Electronic control device for a multi-fuel internal combustion engine

With an electronic control device for an internal combustion engine using an oxygenated compound mixed fuel, operating conditions of the engine are detected, and are utilized to determine fundamental control data for the engine, while the dielectric constant and the refractive index of an oxygenated compound mixed fuel supplied to the engine are detected, and the oxygenated compound content of the mixed fuel is calculated according to the dielectric constant thus detected. The refractive index, and the oxygenated compound content are utilized to estimate the distillation characteristic of the petroleum refined fuel in the mixed fuel. The fundamental control data are corrected by using first correction data determined from the oxygenated compound content and second correction data determined from the distillation characteristic. Thus, with the device, the engine operates stably and correctly at low and middle temperatures irrespective of the oxygenated compound content of the mixed fuel or the nature of gasoline thereof.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates to an electronic control device performing a fuel 
control operation, an ignition control operation, and so forth for an 
internal combustion engine which uses a fuel obtained by mixing an 
oxygenated compound such as methanol, ethanol and MTBE (methyl tertiary 
butyl ether) with a petroleum refined fuel such as gasoline. 
2. Background Art 
Recently, in the United States of America and various European countries, 
in order to decrease the consumption of petroleum and to reduce the air 
pollution by exhaust gas from motor vehicles, a fuel prepared by mixing an 
oxygenated compound such as alcohol and ether with gasoline has been 
employed for motor vehicles. If such an oxygenated compound mixed gasoline 
is used, as it is, for an internal combustion engine matched with a 
gasoline fuel, then the engine suffers from the following difficulties: 
That is, methanol is appreciably different in theoretical air-fuel ratio 
from gasoline, about 6 to 15, and the former is larger in octane value 
that the latter, and the distillation characteristic depends on the 
methanol content. Hence, the operation of the engine is not satisfactory, 
and serious problems to be solved are involved in the driving 
characteristic of the engine and in the quantity of hazardous components 
exhausted therefrom. Thus, in controlling the operation of the engine, it 
is essential to detect the methanol content of the methanol mixed fuel. 
An electronic control device for an internal combustion engine using an 
alcohol mixed fuel as an oxygenated compound mixed fuel has been disclosed 
by Japanese Patent Application (OPI) No. 98540/1981 or 51920/1982 (the 
term "OPI" as used herein means an "unexamined published application"). 
The conventional electronic control device is designed as follows: An 
alcohol content sensor is provided in the pipe through which an alcohol 
mixed fuel is supplied to the engine. That is, by detecting the dielectric 
constant (Japanese Patent Application (OPI) No. 98540/1981) or refractive 
index (Japanese Patent Application (OPI) No. 51920/1982) of the alcohol 
mixed fuel passing through it, the alcohol content of the alcohol mixed 
fuel is detected. The alcohol content thus detected is utilized to adjust 
the supply of the fuel thereby to control the air-fuel ratio, and to 
correct the ignition advance angle thereby to control the ignition timing. 
That is, the fuel injection quantity is increased in proportion to the 
alcohol content to maintain the air-fuel ratio satisfactory. And, since 
alcohol is high in combustion speed, the ignition timing is, in general, 
delayed in proportion to the alcohol content. Furthermore, in the case of 
an alcohol mixed fuel, alcohol is lower in volatility than gasoline, and 
therefore the engine is unsatisfactory in starting characteristic when the 
temperature of the engine is in a range of low and middle temperatures. 
Hence, in the case when the temperature of the engine is in that range, 
especially at the start of the engine and immediately after it, control is 
made according to the alcohol content. 
However, the above-described conventional electronic control device is 
disadvantageous in the following points: With the device, the operation of 
the engine is controlled only according to an alcohol content. Hence, in 
the case when the nature of gasoline mixed with alcohol changes, then the 
driving characteristic of the engine, and the quantity of hazardous 
components exhausted therefrom are adversely affected. That is, the 
volatility of an alcohol mixed fuel affecting the starting characteristic 
of an internal combustion engine depends not only on the alcohol content 
but also the volatility of the gasoline. The volatility of gasoline 
depends on the nature of distillation thereof. Under the condition that 
the temperature of the engine is in the above-described range of low and 
middle temperatures, the starting characteristic of the engine using a 
heavy gasoline low in volatility is lower than that of the engine using a 
light gasoline high in volatility. 
