JPS60108546A - Fuel injection device of engine - Google Patents

Abstract

PURPOSE:To promote the improvement of combustibility, by setting a fuel pressure of the second injection valve, which injects fuel in a high region of intake air quantiy, higher than the fuel pressure of the first injection valve which injects fuel in the full range of operation. CONSTITUTION:The first intake passage 7a arranges the first injection valves 12 injecting fuel in the full range of operation including a low region of intake air quantity. The second intake passage 7b arrages the second injection valves 13 injecting fuel in a high region of intake air quantity. The throttling enables the pressure in a side of the second injection valve to rise higher than the pressure in a side of the first injection valve 12. In this way, an engine can both promote fuel to be atomized into fine particles and reduce a shock when the injection of fuel is switched.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a fuel injection device for an engine.

(Prior art) Two fuel injection valves are arranged for each cylinder of the engine,
The fuel injection from each fuel @ side valve is controlled according to the engine load and other operating conditions, and the first injection valve injects fuel in the entire operating range including the low intake area, and the second injection valve For example, a fuel injection device that injects fuel in a high intake W range to achieve accurate fuel supply control from a low load range to a high load range is known as, for example, the Japanese Utility Model Publication No. 57-50536.
It is well known as shown in No.

In the above-mentioned fuel injection device, if the dangerous fuel injection at d3 is performed with one fuel 1f3I nA injector during high load,
Accuracy decreases when injecting a small amount of fuel at low load, whereas the first injector, which has good supply accuracy in the low flow rate range, injects fuel in the low load range. In a high flow rate range where fuel cannot be supplied, fuel is also injected from the second injection side valve.

Therefore, in order to increase the fuel injection amount in accordance with the increase in the intake air carrier, in order to perform fuel injection by the M2 injector in addition to the fuel injection by the first injector, each injector If the fuel pressure is constant, it is difficult to obtain good injection characteristics over the entire range.If the supply accuracy at low loads is improved, a switching shock will occur at the start of injection from the second injector, which will have a negative impact on drivability. There is a risk of giving.

In other words, in the low injection range, when the fuel pressure is high, the time to perform the predetermined maximum (small) fuel injection is short (and the controllability is reduced), so when the fuel pressure is low, the injection time is longer and the controllability is reduced. On the other hand, when the fuel pressure is low, there is a time delay before the fuel injected into the intake passage flows into the combustion chamber when the fuel injection range shifts to the high injection range and injection from the second injector starts. , temporarily supplying a mixture with a lean air-fuel ratio reduces engine output and causes a shock to drivability.In addition, increasing the fuel pressure reduces the shock during switching and promotes fuel atomization. It is possible to improve combustibility.

(Object of the Invention) In view of the above-mentioned circumstances, the present invention aims to improve fuel injection by simultaneously satisfying the demands of improving fuel supply efficiency and reducing shock during switching in fuel injection using Ml and two-pressure injection valves, thereby achieving good combustion. The object of the present invention is to provide a fuel injection device for an engine that achieves improved performance.

(Structure of the Invention) The M size @ separate device for the engine of the present invention includes a first injection valve that injects fuel in the entire operating range including the low intake air amount area, and a second injection valve that injects fuel in the high intake air amount area. The fuel injection valve is characterized in that the fuel pressure of the second injection valve is set higher than the fuel pressure of the first injection valve.

(Effects of the Invention) According to the present invention, in the low intake air amount region, the first injector with low fuel pressure injects fuel with high precision, and in the high intake amount region, the second injector with high fuel pressure also injects fuel. While this promotes fuel atomization, the scattering distance of the injected fuel when switching to inject fuel from the second injector in addition to the 11114th injector is too large, improving fuel delay and improving responsiveness. This makes it possible to reduce the shock at the time of switching.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 is an overall configuration diagram of an engine equipped with two intake boats.
1 and the second intake boats 3 and 4 are open, and the two first and second exhaust boats 5 and 6 are open, respectively.

