A method for creating a life check template based on a steering screw nut pair model

Abstract

The present application relates to the technical field of modeling and fatigue life checking of steering gear parts, and provides a method for creating a life checking template based on a steering screw and nut pair model, comprising the following steps: Step 1, creating a full-parameterized steering screw and nut pair model; Step 2, creating a parameter setting window; Step 3, preparing a steering load spectrum library; Step 4, preparing a vehicle life and road condition, steering frequency and load distribution database; Step 5, creating a strength and life checking window; the strength and life checking window comprises a load spectrum calculation area, a vehicle life estimation area, a correction parameter setting area, a calculation result display area, a "calculate load and life" button and a checking result display area; Step 6, based on the life fatigue test results, adjusting and calibrating the life checking template. The present application creates a full-parameterized model for the steering screw and nut pair in the recirculating ball steering gear, and creates a quick modeling and strength and fatigue life checking template based on the full-parameterized model, thereby improving the design efficiency.

Description

TECHNICAL FIELD

[0001] The application relates to the modeling and fatigue life checking technical field of a steering gear part, in particular to a creation method of a life checking template based on a steering screw nut pair model. BACKGROUND

[0002] In an automobile steering system, a screw nut pair is used in a circulating ball steering gear. In application, the screw nut pair completes intermittent bidirectional variable load and variable speed movement, bears axial large load and random alternating load, has low speed and low positioning accuracy requirement, and needs to be stably and low-noisely driven. In the design process, the parameter setting, model creation, strength and fatigue life checking of the steering screw nut pair as a key transmission pair are usually preliminarily set and theoretically calculated based on the design experience and general formula of engineers, and then are determined through the verification of product test results after the completion of a physical prototype.

[0003] When the model is created, even if the model is not re-created after the parameter is modified each time, the correlation between parameters and between parameters and geometric sizes is relatively high, and the modification is relatively troublesome. The number of balls in the screw nut pair is relatively large, and the parameter change will affect the number and size of the balls. The point surface body features of each ball are created or modified one by one, the workload is large, and the efficiency is very low.

[0004] When the strength and fatigue life are checked, the general formula for the ball screw pair (steering screw nut pair) in the national standard GB / T17587.5 "Axial rated static load and dynamic load and service life of ball screw pair" is used to calculate the rated static load and rated dynamic load, and to calculate and check the life under the conditions of speed and load. However, in the whole life cycle of a vehicle, due to road conditions, traffic conditions, driving habits, different vehicle types and the like, the steering times and the force conditions of the steering system in the actual driving process are difficult to determine, which makes it difficult to obtain the reasonable equivalent speed, equivalent load and working life (total number of rotations or total time in the whole life cycle) of the steering screw nut pair.

[0005] Generally, each vehicle manufacturer obtains a lot of load history experience and statistical data from the analysis of the load spectrum of a typical user road or an accelerated intensive durability test field of a specific vehicle type. The steering system load spectrum provides the original data of speed and load time history for the steering screw nut pair. For new product design, the load data can be processed and converted into the speed and axial load of the steering screw nut pair according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard or enterprise standard, the load data being processed according to the load data converted from the fatigue test requirements of the steering system in the road test or bench test in the industry standard

[0006] As can be seen from the above, the parameter setting, model creation, load data processing, strength and fatigue life checking calculation of the steering screw nut pair are complicated, and the repeated operations such as frequently adjusting parameters, modifying models and recalculating checking are often required in product development. SUMMARY

[0007] The present application mainly solves the technical problems of the complicated whole process of parameter setting, model creation, load data processing, strength and fatigue life checking calculation of the steering screw nut pair in the prior art, and the repeated operations in product development, and proposes a method for creating a life checking template based on a steering screw nut pair model, a full-parameterized model is created for the steering screw nut pair in a circulating ball type steering gear, and a quick modeling and strength and fatigue life checking template is created based on the full-parameterized model, thereby improving the design efficiency.

[0008] The present application provides a method for creating a life checking template based on a steering screw nut pair model, comprising the following steps:

[0009] Step 1: creating a full-parameterized steering screw nut pair model; the steering screw nut pair model is a full-parameterized three-dimensional model, which comprises a reference, a steering screw 1, a steering nut 8, a first conduit 2, a second conduit 6, a conduit clamp 3, a ball circulating body 7, a screw 4 and a gasket 5;

[0010] Step 2: creating a parameter setting window;

[0011] Step 3: preparing a steering load spectrum library;

[0012] Step 4: preparing a vehicle life and road condition, steering frequency and load distribution database;

[0013] Step 5: creating a strength and life checking window; the strength and life checking window comprises a load spectrum calculation area, a vehicle life estimation area, a correction parameter setting area, a calculation result display area, a “calculate load and life” button and a checking result display area;

[0014] Step 6: adjusting the life checking template based on the life fatigue test results.

[0015] Further, step 1 comprises steps 101 to 104 as follows:

[0016] The step 101: creating a reference model, the reference model comprises creating parameters, relationships, reference points, lines and surfaces, and publishing parameters and references;

[0017] Step 102: creating the steering screw 1, the steering nut 8, the first conduit 2, the second conduit 6 and the conduit clamp 3 models based on the published parameters and references;

[0018] Step 103, create the ball circulating body 7 model including all the balls;

[0019] Step 104, create the steering screw nut pair assembly model.

[0020] Further, the step 101 of creating a reference model includes:

[0021] The reference model is a virtual part that includes all parameters and references, as well as the relationships between parameters, and the parameters and references are published as reference values and references for the creation of other parts;

[0022] The parameters include basic parameters, geometric parameters, and calculated parameters; basic parameters are parameters that must be defined by input and are independent variables for other calculated parameters and geometric parameters; geometric parameters are also parameters that must be input and are basic size values that need to be set for other parts to form entities or sketches; calculated parameters are other important design parameters of the steering screw nut pair, which are calculated from basic parameters or geometric parameters, do not need to be input, and are obtained by setting and calculating through a relationship formula;

[0023] The basic parameters include pitch P h , pitch diameter D pw , ball diameter D w , number of circulating bodies N b , single circulating body bearing circle number n b , nut effective stroke L e , rack modulus m, addendum coefficient h a , dedendum coefficient h f , rack pressure angle α. The number of circulating bodies N b = 2, which meets the industry demand, and is set to 2 by default here, which can be adjusted according to needs from the reference model;

[0024] The geometric parameters include screw contact angle αs, screw raceway radius coefficient sr; nut contact angle α n , nut raceway radius coefficient sn, nut up and down and left and right side allowance e n ; conduit chamfer radius R d , conduit clamp 3 plate thickness m d , conduit stop tongue and screw raceway gap δ, conduit inner diameter coefficient si;

[0025] The calculated parameters include helix angle number of balls S b ; screw outer diameter D s , screw raceway arc radius R s , screw helix start point to end point distance s0, screw length L s0 , screw helix line height L s , screw helix line number Ns ; nut inner diameter d n , nut race arc radius R n , nut length L n0 , nut spiral coil number N n , nut spiral line height L n ; conduit inner diameter d ui , conduit outer diameter d uo , conduit outer diameter eccentricity e d ;

[0026] The relationship between parameters is set as follows:

[0027] Spiral angle (`Pitch P h ` / (π*`Pitch diameter D pw `));

[0028] Ball number S b = length(`Ball cycle body reference\Ball cycle body-group one length S l `) / `Ball diameter D w `;

[0029] Screw outer diameter D s =`Pitch diameter D pw `-2mm;

[0030] Screw race arc radius R s =`Screw race radius coefficient s r `*`Ball diameter D w `;

[0031] Screw spiral starting point to endpoint distance s0=`Pitch P h `*0.6;

[0032] Screw length L s0 =`Nut length L n0 `+`Nut effective stroke L e `;

[0033] Screw spiral line height L s =`Screw length L s0 `-2*`Screw spiral starting point to endpoint distance s0`;

[0034] Screw spiral coil number N s =`Screw spiral line height L s ` / `Pitch P h `;

[0035] Nut inner diameter d n =`Pitch diameter D pw `+2mm;

[0036] Nut race arc radius Rn = `Nut race radius coefficient s n `*`Ball diameter D w` ;

[0037] Nut length L n0 = `Nut number of helical turns N n `*`Pitch P h `;

[0038] Nut number of helical turns N n = (`Single cycle body number of bearing turns n b `+0.5)*`Cycle number N b `-0.5*(`Cycle number N b `-1)`;

[0039] Nut helical line height L n = (`Nut number of helical turns N n `+2)*`Pitch P h `;

[0040] Conduit inner diameter d ui = `Ball diameter D w `*`Conduit inner diameter coefficient si`;

[0041] Conduit outer diameter d uo = `Conduit inner diameter diameter d ui `+1.5mm*2;

[0042] Conduit outer diameter eccentricity

[0043] The reference includes global reference, screw reference, nut reference, conduit reference, conduit clamp reference, ball cycle body reference; The global reference includes origin, XYZ coordinate axis, screw and nut axis; The Z axis is the screw axis and the nut axis, and the midpoint of the length direction of the screw and the nut coincides, and the coinciding midpoint is the origin; The reference of other parts is created with this coordinate system as the reference, as the point line surface reference of the entity feature of each part model creation or the reference of the basic geometry of the sketch, controls the structure and size of each part model;

[0044] The parameters and references created in the above reference are published;

[0045] Further, in step 2, the parameter setting window includes: basic parameters, rack parameters, screw parameters, nut parameters, conduit parameters and “refresh model” function button;

[0046] The basic parameters include: pitch P h , pitch diameter D pw , ball diameter D w , helix angle Circulating body number N b Single circulating body carrying number of turns n b Nut effective stroke L e Ball number S b ; wherein, according to the outer circulation structure, the single circulating body carrying number of turns n b Can only be set to n+0.5 turns;

[0047] The rack parameters include: rack modulus m, addendum coefficient h a * Dedendum coefficient h f * Rack pressure angle α;

[0048] The screw parameters include: screw outer diameter D s Screw contact angle α s Screw raceway arc radius R s Screw raceway radius coefficient s r Screw helix starting point to end point distance s0, screw length L s0 ;

[0049] The nut parameters include: nut inner diameter d n Nut contact angle α n Nut raceway arc radius R n Nut raceway radius coefficient s n Nut up and down and left and right side allowance e n Nut length L n0 ;

[0050] The conduit parameters include: conduit chamfer radius R d Conduit clamp 3 plate thickness m d Conduit stop tongue and screw raceway gap δ, conduit inner diameter coefficient s i Conduit inner diameter d ui Conduit outer diameter d uo .

