A method for self-learning and updating the minimum injection duration

Abstract

The present invention discloses a method for self-learning and updating the minimum allowable injection duration for direct injection engines. The method calculates the relationship between the current injection cylinder injection duration and the minimum allowable injection duration determined in the previous self-learning update. Based on this relationship, whether the fuel is rich or lean, and other preset conditions, the method categorizes operating conditions into four types: those with increased injection duration, four types with decreased injection duration, and other operating conditions. Further self-learning and updating are performed based on the categorized operating conditions. The present invention enables precise control of the minimum allowable injection duration during multiple injections in a direct injection engine.

Description

Technical Field

[0001] The invention relates to the field of engine control, and in particular to a method for self-learning and updating the minimum allowable injection duration. Background Art

[0002] To reduce vibration and noise in direct-injection engines, improve cold-start and emissions performance, and mitigate the risk of oil dilution, different injection times are required based on different engine operating conditions. If the duration of a single injection during multiple injections is too short, the nonlinear characteristics of the injector at low injection rates can lead to extremely poor injection quantity accuracy, impacting fuel economy and emissions.

[0003] Some existing technical solutions offer multiple-injection engine control strategies but fail to consider the specific calculation of injection pulse width. Furthermore, solutions that do propose methods for calculating injection pulse width fail to consider optimizing the injection pulse width when the number of injections decreases. Therefore, a method for self-learning and updating the minimum allowable injection duration is urgently needed to address the lean or rich fuel situation that can occur with multiple injections in direct-injection engines. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to propose a method for self-learning and updating the minimum injection duration allowed, so as to solve the problem that when a direct injection engine injects multiple times, the injection amount accuracy is extremely poor due to the inaccurate control of the minimum injection duration.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for self-learning and updating the minimum injection duration allowed, which determines whether the conditions for activating the self-learning and updating are met. If so, the self-learning and updating value of the minimum injection duration allowed enters the self-learning and updating stage; based on the self-learning and updating value of the minimum injection duration allowed after the last learning and updating, the relationship between the injection duration of the current injection cylinder and the minimum injection duration allowed is calculated;

[0006] When the fuel concentration satisfies the first preset condition, under the same conditions, according to the relationship between the injection duration of the current injection cylinder and the minimum allowable injection duration, and the number of times the third and fourth preset conditions are satisfied, the first injection duration increase operating condition, the first injection duration decrease operating condition, the second injection duration increase operating condition, the second injection duration decrease operating condition, and other operating conditions are obtained;

[0007] When the fuel concentration satisfies the second preset condition, under the same conditions, according to the relationship between the injection duration of the current injection cylinder and the minimum allowable injection duration, and the number of times the third and fourth preset conditions are satisfied, the third injection duration increase operating condition, the third injection duration decrease operating condition, the fourth injection duration increase operating condition, the fourth injection duration decrease operating condition, and other operating conditions are obtained;

[0008] For the above four injection duration increasing operating conditions, the corresponding preset value is added to the allowable minimum injection duration self-learning update value after the last learning update to obtain an updated allowable minimum injection duration self-learning update value; for the above four injection duration decreasing operating conditions, the corresponding preset value is subtracted from the allowable minimum injection duration self-learning update value after the last learning update to obtain an updated allowable minimum injection duration self-learning update value; for the above other operating conditions, the allowable minimum injection duration self-learning update value after the last learning update is not updated;

[0009] The allowed minimum injection time is updated according to the updated self-learning update value.

[0010] Furthermore, the relationship between the current injection cylinder injection time and the minimum allowed injection time is specifically: Value and The size relationship of the values, where is the injection duration of the current injection cylinder, To allow for a minimum injection duration, is the average value of the difference between the fuel rail pressure and the cylinder pressure during the current injection cylinder injection cycle, Based on Determine the initial value of the minimum injection duration allowed by the current injection cylinder, It is the self-learning update value of the minimum injection duration allowed after the last learning update. The default initial value is 0.

[0011] Furthermore, the first precondition is > , and the second precondition has not been met in the previous learning process. The second precondition is < , and the first prerequisite has not been met in the previous learning process, among which, is the average value of the difference in air-fuel ratio, 、 is the air-fuel ratio threshold coefficient, is the correction factor obtained based on different cylinder tests, is the target air-fuel ratio of the engine, is the threshold correction factor.

