JPH0615853B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas recirculation control device for an internal combustion engine, which controls a recirculation amount (recirculation amount) of exhaust gas.

[Conventional technology]

It is well known that so-called exhaust gas recirculation is performed by mixing a part of the exhaust gas into the intake side of the engine in order to reduce nitrogen oxides which are harmful components in the exhaust gas of the internal combustion engine. . The recirculation amount of the recirculated exhaust gas affects the performance of the engine, fuel consumption, etc. in addition to the reduction of nitrogen oxides, so the exhaust gas recirculation amount is accurately controlled according to the operating state of the engine. Is desired.

FIG. 6 is a schematic configuration diagram of a conventional exhaust gas recirculation control device shown in, for example, Japanese Patent Application Laid-Open No. 55-93950. In the figure, (1) is the engine body, (2) is the intake manifold, (3) is the exhaust manifold, and (4) is the intake manifold.
A fuel supply device arranged in (2), (5) a slot valve,
(6) is an intake duct, (7) is an air cleaner, (8) is an engine speed detector, (9) is a negative pressure introducing passage, and (10) is a negative pressure introducing passage (9) through the intake manifold (2). An intake negative pressure detector for detecting pressure, (11) is an exhaust gas recirculation (hereinafter, referred to as EGR) that connects the exhaust manifold (3) and the intake manifold (2).
(12) is an EGR control valve operated by a pressure diaphragm, (13) is an opening detector of the EGR control valve (12), and (14) is E
The GR control circuit, (15) is the atmospheric pressure introducing passage, and (16) is the output signal sent from the EGR control circuit (14).
It is a control negative pressure generator that regulates the control negative pressure that controls the opening and closing degree of 2) by the intake negative pressure and the atmospheric pressure.

In the EGR control device configured as described above, the engine speed and the intake negative pressure, which indicate the operating state of the engine, are
It is detected by the engine speed detector (8) and the intake negative pressure detector (10) and input to the EGR control circuit (14). The EGR control circuit (14) has an EG that is determined according to the operating state of the engine.
The target opening of the R control valve (12) is set, and the control negative pressure is generated so that the comparison deviation between this target opening and the actually measured opening input via the opening detector (13) becomes zero. The output signal is sent to the container (16). That is, based on the output signal sent from the EGR control circuit (14), the output negative pressure is adjusted to the control negative pressure generator (16) by the intake negative pressure and the atmospheric pressure, and the opening degree of the EGR control valve (12) is adjusted. The exhaust gas recirculation amount (hereinafter referred to as the EGR amount) is controlled to determine the comparison deviation to be zero. That is, E
By performing feedback control of the opening of the GR control valve (12) using the output of the opening detector (13), the EGR amount according to the operating state of the engine is obtained.

[Problems to be solved by the invention]

However, according to such a conventional EGR control device, due to long-term use of the EGR control valve (12), a large amount of carbon and the like contained in the exhaust gas adheres to this valve, and E
There is a problem that the initial EGR amount corresponding to the opening / closing degree of the GR control valve (12) changes, and accurate control cannot be performed.

To address this problem, the present applicant uses an oxygen sensor to detect the oxygen concentration in the intake air downstream of the EGR control valve (12), while the target EGR rate is set according to the operating state of the engine. The target oxygen concentration is determined in accordance with the target EGR rate, and the EGR control valve (1 is set in order to make the deviation between the determined target oxygen concentration and the oxygen concentration detected by the oxygen sensor zero.
We are considering a control method to control 2). According to this control method, E is controlled by the oxygen concentration proportional to the mixing ratio of exhaust gas.
Since the GR amount is controlled, accurate control can be performed even if the initial EGR amount corresponding to the opening / closing degree of the EGR control valve (12) changes.

However, when this control method is adopted, the correspondence between the sensor output of the oxygen sensor and the detected oxygen concentration is subtly different due to the variation among the oxygen sensors, and the sensor output of the oxygen sensor may change due to the secular change of the oxygen sensor itself. Correspondence with the detected oxygen concentration fluctuates, and a new problem arises that impedes highly accurate reflux control.

The present invention has been made in view of such a problem, and even if there are variations in the oxygen sensor among individuals, or even if the oxygen sensor itself changes over time, it is possible to prevent highly accurate reflux control. An object of the present invention is to provide an exhaust gas recirculation control device for internal combustion engines.

