JPH0739816B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

The present invention relates to a fuel supply amount control device for an internal combustion engine.

[Conventional technology]

In an internal combustion engine, for example, a fuel injection type internal combustion engine, a fuel supply amount is calculated according to various operating conditions of the engine, and a fuel injection valve is driven so that the calculated amount of fuel is supplied. Although the engine load is an operating condition, it is usual to detect the intake air amount-rotational speed ratio as a load representative factor. The intake air amount is measured by an air flow meter or the like. However, the detection value of a volume flow type intake air amount detector such as an air flow meter does not transiently represent an accurate state of the intake air amount. That is, in the transient state (acceleration) in which the throttle valve is driven from closed to open, the air flow meter measures not only the amount of air filling the engine combustion chamber but also the amount of air filling the intake pipe from the downstream side of the throttle valve to the combustion chamber. measure. This means that the air flow meter measures a value larger than the amount of air actually supplied to the engine as the intake air amount (overshoot). Conversely, a transient state (deceleration) in which the throttle valve is driven from open to closed
Then, it is impossible to measure the fuel that enters the combustion chamber and is filled in the intake pipe from the throttle valve to the combustion chamber. That is, the air flow meter measures a value smaller than the amount of air actually supplied to the engine as the intake air amount (undershoot). Therefore, in order to correct the measured value of the air flow meter to the actual intake air amount value required by the engine during a transition, the rate of change in the measured value of the air flow meter matches the actual change rate of the intake air amount required by the engine. In order to do so, a blunting process (so-called annealing) of the air flow meter measurement value is performed.

[Problems to be solved by the invention]

In the prior art, it was determined by detecting one specific operating state such as a blunting rate (attenuation coefficient) throttle valve opening, a rate of change of the throttle valve opening, a rate of change of the rotational speed (for example, (Kaisho 59-170442). However, it is not possible to accurately compensate the intake air amount detected by the air flow meter in the transient state by simply determining the moderating coefficient under one type of engine operating condition. This becomes a particular problem in an internal combustion engine with a supercharger in which the volume of the intake pipe from the throttle valve to the combustion chamber is large. Therefore, there is a problem that the deviation of the air-fuel ratio becomes large and the emission, drivability and fuel consumption rate deteriorate.

[Means for solving problems]

In FIG. 1, the fuel control system for an internal combustion engine according to the present invention is
Fuel supply means 1 for supplying fuel to the internal combustion engine, and intake air amount detection means 2 for detecting the intake air amount of the internal combustion engine
And a rotation speed detection means 3 for detecting the rotation speed of the internal combustion engine,
Means 4 for calculating the ratio between the intake air amount detected by the intake air amount detection means 3 and the rotation speed detected by the rotation speed detection means 3, and the change ratio of the intake air quantity-rotation speed ratio A first smoothing coefficient calculating means 5 for calculating a first smoothing coefficient so as to decrease together with an increase, and a second smoothing coefficient so as to decrease from the engine speed as the speed increases. The second smoothing coefficient means 6 and the calculated intake air amount-rotational speed ratio are corrected by multiplying this by the first and second smoothing coefficients, and then the fuel amount to be supplied to the internal combustion engine is calculated. The fuel supply amount calculation means 7 is configured to operate.

[Action]

The intake air amount detecting means 2 detects the intake air amount of the combustion engine,
The rotation speed detection means 3 detects the rotation speed of the internal combustion engine.

The intake air amount-rotation speed ratio calculation unit 4 calculates the intake air amount-rotation speed ratio from the intake air amount detected by the intake air amount detection unit 2 and the rotation speed detected by the rotation speed detection unit 3.

The first smoothing coefficient calculation means 5 calculates the first smoothing coefficient from the change rate of the intake air amount-rotational speed ratio so as to decrease with the increase of the change rate, and the second smoothing coefficient calculation means 6
Calculates the second smoothing coefficient from the engine speed so as to decrease as the engine speed increases.

The fuel supply amount calculation means 7 has a first smoothing coefficient and a second smoothing coefficient calculated by the first smoothing coefficient means 5 to the intake air amount-revolution speed ratio calculated by the intake air amount-revolution speed ratio calculation means 4. The second smoothing coefficient calculated by the coefficient calculating means 6 is multiplied and corrected, and the amount of fuel to be supplied to the internal combustion engine is calculated from the corrected intake air amount-rotation speed ratio. [Example] In FIG. Is a cylinder block, 12 is a piston,
Reference numeral 14 is a connecting rod, 15 is a crankshaft, 16 is a combustion chamber, 18 is a cylinder head, 22 is an intake valve, 24 is an intake port, 25 is a fuel injection valve, 26 is an exhaust valve, and 28 is an exhaust port. The intake port 24 has a surge tank 29, an intercooler 30,
It is connected to an air flow meter 34 via a mechanical supercharger 31 and a throttle valve 32. 38 is a distributor.