[0012] Furthermore, the aforementioned injection time increase working condition 1, injection time reduction working condition 1, injection time increase working condition 2, injection time reduction working condition 2 and other working conditions are specifically as follows: under the same conditions, when the fuel concentration meets the preset condition 1, if > , record the number of times CNT1 that the preset condition three is met. If CNT1 is greater than the preset value, this is the injection duration increase condition one. Record the number of times CNT2 that the preset condition four is met. If CNT2 is greater than the preset value, this is the injection duration decrease condition one. If < , record the number of times CNT3 that the preset condition three is met. If CNT3 is greater than the preset value, this situation is the injection time increase working condition two, record the number of times CNT4 that the preset condition four is met. If CNT4 is greater than the preset value, this situation is the injection time decrease working condition two; the conditions that do not meet the above four conditions are other conditions.

[0013] Furthermore, the three working conditions of increasing injection time, decreasing injection time, increasing injection time, decreasing injection time and other working conditions are as follows: under the same conditions, when the fuel concentration meets the preset condition two, if > , record the number of times CNT5 that the preset condition three is met. If CNT5 is greater than the preset value, this is the injection duration increase working condition three. Record the number of times CNT6 that the preset condition four is met. If CNT6 is greater than the preset value, this is the injection duration decrease working condition three. If < , record the number of times CNT7 that the preset condition three is met. If CNT7 is greater than the preset value, this situation is the injection duration increase working condition four, record the number of times CNT8 that the preset condition four is met. If CNT8 is greater than the preset value, this situation is the injection duration decrease working condition four; the conditions that do not meet the above four conditions are other conditions.

[0014] Furthermore, the third precondition is , the fourth precondition is ,in, is the average value of the engine target air-fuel ratio, is the actual air-fuel ratio filtered average value, 、 is the default value.

[0015] Furthermore, when the fuel concentration meets the preset condition 1, if

[0016] ,

[0017] Or when the fuel concentration meets the preset condition 2, if

[0018] ,

[0019] Then the threshold correction coefficient is updated by reducing the corresponding preset value on the threshold correction coefficient after the last self-learning update. It is the threshold correction coefficient after the last self-learning update, and its default initial value is 0.

[0020] Furthermore, if the number of times the other operating conditions occur continuously exceeds a preset number, the threshold correction coefficient is not updated; otherwise, the corresponding preset value is added to the threshold correction coefficient after the last self-learning update for update, and the number of times the other operating conditions occur continuously is cleared after the update.

[0021] Furthermore, the same conditions are defined as: the current injection cylinder number, the number of injections, the injection duration of the current injection cylinder, the average fuel rail pressure, the average fuel rail temperature, the average density of the actual fresh air intake entering the cylinder, the engine target air-fuel ratio, the long-term fuel correction average, the short-term fuel correction average, and the engine cooling water temperature average are all the same.

[0022] Furthermore, the four operating conditions where the fuel concentration meets the preset condition 1 or the four operating conditions where the fuel concentration meets the preset condition 2 have different priorities. When the conditions of the high-priority operating condition are met, the low-priority operating condition is no longer judged.

[0023] Furthermore, once the adjustment of the self-learning update value of the minimum injection duration allowed under one working condition is executed, the accumulation of the number of times of all working conditions under the same injection cylinder is cleared to zero.

[0024] Furthermore, the method for determining whether the self-learning update value of the minimum injection duration is allowed to meet the conditions for self-learning update includes: determining whether preset condition five is met; if so, the self-learning update value of the minimum injection duration is allowed to enter the self-learning update stage; if not, the self-learning inactive stage is entered; when in the self-learning inactive stage, when preset condition five is met, the self-learning stabilization stage is entered; when in the self-learning stabilization stage, when preset condition five and preset condition six are met at the same time, the self-learning activation stage is entered; when in the self-learning activation stage, after completing the continuous reading of various parameters within the preset time, the self-learning update stage is entered.

[0025] Furthermore, preset condition five includes that the engine speed fluctuation is within a preset range, the activation of the oxygen sensor upstream of the catalyst exceeds the preset time, no fuel cut-off occurs in any cylinder, the engine target air-fuel ratio remains unchanged, the fresh air density entering the cylinder fluctuates within a preset range, the number of injections does not change, the injection duration of the current injection cylinder is not less than the preset time and the fluctuation does not exceed the preset time, the intake temperature fluctuation is within the preset range, the fuel rail pressure fluctuation is within the preset range, the fuel rail temperature fluctuation is within the preset range, the engine cooling water temperature fluctuation is within the preset range, the long-term fuel correction coefficient remains unchanged, the short-term fuel correction coefficient fluctuation is within the preset range, the ignition angle efficiency is not lower than the preset value, the engine speed closed loop is not entered, the transmission system does not enter the gear shifting process state and the delay time after the transmission system exits the gear shifting process state exceeds the preset time, and no fault is detected; preset condition six includes that the self-learning stabilization phase is entered for more than the preset time and the self-learning update value of the minimum injection duration allowed is not updated for more than the preset time.

