JP2020094573A - Control device of internal combustion engine and control method of internal combustion engine - Google Patents

Abstract

To provide a control device of an internal combustion engine and a control method of the internal combustion engine capable of preventing an air fuel ratio at a downstream side of a catalyst from becoming excessively rich or leen.SOLUTION: A control device of an internal combustion engine includes a detection portion, a determination portion, and an air-fuel ratio control portion. The detection portion detects a state of an air-fuel ratio at a downstream side of a catalyst in an exhaust passage of the internal combustion engine in which the catalyst is disposed. The determination portion determines a lean change state in which the change of the air-fuel ratio at the downstream side of the catalyst to a lean direction is continued, or a rich change state in which the change to a rich direction is continued, on the basis of the state of the air-fuel ratio detected by the detection portion. The air-fuel ratio control portion controls the air-fuel ratio of an air-fuel mixture supplied to the internal combustion engine on the basis of a result of the determination by the determination portion.SELECTED DRAWING: Figure 1

Description

The present invention relates to an internal combustion engine control device and an internal combustion engine control method.

Conventionally, various technologies have been proposed in which a catalyst is disposed in an exhaust passage of an internal combustion engine to purify exhaust gas (see, for example, Patent Document 1).

JP-A-5-141299

By the way, in the above-mentioned internal combustion engine, in order to efficiently purify exhaust gas in the catalyst, for example, an air-fuel ratio sensor is provided on the downstream side of the catalyst, and the air-fuel ratio becomes close to the theoretical air-fuel ratio based on the output of the air-fuel ratio sensor. Are controlled. Specifically, when the output of the air-fuel ratio sensor indicates lean, the air-fuel ratio is corrected to the rich side, while when the output of the air-fuel ratio sensor indicates rich, the air-fuel ratio is corrected to the lean side.

However, for example, if the air-fuel ratio is corrected to the rich side until just before the output of the air-fuel ratio sensor is switched from lean to rich, the air-fuel ratio may become excessively rich and the purification performance of the catalyst may deteriorate. Conversely, if the air-fuel ratio is corrected to the lean side until just before the output of the air-fuel ratio sensor is switched from rich to lean, the air-fuel ratio may become excessively lean and the purification performance of the catalyst may deteriorate.

The present invention has been made in view of the above, and provides an internal combustion engine control device and an internal combustion engine control method capable of suppressing the air-fuel ratio on the downstream side of a catalyst from becoming excessively rich or lean. The purpose is to do.

In order to solve the above problems and achieve the object, the present invention provides a control device for an internal combustion engine, which includes a detection unit, a determination unit, and an air-fuel ratio control unit. The detection unit detects the state of the air-fuel ratio on the downstream side of the catalyst in the exhaust passage of the internal combustion engine in which the catalyst is arranged. The determination unit, based on the state of the air-fuel ratio detected by the detection unit, the lean change state in which the air-fuel ratio on the downstream side of the catalyst continues to change in the lean direction, or the change in the rich direction continues. It is determined whether it is in the rich change state. The air-fuel ratio control unit controls the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the determination result of the determination unit.

According to the present invention, it is possible to prevent the air-fuel ratio on the downstream side of the catalyst from becoming excessively rich or lean.

FIG. 1 is a diagram showing an outline of a control method for an internal combustion engine according to an embodiment. FIG. 2 is a schematic diagram showing a configuration example of a control system including the control device according to the embodiment. FIG. 3 is a block diagram showing a configuration example of a control system including a control device. FIG. 4 is a diagram showing the correction value information. FIG. 5 is a diagram showing correction value information. FIG. 6 is a diagram showing the correction value information. FIG. 7 is a diagram showing correction value information. FIG. 8 is a time chart explaining the processing of the air-fuel ratio control by the control device. FIG. 9 is a flowchart showing a processing procedure executed by the control device.

Hereinafter, an embodiment of an internal combustion engine control device and an internal combustion engine control method disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

<1. Outline of control method of internal combustion engine>
Hereinafter, first, an outline of a control method of the internal combustion engine executed by the control device will be described with reference to FIG. FIG. 1 is a diagram showing an outline of a control method for an internal combustion engine according to an embodiment.

The control method of the internal combustion engine according to the present embodiment is executed by the control device 10, for example. The control device 10 can perform air-fuel ratio control of the internal combustion engine 40 and the like.

