JP4781449B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that controls an internal combustion engine to which an alcohol-containing fuel mixed with alcohol and gasoline is supplied.

  In addition to gasoline, there is an automobile called a so-called flexible fuel vehicle (FFV) that can run even when an alcohol-containing fuel in which alcohol and gasoline are mixed is supplied.

  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 value.

  Therefore, in such a flexible fuel vehicle, the alcohol concentration value in the fuel is detected by an alcohol concentration sensor provided in the fuel tank, or the average of the air-fuel ratio feedback correction coefficient calculated based on the exhaust air-fuel ratio is calculated. An apparatus that estimates an alcohol concentration based on a correlation between a value and an alcohol concentration value is conventionally known.

  For example, Patent Document 1 proposes a method of performing alcohol concentration learning based on a deviation from a reference value of an air-fuel ratio correction amount obtained by air-fuel ratio control when fuel refueling is performed. A method has been proposed for determining whether or not the fuel amount in the fuel tank has increased by a predetermined amount or more of the fuel supply determination amount.

  In other words, it is possible to detect whether fuel has been refueled in consideration of vehicle shake and the accuracy of the fuel level sensor. If fuel is refueled, the concentration of alcohol contained in the fuel may vary. From this, the alcohol concentration is estimated.

  In Patent Document 2, for example, a torque value output when fuel is injected at a preset injection amount corresponding to the alcohol concentration, and a reference torque value set in advance corresponding to the alcohol concentration. A method has been proposed in which the concentration of alcohol is estimated by comparing the above, and the alcohol concentration is estimated regularly or irregularly even when the oil supply determination is not made.

JP 2008-19830 A (summary column, FIG. 1) JP 2007-137321 A (summary column, FIG. 1)

  However, in the method disclosed in Patent Document 1, when the amount of fuel in the fuel tank is equal to or less than a predetermined fueling determination amount, fuel fueling determination is not made, and therefore, additional fueling to such an extent that fuel fueling cannot be detected is performed. In such a case, the fuel refueling determination is not made despite the refueling, and the alcohol concentration estimation is not performed.

  As a result, since the alcohol concentration is not estimated even after refueling, there is a case where the estimated alcohol concentration before refueling does not match the alcohol concentration of the fuel currently in the fuel tank after refueling. The amount of fuel is adjusted by the estimated concentration value.

  For this reason, the deviation of the air-fuel ratio due to the change in the alcohol concentration of the fuel after refueling is eliminated by adjusting with the above-described feedback correction coefficient during the air-fuel ratio feedback control. Further, in order to eliminate the air-fuel ratio deviation in the entire operation region, generally, the air-fuel ratio is learned based on the feedback correction coefficient, and the result is stored as the air-fuel ratio learned value. That is, when the alcohol concentration estimation is not performed, the alcohol concentration change is finally reflected in the air-fuel ratio learning value by subsequent feedback control.

  On the other hand, the air-fuel ratio learning value originally learns the deviation amount of the air-fuel ratio due to the aging and variation of the fuel system device by the feedback control described above, and at the time of feedback control, the feedback correction coefficient is rich (over-rich) side or lean. Reflect the air-fuel ratio learning value so that the value does not deviate to one of the (lean) sides, and so that the deviation of the air-fuel ratio due to the fact that the feedback correction coefficient is not reflected is not used except during feedback control. The purpose is to adjust the fuel injection amount.

  Also, if the learned value is abnormally biased to the rich side or lean side by learning the air / fuel ratio learning value due to aging and variations in the fuel system, the fuel system will be abnormal. It is also used to detect a malfunction in the fuel system that is judged to be malfunctioning.

  However, when the fuel concentration cannot be determined and the alcohol concentration is not estimated, if the air-fuel ratio shift due to the change in alcohol concentration is reflected in the air-fuel ratio learning value, the air-fuel ratio shift other than the original purpose is learned. As a result, it becomes impossible to sufficiently learn the deviation of the air-fuel ratio due to the secular change and variation of the fuel system device, which is the original purpose, and as a result, the optimal fuel injection amount may not be able to be performed.

  In addition, even if no abnormality has occurred in the fuel system, the malfunction of the fuel system may be erroneously determined by reflecting the air-fuel ratio shift due to the alcohol concentration in the air-fuel ratio learning value.

  Furthermore, when the air-fuel ratio change due to the alcohol concentration is learned as the air-fuel ratio learning value, the fuel supply determination is performed after the learning, and when the alcohol concentration estimation is performed, the air-fuel ratio change due to the alcohol concentration change in the case where the oil-fuel ratio is not already determined in the air-fuel ratio learning value Since the deviation is reflected, there is a problem that the change in the air-fuel ratio according to the actual alcohol concentration is not correctly detected and the alcohol concentration cannot be estimated correctly.

