Optimization method for piston pin hole profile design

Abstract

The present invention provides a method for optimizing the design of a piston pin hole profile, including: pre-designing the initial piston pin hole profile as a non-integer power function curve model based on engine parameters and piston structure; performing pin hole dynamic simulation calculations on the initial piston pin hole profile, continuously optimizing and iterating the piston pin hole deformation based on the calculation results, and determining the optimal pin hole contact pressure and cumulative wear load; determining the optimal piston pin hole cold deformation corresponding to the optimal pin hole contact pressure and cumulative wear load; and fitting and determining the optimal coefficient and optimal power exponent of the non-integer power function curve model based on the optimal piston pin hole cold deformation to determine the optimal piston pin hole profile power function curve model. Through the technical solution of the present invention, the pin hole profile is optimized by designing a non-integer power function curve, etc., which can meet the pressure distribution of the pin hole bearing surface under high explosion pressure, is conducive to the formation of a wedge-shaped lubricating oil film in the pin hole, and can reduce the pin hole contact pressure by 10%-15%.

Description

Technical Field

[0001] The present invention relates to the technical field of piston pin hole design, and in particular to a piston pin hole profile design optimization method. Background Art

[0002] With the continuous improvement of engine emissions and performance targets, piston operating conditions are becoming increasingly demanding. The thermal loads and contact pressures on the piston pin bore are increasing, making it highly susceptible to pin-bore contact friction and wear failure. Therefore, pin-bore profile design becomes particularly important.

[0003] In related technologies, the hyperbolic portion of the pinhole profile is generally designed using a quadratic function. Specifically, the profiles of the front and rear pinholes are each configured as three segments. The middle segment's cross-section along the axis is a straight line, while the cross-sections at both ends along the axis are quadratic function curves. The quadratic function curves at both ends are smoothly connected to the straight line segments. Pinhole profile optimization methods are often based on experimental methods. The profile is optimized based on the contact wear of the pinhole after the test until it meets the design requirements. This has the following technical drawbacks:

[0004] (1) The quadratic function curve of the pin hole shape line is difficult to meet the pressure distribution of the pin hole bearing surface, and is prone to pin hole contact wear and cracks. It is especially difficult to meet the requirements of engine pistons with explosion pressures above 20 MPa.

[0005] (2) Most of the optimization methods for pin hole shape are modified according to the wear conditions after the test. Multiple test verifications increase a large number of repetitive tests, which increases the product development cycle and R&D costs. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0007] To this end, the purpose of the present invention is to provide a piston pin hole profile design optimization method, which optimizes the pin hole profile by designing a non-integer power function curve, etc., which can meet the uniform pressure distribution of the pin hole bearing surface under high explosive pressure, is conducive to the formation of a wedge-shaped lubricating oil film in the pin hole, and the pin hole contact pressure can be reduced by 10%-15%. At the same time, the piston pin hole profile is optimized, which can not only meet the needs of CNC programming and processing, but also can more realistically simulate the actual operating conditions of the pin hole. The calculation results are highly accurate, greatly reducing the number of tests and reducing R&D costs.

[0008] In order to achieve the above-mentioned purpose, the technical solution of the present invention provides a piston pin hole profile design optimization method, comprising: pre-designing the piston pin hole initial profile as a non-integer power function curve model according to engine parameters and piston structure, wherein the non-integer power function curve model is , wherein the power exponent b is a non-integer between 1.4 and 3.5, and the coefficient a is on the order of 10^-4 or 10^-5; performing pin hole dynamic simulation calculation on the initial shape line of the piston pin hole, continuously optimizing and iterating the piston pin hole deformation based on the calculation results, and determining the optimal pin hole contact pressure and cumulative wear load; determining the optimal cold deformation of the piston pin hole corresponding to the optimal pin hole contact pressure and cumulative wear load; and fitting and determining the optimal coefficient and optimal power exponent of the non-integer power function curve model based on the optimal cold deformation of the piston pin hole, and determining the optimal power function curve model of the optimal piston pin hole shape line.

