JPH02259251A - Combustion control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress vehicle surge within a fixed value so as to obtain smooth drivability by always calculating a graphic mean effective pressure being based on an output of an in-cylinder pressure sensor, comparing a calculated result in its standard deviation or change rate with a target value performing correction and determining a fuel injection pulse width. CONSTITUTION:A standard deviation sigmapi(or change rate) 23 of a target graphic mean effective pressure Pi is decided from a basic fuel injection amount Tp, calculated by a basic fuel injection amount calculating means 21 being based on an engine speed Ne and an intake air amount Q, and the engine speed Ne. While calculating an in-cylinder pressure value Ptheta in each crank angle by an in-cylinder pressure value calculating means 24, from its calculating result, the graphic mean effective pressure Pi is calculated by a graphic mean effective pressure calculating means 25. A standard deviation Pim of the graphic mean effective pressure is calculated by a standard deviation calculating means 29 while deciding an operative condition by an operative condition decision means 28 being based on the Pi, Ne and a change rate of throttle opening. At the time of deciding a steady operative condition in the decision means 28, sigmaPi and Pim are compared with each other and corrected in a correction amount decision means 30, on the contrary, at the time of deciding an acceleration operative condition, an injector 9 is controlled so as to increasingly correct a fuel injection pulse width.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention calculates the standard deviation of the indicated average effective pressure based on the in-cylinder pressure value of each cylinder, and corrects the fuel injection pulse width based on the standard deviation of the indicated average effective pressure. The present invention relates to a combustion control device for an internal combustion engine that can improve combustion by controlling combustion fluctuations in the operating state of the internal combustion engine to a set target level.

[Conventional technology]

Generally, combustion control devices for internal combustion engines detect the intake air amount using an air flow meter and calculate the fuel injection amount based on this, but it is difficult to perform appropriate combustion control.

Therefore, a method has been proposed in which the in-cylinder pressure value in the cylinder is directly detected, the intake air amount is calculated based on this, and the appropriate fuel injection amount is set. However, when a compression pressure sensor is used to detect the in-cylinder pressure value in this method, detecting the in-cylinder pressure as an absolute value causes a problem of drift, which is inconvenient.

Conventionally, as shown in Japanese Patent Application Laid-Open No. 61-55336, the in-cylinder pressure value is detected every ignition cycle, and the air-fuel ratio of the engine is set to LBT (the leanest air-fuel ratio to maximize the generated torque). There is known prior art that attempts to improve combustion by performing feedback control so that the

[Problem to be solved by the invention]

However, in the prior art described above, maximum torque can be controlled by increasing or decreasing the air-fuel ratio (fuel injection amount) in a certain steady state, but control due to combustion fluctuations is not taken into account at all, so the maximum torque cannot be obtained. However, the torque fluctuation may become larger than the target value, and control in transient operating states such as during acceleration is not possible, so air-fuel ratio control using the exhaust sensor is insufficient to control the fuel injection amount. Therefore, there is a problem that the indicated mean effective pressure (IMEP) that controls the fuel injection amount becomes too small in a transient driving state, and a surge phenomenon occurs in the vehicle.

The present invention has been proposed to address the above-mentioned problems. Therefore, the indicated mean effective pressure is constantly calculated from the detection signal from the in-cylinder pressure sensor of the cylinder, and based on this, the standard deviation of the indicated mean effective pressure or its fluctuation is calculated. By calculating the internal combustion rate and controlling combustion fluctuations to the set target level in steady-state driving conditions, and by increasing the amount in moderately accelerating driving conditions, it is possible to suppress the surge level when the vehicle is running to below the target value. The object of the present invention is to provide a combustion control device for an engine.

[Means to solve the problem]

