JPH045450A - Fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent burning of catalyst by fixing, at the time of detecting a misfire, feedback correction value to a determined value or the latest value before the misfire, or prohibiting air-fuel ratio feedback correction to stop the fuel supply to the corresponding cylinder. CONSTITUTION:When a CPU 114 inputs trailings of rotating angle signal (generated every 180 deg. CA) from a crank angle sensor 101, it renews cylinder plugs in the order of #1 #3 #4 #2 (ignition order). When the change quantity of intake air quantity per rotation of engine which is the difference between the previous time and this time is a determined value or more from the signal of an intake quantity sensor 4, a flameout is judged to prohibit the fuel injection to the flameout cylinder, feedback correction value is fixed to the latest value before the flameout to stop feedback control, or at the time of misfire detection, the learning correction value is fixed to the latest value before the flameout to stop air-fuel ratio correction. Hence, burning of catalyst can be prevented, safety to misfire is ensured, and deterioration of exhaust gas can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection device for an internal combustion engine (hereinafter abbreviated as engine), and particularly to an air-fuel ratio feedback correction or aging change correction when a misfire is detected. This relates to air-fuel ratio correction.

[Conventional technology]

Conventionally, fuel injection devices for engines having air-fuel ratio correction means for correcting changes over time have been disclosed, for example, in Japanese Patent Publication No. 5917259, Japanese Patent Publication No. 60-60019, and the like. This air-fuel ratio correction is a correction value that is updated slowly over a long period of time to correct for changes in the engine over time, changes in the intake air amount sensor, injectors, etc. over time.
Normally in cars, the battery is hacked up and retains its value even when the key switch is turned off. Further, this value is normally initialized only when the battery is removed. The air-fuel ratio correction for correcting the change over time is normally performed based on the result of air-fuel ratio feedback control based on the output of an air-fuel ratio sensor attached to the exhaust passage.

On the other hand, various methods for detecting engine misfire are known.

For example, a misfire is detected by detecting the internal pressure of a cylinder of the engine using a pressure sensor, and when the internal pressure detected by the pressure sensor becomes less than a predetermined value.

Figure 6 (A) and (B) are 4-cylinder engines with 180” CA.
Figure 6 (A)
Under normal conditions, the rotational angular speed of the engine crankshaft changes regularly, but when one cylinder misfires (B), the rotational speed of the engine crankshaft becomes disordered and changes greatly. Therefore, in the normal state shown in Figure 6 (A), the amount of change in the amount of intake air per engine revolution is within the predetermined value, but when one cylinder misfires in Figure 6 (B), the amount of change in the amount of intake air per engine revolution is within the predetermined value. The amount of change in quantity exceeds a predetermined value. Therefore, it is known that a misfire can be detected and a misfiring cylinder can be identified by determining the amount of change in the amount of intake air per revolution of the engine and comparing it with a predetermined value. To identify the misfiring cylinder in this case,
The cylinder following the cylinder identified by the rotation signal and the cylinder identification signal becomes the misfiring cylinder.

However, at present, the devices that perform air-fuel ratio correction or air-fuel ratio feedback control as described above do not have means for detecting misfires as described above.

[Problems to be Solved by the Invention] Conventional engine fuel injection devices are as described above, so if a misfire occurs in the engine, not only will the unburned fuel gas due to the misfire be emitted into the atmosphere, but the misfire will also cause In addition, with conventional equipment, for example, one cylinder out of four cylinders may misfire, causing a chemical reaction in the catalyst that purifies the exhaust gas, causing an abnormal temperature rise and burning out the catalyst. In this case, a large amount of air is emitted from the misfiring cylinder compared to the combustion exhaust gas from the three cylinders that have not misfired, so the air-fuel ratio sensor measures the exhaust gas as over-lean overall, and the air-fuel ratio feedback control is performed. If this was continued, the other three normal cylinders would have an over-rich air-fuel ratio.

In addition, if air-fuel ratio correction is performed to compensate for changes over time in this state, the problem will continue to affect the next operation even if the key switch is turned off, especially if the misfire is temporary. There were issues such as it being undesirable because it persists.

This invention was made to solve the above problems, and when a misfire is detected, the fuel supply to the misfiring cylinder is stopped, and the air-fuel ratio feedback control or the air-fuel ratio correction for correcting changes over time is applied to the misfire. By dealing with
The object of the present invention is to obtain an engine fuel injection device that can eliminate the above-mentioned disadvantages.

