JPS6375331A - Fuel control device - Google Patents

Abstract

PURPOSE:To eliminate the possibility to ignite gasoline owing to burn-off, by providing an electronic control unit which stops the actuation of a burn-off control part when an output from a heat ray type intake air amount sensor for detecting an intake air amount of an engine is lowered. CONSTITUTION:An intake air amount of a cylinder 8 is detected by a heat ray type intake air amount sensor 2 and is controlled by means of a throttle valve 3. A throttle sensor 4 outputs the opening of the throttle valve 3 to an electronic control unit 10. The electronic control unit 10 controls a fuel injection amount of an injector 9 such that an air-fuel ratio is adjusted to a given value. When an output from the heat ray type intake air amount sensor 2 during burn-off control is reduced to a given value or less, burn-off control is stopped. This constitution eliminates the possibility to ignite gasoline due to burn-off.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention improves the operation of high-temperature incineration (hereinafter referred to as 7) of surface deposits of a hot wire intake air flow sensor used for fuel control of an internal combustion engine. This invention relates to a fuel control device.

[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.

In order 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 in a stopped state to break off deposits on the surface of the hot wire. Regarding the burn-off method, please refer to IP# Kaisho 5.
Since it is explained in Japanese Patent No. 4-76182, 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 air-fuel mixture, which is inconvenient for the intake air amount sensor disposed in the intake passage of a gasoline engine.

Conventionally, in order to avoid ignition of the gasoline mixture, the temperature and rotation speed during engine operation must meet predetermined conditions when bar 7 off is executed, and the excessive gasoline supplied into the intake pipe during the warm-up process must be sufficiently scavenged. Execution is only allowed if it is fully permitted.

Furthermore, after the engine is stopped, the time it takes for the air-fuel mixture to travel upstream from the fuel supply section to reach the intake air amount sensor is determined through experiments, and Non-No-O7 is executed within this time. There is.

[Problem that the invention seeks to solve]

However, even when the burn-off execution conditions described above are met, gasoline may still exist near the intake air amount sensor, and in this state, burn-off causes a reaction that leads to ignition, so the burn-off execution conditions described above are not sufficient. Ta.

The present invention was made in order to solve the above-mentioned problems, and therefore, it is an object of the present invention to provide a fuel control device that does not have the risk of igniting gasoline due to burn-off.

[Means to solve the problem AV]

The fuel control device according to the present invention performs burn-off control (h+) when the output of the hot-wire intake air amount sensor during burn-off control becomes less than a predetermined value, and displays a failure when this burn-off stop is performed repeatedly. It is equipped with a failure detection section.

[For production]

In this invention, when gasoline is present near the intake air amount sensor during non-off control, the output voltage of the intake air amount sensor drops, so the failure detection section detects this abnormal drop and completely stops the burn-off control. However, a failure is displayed when this burn-off stop is performed multiple times.

〔Example〕

FIG. 1 is a diagram showing the configuration of a fuel control device according to an embodiment of the present invention. In this FIG. 1, 1 is an air cleaner. The air that has passed through this air cleaner 1 is stored in a surge tank 5. The air is supplied to a cylinder 8 via an intake manifold 6, and the intake air amount of the cylinder 8 is detected by a hot wire intake air amount sensor (hereinafter referred to as AFS) 2. Further, the 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, picks up 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).

Reference numeral 7 denotes an intake valve driven by a cam (not shown), and the cylinder 8 is actually composed of a plurality of cylinders, although only one 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.

Moreover, the above ECUIO is the fuel injection ft of the injector 9.
- Control is performed so that the amount of air taken into each cylinder 8 is maintained at a constant air ratio (A/F).

This ECUIO has AFS 2 and crank angle sensor 1
1. Start switch 12. Engine cooling water temperature sensor 13
．． The fuel injection amount is determined based on the signal from the throttle sensor 4, and the A pulse width of the fuel injection pulse from the injector 9 is controlled in synchronization with the signal from the crank angle sensor 11.

Additionally, KECUlo generates a burnoff control signal 14 when all of the burnoff conditions are met.

The configuration and operation related to burn-off control of the AFS 2 are the same as those of the AFS 10j, so detailed explanations will be omitted.

FIG. 2 is a block diagram showing the internal configuration of ECUIO. In this FIG. 2, 101 is the crank angle sensor 11
．． 2 is an interface circuit for the 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 enclosure 102 is an AFS2
, the analog signal from the water temperature sensor 13 is input and output to the multiplexer 103. The output of this multiplexer 103 is sent to a Φ (analog/digital) converter 104, which converts the analog signal output from the multiplexer 103 into a digital signal and sends it to the CPU 1.
I am trying to output it to 05.

The CPU 105 has a built-in ROM 105a, a RAM 105b, a timer 105c, and a timer 105dTh, and calculates the injector driving noise ξ width according to a program stored in the ROM 105a based on signals input from the interface circuit 101 and the A/D converter 104. Then, the timer 105c outputs a pulse with a predetermined time width.