On the other hand, the dielectric constant of an alcohol mixed fuel depends 
on the alcohol content, but it scarcely depends on whether the gasoline is 
a heavy one or whether it is a light one. On the other hand, the 
refractive index of the alcohol mixed fuel depends both on the alcohol 
content and the nature of the gasoline, but it is substantially free from 
whether the gasoline is a heavy one or whether it is light one. With a 
heavy gasoline low in volatility, or with a mixed fuel prepared by mixing 
alcohol with the heavy gasoline, the driving characteristic of the engine, 
and the amount of hazardous components exhausted therefrom are adversely 
affected, and at worst the engine cannot be started. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the invention is to eliminate the above-described 
difficulties accompanying a conventional electronic control device for an 
internal combustion engine. 
More specifically, an object of the invention is to provide an electronic 
control device for an internal combustion engine which, even when the 
oxygenated compound content of an oxygenated compound mixed fuel such as 
an alcohol mixed fuel, and/or the nature of a petroleum refined fuel such 
as gasoline therein changes, performs control operations so that the 
engine operates stably and correctly at low and middle temperatures. 
According to one aspect of the invention, there is provided an electronic 
control device for an internal combustion engine using an oxygenated 
compound mixed fuel, the electronic control device includes: dielectric 
constant detecting means for detecting a dielectric constant of the 
oxygenated compound mixed fuel; refractive index detecting means for 
detecting a refractive index of the oxygenated compound mixed fuel; 
oxygenated compound content calculating means for calculating an 
oxygenated compound content of the oxygenated compound mixed fuel from the 
dielectric constant thus detected; distillation characteristic estimating 
means for estimating a distillation characteristic of the petroleum 
refined fuel in the oxygenated compound mixed fuel from the oxygenated 
compound content and the refractive index; and means for correcting 
fundamental control data by using first correction data determined from 
the oxygenated compound content, and second correction data determined 
from the distillation characteristic. 
With the electronic control device, the dielectric constant and the 
refractive index of the oxygenated compound mixed fuel are detected. The 
oxygenated compound content is calculated from the dielectric constant 
thus detected, and the oxygenated compound content thus detected is 
utilized together with the detected refractive index to determine the 
distillation characteristic of the petroleum refined fuel in the 
oxygenated compound mixed fuel. And the first correction data determined 
from the oxygenated compound content, and the second correction data 
determined from the distillation characteristic are utilized to determine 
the fundamental correction data for the engine. 
According to another aspect of the invention, there is provided an 
electronic control device for an internal combustion engine using an 
oxygenated compound mixed fuel, the electronic control device includes: 
refractive index detecting means for detecting a refractive index of the 
mixed fuel; oxygenated compound content calculating means for calculating 
an oxygenated compound content of the mixed fuel from the refractive 
index; means for controlling an air-fuel ratio for the engine so that it 
reaches an aimed air-fuel ratio; means for correcting the oxygenated 
compound content according to the difference between the aimed air-fuel 
ratio and the air-fuel ratio detected; distillation characteristic 
determining means for determining a distillation characteristic of the 
petroleum refined fuel of the mixed fuel from the oxygenated compound 
content thus corrected; and means correcting the fundamental correction 
data by using first correction data determined from the oxygenated 
compound content and second correction data determined from the 
distillation characteristic. 
With the electronic control device, the refractive index of the mixed fuel 
is detected, and the refractive index thus detected is utilized to 
calculate the oxygenated compound content. The air-fuel ratio of the 
engine is so controlled that it reaches the aimed air-fuel ratio, and the 
oxygenated compound content is corrected according to the difference 
between the detected air-fuel ratio and the aimed air-fuel ratio. The 
oxygenated compound content thus corrected is utilized to estimate the 
distillation characteristic of the petroleum refined fuel in the mixed 
fuel. The first correction data determined from the oxygenated compound 
content, and the second correction data determined from the distillation 
characteristic are utilized to correct the fundamental control data for 
the engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Preferred embodiments of the invention will be described with reference to 
the case where an internal combustion engine uses a methanol mixed fuel in 
which the oxygenated compound is methanol. 
