JPH01138337A - Method for controlling fuel injection of internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain an exact fuel injection by obtaining the correction quantity on the basis of the fundamental injection quantity in accordance with engine speed and intake pressure and the injection quantity in accordance with air quantity and also correcting the fundamental injection quantity on the basis of the correction quantity in accordance with the above correction quantity and the time varying quantity of the intake pressure. CONSTITUTION:An internal combustion engine 13 is provided with each fuel injection valve B1-Bm installed in each intake conduit A1-Am connected to a number of combustion chambers E1-Em respectively. In this case, each fuel injection valve B1-Bm is controlled by a processing unit 31 on the basis of each detected signal from each kind of sensor 19, 21, 24, 27, 28 and 30 for detecting the operational conditions of the internal combustion engine 13. The correction quantity is obtained on the basis of the fundamental injection quantity in accordance with engine speed and real intake pressure and the injection quantity in accordance with air quantity. The real fuel injection quantity is obtained by correcting the fundamental injection quantity on the basis of the correcting quantity in accordance with the above correction rate and the time varying rate of the real intake pressure.

Description

TECHNICAL FIELD The present invention relates to a system for controlling the amount of fuel injection in an internal combustion engine.

BACKGROUND ART In a so-called electronically controlled fuel injection device for an internal combustion engine, it is necessary to detect the intake air flow rate in order to determine fuel injection, 1 TAU. As a method for detecting the intake air flow rate, for example, a typical prior art method of determining it from the intake pressure Pm and the rotational speed Ne between the internal combustion engine is known.

In this prior art, for example, the intake pressure detected by a pressure detector installed in the surge tank has a response delay from the actual intake pressure Pm, so it is difficult to stabilize the air-fuel ratio, and the correction is difficult. It required complex calculation processing.

In order to solve this problem, in the method previously proposed by the applicant, the throttle valve opening θ and the rotational speed Ne of the internal combustion engine are
The intake pressure Pmj under a predetermined atmospheric pressure is predicted from , and the fuel injection amount TAU is determined using this predicted iron pressure PmJ and the rotational speed Ne.

With this method, it is possible to predict the intake pressure Pmj corresponding to a change in the throttle valve opening θ. However, during a transient period when the throttle valve opening degree θ changes rapidly, the intake air flow I through the throttle valve does not necessarily correspond to this expected intake pressure Pmj due to the influence of the surge tank, etc., and therefore this prediction If injection is performed with a fuel injection amount corresponding to the intake pressure Pmj, the air-fuel ratio will become so-called over-rich or over-lean.

Problems to be Solved by the Invention An object of the present invention is to provide a method for determining accurate fuel injection JiTAU that takes into account the effects of surge tanks, etc., even in transient situations where the throttle valve opening θ suddenly changes. An object of the present invention is to provide a fuel injection amount control method for an internal combustion engine.

Means for Solving the Problems The present invention calculates the basic injection amount T21 from the rotational speed Ne per unit time of the internal combustion engine and the actual intake pressure Pm, and calculates the basic injection amount T21 corresponding to the air flow rate Q2 flowing into the surge tank. Determine the injection amount TP2, and calculate the correction amount TM from the basic injection amount TPI and the injection amount TP2.
1, and the correction amount TM2 corresponding to the time rate of change of the actual intake pressure Pm.
This is a fuel injection amount control method for an internal combustion engine, characterized in that the basic injection amount TP1 is corrected by correction amounts TM1 and TM2 to obtain an actual fuel injection amount TAU.

In a preferred embodiment, the correction amount TMI is set to 7M1=η(TP
2-TP1), and the actual fuel injection amount TAU is TAU=
It is characterized by being determined by TP 1 +TM1-TM2.

In a preferred embodiment, during acceleration when the correction amount TMI is 0 or more, TPI≦TAU≦TP 1 +TM 1;
Further, during deceleration when the correction amount TMI is not 0, the correction amount TMI is limited so that TPI≧TAU≧TP1+TM1.

Furthermore, in a preferred embodiment, the injection amount TP2 is determined by Q2/Ne, and the correction amount TM2 is calculated by Q4, where Q4 is the amount of air stored in the surge tank.
/Ne.

According to the present invention, first, the basic injection amount TPI is determined from the rotational speed Ne per unit time between the internal combustion engines and the actual intake pressure Pm. The change in the actual intake pressure Pm has a response delay with respect to the change in the throttle valve opening θ, and therefore the basic injection fiTP determined from the actual intake pressure Pm
1 is the optimal fuel injection amount for the intake air flow rate before the throttle valve opening degree θ is changed.

