JP2005048625A - Alcohol concentration estimating device for engine and engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly estimate the alcohol concentration of working fuel even in case that an assumed air-fuel ratio exists in a region with no air-fuel ratio feedback control when alcohol containing fuel is used as the working fuel. <P>SOLUTION: The alcohol concentration estimating device for an engine comprises a target air-fuel ratio setting means 11 for setting a target air-fuel ratio to be richer or leaner than the theoretical air-fuel ratio of the alcohol non-containing fuel, an actual air-fuel ratio detecting means 17 for detecting the actual air-fuel ratio of the working fuel, and an alcohol concentration calculating means 11 for calculating the alcohol concentration of the working fuel in accordance with the ratio of the target air-fuel ratio to the detected actual air-fuel ratio. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine alcohol concentration estimation apparatus and an engine control apparatus.
[0002]
[Prior art]
At the time of air-fuel ratio feedback control in which the theoretical air-fuel ratio is the target air-fuel ratio, the average value M of the air-fuel ratio feedback correction coefficient is calculated based on the output of the air-fuel ratio sensor, and the difference ΔM between this average value M and the reference value 1.0 is calculated. There is one that obtains and estimates the alcohol concentration of the engine fuel based on the difference ΔM (see Patent Document 1). The alcohol concentration of the fuel is estimated because the physical properties of the alcohol are different from those of gasoline. Particularly in an engine using a fuel having a high alcohol concentration, an air-fuel ratio that is an engine control command value according to the alcohol concentration of the fuel used. This is because the ignition timing needs to be changed.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-163992
[0004]
[Problems to be solved by the invention]
By the way, in the conventional apparatus using alcohol-containing fuel as the fuel used, the average value of the air-fuel ratio feedback correction coefficient corresponds to the actual air-fuel ratio of the fuel used, and the reference value 1.0 corresponds to the theoretical air-fuel ratio of the alcohol-free fuel. . Therefore, when using an alcohol-containing fuel, the conventional apparatus estimates the alcohol concentration of the used fuel based on the air-fuel ratio difference between the actual air-fuel ratio of the used fuel and the theoretical air-fuel ratio of the non-alcohol-containing fuel.
[0005]
However, in the alcohol concentration estimation method of the conventional apparatus, when the target air-fuel ratio changes to the rich side or the lean side from the theoretical air-fuel ratio of the alcohol-free fuel, the estimation accuracy of the alcohol concentration of the fuel used decreases. This will be described with reference to FIG. 7. In FIG. 7, the horizontal axis represents the assumed air-fuel ratio, and the vertical axis represents the actual air-fuel ratio of the fuel used when alcohol-containing fuel is used. Here, the assumed air-fuel ratio is a target air-fuel ratio when an alcohol-free fuel is used as a fuel as described later. For example, 14.6 is the theoretical air-fuel ratio of 100% gasoline fuel that is an alcohol-free fuel. When the theoretical air-fuel ratio of this alcohol-free fuel is the target air-fuel ratio, 14.6 is the assumed air-fuel ratio. Become.
[0006]
“E0 line” is each characteristic (straight line) when an alcohol-containing fuel having an ethanol concentration of 0% is used as fuel, and “E85 line” is an alcohol-containing fuel having an ethanol concentration of 85%. . The “ethanol intermediate concentration line” is a characteristic (straight line) when the alcohol-containing fuel of each concentration when the ethanol concentration of 85% is further divided into five is used as fuel. In other words, the “E17 line”, “E34 line”, “E51 line”, and “E68 line” are characteristics when an alcohol-containing fuel having an ethanol concentration of 17%, 34%, 51%, and 68% is used as a fuel. It is.
[0007]
In the conventional device, when the alcohol-containing fuel is used, when the assumed air-fuel ratio is 14.6, air-fuel ratio feedback control based on the air-fuel ratio sensor output is performed. If the actual air-fuel ratio of the fuel used is 16.6, the air-fuel ratio difference from the “E0 line” is 16.6-14.6 = 2.0, and the air-fuel ratio is 2 from the “E0 line”. Since the position separated by 0.0 is approximately halfway between the “E34 line” and the “E51 line”, the ethanol concentration of the fuel used at this time is estimated to be approximately 42.5% (= (34 + 51) / 2) can do.