The nozzle is amplified by the drive circuit 106 and drives the injector 9, thereby injecting fuel from the injector 9 into the cylinder 8. The duration of the injection depends on the width of the nogle.

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

Next, the timer 105d is a timer that outputs a burn-off pulse according to a predetermined program operation, and this pulse is amplified by the drive circuit 107 and sent to the AFS 2.
7 signal 14.

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

A failure output port 108 amplifies the failure signal 16 outputted by the CPU 105 and drives, for example, an indicator lamp 15 as failure display means.

The generation of this failure signal 16 will be explained using FIGS. 3 and 4. In FIG. 3, (a) shows the waveform of the burn-off signal 14, and (b) shows the waveform of the burn-off signal 1.
A when AFS2 is in burn-off operation by 4
The FS output waveform is shown. In the same figure (b), the solid line shows all the normal burn-off operations, from the start of burn-off to the AF
A full voltage V is applied until the hot wire S2 reaches a predetermined temperature, and after the hot wire reaches the predetermined temperature, seven voltages necessary to maintain the predetermined temperature are applied.

However, if there is gasoline near the hot wire, the waveform becomes completely different as shown by the broken line, and the output becomes v
It drops to 3. This is because Ganlin undergoes a thermal oxidation reaction on the surface of the hot wire, and the hot wire is heated by the heat of the reaction, so that the predetermined temperature can be maintained even with almost no heating electrical energy from the burn-off control section. If this condition continues, the oxidation reaction becomes even more intense, leading to ignition of the gasoline and melting of the hot wire. Therefore, the burn-off is compared with the AFS output assertion level Vth during the burn-off operation, and if V is lower than the Vth, the burn-off is stopped to prevent ignition and also to signal the failure signal 16.
to occur.

Next, such an operation will be explained using the flowchart shown in FIG. A burn-off timer control signal is output at Sl. After waiting time S3 for the response of AFS2, all AFS outputs are judged in S4, and V>Vth
At this time, the process moves to S5, and if the burn-off timer has not timed up, the process returns to S4, and the burn-off is continued. If the burn-off timer has timed up in S5, the process moves to S6 to stop the burn-off signal and end the process. Further, if the burn-off condition is not satisfied at Sl, no control is performed and the process ends. Next, in 84, if V:CVth, S
7, it is determined whether the failure flag has already been set, and if it has not been set, the failure flag is set in step S8, and 86. to stop burn-off. Note that it is desirable that the failure flag memory be nonvolatile. If the failure flag is set in S7, the process moves to S9, where a failure signal is output, the indicator lamp is turned on, and burn-off is stopped in S6, and the process ends.

By the way, in the above embodiment, the full failure signal is not output during the first burn-off stop. This is because, although it is a rare case, even if the burn-off conditions are met and all functions are normal, gasoline is present in the AFS 2 and an oxidation reaction will occur due to burn-off.

On the other hand, if burn-off stops occur continuously, there is a high possibility that a failure has occurred in the fuel supply system, such as gasoline leakage from the injector 9. Therefore, when the burn-off stop occurs repeatedly (the second time in this embodiment), a failure signal is output.

Further, in the fuel control device according to the present invention, the drive circuit 107
This is also effective when there is a failure in the transmission line of the burn-off signal 14 and the AFS 2. In other words, if there is a failure in each of these parts and the burn-off operation is not performed normally, the AFS
This is because when the output V falls below a predetermined level vth, a failure signal can be similarly output to indicate a failure.

〔Effect of the invention〕

As described above, according to the fuel control device of the present invention, the presence of gasoline is detected from the AFS output voltage during burn-off operation and burn-off is stopped, so there is no risk of gasoline igniting due to burn-off. Furthermore, since a fault is displayed when the non-operator 7 is repeatedly stopped, it is possible to easily and reliably find and repair a faulty part.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a fuel control device according to an embodiment of the present invention, Fig. 2 is a block diagram of an electronic control unit in the fuel control device, and Fig. 3 is an AFS output at burn-off. FIG. 4 is a flowchart illustrating the operation of the fuel control device according to an embodiment of the present invention. 2... Hot wire intake air flow sensor (AFS), 8... Cylinder, 9... Fuel control valve (injector), 10...
・Electronic control unit) (ECU), 14... Burn-off control signal, 15... Display lamp, 16... Failure signal, 105... CPU, 106, 107... Drive circuit, 108... Fault output circuit. Note that 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 the surface deposits of the hot wire after the engine has stopped; If the output of the hot-wire intake air amount sensor falls below a predetermined value while the fuel control section that controls the fuel control valve based on the calculated value and the burn-off control section are in operation, the operation of the burn-off control section is stopped. The fuel control device also includes a failure detection unit that stores a history of the operation stoppages and displays a failure indication when the operation stops a plurality of times.