JPH028144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling a fuel injection valve of an internal combustion engine, and more particularly to a fuel control device that can maintain constant fuel injection pressure.

In internal combustion engines equipped with fuel injection valves that inject fuel intermittently into the intake pipe, it is important to completely atomize the fuel in order to achieve complete combustion of the fuel and reduce harmful exhaust gases. . In order to perform this fuel atomization, a fuel injection nozzle called a two-fluid injection nozzle, for example, is conventionally known. That is, an air introduction chamber is provided near the fuel injection hole that injects liquid fuel, and air is injected into this air introduction chamber using, for example, the pressure difference between the atmosphere and the pressure inside the intake pipe, thereby atomizing the liquid fuel. It is something that becomes.

On the other hand, electric fuel injection systems (hereinafter referred to as EFI) have been known for some time, but the fuel injection nozzle called an injector used in this EFI generally atomizes the fuel pumped from the fuel pump. It is configured to inject only a certain amount at a certain time. When using the above two-fluid injection nozzle as this injection nozzle, in order to keep the injection amount of this atomized fuel constant, the injection pressure must be adjusted between the fuel pressure in the injector and the air pressure in the air introduction chamber. The differential pressure must always be constant. However, when the operating conditions of the internal combustion engine change,
The pressure inside the intake pipe changes accordingly, and the air pressure inside the air introduction chamber changes accordingly. Therefore, in order to keep the differential pressure constant, it is necessary to change the fuel pressure in response to fluctuations in air pressure.

However, as a means of controlling the fuel pressure of the lever, a pressure regulator is provided in the middle of the fuel pipe, and the air pressure is detected as a negative pressure source of the pressure regulator. Since it is undesirable to disturb the flow of air in the air introduction chamber, it is extremely difficult to detect the air pressure. Therefore, the pressure regulator cannot control the fuel pressure using the air pressure. Can not. If the fuel pressure is determined using the intake negative pressure in the intake pipe, the air pressure in the air introduction chamber is
Due to the pressure difference before and after the orifice formed in the injection nozzle, it is higher than the suction negative pressure in the intake pipe.As a result, if the suction negative pressure is used as it is, the pressure difference is too small and sufficient injection pressure cannot be obtained. , there is a problem of a shortage of injected fuel. In addition, when the suction negative pressure becomes approximately vacuum pressure, air is injected from the air introduction chamber at the speed of sound, and even if the suction negative pressure changes, the air pressure in the air introduction chamber remains constant. Also, the differential pressure becomes too small, and the optimum fuel injection amount cannot be obtained.

In view of the above points, the present invention provides a fuel control device that can obtain a correction coefficient based on a pressure substantially equal to the air pressure in the air introduction chamber and use this coefficient to always obtain the optimum fuel injection amount. A fuel injection mechanism that atomizes and injects liquid fuel injected from a fuel injection hole using air jetted from an air injection hole, an air supply mechanism that supplies air to the air injection hole, and a fuel injection hole that includes the fuel injection hole. an injection hole control mechanism that controls the valve opening time, and the injection hole control mechanism controls the valve opening time according to the pressure of the air pumped through the air supply mechanism, and controls the injection hole from the fuel injection mechanism. The feature is that the amount of atomized fuel that is injected is maximized.

The present invention will be explained below with reference to illustrated embodiments. 1st
In the figure, the upstream side (left side of the figure) of the intake pipe 1 communicates with the atmosphere via an air flow meter and air cleaner (not shown), and the downstream side (right side of the figure) communicates with a cylinder of an internal combustion engine (not shown). This intake pipe 1
A throttle valve 2 is provided in the middle, and a fuel injection mechanism 3 is provided downstream of the throttle valve 2.

The cylindrical casing 4 of the fuel injection mechanism 3 is connected to the intake pipe 1
A cap 5 attached to the pipe wall of the intake pipe 1 and provided at the tip of the casing 4 faces into the intake pipe 1. An annular air introduction chamber 7 is formed between the cap 5 and a sheet member 6 protruding from the tip of the casing 4. Inside this air introduction chamber 7, there is an auxiliary air conduit 1 that communicates with the upstream side of the throttle valve 2 of the intake pipe 1.
8 and an air introduction hole 8 bored on the side of the cap 5. Air introduction chamber 7
Of these, fuel injection holes 9 formed in the seat member 6
The periphery of the fuel injection hole 9 is an annular air injection hole 20, and the liquid fuel discharged from the fuel injection hole 9 is mixed with the air injected from the air injection hole 20 and atomized.
A two-fluid injection hole 10 is opened at the tip of the cap 5, that is, an extension of the fuel injection hole 9, and the atomized fuel in the air introduction chamber 7 is injected into the intake pipe 1 from this two-fluid injection hole 10. .