The internal combustion engine 40 is, for example, an engine of an automobile that uses gasoline as a fuel. Hereinafter, the internal combustion engine 40 may be referred to as the “engine 40”. A catalyst 80 for purifying exhaust gas is arranged in the exhaust passage 70 of the engine 40.

The catalyst 80 has the ability to store oxygen, reduces oxides such as nitrogen oxides (NOx) contained in exhaust gas, and stores oxygen generated by the reduction. Further, the catalyst 80 oxidizes hydrocarbon (HC), carbon monoxide (CO) and the like contained in the exhaust gas by releasing stored oxygen. In this way, the catalyst 80 occludes/releases oxygen and reduces/oxidizes the components contained in the exhaust gas, thereby purifying the exhaust gas.

In order to efficiently purify exhaust gas in the catalyst 80, the control device 10 is provided with, for example, an air-fuel ratio sensor 42 on the downstream side of the catalyst 80, and the air-fuel ratio becomes close to the theoretical air-fuel ratio based on the output of the air-fuel ratio sensor 42. The air-fuel ratio control is performed as follows.

For example, the control device 10 corrects the air-fuel ratio to the rich side when the output of the air-fuel ratio sensor 42 indicates lean, and corrects the air-fuel ratio to the lean side when the output of the air-fuel ratio sensor 42 indicates rich. I have to.

Further, since the catalyst 80 discharges nitrogen oxides (NOx) when the air-fuel ratio becomes leaner, the control device 10 reduces the air-fuel ratio when the output of the air-fuel ratio sensor 42 falls below a predetermined threshold value. The air-fuel ratio control can be performed using the offset correction value that further corrects to the rich side.

By the way, if the control device 10 corrects the air-fuel ratio to the rich side until just before the output of the air-fuel ratio sensor 42 switches from lean to rich, the air-fuel ratio becomes excessively rich and the purification performance of the catalyst deteriorates. There is a risk. Further, when the offset correction value described above is reflected in the air-fuel ratio control until the output of the air-fuel ratio sensor 42 becomes equal to or higher than the predetermined threshold value, the offset correction value is further corrected to the rich side, so that the air-fuel ratio is further rich side. May be.

On the contrary, when the control device 10 corrects the air-fuel ratio to the lean side until the output of the air-fuel ratio sensor 42 is switched from rich to lean, the air-fuel ratio becomes excessively lean and the purification performance of the catalyst deteriorates. There is a risk that Further, unless the offset correction value is reflected in the air-fuel ratio control until the output of the air-fuel ratio sensor 42 falls below a predetermined threshold, the air-fuel ratio may become even leaner.

Therefore, in this embodiment, the air-fuel ratio on the downstream side of the catalyst 80 is prevented from becoming excessively rich or lean.

Specifically, the control device 10 first detects the state of the air-fuel ratio on the downstream side of the catalyst 80 (that is, the value of the air-fuel ratio, or the state where the air-fuel ratio is rich or lean) (step S1). The control device 10 is in a lean change state in which the air-fuel ratio on the downstream side of the catalyst 80 continues to change in the lean direction, or the change in the rich direction continues, based on the detected air-fuel ratio state. It is determined whether the rich change state is set (step S2). Then, the control device 10 performs the air-fuel ratio control based on the determination result (step S3).

Specifically, when it is determined that the air-fuel ratio on the downstream side of the catalyst 80 is in the lean change state, that is, when the change in the lean direction continues, it is estimated that the change in the lean direction continues as it is. Therefore, the control device 10 can reflect, for example, the predetermined addition value in the fuel correction value of the air-fuel ratio control based on the determination result. As a result, for example, it becomes possible to reflect the predetermined addition value in addition to the offset correction value described above in the fuel correction value, so that the air-fuel ratio is largely corrected to the rich side, and as a result, the air on the downstream side of the catalyst 80 is reduced. It is possible to prevent the fuel ratio from becoming excessively lean.

On the other hand, when it is determined that the air-fuel ratio on the downstream side of the catalyst 80 is in the rich change state, that is, when the change in the rich direction continues, it is estimated that the change in the rich direction continues. Therefore, the control device 10 can reflect the predetermined subtraction value in the fuel correction value of the air-fuel ratio control based on the determination result. Accordingly, for example, when the offset correction value is reflected in the fuel correction value, the predetermined subtraction value is reflected, so that the correction of the air-fuel ratio to the rich side can be moderated, and as a result, It is possible to prevent the air-fuel ratio on the downstream side of the catalyst 80 from swinging excessively to the rich side.

