Engine cylinder oil injection condition detection method

Abstract

The invention discloses an engine cylinder oil injection condition detection method, which comprises the following steps: when an engine oil injection performance detection enabling condition is met, obtaining the operation time of each cylinder of an engine at a section of crankshaft operation angle; calculating an average value of the operation time of each cylinder of the engine and a maximum value and a minimum value in the average value; calculating a characteristic coefficient, and determining the value of an initial flag bit and the value of an initial fuel cut flag bit of the fixed cylinder according to the characteristic coefficient and the self-learning correction coefficient; and active fuel cut-off is carried out under the condition that the fuel cut-off enabling condition is met, the value of the fuel cut-off flag bit of each air cylinder is obtained according to the average value of the running time of each air cylinder of the engine in the fuel cut-off state and the maximum value and the minimum value, and whether real fuel cut-off happens to the air cylinders of the engine or not is judged. According to the method, the fuel injection performance of the engine can be detected, whether fuel cut occurs in a fixed air cylinder or not is checked, a driver is reminded to maintain and detect the engine in time, and the engine is protected.

Description

Technical Field

[0001] The invention relates to the technical field of engine control, and in particular to a method for detecting the fuel injection condition of an engine cylinder. Background Art

[0002] Engine combustion will generate torque, but one or more cylinders of the engine may have abnormal combustion problems. If the problem can be identified and located in a fixed cylinder, it means that there is a problem with the ignition or injection of the cylinder, which may be caused by related sensors or injection ignition actuators or wiring harness problems. Therefore, it is necessary to test the engine injection performance and check whether there is a fixed cylinder without oil, so as to remind the driver to repair and inspect the engine in time, and also protect the engine in time. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for detecting the fuel injection condition of an engine cylinder in view of the deficiencies in the prior art. The method can detect the fuel injection performance of the engine and verify whether there is a fixed cylinder that is out of fuel, thereby reminding the driver to repair and inspect the engine in time, and also can protect the engine in time.

[0004] To achieve the above object, according to one aspect of the present invention, a method for detecting the fuel injection condition of an engine cylinder is provided, comprising:

[0005] When the engine fuel injection performance detection enabling condition is met, the running time of each cylinder of the engine at a crankshaft operating angle is obtained;

[0006] Obtaining an average value of the operating time of each cylinder of the engine in a plurality of consecutive sampling periods, and determining a maximum value and a minimum value of the average value of the operating time;

[0007] Calculating a characteristic coefficient according to the maximum value and the minimum value of the running time average value; determining the value of the initial flag of the fixed cylinder according to the characteristic coefficient and the self-learning correction coefficient;

[0008] Determine the value of the initial fuel cut-off flag of the fixed cylinder according to the value of the initial flag; wherein the value of the initial fuel cut-off flag is 0 or 1;

[0009] When the fuel cut-off enabling conditions are met, the engine cylinder whose initial fuel cut-off flag value is 1 is actively cut off from fuel, the average value of the operating time of each engine cylinder in the fuel cut-off state within several consecutive sampling cycles is obtained, and the maximum and minimum values ​​of the average values ​​of the operating time of each engine cylinder in the fuel cut-off state are determined; the value of the fuel cut-off flag of each engine cylinder is determined according to the average value of the operating time of each engine cylinder in the fuel cut-off state and its maximum and minimum values ​​and the value of the initial fuel cut-off flag, and it is judged whether the engine cylinder whose initial fuel cut-off flag value is 1 is actually cut off from fuel.

[0010] The crankshaft operating angle section is the crankshaft angle of each cylinder of the engine from 80° after the cylinder compression top dead center to 260° after the corresponding cylinder compression top dead center, and the operating time of each cylinder of the engine in the crankshaft operating angle section is obtained.

[0011] In the above scheme, the average running time of each cylinder of the engine in a number of consecutive sampling cycles is T n_Avg The maximum value among the average values ​​of the running time of each cylinder of the engine is T max , the minimum value is T min .

[0012] In the above scheme, the characteristic coefficient r CynDetectRaw For several consecutive sampling periods (T max -T min ) / T min The self-learning correction coefficient k Adapt The default initial value is 0, which will be saved after the vehicle is powered off.

