JPS6193249A - Control unit for internal-combustion engine - Google Patents

Abstract

PURPOSE:To secure idling stability as well as prevent exhaust gas from deteriorating, by installing a judging device, judging an idling state, and also a lean monitor level selecting device which makes a lean monitor level in time of idling go up to the specified level. CONSTITUTION:An oxygen sensor 13 emits a signal commensurate to oxygen content in exhaust gas out of an internal-combustion engine 1. An idle switch 16 judges of whether the internal-combustion engine 1 is in an idling state or not. When the internal-combustion engine 1 is in the idling state, a lean monitor level selecting device of a microprocessor 8 makes a lean monitor lever go up to the specified level by degrees. Thus, idling stability is secured and any deterioration in the exhaust gas is preventable.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention performs air-fuel ratio feedback control based on the detection result of an 02 sensor that detects the oxygen concentration of exhaust gas.
The present invention relates to a control device for an internal combustion engine that brings an actual air-fuel ratio close to a stoichiometric air-fuel ratio.

Conventional technology The concentration of oxygen contained in the exhaust gas of an internal combustion engine is detected by an 02 sensor such as a zirconia 02 sensor, and based on the detection result, it is determined whether the air-fuel ratio A/F is in a lean state or a rich state. However, it has been proposed in the past to perform air-fuel ratio feedbank control based on the determination result.

FIG. 3 is a diagram showing the relationship between the state of the air-fuel ratio A/F and the air-fuel ratio correction coefficient FAF. When the air-fuel ratio A/F becomes rich, the air-fuel ratio correction coefficient FAF skips a certain amount, and then It decreases at a predetermined peak, and when the air-fuel ratio A/F becomes lean, it skips a certain amount and then increases at a predetermined slope.

The reason why the air-fuel ratio correction coefficient FAF is adjusted by a certain amount is to eliminate the influence of the response delay of the 02 sensor. By the way, the fuel injection amount TAU is the basic injection amount TP.
The air-fuel ratio correction coefficient FAF is determined by multiplying the air-fuel ratio correction coefficient FAF by the air-fuel ratio correction coefficient FAF.
/ F decreases when the condition is rich and increases when the condition is lean, so basic injection (by injecting the amount of fuel determined by multiplying JTP and the air-fuel ratio correction coefficient FAf') , the actual air-fuel ratio and the stoichiometric air-fuel ratio can be brought closer together.

By performing such air-fuel ratio feedhack control, it is possible to maintain good emissions and fuel efficiency, but
It had the following drawbacks. That is, when the exhaust gas temperature is low and the 02 sensor is not activated, it may be incorrect to determine whether the air-fuel ratio A/F is lean or rich. If air-fuel ratio feedback control is performed based on this erroneous determination result, the fuel injection amount TAυ may be increased in the rich state.

In order to improve these drawbacks, as shown in Figure 4,
In addition to level b (usually about 0.45V), which is used to judge whether the air-fuel ratio A/F is in a rich state or in a low state E, there is also a monitor level level C (usually about 0.45V), which is slightly higher than level b. 0.55Vf1 degree), and if the output signal a of the 02 sensor is continuously below the lean monitor level C for a predetermined period of time or more, it is determined that the 02 sensor is not activated and the air-fuel ratio feedback control is prohibited. Proposed.

In this way, by prohibiting the air-fuel ratio foot pack control when the 02 sensor is in the inactive state, the fuel injection amount TAU will not increase during the rich state, but even in the conventional example described above, It had the following drawbacks.

In other words, the 02 sensor tends to be inactive during idling, when the exhaust gas temperature is lower than when driving, so for example, when the idling state changes from driving, the 02 sensor is inactive. The air-fuel ratio feedback control immediately before it is determined that the engine is running becomes extremely unstable, which has the disadvantage of adversely affecting idle stability and exhaust gas.

Problems to be Solved by the Invention The present invention solves the above-mentioned problems, and its purpose is to prevent the deterioration of idle stability, exhaust gas, etc. associated with air-fuel ratio feedback control that tends to occur during idle. be.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an 02 sensor that outputs a signal corresponding to the oxygen concentration in the exhaust gas of an internal combustion engine, and a system based on the output signal of the 02 sensor. An internal combustion engine comprising: a control means for performing air-fuel ratio feedback control; and a prohibition means for prohibiting the air-fuel ratio feedback control by the control means when the output signal of the 02 sensor is continuously below a lean monitor level for a predetermined period or more. The control device includes a determining means for determining whether or not the internal combustion engine is in an idling state, and a method for gradually increasing the lean monitor level to a predetermined level when the determining means determines that the internal combustion engine is in an idling state. A lean monitor level switching means is provided to increase the lean monitor level.

When the temperature of the working exhaust gas is low (i.e., when the 02 sensor is in an idle state where it is likely to become inactive, the lean monitor level is gradually increased to a predetermined value using the lean monitor level switching means,
Since air-fuel ratio feedback control is prohibited when the 02 sensor is still active, it is possible to prevent deterioration of idle stability, exhaust gas, etc., which conventionally tends to occur during idle.

Embodiment FIG. 1 is a bronze diagram of an embodiment of the present invention, where ■ is an internal combustion engine, 2 is an air cleaner, 3 is an air flow meter,
4 is a throttle chamber, 5 is an intake manifold, 6 is an injector, 7 is a throttle valve, 8 is a microprocessor, 9 is an input section, 10 is an output section, 11 is a memory, 12 is a water temperature sensor that detects the temperature of cooling water, 13 is o
2 sensors, 14 an AD converter, and 16 an idle switch that sets its output signal to "1" when the internal combustion engine 1 is in an idle state.