As described above, in the present embodiment, it is determined whether the air-fuel ratio on the downstream side of the catalyst is in the lean change state or the rich change state, and the air-fuel ratio control is performed based on the determination result. It is possible to prevent the air-fuel ratio on the downstream side of 80 from becoming excessively rich or lean.

<2. Configuration of control system including control device>
Next, the configuration of the control system including the control device 10 according to the present embodiment will be described using FIG. 2 and subsequent figures. FIG. 2 is a schematic diagram showing a configuration example of the control system 1 including the control device 10 according to the embodiment.

As shown in FIG. 2, in the control system 1, the control device 10 performs various controls such as air-fuel ratio control.

In the engine 40, an intake pipe 60 and an exhaust passage 70 are connected to a cylinder (cylinder) 50 via an intake valve 61 and an exhaust valve 71. The intake pipe 60 is provided with a throttle 62 for adjusting the intake air amount and an injector 63 for injecting fuel into the intake pipe 60. An air cleaner 64 is provided on the upstream side of the intake pipe 60, and the air (intake air) that has passed through the air cleaner 64 flows in.

An ignition coil 51 and an ignition plug 52 are provided in the cylinder 50, and a piston 53 is provided in the cylinder 50. The catalyst 80 described above is disposed in the exhaust passage 70.

In the exhaust passage 70, air-fuel ratio sensors 41 and 42 are provided on the upstream side and the downstream side of the catalyst 80, respectively. The air-fuel ratio sensors 41 and 42 are both O2 sensors. As a result, the air-fuel ratios on the upstream side and the downstream side of the catalyst 80 can be detected with a simple configuration. Either one or both of the air-fuel ratio sensors 41 and 42 may be other types of sensors such as an A/F sensor. Further, hereinafter, the air-fuel ratio sensor 41 may be referred to as an "upstream air-fuel ratio sensor 41" and the air-fuel ratio sensor 42 may be referred to as a "downstream air-fuel ratio sensor 42".

FIG. 3 is a block diagram showing a configuration example of the control system 1 including the control device 10. Note that in the block diagram of FIG. 3, only the components necessary for explaining the features of the present embodiment are represented by functional blocks, and the description of general components is omitted.

In other words, each component shown in the block diagram of FIG. 3 is functionally conceptual, and does not necessarily have to be physically configured as shown. For example, the specific form of distribution/integration of each functional block is not limited to that shown in the figure, and all or part of the functional block may be functionally or physically distributed in arbitrary units according to various loads and usage conditions. -It is possible to integrate and configure.

As shown in FIG. 3, the control system 1 includes the above-described control device 10, an engine 40, an upstream air-fuel ratio sensor 41, a downstream air-fuel ratio sensor 42, and an in-vehicle sensor group 100.

The upstream side air-fuel ratio sensor 41 detects the state of the air-fuel ratio on the upstream side of the catalyst 80, and outputs a signal indicating the detected state of the air-fuel ratio to the control device 10. The downstream air-fuel ratio sensor 42 detects the state of the air-fuel ratio on the downstream side of the catalyst 80 and outputs a signal indicating the detected state of the air-fuel ratio to the control device 10.

The in-vehicle sensor group 100 includes, for example, various sensors that detect information necessary for air-fuel ratio control and the like. For example, the vehicle-mounted sensor group 100 includes a rotation speed sensor that detects the engine speed, an intake air amount sensor that detects the intake air amount of the engine 40, a throttle opening sensor that detects the throttle opening of the throttle valve, and the like. However, the present invention is not limited to these.

The control device 10 includes a control unit 20 and a storage unit 30. The storage unit 30 is a storage unit configured by a storage device such as a non-volatile memory or a hard disk drive. The storage unit 30 stores a first rich counter 31, a second rich counter 32, a first lean counter 33, a second lean counter 34, an air-fuel ratio map 35, correction value information 36, various programs and setting data.

The first rich counter 31 is a counter that counts the number of times that it is detected that the state of the air-fuel ratio on the downstream side of the catalyst 80 has changed to the lean direction. As described above, when the change in the lean direction continues, the air-fuel ratio is corrected to the rich side using the predetermined addition value. However, the first rich counter 31 calculates the predetermined addition value to be corrected to the rich side. Used when

Specifically, for example, the output difference Vr between the current state and the previous state of the output of the downstream side air-fuel ratio sensor 42 detected by the detection unit 21 of the control unit 20 described later indicates a change in the lean direction. When the value is in the value state, the air-fuel ratio is changing in the lean direction, so the first rich counter 31 is incremented.

