Method for creating service life checking template based on steering screw nut pair model

Abstract

The invention 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 nut pair model, which comprises the following steps of: 1, creating a fully parameterized steering screw nut pair model; step 2, creating a parameter setting window; step 3, preparing a steering load spectrum library; 4, preparing a whole vehicle service life, road condition, steering frequency and load distribution database; step 5, creating a strength and service life checking window; the strength and service life checking window comprises a load spectrum calculation area, a whole vehicle service life estimation area, a correction parameter setting area, a calculation result display area, a load and service life calculation button and a checking result display area; and step 6, based on a life fatigue test result, adjusting the life checking template. According to the method, the all-parametric model is created for the steering screw nut pair in the recirculating ball type steering gear, and the rapid modeling and strength and fatigue life checking template is created based on the all-parametric model, so that the design efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of modeling and fatigue life verification of steering gear components, and in particular to a method for creating a life verification template based on a steering screw nut pair model. Background Art

[0002] The recirculating ball steering gear in automotive steering systems utilizes a screw-nut pair. In this application, the screw-nut pair performs intermittent, bidirectional, variable-load, and variable-speed motion, bearing heavy axial loads and random alternating loads. It requires low speeds and positioning accuracy, but also requires smooth, low-noise transmission. During the design process, the parameters of the steering screw-nut pair, a key transmission pair, are set, modeled, and their strength and fatigue life verified. These are typically initially determined and theoretically calculated based on engineers' design experience and general formulas. After the physical prototype is completed, these parameters are then verified and confirmed through product testing. To achieve the optimal parameters, repeated parameter modifications, calculations, and sample testing are inevitable, which wastes time and increases R&D costs.

[0003] When creating a model, even if the model does not need to be recreated each time the parameters are modified, there are many connections between the parameters and between the parameters and the geometric dimensions, which makes it troublesome to modify. There are many balls in the screw-nut pair, and parameter changes will affect the number and size of the balls. The point, surface and body features of each ball must be created or modified one by one, which is a lot of work and very inefficient.

[0004] When verifying strength and fatigue life, the static and dynamic load ratings, as well as the life calculation and verification under speed and load conditions, are calculated based on the general formula for ball screw pairs (steering screw nut pairs) in the national standard GB / T17587.5, "Axial Static and Dynamic Load Ratings and Service Life of Ball Screw Pairs." However, throughout the life cycle of a vehicle, due to road and traffic conditions, driving habits, and different vehicle models, the number of turns and the stress conditions on the steering system during actual driving are difficult to determine. This makes it difficult to calculate the movement and load borne by the steering screw nut pair, and thus it is difficult to obtain a reasonable equivalent speed, equivalent load, and service life (the total number of turns or total time over the entire life cycle).

[0005] Vehicle manufacturers typically analyze load spectra for specific vehicle models on typical user roads or in accelerated durability testing. This analysis yields extensive load history experience and statistical data. The steering system load spectrum provides raw data on the steering screw-nut assembly's speed and load-time history. New product designs can be based on the OEM's vehicle positioning, curb weight, fully loaded weight, and vehicle lifespan. This load data can be converted to steering system fatigue test requirements from road or bench testing, based on industry or corporate standards. This load data is then processed and converted to steering screw-nut assembly speed and axial load for strength and life verification.

[0006] As can be seen from the above, the entire process of steering screw nut pair parameter setting, model creation, load data processing, strength and fatigue life verification calculation is complicated, and product development often involves repeated operations such as adjusting parameters, modifying models, and recalculating and verifying. Summary of the Invention

[0007] The present invention mainly solves the technical problems in the prior art such as the complicated process of parameter setting, model creation, load data processing, strength and fatigue life verification calculation of steering screw nut pairs, and frequent repeated operations in product development. A method for creating a life verification template based on the steering screw nut pair model is proposed. A fully parametric model is created for the steering screw nut pair in the recirculating ball steering gear, and a rapid modeling and strength and fatigue life verification template is created based on the full-parameter model to improve design efficiency.

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

[0009] Step 1: Create a fully parametric steering screw-nut pair model; the steering screw-nut pair model is a fully parametric three-dimensional model, including: a reference, a steering screw 1, a steering nut 8, a first conduit 2, a second conduit 6, a conduit clamp 3, a ball circulation body 7, a screw 4, and a washer 5;

[0010] Step 2, create a parameter setting window;

[0011] Step 3, prepare the steering load spectrum library;

[0012] Step 4: Prepare a database of vehicle life, road conditions, steering frequency, and load distribution;

[0013] Step 5: Create a strength and life verification window; the strength and life verification window includes 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 verification result display area;

[0014] Step 6: Adjust the life verification template based on the life fatigue test results.

[0015] Furthermore, step 1 includes the following steps 101 to 104:

[0016] Step 101 is to create a reference model, which includes creating parameters, relationships, reference points, lines, and surfaces, and publishing parameters and references.

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

[0018] Step 103, creating a ball circulation body 7 model including all balls;

[0019] Step 104: Create a steering screw nut assembly model.

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

[0021] Create a reference model. The reference is a virtual part that includes all parameters and benchmarks, as well as the relationships between parameters. The parameters and benchmarks are published as reference values ​​and benchmarks for creating other parts.

[0022] The parameters include: basic parameters, geometric parameters and calculated parameters; basic parameters are parameters that must be input to be defined and are 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 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 and do not require input. They are set and calculated through relational formulas;

[0023] Basic parameters include: pitch P h , pitch circle diameter D pw , ball diameter D w 、Number of loop bodies b 、Number of single-cycle bearing circles n b , nut effective stroke L e ; Rack module m, tooth addendum coefficient h a *、tooth root height coefficient h f *, rack pressure angle α. Currently commonly used number of circulation bodies N b =2, which basically meets industry needs. The default value here is 2 and can be adjusted from the reference model as needed;

[0024] Geometric parameters include: screw contact angle αs, screw raceway radius coefficient sr; nut contact angle α n , nut raceway radius coefficient sn, nut upper and lower left and right side reserves e n ;Chamfer radius R d , Catheter clamp 3 plate thickness m d , the gap between the guide tongue and the screw raceway δ, the guide tube inner diameter coefficient si;

[0025] Calculation parameters include: helix angle Number of balls S b ; Screw outer diameter D s , Screw raceway arc radius R s , the distance from the starting point to the end point of the screw s0, the screw length L s0 , Screw helix height L s , Number of screw coils Ns ;Nut inner diameter d n , nut raceway arc radius R n , nut length L n0 、Number of nut spiral coils N n 、Nut helix height L n ; Inner diameter of the catheter d ui , outer diameter of the catheter d uo , catheter outer diameter eccentricity e d ;

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

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

[0028] Number of balls S b =length(`Ball circulation body base\Ball circulation body-group one length S l `) / `Ball diameter D w `;

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

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

[0031] The distance from the starting point to the end point of the screw is s0 = `pitch P h `*0.6;

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

[0033] Screw helix height L s = `Screw length L s0 `-2*`The distance s0 from the starting point to the end point of the screw;

[0034] Number of screw coils N s = `Screw helix height L s ` / `Pitch P h `;

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

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

[0037] Nut length L n0 = Number of nut spiral coils N n `*` Pitch P h `;

[0038] Number of nut spiral coils N n =(`Number of single-cycle bearing turns n b `+0.5)*`Number of loop bodies N b `-0.5*(`Number of loop bodies N b `-1);

[0039] Nut helix height L n =(Number of nut spiral coils N n `+2)*` pitch P h `;

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

[0041] Catheter outer diameter d uo =`Inner diameter of the catheter d ui `+1.5mm*2;

[0042] Catheter outer diameter eccentricity

[0043] Datums include global datums, screw datums, nut datums, conduit datums, conduit clamp datums, and ball recirculation body datums. Global datums include the origin, XYZ coordinate axes, and screw and nut axes. The Z axis is the screw and nut axes, and the midpoints of the screw and nut lengths coincide, with the origin being the coincident midpoint. Datums referenced by other parts are created based on this coordinate system, serving as point, line, and surface datums for creating solid features in each part model or as references for basic geometric figures in sketches, controlling the structure and dimensions of each part model.