  In addition, even if the concentration estimation is performed regularly or irregularly regardless of the presence or absence of fuel refueling determination as in the method disclosed in Patent Document 2, before the alcohol concentration is estimated when there is a change in the alcohol concentration, When air-fuel ratio learning is performed, the alcohol concentration is erroneously reflected in the air-fuel ratio learning value, and the same problem as the method disclosed in Patent Document 1 can be considered.

  In other words, even if the concentration is estimated regularly or irregularly, it is not sufficient to optimize the air-fuel ratio learning and improve the accuracy of alcohol concentration estimation.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine that suppresses erroneously reflecting a change in an air-fuel ratio due to alcohol concentration in an air-fuel ratio learning value.

An internal combustion engine control apparatus according to the present invention is an internal combustion engine control apparatus for controlling an internal combustion engine to which an alcohol-containing fuel mixed with alcohol and gasoline is supplied, and estimates an alcohol concentration value of the alcohol-containing fuel. An alcohol concentration estimating means, a means for correcting the fuel amount based on the alcohol concentration value estimated by the alcohol concentration estimating means, and an air fuel ratio of the fuel mixture supplied to the internal combustion engine are learned to obtain an air fuel ratio learned value. In the control device for an internal combustion engine provided with an air-fuel ratio learning means, the alcohol concentration estimation means estimates the alcohol concentration when a fuel refueling determination is made or when an engine operation time has passed a predetermined time, when estimating the alcohol concentration, and corrects the amount of fuel using the air-fuel ratio learned value at the time of the previous alcohol concentration estimation

  According to the control device for an internal combustion engine of the present invention, it is possible to suppress erroneously reflecting the change in the air-fuel ratio due to the alcohol concentration in the air-fuel ratio learning value.

It is explanatory drawing which shows schematic structure of the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a flowchart which shows the flow of control which performs alcohol concentration estimation in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a flowchart which shows the flow of control which determines the fuel supply in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a flowchart which shows the flow of control of alcohol concentration estimation in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a time chart which performs alcohol concentration estimation in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention.

  Preferred embodiments of a control apparatus for an internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG.
FIG. 1 shows a schematic configuration of a control device for an internal combustion engine according to Embodiment 1 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.

  An ignition plug 2 is provided in the combustion chamber 1 a of the engine 1, an intake manifold 4 is connected via an intake valve 3, and an exhaust manifold 6 is connected via an exhaust valve 5. Further, a water temperature sensor 7 for detecting the water temperature of the engine cooling water is provided.

  The intake manifold 4 is provided with a throttle valve 8 that controls the amount of intake air, an intake amount sensor 9 that measures the amount of intake air, and an injector 10 that injects and supplies fuel during intake.

  An engine control unit (hereinafter referred to as ECU) 11 controls to inject and supply fuel from the injector 10 during intake so that a predetermined air-fuel ratio is obtained in accordance with operating conditions by an injection command signal. The ECU 10 includes a central processing unit (CPU) 12 that is a central processing unit that executes various arithmetic processes, a ROM (Read Only Memory) (not shown) that stores a control program, and a RAM that stores various data. (Random Access Memory) 13 and a backup RAM (not shown) for holding data even when power is not supplied to the ECU 11 are provided.

  The exhaust manifold 6 includes a first oxygen concentration sensor 14, a first three-way catalyst 15, and a second oxygen concentration as air-fuel ratio detection means that can calculate the air-fuel ratio in the exhaust gas by detecting the oxygen concentration in the exhaust gas. A sensor 16 and a second three-way catalyst 17 are provided.

  The first three-way catalyst 15 and the second three-way catalyst 17 have NOx (nitrogen oxides), HC ( Hydrocarbons) and CO (carbon monoxide) can be simultaneously purified, so the ECU 11 determines the exhaust air-fuel ratio within the aforementioned window range based on the output from the first oxygen concentration sensor 14 provided upstream of the three-way catalyst 15. The exhaust air-fuel ratio feedback (hereinafter referred to as F / B) control is performed so as to vary within the range.

  In addition, the ECU 11 receives a signal from the rotational speed sensor 18 so as to detect the engine rotational speed and to grasp the engine operating state.

  As described above, since the fuel containing alcohol has a different C (carbon) atom content compared to normal gasoline, a large injection amount is required to obtain the same equivalent ratio. When the mixed fuel is supplied to the engine, it is necessary to adjust the fuel injection amount in accordance with the alcohol concentration value in the fuel.

  The ECU 11 estimates the alcohol concentration when the output value of the fuel level sensor 20 provided in the fuel storage device (hereinafter referred to as a fuel tank) 19 increases or when the engine operating time exceeds a predetermined time.

