Bench steady-state load spectrum compilation method for matching electric drive assembly with different vehicle weights

Abstract

The invention discloses a rack steady-state load spectrum compilation method for matching an electric drive assembly with different vehicle weights, and the method comprises the following steps: 1) setting a known batch-produced transmission A and a matched whole vehicle B, completing the collection of road test load data of the whole vehicle B carried by the transmission A, and according to a pseudo-damage theory, obtaining a load spectrum of the transmission A; compilation and experiment of the rack steady-state load spectrum of the transmission A matched with the whole vehicle B are completed, and parameters of the transmission A matched with a new project whole vehicle C need to be compiled; 2) obtaining the total false damage amount U, the load Ti and the cycle index ni of the load Ti; (3) the relation between the total false damage amount U and the whole vehicle mass m, the speed u, the speed ratio i, the vehicle radius r and the like is obtained; 4) determining the load spectrum equivalent damage magnification amplification coefficient of the same electric drive assembly matched with different vehicle weights; and 5) obtaining an amplified load spectrum. The method can be compatible among different vehicles.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicle motor controllers, and in particular to a method for analyzing the sealing performance of new energy vehicle motor controllers. Background Art

[0002] Load spectrum refers to the method of using probability statistics to study the characteristics of load, and the relationship between load level and number of cycles is expressed in the form of graphs, tables, matrices, etc.

[0003] In China, the load spectrum technology started late, and a systematic and complete load spectrum compilation theory system has not been formed. Most of the existing research on load spectrum is used for vehicle fatigue testing, and there is no report on the method of designing transmissions according to the bench steady-state load spectrum. In China, the load spectrum is also mainly concentrated in colleges and universities, and of course some OEMs have conducted research on load spectrum. The main reason for this situation is that the acquisition of load spectrum is based on the material SN curve of the component, that is, the stress-cycle number relationship of the material. However, to obtain the SN curve of the material, it takes a considerable amount of time to get the test results. At present, the SN curve used in the research of most universities is not the actual SN curve of the material, but the generalized SN curve. The load spectrum obtained in this way is not only quite different from the actual load spectrum, but different vehicle weights require different load spectra to reflect, that is, the current bench load spectra of different vehicle weights are not compatible with each other. Summary of the invention

[0004] The present invention provides a method for compiling a steady-state load spectrum of a test bench for matching an electric drive assembly with different vehicle weights, and the present invention can be compatible between different vehicles.

[0005] The technical solutions to the above problems are as follows:

[0006] The method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights includes the following steps:

[0007] 1) Assume that the mass-produced transmission A and the matching vehicle B are known, the road test load data of transmission A equipped with vehicle B has been collected, and according to the pseudo-damage theory, the preparation and experiment of the bench steady-state load spectrum of transmission A matching vehicle B has been completed. It is necessary to prepare the parameters of transmission A matching the new project vehicle C;

[0008] 2) Obtain the total pseudo damage U and load T i , load T i The number of cycles n i ;

[0009] 3) Obtain the relationship between the total amount of pseudo damage U and the vehicle mass m, speed u, speed ratio i, vehicle radius r, etc.;

[0010] 4) Determine the equivalent damage magnification factor of the load spectrum of the same electric drive assembly matching different vehicle weights;

[0011] 5) Obtain the amplified load spectrum.

[0012] The advantages of the present invention are: the transmission A matches the steady-state load spectrum of the new project vehicle C, and the road test load data of the vehicle C is not collected and then condensed into a steady-state bench load spectrum, but the load spectrum of the mass-produced vehicle B is matched by the transmission A to calculate and compile, thus saving a lot of development time and the experimental cost of actually collecting road spectrum data. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0014] like Figure 1 As shown, the method for compiling a steady-state load spectrum of a test bench for matching an electric drive assembly with different vehicle weights of the present invention comprises the following steps:

[0015] 1) Assume that the mass-produced transmission A and the matching vehicle B are known, the road test load data of transmission A equipped with vehicle B has been collected, and according to the pseudo-damage theory, the preparation and experiment of the bench steady-state load spectrum of transmission A matching vehicle B has been completed. It is necessary to prepare the parameters of transmission A matching the new project vehicle C.