[0044] Publish the parameters and benchmarks created in the above reference;

[0045] Furthermore, in step 2, the parameter setting window includes: basic parameters, rack parameters, screw parameters, nut parameters, catheter parameters and a "refresh model" function button;

[0046] Basic parameters include: pitch P h , pitch circle diameter D pw , ball diameter D w , helix angle Number of loops N b 、Number of single-cycle bearing circles n b , nut effective stroke L e 、Number of balls S b ; According to the outer loop structure, the number of single loop bearing turns n b It can only be set to n+0.5 circles;

[0047] Rack parameters include: rack module m, tooth top height coefficient h a *、tooth root height coefficient h f *, rack pressure angle α;

[0048] 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 , the distance from the starting point to the end point of the screw s0, the screw length L s0 ;

[0049] 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 、Reserve amount on the upper, lower, left and right sides of the nut e n , nut length L n0 ;

[0050] Catheter parameters include: Catheter chamfer radius R d 、Conduit clamp 3 plate thickness m d , the gap between the guide tongue and the screw raceway δ, the guide tube inner diameter coefficient s i , inner diameter of the catheter d ui , outer diameter of the catheter d uo .

[0051] Furthermore, the specific process of the "Refresh Model" function button includes the following steps 201 to 211:

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

[0053] Step 202: Obtain parameter values ​​in the parameter setting window and assign them to corresponding basic parameters and geometric parameters in the steering screw nut pair model;

[0054] Step 203: Refresh the parameters in the reference part and then refresh the number of balls S b , and refresh the other parts in the steering screw nut assembly model;

[0055] Step 204: Obtain other calculation parameters in the steering screw-nut pair model and display them in the corresponding text box in the window;

[0056] Step 205 , refreshing the documents corresponding to the models of the screw, the steering nut 8 , the first conduit 2 , the second conduit 6 , and the conduit clamp 3 ;

[0057] Step 206 , setting the ball circulation body 7 as the active document, defining the geometrical shapes and geometrical body names, and refreshing the parameters and benchmarks referenced in the steering screw nut pair model;

[0058] Step 207, delete the ball entity, each spherical surface, and each center point in the original ball circulation body 7 in reverse order. If it is the first creation, "There are no redundant features in the circulation body 1" is displayed;

[0059] Step 208, create a new ball circulation body 7-: read the number of balls S b , set the parameter ratio = 1 / number of balls S b , set the loop parameter i=0to S b -1, use the ball circulation body 7 trajectory line group 1 as the reference curve for creating the center points of each ball on the curve, use point _i as the reference point, and use 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 geometric set loop body - ball center point; use point_i+1 as the ball center and the ball diameter D w / 2 as the radius, create a spherical feature, rename it Sphere_i+1, and place it in the geometry set loop body - ball sphere; finally, use the closed surface feature to fill Sphere_i+1 as a solid, complete the creation of the ball, rename it Ball_i+1, and place it in the geometry loop body - ball body, completing the i-th loop; then enter the next loop until the i=S is completed b -1 loop;

[0060] Step 209: Delete the ball entities, spherical surfaces, and center points of the original ball circulation body 7 in reverse order. If it is the first creation, "There are no redundant features in the circulation body 2" will be displayed.

[0061] Step 210, create a new ball circulation body 72: set the circulation parameter j = 0 to S b -1, use the second set of ball circulation body 7 trajectory lines as the reference curve for creating the center points of each ball on the curve, use point _j as the reference point, and use the ratio = 1 / number of balls S b Offset, create a new ball center point, rename it point_j+1, and place it in the second ball center point of the geometric set loop; use point_j+1 as the center of the ball and the ball diameter D w / 2 as the radius, create a spherical feature, rename it Sphere_j+1, and place it in the second ball sphere of the geometry set loop body; finally, use the closed surface feature to fill Sphere_j+1 as a solid, complete the creation of the ball, rename it Ball_j+1, and place it in the second ball body of the geometry loop body, completing the i-th loop; then enter the next loop until the j=S is completed b -1 loop;

[0062] Step 211: Refresh the ball circulation body 7 model and save the steering screw nut pair model document;

[0063] Step 212: Output the parameters in the window to an EXCEL document and save it to a default folder with the name “basic and geometric parameters-year-month-day-hour-minute-second.xlsx”.

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

[0065] Furthermore, 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: speed n i , axial load F i , time t i , number of cycles N T 、Number of small cycles θ t , Maximum 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 point, modify data point, 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 combo box;

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

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

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

[0070] Step 505, creating function buttons for calculating load and life and a verification result display area;

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

[0072] Step 5021, define the vehicle life parameters; the vehicle life parameters include the average daily driving time T d , Total driving time within the service life T T 、Total number of working life cycles within the service life θ n , total working life time 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, number of cycles, and maximum axial load from the window;

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

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

[0076] Step 5024, determine 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 the equivalent load:

[0087] F nm1 =F nm2 =(Fr1+Fr2+Fr3+Fr4+Fr5+Fr6+Fr7+Fr8+Fr9)^(1 / 3);

[0088] Step 5026, determine the average daily driving time:

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

[0090] Step 5027, determine the total driving time:

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

[0092] Step 5028, determine the total number of laps:

[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 the total time:

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

[0097] Step 50210: calculate the equivalent load F nm1 and F nm2 , average steering wheel speed n m and the total number of cycles in the working life θn , total working life time t max Displayed in the text box corresponding to the calculation result area;

[0098] Step 50211, export the vehicle life estimation data to an EXCEL document with the document name "Vehicle Life Estimation-Year-Month-Day-Hour-Minute-Second.xlsx".

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

[0100] Step 5051, extract the basic parameters of the reference model; the basic parameters include: pitch circle diameter D pw , ball diameter D w , pitch P h 、Number of single-cycle bearing circles 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 axial static load rating C of the screw-nut pair oa and C oam , axial dynamic load rating 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 life span L r and L hr , life L including reliability coefficient ar and L har , and L h1,2 , including the reliability coefficient of the modified life L mar and L hmar ;

[0104] Step 5055, check the axial static torsional strength and fatigue life: static torsional strength Ta Check with rated static load, C oa ≥2×μ×π·T a / P h ; Endurance life is checked by rated dynamic load, L mar ≥L0, L hmar ≥L h0 ;

[0105] Step 5056: calculate the axial static load rating C oa and C oam , axial dynamic load rating C a and C am , including the reliability coefficient of the modified life L mar and L hmar , rated life L 1,2 and L h1,2 Displayed in the text box corresponding to the calculation result area;

[0106] Step 5057: The verification results are displayed in the text box on the right. If both are qualified, "Static Torque Passed / Life Passed" is displayed with a green background. If only one is qualified, "Static Torque Failed / Life Passed" or "Static Torque Passed / Life Failed" is displayed with an orange background. If both are unqualified, "Static Torque Failed / Life Failed" is displayed with a red background.

[0107] Step 5058, open the most recently stored load spectrum EXCEL document at the default address, create a new worksheet, name it "Basic and Geometric Parameters", save the basic and geometric parameters of the steering screw nut pair model at this time in the new worksheet; create another new worksheet, name it "Calculation Results", and name the document "Steering Screw 1 Nut Life Analysis-Year-Month-Day-Hour-Minute-Second.xlsx".

[0108] Furthermore, after step 6, the method further includes: step 7, using a service life verification template to verify the strength and service life of the steering screw nut pair under set parameters; step 7 includes the following steps 701 to 706:

[0109] Step 701: Open the steering screw-nut pair model containing the development template in CATIA software, click the "Show Parameter Setting Window" tool in the custom tool to display the window; modify the white background parameters in the window, click the "Refresh Model" function button to complete the new steering screw-nut pair model, and automatically export the basic and geometric parameters of the model to an EXCEL document;

[0110] Step 702: Click the "Show Strength and Life Verification Window" tool in the custom tool to display the window and input load spectrum data or vehicle life data;

[0111] 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 ;

[0112] Step 704: Select the Instantaneous Method, Proportion Method, Percentage Method, or Vehicle Life Method function button based on the data type to obtain the equivalent speed, equivalent load, and service life and display them in the calculation result area. If the Vehicle Life Method is selected, the vehicle life estimation data is also exported to an Excel document.

[0113] Step 705, set six correction parameters in the "Strength and Life Verification" window;

[0114] Step 706, click "Calculate Load and Life" to complete the axial static load rating C corresponding to the current parameters of the steering screw nut pair. oam , axial dynamic load rating C am The calculation of the value is completed, and the calculation and verification of the life under equivalent speed and equivalent load are completed. The results of whether the strength and life are qualified are displayed in the text box next to it; and the basic and geometric parameters, load spectrum and calculation results are exported to EXCEL documents.

