JP2010203407A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of reducing a processing load in an ECU (Electric Control Unit). <P>SOLUTION: When an output voltage value of an oxygen sensor crosses correction factor changing thresholds L<SB>TH</SB>and R<SB>TH</SB>, an oxygen sensor correction factor K is changed to [β] from [α] and to the [α] from the [β] by interruption processing in this stage. Thus, since an event trigger for changing the oxygen sensor correction factor K is set in the stage when the output voltage value of the oxygen sensor 77 crosses the threshold values L<SB>TH</SB>and R<SB>TH</SB>, the calculation of a sub-feedback correction quantity is stopped except for that. As a result, the processing load of the ECU 6 can be reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine in which an oxygen sensor is provided downstream of a catalyst in an exhaust passage.

For example, in Patent Document 1, a first air-fuel ratio sensor disposed upstream of a catalytic converter having OSC (O ₂ Storage Capacity) capability and a second air-fuel ratio sensor disposed downstream are provided. In the air-fuel ratio control apparatus for an internal combustion engine, a technique has been proposed in which the second air-fuel ratio sensor can satisfactorily correct the reference output of the first air-fuel ratio sensor even when the catalyst is deteriorated or inactive. ing.

  In the technique described in Patent Document 1, the fuel injection amount is controlled based on the output of the first air-fuel ratio sensor, and determined based on the difference between the air-fuel ratio detected by the second air-fuel ratio sensor and the theoretical air-fuel ratio. When the reference output corresponding to the theoretical air-fuel ratio of the first air-fuel ratio sensor is corrected using the correction amount that is generated, the current OSC capability is based on a variable that changes according to the current OSC capability of the catalytic converter. The lower the value is, the smaller the correction amount is.

  In addition, in Patent Document 2, an air-fuel ratio control apparatus for an internal combustion engine that converges the amount of OSC in a three-way catalyst in an optimum region and further improves engine exhaust characteristics when controlling the air-fuel ratio of the internal combustion engine. Proposed.

  According to Patent Document 2, an ECU (Electronic Control Unit) repeats skip control and integral control so that the sensor voltage of a front oxygen sensor provided upstream of a three-way catalyst converges to a reference voltage. A feedback correction coefficient is calculated, and the fuel injection amount is corrected using the correction coefficient. Further, the ECU further skips the skip control amount and the integral control for the skip control amount of the air-fuel ratio feedback correction coefficient so that the sensor voltage of the rear oxygen sensor provided downstream of the three-way catalyst converges to the reference voltage. Fuel ratio sub-feedback control is performed. In the air-fuel ratio sub-feedback control, the ECU expects a large update amount for skip control, and keeps the skip control amount constant for a predetermined time even after shifting to integral control.

  Further, according to Patent Document 3, the exhaust gas emission of the engine is further reduced by changing the threshold value of the oxygen sensor output when correcting the calculated value of the OSC amount according to the operating conditions. A purification device has been proposed.

  This exhaust purification device according to Patent Document 3 includes a sensor that detects an intake air amount of an engine, a catalyst provided in an exhaust passage of the engine, a sensor that detects an air-fuel ratio of exhaust flowing into the catalyst, and an outflow from the catalyst. And a sensor for detecting the oxygen concentration or air-fuel ratio of the exhaust gas to be exhausted. The ECU calculates the OSC amount of the catalyst based on the detected air-fuel ratio of the exhaust gas flowing into the catalyst and the intake air amount of the engine, and based on the calculated OSC amount, the engine's OSC amount becomes a predetermined value. Control the air / fuel ratio. Further, the ECU corrects the OSC amount when the oxygen concentration or air-fuel ratio of the exhaust gas flowing out from the detected catalyst reaches a predetermined threshold value, and corrects this threshold value according to the intake air amount. To do.

  Furthermore, Patent Document 4 proposes a catalyst deterioration detection device for an internal combustion engine that can accurately detect the true degree of catalyst deterioration even when the post-catalyst sensor is deteriorated.

  The catalyst deterioration detection device for an internal combustion engine according to Patent Document 4 is a device for detecting deterioration of a catalyst disposed in an exhaust passage of the internal combustion engine, and a post-catalyst sensor for detecting an exhaust air / fuel ratio downstream of the catalyst. Means for switching the target air-fuel ratio at the same time that the output value of the post-catalyst sensor is inverted to reach the rich judgment value VR, means for detecting a parameter correlated with the degree of deterioration of the post-catalyst sensor, And a means for correcting the rich determination value from VR to a value VRx higher than VR according to the value.

JP-A-8-158915 JP 2000-97083 A Japanese Patent Laid-Open No. 2002-327641 JP 2008-31901 A

  In general air-fuel ratio control (A / F control) of an internal combustion engine, an output signal of an oxygen sensor placed downstream of a catalyst is taken into an ECU, and a feedback correction amount is periodically calculated and reflected in injection. I am doing so.

