JP2672877B2 - Fuel injection device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection device for an internal combustion engine (hereinafter abbreviated as “engine”), and particularly for air-fuel ratio feedback correction or secular change correction when misfire is detected. It is related to the air-fuel ratio correction of.

[Conventional technology]

Conventionally, a fuel injection device for an engine having an air-fuel ratio correction means for correcting a change over time is disclosed in, for example, Japanese Patent Publication No. 59-17259 and Japanese Patent Publication No. 6060019. This air-fuel ratio correction is to update the correction value slowly over a long period of time to correct the change over time of the engine and the change over time of the intake air amount sensor, injector, etc. Values are retained even when the switch is off. Also, the initialization of this value is normally performed only when the battery is removed. Then, the air-fuel ratio correction for correcting the change with time is performed based on the result of the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor normally attached to the exhaust passage.

On the other hand, various methods for detecting engine misfire are known. For example, misfire is detected when the internal pressure of the cylinder of the engine is detected by the pressure sensor and the internal pressure detected by the pressure sensor becomes a predetermined value or less.

FIGS. 7 (A) and 7 (B) show a 4-cylinder engine with a scale on the time axis t every 180 ° C. A. In the normal state of FIG. 7 (A), the rotational angular speed of the crankshaft of the engine changes regularly, but at the misfire of one cylinder in (B), the rotational speed of the crankshaft of the engine is disturbed and greatly changes. Therefore,
In the normal state of FIG. 7 (A), the amount of change in the intake air amount per revolution of the engine is within a predetermined value, but when the misfire of one cylinder in FIG. The amount of change exceeds a predetermined value. Therefore, it is known that misfiring can be detected and the misfiring cylinder can be specified by obtaining the amount of change in the intake air amount per engine revolution and comparing it with a predetermined value. To identify the misfiring cylinder in this case, the cylinder next to the cylinder identified by the rotation signal and the cylinder identification signal is the misfiring cylinder.

However, under the present circumstances, the device for air-fuel ratio correction or air-fuel ratio feedback control as described above does not have the above-mentioned means for detecting misfire.

[Problems to be solved by the invention]

Since the fuel injection device of the conventional engine is as described above, if a misfire occurs in the engine, not only the unburned fuel gas due to the misfire is discharged into the atmosphere, but also the unburned fuel gas due to the misfire is exhausted into the exhaust gas. However, there is a problem in that a chemical reaction occurs in the catalyst for purifying the catalyst, causing an abnormal temperature rise and burning the catalyst.

Further, in the conventional apparatus, for example, when one of the four cylinders misfires, a large amount of air is discharged from the misfired cylinder as compared with the combustion exhaust gas of the three cylinders that have not misfired. There is a problem that the other three cylinders, which are normal, have an overrich air-fuel ratio, which is measured by the air-fuel ratio sensor as lean exhaust gas and the air-fuel ratio feedback control is continued.

In addition, if the air-fuel ratio is corrected to correct the change over time in this state, the adverse effect will affect the next and subsequent operations even if the key switch is turned off, especially when the misfire is transient. However, there are problems such as being unfavorable.

The present invention has been made to solve the above problems.When a misfire is detected, the fuel supply to the misfire cylinder is stopped and the air-fuel ratio feedback control or the air-fuel ratio correction for aging correction is made to misfire. It is an object of the present invention to obtain an engine fuel injection device that can eliminate the above-mentioned adverse effects by taking measures.

[Means for solving the problem]

The engine fuel injection device of the present invention corrects the operating state detection means, the exhaust gas sensor, the misfire detection means, and the fuel injection amount based on the operating state with the feedback correction value based on the detection result of the state of the exhaust gas, In addition, when the misfire is detected, the feedback correction value is fixed to the predetermined value or the latest value before the misfire, or the feedback control means for prohibiting the air-fuel ratio feedback correction, the fuel supply means, and the fuel supply to the cylinder concerned when the misfire is detected. The stopping means for stopping is provided.

