JPS62282265A - Apparatus for discriminating fuel properties - Google Patents

Abstract

PURPOSE:To detect the properties (heavy level) of fuel, by detecting the combustion pressure of an engine and detecting a combustion speed correlated with the properties of fuel used from the detection value. CONSTITUTION:The title apparatus is equipped with a pressure detection means (a) detecting the combustion pressure of an engine, a number-of-rotation detection means (b) detecting the number of rotations of the engine, a load detection means (c) detecting the load of the engine, a temp. detection means (d) detecting the temp. of the engine, a combustion speed detection means (e) operating the combustion speed of fuel used on the basis of the output of the means (a), an operation means (f) operating the combustion speed of standard fuel based on the load, the number of rotations and temp. detected of the engine and a discrimination means (g) discriminating the properties of the fuel used in the engine. The combustion speed of the fuel sued is detected from the combustion pressure of the engine by the means (e) and the combustion speed of the standard fuel is operated from the operation state of the engine by the means (f). Subsequently, both speeds having close relation with the properties of the fuel are set as parameters to discriminate the properties of the fuel used by the means (g).

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a device for determining combustion characteristics of an internal combustion engine, and particularly to a device for determining the level of fuel aggravation using an output value of combustion pressure. .

(Prior Art) In recent years, there has been a tendency for engines to be required to have higher fuel economy and longer operating life, and from this point of view, microcomputers and the like are being applied to more precisely control the amount of fuel supplied.

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

As a conventional fuel supply device, for example, JP-A-6012
There is one described in Japanese Patent No. 8958. In this device, the air-fuel ratio is detected by an oxygen sensor provided in the exhaust pipe, and based on the detection result, the fuel injection amount is manipulated to perform feed-hack control so that the air-fuel ratio reaches a target value.

That is, the injection pulse signal (final injection amount) T i actually output to the injector 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.

Ti = Tp Calculated.

Co= f+KTRM+KMR+KTW+KAS+KA
I+KACC+KH・・・・・・■However, K T R
M: Mixing ratio correction coefficient KMR: Mixing ratio correction coefficient KTW: Water temperature increase correction coefficient KAS: Starting 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 and the air-fuel ratio is lower than the target air-fuel ratio. Make it rich. In addition to this, there is interrupt injection during acceleration,
During sudden acceleration, injection is performed asynchronously and separately from normal fuel injection control.

On the other hand, during a cold start or during warm-up, the oxygen sensor is cold and not activated, so the above feedback control is stopped and the air-fuel ratio is set to the rich side to improve startability and improve engine performance immediately after starting. Intended for stability.

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)
The structure was such that the various correction values described above were calculated and set based on the premise that the properties of the fuel were always constant, using a uniform value that corresponded to the standard fuel as a standard, so the properties of the supplied fuel Even in the case where the fuel weight changes and the fuel weighting level changes accordingly, the air-fuel ratio correction due to the change in the properties of the supplied fuel is not taken into consideration. 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 leaner than the air-fuel ratio calculated based on the use of standard fuel. As a result, the engine is operated leaner than the target air-fuel ratio, resulting in poor combustion conditions and poor starting performance and fuel efficiency. If the startability deteriorates significantly, cranking will be repeated more than necessary, resulting in so-called hafting. Furthermore, such problems become more noticeable when using inferior fuel.

In this way, if various calculations are performed 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. That is, in order to achieve more accurate air-fuel ratio control, it is desirable to take into account differences in the properties of the fuel used.

For these reasons, it is desired to realize a device that can directly detect the properties of fuel, but currently no device that detects the properties of fuel suitable for air-fuel ratio control has been realized.

(Objective of the Invention) Therefore, the present invention detects the combustion pressure of the engine, detects the combustion rate that correlates to the fuel properties of the fuel used from this detected value, and calculates the combustion rate of the reference fuel from the engine operating state. The object of the present invention is to provide a fuel property discriminating device that can accurately detect the properties of the fuel (heaviness level) by discriminating the properties of the fuel used based on both of these combustion velocities.

