JPS62233444A - Fuel control device - Google Patents

Abstract

PURPOSE:To prevent fuel from being erroneously fed and being ignited when a substance adhered to the outer surface of a heat wire in an heat-wire type intake-amount sensor is burn out, by judging the burn-off condition of the above- mentioned sensor so that subsequent control for a fuel control valve is inhibited. CONSTITUTION:An ECU 10 determines the amount of fuel injection in accordance with signals from a heat wire type intake-air amount sensor (AFS) 2, a crank angle sensor 11, a starting switch 12, an engine cooling water temperature switch 13 and a throttle sensor 4, and controls the pulse width of fuel injection pulses for an injector (fuel control valve) 9 in synchronization with the signal from the crank angle sensor 11. Further, the ECU 10 delivers a burn- off control signal 14 when all burn-off conditions are satisfied. In this case, a desired amount of fuel for the engine is computed in accordance with the output from the AFS 2, and in accordance with the thus computed value, the injector 9 is controlled. Further, erroneous operation of a burn-off control section is detected to stop the operation of the injector 9.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a fuel control device that improves the high-temperature incineration (hereinafter referred to as burn-off) operation of surface deposits of a hot-wire type intake air amount sensor used for fuel control of an internal combustion engine. .

[Conventional technology]

Characteristics of hot wire intake air flow sensors change due to substances adhering to the surface of the hot wire, 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. / Regarding the method of gun-off, refer to fF Kaisho 5.
Since it is explained in Japanese Patent No. 4-76182, detailed explanation will be omitted.

It has been found through experiments 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 i o o o'c can ignite the gasoline mixture, which is inconvenient for the intake air amount sensor disposed in the intake passage of the gasoline engine.

Therefore, in order to avoid ignition of the gasoline mixture, it has been necessary to ensure that the temperature and number of revolutions during engine operation meet a predetermined condition when executing 9-turn-off, and that the gasoline that was excessively supplied during the warm-up process is fully absorbed into the intake pipe. Execution is allowed only when the air is scavenged.

Furthermore, after the engine is stopped, the time it takes for the air-fuel mixture to travel upstream from the fuel supply site and reach the intake air amount sensor is determined through experiments, and burn-off is performed within this time.

However, it has been found through experiments that the above-mentioned burn-off execution conditions alone are insufficient, and the burn-off may cause the gasoline mixture to ignite.

[Problem that the invention seeks to solve]

In other words, when the circuit that performs burn-off control malfunctions and burn-off is performed continuously, the output of the intake air flow sensor becomes several ten times the value that is originally output from engine startup to idle operation. ing.

If the engine is started and fuel is supplied in such a malfunctioning state, several ten times the amount of fuel required by the engine will be supplied, and the fuel will not reach full capacity, resulting in a large amount of gasoline remaining in the intake pipe. There is a risk that it will be ignited by a hot ray heated to about 1000'C.

The present invention was made to solve this problem, and an object of the present invention is to provide a fuel supply device that can prevent gasoline from igniting even if burn-off malfunctions.

[Means for solving problems]

The fuel supply device according to the present invention includes a burn-off control section that heats the hot wire, and detects the output of the burn-off control section,
The fuel control valve is provided with means for stopping control of the fuel control valve when the output state corresponds to the burn-off operation.

[Effect]

In this invention, the level of the output signal of the burn-off control section is detected by the means for stopping the control of the fuel control valve, and if this level corresponds to burn-off, an output is generated to stop the fuel control.

〔Example〕

Embodiments of the fuel control device of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a fuel injection control device using a hot wire type intake air amount sensor (hereinafter referred to as AFS) for detecting the intake air amount of an ennon to which one embodiment of the invention is applied.

In this FIG. 1, l is an air cleaner. The air that has passed through this air cleaner 1 is sent to the surge tank 5. Air is taken into the cylinder 8 via the intake fanifold 6. The intake air amount of this cylinder 8 is AFS
2 is used for detection. Further, this intake air amount is controlled by a throttle valve 3. The throttle valve 3 is provided at the inlet of the surge tank 5.

A throttle sensor 4 moves in conjunction with the throttle valve 3, extracts the opening degree of the throttle valve 3 as a voltage signal, and sends the output to an electronic control unit 10 (hereinafter referred to as ECU).

7? ``i'' is an intake valve driven by a cam (not shown), and the cylinder 8 is actually composed of a plurality of cylinders, although only the l-cylinder portion is shown in the figure for the sake of simplicity.

A fuel control valve 9 (hereinafter referred to as an injector) is attached to each cylinder 8.

