JPS62233445A - 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 stopping the control of a fuel injection valve when the output of the above-mentioned sensor is in a condition corresponding to burn-off operation. 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, the output of the AFS 2 is detected during the engine starting, and when the output of the AFS 2 is in a condition corresponding to burn-off operation, the operation of the injector 9 is stopped.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel control system for an internal combustion engine, and particularly to a hot-wire type intake air flow sensor for which high-temperature incineration of surface deposits (prior art). If the material adheres to the surface of the hot wire, the characteristics change, resulting in an error in the amount of fuel supplied to the engine, leading to problems such as deterioration of exhaust gas and deterioration of driving performance. Conventionally, when the hot wire is in a stopped state, the hot wire is heated to a temperature higher than the normal operating temperature, and the deposits on the surface of the hot wire are incinerated (burn-off). In order to effectively perform the burn-off operation, the heating temperature of the hot wire must be 1.
Experiments have shown that the temperature should be around 000°C. However, heating the 7@ 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, conventionally, when executing burn-off, the temperature and rotation speed during engine operation meet predetermined conditions i+! Without l, excessive supply is allowed into the intake pipe during the warm-up process. Further, after the engine is stopped, the time required for the air-fuel mixture to travel upstream from the fuel supply section and reach the intake air amount sensor is determined through experiments, and burn-off is performed within this time.

[Problem that the invention seeks to solve]

However, it has been found through experiments that the above-mentioned determination of the burn-off execution conditions alone is insufficient and that the burn-off may cause the gasoline mixture to ignite. In other words, when the circuit that performs burn-off control malfunctions and burn-off is performed continuously, the output of the intake air sensor becomes several tens of times the value that should be output from engine startup to idling. There is. 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 a large amount of gasoline will remain in the intake pipe without causing a complete explosion.
There was a fear that the heated wire could ignite the fire.

This invention was made in order to eliminate the above-mentioned problems, and its purpose is to provide a fuel control device in which there is no risk of gasoline being ignited even if there is a burn-off malfunction when starting an engine. do.

[Means for solving problems]

The fuel control device according to the present invention includes a burn-off control section that heats the hot wire of the intake air amount sensor, and a fuel control section that detects the output of the intake air amount sensor when starting the engine and controls the fuel when the output is in an output state corresponding to the burn-off operation. It has means for stopping control of the valve.

[For production]

The fuel control valve stop means in this invention detects the state before or during engine startup, compares the output of the intake air amount sensor at that time with a predetermined value, and detects when the output exceeds the predetermined value or Generates an output that stops control of the fuel control valve when the fuel control valve is not within a predetermined range.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. 1st
The figure shows the configuration of a general fuel injection control device using a hot-wire type intake air amount sensor (hereinafter referred to as AFS) that detects the intake air amount of the engine. 1 is an air cleaner, 2 is an AFS, and AFS2 is arranged in the intake passage. 3
4 is a throttle valve that controls the intake air amount of the engine, 4 is a throttle sensor that moves in conjunction with throttle valve 3 and extracts its opening as a voltage signal, 5 is a surge tank, and 6 is an intake manifold. . 7
Reference numeral 8 indicates an intake valve driven by a cam (not shown), and 8 indicates a cylinder. Although only one cylinder of the engine is shown for simplicity, it actually consists of multiple cylinders.

Reference numeral 9 indicates a fuel control valve (hereinafter referred to as an injector) attached to each cylinder 8, and reference numeral 10 controls the fuel injection amount of the injector 9 to a predetermined air/fuel ratio ( This is an electronic control unit (hereinafter referred to as ECU) that controls the A/F ratio. ECU
Reference numeral 10 controls the pulse width of the fuel injection pulse of the injector 9 in synchronization with the signal of 11 based on the signals of the AFS 2, the crank angle sensor 11, the start switch 12, the engine cooling water temperature selector 13, and the throttle sensor 4. Also, EC
When all U101f burn-off conditions are met, a burn-off control signal 14 is generated. The configuration and operation related to burn-off control of AFS 2 are similar to known ones, so detailed explanation will be omitted.

FIG. 2 shows the internal configuration of the ECU 10, 101 is an interface circuit for digital inputs of the crank angle sensor 11 and start switch 12, 102 is an interface circuit for analog inputs for AFS 2 and water temperature sensor 13,
103 is a multiplexer, and the analog input is sequentially converted into a digital value by an A/D converter 104. Also, 105 is ROMI 05 a, RAMI 05
This CPU has built-in timers 105c and 105d, and calculates the injector drive pulse width according to the program stored in the ROM 105a based on the signals input from the interface circuit 101 and the A/D converter 104. Firewood medium dish d+
! ! This is a circuit that amplifies the pulses of +1-1, +1-1, +1-1, and drives the injector 9. Since the above configuration related to fuel opening is conventionally known, a more detailed explanation will be omitted. Further, 105d is a timer that outputs a burn-off pulse according to a program operation.
This pulse is amplified by the drive circuit 107 and provided as the AFS2 hepburn-off signal 14.