[0008]
Now, when the same difference line is drawn so that the air-fuel ratio difference with the “E0 line” becomes 2.0, the assumed air-fuel ratio deviates from 14.6, which is the theoretical air-fuel ratio of the alcohol-free fuel, and is rich. It can be seen that the air-fuel ratio difference 2.0 with respect to the “E0 line” does not uniquely correspond to the alcohol concentration of the fuel used when the fuel cell is on the lean side or lean side. For example, even if an alcohol-containing fuel having an ethanol concentration of 42.5% is used, the air-fuel ratio AF1 is shifted to an air-fuel ratio AF1 smaller than 14.6 immediately after the cold start and before the air-fuel ratio feedback control is started. . At this time, since the position away from the “E0 line” by 2.0 with the air / fuel ratio is above the “E68 line”, the ethanol concentration corresponding to the air / fuel ratio difference of 2.0 from the “E0 line” is as high as 68%. Become. On the other hand, at the time of lean combustion, the air-fuel ratio feedback control is stopped, and the assumed air-fuel ratio shifts to an air-fuel ratio AF2 that is larger than 14.6. At this time, since the position away from the “E0 line” by 2.0 with the air / fuel ratio comes on the “E34 line”, the ethanol concentration corresponding to the air / fuel ratio difference of 2.0 from the “E0 line” becomes 34%. .
[0009]
Thus, when the assumed air-fuel ratio is 14.6 where air-fuel ratio feedback control is performed, it is accurately estimated that the ethanol concentration of the fuel used is 42.5% due to the air-fuel ratio difference 2.0 with respect to the “E0 line”. Although it is possible, when the assumed air-fuel ratio is smaller than 14.6 and the air-fuel ratio AF1 is estimated, the fuel used is estimated to be 68% from the same air-fuel ratio difference 2.0 with the “E0 line”. Even when the air-fuel ratio AF2 is greater than 14.6, if the fuel used is estimated from the same 2.0 air-fuel ratio difference with the “E0 line”, it becomes 34%, and both are erroneously estimated. This is because in the conventional apparatus, when the assumed air-fuel ratio deviates from 14.6, that is, when the air-fuel ratio feedback control is not performed, the alcohol concentration can no longer be uniquely determined from the air-fuel ratio difference. is there.
[0010]
Accordingly, an object of the present invention is to accurately estimate the alcohol concentration of the used fuel even when the assumed air-fuel ratio is in a region where the air-fuel ratio feedback control is not performed when the alcohol-containing fuel is used.
[0011]
[Means for Solving the Problems]
The present invention is intended for an engine using alcohol-containing fuel as a fuel, and sets a target air-fuel ratio that is richer or leaner than the theoretical air-fuel ratio of alcohol-free fuel, and sets the amount of fuel that can be obtained from the target air-fuel ratio. While supplying to the engine, the actual air-fuel ratio of the used fuel is detected, and the alcohol concentration of the used fuel is calculated based on the ratio between the target air-fuel ratio and the detected actual air-fuel ratio.
[0012]
Further, the present invention is directed to an engine using an alcohol-containing fuel as a fuel, and the target air-fuel ratio is set to be richer or leaner than the stoichiometric air-fuel ratio of the alcohol-free fuel, and the amount of fuel obtained from the target air-fuel ratio is obtained. The excess air ratio, which is a value obtained by dividing the target air-fuel ratio by the stoichiometric air-fuel ratio of the alcohol-free fuel, is calculated, the actual air-fuel ratio of the fuel used is detected, and the target air-fuel ratio and this detection are detected. An air-fuel ratio difference from the actual air-fuel ratio is calculated, and the alcohol concentration of the fuel used is calculated based on the ratio between the air-fuel ratio difference and the excess air ratio.
[0013]
Further, the present invention is directed to an engine using an alcohol-containing fuel as a fuel, and a target air-fuel ratio richer or leaner than the stoichiometric air-fuel ratio of the alcohol-free fuel is set, and the amount of fuel from which the target air-fuel ratio can be obtained And the actual air-fuel ratio of the fuel used is detected, the alcohol concentration of the fuel used is calculated based on the ratio between the target air-fuel ratio and the detected actual air-fuel ratio, and the calculated alcohol concentration The engine control command value is corrected based on the above.
[0014]
Further, the present invention is directed to an engine using an alcohol-containing fuel as a fuel, and a target air-fuel ratio richer or leaner than the stoichiometric air-fuel ratio of the alcohol-free fuel is set, and the amount of fuel from which the target air-fuel ratio can be obtained The excess air ratio, which is a value obtained by dividing the target air-fuel ratio by the stoichiometric air-fuel ratio of the alcohol-free fuel, is calculated, the actual air-fuel ratio of the fuel used is detected, and the target air-fuel ratio and this detection are detected. An air-fuel ratio difference from the calculated actual air-fuel ratio is calculated, an alcohol concentration of the fuel used is calculated based on a ratio between the air-fuel ratio difference and the excess air ratio, and an engine control command is calculated based on the calculated alcohol concentration. Configure to correct the value.
