JPS62288335A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the acceleration response, by detecting a property of fuel to be used and correcting an air-fuel ratio at acceleration according to the result of detection. CONSTITUTION:A control device 16 receives signals from an air flow meter 7, a throttle valve opening sensor 9, a combustion pressure sensor 10, an oxygen sensor 14, etc. and regulates a fuel injection quantity of a fuel injection valve 4 to control an air-fuel ratio to a target value. At acceleration of an engine, the fuel injection quantity is further corrected according to a property of fuel to be used in addition to the operational condition. The fuel property is obtained as a content of heavy fraction by computing a measured combustion period from an ignition timing and a combustion peak angle and comparing the period with a reference value. Accordingly, the air-fuel ratio at acceleration may be made always optimum irrespective of a change in the fuel property.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention detects the properties of fuel used in internal combustion engines such as automobiles, and based on the detection results, particularly detects the The present invention relates to a device for appropriately correcting a fuel ratio.

(Prior Art) In recent years, there has been a trend in which engines are required to have higher fuel economy and drivability, and from this point of view, microcomputers and the like are being applied to more precisely control the air-fuel ratio.

In such control, the characteristics of the fuel may also play an important role as input information.

As a conventional air-fuel ratio control device, for example, Japanese Patent Application Laid-Open No. 60-4
There is one described in Japanese Patent No. 5742. In this device, the air-fuel ratio is detected by an oxygen sensor installed in the exhaust pipe, and based on the detection result, the fuel injection amount is manipulated to perform feedback control so that the air-fuel ratio reaches a target value.

In other words, the injection pulse signal output to the injector (
Final injection amount) Ti is calculated according to the following equation (2) based on the detection results of the air-fuel ratio, intake air amount, engine speed, cooling water temperature, etc.

T i = T p x Co x α + Ts...
...■ However, Tp: Basic injection amount co=Various correction coefficient α: Air-fuel ratio feed hack correction coefficient Ts: Voltage correction bone In the above equation 0, the various correction coefficients CO are calculated according to the following equation (2).

Co=1→-K T RM + K M R+ K T
W + K A S + K A I + K A C
C+ K H・・・・・・■ However, KTRM: Mixing ratio correction coefficient KMR: Mixing ratio correction coefficient KTW: Water temperature increase correction coefficient KAS: Start and post-start increase correction coefficient KAI:
After idling increase correction coefficient KACC: Acceleration decrease correction coefficient KH: High water temperature increase correction coefficient Also, at startup, acceleration, and under high load, various corrections are made to improve drivability to adjust the air-fuel ratio to the target air-fuel ratio. Make it richer.In addition to this, there is a separate injection during acceleration,
During sudden acceleration, injection is performed asynchronously and separately from normal fuel injection control.

Note that each of the above correction values is set on the premise that standard fuel (for example, regular gasoline) is used as the fuel supplied to the engine.

(Problems to be Solved by the Invention) However, in such a conventional air-fuel ratio control device, the characteristics of the fuel used in the engine (for example, the level of weight)
Based on a uniform standard that corresponds to PUt$ fuel,
The configuration was such that the various correction values described above were calculated and set on the assumption that the properties of the fuel were always constant, so the properties of the supplied fuel changed and the fuel became heavier as a result. Even if the level changes, air-fuel ratio correction due to changes in the properties of the supplied fuel is not taken into account. Therefore, in such a case, a discrepancy occurs between the air-fuel ratio calculated based on the use of standard fuel and the actual air-fuel ratio, making it difficult to achieve accurate air-fuel ratio control.

For example, when heavy gasoline is used, its volatility is lower than that of regular regular gasoline, and the gasoline components involved in combustion are diluted. Therefore, the actual air-fuel ratio is much leaner than the air-fuel ratio calculated based on the use of standard fuel. As a result, the engine will be operated leaner than the target air-fuel ratio, resulting in poor combustion conditions, which may lead to problems such as hesitation and stumpling (deterioration of acceleration response), especially during acceleration. . When acceleration response deteriorates, it becomes impossible to obtain a smooth acceleration feeling, and not only does drivability deteriorate significantly, but also the exhaust gas concentration increases, which adversely affects exhaust emission characteristics. Furthermore, such problems become more noticeable when using inferior fuel.