  However, recently, various controls have been added to automobiles, and the processing load on the ECU that controls the control is increasing. This is because the software is bloated to incorporate customer needs and comfortable and safe controls.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a control device for an internal combustion engine that can contribute to reducing the processing load of the ECU.

  In order to achieve the above object, an internal combustion engine control apparatus according to the present invention is an internal combustion engine control apparatus in which an oxygen sensor is provided downstream of a catalyst in an exhaust passage, and the output value of the oxygen sensor is corrected. Correction coefficient changing means for changing the oxygen sensor correction coefficient by interruption processing at a stage where the coefficient change threshold is crossed is included.

  According to the above configuration, when the output value of the oxygen sensor crosses the correction coefficient change threshold value, the oxygen sensor correction coefficient is changed by interrupt processing at this stage. Since the event trigger for changing the oxygen sensor correction coefficient is set to a stage where the output value of the oxygen sensor crosses the threshold value in this way, in other cases, the calculation of the sub feedback correction amount is stopped. As a result, the processing load on the ECU can be reduced.

  At a high load, the change in the state of the catalyst becomes faster, so it is necessary to set the rich correction coefficient change threshold value to the rich side while setting the lean correction coefficient change threshold value to the lean side.

  Therefore, in one aspect, the vehicle further includes means for shifting the lean correction coefficient change threshold value to the lean side and shifting the rich correction coefficient change threshold value to the rich side as the load increases.

  The oxygen sensor has a low output due to aging. Therefore, it is necessary to monitor the maximum output of the oxygen sensor in the rich state, and to decrease the base (for example, low load) oxygen sensor correction coefficient change threshold accordingly.

  Therefore, in one aspect, the apparatus further includes means for changing the rich correction coefficient change threshold according to the maximum output value of the oxygen sensor in the rich state.

  When the OSC capability of the catalyst is reduced, the change from lean to rich and the change from rich to lean become faster. That is, the change in the state of the catalyst is accelerated. Therefore, it is necessary to place the rich correction coefficient change threshold on the rich side while setting the lean correction coefficient change threshold on the lean side.

  Therefore, in one aspect, when the OSC capability of the catalyst decreases, when the output of the oxygen sensor starts to change from the lean side to the rich side, the lean correction coefficient change threshold value is shifted to the lean side, while the oxygen sensor output is changed to the lean side. Further included is a means for shifting the rich correction coefficient change threshold value to the rich side when the output of the sensor starts to change from the rich side to the lean side.

  In the case where the OSC capability of the catalyst is large and small and the oxygen sensor correction coefficient is the same, if the catalyst OSC capability is small, the frequency of inversion of the rich state and the lean state of the catalyst increases, and air-fuel ratio hunting occurs. Therefore, when the OSC capability of the catalyst is reduced, the oxygen sensor correction coefficient needs to be reduced.

  Therefore, in one aspect, the correction coefficient changing means includes means for reducing the value of the oxygen sensor correction coefficient as the OSC capability of the catalyst decreases.

  For example, when the oxygen sensor is rich, lean and rich oxygen sensor correction factors are applied when the catalyst is rich and lean. For this reason, the catalyst gradually changes from the rich state to the lean state and from the lean state to the rich state. Therefore, if a certain amount of lean and rich is input immediately before the output of the oxygen sensor is reversed, the lean excessively rich and excessively rich immediately before the reverse. It becomes.

  Therefore, in a certain aspect, there is further included means for changing the oxygen sensor correction coefficient in accordance with the integrated air amount after the oxygen sensor correction coefficient is changed by the correction coefficient changing means.

  When the stoichiometric center of the catalyst is deviated, it is necessary to capture a learning value in order to correct the deviation.

  Therefore, in one aspect, the apparatus further includes means for setting a target of the oxygen sensor as the stoichiometric value of the catalyst and taking in a deviation amount as a learning value, and the correction coefficient changing means until the learning value is taken in. While the change of the oxygen sensor correction coefficient is prohibited, the change of the oxygen sensor correction coefficient by the correction coefficient changing means is permitted after the learning value has been taken in.

  According to the present invention, it is possible to provide a control device for an internal combustion engine that can reduce the processing load of the ECU.