  Therefore, actual processing in the ECU 11 of the control device for the internal combustion engine in the present embodiment shown in FIG. 1 will be described with reference to the flowcharts of FIGS.

2 to 4 are flowcharts from the execution of the alcohol concentration estimation, the switching of the fuel calculation air-fuel ratio learning value, and the re-learning of the air-fuel ratio learning value, which are repeatedly executed during the operation of the ECU 11.

2, the fuel operation during operation of the ECU 11, the air-fuel ratio learning, the fuel calculation air-fuel ratio learned value when the alcohol concentration estimation performed switching, and the routine for re learning of the air-fuel ratio learned value when the alcohol concentration estimation completion is there.

  In the determination routine of FIG. 2, the ECU 11 first performs a fuel supply determination process in step S200. The fuel supply determination process will be described with reference to the flowchart of FIG.

  In the fuel supply determination process of FIG. 3, first, in step S301, the fuel amount in the fuel tank 19 detected this time based on the output value of the fuel level sensor 20 is updated as the current value FTANK, and the process proceeds to step S302.

  In step S302, the previous fuel amount value FTANKB in the fuel tank 19 updated in the previous step S303 is compared with the current value FTANK. If the current value FTANK is smaller, that is, it is determined that the amount of fuel in the fuel tank 19 has decreased compared to the previous time, the process proceeds to step S303, and after the previous value FTANK is updated, the process proceeds to step S304.

  In step S302, if the current value FTANK is large, that is, it is determined that the amount of fuel in the fuel tank 19 has increased, step S303 is skipped and the process proceeds to S304.

  That is, in step S303, it is determined whether the fuel amount has been consumed and decreased, or increased due to fueling or the like, and the previous value FTANKB is updated only when the fuel is consumed.

  Note that the current value FTANK and the previous value FTANKB are information stored in a memory (for example, RAM 13) in the ECU 11, and the information is retained when the ECU 11 is powered off by a backup RAM (not shown). Therefore, the initial values of the current value FTANK and the previous value FTANK when the power is turned on for the first time are set so as not to become indefinite values, for example, by storing the output value of the fuel level sensor 20.

Next, in step S304, the oil supply amount FTANKIN is obtained by the following equation.
FTANKIN = FTANK-FTANKB
The previous value FTANKB is updated when the fuel in the fuel tank 19 is consumed as described above. That is, when the fuel is consumed, it can be said that FTANK <FTANBKB and FTANKIN <0 and no fuel is supplied.

  On the other hand, when the fuel in the fuel tank 19 is increasing, since the previous value FTANKB is not updated, FTANK ≧ FTANKB, and FTANKIN ≧ 0, indicating that fueling may have been performed. I can say that. That is, it is determined in step S305 whether or not refueling has been performed by using the refueling amount FTANKIN obtained by the above calculation.

  In step S305, it is determined whether or not refueling is performed based on whether or not the refueling amount FTANKIN is larger than a predetermined refueling determination amount. Here, the fuel supply amount FTANKIN is a result calculated based on information obtained from the output value of the fuel level sensor 20 as described above. Further, the output value of the fuel level sensor 20 does not always change to the increasing side only when fuel is supplied. There is also a possibility that the fuel tank 19 may fluctuate due to shaking.

  Therefore, in the present embodiment, as an example of a method for determining that fuel has been reliably supplied, as described above, when the fuel supply amount FTANKIN has increased to some extent in step S305, that is, the fuel in the fuel tank 19 has increased from the consumption state. However, this determination method is not limited to this method as long as it can be determined that the fuel has been supplied.

  If it is determined in step S305 that fueling has been performed, the process proceeds to step S306, a flag FLAG1 for determining that fueling has been performed is set, and the processing of this routine ends. If the fuel supply determination is not made in step S305, step S306 is skipped and the process of this routine is finished.

  Here, FLAG 1 is information stored in a memory (for example, RAM 13) in the ECU 11, and as described above, the information is held when the power of the ECU 11 is turned off and is turned on again. Until the concentration estimation is performed in this flow, the fuel supply determination result is retained.

  Returning to FIG. 2, after the oil supply determination process in step S <b> 200, the alcohol concentration estimation permission determination process is performed in step S <b> 201. The alcohol concentration estimation permission determination process will be described with reference to the flowchart of FIG.

  As shown in FIG. 4, in the alcohol concentration estimation permission determination process, it is first determined in step S400 whether FLAG1 is 1, that is, whether refueling is being performed. If it is determined that refueling has been performed, the process proceeds to step S401, and alcohol concentration estimation permission determination is executed.

  If refueling has not been performed, the process proceeds to step S402, where it is determined whether an engine operation time T1 to be described later is equal to or longer than a predetermined time Ts set in advance, and if it is equal to or longer than the predetermined time Ts, the process proceeds to step S401 to estimate alcohol concentration. The permission determination is executed.

