JPH0422050Y2 - - Google Patents

Description

[Detailed explanation of the idea] <Industrial application field> The present invention relates to a fuel supply device for an internal combustion engine.

<Prior Art> In an electronically controlled fuel injection type internal combustion engine, an electromagnetically driven fuel injection valve installed in an intake passage is generally driven by an injection pulse having a pulse width corresponding to the injection amount. In this case, the injection pulse width Ti
is determined by the following equation.

Ti=Tp×COEF+Ts Here, Tp is the basic pulse width, which is determined by the following formula.

Tp=K×Q/N K is a constant, Q is the intake air flow rate, and N is the engine speed. COEF is various correction coefficients.

Ts is a voltage correction amount, which is used to correct changes in the injection flow rate of the fuel injector due to fluctuations in battery voltage (see Japanese Patent Laid-Open No. 59-49346, etc.).

By the way, when such a conventional electronically controlled fuel injection device is installed in a high-output engine, the linearity indicating the relationship between the injection pulse and the injection amount cannot be ensured in the low-frequency pulse.

On the other hand, if the linearity of the low-frequency pulse is ensured, there is a problem that the injection amount becomes insufficient in the high-load region.

Therefore, the injection hole diameter of the fuel injection valve is increased to ensure a high injection amount at high loads, but in this case, the linearity of the Ti-Q (injection amount) characteristic is Since the area that can be secured, that is, the actual usable area shifts to a higher level, it becomes impossible to perform good injection amount control in small injection amount areas such as idling.

Therefore, we reduced the injection rate from once per revolution in conventional engines to once every two revolutions, and instead doubled the effective injection amount per engine (Ti = 2Te + Ts; Te is the effective injection amount). Attempts have been made to use a region with excellent linearity (injection pulse width) to perform good injection amount control even in small injection amount regions such as idling.

However, as the output of engines continues to increase and the nozzle hole diameter increases accordingly, the usable range shifts to the higher injection amount side.
There was a limit to high-precision control.

The present invention was developed in view of these conventional problems, and it is an internal combustion engine that solves the above problems by variably controlling the injection pressure according to the load and correcting the injection pulse width according to the injection pressure. The purpose is to provide a fuel supply system for engines.

<Means for Solving the Problems> For this reason, the present invention, as shown in FIG. Fuel for an internal combustion engine, which includes a valve and a pressure regulator that regulates the pressure of the fuel supplied to the fuel injection valve so that the differential pressure between the pressure of the fuel supplied to the fuel injection valve and the control pressure guided to the control pressure chamber is constant. The supply device includes a constant negative pressure valve that forms a constant negative pressure, basic pulse width setting means that sets the basic pulse width of the injection pulse according to engine operating conditions, and a control pressure chamber of the pressure regulator. In a region where the basic pulse width set by the basic pulse width setting means is less than or equal to the set value, a constant negative pressure is generated by the constant negative pressure valve, and in a region where the basic pulse width exceeds the set value. a switching valve that performs switching control so as to introduce atmospheric pressure; and a pulse width setting device that sets a pulse width by correcting the basic pulse width based on the fuel supply pressure to the fuel injection valve that is switching controlled by the switching valve. , and injection pulse output means for outputting an injection pulse having a pulse width set by the pulse width setting means to the fuel injection valve.

<Function> In the low load area where the basic pulse width is less than the set value,
The constant negative pressure created by the constant negative pressure valve is guided to the control pressure chamber of the pressure regulator by the switching valve. Therefore, the fuel supply pressure to the fuel injection valve whose differential pressure with respect to the constant negative pressure is regulated to be constant also becomes small.
On the other hand, the pulse width setting means corrects the injection pulse width according to the fuel supply pressure controlled by the switching valve and sets the pulse width, so that even at low load, the injection pulse with a larger pulse width is used for fuel injection. Since the pulse width is output to the valve and the linearity of the pulse width-injection amount characteristic can be used, good injection amount control can be performed.

Further, in a high load region where the basic pulse width exceeds a set value, atmospheric pressure is guided to the control pressure chamber of the pressure regulator by the switching valve.

As a result, the fuel supply pressure to the fuel injection valve increases, and accordingly, the pulse width setting means can shorten the pulse width of the injection pulse, so it is possible to secure a high injection amount even at high rotation speeds, and the engine High output can be achieved.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

In FIG. 2 showing one embodiment, an electromagnetic fuel injection valve 4 is provided upstream of a throttle valve 3 in an intake passage of an engine 1.
The injection valve 4 is supplied with fuel, which is sucked from a fuel tank 5 by a fuel pump 6 and whose pressure is regulated by a pressure regulator 7, through a fuel supply passage 8.