The second rich counter 32 is a counter that counts the number of times that it is detected that the state of the air-fuel ratio on the downstream side of the catalyst 80 has changed rapidly in the lean direction.

Specifically, for example, when the output difference Vr of the downstream side air-fuel ratio sensor 42 is a negative value and the output difference Vr is equal to or less than the first threshold value, the downstream side air-fuel ratio of the catalyst 80 is in a lean change state. This is the “second lean change state” in which the change in the lean direction is larger. In such a case, since the state of the air-fuel ratio is changing rapidly in the lean direction, the second rich counter 32 is counted up.

The first lean counter 33 is a counter that counts the number of times it is detected that the state of the air-fuel ratio on the downstream side of the catalyst 80 has changed to the rich direction. As described above, when the change in the rich direction continues, the air-fuel ratio is corrected to the lean side using the predetermined subtraction value, but the first lean counter 33 calculates the predetermined subtraction value to be corrected to the lean side. Used when

Specifically, for example, when the output difference Vr of the downstream side air-fuel ratio sensor 42 is in a positive value state indicating a change in the rich direction, the state of the air-fuel ratio is changing in the rich direction. The lean counter 33 is counted up.

The second lean counter 34 is a counter that counts the number of times that it is detected that the output difference Vr of the downstream side air-fuel ratio sensor 42 has changed rapidly in the rich direction.

Specifically, for example, when the output difference Vr of the downstream side air-fuel ratio sensor 42 is a positive value and the output difference Vr is not less than the second threshold value, the downstream side air-fuel ratio of the catalyst 80 is in a rich change state. This is the “second rich change state” in which the change in the rich direction is larger. In such a case, the second lean counter 34 is incremented because the air-fuel ratio is changing rapidly in the rich direction.

The air-fuel ratio map 35 is a map in which a target air-fuel ratio is set according to the operating state of the engine 40 such as the engine speed.

The correction value information 36 includes information on the correction of the air-fuel ratio using the above-described first and second rich counters 31 and 32 and the first and second lean counters 33 and 34, respectively. The correction value information 36 will be described with reference to FIGS.

FIG. 4 is a diagram showing correction value information 36 regarding correction using the first rich counter 31. As shown in FIG. 4, the first addition value is an example of a predetermined addition value that is corrected to the rich side when the air-fuel ratio is in the lean change state. The first addition value is set to increase as the first rich counter 31 increases. That is, the first addition value is set so that the air-fuel ratio is corrected to the rich side as the first rich counter 31 increases.

FIG. 5 is a diagram showing correction value information 36 regarding correction using the second rich counter 32. As shown in FIG. 5, the second addition value is an example of a second predetermined addition value that is corrected to the rich side when the air-fuel ratio is in the second lean change state. The second added value is set to increase as the second rich counter 32 increases. That is, the second added value is set so that the air-fuel ratio is corrected to the rich side as the second rich counter 32 increases. Note that, for example, the second added value is set to be larger than the first added value, but the present invention is not limited to this, and the first added value and the second added value can be set to arbitrary values.

FIG. 6 is a diagram showing correction value information 36 regarding correction using the first lean counter 33. As shown in FIG. 6, the first subtraction value is an example of a predetermined subtraction value that is corrected to the lean side when the air-fuel ratio is in the rich change state. The first subtraction value is set to increase as the first lean counter 33 increases. That is, the first subtraction value is set so that the air-fuel ratio is corrected to the lean side as the first lean counter 33 increases.

FIG. 7 is a diagram showing the correction value information 36 regarding the correction using the second lean counter 34. As shown in FIG. 7, the second subtraction value is an example of a second predetermined subtraction value that is corrected to the lean side when the air-fuel ratio is in the second rich change state. The second subtraction value is set to increase as the second lean counter 34 increases. That is, the second subtraction value is set to correct the air-fuel ratio to the lean side as the second lean counter 34 increases. Note that, for example, the second subtraction value is set to be larger than the first subtraction value, but the present invention is not limited to this, and the first subtraction value and the second subtraction value can be set to arbitrary values.

Returning to the description of FIG. 2, the control unit 20 is a microcomputer including a detection unit 21, a determination unit 22, and an air-fuel ratio control unit 23, and having a CPU (Central Processing Unit) and the like.