First Embodiment 
An example of an electronic control device for an internal combustion 
engine, which constitutes a first embodiment of the invention, is designed 
as shown in FIG. 1. That is, the electronic control device of the 
invention includes: operating condition detecting means 1 for detecting an 
operating condition of the internal combustion engine which uses a fuel 
prepared by mixing methanol with a petroleum refined fuel; dielectric 
constant detecting means 2 for detecting a dielectric constant of a 
methanol mixed fuel supplied to the engine; refractive index detecting 
means 3 for detecting a refractive index of the methanol mixed fuel; 
methanol content calculating means 4 for calculating a methanol content of 
the mixed fuel from a dielectric constant detected by the dielectric 
constant detecting means 2; and distillation characteristic estimating 
means 5 for estimating a distillation characteristic of the petroleum 
refined fuel in the mixed fuel from a detection value provided by the 
refractive index detecting means 3 and a calculation value provided by the 
methanol content calculating means 4. 
The electronic control device further includes: fundamental control data 
determining means 6 for determining fundamental control data of the engine 
according to the operating conditions detected by the operating condition 
detecting means 1; first correction data determining means 7 for 
determining first correction data according to the output of the methanol 
content calculating means; second correction data determining means 8 for 
determining second correction data according to an estimation value 
provided by the distillation characteristic estimating means 5; and 
multiplying means 9 for obtaining the product of the first and second 
correction data and fundamental control data determined by the fundamental 
control data determining means 6. 
The arrangement of the electronic control device described above is shown 
in FIG. 2 concretely. That is, in FIG. 2, reference numeral 11 designates 
an internal combustion engine; 12, a speed sensor for detecting the speed 
of rotation of the engine 11; 13, a sucked-air flow rate sensor for 
detecting the flow rate of air sucked into the engine; 14, a throttle 
opening sensor provided for a throttle valve 22; 15, an air-fuel ratio 
sensor mounted on an exhaust pipe; 16, a dielectric constant sensor; and 
17, a refractive index sensor. Those sensors 16 and 17 are provided in a 
high pressure pipe 27 downstream of a high pressure filter 28. Further in 
FIG. 2, reference numeral 18 designates a fuel injection valve which is 
coupled to a fuel distributing pipe 29 downstream of the sensors 16 and 
17; 19, an ignition plug; 10, an electronic control section; 21, a cooling 
water temperature sensor; 24, an air cleaner; 25, a fuel tank; 26, a fuel 
pump; 20, a fuel pressure regulator; 30, a suction pipe; and 31, a return 
pipe. 
The electronic control section 10 is as shown in FIG. 3. In FIG. 3, 
reference numeral 101 designates an input interface, to which the outputs 
of sensors 12 through 19 and 21 are applied; 102, a CPU (central 
processing unit); 103, a ROM (read-only memory); 104, an output interface 
for driving the fuel injection valve 18 and the ignition plug 19; and 105, 
a RAM (random access memory). 
Now, the operation of the electronic control device shown in FIGS. 1 
through 3 will be described. 
Upon start of the engine 11, the methanol mixed fuel in the fuel tank 25 is 
pressurized by the fuel pump 26, so that it is supplied to the fuel 
distributing pipe 29 through the high pressure pipe 27 and the high 
pressure filter 28; while the dielectric constant sensor 16 and the 
refractive index sensor 17 detect the dielectric constant .epsilon. and 
the refractive index ND of the fuel, respectively, and apply them to the 
input interface 101 of the electronic control section 10. 
The pressure of the fuel thus supplied is so controlled by the fuel 
pressure regulator 20 that it is constant irrespective to a quantity of 
fuel injected by the fuel injection valve 18, and the remaining fuel is 
returned into the fuel tank 25 through the return pipe 31. On the other 
hand, the operating conditions or data of the engine 11 are detected as 
follows: That is, the speed sensor 12 detects the speed of rotation Ne; 
the sucked-air flow rate sensor 13, the flow rate Qa of sucked air; the 
throttle opening sensor 14, the degree of opening .theta. of the throttle 
valve which represents the acceleration or deceleration of the engine; the 
air-fuel ratio sensor 16, the density .lambda. of exhaust gas; and the 
cooling water temperature sensor 21, the temperature TW of cooling water. 