[0051] Further, the specific process of the "refresh model" function button includes the following steps 201 to 211:

[0052] Step 201, set the active assembly document, define each part, define each parameter;

[0053] Step 202, get the parameter value in the parameter setting window and assign it to the corresponding basic parameters and geometric parameters in the steering screw nut pair model;

[0054] Step 203, refresh the parameters in the reference part, refresh the ball number S b , and refresh other parts in the assembly steering screw nut pair model;

[0055] Step 204, get other calculation parameters in the steering screw nut pair model, display in the window corresponding text box;

[0056] Step 205, refresh the screw, steering nut 8, the first conduit 2, the second conduit 6, conduit clamp 3 model corresponding to the document;

[0057] Step 206, set the ball circulation body 7 to active document, define each geometry set and geometry name, refresh each parameter and reference cited in the steering screw nut pair model;

[0058] Step 207, delete the original ball entity, each sphere, and each center point in the ball circulation body 7 one in reverse order, and if it is the first creation, display "no extra features in circulation body one";

[0059] Step 208, create a new ball circulation body 7 one: read the number of balls S b , set the parameter ratio = 1 / number of balls S b , set the circulation parameter i = 0 to S b -1, take the ball circulation body 7 track line group one as the reference curve for creating each ball center point, take point_i as the reference point, and create a ball center point with a ratio = 1 / number of balls S b offset, rename it as point_i+1, and place it in the geometry set circulation body one ball center point; take point_i+1 as the sphere center, take the ball diameter D w / 2 as the radius, create a spherical feature, rename it as sphere_i+1, and place it in the geometry set circulation body one ball sphere; finally, fill sphere_i+1 with a closed surface feature to complete the creation of a ball, rename it as ball_i+1, and place it in the geometry circulation body one ball body, complete the i-th cycle; then enter the next cycle until the i = S b -1 cycle is completed;

[0060] Step 209, delete the original ball entity, each sphere, and each center point in the ball circulation body 7 two in reverse order, and if it is the first creation, display "no extra features in circulation body two";

[0061] Step 210, create a new ball circulation body 7 two: set the circulation parameter j = 0 to S b -1, take the ball circulation body 7 track line group two as the reference curve for creating each ball center point, take point_j as the reference point, and create a ball center new point with a ratio = 1 / number of balls S b offset, rename it as point_j+1, and place it in the geometry set circulation body two ball center point; take point_j+1 as the sphere center, take the ball diameter D w / 2 as the radius, create a spherical feature, rename it as Sphere_j+1, and place it in the Geometry Set Cycle Two Ball Sphere; finally, fill the Sphere_j+1 with a closed surface feature to create a solid, rename it as Ball_j+1, and place it in the Geometry Body Cycle Two Ball Body, complete the i-th cycle; then enter the next cycle until the j=S b -1 cycle is completed.

[0062] Step 211, refresh the ball cycle 7 model and save the steering screw nut pair model document;

[0063] Step 212, output the parameters in the window to the EXCEL document, save it to the default folder with the name "Basic and Geometric Parameters-Year-Month-Day-Hour-Minute-Second.xlsx".

[0064] Further, in step 3, the load spectrum is stored in the form of a table in the EXCEL document, including four columns of data, the first column is the serial number, the second column is the rotating speed n i , the third column is the load F i , and the fourth column is the time t i .

[0065] Further, step 5 includes the following steps 501 to 505:

[0066] Step 501, create a load spectrum calculation area; the load spectrum calculation area specifically includes 8 input boxes: rotating speed n i , axial load F i , time t i , cycle number N T , small cycle number θ t , maximum rotating speed n max , maximum axial load F max , and static torsional strength T a ; the load spectrum calculation area includes 7 function buttons: add data points, modify data points, load import, load export, instantaneous method, proportion method, and percentage method; the load spectrum calculation area also includes a load spectrum list box and a reference load spectrum selection combination box;

[0067] Step 502, create a whole vehicle life estimation area;

[0068] Step 503, create a correction parameter setting area;

[0069] Step 504, create a calculation result display area;

[0070] Step 505, create a calculation load and life function button and a verification result display area;

[0071] Further, step 502 includes steps 5021 to 50211:

[0072] Step 5021, define vehicle life parameters; the vehicle life parameters include average daily driving time T. d Total driving time T within the service life T Total number of working cycles within the service life θ n Total working life t max Average steering wheel speed n m ;

[0073] Step 5022: Obtain the corresponding service life, mileage, road condition weight, average vehicle speed, average steering angle, steering frequency, load percentage, cycle count, and maximum axial load from the window;

[0074] Step 5023, determine the total number of loops:

[0075] VXH=XH1+XH2+XH3+XH4+XH5+XH6+XH7+XH8+XH9;

[0076] Step 5024: Determine the 9 sets of intermediate load values ​​Fr1, Fr2, Fr3, Fr4, Fr5, Fr6, Fr7, Fr8, and Fr9:

[0077] Fr1=((F max *BFB1 / 100)^3)*(XH1 / VXH);

[0078] Fr2=((F max *BFB2 / 100)^3)*(XH2 / VXH);

[0079] Fr3=((F max *BFB3 / 100)^3)*(XH3 / VXH);

[0080] Fr4=((F max *BFB4 / 100)^3)*(XH4 / VXH);

[0081] Fr5=((F max *BFB5 / 100)^3)*(XH5 / VXH);

[0082] Fr6=((F max *BFB6 / 100)^3)*(XH6 / VXH);

[0083] Fr7=((F max *BFB7 / 100)^3)*(XH7 / VXH);

[0084] Fr8=((F max* BFB8 / 100)^3)*(XH8 / VXH) ;

[0085] Fr9 = ((F max * BFB9 / 100)^3)*(XH9 / VXH) ;

[0086] Step 5025, determine equivalent load:

[0087] F nm1 = F nm2 r1+ F d r2+ F max r3+ F 6 r4+ F max r5+ F T r6+ F d r7+ F max r8+ F n r9)^(1 / 3) ;

[0088] Step 5026, determine average steering time per day:

[0089] T d = S max *10 6 / ((N max *365)*(V12*P11+V22*P21+V32*P31+V42*P41)) ;

[0090] Step 5027, determine total steering time:

[0091] T T = T d *365*N max ;

[0092] Step 5028, determine total number of turns:

[0093] θ n = T T *60*(P11*(θ13*T14+θ15*T16+θ17*T18)+P21*(θ23*T24+θ25*T26

[0094] +θ27*T28)+P31*(θ33*T34+θ35*T36+θ37*T38)+P41*(θ43*T44+θ45*T46+θ47*T48)) / 36000 ;

[0095] Step 5029, determine total time:

[0096] t max = T T / (n m *60) ;

[0097] Step 50210, output the calculated equivalent load F nm1 and F nm2 , average steering speed n m and total number of turns θn Total working life t max Displayed in the text box corresponding to the calculation results area;

[0098] Step 50211: Export the vehicle life estimation data to an Excel document named "Vehicle Life Estimation-Year-Month-Day-Hour-Minute-Second.xlsx".

[0099] Furthermore, step 505 includes steps 5051 to 5058:

[0100] Step 5051, extract basic parameters from the reference model; the basic parameters include: pitch circle diameter D pw Ball diameter D w Pitch P h Number of single-cycle body bearing revolutions n b Nut raceway radius r n Screw raceway radius r s nut raceway contact angle α n Screw raceway contact angle α s ;

[0101] Step 5052, obtain the correction coefficient in the window: C a0 Surface hardness correction factor f h0 C a Surface hardness correction factor f h Precision coefficient f ac Material smelting method coefficient f m Reliability coefficient f ar Lubrication condition coefficient f r ;

[0102] Step 5053, calculate the rated axial static load C of the screw and nut pair. oa and C oam Axial rated dynamic load C a and C am ;

[0103] Step 5054: Calculate the rated life L of the screw-nut pair under equivalent speed and equivalent load. 1,2 and L h1,2 Final lifespan L r and L hr Lifetime L including reliability factor ar and L har and L h1,2 Corrected lifetime L including reliability factor mar and L hmar ;

[0104] Step 5055, check axial static torsional strength and fatigue life: Static torsional strength Ta With rated static load check, C oa ≥ 2 x μ x π x T a / P h With durability life rated dynamic load check, L mar ≥ L0, L hmar ≥ L h0 ;

[0105] Step 5056, the calculation results axial rated static load C oa and C oam , axial rated dynamic load C a and C am , the reliability coefficient containing the modified life L mar and L hmar , the rated life L 1,2 and L h1,2 are displayed in the corresponding text box of the calculation result area;

[0106] Step 5057, the checking results are displayed in the right text box: when both are qualified, "static torque qualified / life qualified" is displayed, and the bottom color is green; only one is qualified, "static torque unqualified / life qualified" or "static torque qualified / life unqualified" is displayed, and the bottom color is orange; both are unqualified, "static torque unqualified / life unqualified" is displayed, and the bottom color is red;

[0107] Step 5058, open the latest stored load spectrum EXCEL document under the default address, create a new worksheet, name it "basic and geometric parameter" worksheet, save the basic and geometric parameters in the new worksheet at this time in the steering screw nut pair model; Create a new worksheet, name it "calculation result" worksheet, and the document name is "steering screw 1 nut life analysis-year-month-day-hour-minute-second.xlsx".

[0108] Further, after step 6, it further includes: step 7, using the life check template, the strength and life check of the steering screw nut pair under the set parameters; Step 7 includes the following steps 701 to step 706:

[0109] Step 701, open the steering screw nut pair model containing the development template in CATIA software, click the "display parameter setting window" tool in the custom tool, and display the window; Modify the white bottom parameters in the window, click the "refresh model" function button, complete the new model of the steering screw nut pair, and automatically export the basic and geometric parameters of the model to the EXCEL document;

[0110] Step 702, click the "strength and life check window" tool in the custom tool to display the window, and input the load spectrum data or vehicle life data;

[0111] Step 703, setting the cycle number N in the "strength and life check" window T , the maximum rotational speed n max , the maximum axial load F max , and the static torsional strength T a ;

[0112] Step 704, selecting the instantaneous method, the proportion method, the percentage method or the whole vehicle life method function button according to the data type, obtaining the equivalent rotational speed, the equivalent load and the working life and displaying them in the calculation result area; if the whole vehicle life method is selected, the whole vehicle life estimation data is also exported to the EXCEL document;

[0113] Step 705, setting 6 correction parameters in the "strength and life check" window;

[0114] Step 706, clicking "calculate load and life", completing the calculation of the axial rated static load C oam , the axial rated dynamic load C am value corresponding to the current parameters of the steering screw and nut pair, completing the calculation and check of the life under the equivalent rotational speed and the equivalent load, and displaying the strength and life qualification results in the adjacent text box; and exporting the basic and geometric parameters, the load spectrum and the calculation results to the EXCEL document.

[0115] The application provides a creation method of a life check template based on a steering screw and nut pair model (hereinafter referred to as the template), which comprises the following steps: firstly, creating a full-parameterized steering screw and nut pair model; checking the model, and modifying the model and refreshing the model for checking until the model is qualified if the model is unqualified; then, based on the qualified full-parameterized model, creating a parameter setting custom window, realizing the setting of basic parameters (white background parameters), automatically refreshing the part model and the assembly model, displaying the calculation parameters (gray background parameters), and outputting the model parameter document; next, preparing the load spectrum or the whole vehicle life data; finally, creating a strength and life check window, realizing the calculation of the equivalent rotational speed and the equivalent load and the working life according to the input load spectrum or the whole vehicle life data, and outputting the load spectrum or the whole vehicle life data document; realizing the calculation of the axial rated static load and the axial rated dynamic load according to the basic parameters in the model; realizing the calculation of the life in each state under the equivalent rotational speed and the equivalent load; and performing the strength and life check, modifying the parameters, refreshing the model, recalculating the axial rated static load and the axial rated dynamic load, rechecking the strength and life, until the model is qualified, and then adding the calculation and check result data in the latest output data document.

[0116] The template of the application integrates the design experience of engineers, standard formula, process conditions of manufacturing enterprises, vehicle load spectrum or vehicle life requirements, and uses self-defined windows to make the implementation of the above complex process simple and fast. After the template is created, the test load spectrum is optimized, the vehicle life calculation data is reasonably set, and the correction coefficient is revised, so that the model is more suitable for the working state of the automobile steering system, and is efficiently and accurately transplanted into new product development to perform spatial structure arrangement, type selection calculation and life checking. BRIEF DESCRIPTION OF DRAWINGS

[0117] Figure 1 is the implementation flowchart of the creation method of the life checking template based on the steering screw nut pair model provided by the application;

[0118] Figure 2 is a structural schematic diagram of the steering screw nut pair model created by the application;

[0119] Figure 3 is a schematic diagram of the parameter setting window created by the application;

[0120] Figure 4 is a schematic diagram of the load spectrum data and curve of Table 1;

[0121] Figure 5 is a schematic diagram of the strength and life checking window;

[0122] Figure 6 is a flowchart of the strength and life checking;

[0123] Figure 7a is a schematic diagram of the output "basic and geometric parameter" document;

[0124] Figure 7b is a schematic diagram of the output "load spectrum" document;

[0125] Figure 7c is a schematic diagram of the output "vehicle life estimation" document;

[0126] Figure 7d is a schematic diagram of the output "calculation result" document. DETAILED DESCRIPTION

[0127] In order to make the technical problems solved by the application, the technical solutions adopted and the technical effects achieved more clear, the application will be further described in detail below in combination with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the application, and not to limit the application. In addition, it should be noted that, in order to facilitate description, only the parts related to the application are shown in the drawings, not all.