The detection unit 21 detects the air-fuel ratio, the engine speed, and the like based on signals output from the upstream air-fuel ratio sensor 41, the downstream air-fuel ratio sensor 42, the in-vehicle sensor group 100, and the like. Then, a signal indicating the detected air-fuel ratio state or the like is output to the determination unit 22, the air-fuel ratio control unit 23, or the like.

The determination unit 22 determines whether the air-fuel ratio on the downstream side of the catalyst 80 is in the lean change state or the rich change state, based on the state of the air-fuel ratio detected by the downstream side air-fuel ratio sensor 42.

For example, the determination unit 22 determines that the difference Vr between the current state (current value) and the previous state (previous value) in the downstream side air-fuel ratio sensor 42 has a negative value indicating a change in the lean direction continuously for a predetermined number of times or more. When detected, it can be determined that the air-fuel ratio on the downstream side of the catalyst 80 is in the lean change state.

The determination of the lean change state is not limited to the above. That is, for example, the determination unit 22 determines that the air-fuel ratio on the downstream side of the catalyst 80 is in the lean change state when the negative value of the difference Vr of the downstream-side air-fuel ratio sensor 42 is continuously detected for a predetermined time. You may.

In addition, the determination unit 22 determines that the downstream side air-fuel ratio of the catalyst 80 is rich when the positive value state in which the difference Vr of the downstream side air-fuel ratio sensor 42 indicates a change in the rich direction is continuously detected a predetermined number of times or more. It is determined to be in a changed state. Note that the determination unit 22 determines that the downstream side air-fuel ratio of the catalyst 80 is in the rich change state when the positive value of the difference Vr of the downstream side air-fuel ratio sensor 42 is continuously detected for a predetermined time. Good.

Further, the determination unit 22 can determine whether the air-fuel ratio on the downstream side of the catalyst 80 is in the second lean change state or the second rich change state. For example, when the difference Vr of the downstream side air-fuel ratio sensor 42 is a negative value and the difference Vr is less than or equal to the first threshold value, the determination unit 22 determines that the downstream side air-fuel ratio of the catalyst 80 is in the second lean change state. To determine. The first threshold value is set to a value at which it is possible to determine that the change in the lean direction is relatively large in the air-fuel ratio on the downstream side of the catalyst 80, but the first threshold value is not limited to this.

Further, when the difference Vr of the downstream side air-fuel ratio sensor 42 is a negative value and the difference Vr is equal to or more than the second threshold value, the determination unit 22 determines that the downstream side air-fuel ratio of the catalyst 80 is in the second rich change state. judge. Then, the determination unit 22 outputs information indicating the above determination result to the air-fuel ratio control unit 23. The second threshold value is set to a value at which it is possible to determine that the change in the rich direction is relatively large in the air-fuel ratio on the downstream side of the catalyst 80, but the second threshold value is not limited to this.

The air-fuel ratio control unit 23 controls the air-fuel ratio based on the determination result of the determination unit and various information stored in the storage unit 30.

For example, the air-fuel ratio control unit 23 controls the air-fuel ratio so that the air-fuel ratio becomes the target air-fuel ratio set based on the air-fuel ratio map 35. Further, the air-fuel ratio control unit 23 corrects the fuel (hereinafter, supply fuel) supplied to the engine 40 depending on whether the output of the downstream side air-fuel ratio sensor 42 is rich or lean, for example. Hereinafter, the correction value used for such correction may be referred to as a “basic correction value”.

Further, the air-fuel ratio control unit 23 can correct the supplied fuel by using an offset correction value that further corrects the air-fuel ratio to the rich side when the output of the air-fuel ratio sensor 42 falls below a predetermined threshold value, for example. When the output of the air-fuel ratio sensor 42 exceeds the predetermined threshold value, the correction using the offset correction value is not performed, but the present invention is not limited to this.

Furthermore, in the air-fuel ratio control unit 23 according to the present embodiment, in addition to the basic correction value and the offset correction value, the first addition value, the second addition value, the first subtraction value, and the second subtraction value are used. The supplied fuel can be corrected to control the air-fuel ratio.

For example, the air-fuel ratio control unit 23 accesses the correction value information 36 when the first rich counter 31 is counted up, that is, when it is determined that the air-fuel ratio on the downstream side of the catalyst is in the lean change state. Then, the first added value corresponding to the first rich counter 31 is read. Then, the air-fuel ratio control unit 23 corrects the supplied fuel using the basic correction value, the offset correction value, and the correction value in which the first addition value is reflected, and controls the air-fuel ratio. This can prevent the air-fuel ratio on the downstream side of the catalyst 80 from becoming excessively lean.