[Means for solving problems]

An exhaust gas recirculation control device for an internal combustion engine according to the present invention includes an exhaust gas recirculation control valve provided in an exhaust gas recirculation passage communicating between an exhaust system and an intake system of the internal combustion engine, and an exhaust gas recirculation passage opening portion of the intake system. A combustible gas passage connected to the intake system so that a gas containing a combustible gas and an oxygen sensor for detecting the oxygen concentration in the intake air, which is provided further downstream, and the combustible gas passage are connected to the intake system. An opening / closing valve that opens and closes by an electric signal, a target exhaust gas recirculation rate determining unit that determines a target exhaust gas recirculation rate according to the operating state of the internal combustion engine, and a target exhaust gas that is determined by this target exhaust gas recirculation rate determining unit. The target oxygen concentration determining means for determining the target oxygen concentration according to the gas recirculation rate is compared with the target oxygen concentration determined by the target oxygen concentration determining means and the oxygen concentration detected by the oxygen sensor. An exhaust gas recirculation control device for an internal combustion engine, comprising: a control means for controlling the opening degree of the exhaust gas recirculation control valve so as to make these comparison deviations zero. A specific operating state detection means for detecting the specific operating state of the engine, and the on-off valve is fully closed during this specific operating state, and based on the oxygen concentration detected by the oxygen sensor at that time, the detected oxygen concentration and the standard oxygen concentration of the atmosphere In order to meet the above condition, a correction means for correcting the correspondence between the sensor output of the oxygen sensor and the detected oxygen concentration is provided.

[Action]

Therefore, according to the present invention, the opening degree of the exhaust gas recirculation control valve is controlled by the oxygen concentration in the intake air to obtain the desired exhaust gas recirculation amount according to the operating state. Even if a large amount of carbon or the like contained in the exhaust gas adheres to this valve due to the use of time, the initial exhaust gas recirculation control characteristic will not be impaired. further,
According to the present invention, when the specific operating state of the internal combustion engine (the state in which the EGR rate is zero) is detected, the oxygen concentration detected by the oxygen sensor in the specific operating state matches the standard oxygen concentration of the atmosphere, Since the correction means for correcting the correspondence between the output of the oxygen sensor and the detected oxygen concentration is provided, it is possible to perform more accurate reflux control that does not change over time. In addition, variations between oxygen sensor solids can be tolerated.