[0115] The present invention provides a method for creating a life verification template (hereinafter referred to as the template) based on a steering screw nut pair model. First, a fully parameterized steering screw nut pair model is created. The model is then verified. If it fails, the problem points are identified and the model is modified. After modification, the model is refreshed and tested again until it passes. Then, based on the qualified fully parameterized model, a parameter setting custom window is created to set basic parameters (white background parameters), automatically refresh the part model and assembly model, display the calculated parameters (gray background parameters), and output the model parameter document. Next, the load spectrum or vehicle life data is prepared. Finally, a strength and life verification window is created to calculate the equivalent speed and equivalent load, as well as the working life based on the input load spectrum or vehicle life data, and output the load spectrum or vehicle life data file; to calculate the axial static load rating and axial dynamic load rating based on the basic parameters in the model; to calculate the life of each state under the equivalent speed and equivalent load; and to perform strength and life verification. If it fails, modify the parameters, refresh the model, recalculate the axial static load rating and axial dynamic load rating, and recheck the strength and life until it passes. Then, add the calculation and verification result data to the aforementioned latest output data file.

[0116] The template of this invention integrates engineers' design experience, standard formulas, manufacturing process conditions, vehicle load spectrum or vehicle life requirements, and utilizes a custom window to simplify and expedite the implementation of this complex process. After the template is created, by optimizing the test load spectrum, rationally setting vehicle life estimation data, and adjusting correction factors, the model is optimized to suit the operating conditions of the automotive steering system. This allows for efficient and accurate integration into new product development, enabling spatial structure layout, model selection calculations, and life verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0117] Figure 1 This is a flow chart of the method for creating a life verification template based on a steering screw nut pair model provided by the present invention;

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

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

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

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

[0122] Figure 6 This is a flow chart of strength and life verification;

[0123] Figure 7a This is a schematic diagram of outputting the "Basic and Geometric Parameters" document;

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

[0125] Figure 7c This is a schematic diagram for outputting the "Vehicle Life Estimation" document;

[0126] Figure 7d This is a schematic diagram of outputting the "Calculation Results" document. DETAILED DESCRIPTION

[0127] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, rather than all of the contents.

[0128] The present invention primarily involves creating a fully parametric steering screw-nut pair model using the parametric design capabilities of the CATIA software platform. Using secondary development techniques and VBA forms, custom windows for parameter settings and strength and life verification are created. Furthermore, load spectra and vehicle life data are prepared. The life verification template (hereinafter referred to as the template) created by the present invention includes the steering screw-nut pair model, a parameter setting window, and a strength and life verification window.

[0129] like Figure 1 As shown, an embodiment of the present invention provides a method for creating a life verification template based on a steering screw nut pair model, comprising the following steps:

[0130] Step 1: Create a fully parameterized steering screw nut pair model.

[0131] Based on CATIA 3D software, a steering screw nut pair model of a car steering recirculating ball steering gear is created. The steering screw nut pair model (see Figure 2 ) is a fully parameterized three-dimensional model, including the following part models: reference, steering screw 1, steering nut 8, first conduit 2, second conduit 6, conduit clamp 3, ball circulation body 7, screw 4 and washer 5. Step 1 includes the following steps 101 to 104:

[0132] Step 101: Create a reference model. The reference model includes creating parameters, relationships, reference points, lines, and surfaces, and publishing parameters and references.

[0133] The present invention first creates a reference model, where the reference is a virtual part including all parameters and benchmarks, as well as the relationship between the parameters, and publishes the parameters and benchmarks as reference values ​​and benchmarks for creating other parts.

[0134] The parameters described include basic parameters, geometric parameters, and calculated parameters. Basic parameters are parameters that must be input to define and serve as independent variables for other calculated and geometric parameters. Geometric parameters are also required input and serve as the foundational dimensional values ​​required to form solids or sketch other parts. Calculated parameters are other important design parameters for the steering screw-nut pair. They are calculated from basic or geometric parameters and do not require input; they are set and calculated using relational formulas.

[0135] Basic parameters include: pitch P h , pitch circle diameter D pw , ball diameter D w 、Number of loop bodies b 、Number of single-cycle bearing circles n b , nut effective stroke L e ; Rack module m, tooth addendum coefficient h a *、tooth root height coefficient h f*, rack pressure angle α. Currently commonly used number of circulation bodies N b =2, which basically meets industry needs. The default value here is 2 and can be adjusted from the reference model as needed.

[0136] Geometric parameters include: screw contact angle αs, screw raceway radius coefficient sr; nut contact angle α n , nut raceway radius coefficient sn, nut upper and lower left and right side reserves e n ;Chamfer radius R of the conduit d 、Conduit clamp 3 plate thickness m d , the gap between the catheter tongue and the screw raceway δ, and the catheter 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 , the distance from the starting point to the end point of the screw s0, the screw length L s0 , Screw helix height L s , Number of screw coils N s ;Nut inner diameter d n , nut raceway arc radius R n , nut length L n0 、Number of nut spiral coils N n 、Nut helix height L n ; Inner diameter of the catheter d ui , outer diameter of the catheter d uo , catheter outer diameter eccentricity e d .

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

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

[0140] Number of balls S b =length(`Ball circulation body base\Ball circulation body-group one length S l `) / `Ball diameter D w `;

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

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

[0143] The distance from the starting point to the end point of the screw is 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*`The distance s0 from the starting point to the end point of the screw;

[0146] Number of screw coils N s = `Screw helix height L s ` / `Pitch P h `;

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

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

[0149] Nut length L n0 = Number of nut spiral coils N n `*` Pitch P h `;

[0150] Number of nut spiral coils N n =(`Number of single-cycle bearing turns n b `+0.5)*`Number of loop bodies N b `-0.5*(`Number of loop bodies N b `-1);

[0151] Nut helix height L n =(Number of nut spiral coils N n `+2)*` pitch P h `;

[0152] Catheter inner diameter d ui =`Ball diameter D w `*` catheter inner diameter coefficient si`;

[0153] Catheter outer diameter d uo =`Inner diameter of the catheter d ui `+1.5mm*2;

[0154] Catheter outer diameter eccentricity

[0155] Datums include global datums, screw datums, nut datums, conduit datums, conduit clamp datums, and ball recirculation body datums. Global datums include the origin, XYZ coordinate axes, and the screw and nut axes. In principle, the Z axis serves as the screw and nut axes, with the midpoints of the screw and nut lengths coinciding, with the origin serving as the coincident midpoint. Datums referenced by other parts are created using this coordinate system as a reference. This serves as the point, line, and surface datums for creating solid features in each part model, or as a reference for sketching basic geometry, controlling the structure and dimensions of each part model.

[0156] Publish the parameters and benchmarks created in the above reference.

[0157] Step 102 : Based on the published parameters and benchmarks, models of the steering screw 1 , the steering nut 8 , the first conduit 2 , the second conduit 6 , and the conduit clamp 3 are created.

[0158] Create each part model based on the published parameters and benchmarks. Reference the screw benchmark to create the extruded outer cylinder of steering screw 1 and cut out multiple cross-section solids to form the outer raceway. Reference the nut benchmark to create the extruded body of steering nut 8 and cut out multiple cross-section solids to form the inner raceway. Create tooth grooves and form multiple teeth in an array, and create the catheter holes and screw holes on steering nut 8. Reference the catheter benchmark to create the outer diameter ribs and inner diameter slot features of the first or second catheter 2 or 6, as well as the slot features for the catheter inlet and outlet. The first and second catheters 2 and 6 have the same structure but different positions. Reference the catheter clamp benchmark to create the extruded thin plate of catheter clamp 3. The shape of the thin plate is determined by the catheter position and outer diameter. Ensure that all modified dimensions and benchmarks of each part model follow the changes when the parameters are modified.

[0159] Step 103: Create a ball circulation body 7 model including all balls.

[0160] Based on the published parameters and the ball circulation body 7 benchmark, the ball circulation body 7 model is created. The ball circulation body 7 includes all ball bodies. The creation of each ball body includes the point surface creation of the ball center, spherical surface and ball solid (closed surface). When modifying the basic parameters, the number of balls S b The position and number of the ball body's point surface bodies will change accordingly. Simply modifying the parameters won't delete redundant ball bodies or add missing ones. Furthermore, the two sets of ball circulation bodies contain a large number of balls, each of which includes the creation of point surfaces. This makes the process repetitive and tedious. A solution is provided in the second step.

[0161] Step 104: Create a steering screw nut assembly model.

[0162] Create a steering screw nut assembly model and assemble the above part models. The parts created based on the published parameters and datums will be arranged in the default position according to the reference datum. Only screw 4 and washer 5 need to be assembled.

[0163] Verify the parametric steering screw-nut pair model, modify basic parameters, and check the model's tracking and accuracy. If it fails, identify the problem, modify the model, and recheck the model until all basic parameters pass the tracking and accuracy tests.

[0164] The above processes of creating the benchmark, part model and assembly model are all commonly used 3D software operation processes. After the creation from step 101 to step 104, the steering screw nut pair model is formed.

[0165] Step 2: Create a parameter setting window.

