JPH0639936B2 - Fuel supply control method for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control method for an internal combustion engine, and more particularly to a differential pressure between a pressure in an intake pipe downstream of an intake throttle valve and a fuel pressure supplied to an electromagnetic fuel injection valve. The present invention relates to a fuel supply control method when the pressure regulation is impossible.

(Prior Art) Fuel is supplied to the electromagnetic fuel injection valve by adjusting the pressure difference between the pressure in the intake pipe downstream of the intake throttle valve of the internal combustion engine and the fuel pressure supplied to the electromagnetic fuel injection valve to a predetermined value by pressure adjusting means. Then, the electromagnetic fuel injection valve is opened for a valve opening time set on the basis of engine operating conditions such as engine rotation speed, intake air flow rate, engine cooling water temperature, battery voltage, etc. A fuel supply control method for an internal combustion engine adapted to supply the fuel to the fuel cell is already widely known.

In this type of fuel supply control method, for example, a pressure regulator (pressure adjusting means) arranged in a fuel supply system of the engine is used to supply fuel pressure to an electromagnetic fuel injection valve and an intake pipe downstream of an intake throttle valve of the engine. Differential pressure from intake pressure ΔP
Is adjusted to a predetermined value, and the fuel maintained at this predetermined pressure difference is injected into the intake pipe.

The fuel injection amount Qf at that time is determined by the following equation.

However, C is a constant, the differential pressure ΔP is a predetermined value of, for example, about 2.5 kg / cm ² , and T is the pulse width of the pulse signal for driving the electromagnetic fuel injection valve to open.

That is, the fuel injection amount Qf is determined only by the valve opening time of the electromagnetic fuel injection valve, that is, the valve opening pulse width T if the differential pressure ΔP in the expression (a) is a predetermined value.

(Problems to be Solved by the Invention) However, in the fuel supply control method as described above, failure of the pressure regulator or clogging of the return pipe from the pressure regulator to the fuel tank,
Alternatively, the pressure difference ΔP may not be adjusted to a predetermined value due to the occurrence of vapor lock or the like.

When the differential pressure ΔP becomes large, for example, when the discharge fuel pressure of the fuel pump is about 6 kg / cm ^{2 and} the intake pressure in the intake pipe is about -500 mm / Hg (-0.68 kg / cm ² ). Differential pressure ΔP
= 6.68 kg / cm ² , and at this time, the fuel injection amount Qf is 1.63 times that in the normal state according to the above-mentioned formula (a). Therefore, the fuel injection amount Qf increases and the air-fuel mixture becomes rich. Further, when the differential pressure ΔP becomes small, the fuel injection amount Qf decreases and the air-fuel mixture becomes lean, which causes a problem that the engine is stopped in any case.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a fuel supply control method capable of appropriately supplying fuel even when pressure adjustment of the supply fuel pressure to the electromagnetic fuel injection valve is impossible.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, the differential pressure between the pressure in the intake pipe downstream of the intake throttle valve of the internal combustion engine and the fuel pressure supplied to the electromagnetic fuel injection valve is adjusted. The fuel whose pressure is adjusted to a predetermined value by the pressure means is supplied to the electromagnetic fuel injection valve, and the electromagnetic fuel injection valve is opened for a valve opening time set based on the engine operating condition to obtain the required fuel amount. In a fuel supply control method for an internal combustion engine adapted to supply to an engine, an intake pipe internal pressure and a supply fuel pressure are respectively detected, and an actual differential pressure between these is detected and detected from the detected intake pipe internal pressure and supply fuel pressure. A fuel for an internal combustion engine, characterized in that an actual differential pressure is compared with the predetermined value to obtain a correction value according to the difference, and the valve opening time set value is corrected based on the obtained correction value. Supply control method Will be provided.

(Operation) When the detected differential pressure value between the intake pipe internal pressure downstream of the intake throttle valve and the fuel pressure supplied to the electromagnetic fuel injection valve does not substantially match the predetermined value to be adjusted by the pressure adjusting means, the adjustment is performed. When the differential pressure cannot be adjusted by the pressure means, the valve opening time set value set based on the engine operating conditions is corrected based on the actual pressure difference between the intake pipe internal pressure and the supplied fuel pressure, and the pressure adjusting means adjusts the supplied fuel pressure. The same amount of fuel that is supplied to the engine when pressure is normally adjusted is supplied to the engine.