1 is a diagram showing a schematic configuration of an engine to which an internal combustion engine control apparatus according to a first embodiment of the present invention is applied and an intake / exhaust system thereof; FIG. It is a block diagram which shows the control system of an engine. It is a timing chart concerning change of an oxygen sensor correction coefficient. It is a figure which shows the output state of the oxygen sensor before and behind a sub learning process. It is a figure for demonstrating schematically the control mechanism of the control apparatus of the internal combustion engine concerning the 2nd Embodiment of this invention. It is a figure which shows the structure of the map for changing the rich correction coefficient change threshold value utilized in the control apparatus of the internal combustion engine concerning the 3rd Embodiment of this invention. It is a figure for demonstrating schematically the control mechanism of the control apparatus of the internal combustion engine concerning the 4th Embodiment of this invention. It is a figure which shows the structure of the map for changing the oxygen sensor correction coefficient utilized in the control apparatus of the internal combustion engine concerning the 5th Embodiment of this invention. It is a figure for demonstrating schematically the control mechanism of the control apparatus of the internal combustion engine concerning the 6th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First embodiment]
In the present embodiment, a case where the control device for an internal heat engine according to the present invention is applied to a four-cylinder gasoline engine for an automobile will be described.

<Mechanical configuration>
FIG. 1 is a diagram showing a schematic configuration of an engine to which the control device for an internal combustion engine according to the first embodiment of the present invention is applied and an intake / exhaust system thereof. FIG. 1 shows only the configuration of one cylinder of the engine.

  In FIG. 1, reference numeral 1 is an engine. The engine 1 includes a piston 12 that forms a combustion chamber 11 and a crankshaft 13 that is an output shaft.

  The piston 12 is connected to the crankshaft 13 via a connecting rod 14, and the reciprocating motion of the piston 12 is converted into rotation of the crankshaft 13 by the connecting rod 14.

  A signal rotor 15 having a plurality of protrusions (teeth) 16 on the outer peripheral surface is attached to the crankshaft 13. A crank position sensor (engine speed sensor) 71 is disposed near the side of the signal rotor 15. The crank position sensor 71 is, for example, an electromagnetic pickup, and generates a pulsed signal (output pulse) corresponding to the protrusion 16 of the signal rotor 15 when the crankshaft 13 rotates.

  A water temperature sensor 72 for detecting the engine water temperature (cooling water temperature) is disposed in the cylinder block 17 of the engine 1.

  A spark plug 2 is disposed in the combustion chamber 11 of the engine 1. The ignition timing of the spark plug 2 is adjusted by the igniter 21. The igniter 21 is controlled by an engine ECU (hereinafter simply referred to as “ECU”) 6.

  An intake passage 3 and an exhaust passage 4 are connected to the combustion chamber 11 of the engine 1. An intake valve 31 is provided between the intake passage 3 and the combustion chamber 11, and the intake passage 3 and the combustion chamber 11 are communicated or blocked by opening and closing the intake valve 31. Further, an exhaust valve 41 is provided between the exhaust passage 4 and the combustion chamber 11, and the exhaust passage 4 and the combustion chamber 11 are communicated or blocked by opening and closing the exhaust valve 41. The opening / closing drive of the intake valve 31 and the exhaust valve 41 is performed by each rotation of the intake camshaft and the exhaust camshaft (both not shown) to which the rotation of the crankshaft 13 is transmitted.

  An air cleaner 32, a hot-wire air flow meter 73, an intake air temperature sensor 74 built in the air flow meter 73, and an electronically controlled throttle valve 33 that adjusts the intake air amount of the engine 1 are disposed in the intake passage 3. . The throttle valve 33 is driven by a throttle motor 34. The opening degree of the throttle valve 33 is detected by a throttle opening degree sensor 75.

  A three-way catalyst 42 is disposed in the exhaust passage 4 of the engine 1. The three-way catalyst 42 has an OSC function (oxygen storage function) for storing (occluding) oxygen. Even if the air-fuel ratio shifts from the stoichiometric air-fuel ratio to a certain extent by this OSC function, HC, CO And NOx can be purified. That is, when the air-fuel ratio of the engine 1 becomes lean and oxygen and NOx in the exhaust gas flowing into the three-way catalyst 42 increase, the three-way catalyst 42 occludes part of the oxygen, thereby reducing and purifying NOx. Promote. On the other hand, when the air-fuel ratio of the engine 1 becomes rich and the exhaust gas flowing into the three-way catalyst 42 contains a large amount of HC and CO, the three-way catalyst 42 releases the oxygen molecules stored therein, Oxygen molecules are given to these HC and CO to promote oxidation and purification.

  An air-fuel ratio sensor (A / F sensor) 76 is disposed in the exhaust passage 4 upstream of the three-way catalyst 42. For example, a limiting current type oxygen concentration sensor is applied to the air-fuel ratio sensor 76, and an output voltage corresponding to the air-fuel ratio is generated over a wide air-fuel ratio region.

An oxygen sensor (O ₂ sensor) 77 is disposed in the exhaust passage 4 on the downstream side of the three-way catalyst 42. As the oxygen sensor 77, for example, an electromotive force type (concentration cell type) oxygen concentration sensor is applied.

