JPS62248837A - Fuel control device - Google Patents

Abstract

PURPOSE:To eliminate the inconvenience of igniting a gasoline which has been blown back due to full-open operation by prohibiting the burn off of the heating coil of an intake air quantity sensor, when said full-open operation is detected during the operation of an engine. CONSTITUTION:An electronic control unit 10 generates a burn off control signal 14 when every burn off condition is satisfied, and sends out the signal to a heating coil type intake air quantity sensor 2. When intake air quantity detected by the intake air quantity sensor 2 becomes higher than a defined value due to full-open operation during the operation of an engine, it judges to be the generation of blow back and resets a burn off flag. Under this condition, if an operation in a defined condition is not performed, the burn off flag is kept reset and the execution of burn off is prohibited. Thereby, it is eliminated that the gasoline which is blown back near the intake air quantity sensor 2 due to full-open operation is ignited by burn off.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention provides a method for burning off the surface of a hot-wire intake air flow sensor used for fuel control of an internal combustion engine. The present invention relates to a fuel control device that prohibits a burn-off operation when full throttle operation is detected during a driving period.

[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 address these problems, when the engine is at a standstill, the hot wire is heated to a temperature above normal operating temperature.
Conventionally, burn-off of deposits on the surface of the hot wire has been carried out. Regarding the method of pierce-off, please refer to Japanese Patent Application Laid-Open No.
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 burn-off operation.

However, heating to a temperature of t-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, conventionally, in order to avoid ignition of the gasoline mixture, when executing the burn-off, the temperature during engine operation and the number of rotations meet a predetermined condition, and the gasoline that was excessively supplied into the intake pipe during the warm-up process is sufficiently scavenged. Execution is allowed only if the

Furthermore, after the engine is stopped, the time required 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 the turn-off is performed within this time.

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]

Even if the engine has been warmed up, the intake air blowback when the engine is running at full throttle will cause a large amount of gasoline accumulated near the fuel control valve to be blown back into the intake pipe, causing the intake air amount sensor to be damaged. Therefore, if the engine is immediately stopped and the above conditions are determined, and then the burn-off is executed, the remaining gasoline may be ignited.

The present invention has been made to solve this problem, and an object of the present invention is to provide a fuel control device that does not cause the possibility of igniting the gasoline mixture when full throttle operation is detected during engine operation.

[Means for solving problems]

In the fuel control device according to the present invention, the operating state of the engine is
The memory e! is set when the second condition is met and reset when the second condition is met! However, when the memory is in the set state after the engine is stopped, control means is provided to execute the turn-off.

[For production]

In this invention, the memory is set when gasoline blown back near the intake air amount sensor due to full-throttle operation is sufficiently scavenged by subsequent moderate operation, and when the memory is in the set state and the pan-off is executed,
Avoid igniting gasoline.

〔Example〕

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

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 sensor 4 moves in conjunction with the throttle valve 3, extracts the opening degree as a voltage signal, and sends it to an electronic control unit 1 (hereinafter referred to as ECU).

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

Cylinder 8 (cylinder) is shown in the figure as engine 1 for simplification.
Although only the cylinder part is shown, it actually consists of multiple cylinders.

Fuel control valve (hereinafter referred to as injector) for each cylinder 8
9 is attached. The ECUI O 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.

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 cooling water 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 pulse width of the injection pulse is controlled.

The ECUIO generates a turn-off control signal 14t- when all of the turn-off conditions are satisfied, and sends it to the AFS2. The configuration and operation related to the turn-off control of AFS2 are similar to known ones, so detailed explanations will be omitted.

FIG. 2 is a block diagram showing the internal configuration of the ECUIO, and in this FIG. 2, 101 is the crank angle sensor 11.
, an interface circuit for the daisymel 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;

Further, 103 is a multiplexer, and an analog/digital converter 104 sequentially converts analog inputs from the AFS 2 and the cooling water temperature sensor 13 into digital values.

105 is ROMI 05 a, RAMI 05 b
A CPU incorporating timers 105c and 105d 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, and 105C outputs a pulse with a predetermined time width.

The pulse output from the timer 105C is sent to the drive circuit 106.
The signal is amplified and drives 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 related programs will be explained in detail with reference to FIG. 3 and the fourth factor.

First, in the operation mode, a series of fuel control operations are performed in step S1. The details of the control are well known and will not be explained here.7 Next, in step S2, the AF
The output Qa of S2 is set to a predetermined value QM in step S3.
Compare with AX. The predetermined value of the pot will be explained using FIG. 5.

Figure 5 (a) shows the complete operating waveform of the intake air amount Qa detected by AFS2 when the engine is running at full throttle, and (in Figure 5) shows the relationship between this intake air tQa and (b) rotation speed. There is.