To achieve this objective, the present invention includes an in-cylinder pressure sensor that detects the combustion pressure in the cylinder, a crank angle sensor that detects the crank angle, a cam angle sensor or a crank angle sensor that detects the engine speed, and an intake sensor that detects the combustion pressure in the cylinder. In a combustion control device comprising an air flow sensor that detects the amount of air, a throttle opening sensor that detects the throttle opening, and a control unit that controls the amount of fuel injection from an injector based on output signals from each of the above sensors. , the control unit includes a basic fuel injection amount calculation means for calculating a basic fuel injection amount based on the engine rotation speed and intake air amount detected by the cam angle sensor or crank angle and the air flow sensor, and a basic fuel injection amount calculation means. target value determining means for determining a target indicated average effective pressure standard deviation or indicated average effective pressure fluctuation rate based on the quantity and engine speed;
In-cylinder pressure value calculation means for calculating an in-cylinder pressure value for each crank angle based on the engine speed, crank angle, and in-cylinder pressure detected by the cam angle sensor, crank angle sensor, and in-cylinder pressure sensor; Indicated average effective pressure calculation means that calculates the indicated average effective pressure from the cylinder pressure value calculation means, the indicated average effective pressure from the indicated average effective pressure calculation means, and the engine speed and throttle from the cam angle or crank angle sensor. an operating state determining means for determining the operating state based on the rate of change in output from the opening sensor; a standard deviation calculating means for calculating the standard deviation of the indicated average effective pressure calculated by the indicated average effective pressure calculating means; When the steady operating state is determined based on the output signal from the operating state determining means, the standard deviation of the indicated average effective pressure calculated by the standard deviation calculating means or its fluctuation rate and the target value determined by the target value determining means are calculated. The present invention is characterized by comprising a correction means for performing a comparison correction, and an increase correction means for increasing the fuel injection pulse width when a slow acceleration driving state is determined based on the output signal from the driving state determining means.

[For production]

In such a configuration, the indicated mean effective pressure is constantly calculated based on the in-cylinder pressure value detected by the in-cylinder pressure sensor, and during steady operation, the standard deviation of the indicated mean effective pressure or its fluctuation rate is compared with the target value. to correct the fuel injection pulse width. Further, in a slow acceleration driving state, a predetermined increase correction is performed.

Therefore, combustion fluctuations during steady operation can be controlled to the set target level, and a drop in the indicated mean effective pressure is prevented during slow acceleration operation, so vehicle surges can be suppressed and comfortable drivability can be achieved. can.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes an engine body, and an intake boat 3 and an exhaust boat 4 are communicated with a combustion chamber 2a of a cylinder head 2, respectively. At the openings of the intake boat 3 and the exhaust boat 4, an intake valve 3a and an exhaust valve 4a are installed, respectively, which open and close at predetermined timing.

An intake system B having a throttle valve 5 is provided upstream of the intake boat 3, and a collector chamber 7 is provided downstream of the throttle valve 5.

An injector 9 is provided in the intake manifold 8 on the downstream side of the collector chamber 7, located near each intake boat 3 of the engine main body 1.

Further, the throttle valve 5 is equipped with a throttle opening sensor l.
O is a crank angle sensor 11 that detects the crank angle of the engine on the crank rotor la of the engine body (2), a cam angle sensor 13 that detects cylinder discrimination and engine rotation speed on the cam rotor 12a of the camshaft 12, and an air cleaner 14. Air flow meter 15 installed on the downstream side of
An air flow sensor 16 is installed in the cylinder head 2 of the engine body 1, and a piezoelectric cylinder pressure sensor 17 is installed in the cylinder head 2 of the engine body 1, facing into each cylinder.

and the throttle opening sensor 10. Crank angle sensor 11. Cam angle sensor 13. Air flow sensor 1
The detection signal from the in-cylinder pressure sensor 17 and the signal amplified from the in-cylinder pressure sensor 17 via the amplifier circuit 18 are input to the control unit 20, respectively.

In the control unit 20, as shown in FIG. 1, the intake air ff1Q detected by the air flow sensor 16, the cylinder discrimination signal and the engine rotation speed Ne detected by the cam angle sensor 13 are input, and the basic fuel injection ff is inputted to the control unit 20.
It has a basic fuel injection amount calculation means 21 that calculates tTp,
The basic fuel injection amount Tp from the basic fuel injection amount calculating means 21 is output to the fuel injection pulse width determining means 22 which determines the actual fuel injection amount TI. Also, here, the signal of the basic fuel injection amount Tp from the basic fuel injection amount calculating means 21 and the engine rotation speed N detected by the cam angle sensor 13 are used.
e is input to the target value determining means 23, and the target standard deviation σpt of the indicated mean effective pressure PI, or the standard deviation σ
The ratio σ between pt and the average value P1g of the indicated average effective pressure P1
Indicated mean effective pressure P expressed by pi/P1s+l
The target variation rate of l is found from the map.

In addition, each cylinder is controlled by signals of the engine speed Ne detected by the cam angle sensor 13, the crank angle θ detected by the crank angle sensor 11, and the cylinder pressure P detected by the cylinder pressure sensor 17 of each cylinder. Cylinder pressure value calculation means 24 that calculates cylinder pressure value Pθ for each crank angle
The signal of the cylinder pressure value Pθ calculated by the cylinder pressure value calculation means 24 is used to calculate the indicated average effective pressure Pl of the cylinder pressure at all times during steady operation other than during startup and warm-up operation. The indicated mean effective pressure is inputted to the indicated mean effective pressure calculation means 25.