Next, the air flow rate Q2 flowing into the surge tank is determined from the actual intake pressure Pm and the throttle valve opening θ or by using a vane, etc., and the injection f corresponding to this air flow rate Q2 is determined.
Find iTP2. This injection jlTP2 is the optimal fuel injection amount for the implicit intake air flow rate Q2 immediately after the throttle valve opening degree θ changes.

Using the injection amount TP2 and the basic injection amount TP1 thus obtained, the correction amount TM1 is obtained by, for example, subtracting the basic injection amount TPI from the injection amount TP2 to compensate for the delay of intake air into the combustion chamber.

Further, a correction amount TM2 corresponding to the time rate of change of the actual intake pressure Pm, that is, corresponding to the influence of the air stored in the surge tank, is determined, and this correction amount TM2 and the correction amount T
The basic injection amount TPI is corrected by subtracting this correction amount TM2 from the sum of the basic injection amount TPI and the correction amount TMI using MI, and the actual fuel injection amount TAU is determined.

As a result, it is possible to accurately follow changes in the intake air flow rate during transitions when the throttle valve opening θ fluctuates, and perform injection at a fuel injection amount TAU that takes into account the effects of surge tanks, etc., and allows the air-fuel ratio to be maintained at all times. ! & can be kept at a reasonable value.

Embodiment FIG. 1 is a block diagram of an embodiment of the present invention. A plurality of combustion chambers E1 to Em are formed in the internal combustion engine 13, and combustion air is supplied to these combustion chambers E1 to Em from an intake pipe 15. A throttle valve 16 is interposed in the intake pipe 15 . Combustion air via the throttle valve 16 is guided from the surge tank 14 to intake pipes A1 to Am provided individually for each combustion chamber E1 to Em. Each intake pipe A1 to A
m is provided with fuel injection valves B1 to Bm, respectively, and in each explosion stroke in each combustion chamber E1 to Em,
Fuel injection amount T determined by the processing device 31 described later
Each of the combustion chambers E1 to Em in which injection is performed in AU is provided with an intake valve C1 to Cm and an exhaust valve D1 to Dm, respectively.

The internal combustion engine 13 includes, for example, four thermosurge tanks 14 having spark plugs 01 to Gm, and a pressure detector 19 for detecting intake pressure. The intake pipe 15 is provided with a temperature detector 27 that detects intake air temperature.

The internal combustion engine 13 is provided with a crank angle detector 28 for detecting the crank angle, and is also provided with a valve opening detector 30 for detecting the opening θ of the throttle valve 16. The temperature of the cooling water of the internal combustion engine 13 is detected by a temperature detector 24 . There is an oxygen concentration detector 2 in the middle of the exhaust pipe 2°.
1 is provided, and exhaust gas is purified by a three-way catalyst 22 and discharged to the outside.

The processing device 31 realized by a microcomputer or the like includes an input interface 32, an analog/digital converter 33 that converts an input analog signal into a digital signal, a processing circuit 34, and an output ink face 35.
and a memory 36. Memory 36 includes read-only memory and random access memory. In the embodiment of the present invention, the fuel injection fiTAU for each explosion stroke injected from the fuel injection valves B1 to Bm is controlled in response to outputs from the detectors 19, 24, 28, 30, etc.

On the other hand, in an automobile manufacturer, under a predetermined atmospheric pressure of 760 mmHg, for example, the intake pressure Pm corresponding to the rotation speed Ne per unit time of the internal combustion engine 13 and the throttle valve opening θ
j is measured. The measurement results are shown in FIG. 2, for example, and the intake pressure Pmj increases as the throttle valve opening θ increases and as the rotational speed Ne of the internal combustion engine 13 decreases. The measurement results shown in Figure 2 are:
Stored in memory 36 as a graph or a table as shown in FIG.

Figure 4 shows the intake pressure P with respect to the change in the throttle valve opening θ.
It is a graph showing changes in m, Pmj, and fuel injection JiTAU, which will be described later. For example, when the throttle valve opening θ suddenly increases as shown in Fig. 4 (1), the expected intake pressure Pmj follows this throttle valve opening θ and becomes as shown in Fig. 4 (2). It changes so that it can be changed. On the other hand, the actual intake pressure Pm changes as shown by the broken line in FIG. 4(2) with a delay from the throttle valve opening θ, and eventually matches the expected intake pressure Pmj.

