JPH09303193A - Fuel property detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel property detecting device to detect fuel property without performing feedback control. SOLUTION: From an amount of intake air and an amount of injection fuel, an air-fuel ratio INAF of intake air is calculated, and from an output from an air-fuel ratio sensor, an air-fuel ratio EXAF is calculated (step 26). A difference ΔA/F=INAF-EXAF therebetween is determined (step 27). ΔA/F is compared with a predetermined given value AH and when an absolute value of ΔA/F is below AH or less, its decided that fuel is stand fuel. When ΔA/F is a positive value exceeding a given value AH, it is decided that fuel is light fuel and when ΔA/F is a negative value exceeding a given value AH, it is decided that fuel is heavy fuel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel property detecting device for an internal combustion engine.

[0002]

2. Description of the Related Art When an engine is started, the inner wall surface of the intake passage is usually dry and the temperature is low. Therefore, in an internal combustion engine in which fuel is injected into the intake passage, for example, into the intake port, when fuel injection is started when the engine is started, a part of the fuel that is initially injected is part of the intake port inner wall surface. Used to wet the engine, some of this fuel is not delivered into the engine cylinders. A part of the fuel injected subsequently adheres to the inner wall surface of the intake port in the form of liquid fuel, but at this time, the temperature of the inner wall surface of the intake port is low, so the adhered fuel is difficult to vaporize. do not do. As a result, when the engine is started, the air-fuel mixture supplied to the engine cylinder becomes thin, and good startability cannot be obtained. Therefore, normally, when the engine is started, the fuel injection amount is increased so that the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder becomes a desired required air-fuel ratio.

However, in particular, the air-fuel ratio at the time of starting the engine is greatly influenced by the properties of the injected fuel, and the air-fuel ratio is large depending on whether the injected fuel is standard fuel, heavy fuel or light fuel. Change. That is, when the injected fuel is a heavy fuel with poor volatility, the fuel adhering to the inner wall of the intake port is not easily vaporized, so the air-fuel ratio becomes leaner than the required air-fuel ratio, and In addition, when the injected fuel is a light fuel with good volatility, the fuel adhering to the inner wall surface of the intake port is easily vaporized, so that the air-fuel ratio becomes richer than the required air-fuel ratio. Therefore, in order to make the air-fuel ratio equal to the required air-fuel ratio when the engine is started, when the injected fuel is heavy fuel, the injection amount is increased compared to when the injected fuel is standard fuel, and the injected fuel is light fuel. In this case, the injection amount may be reduced as compared with the case where the injected fuel is the standard fuel. For that purpose, first, the property of the injected fuel, that is,
Whether the injected fuel is standard fuel or heavy fuel,
It is necessary to detect whether it is a light fuel.

Therefore, the basic fuel injection time required for making the air-fuel ratio the stoichiometric air-fuel ratio is experimentally obtained in advance as a function of the intake air amount and the engine speed, and is stored in the engine exhaust passage. Based on the output signal of the O ₂ sensor, the basic fuel injection time is corrected so that the air-fuel ratio becomes the stoichiometric air-fuel ratio to obtain the actual fuel injection time, and the basic fuel injection time in a predetermined engine operating state and the actual fuel injection time An internal combustion engine is disclosed in which the fuel property is detected from the amount of deviation from the fuel injection time (see Japanese Patent Laid-Open No. 4-279745).

By the way, in the device of the above publication, the fuel injection time TAU is calculated based on the following equation. TAU = TP ・ FAF ・ (1 + FWL + FASE ・ KF
+ FR) · KGi where TP is the basic fuel injection time, FAF is the feedback correction coefficient, FWL is the increase correction coefficient depending on the water temperature, FASE is the correction coefficient at startup, KF is the fuel property correction coefficient, FR is the other correction coefficient, and KGi is Learning coefficients are shown respectively. Here, the fuel property correction coefficient KF is calculated by KF = KF + ΔKF, where ΔKF is the deviation ΔKGi of the learning coefficient KGi.
= KGi-KGi _old , that is, calculated according to the difference between the learning coefficient in the current driving and the learning coefficient in the previous driving.