Further, for example, when the second rich counter 32 is counted up, that is, when it is determined that the air-fuel ratio on the downstream side of the catalyst is in the second lean change state, the air-fuel ratio control unit 23 corrects the correction value. The information 36 is accessed to read the second added value corresponding to the second rich counter 32. Then, the air-fuel ratio control unit 23 corrects the supplied fuel using the basic correction value, the offset correction value, and the correction value in which the second added value is reflected, and controls the air-fuel ratio. This can prevent the air-fuel ratio on the downstream side of the catalyst 80 from becoming excessively lean.

Note that the air-fuel ratio control unit 23 selects the one with the larger addition value when both the first and second addition values are obtained, but is not limited to this and selects the one with the smaller addition value. Alternatively, the average value of the first and second addition values may be selected.

For example, the air-fuel ratio control unit 23 accesses the correction value information 36 when the first lean counter 33 is counted up, that is, when it is determined that the air-fuel ratio on the downstream side of the catalyst is in the rich change state. Then, the first subtraction value corresponding to the first lean counter 33 is read. Then, the air-fuel ratio control unit 23 corrects the supplied fuel using the correction value reflecting the basic correction value, the offset correction value, and the first subtraction value, and controls the air-fuel ratio. This can prevent the air-fuel ratio on the downstream side of the catalyst 80 from becoming excessively rich.

Further, for example, when the second lean counter 34 is counting up, that is, when it is determined that the air-fuel ratio on the downstream side of the catalyst is in the second rich change state, the air-fuel ratio control unit 23 corrects the correction value. The information 36 is accessed to read the second subtraction value corresponding to the second lean counter 34. Then, the air-fuel ratio control unit 23 corrects the supplied fuel using the correction value reflecting the basic correction value, the offset correction value, and the second subtraction value, and controls the air-fuel ratio. This can prevent the air-fuel ratio on the downstream side of the catalyst 80 from becoming excessively rich.

Note that the air-fuel ratio control unit 23 selects the one with the larger subtraction value when both the first and second subtraction values are obtained, but is not limited to this and selects the one with the smaller subtraction value. Alternatively, the average value of the first and second subtraction values may be selected.

Next, the air-fuel ratio control by the control device 10 according to the present embodiment will be described in more detail with reference to FIG. FIG. 8 is a time chart illustrating the process of air-fuel ratio control by the control device 10 according to the present embodiment. In FIG. 8, various values for which the air-fuel ratio control is performed by the control device 10 according to the present embodiment are shown by solid lines, and those of the prior art are shown by broken lines.

As shown by the broken line in FIG. 8, in the conventional technique, for example, when the output of the downstream side air-fuel ratio sensor 42 falls below a predetermined threshold value at time T2, the offset correction value for further correcting the air-fuel ratio to the rich side is corrected. Reflected in the value.

However, since the offset correction value is not reflected in the correction value until the output of the downstream side air-fuel ratio sensor 42 falls below a predetermined threshold value, it cannot meet the speed of decrease of the output of the downstream side air-fuel ratio sensor 42 to the lean side, The air-fuel ratio is too lean.

Further, in the conventional technique, for example, when the output of the downstream side air-fuel ratio sensor 42 exceeds the predetermined threshold value at time T4, the offset correction value is not reflected in the correction value.

However, since the offset correction value was reflected in the correction value until immediately before the output of the downstream side air-fuel ratio sensor 42 exceeded the predetermined threshold value, the air-fuel ratio is excessively rich even if the offset correction value is not reflected. ..

On the other hand, in the control device 10 according to the present embodiment, when the state where the output difference Vr is a negative value continues at time T1, it is determined to be a lean change state, and for example, the first addition value is reflected in the correction value. To be done. That is, the air-fuel ratio is corrected to the rich side. As a result, it is possible to avoid the state in which the air-fuel ratio rapidly changes to the lean side, which has occurred after the time T2 in the related art, and as a result, the air-fuel ratio on the downstream side of the catalyst 80 becomes excessively lean. Can be suppressed.

Further, in the control device 10 according to the present embodiment, when the state where the output difference Vr is a positive value continues at time T3, it is determined to be the rich change state, and, for example, the second subtraction value is reflected in the correction value. To do so. That is, the air-fuel ratio is corrected to the lean side. As a result, it is possible to avoid the state in which the air-fuel ratio rapidly changes to the rich side, which has occurred after the time T4 in the related art, and as a result, the air-fuel ratio on the downstream side of the catalyst 80 becomes excessively rich. Can be suppressed.