[0009] In this technical solution, the initial piston pin hole profile is designed as a non-integer power function curve model, breaking the original mindset of designing as a quadratic function. The resulting optimized piston pin hole profile is more accurate, significantly reducing the number of tests, shortening the product development cycle, and lowering R&D costs. By performing pin hole dynamic simulation calculations on the initial piston pin hole profile, the piston pin hole deformation is continuously optimized and iterated based on the calculation results to determine the optimal pin hole contact pressure and cumulative wear load. The optimal piston pin hole profile power function curve model is then fitted and determined, facilitating the machining of the optimal pin hole profile. The resulting pin hole profile can also meet the pressure distribution requirements of the pin hole bearing surface under high explosion pressure, reducing the pin hole contact pressure by 10%-15%, thereby making the piston more suitable for highly enhanced engine operating conditions.

[0010] Preferably, the piston pin hole shape line design optimization method further comprises: according to the optimal piston pin hole shape line power function curve model, fitting and determining the corresponding high-order integer power polynomial function model, and the high-order integer power polynomial function model is preset as Wherein, the high-order integer power polynomial function model and the optimal piston pin hole shape line power function curve model are in x i The residual at is the smallest and the residual value is less than 10^-4.

[0011] In this technical solution, based on the optimal piston pin hole shape line power function curve model, the corresponding high-order integer power polynomial function model is fitted and determined, and the fitting accuracy is high. The optimal piston pin hole shape line power function curve model is replaced by the high-order integer power polynomial function model to realize the CNC machining of the optimal pin hole shape line, realize the unity of advanced design and CNC machining, and further help to improve the pin hole shape line accuracy, reduce the number of tests, and shorten the product development cycle.

[0012] Preferably, the method of determining the corresponding high-order integer power polynomial function model according to the optimal piston pin hole shape line power function curve model specifically includes the following steps: calculating multiple points (x i ,yi ), wherein i=1, 2, ... n, the value of n is determined according to the length of the piston pin hole curve segment in the piston structure; constructing and determining the relationship between the preset high-order integer power polynomial function model and the optimal piston pin hole shape power function curve model at x i The residual value model at , the residual value model is Among them, a0, a1, ... a k is the coefficient of the desired high-order integer power polynomial function model, and k is the highest power exponent of the desired high-order integer power polynomial function model; the residual value model is converted into an extreme value problem of the residual value δ, and the function of the residual value δ is determined as δ=δ(a0, a1, ... a k ); According to the function of the residual value δ, for a k Find the partial derivative, which is converted into finding the coefficient a k Matrix; Based on MATLAB, Python or Excel programming, fitting calculation determines the coefficient a of the high-order integer power polynomial function model k , determine the high-order integer power polynomial function model.

[0013] In this technical solution, the fitting accuracy of the determined high-order integer power polynomial function model is high. The high-order integer power polynomial function model replaces the optimal piston pin hole shape line power function curve model, which can realize CNC machining of the optimal pin hole shape line. Moreover, the residual value of the high-order integer power polynomial function model and the optimal piston pin hole shape line power function curve model at the same point is less than 10^-4 order of magnitude, the fitting accuracy is high, and the pin hole shape line accuracy is high, which is further conducive to shortening the product development cycle.

[0014] Preferably, the pin hole dynamic simulation calculation specifically includes: defining the lubrication boundary surface between the piston components, and defining the friction coefficient and wear coefficient between each interface, the piston component includes a piston, a cylinder liner, a piston pin, and a connecting rod small end; constructing a finite element mesh model of the piston component; defining the oil film thickness and surface roughness characteristics between the piston components; loading and calculating the thermal deformation of the piston outer circle and the thermal deformation of the piston pin hole based on the finite element mesh model of the piston component and the piston temperature field, and calculating the friction work between the piston pin hole and the piston pin based on the initial shape line of the piston pin hole and converting it into heat energy and inputting it into the piston temperature field for continuous iterative calculation until When the pin hole temperature increases continuously and converges, the final frictional heat deformation is determined to be superimposed on the piston pin hole thermal deformation as the initial piston pin hole thermal deformation; a piston pin hole dynamic simulation calculation model is constructed based on the engine parameters, cylinder pressure curve, piston assembly geometric parameters, piston outer circle thermal deformation and initial piston pin hole thermal deformation, piston stiffness matrix and mass matrix, and piston pin hole lubricating oil film characteristics; according to the piston pin hole dynamic simulation calculation model, the extended Reynolds equation including the oil filling rate is used to perform dynamic simulation calculation of the pin hole, and the calculation results include the pin hole contact pressure and the cumulative wear load within one cycle.