The reason why there is a delay in the actual intake pressure Pm as described above is as follows. That is, during acceleration, the intake air that passes through the throttle valve 16 fills the surge tank 14 with high-density air, and then flows out into each intake pipe line A1 to Am, as shown in FIG. 5(1). . On the other hand, during deceleration, even if the intake air flow rate via the throttle valve 16 decreases, the high-density air in the surge tank 14 flows out into each intake pipe line A1 to Am. Therefore, in the present invention,
Taking into consideration the influence of the surge tank 14, the actual fuel injection amount TAU is determined as follows.

FIG. 6 is a graph showing changes in the intake air flow IQ when the throttle valve opening degree θ changes rapidly. At steady state (rotational speed Ne=Nel, throttle valve opening θ=θ1),
The intake air flow rate Q1 of the internal combustion engine 13, which is determined from the rotational speed Ne and the intake pressure Pm, which are represented by the reference numeral 71, is determined by the reference θ.
A
At the point. Therefore, when the rotational speed Ne of the internal combustion engine 13 is constant, when the intake pressure Pro increases, the intake air flow IL
When Q increases and the throttle valve opening is constant at θ1, when the intake pressure Pm decreases, the intake air flow rate Q increases, and the fuel injection amount also increases accordingly.

When the rotational speed Ne is, for example, 11,000 rpm, and the throttle valve opening changes from θ1, for example, 5° to θ2, for example, 10°, the actual intake pressure Pro and the rotational speed Ne immediately follow this. unable to
Therefore, theoretically, the locus of the intake air flow rate Q is as shown by reference numeral 12: -1, throttle valve opening θ2
, the intake air flow rate Q2 corresponding to the intake pressure Pm rises to point B, and then decreases following the trajectory of the throttle valve opening θ2 as rP rises in the intake pressure Pm, and the expected intake pressure Pm
The intake air flow rate Q3 determined by j reaches the zero point.

Further, in the actual internal combustion engine 13, the trajectory shown by reference numeral 73 is followed due to the influence of the intake path of the surge tank 14, etc. On the other hand, as mentioned in the prior art mentioned above,
If the intake air flow rate Q is determined in response to changes in the rotational speed Ne of the internal combustion engine 13 and the intake pressure Pm, the trajectory shown by reference numeral 11 will be followed, and the intake air amount shown by diagonal lines in FIG. There is a shortage of fuel, and the air-fuel ratio becomes a so-called lean state.

Therefore, in this embodiment, first, the rotational speed Ne of the internal combustion engine 13 is
Basic injection fiTP1 corresponding to the actual intake pressure Pm is determined. Therefore, this basic injection amount TPI corresponds to the intake air flow rate Q1 before the variation of the throttle valve opening θ, and is determined based on the rotational speed Ne, which has relatively little variation, and is shown in Fig. 4 (3). ) is stable as shown by the dashed line.

Next, the actual intake pressure P detected by the pressure detector 19
Intake air flow rate Q2 corresponding to m and throttle valve opening θ
By dividing this intake air flow rate Q2 by the rotational speed Ne, that is, from Q 2 /Ne, the injection amount TP2 per revolution of the internal combustion engine 13 corresponding to the intake air flow rate Q2 is determined. Therefore, this injection JI
TP2 is the injection amount corresponding to the intake air flow rate Q2 immediately after the change in the throttle valve opening θ, and is indicated by a virtual line in FIG. 4(3).

However, the actual intake air flow iQ may vary depending on the influence of the surge tank 14 as mentioned above. As shown in 3, follow the distorted trajectory.

Therefore, in this embodiment, the correction amount T M 1 is determined based on the basic injection amount TP1 and the injection amount TP2 determined as described above based on the following formula.

TM1=η(rP2-TP1)...(1)
Dashidashi η is an intake delay correction coefficient, which is determined by taking into account the time delay until intake air enters the combustion chambers E1 to Em.
For example, it is selected to be around 0.5.

Further, as shown in the second equation, a correction ITM2 corresponding to the magnitude of the time rate of change ΔP m /Δt of the actual intake pressure Pm, that is, the amount of air flowing in and out of the surge tank 14 is determined.

However, V is the capacity of the surge tank 14. In this second equation, the time rate of change ΔPm/Δt is calculated based on the current actual intake pressure Pm and a predetermined period of time, for example, 20m5e.
The difference from the actual intake pressure P m l-+ before c, i.e., is obtained from: and by multiplying this time rate of change ΔPm/Δt and the surge tank capacity ■ as shown in the fourth equation. , the amount of air flowing into the surge tank 14,
The difference between the amount of air flowing out from the surge tank 14, that is, the air xQ4 stored in the surge tank 14 can be determined.