  Signals generated by the air-fuel ratio sensor 76 and the oxygen sensor 77 are each A / D converted and then input to the ECU 6.

  An injector 35 for fuel injection is disposed in the intake passage 3. Fuel of a predetermined pressure is supplied from the fuel tank to the injector 35 by a fuel pump, and the fuel is injected into the intake passage 3. This injected fuel is mixed with intake air to be mixed into the combustion chamber 11 of the engine 1. The air-fuel mixture (fuel + air) introduced into the combustion chamber 11 undergoes a compression stroke of the engine 1 and is then ignited by the spark plug 2 to burn and explode. The piston 12 is reciprocated by the combustion and explosion of the air-fuel mixture in the combustion chamber 11 to rotate the crankshaft 13.

<Engine control system configuration>
FIG. 2 is a block diagram showing an engine control system.

  With reference to FIG. 2, the operating state of the engine 1 is controlled by the ECU 6. The ECU 6 includes a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, a backup RAM 64, and the like.

  The ROM 62 stores various control programs, maps that are referred to when the various control programs are executed, and the like.

  The CPU 61 executes arithmetic processing based on various control programs and maps stored in the ROM 62.

  The RAM 63 is a memory that temporarily stores calculation results in the CPU 61, data input from each sensor, and the like.

  The backup RAM 64 is a nonvolatile memory that stores data to be saved when the engine 1 is stopped.

  The ROM 62, CPU 61, RAM 63, and backup RAM 64 are connected to each other via a bus 67, and are also connected to an external input circuit 65 and an external output circuit 66.

  In addition to the crank position sensor 71, water temperature sensor 72, air flow meter 73, intake air temperature sensor 74, throttle opening sensor 75, air-fuel ratio sensor 76, oxygen sensor 77, the external input circuit 65 includes an accelerator opening sensor 78, A cam angle sensor 79, a knock sensor 7A, and the like are connected. On the other hand, a throttle motor 34 for driving the throttle valve 33, the injector 35, the igniter 21 and the like are connected to the external output circuit 66.

  As described above, the crank position sensor 71 is disposed in the vicinity of the crankshaft 13 and detects the rotation angle and rotation speed of the crankshaft 13.

  The water temperature sensor 72 detects the temperature of the cooling water flowing in the water jacket 17a (see FIG. 1) formed in the cylinder block 17, and transmits the cooling water temperature signal to the ECU 6.

  The air flow meter 73 detects the intake air amount and transmits the intake air amount signal to the ECU 6.

  The intake air temperature sensor 74 is provided integrally with the air flow meter 73, detects the intake air temperature, and transmits the intake air temperature signal to the ECU 6.

  The throttle opening sensor 75 detects the opening of the throttle valve 33 and transmits the throttle opening signal to the ECU 6.

  The air-fuel ratio sensor 76 generates an output voltage corresponding to the air-fuel ratio of the exhaust discharged from the combustion chamber 11 (the exhaust on the upstream side of the three-way catalyst 42), and transmits the output voltage signal to the ECU 6.

  The oxygen sensor 77 generates an output voltage corresponding to the oxygen concentration of the exhaust on the downstream side of the three-way catalyst 42 and transmits the output voltage signal to the ECU 6.

  The accelerator opening sensor 78 detects the opening (operation amount) of the accelerator pedal operated by the driver, and transmits the opening signal to the engine ECU 6.

  The cam angle sensor 79 is disposed in the vicinity of the intake camshaft, and is used as a cylinder discrimination sensor, for example, by outputting a pulse signal corresponding to the compression top dead center of the first cylinder. That is, the cam angle sensor 79 outputs a pulse signal for each rotation of the intake camshaft. As an example of a cam angle detection method using this cam angle sensor, external teeth are formed at one location on the outer peripheral surface of the rotor that rotates integrally with the intake camshaft, and the external teeth are opposed to each other by an electromagnetic pickup. A cam angle sensor 79 is arranged, and when the external teeth pass near the cam angle sensor 79 as the intake cam shaft rotates, the cam angle sensor 79 generates an output pulse. Since this rotor rotates at half the rotational speed of the crankshaft 13, an output pulse is generated every time the crankshaft 13 rotates 720 °. In other words, an output pulse is generated each time a specific cylinder reaches the same stroke (for example, when the first cylinder reaches compression top dead center).

  The knock sensor 7A is a vibration type sensor that detects vibrations of the engine transmitted to the cylinder block 17 by a piezoelectric element type (piezo element type) or an electromagnetic type (magnet and coil).

