Cam-roller micro-geometric design method fusing internal curve hydraulic motor full-cycle alternating characteristics

Abstract

This invention discloses a micro-geometry design method for cam rollers that integrates the full-cycle alternating characteristics of an internal curve hydraulic motor. First, a thermo-elasto-hydrodynamic lubrication model is established, incorporating micro-surface morphology and considering the full-cycle alternating characteristics of the cam roller-cam ring contact pair. These alternating characteristics include alternating entrainment velocity, alternating external load, and alternating equivalent radius of curvature. Second, based on a three-segment micro-geometry design equation, sensitivity and independence analyses are used to determine the roller convexity, micro-geometry design length, and fillet length as the core design variables. Furthermore, a comprehensive optimization objective function is constructed that simultaneously considers robustness under multiple operating conditions and machining accuracy constraints. Finally, a multi-strategy adaptive optimization algorithm is used to iteratively optimize the above variables, obtaining a cam roller micro-geometry profile that significantly homogenizes contact pressure, improves oil film thickness distribution uniformity, and enhances load-bearing capacity. The cam rollers designed using this method can effectively improve lubrication under high pressure and extend the service life of the hydraulic motor.

Description

Technical Field

[0001] This invention belongs to the field of fluid transmission and tribology technology, and in particular relates to a micro-geometry design method for cam rollers that integrates the full-cycle alternating characteristics of an internal curve hydraulic motor. Background Technology

[0002] As a core actuator in heavy equipment, the service life of an internal curve hydraulic motor directly affects the overall reliability of the machine. With increasing working pressure levels, the multiple pairs of cam roller-cam ring friction pairs within the motor are more prone to failure. For example, a 3cm long roller will withstand an additional 1.4 tons of force after pressure increases. Traditional roller designs struggle to adapt to heavy loads and the alternating characteristics caused by the multi-segment curves of the cam ring.

[0003] To improve the contact condition between the roller and the guide rail, existing research mainly focuses on the optimization design of the roller profile. Methods such as logarithmic modification, full convexity modification, and tangential circular arc modification of the roller have been studied and have achieved good results under constant curvature, constant load, and speed conditions. However, in internal curve hydraulic motors, the cam rollers move along the inner curve of the cam ring. The entrainment speed, external load, and even the equivalent radius of curvature at the contact point periodically change with the rotation angle position. This makes traditional micro-geometry design methods based on constant contact conditions difficult to apply. The profile optimized for a fixed position may fail at other positions, or even cause new stress concentrations. Furthermore, most existing studies aim to minimize contact stress under a single working condition, failing to systematically consider the robustness requirements of multiple alternating working conditions throughout the entire cycle. They also generally ignore the sensitivity of micron-level modification amounts to machining accuracy, making it difficult to reliably implement the design results in engineering manufacturing.

[0004] In summary, this invention proposes a micro-geometry design method for cam rollers that can adapt to the alternating characteristics of the entire cycle and take into account the feasibility of processing, so as to fundamentally improve the roller pressure distribution and extend the service life of hydraulic motors under high pressure conditions. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a micro-geometric design method for cam rollers that integrates the full-cycle alternating characteristics of internal curve hydraulic motors. This method calculates the pressure and film thickness distribution between the cam rollers and cam rings using a lubrication model that accurately and effectively considers alternating operating conditions. A three-segment micro-geometric design is then performed on the cam rollers. By optimizing for multiple operating conditions and machining robustness, a cam roller that maintains excellent performance under all operating conditions and is insensitive to machining accuracy is designed, thereby improving the load-bearing capacity and service life of the cam rollers.

[0006] This invention is achieved through the following technical solution: a micro-geometry design method for cam rollers that integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, specifically including the following steps: (1) Based on the line contact thermo-elastohydrodynamic lubrication model, a lubrication model integrating the full-cycle alternating characteristics (alternating entrainment speed, alternating external load and alternating equivalent radius of curvature) is proposed; (2) Based on the model in step (1), a three-segment micro-geometric design equation is proposed to describe the roller profile. Sensitivity and independence analyses of the design parameters are performed to determine the roller convexity Δ. c Micro-geometric design length L c and the length of the rounded corner area L r As a core optimization design variable; (3) Construct a comprehensive optimization objective function, which simultaneously considers the performance robustness of the cam roller under multiple key working conditions throughout the entire cycle, as well as the manufacturing robustness of the roller convexity Δc within the machining accuracy tolerance range; (4) The multi-strategy adaptive hybrid optimization algorithm is used to solve the optimization design variables determined in step (2), and the optimal roller micro-geometry design parameters are obtained by minimizing the comprehensive optimization objective function defined in step (3).