Next, the program related to the operation of the above configuration is shown in FIG.
Let me explain. First, turn on the key switch, start the program with SO, and read the rotation speed N with SL. Next, this rotation speed N is determined at 82, and when the engine is in a state before starting, that is, when N=0, the output VQ of the AFS 2 is read at S3. In S4, it is determined whether vQ is higher or lower than a predetermined value v, h1. VLhl is a voltage value that is set in a range that is lower than the voltage output by AFS 2 during burn-off and higher than the output voltage when the intake air amount is O and burn-off is not performed, or this is converted into the intake air amount. It is a value. When the burn-off control is in a normal state with no malfunction, V, < V,, □, so the injection mode shifts from S6 to S7, and the injection prohibition flag has been reset, so fuel control is performed in S8. Execute. Regarding the content of the fuel control in S8 (well, since it is conventionally known, the explanation will be omitted.Next, when the burn-off control malfunctions and is in the burn-off state, it is VkuvIh, so from S4 to 85
After setting the injection prohibition flag, switch to injection mode S.
Move on to 6.

Then, since the injection prohibition flag is set, the process returns to si from 87 and the fuel control in S8 is not executed.

Next, in S2, when the engine is in a rotating state, the state is N~0, so the process moves to 89, and the state of the starting switch 12 is determined. When in the starting state, that is, when the starting switch 12 is on, the output of the AFS 2 is read in S10, and v,
,, Compare with 2. vth2 is a voltage set within a value range that is lower than the output voltage of AFS 2 that occurs when the engine is started during burn-off of AFs2, and higher than the output voltage when a normal start is performed without performing burn-off. This is the value or the value converted to the intake air amount. When there is no malfunction in the turn-off control and a normal start is performed, v
Q〈■Ih□, so shift to S6 injection mode,
Since the injection prohibition flag has been reset in S7, the fuel side is performed in 88. If the burn-off control is malfunctioning, VQ>vIh2, and after setting the one shot prohibition flag in S5, it moves to the injection mode in S6, and since the injection prohibition flag is set in S7, it returns to 81, and the fuel control is performed. Do not do this. When the starting switch 12 is off in S9, the engine is not in a starting state, and in this case, the process moves directly to S6.

In addition, when vIh2 and vIh2 are at a sharable level as defined above, 310. Abolish SLL and S9
83 as shown by the dotted line, i
It will be J flight. Also, in S2, the engine rotation is determined based on whether N=0 or not, but it is better to determine whether it is higher or lower than the rotation speed at which it can be considered that the engine is actually stopped. purpose, and N does not necessarily have to be 0. Alternatively, it is also possible to make a determination using the start switch 12 and directly shift to the injection mode IJ of S6. In this case, if the engine is started immediately after the program starts, it will not be determined that N=O at 82, and therefore the injection prohibition flag cannot be set. However, since the desired operation can be obtained except in rare cases where starting is performed in an extremely short period of time, there is no problem in practical use.

〔Effect of the invention〕

As described above, according to the present invention, the output of the hot-wire type intake air amount sensor is detected at the time of starting, and burn-off malfunction is determined based on the detected state, and subsequent control of the fuel control valve is prohibited. , gasoline is not supplied based on the erroneous output corresponding to burn-off (therefore, there is no inconvenience caused by igniting gasoline. Also, the above effect can be obtained by simply adding a few programs to the conventional one, and the cost is low. Safety can be greatly improved with almost no change in

[Brief explanation of drawings]

Fig. 1 and Fig. 2 are respectively a configuration diagram of a fuel tank according to the present invention, and Fig. 3 is a configuration diagram of a fuel tank according to the present invention. It is a flow chart of a fuel control device. 2...Hot wire intake air flow sensor (AFS), 9...Fuel control valve (injector), 10...Electronic control unit 1
- (ECU). Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) Calculate the required fuel amount of the engine based on the output of the hot-wire intake air amount sensor installed in the intake passage of the internal combustion engine, and control the fuel control valve based on this calculated value to supply the desired fuel to the engine. The fuel supply control device includes a burn-off control section that heats the hot wire to a temperature higher than the normal operating temperature after the engine is stopped and burns off the surface deposits of the hot wire, and a burn-off control section that determines the output of the hot wire intake air amount sensor when starting the engine. A fuel control device comprising means for stopping control of the fuel control valve when the output is at a level corresponding to the heating state.