[0128] The application mainly comprises creating a full-parameterized steering screw nut pair model based on the parameterized design function of the CATIA software platform, creating parameter setting custom windows and strength and life checking custom windows through secondary development technology and VBA windows, and preparing load spectrum and vehicle life data.

[0129] As shown in Figure 1 , the application embodiment provides a creation method of a life checking template based on a steering screw nut pair model, comprising the following processes:

[0130] Step 1, creating a full-parameterized steering screw nut pair model.

[0131] Based on the CATIA three-dimensional software, a steering screw nut pair model in an automobile steering circulating ball steering gear is created, the steering screw nut pair model (see Figure 2 ) is a full-parameterized three-dimensional model, and the part models contained include: reference, steering screw 1, steering nut 8, first guide pipe 2, second guide pipe 6, guide pipe clamp 3, ball circulating body 7, screw 4 and gasket 5. Step 1 comprises steps 101 to 104 as follows:

[0132] Step 101, creating a reference model, the reference model comprises creating parameters, relationships, reference points, lines and surfaces, and publishing parameters and references.

[0133] The application first creates a reference model, the reference is a virtual part, including all parameters and references, and the relationships between parameters, and the parameters and references are published as the creation reference values and references of other parts.

[0134] The parameters include basic parameters, geometric parameters and calculation parameters. The basic parameters are parameters that must be defined by input, and are independent variables of other calculation parameters and geometric parameters. The geometric parameters are also parameters that must be input, and are basic size values that need to be set for other parts to form an entity or sketch. The calculation parameters are other important design parameters of the steering screw nut pair, which are obtained by calculation of the basic parameters or geometric parameters, and do not need to be input, but are obtained by setting and calculation through the relationship formula.

[0135] The basic parameters include pitch P h , pitch diameter D pw , ball diameter D w , number of circulating bodies N b , single circulating body bearing circle number n b , nut effective stroke L e ; rack modulus m, addendum coefficient h a , dedendum coefficient h f*, rack pressure angle α. The number of cycles N commonly used at present b = 2, basically meet the industry demand, hereinafter referred to as 2, can be adjusted according to the needs of the reference model.

[0136] Geometric parameters include: screw contact angle αs, screw radius coefficient sr; nut contact angle α n , nut radius coefficient sn, nut up and down and left and right side of the amount of e n ; conduit chamfer radius R d , conduit clamp 3 plate thickness m d , conduit blocking tongue and screw raceway clearance δ, conduit inner diameter coefficient si.

[0137] Calculation parameters include: helix angle number of balls S b ; screw outer diameter D s , screw raceway arc radius R s , screw helix start to end distance s0, screw length L s0 , screw helix height L s , screw helix number N s ; nut inner diameter d n , nut raceway arc radius R n , nut length L n0 , nut helix number N n , nut helix height L n ; conduit inner diameter d ui , conduit outer diameter d uo , conduit outer diameter eccentricity e d .

[0138] The relationship between the parameters (according to the relationship formula format in CATIA) is set as follows:

[0139] Helix angle (`pitch P h ` / (π*`pitch diameter D pw `));

[0140] Number of balls S b = length(`ball cycle body reference\ball cycle body-Group one length S l `) / `ball diameter D w `;

[0141] Screw outer diameter D s = `pitch diameter D pw `-2mm;

[0142] Screw raceway arc radius R s = `screw raceway radius coefficient s r `*`ball diameter D w;

[0143] Screw helix start-to-end distance s0 = `Pitch P h `* 0.6;

[0144] Screw length L s0 = `Nut length L n0 + `Nut effective stroke L e `;

[0145] Screw helix height L s = `Screw length L s0 - 2 * `Screw helix start-to-end distance s0`;

[0146] Screw helix turns N s = `Screw helix height L s / `Pitch P h `;

[0147] Nut inner diameter d n = `Pitch circle diameter D pw + 2 mm;

[0148] Nut raceway arc radius Rn = `Nut raceway radius factor s n * `Ball diameter D w` `;

[0149] Nut length L n0 = `Nut helix turns N n * `Pitch P h `;

[0150] Nut helix turns N n = (`Single cycle body load-bearing turns n b + 0.5) * `Cycle body number N b - 0.5 * (`Cycle body number N b - 1);

[0151] Nut helix height L n = (`Nut helix turns N n + 2) * `Pitch P h `;

[0152] Conduit inner diameter d ui = `Ball diameter D w * `Conduit inner diameter factor si`;

[0153] Conduit outer diameter d uo = `Conduit inner diameter diameter d ui + 1.5 mm * 2;

[0154] Conduit outer diameter eccentricity

[0155] The reference includes global reference, screw reference, nut reference, conduit reference, conduit clamp reference, ball circulation body reference. The global reference includes origin, XYZ coordinate axis, screw and nut axis. In principle, the Z axis is the screw axis and the nut axis, and the midpoint of the length direction of the screw and the nut coincides, and the coincident midpoint is the origin. The reference of other parts is created with this coordinate system as the reference, as the point-line-face reference of the entity feature of each part model creation, or the reference of the basic geometry of the sketch, to control the structure and size of each part model.

[0156] The parameters and references created in the above reference are published.

[0157] Step 102, based on the published parameters and references, create steering screw 1, steering nut 8, first conduit 2, second conduit 6 and conduit clamp 3 model.

[0158] Based on the published above parameters and references, create each part model. Reference the screw reference to create the stretched outer cylinder of the steering screw 1 and the multi-section entity cutout to form the outer raceway; reference the nut reference to create the stretched body of the steering nut 8 and the multi-section entity cutout to form the inner raceway, create the tooth slot and array to form multiple teeth, create the conduit hole and screw hole on the steering nut 8; reference the conduit reference to create the outer diameter rib and inner diameter slot feature of the first conduit 2 or the second conduit 6, and create the slot feature of the conduit inlet and outlet, the first conduit 2 and the second conduit 6 are the same structure but different positions; reference the conduit clamp reference to create the stretched sheet of the conduit clamp 3, and determine the sheet shape according to the conduit position and outer diameter. Ensure that all changed sizes and references of each part model follow the changes when modifying the parameters.

[0159] Step 103, create the ball circulation body 7 model including all the balls.

[0160] Based on the published above parameters and ball circulation body 7 reference, create the ball circulation body 7 model. The ball circulation body 7 includes all the ball bodies, the creation of each ball body includes the ball center, the ball surface and the point-face body creation of the ball entity (closed surface). When modifying the basic parameters, the number of balls S b will follow the changes, and the position and number of point-face bodies of the ball body will also follow the changes. Only modifying the parameters cannot delete the redundant ball bodies or add the missing ball bodies, and the number of balls in each ball circulation body 7 group is large, each ball contains the creation of point-face bodies, the process is repetitive and tedious, and the solution is given in the second step.

[0161] Step 104, create the steering screw nut pair assembly model.

[0162] Create the steering screw nut pair assembly model, assemble the above parts model. Based on the release parameters and the reference to create parts will be arranged in the default position according to the reference, only need to assemble screw 4 and washer 5.

[0163] Check the parameterized steering screw nut pair model, modify the basic parameters, check the model of the follow-up and accuracy. If not qualified, according to the problem point to find the error, modify the model, check the model again, until all the basic parameters of the follow-up and accuracy test qualified.

[0164] The above process of creating datum, part model and assembly model is the common operation process of three-dimensional software. After the creation of steps 101 to 104, the steering screw nut pair model is formed.

[0165] Step 2, create parameter setting window.

[0166] The above completes the steering screw nut pair model, modifies the parameters in the model, the interaction is not good, especially in the case of not familiar with the model, it is easy to miss the associated items, and the single parameter modification is also easy to cause model error. Therefore, by creating a custom window (such as Figure 3 ), the automatic parameter value setting, automatic refreshing or rebuilding parts and assembly model is realized. And create "parameter setting window" custom tool in CATIA tool customization to facilitate opening the window.

[0167] As shown in Figure 3 , the parameter setting window includes: basic parameters, rack parameters, screw parameters, nut parameters, guide pipe parameters and "refresh model" function button.

[0168] The basic parameters include: pitch P h , pitch diameter D pw , ball diameter D w , helix angle , number of cycles N b , single cycle body bearing circle number n b , nut effective stroke L e , number of balls S b ; wherein, according to the outer cycle structure, the single cycle body bearing circle number n b can only be set to n+0.5 circle (n=0,1,2,3……).

[0169] The rack parameters include: rack modulus m, addendum coefficient h a *, dedendum coefficient h f *, rack pressure angle α.

[0170] The screw parameters include: screw outer diameter D s , screw contact angle α s , screw raceway arc radius Rs , screw channel radius coefficient s r , screw helix start-to-end distance s0, screw length L s0 ;

[0171] Nut parameters include: nut inner diameter d n , nut contact angle a n , nut channel arc radius R n , nut channel radius coefficient s n , nut up and down and left and right side allowance e n , nut length L n0 ;

[0172] Conduit parameters include: conduit chamfer radius R d , conduit clamp 3 plate thickness m d , conduit stop tongue and screw channel gap d, conduit inner diameter coefficient s i , conduit inner diameter d ui , conduit outer diameter d uo .

[0173] According to experience or process conditions, set the parameter range, when the range is exceeded, the window prompts "** parameter exceeds *** range, please determine again! ", for example: ball diameter D w Limited to 0.3-0.75 times of the pitch P h ; cycle number N b 2; single cycle bearing circle number n b Set to n+0.5 circle (n=0,1,2,3…) ; screw contact angle a s And nut contact angle a n General range is 42°-47°; screw channel radius coefficient s r And nut channel radius coefficient s n Limited range is 0.52-0.62, etc.

[0174] Parameter setting window Figure 3 The white background text box in the input parameter, corresponding to the basic parameters and geometric parameters in the model; gray background text box parameters from the model, corresponding to the calculation parameters in the model, which are calculated by setting the relationship with other parameters in the model, and are automatically read from the model when refreshing the model. Some calculation parameters and size parameters when creating geometric bodies are used as parameters in the model creation process and are not displayed in the window.

[0175] The function of the "refresh model" function button in the parameter setting window includes: setting the parameter value in the model equal to the corresponding parameter value in the window, refreshing the new parameters in the reference part, and refreshing other parts in the assembly, updating the assembly model; refreshing the documents corresponding to each part model and saving, recreating the ball in the ball loop body 7; and displaying other calculation parameters in the model in the window. The specific process of the "refresh model" function button includes the following steps 201 to 211:

[0176] Step 201, setting the active assembly document, defining each part, and defining each parameter.

[0177] Step 202, assigning the parameter value in the parameter setting window (white background textbox) to the corresponding basic parameter and geometric parameter in the steering screw nut pair model.

[0178] Step 203, refreshing the parameters in the reference part, and refreshing the number of balls S b , and refreshing other parts in the assembly steering screw nut pair model.

[0179] Step 204, obtaining other calculation parameters in the steering screw nut pair model and displaying them in the corresponding text box (gray background text box) in the window.

[0180] Step 205, refreshing the documents corresponding to the screw, steering nut 8, first conduit 2, second conduit 6, and conduit clamp 3 models.

