JP2559736B2 - Engine fuel injection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection device for an engine, and more particularly to improvement of a so-called sequential injection system.

(Prior Art and Problems Thereof) Among fuel injectors for engines, there is a fuel injector for which fuel injection is performed in synchronization with the intake stroke of each cylinder, as seen in JP-A-57-59032. . This type of injection method is called sequential injection, and has recently attracted attention as being effective in improving transient response. That is, in the sequential injection method, the injection amount is independently determined for each cylinder, so that fuel injection corresponding to the intake charge amount of each cylinder can be performed.

Therefore, in order to take full advantage of the sequential injection method, it is necessary to perform fuel injection based on the latest data as much as possible. Therefore, the fuel injection timing is such that the total amount of injected fuel is in the cylinder during the intake stroke. It is desirable to set the time as late as possible, provided that it can be filled.

However, when the fuel injection timing is set to take advantage of the sequential injection as described above, the following problems occur. That is, in the intake system of the engine,
There is a tuned engine rotation range where the maximum charging efficiency is obtained based on the natural frequency peculiar to the intake passage, and the characteristic is that the charging efficiency of intake air decreases as the tuned engine rotation distance increases. Explaining this with reference to FIG. 3 and FIG. 4, in the synchronized engine rotation range, intake is performed until the intake valve is closed (see FIG. 3), whereas in the region separated from the synchronized engine rotation range. Then, at the end of the intake stroke, there is a phenomenon in which the intake air is blown back, that is, a part of the fresh air that has entered the cylinder returns to the intake system again (see FIG. 4).
For this reason, when the injection timing is set as late as possible in order to maximize the advantage of sequential injection, a portion of the fuel injected along with the blowback of intake air is recirculated to the intake system as it goes away from the synchronized engine rotation range. Therefore, an error occurs between the fuel injection amount and the actual supply amount. This hinders the advantage of sequential injection in which the injection amount is determined for each cylinder based on the latest data, and the significance of sequential injection disappears.

Such a problem is likely to be remarkable particularly in a supercharging type intake system that utilizes an intake dynamic effect such as inertia or resonance of intake.

Therefore, an object of the present invention is to provide a fuel injection device for an engine that maximizes the advantages of sequential injection and does not cause an error between the injection amount and the actual supply amount due to re-intake of intake air. is there.

(Means and Actions for Solving Problems) In order to achieve the above technical problems, in the present invention, on the premise of a fuel injection device of an engine configured to inject fuel in accordance with an intake stroke, A rotation speed detecting means for detecting the rotation speed of the engine, and a signal from the rotation speed detecting means, and when the rotation speed of the engine is outside the tuning engine rotation range in which it is in tune with the natural frequency of the intake passage, the tuning engine rotation speed And an injection timing adjusting means for advancing the fuel injection timing as compared with when it is in the range.

With such a configuration, in the synchronized engine speed range where the intake charging efficiency is excellent, there is almost no intake blowback, so the latest data can be obtained by taking the fuel injection timing as late as possible. Since it is possible to determine the injection amount based on the above, it is possible to maximize the advantages of the sequential injection.

On the other hand, in the region other than the tuning timing rotation region, the fuel injection timing is advanced, so that the fuel is prevented from flowing back to the intake system due to the blowback of intake air, and the entire amount of injected fuel is filled in the cylinder in the intake stroke. The Rukoto.
Therefore, an error between the fuel injection amount and the actual supply amount can be prevented from occurring. In addition, by advancing the injection timing, the mixing period between the fuel and intake air becomes longer and the fuel vaporizes,
The advantage of combustibility that atomization is promoted is exhibited.

(Example) Hereinafter, the Example of this invention is described based on drawing.

In FIG. 2, reference numeral 1 is a main body of a multi-cylinder engine, and this engine main body 1 is a cylinder block 2 as known.
The combustion chamber 5 is defined by the cylinder head 3 and the piston 4 fitted in the cylinder bore 2a. An ignition plug (not shown) is arranged in the combustion chamber 5, and an intake port 6 and an exhaust port 7 are opened. These ports 6 and 7 are synchronized with an engine output shaft by an intake valve 8 or an exhaust valve 9. Then, it is opened and closed at a known timing.

In the intake passage 10 connected to the intake port 6, an air cleaner 11, an air flow meter 12 for detecting the intake air amount, a slot valve 13, a surge tank 14, and a fuel injection valve 15 are sequentially arranged from the upstream side to the downstream side. Has been done. The fuel injection valve 15 is provided independently for each cylinder, and its injection port 15a is directed toward the valve head of the intake valve 8.

In the intake passage 10, a surge tank 14 and a fuel injection valve 15
A short intake passage 16 is formed between and, and an opening / closing valve 17 is arranged at the downstream end of the intake passage 16. This on-off valve 17 is closed in the low rotation speed region, and while the long intake passage 10 forms the resonance tuning condition in the engine low rotation speed region,
In the high engine speed range, the on-off valve 17 is opened and the short intake passage 16
Is designed to form a resonance tuning condition in the high engine speed region.

In FIG. 2, reference numeral 20 is a control unit, which, as is known, comprises a CPU 21, a storage means 22, and an I / Q port 23. The on-roll unit 20 includes a crank angle sensor 24. Of the crank angle signal (corresponding to the engine speed signal), the throttle opening signal from the opening sensor 26, and the intake air amount signal from the air flow meter 12. Then, the control unit 20 outputs a fuel injection control signal to the fuel injection valve 15 and an open / close control signal to the open / close valve 17.

