JP3006021B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to an air-fuel ratio control device for an internal combustion engine capable of accurately judging a deterioration state of a purification function of a catalyst by a single exhaust sensor. The present invention relates to an air-fuel ratio control device.

[Prior art] In order to satisfy demands such as a low fuel consumption rate and a low exhaust harmful component value in various operating states in an internal combustion engine,
Some have an air-fuel ratio control device. The air-fuel ratio control device for an internal combustion engine is configured, for example, as shown in FIG. In the figure, 102 is an internal combustion engine, 104 is an air cleaner,
106 is an intake manifold, 108 is an intake passage, 110 is a combustion chamber, 1
12 is an exhaust manifold, and 114 is an exhaust passage.

In an intake passage 108 of the internal combustion engine 102, a fuel injection valve 116 that constitutes a fuel system is provided so as to be directed to the combustion chamber 110. The fuel injection valve 116 is connected to a fuel pump 122 in a fuel tank 120 by a fuel passage 118. Fuel passage 11
In the middle of 8, the filter 124 is sequentially arranged from the fuel tank 120 side.
And a pressure regulating valve 126 are provided. Fuel injection valve 116
The fuel is pressure-fed to the fuel passage 118 by the fuel pump 122, dust is removed by the filter 124, and the fuel adjusted to a predetermined pressure by the pressure adjusting valve 126 is injected and supplied to the combustion chamber 110.
Reference numeral 128 denotes a fuel return passage.

The fuel injection valve 116 is connected to a control unit 130 as control means. The control unit 130 includes sensors that input a control factor signal for controlling the fuel injection amount, for example, an air flow meter 132 that detects an intake air amount,
Crank angle sensor 134 for detecting a crank angle (not shown)
A throttle sensor 136 for detecting an opening degree of a throttle valve (not shown), a water temperature sensor 138 for detecting a cooling water temperature of the internal combustion engine 102, a power unit 142 of an ignition coil 140 for detecting an engine speed, and an exhaust sensor serving O ₂ sensor 144 for detecting an exhaust component values, etc. are connected.

The control unit 130 inputs the detection signals of these sensors 132 to 144 to calculate the fuel injection amount, controls the operation of the fuel injection valve 116 according to the fuel injection amount, and injects and supplies the fuel to the combustion chamber 110. , The air-fuel ratio required by the internal combustion engine 102 is controlled.

The control unit 130, the air-fuel ratio of the internal combustion engine 102 is controlled to the target air-fuel ratio by detecting the signal of the O ₂ sensor 144, the exhaust passage 114
The exhaust gas is purified by the catalyst body 146 provided in the above.

Internal combustion engine 102 by the detection signal of such O ₂ sensor 144
Japanese Patent Application Laid-Open No. 63-97846 discloses an air-fuel ratio control device that controls the air-fuel ratio of the exhaust gas to a target air-fuel ratio and purifies the exhaust gas by a catalyst 146 provided in the exhaust passage 114. In the device disclosed in this publication, first and second O ₂ sensors are provided in an upstream exhaust passage and a downstream exhaust passage of a catalyst body, respectively.
The control constant update rate when the detection signal of the O ₂ sensor is lean is larger than the control constant update rate when the detection signal is rich, and the control constant based on the detection signal of the second O ₂ sensor and the first O ₂ The air-fuel ratio is corrected and controlled based on the detection signal of the sensor, whereby the control air-fuel ratio is made rich and the purification function of the catalyst is enhanced.

As a fuel supply control device for purifying exhaust gas with a catalyst, there is one disclosed in Japanese Patent Application Laid-Open No. Sho 60-27756. In the internal combustion engine having a fuel cutoff function, when the catalyst bed temperature of the catalyst body falls below a predetermined value, shutoff of fuel by the fuel cutoff function is stopped, and This is to avoid a decrease in the purification function due to a decrease in the catalyst bed temperature.

[Problems to be solved by the invention]

By the way, the catalyst body may cause deterioration of the purification function due to aging or the like. When a catalyst having a deteriorated purification function is used, exhaust harmful components are released into the air, and it is impossible to avoid pollution of the air.