[0181] Step 206, setting the ball loop body 7 as the active document, defining each geometric set and geometric body name, and refreshing each parameter and reference referenced in the steering screw nut pair model.

[0182] Step 207, deleting the original ball entity (closed surface), each spherical surface, and each center point in the ball loop body 7 in reverse order. If it is the first creation, display "Loop Body One has no extra features".

[0183] Step 208, creating a new ball loop body 7: reading the number of balls S b , setting the parameter ratio = 1 / number of balls S b , setting the loop parameter i = 0 to S b -1, taking the ball loop body 7 trajectory line set one as the reference curve for creating the ball center points on the curve, taking point_i (the base point named point_0 created on the ball loop body 7 trajectory line in the ball loop body 7 model) as the reference point, creating the ball center point with a ratio of 1 / number of balls S b offset, renaming it to point_i+1, and placing it in the geometric set Loop Body One ball center point. Taking point_i+1 as the sphere center, taking the ball diameter D w / 2 as radius, create a spherical surface feature, rename it as Sphere_i+1, and place it in the geometry set cycle body one ball sphere. Finally, fill the Sphere_i+1 with a closed surface feature to make it a solid, complete the creation of a ball, rename it as Ball_i+1, and place it in the geometry cycle body one ball body. Complete the i-th cycle. Then go to the next cycle until the completion of the i = S b -1 cycle.

[0184] Step 209, delete the ball solid (closed surface), each spherical surface, and each center point in the original ball cycle body 7 two in reverse order. If it is the first time to create, display "No extra features in cycle body two".

[0185] Step 210, create a new ball cycle body 7 two: set the cycle parameter j = 0 to S b -1, take the ball cycle body 7 trajectory set two as the reference curve of each ball center point on the creation curve, take the point_j (the base point named point_0 has been created on the ball cycle body 7 two trajectory in the ball cycle body 7 model) as the reference point, and create a new ball center point with a ratio = 1 / ball number S b offset, rename it as point_j+1, and place it in the geometry set cycle body two ball center point. Take the point_j+1 as the center of the sphere, and create a spherical surface feature with the ball diameter D w / 2 as radius, create a spherical surface feature, rename it as Sphere_i+1, and place it in the geometry set cycle body one ball sphere. Finally, fill the Sphere_i+1 with a closed surface feature to make it a solid, complete the creation of a ball, rename it as Ball_i+1, and place it in the geometry cycle body one ball body. Complete the i-th cycle. Then go to the next cycle until the completion of the i = S b -1 cycle.

[0186] Step 211, refresh the ball cycle body 7 model, and save the steering screw nut pair model document.

[0187] Step 212, output each parameter in the window to an EXCEL document, save it to the default folder (such as Figure 7a ) with the name "Basic and geometric parameters-year-month-day-hour-minute-second.xlsx".

[0188] Step 3, prepare the steering load spectrum library.

[0189] The load spectrum acquisition of the automobile provides basic data for the vehicle durability, fatigue failure and safety research. The load measurement of the steering system can be arranged at the steering rocker arm, the steering knuckle connecting kingpin or the steering tie rod, etc. The measurement results are calculated to the output end of the recirculating ball steering gear, and then to the steering screw and nut pair according to the transmission relationship, so as to obtain the rotational speed and axial load thereof. The time history method or the rainflow counting method is generally adopted for measuring the load spectrum of the whole vehicle. For the data measured by the time history method, the positive and negative of the rotational speed n i and the axial load F i vary with time, and the positive and negative of the rotational speed n i are consistent with those of the load F i . The time t i represents the time when the value is taken, and the sampling time interval is appropriately selected to ensure that the values on both sides of the extreme point, the inflection point and the reversing point are not ignored to affect the results. For the data obtained by the rainflow counting method, the corresponding input shaft rotational speed n i and the axial load F i occupy the time length t i , the rotational speed n i and the load F i are both positive and negative and the signs are consistent, the rotational speed n i ±a and the axial load F i ±b are counted to the corresponding rotational speed n i and the axial load F i cumulative time length, and the ranges of a and b are reasonably set.

[0190] When the vehicle manufacturer does not provide the load spectrum, the general practice is to follow the test standards or specific strength tests and durability tests (fatigue life tests), and the load spectrum of the steering screw and nut pair needs to be generated according to the corresponding provisions in the fatigue test. The relevant standards for the durability test of the recirculating ball steering gear include QC / T 29096 “Automobile Steering Gear Assembly Bench Test Method”, QC / T 29097 “Automobile Steering Gear Assembly Technical Requirements”, and QC / T 1081 “Automobile Electric Power Steering Device”. Although QC / T 649 “Automobile Steering Mechanism Performance Requirements and Test Methods” is not a performance and test requirement for the recirculating ball steering gear, it is also a test requirement for the steering system mechanism, and the rotational speed, torque and cycle number of the input end of the static torsional strength and fatigue durability test can be referred to. In addition, large vehicle manufacturers also have their own customized enterprise standards. The fatigue test requirements of the whole vehicle in the above commonly used standards are converted into the rotational speed n i , the load F i and the time t iThe data form of the load spectrum data, and save in the default storage address EXCEL document for call. By the test requirements of the conversion of the load spectrum data is expressed in the form of speed percentage and load percentage of the screw speed and axial load changes in the small cycle of fatigue test, for specific vehicle need to set the highest speed n max and the maximum axial load F max as a percentage of the base. Small cycle is generally from the middle position to the left to reach the specified angle back to the middle position, and then to the right to reach the specified angle back to the middle position, repeat the specified number of small cycle to achieve the set cycle number N T .

[0191] The above any form of load spectrum is stored in the form of table in the EXCEL document (such as Figure 4 ), including four column data, the first column is the serial number (Number), the second column is the speed n i (° / s), the third column is the load F i (N), the fourth column is the time t i (s). To express intuitive can also add curve display.

[0192] The input speed of the test load spectrum data is positive and negative, the force bearing raceway side of the two directions of transmission is not the same, assuming that the two raceway side processing quality is the same, and the probability of stress situation is the same, from one end to see the screw forward as positive, then reverse as negative.

[0193] The relevant durability test requirements in the industry standard are as shown in table 1:

[0194] Table 1 requirements of the industry standard on durability test

[0195]

[0196] From table 1, it can be seen that the test method of the durability test is set to constant input shaft speed, and the output load changes with the waveform or period, which is an accelerated failure bench fatigue test to replace the actual load condition, and the experimental load spectrum can be obtained.

[0197] The requirement of the industry standard for the static torsional strength T a of the product provides reference for the static strength check of the selected parameters of the steering screw nut pair, in which the specific static torsional strength T a requirement is as shown in table 2:

[0198] Table 2 requirements of the industry standard on static torsional strength

[0199]

[0200] The above data may not be accurate due to different revision periods. The data here is only for method presentation and reference only. Please adjust the parameters and data according to the latest standards.

[0201] Step 4, prepare the vehicle life and road conditions, steering frequency and load distribution database.

[0202] When there is no load spectrum for new vehicle design, according to the vehicle manufacturer's vehicle positioning, kerb mass, gross weight, vehicle life and sales area, etc., the equivalent load and equivalent speed of the steering screw nut pair are estimated according to the load distribution, road condition distribution and steering frequency of the specific road condition of the vehicle.

[0203] In addition to the vehicle manufacturer's vehicle life setting, the "Motor Vehicle Use Year and Mileage Reference Value" in the "Motor Vehicle Mandatory Retirement Standard Regulations" requires setting the use year and mileage requirements for the following vehicle types: light cargo, medium and light cargo, heavy cargo, non-operational small and micro passenger cars, non-operational large passenger cars, non-operational medium passenger cars, non-operational large passenger cars, non-operational small and micro passenger cars, non-operational medium passenger cars, non-operational large passenger cars, other small and micro passenger cars, other medium passenger cars, other large passenger cars, special school buses, multi-cylinder low-speed trucks, single-cylinder low-speed trucks, three-wheeled vehicles, and other special vehicles. The default value is set as a template.

[0204] The driving road conditions of the vehicle are generally divided into urban roads, highways, rural roads and mountainous roads. The average driving speed is accumulated in different road conditions, and the average turning angle and steering frequency per minute are estimated. The ratio of driving time to total time on different roads is the road condition weight. The data in the load spectrum (actual vehicle driving load spectrum) is counted and summarized to summarize the frequency of different steering conditions, such as low-speed large-angle U-turn or warehouse entry, normal intersection steering, high-speed small-angle lane changing or obstacle avoidance, etc. Different classification forms of steering conditions can be set according to routine or experience.

[0205] It is difficult to summarize the steering load in the above road conditions and steering conditions. Table 3 refers to the load percentage of the output end loading of the reverse drive fatigue test in QC / T 1081 and the corresponding cycle number requirements, and adds overload conditions to set the default load distribution. The test load is a percentage of the rated load T e .

[0206] Table 3 Output test load and cycle number

[0207] Sequence Test load %T e ]] Number of cycles Sequence Test load %T e ]] Number of cycles 1 40％ 120000 6 90％ 6000 2 50％ 40000 7 100％ 2000 3 60％ 25000 8 110％ 800 4 70％ 15000 9 120％ 500 5 80％ 9000 10 — —

[0208] The steering frequency and steering load summarized above are based on limited information and are intended as a reference for the method of expression. The specific data values ​​for these parameters should be determined based on the vehicle's overall positioning and the OEM's extensive experience. Furthermore, the vehicle's driving process includes left and right turns, assuming that the probability of rotation in each direction is equal and evenly distributed.

[0209] Step 5: Create a strength and lifespan verification window.

[0210] To determine whether the steering screw and nut pair model with the aforementioned set parameters meets the vehicle's requirements for steering transmission strength and fatigue life, the strength and life of the steering screw and nut pair (ball screw and nut pair) are checked according to the calculation methods and formulas in standard GB / T 17587.5. The following section describes how to create a custom strength and life check window (e.g., ...). Figure 5 This feature integrates these tedious and fixed analysis and calculation processes into function buttons, enabling rapid completion of strength and life verification. A custom "Strength and Life Verification Window" is also created within the CATIA tool customization for easy access.

[0211] Depend on Figure 5 As can be seen, the strength and life verification window includes a load spectrum estimation area, a vehicle life estimation area, a correction parameter setting area, a calculation result display area, a "Calculate Load and Life" button, and a verification result display area. Step 5 includes the following steps 501 to 505:

[0212] Step 501: Create the load spectrum estimation region.

[0213] The load spectrum calculation area allows for the input, modification, import, and export of load spectra, as well as the calculation of the equivalent speed, equivalent load, and service life of the steering screw and nut pair based on the load spectrum. Specifically, the load spectrum calculation area includes eight input boxes: speed n i Axial load F i Time t i Number of loops N T Small cycle number θ t Maximum speed n max Maximum axial load F max and static torsional strength T a The load spectrum estimation area includes seven function buttons: Add Data Point, Modify Data Point, Import Load, Export Load, Instantaneous Method, Proportional Method, and Percentage Method. The load spectrum estimation area also includes a load spectrum list box and a reference load spectrum selection combo box.

[0214] The "Add Data Point" function button controls the current rotational speed n. i Axial load F i Time t iData is added to the load spectrum list box. The "modify data point" function button realizes the modification of the rotation speed n i , axial load F i , and time t i . The data of the selected column item in the load spectrum list box is replaced. The "load import" function button realizes the import of a standard load spectrum or a load spectrum arranged into an EXCEL document into the load spectrum list box. The name of the standard load spectrum to be imported needs to be selected in the reference load spectrum selection combo box. The standard load spectrums that have been set include QC / T 29096, QC / T 1081, and QC / T 649, which can be expanded according to the situation. The "load export" function button realizes the export of the data in the load spectrum list box to an EXCEL document, which is stored in the default address for later use. The default storage address and name are displayed below the "calculate load and life" button in the lower right part of the window. The document name is "load spectrum-year-month-day-hour-minute-second.xlsx" (for example Figure 7b ).

