An engine durability verification reliability evaluation method around the B10 life target

Abstract

The present invention discloses a reliability evaluation method for engine durability verification around the B10 life target, comprising the following steps: 1) Prepare for the engine durability test and set the engine B10 life target; 2) Calculate the number of engine durability tests; 3) Run the engine durability test on the test bench and verify the results of the engine durability test; 4) Determine the key components of the qualified parts passing the engine durability test and conduct subjective rating D1 and wear degree rating D2; 5) Obtain the failure mileage represented by the engine durability test; 6) Calculate the reliability at the B10 life of the engine and evaluate the reliability after the engine durability verification. The present invention establishes reasonable durability test duration and sample size with the B10 life as the target, avoiding over-verification and under-verification of the engine durability verification, providing failure samples for evaluating the reliability after the engine durability verification, and saving time and economic costs.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive engine fatigue verification, and specifically refers to a reliability evaluation method for engine durability verification around the B10 life target. Background Art

[0002] When an automotive engine reaches the B10 life mileage, it is expected that 10% of the products will experience failures and require major repairs. Therefore, the B10 life is generally used to represent the reliability of the engine. In the existing engine durability and reliability verification process, if the engine does not fail after completing the durability test for a specified time, it is considered that the engine meets the durability and reliability requirements. Based on the Weibull distribution, which is the theoretical basis of reliability analysis and life inspection, the reliability function curve can be fitted to calculate the reliability under the B10 life and evaluate the reliability of the engine after durability verification. Reliability is the probability that a product can complete the specified function under the specified conditions and within the specified time, and reliability is the ability of a product to complete the specified function under the specified conditions and within the specified time.

[0003] The existing evaluation methods do not focus on achieving the B10 life target. When the B10 life target of the engine durability verification indicates that the reliability of the engine is 0.9, a reasonable design of the engine durability test verification time, sample size, and reliability evaluation method has the following main problems: The verification time of the engine durability test is not determined based on the B10 life mileage target; there is no derivation method for how to equate the engine durability test time to the driving mileage under the customer's normal driving profile; the customer's normal driving profile is the mileage experienced by the vehicle from the time the customer receives the vehicle until the end of the vehicle's life or withdrawal from use. How to extrapolate the failure mileage of the inspected parts after the durability test under the customer's normal driving profile; how to evaluate whether the reliability of the engine after the durability test reaches the B10 life target based on the extrapolated failure mileage samples. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems, provide a reliability evaluation method for engine durability verification around the B10 life target, and more scientifically solve the problems of engine durability verification and reliability evaluation.

[0005] A reliability evaluation method for engine durability verification around the B10 life target includes the following steps:

[0006] S1. Prepare for the engine durability test. Based on the set engine B10 life target, according to the reliability growth model, indirectly calculate the minimum total mileage S of the engine durability test that meets the B10 life target by calculating the reliability of the engine B10; Determine the acceleration factor AF of the engine durability test cycle conditions compared to the customer's normal driving profile, and the accelerated equivalent mileage S of the engine durability test cycle conditions corresponding to the customer's normal driving profile a , and calculate the equivalent mileage T of the engine durability test;

[0007] S2. Calculate the number of times N of the engine durability test: Divide the minimum total mileage S of the engine durability test that meets the B10 life target obtained in step S1 B10 by the equivalent mileage T of the engine durability test, and the quotient of the two is the number of times N of the engine durability test;

[0008] S3. Run the engine durability test on the engine durability bench and verify the results of the engine durability test: The engine participating in the engine durability test is the test piece, and the number of non-failed test pieces is the same as the number of times N of the engine durability test in step S2. If no test piece fails during the engine durability test, the result of the engine durability test is considered passed; if a test piece fails, the result of the engine durability test is considered failed. Return to step S1 to calculate the minimum mileage for verifying the engine durability test in the case of failure, subtract the mileage of the passed engine durability test, obtain the additional mileage required for the engine durability test, and continue the test until no test piece fails;

