JP2656486B2 - Control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for an internal combustion engine, and more particularly to a control device suitable for a spark ignition engine.

[Conventional technology]

The conventional device is, as described in JP-A-59-113269,
In synchronization with the rotation speed fluctuation, the air amount, the fuel amount, and the ignition advance angle of the engine were corrected to prevent the vibration of the engine. But,
No consideration has been given to the fact that the amount of fresh gas changes due to fluctuations in the amount of residual gas, causing combustion fluctuations.

The conventional device is, as described in JP-A-60-26131,
Although the air-fuel ratio was corrected for the rotational speed fluctuation, no consideration was given to the fluctuation of the residual gas amount.

[Problems to be solved by the invention]

In the above prior art, no consideration is given to the modification of the control variable with respect to the fluctuation of the residual gas, so that the flywheel is increased to reduce the fluctuation in the rotation speed, or the change in the rotation speed is detected as in the prior art. However, even if the control variables are modified, there is a problem that the combustion fluctuation in each cycle is not reduced.

An object of the present invention is to reduce combustion fluctuation of an internal combustion engine.

Another object of the invention is to increase the lean burn limit of an internal combustion engine. By increasing this limit, fuel economy can be reduced and harmful exhaust components such as nitrogen oxides, carbon monoxide, and hydrocarbons can be significantly reduced.

By reducing combustion fluctuations, engine and vehicle vibrations are reduced,
Ride comfort is improved.

Conventionally, vibration has been detected, the air-fuel ratio has been corrected, and the engine has been maintained at the lean combustion stability limit. However, no consideration has been given to reducing combustion fluctuations in each cycle of a lean mixture region. In the present invention, the combustion fluctuation in the lean mixture region is reduced,
Increase stability limit.

[Means for solving the problem]

The object is to provide a residual gas estimating means for estimating a residual gas mass remaining without being exhausted to a combustion chamber of an internal combustion engine, and an operating state of the internal combustion engine based on the residual gas mass estimated by the residual gas estimating means. Operating device control means for controlling an operating device for changing the operating device, wherein a rotation increasing rate of a predetermined rotation angle during a power stroke of the internal combustion engine is detected from the rotation of the internal combustion engine from the rotation of the internal combustion engine. A rotation rise rate detection means, wherein the residual gas estimation means includes a storage means for previously storing the residual gas mass with respect to the rotation rise rate, and the storage means stores the residual gas mass from the rotation rise rate detected by the rotation rise rate detection means. This is achieved by estimating the residual gas mass by means.

[Action]

 The experiments revealed the following:

The amount of residual gas depends on the previous combustion. When the temperature of the gas at the end of the exhaust stroke is low, the density of the residual gas is large and the residual gas amount is large. If the amount of residual gas is large,
When the intake pressure is constant, the fresh air amount decreases. When the volume of the intake pipe is extremely small, the intake pressure immediately increases, and the amount of fresh air is restored.However, when the volume of the intake pipe is large, the increase in intake pressure is delayed, and the amount of fresh air remains small. Return to the state. As a result, combustion is delayed, the temperature of gas at the end of the next exhaust stroke increases, and the amount of residual gas decreases. As the residual gas amount decreases, the fresh air amount in the next stroke increases. As described above, even when there is no rotation speed fluctuation, the combustion fluctuation occurs due to the fluctuation of the fresh air amount, and the conventional control method is presented before these facts are revealed. Helpless for reduction.

The above phenomenon can be simply described by mathematical expressions as follows.

The relationship between the residual gas density and the gas density in the intake pipe is Here, V _m: volume of the intake pipe gamma _p: gas density A of the intake pipe, B: constants gamma _e: As shown in the residual gas density, to Zant gas density gamma _e, the volume V _m fraction of the intake pipe Only, the change of the gas density γ _p in the intake pipe is delayed.

On the other hand, since γ _e changes after the change in fresh air and the change in combustion, Here, E and C: constants hold. When equations (1) and (2) are combined, Becomes As is well known in equation (3), a second-order vibration equation
Configure the vibration system.

When the gas density γ _p is small, the fresh air amount is small, and the combustion is delayed. Flame propagation may be delayed due to a delay in firing, and the explosion process may be terminated without completing combustion. At this time, the combustion temperature is low, gamma _e increases. The value of C in the expression (2) becomes negative, and the vibration becomes easy.