Another engine fuel injection device of the present invention comprises a detection means, an exhaust gas sensor, a misfire detection means, and a fuel injection amount corrected by an air-fuel ratio correction value for time-dependent change correction based on a detection result of an exhaust gas state. In addition, when the misfire is detected, the air-fuel ratio correction value is fixed to a predetermined value or the latest value before the misfire, or correction control means for prohibiting the air-fuel ratio correction, fuel supply means, and fuel to the cylinder concerned when the misfire is detected. A stop means for stopping the supply is provided.

(Operation)

In the engine fuel injection device according to the present invention, when the misfire is detected, the fuel supply to the cylinder is stopped by the stopping means, so that the progress of the chemical reaction between the unburned fuel and the catalyst is prevented, and the exhaust gas sensor is affected by the misfire. Separated from the output of
The feedback control means fixes the feedback correction value to a predetermined value or a value immediately before the misfire, or prohibits the feedback correction to prevent overrich.

Another engine fuel injection device according to the present invention is
When a misfire is detected, the fuel supply to the cylinder concerned is stopped, and
Separate from the output of the exhaust gas sensor affected by misfire,
The correction control means fixes the air-fuel ratio correction value to a predetermined value or the latest value before the misfire, or prohibits the correction to prevent overrich.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a fuel injection system for an engine according to an embodiment of the present invention. Reference numeral 1 is a well-known four-cylinder spark ignition type engine, to which an intake passage 2 is connected. An air cleaner 3, an intake air amount sensor 4, and a throttle valve 5 are provided at predetermined locations in the intake passage 2, and a bypass passage 2a for the intake passage 2 is provided before and after the throttle valve 5. The bypass passage 2a is provided with a valve passage control mechanism 6 including an intake control valve (ISC valve) 61 which is an intake amount adjusting means. Reference numeral 7 is an idle switch for detecting the fully closed position of the throttle valve 5, 8 is a temperature sensor for detecting the temperature of the engine 1, and 9 is a start switch for detecting the starting state of the engine 1. Reference numeral 10 is a distributor having a built-in crank angle sensor 101, and a high voltage is distributed to the ignition plug 15. Further, the crank angle sensor 101 outputs a rotation signal and a cylinder identification signal. Reference numeral 17 denotes an exhaust gas sensor that outputs a signal according to the state of the exhaust gas. Reference numeral 11 denotes a control position, which controls the intake control valve 61 based on output signals from the above-mentioned members. Further, the control device 11 drives the injector 12 to perform fuel control, and also controls the igniter 13 to energize the ignition coil 14 whose secondary side is connected to the distributor 10,
Control ignition timing. When the misfire of the engine 1 is detected, the failure display lamp 16 is turned on.

FIG. 2 shows the configuration of the control device 11, and 111 is a digital interface for inputting the rotation signal and the cylinder identification signal by the crank angle sensor 101, the digital output of the starting switch 9 and the idle switch 7, and outputting to the CPU 114.
An analog interface 112 receives analog signals from the intake air amount sensor 4, the temperature sensor 8 and the exhaust gas sensor 17, and inputs the output to the CPU 114 via the A / D converter 113. The CPU 114 has RAM, ROM, timer, etc. built-in, and injectors via the drive circuits 115 to 118 based on the above inputs.
12 (actually, the number is equal to the number of cylinders, but one is shown for simplification in the figure), the intake control valve 61, the igniter 13, and the failure display lamp 16 are controlled.

FIG. 3 shows the structure of the bypass passage control mechanism 6, and the intake control valve 61 is specifically a linear solenoid valve that controls the intake amount by changing the opening area of the passage 2a by duty control. Reference numeral 62 is a wax-type air valve, which adjusts the flow area by utilizing the fact that the wax changes between solid and liquid depending on the temperature of the engine. An air adjusting screw 63 is used for adjusting the amount of air in the bypass passage 2a, and is used for absorbing initial variations. 64 is a throttle adjusting screw, which adjusts the fully closed position of the throttle valve 5,
The leak flow rate when the throttle valve 5 is fully closed is determined.

Since the general operation of the engine section is well known, its explanation is omitted.