The outline of the control by the control unit 20 will be explained. First, as shown in FIG. 5, the switching of the on-off valve 17 is performed by the first torque curve 30 obtained by the long intake passage 10,
With the engine speed N ₁ corresponding to the intersection 32 with the second torque curve 31 obtained by the short intake passage 16 as the boundary, the opening / closing valve 17 is closed when it is smaller than N ₁ and the intake condition is synchronized by the long intake passage 10. When the engine speed is higher than N ₁ , the on-off valve 17 is opened and the short intake passage 16
The intake tuning condition is formed by. Therefore, in the low engine speed region, as shown in FIG.
D ₁ is the tuning engine speed range, and D ₂ is the tuning engine speed range in the high engine speed range.

The synchronized engine rotation regions D ₁ and D ₂ are mapped in advance (the intake system S ₁ shown in FIG. 7), and the engine operating state is in the synchronized engine rotation regions D ₁ and D ₂ shown in FIG. As described above, the fuel injection timing T ₁ in the intake stroke is set, and the engine operating state is the synchronized engine rotation range D ₁ ,
When there is a value other than D ₂ , the injection timing immediately before the intake stroke
T ₂ is adapted to be set, these injection timing T _1, T ₂ is a predetermined crank angle that is set in advance.

Based on the above, a more detailed description will be given based on the flowcharts shown in FIGS. 6 to 8.

FIG. 6 shows the main routine. First, step
In S1, the tuning engine rotation range is determined, and in the next step S2, fuel injection is executed.

Figure 7 is shows the tuning engine speed range determining routine in step S1, in step S3 here, based on the engine speed and the throttle opening, the map S ₁ is the current operating state synchronization engine speed range D _{When set to 1} and D ₂ , the flag K is set to "1",
Flag K when it is outside the tuning engine rotation range D ₁ , D _2.
Is set to "0".

FIG. 2 shows a fuel injection execution routine in the above step S2.
The flag K is determined in S4, and the flag K is "1".
When it is determined that the tuning engine rotation range D ₁ ,
As in D _2, the flow proceeds to step S5, the injection timing T ₁ (Figure 1 reference) calculation of the intake air amount waiting for (step S6), and calculation of the fuel injection amount (step S7), and the fuel injection is made (Step S8). As is known, the calculation of the intake air amount is performed based on the intake air amount signal from the air flow meter 12, and the fuel injection amount is calculated based on the engine speed, the intake air amount, and the like.

On the other hand, in step S4, when the flag K is determined to be "0", the engine operating condition is other than the tuning engine speed region D _1, D _2, and proceeds to step S9, the injection timing T ₂ Wait for the above step S6
The process proceeds to S8, and fuel injection is performed at the injection timing T ₂ (see FIG. 1).

With the above configuration, fuel injection is performed at the injection timing T ₁ in the intake stroke in the synchronized rotation regions D ₁ and D ₂ with excellent intake charging efficiency, so fuel injection based on the latest information for each cylinder is performed. The amount will be determined.

On the other hand, in the regions other than the synchronized rotation regions D ₁ and D ₂ , the fuel is injected at the injection timing T ₂ immediately before the intake stroke, so that the total amount of injected fuel is not affected by the blowback of intake air at the end of the intake stroke. Will be filled inside. Therefore, the occurrence of an error between the fuel injection amount and the actual supply amount is prevented. Further, by advancing the injection timing, the mixing period of the fuel and the intake air becomes longer, and the vaporization and atomization of the fuel are promoted.

The embodiment of the present invention has been described above.
In the system in which the opening degree is gradually adjusted in accordance with the engine operating state, the tuning engine rotation range according to the opening degree of the opening / closing valve 17 is prepared in advance in a plurality of maps (7th map). Map Sn) shown in the figure, and the flag K may be set based on this map Sn.

(Effects of the Invention) As is apparent from the above description, according to the present invention, while making the most of the advantage of sequential injection, the injection amount and the actual supply amount that accompany blowback of intake air outside the synchronized engine rotation range It is possible to prevent the error. Further, in a region other than the synchronized engine rotation range, the mixing period of the fuel and the intake air is extended as the injection timing is advanced, and the combustibility can be improved by promoting the vaporization and atomization of the fuel.

[Brief description of drawings]

FIG. 1 is a diagram showing fuel injection timing in an embodiment, FIG. 2 is an overall configuration diagram of an engine in the embodiment, FIG. 3 is a diagram showing a flow velocity of intake air in an intake passage in a synchronized engine rotation range, and FIG. Is a diagram showing the flow velocity of intake air in the intake passage in a region other than the synchronous engine rotation region, FIG. 5 is a relationship diagram between the length of the intake passage and torque, FIG. 6 is a flowchart showing an example of control in the embodiment, 7 and 8 show a subroutine. 1: Engine body 6: Intake port 8: Intake valve 10: Intake passage 12: Air flow meter 15: Fuel injection valve 15a: Fuel injection valve nozzle 16: Short intake passage 17: Open / close valve 20: Control unit T ₁ : Synchronous engine Injection timing in rotation range T ₂ : Injection timing outside synchronization engine rotation range D ₁ , D ₂ : Synchronization engine rotation range

Claims (1)

(57) [Claims] 1. A fuel injection device for an engine, which is configured to inject fuel in accordance with an intake stroke, and a rotational speed detecting means for detecting the rotational speed of the engine, and an engine for receiving a signal from the rotational speed detecting means. When the number of revolutions of the engine is outside the tuned engine rotational range where it is synchronized with the natural frequency of the intake passage, the injection timing adjusting means for advancing the fuel injection timing compared to when it is in the tuned engine rotational range is provided. A fuel injection device for an engine.