A valve body 12 is slidably fitted into the hole 11 in the lower part of the casing 4 . The valve body 12 is connected to the seat member 6
The device can be seated on the bottom of the fuel injection hole 9 to open and close the fuel injection hole 9 to inject liquid fuel into the air introduction chamber 7.
is open laterally at the bottom of the valve body 12. A spring 14 is mounted between the top of the valve body 12 and the casing 4, so that the valve body 12 is always urged downward to close the fuel injection hole 9. By energizing the solenoid 15 placed around the body 12,
Move upward and open the fuel injection hole 9. As a result, the fuel fed into the casing 4 via the conduit 16 is discharged to the air introduction chamber 7 through the fuel passage hole 13 and the fuel injection hole 9, mixed with air in this chamber 7, and injected. Atomized fuel is injected into the intake pipe 1 from the hole 10. Note that the excitation or demagnetization of the solenoid 15 is controlled by a fuel control section 17, and the configuration of this control section 17 will be described in detail later.

The liquid fuel stored in the tank 19 is transferred to the pump 2
1 and introduced into the casing 4 via the nipple 22 and the conduit 16, and is intermittently discharged from the fuel injection hole 9 by the action of the valve body 12 as described above. Due to the fuel injection operation by the valve body 12, pulsation occurs in the communication pipe 23 between the pump 21 and the casing 4, so a damper 24 is provided in the communication pipe 23 to damp this pulsation. It will be done.

Therefore, fuel is injected from this hole 9 only when the valve body 12 leaves the seat member 6 and opens the fuel injection hole 9, but when the valve body 12 closes the injection hole 9. is the outlet part 25 of the nipple 22
Excess fuel is discharged from the tank 19 via the pressure regulator 26 and recycled to the tank 19. The pressure regulator 26 functions to keep the injection pressure of the atomized fuel injected from the injection hole 10 constant regardless of the negative pressure in the air introduction chamber 7.
It has the configuration shown in FIG. That is, the inside of the casing 27 is divided into two chambers by the diaphragm 28, and among these chambers, the constant pressure chamber 29 is
It communicates with the nipple 22 via a fuel pipe 30 and is connected to the tank 19 via a drain passage 31. The drain passage 31 is opened and closed by a valve body 32 attached to the diaphragm 28. On the other hand, a spring 35 is provided in the variable pressure chamber 33 located on the opposite side of the constant pressure chamber 29, and an inlet portion 37 provided on the fuel injection mechanism 3 side of the auxiliary air conduit 18 is connected via the pressure conduit 34.
communicate with.

Therefore, if the difference between the pressure of the fuel introduced into the constant pressure chamber 29 and the pressure inside the variable pressure chamber 33 is larger than a certain value determined by the elastic force of the spring 35, the valve body 32
The fuel pump rises against the spring 35, opens the drain passage 31, and allows excess fuel to flow back into the tank. As a result, fuel pressure decreases. On the other hand, when the pressure difference is smaller than the predetermined value, the valve body 32 is lowered by the spring 35 to close the drain passage 31 and increase the fuel pressure. By repeating the above operation, the injection pressure is controlled to be constant regardless of the magnitude of the negative pressure in the variable pressure chamber 33, that is, the pressure in the auxiliary air conduit 18.

According to experiments conducted by the present inventors, it has been found that the pressure Py at the input section 37 of the auxiliary air conduit 18 has a proportional relationship with the pressure Px inside the air introduction chamber 7. To explain this with reference to FIGS. 3 and 4, FIG. 3 shows the intake negative pressure P _B downstream of the fuel injection mechanism 3 of the intake pipe 1, that is, immediately before the cylinder.
and the relationship between the above pressure Px and the suction negative pressure P _B
and the above pressure Py are shown respectively.
As mentioned above, it is very difficult to detect the pressure Px while the device is in operation, but the inventors have made it possible to detect this pressure Px by modifying a part of the fuel injection mechanism 3. It was measured. As can be seen from Figure 3, both the pressures Px and Py change in a curved manner with respect to the suction negative pressure P _B , but these pressures Px and Py
According to FIG. 4, which shows the relationship between the two, the pressure Py changes linearly with respect to the pressure Px, and a constant K representing the slope can be easily obtained.

The pressure Py is detected by a pressure sensor 38 connected to the pressure conduit 34 and input to the fuel control section 17. The fuel control unit 17 controls this pressure.
The solenoid 15 of the fuel injection mechanism 3 is energized or demagnetized using Py and the correction coefficient _KF obtained from the above-mentioned constant K, etc., and the opening time of the valve body 12 is controlled.

First, a method of calculating the correction coefficient _KF will be explained.

If the injection pressure is Pz, the fuel pressure is P _F , and the injection pressure required for the engine is P _R , then P _R is a constant that is not related to the pressure Py in the auxiliary air conduit 18, that is, regardless of the operating state of the engine. constant,
Also, it satisfies the relationship P _R = P _F − Py. On the other hand, when the actual injection pressure Pz is expressed using the pressure Px in the air introduction chamber 7, there is a relationship of Pz=P _F −Px, and therefore Pz=P _R +Py−Px. However, as shown in Figure 4, Px=
Since it is KPy, it can be expressed as Pz=P _R +Py−KPy =P _R +(1−K)Py (1).