The signal of the indicated mean effective pressure P1 calculated by the indicated mean effective pressure calculation means 25 is stored in the indicated mean effective pressure storage means 2.
6 and is stored. On the other hand, the throttle opening signal detected by the throttle opening sensor 10 is input to the throttle opening change rate calculation means 27 to calculate the throttle opening change rate dα/dt. , the intake air amount Q detected by the air flow sensor 16, the engine rotation speed Ne detected by the cam angle sensor 13, and the indicated mean effective pressure P1 calculated by the indicated mean effective pressure calculation means 25. The engine has an operating state determining means 28 to which the engine is inputted, and this operating state determining means 28 determines whether the operating state is a steady state or a transient state of slow acceleration, sudden acceleration, or deceleration.

That is, the rate of change IΔQ1 of the intake air amount Q, the rate of change 1ΔNel of the engine speed Ne, and the rate of change 1dα/dtl of the throttle opening are 1ΔQ≦AI and 1ΔNe l, respectively.
When ≦A2, l da /dt l≦A3, it is determined that the operating state is steady, and A1. A2. A3
is a constant value.

When the operating state determining means 28 determines that the operating state is steady, a signal is input to the standard deviation calculating means 29, where the standard deviation σpt of the indicated mean effective pressure pt is input together with the output signal from the indicated mean effective pressure storage means 26. Or the standard deviation σpt of the indicated mean effective pressure pt and the indicated mean effective pressure P
The fluctuation rate of the indicated mean effective pressure Pi is calculated from the ratio σp1/PIa+ with the average value PIm of 1, and the correction amount determining means 80
A signal is output.

In the correction amount determining means 30, the standard deviation σpl of the indicated mean effective pressure P1 determined by the target value determining means 23,
Alternatively, the correction amount β is determined based on the target value of the variation rate of the indicated mean effective pressure Pi and the variation rate σpi/Pfm of the indicated mean effective pressure P1 calculated by the standard deviation calculating means 29.

That is, the average value Pis is calculated from Pim-ΣPI/ from the latest indicated average effective pressure Pl immediately after the determination of the steady operating state, for example, from the memory value 200 cycles, and is the standard set in advance in the target value determining means 23. deviation σpt
is compared with the target value, and the correction amount β is determined by the correction amount determining means 30. In this case, the correction amount β by the correction amount determining means 30 is the standard deviation σpt of the indicated mean effective pressure pt,
Alternatively, if the fluctuation rate σpi/P1m of the indicated mean effective pressure pt is larger than the target value, the amount of fuel is increased, and if it is smaller, the amount of fuel is decreased.

Then, in the fuel injection pulse width determining means 22, the fuel injection pulse width T1 is determined as the sum value γ of the various correction amounts of the correction means 31.
, the correction amount based on the opening/closing valve delay correction term Ts of the injector 9 using the power supply voltage as a parameter, and the correction amount determining means 30
7l-Tp(1+β+
7) Corrected by +Ts, the drive unit 35 outputs a signal of the fuel injection pulse width Ti to the injector 9.

The above-described correction of the fuel injection pulse width is constantly performed as long as the steady state of operation is determined, and so-called feedback control is performed.

In addition, when the driving state determining means 28 determines that the acceleration is slow, the indicated average effective pressure Pi immediately before the slow acceleration determination is
n and the immediately preceding indicated average effective pressure P 1n-1 are compared, and when it is determined that Pin-Pln-1≦0, the increase correction determining means 32 determines the increase correction ΔT1;
When the signal of the increase correction ΔTi determined by the increase correction determination means 32 is input to the fuel injection pulse width determination means 22, the fuel injection pulse width Tl is increased by TI−T1n+ΔT1, and the output signal is used to drive the drive unit 35. It is output to the injector 9 via the injector 9.

Here, the above-mentioned Pin is determined by the driving state determination means 28.
This is the fuel injection pulse width immediately before the determination that ln-Pin-1≦0 was made, and the fuel increase measure at this time is the comparison value Pln-P1n- while the determination of the slow acceleration driving state continues.
This process is repeated until the value of 1 becomes positive or equal to or greater than a certain value.

Further, when the driving state determining means 28 determines that the driving state is a sudden acceleration driving state, the interrupt injection determining means 33 (asynchronous)
A signal is output to the drive unit 35, an asynchronous interrupt signal is output to the drive unit 35, and the injector 9 increases the amount of fuel.

Further, if the driving state determining means 28 determines that the vehicle is in a deceleration driving state, a signal is output to the fuel cut determining means 34, and a fuel cut to the injector 9 is performed via the drive unit 35.