[0166] The above completed steering screw nut pair model, modifying parameters in the model, the interaction is not good, especially when you are not familiar with the model, it is easy to miss the related items, and modifying the parameters alone is also easy to cause the model to report an error. Therefore, by creating a custom window (such as Figure 3 ) to automatically set parameter values ​​and automatically refresh or rebuild part and assembly models. A "Parameter Setting Window" custom tool is created in CATIA tool customization to facilitate opening the window.

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

[0168] Basic parameters include: pitch P h , pitch circle diameter D pw , ball diameter D w , helix angle Number of loops N b 、Number of single-cycle bearing circles n b , nut effective stroke L e 、Number of balls S b ; According to the outer loop structure, the number of single loop bearing turns n b It can only be set to n+0.5 circles (n=0,1,2,3...).

[0169] Rack parameters include: rack module m, tooth top height coefficient h a *、tooth root height coefficient h f *, rack pressure angle α.

[0170] Screw parameters include: screw outer diameter D s , screw contact angle α s , Screw raceway arc radius Rs , screw raceway radius coefficient s r , the distance from the starting point to the end point of the screw s0, the screw length L s0 ;

[0171] 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 、Reserve amount on the upper, lower, left and right sides of the nut e n , nut length L n0 ;

[0172] Catheter parameters include: Catheter chamfer radius R d 、Conduit clamp 3 plate thickness m d , the gap between the guide tongue and the screw raceway δ, the guide tube inner diameter coefficient s i , inner diameter of the catheter d ui , outer diameter of the catheter d uo .

[0173] Set the parameter limit range based on experience or process conditions. When the range is exceeded, a prompt window will appear: "**Parameter exceeds *** range, please confirm again!" For example: ball diameter D w Limited to pitch P h 0.3 to 0.75 times of the number of loops N b =2; the number of single-cycle bearing circles n b Set to n+0.5 turns (n=0,1,2,3……); screw contact angle α s Contact angle α with the nut n The general range is 42°~47°; the screw raceway radius coefficient s r and nut raceway radius coefficient s n The limited range is 0.52 to 0.62, etc.

[0174] Parameter setting window Figure 3 The white text boxes in the middle contain input parameters, corresponding to basic and geometric parameters in the model. The gray text boxes contain parameters obtained from the model, corresponding to calculated parameters in the model. These parameters are calculated in the model by setting relationships with other parameters and are automatically read from the model when the model is refreshed. Some calculated parameters and dimensional parameters used when creating geometric bodies are parameters during the model creation process and are not displayed in the window.

[0175] The "Refresh Model" function button in the parameter setting window has the following functions: setting the parameter values ​​in the model to the corresponding parameter values ​​in the window, refreshing the new parameters in the reference part, refreshing other parts in the assembly, and updating the assembly model; refreshing and saving the documents corresponding to each part model, recreating the balls in ball circulation body 7; and obtaining other calculated parameters in the model and displaying them in the window. The specific process of the "Refresh Model" function button includes the following steps 201 to 211:

[0176] Step 201: Set up an active assembly document, define each part, and define each parameter.

[0177] Step 202: Obtain parameter values ​​(white text box) in the parameter setting window and assign them to corresponding basic parameters and geometric parameters in the steering screw nut pair model.

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

[0179] Step 204: Obtain other calculation parameters in the steering screw-nut pair model and display them in the corresponding text box (gray background text box) in the window.

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

[0181] Step 206: Set the ball circulation body 7 as the active document, define the geometric figure sets and geometric body names, and refresh the parameters and benchmarks referenced in the steering screw nut pair model.

[0182] Step 207, delete the ball entity (closed surface), each spherical surface, and each center point in the original ball circulation body 7 in reverse order. If it is the first creation, it will be displayed "There are no redundant features in circulation body 1".

[0183] Step 208, create a new ball circulation body 7-: read the number of balls S b , set the parameter ratio = 1 / number of balls S b , set the loop parameter i=0to S b -1, use the ball circulation body 7 trajectory line group 1 as the reference curve for creating the center points of each ball on the curve, use point _i (the basic point named point _0 has been created on the ball circulation body 7 trajectory line in the ball circulation body 7 model) as the reference point, and use the ratio = 1 / number of balls S b Offset, create the ball center point, rename it point_i+1, and place it in the geometry set loop body - ball center point. Take point_i+1 as the center of the ball and the ball diameter D w / 2 as the radius, create a spherical feature, rename it Sphere_i+1, and place it in the geometry set loop body - ball sphere. Finally, use the closed surface feature to fill Sphere_i+1 as a solid, complete the creation of the ball, rename it Ball_i+1, and place it in the geometry loop body - ball body, completing the i-th loop. Then enter the next loop until the i=S is completed. b -1 loop.

[0184] Step 209, delete the ball entity (closed surface), each spherical surface, and each center point in the original ball circulation body 7 in reverse order. If it is the first creation, it will be displayed "There are no redundant features in circulation body 2".

[0185] Step 210, create a new ball circulation body 72: set the circulation parameter j = 0 to S b -1, use the second set of ball circulation body 7 trajectory lines as the reference curve for creating the center points of each ball on the curve, use point _j (the basic point named point _0 has been created on the second trajectory line of ball circulation body 7 in the ball circulation body 7 model) as the reference point, and use the ratio = 1 / number of balls S b Offset, create a new ball center point, rename it point_j+1, and place it in the second ball center point of the geometric set loop. Take point_j+1 as the center of the ball and the ball diameter D w / 2 as the radius, create a spherical feature, rename it Sphere_j+1, and place it in the second ball sphere of the geometry set loop body. Finally, use the closed surface feature to fill Sphere_j+1 as a solid, complete the creation of the ball, rename it Ball_j+1, and place it in the second ball body of the geometry loop body, completing the i-th loop. Then enter the next loop until the j=S is completed. b -1 loop.

[0186] Step 211: Refresh the ball circulation body 7 model and save the steering screw nut pair model document.

[0187] Step 212: Output the parameters in the window to an EXCEL document and save it to the default folder (e.g., Figure 7a ).

[0188] Step 3: Prepare the load library.

[0189] The collection of vehicle load spectra provides basic data for vehicle durability, fatigue damage, and safety research. The load measurement of the steering system can be set at the steering rocker arm, the steering knuckle connecting the kingpin, or the steering tie rod. The measurement results are extrapolated to the output end of the recirculating ball steering gear, and then extrapolated to the steering screw nut pair based on the transmission relationship to obtain its speed and axial load. Generally, the load spectrum of the whole vehicle is measured using the time history method or the rain flow counting method. The data measured by the time history method can be conveniently organized into the instantaneous input shaft speed n of the steering screw nut pair. i and axial load F i Data changing over time, speed n i The positive and negative of the load F i The positive and negative are consistent, time t i The sampling time interval is appropriately selected to ensure that the values ​​on both sides of the extreme points, inflection points and reversal points are not ignored and affect the results. For the data obtained by the rain flow counting method, it is convenient to organize the corresponding input shaft speed n obtained by multiple groups of statistics of the steering screw nut pair. i and axial load F i Occupancy time t i Data, speed n i and load F i Both are positive and negative and have the same sign, the speed n i ±a, axial load F i ±b is counted to the corresponding speed n i and axial load F i In the cumulative duration, set the ranges of a and b reasonably.

[0190] When the vehicle manufacturer does not provide a load spectrum, it is generally necessary to follow the test standards or specific strength tests and endurance tests (fatigue life tests). The load spectrum of the steering screw 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 "Bench test method for automotive steering gear assembly", QC / T29097 "Technical requirements for automotive steering gear assembly", and QC / T 1081 "Automobile electric power steering device". Although QC / T 649 "Performance requirements and test methods for automotive steering operating mechanisms" is not aimed at the performance and test requirements of recirculating ball steering gears, it is also a test requirement for the steering system mechanism. The speed, torque and number of cycles at the input end of the static torsional strength and fatigue endurance test can be used as a reference. In addition, large vehicle manufacturers will also have their own customized corporate standards. Convert the fatigue test requirements of the vehicle in the above commonly used standards into the speed n i , load F i , time t iThe load spectrum data in the form of data is saved in the EXCEL document at the default storage address for future use. The load spectrum data converted from the test requirements expresses the changes in screw speed and axial load in the small cycle of the fatigue test in the form of speed percentage and load percentage. For specific models, the maximum speed n needs to be set. max and maximum axial load F max As a percentage base. The small cycle is generally from the middle position to the left to reach the specified angle back to the middle position, then turn right to reach the specified angle back to the middle position, repeat the specified number of small cycles to reach the set number of cycles N T .