[0013] In the above scheme, the method for determining the value of the initial flag of the fixed cylinder according to the characteristic coefficient and the self-learning correction coefficient is:

[0014] If r CynDetectRaw (1+k Adapt )≥r CynDetectOffLim , then the initial flag bit bCynOffRaw The value is 1, otherwise the initial flag bCynOffRaw The value of is 0;

[0015] where r CynDetectOffLim is a threshold coefficient for determining the continuous fuel cutoff of a fixed cylinder. The threshold coefficient is obtained by bench calibration. The specific method is as follows: the threshold coefficient is determined by the average engine speed and the average engine intake density. On the engine bench, the self-learning correction coefficient k Adapt Under the premise of being 0, read the characteristic coefficient r under the active oil cut-off condition CynDetectRaw and the characteristic coefficient r without oil cut-off CynDetectRawThe minimum value of the average value of the characteristic coefficient under the active oil cut-off condition and the characteristic coefficient under the non-oil cut-off condition obtained by multiple samplings is taken as the threshold coefficient r for judging the continuous oil cut-off of the fixed cylinder. CynDetectOffLim ; wherein the average engine speed and the average engine intake density are respectively the average values ​​of the current sampling cycle and the four sampling cycles before it, a total of five sampling cycles; according to the test bench, multiple samplings are performed, and the fixed cylinder continuous oil cut-off is actively set at different engine speeds and different engine intake densities, and the minimum value of the threshold coefficient obtained in multiple samplings is used as the threshold coefficient.

[0016] In the above scheme, the method for determining the value of the initial fuel cut-off flag of the fixed cylinder according to the value of the initial flag is: bCynOffRaw The value of is 1, if:

[0017] The first case: There is an average running time T of the engine cylinder in several consecutive sampling periods. n_Avg With T max equal; and determine its cylinder number;

[0018] Second case: Under the conditions of the first case, there is a preset value X>(T max -T n_Avg ) / T max >0, determine its cylinder number;

[0019] The third case: the running time of the cylinder that meets the first or second case in several consecutive sampling cycles (T n -T max ) / T max All are within the preset range ±Y;

[0020] The fourth case: at least one cylinder does not meet the first case or the second case;

[0021] Fifth case: The cylinder numbers that meet the first or second case are recorded according to the cylinder working order. If the number of cylinders that do not meet the first or second case between two consecutive cylinder numbers that meet the first or second case is not less than 2, then T n_Avg With T min The equal cylinder number is not the next working cylinder number that satisfies the first condition or the second condition;

[0022] If multiple sampling times Cnt CynoffDelay When the first, second, third, fourth, and fifth conditions are met under the above conditions, the initial fuel cut-off flag position b of the cylinder that meets the first or second condition is CynOff The value is 1, the initial fuel cut-off flag of other cylinders is b CynOffis 0;

[0023] The multiple sampling times Cnt CynoffDelay The initial default value is 8, 3≤Cnt CynoffDelay ≤15, and it will be saved after the vehicle is powered off.

[0024] In the above scheme, the method for judging whether the engine cylinder whose initial fuel cut-off flag has a value of 1 has actually been cut off from fuel is:

[0025] Actively cut off fuel for the cylinders that meet the first condition or the second condition, and re-obtain the average running time T of each cylinder of the engine in the fuel cut-off state n_AvgNew and the maximum value T of the average running time of each cylinder of the engine maxNew With the minimum value T minNew ;

[0026] (1) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and When the oil cut-off mark of this cylinder is b CynOffFuelCut =b CynOff =1, the multiple sampling times Cnt CynoffDelay Subtract 1 and save after power off, the self-learning correction coefficient k Adapt Remain unchanged; C1 is the preset value;

[0027] (2) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and If only one of the following is satisfied, the oil cut-off flag of this cylinder is b CynOffFuelCut =0, the number of multiple sampling times Cnt CynoffDelay Remain unchanged; the self-learning correction coefficient And save it after power off;

