JPH0739817B2 - 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. It is usual to detect the engine load as an operating condition or 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 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. This means that the air flow meter causes the intake air amount to be an air amount that is larger than the engine demand. Therefore, in order to temporarily correct the measured value of the air flow meter to the value of the intake air amount required by the engine, first of all, as a measure against overshoot errors, the measured value of the air flow meter (or intake air amount-rotation speed ratio) The upper limit of the calculated value is set (so-called guard processing). Then, in order to match the rate of change of the air flow meter measured value with the actual rate of change of the intake air amount required by the engine, a blunting process (so-called anneal) of the air flow meter measured value is performed.

[Problems to be solved by the invention]

In the prior art, the blunting process of the guarded air flow meter measurement value was performed. That is, when the overshoot amount exceeds a predetermined value, the guard is applied regardless of the degree of acceleration, and the upper limit value of the intake air amount or the intake air-rotation speed ratio is set. However, in this method, since the overshoot amount is not reflected in the fuel injection amount at all, it is difficult to obtain the optimum smoothing degree during the rapid acceleration and the slow acceleration. For example, if the smoothing ratio is made smaller so as to be suitable for the sudden acceleration, the smoothing ratio becomes too small at the slow acceleration, and the air-fuel ratio becomes too rich. On the other hand, if a large proportion is adopted so as to be suitable for gentle acceleration, the driving performance at the time of sudden acceleration cannot be obtained.

In order to solve this problem, it has been proposed to switch the smoothing rate between sudden acceleration and gentle acceleration. Whether the acceleration is sudden or gentle can be known by, for example, whether the supercharger is operating or stopped. Therefore, when the supercharger is operating, reduce the smoothing ratio,
When the supercharger is stopped, increase the annealing rate. However, even with this method, it is difficult to obtain the optimum moderation rate according to the operating state. That is, even when the supercharger is operating, there is a difference between sudden acceleration and gentle acceleration. Therefore, if the smoothing rate is adapted to the sudden acceleration during the operation of the supercharger, the air-fuel ratio becomes excessive during the operation in which the supercharger operates but the acceleration is slow. On the contrary, if it is adapted to the gentle acceleration while the supercharger is operating, the acceleration performance cannot be obtained during the sudden acceleration while the supercharger is operating.

The present invention aims to always obtain an optimum smoothing ratio regardless of the degree of acceleration.

[Means for solving problems]

Referring to FIG. 1, a fuel supply amount control apparatus for an internal combustion engine according to the present invention includes a fuel supply means 1 for supplying fuel to the internal combustion engine and a volume flow type for measuring the amount of intake air supplied to the internal combustion engine. Intake air amount measuring means 2, rotation speed detecting means 3 for detecting the rotation speed of the internal combustion engine, and means 4 for calculating an intake air amount-rotation speed ratio from the detected intake air amount and rotation speed. The means 5 for calculating the fuel supply amount to be supplied to the internal combustion engine by the fuel supply means from the intake air amount-rotation speed ratio, and the calculation of the fuel supply amount by the fuel supply amount calculation means 5 include the intake air amount-rotation speed ratio Means 6 for blunting,
In the calculation of the fuel supply amount by the fuel supply amount calculation means 5, when the blunted intake air amount-rotational speed ratio exceeds the upper limit ground, the guard means 7 adopts the upper limit value as the intake air amount-rotational speed ratio. Composed.

[Action]

The intake air amount measuring means 2 measures the intake air amount supplied to the internal combustion engine by its volume flow rate. Rotation speed detection means 3
Detects the rotational speed of the internal combustion engine.

The intake air amount-rotational speed ratio calculation unit 4 calculates the intake air amount-rotational speed ratio from the ratio between the intake air amount measured by the intake air amount measurement unit 2 and the rotation speed detected by the rotation speed detection unit 3. . The fuel supply amount calculation means 5 calculates the fuel supply amount to be supplied to the internal combustion engine by the fuel supply means 1 from the intake air amount-rotational speed ratio calculation means 4 calculated.

The blunting means 6 blunts the intake air amount-rotation speed ratio when the fuel supply amount calculation means 5 calculates the fuel supply amount.
When the fuel supply amount calculation unit 5 calculates the fuel supply amount, the guard unit 7 adopts the upper limit value as the intake air amount-revolution speed ratio when the blunted intake air amount-revolution speed ratio exceeds the upper limit value. [Embodiment] In FIG. 2, 10 cylinder blocks, 12 are pistons, 14
Is a connecting rod, 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 is connected to an air flow meter 34 via a surge tank 29, an intercooler 30, 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 10a via a belt 35. The pulley 33 on the rotary shaft 32 of the supercharger 31 includes an electromagnetic clutch 37. The electromagnetic clutch 38 is released when the rotation speed is low and the load is low, and the rotation of the crankshaft 10a 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 10a is transmitted to the supercharger 31 to perform supercharging operation.

