A control method and control system for engine enrichment

Abstract

The present application discloses a control method for engine enrichment, the control method includes obtaining the engine speed and load, determining the engine enrichment delay time according to the engine speed and load, determining the engine enrichment coefficient according to the engine speed and load, and determining the engine excess air coefficient according to the engine enrichment delay time and enrichment coefficient. The present application also discloses an engine enrichment control system, the control system includes an acquisition module, a control module and a table lookup module. Since the engine is enriched with a delay and the enrichment coefficient is determined according to the engine speed and load, the risk of the engine downshifting into the enrichment area is reduced, and the engine's power and emissions are taken into account.

Description

Technical Field

[0001] The present application relates to the technical field of engine control, and in particular, to a control method and control system for engine enrichment. Background Art

[0002] With the development of the automobile industry and the intensification of competition, the miniaturization of engines has become a trend in the development of the automobile industry. In order to cope with the increasingly stringent energy conservation and emission reduction and "double credit" policies, many manufacturers have brought small-displacement engines with upgraded technology back to the market. Adding technology and subtracting costs to give full play to the performance of the vehicle. The matching of a small horse (engine) to pull a big car came into being, which not only gave full play to the performance of low-cost, small-displacement engines, but also improved the cost-effectiveness of the vehicle and enhanced the competitiveness of the enterprise.

[0003] The existing approach 1: Based on the current vehicle model and engine matching, by sacrificing power at high speed, prohibiting the engine from downshifting into the enrichment area to ensure emissions. The existing approach 2: Matching large-displacement or supercharged engines, taking into account both power and emissions, but greatly increasing manufacturing costs. However, both methods are difficult to take into account both power and emissions, and manufacturing costs. Therefore, it is extremely important to design an enrichment strategy that meets the above requirements. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a control method and control system for engine enrichment to solve the problem that it is difficult to balance power, emissions and manufacturing costs in existing practices.

[0005] In order to solve the above problems, the present application adopts the following technical solutions:

[0006] The present application provides a method for controlling engine enrichment, the control method comprising:

[0007] Get the engine speed and load;

[0008] Determining a delay time for enrichment of the engine according to the speed and load of the engine;

[0009] determining an enrichment factor of the engine according to the speed and load of the engine;

[0010] The excess air coefficient of the engine is determined according to the delay time of the engine enrichment and the enrichment coefficient.

[0011] Further, the step of determining the excess air coefficient of the engine according to the engine enrichment delay time and the enrichment coefficient specifically includes:

[0012] Obtaining the running time of the engine at the operating point after downshifting;

[0013] If the enrichment coefficient is less than 1, and the delay time of the engine enrichment is greater than or equal to the operation time of the engine at the operating point after the engine is downshifted, the excess air coefficient of the engine is determined as the enrichment coefficient;

[0014] If the enrichment coefficient is less than 1, and the delay time of the engine enrichment is less than the operation time of the engine at the operating point after downshifting, the excess air coefficient of the engine is determined to be 1.

[0015] Furthermore, after the step of obtaining the operating time of the engine at the operating point after the engine is downshifted, the control method further includes:

[0016] If the enrichment coefficient is greater than or equal to 1, the excess air coefficient of the engine is determined to be 1.

[0017] Further, the step of determining the delay time of the engine enrichment according to the speed and load of the engine specifically includes:

[0018] Calibrate the engine under WLTC conditions to determine an enrichment delay schedule, wherein the enrichment delay schedule includes a speed and a load of the engine and a delay time of enrichment of the engine;

[0019] The enrichment delay schedule is looked up based on the speed and load of the engine to determine a delay time for enrichment of the engine.

[0020] Further, the step of determining the enrichment factor of the engine according to the speed and load of the engine specifically includes:

[0021] Performing a bench test on the engine to determine an enrichment coefficient table, wherein the enrichment coefficient table includes the engine speed, load and the engine enrichment coefficient;

[0022] Based on the speed and load of the engine, the enrichment factor table is looked up to determine the enrichment factor of the engine.