[0028] (3) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and If both are not satisfied, the oil cut-off mark of this cylinder is b CynOffFuelCut =0, the multiple sampling times Cnt CynoffDelay Add 2, the self-learning correction coefficient And save it after power off;

[0029] (4) For the initial fuel cut-off flag b CynOff The value of cylinder A is 0. If the average running time of cylinder A is T A_Avg satisfy Then the oil cut-off mark of this cylinder is b CynOffFuelCut =0, the number of multiple sampling times Cnt CynoffDelay Remain unchanged, the self-learning correction coefficient And save after power off; C2 is the preset value;

[0030] (5) In other cases, the cylinder oil cut-off mark is b CynOffFuelCut =0, the number of multiple sampling times Cnt CynoffDelay and the self-learning correction coefficient k Adapt remain unchanged;

[0031] If the value of the initial fuel cut-off flag is 1, the fuel cut-off flag b of the engine cylinder CynOffFuelCut =1, it means that the engine cylinder has a real oil cut-off.

[0032] In the above scheme, the engine injection performance detection enabling conditions include:

[0033] (1) Entering the fire diagnosis area specified in the regulations;

[0034] (2) No request for fuel cut-off;

[0035] (3) The gear position has not changed;

[0036] (4) The clutch is in full engagement;

[0037] (5) Non-uneven road surface;

[0038] (6) The water temperature is within the preset range;

[0039] (7) The throttle opening fluctuation is small during the diagnosis process;

[0040] (8) The engine is in operation.

[0041] In the above scheme, the engine fuel injection performance detection enabling condition is:

[0042] The gear position not changing means that after the gear position changes, it takes a delay exceeding the gear position change preset time to activate the engine cylinder injection condition detection method;

[0043] The clutch is in a fully engaged state means that after the clutch is engaged, it takes a delay exceeding the clutch preset time to activate the engine cylinder injection condition detection method;

[0044] The throttle opening fluctuation during the diagnosis process is small, which means that the difference between the maximum opening and the minimum opening of the throttle within the preset throttle time is smaller than the preset throttle opening difference.

[0045] In the above scheme, the fuel cut-off enabling conditions include:

[0046] (1) satisfying the engine fuel injection performance detection enabling conditions;

[0047] (2) The vehicle speed exceeds the preset value;

[0048] (3) The engine does not experience knock and pre-ignition;

[0049] (4) The exhaust temperature does not exceed the preset protection temperature;

[0050] (5) The gasoline particulate filter does not request automatic regeneration;

[0051] (6) The oxygen storage capacity of the catalyst does not exceed the preset coefficient of its total oxygen storage capacity;

[0052] (7) No failure of components related to the fuel injection system occurs;

[0053] (8) The difference between the average engine speed and the average engine speed obtained during the bench calibration process of the threshold coefficient is within a preset range;

[0054] (9) The difference between the average engine intake density and the average intake density obtained during the bench calibration process of the threshold coefficient is within a preset range.

[0055] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0056] The present invention provides a method for detecting the fuel injection condition of an engine cylinder. The method can detect the fuel injection performance of the engine and check whether any fixed cylinder has experienced fuel cut-off. If it is determined that any fixed cylinder has experienced fuel cut-off, the corresponding cylinder is controlled to be fuel cut-off, and it is determined whether the condition is consistent with the previous condition. If the conditions are consistent, it is confirmed that the fuel cut-off of the cylinder has caused the abnormal combustion, thereby reminding the driver to perform maintenance and inspection on the engine in a timely manner, and the engine can also be protected in a timely manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Also, throughout the accompanying drawings, the same reference figures are used to represent the same components. In the drawings:

[0058] Figure 1 The figure is a flow chart of a method for detecting fuel injection conditions in an engine cylinder according to an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0060] It should be understood that the size of the serial numbers of the steps in the embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0061] Example 1

[0062] The present application provides a method for detecting the fuel injection condition of an engine cylinder. Figure 1 ,include:

[0063] S1, when the engine fuel injection performance detection enabling condition is met, the running time of each cylinder of the engine in a crankshaft operating angle is obtained.