[0009] S4. Determine the subjective rating D1 of the key components of the test pieces that have passed the engine durability test, and determine the wear degree rating D2 of the key components of the test pieces that have passed the engine durability test;

[0010] S5. Obtain the failure mileage S represented by the engine durability test f : Determine the key components whose subjective rating and wear degree rating results of the engine key components in step S4 do not reach the function loss level. By extrapolating the failure mileage of each key component of the engine after the durability test in the customer's normal driving profile, the minimum value among them is the failure mileage S represented by the engine durability test f ;

[0011] S6. For the failure mileage S corresponding to the N engine durability tests obtained in step S5 f1 、S f2 ...S fN , based on the Weibull distribution, fit the reliability function curve, substitute the B10 life into the curve formula to obtain the reliability, and this reliability is the reliability level achieved after the engine durability verification.

[0012] Specifically, in step S1, based on the reliability growth model, indirectly calculate the minimum total mileage S of the engine durability test that meets the B10 life target B10, the reliability of the engine is calculated according to the following formula:

[0013]

[0014] In Equation (1), R(t) represents the reliability of the engine;

[0015] α represents the scale parameter;

[0016] β represents the shape parameter;

[0017] e represents the natural constant;

[0018] t represents the B10 life target mileage of the engine, unit: km;

[0019] According to the reliability growth theory, the parameter of the scale parameter α satisfies the following formula:

[0020]

[0021] In Equation (2): N represents the number of engine durability tests;

[0022] T i represents the equivalent mileage of the i-th engine durability test, unit: km;

[0023] r represents the number of failures;

[0024] C represents the confidence level;

[0025] χ 2 represents the chi-square distribution;

[0026] According to Equation (1) and Equation (2), under the conditions of known B10 life mileage target, shape parameter β = 1, and number of failures r = 0, in reliability statistics, the minimum total mileage S of the B10 life target engine durability test is obtained by looking up the chi-square distribution table B10 .

[0027] Specifically, in step S2, the acceleration factor AF of the engine durability test cycle condition compared to the customer's normal driving profile is calculated by the following formula:

[0028]

[0029] In Equation (3): f d_i represents the hourly fuel consumption of the engine durability test condition, unit: kg / h;

[0030] f c represents the average fuel consumption per 100 kilometers under the customer's normal driving profile, unit: L / 100km;

[0031] ρ represents the fuel density, unit: kg / L;

[0032] t i represents the running time of the durability test condition, unit: h;

[0033] Among them, S represents the equivalent kilometers corresponding to the customer's normal driving profile for the engine durability test cycle, satisfying the following formula

[0034] S = sum{V i ×t i} (4)

[0035] In formula (4): V i represents the vehicle speed corresponding to the engine durability test condition speed under the customer's normal driving profile, unit: km / h;

[0036] t i represents the running time of the durability test condition, unit: h;

[0037] Calculate the vehicle speed corresponding to each engine durability test cycle condition speed under the customer's normal driving profile, satisfying the following formula:

[0038]

[0039] In formula (5): V represents the vehicle speed corresponding to the engine durability test cycle condition speed under the customer's normal driving profile, unit: km / h;

[0040] n represents the engine speed, unit: rpm;

[0041] r represents the tire radius, unit: mm;

[0042] i 1 represents the gear ratio of the main reducer and the drive axle;

[0043] i 2 represents the gear ratio of the gearbox and the drive axle;

[0044] The acceleration equivalent mileage of a single engine durability test cycle converted to the customer's normal driving profile satisfies the following formula:

[0045] S a = AF × S (6)

[0046] The equivalent mileage of a single engine durability test satisfies the following formula:

[0047] T = S a ×n cyc (7)

[0048] In formula (7): n Cycle represents the number of cycles of the engine durability test condition;

[0049] The number N of engine durability tests is obtained through the following calculation formula:

[0050]

[0051] In formula (8): T i represents the equivalent mileage of the i-th engine durability test, unit: km.