<3. Control Process of Control Device According to Embodiment>
Next, a specific processing procedure in the control device 10 will be described with reference to FIG. FIG. 9 is a flowchart showing a processing procedure executed by the control device 10.

As shown in FIG. 9, the control unit 20 of the control device 10 determines whether or not the output difference Vr between the current state and the previous state of the output of the downstream side air-fuel ratio sensor 42 is a negative value indicating a change in the lean direction. Is determined (step S10). When it is determined that the output difference Vr is a negative value (step S10, Yes), the control unit 20 determines whether the first and second lean counters are zero (step S11).

When it is determined that the first and second lean counters are not zero (No in step S11), the control unit 20 clears the first and second lean counters to zero (step S12). When the process of step S12 is completed, or when it is determined that the first and second lean counters are zero (step S11, Yes), the first rich counter is incremented (step S13).

Next, the control unit 20 determines whether or not the output difference Vr of the downstream side air-fuel ratio sensor 42 is less than or equal to the first threshold value (step S14). When it is determined that the output difference Vr of the downstream side air-fuel ratio sensor 42 is equal to or less than the first threshold value (Yes in step S14), the control unit 20 determines that the downstream side air-fuel ratio of the catalyst 80 is in the second lean change state. If it is determined that, the second rich counter is counted up (step S15). On the other hand, when it is determined that the output difference Vr of the downstream side air-fuel ratio sensor 42 is not equal to or less than the first threshold value (step S14, No), the control unit 20 skips the process of step S15.

Next, the control unit 20 calculates the first and second addition values corresponding to the current first and second rich counters based on the correction value information 36 (step S16). Next, the control unit 20 determines whether the calculated first addition value is larger than the second addition value (step S17).

When it is determined that the first addition value is larger than the second addition value (Yes in step S17), the control unit 20 reflects the first addition value in the correction value of the supplied fuel (step S18). On the other hand, the control unit 20 supplies the second addition value when it is not determined that the first addition value is larger than the second addition value (step S17, No), that is, when the second addition value is larger than the first addition value. It is reflected in the fuel correction value (step S19).

In addition, when the control unit 20 determines that the output difference Vr is not a negative value (No in step S10), that is, when the output difference Vr is a positive value indicating a change in the rich direction, the first and second 2 It is determined whether the rich counter is zero (step S20).

When it is determined that the first and second rich counters are not zero (step S20, No), the controller 20 clears the first and second rich counters to zero (step S21). When the process of step S21 ends, or when it is determined that the first and second rich counters are zero (step S20, Yes), the first lean counter is incremented (step S22).

Next, the control unit 20 determines whether the output difference Vr of the downstream side air-fuel ratio sensor 42 is equal to or larger than the second threshold value (step S23). When it is determined that the output difference Vr of the downstream side air-fuel ratio sensor 42 is equal to or more than the second threshold value (step S23, Yes), the control unit 20 determines that the downstream side air-fuel ratio of the catalyst 80 is in the second rich change state. If it is determined that the second lean counter is counted up (step S24). On the other hand, when it is determined that the output difference Vr of the downstream side air-fuel ratio sensor 42 is not equal to or more than the second threshold value (step S23, No), the control unit 20 skips the process of step S24.

Next, the control unit 20 calculates the first and second subtraction values corresponding to the current first and second lean counters based on the correction value information 36 (step S25). Next, the control unit 20 determines whether the calculated first subtraction value is larger than the second subtraction value (step S26).

When it is determined that the first subtraction value is larger than the second subtraction value (Yes at Step S26), the control unit 20 reflects the first subtraction value on the correction value of the supplied fuel (Step S27). On the other hand, the control unit 20 supplies the second subtraction value when it is not determined that the first subtraction value is larger than the second subtraction value (step S26, No), that is, when the second subtraction value is larger than the first subtraction value. This is reflected in the fuel correction value (step S28).

As described above, the control device 10 for the engine 40 according to the embodiment includes the detection unit 21, the determination unit 22, and the air-fuel ratio control unit 23. The detection unit 21 detects the state of the air-fuel ratio on the downstream side of the catalyst 80 in the exhaust passage 70 of the engine 40 in which the catalyst 80 is arranged. The determination unit 22 is based on the state of the air-fuel ratio detected by the detection unit 21, the lean change state in which the air-fuel ratio on the downstream side of the catalyst 80 continues to change in the lean direction, or the change in the rich direction continues. It is determined whether the rich change state. The air-fuel ratio control unit 23 controls the air-fuel ratio of the air-fuel mixture supplied to the engine 40 based on the determination result of the determination unit 22. This can prevent the air-fuel ratio on the downstream side of the catalyst 80 from becoming excessively rich or lean.

Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

10 control device 20 control unit 21 detection unit 22 determination unit 23 air-fuel ratio control unit 40 engine 42 downstream air-fuel ratio sensor 70 exhaust passage 80 catalyst

Claims (6)

A detection unit for detecting the state of the air-fuel ratio on the downstream side of the catalyst in the exhaust passage of the internal combustion engine in which the catalyst is arranged,
Based on the state of the air-fuel ratio detected by the detection unit, in the lean change state in which the downstream side air-fuel ratio of the catalyst continues to change in the lean direction, or in the rich change state in which the change in the rich direction continues. A determination unit that determines whether there is
An air-fuel ratio control unit that controls the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the determination result of the determination unit. The detection unit,
Based on the output of the air-fuel ratio sensor provided on the downstream side of the catalyst, to detect the state of the air-fuel ratio on the downstream side of the catalyst,
The determination unit,
When the difference between the current state and the previous state in the air-fuel ratio sensor is continuously detected for a predetermined number of times, a negative value indicating a change in the lean direction, or the difference is negative for a predetermined time. If detected, it is determined that the air-fuel ratio on the downstream side of the catalyst is in a lean change state,
The air-fuel ratio control unit,
When the determination unit determines that the air-fuel ratio on the downstream side of the catalyst is in the lean change state, it controls the air-fuel ratio by reflecting a predetermined addition value in the correction value of the fuel supplied to the internal combustion engine. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine. The detection unit,
Based on the output of the air-fuel ratio sensor provided on the downstream side of the catalyst, to detect the state of the air-fuel ratio on the downstream side of the catalyst,
The determination unit,
When the difference between the current state and the previous state in the air-fuel ratio sensor is a positive value state indicating a change in the rich direction is continuously detected a predetermined number of times or more, or the difference is a positive value state continues for a predetermined time. If detected, it is determined that the air-fuel ratio on the downstream side of the catalyst is in a rich change state,
The air-fuel ratio control unit,
When the determination unit determines that the air-fuel ratio on the downstream side of the catalyst is in a rich change state, it controls the air-fuel ratio by reflecting a predetermined subtraction value on the correction value of the fuel supplied to the internal combustion engine. The control device for an internal combustion engine according to claim 1 or 2, which is characterized. The determination unit,
When the difference between the current state and the previous state in the air-fuel ratio sensor is a negative value and the difference is less than or equal to the first threshold value, the air-fuel ratio on the downstream side of the catalyst changes from the lean change state to the lean direction. Is judged to be in a large second lean change state,
The air-fuel ratio control unit,
When the determination unit determines that the air-fuel ratio on the downstream side of the catalyst is in the second lean change state, the second predetermined addition value is reflected in the correction value of the fuel supplied to the internal combustion engine to determine the air-fuel ratio. It controls, The control apparatus of the internal combustion engine of Claim 2 or 3 characterized by the above-mentioned. The determination unit,
When the difference between the current state and the previous state in the air-fuel ratio sensor is a positive value and the difference is not less than the second threshold value, the air-fuel ratio on the downstream side of the catalyst changes from the rich change state to the rich direction. Is determined to be in the second rich change state,
The air-fuel ratio control unit,
When the determination unit determines that the air-fuel ratio on the downstream side of the catalyst is in the second rich change state, the second predetermined subtraction value is reflected in the correction value of the fuel supplied to the internal combustion engine to determine the air-fuel ratio. It controls, The control apparatus of the internal combustion engine as described in any one of Claims 2-4 characterized by the above-mentioned. A detection step of detecting the state of the air-fuel ratio on the downstream side of the catalyst in the exhaust passage of the internal combustion engine in which the catalyst is arranged,
Based on the state of the air-fuel ratio detected by the detection step, in the lean change state where the downstream air-fuel ratio of the catalyst continues to change in the lean direction, or in the rich change state where the change to the rich direction continues. A determination step of determining whether there is
An air-fuel ratio control step of controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the determination result of the determination step.

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