[0026] Furthermore, the preset condition six includes that the self-learning stabilization phase is entered for more than a preset time and the self-learning update value of the allowed minimum injection duration is not updated for more than a preset time.

[0027] Furthermore, after entering the self-learning stabilization stage: if the preset condition five is met and the preset condition six is ​​not met, the self-learning stabilization stage is maintained; if both the preset condition five and the preset condition six are not met, the self-learning inactive stage is returned to.

[0028] Furthermore, the injection duration of each injection can be obtained according to the updated minimum allowed injection duration. , specifically: If ,but 0; if ,but .

[0029] The beneficial effects of the present invention are as follows: by calculating the relationship between the current injection cylinder injection time and the minimum allowable injection time, when the fuel is too rich or too lean, the self-learning update value of the minimum allowable injection time is updated according to different working conditions, and the minimum allowable injection time is further updated, thereby avoiding the problem of the direct injection engine's multiple injections causing the injection fuel to be too lean or too rich due to inaccurate control of the minimum allowable injection time, thereby optimizing the combustion economy of the fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of a method for self-learning and updating the minimum allowed injection duration of the present invention;

[0031] Figure 2 This is a flow chart of a method for determining whether conditions for self-learning and updating are met according to the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0033] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the common meanings understood by persons having ordinary skills in the field to which the present disclosure belongs.

[0034] In order to facilitate the understanding of this application document, the following keywords need to be explained as follows:

[0035] : average value of the difference between air-fuel ratios; : air-fuel ratio threshold coefficient; : Correction coefficient based on different cylinder tests; : Engine target air-fuel ratio;

[0036] : Threshold correction coefficient; : The threshold correction coefficient after the last learning update;

[0037] : and difference; : The injection duration of the current injection cylinder; : The average value of the difference between the fuel rail pressure and the cylinder pressure during the current injection cylinder injection cycle; : The initial value of the minimum injection time allowed by the current injection cylinder;

[0038] : Average value of target air-fuel ratio of engine; : Average value of actual air-fuel ratio filtered value;

[0039] : Allow the minimum injection time to self-learn and update the value; : The self-learning update value of the minimum injection duration allowed after the last learning update;

[0040] : Actual air-fuel ratio filtered value; : Actual air-fuel ratio filtered value of the Nth sampling period; : Actual air-fuel ratio original value of the Nth sampling period, N=1.2.3...; : coefficient, and ; : air-fuel ratio filter coefficient; : number of engine cylinders; : Engine speed.

[0041] This embodiment provides a method for self-learning and updating the minimum injection duration value, such as Figure 1 As shown, the following steps are included:

[0042] Determine whether the conditions for activating self-learning update are met. If so, allow the minimum injection duration self-learning update value to enter the self-learning update stage. Specifically, the judgment process is as follows: Figure 2 shown.

[0043] When the following activation conditions are met at the same time, the minimum injection duration self-learning update value is allowed to be updated by self-learning:

[0044] The engine speed fluctuation range is within ±20rpm; the oxygen sensor upstream of the catalyst has been activated for a period of time, which is 0.5s in this embodiment; no fuel cut-off occurs in any cylinder; the engine target air-fuel ratio remains unchanged; the intake density of fresh air entering the cylinder fluctuates within ±15mg / l; the number of injections does not change (the definition of the number of injections is given in patent CN202410313240.0 "A direct injection engine multi-injection control method and system"); the injection duration of the current injection cylinder fluctuates by no more than ±0.2ms; the injection duration of the current injection cylinder is not less than 0.5ms; the intake air temperature fluctuates within ±2°C; the fuel rail pressure fluctuates by no more than ±2kPa; the fuel rail temperature fluctuates by no more than ±1°C; the engine cooling water temperature fluctuates by no more than ±1 ℃; the long-term fuel correction coefficient has not changed (the definition of the long-term fuel correction coefficient can be found in CN202010246641.0 "A self-learning method for long-term fuel correction of a gasoline engine"); the short-term fuel correction coefficient fluctuation range does not exceed ±0.01 (the definition of the short-term fuel correction coefficient can be found in CN202111202932.0 "A method and control system for controlling short-term fuel correction of an engine"); the ignition angle efficiency is not lower than the preset value, which is 0.9 in this embodiment to avoid mislearning due to poor combustion caused by too low ignition angle efficiency; the engine speed closed loop has not been entered; the transmission system has not entered the gear shifting process state and the delay time after the transmission system exits the gear shifting process state exceeds the preset time, which is 0.05s in this embodiment; no faults are detected.

