JPS60209641A - Fuel injection apparatus for internal-combustion engine - Google Patents

Abstract

PURPOSE:To operate an internal-combustion engine smoothly even when the opening of a throttle valve is large, by detecting the maximum value and the minimum value of the frequency of the signals produced by a Karman-vortex flow meter while the engine is rotated by a certain angle, and determining the injection quantity of fuel from a logical frequency. CONSTITUTION:A Karman-vortex flow meter 100 produces a signal having a frequency corresponding to the quantity of intake air drawn to an internal-combustion engine. A means 101 detects the maximum value and the minimum value of the frequency of the signals produced by the flow meter 100 while the engine is rotated a predetermined angle. An arithmetic means 102 calculates the difference of the maximum and minimum values detected by the means 101, while a judging means 103 judges whether the difference detected by the arithmetic means 102 is greater than a predetermined value or not. A mean-value calculating means 104 calculates the mean value of the maximum value and the minimum value obtained by the detecting means 101. In case that judgement is made by the means 103 that the above-mentioned difference is greater than said predetermined value, a means 107 calculates the injection quantity of fuel on the basis of a logical frequency stored in a memory 105. In case that said difference is smaller than the predetermined value, an injection means 108 injects fuel on the basis of the mean value obtained by the calculating means 104.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a fuel injection system for an internal combustion engine, and more particularly to a fuel injection system for an internal combustion engine using a Karman vortex flow needle.

Prior Art and Problems In internal combustion engines, the amount of intake air is generally measured, and the amount of fuel injection is controlled based on the measurement results so that the actual air-fuel ratio matches the stoichiometric air-fuel ratio.

The amount of intake air is measured using various methods, such as using a Karman vortex flow rate needle or the like. The Karman vortex flowmeter utilizes the fact that the amount of intake air is inversely proportional to the Karman vortex generation period, and outputs a signal with a frequency proportional to the amount of intake air.

By the way, an internal combustion engine has an intake stroke, a compression stroke, an explosion stroke,
Since the exhaust stroke is repeated, even if the opening degree of the throttle valve is constant, the amount of intake air will pulsate at a constant cycle. For example, if the internal combustion engine is a 4-cylinder engine, the period of 180°GA rotation of the crankshaft is one period of pulsation, so the frequency f of the output signal of the Karman vortex flow needle changes as shown in Figure 1. Become something to do. As shown in the figure, the frequency f of the output signal of the Karman vortex flow needle
Even if the opening degree of the throttle valve is constant, it changes in a 180° CA cycle, so conventionally, the average value A of the maximum value MAX and minimum value opening N of the frequency f between 180'' and
= ((M to M + MIN) / 2'), and the fuel injection amount is determined based on the average value.

However, the conventional example described above has the following drawbacks.

Figures 2 (A) and (B) show the rotational speed of the internal combustion engine at 1100O.
rp, and the intake pipe negative pressure is -25mmfig, respectively.
' It is a diagram showing the frequency f of the output signal of the Karman vortex flowmeter when the temperature is −10 mmHg;
As can be seen from B), what is the maximum value of the frequency f when the opening of the throttle valve is large and the negative pressure in the intake pipe is small? The difference between lAX and the minimum value FIIN becomes large. Therefore,
When the throttle valve opening is large (for example, when the throttle is fully open), the average value A will deviate greatly from the actual value, so determining the fuel injection amount based on the average value A will not allow smooth operation of the internal combustion engine. It was difficult to do.

In order to improve this drawback, upper limits are set in advance for the rotational speed of the internal combustion engine, and the maximum value MAX and minimum value MI
It has also been proposed to calculate the fuel injection amount based on an upper limit value determined corresponding to the rotational speed when the average value A with respect to N exceeds the upper limit value. According to this method, if the average value A becomes larger than the actual value, the error can be made small, but if the average value becomes smaller than the actual value, the calculated fuel injection amount There was a drawback that the amount was smaller than the required amount, resulting in a lean air-fuel ratio.

OBJECTS OF THE INVENTION The present invention has been made to improve the above-mentioned drawbacks, and its purpose is to enable smooth operation of an internal combustion engine even when the opening degree of the throttle valve is large.