(Embodiment) An embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 3.

FIG. 3 shows the overall structure of a fuel supply control device for carrying out the method of the present invention. For example, an intake pipe 2 is connected to the intake port of each cylinder of a four-cylinder engine 1, and the intake pipe 2 is connected to the atmosphere side. An air cleaner 3 is attached to the opening end, and a Karman vortex type air flow sensor 4 for detecting the intake air flow rate is attached. The air flow sensor 4 is electrically connected to the input side of the electronic control unit (EUC) 5 and supplies the Karman vortex generation period signal (f signal) to the electronic control unit 5.

An intake throttle valve 6 is arranged in the middle of the intake pipe 2, and an intake pressure sensor 7 for detecting the intake pressure Pi in the intake pipe 2 is attached downstream of the throttle valve 6. The intake pressure sensor 7 is electrically connected to the input side of the electronic control unit 5 and supplies an intake pressure signal (Pi signal) to the electronic control unit 5.

Further, in the intake manifold 2a portion of the intake pipe 2, an electromagnetic fuel injection valve 8 (only one intake manifold is shown) is arranged immediately upstream of each intake valve. Each of these fuel injection valves 8 is connected to the electronic control unit 5 and is driven by a drive signal corresponding to the valve opening pulse width Ti 'which is calculated as described below and output from the electronic control unit 5.

Incidentally, 9 is an exhaust pipe, and 9a is an exhaust manifold.

As for the fuel supply system, the pipe 12 connected to the fuel tank 11 is connected to the fuel pump (F
/ P) 13 and a pressure regulator (P / R) 14 as a pressure adjusting means are arranged in this order. From the pipe 12 between the fuel pump 13 and the pressure regulator 14, a pipe 15 connected to the fuel port of each fuel injection valve 8
Is branched for each cylinder, and piping 1 near this branch is provided.
A fuel pressure sensor 16 for detecting the fuel pressure Pf supplied to the fuel injection valve 8 is attached to 2. The fuel pressure sensor 16 is electrically connected to the input side of the electronic control unit 5 and supplies a supply fuel pressure signal (Pf signal) to the electronic control unit 5.

A pressure passage 17 communicating with the intake pipe 2 downstream of the intake throttle valve 6 is connected to the pressure regulator 14 to guide the intake pressure in the intake pipe 2, and a pipe 18 for returning to the fuel tank 11. Are connected.

Then, the fuel discharged from the fuel pump 13 is injected and supplied from each fuel injection valve 8 into the intake port of each cylinder, but the surplus fuel is supplied to the fuel tank 11 through the return pipe 18 via the pressure regulator 14. Is refluxed in. By adjusting the return amount of this excess fuel,
The pressure difference ΔP 'between the intake pressure Pi downstream of the intake throttle valve 6 introduced from the pressure passage 17 and the fuel pressure Pf supplied to the electromagnetic fuel injection valve 8 is adjusted to a predetermined value (for example, 2.5 kg / cm ² ).

On the input side of the electronic control unit 5, the valve opening degree of the intake throttle valve 6 (θ
The throttle sensor 19 for detecting t), the crank angle sensor 20 for detecting the engine speed (N), and various sensors for detecting other engine operating states such as engine cooling water temperature, battery voltage, and atmospheric pressure are electrically connected. It is connected.

Next, the calculation procedure of the valve opening pulse width (valve opening time) of the electromagnetic fuel injection valve 8 by the electronic control unit 5 will be described based on the flowcharts shown in FIGS. At, the detection signals from the various sensors described above are read.

Then, in step 52, the engine speed N is calculated from the detection signal (N signal) from the crank angle sensor 20 read in step 51, and the intake air flow rate is calculated from the Karman vortex generation cycle signal (f signal) from the air flow sensor 4. Q is calculated to calculate the basic valve opening pulse width Tp.

That is, Tp = K × Q / N, where K is a constant.

In step 53, various corrections based on the detection signals from the various sensors (for example, water temperature correction based on the detection signal from the water temperature sensor that detects the cooling water temperature of the engine) are applied to the basic valve opening pulse width Tp obtained in step 52. Then, the valve opening pulse width Ti is calculated.