In this way, if the fuel injection amount during acceleration is calculated on the premise that a uniform fuel such as standard fuel is used as the supplied fuel, some problems will occur in terms of control accuracy. In other words, if you are aiming for more accurate air-fuel ratio control during acceleration,
It is desirable to take into account differences in the fuel properties used.

(Objective of the Invention) Therefore, the present invention detects the properties of the fuel used and appropriately corrects the air-fuel ratio during acceleration based on the detection result, thereby adjusting the air-fuel ratio during acceleration regardless of changes in the properties of the fuel. The purpose is to further improve the engine's acceleration response and drivability.

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device for an internal combustion engine according to the present invention has a property detection means for detecting the properties of the fuel used, as shown in FIG. a, an operating state detecting means for detecting the accelerating operating state of the engine; an air-fuel ratio setting means C for setting the supply air-fuel ratio when the engine is in the accelerating operating state based on the properties of the reference fuel; A correction means d that corrects the supplied air-fuel ratio during the operating state based on the properties of the fuel used, and controls the intake air amount or the fuel supply amount so that the corrected air-fuel ratio is achieved; (iiN) an operating means e for controlling the amount of intake air or fuel supplied based on the signal;

(Function) In the present invention, the properties of the fuel used are detected, and a parameter that determines the air-fuel ratio during acceleration is determined according to the detection result.
(AIR or FUEL) is appropriately corrected. Therefore, regardless of changes in the properties of the fuel used, the air-fuel ratio during acceleration becomes appropriate, improving acceleration response and drivability.

(Example) Hereinafter, the present invention will be explained based on the drawings.

Figures 2 to 12 are diagrams showing the first embodiment of the present invention, in which the combustion rate is detected from the in-cylinder pressure signal as a fuel property detection parameter, and the air-fuel ratio control method is used to determine the fuel property based on this detected value. An example of application to a device is shown.

First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes an engine. Intake air is supplied from an air cleaner 2 to each cylinder through an intake pipe 3, and fuel is injected by an injector (operating means) 4 based on an injection signal St. The exhaust gas combusted in the cylinder is introduced into the catalytic converter 6 through the exhaust pipe 5, and the harmful components (Co, Co,
I C1N Ox ) is purified by a three-way catalyst and discharged.

The intake air flow jlQa is detected by an air flow meter 7 and controlled by a throttle valve 8 in the intake pipe 3. Throttle valve 8
The opening CV is detected by the throttle valve opening sensor 9. Further, the combustion pressure (hereinafter referred to as cylinder pressure) Pa in the cylinder is detected by a pressure sensor IO, which is constituted by a piezoelectric element and is molded as a washer for the spark plug 11.

The pressure sensor 10 detects the cylinder pressure Pa acting on the piezoelectric element via the spark plug 11, and outputs an analog signal having a voltage value corresponding to the cylinder pressure Pa.

The rotation speed N of the engine 1 is detected by the crank angle sensor 12, and the temperature Tw of the cooling water flowing through the water jacket is detected by the crank angle sensor 12.
is detected by the water temperature sensor 13.

Furthermore, the oxygen concentration in the exhaust gas is detected by an oxygen sensor 14, and the oxygen sensor 14 used is one having a characteristic that its output Vs changes suddenly at the stoichiometric air-fuel ratio.

