JPH0621592B2 - 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-rotation speed ratio and the intake pipe negative pressure as load representative factors. However, since these factors are not the load itself, it may not be possible to accurately measure the load transiently. That is, to explain the case of measuring the intake air amount, an air flow meter is installed upstream of the throttle valve, but the air amount measured by this air flow meter is a transient value that opens the throttle valve from closing to opening. In the state, not only the amount of air filling the engine combustion chamber, but also the amount of air filling the intake pipe from the throttle valve downstream to the combustion chamber is measured. Then, if the fuel supply amount is calculated by using the signal from the air flow meter as it is, the fuel amount obviously becomes a transition with respect to the amount of air entering the combustion chamber, which may deteriorate the emission and the fuel consumption rate. Become.

Therefore, as a prior art, the air-fuel ratio is prevented from being roughened in a transient state by performing a blunting process (a smoothing process) for more conservatively correcting the temporal change in the intake air amount data detected by the air flow meter. Things have been proposed. See, for example, Japanese Patent Application No. 59-9976.

[Problems to be solved by the invention]

In the prior application technology, the degree of smoothing is constant. This is because the ratio of the amount of air that is actually filled in the combustion chamber and the amount that is filled in the intake pipe of the combustion chamber means is assumed to be constant in the amount of air measured by the air flow meter during the transition. That is, the idea is that the amount of air actually entering the combustion chamber can be accurately grasped if the amount of air is set to a value that is slightly smaller than the measured value of the air flow meter. However, the ratio of the amount of filling the combustion chamber to the amount of filling the intake pipe in the total amount of air measured by the air flow meter is not always constant, but changes depending on the acceleration, for example, the throttle valve opening. That is, when the throttle valve opening is small, the intake pipe filling amount is large, and as the throttle valve opening increases, the intake pipe filling amount decreases. Therefore, according to the conventional technique in which a certain degree of smoothing is applied regardless of the opening of the throttle valve, it is not possible to control the air-fuel ratio to a desired value over the entire area. That is, during acceleration with a small throttle valve opening, the air-fuel ratio becomes rich, and conversely, during acceleration with a large throttle valve opening, the air-fuel ratio becomes lean.

[Means for solving problems]

In FIG. 1, a fuel supply amount control device for an internal combustion engine comprises a fuel supply means (1) for supplying fuel to the internal combustion engine and an intake air amount detection means (2) for detecting an intake air amount of the internal combustion engine.
The throttle valve opening detection means (3) for detecting the opening size of the throttle valve (32) of the internal combustion engine and the intake air amount detected by the intake air amount detection means (2) Depending on the throttle valve opening detected by the throttle valve opening detection means (2), the smaller the throttle valve opening, the greater the blunting means (4), and the slower the amount of fuel supplied by the fuel supply means (1). And a fuel supply amount calculation means (5) for calculating the intake air amount signal.

[Action]

The intake air amount detecting means (2) detects the intake air amount, and the throttle valve opening degree detecting means (3) detects the opening degree of the throttle valve (32).

The blunting means (4) determines the time change rate of the intake air amount detected by the intake air amount detecting means (2) according to the throttle valve opening degree detected by the throttle valve opening degree detecting means (3). The smaller the value, the greater the slowdown.

The fuel supply amount calculation means (5) calculates the amount of fuel supplied by the fuel supply means (1) according to the blunted intake air amount signal.

〔Example〕

In FIG. 2, 10 is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a combustion chamber, 18 is a cylinder head, 20 is a spark plug, 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. Intake port 24 is surge tank 3
0, air flow meter 34 through throttle valve 32
Connected to. The exhaust port 28 is connected to the exhaust manifold 36. Reference numeral 38 is a distributor, and 40 is an ignition device.

42 is a control circuit as a microcomputer,
Performs necessary calculations using signals from various sensors,
It is programmed to form a fuel injection signal to the fuel injector 25. The control circuit 42 is a central processing unit (CP
U) 44, the memory 46, the input port 48, the output port 50, and the bus 52 that connects them are the basic components. The following sensors are connected to the input port 48. From the air flow meter 34, the intake air amount Q
Is supplied. A throttle sensor 54 is connected to the throttle valve 32, and a signal TA corresponding to the throttle valve opening is supplied to the input port 48. Crank angle sensors 56 and 58 are installed in the distributor 38. The first crank angle sensor 56 generates a signal G for each rotation 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
Generates a signal NE every 30 ° of the crankshaft and can know the engine speed in a known manner. The engine water temperature sensor 60 generates a signal according to the engine water temperature, and the oxygen concentration sensor 62 is installed in the exhaust manifold 28 to know the air-fuel ratio.

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 the free running counter of the control circuit 42 (used to know the current time). The drive circuit is an example, and other types of drive circuits can be adopted.

