JPS60119335A - Air-fuel ratio control device - Google Patents

Abstract

PURPOSE:To avoid engine-stall to enhance the operation ability of an engine, by enabling a signal from a exhaust sensor to be effective only when the input time of the signal exceeds a set value, so that the air-fuel ratio is controlled. CONSTITUTION:An exhaust sensor 10 is disposed in the exhaust system of an engine 4. A control circuit parts 2 enables an input signal from the exhaust sensor 10 to be effective only when the input time of the input signal exceeds a set value, and actuates a control valve 14 to adjust the air-fuel ratio in an intake-air pipe 12 to a predetermined air-fuel ratio. Thus, since the air-fuel ratio may be adjusted in accordance with the running condition of the engine, the operation ability of the engine may be enhanced, and as well the components of exhaust gas are made stable to aim at purifying the exhaust gas.

Description

Detailed Description of the Invention (1) [Technical Field of the Invention] The present invention relates to an air-fuel ratio control device for a mixture supplied to an internal combustion engine, and particularly relates to an air-fuel ratio control device for an air-fuel mixture supplied to an internal combustion engine. The present invention relates to an air-fuel ratio control device that can adjust the air-fuel ratio to a predetermined air-fuel ratio by validating this signal only when the input time of the signal is equal to or longer than a set value.

TECHNICAL BACKGROUND OF THE INVENTION In recent years, for internal combustion engines, in order to improve fuel efficiency and reduce harmful components in exhaust gas, feedback control type air-fuel ratio control devices have been proposed that converge to the air-fuel ratio that should provide the best combustion state. ing. The air-fuel ratio control device detects exhaust gas components using an exhaust sensor installed in the exhaust system, controls the amount of fuel supplied and the amount of air supplied using a correction signal based on this detection signal, and adjusts the air-fuel ratio of the intake mixture to an appropriate air-fuel ratio. Adjust to fuel ratio.

[Problems with Background Art] Incidentally, in a system in which feed-hack control is performed to maintain an appropriate air-fuel ratio based on a signal from an exhaust sensor, low fuel consumption and exhaust gas purification (2) can be sufficiently achieved in steady state. However, in unsteady conditions, such as transient operating conditions or high load conditions, drivability will deteriorate unless the air-fuel ratio is adjusted more closely than the steady state. Therefore, generally, when the transient operating state is detected from intake passage negative pressure, engine speed, etc., feedback control by the exhaust sensor is canceled and the air-fuel ratio is controlled by oven loop control.

However, in oven loop control, since the air-fuel ratio is forced to a constant value, the air-fuel ratio is not constant due to factors such as temperature and atmospheric pressure, and can take various values depending on the conditions. This has the disadvantage of causing deterioration in drivability and fluctuations in exhaust gas components.

In addition, in the feedback control method, Fig. 8 (e
), under normal conditions, the air-fuel ratio correction signal position is Pna
For example, the correction range may expand due to clogging of the slow system passage for air-fuel ratio correction due to changes over time, or under conditions such as high temperatures and high altitudes. . That is, there is a correction signal position due to clogging of the slow system passage, etc. (3) Pa is leaner than the normal position Pna of the rotational speed Na rpm, and Pi is richer than the normal position Pni of the idling rotational speed Nirpm. They may move to each other.

In this way, if the correction signal position is farther away than normal, such as between Pa and Pi, due to a blockage in the slow system passage, etc., the idling speed Ni changes from a certain rotation speed Na rpm.
During transient operation where the rpm suddenly drops, there was a delay in the air-fuel ratio correction signal control as the engine speed fell.

As a result, the air-fuel ratio becomes significantly leaner, resulting in the inconvenience of engine stall Es as shown in FIG. 8(C).

[Object of the Invention] Therefore, the present invention provides a method for controlling the air-fuel ratio according to the engine operating condition without causing the inconvenience of air-fuel ratio fluctuation due to the oven loop control or the inconvenience of control delay due to clogging of the slow system passage for air-fuel ratio correction. The purpose of this invention is to realize an air-fuel ratio control device that can adjust the air-fuel ratio.

[Structure of the Invention] (4) In order to achieve this object, the present invention provides an exhaust sensor in the exhaust system of an internal combustion engine, and only when the input time of the signal input from the exhaust sensor is equal to or longer than a set value, the above-mentioned The present invention is characterized in that it includes a control circuit section that validates an input signal and adjusts the air-fuel ratio to a predetermined air-fuel ratio.