  Here, the predetermined time Ts is set to such a time that the engine cannot be operated originally if fuel is not replenished by refueling or the like although fueling determination is not made.

  The predetermined time Ts can be estimated from the capacity of the fuel tank of the engine, the fuel efficiency, and the like, and is set by setting a value with some margin to the experimentally obtained value. be able to.

  If it is determined in step S402 that the engine operation time T1 is less than the predetermined time Ts, the alcohol concentration estimation is not permitted in step 405, the permission flag FLAG3 = 0 is set, and the concentration estimation completion determination described later is used in step S406. The processing of this routine is finished with the alcohol concentration estimation time T2 = 0.

  Therefore, step S402 is a process for executing the alcohol concentration estimation permission determination when there is a high possibility that the alcohol concentration in the fuel tank 19 has changed due to additional fueling or the like even if the fuel supply determination has not been made. .

  Next, in step S401, it is determined whether air-fuel ratio F / B control is in progress. If the air-fuel ratio F / B control is being performed, it is determined that the concentration estimation is permitted, and the process proceeds to step S403, where it is regarded that the alcohol concentration can be estimated, and the alcohol concentration estimation permission flag FLAG3 = 1 is set.

  Thereafter, the alcohol concentration estimation time T2 is counted in step S404, and the processing of this routine is finished.

  In step S401, if the air-fuel ratio F / B control is not in progress, the processing of steps S405 and S406 is executed, and the processing of this routine is finished.

  In other words, in the present embodiment, the alcohol concentration estimation permission determination process in FIG. 4 is performed when the fuel supply determination is made, or when the air-fuel ratio F / B control is in progress when the engine operation time has elapsed for a predetermined time Ts. Judgment to allow.

  Here, the engine operation time T1 is stored in a memory (for example, the RAM 13) in the ECU 11, and the engine operation time when the engine 11 is stopped or repeatedly operated regardless of whether the power of the ECU 11 is off or on. The initial value when the power is turned on for the first time is 0. Further, the concentration estimation times T2 and FLAG3 are information stored in the RAM 13 in the ECU 11.

  Here, whether or not the air-fuel ratio F / B control is in progress is used as the condition for determining whether or not the alcohol concentration can be estimated. However, if the alcohol concentration can be estimated using the air-fuel ratio, what kind of method is particularly applicable? The method may also be used, and the conditions for determining the concentration estimation permission may be added as necessary depending on other conditions such as water temperature information by the water temperature sensor 7 and engine rotation information by the rotation speed sensor 18, for example. Absent.

  Further, in the present embodiment, the fuel supply determination has been described as an example of the condition for estimating the alcohol concentration other than the condition of the engine operation time T1, but the fuel supply determination process can be omitted in order to save useless processing.

Returning to FIG. 2 again, the processing after step S202 will be described.
In step S202, it is determined whether or not the alcohol concentration estimation permission flag FLAG3 determined in FIG. 4 is 1, that is, whether or not the alcohol concentration estimation permission condition is satisfied. If it is determined that the alcohol concentration estimation permission condition is not satisfied FLAG3 = 0, the process proceeds to step S203.

  In step S203, it is determined whether or not the engine speed is 0 rpm, that is, whether or not the engine is operating. If it is determined that the engine speed is not 0 rpm (during engine operation), the engine operation time T1 is counted in step S204, and the process proceeds to step S205. Conversely, if it is determined that the engine speed is 0 rpm (the engine is not operating), the process proceeds to step S205 without counting the engine operating time T1.

  The engine operation time T1 is used to determine whether or not there is a high possibility that the alcohol concentration in the fuel tank 19 has changed due to additional fueling or the like even if the fueling determination is not made in step S402 in FIG. Value.

In step S205, the fuel injection amount is calculated. In general, the fuel injection amount is calculated by calculating the basic fuel injection amount Fuel_Base based on the rotation speed detected by the rotation speed sensor 18 and the intake air amount detected by the intake air amount sensor 9. Then, the basic fuel injection amount Fuel_Base is determined based on the air-fuel ratio learning value AFLRN, the correction coefficient K_ALCH for the alcohol concentration set in advance from the alcohol concentration estimated value ALCH, the environment correction K_ENV based on the temperature of the internal combustion engine (cooling water temperature), etc. The fuel injection amount Fuel is determined by correction based on the air-fuel ratio F / B correction coefficient α in the fuel ratio F / B, and is given by the following equation (1), for example.
Fuel = Fuel_base × AFLRN × K_ALCH × K_ENV × α
(1)

  If the air-fuel ratio F / B is not in use, α may be forcibly set to 1.0 or may be treated as another fixed value depending on the operating conditions of the engine. The treatment of α in the case where it is not, will not be described because it is not directly related to the gist of the present invention.