The mechanical supercharger 31 is configured, for example, as a roots pump, and the pulley 33 is provided on the rotation shaft 31a thereof. Pulley 3
3 is connected to a pulley 36 on the crankshaft 15 via a belt 35. The pulley 33 on the rotary shaft 31a of the supercharger 31 includes an electromagnetic clutch 37. The electromagnetic clutch 37 is released when the rotation speed is low and the load is low, and the rotation of the crankshaft 15 is not transmitted to the supercharger 31. On the other hand, at the time of high rotation and high load, the electromagnetic clutch 37 is engaged, and the rotation of the crankshaft 15 is transmitted to the supercharger 31 to perform supercharging operation.

Reference numeral 42 is a control circuit as a microcomputer, which performs necessary calculation by signals from various sensors, and outputs a fuel injection signal to the fuel injection valve 25 and a supercharger operating clutch 37.
Is programmed to form a drive signal to.
The control circuit 42 includes a central processing unit (CPU) 44, a memory 46,
The input port 48, the output port 50, and the bus 52 connecting them are the basic components. The following sensors are connected to the input port 48. A signal corresponding to the intake air amount Q is supplied from the air flow meter 34. Crank angle sensors 56, 58 are installed in the distributor 38. The first crank angle sensor 56 generates a signal G for each revolution of the distributor shaft 38 ', that is, for every 720 ° CA, which serves as a reference signal. On the other hand, the second crank angle sensor 58 is the crankshaft 30
By generating a signal NE for each degree, the engine speed can be known in a known manner. Other sensors will also be installed,
Since these are not directly related to the present invention, description thereof will be omitted.

The output port 50 is connected to the fuel injection valve 25 via a fuel injection valve drive circuit 64. The drive circuit 64 includes a comparison register 66, gates 68 and 70, and a bistable circuit 72. Bistable circuit 72
Is set by gate 68 and reset by gate 70. One input of the compare register 66 is connected to a free running counter (used to know the current time) 73 of the control circuit 42. The drive circuit is an example, and other types of drive circuits can be adopted. The output port 50 is also connected to the electromagnetic clutch 38 of the supercharger.

The operation of the control circuit 42 will be described below with reference to a flowchart. Note that the control of the electromagnetic clutch that operates the supercharger itself is not directly related to the present invention, so a description thereof will be omitted.

FIG. 3 shows a fuel injection amount calculation routine, which is executed in the main routine, for example, every 4 ms. In step 100, the intake air amount-rotational speed ratio Q / NE representing the engine load is entered into QN.

At step 102, it is judged if QN ≧ QNSTi ₋₁ . here
QNSTi _-1 is the smoothed _value of the intake air amount-rotation speed ratio obtained at the previous execution of this routine. Ye during engine acceleration
If it is determined to be s, the process proceeds to step 104, and the smoothing coefficient (first smoothing coefficient of the present invention) K2 according to the intake air amount change rate during acceleration is calculated by map. FIG. 6 shows the relationship between the intake air amount change ratio ΔQN and K2. The larger ΔQN, the smaller the value of K2, that is, the smaller the degree of smoothing. This relationship is stored in the memory 46 as a map. Δ
QN can be known from the difference between the intake air amount-rotational speed ratio at the time of executing this routine last time and the intake air amount-rotational speed ratio at this time of executing this routine. Known in this way Δ
The value of K2 corresponding to QN is calculated by interpolation.

In step 106, a smoothing coefficient (second smoothing coefficient of the present invention) K1 corresponding to the engine speed is calculated. 7th
The figure shows the relationship between the engine speed NE and the smoothing coefficient K1.
The higher the number of revolutions, the smaller the smoothing coefficient, that is, the smaller the smoothing degree. The relationship shown in FIG. 7 is stored in the memory 46 as a two-dimensional map. Then, the correction coefficient K1 is interpolated from the actually measured engine speed NE.

In step 108, the product of K1 and K2 is the final smoothing coefficient during acceleration.

In step 110, the smoothed value QNTS of the intake air amount-rotational speed ratio during acceleration is calculated by QNTS = ((K-1) QNTSi- ₁ + QN) / K. In this equation, the smoothed value QNTS is obtained by weighting the current intake air amount-rotational speed ratio QN by 1 and setting the previous smoothed value QN
It means that it is an average value obtained by weighting TSi _-1 with K-1. That is, the intake air amount-rotational speed ratio is corrected so as to be a conservative value than the actual intake air amount-rotational speed ratio QN.

Since QN <QNTSi ₋₁ during deceleration operation, the routine proceeds from step 102 to step 112, and the smoothing coefficient (first smoothing coefficient of the present invention) K4 according to the intake air amount change ratio during deceleration is mapped. Is calculated. The same relationship between ΔQN and K4 as in FIG. 6 is stored in the memory, and the value of K4 corresponding to ΔQN is calculated by interpolation.

In step 114, a smoothing coefficient (second smoothing coefficient of the present invention) K3 corresponding to the engine speed is calculated. 7th
The relationship between the engine speed NE and the smoothing coefficient K3 similar to that in the figure is stored in the memory, and the correction coefficient K3 is interpolated from the measured engine speed NE.

