A method for detecting fuel injection condition of engine cylinder

Abstract

The present invention discloses a method for detecting the fuel injection status of an engine cylinder, comprising: obtaining the operating time of each engine cylinder within a range of crankshaft operating angles when an enabling condition for engine fuel injection performance detection is met; obtaining the average operating time of each engine cylinder and its maximum and minimum values; calculating a characteristic coefficient, and determining the value of an initial flag and an initial fuel cut-off flag for a fixed cylinder based on the characteristic coefficient and a self-learning correction coefficient; and actively cutting fuel when the fuel cut-off enabling condition is met, obtaining the fuel cut-off flag value for each cylinder based on the average operating time of each engine cylinder in the fuel cut-off state and its maximum and minimum values, and determining whether a true fuel cut-off has occurred in the engine cylinder. This method can detect engine fuel injection performance, verify whether a fixed cylinder has experienced fuel cut-off, and alert the driver to promptly perform engine maintenance and inspection to protect the engine.

Description

Technical Field

[0001] The present 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 generates torque, but abnormal combustion may occur in one or more cylinders. If the problem can be identified and located in a specific cylinder, it indicates an ignition or fuel injection problem in that cylinder, possibly caused by a problem with the sensor, fuel injection actuator, or wiring harness. Therefore, it is necessary to test the engine's fuel injection performance and verify whether any specific cylinders are experiencing fuel interruptions. This will alert the driver to timely engine maintenance and inspection, and also provide timely engine protection. 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 response to the shortcomings of the existing technology. The method can detect the fuel injection performance of the engine and verify whether there is a fixed cylinder with fuel outage, thereby reminding the driver to repair and inspect the engine in time, and also protect the engine in time.

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

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

[0006] Calculating an average value of the operating time of each cylinder of the engine within 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 based on the maximum and minimum values ​​of the running time average value; determining the value of the initial flag of the fixed cylinder based on 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 operating time of each engine cylinder in the fuel cut-off state in 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 truly 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 several consecutive sampling periods is T n_Avg The maximum value among the average 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 average value of 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 as follows:

[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 The threshold coefficient is used to judge the continuous oil cut-off of the fixed cylinder. The threshold coefficient is obtained 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 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 period and the four sampling periods before it, a total of five sampling periods; 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 solution, 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: 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 periods (T n -T max ) / T max All are within the preset range ±Y;

[0020] Case 4: At least one cylinder does not meet the conditions of case 1 or case 2;

[0021] Fifth case: The cylinder numbers that meet the first or second case are recorded in the order of cylinder work. 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 condition or the second condition;

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

[0023] The number of 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 solution, the method for determining whether the engine cylinder whose initial fuel cut-off flag has a value of 1 has actually been fuel cut-off is:

[0025] Actively cut off fuel for the cylinders that meet the first or second conditions, 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 number of 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 met, 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 all of the above are not satisfied, the oil cut-off flag of this cylinder is set to 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 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 after power off; C2 is the preset value;

[0030] (5) In other cases, the oil cut-off mark of the cylinder 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 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.

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

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

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

[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 running state.

[0041] In the above solution, the engine fuel injection performance detection enabling conditions include:

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

[0043] The clutch being in a fully engaged state means that after the clutch is engaged, it takes more than a preset clutch 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 solution, 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 fuel injection system related components occurred;

[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 air density and the average intake air 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 a fixed cylinder has experienced fuel cut-off, the corresponding cylinder is controlled to cut off fuel, and it is determined whether the situation is consistent with the previous situation. If the situation is consistent, it is confirmed that the combustion abnormality is caused by the fuel cut-off of the cylinder, thereby reminding the driver to repair and inspect the engine in time, and the engine can also be protected in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. Throughout the drawings, the same reference figures denote 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 objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining 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 may 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 embodiment 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 embodiment of the present application.

[0061] Example 1

[0062] On the one hand, the present invention 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 operating time of each cylinder of the engine in a range of crankshaft operating angles 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) Enter the fire diagnosis area specified in the regulations;

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

[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℃;

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

[0072] (8) The engine is in running state.

[0073] Once the above conditions are met, the engine cylinder injection test can be performed. If the above conditions are not met, the vehicle's operating conditions may cause misjudgment. If the enabling conditions are not met during the diagnosis process, the diagnosis is terminated and the engine cylinder injection test will be performed again when the next diagnostic conditions are met.

[0074] Specifically, in this embodiment, the method for obtaining the running time of each cylinder of the engine in a range of crankshaft operating angles is as follows: a range of crankshaft operating angles is from 80° of crankshaft angle after compression top dead center of each cylinder of the engine to 260° after compression top dead center of its corresponding cylinder, and the running time of each cylinder of the engine in this range of crankshaft operating angles is obtained. The running time in a number of consecutive sampling periods is combined into a 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 subsequent sampling steps are for each cylinder from the crankshaft angle of 80° after compression top dead center to 260° after compression top dead center, that is, the crankshaft rotates 180°.

[0075] S2, calculating 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 5 consecutive sampling periods is calculated, and each cylinder is calculated separately to obtain the average running time of each cylinder T 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 ​​of 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 The current sampling period The average value of the 5 sampling cycles including the 4 sampling cycles before it. 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 judge the continuous oil cut-off of the fixed cylinder. The threshold coefficient is obtained 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 under the condition of no oil interruption 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 air density are the averages of the current sampling cycle and the four preceding sampling cycles, totaling five sampling cycles. Multiple sampling runs are performed on the test bench. Continuous fuel cutoff is actively set for a fixed cylinder at different engine speeds and different engine intake air densities. The minimum threshold coefficient value obtained from these multiple sampling runs is used as the threshold coefficient.