[0045] During the self-learning process, if any of the activation conditions are not met at any stage, the self-learning is terminated and the self-learning inactive stage begins. During the self-learning inactive stage, if the above activation conditions are met, the self-learning stabilization stage begins, which allows the self-learning of the minimum injection duration to be updated. The purpose of the stabilization stage is to ensure that the self-learning activation conditions are stable and reliable.

[0046] During the self-learning stabilization phase, when the reactivation conditions are met, the self-learning activation phase that allows the self-learning update value of the minimum injection duration is entered. The reactivation conditions include: entering the self-learning stabilization phase for more than the preset time , this embodiment takes 5s; the self-learning update value of the minimum injection time is allowed to be updated within the preset time. , in this embodiment, 2880h is taken.

[0047] After entering the self-learning stabilization stage: if the reactivation conditions are not met and the activation conditions are met, it will remain in the self-learning stabilization stage; if both the reactivation conditions and the activation conditions are not met, it will return to the self-learning inactive stage; when both the reactivation conditions and the activation conditions are met, it will enter the self-learning active stage.

[0048] When entering the self-learning activation phase that allows the self-learning update value of the minimum injection time, the continuous time after entering the self-learning activation phase is accumulated and read. The average fuel rail pressure, the average fuel rail temperature, the average engine cooling water temperature, the target engine air-fuel ratio, the actual average fresh air intake density entering the cylinder, the actual air-fuel ratio filter value, the average actual air-fuel ratio filter value, the number of injections, the long-term fuel correction factor, the short-term fuel correction factor, the average air-fuel ratio difference, in this embodiment Take 3s.

[0049] Among them, the actual air-fuel ratio filter value The calculation formula is:

[0050] .

[0051] In this embodiment, Take 10ms, the number of engine cylinders m is 4, The calibration speed is 1000rpm. Take 0.023.

[0052] set up The purpose is to calibrate the engine at different cylinder numbers and speeds without having to do special calibration. It only needs to calibrate the engine at 4 cylinders and a speed of 1000 rpm. , thereby reducing the calibration test work and achieving normalization processing.

[0053] In time Once the conditions are met, the system enters the self-learning update phase where the self-learning update value of the minimum injection duration is allowed.

[0054] The relationship between the current injection cylinder injection duration and the minimum allowable injection duration is calculated based on the self-learning update value of the minimum allowable injection duration after the last learning update.

[0055] Specifically, calculate and difference .

[0056] When the fuel concentration meets preset condition one, under the same conditions, based on the relationship between the injection duration of the current injection cylinder and the minimum allowable injection duration, and the number of times preset conditions three and preset conditions four are met respectively, the injection duration increase operating condition one, injection duration decrease operating condition one, injection duration increase operating condition two, injection duration decrease operating condition two and other operating conditions are obtained.

[0057] For the working condition of increasing injection duration, the corresponding preset value is added to the self-learning update value of the minimum allowable injection duration after the last learning update to obtain the updated self-learning update value of the minimum allowable injection duration; for the working condition of decreasing injection duration, the corresponding preset value is subtracted from the self-learning update value of the minimum allowable injection duration after the last learning update to obtain the updated self-learning update value of the minimum allowable injection duration; for the other working conditions mentioned above, the self-learning update value of the minimum allowable injection duration after the last learning update is not updated.

[0058] Specifically, if > If the fuel is lean during the previous self-learning process, the self-learning update value of the minimum injection duration allowed will not be updated this time; if the fuel is not lean before, it means that the actual air-fuel ratio control is too small, and it is judged that the fuel is rich, so the self-learning update value of the minimum injection duration allowed will be updated.