Configuration of the Invention FIG. 7 is a configuration diagram of the present invention. Power! Leman vortex maximum 1
00 outputs a signal with a frequency corresponding to the intake air amount of the internal combustion engine, and the detection means 101 detects the maximum and minimum values of the frequency of the signal output from the Karman vortex flowmeter 100 while the internal combustion engine rotates at a certain angle. I put it on. The calculating means 102 calculates the difference between the maximum value and the minimum value detected by the detecting means 101, and the determining means 103 determines whether the difference determined by the calculating means 102 is greater than or equal to a predetermined value. is the detection means 10
Calculate the average value of the maximum and minimum values detected in step 1. The memory 105 is provided with an area in which theoretical frequencies are stored corresponding to the rotational speed of the internal combustion engine, and the rotational speed detection means 10
6 detects the rotation speed of the internal combustion engine. If the determining means 103 determines that the difference is greater than or equal to the predetermined value, the fuel injection amount calculation means 107 calculates the fuel injection amount based on the logical frequency stored in the memory 105, and determines whether the difference is equal to or greater than the predetermined value. If it is determined that it is less than the value, the average value calculation means 104
The fuel injection amount is calculated based on the calculated average value, and the injection means 10B injects the amount of fuel corresponding to the calculation result of the calculation means 107.

Embodiment of the invention FIG. 3 is a block diagram of an embodiment of the invention, where 1 is 4.
2 is an air cleaner, 3 is a Karman vortex flow needle that sets the output signal a to "1" each time a Karman vortex is generated, 4 is a throttle chamber, 5 is an intake manifold, 6 is an electromagnetic fuel injector, 7 is a throttle valve, 8 is an opening detector that outputs a signal corresponding to the opening of the throttle valve 7, 9 is a crank angle sensor, 1o is a microprocessor, 11 is a data input section, 12 is a data output section, 13 is a memory.The crank angle sensor 9 outputs a rotation angle position signal C every time the crankshaft rotates by a certain angle, and also outputs a reference position signal d every time the crankshaft reaches the reference position. .

The amount of intake air is determined by the Karman vortex flowmeter 3 from the air cleaner 2.
Fuel is supplied to each cylinder from each branch of an intake manifold 5 via a throttle chamber 4, and fuel is injected into the internal combustion engine 1 from a fuel injector 6. Further, the opening degree of the throttle valve 7 in the throttle chamber 4 is controlled by operating the accelerator pedal.

4 and 5 are flowcharts showing an example of the processing contents of the microprocessor 10.
The operation shown in FIG. 3 will be explained with reference to the drawings.

The microprocessor 10 starts the program shown in FIG. 4 every time the output signal a of the Karman vortex flow meter 3 applied via the data input section 11 becomes "1", and this program is started. The microprocessor 10 first calculates the period T of the signal a (step S1),
Next, the microprocessor 10 compares the maximum value T MAX stored in the memorandum with the period T determined in step S1, and determines whether T > T MAX (step S2). If the determination result is YES, the microprocessor 10 stores the period T determined in step S1 as a new maximum value T MAX in the memory 13 (step S3), and if the determination result is NO, the process moves to step S4. In step S4, the minimum value T MIN stored in the memory 13 is compared with the period T determined in step Sl, and T < TM! Determine whether it is N or not.

If the judgment result is NO, the microprocessor 10 moves to another control program (step S6), and if the judgment result is Y.
In the case of ES, the cycle T determined in step S1 is stored in the memory 13 as a new minimum value TMIN (step S5).
), the program moves on to this retransmission control program (step 36).
. As will be described later, the microprocessor 10 erases the maximum value TMAX and minimum value TMIN stored in the memory 13 each time the rotational angular position of the crankshaft reaches O'' CA or 180' CA. 13 has the rotation angle position of the crankshaft at 0' CA and 180° CA.
The maximum and minimum values of the period T from then to the present are stored.

Further, the microprocessor 10 is a crank angle sensor.

The program shown in FIG. 5 is started every time it is detected that the rotational angular position of the crankshaft becomes 0'CA or 180'CA based on the output signals c and d of 9. When started, the microprocessor 10 first operates at 180°C stored in the memory 13.
＾180 based on the minimum period T MIN in between
The maximum frequency of the output signal a of the Karman vortex flowmeter 3 between
1 based on the maximum period T WAX between °GA
80 “Minimum value of frequency of signal a between CA
IN is set (step S8). Next, the microprocessor 10 calculates the difference ΔF between the maximum value FMAX and the minimum value FMIN.
=FMAX-FMAX (step S9), and then it is determined whether the ΔF is larger than 10% of the maximum value FMAX, that is, whether the following equation (1) holds true (step 510). In addition, equation (1) indicates that the intake pipe negative pressure is approximately -20111
m) This is true when the amount is 1g or less.