Next, in step S206, the alcohol concentration estimated value ALCH is substituted into the alcohol concentration estimated value previous value ALCH_OLD, the alcohol concentration estimated value previous value is updated, and the process proceeds to step S217. This information is stored as a previous value when concentration estimation is not performed for re-learning of an air-fuel ratio learned value after completion of concentration estimation described later.

  In step 217, it is determined whether or not the air-fuel ratio learning condition is satisfied. If it is satisfied, the process proceeds to step S218 to perform air-fuel ratio learning.

  Here, the air-fuel ratio learning condition in step S217 will be described. The air-fuel ratio learning conditions generally include that the air-fuel ratio is in F / B and environmental conditions such as the temperature of the internal combustion engine (cooling water temperature). I don't care about the conditions.

  In step S218, an air-fuel ratio learning value AFLRN is calculated. Here, an example of the air-fuel ratio learning method will be described. The air-fuel ratio learning value AFLRN is generally set when the average value αave of the air-fuel ratio F / B correction coefficient α is larger than the reference value 1.0 (air-fuel ratio = theoretical air-fuel ratio 14.7) during the air-fuel ratio F / B. A predetermined value set in advance is added to the previous value AFLRN (n-1) of the air-fuel ratio learning value. Conversely, when the average value αave of the air-fuel ratio F / B correction coefficient α is smaller than the reference value 1.0, a predetermined value set in advance is subtracted from the previous air-fuel ratio learning value AFLRN (n−1).

  That is, during the air-fuel ratio F / B, the steady value of the air-fuel ratio F / B correction coefficient α is rich or lean with respect to the reference value 1.0 (air-fuel ratio = theoretical air-fuel ratio 14.7). The air-fuel ratio learning is gradually performed so that there is no sudden change in the air-fuel ratio, which is reflected in the arithmetic expression of the expression (1). During the operation of the ECU 11, the processing of FIG. Eventually, α becomes close to the reference value 1.0 (air-fuel ratio = theoretical air-fuel ratio 14.7).

  When the process of step S218 ends, the routine of FIG. 2 ends.

Next, a process when it is determined in step S202 that the alcohol concentration estimation permission condition is satisfied FLAG3 = 1 will be described.
If it is determined in step S202 that the alcohol concentration estimation start condition is satisfied FLAG3 = 1, the process proceeds to step S219, and it is determined by FLAG1 whether or not the fuel supply is determined.

  If FLAG1 = 1 in step S219, that is, if fueling is determined, the process proceeds to step S223, and in step S223, the fuel injection amount Fuel is set by the same arithmetic expression as the expression (1).

  If FLAG1 = 0 in step S219, that is, if the refueling determination is not made, the process proceeds to step S207.

In step S207, a fuel injection amount is calculated for estimating the alcohol concentration when the fuel supply determination is not made. The calculation of the fuel injection amount here is similar to the basic fuel injection amount described in step S205 and the equation (1). However, as shown in the following equation (2), the air-fuel ratio learning used for the calculation is performed. Unlike the case of step S205, the air-fuel ratio learned value AFLRN1 learned again when the previous concentration estimation is completed is used.
Fuel = Fuel_base × AFLRN1 × K_ALCH × K_ENV × α
(2)

Here, the reason for using the air-fuel ratio learned value AFLRN1 learned again when the previous alcohol concentration estimation is completed will be described.

  In a state where the alcohol concentration estimation is not performed even though the alcohol concentration in the fuel tank 19 has changed due to refueling or the like, the alcohol concentration change amount is reflected in the air-fuel ratio F / B correction coefficient α during the air-fuel ratio F / B. Will be.

  As described above, when the concentration estimation is not performed, if the learning condition of step S217 is satisfied, the air-fuel ratio learning is performed in step S218, that is, by the air-fuel ratio F / B correction coefficient α including the alcohol concentration change. The air-fuel ratio is learned. Therefore, in this case, the air-fuel ratio learning value AFLRN becomes a value including a change in alcohol concentration.

Therefore, since the learned value learned again at the previous concentration estimation is considered to be a more appropriate value without using the learned value including the alcohol concentration change described above, the fuel calculation using AFLRN1 will be described later. When the concentration estimation is performed using the F / B correction value, the alcohol concentration change amount is reflected only in the F / B correction value, and the alcohol concentration estimation can be performed with higher accuracy.

  In this case, the air-fuel ratio F / B correction coefficient α may have an initial value of 1.0, but fluctuations in the air-fuel ratio F / B correction coefficient due to the change in the air-fuel ratio learning value to be used (for example, AFALRN and AFLRN1 It is better to suppress an abrupt change in the fuel injection amount before and after the alcohol concentration estimation is performed, for example, by setting the deviation of the initial value as an initial value.

