JPH0474537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply stop control method for stopping fuel supply to an internal combustion engine depending on engine operating conditions and the like.

Conventionally, this type of fuel supply stop control method has kept the fuel supply stop rotation speed constant even when atmospheric pressure changes when a vehicle equipped with a device using this method is operated at low or high altitudes. However, when the engine is operated at high altitudes where the atmospheric pressure decreases, there is a problem in that problems such as engine stalling are more likely to occur when fuel is restored during engine deceleration than at low altitudes.

In view of the above problems, an object of the present invention is to provide a fuel supply stop control method for an internal combustion engine that can prevent engine stall during engine deceleration operation at high altitudes by changing fuel supply return conditions according to altitude or atmospheric pressure. It's about doing.

The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 shows a known four-stroke spark ignition engine installed in an automobile, in which combustion air is sucked in through an air cleaner 2, an adsorption pipe 3, and a throttle valve 4. Further, fuel is supplied from a fuel system (not shown) through electromagnetic fuel injection valves 5 provided corresponding to each cylinder. The exhaust gas after combustion is released into the atmosphere through an exhaust manifold 6 and an exhaust pipe 7. Adsorption tube 3
, a potentiometer-type intake air amount sensor 8 that detects the amount of intake air taken into the engine 1 and outputs an analog voltage according to the amount of intake air, and a pressure detector 9 (hereinafter referred to as "a") that directly detects atmospheric pressure as information equivalent to atmospheric pressure.
HAC sensor) is installed. Alternatively, instead of directly detecting atmospheric pressure, altitude (height from sea level) may be detected and used as information corresponding to atmospheric pressure. The rotational speed sensor 11 detects the rotational speed of the crankshaft of the engine 1 and outputs a pulse signal with a frequency corresponding to the rotational speed. For example, an ignition coil of an ignition device may be used as the rotation speed sensor 11, and an ignition pulse signal from a primary terminal of the ignition coil may be used as the rotation speed signal. A throttle valve position detector 12 is installed on the throttle valve 4 to detect the position of the throttle valve. The control circuit 13 is a circuit that calculates the fuel injection amount based on the detection signals of the sensors 8, 9, 11, and 12, and controls the opening time of the electromagnetic injection valve 5 to adjust the fuel injection amount and control the fuel injection amount. Stops injection.

FIG. 2 is a diagram showing fuel supply stop conditions. When the engine speed is equal to or higher than a predetermined value N _C (hereinafter referred to as cut speed) and the engine is in a deceleration state, fuel supply is stopped. Further, when the engine speed becomes equal to or less than a predetermined value N _R (hereinafter referred to as the return speed), fuel supply is started. Therefore, the dashed line in the figure indicates the fuel supply stop.
Here, whether or not the engine is in a deceleration state can be determined by detecting the throttle valve opening degree using the throttle valve position detector 12.

FIG. 3 shows a first embodiment of the fuel supply stop method of the present invention. Cutting rotation speed N _C explained in Fig. 2
and the value of the return rotation speed N _R is continuously changed with respect to the atmospheric pressure detected by the HAC sensor 9.
That is, the cutting rotation speed N _C and the return rotation speed N _R are set to become higher as the altitude increases.
Alternatively, the gradient of change in N _R with respect to N _C may be made gentler.

FIG. 5 is a diagram showing the output characteristics of the HAC sensor 9, and an output voltage corresponding to atmospheric pressure can be obtained.

FIG. 6 is a diagram showing the configuration of the control circuit 13 for the first embodiment of the present invention described above. The HAC sensor output V _S is input to the impedance converter 23 via a resistor Ro. D ₁ is a diode to prevent inflow, and R ₅ and R ₆ are resistors that determine the charging current of the capacitor C ₁ . V _B is a power supply voltage, and V _R is a reference voltage of the comparator 24, which may be constant or may vary depending on engine parameters such as engine temperature. Ig is an ignition signal, and as shown in the timing chart of FIG. 7, it is shaped into an output A by a waveform shaping circuit 21, and the frequency is divided by a frequency dividing circuit 22 (in this example, the frequency is divided by 3 because there are 6 cylinders). The output signal B is converted into an output B, and the output B is applied to the clock terminal C of the data flip-flop circuit 29. The output B is also applied to the base of the transistor T ₁ via the resistor R ₇ , which causes the transistor T ₁ to conduct and discharge the capacitor C ₁ . Id is a signal from the throttle valve position detector 12, and 25 is a signal from the throttle valve position detector 12.
It is an AND circuit. T _P is a pulse voltage that drives the electromagnetic injection valve 5 that supplies fuel, and an electromagnetic injection valve drive signal is output from the terminal 30 via the inverting element 28 , the NOR circuit 26 , and the amplifier 27 . This T _P is constantly calculated and output even during fuel cut, but its actual output is limited by the NOR circuit 26. In the embodiment shown in FIG. 6, for convenience, the cutting rotation speed NC and the return rotation speed _NR are shown as the same value.