  Then, the ECU 6 performs various controls of the engine 1 based on the detection signals of the various sensors described above. For example, the oxygen concentration in the exhaust gas is calculated based on the outputs of the air-fuel ratio sensor 76 and the oxygen sensor 77 arranged in the exhaust passage 4 of the engine 1, and the actual air-fuel ratio obtained from the calculated oxygen concentration is the target air-fuel ratio. Air-fuel ratio feedback control is performed to control the fuel injection amount injected from the injector 35 into the intake passage 3 so as to coincide with the fuel ratio (for example, the theoretical air-fuel ratio).

<Processing contents of control>
FIG. 3 is a timing chart for changing the oxygen sensor correction coefficient.

As shown in FIG. 3A, when the output voltage value of the input oxygen sensor 77 crosses the lean correction coefficient change threshold value L _TH toward the rich side, the ECU 6 takes this as an opportunity to switch to FIG. As shown in FIG. 3B, the value of the interrupt event flag is switched from “0” to “1”, and as shown in FIG. 3C, the oxygen sensor correction coefficient K is changed from “α” to “α” by interruption processing. Change to “β”, which is shifted to the lean side. When the change of the oxygen sensor correction coefficient K is completed, the ECU 6 returns the value of the interrupt event flag from “1” to “0”.

Then, as shown in FIG. 3A, when the output voltage value of the input oxygen sensor 77 crosses the rich correction coefficient change threshold value R _TH toward the lean side, the ECU 6 uses this as a trigger. As shown in FIG. 3 (B), the value of the interrupt event flag is switched from “0” to “1”, and as shown in FIG. 3C, the oxygen sensor correction coefficient K is changed from “β” to “ Change to “α” shifted to a richer side than “β”. When the change of the oxygen sensor correction coefficient K is completed, the ECU 6 returns the value of the interrupt event flag from “1” to “0”.

In the present embodiment, when the output voltage value of the oxygen sensor 77 crosses the correction coefficient change thresholds L _{TH and} R _TH , the oxygen sensor correction coefficient K is changed from “α” to “β” by interruption processing. In order to enable the correction coefficient changing process to change from “β” to “α”, the sub-learning process is performed by the ECU 6 in the previous stage.

  In the sub-learning process, the ECU 6 sets the target of the oxygen sensor 77 as the stoichiometric value of the three-way catalyst 42, and takes in the deviation as a sub-learning value. For example, when the stoichiometric center of the three-way catalyst 42 is shifted to the rich side, as shown in FIG. 4A, the output voltage signal of the oxygen sensor 77 is input to the ECU 6 in a state where the output voltage signal is shifted to the lean side. Is done. Then, the rich state of the three-way catalyst 42 is shortened, and the ECU 6 determines that the fuel rich state is desired. Therefore, by taking the sub-learning value into the ECU 6 in the sub-learning process, even if the stoichiometric center of the three-way catalyst 42 is deviated as described above, the deviation of the center is as shown in FIG. Since the correction is made with the learning value, the phenomenon shown in FIG. 4A does not occur. Therefore, until the sub-learning value is taken into the ECU 6, the change of the oxygen sensor correction coefficient K by the correction coefficient changing process is prohibited, while the oxygen sensor by the correction coefficient changing process is completed after the sub-learning value has been taken in. The change of the correction coefficient K is permitted.

  Even after the shift to the correction coefficient changing process, the sub-learning value is reflected in the injection amount.

<Action and effect>
According to the present embodiment, the following operations and effects are achieved.

When the output voltage value of the oxygen sensor 77 crosses the correction coefficient change threshold values L _{TH and} R _TH , the oxygen sensor correction coefficient K is changed from “α” to “β” and from “β” to “α” by interrupt processing at this stage. Changed to Since the event trigger for changing the oxygen sensor correction coefficient K is in a stage where the output voltage value of the oxygen sensor 77 crosses the threshold values L _{TH and} R _TH in this way, in other cases, the sub feedback correction amount Calculation is stopped. As a result, the processing load on the ECU 6 can be reduced.

Further, when the output voltage value of the sensor 77 crosses the correction coefficient change thresholds L _{TH and} R _TH , the oxygen sensor correction coefficient K is changed from “α” to “β” and from “β” to “α” by interruption processing. In the previous stage of the correction coefficient changing process to be changed, a sub-learning value is acquired by performing a sub-learning process in which the target of the oxygen sensor 77 is set as the stoichiometric value of the three-way catalyst 42 and the deviation is acquired as a sub-learning value Until then, the change of the oxygen sensor correction coefficient K by the correction coefficient changing process is prohibited. On the other hand, the change of the oxygen sensor correction coefficient K by the correction coefficient change process is permitted after the sub-learning value has been captured. Therefore, the target center shift of the oxygen sensor 77 does not occur after the shift to the correction coefficient changing process.

[Second Embodiment]
FIG. 5 is a diagram for schematically explaining the control mechanism of the control apparatus for an internal combustion engine according to the second embodiment of the present invention.