In the present embodiment, when calculating the alcohol concentration in the state where the fueling determination is performed and the state where the fueling determination is not performed and the alcohol concentration is estimated in the state where the fueling determination is performed, the learning value is not learned again as described later. This will be described as a method of re-learning only at the time of alcohol concentration estimation in a state where fueling determination is not performed.

  Next, after the fuel is calculated in step 207 and the amount of fuel to be injected is set, the alcohol concentration is estimated in step S220.

Hereinafter, the alcohol concentration estimation method in step S220 in the present embodiment will be described.
The theoretical air-fuel ratio of alcohol fuel (for example, 8.9 for 100% ethanol) is smaller than the theoretical air-fuel ratio of gasoline (for example, 14.7), and fuel injection is performed under the same conditions as gasoline when alcohol fuel is used. Since the fuel injection amount is insufficient when the control is performed, the fuel injection amount is adjusted by changing the air-fuel ratio F / B correction coefficient α in the F / B control. The change in the alcohol concentration is reflected in the change in the air / fuel ratio F / B correction coefficient α in the F / B control, whereby the alcohol concentration is calculated from the air / fuel ratio F / B correction coefficient α by the following means. Can do.

The calculation of the alcohol concentration estimated value is performed by first reading the maximum value αmax and the minimum value αmin of the air-fuel ratio F / B correction coefficient α in F / B, and averaging the αmax and αmin, that is, the air-fuel ratio F / B correction coefficient An average value αave of α is calculated.
αave = (αmax + αmin) / 2
Then, a deviation ΔM between the average value αave and the reference value 1.0 at which correction by the air-fuel ratio F / B correction coefficient α is not substantially performed is calculated.
ΔM = αave−1.0
An alcohol concentration estimated value (ALCH) is calculated from a map with the deviation ΔM set in advance as an axis. Here, the larger the ΔM, the larger the alcohol concentration is calculated.

  In the present embodiment, the alcohol concentration is calculated using the air-fuel ratio F / B correction coefficient α, but the method is not particularly limited as long as the alcohol concentration can be calculated.

  Next, in step S221, it is determined whether or not the alcohol concentration estimation time T2 is equal to or longer than a preset time required for alcohol concentration estimation. If it is determined that the alcohol concentration estimation time T2 is equal to or longer than the predetermined time, the alcohol concentration estimation completion flag is set FLAG5 = 1 in step S222, and the process is terminated. Conversely, if it is determined that the alcohol concentration estimation time T2 is less than the predetermined time, the processing ends.

  This is a measure for taking time since the air-fuel ratio F / B correction coefficient α becomes a value that is stabilized to some extent in performing the above-described alcohol concentration estimation. In the present embodiment, alcohol for estimating the alcohol concentration is used. The concentration estimation time T2 is the time after the concentration estimation permission counted in step S404 in FIG. 4 described above.

  Next, in step S208, it is determined whether or not FLAG5 = 1, that is, whether or not alcohol concentration estimation is completed. If it is determined that the alcohol concentration estimation incomplete FLAG5 = 0, the following processing is skipped and the processing of this routine is finished.

  If it is determined that the alcohol concentration estimation completion FLAG5 = 1, it is determined in step S209 whether FLAG1 = 1, that is, whether fuel refueling has been determined, and it is determined that FLAG1 = 0 has not been determined. If YES in step S210, it is determined whether the amount of change in the estimated alcohol concentration is equal to or greater than a predetermined determination value. In this determination, it is determined whether or not the absolute difference | ALCH−ALCH_OLD | between the alcohol concentration estimated value ALCH and the alcohol concentration estimated value previous value ALCH_OLD is greater than or equal to the determination value.

The determination of the deviation | ALCH-ALCH_OLD | between the current value and the previous value of the alcohol concentration is performed in order to determine whether there is a sufficient alcohol concentration deviation for learning again. If the concentration deviation is small, For example, the learning value is not re-learned as the error range.

If it is determined that the change amount of the alcohol concentration estimated value is greater than or equal to the determination value, the air-fuel ratio learning value is learned again in step S211. On the other hand, when it is determined that FLAG1 is determined to be fuel supply = 1, and when it is determined that the amount of change in the estimated alcohol concentration is less than the determination value, the process proceeds to step S212.

In other words, in the case of alcohol concentration estimation when fuel refueling determination has not been made, there is a possibility that sufficient time has passed since the previous alcohol concentration estimation, and during that time the alcohol concentration has changed due to refueling, etc., and is reflected in the learned value by mistake. In this case, the learning value is learned again . When the fuel supply determination is made, this is not the case, and the learning value is not learned again .