Thus, for example, as shown in FIG. 9, the first and second O ₂ sensors 144-1 are provided respectively in the upstream exhaust passage 114-1 and the downstream exhaust passage 114-2 of the catalyst body 146 provided in the exhaust passage 114. 1.14
4-2, and the first and second O ₂ sensors 144-1 and 14-14 are provided.
In some cases, the output of the detection signal of 4-2 is compared under certain conditions to determine the deterioration state of the catalyst body 146.

For example, while the output of the first detection signal of the O ₂ sensor 144-1 is such an output waveform shown in FIG. 10, the second O ₂
When the output of the detection signal of the sensor 144-2 has an output waveform as shown in FIG. 11, it is determined that the deterioration state is small because the purification is performed by the catalyst 146. on the other hand,
While the output of the first detection signal of the O ₂ sensor 144-1 is such an output waveform shown in FIG. 12, a second O ₂ sensor 144
When the output of the detection signal of −2 has an output waveform as shown in FIG. 13, it is determined that the deterioration state is large because the catalyst 146 has not been purified.

Alternatively, the first and second O ₂ sensors 144-1 and 144-2 provided in the upstream exhaust passage 114-1 and the downstream exhaust passage 114-2 of the catalyst body 146 provided in the exhaust passage 114, respectively. The response time of each detection signal is compared under certain conditions to
There is one that determines the deterioration state of 6.

That is, the response time of the 14 detection signals of the first O ₂ sensor 144-1 as shown in FIG., That is a predetermined value from 0V (for example, 0.45
And response time t1 to reach V), in comparing the response time t2 of the detection signal of the second O ₂ sensor 144-2 as shown in FIG. 15, t1 <case of t2 is deteriorated state small Judge that there is,
On the other hand, if t1 ≒ t2, it is determined that the deterioration state is large.

As shown in FIG. 16, a temperature sensor 148 is provided on a catalyst body 146 provided in the exhaust passage 114, and the temperature of the catalyst body is determined by the temperature of the catalyst body.
There is one that determines the deterioration state of 146.

In other words, the catalyst body 146 which has not deteriorated has a high catalyst body temperature due to combustion in the catalyst body 146. Therefore, the temperature of the deteriorated catalyst body 146 decreases because the combustion in the catalyst body 146 is not sufficiently performed. Therefore, as shown in FIG. 17, when the catalyst body temperature of the catalyst body 146 detected by the temperature sensor 148 is Temp.1, which is a high temperature, it is determined that the deterioration state is small.
In the case where the temperature of the catalyst body of No. 6 is the low temperature Temp.2, it is determined that the deterioration state is large.

However, as described above, the provision of the first and second O ₂ sensors and comparing the output of the detection signal and the response time to determine the deterioration state of the catalyst body is costly due to the provision of the _two O ₂ sensors. There is a disadvantage that leads to an increase in Further, variation in detection accuracy of the two O ₂ sensors themselves and, by generating a difference in two deterioration of the O ₂ sensor itself, not give no accurate judgment, there is a disadvantage to make a misjudgment.

Further, in the case where the temperature sensor is provided to determine the deterioration state of the catalyst body based on the temperature of the catalyst body as described above, the temperature of the catalyst body is easily affected by the surrounding temperature environment, so that accurate determination cannot be made. There is an inconvenience of making a misjudgment.

[Object of the invention]

Accordingly, an object of the present invention is to determine the deterioration state of the purifying function of the catalyst using only one exhaust sensor, thereby making it possible to vary the detection accuracy of the exhaust sensor, the deterioration state of the exhaust sensor itself, and the ambient temperature environment. Air-fuel ratio control of an internal combustion engine that can accurately judge the deterioration state of the catalyst body without being affected by the influence, and can reduce cost by being able to judge with only one exhaust sensor without requiring two exhaust sensors It is to implement the device.