The operation of the circuit shown in FIG. 6 will be explained with reference to the timing chart shown in FIG. As the car moves from lowland to highland, the atmospheric pressure decreases, and the output of HAC sensor 9 V _S1 to V _S2
(V _S1 <V _S2 ), HAC sensor 9
Since the output E does not reach the reference voltage V _R when the output V _S =V _S1 , it is assumed that the fuel supply is stopped. However, even if the ignition signal period T is the same, the sensor output
When V _S =V _S2 , the charging current to the capacitor C ₁ increases, so the time constant of the capacitor C ₁ becomes shorter, and the charging waveform of the output E reaches the reference voltage _VR , resulting in a fuel supply state. That is, the sensor output
In order to bring the fuel supply to a halt state when V _S =V _S2 , the period T of the ignition signal Ig shown in the figure must be made shorter. In other words, the fuel supply will not be stopped unless the ignition signal period is below To (To<T), and the sensor output V _S changes from V _S1 to V _S2 , which increases the fuel supply stop engine speed (cutting speed). It is equivalent to doing.

As shown in Fig. 3, depending on the output of the HAC sensor 9,
As the atmospheric pressure decreases, the engine speeds N _C and N _R related to stopping fuel supply can be increased.

FIG. 8 shows a second embodiment of the present invention, and FIG. 9 is a timing chart showing its operation. S in the figure is a switch that is turned on/off depending on the HAC sensor output. In other words, when the atmospheric pressure > P _S is set at the predetermined atmospheric pressure P _S shown in Fig. 4, the switch S
turns on, and turns off when atmospheric pressure < P _S. R ₁
~R ₄ is the resistance value for voltage division of the input of the comparator 23, where {R ₄ /(R ₃ +R ₄ )}<{R ₂ /(R ₁
+R ₂ )} is satisfied.

The other configurations are exactly the same as in FIG. 6 and the operation is also the same, so the explanation will be omitted. That is, when the atmospheric pressure in FIG. 4 falls below a predetermined atmospheric pressure P _S , the engine speeds N _C and N _R for stopping fuel supply are increased.

Furthermore, although this embodiment has been explained using an analog circuit, those skilled in the art will easily understand that the present invention can be implemented using a circuit using a microcomputer. As an example, the cutting rotation speed N _C and the return rotation speed N _R with respect to the atmospheric pressure P shown in Fig. 3 are mapped and stored in memory in advance, and when the computer detects that the engine has entered a deceleration state, the current pressure The cut rotation speed N _C corresponding to P is read out, and if it is determined that the current engine rotation speed N is larger than this cut rotation speed N _C , the output of the electromagnetic injection drive signal T _P is blocked to stop the fuel supply. Bye. Also, regarding recovery, read out the recovery rotation speed N _R corresponding to the atmospheric pressure P,
This can be determined by comparing the magnitude with the engine rotation speed N.

As described above, in the present invention, the return rotation speed N _R at which fuel supply is restored is increased as the atmospheric pressure decreases, so that it is possible to prevent engine stalling during engine deceleration operation at high altitudes. Furthermore, hunting can be prevented by setting the cutting rotation speed N _C higher than the return rotation speed N _R by a predetermined rotation speed.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing the overall outline of the present invention, Figure 2
Figures 3, 4 and 5 are characteristic diagrams, Figures 6 and 7, for explaining the operating characteristics of the present invention.
The figure is an electric circuit diagram and signal waveform diagram showing one embodiment of the invention, and FIGS. 8 and 9 are electric circuit diagrams and signal waveform diagrams showing other embodiments of the invention. 1...Engine, 4...Throttle valve, 9...
Pressure detector, 11...Rotational speed sensor, 12...
Throttle valve position detector, 13...control circuit.

Claims (1)

[Scope of Claims] 1. Fuel supply is stopped when the engine speed becomes equal to or higher than the fuel cut speed during vehicle deceleration, and when the engine speed becomes lower than the fuel return speed after the fuel supply is stopped. In a fuel supply stop control method for an internal combustion engine that restores fuel supply, information corresponding to atmospheric pressure is detected, and the restoration rotational speed is set higher as the atmospheric pressure decreases, or as the atmospheric pressure falls below a predetermined value. Then, the return rotation speed is set to a return rotation speed higher than the value at which the atmospheric pressure is equal to or higher than a predetermined value, and the fuel cut rotation speed is set higher than the return rotation speed by a predetermined rotation speed. Engine fuel supply stop control method.