Next, regarding the operation of the CPU 114 of the control device 11, the rotation signal interrupt processing routine shown in FIG. 4, FIG. 5 (A),
The main routine shown in (B) will be described. CPU114
Normally processes the main routine shown in FIG. 5, but the crank angle sensor 101 outputs the falling edge of the rotation angle signal (180
(Occurring at TDC every ° C) is input as an interrupt input to temporarily interrupt the processing of the main routine and execute the interrupt processing routine shown in FIG. First, step S1
Then, it is determined whether or not the cylinder identification signal is input from the crank angle sensor 101, and if it is input, the cylinder flag is set to the first cylinder (# 1) (hereinafter, referred to as the Gth cylinder (however, G
Is an integer of 1 to 4) is expressed as #G), and if not input, the previous cylinder flag is updated in step S3. This cylinder flag update is # 1 → # 3 → # 4 → # 2
(Ignition order).

For example, if the previous cylinder flag is # 4, this time it is updated to # 2.

In step S4, it is determined by a known method whether or not there is a misfire, and if there is a misfire, the misfire flag of the cylinder is set in step S5, and if no misfire, the misfire flag of the cylinder is reset in step S6.

For example, in this misfire determination, a misfire is determined when the amount of change in the intake air amount per revolution of the engine, which is the difference between the previous time and the current time, is equal to or greater than a predetermined value, and the cylinder next to the cylinder flag is the misfire cylinder. For example, if the cylinder flag is # 2 this time, the misfiring cylinder is # 1, so the misfire flag of # 1 is set. Further, the predetermined value may be changed according to the engine speed. In step S7, the basic fuel injection pulse width τ _B is calculated from the intake air amount per one rotation. In step S8, if C _FB is the feedback correction value for air-fuel ratio feedback correction and C _STDY is the learning correction value as the air-fuel ratio correction value for time-dependent change correction, then τ = τ _B * (C _FB + C _STDY ), So-called feedback correction and learning correction for calculating the fuel injection pulse width τ according to the formula are performed. In step S9, it is determined whether or not the cylinder for which fuel injection is to be performed this time is a misfiring cylinder by setting / resetting the misfiring flag of the cylinder. If it is a misfiring cylinder, proceed to the next without fuel injection. If it is not a misfiring cylinder, step S1.
At 0, the injector 12 is driven through the drive circuit 115 for the time corresponding to the fuel injection pulse width τ obtained in step S8 to inject fuel into the cylinder, and then the process proceeds.

Next, the processing of the main routine will be described with reference to FIG. First, in step S101, it is determined whether or not even one misfire flag is set. If it is set, the process proceeds to step S102, and if all are reset, the process proceeds to step S103. In step S102, the feedback correction value C _FB is set to 1.0, and after setting, the process proceeds to step S108. In step S103, the output of the exhaust gas sensor 17 is set to the A / D converter 1
A / D conversion is performed by 13 and the digital air-fuel ratio value V ₀ is read.
In step S104, it is determined whether or not the air-fuel ratio value V ₀ is greater than or equal to a predetermined value VTH stored in advance. If it is greater than or equal to it, the routine proceeds to step S105, and if it is not greater than or equal to lean, the routine proceeds to step S106. In step S105, the predetermined value I is subtracted from the previous feedback correction value C _FB to update C _FB .
In step S106, it updates the C _FB by adding a predetermined value I to the previous feedback correction value C _FB. In step S107, the feedback correction value C _FB is limited by the upper and lower limit values.
In step S108, the feedback correction value C _FB is averaged to obtain the averaged feedback correction value _FB by K *.
_{FB + (1-K) *} C FB ( where, 0 <K <1) determined according to the formula (where, _FB is the previous value in the formula). Step S1
At 09, it is determined whether or not even one misfire flag is set. If set, the process proceeds to step S110, and if all are reset, the process proceeds to step S111. Steps
In S110, the learning correction value C _STDY is set to 0, and after the setting, the _{process proceeds} .

In step S111, it is determined whether or not the learning condition is satisfied. If the condition is satisfied, the process proceeds to step S112, and if the condition is not satisfied, the process proceeds to the next. This learning condition is an idle state in which the idle switch 7 is on and the engine speed obtained from the cycle of the signal from the crank angle sensor 101 is equal to or lower than a predetermined speed. Steps
In S112, the learning correction value C _STDY is updated by adding the averaged feedback correction value _FB obtained this time to the previous learning correction value C _STDY . In step S113, the feedback correction value C
_The averaged feedback correction value _FB is subtracted from _FB to update the feedback correction value C _FB , and then the process proceeds.