Next, the operation of the control unit 20 will be specifically explained with reference to the flowchart in FIG.

First, in step 5101, the air flow sensor 16° cam angle sensor 13. Crank angle sensor 11. It was detected by the cylinder pressure sensor 17 and the throttle opening sensor IO. Intake air amount Q, engine speed Ne, crank angle θ,
The cylinder pressure P and throttle opening α are read,
In step 5102, the rate of change in throttle opening dα/d
Determine whether t is dα/dt≧0, and dα/dt≦0.
In this case, the process advances to step 5105. Step 5105
Now, compare the engine rotation speed Ne with the predetermined rotation speed N1,
When Ne≦N1, it is determined that the operating state is steady and the process proceeds to step 3.
Proceed to 107. In step 5107, the basic fuel injection f
Basic fuel injection ff1Tp from fi calculation means 21 and correction amount γ from correction means 31.

The signals of Ts and the correction amount β from the correction amount determining means 30 are input to the fuel injection pulse width determining means 22, and the fuel injection pulse width TI is determined by TI-Tp(1+β+γ)+Ts.

Further, when Ne≧N1 in step 5105, it is determined that the deceleration operation is in progress, and the process proceeds to step 3106. Step 8
At 10B, a fuel cut signal from the fuel cut determining means 34 is inputted to the drive unit 35 to perform a fuel cut.

If the throttle opening change rate dα/dt is dα/dt≧0 in step 5102, the process advances to step 8103, where the throttle opening change rate dα/dt is compared with a predetermined change rate number, and dα/dt is compared with a predetermined change rate number. When dt>K, it is determined that the vehicle is in a rapid acceleration driving state, and the process proceeds to step 3104.

In step 5104, the signal from the interrupt injection determining means 31 is output to the drive section 35 to perform asynchronous interrupt injection.

Also, if dα/dt<K in step 5103,
It is determined that the state is a slow acceleration driving state, and the process proceeds to step stog.

In step 8108, P in -P 1n-1>0 is determined from the average effective pressure Pin immediately before the determination of slow acceleration operation and the indicated average effective pressure value P 1n-1 immediately before that.
It is determined whether or not, and if P in -P In-L>O, the process advances to step 5107. In step 5107,
The non-feedback mode is entered and normal fuel injection is performed.

Above, step! If Pin-Pln-1≦0 in 3108, the process advances to step 5109. In step 5109, the signal of the increase correction ΔT1 from the increase correction determining means 32 is input to the fuel injection pulse width determining means 22, and the increase correction ΔT1 is added to the fuel injection pulse width Tin immediately before the determination, which is TI-Tin+ΔT1. Fuel increase will be implemented.

The fuel increase measure in step 5109 is repeated until Pln-Pln-1 in step 5109 becomes positive or a certain value or more, as long as the slow acceleration operation state of Pin-Pln-1≦0 continues in step 5108. .

Next, calculation of the indicated average effective pressure Pl based on the cylinder pressure value P detected by the cylinder pressure sensor 17 will be specifically explained with reference to the flowchart of FIG.

First, in step 5201, the crank angle sensor 11 determines the crank angle at the top dead center of the intake stroke at a reference angle θ.
The process proceeds to step 5202, where the cylinder pressure value Pθ calculated by the cylinder pressure value calculation means 24 based on the signal detected by the cylinder pressure sensor 17 of the engine is read.

Next, in step 8208, the crank angle θ-θR+2 (k+1) is read by the crank angle sensor 11, and the process proceeds to step 5204, where ΔV is calculated from the difference in crank angles.

Here, in step 5203, since the pulse of the cam angle sensor 13 is generated once when the crank angle is 2 revolutions, the crank angle is sampled every 2 degrees, and the stroke volume V and cylinder pressure P shown in FIG. 4 are sampled. Step 52
04 is the amount of change ΔV in cylinder internal volume for every 2 degrees of crank angle.
, and based on the amount of change ΔV in the cylinder internal volume calculated in step 5204, step
In 05, the indicated average effective pressure Pl is obtained from Pi+Δ■φPθ.

On the other hand, in step 8206, counting is performed (
(Reset to -0 when the engine key switch is turned on)
, the process advances to step 5207 to determine whether k is 360 or not.

If the result in step 5207 is -360, the process proceeds to step 8208, where the indicated mean effective pressure calculating means 25 calculates the indicated mean effective pressure P1. The indicated mean effective pressure pt calculated here is sequentially stored in the indicated mean effective pressure storage means 2B in step 5209, and when the number exceeds, for example, 200, the oldest data is deleted and the latest data is stored instead. The indicated average effective pressure P1 is stored.