[0016] 1-1) The road test load data of transmission A equipped with vehicle B has been collected and condensed into a test bench steady-state load spectrum that matches it.

[0017] 1-2) Get the parameters of mass-produced transmission A and matching vehicle B, such as the speed ratio of transmission A, the weight and tire radius of vehicle B. Assume that transmission A matches the new project vehicle C, and get the weight and tire radius of the new project vehicle C.

[0018] 2) Obtain the total pseudo damage U and load T i , load T i The number of cycles n i , the specific process is as follows:

[0019] 2-1) According to the damage equivalence principle, the i-th level torque T i Available j-th level torque T j Replacement;

[0020]

[0021] n i —Number of load cycles at level i; T i — torque of the i-th level; T j —jth level torque; n j —Number of cycles of the jth level load; p—index.

[0022] 2-2) For a certain component of a certain product, the SN curve of the component is fixed. The power function expression of the component (the expression represents the stress radiation The power function formula between the corresponding life span N is:

[0023]

[0024] —stress radiation; N— Corresponding lifespan; C—constant.

[0025] 2-3) Determine the damage level Ui at each level

[0026]

[0027] n i —Number of load cycles at level i; i —Number of load cycles at level i at failure.

[0028] 2-4) The cumulative damage degree U is obtained by summing up the damage degree Ui at each level, and U is less than or equal to 1.0.

[0029]

[0030] 2-5) Get the total pseudo damage U and load T i , load T i The number of cycles n i The formula is:

[0031] ① Based on the above theory, the cumulative damage of the reducer can be calculated from formulas (1), (2), (3) and (4):

[0032]

[0033] ② According to the properties of formula (2), no matter how many i is, is a constant, and the cumulative damage degree U is positively correlated with the load T i , load T i The number of cycles is expressed as formula (6);

[0034]

[0035] For a certain part of a certain product, it is a constant and is related to SN.

[0036] 3) Obtain the relationship between the total pseudo damage amount U and the vehicle mass m, speed u, speed ratio i, vehicle radius r, etc.; the specific process is as follows:

[0037] 3-1) Obtaining engine torque Ttq and wheel end driving torque T t Relationship

[0038] According to Automobile Theory, the engine torque T tq Wheel end driving torque T t relationship.

[0039] T t =T tq i g i0η T (7)

[0040] T t —wheel end driving torque; T tq —engine torque; i g —Transmission ratio; i0—Main reducer ratio; η T — Mechanical efficiency of the drive train;

[0041] 3-2) Obtain wheel end driving force F t and wheel end driving torque T t Relationship

[0042] The torque generated by the engine is transmitted to the drive wheels through the transmission system, generating wheel-end drive torque T t , the driving wheel is T t The ground exerts a circular force on the driving wheel, and the ground exerts a reaction force F on the driving wheel. t That is the wheel end driving force. According to the "Automobile Theory", the relationship between the wheel end driving force and the wheel end driving torque is:

[0043]

[0044] T t —wheel end driving torque; F t —wheel end driving force; r—vehicle radius.

[0045] 3-3) Obtaining engine torque T tq and wheel end driving force F t relationship.

[0046] From the above two formulas (5) and (6), it can be deduced that F t With engine torque T tq , Transmission ratio i g , the transmission ratio of the main reducer i0, the mechanical efficiency of the transmission system η T It is related to factors such as wheel radius r, and the engine torque T is obtained. tq Wheel end driving force F t relationship.

[0047]

[0048] 3-4) Get the wheel end driving force F for different vehicle weights t Influence.

[0049] The wheel end driving force F of the car t Equal to the total driving resistance of the car, F t =∑F, overcoming the driving resistance. The total driving resistance of the car is composed of rolling resistance F f , air resistance F w , Slope resistance F i , acceleration resistance F j composition.