[0006]

However, the learning coefficient K
Since the Gi is calculated according to the value of the feedback correction coefficient FAF, the fuel property correction coefficient KF cannot be updated until the feedback control is performed, and during that time, the optimum correction is not sufficiently performed and exhaust emission deteriorates. There is a problem of doing.

In view of the above problems, it is an object of the present invention to provide a fuel property detecting device which can detect the fuel property without performing feedback control.

[0008]

According to the invention of claim 1, the intake air-fuel ratio detecting means for detecting the air-fuel ratio of the intake air mixture before combustion, and the air-fuel ratio of the exhaust gas after combustion are detected. The exhaust air-fuel ratio detecting means for outputting the variation of the air-fuel ratio as it is in a one-to-one correspondence, the intake air-fuel ratio detecting means for detecting the intake air-fuel mixture air-fuel ratio and the exhaust air-fuel ratio detecting means There is provided a fuel property detecting device for an internal combustion engine, comprising a fuel property judging means for judging the fuel property from the deviation of the exhaust gas air-fuel ratio.

In the fuel property detection device thus constructed, the property of the fuel used for combustion is directly determined from the difference between the air-fuel ratio of the intake air mixture before combustion and the air-fuel ratio of the exhaust gas after combustion. .

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing a configuration of an embodiment of the present invention, and 1 indicates an engine body to which a fuel supply control device of the present invention is applied. Reference numeral 2 denotes an intake pipe. The intake pipe 2 is provided with a fuel injection valve 3, a throttle valve 4, a pressure sensor 5 for detecting the intake pipe pressure, and an air flow meter 6 for detecting the intake air amount. Reference numeral 7 denotes an exhaust pipe. A three-way catalyst 8 for purifying the exhaust gas is attached to the exhaust pipe 7, and an air-fuel ratio sensor 9 for detecting an air-fuel ratio of the exhaust gas is attached upstream of the three-way catalyst.

The air-fuel ratio sensor 9 can distinguish whether the conventional O ₂ sensor is thinner or richer than the theoretical air-fuel ratio, that is, lean or rich, whereas the exhaust gas is exhausted over a wide range including the theoretical air-fuel ratio. Since the current proportional to the fuel ratio is generated (with respect to the applied voltage), the air-fuel ratio of the exhaust gas itself can be detected in a wide range. Therefore, for example, even in the state where the amount is increased during warm-up, not only the rich state but also the air-fuel ratio itself can be obtained.

A fuel tank 10 is a fuel tank 1.
The fuel within 0 is pressure-fed to the fuel injection valve 3 by the fuel pump 11, and the fuel tank 10 is provided with a fuel level sensor 12 for detecting the fuel level. Also, 1
3 is a water temperature sensor that detects the cooling water temperature of the engine, 14 is an engine speed sensor that detects the engine speed, and 15 is a throttle sensor that also serves as an idle switch that determines whether the engine is in an idle state or a non-idle state. Also serves as. In addition, 16 is an ignition plug, 17 is an igniter,
18 is a distributor.

Reference numeral 20 denotes an engine control unit (hereinafter referred to as an ECU). The ECU 20 is composed of a digital computer, and has an input interface circuit 21 and an ADC (analog-to-digital converter) 2 connected to each other.
2. CPU (microprocessor) 23, RAM (random access memory) 24, backup RAM 24
a, a ROM (Read Only Memory) 25, and an output interface circuit 26.

The CPU 23 has an air flow meter 6, O
The output signals of the _two sensors 9, the remaining fuel sensor 12, the water temperature sensor 13, the engine speed sensor 14, the throttle sensor 15 and the like are input via the input interface circuit 21 or further via the ADC 22. The CPU 23 determines the fuel property, which is a feature of the present invention, from the values of the various sensors described above and the values stored in the ROM 25 in advance, and determines the fuel property, which is a feature of the present invention. Other than injection, various control calculations are performed.