[0191] Any of the above load spectra are stored in the form of a table in an EXCEL document (such as Figure 4 ), including four columns of 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 time t i (s). A curve graph can also be added for intuitive expression.

[0192] The input speed of the test load spectrum data has positive and negative directions. The force-bearing raceway sides of the two direction transmissions are different. Assuming that the processing quality of the two raceway sides is the same and the probability of the force conditions is the same, the forward rotation of the screw viewed from one end is positive, and the reverse rotation is negative.

[0193] The relevant durability test requirements in the industry standards are summarized in Table 1:

[0194] Table 1 Requirements for durability testing in industry standards

[0195]

[0196] As can be seen from Table 1, the method for the endurance test in the experiment sets the input shaft speed to be constant, and the output end load varies with the waveform or cycle. This is an accelerated failure bench fatigue test that replaces the actual load condition, from which the experimental load spectrum can be obtained.

[0197] The static torsional strength T of the product in the industry standard a The requirements provide a reference for the static strength verification of the steering screw nut pair selection parameters, among which the specific static torsional strength T a The requirements are summarized in Table 2:

[0198] Table 2 Requirements for static torsional strength in industry standards

[0199]

[0200] The data for the above standards may be inaccurate due to different revision years. The data here is only a method of expression and is for reference only. Please adjust the parameters and data according to the latest standards.

[0201] Step 4: Prepare a database of vehicle life, road conditions, steering frequency, and load distribution.

[0202] When a new vehicle model is designed without a load spectrum, the equivalent load and equivalent speed of the steering screw nut pair are estimated based on the vehicle manufacturer's setting of the vehicle model positioning, curb weight, fully loaded weight, vehicle life and sales area, and based on experience with the load distribution, road condition distribution and steering frequency under the specific road conditions of the vehicle model.

[0203] In addition to the vehicle model life setting of the vehicle manufacturer, the "Reference Value of Motor Vehicle Service Life and Mileage" in the "Regulations on Mandatory Scrapping Standards for Motor Vehicles" requires the following vehicle types: micro-cargo, light-medium-cargo, heavy-cargo, non-commercial micro-passenger buses, non-commercial large-passenger buses, non-commercial medium-sized passenger buses, non-commercial large-passenger buses, micro-passenger rental buses, medium-sized passenger rental buses, large passenger rental buses, other micro-passenger buses, other medium-sized passenger buses, other large passenger buses, special school buses, multi-cylinder low-speed trucks, single-cylinder low-speed trucks, three-wheeled vehicles, and other special vehicle types, which set mandatory limits on the service life and mileage requirements for the corresponding models and set them as the default values ​​in the template.

[0204] Driving conditions are generally categorized by urban roads, highways, rural roads, and mountainous roads. Mileage is accumulated based on average speed under different road conditions, and the average turn angle and number of turns per minute are estimated. The ratio of time spent driving on different road conditions to total driving time is the road condition weight. Data from the load spectrum (actual vehicle driving load spectrum) is statistically analyzed to summarize the frequency of different turning scenarios, such as low-speed, large-angle U-turns or parking, normal intersection turns, and high-speed, small-angle lane changes or obstacle avoidance. Different classification methods can be set to distinguish different turning scenarios based on common practices or experience.

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

[0206] Table 3 Output end test load and cycle times

[0207] Serial number <![CDATA[Test Load %T e > Number of cycles Serial number <![CDATA[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 loads summarized above are based on limited summaries and generalizations and are provided as a guide only. The specific values ​​for these parameters should be determined based on the vehicle's positioning and the manufacturer's extensive experience. The vehicle is divided into left and right turns during driving, and the probability of turning in each direction is assumed to be equal and evenly distributed.

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

[0210] Can the steering gear steering screw nut pair model under the above-mentioned set parameters meet the requirements of the vehicle for steering transmission strength and fatigue life? According to the calculation method and formula in the standard GB / T 17587.5, the strength and life of the steering screw nut pair (ball screw nut pair) are checked. Figure 5 ), solidifying these tedious and fixed analysis and calculation processes into function buttons to quickly complete strength and life verification. A custom tool called "Strength and Life Verification Window" was created in CATIA Tool Customization to facilitate opening the window.

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

[0212] Step 501: Create a load spectrum calculation area.

[0213] The load spectrum calculation area completes the input, modification, import and export of the load spectrum, and calculates the equivalent speed, equivalent load and service life of the steering screw nut pair based on the load spectrum. The load spectrum calculation area specifically includes 8 input boxes: speed n i , axial load F i , time t i , number of cycles N T 、Number of small cycles θ t , Maximum 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 point, modify data point, 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 combo box.

[0214] The "Add data point" function button realizes the current speed n i , axial load F i , time t iThe data is added to the load spectrum list box. The "Modify data point" function button is used to modify the speed n i , axial load F i , time t i The data in the load spectrum list box will replace the selected column item in the load spectrum list box. The "Load Import" function button is used to import the standard load spectrum or the load spectrum that has been organized into an EXCEL document into the load spectrum list box. You must first select the name of the standard load spectrum to be imported in the reference load spectrum selection combo box. The standards 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 is used to export the data in the load spectrum list box to an EXCEL document and save it to 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" (such as Figure 7b ).

[0215] The Instantaneous Method, Ratio Method, and Percentage Method buttons calculate equivalent speed, equivalent load, and service life based on load spectrum data. These functions are based on the most recent Excel file exported from the load spectrum. The service life is the number of revolutions and operating time in the load spectrum.

[0216] The instantaneous method: When the load spectrum provided by the vehicle manufacturer is the data measured by the time history method, the data is organized into the instantaneous speed n of the steering screw nut pair i and axial load F i Data that changes instantaneously over time. The specific implementation process is:

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

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

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

[0220] 4) The first i loop traverses rows 2 to lastRow-1 and calculates the equivalent speed n m and the total number of 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 traverses rows 2 to lastRow-1 and calculates the intermediate value F of the equivalent load 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 the equivalent load: F nm1 =F r ^(1 / 3); F nm2 =F l ^(1 / 3);

[0241] 7) The total working life time t max 、Total number of cycles in working lifeθ n , equivalent speed n m , equivalent load F nm1 and F nm2 Displayed in the corresponding text box in the calculation result area.

[0242] The proportion method: When the load spectrum provided by the vehicle manufacturer is the data obtained by the rain flow counting method, the data is sorted into multiple groups of corresponding speeds n of the steering screw nut pair. i and axial load F iOccupancy time t i The specific implementation process is as follows:

[0243] 1) Open the latest stored load spectrum EXCEL document at the default address and obtain the row number lastRow of the last row in the table;

[0244] 2) Define loop variables i, j, k, and speed n j 、n k , load F k , time t i , t j , t k , number of cycles N T ; Define the variable total working life time t max 、Total number of cycles in working lifeθ n , equivalent speed n m , Equivalent load intermediate value F r and F l , equivalent load F rm1 and F rm2 Variables and assign initial values;

[0245] 3) The first i loop traverses rows 2 to lastRow and calculates the total time t max =t max +t i ;

[0246] 4) The second j loop traverses rows 2 to lastRow and calculates the equivalent speed n m =n m +Abs(n j )*t j / t max , total rotation angle: θ n =θ n +n j *t j / 360;

[0247] 5) The third k loop traverses rows 2 to lastRow and calculates the intermediate value F of the equivalent load 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) The calculated result is the total working life time t max *N T / 3600, total number of cycles in working life θ n , equivalent speed n m , equivalent load F nm1 and F nm2 Displayed in the corresponding text box in the calculation result area.

[0252] The percentage method is often used for load spectrum conversion of standard test, so it is also called standard test method. If there is a corresponding standard test load spectrum in the load spectrum database prepared in step 3, it can be directly referenced; if there is no prepared load spectrum, convert the customer's fatigue test requirements into speed n i , load F i , time t i Enter the data in the form of a window, and then use the "Load Export" function button to output and save it as a standard load spectrum for subsequent reference. The data is the specified speed percentage and load percentage, and the maximum speed n needs to be set max and maximum axial load F max As the base of the percentage, and set the number of cycles N T The specific implementation process is as follows:

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

[0254] 2) Define loop variables i, j, k, and 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 cycles N T ; Define the variable total working life time t max 、Total number of cycles in working lifeθ n , equivalent speed n m , Equivalent load intermediate value Fr and F l , equivalent load F rm1 and F rm2 variables and assign initial values.