Therefore, by dividing this air amount Q4 by the rotational speed Ne, that is, from Q 4 /Ne, the correction amount TM2 corresponding to the amount of air flowing in and out of the surge tank 14 can be obtained as described above. Using this correction amount TM2, the correction amount TMI, and the basic injection amount TP1, the actual fuel injection amount TAU is determined as shown in equation 5.

TAU=TP 1 +TM 1-7M2
(5) The actual fuel injection amount TAU determined in this way is shown by a solid line in FIG. 4 (3). .

In this way, the rotational speed Ne of the internal combustion engine 13 shown in FIG.
The basic injection amount TP1 corresponding to the actual intake pressure Pm and the intake air flow rate Q2 corresponding to the throttle valve opening θ and the intake pressure Pm are stored as a table in the memory 36 in the same way as the predicted intake pressure Pmj described above. Store monkey.

7 to 11 are flowcharts for explaining the operation, and FIG. 7 shows the operation for detecting the rotation speed Ne of the internal combustion engine 13, which is detected by the crank angle detector 28 in step n1. The rotational speed Ne is digitally converted by the analog/digital converter 33 and read into the processing circuit 34. This operation is performed every time the analog/digital converter 33 performs a conversion operation.

FIG. 8 shows the operation for detecting the actual intake pressure Pm. In step nil, the actual intake pressure Pm detected by the pressure detector 19 is converted from analog to digital and read. This operation is performed every time the analog/digital converter 33 performs a conversion operation.

FIG. 9 shows the operation for detecting the throttle valve opening θ, in which the throttle valve opening θ detected by the valve opening detector 30 in step rr21 is digitally converted by the analog/digital converter 33. The data is read into the processing circuit 34. This operation is performed every time the analog/digital converter 33 performs a conversion.

FIG. 10 shows the operation for determining the correction amount TM2, which is performed, for example, every 20 m5ec. step rr 31
Then, the actual intake pressure P which is the difference between the actual intake pressure P m l-1 20 m5ec ago and the current actual intake pressure Pm
The time change rate ΔPm/Δt of m is calculated based on the third equation described above. In step n32, the time rate of change ΔPm/Δt of the actual intake pressure Pm obtained in step n31 based on the fourth equation described above is multiplied by the capacity V of the surge tank 14, and the air stored in the surge tank 14 is Amount Q4
is calculated. In step n33, the air amount Q4 obtained in step n32 is divided by the rotational speed Ne obtained in step n1, and thus step n31
~Step n33 allows the correction amount TM2 to be determined based on the second equation described above.

FIG. 11 shows the operation for determining the actual fuel injection amount TAU, which is performed for each stroke of the internal combustion engine 13, for example.

In step n41, the rotation speed Ne obtained in step n1 and the actual intake pressure Pm obtained in step nil are determined.
The basic injection amount TPI corresponding to the above is read out from the memory 36. In step n42, the expected intake pressure P m j corresponding to the throttle valve opening θ and the rotational speed Ne determined in step n21 is read out from the memory 36.

In step n43, the intake air flow rate Q2 corresponding to the throttle valve opening θ and the actual intake pressure Pm is read from the memory 36. In step n44, the intake air flow rate Q2 obtained in step n43 is divided by the rotational speed Ne to calculate the injection amount TP2. From the basic injection amount TP1 and injection amount TP2 thus obtained, in step n45, the injection amount TP2 is calculated. The correction amount TMI is calculated based on the first equation. In step n46, the actual fuel injection amount T is determined based on the fifth equation.
AU is calculated.

By determining the actual fuel injection amount TAU in this way, the surge tank can be adjusted with good response over the entire transient change in the intake airflow IQ when the throttle valve opening θ changes rapidly. The optimum fuel injection amount TAU can be determined in consideration of the influence of the intake path such as No. 14, and the air-fuel ratio can be stabilized. In addition, in this example,
The memory 36 stores the expected intake pressure Pmj and the basic injection amount TP.
1 and the intake air flow rate Q2 are only stored,
Therefore, the capacity of the memory 36 can be made relatively small to reduce costs.

In the above embodiment, the correction coefficient η is determined by the fact that the intake air is in the combustion chamber E1.
Although the determination is made taking into account the time delay until entering ~Em, as another embodiment of the present invention, the determination may be made in response to the cooling water temperature detected by the temperature detector 24, In addition, from the surge tank 14 to the combustion chambers E1 to E
It may be determined corresponding to the length of the intake path up to m,
Alternatively, the determination may be made in consideration of the fact that the fuel injected from the fuel injection valves B1 to Bm adheres to the pipe walls of the intake pipes A1 to Am.