[0050] Follow the steps below to get the wheel end driving force F for different vehicle weights. t Influence:

[0051] a) The wheel end driving force F of the car t Equal to the total driving resistance of the car, F t Equal to ∑F, overcoming the driving resistance and moving forward:

[0052] F t =ΣF=F f +F w +F i +F j (10)

[0053] F f —Rolling resistance; F w —air resistance; F i —slope resistance; F j —Acceleration resistance.

[0054] b) Due to the elastic hysteresis loss caused by internal friction of the tire, the work done on the tire when it deforms cannot be fully recovered. It is this elastic hysteresis loss of the tire that causes the rolling resistance F f Rolling resistance F f The calculation formula is as follows:

[0055] F f =Gfcosα=mgcosα (11)

[0056] F f —Rolling resistance; G—gravity; α—angle of uphill slope; m-vehicle mass; g-gravity coefficient.

[0057] c) The component of the air force on a car when it is traveling in a straight line in the direction of travel is called air resistance F w , air resistance F w The calculation formula is as follows:

[0058]

[0059] C D —Air resistance coefficient; A—frontal area; u a -speed.

[0060] d) Calculate the component of the vehicle's gravity along the ramp, the slope resistance F i ;

[0061] F i =Gsinα (13).

[0062] e) Calculate the acceleration resistance F j ;

[0063]

[0064] δ—rotational mass conversion factor; m—vehicle mass; —Time derivative of velocity, acceleration.

[0065] 3-5) Calculate the relationship between the fatigue damage degree of the reducer and the vehicle mass, drag coefficient, frontal area, tire radius, and reducer speed ratio of the vehicle, and proceed as follows:

[0066] a1) Based on 3-2), 3-3), and 3-4), and ignoring the relatively small air resistance, the engine torque T is obtained. tq Relationship with vehicle mass m, speed u, speed ratio i, and vehicle radius r:

[0067]

[0068] a2) Because G = mg, Simplifying Equation 15:

[0069]

[0070] a3) Assuming A = gfcosα + gsinα + δa, A and vehicle speed v are related to the vehicle road conditions. Substituting into the above formulas (16) and (6), we get:

[0071]

[0072] U is the total amount of pseudo-damage; m is the mass of the vehicle; u is the speed; i is the speed ratio; r is the radius of the vehicle; Y is a coefficient omitted to simplify the formula, corresponding to a certain part of a certain product, and is a constant; g is the gravity coefficient.

[0073] 4) Determine the equivalent damage magnification factor of the load spectrum of the same electric drive assembly matching different vehicle weights; the specific steps are as follows:

[0074] b1) According to formula (5), we get:

[0075]

[0076] in is a constant, so the total amount of pseudo damage U and The total amount of pseudo damage is proportional to the number of cycles n. i It is a linear proportional relationship and the exponential square of the load It is a linear proportional relationship, which is expressed by formula 19:

[0077]

[0078] b2) In order to compare the corresponding load spectrum strength of the two working conditions, the coefficients are introduced: equivalent damage magnification factor M; total pseudo damage U and The total amount of pseudo damage is proportional to the number of cycles n. i It is a linear proportional relationship and the exponential square of the load It is a linear proportional relationship.

[0079]

[0080] M-equivalent damage magnification factor; U 载荷谱1 —Working condition 1: road test condition with transmission A carrying vehicle B; U 载荷谱2 —Operating condition 2: road test condition with transmission A equipped with new project vehicle C;

[0081] b3) According to formula (15), the engine torque T tq Relationship with vehicle mass m, speed u, speed ratio i, and vehicle radius r;

[0082]

[0083] In general, for all models of a car company, the road spectrum they face in the road test is the same. By simplifying the number of cycles for each working condition, it can be assumed that the time required for different cars to experience each specific working condition is approximately equal, n i载荷谱1 、n i载荷谱2 It can be considered to be similar, so the equivalent damage magnification factor M is approximately:

[0084]

[0085] 5) Obtain the amplified load spectrum.

[0086] According to the equivalent damage magnification factor M, and then according to the total amount of pseudo damage U and The total amount of pseudo damage is proportional to the number of cycles n. iIt is a linear proportional relationship and the exponential square of the load It is a linear proportional relationship, and the equivalent damage magnification factor M is used to amplify the steady-state load spectrum of the transmission A to match the vehicle B.