Furthermore, an exhaust sensor provided in the exhaust system of the internal combustion engine, and a control circuit unit that validates the input signal and adjusts the air-fuel ratio to a predetermined air-fuel ratio only when the input time of the signal input from the exhaust sensor is equal to or longer than a set value. is provided with a detection means for detecting an engine operating state of the internal combustion engine, and when the detecting means detects a predetermined engine operating state, an input is input from the exhaust sensor to the control circuit section. The present invention is characterized in that a control means is provided for adjusting the set value of the input time for validating the signal according to a predetermined engine operating state.

[Embodiments of the Invention] Next, embodiments of the first invention according to the present invention will be described in detail based on the drawings.

In this invention, an input signal is generated from an exhaust sensor (5) installed in the exhaust system of an internal combustion engine, for example, when a signal is manually input from an 02 sensor that detects the oxygen concentration in exhaust gas. This is an air-fuel ratio control device that controls the air-fuel ratio to a predetermined value by activating the air-fuel ratio, and a filter constant is set to adjust this set value according to the operating state.

FIG. 1 shows a schematic system diagram of the present invention. 2
is a control circuit section, which is a central section that performs feedback control of the air-fuel ratio of the carburetor 6 provided in the internal combustion engine 4. The control circuit section 2 takes in an input signal from the 02 sensor 10 provided in the exhaust passage 8 and detects the oxygen concentration in the exhaust gas using a filter constant as described above, and adjusts the air-fuel ratio in the intake passage 12 to a predetermined air-fuel ratio. The control valve 14 is operated to adjust the temperature. This control valve 14 controls opening and closing of the fuel passage or the air passage of the carburetor 6, and adjusts the air-fuel ratio.

FIG. 2 is a block diagram of the control circuit section 2. As shown in FIG. The control circuit section 2 includes a comparison circuit 16 that compares the signal input from the 02 sensor 10 with a reference value, an input circuit 18 that takes in various signals as input, and (6) judge c
P o 20 , and a drive circuit 22 that sends a control signal to the control valve 14 based on the judgment of the CPU 20 . The control circuit unit 2 sets filter constants for the rich signal and lean signal input from the 02 sensor 10, and adjusts the air-fuel ratio to a predetermined air-fuel ratio.

FIG. 3 shows an example of the air-fuel ratio change with respect to this filter constant, in which the filter constant TJL for the lean P of the 02 sensor 10 is kept constant, and the filter constant Tr for the rich signal is varied. For example, if the filter constant Tr for validating the rich signal of the 02 sensor 10 is set large, that is, the valid input time is set to be long, the rich signal will only be valid if it is a signal with a long input time, so the lean signal will be valid. There will be more people. Upon input of these effective rich and lean signals, the control circuit section 2 inclines the air-fuel ratio correction signal to the lynch side, and the drive circuit 22 operates the control valve 14 to lynch the air-fuel ratio.

(7) On the other hand, if the filter constant Tr is set to a small value, the rich signal becomes effective even when the input signal is short-term, so the rich signal becomes larger than the lean signal. Therefore, the control circuit section 2 tilts the air-fuel ratio correction signal toward the lean side and operates the control valve 14 to make the air-fuel ratio lean.

On the other hand, although not shown, if the filter constant Tr for the rich signal of the 02 sensor 10 is constant and the filter constant Tl for the lean signal is changed, contrary to FIG. The control circuit section 2 makes the air-fuel ratio leaner. On the other hand, if the filter constant Ti is set to a small value, the number of effective lean signals increases, and the air-fuel ratio becomes lean.

In this way, the filter constant Tr − of the ridge signal and lean signal input from the 02 sensor 10 to the control circuit section 2
By changing Tz, the air-fuel ratio changes to the lynch side or the lean side. Therefore, by setting the filter constants Tr-Tz of each rich signal and lean signal in various combinations (8), it is possible to adjust to various air-fuel ratios corresponding to the operating conditions.

Therefore, by changing the filter constant, for example, in steady state, the air-fuel ratio is adjusted to a predetermined value, and in unsteady state, the air-fuel ratio is adjusted to the corresponding lynch side or lean side. The air-fuel ratio can be adjusted to improve drivability, and exhaust gas components can be stabilized and cleaned.

