JPS6217103B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic fuel injection device for an engine, and more specifically, the present invention relates to an electronic fuel injection device for an engine, and more particularly, a flow meter that detects the amount of intake air by opening and closing a bypass passage branched from an intake passage of an engine is constantly operated to maintain detection accuracy. The present invention relates to an electronic fuel injection device for an engine operated in a high range.

Generally, compared to an air flowmeter or a current meter as a measuring instrument, an engine intake air amount detection device is required to have a wider detectable range, less pressure loss, and high responsiveness.

Conventionally, as an intake air amount detection device for detecting the intake air amount of an engine, for example,
The invention of No. 111512 (name of the invention: ``Engine intake air amount detection device'') is known.

As shown in FIG.
, an on-off valve 6 provided in the bypass passage 5 of the first vortex flowmeter 2, and a second valve for detecting the total amount of air flowing through the first vortex flowmeter 2 and the bypass passage 5.
a vortex flowmeter 11, and a pipe 10 connects the first
The opening/closing valve 6 is opened and closed by a diaphragm 7 that communicates with the downstream side of the vortex flowmeter 2, and the first vortex flowmeter 2 has good detection accuracy when the amount of intake air is relatively small, and has a large pressure loss. On the other hand, the second vortex flowmeter 11 has good detection accuracy when the amount of intake air is relatively large, and also has low pressure loss.
The intake air amount can be detected accurately over a wide range, from a small air flow rate during startup or idling to a large air flow rate at full load, without increasing pressure loss.

By the way, in the above-mentioned intake air amount detection device,
During transitions in air flow, such as when bypass flow occurs or disappears, turbulence occurs in the flow of intake air upstream of the second vortex flowmeter 11, causing a biased flow of intake air in the intake passage, and 2 and the second vortex flow meter 11's accuracy in detecting the air flow rate is significantly reduced.

Therefore, in an electronic fuel injection system using the intake air amount detection device as described above, even during a transition period when the air flow is switched, the output of the first vortex flowmeter 2 or the second vortex flowmeter 11 is If the amount of fuel to be injected is determined by When the on-off valve 6 opens and closes, there is a problem that the combustibility of the engine decreases and harmful components such as NOx and HC increase in the exhaust gas.

The present invention was made with the focus on the fact that the accuracy of measuring the amount of intake air deteriorates when a flow meter that directly detects the air flow rate deteriorates during transitions such as when bypass flow occurs or disappears. Prevents deterioration of fuel injection accuracy during transient times such as
An object of the present invention is to provide an electronic fuel injection device for an engine that suppresses deterioration in combustibility.

For this reason, the present invention uses a first flow meter that is installed in the intake passage of the engine to directly detect the amount of intake air, and a combination of two quantities among the engine speed, intake pressure, and throttle valve opening. a second flow meter that indirectly detects the amount of intake air; a bypass passage that branches from the intake passage and bypasses the first flow meter; a switching device that opens and closes the bypass passage during a specific operation of the engine; The fuel injection valve is controlled by the output signal of the first flow meter, while the fuel injection valve is controlled by the output signal of the second flow meter for a predetermined period of time in synchronization with the operation of the opening/closing device. The fuel injection control device is characterized in that it includes a fuel injection control device that controls the injection valve.

In the present invention, the second flowmeter has lower measurement accuracy than one that directly detects the amount of intake air during transient periods such as the occurrence or disappearance of bypass flow, but it has a lower measurement accuracy than one that directly detects the amount of intake air. In this way, the amount of intake air during transient periods is indirectly detected by a combination of two variables, engine speed, intake pressure, and throttle valve opening, which can be easily measured with much more precision. without receiving
Measures the amount of intake air during transient periods with stable accuracy.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In Fig. 2, 21 is an air cleaner, 22
Reference numeral 25 indicates an air flow meter as a first flow meter that directly detects the amount of intake air installed in the intake passage 24 of the engine 23, 25 indicates a bypass passage that branches from the intake passage 24 and bypasses the air flow meter 22, and 26 indicates an air flow meter. A solenoid valve 28 as an opening/closing device that opens and closes the bypass passage 25 by a solenoid 27;
is the intake passage 24 downstream of the air flow meter 22
A throttle valve 29 is provided in the intake passage 24 between the throttle valve 28 and the engine 23.
30 is a second flow meter, and 31 is a fuel injection control device.