The air flow meter 7, throttle valve opening sensor 9, and crank angle sensor 12 constitute an operating state detection means 15,
Operating state detection means 15, pressure sensor 10, water temperature sensor 1
The outputs from oxygen sensor 3 and oxygen sensor 14 are input to control unit 16. The control unit 16 has a function as a property detection means together with the pressure sensor 10, and also functions as an air-fuel ratio setting means and a correction means by itself.
(non-volatile memory) 24 and a T10 board 25. The CPU 21 imports necessary external data from the T10 boat 25 according to the program written in the ROM 22, and also imports necessary external data from the RAM 23 and NV.
While exchanging data with the M24, the processing values necessary for fuel property determination and air-fuel ratio control based on the results are calculated, and the processed data is transferred as necessary to the T10.
Output to boat 25. Signals from the sensor group 7.9.10.13.14 are input to the T10 boat 25, and an injection signal Si is output from the T10 boat 25. The ROM 22 stores calculation programs for the CPU 2L, and the RAM 23 and NVM 24 store data used in calculations in the form of a map or the like.

Next, the effect will be explained, but first, changes in fuel properties and their effects will be explained using gasoline as an example.

Gasoline is composed of more than several hundred types of hydrocarbons (HC), and depending on the ratio and bonding style of carbon (C) and hydrogen (H), there are four types: paraffinic, olefinic, naphthenic, allo, and matic. are categorized. As a general tendency, the higher the number of C and H, the higher the boiling point and the higher the fractionation temperature from crude oil (represented by 50% distillation temperature T). Also, the heavy degree of gasoline is T. It is represented by T, which is light (highly volatile). =80~90℃
, T so = 110 for heavy (low volatility)
~120'c, and T, on the market. =95~100℃
The ones with the highest rank are the most widely distributed. Therefore, the aforementioned final injection amount Ti is T. It is determined by making various corrections on the premise that fuel (ie, regular gasoline) with a temperature of 95 to 100° C. is used.

Figure 3 shows changes in the fuel condition when the degree of gasoline heaviness changes as changes in the in-cylinder pressure signal under specified conditions (when the air-fuel ratio, intake air amount, engine temperature, and ignition timing are constant). In addition, P max in the figure is the maximum point of the in-cylinder pressure signal, and θpmax is the crank angle that gives P max. Also, t in the figure is from ignition timing θi to θ
The actual combustion period up to pmax is shown.

As shown in Fig. 3, in the case of light gasoline, the maximum value Pmax of the in-cylinder pressure signal is large and combustion proceeds quickly;
As the fuel becomes heavier, P max decreases and θpma
x moves to the later side. This is the initial stage of combustion (
This is due to the fact that the gasoline component (hatched area in Figure 4) that contributes to combustion from ignition to θpmax decreases as the fuel becomes heavier. When observing this initial combustion light, it is blue overall, and for light gasoline, only blue is observed, and it disappears just after θpmax (i.e.,
combustion has finished). However, in heavy gasoline, θ
Blue combustion light is observed up to pn+ax, but the light is weaker than in the case of light gasoline, and red combustion light is observed immediately after θpmax. In other words, heavy gasoline burns a mixture of fast combustion (bluish white combustion light) and slow combustion (red combustion light), and the fast combustion (bluish white combustion light) contributes to actual combustion. decreases as the fuel becomes heavier.

This means that the heavier the gasoline components that contribute to combustion, the more diluted they become.In other words, as the gasoline becomes heavier, the air-fuel ratio becomes leaner and the combustion speed becomes slower.
(Pmax is on the delayed side).

Furthermore, this phenomenon becomes more noticeable as the engine temperature decreases, as the volatility of heavy gasoline deteriorates and the air-fuel ratio becomes leaner.

In this embodiment, in view of the above-mentioned characteristics of fuel properties, the properties of the fuel are appropriately detected by a program as described later, focusing particularly on the causal relationship using the burning rate as a parameter, and the detected results are Based on this, air-fuel ratio control during acceleration is performed more appropriately.

FIG. 5 is a flowchart showing a program for air-fuel ratio control during acceleration written in the ROM 22, and this program is executed once in synchronization with engine rotation.

First, the intake air lQa is read with Pl, and the engine speed N is read with pg. Rotation speed N is determined by crank angle sensor 1
It is calculated by measuring the interval time of the reference signal (signal every 360 degrees) from 0 or by measuring the number of pulses within a predetermined time of the position signal (signal every 1 degree). Then, P
, the basic injection ITp (Tp=func (Qa, N
)).

