JPH01116262A - Fuel injection quantity control system for internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance control accuracy by obtaining an intake pressure under the predetermined atmospheric pressure being based on an engine speed and a throttle valve opening, delaying this intake pressure through a filter, using an output of this filter and calculating a fuel injection quantity. CONSTITUTION:A processor 31 inputs detection values of an intake air temperature detector 27, crank angle detector 28, throttle valve opening detector 30, cooling water temperature detector 24, O2 sensor 21, etc. The processor 31, being based on an engine speed and a throttle valve opening, sets an intake pressure under the predetermined atmospheric pressure, for instance, 760mmHg. Using a filter constant which obtains a fixed value, when the throttle valve opening is in a predetermined value or more, and increases when the throttle valve opening is in the predetermined value or less, a filter is processed from a value of the intake pressure in the preceding time and its value in this time. The opening time of a fuel injection valve Bm is calculated from the filter processed intake pressure and the engine speed.

Description

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

BACKGROUND ART In so-called electronically controlled fuel injection devices for internal combustion engines, it is necessary to detect the intake air flow rate in order to determine the fuel injection amount. As a method for detecting the intake air flow rate, for example, a typical prior art method is used to detect the intake pressure Pm and the rotational speed N of the internal combustion engine.
A method of finding it from e 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, and therefore accurate fuel injection MTp corresponding to the intake air flow rate is determined. It is not possible.

In order to solve the problem of this prior art, the method previously proposed by the applicant calculates the intake pressure Pmj at a predetermined atmospheric pressure from the throttle valve opening θ and the rotational speed Ne of the internal combustion engine, The fuel injection amount Tp is determined using this intake pressure Pmj and the rotational speed Ne.

With this method, the intake pressure Pmj can be determined relatively accurately in response to changes in the throttle valve opening θ. However, during a transition period when the accelerator pedal is suddenly depressed and the throttle valve opening θ suddenly changes from a small state to a slightly large state, the intake pressure Pmj calculated from the throttle valve opening θ increases rapidly. , the actual intake pressure Pm increases only slowly due to the large influence of the surge tank due to the small flow of air passing through the throttle valve. Therefore, the response is quick with the fuel injection amount Tp determined from the intake pressure Pmj. Too much fuel will result.

Problems to be Solved by the Invention An object of the present invention is to provide a fuel injection amount control method for an internal combustion engine that is capable of determining an accurate fuel injection amount even in a transient state where a sudden change occurs in the throttle valve opening. The goal is to provide the following.

Means for Solving the Problems The present invention calculates the intake pressure under a predetermined atmospheric pressure based on the number of revolutions per unit time of the internal combustion engine and the throttle valve opening, and filters the intake pressure. This is a fuel injection amount control method for an internal combustion engine, which is characterized in that the fuel injection amount is determined using the output of this filter.

In a preferred embodiment, the filter is characterized in that its time constant varies depending on the parameters of the internal combustion engine.

According to the present invention, the number of revolutions per unit time of the internal combustion engine,
The intake pressure under a predetermined atmospheric pressure is determined based on the throttle valve opening. Therefore, the intake pressure can be determined without causing a response delay unlike an intake pressure detector.

The intake pressure thus determined is delayed and derived by a filter. Therefore, the output of this filter corresponds to the change in the actual intake pressure that occurs with a delay from the opening operation of the throttle valve, and the intake air flow rate is determined from the output of this filter and, for example, the above-mentioned rotational speed. By determining the fuel injection amount corresponding to the amount, it is possible to determine the accurate fuel injection amount corresponding to the actual change in the intake pressure.

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 81 to Bm, respectively, and in each explosion stroke in each combustion chamber E1 to Em,
A fuel amount Tp determined by a processing device 31, which will be described later, is injected. Each combustion chamber E1 to Em has an intake valve C.
1 to Cm and exhaust valves D1 to Dm are provided. The internal combustion engine 13 is, for example, a four-stroke ignition internal combustion engine having spark plugs G1 to Gm.

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 . An oxygen concentration detector 21 is provided in the middle of the exhaust pipe 20, and the exhaust gas is purified by a three-way catalyst 22 and discharged to the outside.

A processing device 1731 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, an output interface 35, and a memory 36. Memory 36 includes read-only memory and random access memory. In the embodiment of the present invention, fuel injection valves 81 to Bm inject fuel in response to outputs from detectors 24, 28, 30, etc.
The fuel injection jiTp is controlled for each explosion stroke.

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 FIG. 2 are stored in memory 36 as a graph or a table as shown in FIG.゛The above-mentioned intake pressure Pm
For example, when the throttle valve opening θ suddenly increases as shown in FIG. 4(1), j changes as shown in FIG. 4(2). In this FIG. 4(2), the actual intake pressure Pm is shown by a broken line. In this way, the actual intake pressure Pm cannot follow the throttle valve opening θ, and therefore the calculated intake pressure Pmj is different from the actual intake pressure P.
m, and if injection is performed with the amount of fuel determined using this intake pressure Pmj, the amount of fuel will be excessive.

On the other hand, if the surge tank 14 is equipped with an intake pressure detector or the like to detect the intake pressure,
) is now indicated by a virtual line, and it is understood that a response delay has occurred. Therefore, in this embodiment, the intake pressure Pmj is corrected by a filter operation as described later in the processing circuit 34, and the fuel injection amount Tp is
Find the corrected intake pressure Pmf used in the calculation.

FIG. 5 is a flowchart for explaining the operation of the filter calculation. In the processing circuit 34, for example, a filter operation is performed every predetermined period, that is,
In step n1, a filter constant K stored as a table in the memory 36 is read from the throttle valve opening θ read as described later and, for example, the rotational speed Ne representing the load condition of the internal combustion engine.