[0015]
【The invention's effect】
In the present invention, when the target air-fuel ratio richer or leaner than the stoichiometric air-fuel ratio of the alcohol-free fuel is set, the ratio of the target air-fuel ratio to the actual air-fuel ratio of the fuel used or the target air-fuel ratio is detected. The alcohol concentration of the fuel used is calculated based on the ratio between the air / fuel ratio difference from the actual air / fuel ratio and the excess air ratio, which is the target air / fuel ratio divided by the theoretical air / fuel ratio of the alcohol-free fuel. Therefore, even if the target air-fuel ratio richer or leaner than the stoichiometric air-fuel ratio is set, the ratio and the alcohol concentration of the fuel used are uniquely determined. Even in the region that is set to the rich side or lean side of the air-fuel ratio, that is, the region where air-fuel ratio feedback control cannot be performed, the alcohol concentration of the fuel used is accurately estimated. It can be.
[0016]
According to the present invention, since the engine control command value is corrected based on the calculated alcohol concentration, the target air-fuel ratio is set to a richer side or leaner side than the stoichiometric air-fuel ratio of the alcohol-free fuel, that is, the empty Even in a region where the fuel ratio feedback control cannot be performed, the combustion state of the engine can be controlled as intended.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a control system diagram of an engine control device that can switch between stratified combustion operation and homogeneous combustion operation. The engine is mounted on a vehicle (not shown).
[0019]
In FIG. 1, 1 is an engine body, 2 is an intake pipe, 3 is an exhaust pipe, 4 is a fuel injection valve, 5 is a spark plug, 6 is a throttle valve, and 7 is a step motor (or a DC motor) that drives the throttle valve 6 to open and close. ). Here, the throttle valve 6 and the step motor 7 constitute an electrically controlled throttle device.
[0020]
In the engine, fuel is injected in the latter half of the compression stroke at a load lower than that of the fuel injection valve 4 provided directly facing the cylinder, and the air-fuel mixture formed from the spray remains in a lump using the intake air flow in the cylinder. The air-fuel mixture that reaches the spark plug 5 and reaches the vicinity of the spark plug 5 near the compression top dead center is ignited by the spark plug 5, and as a whole, the ultra lean combustion (air-fuel ratio exceeds 40, for example) Perform stratified combustion). On the high load side, fuel is injected in the intake stroke to accelerate mixing of the fuel and air, and the entire combustion chamber is filled with a homogeneous air-fuel mixture, and a homogeneous combustion operation with a stoichiometric air-fuel mixture is performed.
[0021]
For this reason, the signal of the accelerator opening (the amount of depression of the accelerator pedal) from the accelerator opening sensor 12, the position signal for each unit crank angle from the crank angle sensor 13, and the reference signal for each phase difference of the cylinder stroke, the throttle An intake air flow rate signal from an air flow meter 14 provided in the intake pipe 2 upstream of the valve 6, a cooling water temperature signal from the water temperature sensor 16, an air-fuel ratio sensor 17 (actual air-fuel ratio detection means provided upstream of the three-way catalyst 8 ) Is input to the engine controller 11, and the fuel injection valve so that an optimal air-fuel ratio and an optimal combustion state are obtained in the engine controller 11 depending on the operating conditions (determined by the engine speed and the intake air flow rate). The fuel injection amount from 4 and the fuel injection timing are controlled. For example, if the operating condition is in the lean combustion region (region where the target equivalence ratio Tfbya is smaller than 1.0) on the low load side or the low rotational speed side shown in FIG. 3, the target air-fuel ratio is set to be leaner than the stoichiometric air-fuel ratio. On the other hand, when the stoichiometric combustion region (region where the target equivalence ratio Tfbya is 1.0) on the high load side or high rotational speed side shown in FIG. 3 is reached, the fuel injection timing is set to the intake stroke in which the piston descends, and the target air-fuel ratio is set. It falls within a narrow range centered on the theoretical air-fuel ratio. Further, in order to meet the output demand at the time of full load, the target air-fuel ratio is set to an air-fuel ratio (output air-fuel ratio) smaller than the stoichiometric air-fuel ratio in a region near the full load (region where the target equivalent ratio Tfbya is 1.2). .