[Means for solving the problem]

In order to achieve this object, the present invention provides a first passage bypass passage that communicates a starting end with a first branch portion of an upstream exhaust passage of a catalyst body provided in an exhaust passage of an internal combustion engine, and provides a first passage bypass passage for the catalyst body. A second path bypass passage is provided for communicating the start end side to the second branch portion of the downstream side exhaust passage, and the terminal ends of the first bypass passage and the second bypass passage are gathered at the gathering part and the start side of the gathering bypass passage is provided. And a terminal end of the collective bypass passage is provided so as to communicate with a junction of an exhaust passage downstream of the second branch portion, and the first bypass passage and the second bypass passage are connected to the collective bypass passage. A switching valve for selectively switching communication between the first bypass passage and the collective bypass passage; and a single exhaust sensor provided in the collective bypass passage. The air-fuel ratio of the internal combustion engine is controlled to a target air-fuel ratio by a detection signal of the exhaust sensor in the communication state, and the first bypass passage is connected to the collective bypass passage by the switching valve in a predetermined operation state of the internal combustion engine. The detection signal of the exhaust sensor in the state of the switching communication is compared with the detection signal of the exhaust sensor in the state of switching the second bypass passage to the collective bypass passage by the switching valve, and the catalyst body is deteriorated. A control means for judging a state is provided.

[Action]

According to the configuration of the present invention, the control unit controls the air-fuel ratio of the internal combustion engine to the target air-fuel ratio based on the detection signal of the exhaust sensor in a state where the first bypass passage is switched to the collective bypass passage by the switching valve. In a predetermined operating state of the internal combustion engine, a detection signal of an exhaust sensor in a state in which the first bypass passage is switched to the collective bypass passage by the switching valve and an exhaust gas in a state in which the second bypass passage is switched to the collective bypass passage by the switching valve. Since the deterioration state of the catalyst body is determined by comparing with the detection signal of the sensor, it is possible to determine the deterioration state of the purification function of the catalyst body by using only one exhaust sensor.

〔Example〕

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

1 to 8 show an embodiment of the present invention.
In FIG. 1, 2 is an internal combustion engine, 4 is an intake manifold,
6 is an intake passage, 8 is an exhaust manifold, 10 is an exhaust passage, 12
Is a catalyst.

The internal combustion engine 2 is provided with a fuel supply system such as a fuel injection valve (not shown). Fuel supplied from the intake passage 4 to the internal combustion engine 2 via the intake manifold 6 is burned and discharged from the exhaust manifold 8 to the exhaust passage 10, and the catalyst 12
And is discharged to the outside.

The first branch portion 14 of the exhaust passage 10-1 on the upstream side of the catalyst 12
In addition to the first passage bypass passage 16 communicating the start end side, a second passage bypass passage 20 communicating the start end side to the second branch portion 18 of the downstream exhaust passage 10-2 of the catalyst 12 is provided.

The respective terminal sides of the first bypass passage 16 and the second bypass passage 20 are gathered at the gathering portion 22 to form a combined bypass passage.
Provided in communication with the starting end of 24. The terminal side of the bypass passage 24 is provided so as to communicate with the junction 26 of the exhaust passage 10 downstream of the second branch portion 18.

As shown in FIG. 2, the collecting portion 22 is provided with a switching valve 28 for selectively switching the first bypass passage 16 and the second bypass passage 20 to the collecting bypass passage 24. Moreover, the the set bypass passage 24 is provided with a sole exhaust sensor serving O ₂ sensor 30.

The switching valve 28 includes a valve body 32, a valve shaft 34, and a valve lever 36.
And a return spring 38, and the valve lever 36 is connected to the actuator 42 by a cord 40. This actuator
42 is connected to the control means serving controller 44 together with the O ₂ sensor 30. The switching communication between the first bypass passage 16 and the second bypass passage 20 to the collective bypass passage 24 by the switching valve 28 is airtightly switched so as not to cause leakage of exhaust gas.

The control unit 44 includes, as sensors for inputting control factor signals, for example, a water temperature sensor 46 for detecting a cooling water temperature of the internal combustion engine 2, a pressure sensor 48 for detecting a negative pressure as an intake pressure,
A rotation speed sensor 50 for detecting the engine speed and a vehicle speed sensor 52 for detecting the vehicle speed are connected. A diagnosis lamp 54 is connected to the control unit 44.