In P4, the mixture ratio correction coefficient KMR (KMR=func(T
p, N)) and calculate the mixing ratio correction coefficient K with P.
Look up TRM (KTRM=func (Tp, N)). The mixture ratio correction coefficient KMR1KTRM is an increase correction for high loads and high rotations, and the correction coefficient KMR (coefficients in the explanation method will be abbreviated as appropriate. The same shall apply hereinafter) is for high speed and high load ranges. If so, the value will be greater than 0, and otherwise it will be 0. In addition, the correction coefficient KTRM becomes negative in the low load range below medium speed,
Otherwise, it is 0.

Next, at P, the water temperature increase correction coefficient KTW is looked up according to the cooling water temperature Tw at that time, and at P7, the fuel property correction coefficient KTWD (
KTWD=func (Tso) However, T. : Look up fuel property parameters).

Note that the fuel property parameter T. Regarding the detection of
This will be explained in detail in the program shown in the figure below.

At P, the current correction coefficient KTW is corrected according to the following equation.

KTW=KTW'-KTWD...
・ ・ ・ ・ However, KTW': The value looked up at P. Next, P determines whether the idle switch SW is ON (that is, in the idle state), and if it is OFF, it is determined that it is not in the warm-up state. Judgment, P. Proceed to the next step. P. Now, the elapsed time TAI after the idle switch is turned off is calculated.

Next, in steps P1 to P13, fuel property correction is performed for the post-idle increase correction coefficient. That is, look up the post-idle increase correction coefficient KAI with Pat, and look up the fuel property correction coefficient KAID (KAID=func) with Pl2.
(Tso) ). Furthermore, PI3
The current correction coefficient KAI is calculated according to the following equation (2), and fuel property correction is added.

KAI=KAI ' x KAID x (1-α・TAI) ・・・・・・■ However, KAI
': The value α looked up with P and + is a constant constant. This correction coefficient KAI is determined by the cooling water temperature 7w immediately after the throttle valve 8 changes from closed to open, and the elapsed time after complete explosion TAI is determined. It is determined by the product with KAIZ, and this is looked up. This KAI is used to smooth the start during warm-up, and its size decreases at a constant rate until it reaches O.

At P14, it is determined whether the correction coefficient KAI is negative or not. If it is negative, PIS sets KAI=O and the process proceeds to P16, and if it is not negative, the process directly proceeds to P16.

Next, at Pl6, the rate of change ΔTV○ of the throttle valve opening (TVO)
is calculated based on the difference between the previous TVO value and the current TVOO value, and the change rate ΔTVO is set to a predetermined value a (a
=func(N)).

When ΔTVO≧a, fuel property correction for interrupt injection during acceleration is performed in steps from Pill to Pal. That is, p
Interrupt injection 1i Tadd (Tadd =
Look-amplify func (Tp, N)), ■)1. The fuel property correction coefficient K A D D (K A D D =
Look up func (Tso) ). Next, in Pro, the interrupt injection amount T add is corrected according to the following equation.

Tadd = Tadd 'xKADD ++t++
(2) However, Tadd': Outputs to the injector 4 an injection signal Si having a fuel injection pulse width corresponding to the interrupt injection amount Tadd using the value pat looked up by Pus. That is, in order to improve acceleration performance, interrupt injection is performed only once in addition to the normal injection amount.

In P2□, an air-fuel ratio feedback correction coefficient α is calculated. The air-fuel ratio feedback correction coefficient α is used to correct the deviation between the basic air-fuel ratio and the stoichiometric air-fuel ratio (λ = 1), but since it is well known as well as those described in conventional publicly known documents, it will not be described in detail here. Omit explanation.

Next, P2. Then, the final injection MTi is calculated according to the above-mentioned equations (1) and 0. In Equation 0, the starting and post-starting increase correction coefficient KAS, the acceleration weight loss correction coefficient KACC1, the high water temperature increase correction coefficient KH, and the voltage correction frame 'rS have little relation to the present invention, so their explanations will be omitted.