Further, the ECUIO adjusts the fuel injection amount of the injector 9 to a predetermined air fuel amount (
A/F) ratio is controlled.

This gctrto is AFS2 and crank angle sensor 1
1. Start switch 12. Ennon cooling water temperature sensor 13
．． The fuel injection amount is determined based on the signal from the throttle sensor 4 and the crank angle sensor 1. The pulse width of the fuel injection nocellus of the injector 9 is controlled in synchronization with the signal t.

The ECUIO generates a burn-off control signal 14 when all burn-off conditions are met. 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 diagram showing the internal structure of the ECUIO. In this FIG. 2, 101 is the crank angle sensor 11
．． This is an interface circuit for digital input of the start switch 12. This digital interface circuit 1
The output of 01 is sent to the CPU 105.

Further, the analog interface circuit 102 is AFS2
．． The water temperature sensor is inputted and outputted to the multi-breather 103. The output of this multi-blephr 103 is converted into a dinotal signal by an A/D (analog/diphtal) converter 104, and is outputted to C)'Ut05.

The CPU 105 is ROMI 05 a, RAMI O
5b and timers 105c and 105d, the inductor drive A pulse width is calculated according to the program stored in the ROM 105a based on the signal input from the converter 104 to the interface circuit 101, and is set to a predetermined value by the timer 105e. Outputs a pulse with a time width.

This pulse is amplified by the drive circuit 106 and the injector 9
thereby driving the cylinder 8 from the injector 9.
inject fuel into. Its injection period depends on the width of the /#rus.

Since the above configuration related to fuel control is conventionally known,
A more detailed explanation will be omitted.

Next, although the explanation is omitted, the timer 105d is a timer that outputs a burn-off nockle according to a program operation, and this nockle is amplified by the drive circuit 107 and
2 is given as a burn-off signal 14.

On the other hand, the burn-off signal 14 is again input to the CPU 105 via the digital interface circuit 101. The CPU 105 is programmed in advance so as not to output a drive nozzle to the drive circuit 106 of the injector 9 upon receiving the burn-off signal 14.

Please note that this program is extremely simple, so
Explanation with drawings is omitted.

In the above description, a case has been cited in which information as to whether or not the AFS 2 is in a burn-off state is inputted to the CPU 105 via the digital interface circuit 101. This is for the purpose of protecting the CPU 05, since various induced noises are likely to be superimposed on the wiring 14A from the drive circuit 107 to the AFS2.

Therefore, as long as there is no harmful induced noise, the output of the drive circuit 107 may be directly input to the CPU 105 within the ECUIO.

Next, another embodiment of the ECUIO will be described with reference to FIG. In FIG. 3, the output of the drive circuit 107 is also given to the drive circuit 106. The drive circuit 106 is configured not to send a drive pulse to the injector 9 when the drive circuit 107 is generating an output corresponding to burn-off.

Such a function can be realized with a simple circuit configuration having an r-t function, and a detailed explanation will be omitted.

In the embodiment shown in FIG. 3, it is possible to accurately stop the injector 9 even when the CPU 105 is in a runaway state and is in a burn-off state.

〔Effect of the invention〕

As explained above, in this invention, the burn-off state of the AFS is determined and subsequent control of the injector is prohibited, so gasoline is not supplied based on an erroneous output corresponding to burn-off, and therefore the gasoline is ignited. There will be no inconvenience caused.

Moreover, this effect can be obtained by adding only a few circuits or programs, and the safety can be greatly improved with almost no change in price.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a fuel injection control device to which an embodiment of the fuel control device of the present invention is applied, and FIGS. 2 and 3 are block diagrams of electronic control units used in the fuel control device of the present invention, respectively. It is. 2... AFS, 3... Throttle valve, 4... Throttle sensor, 8... Cylinder, 9... Injector, lO... Electronic control unit, 11... Crank angle sensor, 12...・Starting switch, 105...CP
U, 106°107...drive circuit. In addition, the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A hot wire intake air amount sensor disposed in an intake passage of an internal combustion engine to detect the intake air amount of the engine, a fuel control valve attached to each cylinder of the internal combustion engine to inject fuel into each cylinder, and the internal combustion engine a burn-off control section that heats the hot wire to a temperature higher than the normal operating temperature to incinerate deposits on the upper surface of the hot wire after the hot wire has stopped; A fuel control device comprising means for controlling the fuel control valve based on the calculated value and detecting malfunction of the burn-off control section to stop the operation of the fuel control valve.