[0023] Furthermore, before the step of obtaining the speed and load of the engine, the control method further includes:

[0024] The engine is bench calibrated to determine a rich region of the engine.

[0025] The present application also provides an engine enrichment control system, the control system is used to execute the above control method, the control system includes an acquisition module, a control module and a table lookup module,

[0026] The acquisition module is used to acquire the speed and load of the engine;

[0027] The table lookup module is used to look up the table according to the speed and load of the engine to determine the delay time and enrichment coefficient of the engine enrichment;

[0028] The control module is used to control the excess air coefficient of the engine according to the delay time of the engine enrichment and the enrichment coefficient.

[0029] Furthermore, the control system includes a calibration storage module, and the calibration storage module is used to test the engine, determine an enrichment delay time table and an enrichment coefficient table, and store them.

[0030] Furthermore, the control system further comprises an enrichment zone module, and the enrichment zone module is used to perform a bench calibration test on the engine to determine an enrichment zone of the engine.

[0031] The control method and control system of the engine enrichment of the embodiment of the present application include obtaining the engine speed and load, determining the engine enrichment delay time according to the engine speed and load, determining the engine enrichment coefficient according to the engine speed and load, and determining the engine excess air coefficient according to the engine enrichment delay time and enrichment coefficient. Since the engine enrichment delay time and enrichment coefficient are determined according to the engine speed and load, the engine is enriched and delayed, thereby reducing the risk of the engine entering the enrichment area after downshifting, and taking into account the engine's power and emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A flow chart of a method for controlling engine enrichment provided in an embodiment of the present application;

[0033] Figure 2 A schematic flow chart of step 4 in a method for controlling engine enrichment provided in an embodiment of the present application;

[0034] Figure 3 A schematic flow chart of step 2 in a method for controlling engine enrichment provided in an embodiment of the present application;

[0035] Figure 4 A schematic flow chart of step three in a method for controlling engine enrichment provided in an embodiment of the present application;

[0036] Figure 5 A flow chart of another engine enrichment control method provided in an embodiment of the present application;

[0037] Figure 6 A system block diagram of an engine enrichment control system provided in an embodiment of the present application;

[0038] Figure 7 A schematic diagram of an engine operating condition point provided in an embodiment of the present application, wherein an enrichment area A is displayed;

[0039] Figure 8 A control logic diagram of engine enrichment provided in an embodiment of the present application;

[0040] Fig. 9 Another engine enrichment control logic diagram provided by an embodiment of the present application, wherein the gear position and vehicle speed are displayed; and

[0041] Fig.10 A CO emission diagram of an engine with delayed enrichment provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] The specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0043] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0044] It should be understood that the orientation or position relationship is based on the orientation or position relationship shown in the drawings. These orientation terms are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application.

[0045] In the description of the present application, the terms "first / second" involved are merely used to distinguish similar objects and do not represent a specific order for the objects. It can be understood that "first / second" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0046] The matching of a pony (engine) pulling a big cart came into being, which not only fully utilized the performance of low-cost, small-displacement engines, but also improved the cost-effectiveness of the whole vehicle and enhanced the competitiveness of the enterprise. In order to better understand the matching of the pony pulling the big cart mentioned above, the following is an example of a small SUV matching a 1.5L naturally aspirated engine. In the high-speed stage, the power is guaranteed by downshifting, but downshifting is accompanied by an increase in engine speed, and it enters the engine enrichment area, resulting in worsening emissions. After the engine operating point enters the enrichment area, the emission of CO will emerge sharply, and the emission exceeds the regulatory target. At the same time, the vehicle WLTC (Worldwide Light-duty Test Cycle, Global Unified Light Vehicle Test Cycle) operating conditions impose relevant restrictions on the problem of excessive emissions. For example, in the enrichment area of ​​the engine, λ is less than 1, which is the enrichment area (high speed and high load area). The smaller λ indicates that the engine enrichment coefficient is larger, where λ is the excess air coefficient, which represents the ratio of the actual amount of air supplied to the combustion of fuel to the theoretical amount of air. The engine enrichment area is determined according to the engine performance boundary.