[0022]
Further, immediately after the cold start and before the start of air-fuel ratio feedback control, the target equivalent ratio Tfbya exceeds 1.0, and at this time, the air-fuel ratio is smaller than 14.6.
[0023]
In this way, the air-fuel ratio (target air-fuel ratio) at which the engine is operated is determined by the target equivalent ratio Tfbya. The engine controller 11 uses this target equivalent ratio Tfbya to perform fuel injection during sequential injection according to the following equation. The pulse width Ti [ms] is calculated.
[0024]
Ti = (Tp × Tfbya + Kathos) × HOSETHA
× (α + αm−1) × 2 + Ts (1)
Where Tp: basic injection pulse width,
Kathos; transient correction amount,
HOSETHA: Ethanol concentration correction coefficient,
α: Air-fuel ratio feedback correction coefficient,
αm: learning value of air-fuel ratio,
Ts: Invalid pulse width,
Here, the ethanol concentration correction coefficient HOSETHA in the equation (1) is a function of the ethanol concentration of the fuel used. That is, the engine here uses an alcohol-containing fuel.
[0025]
However, in the equation (1), values other than the ethanol concentration correction coefficient HOSETHA are values matched to 100% gasoline fuel which is an ethanol-free fuel. For this reason, since the combustion state and the air-fuel ratio change when alcohol-containing fuel is used, correcting the fuel supply amount with this ethanol concentration correction coefficient HOSETHA is equivalent to the case where the fuel used is 100% gasoline fuel. The combustion state and the air-fuel ratio are obtained.
[0026]
The engine controller 11 calculates the target drive torque of the vehicle based on the accelerator opening from the accelerator sensor 12 and the vehicle speed from the vehicle speed sensor 18, and calculates the target throttle valve opening based on the target drive torque. The throttle valve opening is controlled via the step motor 7 so as to obtain this target throttle valve opening. At that time, a signal from the throttle sensor 15 is used as a feedback signal.
[0027]
Thus, in the present embodiment, the alcohol-containing fuel is assumed to be the fuel used and the engine, and the target air-fuel ratio corresponding to the operating conditions is set as in the conventional device, and the target air-fuel ratio and the actual air-fuel ratio of the fuel used are set. The ethanol concentration of the fuel used is calculated (estimated) based on this ratio, and the ethanol concentration correction coefficient HOSETHA is calculated based on the calculated ethanol concentration.
[0028]
Here, the target air-fuel ratio is a value for 100% gasoline fuel, and is determined by the target equivalent ratio Tfbya as described later.
[0029]
The calculation of the ethanol concentration of the fuel used and the calculation of the ethanol concentration correction coefficient HOSETHA executed by the engine controller 11 will be described with reference to the flowchart of FIG. The flow in FIG. 2 is executed at regular time intervals (for example, every 10 ms).
[0030]
In step 1, the target equivalent ratio Tfbya [anonymous number] and the air-fuel ratio sensor 17 output VAF are read. In step 2, the target equivalent ratio Tfbya is compared with 1.0.
[0031]
Here, the target equivalence ratio Tfbya is a value obtained by searching the map shown in FIG. 3 after the engine warm-up is completed (the map value is 1.0 only during the engine warm-up from the engine cold start). Even if it is, it will be a value exceeding 1.0). Note that the target equivalent ratio Tfbya is a value that matches the fuel of 100% gasoline.
[0032]
When the target equivalent ratio Tfbya is not 1.0, it is determined that the target air-fuel ratio is not in the stratified combustion region or the output air-fuel ratio region, that is, the air-fuel ratio feedback control condition in which the stoichiometric air-fuel ratio is the target air-fuel ratio. (This target air-fuel ratio is hereinafter referred to as “assumed air-fuel ratio”.) A is calculated by the following equation.
[0033]
A = 14.623 / Tfbya (2)
14.623 in the formula (2) is the stoichiometric air-fuel ratio of 100% gasoline fuel (alcohol-free fuel). In the case of 100% gasoline fuel, for example, in the output air-fuel ratio range, the target equivalent ratio Tfbya = 1.2, and thus the assumed air-fuel ratio A is a value of 12.186.
[0034]
In step 4, the actual air-fuel ratio B of the fuel used is calculated from the air-fuel ratio sensor 17 output VAF by the following equation. For example, the actual air-fuel ratio B is obtained by searching a predetermined table from the air-fuel ratio sensor output VAF.