At Pl4, the final injection ff1Ti is stored in the I10 register, and an injection signal Si having a fuel injection pulse width corresponding to this Ti is output to the injector 4 at a predetermined crank angle.

On the other hand, if the idle switch SW is in the ON state at P9, it is determined that it is warming up, and the elapsed time TAI is reset at PTS (
TAI=O) and jump to P2z.

That is, at this time, the fuel property correction of the post-idle increase correction coefficient and the interruption injection processing during acceleration are not performed. Also,
When ΔT V O < a at Pl'l, it is determined that the rate of change in acceleration is small, and the engine jumps from P, 9 to PzI without performing interrupt injection, and proceeds directly to Pat.

In this way, the fuel injection amount during acceleration (including interrupt injection during acceleration) is appropriately corrected based on the property detection information of the fuel used. For example, when heavy gasoline is used, the amount of gasoline that actually contributes to combustion is smaller than that of standard fuel, and the mixture ratio is effectively lean. On the other hand, according to this device, the level of heavy fuel used is appropriately determined and the deviation from the target air-fuel ratio is appropriately corrected according to the degree of heavy fuel. When quality gasoline is used, the situation in which the amount of gasoline that contributes to combustion is small is corrected. That is, at this time, the total amount of fuel injection amount is corrected to increase. Therefore, a situation in which the mixture ratio becomes lean is effectively avoided, and the original effectiveness of the air-fuel ratio control can be achieved. Furthermore, since the total amount of fuel injection is corrected to increase when performing interrupt injection, it is possible to sufficiently improve acceleration performance.

As a result, during acceleration, the air-fuel ratio during acceleration is corrected to an appropriate value corresponding to the properties of the fuel used at that time, making it possible to suppress the occurrence of hesitation, stumpling, etc. The acceleration response of the engine can be improved. Furthermore, since a smooth acceleration state can be obtained, exhaust emission characteristics can be improved.

FIG. 6 is a flowchart showing a program for detecting the fuel property parameter TSO, and this program is executed once every predetermined time.

Pffl~I), Step 4 is a process of determining whether the engine is in a predetermined operating state. First, Pff
Determine whether the cooling water temperature Tw is within a predetermined range with l,
When Tw, ≦T w S T w t, it is determined that the engine temperature is within a predetermined range, and P is selected. Proceed to. Here, Tw
It is desirable to set Tw within a range of 10°C to 40°C. P'Jt determines whether the engine speed N is within a predetermined range, and determines whether the engine rotation speed N is within a predetermined range (N, ≦N≦N2
), the process advances to Pff3 and it is determined whether the intake air fJQa is within a predetermined range.

Engine speed N and intake air amount Qa are determined by oxygen sensor 1
The range is set within the λ control (air-fuel ratio control) range according to No. 4.

When Qa, ≦Qa≦Qa2, it is determined in P34 whether or not the engine is in a steady state (a state in which there is no sudden acceleration or sudden deceleration), and if it is in a steady state, the process advances to Pus.

Whether or not the engine is in a steady state is determined based on the amount of change in the engine rotational speed N and the intake air amount Qa within a predetermined period of time.

Above P3. ~ If any one of the conditions in each step processing in P24 is not satisfied, it is determined that the engine is not in a predetermined operating state suitable for fuel property determination, and the subsequent processing is canceled (i.e., the return do).

In p3s, the basic combustion rate parameter θc is obtained from a two-dimensional table map with Qa and N as parameters.

Look up (θco-func (Qa, N)).

This reference combustion rate parameter θco represents the combustion rate when using standard fuel, and by comparing it with the combustion rate of the fuel actually used in the step described later, differences in combustion rate (for example, if the fuel is heavy (the combustion rate slows down when the combustion rate decreases) is detected.

Next, + (k+ = f
unc(TV)) from the table map shown in FIG. The temperature correction coefficient of 1 is used to correct the combustion rate, which changes depending on the engine temperature even if the fuel properties are the same, according to the engine temperature Tw, and the reference temperature Two is +
=1. Tw< TW (1 in +<1゜Tw>Two in k
>l.