[0007] Furthermore, in step (1), the key equation for the lubrication model used to simulate the lubrication state of the friction pair throughout the entire cycle, which incorporates alternating characteristics, is: in, x , y These are the radial and axial coordinates of the roller, with the origin at the axial center of the roller. or The viscosity of the lubricating oil. p For oil film pressure distribution, h For oil film thickness distribution, r For the density of lubricating oil, u e For alternating entrainment speed, h 0 represents the thickness of the rigid body's central membrane. R eq Let be the alternating equivalent radius of curvature. h des Initial values ​​for convexity measurement in microgeometry design. v This is the elastic deformation value. d This represents the surface roughness value. t This is the thermoelastic deformation value. Oh This represents the integral region of the pressure distribution. W It is an alternating external load.

[0008] Furthermore, the alternating entrainment speed u eAlternating external load W Alternating equivalent radius of curvature R eq Both are described as the position angle of the cam roller moving along the cam ring. f The function is obtained by solving the relationship between the cam ring curve geometry and the piston assembly kinematics. The equation describing the alternating entrainment speed is: in, u 1 represents the tangential velocity at the contact point between the guide rail and the cam roller. u 2 represents the tangential velocity of the contact point on the roller. n Motor speed, β For pressure angle, l For radial direction, c The angle between the radial tangent and the contact point tangent. v r and v e These are relative velocity and entrainment velocity, respectively.

[0009] The equation describing the alternating external load is: in, d The diameter of the plunger. p d The hydraulic pressure at the bottom of the plunger. r φ , v φ and a φ These are the extreme diameter of the cam roller, the angular velocity, and the angular acceleration, respectively. f The changing trend is determined by the shape of the motor cam ring curve.

[0010] The equation describing the alternating equivalent radius of curvature is: in, R Let the radius of curvature of the roller center trajectory be denoted as . R e Let be the radius of curvature of the cam ring. R g Let be the radius of the cam roller.

[0011] Furthermore, in step (2), the three-segment micro-geometric design equation is used for the micro-geometric profile design of the cam roller, and its equation is expressed as: in, R c The radius of the arc at both ends is designed for micro-geometry. L e The axial length of the cam roller excluding the end fillets r Δ is the end fillet radius. c For the measurement of the roller convexity, L This represents the total axial length of the cam roller. L c For micro-geometry design length, L r This represents the length of the rounded corner area.

[0012] Furthermore, in step (3), the comprehensive optimization objective function F The mathematical expression is a two-layer maximization structure: the inner layer calculates the sub-objective function value of the given design variables under a single working condition. F mn And take all selected working conditions F mn The maximum value is used as the performance index for all selected working conditions under ideal manufacturing conditions. F m The outer layer is sampled within the design convexity tolerance range considering machining errors, and all sampling points are taken. F m The maximum value is taken as the final objective function value. F ,Right now: in, M To determine the number of sampling points within the convexity tolerance range, N The number of selected critical operating conditions throughout the entire lifecycle.

[0013] Furthermore, the sub-objective function F mn It consists of a contact pressure uniformity term, an oil film thickness stability term, and a pressure fluctuation term, and its expression is: Where, max y [ p mn (0, y [] represents the maximum axial pressure value. p mn (0, 0) represents the axial center pressure value; min y [ h mn [0, y)] represents the minimum axial film thickness. h mn (0, 0) represents the axial center film thickness; std[p mn [0, y] represents the standard deviation of the axial pressure distribution.

[0014] Furthermore, in step (4), a multi-strategy adaptive hybrid optimization algorithm can be used for iterative optimization, the purpose of which is to efficiently and robustly find the combination of design parameters that minimizes the objective function.

[0015] The beneficial effects of this invention are: This invention proposes a micro-geometric design method for cam rollers that integrates the full-cycle alternating characteristics of internal curve hydraulic motors. It improves the thermo-elasto-fluidic lubrication model, enabling accurate simulation of the full-cycle alternating contact state of the cam rollers. A three-segment micro-geometric design equation suitable for hydraulic motor rollers is proposed, and a comprehensive optimization objective function is constructed that simultaneously considers robust performance under multiple operating conditions and manufacturing precision. Using this method, a cam roller micro-geometric profile is finally designed that exhibits uniform pressure distribution, high oil film stability, and insensitivity to machining errors under high-pressure alternating conditions. This significantly improves the load-bearing capacity and fatigue life of the cam roller-cam ring friction pair, resulting in a substantial extension of the hydraulic motor's service life. This invention offers advantages such as a systematic design process, comprehensive optimization objectives, and strong engineering applicability. Attached Figure Description

[0016] Figure 1 Flowchart for the geometric numerical model optimization design of the cam roller of the internal curve motor.