[0047] The advantages of enrichment are: enrichment can prevent the engine exhaust temperature from exceeding the standard and reduce the knock frequency, and at the same time can reduce the engine exhaust temperature to meet the exhaust temperature requirements. Therefore, it is extremely important to design a control strategy for engine enrichment to ensure vehicle power while solving the problem of excessive emissions.

[0048] In view of this, if Figure 1 As shown, the embodiment of the present application provides a control method for engine enrichment, the control method comprising:

[0049] S1. Obtain the speed and load of the engine;

[0050] S2. Determine the delay time of engine enrichment according to the engine speed and load;

[0051] S3, determining the enrichment factor of the engine according to the engine speed and load;

[0052] S4. Determine the excess air coefficient of the engine according to the engine enrichment delay time and the enrichment coefficient.

[0053] Specifically, the speed and load of the engine are read through relevant sensors or controllers to obtain the speed and load of the engine. According to the speed and load of the engine, the delay time of the engine enrichment is determined after looking up a table, looking up a map or calculating. Similarly, according to the speed and load of the engine, the enrichment coefficient K of the engine is determined after looking up a table, looking up a map or calculating. According to the determined delay time and enrichment coefficient of the engine enrichment, the excess air coefficient of the engine is determined. For example, under different engine speeds and loads, after multiple calibration experiments, the delay time, enrichment coefficient and excess air coefficient are formed into a pre-stored calibration table. In the subsequent use process, the table is looked up according to different values ​​of the delay time and enrichment coefficient to determine the excess air coefficient.

[0054] For example, when the load is torque, the engine speed and torque are obtained through the ECU, and the delay time of engine enrichment is determined according to the different speed and torque states of the engine. It should be understood that the engine speed change time experienced by the engine to meet the power demand is different under different speed and torque states, and the duration of the enrichment required is also different.

[0055] It should be noted that the existing strategies also use enrichment technology, but they are often designed based on exhaust temperature and knock suppression, and their starting point is often to protect the engine, and their enrichment coefficient depends on the preset exhaust temperature. The engine enrichment control method of the embodiment of the present application is aimed at the engine operating condition of downshifting to meet the power requirements and entering the enrichment area, which is prone to CO emission pollution. Therefore, the specific process of enrichment is enrichment delayed control.

[0056] In the engine enrichment control method of the embodiment of the present application, the engine enrichment delay time and enrichment coefficient are determined according to the engine speed and load, and the engine enrichment is delayed, thereby reducing the risk of the engine entering the enrichment area after downshifting, while taking into account the engine's power and emissions.

[0057] In one embodiment, if Figure 5 As shown, before the step of S1, obtaining the speed and load of the engine, the control method further includes:

[0058] S10. Perform bench calibration on the engine to determine the enrichment region of the engine.

[0059] Specifically, before obtaining the engine speed and load, the engine needs to be bench-calibrated to determine the engine's enrichment area A. Since vehicles of different models and parameters have different enrichment areas A at different engine speeds and torques, when performing enrichment delay control on a specific vehicle, the engine speed and torque are first combined for bench calibration to determine the engine's enrichment area A, and the WLTC engine operating condition point is calibrated. When the engine is running at different operating points, in order to meet the power demand, it is easy to fall into the enrichment area A after downshifting. After the engine is delayed enriched, the engine will run to another operating point, staggering the enrichment area A, thereby avoiding CO emission pollution problems. The engine is bench-calibrated to determine the engine's enrichment area A, and corresponding logical judgments are made based on the engine's speed and torque during operation, so that delayed enrichment is performed according to the specific actual situation, thereby effectively reducing the risk of falling into the enrichment area A.

[0060] For example, based on the calibration of the engine bench, the enrichment area A of the engine is determined, such as Figure 7 As shown in the figure, when λ is less than 1, it is the enrichment area (high speed and high load area), where the smaller λ is, the greater the engine enrichment coefficient is. The engine enrichment area is determined according to the engine performance boundary. The engine can not only reduce the knock frequency, but also reduce the engine exhaust temperature to meet the target exhaust temperature requirements.