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

[0256] 4) The first i loop traverses rows 2 to lastRow and calculates the total time t max =t max +t i ;

[0257] 5) The second j loop traverses rows 2 to lastRow and calculates the equivalent speed n m =n m +Abs(n max *n j / 100)*t j / t max , total rotation angle: θ n =θ n +n max *n j *t j / 36000;

[0258] 6) The third k loop traverses rows 2 to lastRow and calculates the intermediate value F of the equivalent load 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 the equivalent load: F nm1 =F r ^(1 / 3); F nm2 =F l ^(1 / 3);

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

[0263] Step 502: Create a vehicle life estimation area.

[0264] The Vehicle Life Estimation area prepares data for vehicle type, steering load, and frequency, and uses the vehicle life method to estimate the equivalent speed, equivalent load, and service life of the steering screw-nut pair. This includes vehicle type, steering load distribution, road condition distribution, steering frequency distribution, and a "Vehicle Life Method" function button.

[0265] Set the type in the drop-down options of the vehicle type combo box, including the vehicle types listed in step 4. The corresponding mandatory service life and mileage are displayed below. The steering load distribution includes 9 groups of load percentages and cycle times (specific data are shown in Table 3 and Figure 5 The road condition distribution includes urban roads, highways, rural roads, and mountain roads. The corresponding road condition weights and average vehicle speeds are set on the right. The turning frequency distribution on the right shows the turning situations under different road conditions, including the average turning angle and average turning frequency per minute (times / min) under low-speed large-angle turns, normal turns, and high-speed small-angle turns. Different classification methods can be set based on conventions or experience.

[0266] After selecting the vehicle type, all data in the Vehicle Life Estimation area will display default values. The values ​​are derived from the information in Step 4. The data can be adjusted based on actual requirements, but can be used directly without special requirements. Steering does not distinguish between left and right, and opportunities are equal.

[0267] The "Vehicle Life Method" function button estimates the equivalent speed, equivalent load, and service life of the steering screw nut pair based on the above data. Step 502 includes steps 5021 to 50211. The specific implementation process is as follows:

[0268] Step 5021, defining vehicle life parameters;

[0269] The vehicle life parameters include the average daily driving time T d , Total driving time within the service life T T、Total number of working life cycles within the service life θ n , total working life time t max , Average steering wheel speed (equivalent speed) n m ;

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

[0271] Use period N max , mileage S max ; Road condition weight: P11, P21, P31, P41; Average vehicle 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; Number of cycles: VXH, XH1, XH2, XH3, XH4, XH5, XH6, XH7, XH8, XH9; Maximum axial load: F max ;

[0272] Step 5023, determine the total number of cycles:

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

[0274] Step 5024, determine 9 sets of intermediate load values ​​Fr1, Fr2, Fr3, Fr4, Fr5, Fr6, Fr7, Fr8, and 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 the equivalent load.

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

[0286] Step 5026, determine the 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 the total driving time:

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

[0290] Step 5028, determine the total number of 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 the total time:

[0294] t max =T T / (n m *60).

[0295] Step 50210: calculate the equivalent load F nm1 and F nm2 , Average steering wheel speed (equivalent speed) n m (Default 60r / min) and total number of revolutions in working life θ n , total working life time t max Displayed in the text box corresponding to the calculation result area;

[0296] Step 50211, export the vehicle life estimation data to an EXCEL document (such as Figure 7c ), the document name is "Vehicle Life Estimation-Year-Month-Day-Hour-Minute-Second.xlsx".

[0297] As can be seen in the Load Spectrum Calculation and Vehicle Life Estimation areas above, the template uses four data processing methods to calculate the steering screw nut pair's equivalent speed, equivalent load, and service life: the instantaneous method, the proportion method, the percentage method, and the vehicle life method. Select the appropriate calculation method based on the product's actual conditions. The instantaneous method (corresponding to time history method data), the proportion method (corresponding to rainflow counting method data), and the percentage method (standard test method) are based on the relevant parameters and data set in the Load Spectrum Calculation area; the vehicle life method is based on the relevant parameters and data set in the vehicle life estimation area.

[0298] When the load spectrum is expressed in the form of a small cycle repeated multiple times, the number of cycles N needs to be set. T ; When the load spectrum is the entire life history data, the number of cycles N T Set to 1; small cycle number θ t No input is required. After running one of the functions of instantaneous method, proportion method, percentage method or vehicle life method, the calculation is automatically completed and filled in the text box. max and maximum axial load F max Used as the calculation base when using the percentage method. a Set according to customer requirements. If the customer has no requirements and selects the standard load spectrum, it is set by default according to the standard requirements. If 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 The parameters are used for the subsequent calculation of axial dynamic load rating and life. Please refer to the subsequent calculation formula for details.

[0301] Correction parameters include: 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 The corresponding coefficients are set based on the screw and nut material properties, heat treatment, machining accuracy, reliability requirements, and lubrication conditions. The fatigue life results (number of revolutions or operating time) of screw and nut pairs in existing product series are measured through fatigue testing or bench endurance testing. By adjusting the aforementioned six correction parameters within a certain range, the template's calculated results are brought close to the fatigue life test results. After several rounds of coefficient adjustment and result verification, the six correction values ​​are fixed. These values ​​can be used to verify the life of screw and nut pairs with different geometric parameters under similar conditions (such as in recirculating ball steering gears in steering systems).

[0302] Step 504: Create 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 static load rating C oa , axial dynamic load rating C a , Modified axial static load rating C oam , Modified axial dynamic load rating C am , The revised ultimate life L considering reliability mar , The final life L of the modified considering reliability hmar , rated life L ar , rated life L har The calculation results of the instantaneous method, proportion method, percentage method or vehicle life method, as well as the calculation results of the load and life are all displayed in this area.

[0304] Step 505: Create function buttons for calculating load and life and a verification result display area.

[0305] The calculation load and life function button and the verification result display area include a "calculate load and life" function button, a result display text box, a default storage address, the last stored full name and window usage precautions.

[0306] When the steering screw nut pair model with determined parameters is ready, and the equivalent speed, equivalent load, and service life have been calculated, the load calculation and life verification are performed. This is achieved by clicking the "Calculate Load and Life" function button. The calculation results are displayed in the corresponding text boxes in the second and third columns of the calculation result 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 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 bearing circles 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 static load rating C of the screw-nut pair according to the formula in Table 4. oa and C oam , axial dynamic load rating C a and C am ;

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

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

[0313] Step 5056: calculate the axial static load rating C oa and C oam , axial dynamic load rating C a and C am , including the reliability coefficient of the modified life L mar and L hmar , rated life L 1,2 and L h1,2 Displayed in the text box corresponding to the calculation result area;

[0314] Step 5057: The verification results are displayed in the text box on the right. If both are qualified, "Static Torque Passed / Life Passed" is displayed with a green background. If only one is qualified, "Static Torque Failed / Life Passed" or "Static Torque Passed / Life Failed" is displayed with an orange background. If both are unqualified, "Static Torque Failed / Life Failed" is displayed with a red background.

[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", save the basic and geometric parameters of the steering screw nut pair model in the new worksheet; create another new worksheet, name it "Calculation Results", and name the document "Steering Screw 1 Nut Life Analysis-Year-Month-Day-Hour-Minute-Second.xlsx" (such as Figure 7d ).

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

[0317] Table 4 Examples and calculation formulas related to rated load and life

[0318]

[0319]

[0320]

[0321]

[0322] Among them, the axial static load rating C 0a The maximum contact stress between the ball and the raceway is no more than 0.0001×D w The maximum static load allowed when the ball diameter is permanently deformed; u is the number of unloaded balls in each ball ring, n b =2.5 The return ball part is not counted in the number of turns, so it is 0 here; the axial dynamic load rating C a The rated life is 10 6 The constant axial load that the bearing can theoretically withstand under the condition of rotation.

[0323] The default storage location is the user-defined folder location for data placement, which is used to store output files from the "Refresh Model," "Load Export," "Vehicle Life Method," and "Calculate Load and Life" function buttons. The last time a file was saved, the full name of the file was displayed in this text box for use with the "Instantaneous Method," "Ratio Method," and "Percentage Method" function buttons.

[0324] A brief description of the window's scope of application and usage precautions is displayed in the lower right corner of the window to remind users. Please read it before use.