(Means for Solving the Problems) In order to achieve the above object, the fuel property discriminating device according to the present invention has the following features:
As the basic conceptual diagram is shown in Fig. 1, pressure detection means a detects the combustion pressure of the engine, rotation speed detection means detects the engine rotation speed, and load detection means C detects the engine load. , a temperature detection means d for detecting the engine temperature, a combustion speed detection means e for calculating the combustion speed of the fuel used based on the output of the pressure detection means a, an engine load,
Calculating means f for calculating the base fJ and fuel combustion rate based on the rotation speed and engine temperature, and the base fJ and the base #! for the combustion rate of the fuel used. and a determining means g for determining the properties of the fuel used in the engine based on the combustion speed of the fuel.

(Function) In the present invention, the combustion speed of the fuel used is detected from the combustion pressure of the engine, and the combustion speed is determined based on the operating state of the engine. 9. The combustion rate of the fuel is calculated. Then, the properties of the fuel used are determined with high accuracy using these two parameters, which have a close causal relationship with the properties of the fuel.

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

2 to 11 are diagrams showing a first embodiment of the present invention, and are examples in which the present discrimination device is applied to a device for controlling the air-fuel ratio of an internal combustion engine.

First, the configuration will be explained. In FIG. 2, l is 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 4 based on an injection signal Si. The exhaust gas combusted in the cylinder passes through the exhaust pipe 5 and enters the catalytic converter 6.
) is purified by a three-way catalyst and discharged.

The intake air flow rate Qa is detected by an air flow meter (load detection means) 7 and controlled by a throttle valve 8 in the intake pipe 3. Further, the combustion pressure (hereinafter referred to as cylinder pressure) Pa in the cylinder is detected by a pressure sensor (pressure detection means) 9, and the pressure sensor 9 is constituted by a piezoelectric element, and the spark plug 1
It is molded as a 0 washer. Pressure sensor 9
is the cylinder pressure P acting on the piezoelectric element via the spark plug 10
a and outputs an analog signal having a voltage value corresponding to this cylinder pressure Pa.

The rotation speed N of the engine 1 is detected by a crank angle sensor (rotation speed detection means) 11, and the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor (temperature detection means) 12.
Detected by Further, the oxygen concentration in the exhaust gas is detected by an oxygen sensor 13, and an oxygen sensor 13 having a characteristic that its output Vs changes suddenly at the stoichiometric air-fuel ratio is used.

Outputs from the air flow meter 7, pressure sensor 9, crank angle sensor 11, and water temperature sensor 12 are input to the control unit 14, and the control unit 14 determines the properties of the fuel based on information from these sensors. That is, the control unit 14 has functions as a combustion rate detection means, a calculation means, and a discrimination means,
It is composed of an M (non-volatile memory) 18 and an I10 port 19. The CPU 15 reads necessary external data from the I10 boat 19 according to the program written in the ROM 16, and also reads the necessary external data from the RAM! ,7
While exchanging data with the NVM 18 and NVM 18, it calculates the processing values necessary for fuel property determination and air-fuel ratio control based on the results, and outputs the processed data to the I10 boat 19 as necessary. . [Signals from the sensor group 7.9.11.12.13 are input to the 10 boat 9, and an injection signal Si is output from the I10 port 19. The ROM 1.6 stores a calculation program for the CPU 15, and the RAM 17 and NVM 18 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 (C), and depending on the ratio and bonding style of carbon (C) and hydrogen (H), there are four types: paraffinic, olefinic, naphthenic, and aromatic. 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 T50). In addition, the heavy degree of gasoline is represented by T5°, and light (highly volatile) gasoline is T5° -80 to 90°.
T, which is C3 heavy (low volatility). -110~1
It is 20℃, and there are T, on the market. = 95 to 100°C is the most widely distributed. Therefore, the aforementioned final injection amount Ti is T. = 95-100°C fuel (i.e.
This is determined by making various corrections on the assumption that regular gasoline (regular gasoline) will be used.