Control negative pressure or atmospheric pressure, which is switched and controlled by a switching valve 10, is introduced into the control pressure chamber 7a defined by the diaphragm of the pressure regulator 7 through a pressure introduction passage 9, and the other is controlled by a switching valve 10. Injected fuel from the fuel pump 6 is introduced into the fuel pressure adjustment chamber 7b.

Then, surplus fuel is transferred from the fuel pressure adjustment chamber 7b to the return passage 1 so that the fuel supply pressure is higher by a certain pressure difference than the control pressure guided to the control pressure chamber 7a.
1 to the fuel tank 5.

The switching valve 10 is composed of an electromagnetic three-way valve, and has a pressure introduction passage 13 connected to an atmospheric pressure port 10a communicating with the atmosphere and an output port 12a of a constant negative pressure valve 12, which will be described later.
The output port 10 is selectively connected to the pressure introduction passage 9 and the constant negative pressure port 10b is connected to the constant negative pressure port 10b.
Switching is controlled so that it communicates with c.

The constant negative pressure valve 12 is integrally assembled into a part of a negative pressure control solenoid valve (VCM valve) for forming a control negative pressure to be supplied to an auxiliary air control valve for controlling idling speed and an EGR control valve. ing. That is, the other end of the intake negative pressure introduction passage 13, which has one end facing the intake passage 2, is connected to the diaphragm 12b into the negative pressure chamber 12c defined below the diaphragm 12b.
A spring 12d is attached to the negative pressure chamber 12c facing the center and urging the diaphragm 12b upward in the figure, that is, in the direction of increasing the volume of the negative pressure chamber 12c. Further, a diaphragm 12 is provided in an atmospheric pressure chamber 12e defined above the diaphragm 12b.
A spring 12f is attached to bias b downward. According to the structure of the constant negative pressure valve 12, the intake negative pressure changes depending on the engine operating state, but when the intake negative pressure exceeds the set pressure (for example, -120 mmHg), the balance between the springs 12d and 12f causes the diaphragm 12b to move. The opening of the intake negative pressure introduction passage 13 is sealed to keep the negative pressure in the negative pressure chamber 12c constant at the set value.

The constant negative pressure created as described above is directly led to the constant negative pressure port 10b of the switching valve 10, and the degree of communication with atmospheric pressure is maintained through the orifice.
By controlling the duty with a solenoid valve (not shown) incorporated in the VCM valve, a control negative pressure is generated to be supplied to the auxiliary air control valve, EGR control valve, etc. described above.

On the other hand, engine operating state detection signals are input to the control unit 14 from a rotation speed sensor 15 for detecting the engine rotation speed, an air flow meter 16 for detecting the intake air flow rate, a water temperature sensor 17 for detecting the engine cooling water temperature, etc. .

Based on these detection signals, the control unit 14 calculates the basic pulse width of the injection pulse that is output to the fuel injection valve 4 in synchronization with the engine speed,
Switching control of the switching valve 10 according to the basic pulse width, and setting the pulse width by correcting the basic pulse width according to the fuel supply pressure to the fuel injection valve 4 controlled by the switching control, An injection pulse having the pulse width is output to the fuel injection valve 4 to inject the required amount of fuel.

The control by the control unit 14 will be explained below with reference to the flowchart shown in FIG.

In step 1 (denoted as S in the figure), the basic pulse width Tp of the injection pulse is set based on the engine speed N and the intake air flow rate Q using the following equation.

Tp=K・Q/N (K is a constant) This function corresponds to basic pulse width setting means.

In step 2, various correction coefficients COEF are calculated based on the engine cooling water temperature Tw, etc.

In step 3, the voltage correction amount Ts is calculated.

In step 4, it is determined whether the basic pulse width Tp calculated in step 1 is less than or equal to the set value A, and
If it is determined that the load is in the low load area below the set value A,
Proceed to step 5 and connect the switching valve 10 to the constant negative pressure port 10.
b and the output port 10c are set on the side that communicates with each other.

Next, the process proceeds to step 6, where the final pulse width Ti of the injection pulse is calculated using the following equation.

Ti=Tp・COEF+Ts On the other hand, if it is determined in step 4 that Tp is in the high load region exceeding the set value A, proceed to step 7 and switch the switching valve 10 between the atmospheric pressure port 10a and the output port 1.
Set it to the side that communicates with 0c.