[0061] It should be noted that in the WLTC operating condition, it is confirmed that the engine enters the enriched operating condition, and the logic design is carried out for the enriched operating condition area to avoid enrichment and make the emission meet the requirements. Figure 7 As shown, it represents the operating point of the vehicle's engine in the WLTC cycle. When the engine operating point enters the enrichment area A, entering the enrichment area will cause the emission CO to emerge sharply, and the emission exceeds the regulatory target.

[0062] However, the reason for delaying the engine enrichment instead of canceling it is that enrichment is to avoid excessive engine exhaust temperature and reduce knock frequency. In steady-state conditions, if the engine is at the enrichment point, enrichment must be performed to protect the engine. In the WLTC transient cycle condition, a certain enrichment delay is performed for the problem point to avoid enrichment, which not only achieves the purpose of reducing emissions but also does not damage the engine.

[0063] In order to better understand the engine enrichment control method of the embodiment of the present application, each step in the control method is described in detail below.

[0064] S1. Obtain the speed and load of the engine.

[0065] The engine speed and torque are combined for bench calibration to determine the engine enrichment area A. At the same time, the speed and load and other delayed enrichment related parameters are pre-stored after multiple calibration experiments at different engine speeds and loads. In subsequent use, the engine speed and load are obtained through related sensors or controllers, which facilitates the subsequent delayed enrichment control process to obtain other data by corresponding table lookup according to the engine speed and load.

[0066] S2. Determine the delay time of engine enrichment according to the engine speed and load.

[0067] The engine speed and load are read through relevant sensors or controllers, thereby obtaining the engine speed and load. According to the engine speed and load, the engine enrichment delay time is determined after looking up a table, a map or calculation.

[0068] In one embodiment, if Figure 3 As shown, S2, the step of determining the delay time of engine enrichment according to the engine speed and load, specifically includes:

[0069] S21, calibrating the engine under WLTC working condition to determine an enrichment delay schedule, wherein the enrichment delay schedule includes engine speed, load and engine enrichment delay time;

[0070] S22: Based on the engine speed and load, search for an enrichment delay time table to determine a delay time for engine enrichment.

[0071] Specifically, a bench calibration experiment is conducted on the engine, and the engine is calibrated according to the WLTC working condition. Different engine enrichment delay times are determined under different engine speeds and loads. For example, Figure 7 As shown, the engine is subjected to bench calibration experiments, and the enrichment area A under the WLTC condition is calibrated. At the same time, different engine enrichment delay times are calibrated under different engine speeds, loads and gears, and the speed, load and delay time are plotted into tables and curves (see the table below). After the enrichment delay time table is calibrated, the table is looked up according to the obtained engine speed and load to determine the engine enrichment delay time.

[0072] Speed / Torque 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 10 0 0 0 0 0 0 0 0 0 0 20 0 0 0 0 0 0 0 0 0 0 40 0 0 0 0 0 0 0 0 0 0 60 0 0 0 0 0 0 0 0 0 0 80 0 0 0 0 0 0 0 0 3 0 100 0 0 0 0 0 0 3 3 3 0 120 0 0 0 0 0 0 3 3 3 0 140 0 0 0 0 0 0 3 3 3 0 160 0 0 0 0 0 0 3 3 3 0

[0073] It should be noted that in steady-state conditions, if the engine is at an enrichment point, enrichment must be performed to protect the engine. In the WLTC transient cycle condition, a certain enrichment delay is performed for the problem operating point to avoid enrichment, which not only achieves the purpose of reducing emissions but also does not damage the engine.

[0074] S3. Determine the engine enrichment factor according to the engine speed and load.

[0075] The engine speed and torque are obtained through relevant sensors or controllers, and the engine enrichment factor is determined by looking up a table, a graph or calculating the engine speed and torque. It should be noted that the engine load is usually characterized by torque, and the load and torque in the above or below expressions should not be understood as having different meanings.