[0052] Specifically, in the step S4, the key engine components for subjective rating D1 after the engine durability test include: piston rings, pistons, connecting rod bearings, main shaft bearings, cylinder bores; when the subjective rating D1 is level 1, the key component's appearance is intact and there are no scratches, showing excellent performance; when the subjective rating is level 2, the key component's appearance is intact and the surface scratch coverage area does not exceed 10%, showing good performance; when the subjective rating is level 3, the key component's appearance is intact and the surface scratch coverage area is greater than or equal to 10% and less than 60%, showing marginal acceptance; when the subjective rating is level 4, the key component is deformed or distorted, or the surface scratch coverage area is greater than or equal to 60% and less than 85%, showing non-acceptance; when the subjective rating is level 5, the key component is deformed or distorted, or the surface scratch coverage area is greater than or equal to 85%, showing loss of function.

[0053] Specifically, in the step S4, the key engine components for wear degree rating D2 after the engine durability test include: piston rings, pistons, connecting rod bearings, main shaft bearings, cylinder bores. The wear amount of the key components after the engine durability test is divided into 5 levels according to the wear degree; when the wear degree L ≤ 20%G, the wear degree rating D2 is level 1; when 20%G < L ≤ 40%G, the wear degree rating D2 is level 2; when 40%G < L ≤ 60%G, the wear degree rating D2 is level 3; when 60%G < L ≤ 80%G, the wear degree rating D2 is level 4; when 80%G < L ≤ 100%G, the wear degree rating D2 is level 5; when the wear degree rating of the key components after the engine test is level 5, it shows loss of function; where L represents the wear amount degree of the key components, and G represents the critical wear amount threshold for the loss of function of the key components.

[0054] Specifically, in the step S7, the failure mileage of the key components in the engine durability test satisfies the following calculation formula:

[0055]

[0056] From formula (8), the failure mileage represented by the engine durability test is:

[0057] S f = min{s 1 , s 2 , … sx} (9)

[0058] In formula (9): S f represents the failure mileage represented by the engine durability test, unit: km;

[0059] x represents the number of key components in the engine durability test.

[0060] Specifically, the reliability evaluation after engine durability verification is that, based on the B10 target life of the engine, that is, when the engine reliability is 0.9, the failure mileage S of the engine f is the engine durability mileage of the B10 life target engine. The part exceeding the engine durability mileage of the B10 life target when the engine reliability exceeds 0.9 is the failure mileage margin.

[0061] The beneficial effects of the present invention are as follows:

[0062] The present invention establishes a reasonable engine durability test duration and sample size with the B10 life as the target, avoiding over-verification and under-verification of engine durability verification; reasonably proposes a calculation method for converting the engine durability test duration into the equivalent failure mileage under the customer's normal driving profile, providing failure samples for evaluating the engine reliability after durability verification, and does not require all engine durability tests to run until the engine completely fails to obtain failure samples, which can not only evaluate the engine reliability, but also save time and economic costs. Description of the Drawings

[0063] Figure 1 is a flow chart of a reliability evaluation method for engine durability verification around the B10 life target;

[0064] Figure 2 is a comparison performance chart of the subjective rating D1 of key components. Detailed Embodiments

[0065] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0066] The present invention correlates the engine B10 life target with durability test verification. Around the B10 life target, based on the reliability growth theory, it formulates the corresponding engine durability test verification duration and sample size, gives the calculation method of the equivalent mileage of the engine durability test conditions under the customer's normal driving profile, fits the reliability function curve based on the Weibull distribution, calculates the reliability R that meets the B10 life, evaluates the reliability after engine durability verification, and saves time and economic costs.