[0215] The instantaneous method function button, the proportion method function button, and the percentage method function button realize the calculation of the equivalent rotation speed, the equivalent load, and the working life according to the load spectrum data. The implementation of the functions is based on the latest EXCEL document exported by the load. At this time, the working life is the number of rotations and the running time in the load spectrum.

[0216] The instantaneous method: when the load spectrum provided by the vehicle manufacturer is measured by the time history method, the data is arranged as the instantaneous rotation speed n i and the axial load F i that change with time. The specific implementation process is as follows:

[0217] 1) Open the latest load spectrum EXCEL document stored in the default address to obtain the last row lastRow in the table;

[0218] 2) Define the loop variables i and j, define the rotation speed n i , n i+1 , n j , n j+1 , the load F i , F i+1 , F j , F j+1 , the time t i , t i+1 , t j , t j+1 , and the loop number N T ; define the intermediate parameters a, b, c, and d; define the variables working life total time t max , working life total rotation θ n , equivalent rotation speed n m , and equivalent load intermediate value Fr and F l , equivalent load F rm1 and F rm2 variable, and assign initial value;

[0219] 3) Get the number of large loop N T in the window, and calculate the total time t max = (t (lastRow) - t (2)) * N T / 3600;

[0220] 4) The first i loop, traverse the 2 to lastRow-1 row, calculate the equivalent speed n m and total turns θ n :

[0221] When n i *n i+1 ≥0,

[0222] n m = n m + abs (n i +n i+1 ) *(t i+1 -t i ) / (2*t max );

[0223] θ n = θ n + abs (n i +n i+1 ) *(t i+1 -t i ) / 720;

[0224] When n i *n i+1 <0,

[0225] a = abs (n i ) / (abs (n i )+ abs (n i+1 ));

[0226] b = abs (n i+1 ) / (abs (n i )+ abs (n i+1 ));

[0227] n m = n m + (abs (n i )*a / 2+ abs (n i+1 )*b / 2) *(t i+1 -t i ) / t max ;

[0228] θ n = θ n + (abs(n i )*a / 2+abs(n i+1 )*b / 2)*(t i+1 -t i ) / 360;

[0229] 5) The second j loop, which traverses the 2nd to lastRow-1 row, calculates the intermediate value F r and F l ,

[0230] c = abs(F j ) / (abs(F j )+abs(F j+1 ) ;

[0231] d = abs(F j+1 ) / (abs(F j )+abs(F j+1 ) ;

[0232] When F j ≥ 0 and F j+1 ≥ 0, F r = F r + (n j +n j+1 )*(t j+1 -t j ) / (2*n m *t max )*((F j +F j+1 ) / 2)^3;

[0233] When F j ≥ 0 and F j+1 < 0,

[0234] F r = F r +n j *c*(t j+1 -t j )*((F j / 2)^3) / (2*n m *t max ) ;

[0235] F l = F l +n j+1 *d*(t j+1 -t j )*((F j+1 / 2)^3) / (2*nm *t max );

[0236] When F j <0 and F j+1 ≥0,

[0237] F l =F l +n j *c*(t j+1 -t j )*((F j / 2)^3) / (2*n m *t max );

[0238] F r =F r +n j+1 *d*(t j+1 -t j )*((F j+1 / 2)^3) / (2*n m *t max );

[0239] When F j <0 and F j+1 <0, F l =F l +((n j +n j+1 )*(t j+1- t j ) / (2*n m *t max ))*((F j +F j+1) / 2)^3;

[0240] 6) Calculate equivalent load: F nm1 =F r ^(1 / 3); F nm2 =F l ^(1 / 3);

[0241] 7) The calculation results of total working life total time t max , total number of working life turns θ n , equivalent speed n m , equivalent load F nm1 and F nm2 are displayed in the corresponding text boxes in the calculation result area.

[0242] The proportion method: when the load spectrum provided by the vehicle manufacturer is the data obtained by rain flow counting method, the data is arranged into multiple groups of corresponding speed n i and axial load F iOccupation duration t i The data. The specific implementation process is:

[0243] 1) open the latest stored load spectrum EXCEL document under the default address, get the last row number lastRow of the table;

[0244] 2) define loop variables i, j, k, define rotating speed n j , n k , load F k , time t i , t j , t k , loop number N T ; define variables total working life time t max , total working life circle number θ n , equivalent rotating speed n m , equivalent load intermediate value F r and F l , equivalent load F rm1 and F rm2 variable, and assign initial value;

[0245] 3) the first i loop, traversing the 2th to lastRow row, calculating total time t max =t max +t i ;

[0246] 4) the second j loop, traversing the 2th to lastRow row, calculating equivalent rotating speed n m =n m +Abs(n j )*t j / t max , total rotating angle: θ n =θ n +n j *t j / 360;

[0247] 5) the third k loop, traversing the 2th to lastRow row, calculating equivalent load intermediate value F r and F l ,

[0248] When Fk≥0, F r =F r +n k *t k *F k ^3 / (n m *t max )

[0249] When Fk<0, F l =F l +nk *t k *F k ^3 / (n m *t max );

[0250] 6) Calculate the equivalent load: F nm1 =F r ^(1 / 3); F nm2 =F l ^(1 / 3);

[0251] 7) Calculate the total working life time t from the results. max *N T / 3600, Total number of revolutions in working life θ n Equivalent speed n m Equivalent load F nm1 and F nm2 The result will be displayed in the corresponding text box in the calculation results area.

[0252] The percentage method is commonly used for load spectra converted from standard tests, hence it is also called the standard test method. If the load spectrum database prepared in step 3 contains a corresponding standard test load spectrum, it can be directly referenced; otherwise, the customer's fatigue test requirements are converted into rotational speed n. i Load F i Time t i Enter the data in the input window, then use the "Load Export" button to output and save it as a standard load spectrum for later reference. The data consists of specified speed and load percentages, and the maximum rotational speed n needs to be set. max and maximum axial load F max As the base for the percentage, and to set the number of loops N. T The specific implementation process is as follows:

[0253] 1) Open the latest stored load spectrum EXCEL document in the default address and get the last row number of the table;

[0254] 2) Define loop variables i, j, k, and define rotational speed n. j n k Maximum speed n max Load F k Maximum axial load F max Time t i t j t k Number of iterations N T Define the variable as the total working life t. max Total number of revolutions in working life θ n Equivalent speed n m Equivalent load median value Fr and F l , equivalent load F rm1 and F rm2 variable, and assign initial value.

[0255] 3) Get parameters from window: n max , F max , N T ;

[0256] 4) First i loop, traverse 2 to lastRow row, calculate total time t max = t max + t i ;

[0257] 5) Second j loop, traverse 2 to lastRow row, calculate equivalent speed n m = n m + Abs(n max *n j / 100)*t j / t max , total angle: θ n = θ n +n max *n j *t j / 36000;

[0258] 6) Third k loop, traverse 2 to lastRow row, calculate equivalent load intermediate value F r and F l ,

[0259] When F k ≥ 0, F r = F r +(n max *n k / 100)*t k *(F max *F k / 100)^3 / (n m *t max );

[0260] When F k < 0, F l = F l +(n max *n k / 100)*t k *(F max *F k / 100)^3 / (n m *t max );

[0261] 7) Calculate equivalent load: F nm1 = F r (1 / 3); F nm2 = F l (1 / 3);

[0262] 8) Calculate the total time of working life t max * N T / 3600, the total number of working life θ n , equivalent speed n m , equivalent load F nm1 , and F nm2 are displayed in the corresponding text box in the calculation result area.

[0263] Step 502, create a whole vehicle life estimation area.

[0264] The whole vehicle life estimation area completes the whole vehicle type, steering load and frequency data preparation, and estimates the equivalent speed, equivalent load and working life of the steering screw nut pair using the whole vehicle life method. Specifically, it includes the whole vehicle type, steering load distribution, road condition distribution, steering frequency distribution and "whole vehicle life method" function button.

[0265] Set the type in the drop-down options of the whole vehicle type combo box, which includes the whole vehicle types listed in the fourth step. And display the corresponding mandatory service life and mileage below. Steering load distribution includes 9 groups of load percentage and cycle number (specific data as shown in Table 3 and Figure 5 ). Road condition distribution includes urban road, highway, rural road and mountain road, with corresponding road condition weight and average speed on the right. The steering frequency distribution on the right is the steering situation under corresponding different road conditions, including average steering angle and average steering frequency per minute (times / min) under low-speed large steering angle, normal steering and high-speed small steering angle. Different classification methods can be set according to convention or experience.

[0266] After selecting the whole vehicle type, all data in the whole vehicle life estimation area will display the default value. The source of the value is as explained in the fourth step. The data can be adjusted according to actual requirements, and the default value can be used directly without special requirements. Steering is not distinguished between left and right, and opportunities are equal.

[0267] The "whole vehicle life method" function button estimates the equivalent speed, equivalent load and working life of the steering screw nut pair according to the above data. Step 502 includes steps 5021 to 50211, and the specific implementation process is as follows:

[0268] Step 5021, define the whole vehicle life parameters;

[0269] The whole vehicle life parameters include average daily driving time T d , total driving time T T in service life, etc.Total number of working life laps θ in service life n Total working life time t max Average steering wheel speed (equivalent speed) n m ;

[0270] Step 5022, get the corresponding parameters from the window.

[0271] Service life N max Mileage S max ; Road condition weight: P11, P21, P31, P41; Average speed: V12, V22, V32, V42; Average steering angle: θ13, θ23, θ33, θ43, θ15, θ25, θ35, θ45, θ17, θ27, θ37, θ47 steering frequency: T14, T24, T34, T44, T16, T26, T36, T46, T18, T28, T38, T48; Load percentage: BFB1, BFB2, BFB3, BFB4, BFB5, BFB6, BFB7, BFB8, BFB9; Cycle number: VXH, XH1, XH2, XH3, XH4, XH5, XH6, XH7, XH8, XH9; Maximum axial load: F max ;

[0272] Step 5023, determine the total cycle number:

[0273] VXH = XH1 + XH2 + XH3 + XH4 + XH5 + XH6 + XH7 + XH8 + XH9;

[0274] Step 5024, determine the 9 groups of load intermediate values Fr1, Fr2, Fr3, Fr4, Fr5, Fr6, Fr7, Fr8, Fr9:

[0275] Fr1 = ((F max *BFB1 / 100)^3)*(XH1 / VXH);

[0276] Fr2 = ((F max *BFB2 / 100)^3)*(XH2 / VXH);

[0277] Fr3 = ((F max *BFB3 / 100)^3)*(XH3 / VXH);

[0278] Fr4 = ((F max *BFB4 / 100)^3)*(XH4 / VXH);

[0279] Fr5 = ((F max *BFB5 / 100)^3)*(XH5 / VXH);

[0280] Fr6 = ((F max *BFB6 / 100)^3)*(XH6 / VXH) ;

[0281] Fr7 = ((F max *BFB7 / 100)^3)*(XH7 / VXH) ;

[0282] Fr8 = ((F max *BFB8 / 100)^3)*(XH8 / VXH) ;

[0283] Fr9 = ((F max *BFB9 / 100)^3)*(XH9 / VXH) ;

[0284] Step 5025, determine equivalent load.

[0285] F nm1 = F nm2 = (Fr1+Fr2+Fr3+Fr4+Fr5+Fr6+Fr7+Fr8+Fr9)^(1 / 3).

[0286] Step 5026, determine average daily driving time:

[0287] T d = S max *10 6 / ((N max *365)*(V12*P11+V22*P21+V32*P31+V42*P41)).

[0288] Step 5027, determine total driving time:

[0289] T T = T d *365*N max .