[0035]
B = f1 (VAF) (3)
In step 5, the air-fuel ratio difference obtained by subtracting the actual air-fuel ratio B of the used fuel from the assumed air-fuel ratio A is compared with the allowable value ε. The theoretical air-fuel ratio decreases as the ethanol concentration of the fuel used increases (see FIG. 6), and the air-fuel ratio sensor 17 detects a value close to the theoretical air-fuel ratio of the fuel used. The actual air-fuel ratio B of the fuel is also reduced. That is, the greater the air-fuel ratio difference AB, the greater the ethanol concentration of the fuel used. The allowable value ε is a value corresponding to AB when the ethanol concentration of the fuel used is 10%. Therefore, A−B> ε indicates that the ethanol concentration of the fuel used exceeds 10%, and A−B ≦ ε indicates that the ethanol concentration of the fuel used is 10% or less. .
[0036]
When A−B ≦ ε, the process proceeds to step 6 without estimating the ethanol concentration of the fuel used, and the current process is terminated with the ethanol concentration correction coefficient HOSETHA = 1.0. That is, the fuel supply amount is not corrected when the ethanol concentration is 0 to 10%. This is because when the ethanol concentration of the fuel used is 10% or less, the calorific value does not decrease so much and the fuel consumption rate hardly deteriorates, so that it is not necessary to perform correction according to the ethanol concentration of the fuel used.
[0037]
On the other hand, when A−B> ε, the routine proceeds from step 5 to step 7 where the ratio C between the assumed air-fuel ratio A and the actual air-fuel ratio B of the fuel used is calculated by the following equation.
[0038]
C = A / B (4)
In step 8, the ethanol concentration EthaC of the fuel used is calculated from the ratio C by the following equation. For example, the ethanol concentration EthaC is calculated by searching a table having the contents shown in FIG.
[0039]
EthaC = f2 (C) (5)
In step 9, the ethanol concentration correction coefficient HOSETHA is calculated from the ethanol concentration EthaC of the fuel used thus calculated by the following equation.
[0040]
HOSETHA = f3 (EthaC) (6)
For example, an ethanol concentration correction coefficient having a value larger than 1.0 is given so that the amount of fuel supplied to the engine increases as the ethanol concentration increases.
[0041]
On the other hand, when the target equivalent ratio Tfbya = 1.0, it is determined that the air-fuel ratio feedback control condition is set such that the theoretical air-fuel ratio is the target air-fuel ratio. At this time, since the ethanol concentration estimation method of the conventional apparatus (Japanese Patent Laid-Open No. 5-163992) can be used, the process proceeds from Step 2 to Steps 10 to 13 and the ethanol of the fuel used based on the air-fuel ratio feedback correction coefficient α as in the conventional apparatus. Calculate the concentration. That is, in step 10, the maximum value αmax and minimum value αmin per half cycle of the air-fuel ratio feedback correction coefficient α are read, and in step 11 the average value αave per half cycle of the air-fuel ratio feedback correction coefficient is calculated from the following equation. .
[0042]
αave = (αmax + αmin) / 2 (7)
In step 12, the difference ΔM between the average value αave and the reference value 1.0 is obtained, and in step 13, the ethanol concentration EthaC is calculated from the difference ΔM by the following equation. For example, the ethanol concentration EthaC is calculated by searching a table having the contents shown in FIG. 5 from the difference ΔM.
[0043]
EthaC = f4 (ΔM) (8)
In step 9, the ethanol concentration correction coefficient HOSEtha is calculated from the ethanol concentration EthaC by the above-described equation (6).
[0044]
Here, the operation of the present embodiment will be described with reference to FIG. 6. FIG. 6 shows that the upper “E0” in the leftmost column is the ethanol concentration 0 as shown in the upper column in the second column from the left. % Of fuel used. Similarly, “E40” represents a fuel used with an ethanol concentration of 40%, and “E85” represents a fuel used with an ethanol concentration of 85%. The third column from the left represents the theoretical air-fuel ratio of the fuel used, and the theoretical air-fuel ratio of the fuel used decreases as the ethanol concentration increases to 40% and 85%.