This filter constant varies as shown in FIG. 6, for example. That is, if the throttle valve 16 is slightly opened as described above, the intake air is only stored in the surge tank 14 and does not reach each combustion chamber E1 to Em. Therefore, as shown in FIG. When the throttle valve opening θ is smaller than a predetermined value θ1, the filter constant K is increased, and when it is greater than or equal to the predetermined value 81, the filter constant K is set to a constant value.

In step n2, the filter constant K thus obtained is
The intake pressure Pmf is determined based on the formula below.

Using the corrected intake pressure Pmf obtained as described above, the seventh
The fuel injection amount Tp is calculated according to the flowchart shown in the figure. That is, in step s1, the throttle valve opening θ detected by the valve opening detector 30 is read, and in step s2, the rotation speed Ne of the internal combustion engine 13 detected by the crank angle detector 28 is read. In step s3, the intake pressure Pmj corresponding to the throttle valve opening θ and the rotational speed Ne is read from the memory 36. In step S4, from the intake pressure Pmj read in this way, the intake pressure Pmf#(
K is issued. In step s5, the intake pressure Pmf and the rotation speed N
Fuel injection from e! LTp is calculated.

In the above embodiment, the filter constant was changed in accordance with the throttle valve opening θ, but as the rotational speed Ne of the internal combustion engine 13 increases, intake air immediately flows into the combustion chambers E1 to Em. , the influence of the surge tank 14 becomes smaller. Therefore, as another embodiment of the present invention, for example, as shown in FIGS. 8 and 9, the filter constant corresponding to the throttle valve opening θ is set to 1, and the rotational speed Ne
The filter constant K may be determined by multiplying the filter constant corresponding to 2 by 2. In this case, when the filter constant is 1, the amount of change in the small range of the throttle valve opening θ is made larger than the filter constant shown in FIG. 6 described above.

In addition, the filter constant 2 is because, as mentioned above, when the rotational speed Ne increases, the intake air immediately flows in. Therefore, when the rotational speed Ne is less than the predetermined rotational speed Ne1, the amount of change is increased, and when the rotational speed Ne1 is higher than the rotational speed Ne1, the amount of change is increased. is made smaller.

The filter constants determined from these filter constants K 1 and K 2 may be stored in the memory 36 as a map as shown in FIG. 10, for example.

As described above, in the fuel injection amount control method according to the present invention, the predetermined intake pressure Pmj under atmospheric pressure, which is determined from the throttle valve opening θ and the rotation speed Ne of the internal combustion engine 13, is controlled by the throttle valve opening θ, Alternatively, since the intake pressure Pmf used to calculate the fuel injection amount Tp is corrected by the filter constant K based on the throttle valve opening θ and the rotational speed Ne, as described in relation to the background art section. As shown in FIG. is made large, so even if the actual intake pressure Pm does not follow the throttle valve opening θ, the intake pressure Pmf used to calculate the fuel injection amount Tp can be set to a value close to the actual intake pressure Pm. In this way, an accurate intake air flow rate can be determined, and an optimal fuel injection amount can be calculated.

Effects As described above, according to the present invention, the intake pressure under a predetermined atmospheric pressure is determined based on the rotation speed per unit time of the internal combustion engine and the throttle valve opening, and this intake pressure is filtered. Since it is used to calculate the fuel injection amount with a delay, there is no response delay like when using an intake pressure detector, and when the intake pressure at the predetermined atmospheric pressure is used as is. The response is not too fast as in the case of
Accurate fuel injection amount corresponding to changes in actual intake pressure can be determined.

[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 rotational speed Ne of the internal combustion engine 13 and the intake pressure Pmj at each throttle valve opening θ, and FIG.
Figure 4 is a graph showing changes in each intake pressure Pm and Pmj with respect to changes in throttle valve opening θ; Figure 5 is a flowchart for explaining the operation of filter calculation; The figure is a graph showing a change in filter constant with respect to throttle valve opening θ in an embodiment of the present invention.
FIG. 7 is a flowchart for explaining the calculation operation of the fuel injection amount Tp, FIG. 8 is a graph showing a change of 1 in the filter constant with respect to the throttle valve opening θ in another embodiment of the present invention, and FIG. FIG. 8 is a graph showing the change of 2 in the filter constant with respect to the rotational speed Ne of the embodiment shown in FIG. 8, and FIG.
3 is a diagram illustrating the manner in which the filter constant K obtained from the above is stored as a map in the memory 36. FIG. 13... Internal combustion engine, 14... Surge tank, 15.
...Intake pipe, 16...Throttle valve, 24.27...
- Temperature detector, 20... Exhaust pipe, 28... Crank angle detector, 30... Valve opening degree detector, 31... Processing device, 36... Memory, B1 to Bm... fuel injection valve,
E1~Em...Combustion chamber, 01~0m...Spark plug agent Patent attorney Number of strokes Keiichi 1st prisoner 2nd prisoner Fig. 3 Rotation speed Ne 7th prisoner Fig. 8 Fig. 9 Thrositel valve opening θ

Claims (2)

[Claims] (1) Determine the intake pressure under a predetermined atmospheric pressure based on the rotation speed per unit time of the internal combustion engine and the throttle valve opening, and delay the intake pressure by passing it through a filter. A fuel injection amount control method for an internal combustion engine characterized by determining the fuel injection amount using output. (2) The fuel injection amount control method for an internal combustion engine according to claim 1, wherein the filter has a time constant that changes depending on parameters of the internal combustion engine.