Now, the amount of fuel injection required for the engine Q ₀
is the proportional constant C and the valve opening time of the injection mechanism 3 is Q ₀ =C√ _R ×τ However, since the actual injection pressure Pz is expressed by the above equation (1), the valve opening time is If τ is left as is, the injection amount Q becomes Q=C√ _R +(1−)×τ (2). In this equation (2), since K>1 and Py<0, P _R +(1-K)Py>P _R , and Q becomes larger than Q ₀ . Therefore, the valve opening time τ is corrected to make Q=Q ₀ , and K _F τ
Then, C√ _R ×τ=C√ _R + (1−)×K _F τ, so rearranging this becomes. Here, P _R is a value unrelated to Py, so if we rearrange using the constant K' (=1-K/P _R ), we get It is expressed as

Therefore, the fuel control unit 17 calculates K _F using equation (3) and uses various other correction coefficients to determine the valve opening time τ. As shown in FIG. 5, the fuel control section 17 includes a correction calculation circuit 40 that calculates a correction coefficient _KF , a D/A converter 41, and a fuel amount calculation circuit 42 that calculates a valve opening time τ. be done.

The correction calculation circuit 40 includes an amplifier 43 that amplifies the signal from the pressure sensor 38, a 10-bit A/D converter 44 that converts the analog signal output from the amplifier 43 into a digital signal, and this A/D converter. Correction coefficient K _F based on the signal output from 44
It consists of an arithmetic circuit 45 that calculates
uses a commercially available microcomputer.
Numerical calculations using microcomputers are well known, so a detailed explanation will be omitted, but the calculation of equation (3) consists of K'×Py in the first step, 1+K′×Py in the second step, and K'×Py in the third step. 1/1+K′×Py,
In the fourth step, do √11+′× and K _F
seek.

The D/A converter 41 converts the correction coefficient K _F obtained by the correction calculation circuit 40 into an analog voltage, and outputs this to the fuel amount calculation circuit 42 .

The fuel amount calculation circuit 42 is a device that has the same function as the four-cylinder engine electronically controlled fuel injection device already disclosed in Japanese Patent Application Laid-Open No. 49-67016, and uses the intake air amount signal from the air flow meter and the ignition coil. An ignition signal synchronized with the engine crank rotation from The valve opening time of the injection valve is determined by performing various correction calculations according to the operating state of the engine, and the fuel injection mechanism 3 is driven to control the amount of fuel supplied to the engine. In this embodiment, the fuel amount calculation circuit 42 performs correction calculations using the correction coefficient K _F in addition to the various correction calculations described above. This calculation formula is (4)
As shown in the formula.

τ=C _p Q/N (1+K _W +K _A +K _p2 +K _F )+τ _v (4) Here, τ: Valve opening time C _p : Coefficient Q: Intake air amount N: Engine speed K _W : Water temperature correction value K _A : Temperature correction value K _p2 : Correction value of the O ₂ sensor installed in the exhaust pipe τ _v : Invalid time of the valve body 12 As described above, the device of this embodiment has a proportional relationship with the pressure Px in the air introduction chamber 7. Using the pressure Py in a certain auxiliary air conduit 18 and the proportionality constant K between these pressures Px and Py, a correction coefficient K _F is determined, and this coefficient K _F
As one of the calculation elements, the valve body 1 of the fuel injection mechanism 3
This controls the opening time of the second valve. Therefore, the valve opening time can be determined according to the pressure Px, and the optimal fuel injection amount can always be obtained.

The detection position of pressure Py is the auxiliary air conduit 18.
It can be anywhere in , and depending on the position, the constant K
Of course, it is necessary to set .

As described above, according to the present invention, the valve opening time of the fuel injection mechanism can be determined by the correction coefficient depending on the air pressure in the air introduction chamber, so that the optimal fuel injection amount can always be obtained.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the present invention, Fig. 2 is a cross-sectional view showing a pressure regulator, and Fig. 3 shows suction negative pressure (P _B ) and air introduction chamber pressure (Px).
Figure 4 is a graph showing the relationship between air introduction chamber pressure (Px) and the auxiliary air pipe (Py), and Figure 5 shows the fuel control section. It is a system diagram. 3...Fuel injection mechanism, 7...Air introduction chamber, 9...
...Fuel discharge hole, 17...Drain hole control mechanism, 18...
...Auxiliary air conduit, 20...Air injection hole.

Claims (1)

[Claims] 1. A fuel injection mechanism that atomizes and injects liquid fuel injected from a fuel injection hole using air ejected from an air injection hole, an air supply mechanism that supplies air to the air injection hole, and an air supply mechanism that opens the fuel injection hole. an injection hole control mechanism that controls the time for which the injection hole control mechanism adjusts the injection pressure of the atomized fuel injected from the fuel injection mechanism according to the pressure of the air within the air supply mechanism; A fuel control device characterized in that the valve opening time is controlled according to the pressure of the air.