[0064] Specifically, in this embodiment, in order to ensure the accuracy and safety of the engine cylinder injection condition detection, the engine cylinder injection condition detection method of the present invention needs to be performed under enabling conditions to reduce the error of the detection method. In the present invention, the enabling condition judgment sampling period is 10ms, and the engine injection performance detection enabling conditions include:

[0065] (1) Entering the fire diagnosis area specified in the regulations;

[0066] (2) No request for fuel cut-off;

[0067] (3) The gear position has not changed, and after the gear position has changed, a delay of 0.1s is required to activate the engine continuous fuel cut-off verification method;

[0068] (4) The clutch is in full engagement and the engine continuous fuel cut-off verification method can only be activated after a delay of 1 second after the clutch is engaged;

[0069] (5) Non-uneven road surface;

[0070] (6) Water temperature is higher than -6°C;

[0071] (7) The throttle opening fluctuation is small during the diagnosis process, and the difference between the maximum and minimum throttle openings within 0.1 s is less than 15%;

[0072] (8) The engine is in operation.

[0073] After the above conditions are met, the engine cylinder injection condition test can be performed. If the above conditions are not met, the vehicle's working conditions may cause misjudgment. If the enabling conditions are not met during the diagnosis process, the diagnosis is terminated and the engine cylinder injection condition test is performed after the next diagnosis condition is met.

[0074] Specifically, in this embodiment, the method for obtaining the running time of each cylinder of the engine in a section of crankshaft running angle is as follows: a section of crankshaft running angle is a crankshaft angle of 80° after the compression top dead center of each cylinder of the engine to 260° after the compression top dead center of its corresponding cylinder, and the running time of each cylinder of the engine in this section of crankshaft running angle is obtained, and the running time in a number of consecutive sampling periods is composed of the running time array T n [0, 1, 2, 3…], where n is the cylinder number; running time array T n The values ​​of [0, 1, 2, 3…] will be continuously updated; n [0] represents the running time of each cylinder of the engine at the current sampling time, T n [1] represents the running time of each cylinder of the engine in the last sampling, and so on. In particular, all sampling in the subsequent steps is that the crankshaft of each cylinder rotates from 80° after the compression top dead center to 260° after the compression top dead center, that is, the crankshaft rotates 180°.

[0075] S2, obtaining the average running time of each cylinder of the engine in a plurality of consecutive sampling periods, and determining the maximum and minimum values ​​of the average running time.

[0076] Specifically, in this embodiment, the average running time of each cylinder of the engine in five consecutive sampling cycles is calculated, and each cylinder is calculated separately to obtain the average running time T of each cylinder. n_Avg :

[0077]

[0078] Among them, the maximum value of the average running time of each cylinder of the engine is T max , the minimum value is T min : In this example, if the engine is a 4-cylinder engine, then:

[0079] T M ax=max(T 1_A vg,T 2_A vg,T 3_A vg,T 4_A vg);

[0080] T M in=min(T 1_A vg,T 2_A vg,T 3_Avg,T 4_A vg).

[0081] S3, calculating a characteristic coefficient according to the maximum and minimum values ​​in the average value of the running time; determining the value of the initial flag of the fixed cylinder according to the characteristic coefficient and the self-learning correction coefficient.

[0082] Specifically, in this embodiment, the characteristic coefficient r CynDetectRaw is the current sampling period The average value of the 5 sampling cycles before the 4 sampling cycles. Self-learning correction coefficient k Adapt The default initial value is 0, which will be saved after the vehicle is powered off. CynDetectOffLim The threshold coefficient is used to determine the continuous oil cut-off of the fixed cylinder. The threshold coefficient is calibrated on the test bench. The specific method is as follows: the threshold coefficient is determined by the average engine speed and the average engine intake density. On the engine test bench, the self-learning correction coefficient k Adapt Under the premise of being 0, read the characteristic coefficient r under active oil cut-off CynDetectRaw and the characteristic coefficient r without oil cut-off CynDetectRaw The minimum value of the average value of the characteristic coefficients under active oil cut-off and the characteristic coefficients under non-oil cut-off of multiple samplings is taken as the threshold coefficient r for judging the continuous oil cut-off of the fixed cylinder. CynDetectOffLim ; The average engine speed and average engine intake density are the average values ​​of the current sampling cycle and the previous four sampling cycles, a total of five sampling cycles. According to the test bench, multiple samplings are performed, and the fixed cylinder continuous oil cut-off is actively set at different engine speeds and different engine intake densities, and the minimum value of the threshold coefficient obtained in multiple samplings is used as the threshold coefficient.