〔Example〕

Hereinafter, the exhaust gas recirculation control device for an internal combustion engine according to the present invention will be described in detail. FIG. 1 shows an embodiment of this device E
It is a schematic block diagram of a GR control device. In the figure, the sixth
The same reference numerals as those in the figure indicate the same functional elements, and the description thereof is omitted. In the figure, (17) is the EG of the intake manifold (2).
Downstream of the opening to the R passage (11) (engine body (1)
The oxygen sensor is mounted by disposing the sensor part in the side), and is proportional to the oxygen concentration, as in the solid electrolyte oxygen pump type oxygen sensor proposed in, for example, Japanese Patent Laid-Open No. 58-153155. An oxygen sensor that produces a current output (mA). FIG. 2 is a characteristic diagram showing the relationship between the sensor output I _F sent by the oxygen sensor (17) and the oxygen concentration C ₂ . The sensor output I _P sent by the oxygen sensor (17) is EGR.
It is designed to be input to the control circuit (18).
The corresponding oxygen concentration is calculated in the R control circuit (18). In addition, the EGR control circuit (18) receives the engine speed N _E (rpm) input via the engine speed detector (8) and the intake air pressure input via the intake negative pressure detector (10). The target EGR rate K _O (%) corresponding to the pressure P _B (mmHg) is stored (FIG. 3), and the target oxygen concentration C _{O2 is} calculated from the target EGR rate K _O according to the characteristics shown in FIG. Is read.
Then, the EGR control circuit (18) detects the target oxygen concentration C _O2 determined according to the operating state of the engine and the detected oxygen concentration C determined according to the sensor output I _P delivered by the oxygen sensor (17).
₂ is compared with each other, and an output signal that makes these comparison deviations zero is sent to the control negative pressure generator (16), and the EGR control valve (1
The degree of opening and closing of 2) is controlled. (19) is a temperature sensor mounted on the engine body (1) for detecting the temperature of cooling water for cooling the engine. The cooling water temperature T _E of the engine body (1) detected by the temperature sensor (19) is EGR at the time.
The control circuit (18) is adapted to input the cooling water temperature T _E or the signals from the engine speed detector (8) and the intake pressure detector (10) so that the zero state of the EGR rate is EGR. It is designed to be detected by the control circuit (18). That is, when the engine body (1) has just started and the cooling water temperature TE of the engine body (1) is lower than a predetermined temperature, or even when the cooling water temperature is sufficiently high, in a specific operating state such as in an idle state. Is an EGR control valve (12)
Keeps the fully closed state, and the EGR rate becomes zero. That is, the zero state of the EGR rate is grasped in the EGR control circuit (18) by the cooling water temperature T _E from the temperature sensor (19) or the signals from the engine speed detector (8) and the intake pressure detector (10). It is supposed to be done. (20) is the valve operating chamber,
It communicates with a crank chamber (not shown) through a passage (21). The valve operating chamber (20) is communicatively connected to a port (23) provided in the intake pipe (2) by a blow-by gas passage (22).
The port (23) is provided downstream of the throttle valve (5) in the intake flow, that is, upstream of the oxygen sensor (17). The valve operating chamber (20) is connected by a blow-by gas passage (24) immediately downstream of the air cleaner (7). A blow-by gas flow rate control valve (PCV valve) (25) is provided on the valve operating chamber side in the middle of the blow-by gas passage (22), and an on-off valve (26) is further provided. The blow-by gas flow control valve (25) is a conventional one, and is for reducing the amount of blow-by gas according to the load state of the engine to the intake system. The on-off valve (26) is a valve that electrically opens and closes in response to a command from the EGR control circuit (18). The zero state of the EGR rate is
When it is detected in the EGR control circuit (18), the EGR control circuit (18) outputs a command to fully close the on-off valve (26) as an electric signal. Then, the detected oxygen concentration C ₂ after the lapse of a predetermined time is in a specific operation state (a state in which the EGR rate is zero).
Standard oxygen concentration C ₀₂₀ as the detected oxygen concentration in
2 and the comparison result shows that _IP − shown in FIG.
The C ₂ characteristic is adapted to be corrected. That is,
Zero-state EGR rate is detected as a specific operation state, the detected oxygen concentration C ₂ in this particular operating condition in order to conform to the standard oxygen concentration C ₀₂₀ of air, the sensor output I _P and the detection of oxygen concentration of the oxygen sensor (17) The correspondence with C ₂ is adapted to be corrected. As a concrete example of this correction,
For example, when the sensor output I _P of the oxygen sensor to the detection of oxygen concentration C ₂ (17) is a proportional relationship with a offset, FIG. 5 (a) are shown so as to change only the offset value It is conceivable that the correction is performed or that the proportional constant is changed so as to keep the sensor output _IP at a constant value when the detected oxygen concentration C ₂ is zero (FIG. 5 (b)).

As is clear from the above description, according to this example, the target exhaust gas recirculation rate determining means, the target oxygen concentration determining means, the control means, the specific operation state detecting means, and the correcting means are realized by the EGR control circuit (18). ing.

Next, the operation of the EGR control device configured as described above will be described. That is, when the engine body (1) is started, the engine speed N _E and the intake pressure P _B indicating the operating state of the engine are transferred to the EGR via the engine speed detector (8) and the intake pressure detector (10). It is input to the control circuit (18). EGR control circuit (18), depending on the value of the engine speed _{N E} and the intake pressure _{P B} is input, from the target EGR rate _{K O} stored in advance, for example, the target EGR ratio K _oi
Select (Fig. 3). And this selected target EG
Based on the R rate K _Oi , the target oxygen concentration C according to FIG.
Read _O2i . On the other hand, the oxygen concentration of the air exhaust gas in the intake pipe (2) is mixed in, this time is calculated in accordance with Figure 2 than the sensor output I _P for delivering oxygen Sansa (17), the calculated oxygen concentration C _2j And the target oxygen concentration Co2i read out as described above are compared. And this C
_An output signal is sent to the control negative pressure generator (16) so that the comparison deviation between _2j and C _2i becomes zero, and the control negative pressure generator (16)
Regulates the output negative pressure using the pressure in the negative pressure introduction passage (9) and the atmospheric pressure introduction passage (15), controls the opening and closing degree of the EGR control valve (12), and sets the detected oxygen concentration to the target oxygen concentration. Get closer. At this time, if the EGR control valve (12) moves in the opening direction,
Sensor output I _P of the oxygen sensor (17) EGR amount becomes large
The oxygen concentration C _2J corresponding to the above decreases, and the oxygen concentration C _2J increases when _moving in the closing direction. As described above, according to the present embodiment, the opening degree of the EGR control valve (12) is controlled by the oxygen concentration in the intake air to obtain the desired EGR according to the operating state.
Since the amount is obtained, even if a large amount of carbon or the like contained in the exhaust gas adheres to the EGR control valve (12) for a long period of time, the initial EGR control characteristics will not be impaired. .