[0017] Figure 2 This is a flowchart for optimizing the cam roller of a hydraulic motor based on the MAHO algorithm for internal curves.

[0018] Figure 3 This is a schematic diagram of the cam roller-cam ring in an internal curve hydraulic motor.

[0019] Figure 4 A comparison diagram of the oil film pressure between the front and rear cam rollers and cam rings is provided for design purposes.

[0020] Figure 5 A comparison chart of hydraulic motor life tests before and after assembly design of the cam rollers. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific examples. The embodiments of the present invention take the TMS11-1150 internal curve hydraulic motor as an example, but the method is universal.

[0022] like Figure 1 , Figure 2 and Figure 3 As shown, the specific implementation steps of the present invention are as follows: (1) Establish a thermo-elastohydrodynamic (TEHL) lubrication model that integrates full-cycle alternating characteristics. Based on the cam ring curve equation and the kinematics of the plunger assembly, derive and calculate the roller angles at different positions during a high-pressure motion cycle. f Alternating entrainment speed u e Alternating external load W and alternating equivalent radius of curvature R eq These parameters exhibit significant periodic variations. The equation describing the alternating entrainment velocity is: in, u 1 represents the tangential velocity at the contact point between the guide rail and the cam roller. u 2 represents the tangential velocity of the contact point on the roller. n Motor speed, β For pressure angle, l For radial direction, c The angle between the radial tangent and the contact point tangent. v r and v e These are relative velocity and entrainment velocity, respectively.

[0023] The equation describing the alternating external load is: in, d The diameter of the plunger. p d The hydraulic pressure at the bottom of the plunger. r φ , v φ and a φ These are the extreme diameter of the cam roller, the angular velocity, and the angular acceleration, respectively. f The changing trend is determined by the shape of the motor cam ring curve.

[0024] The equation describing the alternating equivalent radius of curvature is: in, R Let the radius of curvature of the roller center trajectory be denoted as . R e Let be the radius of curvature of the cam ring. R g Let be the radius of the cam roller.

[0025] The key equation for integrating the three alternating parameters into the thermo-elasto-fluidic lubrication model is: in, x , y These are the radial and axial coordinates of the roller, with the origin at the axial center of the roller. or The viscosity of the lubricating oil. p For oil film pressure distribution, h For oil film thickness distribution, r For the density of lubricating oil, u e For alternating entrainment speed, h 0 represents the thickness of the rigid body's central membrane. R eq Let be the alternating equivalent radius of curvature. h des Initial values ​​for convexity measurement in microgeometry design. v This is the elastic deformation value. d This represents the surface roughness value. t This is the thermoelastic deformation value. Oh This represents the integral region of the pressure distribution. W For alternating external loads; To achieve accurate solutions for the lubrication model, the formula for calculating the elastic displacement of each point on the line contact surface along the vertical direction is derived based on elasticity theory: in, E To measure the overall elastic modulus, x 0 and x e These are the starting and ending points of the pressure distribution area. The integral variable (representing the x-coordinate of the pressure application point).

[0026] Secondly, the heat generated by heavy-load contact friction shear will produce thermoelastic displacement due to radial free thermal expansion and temperature inhomogeneity, which can be expressed as: The first and second items correspond to the two components of radial free thermal expansion and temperature non-uniformity mentioned above, respectively. i The values ​​represent the rollers and cam rings ( i =1 represents the cam ring. i =2 represents the cam roller); α ei The average linear thermal expansion coefficient of the material; R i The radius of curvature; T s The temperature of the contact surface; vi The Poisson's ratio of the material; T (r) is the radial distribution function of temperature. The energy distribution described above is obtained by solving the conventional energy equation and the heat conduction equation together.

[0027] (2) For the working conditions of the cam roller, a three-segment micro-geometric design equation is proposed. The shape consists of a straight central segment and a circular arc trimming segment tangentially connected at both ends. The equation is expressed as follows: in, R c The radius of the arc at both ends is designed for micro-geometry. L e The axial length of the cam roller excluding the end fillets r Δ is the end fillet radius. c For the measurement of the roller convexity, L This represents the total axial length of the cam roller. L c For micro-geometry design length, L r This represents the length of the rounded corner area.