[0083] According to the characteristic coefficient r CynDetectRaw and self-learning correction factor k Adapt The method for determining the value of the initial flag of the fixed cylinder is: if r CynDetectRaw (1+k Adapt )≥r CynDetectOffLim , then the initial flag bCynOffRaw The value is 1, otherwise the initial flag bCynOffRaw The value of is 0.

[0084] S4, determining the value of the initial oil cut-off flag of the fixed cylinder according to the value of the initial flag.

[0085] Specifically, in this embodiment, the method for determining the value of the flag bit of the fixed cylinder according to the value of the initial flag bit is: bCynOffRaw The value of is 1, if:

[0086] The first case: There is an average running time T of the engine cylinder in 5 consecutive sampling cycles.n_Avg With T max equal; and determine its cylinder number;

[0087] Second case: Under the conditions of the first case, there is a preset value X>(T max -T n_Avg ) / T max >0, determine its cylinder number; in this example, the preset value X is 0.08;

[0088] The third case: the running time of the cylinder that meets the first or second case within 5 consecutive sampling cycles (T n -T max ) / T max All are within the preset range ±Y; in this example, the preset range ±Y is ±0.08;

[0089] The fourth case: at least one cylinder does not meet the first case or the second case;

[0090] Fifth case: The cylinder numbers that meet the first or second case are recorded according to the cylinder working order. If the number of cylinders that do not meet the first or second case between two consecutive cylinder numbers that meet the first or second case is not less than 2, then T n_Avg With T min The cylinder number that is equal is not the next working cylinder number that satisfies the first or second situation. For example, in this example, the engine is a 4-cylinder engine, and the cylinder working sequence is 1-3-4-2-1-3-4-2-…. The cylinder numbers that meet the first or second situation are cylinder 1 and cylinder 2, and the middle working cylinders are cylinder 3 and cylinder 4. Then the T corresponding to cylinder 4 is 4_Avg Not equal to T Min .

[0091] If multiple sampling times Cnt CynoffDelay When the first, second, third, fourth, and fifth conditions are met under the above conditions, the initial fuel cut-off flag position b of the cylinder that meets the first or second condition is CynOff The value of 1 indicates that the cylinder that meets the first or second condition may be continuously cut off from fuel. The initial cut-off flag of other cylinders is b CynOff The value is 0. Multiple sampling times Cnt CynoffDelay The initial default value is 8, 3≤Cnt CynoffDelay ≤15, and will be saved after the vehicle is powered off.

[0092] S5, when the fuel cut-off enabling conditions are met, the engine cylinder whose initial fuel cut-off flag value is 1 is actively cut off from fuel, the average operating time of each engine cylinder in the fuel cut-off state within several consecutive sampling cycles is obtained, and the maximum and minimum values ​​of the average operating time of each engine cylinder in the fuel cut-off state are determined; the value of the fuel cut-off flag of each engine cylinder is determined according to the average operating time of each engine cylinder in the fuel cut-off state and its maximum and minimum values ​​and the value of the initial fuel cut-off flag, and it is judged whether the engine cylinder whose initial fuel cut-off flag value is 1 is actually cut off from fuel.

[0093] Specifically, in the embodiment of the present application, the fuel cut-off enabling conditions include:

[0094] (1) Satisfy the engine fuel injection performance detection enabling conditions;

[0095] (2) The speed exceeds 25 km / h;

[0096] (3) The engine does not experience knock and pre-ignition;

[0097] (4) The exhaust temperature does not exceed the preset protection temperature of 950°C;

[0098] (5) The gasoline particulate filter does not request automatic regeneration;

[0099] (6) The oxygen storage capacity of the catalyst does not exceed 90% of the total oxygen storage capacity;

[0100] (7) No failure of components related to the fuel injection system occurs;

[0101] (8) The difference between the average engine speed and the average engine speed obtained during the bench calibration process with the threshold coefficient is within a preset range; in this example, the preset range is ±20 rpm, where the average engine speed is the average of the current sampling period and the four sampling periods before it, a total of five sampling periods.