Referring to FIG. 5, the feature of the present embodiment is that the lean correction coefficient change threshold L _TH is shifted to the lean side as the engine load increases, while the rich correction coefficient change threshold R _TH is rich. The other structure is the same as that of the first embodiment.

Here, the engine load is low, the lean correction coefficient change threshold value L _TH is at the low load threshold value L _TH -L, and the rich correction change threshold value R _TH is low. The description will be made on the assumption that the engine load is gradually increased as the vehicle travels at the threshold value R _TH -H.

When the output voltage of the oxygen sensor 77 starts to change from lean to rich, the ECU 6 takes in the intake air amount ga (g / sec) detected by the air flow meter 73, and uses the taken in intake air amount ga as a parameter. The high load threshold value L _TH -H of the lean correction coefficient change threshold value L _TH is obtained with reference to the map shown in FIG. At this time, the map shown in FIG. 5B is configured such that the lean correction coefficient change threshold value L _TH decreases as the intake air amount ga increases, that is, as the load increases, so a new setting is made. The high load threshold value L _TH -H to be shifted is shifted to the lean side as shown in FIG.

When the output voltage of the oxygen sensor 77 starts to change from rich to lean, the ECU 6 takes in the intake air amount ga (g / sec) detected by the air flow meter 73, and the acquired intake air amount ga is a parameter. Then, the high load threshold value R _TH -H of the rich correction coefficient change threshold value R _TH is obtained with reference to the map shown in FIG. At this time, the map shown in FIG. 5C is configured so that the rich correction coefficient change threshold L _TH increases as the intake air amount ga increases, that is, as the load increases. As shown in FIG. 5A, the high load threshold value L _TH -H is shifted to the rich side.

In other words, when the output voltage of the oxygen sensor 77 starts to change from lean to rich and from rich to lean, the state of the three-way catalyst 42 starts to change from lean to rich and from rich to lean. Correction coefficient threshold values L _{TH and} R _TH for changing the coefficient K to lean and rich are set. Specifically, at a high load, the state of the three-way catalyst 42 also changes quickly, so the lean correction coefficient change threshold value L _TH is set on the lean side, while the rich correction coefficient change threshold value R _TH is set on the rich side. At.

  According to this embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects can be achieved.

At a high engine load, the state of the three-way catalyst 42 also changes quickly. As the engine load increases, the lean correction coefficient change threshold value L _TH is shifted to the lean side, while the rich correction coefficient change threshold value R _TH. Is shifted to the rich side, so that no hunting occurs in the output of the oxygen sensor 77.

[Third embodiment]
FIG. 6 is a diagram showing the structure of a map for changing the rich correction coefficient change threshold used in the control apparatus for an internal combustion engine according to the third embodiment of the present invention.

Referring to FIG. 6, the feature of the present embodiment is that the rich correction coefficient change threshold value R _TH is changed in accordance with the maximum output voltage value of the oxygen sensor 77 in the rich state. This is the same as the first embodiment.

The map shown in FIG. 6 is configured such that the rich correction coefficient change threshold value R _TH decreases as the maximum output voltage value of the oxygen sensor 77 decreases.

  According to this embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects can be achieved.

The oxygen sensor 77 has a low output due to aging. For example, a voltage that is 0.9V in the rich state is only 0.7V. Therefore, in the present embodiment, the ECU 6 detects the maximum output voltage of the oxygen sensor 77 in the rich state, and performs the rich correction with reference to the map shown in FIG. 6 using the detected maximum output voltage of the oxygen sensor 77 as a parameter. Since the coefficient change threshold value R _TH is obtained, the base (for example, low load) rich correction coefficient change threshold value R _TH is lowered. Therefore, it becomes possible to cope with the aging deterioration of the oxygen sensor 77.

[Fourth embodiment]
FIG. 7 is a diagram for schematically explaining the control mechanism of the control device for the internal combustion engine according to the fourth embodiment of the present invention.

Referring to FIG. 7, the feature of the present embodiment is that when the OSC capability of the three-way catalyst 42 is lowered, the lean correction coefficient is changed when the output voltage of the oxygen sensor 77 starts to change from the lean side to the rich side. While the threshold value L _TH is shifted to the lean side, the rich correction coefficient change threshold value R _TH is shifted to the rich side when the output voltage of the oxygen sensor 77 starts to change from the rich side to the lean side. The configuration of is the same as that of the first embodiment.

When the output voltage of the oxygen sensor 77 starts to change from lean to rich when the OSC capacity of the three-way catalyst 42 is reduced, the ECU 6 uses the OSC capacity of the three-way catalyst 42 at this time as a parameter, as a parameter. The OCS ability small threshold value L _TH -S of the lean correction coefficient change threshold value L _TH is obtained with reference to the map shown in B). At this time, the map shown in FIG. 7B is configured such that the lean correction coefficient change threshold value L _TH decreases as the OSC capability of the three-way catalyst 42 decreases. As shown in FIG. 7A, the small threshold value L _TH -S shifts to the lean side and becomes lower than the OSC capacity large threshold value L _TH -B.