In step 116, the product of K3 and K4 is the final smoothing coefficient K during deceleration.

In step 118, the operation of the smoothed value QNTS of the intake air amount-rotational speed ratio during deceleration is executed by QNTS = ((K-1) QNTSi _-1- QN) / K. In this equation, the smoothed value QNTS is obtained by weighting the current intake air amount-rotational speed ratio QN by 1 and setting the previous smoothed value QN
It means that it is an average value obtained by weighting TSi _-1 with K-1. That is, the intake air amount-rotational speed ratio is corrected so as to be a value larger than the actual intake air amount-rotational speed ratio QN.

In step 120, the basic injection amount TP is calculated by TP = C × QNTS. Here, k is a constant.

In step 122, the final injection amount TAU is calculated by TAU = TP × α (1 + β) + γ. Here, α, β, and γ represent various correction factors such as feedback, water temperature, and acceleration.

In step 124, the current rounded value QNTS is stored at the address of QNTSi _-1 and used in the next routine.

FIG. 4 shows a crank angle interruption routine, which is executed by detecting the crank angle before the fuel injection timing by the crank angle sensors 56 and 58. In step 126, the fuel start time ti is calculated. In step 128, the injection end time te is calculated. The ti, te calculation can be easily calculated from the final injection time TAU so that the injection is performed during the intake stroke in the case of cylinder-specific injection. In step 130, the injection start time ti is set in the comparison register 66.
In step 130, the interrupt enable flag F _A is set,
The fuel injection prohibition flag F _B is reset.

When the injection start time ti arrives, the values of both inputs of the comparison register 66 match, so the same register outputs a High signal and F _A
= 1 and F _B = 0, the gate 68 is turned on and the bistable circuit 74
Is set, fuel injection from the fuel injection valve 25 is started, and at the same time, the time coincidence interrupt routine of FIG. 5 is started. In step 134, the injection end time te is set in the comparison register 66. In step 136, the flag F _A is reset and F _B is set. When the injection end time te comes, both inputs of the comparison register 66 match, so a High signal is output. Since the flags F _A = 0 and F _B = 1 are set, the gate 70 is turned on, the bistable circuit 72 is reset, and the fuel injection valve 25 is closed. The amount TAU calculated in this way
Fuel injection is performed during the desired stroke of the engine.

FIG. 8 is a diagram explaining the operation of the present invention. If acceleration operation is performed, the opening degree of the throttle valve increases rapidly.
The change in the intake air amount-rotational speed ratio QN exhibits an overshoot like l ₁ . The smoothed value QNTS changes like m ₁ .
The diagonal line corresponds to the amount of air for filling the intake system volume.
If there is no anneal treatment, the air-fuel ratio will deviate to the rich side like l ₂ . It is controlled to the set air-fuel ratio like m ₂ by averaging.

〔The invention's effect〕

In the present invention, since the first smoothing coefficient that decreases with an increase in the change ratio of the intake air amount-rotational speed ratio and the second smoothing coefficient that decreases with an increase in the engine rotational speed are used for smoothing, It is possible to execute the smoothing process suitable for the state, and it is possible to control the air-fuel ratio to the set value with high accuracy. Therefore, it is possible to reduce emissions, improve drivability, and increase the fuel consumption rate.

In the embodiment, the intake air amount-rotation speed ratio is blunted, but the intake air amount itself may be blunted, or the basic injection amount may be blunted.

Further, although the embodiment describes the fuel injection system, it may be applied to other fuel supply systems.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention. FIG. 2 is a block diagram of the embodiment. 3 to 5 are flowcharts for explaining the operation of the control circuit. FIG. 6 and FIG. 7 are graphs showing the settings of the smoothing coefficients K2 and K1, respectively. FIG. 8 is a timing chart for explaining the operation of the present invention. 25 …… Fuel injection valve 32 …… Throttle valve 34 …… Air flow meter 38 …… Distributor 42 …… Control circuit 56, 58 …… Crank angle sensor

Claims (1)

[Claims] 1. The following components, namely, fuel supply means for supplying fuel to an internal combustion engine, intake air amount detection means for detecting an intake air amount of the internal combustion engine, and rotational speed for detecting the rotational speed of the internal combustion engine. Detection means, means for calculating the ratio of the intake air amount detected by the intake air amount detection means to the rotation speed detected by the rotation speed detection means, increase of the change ratio from the change ratio of the intake air amount-rotation speed ratio A first smoothing coefficient that is calculated to decrease with
A smoothing coefficient calculating means, a second smoothing coefficient means for calculating a second smoothing coefficient so as to decrease from the engine speed as the speed increases, and a calculated intake air amount-rotational speed ratio 1st and 2nd
A fuel supply amount control device for an internal combustion engine, comprising fuel supply amount calculation means for calculating the amount of fuel to be supplied to the internal combustion engine after being corrected by multiplying by a smoothing coefficient.