An intake passage 7 for supplying intake air is connected to the intake boat 3.4. This intake passage 7 has an air cleaner 8 at its upstream end, and an intake air cylinder detection means 9 (air flow meter) downstream of this air cleaner 8 for detecting the amount of intake air.
is interposed, and the intake passage 7 on the downstream side of the spiracle detection means 9 during intake has a first intake passage 7a and a second intake passage 7b.
It is branched into two parts. The first intake passage 78 is connected to the first intake boat 3 of each combustion chamber 2 via the expansion dormitory 7G, while the second intake passage 7b is connected to the first intake boat 3 of each combustion chamber 2 via the expansion chamber 7d. 2 intake boats 4, respectively.

The inlet portion of the first intake passage 7a (S is the first throttle valve 1 that controls the amount of intake air flowing through the first intake passage 7a).
0, a second throttle valve 11 is provided at the entrance of the second intake passage 7b to control the amount of intake air flowing through the second intake passage 7b. Throttle valve"10
．． 11 is opened and closed in conjunction with the throttle operation. The first throttle valve 10 opens when the load is low and becomes fully open as the load increases, and the second throttle valve 11 begins to open when the opening of the first throttle valve 10 reaches or exceeds the set opening. It becomes fully open as the load increases.

In the first intake passage 7a, a first injection valve 12 for injecting fuel in all operating ranges including the low intake 5H range is disposed for each cylinder, and in the second intake passage 7b.
A second injection valve 13 for injecting fuel in a high intake air amount region is provided for each cylinder. A fuel injection pulse is output as a fuel control signal from the control unit 14 (microcomputer) to the first and second injection valves 12 and 13, and fuel is injected at a predetermined port according to the width of the injection pulse.

The control unit 14 receives an intake air amount signal from the intake air amount detecting means 9, and also receives an engine rotation speed signal from the rotation speed sensor 15. The fuel injection pulse having a predetermined pulse width is output to each injection valve 12 and 13 at a predetermined time by calculating the number of injections.

The fuel pressure of the second injection valve 13 for the high temperature region is set higher than the fuel pressure of the first injection valve 12 for the low flow region. That is, FIG. 2 shows a fuel system for the first injection valve 12 and the second injection valve 13, and the fuel in the fuel tank 16 is supplied from a fuel pump 17 via a filter 18 to a fuel supply passage 19 connected in parallel. This is supplied to the first injection valve 12 and the second injection valve 13, and a throttle 20 is interposed between the first injection valve 12 and the second injection valve 13. The pressure can be increased from the pressure on the first injection valve 12 side. The pressure regulators 21 and 22 that adjust the injection pressure in accordance with the intake pressure are the pressure regulators 21 and 22 for the first injection valve 12.
The set pressure of the pressure regulator 22 for the second injector 13 is set higher than the set pressure of the first injector 12. There is.

FIG. 3 is a flowchart 1 for explaining the operation of the control unit 14. After the start, in step S1, the fuel injection amount corresponding to the operating condition is calculated. Intake air m by air amount detection means 9
oa, engine rotation speed N1 determined by rotation speed sensor 15
From constant K, correction coefficient α, etc., fuel F31 @ injection pulse width τ
Increase (injection time).

Note that the correction coefficient α is used to correct for cold times, etc., and the additional correction value τ0 is used when the fuel injection pulse is the first or second injection valve 12. 13, it takes a certain amount of time for fuel injection to actually start, so this purpose is to correct this rise time. Also, τ
a is the basic injection time taking cold correction etc. into consideration, and τb is the maximum acceleration increase time.

Next, the set pulse width τV for starting fuel injection from the second injector 13 is read out (S2), and it is determined whether the injection pulse width τa + τb calculated in step S1 is greater than or equal to the set pulse width τV (S3). , this judgment is No (low intake ■
If the asynchronous acceleration switch is on (YES), it is determined whether the asynchronous acceleration switch is on (S4), and when the asynchronous acceleration switch is on (YES) and there is a large acceleration state, asynchronous injection is performed in step S5, while this asynchronous acceleration switch is off. (
No>, the injection pulse τp for the first injection valve 12 and the injection pulse τS for the second injection valve 13 are calculated without performing asynchronous injection (S6).