Further, when γ _p decreases, the flame propagation stops halfway, and the fresh air sharply increases. However, at this time, although the amount of fresh air is reduced, the amount of residual gas in the residual gas is increased, so that it acts to stop combustion and increase γ _p .

Therefore, when the residual gas is extremely large, the ignition timing is delayed to prevent a sudden increase in torque.

The cylinder wall has a heat capacity, which also causes the delay of the equation (2).

When the amount of residual gas is large, the amount of fresh air becomes relatively small, so that combustion is almost delayed. In order to avoid this, control variables such as the ignition timing are corrected in accordance with the residual gas amount, the operation is performed so as to prevent the combustion from being delayed, and to prevent the fluctuation of the residual gas amount in the next cycle.

The number of revolutions of the engine is detected by the revolution number detecting means, and the residual gas amount is estimated by the residual gas estimating means based on the detected information. The relationship between the rate of rotation increase during the explosion process and the residual gas amount is determined in advance by experiments, and this is stored in the residual gas estimating means, and the residual gas amount is determined based on the stored value.

Next, the relationship between the residual gas amount and the correction value of the ignition timing was obtained,
This is stored in advance in the control variable correction means.
The estimated residual gas value is input to the correction means to obtain a corrected value of the ignition timing, and the ignition timing is corrected based on the corrected value. Thereby, combustion fluctuation can be prevented. Even in the lean gas mixture region, even when the residual gas amount greatly changes every cycle, combustion fluctuations can be avoided.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. In FIG. 1, an internal combustion engine 1 is composed of a normal gasoline engine. A rotation speed detecting means 2 is connected to the internal combustion engine 1. The means 2 is an optical encoder in which a slit is provided for each crank angle of 1 degree. Residual gas estimation means 4, control variable correction means 3, control variable control means 5
Is composed of a microprocessor. A top dead center mark detection slit of the engine 1 is added to the rotational speed detecting means 2.

The signal passing through the slit of the detecting means 2 is input to the estimating means 4, and the relationship between the time t _b and γ _e required to rotate 90 degrees from the top dead center (FIG. 2) is determined by the estimating means. 4
Is stored in the storage device ROM. If t _b is large, combustion is delayed, and γ _e temporarily decreases and then increases. The value of γ _e of the estimating means 4 is input to the correcting means 3. The storage device ROM of the correcting means 3 has γ _{e in} FIG.
And the correction value Δθ of the ignition timing are stored. γ
_{When e} is large, the fresh air amount is small, Δθ is increased, and the ignition timing θ is advanced at the ignition timing (advance angle) θ = θ ₀ + Δθ. The storage device of the control means 5 stores the relationship between the rotational speed and θ ₀ , obtains θ = θ ₀ + Δθ, and controls the ignition timing of the engine 1.

Hereinafter, the operation of the embodiment of FIG. 1 will be described. Detecting means 2
Seek Yotsute, a t _b of each cycle. When t _b is large, the explosion is late, the combustion is delayed, and therefore, once γ _e
Becomes smaller. Furthermore, when t _b is increased, the temperature is lowered by incomplete combustion, gamma _e increases (Figure 2). T _b is input to the estimating means 4 to determine γ _e . Next, this γ _e is input to the correction means, and Δθ is determined using the relationship shown in FIG.
This Δθ is input to the control means 5 to obtain θ. The ignition timing of the engine 1 is controlled by this θ. When the amount of residual gas is large, that is, when _γe is large, the amount of fresh air in the next cycle is small, so that the ignition timing θ can be advanced and the delay of combustion can be avoided.

FIG. 4 shows a control flowchart for correcting the ignition timing. A correction of Δθ is made to the optimal meeting time θ ₀ stored in the ROM in advance. θ ₀ is detected using the rotation speed and the suction negative pressure or the rotation speed and the basic injection pulse width. Here, the basic injection pulse width T _p is It is.

FIG. 5 shows a control timing chart. The ignition timing correction amount Δθ ₁ is obtained from tb ₁ in the explosion stroke. To correct the ignition timing of the next explosion stroke using the Δθ ₁ of this request.

As the input signal of the residual gas estimating means 4, the temperature of the combustion gas at the end of the exhaust stroke can be used in addition to the rotation speed shown in FIG. Install a platinum thermometer near the exhaust valve,
To measure the T _g. The relationship between γ _e and T _g (FIG. 6) is stored in advance in the storage device of the estimating means 4, and based on this, γ
_e can be obtained. FIG. 7 shows a flow chart.