Furthermore, when the correction JiTM2 used in the above-mentioned embodiment is accelerated when the correction fiTM1 is 0 or more, TPI≦TAU
≦TP 1 + TM 1 ... (6), and when the correction JiTM1 is less than 0 during deceleration, TPI ≧ TAU ≧ TP1 + TP1 ... (7>). By this, for example, when accelerating The maximum of the correction amount TM2 may be limited to the correction amount TM1, and at least the basic injection amount TP1 may be supplied to each combustion chamber E1 to Em, so that so-called engine stalling may be prevented.

Furthermore, in the above embodiment, the expected intake pressure P mj is predicted as the intake pressure under a predetermined atmospheric pressure of, for example, 760 mmHH, and the actual intake pressure P m
Similarly, the atmospheric pressure on the upstream side of the throttle valve 16 is set to the predetermined atmospheric pressure.

Basic injection amount TPI and injection amount TP2. TP4 is required. Therefore, if the actual atmospheric pressure Pa changes at a high altitude, etc., there is a risk of an error occurring. Therefore, a pressure detector is provided upstream of the throttle valve 16, and the actual atmospheric pressure Pa detected by this pressure detector is The predicted intake pressure Pmj may be corrected as follows.

Effects As described above, according to the present invention, the basic injection JiTP1 determined from the rotational speed Ne per unit time of the internal combustion engine and the actual intake pressure Pm, and the air ji flowing into the surge tank.
Calculate the correction amount TMI using the injection ITP2 corresponding to Q2, and correct the basic injection amount TPI using this correction amount TM1 and the correction amount TM2 corresponding to the time rate of change of the actual intake pressure Pm, Since the actual fuel injection JiTAU is determined, even during a transient period when there is a sudden change in the throttle valve opening θ, injection is performed at the fuel injection amount TAtJ, which takes into account the influence of the intake path such as the surge tank. The air-fuel ratio can always be kept at the optimum value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a graph showing the relationship between the throttle valve opening θ and the expected intake pressure Pmj at each rotational speed Ne of the internal combustion engine 13, and FIG. Figure 4 is a graph showing changes in intake pressure Pm, Pmj and fuel injection amount TAU with respect to changes in throttle valve opening θ, Figure 5 is a surge tank to explain the flow of intake air. 14 and FIG. 6 are graphs showing changes in the intake air flow rate Q (H) when the throttle valve opening θ suddenly changes, showing the idea of the present invention.
Figure 11121 is a flowchart for explaining the dynamic flow. 13... Internal combustion engine, 14... Surge tank, 15.
・. Intake pipe, 16...Throttle valve, one...Pressure detector, 24.27...Temperature detector, 20...Exhaust pipe,
28... Crank angle detector, 30... Valve opening degree detector, 31... Processing device, 36... Memory, Al-Am
...Intake pipe, 81~Bm...Fuel injection valve, E1~
Em...Combustion chamber, 01~0m...Spark plug agent Patent attorney Number of strokes Keiichi Part 2 Figure Throttle valve opening e Figure 3 Rotational speed Ne Figure 7 Figure 8 Figure 10 Ize 2 meq4 Figure 9 Figure 11 Figure 4 This deaf engineering village ^・

Claims (4)

[Claims] (1) Determine the basic injection amount TP1 from the rotation speed Ne per unit time of the internal combustion engine and the actual intake pressure Pm, determine the injection amount TP2 corresponding to the air flow rate Q2 flowing into the surge tank, and calculate the basic injection amount. Correction amount TM from TP1 and injection amount TP2
1, and the correction amount TM2 corresponding to the time rate of change of the actual intake pressure Pm.
A fuel injection amount control method for an internal combustion engine, characterized in that the basic injection amount TP1 is corrected by correction amounts TM1 and TM2 to obtain an actual fuel injection amount TAU. (2) The correction amount TM1 is obtained as follows, where η is the intake delay correction coefficient for the combustion chamber, and the actual fuel injection amount TAU is calculated as follows.
2. The fuel injection amount control method for an internal combustion engine according to claim 1, wherein the fuel injection amount is determined by TP1+TM1-TM2. (3) During acceleration when the correction amount TM1 is 0 or more, TP1
Claim 2, characterized in that the correction amount TM1 is limited so that ≦TAU≦TP1+TM1, and when the correction amount TM1 is less than 0 during deceleration, TP1≧TAU≧TP1+TM1. The fuel injection amount control method for the internal combustion engine described. (4) The injection amount TP2 is obtained by Q2/Ne, and the correction amount TM2 is the amount of air stored in the surge tank Q4.
The fuel injection amount control method for an internal combustion engine according to claim 1, 2, or 3, wherein the fuel injection amount is determined by Q4/Ne.