In the above embodiment, as shown by the broken line in FIG. 5, the process of step S102 is removed to fix the feedback correction value C _FB to the latest value before the misfire when the misfire is detected, or the feedback control is stopped, or step S110. _{Alternatively} , the learning correction value C _STDY may be fixed to the latest value before the misfire and the air-fuel ratio correction may be stopped when the misfire is detected.

FIG. 6 shows another embodiment of the present invention, and is a main part of a flowchart for stopping the feedback control and the air-fuel ratio correction and prohibiting the correction when a misfire is detected. This step is replaced with step S8 in FIG. 4, and the other structure and operation are the same as those in the above-mentioned embodiment. In step S81 following step S7, the state of the misfire flag is determined, and 1
If any is set, τ = τ _B is set in step S82 and the process proceeds to step S9. If all are reset, τ = τ _B * (C _FB + C _STDY ) is calculated in step S83, and then step S9 Proceed to.

〔The invention's effect〕

As described above, according to the present invention, when the fuel injection amount is corrected by the feedback correction value based on the detection result of the state of the exhaust gas or the air-fuel ratio correction value for time-dependent change correction, the correction value is set to a predetermined value when misfire is detected. Alternatively, since it is configured to fix the latest value before the misfire or to prohibit the correction value and stop the fuel supply to the cylinder, even if the misfire is transient, the normal cylinder is overrun. This has the effects of preventing the harmful effect of maintaining a rich air-fuel ratio, preventing the catalyst from burning, and being safe against misfire and preventing deterioration of exhaust gas.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an engine section according to an embodiment of the present invention, FIG. 2 is a diagram showing an internal configuration and the like of a control device according to the one embodiment, and FIG. 3 is a diagram showing a configuration of a bypass intake passage, etc. FIG. 4 is a flow chart showing a rotation signal interruption processing routine, FIG. 5 is a flow chart showing a main routine, and FIG. 6 is a main portion showing a main portion of a rotation signal interruption processing routine of another embodiment of the present invention. A flow chart and FIG. 7 are waveform charts showing changes in the rotational angular velocity of the crankshaft with respect to time during normal operation and during misfire of one cylinder. In the figure, 1 ... Engine, 2 ... Intake passage, 4 ... Intake air amount sensor, 11 ... Control device, 12 ... Injector, 17 ...
Exhaust gas sensor, 101 …… Crank angle sensor. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

(57) [Claims] 1. A detecting means for detecting an operating state of an internal combustion engine, an exhaust gas sensor for detecting a state of exhaust gas, a misfire detecting means for detecting misfire of the internal combustion engine for each cylinder, and a misfire detecting cylinder for detecting the misfire. Stop means for stopping the fuel supply of, the fuel injection amount calculated based on the detection result of the operating state is corrected to a predetermined air-fuel ratio by a feedback correction value based on the detection result of the exhaust gas state,
Further, when the misfire is detected by the misfire detecting means, the feedback correction value is fixed to a predetermined value or the latest value before the misfire for all cylinders due to the stop of the fuel supply by the stopping means. A fuel injection device for an internal combustion engine, comprising a control means and a supply means for injecting and supplying fuel to the internal combustion engine under the control of the feedback control means. 2. A detecting means for detecting an operating state of an internal combustion engine, an exhaust gas sensor for detecting a state of exhaust gas, a misfire detecting means for detecting misfire of the internal combustion engine for each cylinder, and a misfire detecting cylinder for detecting the misfire. Stopping means for stopping the fuel supply, the fuel injection amount calculated based on the detection result of the operating state is corrected by an air-fuel ratio correction value for time-dependent correction based on the detection result of the exhaust gas state, and Correction control for prohibiting the air-fuel ratio correction by fixing the air-fuel ratio correction value to a predetermined value or the latest value before the misfire for all cylinders when the fuel supply is stopped by the stopping means when the misfire detection means detects the misfire. A fuel injection device for an internal combustion engine, comprising: means and a supply means for injecting and supplying fuel to the internal combustion engine under the control of the correction control means.