[0067] Figure 1 As shown, a reliability evaluation method for engine durability verification around the B10 life target includes the following steps:

[0068] S1. Prepare for the engine durability test. Based on the set engine B10 life target, according to the reliability growth model, indirectly calculate the minimum total mileage S of the engine durability test that meets the B10 life target by calculating the reliability of the engine B10 ; Determine the acceleration factor AF of the engine durability test cycle condition compared to the customer's normal driving profile, and the accelerated equivalent mileage S of the engine durability test cycle condition corresponding to the customer's normal driving profile a , and calculate the equivalent mileage T of the engine durability test; The customer's normal driving profile is the mileage experienced by the vehicle from the time the customer receives the vehicle to the end of the vehicle's life or withdrawal from use

[0069] S2. Calculate the number of times N of the engine durability test: Divide the minimum total mileage S of the engine durability test that meets the B10 life target obtained in step S1 B10 by the equivalent mileage T of the engine durability test, and the quotient of the two is the number of times N of the engine durability test

[0070] S3. Run the engine durability test on the engine durability bench and verify the results of the engine durability test: The engine participating in the engine durability test is the test piece. The number of non-failed test pieces is the same as the number of times N of the engine durability test in step S2. If no test piece fails during the engine durability test, the result of the engine durability test is considered passed; If a test piece fails, the result of the engine durability test is considered failed. Return to step S1 to calculate the minimum mileage for engine durability test verification in the presence of failures, remove the mileage of the passed engine durability test, obtain the additional mileage required for the engine durability test, and continue the test until no test piece fails

[0071] S4. Subjectively rate the key components of the test pieces that passed the engine durability test in step S3 as D1, and rate the wear degree of the key components of the test pieces that passed the engine durability test as D2

[0072] S5. Obtain the failure mileage S represented by the engine durability test f : Determine the key components whose results of subjective rating and wear degree rating of the engine key components in step S4 do not reach the level of function loss. By extrapolating the failure mileage of each key component of the engine after the engine durability test under the customer's normal driving profile, the minimum value among them is the failure mileage S represented by the engine durability test f ;

[0073] S6. For the failure mileage S corresponding to the N engine durability tests obtained in step S5 f1 , S f2 ...S fN , based on the Weibull distribution, fit the reliability function curve, substitute the B10 life into the curve formula to obtain the reliability, and this reliability is the reliability level achieved after the engine durability verification.

[0074] Specifically, in step S1, according to the reliability theory, based on the reliability growth model, indirectly calculate the minimum total mileage S of the engine durability test that meets the B10 life target B10 , the life distribution of the engine can follow the Weibull distribution. Based on the Weibull distribution, the engine reliability is calculated according to the following formula:

[0075]

[0076] In formula (1), R(t) represents the reliability of the engine;

[0077] α represents the scale parameter;

[0078] β represents the shape parameter;

[0079] e represents the natural constant;

[0080] t represents the B10 life target mileage of the engine, unit: km;

[0081] According to the reliability growth theory, the parameter of the scale parameter α satisfies the following formula:

[0082]

[0083] In formula (2): N represents the number of engine durability tests;

[0084] T i represents the equivalent mileage of the i-th engine durability test, unit: km;

[0085] r represents the number of failures;

[0086] C represents the confidence level;

[0087] χ 2 represents the chi-square distribution;

[0088] According to formula (1) and formula (2), under the condition of knowing the B10 life mileage target, shape parameter β = 1, and number of failures r = 0, in reliability statistics, look up the chi-square distribution table to obtain the minimum total mileage S of the engine durability test for the B10 life target B10 .

[0089] In step S2, the acceleration factor of a single test cycle of the engine durability test compared to the customer's normal driving profile satisfies the following formula:

[0090]

[0091] In formula (3): f d_i represents the hourly fuel consumption of the engine durability test condition, unit: kg / h;

[0092] f c represents the average fuel consumption per 100 kilometers under the customer's normal driving profile, unit: L / 100km;

[0093] ρ represents the fuel density, unit: kg / L;

[0094] The derivation process of formula (3) is as follows: The acceleration factor AF of a single test cycle of the engine durability test compared to the customer's normal driving profile is the ratio of the fuel consumption per 100 kilometers of the engine durability test condition to the average fuel consumption per 100 kilometers under the actual customer's normal driving profile, that is where the fuel consumption per 100 kilometers of the engine durability test condition can be expressed as the ratio of the total fuel consumption of the engine durability test condition to the corresponding equivalent kilometer speed S at 100 kilometers, that is: Therefore, substituting into the formula, we can get:

[0095] Collect the engine speed, hourly fuel consumption, operating duration and other condition information of the engine durability test condition and parameters such as the transmission ratio, final drive ratio, and tire radius of the vehicle model carried; The customer's normal driving profile is the mileage experienced during the period from when the customer receives the vehicle to the end of the vehicle's life or withdrawal from use.

