JPS62255547A - Fuel control device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of ignition to gasoline, by providing an electronic control unit by which motion of incinerating a substance, adhered to the surface of a heat ray type intake air amount sensor (AFS), at a high temperature is executed only when a source switch is in an OFF-state and no engine stop during running occurs. CONSTITUTION:When a source switch 15 is in an ON-state and the number of revolutions of an engine exceeds a given value, fuel is fed from an injector 9 at a given injector drive pulse width. When the number of revolutions of an engine is decreased to the value lower than the given value and an engine stop is decided to occur, no fuel is fed from the injector 9. When the source switch 15 is in an OFF-state, the feed of fuel from the injector 9 is forcibly stopped. When no engine stop is decided to occur, only when resulting from comparison of an output Q from an AFS 2 with an intake air amount Qs from which an engine is almost considered to stop, Q is smaller than or equal to Qs, high temperature incineration motion is executed. Thus, only when no engine stop occurs and the source switch 15 is in an OFF-state, high temperature incineration motion is executed, ignition to gasoline is prevented from occurring.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to high-temperature incineration (hereinafter referred to as burn-off) of surface deposits of a hot wire intake air flow sensor (hereinafter referred to as AFS) used for fuel control of an internal combustion engine. The present invention relates to a fuel control device that prevents gasoline from igniting by not performing it after the engine is stopped.

[Conventional technology]

In the AFS, characteristics 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 address these problems, when the engine is at a standstill, the hot wire is heated to a temperature above normal operating temperature.
Conventionally, it has been carried out to remove deposits on the surface of a hot wire. Regarding the method of punch-off, please refer to Japanese Patent Application Laid-Open No. 54
Since it is explained in Japanese Patent No. 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 pan-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 (as in the past), when executing the burn-off, the temperature and rotation speed during engine operation must meet a predetermined condition, and the gasoline that was excessively supplied into the intake pipe during the warm-up process must be sufficiently scavenged. Execution is allowed only if the Furthermore, the turn-off is executed after a certain period of time has passed after the engine has stopped.

However, it has been found through experiments that the determination of the above-mentioned conditions for executing the parn-off is insufficient, and that the gasoline mixture may be ignited due to the parn-off.

[Problem that the invention seeks to solve]

In other words, after the engine satisfies the above conditions, a large amount of gasoline may be supplied to the intake pipe due to failure of various parts including the fuel control device, causing the engine to stop due to an excessively rich air-fuel ratio (so-called engine stall, hereinafter referred to as engine stall). be.

In this case, since a large amount of gasoline has not been scavenged by the engine, there is an inconvenience that the gasoline will be ignited when the engine burns off.

This invention was made in the ninth attempt to solve this problem.
The object of the present invention is to obtain a fuel control device that can prevent gasoline from igniting.

[Means for solving problems]

The fuel control device according to the present invention sets an engine stall flag and stops controlling the fuel control valve when the number of revolutions falls below a predetermined value when the power switch is in a closed state, and when the power switch is opened, the fuel control valve When the engine stall flag is in the reset state, the heating wire is heated to a temperature higher than the normal operating temperature [4] when the output of the intake air amount sensor becomes below a predetermined value or after a predetermined time period from this point. The device is equipped with a means for incinerating the surface deposits of the hot rays.

[For production]

In this invention, the engine stall flag is set when the engine stalls due to a failure of the fuel control valve during engine operation, and acts to prevent subsequent burn-off, preventing ignition of a large amount of gasoline remaining in the intake pipe. Do it like this.

〔Example〕

Embodiments of the fuel control device of the present invention will be described below with reference to the drawings. Figure 1 shows the AF that detects the intake air amount of the engine.
FIG. 2 is a diagram illustrating the configuration of a fuel control device according to a general example using S.

In this Figure 1, 1 is an air cleaner, 2 is an AFS,
3 is a throttle valve that controls the intake air amount of the engine. The throttle valve 3 is provided within the surge tank 5.

The surge tank 5 communicates with an intake manifold 6. Intake manifold 6 is cylinder 8
(cylinder). An intake valve 7 is provided within the cylinder 8 . The intake valve 7 is 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 is actually composed of a plurality of cylinders. Each cylinder 8 is provided with a fuel control valve (hereinafter referred to as an injector) 9.

An electronic control unit (hereinafter referred to as 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/p) ratio. It looks like this.

The ECUIO determines the fuel injection amount based on the signals from the AFS 2, the crank angle sensor 11, the start switch 12, the engine coolant temperature sensor 13, and the throttle sensor 4, and injects the fuel into the injector 9 in synchronization with the signal from the crank angle sensor 11. The nozzle width of the injection pulse is controlled.

The throttle sensor 4 moves in a delayed manner relative to the throttle valve 3.
This is a companion device that extracts the opening degree as a voltage signal.