[0102] (9) The difference between the average engine intake air density and the average intake air density obtained during the bench calibration process with the threshold coefficient is within a preset range; in this example, the preset range is ±15 mgpl, where the average engine intake air density is the average of the current sampling period and the four sampling periods before it, a total of five sampling periods.

[0103] The method for judging whether the engine cylinder whose initial fuel cut-off flag value is 1 has actually been cut off from fuel is as follows:

[0104] Cut off the fuel supply to the cylinders that meet the first or second conditions, and re-obtain the average running time T of each cylinder of the engine. n_AvgNew and the maximum value T of the average running time of each cylinder of the engine maxNew With the minimum value T minNew ;

[0105] (1) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and When the oil cut-off mark of this cylinder is b CynOffFuelCut =b CynOff =1, multiple sampling times Cnt CynoffDelay Subtract 1 and save after power off, self-learning correction coefficient k Adapt Maintain unchanged; C1 is the preset value, in this example C1 is 0.08;

[0106] (2) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and If only one of the following is satisfied, the oil cut-off flag of this cylinder is b CynOffFuelCut =0, multiple sampling times Cnt CynoffDelay Remain unchanged; self-learning correction coefficient And save it after power off;

[0107] (3) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and If both are not satisfied, the oil cut-off mark of this cylinder is b CynOffFuelCut = 0, multiple sampling times Cnt CynoffDelay Add 2, self-learning correction coefficient And save it after power off;

[0108] (4) For the initial fuel cut-off flag b CynOff The value of cylinder A is 0. If the average running time of cylinder A is T A_Avg satisfy Then the oil cut-off mark of this cylinder is b CynOffFuelCut =0, multiple sampling times Cnt CynoffDelay Maintain unchanged, self-learning correction coefficient And save it after power off; C2 is the preset value, in this example, C2 is 0.2;

[0109] (5) In other cases, the cylinder oil cut-off mark is b CynOffFuelCut =0, multiple sampling times Cnt CynoffDelay and self-learning correction factor k Adapt remain unchanged;

[0110] If the initial fuel cut-off flag value is 1, the fuel cut-off flag b of the engine cylinder CynOffFuelCut =1, it means that the engine cylinder has a real oil cut-off.

[0111] In summary, the engine cylinder injection condition detection method provided by the present invention can detect the engine injection performance and check whether there is a fixed cylinder that has oil outage, thereby reminding the driver to repair and inspect the engine in time, and also can protect the engine in time.

[0112] It should be pointed out that, according to the needs of implementation, the various steps described in this application can be divided into more steps, or two or more steps or partial operations of the steps can be combined into a new step to achieve the purpose of the present invention.

[0113] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting the fuel injection condition of an engine cylinder, characterized in that: include: When the engine fuel injection performance detection enabling condition is met, the running time of each cylinder of the engine at a crankshaft operating angle is obtained; Obtaining an average value of the operating time of each cylinder of the engine in a plurality of consecutive sampling periods, and determining a maximum value and a minimum value of the average value of the operating time; Calculate a characteristic coefficient according to the maximum and minimum values ​​of the running time average values; Determine the value of the initial flag of the fixed cylinder according to the characteristic coefficient and the self-learning correction coefficient; Determine the value of the initial fuel cut-off flag of the fixed cylinder according to the value of the initial flag; wherein the value of the initial fuel cut-off flag is 0 or 1; When the fuel cut-off enabling conditions are met, the engine cylinder whose initial fuel cut-off flag value is 1 is actively cut off from fuel, the average value of the operating time of each engine cylinder in the fuel cut-off state within several consecutive sampling cycles is obtained, and the maximum and minimum values ​​of the average values ​​of the operating time of each engine cylinder in the fuel cut-off state are determined; the value of the fuel cut-off flag of each engine cylinder is determined according to the average value of the operating time of each engine cylinder in the fuel cut-off state and its maximum and minimum values ​​and the value of the initial fuel cut-off flag, and it is judged whether the engine cylinder whose initial fuel cut-off flag value is 1 is actually cut off from fuel.