Figure 3 shows the change in the combustion state when the heavyness of gasoline changes as a change in the in-cylinder pressure signal under specified conditions (when the air-fuel ratio, intake air amount, engine temperature, and ignition timing are constant). be. Note that Pmax in the figure is the maximum point of the cylinder pressure signal, and θpmax is the crank angle that provides Pmax. In addition, the number in the figure is from ignition timing θi to θp.
The actual combustion period up to max 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 (the fuel moves quickly
As the fuel becomes heavier, Pmax decreases and θpmax
shifts to the later side. This is due to the fact that in the initial stage of combustion (from ignition to θpmax), the gasoline component (hatched area in FIG. 4) that contributes to combustion 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, with heavy gasoline, blue combustion light is observed until θpmax, 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 as a mixture of fast combustion (bluish-white combustion light) and slow combustion (red combustion light), and the fast combustion (bluish-white combustion light) that contributes to actual combustion is The heavier the fuel, the less it becomes. 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 pronounced as the engine temperature decreases, as the volatility of heavy gasoline deteriorates and the air-fuel ratio becomes leaner.

In this embodiment, the fuel properties are determined appropriately by the following program, taking into account the above-mentioned characteristics and paying particular attention to the causal relationship using the burning rate as a parameter.

FIG. 5 is a flowchart showing a program for determining fuel properties based on the above basic principle, in which P1 to P1. ．． indicates each step of the flow - This program is executed once every predetermined time.

Steps P and -P4 are processes for determining whether or not the engine is in a predetermined operating state. First, it is determined whether the cooling water temperature Tw is within a predetermined range at P, and TW,≦Tw
When ≦TW2, it is determined that the engine temperature is within a predetermined range, and the process proceeds to P2. Here, it is desirable to set Tw in a range such that Tw=10°C to 40°C. At P2, it is determined whether the engine speed N is within a predetermined range, and if it is within a predetermined range (N, ≦N5Ng), the process proceeds to P3, where it is determined whether the intake air amount Qa is within a predetermined range. do.

Here, the engine speed N and the intake air iQa are set within a λ control (air-fuel ratio control) range by the oxygen sensor 13.

When Qa, ≦Q a fa Q a z, it is determined in P4 whether the engine is in a steady state (no sudden acceleration or sudden deceleration), and if it is in a steady state, the process proceeds to P.

Whether or not it is in a steady state is determined based on the amount of change in the engine rotational speed N and the intake air 4iQa within a predetermined period of time.

If any one of the above-mentioned steps P1 to P4 does not satisfy the conditions, it is determined that the engine is not in the predetermined operating state that was used to determine the fuel properties, and the subsequent processing is canceled ( i.e. return).

At P, the reference burning 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 burning rate parameter θ,. represents the combustion rate when using standard fuel, and by comparing it with the combustion rate of the fuel actually used in the steps described later, it is possible to determine the difference in combustion rate (for example, if the fuel becomes heavier, the combustion rate becomes slower). ) is detected.

Next, in P6, the temperature correction coefficient k, (k, =
func(TV)) is looked up 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 at the reference temperature TW0, k
1 = 1, T W < T Wo and kI < 1° Tw
> T W o and k>l is set.

Next, the combustion peak angle (crank angle at which the cylinder pressure Pa becomes maximum) θp is detected at P, and the process proceeds to Pl+.

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

Further, in P6, the measured combustion period θC, which is the actual combustion period, is calculated from the ignition timing θi and the combustion peak angle θp according to the following equation (2) (see FIG. 7).

θC - θp - θi ... -■ However, θi: Crank angle corresponding to the ignition time θp: Crank angle at which the cylinder pressure Pa becomes maximum (combustion peak angle) θi and θp are shown in Fig. 7 (al). 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 as shown in FIG.