The ECUIO generates a turn-off control signal 14 when all of the turn-off conditions are met. The configuration and operation related to the pan-off control of the AFS2 are similar to those known in the art, so detailed explanations will be omitted. Figure 2 shows ECUIO
This is the internal configuration of

In this FIG. 2, 101 is a crank angle sensor 11;
102 is an interface circuit for the digital input of the start switch 12, 102 is an interface circuit for the analog input of the AFS 2 and the cooling water temperature sensor 13, 103 is a multiplexer, and this analog input is sequentially converted into a digital value by the ~Φ converter 104. .

The CPU 105 has a built-in ROM 105a, a RAM 105b, and timers 105c and 105di, and calculates the injector drive pulse width according to the program stored in the ROM 105a based on the signal input from the converter 104 between the above-mentioned interface circuit 101 and ~. , the timer 105c outputs a pulse with a predetermined time width.

This pulse is amplified by a drive circuit 106, and the injector 9 is driven by this drive circuit 106.

Note that the above configuration related to fuel control is conventionally known, so a detailed explanation will be omitted.

Next, the timer 105d is a timer that outputs a turn-off pulse according to the program operation shown in FIG.

Hereinafter, the program related to the burn-off will be explained in detail with reference to FIG.

First, in step S1, the key switch is determined.
If it is in the N state, it is determined in step S2 whether the rotational speed N is higher than a predetermined value NS.

The predetermined value NS corresponds to the rotation speed at which the engine can be considered to be stopped.

If N > NS, the engine is operating normally, so the engine stall flag is reset in step S3, and N
If <NS, an engine stall flag is set in step S4.

Next, in step S5, the state of the engine stall flag is determined, and if it is in the reset state, fuel control is executed in step S6, and the process returns to step S1.

If the engine stall flag is set, step 56t
- Do not supply fuel unnecessarily without passing through and returning to step S1.

Again, in step S1, if the key switch is in the OFF state, fuel is not needed, so the injector 9 is forcibly stopped in step S7.

Note that if the power to the injector 9 is to be cut off in conjunction with a key switch, step S7 may be omitted.

Next, in step S8, the engine stall flag is determined. If there is no engine stall before the key switch is turned off, the engine stall flag has been reset, so the process moves to step S9 and the output Q of the AFS 2 is compared with a predetermined value QS. This predetermined value QS corresponds to a value at which the intake air amount can be considered to be almost at a standstill. When the intake air amount decreases until Q≦QS, a timer is activated in step S10. The time limit of the timer is Q≦□
It is determined according to the time it takes for the intake air amount to become □□ and then to completely decrease to O.

Next, in step Sll, parn-off is executed.

If it is acceptable to parn off in the state of 4L, Q = QS, step 810 can be omitted.

In step S8 again, if the engine stall flag is set, the process ends without going through steps 89 to Sll, so if the engine stall has occurred before the key switch is turned off, the burn-off t-% process is not performed.

Note that the execution of the look-off has already been explained with reference to FIG.

〔Effect of the invention〕

As described above, this invention prevents unnecessary injection of gasoline when an engine stall occurs or when a key switch is turned off, sets an engine stall flag when an engine stall occurs during driving, and sets a key switch when the engine stalls. Since the turn-off pulse is activated only when the switch is turned off and the engine stall flag is in the reset state (that is, there was no engine stall during operation), it is possible to prevent malfunctions of fuel system parts such as the injector. When an engine stall occurs and an excessive amount of gasoline remains in the intake pipe, the system does not turn off and there is no risk of gasoline igniting.

In addition, since the pier-off is executed immediately after the intake air volume stops, even if gasoline remains in the intake pipe, the pier-off is performed before the evaporative gas reaches the AFS area. Not only is it doubly safe, but it also has the excellent effect of being able to obtain the above effects by adding a few extra steps to the program.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an emergency embodiment of the fuel control device of the present invention, FIG. 2 is a block diagram showing the internal configuration 2 of the ECU in the fuel control device of FIG. 1, and FIG. 3 is a flowchart showing an example of execution of a control device program. 2...AFS, 3...Throttle valve, 4...Throttle sensor, 8...Cylinder, 9...Injector, 10...ECUL 11...Crank angle sensor, 12...Start Switch, 13...Cooling water temperature sensor, 105...CPU. 105a=ROM, 1105b=RA, 105c, 1
05d...Timer, 106, 107...Drive circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A device that calculates the engine's required fuel amount based on the output of a hot-wire intake air amount sensor installed in the intake passage of an internal combustion engine, and controls the fuel control valve based on this calculated value to supply the desired fuel to the engine. When the power switch is in a closed state and the rotation speed is below a predetermined value, an engine stop flag is set and the control of the fuel control valve is stopped, and when the power switch is opened, the control of the fuel control valve is stopped. When the engine stops and the engine stop flag is in a reset state, the hot wire is heated to a temperature higher than the normal operating temperature at the point when the output of the intake air amount sensor becomes less than a predetermined value or after a predetermined time period from this point. A fuel control device comprising a means for incinerating surface deposits.