Further, if k is not 360 in step 5207, the process returns to step 5202.

Furthermore, in step 5209, the indicated mean effective pressure P1
is stored in the indicated mean effective pressure storage means 26, the process proceeds to step 5210, where the indicated mean effective pressure pt and values are reset, and the process returns to step 5202 to repeatedly calculate the indicated mean effective pressure pt. Stored.

In this embodiment, the engine rotation speed is detected by the cam angle sensor, but it is of course possible to detect it by the crank angle or the pulse of the ignition coil.

As described above, the combustion control according to the present invention corrects the fuel injection pulse width TI by comparing the standard deviation σpt of the indicated mean effective pressure PI calculated from the in-cylinder pressure Pθ with a target value to compensate for combustion fluctuations in a steady operating state. In the case of slow acceleration operation, the average value P1n of the indicated average effective pressure immediately before the determination is made and the average value P1n-1 of the immediately preceding indicated average effective pressure. In view of this relationship, since fuel increase measures are properly carried out, a good combustion state is obtained, and the vehicle surge phenomenon due to the influence of the indicated mean effective pressure is reduced. .

〔Effect of the invention〕

As explained above, according to the present invention, the indicated average effective pressure is constantly calculated based on the in-cylinder pressure value detected by the in-cylinder pressure sensor, and the standard deviation or The fuel injection pulse width is determined by correcting the fluctuation rate of the indicated mean effective pressure by comparing it with the target value, and combustion control is performed. Therefore, the fluctuation of the indicated mean effective pressure, which is the cause of vehicle surge in steady-state operating conditions, is reduced to the set target level. Since it can be controlled, vehicle surge can be suppressed within a certain value and smooth drivability can be obtained.

Furthermore, since the fuel injection pulse width is increased and corrected even during mild acceleration driving conditions, a decrease in the indicated mean effective pressure is prevented, improving combustion and reducing the surge level during actual vehicle driving to below the target value. It can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of a control unit showing a combustion control device for an internal combustion engine according to the present invention, FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 3 is a flowchart, and FIG. An indicator diagram of stroke volume and cylinder pressure, and FIG. 5 is a flowchart showing calculation of the indicated average effective pressure. lO... Throttle opening sensor, ll... Crank angle sensor, 13... Cam angle sensor, 16... Air flow sensor, 17... Cylinder pressure sensor, 20... Control unit, 21... ... Basic fuel injection amount calculation means, 22 ... Fuel injection pulse width determination means, 23 ...
Target value determining means, 24... Cylinder pressure value calculating means, 25
... Indicated average effective pressure calculating means, 27... Throttle opening change rate calculating means, 28... Operating state determining means,
29...Standard deviation calculating means, 30...Correction amount determining means, 32...Increase correction determining means.

Claims (1)

[Claims] A cylinder pressure sensor that detects combustion pressure in a cylinder, a crank angle sensor that detects a crank angle, a cam angle sensor or a crank angle sensor that detects engine speed, and an intake air amount. In a combustion control device that includes an air flow sensor, a throttle opening sensor that detects a throttle opening, and a control unit that controls the amount of fuel injection from an injector based on output signals from each of the sensors, the control unit includes: The basic fuel injection amount calculation means calculates the basic fuel injection amount from the engine rotation speed and intake air amount detected by the cam angle sensor or crank angle and the air flow sensor, and the basic fuel injection amount and the engine rotation speed. target value determining means for determining a target indicated average effective pressure standard deviation or indicated average effective pressure fluctuation rate; and engine rotation speed, crank angle, and cylinder pressure detected by the cam angle sensor, crank angle sensor, and cylinder pressure sensor. an in-cylinder pressure value calculation means for calculating an in-cylinder pressure value for each crank angle based on the in-cylinder pressure value calculation means; an indicated average effective pressure calculation means for calculating an indicated average effective pressure from the in-cylinder pressure value calculation means; an operating state determining means for determining the operating state based on the indicated average effective pressure from the effective pressure calculating means, the engine speed from the cam angle or crank angle sensor, and the output change rate from the throttle opening sensor; a standard deviation calculating means for calculating the standard deviation of the indicated average effective pressure calculated by the effective pressure calculating means; and a standard deviation calculating means for calculating the standard deviation of the indicated average effective pressure calculated by the standard deviation calculating means when the steady operating state is determined based on the output signal from the operating state determining means. a correction means for comparing and correcting the standard deviation of the indicated average effective pressure or its fluctuation rate with the target value determined by the target value determining means; 1. A combustion control device for an internal combustion engine, comprising: an increase correction means for increasing the fuel injection pulse width.