[0045]
The top row of the fourth and subsequent columns from the left is
<a> Estimated air-fuel ratio A when the fuel increase rate is changed to 10%, 20%, and 30% with respect to the fuel used with 0% ethanol concentration (100% gasoline fuel), and the excess air ratio at that time λ, the ratio C of “E0”, and the middle and lower columns in the fourth and subsequent columns from the left
<B> For two fuels with different ethanol concentrations ("E40" and "E85"), the actual air-fuel ratio B when the fuel increase rate is changed to 10%, 20%, 30%, The excess air ratio λ, the air-fuel ratio difference D (= A−B) with “E0”, and the ratio C with “E0” are summarized.
[0046]
Note that the increase rate is set to 10%, 20%, and 30% by setting the target equivalent ratio Tfbya to 1.1, 1.2, and 1.3.
[0047]
In this case, adopting the air-fuel ratio difference D with “E0” corresponds to the conventional device (Japanese Patent Laid-Open No. 5-163992), and this embodiment adopts the ratio C with “E0”. Therefore, the conventional apparatus and this embodiment will be examined for “E40” and “E85”, respectively.
[0048]
<1> “E40”:
It is necessary to uniquely determine the ethanol concentration of the fuel used, 40%, and the air-fuel ratio difference D between “E0”. When the assumed air-fuel ratio A is changed to 13.294, 12.186, 11.248, the actual air-fuel ratio B changes to 11.165, 10.235, 9.448. Therefore, the air-fuel ratio with “E0” When the difference D is obtained, it is 2.129 (= 13.294-11.165), 1.951 (= 12.886-10235), 1.800 (= 111.248-9.448). It has changed. That is, in the conventional apparatus, while the ethanol concentration of the fuel used is constant at 40%, the air-fuel ratio difference D from “E0” changes according to the assumed air-fuel ratio A. The air-fuel ratio difference D between 40% and “E0” cannot be uniquely determined.
[0049]
On the other hand, in this embodiment, the ratio C to “E0” is 1.191 (= 13.294 / 11.165) when the increase rate is 10%, and 1.191 (= 12.12 when the increase rate is 20%. 186 / 10.235), and when the increase rate is 30%, it is 1.191 (= 11248 / 9.448) and does not change even if the assumed air-fuel ratio A is changed to the rich side. That is, according to the present embodiment, even if the assumed air-fuel ratio A changes to the rich side, 40% which is the ethanol concentration of the fuel used and 1.191 which is the ratio C of “E0” is uniquely determined. .
[0050]
<2> “E85”:
The air fuel ratio difference D between 85%, which is the ethanol concentration of the fuel used, and “E0” needs to be uniquely determined. When the assumed air-fuel ratio A is changed to 13.294, 12.186, 11.248, the actual air-fuel ratio B changes to 8.892, 8.151, 7.524. When the difference D is calculated, it is 4.402 (= 13.294-8.892), 4.035 (= 12.186-8.151), 3.694 (= 111.248-7.524). It has changed. That is, in the conventional apparatus, while the ethanol concentration of the fuel used is constant at 85%, the air-fuel ratio difference D from “E0” changes according to the assumed air-fuel ratio A, and the ethanol concentration of the fuel used is 85. % And the air-fuel ratio difference D between “E0” cannot be uniquely determined.
[0051]
On the other hand, in the present embodiment, the ratio C with “E0” is 1.495 (= 13.294 / 8.892) when the increase rate is 10%, and 1.495 (= 12.0 when the increase rate is 20%. 186 / 8.151), when the increase rate is 30%, it becomes 1.495 (= 111.248 / 7.524), and even if the assumed air-fuel ratio A is changed to the rich side, it does not change. That is, according to the present embodiment, even if the assumed air-fuel ratio A changes to the rich side, 85%, which is the ethanol concentration of the fuel used, and 1.495, which is the ratio C of “E0”, are uniquely determined. .
[0052]
In FIG.
(A) When the assumed air-fuel ratio A is changed to the rich side,
(B) Two cases where the ethanol concentration of the fuel used is 40% or 85%
Although only shown, FIG. 6 is merely representative in these cases,
(C) When the assumed air-fuel ratio A is changed to the lean side,
(D) When the ethanol concentration of the fuel used is a concentration other than 40% or 85% of the maximum 100%
It is confirmed that the same results as <1> and <2> are obtained.
[0053]
The two combinations (1.191, 40%) and (1.495, 85%) of the ratio C of “E0” obtained by the above <1> and <2> and the ethanol concentration of the fuel used are shown in FIG. This is a value on the characteristics of the ethanol concentration shown. Therefore, the characteristics shown in FIG. 4 can be obtained by writing each combination of the ratio C of “E0” obtained in the cases (c) and (d) and the ethanol concentration of the fuel used.