[0059] Record the same conditions Greater than 0 and satisfies The number of times CNT1, In this embodiment, the value is 0.02. Once CNT1 is greater than the preset value, the value is 5, indicating that the current injection duration is too short, which may cause air-fuel ratio fluctuations and the minimum injection duration needs to be increased. This situation is called injection duration increase condition 1, and the value is updated. .

[0060] Record the same conditions Greater than 0 and satisfies The number of times CNT2, In this embodiment, the value is 0.01. Once CNT2 is greater than the preset value, the value is 5, indicating that the current injection duration is long and is not likely to cause air-fuel ratio fluctuations. The minimum injection duration needs to be reduced. This situation is called injection duration reduction condition 1, and the value is updated. .

[0061] Record the same conditions Less than 0, and satisfies Once CNT3 is greater than the preset value, in this embodiment, it is set to 5, indicating that the current injection duration is extremely short, which is likely to cause air-fuel ratio fluctuations and requires a significant increase in the minimum injection duration. This situation is called injection duration increase condition 2, and the update .

[0062] Record the same conditions met Less than 0 and satisfies Once CNT4 is greater than the preset value, the value is set to 5 in this embodiment, indicating that the current injection duration is very short and is not likely to cause air-fuel ratio fluctuations. The minimum injection duration needs to be reduced to a large extent. This situation is called the injection duration reduction working condition 2, and the update .

[0063] Under other working conditions No update.

[0064] If the number of times other working conditions occur continuously exceeds the preset number, which is 20 in this embodiment, then Do not update; otherwise ,exist After the update, the consecutive times of other working conditions are reset to zero, and then continue to accumulate from 0.

[0065] In any of the above 4 situations, if , then update , that is, due to After the update, the minimum injection duration also needs to be updated. At this time, the operating condition range that allows entering this situation is increased, and further judgment is made as to whether the minimum injection duration also needs to be updated under other operating conditions.

[0066] The priorities of the second working condition of increasing the injection duration, the first working condition of increasing the injection duration, the first working condition of decreasing the injection duration, and the second working condition of decreasing the injection duration are getting lower and lower. If the working condition with a high priority is met, the working condition with a low priority will no longer be judged, and the learning coefficient update with a low priority will not be executed.

[0067] When the fuel concentration meets the preset condition two, under the same conditions, according to the relationship between the injection time of the current injection cylinder and the minimum allowable injection time, and the number of times the preset conditions three and four are met respectively, the injection time increase working condition three, the injection time decrease working condition three, the injection time increase working condition four, the injection time decrease working condition four and other working conditions are obtained.

[0068] For the working condition of increasing injection duration, the corresponding preset value is added to the self-learning update value of the minimum allowable injection duration after the last learning update to obtain the updated self-learning update value of the minimum allowable injection duration; for the working condition of decreasing injection duration, the corresponding preset value is subtracted from the self-learning update value of the minimum allowable injection duration after the last learning update to obtain the updated self-learning update value of the minimum allowable injection duration; for the other working conditions mentioned above, the self-learning update value of the minimum allowable injection duration after the last learning update is not updated.

[0069] Specifically, if < If the fuel was too rich in the previous learning process, the self-learning update value of the minimum injection duration allowed will not be updated this time; if the fuel was not too rich in the previous learning process, it means that the actual air-fuel ratio control is too large, and it is judged that the fuel is too lean, so the self-learning update value of the minimum injection duration allowed will be updated.

[0070] Record the same conditions met Greater than 0 and satisfies The number of times CNT5 is calculated. If CNT5 is greater than the preset value, in this embodiment, it is set to 5, indicating that the current injection duration is short, which is likely to cause air-fuel ratio fluctuations and the minimum injection duration needs to be increased. This situation is called injection duration increase working condition three. The injection duration that needs to be increased in injection duration increase working condition three must not be less than the injection duration that needs to be increased in injection duration increase working condition one. The main reason is that the fuel injection is lean at this time and the minimum injection duration needs to be further increased to avoid further leaning and update .

[0071] Record the same conditions met Greater than 0 and satisfies The number of times CNT6 is calculated. If CNT6 is greater than the preset value, in this embodiment, it is set to 5, indicating that the current injection duration is long and is not likely to cause air-fuel ratio fluctuations. The minimum injection duration needs to be reduced. This situation is called injection duration reduction working condition three. The injection duration that needs to be reduced in injection duration reduction working condition three must not be greater than the injection duration that needs to be reduced in injection duration reduction working condition one. The main reason is that the fuel injection is lean at this time. The injection duration cannot be reduced too much to avoid further leaning, and the fuel injection is updated. .