The control unit 44 receives the detection signals of these sensors 30 and 46 to 52 and controls the fuel supply system to control the air-fuel ratio required by the internal combustion engine 2.

Further, the control unit 44 controls the first bypass passage by the switching valve 28.
16 in the state of being switched to the collective bypass passage 24
The detection signal of the O ₂ sensor 30 to control the air-fuel ratio of the internal combustion engine 2 to the target air-fuel ratio in a predetermined operating state of the internal combustion engine 2, for example, water temperature is 80~90 ℃ (Δ5 ℃), the negative pressure -450 ~ -500mmHg (Δ-10mmHg), engine speed 2500 ~
In an operating state such as 3000 rpm (Δ200 rpm) and a vehicle speed of 50 to 60 km / h (Δ5 km / h), the first bypass passage is switched by the switching valve 28.
16 in the state of being switched to the collective bypass passage 24
O ₂ compares the detection signal of the sensor 30, and a detection signal of the O ₂ sensor 30 in the state where the through switching換連the second bypass passage 20 to the set bypass passage 24 by switching valve 28 in a predetermined operating state of the internal combustion engine 2, This is for determining the state of deterioration of the catalyst body 12.

 Next, the operation will be described.

In a normal operation state of the internal combustion engine 2, as shown in FIG.
The first bypass passage 16 is collected by the switching valve 28.
Switch communication with 24. In this state, the control unit 44
Controls the air-fuel ratio of the internal combustion engine 2 to the target air-fuel ratio by detecting signals of the O ₂ sensor 30.

Further, in a predetermined operation state of the internal combustion engine 2, the control unit 44 controls the first bypass passage by the switching valve 28 as shown in FIG.
16 in the state of being switched to the collective bypass passage 24
O ₂ and the detection signal of the sensor 30, compares the detection signal of the O ₂ sensor 30 in the state where the through switching換連by switching valve 28 as shown in FIG. 4 the second bypass passage 20 to the set bypass passage 24, the catalyst body The deterioration state of 12 is determined.

For example, as the predetermined operation state of the internal combustion engine 2, the water temperature is 80
~ 90 ℃ (Δ5 ℃), negative pressure is -450 ~ -500mmHg (Δ-10mm
Hg), in an operating state where the engine speed is 2500 to 3000 rpm (Δ200 rpm) and the vehicle speed is 50 to 60 km / h (Δ5 km / h) and is stable, the switching valve 28 is used as shown in FIG. The first bypass passage 16 is switched to communicate with the collective bypass passage 24. In this state, the detection signal of the O ₂ sensor 30 due to the exhaust of the first bypass passage 16 before passing through the catalyst body 12 is taken into the control unit 44 for a predetermined time and stored.

After a lapse of a predetermined time, the second bypass passage 20 is switched to the collective bypass passage 24 by the switching valve 28 as shown in FIG. In this state, the detection signal of the O ₂ sensor 30 due to the exhaust of the second bypass passage 20 after passing through the catalyst body 12 is taken into the control 44.

The control unit 44 compares the stored detection signal of the O ₂ sensor 30 due to the exhaust of the first bypass passage 16 with the currently detected detection signal of the O ₂ sensor 30 due to the exhaust of the second bypass passage 20, The deterioration state of the catalyst body 12 is determined. As a result, the deterioration state of the catalyst body 12 is determined within the predetermined time.

 The determination of the deterioration state of the catalyst body 12 is performed as follows.

In a predetermined operation state, the output of the detection signal of the O ₂ sensor 30 by the exhaust of the first bypass passage 16 in a state where the first bypass passage 16 is switched to the collective bypass passage 24 by the switching valve 28 as shown in FIG. FIG. 6 shows the output of the detection signal of the O ₂ sensor 30 in a state where the second bypass passage 20 is switched to the collective bypass passage 24 by the switching valve 28 in the predetermined operation state, in contrast to the output waveform. In the case of such an output waveform, it is determined that the deterioration state is small because the purification is performed by the catalyst 12.