[0054]
As described above, in the present embodiment (the invention described in claim 1), the actual air-fuel ratio B of the fuel used is calculated on the premise of the engine using the alcohol-containing fuel, and the assumed air-fuel ratio A (target air-fuel ratio) and this Since the ethanol concentration EthaC of the fuel used is calculated (estimated) based on the ratio C to the actual air-fuel ratio B, the assumed air-fuel ratio A is richer than the theoretical air-fuel ratio (14.623) of fuel with 100% gasoline. The ethanol concentration EthaC of the fuel used can be obtained with high accuracy even in a state where the fuel concentration changes to either side of the lean side.
[0055]
Further, according to the present embodiment (the invention described in claim 3), the fuel supply amount (engine control command value) to the engine is corrected based on the calculated ethanol concentration EthaC (alcohol concentration). Even in a region where A is set to be richer or leaner than the stoichiometric air-fuel ratio of 100% gasoline, that is, in a region where air-fuel ratio feedback control cannot be performed, the combustion state of the engine can be controlled as intended.
[0056]
In the embodiment, the case where the parameter for calculating the ethanol concentration of the used fuel is the ratio C between the assumed air-fuel ratio A and the actual air-fuel ratio B of the used fuel is described, but the present invention is not limited to this. For example, a value (D / λ) obtained by dividing the air-fuel ratio difference D from “E0” by the excess air ratio λ may be used as a parameter (second embodiment).
[0057]
This will be described with reference to FIG. 6 again. A value (D / λ) obtained by dividing the air-fuel ratio difference D from “E0” by the excess air ratio λ is added to “E40” and “E85”. I am writing in. The D / λ is as follows.
[0058]
<3> “E40”:
When the assumed air-fuel ratio A is changed to 13.294, 12.186, and 11.248, the excess air ratio λ is 0.909 (= 13.294 / 14.623), 0.833 (= 12.1186). /14.623) and 0.769 (= 111.248 / 14.623). Further, the air-fuel ratio difference D from “E0” changes to 2.129, 1.951, and 1.800 as described above. However, D / λ is 2.342 (= 2.129 / 0.909) when the increase rate is 10%, and 2.342 (= 1.951 / 0.833) when the increase rate is 20%. When it is 30%, it becomes 2.341 (= 1.800 / 0.769), which is almost unchanged.
[0059]
<4> “E85”:
When the assumed air-fuel ratio A is changed to 13.294, 12.186, and 11.248, the excess air ratio λ changes to 0.909, 0.833, and 0.769. Further, the air-fuel ratio difference D changes to 4.402, 4.035, 3.694 as described above. However, D / λ is 4.843 (= 4.402 / 0.909) when the rate of increase is 10%, and 4.844 (= 4.035 / 0.833) when the rate of increase is 20%. When it is 30%, it is 4.843 (= 3.694 / 0.769), which is almost unchanged.
[0060]
FIG. 6 shows only two cases where the assumed air-fuel ratio A is changed to the rich side as described above and the ethanol concentration of the fuel used is 40% and 85%, but FIG. 6 shows these cases. Even when the assumed air-fuel ratio A is changed to the lean side, and when the ethanol concentration of the fuel used is a concentration other than 40% and 85% of up to 100%, the above <3> and <4> have been confirmed to be the same result.
[0061]
As described above, the ethanol concentration of the fuel used is uniquely determined in a state where the assumed air-fuel ratio A changes to the rich side or the lean side also by the ratio of the air-fuel ratio difference D to “E0” and the excess air ratio λ. (The invention according to claim 2).
[0062]
Although the embodiment has been described in the case where the alcohol is ethanol, it is not limited thereto.
[0063]
The first embodiment has been described in the case of the ratio C in which the numerator is the assumed air-fuel ratio A and the denominator is the actual air-fuel ratio B of the used fuel. It does not matter if it is a ratio.
[0064]
In the second embodiment, the ratio of the air-fuel ratio D to the numerator “E0” and the ratio of the excess air ratio λ to the denominator has been described. However, the air-fuel ratio difference D to the denominator “E0” and the numerator to the excess air ratio. A ratio of λ may be used.
[0065]
In the embodiment, the case where the fuel supply amount (Tp) to the engine is corrected based on the ethanol concentration of the fuel used has been described, but the ignition timing may be corrected. Note that a method of correcting the ignition timing based on the alcohol concentration of the fuel used is known from Japanese Patent Laid-Open No. 2-125967, so that it may be used.