Further, FIG. 2 is a flowchart showing the processing contents of the microprocessor 8, and the operation of FIG. 1 will be explained below with reference to the same figure.

The microprocessor 8 performs the process shown in the flowchart of FIG. 2 at regular intervals during the process flow, and in step S1, it determines whether the internal combustion engine 1 is in an idle state based on a signal from the idle switch 16. Decide whether or not. If the determination result in step S1 is NO, the microprocessor 8 sets the lean monitor level L to LL (
0.55V), and then in step S2), the count value CN of the counter A provided internally in software.
TA is set to 0, step S3), and then the process moves to step S9. Note that the counter A is incremented at regular intervals by another routine.

Further, if the determination result in step S1 is YES, the microprocessor 8 determines whether the count value CNTA of the counter A has become equal to or greater than a predetermined set value TA (step S4). Since counter A is incremented at regular intervals by another routine as described above, its count value CNTA is
3 or corresponds to the time since the count value CNTA was set to 0 in step S8, and the set value TA
is set to a value corresponding to, for example, 100 m5ec. If the determination result in step S4 is YES, the microprocessor 8 determines the current lean monitor level L.
The value obtained by adding a predetermined value ΔL (for example, 0.02V) to the value is set as the new lean monitor level L (Sten 7"S5).
Then, it is determined whether the new lean monitor level L obtained in step S5 is equal to or higher than a predetermined value L2 (for example, 0.7■) (step S6). If the determination result in step S6 is YES, the microprocessor 8 sets the lean monitor level L obtained in step S5 to the predetermined value L.
2 (step S7, then the count value CNTA of the counter A is set to 0 and step S8), and if the determination result in step S6 is NO, the process in step S8 is directly performed without performing the process in step S7.

That is, in steps 84 to S8, when the internal combustion engine is in an idle state, the count value C of the counter A is
Every time NTA becomes TA), the lean monitor level L is changed to ΔL.
The process of increasing the lean monitor level L by increments is repeated until the lean monitor level L reaches L2.

Furthermore, when the process of step S8 is completed, the microprocessor 8 compares the level of the signal a applied from the 02 sensor 13 via the AD converter 14 with the lean monitor level L obtained in step S2, S5 or S7 ( Step S9). If it is determined in step S9 that a is greater than or equal to a, that is, if it is determined that the output voltage of the 02 sensor 13 is equal to or higher than the lean monitor level L, the microprocessor 8 uses a counter B provided internally as software.
Set the count value CNTB to O (Step 5IO), then enable air-fuel ratio feedback control in Step 51.
1), then move on to other control steps. Furthermore, counter B
Like the counter A described above, is incremented at regular intervals by another routine, and the count value CNTB corresponds to the time since the count value CNTB was set to 0 in step 510.

Further, if the determination result in step S9 is NO, the microprocessor 8 determines whether the count value CNTB of the counter B is greater than or equal to a predetermined value TB (for example, a value corresponding to 8 seconds). The result is NO
In the case of , perform the process of step Sll and the judgment result is Y.
In the case of ES, air-fuel ratio feedback control is prohibited (steer knob 513), and then the process moves to other control steps.

That is, in steps 39 to S13, if the level of the output signal a of the 02 sensor 13 remains below the lean monitor level L for a predetermined period of time or more (steer knob S9, 512)
, prohibits air-fuel ratio feedback control (step 51
3) It is a thing.・Although in the above-described embodiment, the lean monitor level L is gradually increased at predetermined intervals, it is also possible to gradually increase the lean monitor level L every time the internal combustion engine rotates by a predetermined angle. Of course it's a good thing.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention gradually increases the lean monitor level to a predetermined value when the 02 sensor is in an idle state where it is likely to become inactive, and when the 02 sensor is still active, the air-fuel ratio feedbank Since it prohibits control, it is difficult to improve idle stability, which was likely to occur during idle.
This has the advantage of preventing deterioration due to exhaust gas, etc.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a flowchart showing the processing contents of the microprocessor 8, and Fig. 3 shows the relationship between the state of the air-fuel ratio A/F and the air-fuel ratio correction coefficient FAF. Diagram, FIG. 4 is a diagram illustrating the operation of the conventional example. ■ is an internal combustion engine, 2 is an air cleaner, 3 is an air flow meter, 4 is a throttle chamber, 5 is an intake manifold, 6 is an injector, 7 is a throttle valve, 8 is a microprocessor, 9 is an input part, 10 is an output part, 11 is a Memory, 12 is water temperature sensor, 13 is 02 sensor, 14 is A
D converter 16 is an idle switch. Patent applicant Fujitsu Ten Ltd. Patent attorney Gobe Tamamushi (1 other person) Figure 1 5; Intake manifold Figure 2 2゜ Figure 3 Figure 4

Claims (1)

[Claims] an O_2 sensor that outputs a signal corresponding to the oxygen concentration in exhaust gas of an internal combustion engine; a control means that performs air-fuel ratio feedback control based on the output signal of the O_2 sensor; and a prohibition means for prohibiting the air-fuel ratio feedback control by the control means when the air-fuel ratio feedback control is below the lean monitor level, in the control device for an internal combustion engine, determining whether the internal combustion engine is in an idle state. and lean monitor level switching means for gradually increasing the lean monitor level to a predetermined level when the determining means determines that the internal combustion engine is in an idle state. Device.