The data thus detected are applied to the input interface 101 of the 
electronic control section 10. 
According to a control program stored in the ROM 103, the CPU 102 controls 
the input interface 101 to read the operating data of the engine 11, and 
the dielectric constant .epsilon. and the refractive index ND of the fuel. 
The CPU 102 utilizes the operating data of the engine, to calculate 
fundamental control data for the fuel injection quantity of the fuel 
injection valve 18, and the ignition timing of the ignition plug 19; and 
utilizes the dielectric constant .epsilon. and the refractive index ND to 
calculate two correction data thereby to correct the fundamental control 
data. The CPU controls the output interface 104 according to the 
fundamental control data thus corrected, thereby to drive the fuel 
injection valve 18 and the ignition plug 19. In the above-described 
calculations, the RAM 105 is used to hold the data temporarily. 
The dielectric constant sensor 16 and the refractive index sensor 17 are 
designed as shown in FIG. 4. 
The dielectric constant sensor 16 includes a pair of electrodes 61a and 61b 
which are set in the fuel flow path formed in a pipe-shaped container 67 
inserted in the high pressure pipe 27, thus forming a capacitor. As the 
methanol content M of the methanol mixed fuel flowing between the 
electrodes 61a and 61b increases, the dielectric constant .epsilon. is 
increased as shown in FIG. 6, and the capacitance C of the capacitor is 
also increased. The capacitance C is detected by a capacitance detecting 
circuit 62 made up of an LC oscillation circuit or RC oscillation circuit, 
as a result of which a signal corresponding to the dielectric constant 
.epsilon. of the fuel is outputted. 
On the other hand, the refractive index sensor 17, as shown in FIG. 4, 
includes: a columnar prism 72 set in the fuel flow path in the pipe-shaped 
container 67. The prism 72 has a wetted surface at one end which is 
oblique with respect to the incident optical axis. The refractive index 
sensor 17 further comprises: a reflecting mirror 73 confronted with the 
wetted surface; an LED (light emitting diode) 71; a focusing lens 74; and 
a light position detecting element 75. Those components 71, 74 and 75 are 
provided on the side of the other end of the prism. When light is applied 
from the LED 71 to the columnar prism 72, then it is refracted at the 
wetted surface of the prism 72 at an angle of refraction corresponding to 
the refractive index of the fuel, and then reflected by the reflecting 
mirror 73. The light thus reflected is refracted at the wetted surface 
again in the same manner, thus passing through the columnar prism 72. As a 
result, it is focused on the light position detecting element 75 by the 
focusing lens 74. 
As the refractive index ND of the fuel changes, the angle of refraction at 
the wetted surface of the columnar prism 72 is changed, and the optical 
path to the focusing lens 74 is therefore changed. As a result, the 
position of light focused on the light position detecting element 75 is 
changed. The position of light thus changed is detected by an light 
position detecting circuit 76, which outputs a signal corresponding to the 
refractive index ND of the fuel. The refractive index ND of the fuel 
depends not only on the methanol content M but also the nature of the 
gasoline with which methanol is mixed, as shown in FIG. 6. 
The operation of the electronic control section 10 will be described with 
reference to FIG. 5, a flow chart. 
Upon start of the engine, the CPU 102 reads the dielectric constant 
.epsilon. of the fuel in Step S1, and reads the refractive index ND.sub.f 
of the fuel in Step S2. In Step S3, the CPU calculates a methanol content 
M.sub.f by using the relationships between dielectric constants .epsilon. 
and methanol contents M which are as shown in FIG. 6 and stored in the ROM 
103. In Step S4, the CPU calculates first correction data CF1 and CI1 
respectively for the fuel injection quantity and the ignition timing with 
respect to the methanol content M.sub.f. 
In Step S5, the methanol refractive index ND.sub.m stored in the ROM 103, 
the methanol content M.sub.f calculated, and the refractive index ND.sub.f 
detected are utilized to calculate according to the following Equation (1) 
the refractive index ND.sub.0 provided when the methanol content is 0: 
EQU ND.sub.0 =ND.sub.m -100*(ND.sub.f -ND.sub.m)/(M.sub.f -100) (1) 
The relationships between distillation temperatures TD and refractive 
indexes ND as shown in FIG. 7, which are stored in the ROM 103, are 
utilized, to estimate a gasoline distillation temperature TD.sub.0 with 
respect to the refractive index ND.sub.0. 