Next, the determination of the fuel property according to the present invention will be described. First, the concept will be explained. Since heavy fuel is difficult to atomize, the amount of fuel actually sent into the combustion chamber of the engine and burned is smaller than the amount of fuel injected from the fuel injection valve 3, and as a result, the air-fuel ratio EXAF of exhaust gas is It becomes larger (thinner), and conversely, since the light fuel is easily atomized, the amount of fuel actually sent to the combustion chamber of the engine and burned is larger than the amount of fuel injected from the fuel injection valve 3, resulting in Exhaust gas air-fuel ratio EXA
F becomes small (dense). Therefore, the air-fuel ratio INAF of the intake air-fuel mixture supplied after the engine is started is compared with the air-fuel ratio EXAF of the exhaust gas. If INAF> EXAF, it is determined that the fuel is light, and if INAF <EXAF, it is determined that the fuel is heavy. Is what you do. The fuel property may change only when refueling is performed, and may not change when refueling is not performed. Therefore, this determination is performed only when it is determined that refueling has been performed. In addition, the determination is made in the accelerated operation state because the difference between the heavy fuel and the light fuel is more likely to be clarified in the operation state where the influence of the atomization of the fuel is large.

FIG. 2 is a flowchart of the calculation for determining the fuel property based on the above idea. First, at step 21, the value FTV _OLD of the fuel gauge 12 at the end of the previous operation stored in the backup RAM and the current value FTV of the fuel gauge 12 are read, and at step 22, there is a difference between these values. Determine whether or not. As a result, if it is determined that there is no difference, the refueling has not been performed, so calculation is not performed and the process ends. If it is determined that there is a difference, the process proceeds to step 23. In step 23, the change ΔTA in the opening degree TA of the throttle sensor 15 is calculated, and in step 24
Then, whether the value is positive or negative is determined, and if positive, it is determined that the acceleration operation is currently being performed and the operating state is suitable for the fuel property determination calculation, and the calculation in step 25 and subsequent steps is executed. On the contrary, if negative, it is determined that the operating state is not suitable for the fuel property determination calculation, and the process returns to step 23 and is repeated until the operating state is suitable for the determination calculation.

At step 25, the output VAFM of the air flow meter 6, the fuel injection time TAU calculated by the ECU 20 by the formula described later, the output VEXAF of the A / F sensor 9
In step 26, the air-fuel ratio INAF of the intake air-fuel mixture and the air-fuel ratio EXAF of the exhaust gas are calculated from the output VAFM of the air flow meter 6 and the fuel injection time TAU, and in step 27 the difference ΔA from the air-fuel ratio INAF of the intake air-fuel mixture is calculated. / F is calculated. Note that, of the above, the fuel injection time TAU is corrected by the correction coefficient determined by the fuel property instruction value FQIND, but since the new fuel property instruction value FQIN is currently being calculated, the fuel property instruction before refueling is indicated. The value of the value FQIND is used.

In step 28, Δ obtained in step 27
The A / F is compared with a predetermined allowable width AH. As a result, if the absolute value of ΔA / F is smaller than the judgment value AH, it is judged that the fuel property is the standard fuel, and the routine proceeds to step 29, where the fuel property instruction value FQIND is set to the value 0 indicating that it is the standard fuel, and the process ends. To do. If the absolute value of ΔA / F is larger than the judgment value AH, the process proceeds to step 30 and ΔA / F
Is greater than the allowable width AH and is a positive value.
If it is ES, it is determined that the fuel is a light fuel, and the routine proceeds to step 31, where the fuel property instruction value FQIND is set to a value 1 indicating that it is a light fuel, and the process ends.

If NO is determined in step 30, the air-fuel ratio INAF exceeds the predetermined range and the exhaust gas air-fuel ratio EXA is exceeded.
It is determined that the fuel is larger than F, and it is judged that the fuel is heavy fuel, and the routine proceeds to step 32, where the fuel property instruction value FQIND
Is set to a value of 2 indicating that the fuel is heavy fuel, and the process ends. Fuel property indication value FQIND selected according to this fuel property
The value of is stored in the backup RAM 24a, is stored even when the engine is stopped, and is not updated until the next fuel supply.

In the present invention, the determination of the fuel property is performed as described above, and is performed regardless of the feedback control of the fuel injection amount. Therefore, it is possible to make a judgment even when the engine has not warmed up and the amount of fuel has been increased, and as a result, the frequency of fuel property judgments increases, and control according to the new fuel property is performed. The time to start is shortened as compared with the above-mentioned prior art.