[0096] The corresponding equivalent kilometers of the engine durability test cycle under the customer's normal driving profile satisfy the following formula:

[0097] S = sum{V i ×t i} (4)

[0098] In formula (4): S represents the corresponding equivalent kilometers of the engine durability test condition speed under the customer's normal driving profile, unit: km;

[0099] V i represents the corresponding vehicle speed of the engine durability test condition speed under the customer's normal driving profile, unit: km / h;

[0100] t i represents the operating time of the durability test condition, unit: h.

[0101] The corresponding vehicle speeds of the engine durability test cycle at various operating conditions under the customer's normal driving profile satisfy the following formula:

[0102]

[0103] In Equation (5): V represents the corresponding vehicle speed of the engine durability test cycle operating condition speed under the customer's normal driving profile, unit: km / h;

[0104] n represents the engine speed, unit: rpm;

[0105] r represents the tire radius, unit: mm;

[0106] i 1 represents the gear ratio of the main reducer and the drive axle;

[0107] i 2 represents the gear ratio of the transmission and the drive axle;

[0108] The derivation process of Equation (5) is as follows: The corresponding vehicle speed of the engine durability test operating condition speed under the customer's normal driving profile satisfies the formula that the wheel linear speed is the current vehicle speed V 1 , unit m / s, V 1 =rω 1 , the wheel angular velocity ω 1 is ω 1 =2πn 1 ; ω 1 represents the angular velocity of the wheel, unit: rad / s, the wheel speed is At this time, the engine speed n and the wheel speed n 1 are in the unit of r / s; thus, the corresponding vehicle speed of the engine durability test operating condition speed under the customer's normal driving profile can be obtained After converting the unit of the corresponding vehicle speed of the engine durability test operating condition speed under the customer's normal driving profile to km / h and converting the unit of n from r / s to r / min, i.e., rpm, the calculation formula for the corresponding vehicle speed V of the engine durability test operating condition speed under the customer's normal driving profile is

[0109] The acceleration equivalent mileage of a single engine durability test cycle converted to the customer's normal driving profile satisfies the following formula:

[0110] S a =AF×S (6)

[0111] The equivalent mileage of a single engine durability test satisfies the following formula:

[0112] T = S a ×n cyc (7)

[0113] In formula (7): n Cycle represents the number of cycles of the engine durability test conditions;

[0114] The number of times N of the engine durability test is obtained through the following calculation formula:

[0115]

[0116] In formula (8): T i represents the equivalent mileage of the i-th engine durability test, unit: km.

[0117] As Figure 2 shown, in the step S4, the key engine components for subjective rating D1 after the engine durability test include: piston ring, piston, connecting rod bearing, main bearing, cylinder bore; when the subjective rating D1 is level 1, the key component has a perfect appearance and no scratches, showing excellent performance; when the subjective rating is level 2, the key component has a perfect appearance and the surface scratch coverage area does not exceed 10%, showing good performance; when the subjective rating is level 3, the key component has a perfect appearance and the surface scratch coverage area is greater than or equal to 10% and less than 60%, showing marginal acceptance; when the subjective rating is level 4, the key component is deformed or distorted, or the surface scratch coverage area is greater than or equal to 60% and less than 85%, showing non-acceptance; when the subjective rating is level 5, the key component is deformed or distorted, or the surface scratch coverage area is greater than or equal to 85%, showing loss of function.