Next, the electronic control unit 5 detects the supply fuel pressure Pf to the electromagnetic fuel injection valve 8 by the detection signal (Pf signal) from the fuel pressure sensor 16 at step 54, and at step 55 the detection signal (from the intake pressure sensor 7 ( (Pi signal), the intake pressure Pi in the intake pipe 2 downstream of the intake throttle valve 6 is detected.
Next, the differential pressure ΔP '(= Pf-Pi) between the supplied fuel pressure Pf and the intake pressure Pi is calculated from these detected values (step 56).

In step 57, the correction coefficient K is set to the value 1.

Then, in step 58, the electronic control unit 5 determines whether or not the pressure regulator 14 adjusts the differential pressure ΔP ′ satisfactorily. That is, it is determined whether or not the differential pressure ΔP 'calculated in step 56 is substantially a predetermined value, for example, ΔP' = 2.5 (kg / cm ² ) in this embodiment, and when the determination is affirmative (YES) ( (When there is no abnormality in the operation of the pressure regulator 14, etc.), the process directly proceeds to step 59, and the valve opening pulse width Ti set in step 53 is set to step 57.
The corrected valve opening pulse width Ti ′ (= K × Ti) is calculated by multiplying the correction coefficient value (K = 1) set in step 1, and the drive signal corresponding to this Ti ′ value is output to the electromagnetic fuel injection valve 8. (Step 60). In this case, the valve opening pulse width Ti calculated in step 53 is not substantially corrected.

On the other hand, when the determination in step 58 is negative (NO), the pressure regulator 14 fails or the return pipe 18 from the pressure regulator 14 to the fuel tank 11 is returned.
Differential pressure Δ due to clogging of
When it is judged that P'cannot be regulated to a predetermined value (abnormal condition), the routine proceeds to step 61.

In step 61, the differential pressure ΔP 'calculated in step 56
Correction factor based on Is calculated, and the correction coefficient value (K
= 1) is replaced. Then, in step 59, the corrected valve opening pulse width Ti ′ (= K × Ti) is calculated using the replaced correction coefficient K, but the correction coefficient K calculated in step 61 is opened. By multiplying the pulse width Ti, the valve opening pulse width Ti 'corresponding to the variation of the differential pressure ΔP' with respect to the predetermined value can be obtained. Then, in step 60, the drive signal corresponding to the Ti ′ value is output to the electromagnetic fuel injection valve 8.

As described above, according to the present invention, the intake pipe internal pressure downstream of the intake throttle valve of the internal combustion engine and the fuel supply pressure supplied to the electromagnetic fuel injection valve are respectively detected, and the detected intake pipe internal pressure and supply fuel are detected. These actual differential pressures are detected from the pressure, the detected actual differential pressures are compared with a predetermined value to obtain a correction value according to the difference, and the valve opening time set value is corrected based on the obtained correction value. As a result, even if the pressure adjusting means fails, the piping of the fuel supply system is clogged, or vapor lock occurs, it is possible to always supply an appropriate amount of fuel to the engine regardless of the occurrence of these abnormal situations. As a result, it is possible to obtain an effect that it is possible to prevent the engine from stopping.

[Brief description of drawings]

1 and 2 are flowcharts for explaining a fuel supply control procedure according to the method of the present invention, and FIG. 3 is an overall configuration diagram of a fuel supply control device for carrying out the method of the present invention. 1 ... Engine, 2 ... Intake pipe, 2a ... Intake manifold,
5 ... Electronic control device, 6 ... Intake throttle valve, 7 ... Intake pressure sensor, 8 ... Electromagnetic fuel injection valve, 14 ... Pressure regulator, 16 ... Fuel pressure sensor.

Claims (1)

[Claims] Claim: What is claimed is: 1. A fuel, the pressure of which is regulated to a predetermined value by a pressure regulator by a pressure difference between a pressure in an intake pipe downstream of an intake throttle valve of an internal combustion engine and a fuel pressure supplied to the electromagnetic fuel injection valve, to the electromagnetic fuel injection valve. A fuel supply control method for an internal combustion engine, which supplies the electromagnetic fuel injection valve for a valve opening time set based on engine operating conditions to supply a required fuel amount to the engine. The pressure and the supplied fuel pressure are respectively detected, the actual differential pressure between these is detected from the detected intake pipe internal pressure and the supplied fuel pressure, and the detected actual differential pressure is compared with the predetermined value and corrected according to the difference. A fuel supply control method for an internal combustion engine, wherein a value is obtained, and the valve opening time set value is corrected based on the obtained correction value.