[0087] example

[0088] A certain reducer project A is equipped with three models of customers, B, C, and D. One of the complete vehicles B has been mass-produced. The road test load data of transmission A equipped with complete vehicle B has been collected and condensed into a steady-state bench load spectrum that matches it as shown in Table 3. Based on the most stringent model, the strength is evaluated to see whether it meets the requirements.

[0089] Table 1 Information of three models

[0090]

[0091] According to formula (15), the cumulative damage U is proportional to the maximum full load weight (Kg) to the pth power and the tire rolling radius r (mm) to the p-1th power. Through comparative calculation, the damage magnification factor is calculated, and the steady-state bench load spectrum of the mass production project is amplified to form the steady-state bench load spectrum of the new project vehicle C matched with the transmission A.

[0092] Table 2 Damage magnification factor

[0093]

[0094] The steady-state bench load spectrum of the mass-produced project is known, and the damage magnification factor is calculated based on the vehicle weight and wheel diameter, and finally the damage magnification factor of the load spectrum corresponding to the new model is obtained. The simplest way to calculate the steady-state bench load spectrum of the new model is to directly process the steady-state time as a multiple of the damage magnification factor.

[0095] Table 3 Steady-state load spectrum of reducer project A matching mass-produced vehicle model B

[0096]

[0097] The total amount of pseudo damage is and the number of cycles n i It is a linear proportional relationship. In the load spectrum of mass-produced models, the time is processed according to the multiple of the damage multiplier magnification factor to form the bench steady-state load spectrum of the new model.

[0098] Table 4 Steady-state load spectrum of reducer project A matching mass-produced vehicle model C

[0099]

[0100] The above-mentioned embodiments are some embodiments of the present invention, but not all embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and cannot be simply understood as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

Claims

1. A method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights, characterized in that: The following steps are involved: 1) Assume that the mass-produced transmission A and the matching vehicle B are known, the road test load data of transmission A equipped with vehicle B has been collected, and according to the pseudo-damage theory, the preparation and experiment of the bench steady-state load spectrum of transmission A matching vehicle B has been completed. It is necessary to prepare the parameters of transmission A matching the new project vehicle C; 2) Obtain the total pseudo damage U and load T i , load T i The number of cycles n i ; 3) Obtain the relationship between the total pseudo damage amount U and the vehicle mass m, speed u, speed ratio i, vehicle radius r, etc.; 4) Determine the equivalent damage magnification factor of the load spectrum of the same electric drive assembly matching different vehicle weights; 5) Obtain the amplified load spectrum.

2. The method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights according to claim 1 is characterized in that: In step 2), the total pseudo damage U and load T are obtained i , load T i The number of cycles n i The process is as follows: 2-1) According to the damage equivalence principle, the i-th level torque T i Available j-th level torque T j Replacement; n i —Number of load cycles at level i; T i — torque of the i-th level; T j —jth level torque; n j —Number of cycles of the jth load level; p—index; 2-2) The SN curve of the component is fixed, and the power function expression of the component is: — stress radiation; Corresponding life span; C—constant; 2-3) Determine the damage level Ui at each level n i —Number of load cycles at level i; i —Number of load cycles at level i at failure; 2-4) The cumulative damage degree U is obtained by summing up the damage degree Ui at each level, and U is less than or equal to 1.0; 2-5) Get the total pseudo damage U and load T i , load T i The number of cycles n i The formula is: ① Based on the above, the cumulative damage of the reducer can be calculated from formulas (1), (2), (3) and (4): ② According to the properties of formula (2), no matter how many i is, is a constant, and the cumulative damage degree U is positively correlated with the load T i , load T i The number of cycles is expressed as formula (6); For a certain part of a certain product, it is a constant and is related to SN.