[0118] Table 1 Subjective rating table of key components

[0119]

[0120] The key engine components for wear degree rating D2 after the engine durability test include: piston ring, piston, connecting rod bearing, main bearing, cylinder bore. The wear amount of the key components after the engine durability test is divided into 5 levels; when the wear degree L ≤ 20%G, the wear degree rating D2 is level 1; when 20%G < L ≤ 40%G, the wear degree rating D2 is level 2; when 40%G < L ≤ 60%G, the wear degree rating D2 is level 3; when 60%G < L ≤ 80%G, the wear degree rating D2 is level 4; when 80%G < L ≤ 100%G, the wear degree rating D2 is level 5; when the wear degree rating of the key components after the engine test is level 5, it shows loss of function; where L represents the wear degree of the key components, and G represents the critical wear amount threshold of the key components for loss of function.

[0121] Table 2 Wear degree rating table of key components

[0122]

[0123] Wherein, G in Table 2 represents the critical wear amount threshold of function loss.

[0124] Specifically, in step S7, an engine durability test is a durability test with a fixed duration. After the engine durability test, the key components may not necessarily reach the degree of function loss, and it can still serve for a certain period under the normal driving profile of the customer. By extrapolating the failure mileage of each key component after the engine durability test under the normal driving profile of the customer, the failure mileage when the key components after the engine durability test reach the degree of function loss is determined. The key components after the engine durability test include: piston rings, pistons, connecting rod bearings, main shaft bearings, and cylinder bores. The minimum value among their respective failure mileages under the normal driving profile of the customer is the failure mileage represented by this engine durability test. The failure mileage of the key components satisfies the following calculation formula:

[0125]

[0126] The derivation process of formula (8) is as follows: The failure mileage S of the key components of the engine in the engine durability test when the subjective rating is level 5 主观 is equal to the ratio of the acceleration equivalent mileage S a under the normal driving profile corresponding to the engine durability test cycle condition when the subjective rating of the key components of the engine is level D1, that is By transformation, we can get

[0127] The failure mileage S of the key components of the engine in the engine durability test when the wear degree rating is level 5 磨损 is equal to the acceleration equivalent mileage S a under the normal driving profile corresponding to the engine durability test cycle condition when the wear degree rating of the key components of the engine is level D2, that is By transformation, we can get

[0128] Combining the subjective rating D1 of the key components of the engine and the wear degree rating D2 of the key components of the engine, the failure mileage S of the key components of the engine when the subjective rating is made in the engine durability test 主观 and the failure mileage S 磨损 of the key components of the engine when the wear degree rating is made in the engine durability test, the minimum value of which is the acceleration equivalent mileage S a under the normal driving profile for the conversion of the engine durability test conditions, and it satisfies the following formula:

[0129] From formula (8), the failure mileage represented by the engine durability test is:

[0130] S f = min{s 1 ,s 2 ,… s x} (9)

[0131] In Equation (9): S f represents the failure mileage represented by the engine durability test, unit: km;

[0132] x represents the number of key components in the engine durability test.

[0133] The failure mileages S f1 、S f2 ... S fN corresponding to N engine durability tests, based on the Weibull distribution, fit the reliability function curve, substitute the B10 life into the curve formula to obtain the reliability, and this reliability is the reliability level achieved after the engine durability verification.

[0134] The reliability evaluation after the engine durability verification is that, based on the engine B10 target life, that is, when the engine reliability is 0.9, the failure mileage S f of the engine is the engine durability mileage of the B10 life target, and the part of the failure mileage exceeding the engine durability mileage of the B10 life target when the engine reliability exceeds 0.9 is the failure mileage margin.

[0135] In summary, the present invention correlates the engine B10 life target with the durability test verification, formulates the corresponding engine durability test verification duration and sample size based on the reliability growth theory around the B10 life target, gives the calculation method of the equivalent mileage of the engine durability test working condition under the customer's normal driving profile, and extrapolates the equivalent failure mileage of the engine durability test under the customer's normal driving profile through the subjective rating and wear degree rating of the key components after the test verification, so as to evaluate the engine reliability after the durability verification through the Weibull distribution, establish a reasonable engine durability test duration and sample size with the B10 life as the target, and avoid over-verification and under-verification of the engine durability verification; reasonably proposes a calculation method for converting the engine durability test duration into the equivalent failure mileage under the customer's normal driving profile, provides a failure sample for evaluating the engine reliability after the engine durability verification, and does not require all engine durability tests to run until the engine completely fails to obtain the failure sample, which can not only evaluate the engine reliability, but also save time and economic costs.