The second flowmeter 30 is composed of an engine speed detection circuit 32 and a throttle opening sensor 33, and in the embodiment shown in FIG. The engine speed signal and throttle opening signal are input to the map control calculation circuit 34 of the fuel injection control device 31, which will be described below, and the intake air amount is indirectly calculated using the map recorded in the map control calculation circuit 34. Based on this intake air amount, the amount of fuel injected from the fuel injection valve 29 when the electromagnetic valve 26 opens and closes is controlled.

The fuel injection control device 31 includes a map control calculation circuit 34, a reference setting circuit 35, a comparison circuit 36, a timer 37, a calculation circuit 38, and a switching circuit 39.

As shown in FIG. 3, the map control arithmetic circuit 34 calculates a region where the intake air amount is almost equal based on equal intake air amount lines l ₁ , l ₂ , l ₃ , l ₄ , . . . A read-only memory (not shown, hereinafter referred to as ROM) in which the intake air amount for the engine speed and throttle opening is written as the address of the engine speed and throttle opening.
It is abbreviated as ) and a fuel injection amount calculation circuit (not shown) that determines the fuel injection amount based on the intake air amount output from the ROM. , map-controls the fuel injection amount.

On the other hand, as shown in FIG. 4, the reference setting circuit 35 determines the throttle opening relative to the engine speed S
The reference signal is input to a comparison circuit 36 together with the throttle opening signal output from the throttle opening sensor 33, and the comparison circuit 36 compares these reference signals and the throttle opening signal. I try to compare the size.

As shown in FIG. 4, the comparison circuit 36 calculates the magnitude of the reference signal for one engine speed x ₀ as S(x ₀ ), and the actual throttle openings as SO ₁ and SO ₂ , So ₂ > S(x ₀ ), it outputs a “High” signal, and when So ₁ < S(x ₀ ), it outputs a “Low” signal.
Outputs the signal.

The output signal of the comparison circuit 36 above is the solenoid 2
7. Input to timer 37 and arithmetic circuit 38.

The solenoid 27 is energized by the "High" output signal of the comparison circuit 36 to open the solenoid valve 26, thereby opening the bypass passage 25.

On the other hand, the timer 37 is triggered at the timing of the rise of the output signal from the comparison circuit 36 from "Low" to "High" and the fall from "High" to "Low", respectively, and causes the switching circuit 39 to perform a switching operation. The fuel injection amount is controlled by the output signal of the map control calculation circuit 34 for the settling time of the timer 37.

The arithmetic circuit 38 receives an air flow signal input from the air flow meter 22 and the engine rotation speed detection circuit 3.
This is a circuit that calculates the optimal fuel injection amount from the engine speed signal input from 2, and its output signal is
It is input to the switching circuit 39 together with the output signal of the map control calculation circuit 34 described above.

In FIG. 2, the output signal of the comparator circuit 36 is input to the arithmetic circuit 38 by the solenoid valve 2.
6 is opened and air flows also into the bypass passage 25, the amount of air passing through the air flow meter 22 is changed from the amount of intake air passing through the intake passage 24 to the amount of air passing through the bypass passage 25.
5. Therefore, when the output signal of the comparison circuit 36 is "High" (when the bypass passage 25 is open), the fuel injection value is calculated by subtracting the air flow rate signal output from the air flow meter 22. This is to switch the quantity function.

Next, the operation of the electronic fuel injection system of the engine 23 shown in FIG. 2 will be explained.