In the above-mentioned low intake air region, the injection pulse τ for the second injection valve 13 is
S is set to zero, and the first injector 12 is controlled by the control signal of the injection pulse width τp determined in step S1 only by the first injector 12 without injecting negative fuel from the second injector 13. to perform fuel injection (810)
.

On the other hand, if the determination in step S3 is YES and the high intake air is placed, it is similarly determined whether the asynchronous acceleration switch is on (S7), and the asynchronous acceleration switch is on (YES>
When the acceleration state is large, asynchronous injection is performed in step S8, while the asynchronous acceleration switch is turned off (N
o), the injection pulse τp for the first injection valve 12 and the injection pulse τS for the second injection valve 13 are calculated without performing asynchronous injection (S9), and this control signal causes the first injection pulse to be calculated.
Then, the second injection valve 12.13 is driven to perform fuel injection (S10). In this example, the first injection valve 12 and the second injection valve 13 are set to inject the same amount of fuel (half each).

In the above fuel injection, the outputs of the injection pulses τp and τS when performing asynchronous injection in a high injection amount range are as shown in FIG.

FIG. 5 shows a modified example, in which each cylinder 2 of the engine 1 is formed with one intake bow 1-3 and an exhaust port 5, and the intake boat 3 has one intake passage 7. is connected to the intake passage 7 connected to each cylinder 2 from the expansion chamber 7C downstream of the throttle valve 10, the 11111st valve 12 is connected to the downstream side near the combustion v2, and the second injection valve 13 is connected to the upstream side of this. are arranged respectively, and this first injection valve 1
2 and the second injection valve 13, a fuel injection pulse is outputted by the same fuel injection valve 14 as in the previous example, and its injection 11JfM and switching timing are controlled. The fuel pressure of the injection valve 13 is set higher than the fuel pressure of the first injection valve 12.

a5. In the above embodiment, as shown in FIGS. 1 and 5, the first injection valve 12 is disposed in the downstream portion of the intake passage 7 relatively close to the combustion chamber 2, and this first injection valve The fuel injected from the first injector 12 is quickly supplied to the combustion chamber 2 to improve the responsiveness of the fuel to increases and decreases in the amount of intake air. 12
It is disposed in the intake passage 7 on the more upstream side to improve mixing and atomization of the injected QJ fuel and intake air, thereby promoting atomization.

Further, the first throttle valve 10 that controls the amount of intake air flowing through the first intake passage 7a is connected to the first intake passage 7a as shown in FIG.
In addition to intervening at the inlet of the second throttle valve 11, the same control effect can be obtained by interposing it in the intake passage 7 upstream of the second throttle valve 11.

Furthermore, as a structure for changing the fuel pressure between the first injection valve 12 and the second injection valve 13, in addition to the structure shown in FIG. Adoptable.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an engine fuel injection device according to an embodiment of the present invention, FIG. 2 is a system diagram showing a fuel supply system to an injection valve, FIG. 3 is a flowchart diagram of a control unit, and FIG. FIG. 3 is an explanatory diagram showing an example of the fuel injection pulse output to the injection valve, and FIG. 5 is a one-stop configuration diagram of the engine fuel injection device in a modified example. 1...Engine 2...Combustion chamber 3.4
...Intake boat 7.7a, 7b ...Intake passage 10.11 ... Throttle valve 12 ... First injection valve 13 ... Second injection valve 14...Control unit 17...
...Fuel pump 21.22...Pressure regulator Fig. 1 0645"4p<bpp b 1N2 Fig. 114 Fig. rs m ■ iIB Fig. @ Fig. 5

Claims (1)

[Claims] (1) In an engine fuel injection device comprising a first injection valve that injects fuel in the entire operating range including a low intake area, and a second injection valve that injects fuel in a high intake air amount area, A fuel injection device for an engine, characterized in that the fuel pressure of two injection valves is set higher than the fuel pressure of a first injection valve.