[0136] The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention accordingly. Any equivalent transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A reliability evaluation method for engine durability verification around the B10 life target, characterized in that: It includes the following steps: S1. Prepare for the engine durability test. Based on the set engine B10 life target, according to the reliability growth model, indirectly calculate the minimum total mileage S of the engine durability test that meets the B10 life target by calculating the reliability of the engine B10 ; By determining the acceleration factor AF of the engine durability test cycle conditions compared to the customer's normal driving profile and the accelerated equivalent mileage S of the engine durability test cycle conditions corresponding to the customer's normal driving profile a , calculate the equivalent mileage T of the engine durability test; The acceleration factor AF of the engine durability test cycle conditions compared to the customer's normal driving profile is calculated by the following formula: In the above formula: f d_i represents the hourly fuel consumption under the engine durability test condition, unit: kg / h; f c represents the average fuel consumption per 100 kilometers under the normal driving profile of the customer, unit: L / 100km; ρ represents the fuel density, unit: kg / L; t i Indicates the running time of the durability test condition, unit: h; Wherein, S represents the equivalent kilometers corresponding to the customer's normal driving profile for the engine durability test cycle, satisfying the following formula: S = sum{V i × t i} In the above formula: Vi represents the corresponding vehicle speed of the engine durability test condition speed under the customer's normal driving profile, unit: km / h; Calculate the corresponding vehicle speed of each engine durability test cycle condition speed under the customer's normal driving profile, satisfying the following formula: In the above formula: V represents the corresponding vehicle speed of the engine durability test cycle condition speed under the customer's normal driving profile, unit: km / h; n represents the engine speed, unit: rpm; r represents the tire radius, unit: mm; i 1 represents the gear ratio of the main reducer and the drive axle; i 2 represents the gear ratio of the gearbox to the drive axle; The acceleration equivalent mileage of a single engine durability test cycle converted to the customer's normal driving profile satisfies the following formula: S a = AF × S The equivalent mileage of a single engine durability test satisfies the following formula: T = S a × n cycle In the above formula: n Cycle represents the number of cycles of the engine durability test working condition; S2. Calculate the number of engine durability tests N: Divide the minimum total mileage S of the engine durability test that meets the B10 life target obtained in step S1 by the equivalent mileage T of the engine durability test. The quotient of the two is the number of engine durability tests N; B10 The quotient of the two is the number of engine durability tests N; The number N of engine durability tests is obtained by the following calculation formula: In the above formula: T i represents the equivalent mileage of the i-th engine durability test, unit: km; S3. Run the engine durability test on the engine durability bench and verify the results of the engine durability test: The engine participating in the engine durability test is the test piece. The number of non-failed test pieces is the same as the number N of engine durability tests in step S2. If no test piece fails during the engine durability test, the engine durability test result is considered passed; if a test piece fails, the engine durability test result is considered failed. Return to step S1 to calculate the minimum mileage of engine durability test verification in the case of failure, remove the passed engine durability test mileage, obtain the additional engine durability test mileage that needs to be added, and continue the test until no test piece fails; S4. Subjectively rate D1 the key components of the test pieces that passed the engine durability test in step S3, and rate D2 the wear degree of the key components of the test pieces that passed the engine durability test; S5. Obtain the failure mileage S represented by the engine durability test f : Identify the critical components whose subjective rating and wear rating results in step S4 do not reach the level of function loss. By extrapolating the failure mileage of each critical component after the engine durability test under the normal driving profile of the customer, the minimum value among them is the failure mileage S represented by the engine durability test f ; S6. For the failure mileage S corresponding to the N engine durability tests obtained in step S5 f1 , S f2 ... S fN , based on the Weibull distribution, fit the reliability function curve, substitute the B10 life into the curve formula to obtain the reliability, and this reliability is the reliability level achieved after the engine durability verification.