[0076] In one embodiment, S3, the step of determining the enrichment factor of the engine according to the speed and load of the engine, specifically includes:

[0077] S31, performing a bench test on the engine to determine an enrichment coefficient table, wherein the enrichment coefficient table includes the engine speed, load, and engine enrichment coefficient;

[0078] S32. Based on the engine speed and load, check the enrichment factor table to determine the enrichment factor of the engine.

[0079] Specifically, a bench calibration experiment is performed on the engine, and the engine is calibrated according to the WLTC working condition. At different engine speeds and loads, different engine enrichment factors are determined. For example, Figure 7 As shown in the figure, the engine is subjected to bench calibration experiment, and the enrichment area A under the WLTC working condition is calibrated. At the same time, different engine enrichment coefficients are calibrated under different engine speeds, loads and gears, and the speed, load and enrichment coefficient are plotted into tables and curves. After the enrichment coefficient table is calibrated, the enrichment coefficient is determined by looking up the table according to the obtained engine speed and load. It should be noted that after the enrichment coefficient is determined, the excess air coefficient of the engine is further determined according to the engine operation conditions at different speeds and torques.

[0080] S4. Determine the excess air coefficient of the engine according to the engine enrichment delay time and the enrichment coefficient.

[0081] After the delay time and the enrichment coefficient of the engine are determined, the excess air coefficient of the engine is determined according to the different delay times, enrichment coefficients and engine operation conditions of the engine enrichment. For example, according to the comparison between the enrichment coefficient and coefficient 1, the delay time of the engine enrichment is compared with the different operating time of the engine operating point before and after the engine downshift, so as to determine the excess air coefficient of the engine under different conditions.

[0082] For example, under different engine speeds and loads, the delay time, enrichment factor and air-fuel ratio are formed into a pre-stored calibration table after multiple calibration experiments. In subsequent use, the table is looked up according to different values ​​of delay time and enrichment factor to determine the excess air coefficient.

[0083] In one embodiment, if Figure 2 As shown, S4, the step of determining the excess air coefficient of the engine according to the delay time and the enrichment coefficient of the engine, specifically includes:

[0084] S41, obtaining the engine running time at the operating point after downshifting;

[0085] S42, if the enrichment coefficient is less than 1, and the delay time of the engine enrichment is greater than or equal to the engine running time at the operating point after the engine is downshifted, the excess air coefficient of the engine is determined as the enrichment coefficient;

[0086] S43: If the enrichment coefficient is less than 1, and the delay time of the engine enrichment is less than the running time of the engine at the operating point after the engine is downshifted, the excess air coefficient of the engine is determined to be 1.

[0087] Specifically, after the delay time and the enrichment coefficient of the engine are determined, the operation time of the engine at the operating point after the engine is downshifted is obtained, and the delay time of the engine enrichment is compared with the operation time of the engine at the operating point after the engine is downshifted. If the enrichment coefficient is less than 1, and the delay time of the engine enrichment is greater than or equal to the operation time of the engine at the operating point after the engine is downshifted, the excess air coefficient of the engine is determined as the enrichment coefficient. If the enrichment coefficient is less than 1, and the delay time of the engine enrichment is less than the operation time of the engine at the operating point after the engine is downshifted, the excess air coefficient of the engine is determined to be 1.

[0088] It should be understood that if Fig. 9 As shown in the figure, the engine running time at the operating point after downshifting represents the duration of the "concave" change in gear position or the duration of the "convex" change in speed. Comparing the engine running time at the operating point after downshifting with the delay time of engine enrichment can effectively reduce the risk of the engine falling into the enrichment area A after downshifting (see Figure 7 ).

[0089] In one embodiment, after the step of S41, obtaining the engine operating time at the operating point after downshifting, the control method further includes:

[0090] S44: If the enrichment coefficient is greater than or equal to 1, the excess air coefficient of the engine is determined to be 1.

[0091] Specifically, after the delay time and enrichment coefficient of the engine enrichment are determined, the excess air coefficient of the engine is determined according to the different delay times and enrichment coefficients of the engine enrichment and the engine operating conditions. If the enrichment coefficient is greater than or equal to 1, the excess air coefficient of the engine is determined to be 1.