In Step S6, the distillation temperature TD.sub.0 is utilized to calculate 
second correction data CF2 and CI2 respectively for the fuel injection 
quantity and the ignition timing. 
As for the gasoline distillation temperature TD, it is suitable in 
correlation with the refractive index ND to use a 50% distillation 
temperature which concerns the driving characteristic of the engine most 
when the latter is at low and middle temperatures. It has been confirmed 
that, as shown in FIG. 7, the 50% distillation temperature is 
substantially proportional to the refractive index. 
In this embodiment, the distillation temperature is an example of a 
representative quantity of the distillation characteristic. The 
distillation temperature indicates a temperature of a predetermined 
distillation ratio on a distillation ratio (%)--distillation temperature 
(.degree.C.) curve, namely, the distillation characteristic. In addition 
to this, a distillation ratio which is a distillation at a predetermined 
distillation temperature can be applied as the representative quantity. 
In Step S7, the CPU receives operating data D (Ne, Qa, .theta., .lambda. 
and TW) from the operating data sensors 12 through 15 and 21 (FIGS. 2 and 
3). In Step S7, the operating data D thus received are utilized to 
calculate fundamental control data for the fuel injection quantity and the 
ignition timing. 
In Step S9, it is determined from the operating data D whether the engine 
performs a starting operation at low temperature start, or whether it 
performs an accelerating operation at low temperature, or else. When it is 
determined that the engine performs the starting operation at low 
temperature or the accelerating operation at low temperature, Step S10 is 
effected. In Step S10, the fuel injection quantity of the fuel injection 
valve 18, and the ignition timing of the ignition plug 19 are controlled 
according to the products of the fundamental control data and the first 
and second correction data. When the engine is in other operating 
conditions, in Step S11 the fuel injection quantity and the ignition 
timing are controlled according to the products of the fundamental control 
data and the first correction data. 
The above-described first embodiment performs control operations as 
follows: In the case where the internal combustion engine using the 
methanol mixed fuel performs the starting operation at low temperature or 
the accelerating operation at low temperature which depends greatly on the 
volatility of gasoline, the fuel injection quantity of the fuel injection 
valve 18 and the ignition timing of the ignition plug 19 are correctively 
controlled by using not only the methanol content but also the 
distillation temperature of gasoline; i.e., the volatility of gasoline. 
When the engine is in other operating conditions: that is, the operating 
condition of the engine is scarcely affected by the volatility of 
gasoline, the fuel injection quantity and the ignition timing are 
correctively controlled by using only the methanol content. Hence, 
irrespective of the nature of the base material, gasoline, the engine is 
operated stably and suitably at all times, and the driving characteristic 
of the engine is improved while the quantity of hazardous components 
exhausted by the latter is decreased. 
In the first embodiment described above, the engine uses the fuel prepared 
by mixing methanol with gasoline. However, it should be noted that the 
technical concept of the invention is applicable to the case where the 
engine uses a fuel which is prepared by mixing oxygenated compounds such 
as other alcohols and MTBE with a petroleum refined fuel, or the case 
where the engine uses a petroleum refine fuel mixed by nothing. 
Furthermore, in the first embodiment, the dielectric constant sensor 6 and 
the refractive index sensor 7 are arranged in the high pressure pipe 27 
downstream of the high pressure filter 28. However, they may be provided 
inside the fuel tank 25. 
Second embodiment 
Another example of the electronic control device, which constitutes a 
second embodiment of the invention, as shown in FIG. 8, includes: methanol 
content calculating means 32 for calculating an methanol content of a 
methanol mixed fuel from a detection value outputted by refractive index 
detecting means 3; distillation characteristic estimating means for 
estimating an distillation characteristic of the petroleum refined fuel of 
a methanol mixed fuel from a calculation value provided by the methanol 
content calculating means; multiplying means 34 for obtaining a product of 
fundamental control data and first correction data; another multiplying 
means 35 for multiplying an output of the multiplying means 34 by second 
correction data; aimed air-fuel ratio setting means 36 for setting an 
aimed air-fuel ratio; air-fuel ratio detecting means 37; and subtracting 
means 38 for outputting the difference between the aimed air-fuel ratio 
and an actually detected air-fuel ratio, to correct the operation of the 
methanol content calculating means. The remaining parts are the same as 
those in the electronic control device shown in FIG. 1. 