[0072] Record the same conditions met Less than 0 and satisfies The number of times CNT7 is reached. If CNT7 is greater than the preset value, in this embodiment, it is set to 5, indicating that the current injection duration is extremely short, which is likely to cause air-fuel ratio fluctuations, and it is necessary to significantly increase the minimum injection duration. This situation is called injection duration increase working condition 4. The injection duration that needs to be increased in injection duration increase working condition 4 must not be less than the injection duration that needs to be increased in injection duration increase working condition 2. The main reason is that the fuel injection is lean at this time, and it is necessary to further increase the minimum injection duration to avoid further leanness, and update .

[0073] Record the same conditions met Less than 0 and satisfies The number of times CNT8 is reached. Once CNT8 is greater than the preset value, the value is set to 5 in this embodiment, indicating that the current injection duration is extremely short, but it is not likely to cause air-fuel ratio fluctuations, and the minimum injection duration needs to be significantly reduced. This situation is called injection duration reduction working condition 4. The injection duration that needs to be reduced in injection duration reduction working condition 4 must not be greater than the injection duration that needs to be reduced in injection duration reduction working condition 2. The main reason is that the fuel injection is lean at this time, and the injection duration cannot be reduced too much to avoid further leaning, and the update is performed. .

[0074] Under other working conditions, the self-learning update value of the minimum injection duration is not updated.

[0075] If the number of times other working conditions occur continuously exceeds the preset number, which is 20 in this embodiment, then Do not update; otherwise ,exist After the update, the consecutive times of other working conditions are reset to zero, and then continue to accumulate from 0.

[0076] In any of the above four situations,

[0077] like , then update , that is, due to After the update, the minimum injection duration also needs to be updated. At this time, the operating condition range that allows entering this situation is increased, and further judgment is made as to whether the minimum injection duration also needs to be updated under other operating conditions.

[0078] The priorities of the fourth working condition of increasing the injection duration, the third working condition of increasing the injection duration, the third working condition of decreasing the injection duration, and the fourth working condition of decreasing the injection duration are getting lower and lower. If the working conditions with high priority are met, the working conditions with low priority will no longer be judged, and the learning coefficient update with low priority will not be executed.

[0079] Once the self-learning update value adjustment of the allowable minimum injection duration under one of the above working conditions is executed, the cumulative number of times of all working conditions under the same injection cylinder is cleared to zero.

[0080] In this embodiment, the same parameters as the current injection cylinder number, the number of injections, the injection duration of the current injection cylinder, the average fuel rail pressure, the average fuel rail temperature, the average density of the fresh air actually entering the cylinder, the target engine air-fuel ratio, the average long-term fuel correction, the average short-term fuel correction, and the average engine cooling water temperature are defined as the same conditions.

[0081] The self-learning updated values ​​of the minimum injection duration allowed for different operating conditions are stored in the non-volatile EEPROM memory. The EEPROM has an initial default value of 0. The stored value in the EEPROM is updated after the self-learning of the updated value of the minimum injection duration allowed is completed.

[0082] The allowed minimum injection time is updated according to the updated self-learning update value.

[0083] The present invention obtains the relationship between the current injection cylinder injection duration and the minimum allowable injection duration determined by the self-learning update value of the minimum allowable injection duration after the last self-learning update. Based on this relationship and a determination of whether the fuel is too rich or too lean, the operating conditions are divided into four injection duration increase conditions, four injection duration decrease conditions, and other operating conditions. The self-learning update value of the minimum allowable injection duration is further updated, and the updated minimum allowable injection duration is calculated by combining the obtained updated self-learning update value of the minimum allowable injection duration with the minimum allowable injection duration determined based on the difference between the fuel rail pressure and the in-cylinder pressure. The present invention optimizes the control of the minimum allowable injection duration, solves the problem of poor injection quantity accuracy at low injection quantities caused by the nonlinear characteristics of the injector during multiple injections in a direct injection engine, and optimizes fuel combustion economy.