[0092] like Figure 8As shown, if the current enrichment coefficient K is less than 1, then L = 1. After the engine time is greater than or equal to T, then M = 1. At this time, the coefficient N of λ is equal to the current K. For example, the engine time is the time spent on the gear shift (refer to Fig. 9 The delayed enrichment time coefficient T is compared with the time experienced by the gear change in this process. For example, the time experienced by the gear change is 5s, and the delayed enrichment time coefficient T obtained by looking up the table is 3s, and the enrichment coefficient K is less than 1. At this time, λ is 1 within 3s after downshifting, and λ is the enrichment coefficient K after 3s of downshifting.

[0093] If the current enrichment coefficient K is less than 1, that is, L=1, and the time the engine has been running is less than T, then M=0, and the coefficient N of λ is equal to 1 at this time.

[0094] If the current enrichment coefficient K≥1, that is, L=0, the coefficient N of λ is equal to 1 at this time.

[0095] like Fig. 9 As shown in the figure, during the engine acceleration process, due to power demand, the TCU (Transmission-Control-Unit) issues a downshift command, the gearbox receives and executes the downshift, at which time the engine speed increases and enters the enrichment area. After a certain period of time (t time), the power demand decreases, the gearbox shifts up, and the engine speed avoids the enrichment area. Figure 8 After the delayed enrichment logic in the engine downshift process, the air-fuel ratio enrichment coefficient is delayed for t time and remains 1 during the t time. The t time is determined according to the time when the engine enters the enrichment.

[0096] like Figure 6 As shown, the embodiment of the present application also provides a control system 100 for engine enrichment, the control system 100 is used to execute the above-mentioned control method, the control system 100 includes an acquisition module 110, a control module 130 and a table lookup module 120, the acquisition module 110 is used to acquire the speed and load of the engine, the table lookup module 120 is used to look up the table according to the speed and load of the engine to determine the delay time and enrichment coefficient of the engine enrichment, and the control module 130 is used to control the excess air coefficient of the engine according to the delay time and enrichment coefficient of the engine enrichment.

[0097] Specifically, through the engine bench calibration test, the relationship between the engine speed and torque, the engine enrichment delay time, and the enrichment coefficient is plotted into a graph and stored in a corresponding storage medium. After the acquisition module 110 acquires the engine speed and load, the table lookup module 120 performs a table lookup according to the engine speed and load to determine the engine enrichment delay time and enrichment coefficient. The control module 130 determines the engine excess air coefficient according to the engine enrichment delay time and enrichment coefficient, and controls the operation according to the determined excess air coefficient.

[0098] For example, the control module 130 is an ECU (Electronic Control Unit), the acquisition module 110 acquires the engine speed and load, the table lookup module 120 looks up the table according to the engine speed and load, and determines the delay time and enrichment coefficient of the engine enrichment. The table lookup module 120 transmits the delay time and enrichment coefficient of the engine enrichment to the ECU through CAN communication. The ECU performs logical judgment based on the engine speed and load, the delay time and enrichment coefficient of the engine enrichment, determines the excess air coefficient of the engine, and controls the engine to operate according to the excess air coefficient after delayed enrichment control.

[0099] Through the acquisition module 110, the control module 120 and the table lookup module 130, the control system 100 determines the delay time and enrichment coefficient of the engine according to the engine speed and load, and delays the enrichment of the engine, thereby reducing the risk of the engine entering the enrichment area after downshifting, and taking into account the engine's power and emissions.

[0100] In one embodiment, the control system 100 includes a calibration storage module, which is used to test the engine, determine the enrichment delay time table and the enrichment coefficient table, and store them.

[0101] Specifically, the control system 100 includes a calibration storage module, which stores data of the engine bench calibration test. For example, the calibration storage module plots the relationship between the engine speed and torque, and the engine enrichment delay time into a chart. The calibration storage module plots the relationship between the engine speed and torque, and the engine enrichment coefficient into a chart. The table lookup module 130 performs a corresponding table lookup from the calibration storage module according to the engine speed and load, thereby obtaining the engine enrichment delay time and enrichment coefficient.