The second example of the electronic control device is shown concretely in 
FIG. 9. As is apparent from comparison between FIGS. 9 and 2, the second 
example is different from the first example in that the dielectric 
constant sensor 16 is eliminated. The electronic control section 10 is as 
shown in FIG. 10. As is seen from FIGS. 10 and 3, the electronic control 
section 10 in FIG. 10 is substantially similar in arrangement to the one 
shown in FIG. 3. 
The electronic control device shown in FIGS. 8 through 10 operates as 
follows: 
When the engine 11 starts, the methanol mixed fuel in the fuel tank 25 is 
pressurized by the fuel pump 26, so that it is supplied to the fuel 
distributing pipe 29 through the high pressure pipe 27 and the high 
pressure filter 28; while the refractive index sensor 17 detects the 
refractive index ND of the fuel, and applies it to the input interface 101 
of the electronic control section 10. 
The pressure of the fuel thus supplied is so controlled by the fuel 
pressure regulator 20 that it is constant irrespective to a quantity of 
fuel injected by the fuel injection valve 18, and the remaining fuel is 
returned into the fuel tank 25 through the return pipe 31. On the other 
hand, the operating conditions of the engine 11, namely, the speed of 
rotation Ne, the flow rate Qa of sucked air, the degree of opening .theta. 
of the throttle valve, the air-fuel ratio .lambda., and the cooling water 
temperature TW are detected by the sensors 12 through 15 and 21. The data 
thus detected are applied to the input interface 101 of the electronic 
control section 10. 
According to a control program stored in the ROM 103, the CPU 102 controls 
the input interface 101 to read the operating data of the engine 11, and 
the air-fuel ration .lambda. and the refractive index ND of the fuel. The 
CPU 102 utilizes the operating data of the engine, to calculate a quantity 
of fuel injected by the fuel injection valve 18, and the ignition timing 
of the ignition plug 19, and calculates a methanol content from the 
air-fuel ratio .lambda. and the refractive index ND, to obtain first 
correction data, and estimates the distillation characteristic of the 
gasoline from the methanol content, to obtain second correction data. The 
CPU corrects the fundamental control data by using the first and second 
control data, and applies the fundamental correction data thus corrected 
to the output interface 104, thereby to control the fuel injection 
quantity the fuel injection valve 18 and the ignition timing of the 
ignition plug 19. 
The arrangement of the refractive index sensor 17 is as shown in FIG. 11. 
As is apparent from comparison of FIGS. 11 and 4, FIG. 11 is obtained by 
removing the dielectric constant sensor 16 from FIG. 4. The operation of 
the sensor 17 is equal to that of the sensor 17 shown in FIG. 4. The 
refractive index ND of the fuel, as shown in FIG. 13, depends not only on 
the methanol content but also on the nature of gasoline. 
The operation of the electronic control section 10 will be described with 
reference to a flow chart of FIG. 12. 
In Step S1, the CPU 102 controls the input interface 101 to read the 
operating data D (Ne, Qa, .theta. and TW) of the engine 11 from the 
sensors 12, 13, 14 and 21. In Step S2, the CPU utilizes the operating data 
D to calculate fundamental control data BF0 and BI0 respectively for the 
fuel injection quantity and the ignition timing. 
In Step S3, the CPU reads the refractive index ND.sub.f of the fuel from 
the refractive index sensor 17. In Step S4, the CPU utilizes the relation 
(the line ND.sub.f -M.sub.f) between the refractive index and the methanol 
content of the mixture of methanol and gasoline having a predetermined 
nature which is stored in the ROM 103 in advance and indicated by the 
before-correction line "mb" in FIG. 13, thereby to calculate the methanol 
content M.sub.f from the ND.sub.f thus read. In Step S5, the CPU 
calculates first correction data CF1 and CI1 for the fuel injection 
quantity and the ignition timing with respect to the methanol content 
M.sub.f. In Step S6, the fundamental control data BF0 and BI0 are 
multiplied by the first correction data CF1 and CI1, to provide correction 
control data BF and BI, respectively. 