The operation of the control circuit 42 will be described below with a hello chart. FIG. 3 shows a fuel material injection amount calculation routine, which is executed in the main routine, for example, every 4 ms. In step 100, the intake air amount Q and the engine speed NE are read. It is assumed that these data have been stored in a predetermined area of the memory (RAM) by a routine not described. In step 102, the calculation of the intake air amount-rotational speed ratio Q / NE as the load equivalent value is executed. In step 104, the throttle valve opening TA is read. In step 106, the operation of the moderation degree K for the throttle valve opening TA is executed. A desired relationship (for example, a straight line or a step characteristic as shown in FIG. 5) is set so that the smoothing degree K becomes smaller as the throttle valve opening TA increases. This relationship is stored in the ROM area of the memory 46, and the operation of the moderation degree K is executed from the measured throttle valve opening TA.

In step 108, the intake air amount smoothing value QNS is calculated by the following calculation formula.

QNS = (Q / NE + (K-1) × QNS) / K This formula calculates the average value QNS by weighting the current intake air amount-rotation speed ratio Q / NE by 1 to the previous average value QNS. K-
This means an average value with a weight of 1. That is,
The intake air amount-rotational speed ratio is corrected so as to be a more conservative value than the actual intake air amount-rotational speed ratio Q / NE. The larger the value of K, the smaller the current contribution of Q / NE, and the stronger the degree of smoothing. The method of smoothing arithmetic processing is not limited to the above, and other methods can be adopted. For example, it is possible to sum Q / NE up to K times before and divide by K to obtain QNS.

In step 110, the basic injection amount Tp is calculated by Tp = k × QNS. Here, k is a constant.

In step 112, 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.

FIG. 4 shows a crank angle interrupt routine, which is executed by detecting the crank angle before the fuel injection timing by the crank angle sensors 56 and 58. In step 120, the injection start time t _i is calculated. In step 122, the injection end time t _e is calculated. t _i , t _e
The calculation of can be easily calculated from the final injection amount so that the injection is performed during the intake stroke in the case of cylinder-by-cylinder injection. In step 14, the injection start time t _i is set in the comparison register 66. In step 126, flags F _A and F _B are set. The injection start time t _i arrives, compare registers the value of both the input 66 matches the register outputs a High _{signal, F} A, F B = ₁ the gate 68 are turned ON bistable circuit 74 because it is 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 128, the injection end time t _e is the comparison register 6
Set to 6. In step 130, flags F _A and F _B
Is reset. When the injection end time comes, both inputs of the comparison register 66 match, so a High signal is output. Since the flags F _A and F _B = 0, the gate 70 is turned on, the bistable circuit 72 is reset, and the fuel injection valve 25 is closed. The amount TA calculated in this way
U thermal injection is performed during the desired stroke of the engine.

FIG. 7 is a diagram explaining the operation of the present invention. It is assumed that the acceleration operation is performed at the time points and. The throttle valve opening TA at each acceleration operation time is shown in (c), and the change in the intake air amount-rotation speed ratio Q / NE is shown in (d). The change in the smoothed value QNS of the intake air amount-rotational speed ratio is shown in (e), but the thick line shows the present invention in which the smoothed degree K is changed according to the opening of the throttle valve, and the thin line shows the conventional smoothed degree. . In the present invention, when the throttle valve opening is small, the intake air amount-rotational speed ratio smoothing value QNS is larger than in the conventional case, and when the throttle valve opening is large, the smoothing value QNS is smaller than in the conventional case. Irregularity of the air-fuel ratio is controlled at the time of acceleration ,,, as shown in (b) regardless of the throttle valve opening. Conventionally, there was a problem that a lean spike like L in (a) or a rich spike like R was likely to occur, but the present invention solves this problem.

〔The invention's effect〕

According to the present invention, the intake air amount is blunted at a low throttle valve opening amount and is made small at a high throttle valve opening amount, and the fuel supply amount is calculated from the blunted intake air amount to obtain a low throttle valve opening amount. There is an effect that an appropriate air-fuel ratio can be obtained in either acceleration or acceleration from a high throttle valve opening.

Further, although the embodiment describes the fuel injection system, it is also possible to adopt a fuel supply system having a larger number than that.

[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 is a graph explaining the setting of the smoothing degree. FIG. 7 is a timing diagram illustrating the operation of the present invention. 25 ... Fuel injection valve 32 ... Throttle valve 34 ... Air flow meter 38 ... Distributor 40 ... Throttle sensor 42 ... Control circuit 56, 58 ... Crank angle sensor

Claims (1)

[Claims] 1. A fuel supply amount control apparatus for an internal combustion engine, a fuel supply means for supplying fuel to the internal combustion engine, an intake air amount detection means for detecting an intake air amount of the internal combustion engine, and a throttle valve for the internal combustion engine. Of the throttle valve opening detecting means for detecting the opening degree of the throttle valve and the time change rate of the intake air amount detected by the intake air amount detecting means depending on the throttle valve opening degree detected by the throttle valve opening detecting means. A fuel supply for an internal combustion engine, which comprises: a blunting means for blunting as the throttle valve opening becomes smaller; and a fuel supply amount computing means for computing the fuel amount supplied by the fuel supply means in accordance with the blunted intake air amount signal. Quantity control device.