[0084] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for self-learning and updating the minimum injection duration allowed, characterized in that: include: Determine whether the conditions for activating self-learning update are met. If so, allow the minimum injection duration self-learning update value to enter the self-learning update stage; Calculate the relationship between the current injection cylinder injection time and the minimum allowable injection time based on the self-learning update value of the minimum allowable injection time after the last learning update; When the fuel concentration satisfies the first preset condition, under the same conditions, according to the relationship between the injection duration of the current injection cylinder and the minimum allowable injection duration, and the number of times the third and fourth preset conditions are satisfied, the first injection duration increase operating condition, the first injection duration decrease operating condition, the second injection duration increase operating condition, the second injection duration decrease operating condition, and other operating conditions are obtained; When the fuel concentration satisfies the second preset condition, under the same conditions, according to the relationship between the injection duration of the current injection cylinder and the minimum allowable injection duration, and the number of times the third and fourth preset conditions are satisfied, the third injection duration increase operating condition, the third injection duration decrease operating condition, the fourth injection duration increase operating condition, the fourth injection duration decrease operating condition, and other operating conditions are obtained; For the above four injection duration increasing operating conditions, the corresponding preset value is added to the allowable minimum injection duration self-learning update value after the last learning update to obtain an updated allowable minimum injection duration self-learning update value; for the above four injection duration decreasing operating conditions, the corresponding preset value is subtracted from the allowable minimum injection duration self-learning update value after the last learning update to obtain an updated allowable minimum injection duration self-learning update value; for the above other operating conditions, the allowable minimum injection duration self-learning update value after the last learning update is not updated; The allowed minimum injection time is updated according to the updated self-learning update value.

2. The method for self-learning and updating the minimum injection duration according to claim 1, characterized in that: The relationship between the current injection cylinder injection time and the minimum allowed injection time is specifically: Value and The size relationship of the values, where is the injection duration of the current injection cylinder, To allow for a minimum injection duration, is the average value of the difference between the fuel rail pressure and the cylinder pressure during the current injection cylinder injection cycle, Based on Determine the initial value of the minimum injection duration allowed by the current injection cylinder, It is the self-learning update value of the minimum injection duration allowed after the last learning update. The default initial value is 0.

3. The method for self-learning and updating the minimum injection duration according to claim 1, characterized in that: The first precondition is > , and the second precondition has not been met in the previous learning process. The second precondition is < , and the first prerequisite has not been met in the previous learning process, among which, is the average value of the difference in air-fuel ratio over a continuous period of time after entering the self-learning activation phase. 、 is the air-fuel ratio threshold coefficient, is the correction factor obtained based on different cylinder tests, is the target air-fuel ratio of the engine, is the threshold correction factor.

4. The method for self-learning and updating the minimum injection duration according to claim 2, characterized in that: The aforementioned injection duration increase working condition 1, injection duration decrease working condition 1, injection duration increase working condition 2, injection duration decrease working condition 2 and other working conditions are specifically when the fuel concentration meets the preset condition 1, under the same conditions: like , record the number of times CNT1 that the preset condition three is met. If CNT1 is greater than the preset value, this is the injection duration increase condition 1. Record the number of times CNT2 that the preset condition four is met. If CNT2 is greater than the preset value, this is the injection duration decrease condition 1. like , record the number of times CNT3 that the preset condition three is met. If CNT3 is greater than the preset value, this is the second condition where the injection duration is increased. Record the number of times CNT4 that the preset condition four is met. If CNT4 is greater than the preset value, this is the second condition where the injection duration is reduced. Other working conditions are those that do not meet the above four working conditions.

5. The method for self-learning and updating the minimum allowed injection duration according to claim 2, characterized in that: The aforementioned injection duration increase working condition 3, injection duration decrease working condition 3, injection duration increase working condition 4, injection duration decrease working condition 4 and other working conditions are specifically when the fuel concentration meets the preset condition 2, under the same conditions: like , record the number of times CNT5 that the preset condition three is met. If CNT5 is greater than the preset value, this is the injection duration increase working condition three. Record the number of times CNT6 that the preset condition four is met. If CNT6 is greater than the preset value, this is the injection duration decrease working condition three. like , record the number of times CNT7 that the preset condition three is met. If CNT7 is greater than the preset value, this is the fourth condition where the injection duration is increased. Record the number of times CNT8 that the preset condition four is met. If CNT8 is greater than the preset value, this is the fourth condition where the injection duration is reduced. Other working conditions are those that do not meet the above four working conditions.

6. The method for self-learning and updating the minimum injection duration according to claim 1, characterized in that: Precondition three is , the fourth precondition is ,in, is the average value of the engine target air-fuel ratio during the continuous time after entering the self-learning activation phase, is the actual air-fuel ratio filtered average value within a continuous period after entering the self-learning activation phase. 、 is the default value.