On the other hand, in a predetermined operation state, the O ₂ sensor 30 by the exhaust of the first bypass passage 16 in a state where the first bypass passage 16 is switched to the collective bypass passage 24 by the switching valve 28.
7 has an output waveform as shown in FIG.
When the output of the detection signal of the O ₂ sensor 30 has the output waveform as shown in FIG. 8 in a state where the bypass passage 20 is switched to the collective bypass passage 24, the purification is performed by the catalyst body 12. It is determined that the deterioration state is large.
When it is determined that the state of deterioration of the catalyst 12 is large, the diagnosis lamp 54 is turned on.

In this manner, the control unit 44 controls the detection signal of the O ₂ sensor 30 in a state in which the first bypass passage 16 is switched to the collective bypass passage 24 by the switching valve 28 in a predetermined operation state of the internal combustion engine 2, and the switching valve. Second bypass passage by 28
20 in the state of being switched to the collective bypass passage 24
Since the deterioration state of the catalyst 12 is determined by comparing the detection signal of the O ₂ sensor 30 with the detection signal, the deterioration state of the purification function of the catalyst 12 can be determined by the single O ₂ sensor 30.

Therefore, in the determination of two conventional O ₂ deteriorated state of the catalytic body according to the sensor there is an inconvenience which can not without an accurate determination due to the influence of variations in the detection accuracy of the O ₂ sensor itself, only O ₂ sensor 30 By judging the deterioration state of the purification function of the catalyst 12, the influence of the variation in the detection accuracy of the O ₂ sensor can be eliminated to make an accurate judgment. Further, in the determination of two conventional O ₂ deteriorated state of the catalytic body by a sensor, but there is an inconvenience which can not form a precise comparison due to the effect of the difference in the deterioration state of the two O ₂ sensors due to aging or the like By judging the deterioration state of the purifying function of the catalyst 12 using only one O ₂ sensor 30, the influence of the difference between the deterioration states of the _two O ₂ sensors can be eliminated to make an accurate judgment. Further, the influence of the surrounding temperature environment, such as the judgment based on the catalyst body temperature of the catalyst body 12, can be eliminated.

As a result, as in the case where two conventional O ₂ sensors are provided, there is a difference in the detection accuracy of the O ₂ sensor itself, the influence of the difference in the deterioration state of the O ₂ sensor, the influence of the surrounding temperature environment, etc. without the deteriorated state of the catalytic body 12 can be accurately determined, the cost can be reduced because it can be determined by only the O ₂ sensor without requiring two O ₂ sensors.

〔The invention's effect〕

Thus, according to the present invention, by the control means,
The air-fuel ratio of the internal combustion engine is controlled to the target air-fuel ratio by the detection signal of the exhaust sensor in a state where the first bypass passage is switched to the collective bypass passage by the switching valve, and the first valve is operated by the switching valve in a predetermined operation state of the internal combustion engine. The detection signal of the exhaust sensor when the bypass passage is switched to the collective bypass passage is compared with the detection signal of the exhaust sensor when the second bypass passage is switched to the collective bypass passage by the switching valve. Since the deterioration state is determined, it is possible to determine the deterioration state of the purification function of the catalyst using only one exhaust sensor.

Therefore, unlike the case where two conventional exhaust sensors are provided, the catalyst body is not affected by variations in the detection accuracy of the exhaust sensors themselves, differences in the deterioration state of the exhaust sensors, and the influence of the surrounding temperature environment. Can be accurately determined, and the cost can be reduced by determining using only one exhaust sensor without using two exhaust sensors.