[Means for Solving the Problems] The engine fuel injection device of the present invention includes an operating state detection means, an exhaust gas sensor, a misfire detection means, and a fuel injection amount based on the operating state as a result of detection of the exhaust gas state. feedback control means for correcting with a feedback correction value based on a misfire and fixing the feedback correction value to a predetermined value or the latest value before the misfire or prohibiting the air-fuel ratio feedback correction when a misfire is detected; A stop means is provided for stopping the fuel supply to the cylinder at the time of detection.

Another engine fuel injection device of the present invention includes a detection means, an exhaust gas sensor, a misfire detection means, and corrects the fuel injection amount using an air-fuel ratio correction value for correcting changes over time based on the detection result of the state of the exhaust gas. and a correction control means for fixing the air-fuel ratio correction value to a predetermined value or the latest value before the misfire or prohibiting the air-fuel ratio correction when a misfire is detected, a fuel supply means, and a fuel supply means for supplying fuel to the cylinder when a misfire is detected. A stop means is provided to stop the supply.

[For production]

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

Another engine fuel injection device according to the present invention stops the fuel supply to the relevant cylinder when a misfire is detected, and separates it from the output of the exhaust gas sensor affected by the misfire, and controls the air-fuel ratio correction value by the correction control means. is fixed to a predetermined value or the latest value before the misfire, or correction is prohibited to prevent over-richness.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows a fuel injection system for an engine according to an embodiment of the present invention. Reference numeral 1 denotes, for example, a well-known four-cylinder spark ignition type engine, and an intake passage 2 is connected to the engine 1. At predetermined locations in the intake passage 2, an air cleaner 3 and an intake air amount sensor 4 are installed.
A bypass passage 2a of the intake passage 2 is provided before and after the throttle valve 5. Further, a bypass passage control mechanism 6 comprising an intake control valve (ISC valve) 61 serving as intake air amount adjusting means is provided in the bypass passage 2a.

7 is an idle switch that detects the fully closed position of the throttle valve 5; 8 is a temperature sensor that detects the temperature of the engine 1; and 9 is a start switch that detects the starting state of the engine 1. Reference numeral 10 denotes a power distributor incorporating a crank angle sensor 101, and a high voltage is distributed to the spark plug 15. Further, the crank angle sensor 101 outputs a rotation signal and a cylinder identification signal. 17
is an exhaust gas sensor that outputs a signal according to the state of exhaust gas. Reference numeral 11 denotes a control device, which controls the intake control valve 61 based on output signals from each of the above-mentioned members.

Further, the control device 11 controls the fuel by driving the injector 12, and controls the igniter 13 to control the energization time and ignition timing of the ignition coil 14 whose secondary side is connected to the power distributor IO. Further, when a misfire in the engine 1 is detected, the failure indicator lamp 16 is turned on.

FIG. 2 shows the configuration of the control device 11, in which 111 is a digital interface that receives the rotation signal and cylinder identification signal from the crank angle sensor 101, the digital outputs of the start switch 9 and the idler switch, and outputs them to the CPU 114; This is an analog interface that receives analog signals from the intake air amount sensor 4, temperature sensor 8, and exhaust gas sensor 17, and inputs the output to the CPU 114 via the A/D converter 113. CPU114 is RA
M, ROM, timer, etc. are built in, and based on each of the above inputs, the injector 12 (actually there are as many as the number of cylinders, but one is shown for simplicity), the intake air Control valve 61, igniter 13 and failure indicator lamp 16.

FIG. 3 shows the configuration of the bypass passage control mechanism 6, and specifically, the intake control valve 61 is controlled by the passage 2a by duty control.
This is a near solenoid valve that controls the amount of intake air by changing the opening area of the valve. 62 is a wax type air valve, which adjusts the flow area by utilizing the fact that Wank changes between solid and liquid depending on the temperature of the engine. Reference numeral 63 denotes an air adjustment screw used to adjust the amount of air in the bypass passage 2a, and is used to absorb initial variations. 64 is a throttle adjustment screw, which adjusts the fully closed position of the throttle valve 5 and determines the leakage flow rate when the throttle valve 5 is fully closed.