7. The method for self-learning and updating the minimum injection duration according to claim 3, characterized in that: When the fuel concentration meets the preset condition 1, if ， Or when the fuel concentration meets the preset condition 2, if ， Then the threshold correction coefficient is updated by reducing the corresponding preset value on the threshold correction coefficient after the last self-learning update. It is the threshold correction coefficient after the last self-learning update, and its default initial value is 0.

8. The method for self-learning and updating the minimum injection duration according to claim 1, characterized in that: If the number of times the other operating conditions occur continuously exceeds the preset number, the threshold correction coefficient is not updated. Otherwise, the corresponding preset value is added to the threshold correction coefficient after the last self-learning update for update, and the number of times the other operating conditions occur continuously is cleared after the update.

9. The method for self-learning and updating the minimum injection duration according to claim 1, characterized in that: The same conditions are defined as: the current injection cylinder number, injection times, injection duration of the current injection cylinder, the average value of the fuel rail pressure in the continuous time after entering the self-learning activation stage, the average value of the fuel rail temperature in the continuous time after entering the self-learning activation stage, the average value of the actual fresh air intake density entering the cylinder in the continuous time after entering the self-learning activation stage, the engine target air-fuel ratio, the average value of the long-term fuel correction in the continuous time after entering the self-learning activation stage, the average value of the short-term fuel correction in the continuous time after entering the self-learning activation stage and the average value of the engine cooling water temperature in the continuous time after entering the self-learning activation stage under different working conditions are the same.

10. The method for self-learning and updating the minimum allowed injection duration according to claim 1, characterized in that: The four operating conditions where the fuel concentration meets the preset condition 1 or the four operating conditions where the fuel concentration meets the preset condition 2 have different priorities. When the conditions of the high-priority operating condition are met, the low-priority operating condition is no longer judged.

11. The method for self-learning and updating the minimum allowed injection duration according to claim 1, characterized in that: Once the adjustment of the self-learning update value of the minimum injection duration allowed under one of the working conditions is executed, the accumulation of the number of times of all working conditions under the same injection cylinder is cleared to zero.

12. The method for self-learning and updating the minimum allowed injection duration according to claim 1, characterized in that: The method for determining whether the self-learning update value of the minimum injection duration is allowed to meet the conditions for self-learning update includes: determining whether preset condition five is met, if so, the self-learning update value of the minimum injection duration is allowed to enter the self-learning update stage, if not, enter the self-learning inactive stage; when in the self-learning inactive stage, when preset condition five is met, enter the self-learning stabilization stage; when in the self-learning stabilization stage, when preset condition five and preset condition six are met at the same time, enter the self-learning activation stage; when in the self-learning activation stage, after completing the continuous reading of various parameters within the preset time, enter the self-learning update stage.

13. The method for self-learning and updating the minimum allowed injection duration according to claim 12, characterized in that: Preset condition five includes: engine speed fluctuation within a preset range; activation of the oxygen sensor upstream of the catalyst exceeds the preset time; no fuel cut-off occurs in any cylinder; the engine target air-fuel ratio remains unchanged; the density of fresh air entering the cylinder fluctuates within a preset range; the number of injections remains unchanged; the injection duration of the current injection cylinder is not less than the preset time and the fluctuation does not exceed the preset time; the fluctuation of the intake air temperature is within a preset range; the fluctuation of the fuel rail pressure is within a preset range; the fluctuation of the fuel rail temperature is within a preset range; the fluctuation of the engine cooling water temperature is within a preset range; the long-term fuel correction factor remains unchanged; the fluctuation of the short-term fuel correction factor is within a preset range; the ignition angle efficiency is not lower than the preset value; the engine speed closed loop is not entered; the transmission system has not entered the gear shifting process state and the delay time after the transmission system exits the gear shifting process state exceeds the preset time; and no fault is detected.

14. The method for self-learning and updating the minimum allowed injection duration according to claim 12, characterized in that: Preset condition six includes entering the self-learning stabilization phase for more than a preset time and the self-learning update value of the allowed minimum injection duration not being updated for more than a preset time.

15. The method for self-learning and updating the minimum allowed injection duration according to claim 12, characterized in that: After entering the self-learning stabilization stage: if preset condition five is met and preset condition six is ​​not met, it remains in the self-learning stabilization stage; if both preset condition five and preset condition six are not met, it returns to the self-learning inactive stage.

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