Next, how the fuel property determined as described above is reflected in the calculation of the actual fuel injection amount will be described. First, the fuel injection amount when the engine is started will be described. When the engine is started, the fuel injection amount (injection time of each fuel injection valve) TAU is calculated by the following equation (1). TAU = TAUST × KNEST × KBST × KPA (1) Here, TUST is the basic injection amount at the time of start, which is determined according to the water temperature THW, and as shown in FIG. 3, the standard fuel, the light fuel, and the heavy fuel Has different values corresponding to the fuel, RO
It is stored in M25. KNEST is a correction coefficient based on the engine speed NE, KBST is a correction coefficient based on the battery voltage VB, and KPA is a correction coefficient based on the atmospheric pressure PA. FIG. 4 shows a flow chart of the calculation of the fuel injection amount at the time of starting. Since the fuel property is not determined at the time of engine start, the fuel property instruction value determined at the previous operation and stored in the backup RAM 24a. The starting basic injection amount TAUST is determined based on FQIND.

Next, the calculation of the fuel injection amount after the engine is started will be described. The engine starts and the engine speed N
When E exceeds a predetermined value, the engine intake air amount Q and the engine speed N are set instead of the above equation (1).
It is calculated from the following equation (2) based on E. TAU = GA × KINJ × (1 + FWLOTP) × FAF + FMW (2)

Here, GA is the intake air amount (Q / NE) per revolution of the engine, KINJ is a conversion constant for converting the engine intake air amount GA to the basic fuel injection amount, and FWLOT.
P is a correction coefficient during warm-up and during high load (for example, due to a decrease in exhaust gas temperature), FAF is an air-fuel ratio correction coefficient generated based on the signal of the air-fuel ratio sensor 9, and FMW is the wall adhesion fuel. Is a correction coefficient for correcting the fuel injection amount. FIG. 5 shows a flowchart of the calculation of the above formula (2).

FWLOTP is further expressed by the following equation (3). FWLOTP = (FWLB + FWLD) × KWL + FASE (3) Here, FWLB is a basic value determined by the water temperature THW, and as shown in FIG. 6, different values are set for the standard fuel, the light fuel, and the heavy fuel. It is stored in the ROM 25. FWLD is a warm-up increase attenuation coefficient and does not change depending on the fuel property. KWL is a correction coefficient depending on the engine speed and does not change depending on the fuel property. FASE
Is the increase coefficient after starting. A flow chart of the calculation of the above formula (3) is shown in FIG.
It is read from the map of FIG. 6 based on the fuel property instruction value FQIND stored in M24a.

FASE is when the calculation of equation (2) begins.
Initial value is given to the
It is reduced with a predetermined attenuation rate KASE. initial value
FASE₁As shown in Fig. 8,
However, they have different values and are stored in the ROM 25. FIG.
Is a flowchart of a routine for calculating FASE
Is the initial value FASE ₁Is stored in the backup RAM 24a
Based on the stored fuel property indication value FQIND,
It is read from the map (step 93). And F
Damped until ASE reaches zero.

10 and 11 show the calculation of the air-fuel ratio correction coefficient FAF.
It is a flowchart which shows an output routine. This routine is
It is executed by the ECU 20 at regular intervals. This luch
Output of the A / F sensor 9₁The comparison voltage V_R1(Reason
Of the air-fuel ratio (voltage equivalent to 14.5)
The air-fuel ratio is richer than the theoretical air-fuel ratio (V₁> V_R1)When
The air-fuel ratio correction coefficient FAF is decreased to the lean (V₁≤
V _R1In the case of), control is performed to increase FAF. this
Causes some error in the air flow meter 3 etc.
Even if the engine air-fuel ratio is
It is.