Next, P, 3? The combustion peak angle (crank angle at which the cylinder pressure Pa becomes maximum) θp is detected at , and the process proceeds to I''Im.

Note that the detection of θp will be described in detail in the program described later.

Furthermore, in pats, ignition timing θi and combustion peak angle θp
The measured combustion period θC, which is the actual combustion period, can be calculated from the following formula■
Calculate according to (see Figure 8).

θC = θp - θi ・Old...■ However, θi: Crank angle corresponding to the ignition time θp: Crank angle at which the cylinder pressure Pa becomes maximum (combustion peak angle) θ11 θp is as shown in Figure 8 (a). The reference crank angle θref at which a (H) level pulse is generated in a predetermined reference crank angle signal Sr is used as a reference, and as shown in FIG.

In P39, the product θC1 (θc,=
, XθC). This θC8 corresponds to the actual combustion rate parameter detected under reference conditions. Next, at P4°, the difference Δθc between the measured combustion period θc1 under the reference condition and the reference combustion rate parameter θC0 is calculated according to the following equation (2).

Δθc, = θC1-0C6...■ In other words, here, the combustion rate parameter θc0 when using standard fuel under standard conditions and the combustion rate parameter of the fuel actually used (measured combustion period) The difference with θC8 is detected. Since the combustion rate has a certain correlation depending on the properties of the fuel, if the combustion rate is detected accurately, it becomes possible to appropriately determine the properties of the fuel.

Furthermore, the moving average θCi of ΔθC2 at Pa1.

is calculated according to the following formula (■).

However, for rn: constant P4□, the fuel property parameter T5° is looked up from a table map having characteristics as shown in FIG. 9 based on the value of Δθ01', and P4. And this T. The value of N
'Store in VM (non-volatile memory) 24.

In this way, by comparing the difference in combustion rate due to the properties of the fuel used with the combustion rate of the standard fuel, the fuel property parameters of the fuel used at that time can be appropriately determined.

FIG. 10 is a flowchart showing a program for detecting the fuel peak angle θp, and this process is performed in the step Pff? described in FIG. 6 above. corresponds to This program is executed once every 2 degrees of crank angle.

First, use PSI to determine whether the current crank angle (piston position) θ corresponds to compression top dead center TDC. After A/D converting the signal and storing it as a cylinder pressure conversion value A Do, the process proceeds to PS3. On the other hand, when θ≠TDC, the process jumps from PS2 and proceeds to PS3.

At PS3, it is determined whether the crank angle θ is greater than or equal to the TDC excess value (TDC+α°) shown in FIG. 11, that is, whether the engine 1 has rotated by a degree or more beyond TDC. Here, α is set to 2° to f''. This is because the peak of the cylinder pressure Pa due to combustion (hereinafter referred to as the combustion peak) appears after TDC, so a dead zone of α° is set to This is to avoid mistakenly using the cylinder pressure Pa as the combustion peak value.

When θ<TDC+α°, that is, when θ is before top dead center (BTDC) or when TDC≦θ<TDC+α°, the current routine ends. On the other hand, θ≧TDC+
When α°, processing for detecting combustion peak angles after PS4 is executed. First, at PS4, it is determined whether the crank angle θ exceeds the combustion peak angle determination limit value θe. θ
e is a crank angle at which it can be assumed that combustion in the cylinder has been sufficiently completed, and is set to a predetermined value exceeding TDC (11th
(see figure).

The combustion peak is assumed to be between TDC and θθ, and points F and F shown in FIG. 11 correspond to this, for example (curve X represents different combustion conditions). Therefore, the A/D conversion process of the in-cylinder pressure Pa for determining the combustion peak is performed up to θe.

When θ≦θe in PS4, count θ in PSS θ
The counter is incremented, and the cylinder pressure Pa at this time is A/D converted by psth to the cylinder pressure conversion charger AD,
Find and memorize this. Next, the difference value ΔP between the converted cylinder pressure value AD and A Da is determined using PSI, and the process proceeds to PSll. The difference value ΔP will be a positive value if the cylinder pressure Pa is increasing, and will be a negative value if it is decreasing.