When the output voltage of the oxygen sensor 77 begins to change from rich to lean, the ECU 6 performs rich correction with reference to the map shown in FIG. 7C, using the OSC capability of the three-way catalyst 42 as a parameter. The OSC capability small threshold value R _TH -S of the coefficient change threshold value R _TH is obtained. At this time, the map shown in FIG. 7C is configured such that the rich correction coefficient change threshold L _TH increases as the OSC capacity of the three-way catalyst 42 decreases, so the newly set OCS capacity is set. As shown in FIG. 7A, the small threshold value L _TH -S shifts to the rich side and becomes higher than the large capacity threshold value L _TH -B.

  According to this embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects can be achieved.

When the OSC capability of the three-way catalyst 42 is reduced, the change from lean to rich and from rich to lean is accelerated, but when the OSC capability of the three-way catalyst 42 is reduced, the output voltage of the oxygen sensor 77 is rich from the lean side. The lean correction coefficient change threshold value L _TH is shifted to the lean side when it starts to change to the lean side, while the rich correction coefficient change threshold value R when the output voltage of the oxygen sensor 77 starts to change from the rich side to the lean side. _{Since TH} is shifted to the rich side, hunting does not occur in the output of the oxygen sensor 77.

[Fifth embodiment]
FIG. 8 is a diagram showing the structure of a map for changing the oxygen sensor correction coefficient used in the control apparatus for an internal combustion engine according to the fifth embodiment of the present invention.

Referring to FIG. 8, the feature of the present embodiment is that, in the correction coefficient changing process, the values of oxygen sensor correction coefficients K _L and K _R are reduced as the OSC capability of the three-way catalyst 42 decreases. There are other configurations similar to those of the first embodiment.

When the input output voltage value of the oxygen sensor 77 crosses the lean correction coefficient change threshold value L _TH toward the rich side, the ECU 6 uses this as a trigger to change the value of the interrupt event flag from “0” to “ switch to 1 ", the OSC capability of the three-way catalyst 42 at this time as Paremeta, obtaining the lean oxygen sensor correction coefficient K _L with reference to the map shown in FIG. 8 (a). In this case, the map shown in FIG. 8 (A), since the three-way lean oxygen sensor correction coefficient K _L as ОCS capacity is lower in the catalyst 42 is configured to be smaller, the lean oxygen sensor correction is newly set The coefficient K _L is set smaller as the OCS capability of the three-way catalyst 42 becomes lower.

Then, when the output voltage value of the input oxygen sensor 77 crosses the rich correction coefficient change threshold value R _TH toward the lean side, the ECU 6 sets the value of the interrupt event flag to “0” as a trigger. The rich oxygen sensor correction coefficient K _R is obtained with reference to the map shown in FIG. 8B using the OSC capability of the three-way catalyst 42 as a parameter. In this case, the map shown in FIG. 8 (B), so as ОCS ability of the three-way catalyst 42 becomes lower rich oxygen sensor correction factor K _R is configured to be smaller, the lean oxygen sensor correction is newly set The coefficient K _R is set smaller as the OCS capability of the three-way catalyst 42 becomes lower.

  According to this embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects can be achieved.

In the case where the OSC capacity of the three-way catalyst 42 is large and small and the oxygen sensor correction coefficients K _L and K _R are the same, if the OSC capacity of the three-way catalyst 42 is small, the rich state and the lean state of the three-way catalyst 42 are reversed. This increases the frequency of air-fuel ratio hunting. Therefore, in the correction coefficient changing process, the values of the oxygen sensor correction coefficients K _L and K _R are made smaller as the OSC capability of the three-way catalyst 42 decreases, so that air-fuel ratio hunting does not occur. .

[Sixth Embodiment]
FIG. 9 is a diagram for schematically explaining the control mechanism of the control apparatus for an internal combustion engine according to the sixth embodiment of the present invention.

Referring to FIG. 9, the feature of the present embodiment is that oxygen sensor correction coefficients K _L and K _R are changed in accordance with the integrated air amount after the oxygen sensor correction coefficient is changed in the above correction coefficient changing process, and The upper limit guard value G _MAX and the lower limit guard value G _MIN are set so that the oxygen sensor correction coefficients K _L and K _R after the change do not become “1”, and other configurations are the first embodiment. It is the same.