Assuming that the engine 23 is currently rotating at idle, the throttle opening S of the throttle valve 28 is small and falls within the region Ao ₁ below the curve S(x) in FIG.

Therefore, the output signal of the comparison circuit 36 is “Low”
Solenoid 27 is deenergized and solenoid valve 2
6 closes the bypass passage 25, and the switching circuit 3
Reference numeral 9 operates the fuel injection valve 29 based on the output signal of the arithmetic circuit 38.

In the above state, as shown in FIG.
From t ₀ , the throttle opening of the throttle valve 28 increases and the amount of intake air increases, and at time t ₁ , the amount of intake air passing through the intake passage 24 reaches the air flow meter 2.
If the maximum allowable amount _Fnax that guarantees the accuracy of 2 is exceeded, the throttle opening S will change according to the curve S in Fig. 4.
It enters the area Ao ₂ above (x) and comparator circuit 36
The output signal rises from “Low” to “High”.

As mentioned above, the output signal of the comparator circuit 36 is
When rising from "Low" to "High", the solenoid 27 is energized and the electromagnetic valve 26 opens, and arrows A ₂₅ ,
The amount of air flowing through the air flow meter 22 is as shown by curve n ₀ in _FIG .
However, at this time, the arithmetic circuit 38 uses the output signal of the comparison circuit 36 to calculate the output signal of the air flow meter 22 when air is flowing through the bypass passage 25 at a predetermined rate, as shown by the curve m ₀ in FIG. Switch as shown. That is, there is a delay in the response of the solenoid valve 26, and when the solenoid valve 26 is opened, the bypass passage 2
6, a predetermined proportion of air does not flow immediately to the measuring plate (not shown) of the air flow meter 22.
, the actual output signal of the air flow meter 22 changes as shown by the curve n ₀ , and there is a deviation from the air amount signal (curve m ₀ ) at the time of switching in the arithmetic circuit 38, resulting in a change in the intake air amount. Fuel injection amount cannot be controlled accurately.

However, at this time, the timer 37 is set at time t ₁
The fuel injection amount of the fuel injection valve 29 is triggered by
The switching circuit 39 causes the output signal of the map control calculation circuit 34 to change the output signal of the map control calculation circuit 34 only during the time T ₀ until the time t ₂ when the output signal of the air flow meter 22 follows the normal rate of air flow passing through the air flow meter 22. It will be controlled.

Therefore, even if there is a response delay in the output signal of the air flow meter 22 as described above, the fuel injection amount of the fuel injection valve 29 is adjusted to the optimum amount by the map calculation circuit 34 from time _{t 1} to time t 2. The engine's combustibility will not be reduced.

Next, when the settling time T ₀ of the timer 37 has elapsed at the above-mentioned time t ₂ , the fuel injection amount of the fuel injection valve 29 is again controlled by the output signal of the arithmetic circuit 38 .

However, at this time, since the bypass passage 25 is open and a predetermined amount of air is flowing, the function of the fuel injection amount relative to the output signal of the air flow meter 22 is changed, and fuel is injected accurately.

After the intake air amount becomes constant between time t ₃ and t ₄ in FIG. 5, the intake air amount gradually decreases at time t ₄ , and at time t ₅ , the throttle opening for that engine speed becomes Area under curve S(x) in Figure 4
When Ao ₁ is entered, the output signal of the comparison circuit 36 rises from "High" to "Low", the solenoid 27 is deenergized, the solenoid valve 26 is closed, the bypass passage 25 is closed, and the amount of air passing through the air flow meter 22 is Increase rapidly. As a result, the measuring plate of the air flow meter 22 opens rapidly and becomes larger than the opening corresponding to the actual amount of intake air.

