air-fuel ratio detection means Until the air-fuel ratio can be detected, near the concentration where the alcohol concentration of the fuel with the highest alcohol concentration and the alcohol concentration of the fuel with the lowest alcohol concentration among the fuels that may be refueled are approximately moderate. A control device for an internal combustion engine, wherein the fuel injection amount is corrected in accordance with a provisional alcohol concentration fixed value fixed to the value of: The start determination unit includes at least one of a starter motor drive number detection unit that detects the number of drive times of the starter motor, and an engine state detection unit that detects a difference between an engine stalled state and a state in which the engine is not stalled,
The control device for an internal combustion engine according to claim 1, wherein the start determination of the internal combustion engine is performed by using at least one of the starter motor drive frequency detection means and the engine state detection means.

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