Since the general operation of the engine section is well known, a description thereof will be omitted.

Next, the fourth section regarding the operation of the CPU 114 of the control device 11 will be explained.
Rotation signal interrupt processing routine shown in the figure, No. 511iJ
This will be explained using the main routines shown in (A) and (B). The CPU 114 normally processes the main routine shown in FIG.
When input, this is used as an interrupt input, and the processing of the main routine is temporarily interrupted, and the interrupt processing routine shown in FIG. 4 is executed. First, in step S1, it is determined whether or not a cylinder identification signal has been input from the crank angle sensor 101. If the cylinder identification signal is input manually, in step S2, the cylinder flag is set to the first cylinder (II) (hereinafter referred to as the G cylinder). , G is an integer from 1 to 4) is expressed as IIG), and if no input has been made, the previous cylinder flag is updated in step S3.

This cylinder flag is updated in the order of 11→13→#4→I2 (ignition order).

For example, if the previous cylinder flag was I4, it is updated to +12 this time.

In step S4, it is determined whether or not there is a misfire using a well-known method. If it is a misfire, the misfire flag for the cylinder is set in step S5, and if it is not a misfire, the misfire flag for the cylinder is reset in step S6.

For example, in this misfire determination, a misfire is determined when the amount of change, which is the difference between the previous and current intake air amounts per engine rotation, is greater than a predetermined value, and the cylinder next to the cylinder flag becomes a misfire cylinder. For example, if the cylinder flag is #2 this time, the misfire cylinder will be #l, so the misfire flag #l is set. Further, the predetermined value may be changed depending on the engine speed. Step S7
Then, the basic fuel injection pulse width τ is determined from the amount of intake air per rotation.

Calculate. In step S8, if the feedback correction value for the air-fuel ratio feedhack correction is CFB, and the learning correction value as the air-fuel ratio correction value for the aging change correction is C5TDV, then τ-r** (CFB + C5ryJO) So-called feedback correction and learning correction are performed to calculate the pulse width τ.In step S9, it is determined whether the cylinder to which fuel injection is to be performed this time is a misfire cylinder or not by setting/resetting the misfire flag of the cylinder.Misfire If it is a cylinder, proceed to the next one without injecting fuel, and if it is not a misfiring cylinder, in step SIO, the injector 12 is driven via the drive circuit 115 for the time of the fuel injection pulse width τ obtained in step S8, and the cylinder is injected. Perform fuel injection and move on to the next step.

Next, the processing of the main routine will be explained with reference to FIG. First, in step 5101, it is determined whether or not even one misfire flag is set. If it is set, the process proceeds to step 5102; if all have been reset, the process proceeds to step 5103. In step 5102, the feedback correction value CFB is set to 1.0, and after setting, the process proceeds to step knob 5108. In step 5103, the output of the exhaust gas sensor 17 is converted into an A/D converter 113.
D-convert and read the digital air-fuel ratio value v0.

In step 5104, the air-fuel ratio value ■. It is determined whether or not VTH is greater than or equal to a predetermined value VTH stored in advance. If it is above, it is rich, so the process proceeds to step 5105; if not, it is lean, so the process proceeds to step 5106. In step 5105, a predetermined value (j!) is determined from the previous feedback correction value CFI.
Update CFII by subtracting I. Step 5106
Now, the previous feedback correction (ICrm is set to the predetermined value I).
The CFI is updated by applying power. In step 5107,
The feedback correction value CFI is limited by upper and lower limit values. In step 5108, the feedback correction value CFI is averaged and the averaged feed hack correction value CFB is calculated as K''CFl+(1-K) umbrella CFB (where 0<K<
Calculate according to the formula 1) (however, CFB in the formula is the previous value).

In step 5109, it is determined whether or not even one misfire flag is set. If it is set, the process advances to step 5110, and if all have been reset, step S
] Proceed to step 11. In step 5ilo, the learning correction value CS
Set TO/ to O, and then turn on the heat.

In step 5111, it is determined whether the learning condition is satisfied,
If the condition is met, the process advances to step 5112; if the condition is not met, the process advances to the next step. This learning condition is an idling state in which the idle switch 7 is on and the engine rotational speed determined from the period of the signal from the crank angle sensor 101 is equal to or less than a predetermined rotational speed.