[0290] Step 5028, determine total laps:

[0291] θ n = T T *60*(P11*(θ13*T14+θ15*T16+θ17*T18)+P21*(θ23*T24+θ25*T26

[0292] +θ27*T28)+P31*(θ33*T34+θ35*T36+θ37*T38)+P41*(θ43*T44+θ45*T46+θ47*T48)) / 36000.

[0293] Step 5029, determine total time:

[0294] t max = T T (n m *60)。

[0295] Step 50210, the calculation result equivalent load F nm1 and F nm2 , steering wheel average speed (equivalent speed) n m (default 60 r / min) and total number of working life θ n , total working life t max are displayed in the corresponding text box of the calculation result area;

[0296] Step 50211, export the whole vehicle life estimation data to the EXCEL document (such as Figure 7c ), and the document name is "whole vehicle life estimation-year-month-day-hour-minute-second.xlsx".

[0297] As can be seen from the load spectrum calculation area and the whole vehicle life estimation area, the input of the load data in the template is calculated by the four data processing methods of instantaneous method, proportion method, percentage method and whole vehicle life method in the load spectrum calculation area or the whole vehicle life estimation area. The equivalent speed, equivalent load and working life of the steering screw nut pair are calculated according to the actual situation of the product. Among them, the instantaneous method (corresponding to the time history method data), the proportion method (corresponding to the rain flow counting method data) and the percentage method (standard test method) are based on the related parameters and data set in the load spectrum calculation area; the whole vehicle life method is based on the related parameters and data set in the whole vehicle life estimation area.

[0298] When the load spectrum is expressed in the form of small cycle repeated multiple times, the cycle number N T needs to be set; when the load spectrum is the whole life history data, the cycle number N T is set to 1; the small cycle number θ t does not need to be input, and is automatically calculated after running one of the functions of instantaneous method, proportion method, percentage method or whole vehicle life method, and is filled in the text box. The maximum speed n max and the maximum axial load F max are used as the calculation base when the percentage method is used. The static torsional strength T a is set according to customer requirements, and when the customer has no requirements and selects the standard load spectrum, it is set by default according to the standard requirements; when it is a non-standard load spectrum, it is set according to the specific product.

[0299] Step 503, create a correction parameter setting area.

[0300] The correction parameter setting area includes: surface hardness coefficient f h0 , surface hardness coefficient f h , precision coefficient fac , material smelting coefficient f m , reliability coefficient f ar , lubrication condition coefficient f r Each parameter is used for subsequent calculation of axial rated dynamic load and life, see subsequent calculation formula.

[0301] The correction parameters include: C a0 , surface hardness correction coefficient f h0 , C a , surface hardness correction coefficient f h , precision coefficient f ac , material smelting method coefficient f m , reliability coefficient f ar , lubrication condition coefficient f r According to the material properties of screw nut, heat treatment, machining precision, reliability requirements and lubrication conditions, the corresponding coefficients are set. The test fatigue life results (rotation cycles or running time) of the existing product series screw nut pair fatigue test or product bench durability test are adjusted within a certain range by adjusting the above six correction parameters, so that the calculation results of the template are close to the fatigue life test results. After several rounds of adjustment of the coefficients and results, the six correction values are fixed, which can be used for life checking of screw nut pairs with different geometric parameters under similar conditions (in the recirculating ball steering gear of the steering system).

[0302] Step 504, creating a calculation result display area.

[0303] The calculation result display area includes: equivalent speed n m , forward equivalent load F nm1 , reverse equivalent load F nm2 , working life time t max , axial rated static load C oa , axial rated dynamic load C a , corrected axial rated static load C oam , corrected axial rated dynamic load C am , corrected final life L considering reliability mar , corrected final life L considering reliability hmar , rated life L ar , rated life L har The calculation results of instantaneous method, proportion method, percentage method or whole vehicle life method, and the calculation results of load and life are displayed in this area.

[0304] Step 505, creating a calculation load and life function button and a verification result display area.

[0305] The "Calculate Load and Lifetime" function button and the verification result display area include the "Calculate Load and Lifetime" function button, the result display text box, the default storage address, the last stored full name, and instructions for window usage.

[0306] Once the steering screw and nut pair model with determined parameters is ready, and the equivalent speed, equivalent load, and service life have been calculated, the next step is to calculate the load and verify the service life. This is achieved using the "Calculate Load and Service Life" function button. The calculation results are displayed in the corresponding text boxes in the second and third columns of the calculation results display area, and the static torsional strength and fatigue life verification results are displayed in the text box to the right of the button. Step 505 includes steps 5051 to 5058, and the specific implementation process is as follows:

[0307] Step 5051: Extract the basic parameters from the reference model.

[0308] The basic parameters include: pitch circle diameter D pw Ball diameter D w Pitch P h Number of single-cycle body bearing revolutions n b Nut raceway radius r n Screw raceway radius r s nut raceway contact angle α n Screw raceway contact angle α s ;

[0309] Step 5052, obtain the correction coefficient in the window: C a0 Surface hardness correction factor f h0 C a Surface hardness correction factor f h Precision coefficient f ac Material smelting method coefficient f m Reliability coefficient f ar Lubrication condition coefficient f r ;

[0310] Step 5053: Calculate the axial rated static load C of the screw and nut pair according to the formula in Table 4. oa and C oam Axial rated dynamic load C a and C am ;

[0311] Step 5054: Calculate the rated life L of the screw-nut pair under equivalent speed and equivalent load according to the formula in Table 4. 1,2 and L h1,2 Final lifespan L r and L hr Lifetime L including reliability factor ar and L har and Lh1,2 , the modified life L with reliability coefficient mar and L hmar ;

[0312] Step 5055, check the axial static torque strength and fatigue life according to the formula in Table 4: static torque strength T a Check with rated static load, C oa ≥ 2 x μ x π x T a / P h ; endurance life is checked with rated dynamic load, L mar ≥ L0, L hmar ≥ L h0 ;

[0313] Step 5056, the calculation results of axial rated static load C oa and C oam , axial rated dynamic load C a and C am , modified life L with reliability coefficient mar and L hmar , rated life L 1,2 and L h1,2 are displayed in the corresponding text box in the calculation result area;

[0314] Step 5057, the checking results are displayed in the right text box: when both are qualified, "static torque qualified / life qualified" is displayed, and the background color is green; only one is qualified, "static torque unqualified / life qualified" or "static torque qualified / life unqualified" is displayed, and the background color is orange; both are unqualified, "static torque unqualified / life unqualified" is displayed, and the background color is red;

[0315] Step 5058, open the latest stored load spectrum EXCEL document in the default address, create a new worksheet, name it "basic and geometric parameters" worksheet, save the basic and geometric parameters in the steering screw nut pair model at this time in the new worksheet; create a new worksheet, name it "calculation results" worksheet, and the document name is "steering screw 1 nut life analysis-year-month-day-hour-minute-second.xlsx" (such as Figure 7d ).

[0316] The above process mainly uses the example values and calculation formulas of the parameters related to rated load and life in standard GB / T 17587.5, which are summarized in Table 4 as follows:

[0317] Table 4: Example and calculation formula of rated load and life

[0318]

[0319]

[0320]

[0321]

[0322] wherein the axial static load rating C 0a is the maximum static load allowed for the bearing, which is the load at which the balls and raceway areas are subjected to a contact stress of not more than 0.0001 x D w ball diameter without permanent deformation of the balls; z u is the number of balls in each ring that are not loaded, n b = 2.5 the number of balls in the ring is not counted, here 0; axial dynamic load rating C a is the constant axial load that can be theoretically supported under the condition that the rated life is 10 6 revolutions.

[0323] The default storage address is the folder address of the displayed user-defined placement data, which is used to store the documents output by the "refresh model", "load export", "vehicle life method" and "calculate load and life" function buttons. The last storage full name is the document name displayed in this text box when the "load export", "vehicle life method" and "calculate load and life" function button output documents, ready for calling in the "instant method", "occupancy method" and "percentage method" function buttons.

[0324] The lower right corner of the window displays a brief description of the scope of application and usage notes of the window, prompting the user to read before use.

[0325] Based on the above, the following processes are realized in each area of the strength and life checking window (see Figure 6) : preparing load spectrum data or vehicle life data according to collected vehicle demand, if load spectrum data is obtained, inputting or importing load spectrum prepared in step 3, inputting maximum rotational speed, maximum axial load, cycle number, static torsional strength, then exporting load spectrum output as a document for standby, and then calculating equivalent rotational speed and equivalent load under load spectrum according to data, and calculating working life under load spectrum; if vehicle life data is obtained, inputting vehicle type, road condition distribution, steering frequency, load distribution data prepared in step 4, and inputting maximum rotational speed, maximum axial load, cycle number, static torsional strength, estimating equivalent rotational speed and equivalent load under vehicle life according to data, and estimating working life under vehicle life, and then outputting as a document for standby. Extracting basic parameters from the above full-parameterized model of steering screw and nut pair, setting correction parameters, calculating axial rated static load and axial rated dynamic load; calculating the state life under equivalent rotational speed and equivalent load according to the above calculated equivalent rotational speed and equivalent load results; then performing strength and life checking, comparing axial rated static load with static torsional strength, and comparing calculated life with working life; when the former is larger, the strength and life checking is qualified, the above latest output data document is opened, and the calculation and checking result data is stored in a new worksheet; when the latter is larger, the strength and life checking is unqualified, the parameters are modified, the model is refreshed, the axial rated static load and axial rated dynamic load are recalculated, and the life is rechecked.

[0326] Step 6: Adjusting the life checking template based on the fatigue test results.

[0327] The purpose of adjusting the template is to optimize the template by using the fatigue test results of the existing product series, so that the template fits the actual test results and is applied to new product development, thereby improving the research and development efficiency and accuracy. The method is to adjust each parameter in the correction parameter setting area, so that the life calculation result of the template is consistent with the fatigue test result. The workload of adjusting the template is very large, including the correction coefficient adjustment of C 0a and C a , and the correction coefficient adjustment of L ar and L mar . A large amount of calibration data and scientific data statistical methods can improve the accuracy and reliability of the template. The reference values of the parameters (except the lubrication condition coefficient) are given in the standard GB / T 17587.5, but the specific physical objects will be affected by various factors and produce deviations.

[0328] Step 601: Correction coefficient adjustment of C 0a and C a .

[0329] From the formula C oam =C oa ·f h0 ·f ac and C am =Ca ·f h ·f ac ·f m It can be seen that the surface hardness coefficient f h0 , the surface hardness coefficient f h , the precision coefficient f ac , the material smelting coefficient f m are used to correct the axial rated static load C 0am and the rated dynamic load C am . Based on the definition and related requirements of the axial rated static load C 0a and the axial rated dynamic load C a in the standard GB / T 17587.5, the test experiment is carried out to determine the correction coefficient.

[0330] Step 602, the correction coefficient of L ar and L mar is adjusted.

[0331] From the formula L ar = L r ·f ar ·f r and L mar = L mr ·f ar ·f r It can be seen that the reliability coefficient f ar , the lubrication condition coefficient f r are used to correct the corrected life L ar and L mar containing the reliability coefficient. The corresponding whole vehicle fatigue load spectrum or product durability test data of the existing product is prepared and the parameters and data are input into the template by referring to the method of the third step or the fourth step, so as to ensure that the corresponding parameter steering screw nut pair model bears the same equivalent speed and equivalent load as the actual one, and the calculation and checking process is completed. When the test result is the rotation circle number or rotation time until fatigue failure, theoretically, it should be equal to the value of L ar when f mar = 1, the correction f r is made so that the calculation result of L mar / L hmar of the template is consistent with the rotation circle number or rotation time of the fatigue test. When the test result is the completion of the specified rotation circle number or rotation time, the correction f ar is made so that the calculation result of L mar / L hmar of the template is consistent with the rotation circle number or rotation time of the fatigue test. The value of the reliability coefficient f ar or the lubrication condition coefficient f r corrected each time is difficult to be equal, and a scientific method is adopted to statistically analyze it, such as the mean value method, the median method, the standard deviation and the variation coefficient method, so as to determine the scientific correction parameter value.