Moreover, the value becomes very small near the combustion peak time. P
At Sa, the absolute value 1ΔP1 of the difference value ΔP is compared with the reference value ΔP0. The reference value ΔP0 is a value for determining whether the change in the cylinder pressure Pa has become substantially flat. 1ΔP1≦
When ΔP0, it is determined that the change in the cylinder pressure Pa is approximately flat, and the PSI stores the count value of the θ counter as the combustion peak angle θp, and at P6°, the cylinder pressure conversion value AD of this routine, AD, to end the routine.

On the other hand, when 1ΔpH>ΔP0, it is determined that the condition is not flat and the process proceeds to Pb0.

Here, the cylinder pressure P satisfies the condition 1ΔP1≦ΔP0.
This is when a is at its maximum, minimum, maximum, or minimum. Note that such a state determination is not limited to the example of this embodiment, and may be performed using, for example, the differential value of the cylinder pressure Pa.

The manner in which the actual cylinder pressure Pa changes under the condition of 1ΔP1≦ΔP0 can be summarized in the examples shown in FIGS. 12(a) to 12(C).

FIG. 12(a) shows the most common Pa change curve. In this example, 1ΔP1≦ΔP after TDC
The crank angle that satisfies the condition of 0 is θp, and the combustion peak angle can be easily determined. Figure 12(b),
(C) is a case of low load, and a state occurs in which Pa becomes flat at two locations after TDC. In the case of Fig. 12(b), the value Paro when the cylinder pressure Pa at θp is TDC
c becomes smaller, and in the middle there is a local minimum value Pa2.
appears. However, in this case, Pa2 appears, so Pa
2 becomes a large value, and it is possible to identify θp. On the other hand, in the case of Fig. 12(C), no minimum value appears and the flat part Pa
After , pa, which corresponds to the combustion peak angle θp, appears (P a , < Pa3). This is a case where the combustion pressure is very low, and it is actually difficult to detect θp using the A/D conversion method.

Although it is possible to distinguish by performing differential processing on Pa,
A little more accurate. However, it is only at extremely low loads that Pa uniformly decreases after TDC, and in this case, the detection of θp is stopped and the operating state (engine speed N
and load Qa).

In this way, θ is TDC+α0. - θe, the combustion peak angle θp can be accurately detected by the above-mentioned A/D conversion method.

On the other hand, when θ≧θe in PS4, it is determined that combustion in the cylinder has been sufficiently completed, and in P61, the average value of θp over the past several times is calculated, increasing the reliability of θp as data, and calculating the current value. End the routine.

Note that detection of the combustion peak angle is not limited to the method using a piezoelectric element such as an in-cylinder pressure sensor. For example, the detection of the combustion peak angle can also be performed by detecting the light inside the combustion chamber through a glass window and an optical fiber, and identifying this detected light. It's okay.

In this way, in this embodiment, attention is paid to the correlation between the fuel properties and the combustion rate, and by accurately detecting the combustion rate of the used fuel, the properties of the used fuel are appropriately determined.

Then, the accurately detected fuel property parameter T. is applied to the fuel injection amount during acceleration, it is possible to eliminate the problem of deviation in air-fuel ratio control during acceleration due to differences in fuel properties, which was pointed out in the conventional problem.

FIG. 13 is a diagram showing a second embodiment of the present invention. In this embodiment, in addition to the processing of the first embodiment, when the output of the oxygen sensor indicates a lean state during acceleration, the interrupt injection amount T
add and the post-idle increase correction coefficient KAI are further corrected to the increase side.

In explaining this embodiment, steps that perform the same processing as in the first embodiment will be given the same numbers and their explanations will be omitted, and steps that are different will be given step numbers circled and their contents will be explained. .