Here, the air-fuel ratio learning value in step S211 will be described again . When the estimated alcohol concentration value is updated, the air / fuel ratio learning value may reflect the change in the air / fuel ratio due to the alcohol concentration. Remove changes in fuel ratio.

  As a method of resetting the air-fuel ratio learning value AFLRN, the air-fuel ratio learning value AFLRN before resetting, the current alcohol concentration estimated value ALCH, and the alcohol concentration estimated value previous value ALCH_OLD are preliminarily set according to the alcohol concentration described in the above equation (1). The correction coefficient K_ALCH and the correction coefficient K_ALCH_OLD based on the previous alcohol concentration estimated value are used.

When the air-fuel ratio learning value before resetting, that is, the air-fuel ratio learning value before alcohol concentration estimation is AFLRN (n-1), the air-fuel ratio learning is obtained by multiplying the change rate of the correction coefficient according to the alcohol concentration estimation value. The value AFLRN is reset.
AFLRN = AFLRN (n−1) × K_ALCH_OLD ÷ K_ALCH

  In other words, the amount of change in the alcohol concentration obtained by using the previous air-fuel ratio learning value in the current alcohol concentration estimation is reflected in the air-fuel ratio learning value before the alcohol concentration estimation. The correction is made to the learning value, and the change amount of the alcohol concentration erroneously reflected in the air-fuel ratio learning value AFLRN can be removed and reset to an appropriate value.

  Next, steps S212 to S215 are treatments when the alcohol concentration estimation is completed, and are preparations for the next alcohol concentration estimation.

  In step S212, the air-fuel ratio learning value AFLRN1 is set to the air-fuel ratio learning value AFLRN. In step S213, the fuel supply determination flag is cleared FLAG1 = 0, and in step S214, the alcohol concentration estimation start condition flag is cleared FLAG3 = 0. In step S215, the engine operation time T1 is reset to 0, and the processing of this routine ends.

  As described above, the control device for the internal combustion engine according to the first embodiment has been described. However, the present invention is not limited to this embodiment, and various modifications can be made without departing from the scope of the present invention. Can be adopted. For example, in the present embodiment, the fuel refueling determination unit in step S200 has been described with reference to FIG. 3, but the determination unit is not particularly limited as long as fuel refueling can be detected.

  Further, in the present embodiment, the alcohol concentration estimating means in step S415 is not particularly limited as long as the alcohol concentration estimation based on the air-fuel ratio change can be performed.

  Further, in the present embodiment, the fuel supply determination has been described as an example of the condition for estimating the alcohol concentration other than the engine operating time condition. However, the fuel supply determination process can be omitted in order to save unnecessary processing. When the fuel supply determination process is omitted, the processes of step S219, step S223, and step S209 are omitted.

  As described above, the control apparatus for an internal combustion engine according to the first embodiment has been described. Next, the effect will be described with reference to FIG. 5 using a time chart.

  FIG. 5 is a time chart for performing the alcohol concentration estimation. The solid line indicates the operation of the control device for the internal combustion engine according to the first embodiment, and the dotted line indicates the operation of the prior art.

  First, with the alcohol concentration in the fuel tank 19 being 0% until time t0, fuel is supplied at the timing of time t0, and the alcohol concentration in the fuel tank 19 varies to 30%. Also, fuel refueling determination is performed here.

  From time t0 to time t1, the air-fuel ratio fluctuates due to the influence of the alcohol concentration, and the alcohol concentration estimated value 30% is calculated at the timing of time t1 by estimating the alcohol concentration from the fluctuating air-fuel ratio. In general, when the estimated alcohol concentration is calculated, the air-fuel ratio is reset.

  Next, refueling is performed at time t2, and the alcohol concentration in the fuel tank 19 increases to 40%. Here, since the fuel supply determination is not performed, the alcohol concentration is not estimated. During the period from time t2 to time t3, the air-fuel ratio fluctuates due to the influence of the alcohol concentration.

  Then, the air-fuel ratio learning value varies due to air-fuel ratio learning from the timing of time t3. As a result, the air-fuel ratio converges to 1.0 from time t3 to time t4, and the air-fuel ratio learning value absorbs fluctuations in the air-fuel ratio due to changes in alcohol concentration.

  Next, alcohol concentration estimation that is not related to the fuel supply determination is performed from the timing of time t5. Here, in the prior art, since the air-fuel ratio learning value in which the air-fuel ratio fluctuation corresponding to the alcohol concentration of 10% is absorbed is used for fuel calculation, the air-fuel ratio does not fluctuate and the alcohol concentration estimation is performed even if the alcohol concentration estimation is performed The value does not change.