Further, the intake pipe pressure P can be used as an input signal of the residual gas estimating means 4. Deviation value Δ of intake pipe pressure P
The relationship between P and γ _e (FIG. 8) is determined in advance by the estimation means 4.
Γ _e can be obtained based on this. FIG. 9 shows a flow chart.

Residual gas amount increases, gamma if _e is large, the fresh air amount is decreased, when the throttle valve opening degree is constant, the intake pipe pressure P
Increase. That is, ΔP increases.

Above, t _b, T _g, the value of ΔP, since also affected by the rotational speed, separately, a rotation number detecting means 2 detects the rotational speed to remove the influence of the rotational speed, taking only the residual gas fraction put out.

The control variable correction means 3 includes a correction value Δθ of the ignition timing.
Besides, it is also possible to use a correction value Delta] Q _a of設料amount correction value Delta] Q _f air quantity. The fuel is supplied to the engine 1 by a fuel injection valve, and the fuel amount is corrected by controlling the valve opening time. If γ _e is large, increase ΔQ _f and
Increase the amount of fuel per intake stroke to avoid fuel delays due to increased residual gas (Figure 10). This greatly reduces the cycle-to-cycle variation of the fuel. FIG. 11 shows a flow chart. FIG. 12 shows a timing chart. Calculate ΔQ _f1 from tb ₁ and correct the fuel amount.

When fuel is preliminarily mixed with air and supplied to a cylinder as in a carburetor, the supplied fuel amount is proportional to the fresh air amount. If the but connexion, gamma _e is large, open throttle valve, increasing the correction value Delta] Q _a of air quantity, (Figure 13) increases the intake pipe pressure, Yotsute to increase the density of the fresh air, the gamma _e It is possible to prevent a decrease in the fresh air amount due to the increase, and to reduce the fluctuation of the fuel for each cycle. FIG. 14 shows a flow chart.

Although the above description has been mainly directed to a single cylinder engine, it can be similarly applied to a multi-cylinder engine. The same applies to diesel engines. At this time, the fuel injection timing becomes the control variable instead of the ignition timing.

The fuel injection timing is corrected according to the relationship between the residual gas density and the fuel injection timing shown in FIG. If the residual gas amount is large, the combustion is delayed, so that the fuel may be injected earlier.

 FIG. 16 shows a flow chart.

FIG. 17 shows an example in which the present invention is applied to a fuel injection gasoline engine. The fuel amount is controlled by the solenoid valve 6. The rotation speed is obtained by using the angle pulse signal of the crank angle sensor 7 (FIG. 18). A stroke discrimination signal for detecting top dead center is output to the crank angle sensor at top dead center and bottom dead center. By making one of the signals output longer in time with respect to the other signal, each process can be distinguished.

Using this stroke determination signal and the angle signal, the top dead center of the explosion stroke can determine the time t _b required for the 90-degree rotation.

Using this t _b and n, gamma _e has been stored in the ROM, Δθ, ΔQ
the value of _f to search, θ, to modify the Q _f.

In the context of t _b and gamma _e as shown in FIG. 2, gamma _e
Has two values for t _b . t _b is gamma _e is greatly reduced, the the t _bc t _b when the increase again. Since t _bc is determined by the rotation speed and the air-fuel ratio, if it is stored in advance in the ROM, t _bc can be obtained according to the operating conditions. If t _b is greater than t _bc , the residual gas is too much and misfires, so the amount of gas in the mixture increases and the fuel speed increases.
_Vc increases, and the exhaust gas temperature _Tg decreases.

FIG. 20 shows a control flow chart. RPM, A /
F, obtains a t _bc from t _b, t _b is the case t _bc smaller obtains the ignition timing correction amount [Delta] [theta] ₁ from Matsupu 1, t _b is the ignition timing correction amount [Delta] [theta] ₂ from Matsupu 2 larger than t _bc Ask.

As shown in FIG. 21, Map 1 and Map 2
Increases Δθ with γ _e , and in Map 2 it decreases with γ _e . That is, in the operating range where no misfire occurs, the ignition timing is advanced with the increase in the residual gas amount. On the other hand, in an operating range where a misfire occurs, the ignition timing is delayed along with an increase in the residual gas amount in order to prevent a sharp rise in torque.