The output signal of the air flow meter 22 at this time is larger than the output signal corresponding to the amount of intake air actually supplied to the engine 23, but in this case as well, due to the action of the timer 37 and the switching circuit 39, the fuel injector 29 The injection amount is controlled by the output signal of the map control calculation circuit 34, and
Regardless of the response delay of the output signal, the amount is controlled to an optimum level, and the combustion performance of the engine does not deteriorate.

Thereafter, when the settling time T ₀ of the timer 87 has elapsed at time t ₆ , the fuel injection amount of the fuel injection valve 29 is changed again to
Controlled by the output signal of the arithmetic circuit 38, the engine enters idling rotation at time _t7 .

As described above, the fuel injection amount of the fuel injection valve 29 is optimally controlled by the output signals of the map control calculation circuit 34 and the calculation circuit 38.

In addition, in the embodiment shown in FIG. 2, the second flowmeter 3
By providing an intake pressure sensor at 0 and combining the intake pressure sensor with the engine rotation detection circuit 32 or the throttle opening sensor 33, the amount of intake air can be indirectly detected. It may be provided between the opening sensor 33 and the comparison circuit 36 to output a reference engine speed signal corresponding to the throttle opening, that is, intake pressure, throttle opening, and engine speed. One of the signals may be input to the reference setting circuit 35 and compared with the other signal.
Furthermore, instead of the solenoid valve 26 and the solenoid 27,
The diaphragm 8 and on-off valve 6 shown in FIG. 1 can also be used.

Note that the present invention also provides a first flow meter 22 that is interposed in the intake passage 24 by interposing a flow meter in the bypass passage 25 as well.
The above flow meter can also be applied to one in which the flow meter is operated by switching alternately.

As is clear from the detailed explanation above, the present invention is capable of controlling the generation and disappearance of bypass flow by switching the opening/closing device for opening and closing the bypass passage that branches from the intake passage and bypasses the first flow meter. During transients, it is possible to easily measure much more precisely than directly detecting the amount of intake air by combining two quantities: engine speed, intake pressure, and throttle valve opening. The second system has stable detection accuracy for detecting the amount of intake air.
Since fuel injection is performed by indirectly detecting the amount of intake air using a flow meter, the drop in fuel injection accuracy during transient periods is suppressed, and there is no reduction in engine combustibility.
The first flowmeter, which directly detects the amount of intake air, operates in a region with high detection accuracy, and the
Harmful components such as NOx and HC can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional intake air amount detection device for an engine, FIG. 2 is a block diagram of an electronic fuel injection device for an engine according to the present invention, and FIG. Figure 4 is an explanatory diagram of the curve showing the reference signal of the throttle opening output from the reference setting circuit, and Figure 5 is an explanatory diagram of the operation of the electronic fuel injection system of the engine shown in Figure 2. FIG. 6 is an explanatory diagram showing the relationship between the output signal of the air flow meter corrected by the arithmetic circuit and the actual output signal of the air flow meter. 22... Air flow meter (first flow meter), 2
3...Engine, 24...Intake passage, 25...Bypass passage, 26...Solenoid valve, 27...Solenoid, 29...Fuel injection valve, 30...Second flow meter,
31... fuel injection control device, 34... map control calculation circuit, 37... timer, 38... calculation circuit,
39...Switching circuit.

Claims (1)

[Claims] 1. A first flow meter that is installed in the intake passage of the engine and directly detects the amount of intake air, and 2 of the engine speed, intake pressure, and throttle valve opening.
a second flow meter that indirectly detects the amount of intake air by a combination of two quantities; a bypass passage that branches from the intake passage and bypasses the first flow meter; and an opening and closing that opens and closes the bypass passage during specific engine operations. and the fuel injection valve is controlled by the output signal of the first flowmeter, and when the opening/closing device is switched on/off, the output signal of the second flowmeter is controlled for a predetermined period of time in synchronization with the operation of the opening/closing device. An electronic fuel injection device for an engine, comprising: a fuel injection control device for controlling the fuel injection valve.