The flowcharts of FIGS. 10 and 11 will be briefly described below. Step 101 is a feedback control execution condition (for example, activation of the A / F sensor 9 and completion of engine warm-up). Is determined, and the FAF calculation in and after step 102 is performed only when the condition is satisfied. Step 102
From step 115 to step 115 is the determination of the air-fuel ratio. The flag F1 shown in steps 109 and 115 indicates that the engine air-fuel ratio is rich (F1 = 1) or lean (F1).
1 = 0), which is an air-fuel ratio flag indicating that F1 = 0 to F
To switch from 1 to 1 (lean to rich), the A / F sensor 9 continues for a predetermined time (TDR) or longer and the rich signal (V ₁
> V _R1 ) is output, F1 = 1 to F1 = 0
The switching from (rich to lean) is continued by the A / F sensor 9 for a predetermined time (TDL) or longer and the lean signal ((V ₁ ≦ V
_R1 ) is output. CDLY is a counter for determining the air-fuel ratio flag switching timing.

At steps 116 to 128, FAF is increased or decreased according to the value of the flag F1 set as described above. That is, when F1 = 0 (lean), first F
Immediately after changing (reversing) from 1 = 1 to F1 = 0 (rich to lean), FAF is skippedly increased by a relatively large value RSR (step 120), and thereafter F1 =
While it is 0, the FAF is gradually increased by a relatively small value KIR each time the routine is executed (step 123). Further, in the case of F1 = 1 (rich), the FAF is reduced by a relatively large value RSL immediately after reversing from F1 = 0 to F1 = 1 (lean to rich) (step 12
1) After that, while F1 = 1, the FAF is gradually decreased by a relatively small value KIL each time the routine is executed (step 124). Further, the value of FAF calculated above is the minimum value (FAF = 0.8 in the embodiment of the present invention).
And the maximum value (FAF = 1.2) are not exceeded (steps 125 to 128).

FIG. 12 shows counters CDLY (same (B)) and F1 (same (C) for changes in the air-fuel ratio (A / F) (FIG. 12 (A)) when the control of FIGS. ), F
The change of AF (the same (D)) is shown, and as shown in FIG. 12 (D), the value of FAF fluctuates around the value corresponding to the stoichiometric air-fuel ratio.

Next, the wall surface adhesion correction coefficient FMW will be described. The wall adhesion correction coefficient FMW is for preventing the air-fuel ratio from shifting during a transition. In a steady state (rotation speed, intake pipe pressure, water temperature, etc.), a certain amount of fuel is stably attached near the intake port of the engine. This stable amount of fuel changes depending on the intake pipe pressure. , The higher the absolute pressure of the intake pipe, that is, the higher the load, the greater the amount of adhesion, and the lower the absolute pressure of the intake pipe, the more
That is, the lower the load, the smaller the amount of adhesion.

Therefore, at the time of acceleration when the intake pipe pressure becomes high, the amount of fuel adhering increases and all of the injected fuel does not flow into the combustion chamber, the air-fuel ratio becomes lean, and conversely, the intake pipe pressure becomes At the time of deceleration, which becomes low, the amount of fuel adhering to the wall surface increases the amount of fuel flowing into the combustion chamber, and the air-fuel ratio becomes rich. Therefore, in order to prevent the above-described transition of the air-fuel ratio during the transition, the FMW is increased during acceleration and decreased during deceleration.

Therefore, the amount of fuel adhering in a steady state is stored in the ROM 25 as a map as shown in FIG. 13 for the intake pipe pressure PM, and based on the intake pipe pressure PM when the intake valve is closed, The attached fuel amount QMW is calculated from the map. Then, the change amount DLQMW is obtained, and it is considered that the adhesion amount is insufficient or excessive by this amount, and the amount is increased or decreased by the insufficient amount or excess amount.

However, in reality, the amount of change in QMW DLQM
The fuel corresponding to W does not adhere to or separate from the wall surface by a single injection, but adheres to or separates from the wall surface after several injections. The details are omitted here, and f is calculated as a function of the change amount DLQMW of QMW.
It will be represented by DLQMW. However, since the FMW is naturally affected by the fuel property, the fDLQMW is multiplied by the fuel property correction term FQLTY, and the FMW is expressed by the following equation. FMW = fDLQMW × FQLTY (4) Then, the value of the correction term FQLTY based on the fuel property is stored in the ROM 25 separately for the standard fuel, the light fuel, and the heavy fuel.