In P, the product θC1 (θcl =
, XθC). This θC3 corresponds to the actual combustion rate parameter detected under reference conditions. Then Pl. The measured combustion period θC+ and the reference combustion rate parameter θ, under reference conditions. The difference Δθc from Δθc is calculated according to the following equation.

Δθ(,=θcl−θ,. ・・・・・・■In other words, here, the combustion rate parameter θ when using the standard fuel under standard conditions. and the combustion rate parameter of the fuel actually used. (Total and 1μ, '5°1, baking period) θC
7 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 ΔθC3″ of ΔθC1 at pH is calculated using the following formula ■
Calculate according to

m
m (current Δθo1)...
■ However, m: constant P, □ looks up the fuel property parameter T, based on the value of Δθ01'' from a table map having characteristics as shown in Fig. 8, and the value of T,. N
VM (non-volatile memory) Stores every day.

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. Therefore, it is possible to provide a fuel property determining device suitable for air-fuel ratio control, which has been desired in the past.

FIG. 9 is a flowchart showing a program for detecting the combustion peak angle θp, and this process corresponds to step P7 described in FIG. 5 above. This program is executed once every 2 degrees of crank angle.

First, PZI determines whether the current crank angle (piston position) θ corresponds to the compression top dead center TDC, and then
In the case of TDC, the analog signal representing the cylinder pressure pa is A/D converted at P2□ and stored as the cylinder pressure conversion value ADO.
Proceed to Z3. On the other hand, when θ≠TDC, jump P2□ and proceed to Puff.

In PZj, it is determined whether the crank angle θ is greater than or equal to the TDC excess value (TDC+α°) shown in FIG. This is set at 2° to 4°.This is because the peak of the cylinder pressure Pa due to combustion (hereinafter referred to as the combustion peak) appears after TDC, so an unfavorable zone of α is set to set the cylinder pressure Pa at TDC. This is to avoid mistakenly adopting it as the combustion peak value.

When θ<TDC+α°, that is, θ
DC) or TDC≦θ<TDC+α, the current routine ends. On the other hand, when θ≧TDC+α°, processing for detecting combustion peak angles after PZ4 is executed. First, it is determined by pza whether the crank angle θ exceeds the combustion peak angle determination limit value θe. θe is the crank angle at which it can be assumed that combustion in the cylinder has been sufficiently completed,
It is set to a predetermined value exceeding TDC (see FIG. 10).

The combustion peak is assumed to be between TDC and θe, and corresponds to this, for example, at points F+ and F2 shown in FIG. 10 (curve X represents different combustion conditions). Therefore, A of the cylinder pressure Pa for determining the combustion peak,
/D conversion processing is performed up to θθ.

When θ≦θe in F24, count θ with pzs θ
The counter is incremented, and the cylinder pressure pa at this time is A/D converted by pza to obtain a cylinder pressure conversion value ADl, which is stored. Next, the difference value ΔP between the converted cylinder pressure value ADl and A Do is determined using Phi, and the process proceeds to the 22nd. Difference value ΔP
is a positive value if the cylinder pressure Pa is increasing, and is negative if it is decreasing. Moreover, the value becomes very small near the combustion peak time. In P2B, the absolute value IΔP1 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. When 1ΔP1≦ΔPo, it is determined that the change in the cylinder pressure Pa is approximately flat, and at F29, the count value of the θ counter is stored as the combustion peak angle θp, and at F30, the cylinder pressure conversion value AD of this routine is ADO. to end the routine. On the other hand, when 1ΔPI>ΔP0, it is determined that the surface is not flat and the process proceeds to F3°.

Here, the cylinder pressure P satisfies the condition 1ΔP1≦ΔPa.
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. 1ΔP
The manner in which the actual cylinder pressure pa changes under the condition of 1≦ΔP0 can be summarized in the examples shown in FIGS. 11(a) to 11(c). 11th
Figure (a) shows the most common Pa change curve.