Of course, the filter constant can also be changed automatically or manually depending on the operating conditions such as the above-mentioned high temperature and high altitude conditions.

Figure 4.5 shows the configuration of the second invention of this invention, and
．． The same components as in FIG. 2 are given the same reference numerals.

In Fig. 4.5, control is performed to adjust the air-fuel ratio to a predetermined value using the 02 sensor 10 and a filter constant that makes the input signal valid only when the input time of the signal input from the 02 sensor 10 is equal to or greater than a set value. The air-fuel ratio control device comprising the circuit section 2 is further provided with (9) a detection means for detecting the engine operating state and a control means for adjusting the filter constant according to the operating state.

In the figure, a rotation speed sensor 24 and an idle switch 26 are provided as detection means. The rotation speed sensor 24 detects the rotation speed of the internal combustion engine 4, and the detected signal is input to the control circuit section 2 via the input circuit 18. The idle switch 26 detects whether the engine is in an idling state based on the opening degree of the throttle valve 28. This idle switch 26 is turned on when the engine is in an idling state,
This signal is input to the control circuit section 2 in the same manner as the signal from the rotation speed sensor 16.

A rotation speed sensor 2 that detects the operating state of these internal combustion engines 4
When the signals from the 02 sensor 10 and the idle switch 26 detect a predetermined engine operating state, which will be described later, the control circuit section 2 detects the signal input from the 02 sensor 10 in order to adjust the air-fuel ratio according to the operating state. Vary the filter constant.

In this embodiment, 24 rotational speed sensors (10) are used to control the air-fuel ratio in order to converge to the air-fuel ratio that should provide the best combustion state when the rotational speed is below a certain rpm or when the idle switch 26 is off. The circuit unit 2 adjusts the filter constants of both the rich signal and the lean signal input from the 02 sensor 10 to T. On the other hand, in an unsteady state such as a transient operating state where the rotational speed sensor 24 is higher than the predetermined rotational speed N1rpm and the idle switch 26 is on, the control circuit unit is configured to enrich the air-fuel ratio as shown in FIG. 2 adjusts the filter constant of the rich signal input from the 02 sensor 10 to T2 and the filter constant of the lean signal to T3. The filter constants T2 and T3 are set to 'r2>T, so 02
The rich signal manually inputted from the sensor sensor 10 is not valid unless it is a long time signal, and the lean signal is valid even if it is a short time signal. Therefore, as shown in FIG. 6, in an unsteady state, the control circuit section 2 inclines the air-fuel ratio correction signal to the rich side to enrich the air-fuel ratio.

Filter constant (11) depending on the operating state with this configuration The operation of the air-fuel ratio control device that changes the air-fuel ratio will be explained.

During steady state, the input signal from the 02 sensor sensor 10 is taken in with a filter constant Tl, and the air-fuel ratio fl is adjusted to a predetermined air-fuel ratio. On the other hand, for example, if the slow system passage for air-fuel ratio correction is clogged, or under high-temperature/high-altitude conditions, the position of the air-fuel ratio correction signal may change at a certain rotational speed as shown in FIG. At several Narpm, the engine may move to a position Pa on the leaner side than the normal position Pna, and at an idling speed Nirpm, it may move to a position Pi on the richer side than the normal position Pni.

In this way, when the position Pa - Pi of the correction signal is far apart, the idling rotation speed Nj changes from a certain rotation speed Na rpm.
During transient operation when the engine speed is lowered to 1, the delay in the correction signal causes the air-fuel ratio to become over-lean as shown by the solid line in FIG. Figure 8(C)).

In this case, it is possible to set a rich air-fuel ratio by open-loop control, but as described above, it is difficult to converge to a constant value depending on the conditions.

(12) Therefore, the present invention changes the filter constant as described above during transient operation under such conditions.
As shown by the broken line in Figure (e), the air-fuel ratio is feedback-controlled to prevent over-lean and engine stall.

This operation will be explained using flowchart 1 in FIG.

Either the idle switch 26 is off or the engine speed is below the predetermined speed N1 rpm (see Figure 8).
b) (See (c)) During steady state, <02 sensor 1 as described above.
The filter constants of the Sochi signal and Lean signal are manually adjusted from 0 to T1 to control the air-fuel ratio to a predetermined value.