Next, the process proceeds to step 8, where the final pulse width Ti of the injection pulse is calculated using the following equation.

Ti=Tp・COEF・P+Ts Here, P is the pressure correction set to shorten the pulse width Ti and keep the fuel supply amount constant since the fuel supply pressure increases due to switching control of the switching valve 10. It is a coefficient.

The injection pulse having the pulse width Ti calculated in this way is outputted to the fuel injection valve 4 in synchronization with the engine rotation by a drive circuit (not shown) provided in the control unit 14 (injection pulse output means), and the engine is operated. An amount of fuel corresponding to the state is injected and supplied.

If such control is carried out, in the low load region proceeding to step 5, the constant negative pressure formed by the constant negative pressure valve 12 is introduced into the control pressure chamber 7a of the pressure regulator 7, so that a certain difference is maintained between the constant negative pressure and the constant negative pressure created by the constant negative pressure valve 12. The added fuel supply pressure is controlled to be small. Then, in step 6, the pulse width Ti can be set to a large value in accordance with the fuel supply pressure controlled to be small.
It is possible to use a pulse width-injection amount characteristic with good linearity, thereby achieving good injection amount control and stabilizing engine operating performance in a low load range including idling.

On the other hand, in the high load region proceeding to step 7, atmospheric pressure is introduced to the control pressure chamber 7a of the pressure regulator 7, so that the fuel supply pressure, which is obtained by adding a constant differential pressure to this atmospheric pressure, is controlled to be large. And step 8
In this case, the pulse width Ti can be shortened by multiplying the correction coefficient P according to the largely controlled fuel supply pressure, so even if the pulse output interval becomes short at high engine speeds, a high injection amount can be ensured, and the engine speed can be reduced. It can promote output.

The function of calculating the pulse width Ti in steps 6 and 8 based on the determination result in step 4 corresponds to the pulse width setting means.

In addition, since the configuration uses a low negative pressure valve pre-installed in the CVM valve etc. to switch the fuel adjustment pressure by the pressure regulator, it is only necessary to add air piping, for example, to change the adjustment pressure. Compared to a configuration in which two different pressure regulators are installed and used selectively, this method does not require changes to the fuel piping system, so it is advantageous in terms of heat resistance and layout, and can be implemented at low cost. be.

<Effects of the invention> As explained above, according to the invention, the fuel supply pressure is made variable according to the load, and the pulse width of the injection pulse is corrected accordingly.
In addition to achieving good injection amount control in the low load range,
It is possible to increase the engine output by ensuring the injection amount in the high load region. Further, it has the advantage of being relatively simple in structure, advantageous in terms of heat resistance and layout, and being able to be implemented at low cost.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of the present invention;
The figure shows the configuration of one embodiment of the present invention, FIG. 3 is a flowchart showing the pulse width setting routine of the same embodiment, and FIG. 4 is a diagram showing the pulse width-injection amount characteristics at different nozzle hole diameters. be. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 4... Fuel injection valve, 7... Pressure regulator, 7a... Control pressure chamber, 8... Fuel supply passage, 10... Switching valve,
12... constant negative pressure valve, 14... control unit, 15... rotation speed sensor, 16... air flow meter.

Claims (1)

[Scope of utility model registration request] A fuel injection valve is provided that is driven to open by an injection pulse and injects fuel in an amount corresponding to the width of the pulse into an intake passage, and the pressure of the fuel supplied to the fuel injection valve is controlled to be guided to a control pressure chamber. In a fuel supply system for an internal combustion engine, which is equipped with a pressure regulator that regulates the pressure so that the differential pressure is constant, the fuel supply system includes a constant negative pressure valve that forms a constant negative pressure, and the injection In a region where the basic pulse width set by the basic pulse width setting means for setting the basic pulse width of the pulse and the basic pulse width setting means in the control pressure chamber of the pressure regulator is equal to or less than the set value, a switching valve that conducts switching control such that the constant negative pressure formed by the constant negative pressure valve is guided and atmospheric pressure is guided in a region where the basic pulse width exceeds a set value, and the basic pulse width is controlled to be switched by the switching valve. pulse width setting means for setting the pulse width by correcting it based on the fuel supply pressure to the fuel injection valve;
A fuel supply device for an internal combustion engine, comprising injection pulse output means for outputting an injection pulse having a pulse width set by the pulse width setting means to a fuel injection valve.