Reference numeral 42 denotes a control circuit as a microcomputer, which performs necessary calculation by signals from various sensors, a fuel injection signal to the fuel irradiation 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 rotation of the distributor shaft 38a, 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 invention, the description is 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. The control itself of the electromagnetic clutch 37 that operates the supercharger 31 is not directly related to the present invention, and therefore its explanation is 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 QN is calculated by QN = C / (U × NE). Here, NE is the engine speed and U is a value measured by an air flow meter, which is obtained as a signal proportional to the reciprocal of the intake air amount Q. C is a constant and is a characteristic value determined by the air flow meter.

At step 102, the smoothed value QN ^{* of the} intake air amount-rotation speed ratio
Operation is performed by _{^{QN * = ((K 1 -1}} ) QN 0 + QN) / K 1. Where QN ₀ is the value of the intake air amount-rotation speed ratio QN obtained when this routine was last executed, K ₁
It is a rounding constant (> 1.0). This formula is the averaged value QN ^*
Means that the current intake air amount-rotational speed ratio QN is a weighted value of 1 and the previous smoothed value QN ₀ is weighted by K ₁ -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.

In step 103, the smoothed value QN ^* is the intake air amount-rotational speed ratio Q.
It is transferred to the memory address that stores N. Step 104
Then, it is determined whether or not QN is larger than the maximum value QNMAX of the intake air amount-rotation speed ratio. If it exceeds the maximum value, step 105 puts QNMAX in QN. Therefore, the intake air amount-rotational speed ratio used to calculate the fuel injection amount is guarded so as not to exceed QNMAX. In step 106, this QN is transferred to the memory address QN ₀ that stores the previous intake air amount-rotation speed ratio. In step 107, the basic injection amount
TP is calculated by Tp = k × QN. Here, k is a constant.

In step 108, 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 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 114, the fuel start time ti is calculated. In step 116, the injection end time te is calculated. The calculation of ti, te 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 118, the injection start time ti is set in the comparison register 66.
In step 120, the interrupt enable flag F _A is set,
The fuel injection prohibition flag F _B is reset.

When the irradiation 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 128, the injection end time te is set in the comparison register 66. In step 130, 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. 6 is a diagram explaining the operation of the present invention. If the acceleration operation is performed at the time, the opening of the throttle valve increases rapidly (for example, it is assumed that the throttle valve is opened from the idle opening by 20 °). QN stands up from here. If the acceleration is a rapid acceleration such as l, the change in the intake air amount-rotational speed ratio QN is l ₁
A large overshoot is obtained as in, and the overshoot is small as in m ₁ when the acceleration is performed slowly as in m. The smoothed value QN ^* depends on whether it is accelerated, steep or slow.
It changes like l ₂ , m ₂ . That is, when the acceleration is rapid, the smoothed value is large, and when the acceleration is small, the smoothed value is small, and the smoothed value according to the acceleration ratio is obtained. The guard value is n, and the intake air amount-rotation speed ratio for calculating the fuel injection amount does not exceed this value QNMAX.

〔The invention's effect〕

In the present invention, when calculating the fuel supply amount to be supplied to the internal combustion engine from the intake air amount-rotational speed ratio, the intake air amount-rotational speed ratio is blunted, and the blunted intake air amount-
When the rotation speed ratio exceeds the upper limit value, the upper limit value is guarded to be used as the intake air amount measurement value. Therefore, the acceleration ratio is reflected in the intake air amount to apply the guard-rotation speed ratio. Thus, it is possible to perform the optimum smoothing according to the acceleration rate.

Since it is not necessary to switch the moderation rate depending on whether the acceleration is rapid or gentle as in the conventional case, the program can be simplified correspondingly and the number of words required for the computer can be saved.

In the embodiment, the intake air amount-rotational speed ratio is smoothed and guarded. However, the intake air amount itself is smoothed and guarded, and then the basic injection amount can be calculated.
Furthermore, the basic injection amount may be smoothed and guarded.

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

BRIEF DESCRIPTION OF THE 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 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. A fuel supply means for supplying fuel to an internal combustion engine, a volume flow type intake air quantity measuring means for measuring an intake air quantity supplied to the internal combustion engine, Rotation speed detection means for detecting the rotation speed of the engine, means for calculating the intake air amount-rotation speed ratio from the detected intake air amount and rotation speed, internal combustion engine by the fuel supply means from the intake air amount-rotation speed ratio Means for calculating the fuel supply amount to be supplied to the fuel supply amount calculation means, means for reducing the intake air amount-rotation speed ratio in calculating the fuel supply amount by the fuel supply amount calculation means, and calculation of the fuel supply amount by the fuel supply amount calculation means,
A fuel supply amount control device for an internal combustion engine, comprising: guard means that adopts an upper limit value as the intake air amount-rotation speed ratio when the blunted intake air amount-rotation speed ratio exceeds the upper limit value.