JPH0463220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention is directed to high-temperature incineration (hereinafter referred to as
The present invention relates to a fuel control device that eliminates the risk of igniting a gasoline mixture when performing burn-off.

[Conventional technology]

Characteristics of hot wire intake air flow sensors change due to substances adhering to the hot wire surface, resulting in errors in the amount of fuel supplied to the engine, leading to problems such as deterioration of exhaust gas and deterioration of driving performance.

To deal with this problem, it has been conventional practice to heat the hot wire to a temperature above the normal operating temperature when the engine is stopped to burn off deposits on the surface of the hot wire. The burn-off method is explained in Japanese Patent Laid-Open No. 76182/1982, so a detailed explanation will be omitted.

Experiments have shown that the heating temperature of the hot wire should be around 1000°C in order to effectively perform the burn-off operation.

However, heating the hot wire to 1000° C. can ignite the gasoline mixture, which is inconvenient for the intake air amount sensor disposed in the intake passage of a gasoline engine.

Therefore, in order to avoid ignition of the gasoline mixture, conventional methods have been used to ensure that the temperature and rotational speed during engine operation meet predetermined conditions when performing burn-off, and that the excess gasoline supplied into the intake pipe during the warm-up process is sufficiently scavenged. Execution is allowed only if the

However, it has been found through experiments that merely determining the burn-off execution conditions described above is insufficient, and burn-off may cause the gasoline mixture to ignite.

[Problem that the invention seeks to solve]

In other words, even if the engine has warmed up, there may be a large amount of gasoline accumulated near the fuel control valve due to intake air blowback when the engine is operated at full throttle, and the gasoline may accumulate rapidly after the engine has stopped. There is an inconvenience that the gasoline mixture flows up to the vicinity of the intake air amount sensor, and if burn-off is performed in this state, the gasoline will be ignited.

The present invention was made to solve this problem, and an object of the present invention is to provide a fuel supply device that does not have the risk of igniting a gasoline mixture.

[Means for solving problems]

In the fuel control device according to the present invention, when the engine is stopped, the time from the time when the engine intake is determined to have stopped based on the output of the intake air amount sensor is shorter than the time during which the accumulated gasoline vaporizes and flows up to the vicinity of the intake air amount sensor. 0
A means for controlling the burn-off within the above time period is provided.

[Effect]

In this invention, after intake air stops, burn-off is performed to prevent gasoline from igniting after the gasoline accumulated in the fuel supply section vaporizes and flows up to the vicinity of the intake air amount sensor.

〔Example〕

Embodiments of the fuel control device of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram showing the configuration of one embodiment of the hot wire intake air flow sensor (hereinafter referred to as AFS) that detects the intake air amount of the engine.
1 is a diagram showing the configuration of a fuel control device using the fuel control device.

In this figure 1, 1 is the air cleaner, 2 is the AFS,
3 is a throttle valve that controls the intake air amount of the engine.

The throttle sensor 4 moves in conjunction with the throttle valve 3, extracts its opening as a voltage signal, and sends it to an electronic control unit 10 (hereinafter referred to as ECU).
It is now being sent to

Further, an intake manifold 6 is connected to the surge tank 5 , and the intake manifold 6 is connected to a cylinder 8 . The cylinder 8 is provided with an intake valve 7 driven by a cam (not shown).

In the figure, only one cylinder portion of the engine is shown for the sake of simplicity, but the cylinder 8 (cylinder) is actually composed of multiple cylinders.

A fuel control valve (hereinafter referred to as an injector) 9 is attached to each cylinder 8. The ECU 10 controls the fuel injection amount of the injector 9 so that the amount of air taken into each cylinder 8 becomes a predetermined air-fuel (A/F) ratio.

ECU10 is AFS2 and crank angle sensor 1
1. The fuel injection amount is determined based on the signals of the starting switch 12, the engine cooling water temperature sensor 13, and the throttle sensor 4, and the crank angle sensor 11
The pulse width of the fuel injection pulse of the injector 9 is controlled in synchronization with the signal.

The ECU 10 generates a burn-off control signal 14 when all of the burn-off conditions are met, and the AFS
It is now being sent to 2. The configuration and operation related to burn-off control of AFS2 are the same as those known in the art, so detailed explanations will be omitted.

FIG. 2 is a block diagram showing the internal configuration of the ECU 10. In this FIG.
The analog input interface circuit of the cooling water temperature sensor 13, 103 is a multiplexer, and the A/
By D (analog/digital) converter 104
Analog inputs from the AFS 2 and cooling water temperature sensor 13 are sequentially converted into digital values.

105 is a CPU that has a built-in ROM 105a, RAM 105b, and timers 105c and 105d, and is connected to the interface circuit 101 and A/
Based on the signal input from the D converter 104,
The injector drive pulse width is calculated according to the program stored in the ROM 105a, and a pulse of a predetermined time width is outputted by the timer 105c.

The pulse outputted from the timer 105c is amplified by a drive circuit 106 to drive the injector 9. Since the above configuration related to fuel control is conventionally known, a more detailed explanation will be omitted.

Next, the timer 105d is a timer that outputs a burn-off pulse according to the program operation shown in FIG. The program related to burn-off will be explained in detail below with reference to FIG.

This FIG. 3 shows only the control from engine stop to burn-off, and the fuel control in the operating state is omitted. The output Qa of AFS2 is read in step S1, and this is calculated as the intake air amount Qth in step S2.
Compare with.

As shown in FIG. 4, the intake air amount Qth is set to a value at which it can be considered that the intake air has almost stopped.

When Qa<Qth holds true, move to step S3,
A timer is set. In Fig. 4, the time limit of the timer is longer than the time T required for the output Qa to fall below the intake air amount Qth and become almost completely 0, and after the intake air amount stops, the residual gasoline in the fuel supply section evaporates and flows upstream. It is set to a shorter time than the arrival time.

When time-over is determined in step S4,
Move to step S5 and execute burn-off.
Incidentally, if the intake air amount attenuates rapidly after the engine is stopped, burn-off may be performed immediately after Qa<Qth is satisfied. In that case, step
It goes without saying that S4 can be omitted.

〔Effect of the invention〕

As explained above, this invention is designed to perform burn-off after the engine stops, after the intake air amount has almost stopped, until the residual gasoline vaporizes and goes upstream from the fuel supply section, so that the gasoline can be ignited. There are no inconveniences, and it has the excellent feature that the above effects can be achieved with a few additions to the program.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the fuel control device of the present invention, FIG. 2 is a block diagram showing the internal configuration of the ECU in the fuel control device of FIG. 1, and FIG. FIG. 4 is a flowchart showing an example of the program of the control device, and is an output waveform diagram of the AFS when the engine is stopped. 2...AFS, 3...Throttle valve, 4...Throttle sensor, 8...Cylinder, 9...Injector, 10...ECU, 11...Crank angle sensor, 12...Start switch, 13...Cooling Water temperature sensor, 105...CPU, 105a...ROM,
105b...RAM, 105c, 105d...Timer, 106, 107...Drive circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A means for supplying fuel to the internal combustion engine in response to the operation of the fuel control valve; a hot wire intake air amount sensor disposed in the intake passage of the internal combustion engine to detect the amount of intake air;
When the internal combustion engine is stopped, from the time when it is determined from the output of the intake air amount sensor that the intake air of the internal combustion engine has stopped, the fuel accumulated in the intake passage vaporizes and flows up to the vicinity of the intake air amount sensor. 1. A fuel control device comprising means for controlling a hot wire to heat the hot wire to a temperature higher than the normal operating temperature within a time period of 0 or more and to incinerate deposits on the surface of the hot wire.