In this example, IΔP1≦ΔP after TDC.

The crank angle that satisfies the following conditions is θp, and the combustion peak angle can be easily determined. Figure 11(b), (
In c), when the load is low, a situation occurs where Pa becomes flat at two locations after TDC. In the case of Fig. 11(b), θ
Value PaTDC when cylinder pressure Pa1 is TDC when p
As the value becomes smaller than , a local minimum value Pat appears in the middle. However, in this case, Pa2 appears, so Pa
When t becomes the maximum value, θp can be identified. On the other hand, in the case of Fig. 11(c), no minimum value appears and the flat part Pa
After j is Pa corresponding to the combustion peak angle θp.

appears (P a, <p aj ). This is the case when the combustion pressure is very low, and in A/D conversion method 2, θ is actually
It becomes difficult to detect p.

Incidentally, it is possible to distinguish by performing differential processing of Pa, but
A little more accurate. However, pa uniformly decreases after TDC in this way only when the load is extremely low, and in this case, the detection of θp is stopped and the operating state B (engine speed N
and load Qa, ).

In this way, if θ is within the range of TDC+α° to 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 at F24, it is determined that the combustion in the cylinder has been sufficiently completed, and at F31, the average value of θp over the past few times is calculated, and the Finish this 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.

Therefore, according to this embodiment, a device that can directly detect fuel properties can be realized, and if this is applied to an air-fuel ratio control device,
It is possible to solve the problems of control deviations due to differences in fuel properties, which were pointed out in the conventional problems.

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 heaviness level of the fuel used is appropriately determined and the deviation from the target air-fuel ratio is appropriately corrected according to the degree of heaviness. When heavy 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. As a result, drivability is improved by preventing deterioration of combustion conditions! ! ! It is possible to significantly improve the fuel efficiency, cost, and exhaust emission characteristics, and to maintain the air-fuel ratio in an optimal state even when using inferior fuel.

Furthermore, this embodiment does not require special sensors or members, and conventional parts can be used as they are, so there is no need to modify the hardware of the device.

In other words, since it is possible to provide the device with only software support, it is possible to avoid complication of the device and increase in cost.

In the first embodiment described above, the combustion peak angle θp is calculated in order to detect the burning rate parameter, but the burning rate parameter may be detected by other methods, and this aspect will be described in the following second embodiment.
This will be shown in examples.

12 to 14 are diagrams showing a second embodiment of the present invention,
In this embodiment, the value of the cylinder pressure at a predetermined crank angle after TDC is used as the combustion rate parameter.

The hardware configuration of this embodiment is the same as that of the first embodiment, so a diagram of the hardware configuration will be omitted. Note that the program of this embodiment is executed for every unit crank angle (for example, 1°) after TDC.

In the program shown in FIG. 12, step P0 is a process for determining whether or not the engine is under a predetermined condition, and corresponds to the steps P1 to P of the first embodiment. If the predetermined conditions are not met, the subsequent processing is canceled (return) as in the first embodiment.

If the engine is under the specified conditions, T I)C at P4□
The latter crank angle θ is the predetermined discrimination crank angle θ.

Determine whether it is equal to or not. That is, in this step, the timing for detecting the in-cylinder pressure P for determining the combustion rate parameter is set, and is θ-θ. In this case, the process proceeds to the steps after P43. Here, the determined crank angle θ.

is a predetermined crank angle after TDC, for example, the crank angle θpmax that gives Pmax of light gasoline in FIG.
(This θpmax is a known value through actual measurement or the like). Therefore, in this example, θ
. is set to θpmax for light gasoline, but it may be set to any value as long as the difference in in-cylinder pressure (combustion pressure) due to fuel properties is noticeable.

Note that if the predetermined conditions are not met, the subsequent processing is canceled (return).

Next, at Pa3, the analog signal representing the cylinder pressure P when the crank angle θ is θ=θ is converted to/D and recorded as the cylinder pressure converted value Pθ0, and then the process proceeds to P44.