[0332] Step 7, using the service life check template, the strength and service life of the steering screw nut pair under the set parameters are checked.

[0333] After the template is adjusted, it is used for the rapid modeling of the steering screw nut pair in the new product design and the strength and service life check, and step 7 includes steps 701 to 706, and the specific operation process is as follows:

[0334] Step 701, open the steering screw nut pair model containing the development template in the CATIA software, click the “display parameter setting window” tool in the custom tool, and display the window. Modify the white bottom parameters in the window, click the “refresh model” function button, complete the new model of the steering screw nut pair, and automatically export the basic and geometric parameters of the model to the EXCEL document (such as Figure 7a ).

[0335] Step 702, click the “display strength and service life check window” tool in the custom tool to display the window, and input the load spectrum data or vehicle life data.

[0336] Step 7021, if the vehicle has a load spectrum, input the parameter rotating speed n i , axial load F i and time t i in the load spectrum calculation area of the window one by one, click the “add data point” function button to store the data in the load spectrum list box, and store the data in the list box one by one until all the load spectrum data is completed. The data can also be placed in the EXCEL document (.xlsx or.xls), and then all the load spectrum data is imported into the load spectrum list box. The method is to select the alternative standard in the drop-down item of the combination box, which can select QCT649 standard load spectrum, QCT1081 standard load spectrum, QCT29096 standard load spectrum and large enterprise standard load spectrum requirements. Other saved load spectrum can be input in the combination box. Click the “load import” function button to complete the load spectrum import.

[0337] Step 7022, if the data needs to be modified or adjusted, double-click the list item, and the corresponding content rotating speed n i , load F i and time t iThe data will be displayed in the left text box, modify the data in the text box, and then click the "modify data point" function button to complete the data modification. If a group of data needs to be deleted, select the list item and press the "Delete" key on the keyboard to delete the data and automatically modify the data sequence of the subsequent list items. After the load spectrum data in the load spectrum list box is prepared, click the "load export" function button to obtain the equivalent speed, equivalent load and working life displayed in the calculation result area, and export the load spectrum data to the EXCEL document (such as Figure 7b ).

[0338] Step 7023, when the whole vehicle life method is selected, select the whole vehicle type in the drop-down option of the "whole vehicle life estimation area" group box, and all the data of the service life, driving distance, steering load distribution, road condition distribution and steering frequency distribution will be displayed as default values, which can be modified according to the actual situation.

[0339] Step 703, set the cycle number N T , the maximum speed n max (percentile method), the maximum axial load F max (percentile method) and static torsional strength T a in the "strength and life check" window.

[0340] Step 704, select the instantaneous method, proportion method, percentile method or whole vehicle life method function button according to the data type, obtain the equivalent speed, equivalent load and working life and display them in the calculation result area. If the whole vehicle life method is selected, the whole vehicle life estimation data will also be exported to the EXCEL document (such as Figure 7c ).

[0341] Step 705, set 6 correction parameters in the "strength and life check" window.

[0342] Step 706, click "calculate load and life" to complete the calculation of the axial rated static load C oam , the axial rated dynamic load C am of the corresponding steering screw and nut pair under the current parameters, complete the calculation and check of the life under the equivalent speed and equivalent load, and display the strength and life qualification results in the adjacent text box (such as Figure 5 ). And output the basic and geometric parameters, load spectrum (or whole vehicle life estimation data) and calculation results to the EXCEL document (such as Figure 7d ).

[0343] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments are modified, or some or all of the technical features are replaced by equivalents, without changing the essence of the corresponding technical solutions out of the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for creating a life verification template based on a steering screw and nut pair model, characterized in that, Includes the following processes: Step 1, create a fully parameterized steering screw and nut assembly model; the steering screw and nut assembly model is a fully parameterized three-dimensional model, including: reference, steering screw (1), steering nut (8), first guide tube (2), second guide tube (6), guide tube clamp (3), ball recirculator (7), screw (4) and washer (5); Step 2: Create a parameter setting window; Step 3: Prepare the spectral library for the shifting load; Step 4: Prepare a database of vehicle lifespan, road conditions, steering frequency, and load distribution. Step 5: Create a strength and life verification window; the strength and life verification window includes a load spectrum estimation area, a vehicle life estimation area, a correction parameter setting area, a calculation result display area, a "Calculate Load and Life" button, and a verification result display area; Step 6: Adjust the life verification template based on the life fatigue test results; Step 601, C 0a and C a Adjustment of correction coefficients; From the formula It can be seen that the surface hardness coefficient f h0 Surface hardness coefficient f h Precision coefficient f ac Material smelting coefficient f m Used to correct the axial rated static load C 0am and rated dynamic load C am Based on standard GB / T 17587.5, the axial rated static load C 0a and axial rated dynamic load C a Based on the definition and related requirements, conduct test experiments to determine the correction coefficient; Step 602, L ar and L mar Adjustment of correction coefficients; From the formula It can be seen that the reliability coefficient Lubrication condition coefficient Used to correct the lifespan containing a reliability factor. Prepare parameters and data for the existing product's corresponding vehicle fatigue load spectrum or product durability test data, referring to the methods in steps three or four, and input them into the template. Ensure that the steering screw and nut pair model with the corresponding parameters bears the same equivalent speed and equivalent load as in reality, and complete the calculation and verification process. When the test result is the number of rotations or rotation time until fatigue failure, theoretically it should be consistent with... The calculation results are consistent with the number of rotations or rotation time in the fatigue test; when the test result is the completion of the specified number of rotations or rotation time, a correction is made. The calculation results are consistent with the number of rotations or rotation time in the fatigue test; the correction factor is applied each time. The values ​​are rarely equal, so scientific methods such as the mean method, median method, standard deviation and coefficient of variation method are used to conduct statistical analysis to determine scientific correction parameter values.

2. The method for creating a life verification template based on a steering screw and nut pair model according to claim 1, characterized in that, Step 1 includes the following steps 101 to 104: Step 101 involves creating a reference model, which includes creating parameters, relationships, and reference points, lines, and surfaces, and publishing the parameters and references. Step 102: Based on the published parameters and benchmarks, create models of the steering screw (1), steering nut (8), first conduit (2), second conduit (6), and conduit clamp (3); Step 103, create a ball circulation body (7) model that includes all the balls; Step 104: Create the assembly model of the steering screw and nut pair.

3. The method for creating a life verification template based on a steering screw and nut pair model according to claim 2, characterized in that, Step 101, creating a reference model, includes: Create a reference model, which is a virtual part that includes all parameters and datums, as well as the relationships between parameters. Publish the parameters and datums as reference values ​​and benchmarks for creating other parts. The parameters include: basic parameters, geometric parameters, and calculated parameters; basic parameters are parameters that must be defined by input and are the independent variables of other calculated parameters and geometric parameters; geometric parameters are also parameters that must be input and are the basic dimensional values ​​that need to be set for other parts to form solids or sketches; calculated parameters are other important design parameters of the steering screw nut pair, which are calculated from basic parameters or geometric parameters, do not need to be input, and are set and calculated through relational formulas. Basic parameters include: pitch P h Pitch circle diameter D pw Ball diameter D w Number of loop bodies N b Number of single-cycle body bearing revolutions n b Effective stroke of nut L e Rack module m, addendum coefficient h a *, Tooth root height coefficient h f * Rack pressure angle α; Number of cycles N (currently commonly used) b =2, which basically meets the industry requirements. The default value here is 2, and it can be adjusted from the reference model as needed. Geometric parameters include: screw contact angle αs, screw raceway radius coefficient sr; nut contact angle α n , Nut raceway radius coefficient sn, Nut top, bottom, left and right allowance e n ; Chamfer radius R of the conduit d 3mm thick catheter clamp d δ, the clearance between the guide tongue and the screw raceway; si, the inner diameter coefficient of the guide; The calculation parameters include: helix angle φ and number of balls S. b Screw outer diameter D s Screw raceway radius R s , Distance s0 from the starting point to the end point of the screw helix, Screw length L s0 Screw helix height L s Number of screw spiral coils N s ; Nut inner diameter d n nut raceway radius R n Nut length L n0 Number of nut spiral coils N n Nut helix height L n ; Catheter inner diameter d ui outer diameter of the catheter d uo Catheter outer diameter eccentricity e d ; The relationships between the parameters are set as follows: Helix angle φ = atan(`Pitch P h ` / π*` Pitch circle diameter D pw ` )); Number of balls S b =length(`Ball recirculation body reference\Ball recirculation body-Group 1 lengthS` l ` ) / ` Ball diameter D w `; Screw outer diameter D s = `Pitch circle diameter D` pw -2mm; Screw raceway radius R s =`Screw raceway radius coefficient s r *`Ball diameter D w `; The distance from the starting point to the end point of the screw helix is ​​s0 = pitch P h *0.6; Screw length L s0 = Nut length L n0 ` +` Nut effective stroke L e `; Screw helix height L s =`Screw length L s0 ` -2*` Distance s0` from the starting point to the end point of the screw helix; Number of screw spiral coils N s =`Screw helix height L s Pitch P h `; Nut inner diameter d n =`Pitch circle diameter D pw +2mm; Nut raceway radius Rn = Nut raceway radius coefficient s n *`Ball diameter D w` ; Nut length L n0 =`Number of nut spiral coils N n Pitch P h `; Number of nut spiral coils N n =(`Number of single-cycle load cycles n b ` +0.5)*` Number of loop bodies N b -0.5*(Number of loop bodies N) b -1); Nut helix height L n =(Number of nut spiral coils N) n ` +2)*` Pitch P h `; Inner diameter of the catheter d ui =`Ball diameter D w ` *`Diameter coefficient si`; outer diameter of the catheter d uo =`Diameter of the conduit d ui +1.5mm*2; Catheter outer diameter eccentricity e d = (`Distance S of the horizontal line of the duct bead return line from the axis) d / cos(`helix angle φ` )-`conduit chamfer radius R d ` )*sin(`helix angle φ` ) / 2; The datum includes the global datum, screw datum, nut datum, guide tube datum, guide tube clamp datum, and ball recirculation body datum. The global datum includes the origin, XYZ coordinate axes, and screw and nut axes. The Z-axis is used as the screw and nut axes, and the midpoints of the screw and nut along their lengths coincide, with the coincident midpoint being the origin. Other references for parts are created based on this coordinate system, serving as the point, line, and surface datums for creating solid features of each part model or as the reference for the basic geometry of sketches, controlling the structure and dimensions of each part model. Publish the parameters and benchmarks created in the above reference.

4. The method for creating a life verification template based on a steering screw and nut pair model according to claim 1, characterized in that, In step 2, the parameter setting window includes: basic parameters, rack parameters, screw parameters, nut parameters, guide tube parameters, and a "refresh model" function button; Basic parameters include: pitch P h Pitch circle diameter D pw Ball diameter D w Helix angle φ, number of cycles N b Number of single-cycle body bearing revolutions n b Effective stroke of nut L e Number of balls S b Among them, based on the outer circulation structure, the number of revolutions n of a single circulation body is determined. b It can only be set to n+0.5 cycles; The rack parameters include: rack module m, addendum coefficient h. a *, Tooth root height coefficient h f * Rack pressure angle α; Screw parameters include: screw outer diameter D s Screw contact angle α s Screw raceway radius R s Screw raceway radius coefficient s r , Distance s0 from the starting point to the end point of the screw helix, Screw length L s0 ; Nut parameters include: nut inner diameter d n Nut contact angle α n nut raceway radius R n Nut raceway radius coefficient s n , nut top, bottom, left and right sides reserved amount e n Nut length L n0 ; Catheter parameters include: catheter chamfer radius R d 1. The thickness of the guide clamp (3) plate is m d δ, clearance between the guide tongue and the screw raceway, and guide inner diameter coefficient s i , catheter inner diameter d ui outer diameter of the catheter d uo .