In Step S7, it is determined from the operating data D whether or not the 
supply of fuel is in an air-fuel ratio feedback mode. When it is 
determined that it is in the air-fuel ratio feedback mode, then in Step 
S8, the correction control data BF is multiplied by a feedback coefficient 
CFB, to provide fuel control data DF. The fuel control data DF thus 
provided is utilized to determine the period of time for which the fuel 
injection valve 18 is opened, thereby to control the fuel injection 
quantity. Initially, the coefficient CFB is set to one (1). 
The operation of the electronic control device will be described with 
reference to the case where the actual nature of the base material, 
gasoline, is heavier than the nature of gasoline corresponding to the 
before-correction line "mb" which is stored in the ROM 103; that is, the 
gasoline is large in refractive index. In this case, the methanol content 
M.sub.fb which is obtained from the detected refractive index ND.sub.f by 
using the before-correction line "mb" stored in the ROM 103 is smaller 
than the actually detected methanol content M.sub.f. Therefore, if the 
fuel injection is carried out with the value corrected by the data 
M.sub.fb, then the fuel injection quantity becomes short because methanol 
is larger than gasoline in the quantity of fuel required for providing an 
ideal air-fuel ratio, and accordingly the air-fuel ratio becomes 
excessively small. 
Hence, in Step S9, the output signal of the air-fuel ratio sensor 15 is 
read, and in Step S10 it is determined whether or not the air-fuel ratio 
.lambda. is one (1) which is a theoretical air-fuel ratio. When .lambda. 
is not one (1), in Step S11 the coefficient CFB is changed, and Step S1 is 
effected again. That is, in this case, the detected air-fuel ratio is 
extremely small. Therefore, the fuel injection quantity is increased by 
gradually increasing the coefficient CFB so that the air-fuel ratio 
.lambda. reaches one (1). 
Accordingly, when the air-fuel ratio .lambda. is the theoretical value "1", 
the coefficient CFB corresponds to the ratio of the methanol content 
M.sub.f to the assumed methanol content M.sub.fb. Therefore, in Step S12, 
the line ND.sub.f -M.sub.f is modified with the actual methanol content 
M.sub.f corrected with the coefficient CFB, and is then stored as an 
after-correction line "ma" in the ROM 103 again. The coefficient CFB is 
reset in Step S13. That is, in Steps S1 through S13, the line ND.sub.f 
-M.sub.f indicating the mixture of methanol and the base material gasoline 
is renewed at all times, so that the actual methanol content M.sub.f is 
obtained. 
When, in Step S7, the air-fuel ratio feedback mode is not effected, Step 
S14 is effected. In Step S14, it is determined from the operating data D 
whether the engine 11 performs the starting operation at low temperature 
or the accelerating operation at low temperature, or else. When it is 
determined that the engine performs the starting operation at low 
temperature, Step S15 is effected. In Step S15, the line ND.sub.f -M.sub.f 
"ma" stored in the ROM 103 is utilized to calculate the refractive index 
provided when the methanol content M is zero; i.e., the refractive index 
ND.sub.0 of the base material, gasoline, as indicated in FIG. 13. And the 
distillation temperature TD.sub.0 of the base material, gasoline, is 
estimated from the refractive index ND.sub.0 with reference to FIG. 7 
indicating the relationships between refractive indexes ND and 
distillation temperatures TD. In Step S16, the distillation temperature 
thus estimated is utilized to calculate second correction data CF2 and CI2 
for the fuel injection quantity and the ignition timing with respect to 
the gasoline distillation temperature TD.sub.0. Thereafter, in Step S17, 
the data BF and BI, which are obtained by correcting the fundamental 
control data with the first correction data corresponding to the methanol 
content, are corrected with the second correction data corresponding to 
the nature of the gasoline, so that the fuel injection valve 18 and the 
ignition plug 19 are suitably controlled. 