2. The method for detecting the fuel injection condition of an engine cylinder according to claim 1, characterized in that: The method for obtaining the running time of each cylinder of the engine in a crankshaft operating angle is: The crankshaft operating angle section is the crankshaft angle of each cylinder of the engine from 80° after the cylinder compression top dead center to 260° after the corresponding cylinder compression top dead center, and the operating time of each cylinder of the engine in the crankshaft operating angle section is obtained.

3. The method for detecting the fuel injection condition of an engine cylinder according to claim 1, characterized in that: The average running time of each cylinder of the engine in a number of consecutive sampling cycles is T n_Avg The maximum value among the average values ​​of the running time of each cylinder of the engine is T max , the minimum value is T min .

4. The method for detecting the fuel injection condition of an engine cylinder according to claim 3, characterized in that: The characteristic coefficient r CynDetectRaw For several consecutive sampling periods (T max -T min ) / T min The self-learning correction coefficient k Adapt The default initial value is 0, which will be saved after the vehicle is powered off.

5. The method for detecting the fuel injection condition of an engine cylinder according to claim 4, characterized in that: The method for determining the value of the initial flag of the fixed cylinder according to the characteristic coefficient and the self-learning correction coefficient is: If r CynDetectRaw (1+k Adapt )≥r CynDetectOffLim , then the initial flag bit bCynOffRaw The value is 1, otherwise the initial flag bCynOffRaw The value of is 0; where r CynDetectOffLim is a threshold coefficient for determining the continuous fuel cutoff of a fixed cylinder. The threshold coefficient is obtained by bench calibration. The specific method is as follows: the threshold coefficient is determined by the average engine speed and the average engine intake density. On the engine bench, the self-learning correction coefficient k Adapt Under the premise of being 0, read the characteristic coefficient r under the active oil cut-off condition CynDetectRaw and the characteristic coefficient r without oil cut-off CynDetectRaw The minimum value of the average value of the characteristic coefficient under the active oil cut-off condition and the characteristic coefficient under the non-oil cut-off condition obtained by multiple samplings is taken as the threshold coefficient r for judging the continuous oil cut-off of the fixed cylinder. CynDetectOffLim ; wherein the average engine speed and the average engine intake density are respectively the average values ​​of the current sampling cycle and the four sampling cycles before it, a total of five sampling cycles; according to the test bench, multiple samplings are performed, and the fixed cylinder continuous oil cut-off is actively set at different engine speeds and different engine intake densities, and the minimum value of the threshold coefficient obtained in multiple samplings is used as the threshold coefficient.

6. The method for detecting the fuel injection condition of an engine cylinder according to claim 5, characterized in that: The method for determining the value of the initial oil cut-off flag of the fixed cylinder according to the value of the initial flag is: In the initial flag bCynOffRaw The value of is 1, if: The first case: There is an average running time T of the engine cylinder in several consecutive sampling periods. n_Avg With T max equal; and determine its cylinder number; Second case: Under the conditions of the first case, there is a preset value X>(T max -T n_Avg ) / T max >0, determine its cylinder number; The third case: the running time of the cylinder that meets the first or second case in several consecutive sampling cycles (T n -T max ) / T max All are within the preset range ±Y; The fourth case: at least one cylinder does not meet the first case or the second case; Fifth case: The cylinder numbers that meet the first or second case are recorded according to the cylinder working order. If the number of cylinders that do not meet the first or second case between two consecutive cylinder numbers that meet the first or second case is not less than 2, then T n_Avg With T min The equal cylinder number is not the next working cylinder number that satisfies the first condition or the second condition; If multiple sampling times Cnt CynoffDelay When the first, second, third, fourth, and fifth conditions are met, the flag position of the cylinder that meets the first or second condition is the initial fuel cut-off flag position b CynOff The value is 1, the initial fuel cut-off flag of other cylinders is b CynOff The value of is 0; The multiple sampling times Cnt CynoffDelay The initial default value is 8, 3≤Cnt CynoffDelay ≤15, and it will be saved after the vehicle is powered off.