[0083] According to the characteristic coefficient r CynDetectRaw and self-learning correction coefficient 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 of the fixed cylinder according to the value of the initial flag is as follows: bCynOffRaw The value of is 1, if:

[0086] Case 1: There is an average running time T of the engine cylinder in 5 consecutive sampling periods.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 in 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] Case 4: At least one cylinder does not meet the conditions of case 1 or case 2;

[0090] Fifth case: The cylinder numbers that meet the first or second case are recorded in the order of cylinder work. 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 case. For example, in this example, the engine is a 4-cylinder engine, and the cylinder working order is 1-3-4-2-1-3-4-2-…. The cylinder numbers that meet the first or second case 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 If the first, second, third, fourth, and fifth conditions are met, the initial oil cut-off flag position b of the cylinder that meets the first or second condition is CynOff The value is 1, indicating that the cylinder that meets the first or second conditions may experience continuous fuel cut-off. The initial fuel cut-off flag bit b of other cylinders 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 in 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 fuel injection system related components occurred;

[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 preceding it, a total of five sampling periods.

[0103] The method for determining whether the engine cylinder with the initial fuel cut-off flag value of 1 has actually been fuel cut-off 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 met, 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 oil cut-off flag b CynOff The value of the cylinder is 1, if and If all of the above are not satisfied, the oil cut-off flag of this cylinder is set to 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 oil 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 flag 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 oil cut-off mark of the cylinder is b CynOffFuelCut =0, multiple sampling times Cnt CynoffDelay and self-learning correction coefficient 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 fuel injection condition detection method provided by the present invention can detect the engine fuel injection performance and verify whether there is a fixed cylinder with fuel outage, thereby reminding the driver to repair and inspect the engine in time, and also protecting 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 split into more steps, or two or more steps or partial operations of the steps can be combined into new steps 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 merely 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 scope of protection 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 conditions are met, the operating time of each cylinder of the engine at a certain crankshaft operating angle is obtained; Calculating an average value of the operating time of each cylinder of the engine within a plurality of consecutive sampling periods, and determining a maximum value and a minimum value of the average value of the operating time; Calculating a characteristic coefficient based on the maximum and minimum values ​​of the running time average values; Determining 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 operating time of each engine cylinder in the fuel cut-off state in 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 truly 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 certain 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 several consecutive sampling periods 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 average value of 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 as follows: if r CynDetectRaw (1+ k Adapt )≥ r CynDetectOffLim , then the initial flag bit b CynOffRaw The value is 1, otherwise the initial flag b CynOffRaw The value of is 0; in r CynDetectOffLim The threshold coefficient is used to judge the continuous oil cut-off of the fixed cylinder. The threshold coefficient is obtained 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 under the condition of active oil cut-off r CynDetectRaw and the characteristic coefficients without oil cut-off r 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 for judging the continuous oil cut-off of the fixed cylinder. r CynDetectOffLim ; wherein the average engine speed and the average engine intake density are respectively the average values ​​of the current sampling period and the four sampling periods before it, a total of five sampling periods; 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 fuel cut-off flag of the fixed cylinder according to the value of the initial flag is as follows: In the initial flag b CynOffRaw The value of is 1, if: Case 1: There is an average running time of the engine cylinder in several consecutive sampling periods T n-Avg and 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; Case 4: At least one cylinder does not meet the conditions of case 1 or case 2; Fifth case: The cylinder numbers that meet the first or second case are recorded in the order of cylinder working. 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 and T min The cylinder number that is equal is not the next working cylinder number that satisfies the first condition or the second condition; If multiple sampling times Cnt CynoffDelay If 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 oil cut-off flag position. b CynOff The value is 1, the initial oil cut-off flag of other cylinders b CynOff The value of is 0; The number of 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 determining whether the engine cylinder whose initial fuel cut-off flag has a value of 1 has actually been fuel cut-off is as follows: Actively cut off fuel for the cylinders that meet the first or second conditions, and re-obtain the average running time of each cylinder of the engine in the fuel cut-off state T n-AvgNew and the maximum value of the average running time of each cylinder of the engine in the fuel cut-off state T maxNew With minimum value T minNew ; (1) For the initial oil 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 number of multiple samplings Cnt CynoffDelay Subtract 1 and save after power off, the self-learning correction coefficient k Adapt Remain unchanged; C 1 is the default value; (2) For the initial oil cut-off flag b CynOff For a cylinder with a value of 1, if , ,and If only one of the following is met, the oil cut-off flag of this cylinder will be b CynOffFuelCut =0, the number of multiple samplings Cnt CynoffDelay Remain unchanged; the self-learning correction coefficient , and save it after power off; (3) For the initial oil cut-off flag b CynOff The value of the cylinder is 1, if , ,and If all of the above are not satisfied, the oil cut-off mark of this cylinder will be 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 oil 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 flag of this cylinder b CynOffFuelCut =0, the number of multiple samplings Cnt CynoffDelay Remain unchanged, the self-learning correction coefficient , and save it after power off; C 2 is the default value; (5) In other cases, the oil cut-off mark of the cylinder b CynOffFuelCut =0, the number of multiple samplings Cnt CynoffDelay and the self-learning correction coefficient k Adapt remain unchanged; If the initial fuel cut-off flag value is 1, the fuel cut-off flag of the engine cylinder b 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 conditions include: The gear position not changing means that after the gear position changes, it takes more than the gear position change preset time to activate the engine cylinder injection condition detection method; The clutch being in a fully engaged state means that after the clutch is engaged, it takes more than a preset clutch 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 5, 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 using the threshold coefficient is within a preset range; (9) The difference between the average engine intake air density and the average intake air density obtained during the bench calibration process using the threshold coefficient is within a preset range.

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