[0028] The initial design parameter set was preliminarily determined through manufacturing feasibility analysis. Subsequently, based on global sensitivity analysis, significantly influential design parameters were identified. Further correlation analysis was conducted to determine whether the various design variables were independent. Finally, the parameter set was determined using x=[Δc, L c , L r ] as a set of optimization design variables.

[0029] (3) The objective function design aims to ensure the roller profile maintains stable performance under full-cycle alternating conditions and is robust to machining errors. For a given set of design variables x, the actual machining value of its convexity has tolerance. t ol Determined based on the machining accuracy level. Within the range [Δ] c - t ol / 2, Δ c + t ol / 2] Take evenly within M Δ at each sampling point c m , where m is the sampling point number, representing possible machining contour deviations. For each sampling point Δ c m Considering the selection over the entire motion cycle NKey operating conditions (covering different) R eqn , W n , u en The combination of n, where n is the working condition number).

[0030] The pressure and film thickness distribution under each working condition were calculated using the TEHL model from step (1), and the sub-objective function value was calculated. F mn ,Right now: Where, max y [ p mn (0, y [] represents the maximum axial pressure value. p mn (0, 0) represents the axial center pressure value; min y [ h mn [0, y)] represents the minimum axial film thickness. h mn (0, 0) represents the axial center film thickness; std[ p mn [0, y] represents the standard deviation of the axial pressure distribution.

[0031] The objective function value F mn This comprehensively reflects the uniformity of contact pressure, film thickness stability, and the degree of pressure fluctuation. The sampling point Δ is defined as follows. c m performance indicators F m For all working conditions F mn The maximum value, that is: This ensures it can withstand the most severe operating conditions. Finally, the final objective function value of this set of design variables x is defined. F For all sampling points F m The maximum value in, that is: The dual-layer Max structure ensures that the optimization search targets design parameters that maintain optimal performance across all critical operating conditions throughout the entire lifecycle, even under the most adverse conditions caused by manufacturing inaccuracies.

[0032] (4) Integrate the above model and objective function into the optimization process, and use a multi-strategy adaptive hybrid optimization algorithm to iteratively optimize the design variable set x in order to minimize the final objective function value. F The goal is to improve the load-bearing capacity and lubrication condition of the cam rollers. The optimization algorithm parameters can be adjusted based on the iteration results, and the range of design variable groups should be set according to manufacturing feasibility and the specific cam rollers to be optimized.

[0033] To further illustrate this with a specific example, consider the TMS11-1150 internal curve hydraulic motor, specifically the cam roller radius. R g The diameter is 15 mm, the cam roller length is 30 mm, and the plunger diameter is... d The pressure at the bottom of the plunger is 50 mm. p d The pressure is 42 MPa, and the motor speed is... n The cam ring speed is 65 rpm, and the cam ring curve is a constant acceleration and deceleration curve with a minimum extreme diameter. r φ0 The stroke is 105.7 mm. h p The amplitude of the high-voltage action is 12.3 mm. f x The angle is 30°. Considering a machining accuracy of level two, the sampling point is set as follows: M The number is 10, and the number of multiple working conditions is [number missing]. N Set the range of micro-geometric parameters for the cam roller to 20, and the roller convexity measurement Δ. c The micro-geometry design length is [0, 40] μm. L c The length of the rounded corner area is [2, 8] mm. L r The value is [0.5, 2] mm. The above micro-geometry design method is used for the design, and Δ is designed. c , L c , L r The diameters are 12.483 μm, 4.052 mm, and 0.971 mm, respectively. The objective function result obtained with the initial parameters is 1.8065, and the objective function result obtained with the designed parameters is 1.3555. The oil film pressure and motor life test results before and after the design parameters are compared as follows: Figure 4 and Figure 5As shown, compared to the original cam roller, the micro-geometry-designed cam roller effectively reduces pressure concentration caused by edge effects at different positions on the cam ring, resulting in more uniform contact pressure and oil film thickness, and improving the roller's high-pressure load-bearing capacity. Motor life test results show that the motor with the micro-geometry-designed cam roller has a lifespan nearly 20 times longer than the motor with the original cam roller, improving the motor's operational reliability and service life.

[0034] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A micro-geometry design method for cam rollers that integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, characterized in that, The method includes the following steps: (1) Based on the line contact thermo-elastohydrodynamic lubrication model, a lubrication model integrating full-cycle alternating characteristics is constructed. The alternating characteristics include alternating entrainment speed, alternating external load and alternating equivalent radius of curvature, which are used to simulate the lubrication state of the friction pair in the full cycle. (2) Based on the lubrication model of the integrated full-cycle alternating characteristics in step (1), the roller micro-geometric design profile is described based on the three-segment micro-geometric design equation. By conducting sensitivity analysis and independence analysis on the design parameters, the roller convexity, micro-geometric design length and fillet length are determined as the core optimization design variables. (3) Construct a comprehensive optimization objective function, which simultaneously considers the performance robustness of the cam roller under multiple key working conditions throughout the entire cycle, and the manufacturing robustness of the roller convexity within the machining accuracy tolerance range: (4) The multi-strategy adaptive hybrid optimization algorithm is used to optimize the design variables determined in step (2) and iterate them to minimize the comprehensive optimization objective function in step (3) to obtain the optimal roller micro-geometry design parameters.

2. The cam roller micro-geometry design method according to claim 1, which integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, is characterized in that... The key equation for integrating alternating characteristics in the lubrication model is: in, x , y These are the radial and axial coordinates of the roller, with the origin at the axial center of the roller. η The viscosity of the lubricating oil. p For oil film pressure distribution, h For oil film thickness distribution, ρ For the density of lubricating oil, u e For alternating entrainment speed, h 0 represents the thickness of the rigid body's central membrane. R eq Let be the alternating equivalent radius of curvature. h des Initial values ​​for convexity measurement in microgeometry design. v This is the elastic deformation value. δ This represents the surface roughness value. t This is the thermoelastic deformation value. Ω This represents the integral region of the pressure distribution. W It is an alternating external load.

3. The cam roller micro-geometry design method according to claim 1, which integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, is characterized in that... In step (1), the alternating entrainment speed u e Alternating external load W Alternating equivalent radius of curvature R eq Both are described as the position angle of the cam roller moving along the cam ring. φ The function is obtained by solving the relationship between the geometry of the cam ring curve and the kinematics of the piston assembly.

4. The cam roller micro-geometry design method according to claim 3, which integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, is characterized in that... The equation describing the alternating entrainment velocity is: in, u 1 represents the tangential velocity at the contact point between the guide rail and the cam roller. u 2 represents the tangential velocity of the contact point on the roller. n Motor speed, β For pressure angle, l For radial direction, γ The angle between the radial tangent and the tangent at the point of contact. v r and v e These are relative velocity and entrainment velocity, respectively. The equation describing the alternating external load is: in, d The diameter of the plunger. p d The hydraulic pressure at the bottom of the plunger. ρ φ , v φ and a φ These are the extreme diameter of the cam roller, the angular velocity, and the angular acceleration, respectively. φ The changing trend is determined by the shape of the motor cam ring curve; The equation describing the alternating equivalent radius of curvature is: in, R Let the radius of curvature of the roller center trajectory be denoted as . R e Let be the radius of curvature of the cam ring. R g Let be the radius of the cam roller.

5. The cam roller micro-geometry design method according to claim 1, which integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, is characterized in that... In step (2), the three-segment microgeometric design equation is expressed as follows: in, R c The radius of the arc at both ends is designed for micro-geometry. L e The axial length of the cam roller excluding the end fillets r The end fillet radius is Δ c For the measurement of the roller convexity, L This represents the total axial length of the cam roller. L c For micro-geometry design length, L r This represents the length of the rounded corner area.

6. The cam roller micro-geometry design method according to claim 1, which integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, is characterized in that... In step (3), the comprehensive optimization objective function F The mathematical expression is a two-layer maximization structure: the inner layer calculates the sub-objective function value of the given design variables under a single working condition. F mn And take all selected working conditions F mn The maximum value is used as the performance index for all selected working conditions under ideal manufacturing conditions. F m The outer layer is sampled within the design convexity tolerance range considering machining errors, and all sampling points are taken. F m The maximum value is taken as the final objective function value. F ,Right now: in, M To determine the number of sampling points within the convexity tolerance range, N The number of selected critical operating conditions throughout the entire lifecycle.

7. The cam roller micro-geometry design method according to claim 6, which integrates the full-cycle alternating characteristics of an internal curve hydraulic motor, is characterized in that... The sub-objective function F mn It consists of a pressure uniformity term, an oil film thickness stability term, and a pressure fluctuation term, and its expression is: Where, max y [ p mn (0, y [] represents the maximum axial pressure value. p mn (0, 0) represents the axial center pressure value; min y [ h mn [0,y)] represents the minimum axial film thickness. h mn (0, 0) represents the axial center film thickness; std[ p mn [0, y] represents the standard deviation of the axial pressure distribution.

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