As shown in FIG. 9A, when the output voltage value of the input oxygen sensor 77 crosses the lean correction coefficient change threshold value L _TH toward the rich side, the ECU 6 takes this as an opportunity to switch to FIG. As shown in FIG. 3B, the value of the interrupt event flag is switched from “0” to “1”, and the oxygen sensor correction coefficient K is shifted to the lean side by interruption processing as shown in FIG. Thereafter, ECU 6 is a cumulative air amount as Paremeta obtains a lean oxygen sensor correction coefficient K _L with reference to the map shown in FIG. 9 (E). At this time, the map shown in FIG. 9E is configured such that the lean oxygen sensor correction coefficient K _L increases as the integrated air amount increases, so the newly set lean oxygen sensor correction coefficient K _L is As shown in FIGS. 9C and 9D, as the integrated air amount increases, the upper limit guard value G _MAX is set to be larger.

Then, as shown in FIG. 9A, when the output voltage value of the input oxygen sensor 77 crosses the rich correction coefficient change threshold value R _TH toward the lean side, the ECU 6 uses this as a trigger. As shown in FIG. 9B, the value of the interrupt event flag is switched from “0” to “1”, and as shown in FIG. 3D, the oxygen sensor correction coefficient K is shifted to the rich side by interrupt processing. . Thereafter, the ECU 6 obtains the lean oxygen sensor correction coefficient K _R with reference to the map shown in FIG. 9F using the integrated air amount as a parameter. In this case, the map shown in FIG. 9 (F), since the lean oxygen sensor correction factor K _R as the integrated air amount increases is configured to be smaller, the lean oxygen sensor correction factor K _R which is newly set As shown in FIGS. 9C and 9D, the lower limit guard value _GMIN is set as a lower limit as the integrated air amount increases.

  According to this embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects can be achieved.

For example, when the oxygen sensor 77 is rich, the three-way catalyst 42 is in the rich state and the lean state, and the lean and rich oxygen sensor correction coefficients K _L and K _R are applied. The lean state and the lean state change to the rich state. Therefore, if a certain amount of lean and rich is input until just before the output of the oxygen sensor 77 is inverted, the lean and rich will be excessive immediately before the inversion. Therefore, in the present embodiment, the oxygen sensor correction coefficients K _L and K _R are changed in accordance with the integrated air amount after the oxygen sensor correction coefficient is changed in the correction coefficient changing process. Can be avoided.

In addition, since the upper limit guard value G _MAX and the lower limit guard value G _MIN are set so that the oxygen sensor correction coefficients K _L and K _R after the change do not become “1”, the state of the three-way catalyst 42 is also lean. It is possible to reverse the rich.

  The present invention is not limited to the above-described embodiment, and various design changes and modifications can be made within the scope of the appended claims.

4 Exhaust passage 42 Three-way catalyst 6 ECU
77 Oxygen sensor

Claims (7)

A control device for an internal combustion engine in which an oxygen sensor is provided downstream of the catalyst in the exhaust passage,
A control apparatus for an internal combustion engine, comprising: correction coefficient changing means for changing an oxygen sensor correction coefficient by an interruption process when an output value of the oxygen sensor crosses a threshold value. The control apparatus for an internal combustion engine according to claim 1,
A control for an internal combustion engine, further comprising means for shifting the lean correction coefficient change threshold value to the lean side as the load increases, while shifting the rich correction coefficient change threshold value to the rich side apparatus. The control apparatus for an internal combustion engine according to claim 1,
The control apparatus for an internal combustion engine, further comprising means for changing a rich correction coefficient change threshold value in accordance with a maximum output value of the oxygen sensor in a rich state. The control apparatus for an internal combustion engine according to claim 1,
When the OSC capability of the catalyst is reduced, when the output of the oxygen sensor starts to change from the lean side to the rich side, the lean correction coefficient change threshold is shifted to the lean side, while the output of the oxygen sensor is on the rich side. A control device for an internal combustion engine, further comprising means for shifting the rich correction coefficient change threshold value to the rich side when starting to change from the lean side to the lean side. The control apparatus for an internal combustion engine according to claim 1,
The control apparatus for an internal combustion engine, wherein the correction coefficient changing means includes means for reducing the value of the oxygen sensor correction coefficient as the OSC capability of the catalyst decreases. The control apparatus for an internal combustion engine according to claim 1,
The control apparatus for an internal combustion engine, further comprising means for changing the oxygen sensor correction coefficient in accordance with the integrated air amount after the oxygen sensor correction coefficient is changed by the correction coefficient changing means. The control apparatus for an internal combustion engine according to claim 1,
A means for setting the target of the oxygen sensor as the stoichiometry of the catalyst and taking in the amount of deviation as a learning value;
Until the learning value is taken in, the change of the oxygen sensor correction coefficient by the correction coefficient changing means is prohibited, while the change of the oxygen sensor correction coefficient by the correction coefficient changing means is allowed after the learning value has been taken in. A control device for an internal combustion engine.

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