[0066]
Finally, the function of the target air-fuel ratio setting means described in claim 1 is performed by the engine controller 11, and the function of the alcohol concentration calculation means is performed by steps 7 and 8 in FIG.
[Brief description of the drawings]
FIG. 1 is a control system diagram of an embodiment of the present invention.
FIG. 2 is a flowchart for explaining the calculation of the ethanol concentration of the fuel used and the calculation of the ethanol concentration correction coefficient.
FIG. 3 is a characteristic diagram of a target equivalent ratio.
FIG. 4 is a characteristic diagram of ethanol concentration of fuel used with respect to ratio C.
FIG. 5 is a characteristic diagram of ethanol concentration of fuel used with respect to the difference ΔM.
FIG. 6 is a table summarizing characteristics at “E0”, “E40”, and “E80”.
FIG. 7 is a characteristic diagram for explaining the relationship between the assumed air-fuel ratio and the actual air-fuel ratio of the fuel used.
[Explanation of symbols]
4 Fuel injection valve
5 Spark plug
11 Engine controller
17 Air-fuel ratio sensor (actual air-fuel ratio detection means)

Claims (5)

An alcohol concentration estimation device for an engine using an alcohol-containing fuel as a fuel,
Target air-fuel ratio setting means for setting a target air-fuel ratio richer or leaner than the theoretical air-fuel ratio of the alcohol-free fuel;
Fuel supply means for supplying the engine with an amount of fuel that can achieve the target air-fuel ratio;
An actual air-fuel ratio detecting means for detecting the actual air-fuel ratio of the fuel used;
An alcohol concentration estimating apparatus for an engine, comprising: an alcohol concentration calculating means for calculating an alcohol concentration of a fuel used based on a ratio between the target air fuel ratio and the detected actual air fuel ratio. An alcohol concentration estimation device for an engine using an alcohol-containing fuel as a fuel,
Target air-fuel ratio setting means for setting the target air-fuel ratio to be richer or leaner than the stoichiometric air-fuel ratio of the alcohol-free fuel;
Fuel supply means for supplying the engine with an amount of fuel that can achieve the target air-fuel ratio;
An excess air ratio calculating means for calculating an excess air ratio that is a value obtained by dividing the target air fuel ratio by the theoretical air fuel ratio of the alcohol-free fuel;
An actual air-fuel ratio detecting means for detecting the actual air-fuel ratio of the fuel used;
An air-fuel ratio difference calculating means for calculating an air-fuel ratio difference between the target air-fuel ratio and the detected actual air-fuel ratio;
An alcohol concentration estimating apparatus for an engine, comprising: an alcohol concentration calculating means for calculating an alcohol concentration of a fuel used based on a ratio between the air-fuel ratio difference and the excess air ratio. An engine control device using alcohol-containing fuel as a fuel,
Target air-fuel ratio setting means for setting a target air-fuel ratio richer or leaner than the theoretical air-fuel ratio of the alcohol-free fuel;
Fuel supply means for supplying the engine with an amount of fuel that can achieve the target air-fuel ratio;
An actual air-fuel ratio detecting means for detecting the actual air-fuel ratio of the fuel used;
Alcohol concentration calculating means for calculating the alcohol concentration of the fuel used based on the ratio between the target air-fuel ratio and the detected actual air-fuel ratio;
An engine control device comprising engine command value correction means for correcting an engine control command value based on the calculated alcohol concentration. An engine control device using alcohol-containing fuel as a fuel,
Target air-fuel ratio setting means for setting a target air-fuel ratio richer or leaner than the theoretical air-fuel ratio of the alcohol-free fuel;
Fuel supply means for supplying the engine with an amount of fuel that can achieve the target air-fuel ratio;
An excess air ratio calculating means for calculating an excess air ratio that is a value obtained by dividing the target air fuel ratio by the theoretical air fuel ratio of the alcohol-free fuel;
An actual air-fuel ratio detecting means for detecting the actual air-fuel ratio of the fuel used;
An air-fuel ratio difference calculating means for calculating an air-fuel ratio difference between the target air-fuel ratio and the detected actual air-fuel ratio;
Alcohol concentration calculation means for calculating the alcohol concentration of the fuel used based on the ratio between the air-fuel ratio difference and the excess air ratio;
An engine control device comprising engine command value correction means for correcting an engine control command value based on the calculated alcohol concentration. 5. The engine control apparatus according to claim 3, wherein the engine control command value is a fuel supply amount or an ignition timing to the engine.

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