On the other hand, if the accelerator is returned under conditions such as the slow system passage for air-fuel ratio correction being clogged, and a transient operation state occurs, as shown in Fig. 8 (
As shown in b), the idle switch 26 is turned on at time t1. Further, it is determined whether the rotational speed Na rpm detected by the rotational speed sensor 24 is equal to or higher than a predetermined rotational speed Nl rpm.

The engine speed decreases from the rotation speed Ma rpm at time t1 (
13) Since the number is greater than or equal to the predetermined rotation speed N1, the filter constant of the rich signal input from the control circuit unit 2 and sensor sensor +10 is adjusted to T2 and the filter constant of the lean signal is adjusted to T3 as described above. .

As a result, as shown in FIG. 8, the short rich signal R8 from the 02 sensor 10 is not taken in, so the control circuit section 2 inclines the air-fuel ratio correction signal to the rich side to enrich the air-fuel ratio.

This enrichment of the air-fuel ratio cannot be incorporated because the input time Tra of the Sochi signal Ra is shorter than the filter constant T2, as shown in FIG. 8(b).
This continues from the lean signal La immediately before time t1.

Therefore, as shown by the broken line in FIG. 8(e), the air-fuel ratio correction signal moves to the rich side from time t1 to t2, and at times 1 and 2, it reaches the correction signal position Pi at the idling speed Nirpm. . After time t2, the idling rotational speed Nirpm is at the correction signal position Pi, so that the air-fuel ratio is prevented from becoming over-lean as shown by the broken line in FIG. 8(a).

(14) Therefore, engine stall Es due to over-lean during transient operation can be prevented.

[Effects of the Invention] As described above, according to the present invention, the air-fuel ratio is adjusted by making the signal valid only when the input time of the signal input from the exhaust sensor is equal to or longer than the set value. Air fuel ratio can be adjusted. Further, the engine operating state can be detected and the air-fuel ratio can be adjusted to the rich side or lean side using a set value corresponding to the predetermined operating state.

Therefore, for example, in transient operating conditions, open-loop control does not cause the inconvenience of air-fuel ratio fluctuations, and if the slow system passage for air-fuel ratio correction is clogged, control can be performed when the correction range is expanded under conditions of high temperature and high altitude. Over-lean caused by delay can be prevented, and engine stall caused by this over-lean can be avoided.

Furthermore, since the air-fuel ratio can be adjusted to the rich side or lean side depending on the operating conditions, drivability can be improved (15), and exhaust gas components can be stabilized and purified. Furthermore, since the air-fuel ratio can be adjusted, it becomes easy to select the mounting position of the exhaust sensor and adapt the fuel distribution.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, Fig. 1 is a schematic system diagram, Fig. 2 is a block diagram, Fig. 3 is a diagram showing the relationship between filter constant and air-fuel ratio, and Fig. 4.5 is a diagram showing the second invention. FIG. 6 is a diagram showing the 02 sensor signal and air-fuel ratio correction signal voltage, FIG. 7 is a flowchart, and FIG. 8 is a timing diagram. In the figure, 2 is a control circuit, 4 is an internal combustion engine, 6 is a carburetor, IO is an 02 sensor, 14 is a control valve, 24 is a rotation speed sensor, and 26 is an idle switch. Agent Patent attorney Yoshimi Nishigo Patent attorney Yukio Harada (16) Figure 1 Figure 2 Figure 3 Small ← →Fill for Rokusuraisa @ and (Tr) Figure 4---- ■ \ 1 - CJy `` 2 6 826 24 1 y ノ

Claims (1)

[Claims] 1. An exhaust sensor is provided in the exhaust system of the internal combustion engine, and the human input signal is enabled only when the input time of the signal input from the exhaust sensor is equal to or longer than a set value, and the air-fuel ratio is adjusted to a predetermined value. What is claimed is: 1. An air-fuel ratio control device comprising: a control circuit section for controlling the air-fuel ratio; 2. An exhaust sensor provided in an exhaust system of an internal combustion engine, and a control circuit unit that validates the input signal and adjusts the air-fuel ratio to a predetermined air-fuel ratio only when the input time of the signal input from the exhaust sensor is equal to or longer than a set value. is provided with a detection means for detecting an engine operating state of the internal combustion engine, and when the detecting means detects a predetermined engine operating state, an input is input from the exhaust sensor to the control circuit section. An air-fuel ratio control device comprising: a control means for adjusting the set value of the input time for validating the signal according to a predetermined engine operating state.