2. The reliability evaluation method for engine durability verification around the B10 life target according to claim 1, characterized in that: In the step S1, based on the reliability growth model, the minimum total mileage S of the engine durability test to meet the B10 life target is indirectly calculated B10 , and the reliability of the engine is calculated according to the following formula: In formula (1), R(t) represents the reliability of the engine; α represents the scale parameter; β represents the shape parameter; e represents the natural constant; t represents the engine B10 life target mileage, unit: km; According to the reliability growth theory, the parameter of the scale parameter α satisfies the following formula: In formula (2): N represents the number of engine durability tests; T i Indicates the equivalent mileage of the i-th engine durability test, unit: km; r represents the number of failures; C represents the confidence level; χ 2 represents a chi-square distribution; According to Equation (1) and Equation (2), under the conditions of knowing the B10 life mileage target, shape parameter β = 1, and failure times r = 0, in reliability statistics, the minimum total mileage S of the engine durability test for the B10 life target is obtained by looking up the chi-square distribution table. B10 .

3. The reliability evaluation method for engine durability verification around the B10 life target according to claim 1, characterized in that: In the step S4, the key engine components for subjective rating D1 after the engine durability test include: piston rings, pistons, connecting rod bearings, main shaft bearings, and cylinder bores. When the subjective rating D1 is level 1, the key component's appearance is intact and there are no scratches, indicating excellent performance; when the subjective rating is level 2, the key component's appearance is intact and the surface scratch coverage area does not exceed 10%, indicating good performance; when the subjective rating is level 3, the key component's appearance is intact and the surface scratch coverage area is greater than or equal to 10% and less than 60%, indicating marginal acceptance; when the subjective rating is level 4, the key component is deformed or distorted, or the surface scratch coverage area is greater than or equal to 60% and less than 85%, indicating non-acceptance; when the subjective rating is level 5, the key component is deformed or distorted, or the surface scratch coverage area is greater than or equal to 85%, indicating loss of function.

4. The method for evaluating the reliability of engine durability verification around the B10 life target according to claim 1, characterized in that: In the step S4, the key engine components for wear rating D2 after the engine durability test include: piston rings, pistons, connecting rod bearings, main shaft bearings, and cylinder bores. The wear amount of the key components after the engine durability test is divided into 5 levels according to the wear degree level; when the wear degree L ≤ 20%G, the wear rating D2 is level 1; when 20%G < L ≤ 40%G, the wear rating D2 is level 2; when 40%G < L ≤ 60%G, the wear rating D2 is level 3; when 60%G < L ≤ 80%G, the wear rating D2 is level 4; when 80%G < L ≤ 100%G, the wear rating D2 is level 5; when the wear rating of the key components after the engine test is level 5, it indicates loss of function; where L represents the wear amount degree of the key components, and G represents the critical wear amount threshold for the loss of function of the key components.

5. The method for evaluating the reliability of engine durability verification around the B10 life target according to claim 1, characterized in that: In the step S5, the failure mileage of the key components in the engine durability test satisfies the following calculation formula: From the above formula, the failure mileage represented by the engine durability test is: S f = min{s 1 , s 2 , … s x} In the above formula: S f represents the failure mileage represented by the engine durability test, unit: km; x represents the number of key components in the engine durability test.

6. The method for evaluating the reliability of engine durability verification around the B10 life target according to claim 1, characterized in that: In the step S6, the reliability evaluation after the engine durability verification is that, based on the engine B10 target life, that is, when the engine reliability is 0.9, the failure mileage S of the engine f is the engine durability mileage of the B10 life target engine. When the engine reliability exceeds 0.9, the part exceeding the engine durability mileage of the B10 life target engine is the failure mileage margin.

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