In step 5112, the previous learning correction value C5TDV
The averaged feedback correction value CF found this time! is added to update the learning correction value CSTD/. Step 5113
Now, the averaged feed hack correction (1ICFI) is subtracted from the feedback correction value CFI to update the feedback correction value crg, and the averaged feedback correction value CFI is
Set I to 1.0, and then turn on the fire.

In the above embodiment, as shown by the broken line in FIG. 5, the process in step 5102 is removed, and when a misfire is detected, the feedback correction value CFl+ is fixed to the latest value before the misfire and the feed hack control is stopped, or the step 5110 It is also possible to remove the process described above, fix the learning correction value csrna to the latest value before the misfire, and stop the air-fuel ratio correction when a misfire is detected.

FIG. 6 shows another embodiment of the present invention, and is the main part of a flowchart for stopping feedback control and air-fuel ratio correction and prohibiting the correction when a misfire is detected. This step replaces step S8 in FIG. 4, and the other configurations and operations are the same as in the above embodiment. Step S7
In the next step S81, the state of the misfire flag is determined, and if even one is set, τ- is set in step S82.
τ, and proceeds to step S9. If all are recent, in step S83, τ−τTomimoto (CFI+C5toy)
) is calculated, the process proceeds to step S9.

[Effects of the Invention] As described above, according to the present invention, when the fuel injection amount is corrected using the feedback correction value based on the detection result of the exhaust gas state or the air-fuel ratio correction value for time-dependent change correction, when a misfire is detected, Since the correction value is fixed to a predetermined value or the latest value before the misfire, or the correction is prohibited and the fuel supply to the relevant cylinder is stopped, it is possible to prevent catalyst burnout and prevent misfire. It is safe and has the effect of preventing deterioration of exhaust gas.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an engine section according to an embodiment of the present invention, FIG. 2 is a diagram showing the internal configuration of a control device according to the above-mentioned embodiment, and FIG. 3 is a diagram showing the configuration of a bypass intake passage, etc. FIG. 4 is a flow diagram showing the rotation signal interrupt processing routine, FIG. 5 is a flow diagram showing the main routine, and FIG. 6 is a main part showing the main part of the rotation signal interrupt processing routine according to another embodiment of the present invention. The flowchart, FIG. 7, is a waveform diagram showing changes in the rotational angular velocity of the crankshaft with respect to time in a normal state and in a case where one cylinder misfires. In the figure, 1.99 engine, 2... intake passage, 4... intake air amount sensor, 11... control device, 12... injector, 17... exhaust gas sensor, 101... crank angle sensor. Note that the same reference numerals in the figures indicate the same or equivalent parts. 1 ~ Dimension = early vertical δ To agent Oiwa Masu Yu 4 Figure 3 Figure 5 Figure (A) Figure 5 (8) IF5 Figure (A) Rotation angular velocity Rotation angular velocity 6 Go to Figure S7 Yo S9

Claims (2)

[Claims] (1) A detection means for detecting the operating state of the internal combustion engine, an exhaust gas sensor for detecting the state of exhaust gas, a misfire detection means for detecting a misfire of the internal combustion engine for each cylinder, and based on the detection result of the operating state. The calculated fuel injection amount is corrected to a predetermined air-fuel ratio using a feedback correction value based on the detection result of the exhaust gas state, and when a misfire is detected, the feedback correction value is changed to a predetermined value or the latest value before the misfire. a feedback control means for injecting and supplying fuel to the internal combustion engine under control of the feedback control means; and a stop means for stopping fuel supply to the cylinder when a misfire is detected. A fuel injection system for internal combustion engines. (2) a detection means for detecting the operating state of the internal combustion engine, an exhaust gas sensor for detecting the state of exhaust gas, a misfire detection means for detecting a misfire of the internal combustion engine for each cylinder, and based on the detection result of the operating state. correcting the fuel injection amount calculated by using an air-fuel ratio correction value for correcting changes over time based on the detection result of the state of the exhaust gas, and when a misfire is detected, the air-fuel ratio correction value is set to a predetermined value or the latest value before the misfire. correction control means for fixing or prohibiting the air-fuel ratio correction; supply means for injecting and supplying fuel to the internal combustion engine under control of the correction control means; and stop means for stopping fuel supply to the cylinder when a misfire is detected. A fuel injection device for internal combustion engines.