At Pa4, the basic injection iTp is looked mapped from a two-dimensional table map with θa and N as parameters. Then, in P4S, the cylinder pressure conversion value Pl normalized by the load at that time is calculated according to the following equation.

P,=Pθ. /Tp...■Here, the cylinder pressure conversion value Pθ changes depending on the state of the engine load (for example, intake air amount). is processed into a normalized parameter (Pθo/Tp) that excludes the influence of load. This standard 4ζ converted cylinder pressure conversion value P, represents the magnitude of the cylinder pressure based on the fuel actually used at that time, and the reference cylinder pressure conversion when using standard fuel, which will be described later in P. 46. Value P. The combustion rate parameter dp/dθ (however, d
Since θ is constant, dθ is omitted).

In P46, the reference cylinder pressure conversion value P o I P o
= func(N)) from the table map.

This reference cylinder pressure conversion value P0 is the value obtained by dividing the cylinder pressure conversion value Pθ when using standard fuel (that is, regular gasoline (T, -95,5"C) by the basic injection amount 'rp. , there is a slight change depending on the engine speed N.

Next, in P47, the temperature correction coefficient akz (kz = r
unc(TW)) is looked up from the table map shown in FIG. The temperature correction coefficient of 2 is for correcting the in-cylinder pressure conversion value, which changes depending on the engine temperature even if the fuel properties are the same, in accordance with the engine temperature Tw, and corresponds to the temperature correction coefficient of 1 in the first embodiment.

In pan, a combustion rate parameter ΔP based on the difference in cylinder pressure conversion values is calculated according to the following equation (2).

ΔP + = k z ・P, -P, ...
・■ However, PI Two-part internal pressure conversion value Po: Standard cylinder pressure conversion value As shown above, the size of the cylinder pressure conversion value has a certain correlation depending on the fuel properties (as the fuel becomes heavier, the value of Pθ. Therefore, if this in-cylinder pressure conversion value is accurately detected, the properties of the fuel can be appropriately determined.

Furthermore, at Pd2, the moving average ΔPI' of ΔP1 is calculated according to the following equation (2).

+□ (current Δp+)...■ However, m: constant pso, fuel property parameter T, based on the value of ΔP19. is looked up from a table map having the characteristics shown in FIG. 14, and this T is determined in PSI. The value of N
Store in VM (non-volatile memory) 18.

The above Paq, P. , PSI correspond to the processing of steps PzSP+□ and PI3 in the first embodiment, respectively.

In this way, by comparing the cylinder pressure conversion value depending on the properties of the fuel used with the cylinder pressure conversion value of standard fuel as a reference,
Similarly to the first embodiment, the fuel property parameters of the fuel used can be appropriately determined.

In addition to the effects of the first embodiment, this embodiment eliminates the need for the routine for calculating the combustion peak angle θp shown in FIG. Gender disappears. Therefore, the time required for the fuel property determination program is short, and the open time (off time) of the program can be sufficiently long. As a result, other programs such as ignition timing and air-fuel ratio control can be executed frequently during this period, which has the advantage of improving the accuracy of these controls.

Furthermore, by not performing processing every 2 degrees of crank angle, fuel property discrimination processing is possible up to a high rotation range.

FIG. 15 is a diagram showing a third embodiment of the present invention, which is the same as the second embodiment except that a step of detecting the in-cylinder pressure conversion value also when θ=TDC is added. be. In explaining this embodiment, steps that perform the same processing as in the second embodiment will be given the same numbers and their explanations will be omitted, and steps that are different will be given step numbers surrounded by O marks and their contents will be explained. .

In the program shown in Figure 15, after passing through Par, P, 1
It is determined whether the current crank angle θ corresponds to the compression top dead center TDC, and when θ=TDC, the analog signal representing the cylinder pressure P is changed A/D in P62 to obtain the cylinder pressure conversion value P.
After storing it as TDC, proceed to paz. On the other hand, θ≠TD
If it is C, jump to P6g and proceed to P4□.