3. The method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights according to claim 2 is characterized in that: Step 3) The relationship between the total pseudo damage amount U and the vehicle mass m, speed u, speed ratio i, vehicle radius r, etc. is obtained as follows: 3-1) Obtaining engine torque T tq and wheel end driving torque T t Relationship T t =T tq i g i0η T (7) T t —wheel end driving torque; T tq —engine torque; i g —Transmission ratio; i0—Main reducer ratio; η T — Mechanical efficiency of the drive train; 3-2) Obtain wheel end driving force F t and wheel end driving torque T t Relationship T t —wheel end driving torque; F t —wheel end driving force; r—vehicle radius; 3-3) Obtaining engine torque T tq and wheel end driving force F t Relationship 3-4) Get the wheel end driving force F for different vehicle weights t Influence; 3-5) Calculate the relationship between the degree of fatigue damage to the reducer and the vehicle mass, drag coefficient, frontal area, tire radius, and reducer speed ratio.

4. The method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights according to claim 3 is characterized in that: Follow the steps below to get the wheel end driving force F for different vehicle weights. t Influence: a) The wheel end driving force F of the car t Equal to the total driving resistance of the car, F t Equal to ∑F, overcoming the driving resistance and moving forward: F t =∑F=F f +F w +F i +F j (10) F f —Rolling resistance; F w —air resistance; F i —slope resistance; F j — acceleration resistance; b) Calculate the rolling resistance F f : F f =Gfcosα=mgcosα (11) F f —Rolling resistance; G—gravity; α—angle of uphill slope; m- vehicle mass; g- gravity coefficient; c) Calculate the air resistance F w C D —Air resistance coefficient; A—frontal area; u a -speed; d) Calculate the component of the vehicle's gravity along the ramp, the slope resistance F i ; F i =Gsinα (13) e) Calculate the acceleration resistance F j ; δ—rotational mass conversion factor; m—vehicle mass; —Time derivative of velocity, acceleration.

5. The method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights according to claim 4 is characterized in that: Follow the steps below to calculate the relationship between the fatigue damage degree of the reducer and the vehicle mass, drag coefficient, frontal area, tire radius, and reducer speed ratio of the vehicle: a1) Based on 3-2), 3-3), and 3-4), and ignoring the relatively small effect of air resistance, the engine torque T is obtained. tq Relationship with vehicle mass m, speed u, speed ratio i, and vehicle radius r: a2) Because G = mg, Simplify formula (15): a3) Assuming A = gfcosα + gsinα + δa, A and vehicle speed v are related to the vehicle road conditions. Substituting into the above formulas (16) and (6), we get: U—total amount of pseudo damage; m-vehicle mass; u-speed; i-speed ratio; r-vehicle radius; Y-a coefficient omitted to simplify the formula, corresponding to a certain part of a certain product, and is a constant; g-gravity coefficient.

6. The method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights according to claim 5 is characterized in that: In step 4), the equivalent damage magnification factor of the load spectrum matching different vehicle weights of the same electric drive assembly is determined according to the following steps; b1) According to formula (5), we get: in is a constant, so the total amount of pseudo damage U and The total amount of pseudo damage is proportional to the number of cycles n. i It is a linear proportional relationship and the exponential square of the load It is a linear proportional relationship, which is expressed by formula 19: b2) In order to compare the corresponding load spectrum strength of the two working conditions, the coefficient is introduced: equivalent damage magnification factor M; M-equivalent damage magnification factor; U 载荷谱1 —Working condition 1: road test condition with transmission A carrying vehicle B; U 载荷谱2 —Operating condition 2: road test condition with transmission A equipped with new project vehicle C; B3) According to formula (15), the engine torque T tq Relationship with vehicle mass m, speed u, speed ratio i, and vehicle radius r; 7. The method for compiling a steady-state load spectrum of a test bench for matching electric drive assemblies with different vehicle weights according to claim 6 is characterized in that: According to the equivalent damage magnification factor M, and then according to the total amount of pseudo damage U and The total amount of pseudo damage is proportional to the number of cycles n. i It is a linear proportional relationship and the exponential square of the load It is a linear proportional relationship, and the equivalent damage magnification factor M is used to amplify the steady-state load spectrum of the transmission A to match the vehicle B.

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