5. The method for creating a life verification template based on a steering screw and nut pair model according to claim 4, characterized in that, The specific process for the "Refresh Model" function button includes the following steps 201 to 211: Step 201: Set up the active assembly document, define each part, and define each parameter; Step 202: Obtain the parameter values ​​from the parameter setting window and assign them to the corresponding basic and geometric parameters in the steering screw nut pair model; Step 203: Refresh the parameters in the reference part, and then refresh the number of balls S. b And refresh other parts in the assembly steering screw and nut pair model; Step 204: Obtain other calculation parameters in the steering screw nut pair model and display them in the corresponding text boxes in the window; Step 205: Refresh the documents corresponding to the models of screw, steering nut (8), first conduit (2), second conduit (6), and conduit clamp (3); Step 206: Set the ball reel body (7) as the active document, define each set of geometry and geometry name, and refresh the parameters and references referenced in the steering screw nut pair model; Step 207: Delete the ball entities, spheres, and center points in the original ball loop body (7) in reverse order. If this is the first time it is created, it will display "There are no redundant features in the loop body". Step 208, Create a new ball loop (7) 1: Read the number of balls S b Set the parameter ratio = 1 / number of balls S b Set the loop parameter i=0 to S b -1, using the trajectory line group of the ball circulation body (7) as the reference curve for creating the center point of each ball on the curve, with point _i as the reference point, according to the ratio = 1 / number of balls S b Offset, create the ball center point, rename it to point_i+1, and place it in the ball center point of the geometry set loop body; With point _i+1 as the center of the ball and the diameter D of the ball as the center, w Using / 2 as the radius, create a spherical feature, rename it to Sphere_i+1, and place it within the geometry set loop body – Ball Sphere; finally, fill Sphere_i+1 with a closed surface feature to create a solid, rename it to Ball_i+1, and place it within the geometry set loop body – Ball Body, completing the i-th iteration; then proceed to the next iteration until the i=S-th iteration is completed. b -1 loop; Step 209: Delete the ball entities, spheres, and center points in the original ball loop body (7) in reverse order. If this is the first time it is created, it will display "There are no redundant features in loop body 2". Step 210, Create a new ball bearing loop (7) II: Set the loop parameter j=0 to S b -1, using the trajectory line group 2 of the ball circulation body (7) as the reference curve for creating the center point of each ball on the curve, with point _j as the reference point, according to the ratio = 1 / number of balls S b Offset, create a new ball center point, rename it to point_j+1, and place it in the center point of the second ball of the geometry set loop body; With point _j+1 as the center of the ball and the diameter D of the ball as the center... w Using / 2 as the radius, create a spherical feature, rename it to Sphere_j+1, and place it within the second loop body of the geometry set, the Sphere_j+1. Finally, fill Sphere_j+1 with a closed surface feature to create a solid, rename it to Ball_j+1, and place it within the second loop body of the geometry set, completing the i-th iteration. Then proceed to the next iteration until the j=S-th iteration is completed. b -1 loop; Step 211, refresh the ball bearing circulation body (7) model and save the steering screw nut pair model document; Step 212: Output the parameters in the output window to an Excel document and save it in the default folder with the name "Basic and Geometric Parameters-Year-Month-Day-Hour-Minute-Second.xlsx".

6. The method for creating a life verification template based on a steering screw and nut pair model according to claim 1, characterized in that, In step 3, the load spectrum is stored in an Excel document in tabular form, including four columns of data: the first column is the serial number, the second column is the rotational speed n. i The third column is the load F. i The fourth column is time t. i .

7. The method for creating a life verification template based on a steering screw and nut pair model according to claim 1, characterized in that, Step 5 includes the following steps 501 to 505: Step 501, create a load spectrum estimation area; the load spectrum estimation area specifically includes 8 input boxes: rotational speed n i Axial load F i Time t i Number of loops N T Small cycle number θ t Maximum speed n max Maximum axial load F max and static torsional strength T a The load spectrum estimation area includes seven function buttons: Add Data Point, Modify Data Point, Import Load, Export Load, Instantaneous Method, Proportional Method, and Percentage Method; the load spectrum estimation area also includes a load spectrum list box and a reference load spectrum selection combo box. Step 502: Create the vehicle life estimation area; Step 503: Create the correction parameter setting area; Step 504: Create a display area for calculation results; Step 505: Create the function buttons for calculating load and lifespan and the verification result display area.

8. The method for creating a life verification template based on a steering screw and nut pair model according to claim 7, characterized in that, Step 502 includes steps 5021 to 50211: Step 5021, define vehicle life parameters; the vehicle life parameters include average daily driving time T. d Total driving time T within the service life T Total number of working cycles within the service life θ n Total working life t max Average steering wheel speed n m ; Step 5022, obtain the following parameters from the window: usage years N max Mileage S max Road condition weights: P11, P21, P31, P41; Average vehicle speeds: V12, V22, V32, V42; Average steering angles: θ13, θ23, θ33, θ43, θ15, θ25, θ35, θ45, θ17, θ27, θ37, θ47; Steering frequencies: T14, T24, T34, T44, T16, T26, T36, T46, T18, T28, T38, T48; Load percentages: BFB1, BFB2, BFB3, BFB4, BFB5, BFB6, BFB7, BFB8, BFB9; Number of cycles: VXH, XH1, XH2, XH3, XH4, XH5, XH6, XH7, XH8, XH9; Maximum axial load: F max ; Step 5023, determine the total number of loops: VXH = XH1 + XH2 + XH3 + XH4 + XH5 + XH6 + XH7 + XH8 + XH9; Step 5024: Determine the 9 sets of intermediate load values ​​Fr1, Fr2, Fr3, Fr4, Fr5, Fr6, Fr7, Fr8, and Fr9: Fr1 = ((F max * BFB1 / 100) ^ 3) * (XH1 / VXH); Fr2 = ((F max * BFB2 / 100) ^ 3) * (XH2 / VXH); Fr3 = ((F max * BFB3 / 100) ^ 3) * (XH3 / VXH); Fr4 = ((F max * BFB4 / 100) ^ 3) * (XH4 / VXH); Fr5 = ((F max * BFB5 / 100) ^ 3) * (XH5 / VXH); Fr6 = ((F max * BFB6 / 100) ^ 3) * (XH6 / VXH); Fr7 = ((F max *BFB7 / 100)^3)*(XH7 / VXH); Fr8 = ((F max * BFB8 / 100) ^ 3) * (XH8 / VXH); Fr9 = ((F max * BFB9 / 100) ^ 3) * (XH9 / VXH); Step 5025, determine the equivalent load: F nm1 =F nm2 =(Fr1+Fr2+Fr3+Fr4+Fr5+Fr6+Fr7+Fr8+Fr9)^(1 / 3); Step 5026, determine the average daily driving time: T d = S max * 10 6 / ((N max * 365) * (V12 * P11 + V22 * P21 + V32 * P31 + V42 *P41)); Step 5027, determine the total driving time: T T =T d * 365 * N max ; Step 5028, determine the total number of laps: i n = T T * 60 *(P11* (θ13 * T14 + θ15 * T16 + θ17 * T18) +P21* (θ23 * T24 +θ25 * T26 + θ27 * T28) +P31*(θ33 * T34 + θ35 * T36 + θ37 * T38)+P41* (θ43 *T44 + θ45 * T46 + θ47 * T48)) / 36000; Step 5029, determine the total time: t max = T T / (n m * 60); Step 50210, calculate the equivalent load F. nm1 and F nm2 Average steering wheel speed n m and total number of revolutions in working life θ n Total working life t max Displayed in the text box corresponding to the calculation results area; Step 50211: Export the vehicle life estimation data to an Excel document named "Vehicle Life Estimation-Year-Month-Day-Hour-Minute-Second.xlsx".

9. The method for creating a life verification template based on a steering screw and nut pair model according to claim 8, characterized in that, Step 505 includes steps 5051 to 5058: Step 5051, extract basic parameters from the reference model; the basic parameters include: pitch circle diameter D pw Ball diameter D w Pitch P h Number of single-cycle body bearing revolutions n b Nut raceway radius r n Screw raceway radius r s nut raceway contact angle α n Screw raceway contact angle α s ; Step 5052, obtain the correction coefficient in the window: C a0 Surface hardness correction factor f h0 C a Surface hardness correction factor f h Precision coefficient f ac Material smelting method coefficient f m Reliability coefficient f ar Lubrication condition coefficient f r ; Step 5053, calculate the rated axial static load C of the screw and nut pair. oa and C oam Axial rated dynamic load C a and C am ; Step 5054: Calculate the rated life L of the screw-nut pair under equivalent speed and equivalent load. 1,2 and L h1,2 Final lifespan L r and L hr Lifetime L including reliability factor ar and L har and L h1,2 Corrected lifetime L including reliability factor mar and L hmar ; Step 5055, check axial static torsional strength and fatigue life: Static torsional strength T a Verify using the rated static load. ； Step 5056, calculate the axial rated static load C. oa and C oam Axial rated dynamic load C a and C am Corrected lifetime L including reliability factor mar and L hmar Rated life L 1,2 and L h1,2 Displayed in the text box corresponding to the calculation results area; Step 5057: The verification results are displayed in the text box on the right: if all are qualified, "Static Torque Qualified / Lifetime Qualified" is displayed with a green background; if only one is qualified, "Static Torque Unqualified / Lifetime Qualified" or "Static Torque Qualified / Lifetime Unqualified" is displayed with an orange background; if neither is qualified, "Static Torque Unqualified / Lifetime Unqualified" is displayed with a red background. Step 5058: Open the latest stored load spectrum EXCEL document at the default address, create a new worksheet named "Basic and Geometric Parameters" and save the basic and geometric parameters of the steering screw nut pair model at this time in the new worksheet; then create another new worksheet named "Calculation Results" and name the document "Steering Screw 1 Nut Life Analysis - Year - Month - Day - Hour - Minute - Second.xlsx".

10. The method for creating a life verification template based on a steering screw and nut pair model according to claim 1, characterized in that, Following step 6, the process also includes: Step 7, service life verification template, to verify the strength and service life of the steering screw and nut pair under set parameters; Step 7 includes the following steps 701 to 706: Step 701: Open the steering screw and nut pair model containing the development template in CATIA software. Click the "Show Parameter Setting Window" tool in the custom tools to display the window. Modify the parameters with the white background in the window, and click the "Refresh Model" function button to complete the new model of the steering screw and nut pair. The basic and geometric parameters of the model will be automatically exported to an EXCEL document. Step 702: In the custom tools, click the "Show Strength and Life Verification Window" tool to display the window and enter the load spectrum data or vehicle life data; Step 703, set the number of cycles N in the "Strength and Life Check" window. T Maximum speed n max Maximum axial load F max and static torsional strength T a ; Step 704: Select the instantaneous method, proportion method, percentage method, or whole vehicle life method function button according to the data type to obtain the equivalent speed, equivalent load, and working life and display them in the calculation results area; if the whole vehicle life method is selected, the whole vehicle life estimation data will also be exported to an EXCEL document. Step 705: Set 6 correction parameters in the "Strength and Life Verification" window; Step 706, click "Calculate Load and Life" to complete the axial rated static load C of the current parameters of the corresponding steering screw nut pair. oam Axial rated dynamic load C am The system calculates the values, completes the calculation and verification of the equivalent speed and equivalent load life, and displays the results of whether the strength and life are qualified in the adjacent text box; it also outputs the basic and geometric parameters, load spectrum and calculation results to an EXCEL document.

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