[0015] In this technical solution, the construction of the piston pin hole dynamic simulation calculation model takes into account the friction and wear between the contact surfaces of components and the lubricating oil film and surface microscopic features of the pin hole contact surface, so that the optimization accuracy of the pin hole shape line is higher. By optimizing the pin hole deformation and continuously iterating the pin hole thermal deformation and the deformation caused by frictional heat to simulate the contact wear of the pin hole, the accuracy of the optimal piston pin hole shape line power function curve model is further improved, which is further conducive to improving the pin hole shape line accuracy, reducing the number of tests, and shortening the product development cycle.

[0016] Preferably, the definition of the lubrication boundary surface between the piston components and the definition of the friction coefficient and wear coefficient between each interface specifically include: defining the piston ring land, the piston pin hole, the piston skirt, the contact interface between the piston pin and the piston pin hole, and the contact interface between the piston pin and the connecting rod small end hole as lubrication boundary surfaces, and establishing an elastic liquid dynamic lubrication model between the piston pin hole and the piston pin, and the connecting rod small end hole and the piston pin matching surface; defining the friction coefficient and wear coefficient between each interface, wherein the friction coefficient value range is 0.05-0.15, and the wear coefficient is on the order of 10^-8.

[0017] Preferably, the construction of the finite element mesh model of the piston assembly specifically includes: using tetrahedral meshes to construct the piston and connecting rod end, and using hexahedral meshes to construct the piston pin, cylinder liner and bearing shell; using the common node method to map the nodes on the back of the shell to the surface of the connecting rod end hole; setting 20-40 mesh nodes circumferentially on the surface of the piston pin hole, and setting 10-15 mesh nodes along the axial direction of the piston pin hole; when processing the lubrication boundary surface, simplifying the tapered surface of the piston pin hole to a cylindrical surface with the same size as the piston pin hole.

[0018] Preferably, the definition of the oil film thickness and surface roughness characteristics between the piston components specifically includes: defining the oil film thickness between the piston components, where the oil film thickness ranges from 5 μm to 20 μm; and calculating the surface roughness characteristics based on the Greenwood-Tripp contact model, wherein the surface roughness characteristics include the root mean square of the roughness peak height σ, the roughness peak curvature radius β, and the composite roughness surface density γ. The Greenwood-Tripp contact model includes:

[0019]

[0020]

[0021] 0.01<σβγ<0.05,

[0022] Among them, Z s Characterized by the average roughness peak height, σ s It is represented by the standard deviation peak height, n is represented by the total number of rough features, z i Characterized by the height value of the i-th roughness feature, i = 1, 2...n; Characterized by the average height of the roughness feature, n s Characterized by the total number of statistical rough peaks.

[0023] In this technical solution, the specific construction and definition of the lubrication boundary surface, friction coefficient, wear coefficient, finite element mesh model of the piston assembly, oil film thickness and surface roughness characteristics between the piston components in the construction of the piston pin hole dynamic simulation calculation model are further optimized, ensuring the accuracy of the construction of the piston pin hole dynamic simulation calculation model. In addition, multiple factors such as the friction and wear between the contact surfaces of the components and the lubricating oil film and surface microscopic characteristics of the pin hole contact surface are taken into consideration, so that the optimized optimal piston pin hole shape line power function curve model has higher accuracy, which is further conducive to reducing the number of tests and shortening the product development cycle.

[0024] Preferably, after each iteration of optimizing the piston pin hole deformation according to the calculation results of the pin hole dynamic simulation calculation, the friction work between the piston pin hole and the piston pin is calculated according to the piston pin hole deformation and converted into heat energy and input into the piston temperature field for continuous iterative calculation until the pin hole temperature continuously increases and tends to converge, and the final friction heat deformation is determined, which is sequentially superimposed on the initial piston pin hole thermal deformation to determine the current piston pin hole thermal deformation corresponding to the current piston pin hole deformation.

[0025] In this technical solution, during the iterative optimization of the pin hole deformation, the pin hole's thermomechanical deformation and the deformation caused by frictional heat are continuously iterated to simulate the contact wear of the pin hole, further improving the accuracy of the pin hole shape design optimization.

[0026] Preferably, the determining of the optimal cold deformation of the piston pin hole corresponding to the optimal pin hole contact pressure and the cumulative wear load specifically includes: determining the deformation of the piston pin hole corresponding to the optimal pin hole contact pressure and the cumulative wear load; determining the thermal-mechanical deformation of the piston pin hole corresponding to the deformation of the piston pin hole; and subtracting the thermal-mechanical deformation of the piston pin hole from the deformation of the piston pin hole to determine the optimal cold deformation of the piston pin hole.