When operating at full throttle, the backflow caused by blowback from the engine is A.
Pass through FSZ. AFS2 cannot detect the direction of airflow, and outputs reverse airflow in the same way as normal airflow, as shown in the shaded area in Figure 5(a).9 Therefore, when there is blowback, the output of AFS2 will be lower than that of true intake air. becomes excessive.

In addition, No. 5 [9 (b) shows the relationship between the intake air amount Qa (AFS output) and the engine speed at full throttle, and shows that the intake air amount Qa exceeds the true value by a wide margin in the low rotation region where blowback is strong. The situation is shown.

Needless to say, this region corresponds to the region where gasoline is blown back as described above. The air intake is predetermined to be slightly larger than the true intake air amount when the engine is fully opened.

Here, we return to the explanation of FIG. 3 again. In this FIG. 3, when Qa > QMAX is established in step S3,
In other words, when the engine is operating at full throttle, causing blowback, it is determined that burn-off is not possible, and the burn-off flag is reset in step S4. In step S3, when Qa≦exposure α, the process moves to step S8, and when the number of rotations N exceeds 200 Orpm, step S9
Determine whether the water temperature is 60°C or higher.

When the water temperature is 60° C. or higher, the engine has finished warming up and is running at high speed, so gasoline that was excessively supplied during the warming process and remained in the intake pipe has been sufficiently scavenged. Therefore, it is determined that burn-off is possible, and a burn-off flag is set in step S10.

If it takes time to clean, it is recommended to set the flag in step 810 with an appropriate delay.

Note that steps 88 to 810 are based on logic used in conventionally known devices.

Next, in step 811 shown in FIG. 4, the state of the key switch is determined, and if it is on, the engine operation mode continues, so the process returns to step S1 in FIG. 3.

If the key switch is in the OFF state, transition to burn-off mode, determine the burn-off flag in step 812,
If it is in the set state, the process moves to step 814. In step 814, it is determined whether 5 seconds have elapsed since the key switch was turned on. This is a time period determined based on the time it takes for the engine to completely stop after the key switch is turned off, the air flow in the intake pipe to completely stop, and for the air-fuel mixture to travel upstream from the fuel supply section to the vicinity of AFS2. When 5 seconds have elapsed, the process moves to step 815 to execute pan-off.

It has already been explained with reference to FIG. 2 that a noggle of about 1 second is generated during pan-off and is fed to the AFS2.

The above was the flow of the situation when the burn or flag was set.
The turn-off flag remains reset in step S4 until the operation at 0° C. or higher is performed, and if the shift to the turn-off mode is made in this state, the process ends without executing the turn-off, as determined in step S12.

Therefore, the inconvenience of executing the burn-off and igniting while the gasoline blown back due to full-throttle operation remains does not occur.

In the above explanation, the detection of full throttle operation was performed by comparing the output of AFS2 with the value .about.■ which exceeds the true intake air amount.

However, since the false garden only needs to take a value close to that of full-open operation, it goes without saying that the same effect can be obtained even if it is set to a value smaller than the true intake air amount at full-open operation.

Further, as other methods of fully open detection, the same effect can be obtained by using the output of the throttle sensor 4 or using a switch that operates when the throttle valve 3 is in the fully open position.

〔Effect of the invention〕

As explained above, this invention detects full-throttle operation and prohibits burn-off for a predetermined period of time after the end of full-throttle operation, thereby eliminating the inconvenience of igniting gasoline blown back by full-throttle operation.

In addition, since full-throttle operation can be detected using the output of the t-AFS, and the control logic for prohibiting burn-off can be achieved with a few additions to the program, the above effects can be obtained at almost the same price as conventional equipment. It has excellent characteristics.

[Brief explanation of drawings]

FIG. 1 is a block diagram 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 FIGS. 3 and 4 are 70-chart for explaining an example of program execution of the fuel control device of the present invention, and FIG. 5 are output waveform diagrams at full throttle operation of the AFS in the fuel control device of the present invention. 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,
'1'05...CPU, 105 a---ROM, 1
05b=RAM. 105c, 105d... timer, 106, 107...
・Drive circuit. In addition, the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] means for supplying fuel to the internal combustion engine in accordance with 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; and an operating state of the internal combustion engine that is determined in advance. is set when the first condition is met,
It has a memory that is reset when a second condition is met, and when the memory is in the set state after the internal combustion engine is stopped, the hot wire is heated to a temperature higher than the normal operating temperature to incinerate deposits on the surface of the hot wire. A fuel control device comprising a means for controlling the fuel.