The control operation of the EGR control valve (12) has been described above, but when the EGR control valve (12) is in the closed state, that is, E
When the GR control rate becomes zero, the characteristic operation of the present invention is performed inside the EGR control circuit (18). In other words, the engine body (1) will be started soon after the engine body is started.
(1) When the cooling water temperature T _E is lower than the predetermined temperature or, in certain operating conditions, such as when the coolant temperature is in the idle state even if sufficiently high, EGR control valve (12) maintains the fully closed state , The EGR rate becomes zero. Therefore, the EGR rate should be zero in the EGR control circuit (18) due to the cooling water temperature T _E from the temperature sensor (19) or the signals from the engine speed detector (8) and the intake pressure detector (10). When is detected, immediately, a command to fully close the on-off valve (26) in the middle of the blow-by gas passage (22) is issued to fully close the valve. Regarding the other blow-by passage (24), in the state where the EGR rate becomes zero as described above, there is no intake of blow-by gas into the intake system, so an on-off valve is not necessary. After a predetermined time has elapsed operation is completed above, the detection of oxygen concentration at that time is and the standard oxygen concentration C _O2O of C ₂ and the atmosphere is compared, C
The correspondence between the sensor output I _P of the oxygen sensor (17) and the detected oxygen concentration C ₂ is corrected so as to match ₂ with C _O2O . That is, when the EGP rate is zero, the oxygen concentration of the intake air detected by the oxygen sensor (17) is equal to the oxygen concentration of the atmosphere, and the oxygen concentration C ₂ detected at this time should match the standard oxygen concentration C _O2O. By correcting the correspondence relationship, it is possible to largely allow the variation between the individual oxygen sensors incorporated in the control system, and also to correct the electrochemical secular change of the oxygen sensor.

Next, the technical significance of fully closing the open / close valve (26) of the combustible gas passage (22) and the operation / effect thereof in a specific operating state where the EGR rate is zero will be described. When flammable gas (gas containing a large amount of hydrocarbon components) enters the detection part of the oxygen sensor (17), the sensor detection part will reach a high temperature (800 ℃ ~
Since it is 900 ℃), flammable components cause combustion and oxidation reaction. Therefore, the oxygen in the vicinity of the detection part changes to water vapor, carbon dioxide, etc., and the oxygen concentration substantially detected by the oxygen sensor (17) is lower than the oxygen concentration in the actual intake pipe (2). Become. If the target EGR rate is zero and the oxygen sensor (17) output produces the above error in a specific operating state where the oxygen concentration in the intake pipe (2) is the standard oxygen concentration in the atmosphere, the sensor output Correct correction of the correspondence between the detected oxygen concentration and the detected oxygen concentration becomes impossible. In order to prevent such an error from occurring, an on-off valve (2
6) is provided to control opening / closing. Note that a large amount of gas enters during a specific operating condition, which is easily affected by this, but in other than the specific operating condition, the intake pipe (2) has a large amount of air (oxygen amount), and conversely the intake of combustible gas. Is less likely to be affected by flammable gas.

In this embodiment, the EGR control valve (12) is operated by negative pressure through the pressure diaphragm, but it may be a stepping motor or a combination of a DC motor and gears.

Further, in the present embodiment, an example in which the blow-by gas passage (22) is provided with an on-off valve, but other than this, a passage for a gas containing a combustible gas, which is connected to the intake pipe, is an internal combustion engine. There is a purge gas passage installed in the engine for purging the canister (adsorber) that adsorbs the gas generated from the fuel system, and the object of the present invention can be achieved by the same configuration and operation as the above embodiment. To be

Further, in the embodiment of FIG. 1, a drawing in which the opening port of the blow-by gas passage (22) to the intake pipe (2) is provided on the upstream side of the opening of the EGR gas passage is shown. The position is not limited to this, and the position may be downstream of the opening of the EGR gas passage, and further downstream of the oxygen sensor.