The amount of change in QMW DLQMW is the amount of adhered fuel QM at the intake pipe pressure when the intake valve of the current rotation is closed.
The difference between the adhering fuel amount QMW _-720 at the intake pipe pressure when the intake valve is closed before W and 720 ° CA is corrected by the rotation speed KNE.
Take a call. The correction based on the rotation speed is performed because the amount of change in the adhered fuel amount QMW varies depending on the rotation speed, and the higher the rotation speed, the smaller. FIG. 14 shows a flowchart of the calculation of the above formula (4), and FQLTY is a backup R.
Fuel property indication value FQIND stored in AM 24a
Loaded from the map based on.

As described above, the value of TAUST in the process of calculating the fuel injection amount at the start, and FWLB, FASE, FMW in the process of calculating the fuel injection amount after the start are corrected according to the fuel property. The FAF corrected by the fuel property in the technology is not corrected.

[0036]

According to the claims of the present invention, the determination of the fuel property is executed irrespective of the feedback control of the fuel injection amount, and the warm-up of the engine is not completed and the increase correction is performed. It is possible to make a judgment even in such a state, and the time until the control according to the new fuel property is started is shortened compared to the above-mentioned prior art which was dependent on the execution of feedback control, and as a result, when the engine is cold. It is possible to reduce harmful components in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a flowchart of a calculation for determining a fuel property.

FIG. 3 is a diagram showing changes in a basic injection amount at start TAUST with respect to water temperature and fuel properties.

FIG. 4 is a flowchart for calculating a fuel injection time at startup.

FIG. 5 is a flowchart for calculating a fuel injection time after starting.

FIG. 6 is a diagram showing changes in a warm-up increase attenuation coefficient FWLB with respect to water temperature and fuel properties.

FIG. 7 is a flowchart for calculating a fuel injection time after starting.

FIG. 8: Increase coefficient F after starting for water temperature and fuel property
It is a figure which shows the change of the initial value of ASE.

FIG. 9 is a flowchart for calculating a correction coefficient FASE after starting.

FIG. 10 is a flowchart for calculating a feedback correction coefficient FAF.

FIG. 11 is a flowchart for calculating a feedback correction coefficient FAF.

FIG. 12 is a time chart for explaining changes in the feedback correction coefficient FAF.

FIG. 13 is a diagram showing changes in the amount of fuel adhering to the wall surface with respect to the intake pipe pressure in a steady state.

FIG. 14 is a flowchart for calculating a wall surface adhesion correction coefficient FMW.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine body 2 ... Intake pipe 3 ... Fuel injection valve 4 ... Throttle valve 5 ... Pressure sensor 6 ... Air flow meter 7 ... Exhaust pipe 8 ... Three-way catalyst 9 ... A / F sensor 10 ... Fuel tank 11 ... Fuel pump 12 ... Fuel level sensor 13 Water temperature sensor 14 Engine speed sensor 15 Throttle sensor 16 Spark plug 17 Igniter 18 Distributor 20 ECU

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michio Furuhashi 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Toshinari Nagai 1 Toyota Town, Aichi Prefecture, Toyota Motor Corporation ( 72) Inventor Tadayuki Nagai 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Takashi Kawai 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation, (72) Inventor, Kenji Harima Aichi Prefecture Toyota City, Toyota-City 1 Toyota Motor Corporation (72) Inventor Yuichi Goto 1 Toyota-Cho, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Takayuki Otsuka Toyota-City, Toyota City Aichi Prefecture Car Co., Ltd.

Claims (1)

[Claims] 1. An intake air-fuel ratio air-fuel ratio detection means for detecting an air-fuel ratio of an intake air-fuel mixture before combustion, and an air-fuel ratio of exhaust gas after combustion to detect a change in the air-fuel ratio.
Exhaust air-fuel ratio detecting means for outputting the one-to-one correspondence as it is, deviation between the intake air-fuel ratio detected by the intake air-fuel ratio detecting means and the exhaust gas air-fuel ratio detected by the exhaust air-fuel ratio detecting means A fuel property detecting device for an internal combustion engine, comprising a fuel property determining means for directly determining a fuel property from the fuel cell.