[0102] In one embodiment, the control system further includes an enrichment partition module, and the enrichment partition module is used to perform a bench calibration test on the engine to determine an enrichment region of the engine.

[0103] Specifically, the control system 100 includes an enrichment partitioning module, which partitions different operating conditions in the engine bench calibration test. For example, the enrichment partitioning module divides the engine enrichment area according to the engine speed and torque, and marks the enrichment area A. When the engine runs to the corresponding operating point and the engine is downshifted, the engine enrichment control method is executed.

[0104] In order to better understand the engine enrichment control method of the embodiment of the present application, the following is combined with Figure 8 and Fig. 9 The specific process of engine enrichment control is described in detail.

[0105] The control logic of engine enrichment is as follows Figure 8 As shown in the figure, during the driving process of the vehicle, the corresponding engine speed and load are determined accordingly, thereby determining the engine enrichment coefficient K and. Among them, the enrichment calibration table is determined by the engine speed and load, the enrichment calibration table is completed by bench calibration, and the delay time calibration table is determined by the engine speed and load. The calibration table is based on the enrichment area of ​​the WLTC working condition, and adaptive matching and calibration are performed to obtain the corresponding delayed enrichment time coefficient T at this working point.

[0106] (1) If the current enrichment coefficient K is less than 1, then L = 1. After the engine time is greater than or equal to T, then M = 1. At this time, the coefficient N of λ is equal to the current K. For example, the engine time can be identified as the time spent on the gear shift (refer to Fig. 9 The delayed enrichment time coefficient T is compared with the time experienced by the gear change in this process. If the time experienced by the gear change is 5s, the delayed enrichment time coefficient T obtained by looking up the table is 3s, and the enrichment coefficient K is less than 1. At this time, λ is 1 within 3s after downshifting, and λ is the enrichment coefficient K after 3s of downshifting.

[0107] (2) If the current enrichment coefficient K is less than 1, that is, L = 1, and the time elapsed by the engine is less than T, then M = 0, and the coefficient N of λ is equal to 1. For example, the time elapsed by the engine can be identified as the time elapsed by the gear shift (refer to Fig. 9 The process of recovery after the mid-gear position drops), compare the delayed enrichment time coefficient T with the time experienced by the gear change in this process. If the time experienced by the gear change is 2s, the delayed enrichment time coefficient T obtained by looking up the table is 3s, and the enrichment coefficient K is less than 1. At this time, the coefficient N of λ is determined to be 1.

[0108] (3) If the current enrichment coefficient K ≥ 1, that is, L = 0, then the coefficient N of λ is equal to 1.

[0109] For example, Fig. 9As shown in the figure, during the engine acceleration process, due to power demand, the TCU (Transmission-Control-Unit) issues a downshift command, the gearbox receives and executes the downshift, at which time the engine speed increases and enters the enrichment area. After a certain period of time (t time), the power demand decreases, the gearbox shifts up, and the engine speed avoids the enrichment area. Figure 8 After the delayed enrichment logic in the engine downshift-upshift process, the enrichment coefficient of the excess air coefficient is delayed by t time and remains 1 during t time. The t time is determined according to the time when the engine enters enrichment.

[0110] It should be noted that the control method of engine enrichment in this application is based on the National VI WLTC operating condition. The existing control method causes the engine operating condition to enter the enrichment area when downshifting to meet the power requirements. The control method of engine enrichment in this application designs an enrichment delay strategy based on the above-mentioned problem, wherein the Map of the engine enrichment strategy is determined by the engine speed and torque. Although enrichment technology is also used in existing strategies, it is often designed based on the exhaust temperature and excess air coefficient. Its starting point is often to meet the exhaust temperature requirements, and its enrichment excess air coefficient depends on the preset exhaust temperature.

[0111] like Fig.10 As shown, after adopting the engine enrichment control method of the present application, since the enrichment delay control strategy is adopted in the control process, it can be clearly seen that CO is sharply reduced in the high-speed section, meeting the emission regulations.