7. The method for detecting the fuel injection condition of an engine cylinder according to claim 6, characterized in that: The method for judging whether the engine cylinder whose initial fuel cut-off flag has a value of 1 has actually been fuel cut-off is: Actively cut off fuel for the cylinders that meet the first condition or the second condition, and re-obtain the average running time T of each cylinder of the engine in the fuel cut-off state n_AvgNew and the maximum value T of the average running time of each cylinder of the engine in the fuel cut-off state maxNew With the minimum value T minNew ; (1) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and When the oil cut-off mark of this cylinder is b CynOffFuelCut =b CynOff =1, the multiple sampling times Cnt CynoffDelay Subtract 1 and save after power off, the self-learning correction coefficient k Adapt remain unchanged; Where C1 is the preset value; (2) For the initial fuel cut-off flag b CynOff For a cylinder with a value of 1, if and If only one of the following is satisfied, the oil cut-off flag of this cylinder is b CynOffFuelCut =0, the number of multiple sampling times Cnt CynoffDelay Remain unchanged; the self-learning correction coefficient And save it after power off; (3) For the initial fuel cut-off flag b CynOff The value of the cylinder is 1, if and If both are not satisfied, the oil cut-off mark of this cylinder is b CynOffFuelCut =0, the multiple sampling times Cnt CynoffDelay Add 2, the self-learning correction coefficient And save it after power off; (4) For the initial fuel cut-off flag b CynOff The value of cylinder A is 0. If the average running time of cylinder A is T A_Avg satisfy The oil cut-off mark of this cylinder is b CynOffFuelCut =0, the number of multiple sampling times Cnt CynoffDelay Remain unchanged, the self-learning correction coefficient And save after power off; C2 is the preset value; (5) In other cases, the cylinder oil cut-off mark is b CynOffFuelCut =0, the number of multiple sampling times Cnt CynoffDelay and the self-learning correction coefficient k Adapt remain unchanged; If the value of the initial fuel cut-off flag is 1, the fuel cut-off flag b of the engine cylinder CynOffFuelCut =1, it means that the engine cylinder has a real oil cut-off.

8. The method for detecting the fuel injection condition of an engine cylinder according to claim 1, characterized in that: The engine fuel injection performance detection enabling conditions include: (1) Entering the fire diagnosis area specified in the regulations; (2) No request for fuel cut-off; (3) The gear position has not changed; (4) The clutch is in full engagement; (5) Non-uneven road surface; (6) The water temperature is within the preset range; (7) The throttle opening fluctuation is small during the diagnosis process; (8) The engine is in operation.

9. The method for detecting the fuel injection condition of an engine cylinder according to claim 8, characterized in that: The engine fuel injection performance detection enabling condition: The gear position not changing means that after the gear position changes, it takes a delay exceeding the gear position change preset time to activate the engine cylinder injection condition detection method; The clutch is in a fully engaged state means that after the clutch is engaged, it takes a delay exceeding the clutch preset time to activate the engine cylinder injection condition detection method; The throttle opening fluctuation during the diagnosis process is small, which means that the difference between the maximum opening and the minimum opening of the throttle within the preset throttle time is smaller than the preset throttle opening difference.

10. The method for detecting the fuel injection condition of an engine cylinder according to claim 1, characterized in that: The fuel cut-off enabling conditions include: (1) satisfying the engine fuel injection performance detection enabling conditions; (2) The vehicle speed exceeds the preset value; (3) The engine does not experience knock and pre-ignition; (4) The exhaust temperature does not exceed the preset protection temperature; (5) The gasoline particulate filter does not request automatic regeneration; (6) The oxygen storage capacity of the catalyst does not exceed the preset coefficient of its total oxygen storage capacity; (7) No failure of components related to the fuel injection system occurs; (8) The difference between the average engine speed and the average engine speed obtained during the bench calibration process of the threshold coefficient is within a preset range; (9) The difference between the average engine intake density and the average intake density obtained during the bench calibration process of the threshold coefficient is within a preset range.

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