Then, after P44, θ=θ at pai. cylinder pressure converted value Pθ at the time. and the cylinder pressure converted value PTDC when θ=TDC, the difference ΔPθ. is calculated according to the following formula (■).

ΔPθ. =Pθ. -Ptnc...■ That is, in this embodiment, Pθ of the second embodiment. ΔPθ instead of
. is used. In addition, in P64, in the same way as step P4S of the second embodiment, the cylinder pressure converted value ΔPθ normalized by the load is calculated according to the following formula [phase], and in P6S, the standard cylinder pressure converted value ΔPo (ΔP,=func (N ) ) from the table map.

ΔPθ=ΔPθ. /Tp ・Old... [phase] Furthermore,
P4? After that, in step P66, the combustion rate parameter ΔP1 is calculated according to the following equation (2) in the same way as step P4a of the second embodiment.

ΔP, = kz ・ΔPθ−Δpo ”””@However, k
2: Processing after the temperature correction coefficient is the same as in the second embodiment. In this way, in this embodiment, instead of processing the cylinder pressure conversion value Pθ as it is, the cylinder pressure conversion value PTa1l when θ=TDC is processed as follows:
Since the subsequent processing is performed using the difference ΔPθ between
Changes in cylinder pressure due to differences in fuel properties can be detected more clearly, leading to improved accuracy. Therefore, in this embodiment, in addition to the effects of the second embodiment, fuel property parameters that are even more positive and blind can be detected.

(Effects) According to the present invention, the combustion speed of the fuel used is detected from the combustion pressure of the engine, the fuel speed of the reference fuel is calculated from the operating state of the engine, and the properties of the fuel used are determined based on these two combustion speeds. Therefore, it is possible to provide a fuel property discriminating device that can accurately discriminate fuel properties at low cost.

As a result, if this device is applied to air-fuel ratio control of an internal combustion engine, it is possible to perform accurate air-fuel ratio correction and achieve effective air-fuel ratio control.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 11 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 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. 5 is a flowchart showing the fuel property discrimination program, FIG. 6 is a table map of the temperature correction coefficient of 1, FIG. 7(a) is a diagram showing the reference crank angle signal, and FIG. b) is a diagram showing the change in cylinder pressure in relation to the reference crank angle signal, and FIG. 8 is the fuel property parameter T. Figure 9 is a flowchart showing the program for detecting the combustion peak angle.
Figure 10 is a diagram showing the change in cylinder pressure, Figure 11 (a)
~(C) are diagrams each showing general changes in cylinder pressure to explain the effect, and Figures 12 to 14 are diagrams showing the second variation of the present invention.
FIG. 12 is a flowchart showing a program for determining the fuel properties, FIG. 13 is a table map of the temperature correction coefficient of 2, and FIG. 14 is the fuel property parameter T. FIG. 15 is a flowchart showing a fuel property determination program according to a third embodiment of the present invention. 1... Engine, 7... Air flow meter (load detection means), 9
......Pressure sensor (pressure detection means), 11...
...Crank angle sensor (rotation speed detection means), 12...
...Water temperature sensor (temperature detection means), 14...
- Control unit (burning rate detection means, calculation means, discrimination means).

Claims (1)

[Scope of Claims] a) Pressure detection means for detecting the combustion pressure of the engine; b) Rotation speed detection means for detecting the engine speed; c) Load detection means for detecting the engine load; d) e) a combustion speed detection means for calculating the combustion speed of the fuel used based on the output of the pressure detection means; and f) a combustion speed detection means for calculating the combustion speed of the fuel used based on the output of the pressure detection means; 1. A fuel property discriminating device comprising: computing means for computing a combustion rate; and g) discriminating means for discriminating properties of fuel used in an engine based on the combustion rate of the used fuel and the combustion rate of a reference fuel.