[0112] It should be noted that from a cost perspective, a small SUV equipped with a 1.5L naturally aspirated engine has a clear disadvantage in terms of power. In order to ensure power, frequent downshifting is inevitable during acceleration, but at the same time, emissions are taken into account. Downshifting is prohibited in some operating conditions to avoid entering the enrichment condition. The present invention can take into account both emissions and power at the same time, avoiding enrichment during the downshift process to ensure emissions. On the other hand, the control strategy of delayed enrichment is used to reduce CO emissions, rather than increasing precious metals in the post-treatment system to reduce emissions, thereby reducing manufacturing costs.

[0113] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the same. Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present application.

Claims

1. A method for controlling engine enrichment, characterized in that: The control method comprises: Get the engine speed and load; Determining a delay time for enrichment of the engine according to the speed and load of the engine; determining an enrichment factor of the engine according to the speed and load of the engine; Determining an excess air coefficient of the engine according to a delay time of the engine enrichment and the enrichment coefficient; The step of determining the excess air coefficient of the engine according to the engine enrichment delay time and the enrichment coefficient specifically includes: Obtaining the running time of the engine at the operating point after downshifting; If the enrichment coefficient is less than 1, and the delay time of the engine enrichment is greater than or equal to the operation time of the engine at the operating point after the engine is downshifted, the excess air coefficient of the engine is determined as the enrichment coefficient; If the enrichment coefficient is less than 1, and the delay time of the engine enrichment is less than the operation time of the engine at the operating point after downshifting, the excess air coefficient of the engine is determined to be 1.

2. The control method according to claim 1, characterized in that: After the step of obtaining the engine operating time at the operating point after downshifting, the control method further includes: If the enrichment coefficient is greater than or equal to 1, the excess air coefficient of the engine is determined to be 1.

3. The control method according to claim 1, characterized in that: The step of determining the delay time of the engine enrichment according to the speed and load of the engine specifically comprises: Calibrate the engine under WLTC conditions to determine an enrichment delay schedule, wherein the enrichment delay schedule includes a speed and a load of the engine and a delay time of enrichment of the engine; The enrichment delay schedule is looked up based on the speed and load of the engine to determine a delay time for enrichment of the engine.

4. The control method according to claim 1, characterized in that: The step of determining the enrichment factor of the engine according to the speed and load of the engine specifically comprises: Performing a bench test on the engine to determine an enrichment coefficient table, wherein the enrichment coefficient table includes the engine speed, load and the engine enrichment coefficient; Based on the speed and load of the engine, the enrichment factor table is looked up to determine the enrichment factor of the engine.

5. The control method according to claim 1, characterized in that: Before the step of obtaining the speed and load of the engine, the control method further includes: The engine is bench calibrated to determine a rich region of the engine.

6. An engine enrichment control system, characterized in that: The control system is used to execute the control method according to any one of claims 1 to 5, and the control system includes an acquisition module, a control module and a table lookup module. The acquisition module is used to acquire the speed and load of the engine, and to acquire the running time of the engine at the operating point after downshifting; The table lookup module is used to look up the table according to the speed and load of the engine to determine the delay time and enrichment coefficient of the engine enrichment; The control module is used to control the excess air coefficient of the engine according to the delay time of the engine enrichment and the enrichment coefficient; if the enrichment coefficient is less than 1 and the delay time of the engine enrichment is greater than or equal to the time the engine runs at the operating point after downshifting, the excess air coefficient of the engine is determined to be the enrichment coefficient; if the enrichment coefficient is less than 1 and the delay time of the engine enrichment is less than the time the engine runs at the operating point after downshifting, the excess air coefficient of the engine is determined to be 1.

7. The control system according to claim 6, characterized in that: The control system includes a calibration storage module, which is used to test the engine, determine an enrichment delay time table and an enrichment coefficient table, and store them.

8. The control system according to claim 6, characterized in that: The control system further includes an enrichment partition module, which is used to perform a bench calibration test on the engine to determine an enrichment region of the engine.

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