[0027] In this technical solution, the piston pin hole deformation is subtracted from the piston pin hole thermal deformation to determine the optimal piston pin hole cold deformation, thereby determining the optimal piston pin hole shape line power function curve model. The influence of factors such as the friction and wear coefficient and the rough peak characteristics of the pin hole surface is taken into account, further improving the accuracy of the optimal piston pin hole shape line power function curve model.

[0028] The technical solution of the present invention also proposes a computer device, which includes a processor, and the processor is used to implement the steps of the piston pin hole shape line design optimization method proposed in any one of the technical solutions of the present invention when executing a computer program stored in a memory.

[0029] In this technical solution, the computer device includes a processor, which is used to implement the steps of the piston pin hole line design optimization method proposed in any one of the technical solutions of the present invention when executing the computer program stored in the memory. Therefore, it has all the beneficial effects of the piston pin hole line design optimization method proposed in any one of the technical solutions of the present invention, which will not be repeated here.

[0030] The piston pin hole profile optimization design method proposed in the present invention has the following beneficial technical effects:

[0031] (1) The piston pin hole shape optimization design method proposed in the present invention optimizes the pin hole shape by designing a non-integer power function curve, etc. The pin hole shape obtained by the design optimization can meet the pressure distribution of the pin hole bearing surface under high explosion pressure, which is conducive to the formation of a wedge-shaped lubricating oil film in the pin hole. The pin hole contact pressure can be reduced by 10%-15%, thereby making the piston better suitable for the high-intensity operating conditions of the engine.

[0032] (2) The piston pin hole shape optimization design method proposed in the present invention takes into account the friction and wear between the contact surfaces of the components and the lubricating oil film and surface microscopic features of the pin hole contact surface. By optimizing the pin hole deformation and continuously iterating the pin hole thermal deformation and the deformation caused by frictional heat, the contact wear of the pin hole is simulated. The calculation accuracy is high, the number of tests is reduced, the product development cycle is shortened, and the development cost is reduced.

[0033] (3) The piston pin hole shape optimization design method proposed in the present invention optimizes the piston pin hole shape, simulates the actual operating conditions of the pin hole more realistically, and has high calculation accuracy. The optimal piston pin hole shape power function curve model is replaced by a high-order integer power polynomial function model, which can realize CNC machining of the optimal pin hole shape. The residual value of the high-order integer power polynomial function model and the optimal piston pin hole shape power function curve model at the same point is less than 10^-4 order of magnitude, with high fitting accuracy and high pin hole shape accuracy, which is further conducive to shortening the product development cycle.

[0034] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0036] Figure 1 A schematic flow chart of a piston pin hole profile design optimization method according to one embodiment of the present invention is shown;

[0037] Figure 2 A schematic flow chart of a piston pin hole profile design optimization method according to another embodiment of the present invention is shown;

[0038] Figure 3 Shows the schematic structural diagram of the piston grid and lubrication boundary surface;

[0039] Figure 4 Shows the schematic structural diagram of the piston pin grid and lubrication boundary surface;

[0040] Figure 5 shows a schematic diagram of surface roughness features;

[0041] Figure 6 The figure shows the fitting curve of the optimal piston pin hole shape power function curve model and the corresponding high-order integer power polynomial function model.

[0042] in, Figure 3 and Figure 4 The corresponding relationship between the reference numerals and components is as follows:

[0043] 102 Lubrication boundary surface between power land and cylinder bore, 104 Lubrication boundary surface between second ring land and cylinder bore, 106 Lubrication boundary surface between third ring land and cylinder bore, 108 Lubrication boundary surface between piston skirt and cylinder bore, 110 Lubrication boundary surface between piston pin hole and piston pin, 112 Lubrication boundary surface between piston pin and piston pin hole, 114 Lubrication boundary surface between piston pin and connecting rod small end hole. DETAILED DESCRIPTION

[0044] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0046] like Figure 1 As shown, the piston pin hole profile design optimization method according to an embodiment of the present invention includes the following steps:

[0047] S102, pre-designing the initial shape of the piston pin hole as a non-integer power function curve model based on the engine parameters and the piston structure, the non-integer power function curve model is Among them, the power exponent b is a non-integer between 1.4 and 3.5, and the coefficient a is on the order of 10^-4 or 10^-5;

[0048] S104, performing pin hole dynamic simulation calculation on the initial shape of the piston pin hole, and continuously optimizing and iterating the piston pin hole deformation based on the calculation results to determine the optimal pin hole contact pressure and cumulative wear load;

[0049] S106, determining the optimal piston pin hole cold deformation corresponding to the optimal pin hole contact pressure and the accumulated wear load;

[0050] S108 , based on the optimal piston pin hole cold deformation, determine the optimal coefficient and optimal power exponent of the non-integer power function curve model by fitting, and determine the optimal piston pin hole shape line power function curve model.

[0051] By optimizing the pinhole profile through designs such as non-integer power function curves, the pinhole's actual operating conditions are more realistically simulated. The resulting calculations are highly accurate, ensuring uniform pressure distribution across the pinhole's bearing surface under high explosive pressures. This facilitates the formation of a wedge-shaped lubricating film, reducing pinhole contact pressure by 10%-15%, thereby making the piston more suitable for high-strength engine operating conditions. The design considers friction and wear between component contact surfaces, as well as the lubricating film and surface microscopic features of the pinhole contact surface. Pinhole contact wear is simulated by optimizing pinhole deformation and continuously iterating deformation caused by thermomechanical and frictional heat generation. This results in highly accurate calculations, reduces the number of tests, shortens product development cycles, and reduces R&D costs.

[0052] like Figure 2 As shown, the piston pin hole profile design optimization method according to an embodiment of the present invention includes the following steps:

[0053] S202, pre-designing the initial shape of the piston pin hole as a non-integer power function curve model based on the engine parameters and the piston structure, the non-integer power function curve model is Among them, the power exponent b is a non-integer between 1.4 and 3.5, and the coefficient a is on the order of 10^-4 or 10^-5;

[0054] S204, defining lubrication boundary surfaces between piston components, and defining friction coefficients and wear coefficients between each interface, wherein the piston component includes a piston, a cylinder liner, a piston pin, and a connecting rod end;

[0055] Specifically, the piston ring land, piston pin hole, piston skirt, piston pin and piston pin hole contact interface, and piston pin and connecting rod small end hole contact interface are defined as lubrication boundary surfaces, such as Figure 3 and Figure 4 As shown, the lubrication boundary surface 102 between the power bank and the cylinder bore, the lubrication boundary surface 104 between the second ring bank and the cylinder bore, the lubrication boundary surface 106 between the third ring bank and the cylinder bore, the lubrication boundary surface 108 between the piston skirt and the cylinder bore, the lubrication boundary surface 110 between the piston pin hole and the piston pin, the lubrication boundary surface 112 between the piston pin and the piston pin hole, and the lubrication boundary surface 114 between the piston pin and the connecting rod small end hole. An elastic liquid dynamic lubrication model is established between the matching surfaces between the piston pin hole and the piston pin, and between the connecting rod small end hole and the piston pin; the friction coefficient and wear coefficient between each interface are defined, wherein the friction coefficient ranges from 0.05 to 0.15, and the wear coefficient is on the order of 10^-8.

[0056] S206, constructing a finite element mesh model of the piston assembly;

[0057] Specifically, tetrahedral meshes are used to construct the piston and connecting rod end, and hexahedral meshes are used to construct the piston pin, cylinder liner, and bearing. The common node method is used to map the nodes on the bearing back to the surface of the connecting rod end hole. 20-40 mesh nodes are set circumferentially on the surface of the piston pin hole, and 10-15 mesh nodes are set axially along the piston pin hole. When processing the lubrication boundary surface, the tapered surface of the piston pin hole is simplified to a cylindrical surface with the same size as the piston pin hole.

[0058] S208, defining the oil film thickness and surface roughness characteristics between piston components;

[0059] Specifically, the oil film thickness between the piston components is defined, and the oil film thickness range is 5um-20um. Based on the Greenwood-Tripp contact model, the surface roughness characteristics are calculated, where the surface roughness characteristics include the root mean square of the roughness peak height σ, the roughness peak curvature radius β, and the composite roughness surface density γ. The Greenwood-Tripp contact model includes:

[0060]

[0061]

[0062] 0.01<σβγ<0.05, where Z s Characterized by the average roughness peak height, σ s It is represented by the standard deviation peak height, n is represented by the total number of rough features, z i Characterized by the height value of the i-th roughness feature, i = 1, 2...n; Characterized by the average height of the roughness feature, n s Characterized by the total number of statistical roughness peaks. The calculated surface roughness characteristics are as follows Figure 5 shown.

[0063] S210, based on the finite element mesh model of the piston assembly and the piston temperature field, load and calculate the thermal mechanical deformation of the piston outer circle and the piston pin hole, and calculate the friction work between the piston pin hole and the piston pin based on the initial shape of the piston pin hole. The work is converted into heat energy and input into the piston temperature field. The calculation is iteratively performed until the pin hole temperature continuously increases and converges. The final frictional heat deformation is determined and superimposed on the piston pin hole thermal mechanical deformation to serve as the initial piston pin hole thermal mechanical deformation.

[0064] S212, constructing a piston pin hole dynamic simulation calculation model based on engine parameters, cylinder pressure curve, piston assembly geometric parameters, piston outer circle thermal mechanical deformation and initial piston pin hole thermal mechanical deformation, piston stiffness matrix and mass matrix, and piston pin hole lubricating oil film characteristics;

[0065] S214, according to the piston pin hole dynamic simulation calculation model, using the extended Reynolds equation including the oil filling rate, the pin hole dynamic simulation calculation is performed. The calculation results include the pin hole contact pressure and the cumulative wear load within one cycle;

[0066] S216, based on the calculation results, continuously optimizes and iterates the piston pin hole deformation to determine the optimal pin hole contact pressure and cumulative wear load.

[0067] After each iteration of optimizing the piston pin hole deformation based on the calculation results of the pin hole dynamic simulation, the friction work between the piston pin hole and the piston pin is calculated based on the piston pin hole deformation and converted into heat energy and input into the piston temperature field for continuous iterative calculation until the pin hole temperature continues to increase and converges. The final friction heat deformation is determined and superimposed on the initial piston pin hole thermal deformation in turn to determine the current piston pin hole thermal deformation corresponding to the current piston pin hole deformation.

[0068] S218, determining the piston pin hole deformation corresponding to the optimal pin hole contact pressure and cumulative wear load;

[0069] S220, determining the piston pin hole thermal deformation corresponding to the piston pin hole deformation;

[0070] S222, subtracting the piston pin hole thermal deformation from the piston pin hole deformation to determine the optimal piston pin hole cold deformation;

[0071] S224, fitting and determining the optimal coefficient and optimal power exponent of the non-integer power function curve model based on the optimal piston pin hole cold deformation, and determining the optimal piston pin hole shape power function curve model;

[0072] S226, calculate multiple points (x i ,y i ), where i = 1, 2, ... n, and the value of n is determined according to the length of the piston pin hole curve section in the piston structure;

[0073] S228, constructing a predetermined high-order integer power polynomial function model and an optimal piston pin hole shape power function curve model in x i The residual value model at , the residual value model is Among them, a0, a1, ... a k is the coefficient of the required high-order integer power polynomial function model, and k is the highest power exponent of the required high-order integer power polynomial function model;

[0074] S230, convert the residual value model into a problem of finding the extreme value of the residual value δ, and determine the function of the residual value δ=δ(a0, a1, ... a k );

[0075] S232, according to the function of the residual value δ, k Find the partial derivative, which is converted into finding the coefficient a k Matrix of

[0076] S234, based on MATLAB, Python or Excel programming, fitting calculation to determine the coefficient a of the high-order integer power polynomial function model k , determine the high-order integer power polynomial function model.

[0077] Specifically, the optimal piston pin hole shape power function curve model is y=3.77*10 -5 x 2.3 For example, according to the above method, the high-order integer power polynomial function model determined by Excel programming fitting is Y=-3.78*10 -5 x+5.81*10 -5 x 2 +2.12*10 -6 x 3 , the fitting curve is as follows Figure 6 As shown in the figure, it can be seen that the two curves are basically coincident. The end point of the straight section of the pin hole is the starting point 0 of the curve. The distance x between the two curves relative to the starting point 0 is calculated. i The value y at i 、Y i The residual values of the two curves are shown in Table 1 below.

[0078] Table 1

[0079] <![CDATA[x i / mm]]> 0 1 3 5 7 9 11 <![CDATA[y i / mm]]> 0 3.768E-05 0.0004715 0.00152664 0.003310 0.0059001 0.0093607 <![CDATA[Y i / mm]]> 0 2.243E-05 0.0004666 0.00152799 0.003308 0.0059095 0.0094332 Residual value δ 0 2.243E-05 4.9E-06 1.35E-06 2.0E-06 9.4E-06 7.25E-05

[0080] As can be seen, the curve residuals at the same points between the fitted curve and the original design curve are less than 10^-5, indicating that the fitted high-order integer power polynomial function is highly accurate. Generally, a high-order integer power exponent of 3 or 4 is sufficient to meet the required fitting accuracy, eliminating the need to fit higher-order power polynomials. Replacing the optimal piston pin hole profile power function curve model with a high-order integer power polynomial function model enables CNC machining of the optimal pin hole profile, achieving high fitting accuracy and pin hole profile precision, further contributing to shortening product development cycles.

[0081] The steps in the method of the present invention can be adjusted in sequence, combined, or deleted according to actual needs.

[0082] The units in the device of the present invention can be combined, divided and deleted according to actual needs.

[0083] Those skilled in the art will appreciate that all or part of the steps in the various methods of the above embodiments can be completed by instructing related hardware through a program. The program can be stored in a computer-readable storage medium, and the storage medium includes a read-only memory (ROM), a random access memory (RAM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a one-time programmable read-only memory (OTPROM), an electronically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, magnetic disk storage, magnetic tape storage, or any other computer-readable medium capable of carrying or storing data.

[0084] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0085] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A piston pin hole profile design optimization method, characterized in that: include: The initial shape of the piston pin hole is pre-designed according to the engine parameters and the piston structure as a non-integer power function curve model. The non-integer power function curve model is Among them, the power exponent b is a non-integer between 1.4 and 3.5, and the coefficient a is on the order of 10^-4 or 10^-5; Performing pin hole dynamic simulation calculation on the initial shape of the piston pin hole, continuously optimizing and iterating the piston pin hole deformation based on the calculation results, and determining the optimal pin hole contact pressure and cumulative wear load; After each iteration of optimizing the piston pin hole deformation based on the calculation results of the pin hole dynamic simulation calculation, the friction work between the piston pin hole and the piston pin is calculated based on the piston pin hole deformation and converted into heat energy and input into the piston temperature field for continuous iterative calculation until the pin hole temperature continuously increases and converges, and the final friction heat deformation is determined, which is sequentially superimposed on the initial piston pin hole thermal deformation to determine the current piston pin hole thermal deformation corresponding to the current piston pin hole deformation; determining an optimal piston pin hole cold deformation corresponding to the optimal pin hole contact pressure and cumulative wear load; According to the optimal piston pin hole cold deformation, the optimal coefficient and optimal power exponent of the non-integer power function curve model are determined by fitting, and the optimal piston pin hole shape power function curve model is determined; According to the optimal piston pin hole shape line power function curve model, the corresponding high-order integer power polynomial function model is determined by fitting, and the preset high-order integer power polynomial function model is Wherein, the high-order integer power polynomial function model and the optimal piston pin hole shape line power function curve model are in x i The residual at is the smallest and the residual value is less than 10^-4.

2. The piston pin hole profile design optimization method according to claim 1, characterized in that: The method of fitting and determining a corresponding high-order integer power polynomial function model based on the optimal piston pin hole shape power function curve model specifically includes the following steps: According to the optimal piston pin hole shape power function curve model, multiple points (x i ,y i ), where i = 1, 2, ... n, and the value of n is determined according to the length of the piston pin hole curve section in the piston structure; Construct and determine the preset high-order integer power polynomial function model and the optimal piston pin hole shape line power function curve model in x i The residual value model at , the residual value model is Among them, a0, a1, ... a k is the coefficient of the required high-order integer power polynomial function model, and k is the highest power exponent of the required high-order integer power polynomial function model; The residual value model is transformed into a problem of finding the extreme value of the residual value δ, and the function of the residual value δ is determined as δ=δ(a0, a1, ... a k ); According to the function of the residual value δ, for a k Find the partial derivative, which is converted into finding the coefficient a k Matrix of Based on MATLAB, Python or Excel programming, the coefficient a of the high-order integer power polynomial function model is determined by fitting calculation k , determine the high-order integer power polynomial function model.

3. The piston pin hole profile design optimization method according to claim 1, characterized in that: The pin hole dynamic simulation calculation specifically includes: Defining lubricated boundary surfaces between piston components, and defining friction coefficients and wear coefficients between each interface, wherein the piston component includes a piston, a cylinder liner, a piston pin, and a connecting rod end; Construct a finite element mesh model of the piston assembly; Define the oil film thickness and surface roughness characteristics between piston components; Based on the finite element mesh model of the piston assembly and the piston temperature field, the piston outer circle thermal mechanical deformation and the piston pin hole thermal mechanical deformation are loaded and calculated. The friction work between the piston pin hole and the piston pin is calculated based on the initial shape line of the piston pin hole and converted into heat energy and input into the piston temperature field. The calculation is iterated continuously until the pin hole temperature continuously increases and tends to converge. The final friction heat deformation is determined and superimposed on the piston pin hole thermal mechanical deformation to serve as the initial piston pin hole thermal mechanical deformation. A piston pin hole dynamic simulation calculation model is constructed based on the engine parameters, cylinder pressure curve, piston assembly geometric parameters, piston outer circle thermal deformation and initial piston pin hole thermal deformation, piston stiffness matrix and mass matrix, and piston pin hole lubricating oil film characteristics; According to the dynamic simulation calculation model of the piston pin hole, the extended Reynolds equation including the oil filling rate is used to simulate the dynamic calculation of the pin hole. The calculation results include the pin hole contact pressure and the accumulated wear load within one cycle.

4. The piston pin hole profile design optimization method according to claim 3, characterized in that: Defining the lubricated boundary surfaces between the piston components and defining the friction coefficient and wear coefficient between the interfaces specifically includes: The piston ring land, piston pin hole, piston skirt, contact interface between piston pin and piston pin hole, and contact interface between piston pin and connecting rod small end hole are defined as lubrication boundary surfaces. An elastic-hydrodynamic lubrication model is established between the piston pin hole and piston pin, and between the connecting rod small end hole and piston pin. The friction coefficient and wear coefficient between each interface are defined, where the friction coefficient ranges from 0.05 to 0.15 and the wear coefficient is on the order of 10^-8.

5. The piston pin hole profile design optimization method according to claim 4, characterized in that: The constructing of the finite element mesh model of the piston assembly specifically includes: The piston and connecting rod end are constructed using tetrahedral meshes, while the piston pin, cylinder liner and bearing are constructed using hexahedral meshes. The common node method is used to map the nodes on the tile back to the surface of the small head hole of the connecting rod; 20-40 mesh nodes are set on the circumferential direction of the piston pin hole surface, and 10-15 mesh nodes are set along the axial direction of the piston pin hole. When processing the lubrication boundary surface, the tapered surface of the piston pin hole is simplified to a cylindrical surface with the same size as the piston pin hole.

6. The piston pin hole profile design optimization method according to claim 3, characterized in that: The definition of the oil film thickness and surface roughness characteristics between piston components specifically includes: Define the oil film thickness between piston components. The oil film thickness range is 5μm-20μm. Based on the Greenwood-Tripp contact model, the surface roughness characteristics are calculated, wherein the surface roughness characteristics include the root mean square of the roughness peak height σ, the roughness peak curvature radius β, and the composite roughness surface density γ. The Greenwood-Tripp contact model includes: 0.01<σβγ<0.05, Among them, Z s Characterized by the average roughness peak height, σ s It is represented by the standard deviation peak height, n is represented by the total number of rough features, z i Characterized by the height value of the i-th roughness feature, i = 1, 2...n; Characterized by the average height of the roughness feature, n s Characterized by the total number of statistical rough peaks.

7. The piston pin hole profile design optimization method according to claim 1, characterized in that: Determining the optimal piston pin hole cold deformation corresponding to the optimal pin hole contact pressure and cumulative wear load specifically includes: determining a piston pin hole deformation corresponding to the optimal pin hole contact pressure and cumulative wear load; determining a thermal mechanical deformation of a piston pin hole corresponding to the deformation of the piston pin hole; The optimal piston pin hole cold deformation is determined by subtracting the piston pin hole thermal deformation from the piston pin hole deformation.

8. A computer device comprising a processor, wherein the processor is configured to implement the steps of the piston pin hole profile design optimization method according to any one of claims 1 to 7 when executing a computer program stored in a memory.

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