However, in the control apparatus for an internal combustion engine according to the first embodiment, the fuel calculation air-fuel ratio learning value is replaced with the air-fuel ratio learning value at the time of completion of the previous alcohol concentration estimation. Thereby, the air-fuel ratio starts to fluctuate. An estimated alcohol concentration value of 40% is calculated at the time t6 by estimating the alcohol concentration from the changed air-fuel ratio, and the air-fuel ratio is reset. Here, since the estimated alcohol concentration value fluctuates, the air-fuel ratio learning value is learned again, and the change due to the influence of the alcohol concentration is removed.

  Next, fuel supply is performed at the timing of time t7, and the alcohol concentration in the fuel tank 19 changes to 80%. The air-fuel ratio fluctuates from time t7 to time t8 due to the influence of the alcohol concentration, and the alcohol concentration estimation is completed from the air-fuel ratio that fluctuated at the timing of time t8. Reset the air / fuel ratio. Here, in the prior art, since the influence of the alcohol concentration of 10% is absorbed in the air-fuel ratio learning value, the alcohol concentration estimated value becomes 70%, and the alcohol concentration in the fuel tank 19 and the alcohol concentration estimated value coincide with each other. In addition, the influence of the alcohol concentration of 10% remains absorbed in the air-fuel ratio learning value.

  Conversely, in the control apparatus for an internal combustion engine according to the first embodiment, the alcohol concentration estimated value 80% is calculated, the alcohol concentration in the fuel tank 19 matches the alcohol concentration estimated value, and the influence of the alcohol concentration is learned by air-fuel ratio learning. The value can be ignored.

  As described above, according to the control apparatus for an internal combustion engine according to the first embodiment, when the alcohol concentration is estimated, the ECU 11 cannot determine the refueling in spite of the state where the concentration has changed due to, for example, supplementary refueling. When it is not possible to detect that the change in alcohol concentration has been detected and the previously estimated alcohol concentration has changed from the previously estimated alcohol concentration, the change in alcohol concentration is regarded as a change due to the change in the air-fuel ratio. Remove from value. That is, it is possible to suppress the change in the air-fuel ratio due to the alcohol concentration from being erroneously reflected in the air-fuel ratio learning value. This makes it possible to optimally reflect the air-fuel ratio shift due to aging and variations in the air-fuel ratio learning value.

  Further, it is possible to prevent erroneous determination of the fuel system monitor that detects the fuel system abnormality by optimally reflecting the learned value in the air-fuel ratio.

Furthermore, when estimating the alcohol concentration regardless of fuel refueling, the learning value is re-learned from the air-fuel ratio learning value at the previous refueling determination that does not include the change in air-fuel ratio due to the change in alcohol concentration in the adjustment of the fuel amount. The air-fuel ratio learning value can be reflected in the fuel injection amount, and the accuracy of alcohol concentration estimation can be improved.

DESCRIPTION OF SYMBOLS 1 Engine 1a Combustion chamber 2 Spark plug 3 Intake valve 4 Intake manifold 5 Exhaust valve 6 Exhaust manifold 7 Water temperature sensor 8 Throttle valve 9 Intake amount sensor 10 Injector 11 Engine control unit (ECU)
12 CPU
13 RAM
14 First oxygen concentration sensor 15 First three-way catalyst 16 Second oxygen concentration sensor 17 Second three-way catalyst 18 Rotational speed sensor 19 Fuel storage device (fuel tank)
20 Fuel level sensor

Claims (3)

A control device for an internal combustion engine for controlling an internal combustion engine to which an alcohol-containing fuel mixed with alcohol and gasoline is supplied,
Alcohol concentration estimation means for estimating an alcohol concentration value of the alcohol-containing fuel;
Means for correcting the fuel amount by the alcohol concentration value estimated by the alcohol concentration estimating means;
In an internal combustion engine control device comprising: an air-fuel ratio learning means that learns an air-fuel ratio of a fuel mixture supplied to the internal combustion engine and obtains an air-fuel ratio learning value ;
The alcohol concentration estimation means estimates the alcohol concentration when a fuel refueling determination is made or when the engine operation time has passed a predetermined time, and when estimating the alcohol concentration, the air-fuel ratio at the time of previous alcohol concentration estimation A control apparatus for an internal combustion engine, wherein a fuel amount is corrected using a learning value . 2. The control apparatus for an internal combustion engine according to claim 1 , further comprising means for relearning the air-fuel ratio learning value when there is a change in the alcohol concentration detected by the alcohol concentration estimating means. Means for learning the air-fuel ratio learned value again, when the re-learning the air-fuel ratio learning value based on the change in the alcohol concentration estimated by the alcohol concentration estimation means, the alcohol concentration change rate from the current air-fuel ratio learned value The control apparatus for an internal combustion engine according to claim 1 or 2, wherein