[0325] In summary, the following processes are implemented in each area of ​​the strength and life verification window (see Figure 6): Prepare load spectrum data or vehicle life data according to the collected vehicle requirements. If load spectrum data is obtained, input or import the load spectrum prepared in step 3, input the maximum speed, maximum axial load, number of cycles, and static torsional strength, and then export the load spectrum as a document for backup. Then, calculate the equivalent speed and equivalent load under the load spectrum based on the data, and calculate the working life under the load spectrum; if vehicle life data is obtained, input the vehicle type, road condition distribution, steering frequency, and load distribution data prepared in step 4, and input the maximum speed, maximum axial load, number of cycles, and static torsional strength. Estimate the equivalent speed and equivalent load under the vehicle life based on the data, estimate the working life under the vehicle life, and then output it as a document for backup. Extract basic parameters from the fully parametric model of the steering screw-nut pair, set correction parameters, and calculate the axial static load rating and axial dynamic load rating; calculate the life of each state under the equivalent speed and equivalent load results based on the above-mentioned estimated equivalent speed and equivalent load results; then perform strength and life verification, compare the axial static load rating with the static torsional strength, and compare the calculated life with the working life; when the former is larger, the strength and life verification is qualified, open the latest output data document mentioned above, and store the calculation and verification result data in a new worksheet; when the latter is larger, the strength and life verification is unqualified, modify the parameters, refresh the model, recalculate the axial static load rating and axial dynamic load rating, and recalibrate the life.

[0326] Step 6: Adjust the life verification template based on the life 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 the development of new products to improve R&D efficiency and accuracy. The method is to adjust the parameters in the correction parameter setting area so that the life calculation results of the template are consistent with the fatigue test results. The workload of adjusting the template is very large, including C 0a and C a Correction coefficient adjustment, and L ar and L mar Correction coefficient adjustment. Large amounts of verification data and scientific statistical methods will improve the accuracy and reliability of the template. Standard GB / T 17587.5 already provides reference values ​​for parameters (except the lubrication condition coefficient), but actual objects may deviate due to various factors.

[0328] Step 601, C 0a and C a Correction factor adjustment.

[0329] From 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 , surface hardness coefficient f h , precision coefficient f ac , material smelting coefficient f m For correcting the axial static load rating C 0am and rated dynamic load C am Based on the axial static load rating C in standard GB / T 17587.5 0a and axial dynamic load rating C a According to the definition and relevant requirements, test experiments are carried out to determine the correction factor.

[0330] Step 602, L ar and L mar Correction factor adjustment.

[0331] According to 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 , lubrication condition coefficient f r Used to correct the modified life L including the reliability coefficient ar and L mar . Prepare the parameters and data for the vehicle fatigue load spectrum or product durability test data corresponding to the existing product, refer to the third or fourth step, and input them into the template to ensure that the corresponding parameters of the steering screw nut pair model are subjected to the same equivalent speed and equivalent load as the actual one, and complete the calculation and verification process. When the test result is the number of rotations or rotation time until fatigue failure, it should theoretically be consistent with f ar =1 when L mar The values ​​are equal, correct f r Make the template L mar / L hmar The calculated result is consistent with the number of revolutions or rotation time of the fatigue test. When the test result is that the specified number of revolutions or rotation time is completed, the f ar Make the template L mar / L hmar The calculated result is consistent with the number of revolutions or rotation time of the fatigue test. ar Or lubrication condition factor f r The values ​​of are difficult to be equal, so scientific methods are used to conduct statistical analysis, such as the mean method, median method, standard deviation and coefficient of variation method, to determine the scientific correction parameter values.

[0332] Step 7: Use the service life verification template to verify the strength and service life of the steering screw nut pair under the set parameters.

[0333] After the template adjustment is completed, it is used for rapid modeling and strength and life verification of the steering screw nut pair in the new product design. Step 7 includes the following steps 701 to 706. The specific operation process is as follows:

[0334] Step 701: Open the steering screw nut pair model containing the development template in CATIA software, click the "Show Parameter Setting Window" tool in the custom tool to display the window. Modify the white background parameters in the window, click the "Refresh Model" function button to complete the new steering screw nut pair model, and automatically export the basic and geometric parameters of the model to an EXCEL document (such as Figure 7a ).

[0335] Step 702: Click the "Show Strength and Life Verification Window" tool in the custom tool to display the window and input load spectrum data or vehicle life data.

[0336] Step 7021: If the vehicle model has a load spectrum, enter the speed parameter n one by one in the load spectrum calculation area of ​​the window. i , axial load F i and time t i , click the "Add Data Point" function button to store the data in the load spectrum list box, and enter and store the data one by one in the list box until all the load spectrum data is completed. You can also place the data in an EXCEL document (.xlsx or .xls), and then import all the load spectrum data into the load spectrum list box. The method is to first select the alternative standard in the drop-down item of the combo box. You can select the QCT649 standard load spectrum, QCT1081 standard load spectrum, QCT29096 standard load spectrum, and the standard load spectrum requirements of large enterprises. For other saved load spectra, you can enter the full name of the required load spectrum EXCEL document in the combo box. Click the "Load Import" function button to complete the load spectrum import.

[0337] Step 7022: If any set of data needs to be modified or adjusted, double-click the list item and the corresponding content speed n i , load F i and time t iThe data will be displayed in the text box on the left. 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 this list item and press the "Delete" key on the keyboard to delete the data, and the subsequent column data numbers will be automatically modified. 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 an EXCEL document (such as Figure 7b ).

[0338] In step 7023, when the vehicle life method is selected, select the vehicle type in the drop-down option of the "Vehicle Life Estimation Area" combo box. All the data below, such as service life, mileage, steering load distribution, road condition distribution and steering frequency distribution, will display default values ​​and can be modified according to actual conditions.

[0339] Step 703: Set the number of cycles N in the "Strength and Life Check" window. T , Maximum speed n max (Percentage method), maximum axial load F max (Percentage method) and static torsional strength T a .

[0340] Step 704: Select the instantaneous method, proportion method, percentage method or 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 result area. If the vehicle life method is selected, the vehicle life estimation data will also be exported to an EXCEL document (such as Figure 7c ).

[0341] Step 705: Set six correction parameters in the "Strength and Life Verification" window.

[0342] Step 706, click "Calculate Load and Life" to complete the axial static load rating C corresponding to the current parameters of the steering screw nut pair. oam , axial dynamic load rating C am The calculation of the value is completed, and the calculation and verification of the life under equivalent speed and equivalent load are completed. The results of strength and life are displayed in the text box next to it (such as Figure 5 ). And output basic and geometric parameters, load spectrum (or vehicle life estimation data) and calculation results to 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 invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications to the technical solutions described in the above embodiments, or equivalent replacement of some or all of the technical features therein, do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for creating a life verification template based on a steering screw nut pair model, characterized in that: The following processes are included: Step 1, creating a fully parametric steering screw nut pair model; the steering screw nut pair model is a fully parametric three-dimensional model, including: a reference, a steering screw (1), a steering nut (8), a first conduit (2), a second conduit (6), a conduit clamp (3), a ball circulation body (7), a screw (4) and a washer (5); Step 2, create a parameter setting window; Step 3, prepare the steering load spectrum library; Step 4: Prepare a database of vehicle life, 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 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 verification result display area; Step 6: Adjust the life verification template based on the life fatigue test results.

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

3. The method for creating a life verification template based on a steering screw nut pair model according to claim 2, characterized in that: The step 101, creating a reference model, includes: Create a reference model. The reference is a virtual part that includes all parameters and benchmarks, as well as the relationships between parameters. The parameters and benchmarks are published 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 input to be defined and are 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 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 and do not require input. They 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 b 、Number of single-cycle bearing circles n b , nut effective stroke L e ; Rack module m, tooth addendum coefficient h a *、tooth root height coefficient h f *, rack pressure angle α. Currently commonly used number of circulation bodies N b =2, which basically meets industry needs. The default value here is 2 and 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 upper and lower left and right side reserves e n ;Chamfer radius R of the conduit d , Catheter clamp 3 plate thickness m d , the gap between the guide tube tongue and the screw raceway δ, and the guide tube inner diameter coefficient si; Calculation parameters include: helix angle Number of balls S b ; Screw outer diameter D s , Screw raceway arc radius R s , the distance from the starting point to the end point of the screw s0, the screw length L s0 , Screw helix height L s , Number of screw coils N s ;Nut inner diameter d n , nut raceway arc radius R n , nut length L n0 、Number of nut spiral coils N n 、Nut helix height L n ; Inner diameter of the catheter d ui , outer diameter of the catheter d uo , catheter outer diameter eccentricity e d ; The relationship between the parameters is set as follows: Number of balls S b =length(`Ball circulation body base\Ball circulation body-group one length S l `) / `Ball diameter D w `; Screw outer diameter D s =`Pitch circle diameter D pw `-2mm; Screw raceway arc 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 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*`The distance s0 from the starting point to the end point of the screw; Number of screw coils N s = `Screw helix height L s ` / `Pitch P h `; Nut inner diameter d n =`Pitch circle diameter D pw `+2mm; Nut raceway arc 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 bearing turns 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 `; Catheter inner diameter d ui =`Ball diameter D w `*` catheter inner diameter coefficient si`; Catheter outer diameter d uo =`Inner diameter of the catheter d ui `+1.5mm*2; Datums include global datums, screw datums, nut datums, conduit datums, conduit clamp datums, and ball recirculation body datums. Global datums include the origin, XYZ coordinate axes, and screw and nut axes. The Z axis is the screw and nut axes, and the midpoints of the screw and nut lengths coincide, with the origin being the coincident midpoint. Datums referenced by other parts are created based on this coordinate system, serving as point, line, and surface datums for creating solid features in each part model or as references for basic geometric figures in 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 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, catheter parameters and a "Refresh Model" function button; Basic parameters include: pitch P h , pitch circle diameter D pw , ball diameter D w , helix angle Number of loops N b 、Number of single-cycle bearing circles n b , nut effective stroke L e 、Number of balls S b ; According to the outer loop structure, the number of single loop bearing turns n b It can only be set to n+0.5 circles; Rack parameters include: rack module m, tooth top height 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 arc radius R s , screw raceway radius coefficient s r , the distance from the starting point to the end point of the screw s0, the screw length L s0 ; 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 、Reserve amount on the upper, lower, left and right sides of the nut e n , nut length L n0 ; Catheter parameters include: Catheter chamfer radius R d 、Catheter clamp (3) plate thickness m d , the gap between the guide tongue and the screw raceway δ, the guide tube inner diameter coefficient s i , inner diameter of the catheter d ui , outer diameter of the catheter d uo .