ΔF > F MAX /10 --- (1) If the judgment result in step S10 is NO, that is, if the opening degree of the throttle valve 7 is small and the difference between the maximum value F MAX and the minimum value F MIN is small, the micro The processor 10 has the maximum value F
The average value A of MAX and the minimum value F MIN is determined as A = (to FM8 + F MIN ) /2 (step 511), and then the fuel injection amount is determined based on the average value A (step 51).
4). Furthermore, if the judgment result is YES, that is, the opening degree of the throttle valve 7 is large, the maximum value F MAX and the minimum value F MIN
If the difference is large, the microprocessor 10 detects the rotational speed N of the internal combustion engine based on the output signal C of the crank angle sensor 9 (step 512). As shown in FIG. 6, the memory 13 is provided with an area corresponding to the rotational speed N of the internal combustion engine in which a frequency theoretically calculated based on the rotational speed N is stored. - When the rotation speed N of the internal combustion engine is detected by the engine S12, 1. Step 513) Read out the frequency F that is specified.
・Calculate the fuel injection amount based on the frequency F (Step 5)
14). Note that the rotation speed N detected in step S12 is N2.
If <N≦N3, frequency F3 will be read from memory 13.

Next, the microprocessor 10 applies a control signal to the data output unit 12 to set the output signal e to "1", and causes the fuel injector 6 to inject fuel for a time corresponding to the fuel injection amount determined in step S14 (step 515).
), then the maximum value T MA stored in the memory 13
(step 516)
, moves on to the control program for this retransmission (step 517).
.

In this way, in this embodiment, the difference F between the maximum value F MAX and the minimum value F MIN of the frequency of the output signal a of the Karman vortex flowmeter 3 between 180° and 180 degrees is 10% of the maximum value, Even when the opening degree of the valve 7 is large, the internal combustion engine can be operated smoothly.

In addition, in the above-mentioned embodiment, the difference ΔF is the maximum value F MA
When the intake pipe negative pressure becomes 10% or more of X, the fuel injection amount is calculated based on the frequency F stored in the memory 13. The invention is not limited to this, as long as the fuel injection amount is calculated based on the stored frequency F.

As described in detail, the present invention is based on the maximum and minimum frequencies of the signal output from the Karman vortex flow needle while the internal combustion engine rotates at a certain angle (180 degrees in the embodiment). Therefore, if the difference is greater than a predetermined value, that is, if the opening degree of the throttle valve is large, the fuel injection amount is determined based on the theoretical frequency corresponding to the rotation speed stored in the memory. This has the advantage that the internal combustion engine can be operated smoothly even when the throttle valve is opened to a large degree.

[Brief explanation of drawings]

Figure 2 (A) and (B) are diagrams showing changes in the frequency of the output signal of the Karman vortex flow needle, Figure 3 is a block diagram of an embodiment of the present invention, and Figures 4 and 2 are diagrams showing changes in the frequency of the output signal of the Karman vortex flow needle. Figure 5 is a flowchart showing an example of the processing contents of the microprocessor;
The figure shows the contents stored in the memory, and FIG. 7 is a block diagram of the present invention. 1 is the internal combustion engine, 2 is the air cleaner, 3,100 is the force JL
/? 4 is the throttle chamber, 5 is the intake manifold, 6 is the fuel injector,
7 is a throttle valve, 8 is an opening detector, 9 is a crank angle sensor, 10 is a microprocessor, 11 is a data input section, 12 is a data input section, 13, 105 is a memory, 101
102 is a detection means, 102 is a calculation means, 103 Patent applicant: Fujitsu Ten Ltd. (one other person), Patent attorney Gobe Tamamushi (
Figure 1 Figure 2 (A) (8) Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] a Karman vortex flow needle that outputs a signal with a frequency corresponding to the intake air amount of the internal combustion engine; and maximum and minimum values of the frequency of the signal output from the Karman vortex flowmeter while the internal combustion engine rotates at a certain angle. a detection means for detecting the detection means; a calculation means for calculating the difference between the maximum value and the minimum value detected by the detection means;
a determining means for determining whether the difference determined by the calculating means is equal to or greater than a predetermined value; an average value calculating means for calculating an average value between the maximum value and the minimum value detected by the detecting means; a rotation speed detection means for detecting the rotation speed of the engine; a memory provided with an area in which a theoretical frequency is stored corresponding to the rotation speed of the internal combustion engine; If it is determined, the fuel injection amount is calculated based on the theoretical frequency stored in an area of the memory corresponding to the detection result of the rotation speed detection means, and the determination means determines that the difference is less than or equal to the predetermined value. If it is determined that 1. A fuel injection device for an internal combustion engine, comprising an injection means for injecting fuel into the engine.