As for the distillation temperature TD, in correlation with the refractive 
index ND it is suitable to employ a 50% distillation temperature which 
concerns the driving characteristic of the engine at low and middle 
temperatures greatly. It has been confirmed that, as shown in FIG. 7, the 
50% distillation temperature is substantially in proportion to the 
refractive index. When the operation of the engine is not the start at low 
temperature nor the acceleration at low temperature, Step S18 is effected. 
In Step S18, control is performed by using the data obtained by 
multiplying the fundamental control data by the first correction data CF1 
and CI1 corresponding to the methanol content. 
In the second embodiment, in the case where the internal combustion engine 
using the methanol mixed fuel performs the starting operation at low 
temperature or of the accelerating operation at low temperature which 
depends greatly on the volatility of gasoline, the fuel injection quantity 
of the fuel injection valve 18 and the ignition timing of the ignition 
plug 19 are corrected by using not only the methanol content but also the 
distillation temperature of gasoline; that is, the volatility thereof. In 
the case where the operating the engine is other than the starting 
operation or accelerating operation at low temperature, thus being 
scarcely affected by the volatility of gasoline, the fuel injection 
quantity and the ignition timing are corrected by using only the methanol 
content. Therefore, the operating conditions of the engine can be 
maintained stable and suitable irrespective of the nature of the base 
material, gasoline, of the fuel. Accordingly, the driving characteristic 
of the engine is improved, and the quantity of hazardous components 
exhausted by the engine is reduced. 
In the second embodiment, the theoretical air-fuel ratio sensor is employed 
as the air-fuel ratio sensor 15. However, the air-fuel ratio feedback may 
be carried out by using a wide range air-fuel ratio sensor capable of 
detecting air-fuel ratios in a wide range. In this case, the number of 
chances for renewing the line of refractive index vs. methanol content is 
increased, and the correction of data is improved in accuracy as much. 
Similarly as in the first embodiment, the refractive index sensor 17 may be 
provided inside the fuel tank 25. In addition, fuels may be used which are 
prepared by mixing oxygenated compounds such as other alcohols and MTBE 
with a petroleum refined fuel. Alternatively, a petroleum refined fuel may 
be used as it is. 
As was described above, with the electronic control device according to the 
first aspect of the invention, the operating conditions of the engine are 
utilized for determination of the fundamental control data of it. The 
first correction data are determined according to the oxygenated compound 
content which is calculated from the dielectric constant of the oxygenated 
compound mixed fuel, and the second correction data are determined 
according to the distillation characteristic which is estimated from the 
oxygenated compound content and the refractive index detected. The first 
and second correction data thus determined are utilized for correction of 
the fundamental control data. Hence, with the electronic control device of 
the invention, the engine operates stably and correctly at low and middle 
temperatures even when the oxygenated compound content or the nature of 
gasoline changes. Thus, the driving characteristic of the engine is 
improved, and the quantity of hazardous components exhausted from it is 
reduced. 
Furthermore, with the electronic control device according to the second 
aspect of the invention, the fundamental control data of the engine are 
determined from the operating conditions of the latter, and the first 
correction data are determined from the oxygenated compound content which 
is calculated from the refractive index of the oxygenated compound mixed 
fuel which is supplied to the engine. The first correction data thus 
obtained are utilized to correct the fundamental control data so that the 
air-fuel ratio of the engine reaches the aimed air-fuel ratio. The 
oxygenated compound content is corrected according to the difference 
between the aimed air-fuel ratio and the actually detected air-fuel ratio. 
The oxygenated compound content corrected when the engine is in the 
predetermined operation mode, is utilized to estimate the distillation 
characteristic of the petroleum refined fuel in the mixed fuel, thereby to 
determine the second correction data. The first and second correction data 
thus obtained are utilized for correction of the fundamental control data. 
Hence, similarly, with the electronic control device, the engine operates 
stably and correctly at low and middle temperatures irrespective of the 
oxygenated compound content or the nature of gasoline. Thus, the driving 
characteristic of the engine is improved, and the quantity of hazardous 
components exhausted from it is reduced. 
While there has been described in connection with the preferred embodiments 
of the invention, it will be obvious to those skilled in the art that 
various changes and modifications may be made therein without departing 
from the invention, and it is aimed, therefore, to cover in the appended 
claims all such changes and modifications as fall within the true spirit 
and scope of the invention.