In the program shown in Figure 13, the rate of change ΔTV at PI7
When O is smaller than the predetermined value a (ΔTVO<a), P? Reset the interrupt injection amount Tadd with l (Tadd
=0) Go to ptz. Oxygen sensor 14 at p, z
Detects the output Voz of
b is a value corresponding to the stoichiometric air-fuel ratio (λ=1)).

When Vo, <b, it is determined that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio (λ=1), and after that, T add and KAI are corrected in steps P0 to P7S, and Vo, ≧b.
If so, it is judged to be on the rich side and jumps directly to pz+. That is, the correction coefficient KOz (Ko
t =func (Tp, N)), and P
T add is corrected using VA according to the following formula (2).

Tadd = Tadd 'X K o ,
-・-・-■ However, Tadd ": The value calculated by P2°. Then, KAI is corrected by P?S according to the following formula [phase].

KA I = KA I “X K oz −・−” [
However, in this embodiment, similarly to the first embodiment, the fuel injection amount during acceleration is appropriately corrected based on the fuel property detection information, and the fuel injection amount during acceleration is When the fuel ratio is lean,
Since T'add and KAI, which have undergone fuel property correction, are further corrected to increase the amount, it is possible to further improve acceleration performance.

In each of the above embodiments, the fuel property detection method is to detect the combustion rate as shown in FIGS. 6 to 12,
Based on this detected value, the fuel property parameter T, is determined. Although the present invention is not limited to this, for example, it may be determined by detecting combustion light with an optical fiber sensor, or it may be determined based on the response delay of the air-fuel ratio under accelerated driving conditions. Needless to say, it is also possible to adopt a mode in which the determination is made based on the response delay of a parameter that correlates with the generated torque (or indicated mean effective pressure) under accelerated driving conditions.

(Effects) According to the present invention, the properties of the fuel used are detected, and the parameter (A I R or FUEL) that determines the air-fuel ratio during acceleration is appropriately corrected based on the detection result. Regardless of changes in properties, the air-fuel ratio during acceleration can always be optimized, and both acceleration response and drivability can be improved.

[Brief explanation of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 12 are diagrams showing a first embodiment of the present invention, and FIG. 2 is an overall configuration diagram thereof,
Figure 3 shows the relationship between the crank angle signal and the in-cylinder pressure signal to show the change in the combustion state when the heavyness of the gasoline changes, and Figure 4 shows the proportion of gasoline components depending on the heavyness. Figure 5 is a flowchart showing the program for air-fuel ratio control during acceleration, Figure 6 is a flowchart showing the program for determining fuel properties, - Figure 7 is a table map of the temperature correction coefficient of 1, FIG. 8(a) is a diagram showing the reference crank angle signal, FIG. 8(b) is a diagram showing changes in cylinder pressure in relation to the reference crank angle signal, and FIG. 9 is a diagram showing the fuel property parameter T5°. Figure 10 is a flowchart showing the program for detecting the combustion peak angle, Figure 11 is a diagram showing the change in cylinder pressure, and Figures 12 (a) to (C) are for explaining the operation. FIG. 13 is a flowchart showing a program for controlling the air-fuel ratio during acceleration according to a second embodiment of the present invention. 1...Engine, 4...Injector (operating means), 15...
... Operating state detection means, 16... Control unit (property detection means, air-fuel ratio setting means, correction means). Fig. 3 Fig. 4 is the rental office Fig. 8 'ref 'i TDCffp crank angle - Fig. 9 Fig. 11 Crank angle e□

Claims (1)

[Claims] a) property detection means for detecting the properties of the fuel used; b) operating state detection means for detecting the accelerated operating state of the engine; and c) supply air-fuel ratio when the engine is in the accelerated operating state. d) correcting the supplied air-fuel ratio when the engine is in an accelerated operating state based on the properties of the fuel used, and adjusting the air-fuel ratio to the corrected air-fuel ratio; An internal combustion engine comprising: a correction means for controlling the amount of intake air or the amount of fuel supplied; and e) an operation means for controlling the amount of intake air or fuel supplied based on a signal from the correction means. Air-fuel ratio control device.