[Brief description of the drawings]

1 to 8 show an embodiment of the present invention, FIG. 1 is a schematic configuration diagram of an air-fuel ratio control device for an internal combustion engine, FIG. 2 is an enlarged perspective view of a switching valve portion, and FIG. 3 is a first bypass passage. FIG. 4 is a cross-sectional explanatory view of a state in which the second bypass passage is switched to the collective bypass passage, and FIG. 5 is a cross-sectional explanatory view of a state in which the second bypass passage is switched to the collective bypass passage. FIG. 6 is a diagram showing an output waveform of a detection signal of the _two sensors, FIG. 6 is a diagram showing an output waveform of a detection signal of the O ₂ sensor when the catalyst body is not deteriorated by exhaustion of the second bypass passage, and FIG. FIG. 8 is a diagram showing an output waveform of a detection signal of the O ₂ sensor due to exhaust gas in the first bypass passage. FIG. 8 shows an output waveform of a detection signal of the O ₂ sensor when the catalyst body is deteriorated due to exhaust gas in the second bypass passage. FIG. 9 to 18 show a conventional example, FIG. 9 is a cross-sectional view of a catalyst body provided with first and second O ₂ sensors in an upstream exhaust passage and a downstream exhaust passage, and FIG. The first O ₂ provided in the exhaust passage
FIG. 11 is an output waveform diagram of a detection signal of the sensor, FIG. 11 is an output waveform diagram of a detection signal of the second O ₂ sensor provided in the downstream exhaust passage when the catalyst body is not deteriorated, and FIG. The figure showing the output waveform of the detection signal of the first O ₂ sensor provided in the passage,
FIG. 13 is a diagram showing an output waveform of a detection signal of a _second O ₂ sensor provided in the downstream exhaust passage when the catalyst body is deteriorated,
FIG. 14 is a diagram showing a response time of a detection signal of a first O ₂ sensor provided in an upstream exhaust passage, and FIG. 15 is a response time of a detection signal of a _second O ₂ sensor provided in a downstream exhaust passage. The figure showing the
FIG. 16 is a sectional view of a catalyst body provided with a temperature sensor, FIG. 17 is a diagram showing a temperature for judging a deterioration state due to the catalyst body temperature, and FIG.
The figure is a schematic configuration diagram of an air-fuel ratio control device for an internal combustion engine. In the figure, 2 is an internal combustion engine, 4 is an intake manifold, 6 is an intake passage, 8 is an exhaust manifold, 10 is an exhaust passage, 12 is a catalyst, 14 is a first branch portion, 16 is a first passage bypass passage, and 18 is a first passage bypass passage. The second branch portion, 20 is the second road bypass passage, 22 is the collecting portion, 24
Is the collective bypass passage, 26 is the junction, 28 is the switching valve, 30 is O ₂
A sensor, 42 is an actuator, 44 is a control unit, 46 is a water temperature sensor, 48 is a pressure sensor, 50 is a rotation speed sensor, 52 is a vehicle speed sensor, and 54 is a diagnosis lamp.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/14 F02D 41/22 F01N 3/20

Claims (1)

(57) [Claims] A first bypass passage communicating with a start end of a first branch portion of an upstream exhaust passage of a catalyst body provided in an exhaust passage of an internal combustion engine is provided, and a second bypass passage of a downstream exhaust passage of the catalyst body is provided. A second path bypass passage communicating with the start end side of the branch portion is provided, and respective end sides of the first bypass passage and the second bypass passage are gathered at the collecting portion and provided so as to communicate with the starting end side of the collective bypass passage. An end side of the collective bypass passage is provided so as to communicate with a junction of the exhaust passage downstream of the second branch portion, and the first bypass passage and the second bypass passage are selectively switched to the collective bypass passage. A switching valve is provided in the collecting portion and a single exhaust sensor is provided in the collecting bypass passage, and the first bypass passage is switched to the collecting bypass passage by the switching valve. An air-fuel ratio of the internal combustion engine is controlled to a target air-fuel ratio by a detection signal of an exhaust sensor, and in a state where the first bypass passage is switched to the collective bypass passage by the switching valve in a predetermined operation state of the internal combustion engine. Control means for comparing a detection signal of the exhaust sensor with a detection signal of the exhaust sensor in a state where the second bypass passage is switched to the collective bypass passage by the switching valve to determine a deterioration state of the catalyst body; An air-fuel ratio control device for an internal combustion engine, comprising: