Engine system

Abstract

To provide a technique capable of appropriately executing learning processing.SOLUTION: An engine system includes: an engine; an exhaust pipe; a catalyst mounted to the exhaust pipe; a front air-fuel ratio sensor provided upstream of the catalyst of the exhaust pipe; a rear air-fuel ratio sensor provided downstream of the catalyst of the exhaust pipe; and a control device that executes feedback processing for performing feedback control of a fuel injection amount so that a front air-fuel ratio detected by the front air-fuel ratio sensor becomes a target air-fuel ratio and learning processing for learning a learning value for correcting the target air-fuel ratio on the basis of a rear air-fuel ratio detected by the rear air-fuel ratio sensor. When a difference between a maximum value and a minimum value of the rear air-fuel ratio for a predetermined period is less than a predetermined amount, the control device interrupts the execution of the learning processing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to an engine system. [Background technology]

[0002] Patent Document 1 discloses an engine system including an engine, an exhaust pipe, a catalyst attached to the exhaust pipe, a front air-fuel ratio sensor provided upstream of the catalyst in the exhaust pipe, and a rear air-fuel ratio sensor provided downstream of the catalyst in the exhaust pipe, and a control device that executes a feedback process that feedback controls the fuel injection amount so that the front air-fuel ratio detected by the front air-fuel ratio sensor becomes a target air-fuel ratio, and a learning process that learns a learning value that corrects the target air-fuel ratio based on the rear air-fuel ratio detected by the rear air-fuel ratio sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-89040 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in an engine system, oxygen is stored in a catalyst while a fuel cut is being performed. In general, the target air-fuel ratio immediately after the fuel cut is completed is set to a value richer than the theoretical air-fuel ratio. In this case, the air-fuel ratio of the exhaust gas discharged from the engine becomes smaller than the theoretical air-fuel ratio (i.e., becomes rich). For this reason, it is considered that the rear air-fuel ratio also becomes richer than the theoretical air-fuel ratio. However, in a state in which oxygen is stored in the catalyst, when the exhaust gas passes through the catalyst, the exhaust gas is purified by the oxygen stored in the catalyst. As a result, the air-fuel ratio of the exhaust gas after passing through the catalyst (i.e., the rear air-fuel ratio) becomes close to the theoretical air-fuel ratio. That is, an unintended deviation may occur between the air-fuel ratio of the exhaust gas before passing through the catalyst and the air-fuel ratio of the exhaust gas after passing through the catalyst. If a learning process is performed in such a situation, the target air-fuel ratio is corrected in an unintended direction.

[0005] This specification provides a technique that can appropriately execute the learning process. [Means for solving the problem]

[0006] In a first aspect of the present technology, an engine system includes an engine, an exhaust pipe, a catalyst attached to the exhaust pipe, a front air-fuel ratio sensor provided upstream of the catalyst in the exhaust pipe, a rear air-fuel ratio sensor provided downstream of the catalyst in the exhaust pipe, and a control device that executes a feedback process for feedback-controlling a fuel injection amount so that the front air-fuel ratio detected by the front air-fuel ratio sensor becomes a target air-fuel ratio, and a learning process for learning a learning value for correcting the target air-fuel ratio based on the rear air-fuel ratio detected by the rear air-fuel ratio sensor. When the difference between the maximum value and the minimum value of the rear air-fuel ratio in a predetermined period is less than a predetermined amount, the control device interrupts the execution of the learning process. Note that the learning value for correcting the target air-fuel ratio may be learned using machine learning.

[0007] As described above, immediately after the fuel cut is completed, a certain amount of oxygen is stored in the catalyst, so even if the air-fuel ratio of the exhaust gas discharged from the engine is in a rich state, the air-fuel ratio of the exhaust gas after passing through the catalyst is maintained close to the theoretical air-fuel ratio. That is, even if the air-fuel ratio upstream of the catalyst (i.e., the front air-fuel ratio) fluctuates, the air-fuel ratio downstream of the catalyst (i.e., the rear air-fuel ratio) is suppressed from fluctuating. For this reason, in the above configuration, if the maximum fluctuation width (the difference between the maximum value and the minimum value) of the rear air-fuel ratio in a predetermined period is less than a predetermined amount, it is determined that there is a possibility of an unintended deviation between the front air-fuel ratio and the rear air-fuel ratio, and the execution of the learning process is interrupted. As a result, it is possible to suppress the target air-fuel ratio from being corrected in an unintended direction, and it is possible to maintain the target air-fuel ratio at an appropriate value. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing the configuration of an engine system 2. [Diagram 2] 4 is a flowchart of a determination process executed by a control device 16. [Diagram 3] FIG. 2 is a diagram showing a time chart in the engine system 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Example) 1, the engine system 2 includes an engine 10, an exhaust pipe 12, a catalyst 14 provided in the exhaust pipe 12, a control device 16, a front air-fuel ratio sensor 20, and a rear air-fuel ratio sensor 22. The engine system 2 is installed in an engine vehicle, a hybrid vehicle, a plug-in hybrid vehicle, or the like. The catalyst 14 purifies chemical substances contained in the exhaust gas discharged from the engine 10. The catalyst 14 is, for example, a three-way catalyst, and oxidizes or reduces hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx).

[0010] The front air-fuel ratio sensor 20 is provided upstream of the catalyst 14 in the exhaust pipe 12. The rear air-fuel ratio sensor 22 is provided downstream of the catalyst 14 in the exhaust pipe 12. The front air-fuel ratio sensor 20 and the rear air-fuel ratio sensor 22 detect the air-fuel ratio of the exhaust gas flowing through the exhaust pipe 12. Hereinafter, the air-fuel ratio detected by the front air-fuel ratio sensor 20 and the air-fuel ratio detected by the rear air-fuel ratio sensor 22 will be referred to as the "front air-fuel ratio" and the "rear air-fuel ratio", respectively.

[0011] The control device 16 is composed of a CPU, a ROM, a RAM, etc. The control device 16 is configured to be able to execute a feedback process using the front air-fuel ratio and a learning process using the rear air-fuel ratio. Hereinafter, feedback may be referred to as "F / B". In the F / B process, the control device 16 feedback controls the fuel injection amount of the engine 10 so that the front air-fuel ratio becomes a target air-fuel ratio (control center air-fuel ratio). In the learning process, the control device 16 learns a learning value for correcting the target air-fuel ratio based on the rear air-fuel ratio. Specifically, the control device 16 calculates the learning value based on the deviation between the average value of the rear air-fuel ratio in a first predetermined period and the reference air-fuel ratio. The reference air-fuel ratio is, for example, a theoretical air-fuel ratio. Then, the control device 16 calculates (corrects) the target air-fuel ratio using the reference air-fuel ratio and the learning value.

[0012] (Decision process; Figure 2) The determination process executed by the control device 16 of the engine system 2 will be described with reference to Fig. 2. The control device 16 executes the process of Fig. 2 at predetermined intervals.

[0013] In S10, the control device 16 calculates the amount of fluctuation of the rear air-fuel ratio in the second predetermined period. The control device 16 specifies the maximum value of the rear air-fuel ratio in the second predetermined period and the minimum value of the rear air-fuel ratio in the second predetermined period. The control device 16 calculates the amount of fluctuation of the rear air-fuel ratio by subtracting the specified minimum value from the specified maximum value.

[0014] In S12, the control device 16 determines whether the amount of fluctuation identified in S10 is less than a predetermined amount. If the amount of fluctuation is less than the predetermined amount (YES in S12), the control device 16 proceeds to S14. On the other hand, if the amount of fluctuation is equal to or greater than the predetermined amount (NO in S12), the control device 16 proceeds to S16.

[0015] In S14, the control device 16 suspends the execution of the learning process. As a result, the learning value and the target air-fuel ratio are no longer updated. When S14 ends, the control device 16 ends the process in FIG.

[0016] In addition, in S16, the control device 16 permits the execution of the learning process. This allows the learning value and the target air-fuel ratio to be continuously updated. When S16 ends, the control device 16 ends the process of FIG.

[0017] (Specific case: Figure 3) With reference to Fig. 3, a specific case realized by the determination process in Fig. 2 will be described. In Fig. 3, the upper side of the learned value corresponds to the rich side, and the lower side corresponds to the lean side.

[0018] At time T0 in Fig. 3, the control device 16 calculates the amount of fluctuation in the rear air-fuel ratio (S10 in Fig. 2), determines that the identified amount of fluctuation is equal to or greater than a predetermined amount (S12), and permits execution of the learning process. At time T0, the rear air-fuel ratio is leaner than the reference air-fuel ratio, so the control device 16 corrects the learning value to the rich side. As a result, the target air-fuel ratio (not shown) is corrected to the rich side. From time T0 to time T1, the amount of fluctuation in the rear air-fuel ratio is equal to or greater than a predetermined amount, and the rear air-fuel ratio is leaner than the reference air-fuel ratio, so the learning value is corrected to the rich side, and the target air-fuel ratio is corrected to the rich side.

[0019] At time T1, the control device 16 determines that the amount of change in the rear air-fuel ratio is less than a predetermined amount (S12) and suspends the execution of the learning process. This stops the update of the learning value and the target air-fuel ratio. From time T1 to time T2 thereafter, the amount of change in the rear air-fuel ratio is less than the predetermined amount, so the learning value is not updated.

[0020] At time T2, the control device 16 determines that the amount of change in the rear air-fuel ratio is equal to or greater than a predetermined amount (S12) and permits execution of the learning process. At time T2, the rear air-fuel ratio is richer than the target air-fuel ratio, so the control device 16 corrects the learning value to the lean side. As a result, the target air-fuel ratio (not shown) is corrected to the lean side. Thereafter, as the rear air-fuel ratio gradually shifts to the rich side, the learning value gradually shifts to the lean side.

[0021] As described above, the engine system 2 includes the engine 10, the exhaust pipe 12, the catalyst 14, the front air-fuel ratio sensor 20, the rear air-fuel ratio sensor 22, and the control device 16 that executes an F / B process for feedback controlling the fuel injection amount so that the front air-fuel ratio becomes the target air-fuel ratio, and a learning process for learning a learning value for correcting the target air-fuel ratio based on the rear air-fuel ratio. The control device 16 suspends the execution of the learning process when the amount of change in the rear air-fuel ratio during a second predetermined period (an example of a "predetermined period") is less than a predetermined amount (YES in S12 in FIG. 2).

[0022] For example, immediately after the fuel cut is completed, a certain amount of oxygen is stored in the catalyst 14, so that even if the air-fuel ratio of the exhaust gas discharged from the engine 10 is in a rich state, the air-fuel ratio of the exhaust gas after passing through the catalyst 14 is maintained close to the theoretical air-fuel ratio. That is, even if the air-fuel ratio upstream of the catalyst 14 (i.e., the front air-fuel ratio) fluctuates, the air-fuel ratio downstream of the catalyst 14 (i.e., the rear air-fuel ratio) is suppressed from fluctuating. For this reason, in the above configuration, if the maximum fluctuation width (the difference between the maximum value and the minimum value) of the rear air-fuel ratio in the second predetermined period is less than a predetermined amount, it is considered that there is a possibility of an unintended deviation between the front air-fuel ratio and the rear air-fuel ratio, and the execution of the learning process is interrupted. As a result, it is possible to suppress the target air-fuel ratio from being corrected in an unintended direction, and it is possible to maintain the target air-fuel ratio at an appropriate value. [Explanation of symbols]

[0023] 2: engine system, 10: engine, 12: exhaust pipe, 14: catalyst, 16: control device, 20: front air-fuel ratio sensor, 22: rear air-fuel ratio sensor

Claims

[Claim 1] An engine system The engine, Exhaust pipe and A catalyst attached to the exhaust pipe; a front air-fuel ratio sensor provided in the exhaust pipe upstream of the catalyst; a rear air-fuel ratio sensor provided in the exhaust pipe downstream of the catalyst; a control device that executes a feedback process for feedback controlling a fuel injection amount so that a front air-fuel ratio detected by the front air-fuel ratio sensor becomes a target air-fuel ratio, and a learning process for learning a learning value for correcting the target air-fuel ratio based on a rear air-fuel ratio detected by the rear air-fuel ratio sensor, the control device interrupts execution of the learning process when a difference between a maximum value and a minimum value of the rear air-fuel ratio in a predetermined period is less than a predetermined amount. Engine system.

Images