In the air metering method shown in FIG. 22, the amount of air detected by the air flow meter (this is always the amount of air passing through the throttle
n), the fuel injection amount _GfL is determined as follows.

Here, α ₀ is the set air-fuel ratio, and Ne is the engine speed.

Since gin is constant under the speed of sound, Becomes P _B is the intake pressure, _Ra is the gas constant of air, T _B is the intake air temperature, V _ST is the stroke volume, η _v is the volumetric efficiency, and the subscript 0 represents the idle equilibrium state.

On the other hand, the cylinder intake air amount G _acy is Becomes

Therefore, the air-fuel ratio α of the air-fuel mixture sucked into the cylinder
_cy is Becomes That is, the air-fuel ratio fluctuates, and the engine tends to become unstable. That is, if η _v changes due to the residual gas amount or the like, the air-fuel ratio changes, and as a result, the rotation speed increases.

Therefore, the fuel injection amount G _fL given that Α _cy is not affected by η _v .

here, There is a relationship. Δ represents fluctuation. N ゜ is the time derivative of N, and K ₁ is a constant. According to this equation, when the residual gas amount is large, the combustion is slowed down, so that the engine torque is reduced. Since the relationship between the torque and the number of revolutions is Te = IeN ゜, this indicates that N ゜ becomes smaller.

Thank you If it transforms Therefore, the fuel injection amount G _fL is Like K ₂ is a constant.

Pressure metering system as well, the fuel injection amount G _fD is defined by _{G fD = K D P B η} v N e. K _D is a constant.

Therefore, the air-fuel ratio α _cy That is, it is understood that the pressure measurement method is not affected by the residual gas.

The above explanation was for the case where there was no fuel transportation delay,
Even when there is a delay in injection, fluctuations in the number of revolutions can be reduced by controlling the fuel amount in the same manner. The time at which fuel is injected is denoted by i-n, and the time at which fuel is sucked into the cylinder is denoted by i.

In the air metering method here, The amount of fuel is controlled as follows.

In the pressure measurement method, G _fDi-n = K _D P _Bi η _vi N _ei where Becomes illusion detects the eta _v from Matsupu of P _B and N _e, the fuel from the value at the time of eta _vi-n to estimate the value of eta _vi when drawn into the cylinder.

[Effect of the Invention] According to the present invention, the state of the residual gas in each cycle is estimated, and the control variables of the engine such as the fuel amount and the ignition timing can be corrected based on the estimated value. Combustion fluctuations accompanying fluctuations in fresh air volume due to fluctuations in air volume are avoided,
The generated torque and rotation speed fluctuation in each cycle of the engine are reduced from 20% to within 3%.

Further, since a delay in the combustion accompanying the increase in the residual gas amount is avoided, the lean burn limit air-fuel ratio increases from 22 to 25. This increase in air-fuel ratio reduces fuel consumption by 5%, nitrogen oxides by 50%, carbon monoxide by 10%, and hydrocarbons by 20%.

[Brief description of the drawings]

FIG. 1 and FIG. 17 are configuration diagrams of one embodiment of the present invention, and FIG.
FIG. 3, FIG. 6, FIG. 6, FIG. 8, FIG. 10, FIG.
FIG. 15, FIG. 18, FIG. 18, FIG. 19, FIG. 21, and FIG. 22 are explanatory diagrams of the operation, FIG. 4, FIG. 7, FIG.
The drawing is a control flow chart, and FIGS. 5 and 12 are control timing charts. DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Revolution detection means, 3 ... Control variable correction means, 4 ... Residual gas estimation means, 5 ... Control variable control means, 6 ... Solenoid valve, 7 ... Crank angle sensor .

Claims (1)

(57) [Claims] 1. A residual gas estimating means for estimating a residual gas mass remaining without being exhausted into a combustion chamber of an internal combustion engine, and an operation of the internal combustion engine based on the residual gas mass estimated by the residual gas estimating means. Operating device control means for controlling an operating device for changing a state, a control device for the internal combustion engine, comprising: detecting a rotation increase rate of a predetermined rotation angle during an explosion stroke of the internal combustion engine from the rotation of the internal combustion engine. The residual gas estimating means includes a storage means for storing the residual gas mass with respect to the rotational rise rate in advance. A control device for an internal combustion engine, wherein the residual gas mass is estimated by a storage means.