Further, in the above-described embodiment, the case where the target EGR rate is obtained by the engine speed N _E and the suction pressure P _B has been described, but the present invention is not limited to this. For example, it is obtained by the engine speed N _E and the intake air flow rate. However, the same effect as that of the above-described embodiment can be obtained.

〔The invention's effect〕

As described above, according to the exhaust gas recirculation control device for an internal combustion engine of the present invention, the EGR amount is controlled by the oxygen concentration proportional to the mixing ratio of the exhaust gas, while the engine is in a specific operating state (when the EGR ratio is zero. When a certain condition is detected,
Correspondence between the sensor output of the oxygen sensor and the detected oxygen concentration so that the on-off valve installed in the middle of the flammable gas passage is fully closed and the oxygen concentration detected by the oxygen sensor in this specific operating condition matches the standard oxygen concentration of the atmosphere. The relationship is corrected, and even if there are variations among the oxygen sensors, or even if the oxygen sensors themselves change over time, highly accurate reflux control is not hindered. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an exhaust gas recirculation control device for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is a sensor output I _P sent by an oxygen sensor used in this EGR control device and a detected oxygen concentration C ₂ And FIG. 3 is a characteristic diagram showing a target EGR rate K _O corresponding to the engine speed N _E and the intake pressure P _B input to the device EGR control circuit, and FIG. 4 is a target diagram. FIG. 5 is a characteristic diagram showing a target oxygen concentration C _{O2 associated} with the EGR rate K _O , FIG. 5 is a diagram showing a correspondence relation between the detected oxygen concentration C ₂ and the oxygen sensor output I _P after initial and correction, and FIG. It is a schematic block diagram of the conventional EGR control apparatus. (1) …… Engine body, (2) …… Intake pipe, (3) …… Exhaust pipe, (8) …… Engine speed detector, (10) …… Intake pressure detector, (11) …… Exhaust gas recirculation passage, (12) …… Exhaust gas recirculation control valve, (13) …… Opening position detector, (16) …… Control negative pressure generator, (17) …… Oxygen sensor, (14) (18 ) ... Exhaust gas recirculation control circuit, (19) ... Temperature sensor, (22) (24) ... Blow-by gas passage, (25) ... Blow-by gas flow control valve, (26)
...... Open / close valve. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyoshi Suzuki, 840 Chiyoda-cho, Himeji City, Hyogo Prefecture Mitsubishi Electric Corporation Himeji Manufacturing Co., Ltd. (56) References JP-A-60-138264 (JP, A) JP-A-60 -11664 (JP, A)

Claims (3)

[Claims] 1. An exhaust gas recirculation control valve provided in an exhaust gas recirculation passage communicating between an exhaust system and an intake system of an internal combustion engine, and an exhaust gas recirculation control valve provided downstream of an opening portion of the exhaust gas recirculation passage of the intake system in intake air. An oxygen sensor for detecting the oxygen concentration, a combustible gas passage connected to the intake system for inhaling a gas containing a combustible gas into the engine, and an on-off valve for opening and closing the combustible gas passage by an electric signal. And a target exhaust gas recirculation rate determining means for determining a target exhaust gas recirculation rate according to the operating state of the internal combustion engine, and a target oxygen according to the target exhaust gas recirculation rate determined by the target exhaust gas recirculation rate determining means. The target oxygen concentration determining means for determining the concentration is compared with the target oxygen concentration determined by the target oxygen concentration determining means and the oxygen concentration detected by the oxygen sensor, and the above-mentioned exhaust is set in order to make the comparison deviation between them zero. An exhaust gas recirculation control device for an internal combustion engine, comprising: a control means for controlling an opening degree of a gas recirculation control valve, wherein a specific operating state detection for detecting a zero state of the exhaust gas recirculation rate as a specific operating state of the internal combustion engine. And means for fully closing the on-off valve during this specific operation state, and based on the detected oxygen concentration of the oxygen sensor at that time, in order to match the detected oxygen concentration with the standard oxygen concentration of the atmosphere, the sensor output of the oxygen sensor and An exhaust gas recirculation control device for an internal combustion engine, comprising: a correction unit that corrects a correspondence relationship with a detected oxygen concentration. 2. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the combustible gas passage is a blow-by gas passage of the internal combustion engine. 3. The combustible gas passage is a purge gas passage installed in the engine for purging a canister that adsorbs gas generated from a fuel system of an internal combustion engine. Exhaust gas recirculation control device for internal combustion engine.