5. The method for creating a life verification template based on a steering screw nut pair model according to claim 4 is characterized in that: The specific process of 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 parameter values ​​in the parameter setting window and assign them to corresponding basic parameters 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 the other parts in the steering screw nut assembly model; Step 204: Obtain other calculation parameters in the steering screw nut pair model and display them in the corresponding text box in the window; Step 205, refreshing the documents corresponding to the models of the screw, the steering nut (8), the first conduit (2), the second conduit (6), and the conduit clamp (3); Step 206, setting the ball circulation body (7) as the active document, defining the geometrical figure sets and geometrical body names, and refreshing the parameters and benchmarks referenced in the steering screw nut pair model; Step 207, delete the ball entity, each spherical surface, and each center point in the original ball circulation body (7) in reverse order. If it is the first creation, it will be displayed as "There are no redundant features in the circulation body 1"; Step 208, create a new ball circulation body (7) 1: read the number of balls S b , set the parameter ratio = 1 / number of balls S b , set the loop parameter i=0to S b -1, using the ball circulation body (7) trajectory line group 1 as the reference curve for creating the center points 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 geometry set loop body - ball center point; Take point _i+1 as the center of the ball and the ball diameter D w / 2 as the radius, create a spherical feature, rename it Sphere_i+1, and place it in the geometry set loop body - ball sphere; finally, use the closed surface feature to fill Sphere_i+1 as a solid, complete the creation of the ball, rename it Ball_i+1, and place it in the geometry loop body - ball body, completing the i-th loop; then enter the next loop until the i=S is completed b -1 loop; Step 209, delete the ball entities, spherical surfaces, and center points of the second ball circulation body (7) in reverse order. If it is the first creation, "There are no redundant features in the second circulation body" will be displayed; Step 210, create a new ball circulation body (7) 2: set the circulation parameter j = 0 to S b -1, using the second set of ball circulation body (7) trajectory lines as the reference curve for creating the center points 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 point_j+1, and place it in the second ball center point of the geometry set loop; Take point _j+1 as the center of the ball and the ball diameter D w / 2 as the radius, create a spherical feature, rename it Sphere_j+1, and place it in the second ball sphere of the geometry set loop body; finally, use the closed surface feature to fill Sphere_j+1 as a solid, complete the creation of the ball, rename it Ball_j+1, and place it in the second ball body of the geometry loop body, completing the i-th loop; then enter the next loop until the j=S is completed b -1 loop; Step 211, refresh the ball circulation body (7) model and save the steering screw nut pair model document; Step 212: Output the parameters in the window to an EXCEL document and save it to 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 nut pair model according to claim 1, characterized in that: In step 3, the load spectrum is stored in an EXCEL document in a table format, including four columns of data, the first column is the serial number, the second column is the 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 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 calculation area; the load spectrum calculation area specifically includes 8 input boxes: speed n i , axial load F i , time t i , number of cycles N T 、Number of small cycles θ t , Maximum 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 point, modify data point, 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 combo box; Step 502, creating a vehicle life estimation area; Step 503, creating a correction parameter setting area; Step 504, creating a calculation result display area; Step 505: Create function buttons for calculating load and life and a verification result display area.

8. The method for creating a life verification template based on a steering screw nut pair model according to claim 7, characterized in that: Step 502 includes steps 5021 to 50211: Step 5021, define the vehicle life parameters; the vehicle life parameters include the average daily driving time T d , Total driving time within the service life T T 、Total number of working life cycles within the service life θ n , total working life time t max , average steering wheel speed n m ; Step 5022: Obtain the corresponding service life, mileage, road condition weight, average vehicle speed, average steering angle, steering frequency, load percentage, number of cycles, and maximum axial load from the window; Step 5023, determine the total number of cycles: VXH=XH1+XH2+XH3+XH4+XH5+XH6+XH7+XH8+XH9; Step 5024, determine 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); <h2 style=";text-align:left;direction:ltr">Fr7=((F<h2 style=";text-align:left;direction:ltr"> max <h2 style=";text-align:left;direction:ltr"> *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: <h2 style=";text-align:left;direction:ltr">F<h2 style=";text-align:left;direction:ltr"> nm1 <h2 style=";text-align:left;direction:ltr"> =F<h2 style=";text-align:left;direction:ltr"> nm2 <h2 style=";text-align:left;direction:ltr"> =(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 the total number of cycles in the working life θ n , total working life time t max Displayed in the text box corresponding to the calculation result 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 nut pair model according to claim 8, characterized in that: Step 505 includes steps 5051 to 5058: Step 5051, extract the basic parameters of the reference model; the basic parameters include: pitch circle diameter D pw , ball diameter D w , pitch P h 、Number of single-cycle bearing circles 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 axial static load rating C of the screw-nut pair oa and C oam , axial dynamic load rating 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 life span L r and L hr , lifespan including reliability coefficient L ar and L har , and L h1,2 , including the reliability coefficient of the modified life L mar and L hmar ; Step 5055, check the axial static torsional strength and fatigue life: static torsional strength T a Check with rated static load, C oa ≥2×μ×π·T a / P h ; Endurance life is checked by rated dynamic load, L mar ≥L0, L hmar ≥L h0 ; Step 5056: calculate the axial static load rating C oa and C oam , axial dynamic load rating C a and C am , including the reliability coefficient of the modified life L mar and L hmar , rated life L 1,2 and L h1,2 Displayed in the text box corresponding to the calculation result area; In step 5057, the verification results are displayed in the text box on the right. If both are qualified, "Static Torque Passed / Life Passed" is displayed with a green background. If only one is qualified, "Static Torque Failed / Life Passed" or "Static Torque Passed / Life Failed" is displayed with an orange background. If both are unqualified, "Static Torque Failed / Life Failed" is displayed with a red background. Step 5058: Open the most recently stored load spectrum EXCEL document at the default address, create a new worksheet, name it "Basic and Geometric Parameters", and save the basic and geometric parameters of the steering screw nut pair model in the new worksheet; then create a new worksheet, name it "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 nut pair model according to claim 1, characterized in that: After step 6, the method further includes: step 7, using a service life verification template to verify the strength and service life of the steering screw nut pair under set parameters; step 7 includes the following steps 701 to 706: Step 701: Open the steering screw-nut pair model containing the development template in CATIA software, click the "Show Parameter Setting Window" tool in the custom tool to display the window; modify the white background parameters in the window, click the "Refresh Model" function button to complete the new steering screw-nut pair model, and automatically export the basic and geometric parameters of the model to an EXCEL document; Step 702: Click the "Show Strength and Life Verification Window" tool in the custom 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 Vehicle Life Method function button based on the data type to obtain the equivalent speed, equivalent load, and service life and display them in the calculation result area. If the Vehicle Life Method is selected, the vehicle life estimation data is also exported to an Excel document. Step 705: Set six correction parameters in the "Strength and Life Verification" window; Step 706, click "Calculate Load and Life" to complete the axial static load rating C corresponding to the current parameters of the steering screw nut pair. oam , axial dynamic load rating C am The calculation of the value is completed, and the calculation and verification of the life under equivalent speed and equivalent load are completed. The results of whether the strength and life are qualified are displayed in the text box next to it; and the basic and geometric parameters, load spectrum and calculation results are exported to EXCEL documents.

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